Cu.SUB.y./MMgO.SUB.x .interfacial catalyst for selective alkyne hydrogenation and its preparation method

Abstract

Cu.sub.y/MMgO.sub.x interfacial catalyst for selective alkyne hydrogenation and its preparation method are disclosed. The preparation method of the catalyst includes: the mixture of salt and alkali solution is nucleated momentarily by nucleation/crystallization isolation method, preparing the composite metal hydroxide Cu.sub.yMMg.sub.4-LDHs as precursor, which has typical hexagonal morphology of the double hydroxide; the precursor is topologically transformed by heat treatment to produce unsaturated oxide; the catalyst with Cu.sub.y-MMgO.sub.x interface structure is prepared by separating and electronically modifying Cu particles. By adjusting the ratio of Cu.sup.2+/M.sup.3+ in LDHs, the electronic and geometric structure of Cu.sub.y-MMgO.sub.x interface can be flexibly controlled, thus enhancing the reaction activity, product selectivity and stability. The catalyst can be used in the selective hydrogenation of various alkynes in the fields of petrochemical and fine chemical industry, with the outstanding catalytic activity and C═C double bond selectivity. The catalyst also has good reusability.

Claims

1. A method for preparing Cu.sub.y/MMgO.sub.x interfacial catalyst for selective alkyne hydrogenation comprising the following steps: A. Prepare the mixed salt solution by dissolving Cu salt, Mg salt and M salt in 100 ml deionized water according to the metal ion molar ratio of 1˜8/1˜4/1, the total amount of three metal ions is 1.0˜1.6 mol.Math.L.sup.−1; two kinds of alkali solutions are dissolved in deionized water to prepare alkali solution with concentration of 1.0˜1.6 mol.Math.L.sup.−1; Cu salt comprises Cu(NO.sub.3).sub.2.3H.sub.2O or CuCl.sub.2; Mg salt comprises Mg(NO.sub.3).sub.2.6H.sub.2O or MgCl.sub.2; M salt is any one of Fe(NO.sub.3).sub.3.9H.sub.2O, FeCl.sub.3, Cr(NO.sub.3).sub.3.9H.sub.2O, CrCl.sub.3, VCl.sub.3; alkali solutions are any two of NaOH, KOH, Na.sub.2CO.sub.3 or NaHCO.sub.3; B. Turn on the nucleation reactor, set the stator-rotor gap of the reactor to be 0.1˜0.5 mm and the rotation speed to be 100˜3000 rpm, and transport the mixed salt solution and alkali solution in step A to the reactor at a rate of 0.5˜2 mL.Math.min.sup.−1 by a peristaltic pump for nucleation, and control the total number of metal cations in the salt solution to be equal to the number of anions in the alkali solution; collect nucleation slurry at slurry outlet; C. The nucleation slurry is transferred to a reaction kettle and crystallized at 60˜180° C. for 18˜36 h; after naturally cooling down to ambient temperature, the crystallized products are centrifuged and washed to neutral with deionized water, and then dried at 50˜80° C. for 24˜36 h, obtaining the layered double hydroxides (LDHs), namely Cu.sub.yMMg.sub.4-LDHs precursor, where y is any integer between 1 and 8; D. The Cu.sub.yMMg.sub.4-LDHs precursor obtained in step C is heated to 240˜300° C. at a heating rate of 5˜10° C..Math.min.sup.1 and calcined for 2˜6 h, obtaining the corresponding mixed metal oxide of Cu.sub.yMMg.sub.4-MMO, where y is any integer between 1 and 8; E. The Cu.sub.yMMg.sub.4-MMO obtained in step D is reduced at 400˜800° C. at a heating rate of 5˜10° C..Math.min.sup.1 in an atmosphere of 10 vol. % H.sub.2/N.sub.2 for 4˜6 h; after naturally cooling down to ambient temperature, 3 vol. % O.sub.2/N.sub.2 is introduced to passivate for 0.5˜1 h, obtaining Cu.sub.y-MMgO.sub.x interfacial catalyst, where y is any integer between 1 and 8; x is any number between 1 and 2.5.

