CN1050594C

CN1050594C - Methylbenzene disproportionating and alkyl group transfering process

Info

Publication number: CN1050594C
Application number: CN96116470A
Authority: CN
Inventors: 程文才; 杨德琴
Original assignee: Sinopec Shanghai Research Institute of Petrochemical Technology; China Petrochemical Corp
Current assignee: Sinopec Shanghai Research Institute of Petrochemical Technology; China Petrochemical Corp
Priority date: 1996-08-20
Filing date: 1996-08-20
Publication date: 2000-03-22
Anticipated expiration: 2016-08-20
Also published as: CN1174184A

Abstract

The present invention relates to a technique for the disproportionation and the transalkylation of toluene, which adopts a catalyst of mordenite with the silicaalumina ratio SiO2/Al2O3 of 10 to 30(mole/mole). Under the conditions of the reaction temperature of 320 to 500 DEG C, the raw material airspeed of 0.5 to 2.0 hours <->, the reaction pressure of 1.0 to 8.0MPa, and the hydrogen / hydrocarbon molecular ratio of 4 to 10, the toluene reacts with a C9 aromatic hydrocarbon raw material containing C10 aromatic hydrocarbon in a fixed bed. The technique has the characteristics that more C10 aromatic hydrocarbon can be contained in the raw material, and the conversion rates of the toluene and C9 aromatic hydrocarbon are high, and the present invention can be widely used in industrial production.

Description

Toluene disproportionation and alkyl transfer process

The present invention relates to a toluene disproportionation and transalkylation process, particularly to a process for producing benzene and xylene by the disproportionation and transalkylation of toluene and carbon nonaromatic hydrocarbon raw materials.

Toluene disproportionation and carbon nonaromatic hydrocarbon transalkylation yield increase of benzene and xylene, and is an effective means for adjusting the production demand balance of each component in petroleum aromatic hydrocarbon and meeting the requirements of petrochemical industry on benzene and xylene. The prior disproportionation and transalkylation process and catalyst require the content of the carbon-decaaromatic hydrocarbon in the raw material to be below 2 percent so as to ensure that the catalyst has better stability. In the product separation process, the carbon deca-aromatic hydrocarbon is removed, and the carbon deca-aromatic hydrocarbon content of the cyclic carbon nona-aromatic hydrocarbon meets the requirement. Therefore, the discarded heavy component contains about 15 to 30 percent of carbon nonaaromatics, so that the loss of the useful carbon nonaaromatics raw material for transalkylation is large. The toluene disproportionation process is described in US4761514 patent. The process uses mordenite with a silicon-aluminum ratio of more than 30 as a catalyst, and toluene containing ethylbenzene as a raw material to carry out disproportionation reaction, wherein the raw material does not contain deca-arene. The document US3551509 discloses a toluene raw material containing nona-and deca-aromatics, which is prepared by adding two rare earth metals and taking zeolite with a silicon-aluminum ratio of 2-12 as a catalyst, and the catalyst is heated at a temperature of 700-1100 ℃ F, and the weight space velocity is 0.2-5 hours^-1The process adopts a moving bed and a large-aperture catalyst, and although the amount of the carbon-deca aromatic hydrocarbon contained in the raw material is large, the conversion rate of toluene disproportionation is low and is only 22.96% at most.

Two main reactions of toluene disproportionation and transalkylation are toluene disproportionation to produce benzene and xylene and toluene and trimethylbenzene reaction to produce xylene. However, under the reaction conditions, side reactions may occur simultaneously to produce a small amount of carbon deca-aromatics, which are usually discarded as by-products, increasing the raw material consumption. For example: a small amount of trimethylbenzene is subjected to disproportionation reaction to generate dimethylbenzene and tetramethylbenzene:

by means of the process and catalyst of the present invention, the following reactions of the carbon decarens under the disproportionation and transalkylation reaction conditions can be carried out to convert the carbon decarens into lower grade aromatics, which become useful raw materials. For example, the transalkylation of tetramethylbenzene with benzene to produce trimethylbenzene and toluene:

and (3) performing hydrogenation dealkylation on the tetramethylbenzene to generate trimethylbenzene and methane:

both of these reactions convert the decaaromatic hydrocarbon to the useful feedstock carbon nonaaromatic hydrocarbons and toluene for disproportionation and transalkylation.

In order to overcome the disadvantages of the above documents, the present invention aims to provide a process which allows the raw material to contain more carbon nonaromatic hydrocarbon and has higher toluene disproportionation conversion rate during the reaction of toluene and carbon nonaromatic hydrocarbon.

The purpose of the invention is realized by the following technical scheme: a process for disproportionation and alkyl transfer of toluene features that the toluene as raw material contains nona-and deca-aryls, mordenite as catalyst, and the ratio of Si to Al of mordenite is SiO₂/Al₂O₃The molecular ratio is 10-30 mol/mol, the aperture of the catalyst is 4-8 Å, the reaction temperature is 320-550 ℃, the reaction pressure is 1.0-8.0 MPa, the hydrogen/hydrocarbon molecular ratio is 4-10 mol/mol, and the weight space velocity of the raw material is 0.5-2.0 hours^-1Under the condition, benzene, ethylbenzene and xylene are generated by reaction in a fixed bed.

