A synthetic method of p-tert-butyltoluene

Abstract

The present invention discloses a method for synthesizing p-tert-butyltoluene, which comprises the following steps: (1) impregnating MCM-22 molecular sieve in a solution containing phosphoric acid and / or phosphate, taking it out and calcining to obtain a modified MCM-22 molecular sieve; (2) using toluene and isobutene as reactants and the modified MCM-22 molecular sieve as a catalyst to carry out a reaction to obtain p-tert-butyltoluene. By preparing the modified MCM-22 molecular sieve catalyst, the present invention no longer uses liquid acid in the reaction process, greatly reducing the environmental protection pressure, and at the same time, there is no need to use relatively expensive corrosion-resistant equipment; by adding a small amount of tert-butanol to the raw material toluene, the polymerization of isobutene is inhibited, and the selectivity of p-tert-butyltoluene is improved.

Description

Technical Field

[0001] The present invention relates to a method for synthesizing p-tert-butyltoluene, belonging to the technical field of catalytic synthesis of monocyclic aromatic hydrocarbons. Background Art

[0002] p-tert-Butyltoluene is an important chemical raw material and organic intermediate. Its derivatives such as p-tert-butylbenzaldehyde, p-tert-butylbenzoic acid, methyl p-tert-butylbenzoate, p-tert-butylbenzyl chloride, etc. all have wide applications. For example, p-tert-butylbenzoic acid can be mainly applied to: ① an improver in the synthesis of alkyd resins; ② an additive in oils such as cutting oils and lubricating oils; ③ a nucleating agent for polypropylene; ④ its metal salts can be used as stabilizers for polyvinyl chloride. p-tert-Butylbenzyl chloride is widely used in the production of pharmaceuticals and pesticides, and p-tert-butylbenzaldehyde is an important raw material for fine chemicals such as pharmaceuticals, dyes, and fragrances, as well as electronic chemicals, and is also an intermediate for producing anti-allergy drugs, especially with a large demand in the synthesis of fragrances and flavors.

[0003] According to different raw materials, the synthesis of p-tert-butyltoluene can be mainly divided into the following three routes:

[0004] ① Alkylation of toluene with isobutene: The catalysts used in this method are concentrated H2SO4, clay / calcium oxide, etc. The reaction yield is above 80%. Due to the difficult transportation of isobutene raw materials, this method is mainly applied to enterprises where isobutene is easily available; moreover, a large amount of liquid waste acid is generated during the production process, resulting in great environmental protection pressure.

[0005] ② Alkylation of toluene with tert-butanol: The catalysts used in this method are urea / sulfuric acid, TeCl4, BF 3- polyphosphoric acid, HF / FSO3H, etc. The reaction yield is between 44 - 85%, and the yield is relatively low.

[0006] ③ Alkylation of toluene with tert-butyl chloride: The catalysts used in this method are anhydrous A1C13, Mo(CO)6, (NaCl + AlCl3), etc. The reaction yield is about 73%. Since a large amount of HCl gas is generated during the reaction, strict requirements are imposed on the equipment.

[0007] For the above-mentioned first synthesis route of alkylation of toluene with isobutene, Chinese Patent CN104926590A uses a kettle reactor for the alkylation reaction of toluene with isobutene, introducing a new protonic acid - p-toluenesulfonic acid as the catalyst, enabling the alkylation reaction to be carried out under atmospheric pressure, reducing the amount of concentrated sulfuric acid used to one-twelfth of the original amount, and the p-toluenesulfonic acid and concentrated sulfuric acid catalysts can be recycled multiple times, generally more than 16 times. However, the use of concentrated sulfuric acid cannot be completely avoided, and the reaction is an intermittent process, with relatively cumbersome operations and unable to achieve continuous production.

[0008] Considering that the use of liquid acid catalysts inevitably causes serious problems such as equipment corrosion and environmental pollution. Therefore, researchers have gradually used solid catalysts to replace liquid catalysts for the catalytic synthesis of p-toluenesulfonic acid. However, this solid catalyst is mostly applied in the case of using toluene and tert-butanol as reaction raw materials. For example, Patent CN 102199068 A discloses a production method of p-tert-butyltoluene. This reaction route uses toluene and tert-butanol as reaction raw materials and catalytically prepares p-tert-butyltoluene through the mesoporous molecular sieve catalyst MCM-41, and the selectivity of the reaction is relatively high, reaching more than 80%. When using toluene and isobutene as reaction raw materials and using solid acid to catalytically synthesize p-tert-butyltoluene, there are few reference literatures. When directly using molecular sieve as the catalyst, the selectivity and yield of the reaction are not high. Summary of the Invention

[0009] The technical problem to be solved by the present invention is that when using a solid acid catalyst to catalyze the synthesis of p-tert-butyltoluene from toluene and isobutene, there are many side reactions, and the product selectivity still needs to be improved.