2. The method for preparing Cu.sub.y/MMgO.sub.x interfacial catalyst for selective hydrogenation of alkyne of claim 1, wherein the metal ion molar ratio of Cu, Mg, M in the mixed salt solution in step A is 6˜8/4/1; M salt is Fe(NO.sub.3).sub.3.9H.sub.2O or FeCl.sub.3; y in step C and E is 6, 7 or 8.

3. A Cu.sub.y/MMgO.sub.x interfacial catalyst prepared according to the method of claim 1, wherein Cu is the active component, MMgO.sub.x is the carrier, and M represents one of the reducible transition metals: Fe, Cr and V; x is the number of oxygen atoms in the carrier oxide, x=1˜2.5; y is the ratio of Cu to metal M, being any integer between 1 and 8; the active metal component Cu was uniformly dispersed on the surface of MMgO.sub.x.

4. The Cu.sub.y/MMgO.sub.x interfacial catalyst of claim 3, wherein M represents Fe, y is 6, 7 or 8.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the X-ray diffraction (XRD) results of the catalyst precursor Cu.sub.2FeMg.sub.4-LDHs prepared in embodiment 1.

(2) FIG. 2 shows the SEM image of the catalyst precursor Cu.sub.2FeMg.sub.4-LDHs LDHs prepared in embodiment 1.

(3) FIG. 3 shows the HRTEM and its mapping figure of Cu.sub.2/FeMgO.sub.x catalyst prepared in embodiment 1. A is at the scale of 250 nm and B is the local amplification of A.

(4) FIG. 4 shows the experimental results of Cu.sub.2/FeMgO.sub.x catalyst prepared in embodiment 1 in selective acetylene hydrogenation. A shows the curve of acetylene conversion versus temperature, B shows the curve of ethylene selectivity versus acetylene conversion.

(5) FIG. 5 shows the experimental results of Cu.sub.6/FeMgO.sub.x catalyst prepared in embodiment 2 in selective acetylene hydrogenation. A shows the curve of acetylene conversion versus temperature, B shows the curve of ethylene selectivity versus acetylene conversion.

(6) FIG. 6 shows the stability curve of Cu.sub.6/FeMgO.sub.x catalyst prepared in embodiment 2 in acetylene selective hydrogenation.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(7) As shown in FIG. 1, LDHs with good crystal structure have been successfully prepared.

(8) FIG. 2 is a scanning electron microscope (SEM) image of the catalyst precursor composite metal hydroxide Cu.sub.2FeMg.sub.4-LDHs prepared in embodiment 1. From the SEM image, it can be seen that the LDHs are hexagonal.

(9) FIG. 3 shows the HRTEM and its mapping figure of Cu.sub.2/FeMgO.sub.x catalyst prepared in embodiment 1. A is at the scale of 250 nm and B is the local amplification of A. It can be seen that the active metal components are uniformly dispersed on the surface of the carrier, and the Cu-MMgO.sub.x interface structure is formed.

(10) FIG. 4 shows the experimental results of Cu.sub.2/FeMgO.sub.x catalyst prepared in embodiment 1 in selective acetylene hydrogenation. A shows the curve of acetylene conversion versus temperature, B shows the curve of ethylene selectivity versus acetylene conversion. When the reaction temperature is 225° C., the acetylene conversion is close to 100%, and the ethylene selectivity is 92%.

(11) FIG. 5 shows the experimental results of Cu.sub.6/FeMgO.sub.x catalyst prepared in embodiment 2 in selective acetylene hydrogenation. A shows the curve of acetylene conversion versus temperature, B shows the curve of ethylene selectivity versus acetylene conversion. When the reaction temperature is 190° C., the acetylene conversion is close to 100%, and the ethylene selectivity is 94%.

(12) FIG. 6 shows the stability curve of Cu.sub.6/FeMgO.sub.x catalyst prepared in embodiment 2 in selective acetylene hydrogenation. The catalyst reacts continuously for 40 h, and collects a sampling point every 8 h. The conversion of acetylene is 85% and the selectivity of ethylene is 94%±3%, no significant change.

