Catalyst for producing paraxylene by co-conversion of methanol and/or dimethyl ether and C4 liquefied gas, method for preparing the same and method for using the same

Abstract

This application provides a catalyst for producing paraxylene by co-conversion of methanol and/or dimethyl ether and C.sub.4 liquefied gas, and preparation and application thereof. The catalyst is an aromatization molecular sieve catalyst with a shape-selective function co-modified by bimetal and siloxane compound. Methanol and/or dimethyl ether and C.sub.4 liquefied gas are fed in reactor together, wherein aromatization reaction occurring on a modified shape-selective molecular sieve catalyst. The yield of aromatics is effectively improved, in which paraxylene is the main product. In products obtained by co-conversion of methanol and/or dimethyl ether and C.sub.4 liquefied gas, the yield of aromatics is greater than 70 wt %, and the content of paraxylene in aromatics is greater than 80 wt %, and the selectivity of paraxylene in xylene is greater than 99 wt %.

Claims

1. A process for producing paraxylene by co-conversion of methanol and/or dimethyl ether and C.sub.4 liquefied gas, comprising the steps as follows: passing a gas mixture containing methanol and/or dimethyl ether and C.sub.4 liquefied gas through a reactor comprising an aromatization molecular sieve catalyst with a shape-selective function to produce paraxylene by aromatization reaction; wherein said aromatization reaction is carried out at a temperature from 400 C. to 550 C., a pressure from atmospheric pressure to 2 MPa and a weight hourly space velocity of said gas mixture from 1 h.sup.1 to 10 h.sup.1; wherein said aromatization molecular sieve catalyst comprises HZSM-5 and/or HZSM-11 zeolite molecular sieve co-modified by bimetal and a siloxane compound; wherein said bimetal are zinc and gallium; wherein said siloxane compound has the structural formula ##STR00003## wherein, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are independently selected from C.sub.1-C.sub.10 alkyl group, and wherein a loading amount of said zinc is 0.5-8 wt % of a total weight of said catalyst, a loading amount of said gallium is 0.5-8 wt % of the total weight of said catalyst, and a loading amount of said siloxane compound, which is based on silicon oxide, is 0.5-10 wt % of the total weight of said catalyst; wherein the process comprises the following step to prepare said aromatization molecular sieve catalyst: (a) impregnating a molecular sieve comprising HZSM-5 and/or HZSM-11 in a solution containing at least one soluble salt of one of zinc or gallium, which is then filtered, dried and calcined to obtain a metal-modified molecular sieve; (b) impregnating said metal-modified molecular sieve obtained from step (a) in a solution containing at least one soluble salt of the other of zinc or gallium, which is then filtered, dried and calcined to obtain a bimetal-modified molecular sieve; and (c) impregnating said bimetal-modified molecular sieve obtained from step (b) in a siloxane compound, which is then filtered, dried and calcined to obtain said aromatization molecular sieve catalyst.

2. The process according to claim 1, wherein said siloxane compound is tetraethoxysilane.

3. The process according to claim 1, wherein said process is conducted in a fixed bed or a fluidized bed reactor.

Description

DETAILED DESCRIPTION OF EMBODIMENT

(1) The present application is described in details by referring to the following Examples, but not limited to the Examples.

(2) In the following Examples, the reagents and raw materials are all obtained by commercial purchase and wt % means the weight percentage, unless indicated otherwise. In present application, the parts, percentages and amounts are all based on weight, unless indicated otherwise.

Example 1: Preparation of a Catalyst Used in Fixed Bed

(3) 1) 500 g of the raw powder containing a template agent inside of ZSM-5 zeolite molecular sieve (from The Catalyst Plant of Nankai University, molar ratio of SiO.sub.2/Al.sub.2O.sub.3=50) was calcined at 550 C. to remove the template agent, and then ion-exchanged four times with 0.5 mol/L ammonium nitrate solution at water-bath 80 C., and then dried out in air at 120 C., and then calcined at 550 C. for 3 hours. Then HZSM-5 zeolite molecular sieve was obtained.

(4) 2) 20 g of the HZSM-5 zeolite molecular sieve obtained from step 1) was impregnated in zinc nitrate [Zn(NO.sub.3).sub.2] solution with mass percent concentration of 5% at room temperature for 4 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a zinc metal-modified HZSM-5 zeolite molecular sieve.

(5) 3) The zinc metal-modified HZSM-5 zeolite molecular sieve obtained from step 2) was impregnated in gallium nitrate [Ga(NO.sub.3).sub.2] solution with mass percent concentration of 8% at room temperature for 4 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a gallium and zinc bimetal-modified HZSM-5 zeolite molecular sieve.

(6) 4) The gallium and zinc bimetal-modified HZSM-5 zeolite molecular sieve obtained from step 3) was impregnated in tetraethoxysilane (TEOS) at room temperature for 24 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a HZSM-5 zeolite molecular sieve catalyst co-modified by gallium and zinc bimetal and siloxane compound, which was named as CPX-01.