[0010] To solve any one or more of the above technical problems, the present invention provides a method for synthesizing p-tert-butyltoluene, including the following steps:

[0011] (1) Immerse MCM-22 molecular sieve in a solution containing phosphoric acid and / or phosphate, take it out and calcine to obtain modified MCM-22 molecular sieve;

[0012] (2) Use toluene and isobutene as reactants and modified MCM-22 molecular sieve as the catalyst to carry out the reaction to obtain p-tert-butyltoluene.

[0013] The present invention modifies MCM-22 molecular sieve with phosphoric acid / phosphate, and unexpectedly finds that the modified MCM-22 molecular sieve can reduce side reactions and improve the product selectivity in the reaction of catalytically synthesizing p-tert-butyltoluene from toluene and isobutene as reactants.

[0014] The inventor tested the specific surface area of the MCM-22 molecular sieve before and after modification, and found that the specific surface area decreased after modification, and the average pore diameter increased from about 50 Å to about 95 Å, that is, some micropores were blocked, so the average pore diameter increased.

[0015] Therefore, the inventor speculated based on the above test results that the modification of MCM-22 molecular sieve with phosphoric acid / phosphate can adjust the pore diameter of the molecular sieve pore channel, thereby reducing the formation of m-tert-butyltoluene. Theoretically analyzed, due to the decrease in the amount of strong acid and the increase in the amount of weak acid in the modified catalyst, it can not only inhibit the polymerization reaction of isobutene on the surface of MCM-22 molecular sieve, but also will not generate other by-products.

[0016] Preferably, step (2) further includes adding tert-butanol to the reactants and then carrying out the reaction. The present invention surprisingly discovers that adding a small amount of tert-butanol in the reaction can inhibit the polymerization of isobutene and improve the selectivity to p-tert-butyltoluene.

[0017] In step (2), tert-butanol is added to toluene, and the mass fraction of tert-butanol in the toluene solution is 2-6%.

[0018] Preferably, in step (2), the reaction is divided into three stages. In the first stage of the reaction, toluene and a part of isobutene are added as reactants, and in the second and third stages of the reaction, the remaining part of isobutene is added as a reactant. Specifically, in terms of molar ratio, the isobutene added in the first stage, the second stage, and the third stage respectively accounts for 50%, 30%, and 20% of the total isobutene, or each stage accounts for 1 / 3.

[0019] As some preferred embodiments of the present invention, two additional feed inlets are provided in the middle of the reactor so that isobutene can be introduced. The positions of the two feed inlets can divide the length direction of the reactor into three equal parts, so that the catalyst dosage in each stage of the reactor is the same, and the amount of isobutene introduced through each feed inlet is also the same.

[0020] Preferably, in step (1), the specific surface area of the MCM-22 molecular sieve is 450-500 m 2 / g, and the silica-alumina ratio is 50-60.

[0021] Preferably, in step (1), the impregnation time of the MCM-22 molecular sieve is 1-5 hours.

[0022] Preferably, in step (1), the calcination temperature is 400-700 °C, and the calcination time is 2-6 hours.

[0023] Preferably, in step (1), the phosphate is selected from one or more of ammonium dihydrogen phosphate, ammonium hydrogen phosphate, and sodium metaphosphate; preferably, the mass fraction of the phosphoric acid or phosphate solution is 8-20%.

[0024] Preferably, the molar ratio of toluene to isobutene is 2.5-4.5:1.

[0025] Preferably, the space velocity of toluene feed (both refer to the volume space velocity, the same below) is 2.0-4.0 h -1 . Specifically, it means that the volume space velocity of the toluene fed into the catalyst bed of the first-stage reactor is 2.0-4.0 h -1 . The above toluene can be a toluene solution, that is, it may contain tert-butanol.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. The present invention synthesizes p-tert-butyltoluene by using a modified MCM-22 molecular sieve catalyst. During the reaction process, liquid acid is no longer used, significantly reducing the environmental protection pressure. At the same time, there is no need to use relatively expensive corrosion-resistant equipment. The present invention uses a solid acid catalyst to modify the MCM-22 molecular sieve. Compared with the unmodified MCM-22 molecular sieve, it can improve the selectivity of the product p-tert-butyltoluene. Compared with other molecular sieve (such as MCM-41 molecular sieve) catalysts, the present invention changes the reaction raw materials by using isobutene instead of tert-butanol to react with toluene, providing a new catalytic synthesis route for the synthesis of p-tert-butyltoluene.

