Method for directly preparing aromatics from syngas

Abstract

A method for preparing aromatics from syngas, which includes a) contacting a raw material stream containing syngas with a catalyst in a reaction zone under reaction conditions sufficient to convert at least part of the raw material to obtain a reaction effluent; b) separating the reaction effluent to obtain at least a recycle stream containing gas-phase hydrocarbons having 1 to 4 carbon atoms and unconverted syngas and a liquid stream containing hydrocarbons having 5 or more carbon atoms; c) returning the recycle stream to the reaction zone; and d) separating aromatic products from the liquid stream, wherein the catalyst includes at least one of an inert carrier-confined highly dispersed metal oxide material, an acidic molecular sieve, and, optionally, graphite powder and a dispersant.

Claims

1. A method for preparing aromatics from syngas, comprising: a) contacting a raw material stream containing syngas with a catalyst in a reaction zone under reaction conditions sufficient to convert at least part of the raw material to obtain a reaction effluent; b) separating the reaction effluent to obtain at least a recycle stream containing gas-phase hydrocarbons having 1 to 4 carbon atoms and unconverted syngas and a liquid stream containing hydrocarbons having 5 or more carbon atoms; c) returning the recycle stream to the reaction zone; and d) separating aromatic products from the liquid stream, wherein the catalyst comprises at least one of an inert carrier-confined highly dispersed metal oxide material, an acidic molecular sieve, and a graphite powder and a dispersant, wherein in the inert carrier-confined highly dispersed metal oxide material, the inert carrier is at least one of silicon oxide and aluminum oxide, and the content of the metal oxide in terms of metal is less than or equal to 10% by mass, based on the weight of the inert carrier-confined highly dispersed metal oxide material; and the acidic molecular sieve is selected from modified acidic ZSM-5 molecular sieve, modified acidic ZSM-11 molecular sieve and mixtures thereof.

2. The method of claim 1, wherein the reaction zone comprises a fixed bed reactor, or a plurality of fixed bed reactors in series and/or parallel; the reaction conditions comprise: a reaction temperature of ranging from 300 C. to 450 C., a reaction pressure of ranging from 0.5 MPa to 10.0 MPa, a molar ratio of hydrogen to carbon monoxide in the syngas of ranging from 1:9 to 9:1, and the volume hourly space velocity of syngas under the standard state of ranging from 1000 h.sup.1 to 20000 h.sup.1; the aromatics are at least one selected from monocyclic aromatics having 6 to 11 carbon atoms; the gas-phase hydrocarbons having 1 to 4 carbon atoms are at least one selected from methane, ethane, ethylene, propane, cyclopropane, propylene, n-butane, isobutane, cyclobutane, 1-butene, 2-butene, isobutene and butadiene; the metal oxide is an oxide of at least one of zinc, chromium, zirconium, copper, manganese, platinum and palladium; the content of the metal oxide in the inert carrier-confined highly dispersed metal oxide material in terms of metal is less than or equal to 5% by weight, based on the weight of the inert carrier-confined highly dispersed metal oxide material; the particle size of the metal oxide in the inert carrier-confined highly dispersed metal oxide material is less than or equal to 100 nm; the modification of the acidic molecular sieve is one or more of phosphorus modification, boron modification, silicon modification, alkaline earth metal modification and rare earth metal modification; the atomic ratio of silicon to aluminum in the acidic ZSM-5 and ZSM-11 molecular sieves is Si/Al=3 to 200; and the shape of the catalyst is spherical, bar-shaped, cylindrical, semi-cylindrical, prismatic, clover-shaped, ring-shaped, pellet-shaped, regular or irregular particle-shaped or plate-shaped.

3. The method of claim 1, wherein the catalyst comprises a range from 10% to 90% by weight of the inert carrier-confined highly dispersed metal oxide material, a range from 10% to 90% by weight of the acidic molecular sieve, ranging from 0% to 10% by weight of the graphite powder, and a range from 0% to 40% by weight of the dispersant; wherein the total content of the inert carrier-confined highly dispersed metal oxide material and the acidic molecular sieve is in a range from 60% to 100% by weight, and the weight percentage is based on the total weight of the catalyst.