Embodiment 1

(13) A. Dissolve 6.90 g Cu(NO.sub.3).sub.2.3H.sub.2O, 5.77 g Fe(NO.sub.3).sub.3.9H.sub.2O and 14.65 g Mg(NO.sub.3).sub.2.6H.sub.2O in 100 ml deionized water to prepare mixed salt solution; dissolve 6.40 g NaOH and 3.03 g Na.sub.2CO.sub.3 in 100 ml deionized water to prepare alkali solution; B. Turn on the nucleation reactor, set the stator-rotor gap of the reactor to be 0.2 mm and the rotation speed to be 3000 rpm, and transport 100 ml mixed salt solution and 100 ml alkali solution in step A to the reactor at the rate of 1.5 mL.Math.min.sup.−1 by a peristaltic pump for nucleation; collect nucleation slurry at slurry outlet; C. The nucleation slurry is transferred to a reaction kettle and crystallized at 120° C. for 24 h, after naturally cooling down to ambient temperature, the crystallized products are centrifuged and washed to neutral with deionized water, and then dried at 60° C. for 24 h, obtaining Cu.sub.2FeMg.sub.4-LDHs; D. The Cu.sub.2FeMg.sub.4-LDHs obtained in step C is heated to 300° C. at a heating rate of 10° C..Math.min.sup.−1 and calcined for 4 h, obtaining Cu.sub.2FeMg.sub.4-MMO; E. The Cu.sub.2FeMg.sub.4-MMO obtained in step D is reduced at 500° C. at a heating rate of 2° C..Math.min.sup.−1 in an atmosphere of 10 vol. % H.sub.2/N.sub.2 for 4 h. After naturally cooling down to ambient temperature, 3 vol. % O.sub.2/N.sub.2 is introduced to passivate for 0.5 h, obtaining Cu.sub.2-MMgO.sub.x interfacial catalyst. The Cu/Fe ratio is 2/1.

(14) The catalyst is used for selective acetylene hydrogenation:

(15) The 200 mg catalyst is mixed with 1.9 g quartz sand with particle size of 40-70 mesh. The catalyst mixture or catalyst is filled in a quartz reaction tube with a diameter of 8 mm. The sample is activated in 5 vol. % H.sub.2/N.sub.2 mixture for 2 h before reaction, and then cooled to room temperature naturally. The temperature of catalyst performance test is 120-250° C. The gas composition of the reaction feed gas is 0.33% acetylene/1.02% hydrogen/32.86% ethylene/nitrogen balance gas. The test pressure is 4 bar and the airspeed is 10032 h.sup.−1. The composition and content of reactants and products are analyzed by gas chromatography, and the data processing method is unified method. To ensure the test accuracy, the results are recorded after reaching the specified temperature for 25 minutes. The test is conducted in three groups, and the average value is the catalytic performance data at this temperature. The results are shown in FIG. 4.

Embodiment 2

(16) A. Dissolve 13.18 g Cu(NO.sub.3).sub.2.3H.sub.2O, 3.67 g Fe(NO.sub.3).sub.3.9H.sub.2O and 9.32 g Mg(NO.sub.3).sub.2.6H.sub.2O in 100 ml deionized water to prepare mixed salt solution; dissolve 6.40 g NaOH and 1.93 g Na.sub.2CO.sub.3 in 100 ml deionized water to prepare alkali solution; B. Turn on the nucleation reactor, set the stator-rotor gap of the reactor to be 0.2 mm and the rotation speed to be 3000 rpm, and transport 100 ml mixed salt solution and 100 ml alkali solution in step A to the reactor at the rate of 1.5 mL.Math.min.sup.−1 by a peristaltic pump for nucleation; collect nucleation slurry at slurry outlet; C. The nucleation slurry is transferred to a reaction kettle and crystallized at 120° C. for 24 h, after naturally cooling down to ambient temperature, the crystallized products are centrifuged and washed to neutral with deionized water, and then dried at 60° C. for 24 h, obtaining Cu.sub.6FeMg.sub.4-LDHs; D. The Cu.sub.2FeMg.sub.4-LDHs obtained in step C is heated to 300° C. at a heating rate of 10° C..Math.min.sup.−1 and calcined for 4 h, obtaining Cu.sub.6FeMg.sub.4-MMO; E. The Cu.sub.2FeMg.sub.4-MMO obtained in step D is reduced at 500° C. at a heating rate of 2° C..Math.min.sup.−1 in an atmosphere of 10 vol. % H.sub.2/N.sub.2 for 4 h. After naturally cooling down to ambient temperature, 3 vol. % O.sub.2/N.sub.2 is introduced to passivate for 0.5 h, obtaining Cu.sub.2-MMgO.sub.x interfacial catalyst. The Cu/Fe ratio is 6/1.

