Palladium-based supported hydrogenation catalyst, and preparation method and application thereof

Abstract

The present invention relates to a palladium-based supported hydrogenation catalyst and a preparation method and application thereof. The catalyst is prepared by the following method: impregnating an Al.sub.2O.sub.3-containing carrier with an organic solution containing a bipyridine derivative having hydroxy group, optionally drying followed by impregnating with a mixed solution containing the main active component palladium ions and the auxiliary active component M.sup.n+ ions, where M is one selected from Ag, Au, Ni, Pb and Cu; and then optionally drying, and calcining to obtain the catalyst. The preparation method provided by the present invention allows Pd atoms and M atoms to be highly uniformly dispersed on the carrier, which overcomes the adverse impact of the surface tension of the impregnation solution and the solvation effect on the dispersibility of active components. The palladium-based supported hydrogenation catalyst provided by the present invention has excellent hydrogenation activity, ethylene selectivity and anti-coking performance, and can be used in a selective hydrogenation process of C2 fraction.

Claims

1. A method of preparing a palladium-based supported hydrogenation catalyst, comprising: impregnating an Al.sub.2O.sub.3-containing carrier with an organic solution containing a bipyridine compound; optionally drying followed by impregnating with a mixed solution containing palladium ions and M metal cations, wherein the M metal cations is selected from one of Ag, Au, Ni, Pb or Cu; and optionally drying, and calcining to obtain the palladium-based supported hydrogenation catalyst; wherein, the bipyridine compound is 4,4-dihydroxy-2,2-bipyridine and/or 6,6-dihydroxy-3,3-bipyridine.

2. The method according to claim 1, wherein the impregnation of the Al.sub.2O.sub.3-containing carrier with the organic solution containing the bipyridine compound is carried out at 20-60 C., and the impregnation duration is 2 to 24 hours.

3. The method according to claim 1, wherein the impregnation of the bipyridine compound impregnated Al.sub.2O.sub.3 precursor with the mixed solution is carried out at 30-100 C., and the impregnation duration is 2 to 24 hours.

4. The method according to claim 1, wherein the calcination temperature is 300-600 C., and the duration is 2 to 12 hours.

5. The method according to claim 1, wherein the Al.sub.2O.sub.3-containing carrier comprises alumina and/or a mixture containing alumina and an additional oxide, wherein the additional oxide includes a combination of one or more of silica, titania, magnesium oxide and calcium oxide.

6. The method according to claim 1, wherein a crystal form of Al.sub.2O.sub.3 in the Al.sub.2O.sub.3-containing carrier is , , , , or a mixed crystal form of some of these crystal forms.

7. The method according to claim 1, wherein the Al.sub.2O.sub.3-containing carrier is in the form of spherical, tooth-spherical, cylindrical, ring, bar, three-leaf clover or four-leaf clover shape.

8. The method according to claim 1, wherein the molar ratio of the palladium ions to the M metal cations in the mixed solution is 1-100:1.

9. The method according to claim 1, wherein in the mixed solution, when M is Ag, the molar ratio of Ag to Pd is 0.4-10:1; when M is Au, the molar ratio of Au to Pd is 0.5-15:1; when M is Ni, the molar ratio of Ni to Pd is 0.4-20:1; when M is Pb, the molar ratio of Pb to Pd is 1-10:1; when M is Cu, the molar ratio of Cu to Pd is 1-10:1.

10. The method according to claim 1, wherein the pH of the mixed solution is 1.5-4.0.

11. The method according to claim 1, further comprising subjecting the palladium-based supported hydrogenation catalyst to a reduction treatment with a hydrogen-containing gas before use thereof, to obtain the reduced palladium-based supported hydrogenation catalyst.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a flow chart of a back-end hydrogenation process of C2 fraction with a sequential separation procedure.

(2) FIG. 2 is a flow chart of a front-end deethanization hydrogenation process of C2 fraction.

(3) FIG. 3 is a flow chart of a front-end depropanization hydrogenation process of C2 fraction.

(4) FIG. 4 is a flow chart of an ethylene refining process with a sequential separation procedure.

(5) FIG. 5 is a flow chart of an ethylene refining process with a front-end deethanization hydrogenation procedure.

(6) FIG. 6 is a flow chart of a Methanol-to-olefin (MTO) process with a sequential separation procedure.

(7) FIG. 7 is a flow chart of an ethylene refining process with a front-end depropanization hydrogenation procedure.

(8) FIG. 8 is a flow chart of a Methanol-to-olefin (MTO) process with a front-end depropanization hydrogenation procedure.

DESCRIPTION OF SYMBOLS OF MAIN COMPONENTS

(9) 1Oil washing tower, 2Water washing tower, 3Alkaline washing tower, 4Dryer, 5Demethanizer, 6Deethanizer, 7C2 hydrogenation reactor, 8Compressor, 9Ethylene refining column, 10Ethylene refining reactor, 11Depropanizer, 12Propylene refining column, 13Methanol-to-ethylene reactor, 14Regenerator, 15Separator, 16Reactor for dehydration of methanol to dimethyl ether, 17Methanol-to-propylene reactor, 18Pre-quench separator, 19Quench separator, 20Four-level compressor, 21Four-level separator.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(10) Analysis and Testing Methods: Specific surface area: in accordance with the standard GB/T-5816; Pore volume: in accordance with the standard GB/T-5816; Bulk density: in accordance with the standard Q/SY142-2006; Pd, Ag, Au, Ni, Cu or Pb content in the catalyst: using a plasma emission spectrometer or an atomic absorption spectrometer (in accordance with the standard GB/T 1537-94); Ethylene selectivity=(the molar percentage of ethylene after reactionthe molar percentage of ethylene prior to reaction)/(the molar percentage of acetylene before reactionthe molar percentage of acetylene after reaction).

EXAMPLE 1

(11) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 3.5 mm, a specific surface area of 20.0 m.sup.2/g, a pore volume of 0.48 mL/g and a bulk density of 0.82 g/cm.sup.3 was weighed. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-50 nm and 300-500 nm, respectively.

(12) 34.12 g of 4,4-dihydroxy-2,2-bipyridine was dissolved in 650 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 2 hours, to allow 4,4-dihydroxy-2,2-bipyridine in the solution to be fully supported on the carrier. Then the solid reaction product was dried at 60 C. for 10 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(13) 0.37 g of Pd(NO.sub.3).sub.2 and 0.79 g of AgNO.sub.3 were dissolved in 600 mL of deionized water and the pH was adjusted to 3.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 10 minutes and allowed to stand for 2 hours. The residual liquid was decanted and the solid reaction product was dried at 120 C. for 4 hours, to obtain a (PdAg)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Ag) is 30).

(14) The above (PdAg)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 550 C. for 3 hours to obtain a (PdAg)/Al.sub.2O.sub.3 catalyst.

(15) The above (PdAg)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1 at 120 C. for 3 hours, to obtain a reduced palladium-based supported hydrogenation catalyst S1. The Pd content and the Ag content in this catalyst S1 were measured to be 0.03 wt. % and 0.10 wt. %, respectively.

COMPARATIVE EXAMPLE 1

(16) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 3.5 mm, a specific surface area of 20.0 m.sup.2/g, a pore volume of 0.48 mL/g and a bulk density of 0.82 g/cm.sup.3 was weighed. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-50 nm and 300-500 nm, respectively.

(17) 8.9 g of polyvinyl chloride (PVC) was dissolved in 800 mL of tetrahydrofuran (THF) to obtain a solution. The carrier was impregnated in the solution and allowed to stand for 2 hours, to allow the PVC in the solution to adsorb onto the carrier surface. The solid reaction product was dried at 60 C. for 10 hours, to obtain a PVC/Al.sub.2O.sub.3 precursor.

(18) 19.28 g of dicyandiamide and 4.0 g of Na.sub.2CO.sub.3 were heated and dissolved in 1000 mL of deionized water, and then the above PVC/Al.sub.2O.sub.3 precursor was added and reacted under reflux for 1 hour. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 60 C. for 10 hours, to obtain a functionalized PVC/Al.sub.2O.sub.3 precursor.