4. The method of claim 1, wherein the catalyst comprises a range from 20% to 80% by weight of the inert carrier-confined highly dispersed metal oxide material, a range from 20% to 80% by weight of the acidic molecular sieve, ranging from 0% to 5% by weight of the graphite powder, and a range from 0% to 30% by weight of the dispersant, the weight percentage is based on the total weight of the catalyst.

5. The method of claim 1, wherein the average particle size of the inert carrier-confined highly dispersed metal oxide material is less than or equal to 5 mm, and the average particle size of the acidic molecular sieve is less than or equal to 5 mm.

6. The method of claim 1, further comprising preparing the catalyst by the following steps: (1) providing an inert carrier-confined highly dispersed metal oxide material; (2) providing a modified acidic molecular sieve; and (3) mixing at least one of the inert carrier-confined highly dispersed metal oxide material obtained in step (1), the modified acidic molecular sieve obtained in step (2) and optional graphite powder and dispersant, and molding the resulting mixture.

7. The method of claim 6, wherein the method for preparing the catalyst further comprises at least one of: in step (1), the inert carrier-confined highly dispersed metal oxide material is prepared by a precipitation-calcination method, or the inert carrier-confined highly dispersed metal oxide material is prepared by a sol-gel method; the modified acidic molecules are selected from ZSM-5 molecular sieve and ZSM-11 molecular sieve modified with phosphorus, boron, silicon, alkaline earth and/or rare earth metals; and in step (3), the mixture is molded into catalyst particles using an extrusion method or a molding method.

8. The method of claim 6, wherein in step (1) of the method for preparing the catalyst, the inert carrier-confined highly dispersed metal oxide material is provided by a method comprising the steps of: formulating a salt of catalyzing active metal and an aluminum salt into an aqueous solution of mixed metal salt; contacting the aqueous solution of mixed metal salt with an aqueous solution of precipitant to coprecipitate the metal ions in the aqueous solution of mixed metal salt; aging; and washing, drying, and calcining the precipitate to prepare the inert carrier-confined highly dispersed metal oxide material.

9. The method of claim 8, further comprising at least one of: the salt of catalyzing active metal and the aluminum salt are selected from hydrochloride, sulfate and nitrate; the precipitant is selected from sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate, ammonium bicarbonate, ammonia water, sodium hydroxide, potassium hydroxide and mixtures thereof; the coprecipitation is performed at ranging from 0 C. to 90 C.; the pH value during the coprecipitation is in a range from 7.0 to 8.5; the aging time is not less than 1 h; and the calcination is performed at ranging from 300 C. to 700 C.

10. The method of claim 6, wherein in step (1) of the method for preparing the catalyst, the inert carrier-confined highly dispersed metal oxide material is provided by a method comprising the steps of: adding an aqueous solution of a salt of catalyzing active metal and an aqueous solution of a precipitant to the siloxy group compound, allowing the coprecipitation and sol-gel reaction to proceed, and then washing, drying and calcining the obtained gel to prepare the inert carrier-confined highly dispersed metal oxide material.

11. The method of claim 10, further comprising at least one of: the precipitant is selected from ammonium carbonate, ammonia water, ammonium bicarbonate, ammonium dihydrogen carbonate, urea and mixtures thereof; the siloxy group compound is an alkyl orthosilicate, selected from methyl orthosilicate, ethyl orthosilicate, n-propyl orthosilicate, isopropyl orthosilicate, n-butyl orthosilicate, isobutyl orthosilicate, t-butyl orthosilicate and mixtures thereof.

12. The method of claim 1, wherein the reaction conditions comprise: a reaction temperature of ranging from 320 C. to 400 C., a reaction pressure of ranging from 5.0 MPa to 10.0 MPa, a molar ratio of hydrogen to carbon monoxide in the syngas of ranging from 1:9 to 1:1, and the volume space velocity of syngas under the standard state of ranging from 1000 h.sup.1 to 5000 h.sup.1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic diagram of the C.sub.1-4 gas-phase hydrocarbon circulation process in Examples 19-24 of the present application.

(2) FIG. 2 is an XRD diagram of material A in Example 1 of the present application.

(3) FIG. 3 is an XRD diagram of the material REF-1 in Comparative Example 1 of the present application.