[0028] 2. By adding a small amount of tert-butanol to the raw material toluene, the polymerization of isobutene is inhibited, and the selectivity of p-tert-butyltoluene is improved. Brief Description of the Drawings

[0029] Figure 1 It shows the XRD pattern of the MCM-22 molecular sieve synthesized by the present invention. Detailed Embodiments

[0030] In the examples and comparative examples, the conversion rate of isobutene and the selectivity of each product are calculated by the following formula.

[0031]

[0032]

[0033]

[0034]

[0035] The MCM-22 molecular sieve used in the present invention is self-made, and the preparation method is as follows: Dissolve 1.0 g of sodium aluminate in 80 mL of distilled water, add 0.8 g of sodium hydroxide, and after complete dissolution, slowly add 0.15 mL of the template agent cyclohexylamine (HMI) dropwise with a dropper. After stirring, add 50 mL of a 30% mass fraction silica sol (calculated as oxides, the molar ratio of the reaction solution is SiO2∶Al2O3∶Na2O∶HMI∶H2O = 1∶0.015∶0.15∶0.03∶45). Continue to stir the obtained solution for 2 h and then put it into a crystallization kettle, and carry out static crystallization in an oven at 150 °C for 48 h. The solid matter is obtained by suction filtration, washed and then dried overnight in an oven at 100 °C, and then calcined at 550 °C for 5 h to remove the template agent to obtain the finished product. The finished molecular sieve product is used for XRD testing to obtain the XRD pattern ( Figure 1 ), and after verification, this finished product is the MCM-22 molecular sieve.

[0036] After testing, the characteristics of the molecular sieve obtained by the present invention are: the specific surface area is 480 m 2 / g, average pore diameter 51 Å, silica-alumina ratio 55.

[0037] In the present invention, all chemical reagents other than MCM-22 molecular sieve are obtained through outsourcing.

[0038] In the present invention, the test principle for selectivity and conversion rate is as follows: The reaction mixture is passed through a gas-liquid separation tank, the compositions of the gas and liquid phases are analyzed respectively, the weight of the liquid phase is weighed, the weight of the gas phase is calculated based on the feed amount, the amounts of various products are calculated based on the weight and composition, and the conversion rate and selectivity are calculated according to the above formula.

[0039] Example 1

[0040] This example provides a method for synthesizing p-tert-butyltoluene, and the steps are as follows:

[0041] (1) Weigh 12.5 g of diammonium hydrogen phosphate and dissolve it in 90 mL of water. Immerse 50 mL of MCM-22 molecular sieve (self-made, characterized by: specific surface area 480 m 2 / g, average pore diameter 51 Å, silica-alumina ratio 55) for 3 hours in a 40 °C water bath. After filtration and washing, dry at 120 °C for 4 hours and calcine at 550 °C for 4 hours to obtain a modified MCM-22 molecular sieve catalyst (characterized by: specific surface area 305 m 2 / g, average pore diameter 90 Å).

[0042] (2) Load the above catalyst into a fixed-bed adiabatic tubular reactor in three sections (the loading amount of each section of catalyst is the same). The structure of the reactor is: There are 2 additional feed ports in the middle of the tubular reactor. The tubular reactor is divided into three sections of equal length in the length direction. The feed of isobutene in each section is the same. All tert-butanol and toluene are added during the reaction in the first section; 60 mL of the modified MCM-22 molecular sieve catalyst is loaded into the reactor and evenly loaded in three sections.

[0043] Toluene containing 5% tert-butanol (mass ratio of tert-butanol to toluene is 5:95) and part of isobutene (1 / 3 of the total amount) are preheated to 150 °C and then fed into the catalyst bed layer of the first-section reactor for reaction. The feed amount of toluene (containing 5% tert-butanol) per hour is three times that of the catalyst (volume space velocity), i.e., 180 mL. The total molar ratio of toluene / isobutene is 3.5, and the reaction pressure is 1.0 MPa.

[0044] (3) Part of isobutene (1 / 3 of the total amount) is preheated to 150 °C and then fed into the inlet of the second-section reactor, mixed with the material after the reaction in the first-section reactor, and enters the second-section reactor for reaction under the same reaction conditions as in step (2).