(19) 0.37 g of Pd(NO.sub.3).sub.2 and 0.79 g of AgNO.sub.3 were dissolved in 600 mL of deionized water and the pH was adjusted to 3.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above functionalized PVC/Al.sub.2O.sub.3 precursor was added into the mixed solution and stirred for 0.5 hours. The residual liquid was decanted. The solid reaction product was washed to neutrality with deionized water and then dried at 120 C. for 4 hours, to obtain a (PdAg)-PVC/Al.sub.2O.sub.3 precursor.

(20) The above (PdAg)-PVC/Al.sub.2O.sub.3 precursor was calcinated in an air atmosphere at 550 C. for 2 hours to obtain a (PdAg)/Al.sub.2O.sub.3 catalyst.

(21) The above (PdAg)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D1. The Pd content and the Ag content in this catalyst D1 were measured to be 0.03 wt. % and 0.10 wt. %, respectively.

Catalyst Application

(22) The catalysts prepared in Example 1 and Comparative Example 1 were respectively used in the back-end hydrogenation process of C2 fraction with a sequential separation procedure. The process flow chart is shown in FIG. 1. The C2 fraction obtained by steam cracking of petroleum hydrocarbon is treated by sequentially passing through an oil washing tower 1, a water washing tower 2, an alkaline washing tower 3, a dryer 4, a demethanizer 5 and a deethanizer 6 and then entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, wherein compressors 8 are provided between the water washing tower 2 and the alkaline washing tower 3 and between the demethanizer 5 and the deethanizer 6.

(23) The reaction was carried out with two C2 hydrogenation reactors in series, i.e., the outlet material of the first section reactor entered the second section reactor. Each reactor has an independent gas dispensing system, and both reactors are fixed-bed adiabatic reactors.

(24) The composition of the C2 materials treated in the C2 hydrogenation reactor was: 1.58% of C.sub.2H.sub.2, 81.55% of C.sub.2H.sub.4 and 16.87% of C.sub.2H.sub.6 (in percentage by volume).

(25) Reaction conditions: the space velocity of the material gas was 2000 h.sup.1, the reaction pressure was 1.7 MPa, the catalyst loading in both reactors was 450 mL, H.sub.2/C.sub.2H.sub.2 in the first section reactor=1.5:1 (molar ratio), and H.sub.2/C.sub.2H.sub.2 in the second section reactor=3:1 (molar ratio). The results of the reaction for 500 hours are shown in Table 1.

(26) TABLE-US-00001 TABLE 1 Inlet Temper- C.sub.2H.sub.2 Green temper- ature residual Ethylene oil Reactor ature rise amount selectivity amount Catalyst section ( C.) ( C.) (v/v %) (%) (g) S-1 First 40 28 0.15 78 5.5 section Second 50 12 0 46 3.9 section D-1 First 40 30 0.28 70 9.2 section Second 50 16 0.11 39 6.3 section

EXAMPLE 2

(27) 500 g of a spherical carrier containing 440 g of -Al.sub.2O.sub.3 and 60 g of titania, having 2.5 mm, a specific surface area of 50 m.sup.2/g and a pore volume of 0.75 mL/g was weighed.

(28) 6.82 g of 4,4-dihydroxy-2,2-bipyridine was dissolved in 600 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 8 hours, to allow 4,4-dihydroxy-2,2-bipyridine in the solution to be fully supported on the carrier. Then the solid reaction product was dried at 110 C. for 6 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(29) 0.38 g of palladium chloride and 1.72 g of chloroauric acid were dissolved in 600 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of hydrochloric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 1 hour and allowed to stand for 8 hours. The residual liquid was decanted, to obtain a (PdAu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Au) is 5.03).

(30) The above (PdAu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 500 C. for 6 hours to obtain a (PdAu)/Al.sub.2O.sub.3 catalyst S2. The Pd content and the Au content in this catalyst were measured to be 0.045 wt. % and 0.20 wt. %, respectively.

COMPARATIVE EXAMPLE 2

(31) 500 g of a spherical carrier containing 440 g of -Al.sub.2O.sub.3 and 60 g of titania, having 2.5 mm, a specific surface area of 50 m.sup.2/g and a pore volume of 0.75 mL/g was weighed.

(32) 2.2 g of polystyrene-acrylonitrile (SAN) was added to 600 mL dimethylformamide (DMF), and stirred at room temperature until the SAN was completely dissolved to obtain a solution. The above carrier was added to the solution, fully stirred and allowed to stand for 1 hour. The solid reaction product was dried at 120 C. for 6 hours, to obtain a SAN/Al.sub.2O.sub.3 precursor.

(33) The above SAN/Al.sub.2O.sub.3 precursor was added into 1000 mL of deionized water, and 57.6 g of ethylenediamine was added, stirred until the precursor was completely dissolved and then reacted under reflux for 1 hour. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 80 C. for 5 hours, to obtain a functionalized SAN/Al.sub.2O.sub.3 precursor.

(34) 0.38 g of palladium chloride and 1.72 g of chloroauric acid were dissolved in 1200 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of hydrochloric acid to obtain a mixed solution. The above functionalized SAN/Al.sub.2O.sub.3 precursor was added into the mixed solution and stirred for 2 hours. The residual liquid was decanted and the solid reaction product was washed to neutrality with deionized water, to obtain a (PdAu)-SAN/Al.sub.2O.sub.3 precursor.

(35) The above (PdAu)-SAN/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 380 C. for 2 hours to obtain a (PdAu)/Al.sub.2O.sub.3 catalyst D2. The Pd content and the Au content in this catalyst were measured to be 0.045 wt. % and 0.20 wt. %, respectively.

Catalyst Application

(36) The catalysts prepared in Example 2 and Comparative Example 2 were respectively used in the back-end hydrogenation process of C2 fraction with a sequential separation procedure. The process flow chart is shown in FIG. 1.

(37) The reaction was carried out with two C2 hydrogenation reactors in series, i.e., the outlet material of the first section reactor entered the second section reactor. Each reactor has an independent gas dispensing system, and both reactors are fixed-bed adiabatic reactors.

(38) The composition of the C2 materials treated in the C2 hydrogenation reactor was: 1.7% of C.sub.2H.sub.2, 74.3% of C.sub.2H.sub.4 and 24.0% of C.sub.2H.sub.6 (in percentage by volume).

(39) Reaction conditions: the space velocity of the material gas was 4000 h.sup.1, the reaction pressure was 1.2 MPa, the catalyst loading for both reactors was 500 mL, H.sub.2/C.sub.2H.sub.2 in the first section reactor=1.6:1 (molar ratio), and H.sub.2/C.sub.2H.sub.2 in the second section reactor=2.8:1 (molar ratio). The results of the reaction for 1000 hours are shown in Table 2.

(40) TABLE-US-00002 TABLE 2 Inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Ethylene Green oil Reactor ature rise amount increment selectivity amount Catalyst section ( C.) ( C.) (v/v %) (mol %) (%) (g) S-2 First 38 16 0.14 1.2 85 7.0 section Second 45 5 0 50 3.0 section D-2 First 40 20 0.34 0.5 65 10.6 section Second 50 10 0.09 32 6.7 section

EXAMPLE 3

(41) 500 g of a cylindrical carrier containing 400 g of -Al.sub.2O.sub.3 and 100 g of magnesium oxide, having 4.5 mm, a height of 4.5 mm, a specific surface area of 17 m.sup.2/g and a pore volume of 0.33 mL/g was weighed.

(42) 82.65 g of 6,6-dihydroxy-3,3-bipyridine was dissolved in 650 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 12 hours, to allow 6,6-dihydroxy-3,3-bipyridine in the solution to be fully supported on the carrier, the solid reaction product was dried at 120 C. for 4 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(43) 0.68 g of Pd(NO.sub.3).sub.2 and 2.43 g of Ni(NO.sub.3).sub.2.6H.sub.2O were dissolved in 600 mL of deionized water and the pH was adjusted to 3.4 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 60 minutes and allowed to stand for 10 hours. The residual liquid was decanted, to obtain a (PdNi)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Ni) is 40).