(17) The prepared catalyst is used for selective acetylene hydrogenation: the reaction conditions are the same as those in embodiment 1,

(18) The results of catalytic performance are shown in FIG. 5-6.

Embodiment 3

(19) A. Dissolve 13.18 g Cu(NO.sub.3).sub.2.3H.sub.2O, 3.64 g Cr(NO.sub.3).sub.3.9H.sub.2O and 9.32 g Mg(NO.sub.3).sub.2.6H.sub.2O in 100 ml deionized water to prepare mixed salt solution; dissolve 8.98 g KOH and 1.93 g Na.sub.2CO.sub.3 in 100 ml deionized water to prepare alkali solution; B. Turn on the nucleation reactor, set the stator-rotor gap of the reactor to be 0.2 mm and the rotation speed to be 3000 rpm, and transport 100 ml mixed salt solution and 100 ml alkali solution in step A to the reactor at a rate of 1.0 mL.Math.min.sup.−1 by a peristaltic pump for nucleation; collect nucleation slurry at slurry outlet; C. The nucleation slurry is transferred to a reaction kettle and crystallized at 120° C. for 24 h, after naturally cooling down to ambient temperature, the crystallized products are centrifuged and washed to neutral with deionized water, and then dried at 60° C. for 24 h, obtaining Cu.sub.6CrMg.sub.4-LDHs; D. The Cu.sub.6CrMg.sub.4-LDHs obtained in step C is heated to 300° C. at a heating rate of 10° C..Math.min.sup.−1 and calcined for 4 h, obtaining Cu.sub.6CrMg.sub.4-MMO; E. The Cu.sub.6CrMg.sub.4-MMO obtained in step D is reduced at 500° C. at a heating rate of 5° C..Math.min.sup.−1 in an atmosphere of 10 vol. % H.sub.2/N.sub.2 for 4 h. After naturally cooling down to ambient temperature, 3 vol. % O.sub.2/N.sub.2 is introduced to passivate for 0.5 h, obtaining Cu.sub.6—CrMgO.sub.x interfacial catalyst. The Cu/Fe ratio is 6/1.

Embodiment 4

(20) A. Dissolve 13.18 g Cu(NO.sub.3).sub.2.3H.sub.2O, 1.43 g VCl.sub.3 and 9.32 g Mg(NO.sub.3).sub.2.6H.sub.2O in 100 ml deionized water to prepare mixed salt solution; dissolve 6.40 g NaOH and 1.53 g NaHCO.sub.3 in 100 ml deionized water to prepare alkali solution; B. Turn on the nucleation reactor, set the stator-rotor gap of the reactor to be 0.2 mm and the rotation speed to be 3000 rpm, and transport 100 ml mixed salt solution and 100 ml alkali solution in step A to the reactor at a rate of 2.0 mL.Math.min.sup.−1 by a peristaltic pump for nucleation; collect nucleation slurry at slurry outlet; C. The nucleation slurry is transferred to a reaction kettle and crystallized at 120° C. for 24 h, after naturally cooling down to ambient temperature, the crystallized products are centrifuged and washed to neutral with deionized water, and then dried at 60° C. for 24 h, obtaining Cu.sub.6VMg.sub.4-LDHs; D. The Cu.sub.6VMg.sub.4-LDHs obtained in step C is heated to 300° C. at a heating rate of 10° C..Math.min.sup.−1 and calcined for 4 h, obtaining Cu.sub.6VMg.sub.4-MMO; E. The Cu.sub.6CrMg.sub.4-MMO obtained in step D is reduced at 600° C. at a heating rate of 5° C..Math.min.sup.−1 in an atmosphere of 10 vol. % H.sub.2/N.sub.2 for 4 h. After naturally cooling down to ambient temperature, 3 vol. % O.sub.2/N.sub.2 is introduced to passivate for 0.5 h, obtaining Cu.sub.6—VMgO.sub.x interfacial catalyst. The Cu/V ratio is 6/1.