Example 2: Preparation of a Catalyst Used in Fixed Bed

(7) 1) 20 g of the HZSM-5 zeolite molecular sieve obtained from step 1) in Example 1 was impregnated in gallium nitrate [Ga(NO.sub.3).sub.2] solution with mass percent concentration of 10% at room temperature for 4 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a gallium metal-modified HZSM-5 zeolite molecular sieve.

(8) 2) The gallium metal-modified HZSM-5 zeolite molecular sieve obtained from step 1) was impregnated in a zinc nitrate [Zn(NO.sub.3).sub.2] solution with mass percent concentration of 8% at room temperature for 4 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a gallium and zinc bimetal-modified HZSM-5 zeolite molecular sieve.

(9) 3) The gallium and zinc bimetal-modified HZSM-5 zeolite molecular sieve obtained from step 2) was impregnated in tetraethoxysilane (TEOS) at room temperature for 24 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a HZSM-5 zeolite molecular sieve catalyst co-modified by gallium and zinc bimetal and siloxane compound, which was named as CPX-02.

Example 3: Preparation of a Catalyst Used in Fluidized Bed

(10) 1) 200 g of the HZSM-5 zeolite molecular sieve obtained from step 1) in Example 1 was impregnated in zinc nitrate [Zn(NO.sub.3).sub.2] solution with mass percent concentration of 10% at room temperature for 4 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a zinc metal-modified HZSM-5 zeolite molecular sieve.

(11) 2) The zinc metal-modified HZSM-5 zeolite molecular sieve obtained from step 1) was impregnated in a gallium nitrate [Ga(NO.sub.3).sub.2] solution with mass percent concentration of 15% at room temperature for 4 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a gallium and zinc bimetal-modified HZSM-5 zeolite molecular sieve.

(12) 3) The gallium and zinc bimetal-modified HZSM-5 zeolite molecular sieve obtained from step 2) was impregnated in tetraethoxysilane (TEOS) at room temperature for 24 hours, and then dried out at 120 C. after the supernatant liquid was decanted, and then calcined in air 550 C. for 6 hours to obtain a HZSM-5 zeolite molecular sieve co-modified by gallium and zinc bimetal and siloxane compound.

(13) 4) The HZSM-5 zeolite molecular sieve co-modified by gallium and zinc bimetal and siloxane compound from step 3) was mixed with kaoline, silica sol, alumina sol and deionized water into slurry. The mass ratio of the zeolite molecular sieve:kaoline:dry basis of silica sol:dry basis of alumina sol was 30:32:26:12. And the solid content in the slurry was about 35 wt %. And then the slurry was aged at room temperature for 5 hours, and then molded by spray drying after grinded by colloid mill to obtain the microsphere catalyst with the particle size of 20-100 m. Elemental analysis showed that based on the total weight of the catalyst, the catalyst contained 2.3 wt % zinc, 3.1 wt % gallium, and 5.3 wt % siloxane compound calculated according to silicon oxide. The catalyst was named as CPX-03.

Example 4: Catalyst Evaluation in Fixed Bed Reactor

(14) CPX-01 from Example 1 and CPX-02 from Example 2 were used as the catalysts in the reaction. 5 g catalyst was loaded in a fixed bed reactor, and then treated in air at 550 C. for 1 hour followed by a cooling process in nitrogen to reach the reaction temperature of 450 C., 0.15 MPa. Methanol and C.sub.4 liquefied gas were pumped into a vaporizer, mixed into raw materials at a temperature of 200 C., and then contacted with the catalyst in the reactor. The raw materials with methanol and C.sub.4 liquefied gas in ratio of 50:50 were fed in the reactor with a total weight hourly space velocity of 2 h.sup.1. Distribution of raw materials and waterless products were shown in Table 1. On CPX-01 catalyst and CPX-02 catalyst, the yields of aromatics in waterless products were 71.31 wt % and 73.03 wt %, and the contents of paraxylene in aromatics were 87.17 wt % and 86.67 wt %, and the selectivities of paraxylene in xylene isomers were 99.41 wt % and 99.32 wt %, respectively.

(15) TABLE-US-00001 TABLE 1 Distribution of raw materials and waterless products Catalyst CPX-01 CPX-02 Yield of aromatics in 71.31 73.03 hydrocarbons (wt %) Content of paraxylene 87.17 86.67 in aromatics (wt %) Selectivity of paraxylene 99.41 99.32 in xylene isomers (wt %) Distribution of raw materials and products (wt %) raw materials products products methanol 50.00 C.sub.3 0.81 C.sub.4 alkane 10.96 C.sub.4 olefins 37.52 C.sub.5.sup.+ 0.72 C.sub.1-C.sub.5 28.69 26.97 benzene 0.02 0.02 methylbenzene 0.45 0.45 ethylbenzene 0.62 0.63 paraxylene 62.16 63.29 m-xylene 0.06 0.08 o-xylene 0.31 0.36 C.sub.9.sup.+ 7.69 8.20 Total 100.00 100.00 100.00 *C.sub.5.sup.+: hydrocarbons with carbon number not less than five; C.sub.9.sup.+: hydrocarbons with carbon number not less than nine.