(44) The above (PdNi)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 8 hours to obtain a (PdNi)/Al.sub.2O.sub.3 catalyst.

(45) The above (PdAg)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S3. The Pd content and the Ni content in this catalyst S3 were measured to be 0.056 wt. % and 0.098 wt. %, respectively.

COMPARATIVE EXAMPLE 3

(46) 500 g of a cylindrical carrier containing 400 g of -Al.sub.2O.sub.3 and 100 g of magnesium oxide, having 4.5 mm, a height of 4.5 mm, a specific surface area of 17 m.sup.2/g and a pore volume of 0.33 mL/g was weighed.

(47) 8.9 g of polyvinyl chloride (PVC) was dissolved in 800 mL of tetrahydrofuran (THF) to obtain a solution. The above carrier was impregnated in the solution and allowed to stand for 2 hours, to allow the PVC in the solution to adsorb onto the carrier surface. The solid reaction product was dried at 60 C. for 10 hours, to obtain a PVC/Al.sub.2O.sub.3 precursor.

(48) 19.28 g of dicyandiamide and 4.0 g of Na.sub.2CO.sub.3 were heated and dissolved in 1000 mL of deionized water, and then the above PVC/Al.sub.2O.sub.3 precursor was added and reacted under reflux for 1 hour. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 60 C. for 10 hours, to obtain a functionalized PVC/Al.sub.2O.sub.3 precursor.

(49) 0.68 g of Pd(NO.sub.3).sub.2 and 2.43 g of Ni(NO.sub.3).sub.2.6H.sub.2O were dissolved in 2400 mL of deionized water and the pH was adjusted to 3.4 with an appropriate amount of nitric acid to obtain a mixed solution. The above functionalized PVC/Al.sub.2O.sub.3 precursor was added into the mixed solution and stirred for 0.5 hours. The residual liquid was decanted. The solid reaction product was washed to neutrality with deionized water and then dried at 120 C. for 4 hours, to obtain a (PdNi)-PVC/Al.sub.2O.sub.3 precursor.

(50) The above (PdNi)-PVC/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 8 hours to obtain a (PdNi)/Al.sub.2O.sub.3 catalyst.

(51) The above (PdNi)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D3. The Pd content and the Ni content in this catalyst D3 were measured to be 0.056 wt. % and 0.098 wt. %, respectively.

Catalyst Application

(52) The catalysts prepared in Example 3 and Comparative Example 3 were respectively used in the front-end deethanization process of C2 fraction. The process flow chart is shown in FIG. 2. The C2 fraction obtained by steam cracking of petroleum hydrocarbon is treated by sequentially passing through an oil washing tower 1, a water washing tower 2, an alkaline washing tower 3, a dryer 4 and a deethanizer 6 and then entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, followed by treatment in a demethanizer 5, wherein compressors 8 are provided between the water washing tower 2 and the alkaline washing tower 3 and between the deethanizer 6 and the C2 hydrogenation reactor 7.

(53) The reaction was carried out with one C2 hydrogenation reactor. The reactor has a gas dispensing system and is a fixed-bed adiabatic reactor.

(54) The reaction materials come from the top of the deethanizer and the composition thereof is shown in Table 3.

(55) TABLE-US-00003 TABLE 3 Raw materials for hydrogenation H.sub.2 C.sub.2H.sub.2 C.sub.2H.sub.4 C.sub.2H.sub.6 CH.sub.4 CO Content 25.32 0.5 34.3 8.88 31 0.005 (v/v %)

(56) Reaction conditions: the space velocity of the material gas is 7000 h.sup.1, the reaction pressure is 3.0 MPa, and the catalyst loading for the reactors is 500 mL. The results of the reaction for 500 hours are shown in Table 4.

(57) TABLE-US-00004 TABLE 4 Inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Green oil ature rise amount selectivity amount Catalyst ( C.) ( C.) (v/v %) (%) (wt. %) S-3 100 41 0.02 54 0.5 D-3 100 44 0.08 32 2.0

EXAMPLE 4

(58) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 2.4 mm, a specific surface area of 18.0 m.sup.2/g and a pore volume of 0.16 mL/g was weighed.

(59) 53.26 g of 4,4-dihydroxy-2,2-bipyridine was dissolved in 600 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 16 hours, to allow 4,4-dihydroxy-2,2-bipyridine to be fully supported on the carrier. Then the solid reaction product was dried at 120 C. for 5 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(60) 0.61 g of Pd(NO.sub.3).sub.2 and 3.90 g of Pb(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 3.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 10 minutes and allowed to stand for 12 hours. The residual liquid was decanted and the solid reaction product was dried at 90 C. for 8 hours, to obtain a (PdPb)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Pb) is 20).

(61) The above (PdPb)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 8 hours to obtain a (PdPb)/Al.sub.2O.sub.3 catalyst.

(62) The above (PdPb)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 115 C. for 3 hours with a mixed gas of N.sub.2:H.sub.2 in a molar ratio of 1:1 at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S4. The Pd content and the Pb content in this catalyst S4 were measured to be 0.05 wt. % and 0.48 wt. %, respectively.

COMPARATIVE EXAMPLE 4

(63) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 2.4 mm, a specific surface area of 18.0 m.sup.2/g and a pore volume of 0.16 mL/g was weighed.

(64) 3.3 g of polystyrene-acrylonitrile (SAN) was added to 600 mL dimethylformamide (DMF), and stirred at room temperature until the SAN was completely dissolved to obtain a solution. The above carrier was added to the solution, fully stirred and allowed to stand for 1 hour. The solid reaction product was dried at 120 C. for 6 hours, to obtain a SAN/Al.sub.2O.sub.3 precursor.

(65) The above SAN/Al.sub.2O.sub.3 precursor was added into 1000 mL of deionized water, and 85.2 g of ethylenediamine was added, stirred until the precursor was completely dissolved and reacted under reflux for 1 hour. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 80 C. for 5 hours, to obtain a functionalized SAN/Al.sub.2O.sub.3 precursor.

(66) 0.61 g of Pd(NO.sub.3).sub.2 and 3.90 g of Pb(NO.sub.3).sub.2 were dissolved in 1200 mL of deionized water and the pH was adjusted to 2.7 with an appropriate amount of nitric acid to obtain a mixed solution. The above functionalized SAN/Al.sub.2O.sub.3 precursor was added into the mixed solution and stirred for 2 hours. The residual liquid was decanted and the solid reaction product was washed to neutrality with deionized water, to obtain a (PdPb)-SAN/Al.sub.2O.sub.3 precursor.

(67) The above (PdPb)-SAN/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 8 hours to obtain a (PdPb)/Al.sub.2O.sub.3 catalyst.

(68) The above (PdPb)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 115 C. for 3 hours with a mixed gas of N.sub.2:H.sub.2 in a molar ratio of 1:1 at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D4. The Pd content and the Pb content in this catalyst D4 were measured to be 0.05 wt. % and 0.48 wt. %, respectively.

Catalyst Application

(69) The catalysts prepared in Example 4 and Comparative Example 4 were respectively used in the front-end depropanization hydrogenation process of C2 fraction. The process flow chart is shown in FIG. 3. The C2 fraction obtained by steam cracking of petroleum hydrocarbon is treated by sequentially passing through an oil washing tower 1, a water washing tower 2, an alkaline washing tower 3, a dryer 4 and a depropanizer 11 and then entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, followed by treatment in a demethanizer 5, wherein compressors 8 were provided between the water washing tower 2 and the alkaline washing tower 3 and between the depropanizer 11 and the C2 hydrogenation reactor 7.

(70) The reaction was carried out with two C2 hydrogenation reactors in series, i.e., the outlet material of the first section reactor entered the second section reactor. Each reactor has an independent gas dispensing system, and both reactors are fixed-bed adiabatic reactors.