In the technical scheme, the preferable range of the reaction pressure is 2.0-5.0 MPa, the preferable range of the reaction temperature is 340-480 ℃, the preferable range of the hydrogen/hydrocarbon molecular ratio is 4-8 mol/mol, and the silicon-aluminum ratio SiO of the mordenite catalyst is₂/Al₂O₃The preferred range of the molecular ratio is 15-25 mol/mol, and the preferred range of the pore diameter of the catalyst is 6-8 Å.

The preparation method of the mordenite catalyst comprises the following steps: high-silicon mordenite is synthesized according to the method of Chinese patent 89106793.0(CN1050011A), then treated by ammonium salt solution, and washed by deionized water to remove sodium ions. Mixing the sodium-removed mordenite with pseudo-boehmite, adding dilute nitric acid, kneading, extruding, granulating and roasting to obtain the catalyst.

The toluene disproportionation and transalkylation process of the invention allows the raw material to contain 0.1-8.0 wt% of the carbon nonaromatic hydrocarbon, so that ① has three obvious advantages that the carbon nonaromatic hydrocarbon content discharged and taken away by the heavy component is reduced due to the fact that the raw material allows the carbon nonaromatic hydrocarbon content to reach 8 wt%, ② reaction raw material allows the carbon nonaromatic hydrocarbon content to reach 8 wt%, the loss of the raw material carbon nonaromatic hydrocarbon caused by the disproportionation of trimethylbenzene to generate the carbon nonaromatic hydrocarbon is reduced, the product yield is also improved, part of the carbon nonaromatic hydrocarbon in ③ raw material is converted into lower-level aromatic hydrocarbon such as the carbon nonaromatic hydrocarbon, the raw material is contributed to the disproportionation and transalkylation reaction, the product yield is also improved, in addition, the conversion rate of the reaction of the process per se and the total mole of the carbon nonaromatic hydrocarbon is up to 42-43%, the product yield of the device is greatly improved, and the satisfactory effect is obtained.

[ example 1 ]

1000g (50 percent of water) of high-silicon mordenite with the silicon-aluminum ratio of 10-30 (mol/mol) synthesized by the method of Chinese patent 89106793.0(CN1050011A), wherein the aperture of the mordenite is 4-8 Å, and 2000ml of NH with the concentration of 10 percent is added into the mordenite₄Adding the Cl solution into a 5000ml three-neck flask with a stirring device, raising the temperature of the feed liquid to 90 ℃ while stirring, then continuing stirring and keeping the temperature for 4 hours, and filtering out the mother liquid. Repeating the steps for 3-5 times, filtering again, washing the filter cake with deionized water, and washing away chloride ions-. And drying the filter cake in an oven at 110 ℃ overnight until the water content of the filter cake is below 10%, and analyzing the content of the mordenite sodium ions to be lower than 0.15 wt%. Mixing the sodium-removed mordenite with pseudo-boehmite (about 30% after burning weight loss at 550 ℃), adding dilute nitric acid for kneading, extruding strips, granulating and roasting to obtain the catalyst with the diameter of 1.6-1.8 mm and the length of 3-4 mm.[ example 2 ]

20g of the catalyst prepared in example 1, having a silica-alumina ratio of 26 (mol/mol) and a catalyst pore diameter of 7 Å, was packed in a fixed bed having an inner diameter of 20mm and a length of 1200mmIn the reactor, the lower part of the catalyst is supported by glass balls, and the upper part is filled with glass balls for vaporizing and preheating raw materials. The raw materials for the reaction are toluene and carbon nonaromatic hydrocarbon, the weight ratio of which is about 60/40, and the raw materials comprise, by weight, 0.08% of benzene, 58.14% of toluene, 0.15% of ethylbenzene, 0.50% of xylene, 1.14% of propyl benzene, 15.05% of methyl ethyl benzene, 23.61% of trimethylbenzene, 0.80% of carbon decaaromatic hydrocarbon, 0.53% of the others, and 2.0hr at WHSV^-1The reaction pressure is 3.0MPa, the hydrogen/hydrocarbon molecular ratio is 4.4/1, the reaction temperature is 375 ℃, the total conversion rate of toluene and carbon nonaarene is 42.9 percent, the conversion rate of toluene is 35.44 percent, the conversion rate of carbon nonaarene is 57.96 percent, and the selectivity of generating benzene and carbon octaarene is 96.7 percent. The reaction liquid product contains 8.84 percent of benzene, 38.5 percent of toluene, 32.07 percent of C-octaarene, 17.16 percent of C-nonaarene and 2.04 percent of C-decaarene by weight percentage. [ example 3 ]