DETAILED DESCRIPTION

(4) The present invention will be described in detail below with reference to the examples, but the present invention is not limited to these examples.

(5) Unless otherwise specified, the raw materials in the examples of the present invention are purchased through commercial channels.

(6) In the examples, two Agilent 7890 gas chromatographs with a gas autosampler, a TCD detector connected to a TDX-1 packed column, and a FID detector connected to a FFAP and PLOT-Q capillary column are used for automatic gas composition analysis.

(7) In the examples, conversion and selectivity are calculated based on carbon moles:

(8) For the case of single-pass conversion of syngas and no material recycling:
Conversion rate of carbon monoxide=[(number of moles of carbon monoxide in the feed)(number of moles of carbon monoxide in the discharge)](number of moles of carbon monoxide in the feed)100%.
Selectivity of aromatics=(number of moles of aromatics in the discharge)(number of moles of all hydrocarbon products in the discharge)100%.

(9) For the return of C.sub.1-4 gas-phase hydrocarbon products to the reaction zone (see FIG. 1):
Selectivity of aromatics=number of moles of aromatics in Component III(sum of number of moles of all hydrocarbons in Component I and Component II)100%.

(10) The return of C.sub.1-4 gas-phase hydrocarbon products to the reaction zone has little effect on the conversion rate of CO.

(11) Inert Carrier-Confined Highly Dispersed Metal Oxide Material

Example 1

(12) 1 L of a mixed nitrate aqueous solution containing 0.05 mol/L Zn.sup.2+ and 1.0 mol/L Al.sup.3+ was prepared, a 0.5 mol/L ammonia solution was slowly added to it. The temperature of the coprecipitation reaction was controlled to 70 C. and the pH was 7.2 to coprecipitate the metal ions, and aged at this temperature for 4 h, filtered, washed and dried, and calcined at 500 C. for 4 h to obtain the alumina inertcontrol-confined highly dispersed zinc oxide material, which was designated as A. The mass fraction of zinc in A was 8.3%, and the XRD diagram was shown in FIG. 2.

Example 2

(13) 1 L of a mixed nitrate aqueous solution containing 0.02 mol/L Zn.sup.2+, 0.02 mol/L Cr.sup.3+ and 1.0 mol/L Al.sup.3+ was prepared, a 1.0 mol/L ammonium carbonate solution was slowly added to it. The temperature of the coprecipitation reaction was controlled to 70 C. and the pH was 7.5 to coprecipitate the metal ions, and aged at this temperature for 4 h, filtered, washed and dried, and calcined at 500 C. for 4 h to obtain the alumina inertcontrol-confined highly dispersed zinc-chromium oxide material, which was designated as B. The mass fraction of zinc in B was 3.1%, and the mass fraction of chromium in B was 2.5%.

Example 3

(14) 1 L of a mixed nitrate aqueous solution containing 0.01 mol/L Zn.sup.2+, 0.01 mol/L Zr.sup.4+ and 1.0 mol/L Al.sup.3+ was prepared, a 1.2 mol/L sodium carbonate solution was slowly added to it. The temperature of the coprecipitation reaction was controlled to 70 C. and the pH was 7.3 to coprecipitate the metal ions, and aged at this temperature for 4 h, filtered, washed and dried, and calcined at 500 C. for 4 h to obtain the alumina inertcontrol-confined highly dispersed zinc-zirconium oxide material, which was designated as C. The mass fraction of zinc in C was 1.5%, and the mass fraction of zirconium in C was 2.1%.

Example 4

(15) 1 L of a mixed nitrate aqueous solution containing 0.01 mol/L Zn.sup.2+, 0.02 mol/L Cu.sup.2+ and 1.0 mol/L Al.sup.3+ was prepared, a 1.5 mol/L potassium carbonate solution was slowly added to it. The temperature of the coprecipitation reaction was controlled to 70 C. and the pH was 7.9 to coprecipitate the metal ions, and aged at this temperature for 4 h, filtered, washed and dried, and calcined at 500 C. for 4 h to obtain the alumina inertcontrol-confined highly dispersed zinc-copper oxide material, which was designated as D. The mass fraction of zinc in D was 1.5%, and the mass fraction of copper in D was 3.1%.