(71) The reaction materials come from the top of the depropanizer and the composition thereof is shown in Table 5.

(72) TABLE-US-00005 TABLE 5 Raw materials for hydrogenation H.sub.2 C.sub.2H.sub.2 C.sub.2H.sub.4 C.sub.2H.sub.6 CH.sub.4 C.sub.3H.sub.6 C.sub.3H.sub.8 PDMA CO C.sub.4+ Content 18 0.6 33 6.2 26.2 13 2 0.8 0.2 0.47 (v/v %)

(73) Reaction conditions: the space velocity of the material gas is 4000 h.sup.1, the reaction pressure is 3.5 MPa, and the catalyst loading for both reactors is 500 mL. The results of the reaction for 200 hours are shown in Table 6.

(74) TABLE-US-00006 TABLE 6 C.sub.2H.sub.2 Inlet Temperature residual Ethylene Green oil Reactor temperature rise amount selectivity amount Catalyst Period section ( C.) ( C.) (v/v %) (%) (wt. %) S-4 0-50 h First 80 20 0.23 82 1.9 section Second 90 11 0.01 51 1.3 section D-4 0-50 h First 80 25 0.48 35 7.0 section Second 90 16 0.20 30 4.1 section S-4 50- First 80 20 0.21 82 2.6 100 h section Second 90 11 0.01 65 1.5 section D-4 50- First 80 25 0.28 66 9.0 100 h section Second 90 18 0.09 45 4.9 section S-4 100- First 80 20 0.22 86 2.6 150 h section Second 90 11 0.02 68 1.4 section D-4 100- First 80 20 0.65 63 9.9 150 h section Second 90 16 0.20 45 6.2 section

EXAMPLE 5

(75) 500 g of a tooth-spherical -Al.sub.2O.sub.3 carrier containing 460 g of -Al.sub.2O.sub.3 and 40 g of titania, having 4.2 mm, a specific surface area of 45.0 m.sup.2/g, a pore volume of 0.35 mL/g and a bulk density of 0.77 g/cm.sup.3 was weighed. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-35 nm and 200-450 nm, respectively.

(76) 15.79 g of 6,6-dihydroxy-3,3-bipyridine was dissolved in 650 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 12 hours, to allow 6,6-dihydroxy-3,3-bipyridine in the solution to be fully supported on the carrier, the solid reaction product was dried at 120 C. for 4 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(77) 0.25 g of Pd(NO.sub.3).sub.2 and 0.59 g of Cu(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.1 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 1 hour and allowed to stand for 8 hours. The residual liquid was decanted and the solid reaction product was dried at 100 C. for 8 hours, to obtain a (PdCu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Cu) is 20).

(78) The above (PdCu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 6 hours to obtain a (Pd+Cu)/Al.sub.2O.sub.3 catalyst.

(79) The above (PdCu)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S5. The Pd content and the Cu content in this catalyst S5 were measured to be 0.02 wt. % and 0.04 wt. %, respectively.

COMPARATIVE EXAMPLE 5

(80) 500 g of a tooth-spherical -Al.sub.2O.sub.3 carrier containing 460 g of -Al.sub.2O.sub.3 and 40 g of titania, having 4.2 mm, a specific surface area of 45.0 m.sup.2/g, a pore volume of 0.35 mL/g and a bulk density of 0.77 g/cm.sup.3 was weighed. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-35 nm and 200-450 nm, respectively.

(81) 16.0 g of chlorinated polyethylene (CPE) was dissolved in 800 mL of tetrahydrofuran (THF), and 480 g of dicyandiamide and 4.0 g of Na.sub.2CO.sub.3 were added, stirred until they were completely dissolved and reacted under reflux for 2 hours. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water, to obtain a functionalized CPE solution.

(82) 0.25 g of Pd(NO.sub.3).sub.2, 0.59 g of Cu(NO.sub.3).sub.2 and 1 mL of nitric acid were added to the functionalized CPE solution and stirred for 1 hour, to obtain a (PdCu)-CPE precursor solution.

(83) The above carrier was added to the (PdCu)-CPE precursor solution, fully stirred and allowed to stand for 4 hours. The residual liquid was decanted. The solid reaction product was washed to neutrality with deionized water and then dried at 100 C. for 8 hours, to obtain a (PdCu)-CPE/Al.sub.2O.sub.3 precursor.

(84) The above (PdCu)-CPE/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 8 hours to obtain a (PdCu)/Al.sub.2O.sub.3 catalyst.

(85) The above (PdCu)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D5. The Pd content and the Cu content in this catalyst D5 were measured to be 0.02 wt. % and 0.04 wt. %, respectively.

Catalyst Application

(86) The catalysts prepared in Example 5 and Comparative Example 5 were respectively used in the front-end depropanization hydrogenation process of C2 fraction. The process flow chart is shown in FIG. 3.

(87) The reaction was carried out with two C2 hydrogenation reactors in series, i.e., the outlet material of the first section reactor entered the second section reactor. Each reactor has an independent gas dispensing system, and both reactors are fixed-bed adiabatic reactors.

(88) The reaction materials come from the top of the depropanizer and the composition thereof is shown in Table 7.

(89) TABLE-US-00007 TABLE 7 Raw materials for hydrogenation H.sub.2 C.sub.2H.sub.2 C.sub.2H.sub.4 C.sub.2H.sub.6 CH.sub.4 C.sub.3H.sub.6 C.sub.3H.sub.8 PDMA CO C.sub.4+ Content 18.0 0.7 35.6 6.2 24.5 11 3.0 0.6 0.2 0.3 (v/v %)

(90) Reaction conditions: the space velocity of the material gas is 8000 h.sup.1, the reaction pressure is 3.6 MPa, the catalyst loading for both reactors is 500 mL, and the results of the reaction for 1000 hours are shown in Table 8.

(91) TABLE-US-00008 TABLE 8 Inlet Temperature C.sub.2H.sub.2 residual Ethylene Green oil Reactor temperature rise amount selectivity amount Catalyst section ( C.) ( C.) (v/v %) (%) (wt. %) S-5 First 75 23 0.28 75 4.3 section Second 80 14 0.02 46 1.1 section D-5 First 75 27 0.45 37 8.8 section Second 80 18 0.16 22 3.8 section

EXAMPLE 6

(92) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 4.0 mm, a specific surface area of 20.0 m.sup.2/g, a pore volume of 0.48 mL/g and a bulk density of 0.87 g/cm.sup.3 was weighed. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-50 nm and 200-500 nm, respectively.

(93) 167.81 g of 4,4-dihydroxy-2,2-bipyridine was dissolved in 650 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 2 hours, to allow 4,4-dihydroxy-2,2-bipyridine in the solution to be fully supported on the Al.sub.2O.sub.3 carrier. Then the solid reaction product was dried at 60 C. for 10 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(94) 0.49 g of Pd(NO.sub.3).sub.2 and 1.57 g of AgNO.sub.3 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.7 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 10 minutes and allowed to stand for 2 hours. The residual liquid was decanted and the solid reaction product was dried at 120 C. for 4 hours, to obtain a (PdAg)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Ag) is 80).

(95) The above (PdAg)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 550 C. for 2 hours to obtain a (PdAg)/Al.sub.2O.sub.3 catalyst.

(96) The above (PdAg)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S6. The Pd content and the Ag content in this catalyst S6 were measured to be 0.04 wt. % and 0.20 wt. %, respectively.

COMPARATIVE EXAMPLE 6

(97) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 4.0 mm, a specific surface area of 20.0 m.sup.2/g, a pore volume of 0.48 mL/g and a bulk density of 0.87 g/cm.sup.3 was weighed. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-50 nm and 200-500 nm, respectively.

(98) 8.9 g of polyvinyl chloride (PVC) was dissolved in 800 mL of tetrahydrofuran (THF) to obtain a solution. The above carrier was impregnated in the solution and allowed to stand for 2 hours, to allow the PVC in the solution to adsorb onto the carrier surface. The solid reaction product was dried at 90 C. for 6 hours, to obtain a PVC/Al.sub.2O.sub.3 precursor.