Embodiment 5

(21) A. Dissolve 13.18 g Cu(NO.sub.3).sub.2.3H.sub.2O, 3.67 g Fe(NO.sub.3).sub.3.9H.sub.2O and 9.32 g Mg(NO.sub.3).sub.2.6H.sub.2O in 100 ml deionized water to prepare mixed salt solution; dissolve 1.93 g Na.sub.2CO.sub.3 and 1.53 g NaHCO.sub.3 in 100 ml deionized water to prepare alkali solution; B. Turn on the nucleation reactor, set the stator-rotor gap of the reactor to be 0.3 mm and the rotation speed to be 2000 rpm, and transport 100 ml mixed salt solution and 100 ml alkali solution in step A to the reactor at a rate of 2.0 mL.Math.min.sup.−1 by a peristaltic pump for nucleation; collect nucleation slurry at slurry outlet; C. The nucleation slurry is transferred to a reaction kettle and crystallized at 120° C. for 18 h, after naturally cooling down to ambient temperature, the crystallized products are centrifuged and washed to neutral with deionized water, and then dried at 60° C. for 24 h, obtaining Cu.sub.6FeMg.sub.4-LDHs-120; D. The Cu.sub.6FeMg.sub.4-LDHs-120 obtained in step C is heated to 300° C. at a heating rate of 10° C..Math.min.sup.−1 and calcined for 4 h, obtaining Cu.sub.6FeMg.sub.4-MMO-120; E. The Cu.sub.6FeMg.sub.4-MMO-120 obtained in step D is reduced at 500° C. at a heating rate of 5° C..Math.min.sup.−1 in an atmosphere of 10 vol. % H.sub.2/N.sub.2 for 4 h. After naturally cooling down to ambient temperature, 3 vol. % O.sub.2/N.sub.2 is introduced to passivate for 0.5 h, obtaining Cu.sub.6—FeMgO.sub.x-120 interfacial catalyst. The Cu/Fe ratio is 6/1.

Embodiment 6

(22) A. Dissolve 13.18 g Cu(NO.sub.3).sub.2.3H.sub.2O, 3.67 g Fe(NO.sub.3).sub.3.9H.sub.2O and 9.32 g Mg(NO.sub.3).sub.2.6H.sub.2O in 100 ml deionized water to prepare mixed salt solution; dissolve 6.40 g NaOH and 1.93 g Na.sub.2CO.sub.3 in 100 ml deionized water to prepare alkali solution; B. Turn on the nucleation reactor, set the stator-rotor gap of the reactor to be 0.4 mm and the rotation speed to be 3500 rpm, and transport 100 ml mixed salt solution and 100 ml alkali solution in step A to the reactor at a rate of 0.5 mL.Math.min.sup.−1 by a peristaltic pump for nucleation; collect nucleation slurry at slurry outlet; C. The nucleation slurry is transferred to a reaction kettle and crystallized at 100° C. for 36 h, after naturally cooling down to ambient temperature, the crystallized products are centrifuged and washed to neutral with deionized water, and then dried at 60° C. for 24 h, obtaining Cu.sub.6FeMg.sub.4-LDHs-100; D. The Cu.sub.6FeMg.sub.4-LDHs-100 obtained in step C is heated to 300° C. at a heating rate of 10° C..Math.min.sup.−1 and calcined for 4 h, obtaining Cu.sub.6FeMg.sub.4-MMO-100; E. The Cu.sub.6FeMg.sub.4-MMO-100 obtained in step D is reduced at 400° C. at a heating rate of 4° C. min.sup.−1 in an atmosphere of 10 vol. % H.sub.2/N.sub.2 for 4 h. After naturally cooling down to ambient temperature, 3 vol. % O.sub.2/N.sub.2 is introduced to passivate for 1 h, obtaining Cu.sub.6—FeMgO.sub.x-100 interfacial catalyst. The Cu/Fe ratio is 6/1.