Example 5

(16) 100 mL of a mixed nitrate aqueous solution containing 0.2 mol/L Zn.sup.2+ and 0.2 mol/L Cr.sup.3+ was prepared. 100 mL of 1.0 mol/L urea aqueous solution was prepared. The above two solutions were added dropwise to 1 mol of tetraethyl orthosilicate, reacted at room temperature for 24 h, obtained a gel, dried at 100 C., and calcined at 500 C. for 4 h to obtain the silicon oxide inertcontrol-confined highly dispersed zinc-chromium oxide material, which was designated as E. The mass fraction of zinc in E was 1.8%, and the mass fraction of chromium in E was 1.5%.

Example 6

(17) 100 mL of a mixed nitrate aqueous solution containing 0.2 mol/L Zn.sup.2+ and 0.2 mol/L Zr.sup.4+ was prepared. 100 mL of 1.0 mol/L urea aqueous solution was prepared. The above two solutions were added dropwise to 1 mol of tetraethyl orthosilicate, reacted at room temperature for 24 h, obtained a gel, dried at 100 C., and calcined at 500 C. for 4 h to obtain the silicon oxide inertcontrol-confined highly dispersed zinc-chromium oxide material, which was designated as F. The mass fraction of zinc in F was 1.8%, and the mass fraction of zirconium in F was 2.5%.

Comparative Example 1

(18) 1 L of a mixed nitrate aqueous solution containing 1.0 mol/L Zn.sup.2+, 0.50 mol/L Cr.sup.3+ and 0.20 mol/L Al.sup.3+ was prepared, a 1.0 mol/L ammonium carbonate solution was slowly added to it. The temperature of the coprecipitation reaction was controlled to 70 C. and the pH was 7.5 to coprecipitate the metal ions, and aged at this temperature for 4 h, filtered, washed and dried, and calcined at 500 C. for 4 h to obtain the zinc-chromium composite oxide, which was designated as REF-1. The XRD diagram of REF-1 was shown in FIG. 3. Preparation Of Modified Acidic Molecular Sieve

Example 7

(19) The sodium-type ZSM-5 (Nankai University Catalyst Plant) with Si/Al=25 (atomic ratio) was exchanged with 0.8 mol/L ammonium nitrate aqueous solution three times at 80 C. to obtain the ammonium-type ZSM-5 molecular sieve, calcined at 550 C. for 4 h in air atmosphere, then immersed in (NH.sub.4).sub.2HPO.sub.4 aqueous solution at room temperature for 24 h at equal volume. After drying, it was calcined at 550 C. for 4 h in air atmosphere to obtain an acidic ZSM-5 molecular sieve with a P mass fraction of 4%, which was designated as G.

Example 8

(20) The sodium-type ZSM-5 (Nankai University Catalyst Plant) with Si/Al=200 (atomic ratio) was exchanged with 0.8 mol/L ammonium nitrate aqueous solution three times at 80 C. to obtain the ammonium-type ZSM-5 molecular sieve, calcined at 550 C. for 4 h in air atmosphere, then immersed in H.sub.3BO.sub.3 aqueous solution at room temperature for 24 h at equal volume. After drying, it was calcined at 550 C. for 4 h in air atmosphere to obtain an acidic ZSM-5 molecular sieve with a B mass fraction of 8%, which was designated as H.

Example 9

(21) The sodium-type ZSM-11 (Aoke Co., Ltd.) with Si/Al=40 (atomic ratio) was exchanged with 0.8 mol/L ammonium nitrate aqueous solution three times at 80 C. to obtain the ammonium-type ZSM-11 molecular sieve, calcined at 550 C. for 4 h in air atmosphere, then immersed in H.sub.3BO.sub.3 aqueous solution at room temperature for 24 h at equal volume. After drying, it was calcined at 550 C. for 4 h in air atmosphere to obtain an acidic ZSM-11 molecular sieve with a B mass fraction of 8%, which was designated as I.