(99) 119.28 g of dicyandiamide and 4.0 g of Na.sub.2CO.sub.3 were heated and dissolved in 1000 mL of deionized water, and then the above PVC/Al.sub.2O.sub.3 precursor was added and reacted under reflux for 1 hour. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 60 C. for 10 hours, to obtain a functionalized PVC/Al.sub.2O.sub.3 precursor.

(100) 0.49 g of Pd(NO.sub.3).sub.2 and 1.57 g of AgNO.sub.3 were dissolved in 200 mL of deionized water and the pH was adjusted to 2.7 with an appropriate amount of nitric acid to obtain a mixed solution. The above functionalized PVC/Al.sub.2O.sub.3 precursor was added into the mixed solution and stirred for 0.5 hours. The residual liquid was decanted. The solid reaction product was washed to neutrality with deionized water and then dried at 120 C. for 4 hours, to obtain a (PdAg)-PVC/Al.sub.2O.sub.3 precursor.

(101) The above (PdAg)-PVC/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 550 C. for 2 hours to obtain a (PdAg)/Al.sub.2O.sub.3 catalyst.

(102) The above (PdAg)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D6. The Pd content and the Ag content in this catalyst D6 were measured to be 0.038 wt. % and 0.19 wt. %, respectively.

Catalyst Application

(103) The catalysts prepared in Example 6 and Comparative Example 6 were respectively used in the ethylene refining process with a sequential separation procedure. The process flow chart is shown in FIG. 4. The C2 fraction obtained by steam cracking of petroleum hydrocarbon is treated by sequentially passing through an oil washing tower 1, a water washing tower 2, an alkaline washing tower 3, a dryer 4, a demethanizer 5 and a deethanizer 6 and then entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, and then treated by sequentially passing through an ethylene refining column 9 and an ethylene refining reactor 10, wherein compressors 8 were provided between the water washing tower 2 and the alkaline washing tower 3 and between the demethanizer 5 and the deethanizer 6.

(104) The reaction was carried out with one C2 hydrogenation reactor. The reactor has a gas dispensing system and is a fixed-bed adiabatic reactor.

(105) The content of C.sub.2H.sub.2 in the reaction material entering the C2 hydrogenation reactor was 5 L/L.

(106) Reaction conditions: the space velocity of the material gas is 2500 h.sup.1, the reaction pressure is 2.0 MPa, the catalyst loading for the reactor is 200 mL, and the content of H.sub.2 in the reactor is 10 L/L. The results of the reaction for 500 hours are shown in Table 9.

(107) TABLE-US-00009 TABLE 9 Reactor inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Green oil ature rise amount selectivity amount catalyst ( C.) ( C.) (L/L) (%) (g) S-6 35 4 0 55 0.8 D-6 35 6 1.4 37 1.9

EXAMPLE 7

(108) 500 g of a cylindrical -Al.sub.2O.sub.3 carrier having 3.5 mm, a height of 3.5 mm, a specific surface area of 47.0 m.sup.2/g, a pore volume of 0.30 mL/g and a bulk density of 0.70 g/cm.sup.3 was weighed. The carrier after modification with alkaline earth element Mg has a Mg content of 0.35 wt. %. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-30 nm and 100-450 nm, respectively.

(109) 5.30 g of 4,4-dihydroxy-2,2-bipyridine was dissolved in 600 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 10 hours, to allow 4,4-dihydroxy-2,2-bipyridine in the solution to be fully supported on the carrier. Then the solid reaction product was dried at 100 C. for 6 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(110) 0.61 g of Pd(NO.sub.3).sub.2 and 0.21 g of chloroauric acid were dissolved in 600 mL of deionized water and the pH was adjusted to 3.0 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 1 hour and allowed to stand for 10 hours. The residual liquid was decanted and the solid reaction product was dried at 90 C. for 10 hours, to obtain a (PdAu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Au) is 10).

(111) The above (PdAu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 600 C. for 2 hours to obtain a (PdAu)/Al.sub.2O.sub.3 catalyst.

(112) The above (PdAu)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S7. The Pd content and the Au content in this catalyst S7 were measured to be 0.05 wt. % and 0.02 wt. %, respectively.

COMPARATIVE EXAMPLE 7

(113) 500 g of a cylindrical -Al.sub.2O.sub.3 carrier having 3.5 mm, a height of 3.5 mm, a specific surface area of 47.0 m.sup.2/g, a pore volume of 0.30 mL/g and a bulk density of 0.70 g/cm.sup.3 was weighed. The carrier after modification with alkaline earth element Mg has a Mg content of 0.35 wt. %. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-30 nm and 100-450 nm, respectively.

(114) 0.61 g of Pd(NO.sub.3).sub.2 was added to 300 mL of deionized water, and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a solution. The above carrier was added to the solution and stirred for 5 minutes. The residual liquid was decanted and the solid reaction product was dried at 110 C. for 6 hours, to obtain a Pd/Al.sub.2O.sub.3 precursor.

(115) 0.21 g of chloroauric acid was dissolved in 600 mL of deionized water to obtain a solution. The above Pd/Al.sub.2O.sub.3 precursor was added to the solution and stirred for 5 minutes. The residual liquid was decanted. The solid reaction product was dried at 110 C. for 6 hours and then calcined in an air atmosphere at 500 C. for 4 hours to obtain a (PdPb)/Al.sub.2O.sub.3 catalyst.

(116) The above (PdAu)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D7. The Pd content and the Au content in this catalyst D7 were measured to be 0.05 wt. % and 0.02 wt. %, respectively.

Catalyst Application

(117) The catalysts prepared in Example 7 and Comparative Example 7 were respectively used in the ethylene refining process with a front-end deethanization hydrogenation process procedure. The process flow chart is shown in FIG. 5. The C2 fraction obtained by steam cracking of petroleum hydrocarbon is treated by sequentially passing through an oil washing tower 1, a water washing tower 2, an alkaline washing tower 3, a dryer 4 and a deethanizer 6 and then entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, and then treated by sequentially passing through a demethanizer 5, an ethylene refining column 9 and an ethylene refining reactor 10, wherein compressors 8 were provided between the water washing tower 2 and the alkaline washing tower 3 and between the deethanizer 6 and the C2 hydrogenation reactor 7.

(118) The reaction was carried out with one C2 hydrogenation reactor. The reactor has a gas dispensing system and is a fixed-bed adiabatic reactor.

(119) The content of C.sub.2H.sub.2 in the reaction material entering the C2 hydrogenation reactor was 15 L/L.

(120) Reaction conditions: the space velocity of the material gas is 8000 h.sup.1, the reaction pressure is 1.8 MPa, the catalyst loading for the reactor is 500 mL, and the H.sub.2/C.sub.2H.sub.2 in the reactor=5:1 (molar ratio). The results of the reaction for 500 hours are shown in Table 10.

(121) TABLE-US-00010 TABLE 10 Reactor inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Green oil ature rise amount selectivity amount Catalyst ( C.) ( C.) (L/L) (%) (g) S-7 30 14 0 80 1.5 D-7 30 13 1.3 33 5.8

EXAMPLE 8

(122) 500 g of a cylindrical -Al.sub.2O.sub.3 carrier having 4.5 mm, a height of 4.5 mm, a specific surface area of 50.0 m.sup.2/g, a pore volume of 0.31 mL/g and a bulk density of 0.73 g/cm.sup.3 was weighed. The carrier after modification with alkaline earth element Mg has a Mg content of 0.15 wt. %. The pore size of the carrier is 20-220 nm.