[0045] (4) Preheat the remaining isobutene (1 / 3 of the total amount) to 150 °C and then feed it into the inlet of the third reactor. Mix it with the material after the reaction in the second reactor and enter the third reactor for reaction under the same reaction conditions as in step (2).

[0046] After the above three-stage reaction, the conversion rate of isobutene is 99.0%, the selectivity for p-tert-butyltoluene is 85.0%, the selectivity for m-tert-butyltoluene is 14.0%, and the selectivity for isobutene polymer is 1.0%.

[0047] Example 2

[0048] This example is the same as Example 1, except that all raw materials are preheated to 170 °C before entering the reactor.

[0049] After the reaction, the conversion rate of isobutene is 99.6%, the selectivity for p-tert-butyltoluene is 84.2%, the selectivity for m-tert-butyltoluene is 12.6%, and the selectivity for isobutene polymer is 3.2%.

[0050] Example 3

[0051] This example is the same as Example 1, except that the feed molar ratio of toluene / isobutene is 2.5.

[0052] After the reaction, the conversion rate of isobutene is 98.5%, the selectivity for p-tert-butyltoluene is 80.0%, the selectivity for m-tert-butyltoluene is 15.4%, and the selectivity for isobutene polymer is 4.6%.

[0053] Example 4

[0054] This example is the same as Example 1, except that tert-butanol is not added to the reactants.

[0055] After the reaction, the conversion rate of isobutene is 99.6%, the selectivity for p-tert-butyltoluene is 80.1%, the selectivity for m-tert-butyltoluene is 11.5%, and the selectivity for isobutene polymer is 8.4%.

[0056] Example 5

[0057] This example is the same as Example 1, except that in the reactants, the addition amount of tert-butanol in toluene is 2.5% (i.e., the mass ratio of tert-butanol to toluene is 2.5:97.5).

[0058] After the reaction, the conversion rate of isobutene is 99.4%, the selectivity for p-tert-butyltoluene is 82.4%, the selectivity for m-tert-butyltoluene is 10.2%, and the selectivity for isobutene polymer is 7.4%.

[0059] Example 6

[0060] This example is the same as Example 1, except that: in the reactants, the addition amount of tert-butanol in toluene is 10% (i.e., the mass ratio of tert-butanol to toluene is 10:90).

[0061] After the reaction, the conversion rate of isobutene is 72.4%, the selectivity for p-tert-butyltoluene is 89.5%, the selectivity for m-tert-butyltoluene is 9.7%, and the selectivity for isobutene polymer is 0.8%.

[0062] Example 7

[0063] This example is the same as Example 1, except that: the molecular sieve MCM-22 is modified with phosphoric acid.

[0064] After the reaction, the conversion rate of isobutene is 99.4%, the selectivity for p-tert-butyltoluene is 85.0%, the selectivity for m-tert-butyltoluene is 14.0%, and the selectivity for isobutene polymer is 1.0%.

[0065] Example 8

[0066] This example is the same as Example 1, except that: the molecular sieve MCM-22 is modified with a 10% by mass solution of diammonium hydrogen phosphate.

[0067] After the above three-stage reaction, the conversion rate of isobutene is 99.3%, the selectivity for p-tert-butyltoluene is 84.8%, the selectivity for m-tert-butyltoluene is 13.5%, and the selectivity for isobutene polymer is 1.7%.

[0068] Comparative Example 1

[0069] This comparative example is the same as Example 1, except that: the catalyst used in step (2) is unmodified MCM-22 molecular sieve of the same mass, that is, step (1) of Example 1 is not required.

[0070] After the reaction, the conversion rate of isobutene is 99.5%, the selectivity for p-tert-butyltoluene is 75.6%, the selectivity for m-tert-butyltoluene is 16.5%, and the selectivity for isobutene polymer is 7.9%.

[0071] Comparative Example 2

[0072] This comparative example is the same as Comparative Example 1, except that: the catalyst used in step (2) is ZSM-5 molecular sieve of the same mass (purchased from Jiangsu Guoci New Materials Technology Co., Ltd.).

[0073] After the reaction, the conversion rate of isobutene is 99.0%, the selectivity for p-tert-butyltoluene is 72.3%, the selectivity for m-tert-butyltoluene is 14.5%, and the selectivity for isobutene polymer is 13.2%.

[0074] Comparative Example 3

[0075] This comparative example is the same as Example 1, except that: the catalyst used in step (2) is silica-alumina gel of the same mass (purchased from Qingdao Ocean Chemical Industry Co., Ltd.).