Example 10

(22) The sodium-type ZSM-5 (Aoke Co., Ltd.) with Si/Al=3 (atomic ratio) was exchanged with 0.8 mol/L ammonium nitrate aqueous solution three times at 80 C. to obtain the ammonium-type ZSM-5 molecular sieve, calcined at 550 C. for 4 h in air atmosphere, a solution of tetraethyl orthosilicate in cyclohexane was used to react at 50 C. for 4 h. After evaporation, it was calcined at 550 C. for 4 h in air atmosphere to obtain an acidic ZSM-5 molecular sieve with a Si mass fraction of 8% (excluding the original Si in the molecular sieve), which was designated as J.

Example 11

(23) The sodium-type ZSM-5 (Fuxu Co., Ltd.) with Si/Al=80 (atomic ratio) was exchanged with 0.8 mol/L ammonium nitrate aqueous solution three times at 80 C. to obtain the ammonium-type ZSM-5 molecular sieve, calcined at 550 C. for 4 h in air atmosphere, nitrogen carried 5% by volume of tetramethylsilane was used, treated at 200 C. for 3 h, calcined at 550 C. for 4 h in air atmosphere to obtain an acidic ZSM-5 molecular sieve with a Si mass fraction of 2% (excluding the original Si in the molecular sieve), which was designated as K.

Example 12

(24) The sodium-type ZSM-5 (Nankai University Catalyst Plant) with Si/Al=60 (atomic ratio) was exchanged with 0.8 mol/L ammonium nitrate aqueous solution three times at 80 C. to obtain the ammonium-type ZSM-5 molecular sieve, calcined at 550 C. for 4 h in air atmosphere, then immersed in mixed aqueous solution of magnesium nitrate and cerous nitrate at room temperature for 24 h at equal volume. After drying, it was calcined at 550 C. for 4 h in air atmosphere to obtain an acidic ZSM-5 molecular sieve with Mg and Ce mass fractions of 4% and 1% respectively, which was designated as L.

(25) Mixed Catalyst Preparation

Example 13

(26) The inertcontrol-confined highly dispersed metal oxide material A in Example 1 and the acidic molecular sieve G in Example 7 were uniformly mixed at a mass fraction of the inertcontrol-confined highly dispersed metal oxide material A of 75% and crushed into powder of less than 0.05 mm, and then compressed and sieved to make a 1-2 mm particle catalyst, which was designated as M. The preparation scheme was summarized in Table 1.

Examples 14-18

(27) The preparation method was similar to Example 13, and the specific scheme was shown in Table 1.

Comparative Example 2

(28) The metal composite oxide REF-1 in Comparative Example 1 and the acidic molecular sieve G in Example 7 were uniformly mixed at a mass fraction of the inertcontrol-confined highly dispersed metal oxide material A of 75% and crushed into powder of less than 0.05 mm, and then compressed and sieved to make a 1-2 mm particle catalyst, which was designated as REF-2.

(29) TABLE-US-00001 TABLE 1 Preparation scheme of mixed catalyst Mass Fraction Inert Mixed of Inert Carrier-confined Acidic Carrier-confined Highly Dispersed Molecular Highly Dispersed Catalyst Metal Oxide Sieve Metal Oxide Example No. Material No. No. Material 13 M A G 75% 14 N B H 10% 15 O C I 90% 16 P D J 50% 17 Q E K 80% 18 R F L 65%

(30) Catalyst Performance Test

Example 19

(31) 500 g of the catalyst M was packed into a stainless steel reaction tube with an inner diameter of 28 mm, activated with 1000 ml/min hydrogen at 300 C. for 4 h, and reacted under the following conditions: reaction temperature (T)=400 C., reaction pressure (P)=4.0 MPa, the volumetric space velocity (GHSV) under standard conditions=6000 h.sup.1, and the volume fraction V(H.sub.2)% of hydrogen in the syngas (mixed gas of CO and H.sub.2)=40%. After the reaction was stabilized, the product was analyzed by gas chromatography to obtain the conversion rate of carbon monoxide and the selectivity of aromatics when C.sub.1-4 gas-phase hydrocarbons were not recycled. The reaction results were shown in Table 2. Then, under the same reaction conditions, C.sub.1-4 gas-phase hydrocarbons were returned to the reaction zone (as shown in FIG. 1). After the reaction was stabilized, when C.sub.1-4 gas-phase hydrocarbons were recycled, the selectivity of aromatics was obtained. The reaction results were also shown in Table 2.