(123) 130.79 g of 4,4-dihydroxy-2,2-bipyridine was dissolved in 650 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 8 hours, to allow 4,4-dihydroxy-2,2-bipyridine in the solution to be fully supported on the carrier. Then the solid reaction product was dried at 90 C. for 8 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(124) 1.03 g of Pd(NO.sub.3).sub.2 and 6.94 g of Ni(NO.sub.3).sub.2.6H.sub.2O were dissolved in 500 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 1 hour and allowed to stand for 8 hours. The residual liquid was decanted and the solid reaction product was dried at 110 C. for 6 hours, to obtain a (PdNi)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Ni) is 25).

(125) The above (PdNi)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 500 C. for 4 hours to obtain a (PdNi)/Al.sub.2O.sub.3 catalyst.

(126) The above (PdNi)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S8. The Pd content and the Ni content in this catalyst S8 were measured to be 0.084 wt. % and 0.28 wt. %, respectively.

COMPARATIVE EXAMPLE 8

(127) 500 g of a cylindrical -Al.sub.2O.sub.3 carrier having 4.5 mm, a height of 4.5 mm, a specific surface area of 50.0 m.sup.2/g, a pore volume of 0.31 mL/g and a bulk density of 0.73 g/cm.sup.3 was weighed. The carrier after modification with alkaline earth element Mg has a Mg content of 0.15 wt. %. The pore size of the carrier is 20-220 nm.

(128) 2.2 g of polystyrene-acrylonitrile (SAN) was added to 600 mL dimethylformamide (DMF), and stirred at room temperature until the SAN was completely dissolved to obtain a solution. The above carrier was added to the solution, fully stirred and allowed to stand for 1 hour. The solid reaction product was dried at 80 C. for 5 hours, to obtain a SAN/Al.sub.2O.sub.3 precursor.

(129) The above SAN/Al.sub.2O.sub.3 precursor was added into 1000 mL of deionized water, and 57.6 g of ethylenediamine was added, stirred until the precursor was completely dissolved and reacted under reflux for 4 hours. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 80 C. for 5 hours, to obtain a functionalized SAN/Al.sub.2O.sub.3 precursor.

(130) 1.03 g of Pd(NO.sub.3).sub.2 and 6.94 g of Ni(NO.sub.3).sub.2.6H.sub.2O were dissolved in 500 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above functionalized SAN/Al.sub.2O.sub.3 precursor was added into the mixed solution, and stirred for 5 minutes. The residual liquid was decanted. The solid reaction product was washed to neutrality with deionized water and dried at 100 C. for 3 hours, to obtain a (PdNi)-SAN/Al.sub.2O.sub.3 precursor.

(131) The above (PdNi)-SAN/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 4 hours to obtain a (PdNi)/Al.sub.2O.sub.3 catalyst.

(132) The above (PdNi)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D8. The Pd content and the Ni content in this catalyst D8 were measured to be 0.084 wt. % and 0.28 wt. %, respectively.

Catalyst Application

(133) The catalysts prepared in Example 8 and Comparative Example 8 were respectively used in the Methanol-to-olefin (MTO) process with a sequential separation procedure. The process flow chart is shown in FIG. 6. The product produced by a Methanol-to-ethylene reactor 13 is treated by sequentially passing through an oil washing tower 1, a water washing tower 2, an alkaline washing tower 3, a dryer 4, a demethanizer 5 and a deethanizer 6, and then the overhead product of the deethanizer 6 entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, followed by treatment in an ethylene refining reactor 10; the bottom product of the deethanizer 6 is treated by sequentially passing through a propylene refining column 12 and a depropanizer 11; wherein the Methanol-to-ethylene reactor 13 was also connected to a regenerator 14.

(134) The reaction was carried out with one C2 hydrogenation reactor. The reactor has a gas dispensing system and is a fixed-bed adiabatic reactor.

(135) The content of C.sub.2H.sub.2 in the reaction material entering the C2 hydrogenation reactor was 10 L/L.

(136) Reaction conditions: the space velocity of the material gas is 6000 h.sup.1, the reaction pressure is 2.0 MPa, the catalyst loading for the reactor is 300 mL, and the H.sub.2/C.sub.2H.sub.2 in the reactor=5:1 (molar ratio). The results of the reaction for 500 hours are shown in Table 11.

(137) TABLE-US-00011 TABLE 11 Reactor inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Green oil ature rise amount selectivity amount Catalyst ( C.) ( C.) (L/L) (%) (g) S-8 32 6 0 45 1.8 D-8 32 9 0.2 12 2.9

EXAMPLE 9

(138) 500 g of a cylindrical Al.sub.2O.sub.3 carrier of a mixed crystal form of and , having 4.5 mm, a height of 4.5 mm, a specific surface area of 48.0 m.sup.2/g, a pore volume of 0.32 mL/g and a bulk density of 0.73 g/cm.sup.3 was weighed. The carrier after modification with alkaline metal element Na has a Na content of 0.12 wt. %. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-35 nm and 200-450 nm, respectively.

(139) 106.52 g of 4,4-dihydroxy-2,2-bipyridine was dissolved in 600 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 8 hours, to allow 4,4-dihydroxy-2,2-bipyridine in the solution to be fully supported on the carrier, the solid reaction product was dried at 90 C. for 8 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(140) 0.49 g of Pd(NO.sub.3).sub.2 and 1.77 g of Cu(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 1 hour and allowed to stand for 8 hours. The residual liquid was decanted and the solid reaction product was dried at 100 C. for 8 hours, to obtain a (PdCu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Cu) is 50).

(141) The above (PdCu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 500 C. for 4 hours to obtain a (PdCu)/Al.sub.2O.sub.3 catalyst.

(142) The above (PdCu)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S9. The Pd content and the Cu content in this catalyst S9 were measured to be 0.04 wt. % and 0.12 wt. %, respectively.

COMPARATIVE EXAMPLE 9

(143) 500 g of a cylindrical Al.sub.2O.sub.3 carrier of a mixed crystal form of and , having 4.5 mm, a height of 4.5 mm, a specific surface area of 48.0 m.sup.2/g, a pore volume of 0.32 mL/g and a bulk density of 0.73 g/cm.sup.3 was weighed The carrier after modification with alkaline metal element Na has a Na content of 0.12 wt. %. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 20-35 nm and 200-450 nm, respectively.

(144) 2.2 g of polystyrene acrylonitrile (SAN) was added to 600 mL dimethylformamide (DMF), and stirred at room temperature until the SAN was completely dissolved to obtain a solution. The above carrier was added to the solution, fully stirred and allowed to stand for 1 hour. The solid reaction product was dried at 70 C. for 5 hours, to obtain a SAN/Al.sub.2O.sub.3 precursor.

(145) The above SAN/Al.sub.2O.sub.3 precursor was added into 1000 mL of deionized water, and 57.6 g of ethylenediamine was added, stirred until the precursor was completely dissolved and reacted under reflux for 4 hours. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 80 C. for 3 hours, to obtain a functionalized SAN/Al.sub.2O.sub.3 precursor.

(146) 0.49 g of Pd(NO.sub.3).sub.2 and 1.77 g of Cu(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above functionalized SAN/Al.sub.2O.sub.3 precursor was added into the mixed solution and stirred for 5 minutes. The residual liquid was decanted. The solid reaction product was washed to neutrality with deionized water, and then dried at 120 C. for 5 hours, to obtain a (PdCu)-SAN/Al.sub.2O.sub.3 precursor.

(147) The above (PdCu)-SAN/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 500 C. for 4 hours to obtain a (PdCu)/Al.sub.2O.sub.3 catalyst.

(148) The above (PdCu)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D9. The Pd content and the Cu content in this catalyst D9 were measured to be 0.04 wt. % and 0.12 wt. %, respectively.

Catalyst Application

(149) The catalysts prepared in Example 9 and Comparative Example 9 were respectively used in the ethylene refining process with a front-end depropanization hydrogenation procedure. The process flow chart is shown in FIG. 7. The C2 fraction obtained by steam cracking of petroleum hydrocarbon is treated by sequentially passing through an oil washing tower 1, a water washing tower 2, an alkaline washing tower 3, a dryer 4 and a depropanizer 11, and then entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, and then treated by sequentially passing through a demethanizer 5, a deethanizer 6, an ethylene refining column 9 and an ethylene refining reactor 10, wherein compressors 8 were provided between the water washing tower 2 and the alkaline washing tower 3 and between the depropanizer 11 and the C2 hydrogenation reactor 7.