Example 5: Catalyst Evaluation in Fixed Bed

(16) CPX-01 from Example 1 and CPX-02 from Example 2 were used as the catalysts in the reaction. 5 g catalyst was loaded in a fixed bed reactor, and then treated in air at 550 C. for 1 hour followed by a cooling process in nitrogen to reach the reaction temperature of 450 C., 0.1 MPa. Methanol and C.sub.4 liquefied gas were pumped into a vaporizer, mixed into raw materials at a temperature of 200 C., and then contacted with the catalyst in the reactor. The raw materials with methanol and C.sub.4 liquefied gas in ratio of 30:70 were fed in the reactor with a total weight hourly space velocity of 2 h.sup.1. Distribution of raw materials and waterless products were shown in Table 2. On CPX-01 catalyst and CPX-02 catalyst, the yields of aromatics in waterless products were 75.21 wt % and 79.01 wt %, and the contents of paraxylene in aromatics were 85.88 wt % and 85.74 wt %, and the selectivities of paraxylene in xylene isomers were 99.21 wt % and 99.19 wt %, respectively.

(17) TABLE-US-00002 TABLE 2 Distribution of raw materials and products Catalyst CPX-01 CPX-02 Yield of aromatics in 75.21 79.01 hydrocarbons (wt %) Content of paraxylene 85.88 85.74 in aromatics (wt %) Selectivity of paraxylene 99.21 99.19 in xylene isomers (wt %) Distribution of raw materials and products (wt %) Raw materials Products Products methanol 30.00 C.sub.3 1.13 C.sub.4 alkane 15.34 C.sub.4 olefins 52.52 C.sub.5.sup.+ 1.01 C.sub.1-C.sub.5 24.79 20.99 benzene 0.02 0.02 methylbenzene 0.45 0.47 ethylbenzene 0.63 0.66 paraxylene 64.59 67.74 m-xylene 0.10 0.12 o-xylene 0.41 0.43 C.sub.9.sup.+ 9.00 9.56 Total 100.00 100.00 100.00 *C.sub.5.sup.+: hydrocarbons with carbon number not less than five; C.sub.9.sup.+: hydrocarbons with carbon number not less than nine.

Example 6: Catalyst Evaluation in Fluidized Bed

(18) CPX-03 from Example 3 was used as the catalyst in the reaction. 10 g catalyst was loaded in a fluidized bed reactor, and then treated in air at 550 C. for 1 hour followed by a cooling process in nitrogen to reach the reaction temperature of 450 C., 0.1 MPa. Methanol and C.sub.4 liquefied gas were pumped into a vaporizer, mixed into raw materials at a temperature of 200 C., and then contacted with the catalyst in the reactor. Two raw materials with methanol and C.sub.4 liquefied gas in ratios of 50:50 and 30:70 were fed in the reactor with a total weight hourly space velocity of 2 h.sup.1, respectively. Distribution of raw materials and waterless products were shown in Table 2. The yields of aromatics in waterless products were 70.12 wt % and 72.87 wt %, and the contents of paraxylene in aromatics were 84.47 wt % and 85.21 wt %, and the selectivities of paraxylene in xylene isomers were 99.04 wt % and 99.08 wt %, respectively.

(19) TABLE-US-00003 TABLE 3 Distribution of raw materials and products Catalyst CPX-03 CPX-03 Yield of aromatics in 70.12 72.87 hydrocarbons (wt %) Content of paraxylene 84.47 85.21 in aromatics (wt %) Selectivity of paraxylene 99.04 99.08 in xylene isomers (wt %) Distribution of raw materials and products (wt %) Raw Raw materials Products material Products methanol 50.00 30.00 C.sub.3 0.81 1.13 C.sub.4 alkane 10.96 15.34 C.sub.4 olefins 37.52 52.52 C.sub.5.sup.+ 0.72 1.01 C.sub.1-C.sub.5 29.88 27.13 benzene 0.02 0.02 methylbenzene 0.44 0.46 ethylbenzene 0.61 0.64 paraxylene 59.23 62.10 m-xylene 0.15 0.16 o-xylene 0.42 0.42 C.sub.9.sup.+ 9.24 9.08 Total 100.00 100.00 100.00 *C.sub.5.sup.+: hydrocarbons with carbon number not less than five; C.sub.9.sup.+: hydrocarbons with carbon number not less than nine.