Examples 20-24

(32) The reaction conditions and reaction results were shown in Table 1. Other operations were the same as in Example 19.

Comparative Example 3

(33) 500 g of the catalyst REF-2 was packed into a stainless steel reaction tube with an inner diameter of 28 mm, activated with 1000 ml/min hydrogen at 300 C. for 4 h, and reacted under the following conditions: reaction temperature (T)=400 C., reaction pressure (P)=4.0 MPa, the volumetric space velocity (GHSV) under standard conditions=6000 h.sup.1, and the volume fraction V(H.sub.2)% of hydrogen in the syngas (mixed gas of CO and H.sub.2)=40%. After the reaction was stabilized, the product was analyzed by gas chromatography to obtain the conversion rate of carbon monoxide and the selectivity of aromatics when C.sub.1-4 gas-phase hydrocarbons were not recycled. The reaction results were shown in Table 2. Then, under the same reaction conditions, C.sub.1-4 gas-phase hydrocarbons were returned to the reaction zone (as shown in FIG. 1). After the reaction was stabilized, when C.sub.1-4 gas-phase hydrocarbons were recycled, the selectivity of aromatics was obtained. The reaction results were also shown in Table 2.

(34) TABLE-US-00002 TABLE 2 Catalytic reaction results in Examples 19-24 and Comparative Example 3 Selectivity of Selectivity of Conversion Aromatics When C.sub.1-4 Aromatics When C.sub.1-4 Examples/ Rate of Gas-phase Gas-phase Comparative Reaction Carbon Hydrocarbons were Hydrocarbons were Example Catalyst Condition Monoxide (%) not Recycled (%) Recycled (%) Example 19 M T = 400 C.; 20.3 56.0 97.1 P = 4.0 MPa; GHSV = 6000 h.sup.1; V(H.sub.2) % = 40% Example 20 N T = 370 C.; 58.0 32.7 95.2 P = 0.0 MPa; GHSV = 20000 h.sup.1; V(H.sub.2) % = 90% Example 21 O T = 300 C.; 17.3 68.7 94.8 P = 0.5 MPa; GHSV = 1000 h.sup.1; V(H.sub.2) % = 10% Example 22 P T = 450 C.; 38.9 59.1 97.7 P = 3.0 MPa; GHSV = 8000 h.sup.1; V(H.sub.2) % = 65% Example 23 Q T = 390 C.; 29.1 65.4 98.1 P = 5.0 MPa; GHSV = 7000 h.sup.1; V(H.sub.2) % = 30% Example 24 R T = 340 C.; 28.0 47.1 96.3 P = 7.0 MPa; GHSV = 12000 h.sup.1; V(H.sub.2) % = 75% Example 3 REF-2 T = 400 C.; 12.3 10.5 28.3 P = 4.0 MPa; GHSV = 6000 h.sup.1; V(H.sub.2) % = 40%
Catalyst Regeneration Performance Test

Example 25

(35) The deactivated catalyst in Example 19 was treated with a mixture of 2% oxygen and 98% nitrogen by volume at 550 C. for 10 h to regenerate the catalyst for one round and react under the conditions of Example 19. It was regenerated for five rounds in the same way, and the catalytic activity data after 500 h of each round of reaction was selected for comparison. The results were shown in Table 3.

(36) TABLE-US-00003 TABLE 3 Catalytic reaction results in Example 25 Selectivity of Selectivity of Aromatics Aromatics Conversion When C.sub.1-4 When C.sub.1-4 Rate of Gas-phase Gas-phase Carbon Hydrocarbons Hydrocarbons Life Number of Monoxide were not were of Each Regeneration (%) Recycled (%) Recycled (%) Round (h) 1 20.3 54.3 96.1 3500 2 21.0 53.9 95.3 3700 3 21.5 55.6 96.7 3400 4 21.1 55.0 96.0 3500 5 20.7 52.3 94.5 3600

(37) The above are only a few examples of the present application, and are not intended to limit the present application in any way. Although the present application is disclosed in the above with preferred example, it is not intended to limit the present application. Any one skilled in the art can understand that other changes and modifications by using the above technical content without departing from the scope of the technical solution of the present application are equivalent to equivalent embodiments and belong to the scope of the technical solution.