(150) The reaction was carried out with one C2 hydrogenation reactor. The reactor has a gas dispensing system and is a fixed-bed adiabatic reactor.

(151) The content of C.sub.2H.sub.2 in the reaction material entering the C2 hydrogenation reactor was 12 L/L.

(152) Reaction conditions: the space velocity of the material gas is 20000 h.sup.1, the reaction pressure is 2.0 MPa, the catalyst loading for the reactor is 500 mL, and the H.sub.2/C.sub.2H.sub.2 in the reactor=5.6:1 (molar ratio). The results of the reaction for 1000 hours are shown in Table 12.

(153) TABLE-US-00012 TABLE 12 Reactor inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Green oil ature rise amount selectivity amount Catalyst ( C.) ( C.) (L/L) (%) (g) S-9 32 11 0 69 0.8 D-9 32 12 0.5 17 2.7

EXAMPLE 10

(154) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 4.0 mm, a specific surface area of 20.0 m.sup.2/g, a pore volume of 0.52 mL/g and a bulk density of 0.85 g/cm.sup.3 was weighed. The pore size of the carrier is 80-350 nm.

(155) 69.5 g of 6,6-dihydroxy-3,3-bipyridine was dissolved in 700 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 2 hours, to allow 6,6-dihydroxy-3,3-bipyridine to be fully supported on the carrier. Then the solid reaction product was dried at 60 C. for 10 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(156) 0.49 g of Pd(NO.sub.3).sub.2 and 1.82 g of Pb(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.7 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 10 minutes and allowed to stand for 2 hours. The residual liquid was decanted and the solid reaction product was dried at 120 C. for 4 hours, to obtain a (PdPb)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Pb) is 20).

(157) The above (PdPb)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 550 C. for 2 hours to obtain a (PdPb)/Al.sub.2O.sub.3 catalyst.

(158) The above (PdPb)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S10. The Pd content and the Pb content in this catalyst S10 were measured to be 0.04 wt. % and 0.23 wt. %, respectively.

COMPARATIVE EXAMPLE 10

(159) 500 g of a spherical -Al.sub.2O.sub.3 carrier having 4.0 mm, a specific surface area of 20.0 m.sup.2/g, a pore volume of 0.52 mL/g and a bulk density of 0.85 g/cm.sup.3 was weighed. The pore size of the carrier is 80-350 nm.

(160) 8.9 g of polyvinyl chloride (PVC) was dissolved in 800 mL of tetrahydrofuran (THF) to obtain a solution. The above carrier was impregnated in the solution and allowed to stand for 2 hours to allow the PVC in the solution to adsorb onto the carrier surface. The solid reaction product was dried at 100 C. for 3 hours, to obtain a PVC/Al.sub.2O.sub.3 precursor.

(161) 119.28 g of dicyandiamide and 4.0 g of Na.sub.2CO.sub.3 were heated and dissolved in 1000 mL of deionized water, and then the above PVC/Al.sub.2O.sub.3 precursor was added and reacted under reflux for 1 hour. After cooling to room temperature, the solid reaction product was washed to neutrality with deionized water and then dried at 60 C. for 10 hours, to obtain a functionalized PVC/Al.sub.2O.sub.3 precursor.

(162) 0.49 g of Pd(NO.sub.3).sub.2 and 1.82 g of Pb(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above functionalized PVC/Al.sub.2O.sub.3 precursor was added into the mixed solution and stirred for 0.5 hours. The residual liquid was decanted. The solid reaction product was washed to neutrality with deionized water and then dried at 120 C. for 4 hours, to obtain a (PdPb)-PVC/Al.sub.2O.sub.3 precursor.

(163) The above (PdPb)-PVC/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 550 C. for 2 hours to obtain a (PdPb)/Al.sub.2O.sub.3 catalyst.

(164) The above (PdPb)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 120 C. for 3 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 200 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D10. The Pd content and the Pb content in this catalyst D10 were measured to be 0.04 wt. % and 0.23 wt. %, respectively.

Catalyst Application

(165) The catalysts prepared in Example 10 and Comparative Example 10 were respectively used in the Methanol-to-olefin (MTO) process with a front-end depropanization hydrogenation procedure. The process flow chart is shown in FIG. 8. Methanol was treated by sequentially passing through a reactor 16 for dehydration of methanol to dimethyl ether (i.e., DME reactor), a methanol-to-propylene reactor (i.e., MTP reactor) 17, a pre-quench separator 18, a quench separator 19, a four-level compressor 20, a four-level separator 21 and a dryer 4, and then entered a C2 hydrogenation reactor 7 for selective hydrogenation to remove traces of acetylene, followed by treatment in a demethanizer 5 and a deethanizer 6 sequentially.

(166) The reaction was carried out with one C2 hydrogenation reactor. The reactor has a gas dispensing system and is a fixed-bed adiabatic reactor.

(167) The content of C.sub.2H.sub.2 in the reaction material entering the C2 hydrogenation reactor was 5.3 L/L.

(168) Reaction conditions: the space velocity of the material gas is 2700 h.sup.1, the reaction pressure is 2.0 MPa, the catalyst loading for the reactor is 500 mL, and the H.sub.2/C.sub.2H.sub.2 in the reactor=5:1 (molar ratio). The results of the reaction for 1000 hours are shown in Table 13.

(169) TABLE-US-00013 TABLE 13 Reactor inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Green oil ature rise amount selectivity amount Catalyst ( C.) ( C.) (L/L) (%) (g) S-10 32 7 0 44 1.5 D-10 32 8 1.0 24 2.7

EXAMPLE 11

(170) 500 g of a cylindrical Al.sub.2O.sub.3 carrier having 4.5 mm, a height of 4.5 mm, a specific surface area of 10.0 m.sup.2/g, a pore volume of 0.21 mL/g and a bulk density of 0.75 g/cm.sup.3 was weighed, and it contained 487.5 g of Al.sub.2O.sub.3 and 12.5 g of magnesium oxide, wherein Al.sub.2O.sub.3 was in a mixed crystal form of and . The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 100-180 nm and 350-750 nm, respectively.

(171) 47.2 g of 6,6-dihydroxy-3,3-bipyridine was dissolved in 600 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 10 hours, to allow 6,6-dihydroxy-3,3-bipyridine to be fully supported on the carrier. Then the solid reaction product was dried at 100 C. for 6 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(172) 0.37 g of Pd(NO.sub.3).sub.2 and 1.18 g of AgNO.sub.3 were dissolved in 450 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 1 hour and allowed to stand for 10 hours. The residual liquid was decanted and the solid reaction product was dried at 90 C. for 10 hours, to obtain a (PdAg)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Ag) is 30).

(173) The above (PdAg)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 600 C. for 2 hours to obtain a (PdAg)/Al.sub.2O.sub.3 catalyst.

(174) The above (PdAg)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 100 C. for 4 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 300 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst S11. The Pd content and the Ag content in this catalyst S11 were measured to be 0.03 wt. % and 0.15 wt. %, respectively.

COMPARATIVE EXAMPLE 11

(175) 500 g of a cylindrical Al.sub.2O.sub.3 carrier having 4.5 mm, a height of 4.5 mm, a specific surface area of 10.0 m.sup.2/g, a pore volume of 0.21 mL/g and a bulk density of 0.75 g/cm.sup.3 was weighed, and it contained 487.5 g of Al.sub.2O.sub.3 and 12.5 g of magnesium oxide, wherein Al.sub.2O.sub.3 was in a mixed crystal form of and . The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 100-180 nm and 350-750 nm, respectively.