The catalyst prepared by the method of example 1 had a silica to alumina ratio of SiO₂/Al₂O₃22 (mol/mol), catalyst pore size 6 Å, and substantially the same reaction conditions as in example 2, except that the reaction temperature was 380 ℃, the feed composition was, in weight percent, 0.08% benzene, 59.75% toluene, 0.21% ethylbenzene, 0.56% xylene, 1.59% propylbenzene, 11.58% ethylbenzene, 21.63% trimethylbenzene, 4.12% carbano-arene, and 0.48% others, the total conversion of toluene and carbano-arene was 42.20%, the conversion of toluene was 36.57%, the conversion of carbano-arene was 54.79%, and the selectivity to benzene and carbano-octaarene was 97.4%, the reaction liquid product composition was, in weight percent, 8.47% benzene, 39.07% toluene, 32.04% carbano-octaarene, 16.22% carbano-nonaarene, and 2.89% carbano more than example 2, but the selectivity was significantly improved, and the conversion did not tend to decrease in 48 hours, indicating good stability [ example 4 ] (example 4 ]

The catalyst prepared by the method of example 1 had a silica to alumina ratio of SiO₂/Al₂O₃25 (mol/mol), a catalyst pore diameter of 6.5 Å, and substantially the same reaction conditions as in example 2 except that the starting materials consist, in weight percent, of 0.08% benzene and60.24% of benzene, 0.20% of ethylbenzene, 0.54% of xylene, 1.69% of propylbenzene, 11.93% of methyl ethyl benzene, 22.08% of trimethylbenzene, 2.76% of carbon deca-arene and 0.48% of other components, the reaction time is 700-1000 hours (0-700 hours are other reaction condition tests), the total conversion rate of toluene and carbon nona-arene is maintained to be about 42.50%, the reaction temperature is increased from 397 ℃ to 400 ℃, the temperature increasing speed is slow, the components of reaction liquid products comprise 8.72% of benzene, 2.06% of ethylbenzene and 2.06% of xylene in percentage by weight32.75 percent and the average content of the decaarene is 2.65 percent, which shows that the activity of the catalyst is stable, no decaarene is generated in the reaction, and the content of the decaarene in the product is lower than that in the raw material. [ example 5 ]

Catalyst prepared by the method of example I having a silica to alumina ratio of SiO₂/Al₂O₃18 (mol/mol), catalyst pore diameter 8 Å, with the reaction feed composition of example 4 at a WHSV of 0.5 h^-1The reaction pressure is 2.0MPa, the hydrogen/hydrocarbon molecular ratio is 6/1, and the reaction temperature is 340 ℃, so that the total conversion rate of toluene and carbon nonaarene is 41.4%, the conversion rate of toluene is 34.98%, the conversion rate of carbon nonaarene is 55.22%, the selectivity of benzene and carbon octaarene is 96.8%, the reaction liquid product comprises, by weight percent, 7.54% of benzene, 39.79% of toluene, 32.68% of carbon octaarene, 16.69% of carbon nonaarene and 2.86% of carbon decaarene. [ example 6 ]

Catalyst prepared by the method of example 1 having a silica to alumina ratio of SiO₂/Al₂O₃16 (mol/mol), a catalyst pore diameter of 4 Å, and the catalyst composition of example 4, but with a decaaromatic content of 8.0% by weight and a WHSV of 0.9 h^-1The reaction pressure was 4.0MPa, the hydrogen/hydrocarbon molecular ratio was 6/1, and the reaction temperature was 376 ℃. The reaction results showed that the total conversion of toluene and nona-carbon aromatics was 40.6%, the conversion of toluene was 34.9%, and the conversion of nona-carbon aromatics was 52.8%. The composition of the reaction liquid product in weight percentage is 7.63% of benzene, 37.94% of toluene, 33.38% of C-eight aromatic hydrocarbon, 16.69% of C-nine aromatic hydrocarbon and 3.21% of C-ten aromatic hydrocarbon.

Claims

1. A toluene disproportionation and transalkylation process is characterized in that raw material toluene contains nona-and deca-aromatics, mordenite is used as a catalyst, the reaction temperature is 320-550 ℃, and the weight space velocity of the raw material is 0.5-2.0 hours^-1Under the conditions of (1) reacting in a fixed bed to produce benzene, ethylbenzene and xylenes, characterized in that the mordenite catalyst has a silica-alumina ratio of SiO₂/Al₂O₃The molecular ratio is 10-30 mol/mol, the pore diameter of the catalyst is 4-8 Å, the hydrogen/hydrocarbon molecular ratio is 4-10 mol/mol, and the reaction pressure is 1.0-8.0 MPa.

2. The toluene disproportionation and transalkylation process of claim 1 wherein the reaction pressure is 2.0-5.0 MPa.

3. The toluene disproportionation and transalkylation process of claim 1 wherein the reaction temperature is 340-480 ℃.

4. The toluene disproportionation and transalkylation process of claim 1 wherein the ratio of Si to Al is SiO₂/Al₂O₃The molecular ratio is 15 to 25 mol/mol.

5. The toluene disproportionation and transalkylation process of claim 1 wherein the hydrogen/hydrocarbon molecular ratio is in the range of 4 to 8 moles/mole.

6. The toluene disproportionation and transalkylation process of claim 1 wherein the mordenite catalyst has a pore size of 6 to 8 Å.