(176) 0.37 g of Pd(NO.sub.3).sub.2 and 1.18 g of AgNO.sub.3 were dissolved in 450 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The mixed solution was sprayed onto the above carrier and then shaken for 0.5 hour. The residual liquid was decanted. The solid reaction product was dried at 90 C. for 10 hours and then calcined in an air atmosphere at 600 C. for 2 hours to obtain a (PdAg)/Al.sub.2O.sub.3 catalyst.

(177) The above (PdAg)/Al.sub.2O.sub.3 catalyst was placed in a fixed-bed reactor, and subjected to a reduction treatment at 100 C. for 4 hours with a hydrogen gas having a purity of 99.9% at a space velocity of 300 h.sup.1, to obtain a reduced palladium-based supported hydrogenation catalyst D11. The Pd content and the Ag content in this catalyst D11 were measured to be 0.03 wt. % and 0.15 wt. %, respectively.

Catalyst Application

(178) The catalysts prepared in Example 11 and Comparative Example 11 were respectively used in the front-end depropanization hydrogenation process of C2 fraction. The process flow chart is shown in FIG. 3.

(179) The reaction was carried out with three C2 hydrogenation reactors in series, i.e., the outlet material of the first section reactor entered the second section reactor and the outlet material of the second section reactor entered the third section reactor. Each reactor has an independent gas dispensing system, and these reactors are each fixed-bed adiabatic reactors.

(180) The reaction materials come from the top of the depropanizer and the composition thereof is shown in Table 14.

(181) Reaction conditions: the space velocity of the material gas is 10000 h.sup.1, the reaction pressure is 3.9 MPa, and the catalyst loading for the three reactors is 500 mL. The results of the reaction for 1000 hours are shown in Table 15.

(182) TABLE-US-00014 TABLE 14 H.sub.2 C.sub.2H.sub.2 C.sub.2H.sub.4 C.sub.2H.sub.6 CH.sub.4 C.sub.3H.sub.6 C.sub.3H.sub.8 PDMA CO C.sub.4+ Content 16.0 0.9 39.0 9.5 19.5 12 2.0 0.7 0.1 0.3 (v/v %)

(183) TABLE-US-00015 TABLE 15 Temper- Inlet ature C.sub.2H.sub.2 residual Ethylene Green oil Reactor temperature rise amount selectivity amount Catalyst section ( C.) ( C.) (v/v %) (%) (wt. %) S-11 First 78 17 0.49 87 3.5 section Second 86 14 0.18 76 2.6 section Third 93 7 0 63 1.4 section D-11 First 78 20 0.68 49 4.0 section Second 86 16 0.47 40 3.2 section Third 93 10 0.18 32 2.9 section

EXAMPLE 12

(184) 500 g of a cylindrical carrier containing 481.5 g of -Al.sub.2O.sub.3, 12.5 g of magnesium oxide and 6 g of calcium oxide, having 4.5 mm, a height of 4.5 mm, a specific surface area of 8.0 m.sup.2/g, a pore volume of 0.38 mL/g and a bulk density of 0.75 g/cm.sup.3 was weighed The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 100-180 nm and 350-750 nm, respectively.

(185) 16.68 g of 6,6-dihydroxy-3,3-bipyridine was dissolved in 650 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand for 12 hours, to allow 6,6-dihydroxy-3,3-bipyridine in the solution to be fully supported on the carrier, the solid reaction product was dried at 120 C. for 4 hours, to obtain a hydroxy-bipyridine/Al.sub.2O.sub.3 precursor.

(186) 0.49 g of Pd(NO.sub.3).sub.2 and 0.83 g of Cu(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was added into the mixed solution, stirred for 1 hour and allowed to stand for 12 hours. The residual liquid was decanted and the solid reaction product was dried at 120 C. for 4 hours, to obtain a (PdCu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor (wherein the molar ratio of hydroxy-bipyridine to (Pd+Cu) is 15).

(187) The above (PdCu)-hydroxy-bipyridine/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 450 C. for 8 hours to obtain a (PdCu)/Al.sub.2O.sub.3 catalyst S12. The Pd content and the Cu content in this catalyst S12 were measured to be 0.04 wt. % and 0.056 wt. %, respectively.

COMPARATIVE EXAMPLE 12

(188) 500 g of a cylindrical carrier containing 481.5 g of -Al.sub.2O.sub.3, 12.5 g of magnesium oxide and 6 g of calcium oxide, having 4.5 mm, a height of 4.5 mm, a specific surface area of 8.0 m.sup.2/g, a pore volume of 0.38 mL/g and a bulk density of 0.75 g/cm.sup.3 was weighed. The pore size of the carrier exhibits a bimodal pore size distribution with pore sizes of 100-180 nm and 350-750 nm, respectively.

(189) 6.0 g of dodecylpyridine hydrochloride was dissolved in 600 mL of ethanol to obtain a solution. The above carrier was impregnated in this solution and allowed to stand at room temperature for 48 hours. The solid reaction product was dried at 120 C. for 4 hours to obtain a Al.sub.2O.sub.3 precursor containing C.sub.12H.sub.25C.sub.5H.sub.4N.HCl.

(190) 0.49 g of Pd(NO.sub.3).sub.2 and 0.83 g of Cu(NO.sub.3).sub.2 were dissolved in 600 mL of deionized water and the pH was adjusted to 2.5 with an appropriate amount of nitric acid to obtain a mixed solution. The above Al.sub.2O.sub.3 precursor containing C.sub.12H.sub.25C.sub.5H.sub.4N.HCl was added into the mixed solution and allowed to stand for 2 hours. The residual liquid was decanted and the solid reaction product was dried at 120 C. for 4 hours, to obtain a (PdCu)-alkylpyridine hydrochloride/Al.sub.2O.sub.3 precursor.

(191) The above (PdCu)-alkylpyridine hydrochloride/Al.sub.2O.sub.3 precursor was calcined in an air atmosphere at 500 C. for 2 hours to obtain a (PdCu)/Al.sub.2O.sub.3 catalyst D12. The Pd content and the Cu content in this catalyst D12 were measured to be 0.04 wt. % and 0.056 wt. %, respectively.

Catalyst Application

(192) The catalysts prepared in Example 12 and Comparative Example 12 were respectively used in the front-end deethanization hydrogenation process of C2 fraction. The process flow chart is shown in FIG. 2.

(193) The reaction was carried out with one C2 hydrogenation reactor. The reactor has a gas dispensing system and is a fixed-bed adiabatic reactor.

(194) The reaction materials come from the top of the deethanizer and the composition thereof is shown in Table 16.

(195) Reaction conditions: the space velocity of the material gas is 12000 h.sup.1, the reaction pressure is 3.6 MPa, and the catalyst loading for the reactor is 500 mL. The results of the reaction for 1000 hours are shown in Table 17.

(196) TABLE-US-00016 TABLE 16 H.sub.2 C.sub.2H.sub.2 C.sub.2H.sub.4 C.sub.2H.sub.6 CH.sub.4 CO C.sub.4+ Content (v/v %) 30 0.6 33.2 5.88 30 0.008 0.312

(197) TABLE-US-00017 TABLE 17 Reactor inlet Temper- C.sub.2H.sub.2 temper- ature residual Ethylene Green oil ature rise amount selectivity amount Catalyst ( C.) ( C.) (L/L) (%) (wt. %) S-12 85 32 0.5 60 1.9 D-12 85 34 475 28.6 15.6

(198) It can be seen from the above Examples and Comparative Examples that as compared with the catalyst prepared by the conventional impregnation method, the catalyst prepared by using a carrier comprising chlorine-containing organics and the catalyst prepared by grafting the functional group with an organic polymer compound and being supported on a carrier, when the content of the active components is the same, all the catalysts prepared by the method of the present invention exhibit more excellent activity, selectivity and anti-coking performance when used in various selective hydrogenation processes of acetylene, and the amount of green oil generated during the hydrogenation is also greatly reduced. Meanwhile, the reduction in the amount of the green oil production reduces the coverage of active centers of the catalyst by the by-products, the activity and selectivity of the catalyst are well maintained, and the service life of the catalyst is extended.