[0076] After the reaction, the conversion rate of isobutene is 86.1%, the selectivity for p-tert-butyltoluene is 65.2%, the selectivity for m-tert-butyltoluene is 19.8%, and the selectivity for isobutene polymer is 15.0%.

[0077] Comparative Example 4

[0078] This comparative example is the same as Comparative Example 1, except that: the catalyst used in step (2) is unmodified MCM-41 molecular sieve (purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.).

[0079] After the reaction, the conversion rate of isobutene is 92.6%, the selectivity for p-tert-butyltoluene is 76.3%, the selectivity for m-tert-butyltoluene is 20.2%, and the selectivity for isobutene polymer is 3.5%.

[0080] Comparative Example 5

[0081] This comparative example is the same as Example 1, except that: the catalyst used in step (2) is modified MCM-41 molecular sieve (purchased from Jiangsu Xianfeng Nano Materials Technology Co., Ltd.), that is, the object of modification is changed from MCM-22 to MCM-41.

[0082] After the reaction, the conversion rate of isobutene is 90.5%, the selectivity for p-tert-butyltoluene is 78.6%, the selectivity for m-tert-butyltoluene is 19.2%, and the selectivity for isobutene polymer is 2.2%.

[0083] Data analysis:

[0084] Comparing Example 1 and Comparative Example 1, it can be seen that for the molecular sieve catalyst modified by phosphate, although the catalytic activity slightly decreases (the conversion rate of isobutene decreases), the selectivity for p-tert-butyltoluene significantly increases, and the amount of isobutene polymer also significantly decreases.

[0085] Comparing Example 1 and Comparative Example 2, it can be seen that using ZSM-5 molecular sieve as the catalyst, although it also has good catalytic activity (high conversion rate of isobutene), due to the difference in the number and type of acid centers, there are more side reactions of isobutene polymerization, the content of isobutene polymer in the product is high, and the selectivity of the target product is low.

[0086] Comparing Example 1 and Comparative Example 3, it can be seen that due to the difference in acid centers, isobutene is prone to polymerization on the amorphous silica-alumina catalyst, and due to the lack of shape-selective effect of pores, the amount of m-tert-butyltoluene generated is more.

[0087] Comparing Comparative Example 1 and Comparative Example 4, it can be seen that since the pores are mainly mesopores, the shape selectivity is inferior to that of MCM-22 molecular sieve, so the selectivity of p-tert-butyltoluene is low; in addition, due to the difference in acid sites, its catalytic activity is also low (low conversion rate of isobutene).

[0088] Comparing Comparative Example 4 and Comparative Example 5, it can be seen that after modifying MCM-41 molecular sieve by the method of the present invention, the conversion rate of isobutene is further reduced, and the selectivity of p-tert-butyltoluene is also inferior to that of the catalyst prepared by the present invention.

[0089] It should be noted that the above-described embodiments are only used to explain the present invention and do not constitute any limitation to the present invention.

Claims

1. A method for synthesizing p-tert-butyltoluene, characterized in that, Comprising the following steps: (1) Immerse MCM-22 molecular sieve in a solution containing phosphoric acid and / or phosphate, take it out and obtain the modified MCM-22 molecular sieve through calcination; (2) Use toluene and isobutene as reactants and the modified MCM-22 molecular sieve as a catalyst to carry out a reaction to obtain p-tert-butyltoluene; Step (2) further includes adding tert-butanol to the reactants and then carrying out the reaction; In step (1), the specific surface area of the MCM-22 molecular sieve is 450-500 m 2 / g, and the silica-alumina ratio is 50-60; the impregnation time of the MCM-22 molecular sieve is 1-5 hours; the calcination temperature is 400-700 °C, and the calcination time is 2-6 hours.

2. The synthesis method according to claim 1, characterized in that, In step (2), tert-butanol is added to toluene, and the mass fraction of tert-butanol in the toluene solution is 2-12%; 3. The synthesis method according to claim 1 or 2, characterized in that, The phosphate in step (1) is selected from one or more of ammonium dihydrogen phosphate, ammonium hydrogen phosphate and sodium metaphosphate; 4. The synthesis method according to claim 1 or 2, characterized in that, In step (1), the mass fraction of the solution containing phosphoric acid and / or phosphate is 8-20%; 5. The synthesis method according to claim 1 or 2, characterized in that, The molar ratio of toluene to isobutene is 2.5-4.5:

1.

6. The synthesis method according to claim 1 or 2, characterized in that, The volumetric space velocity of toluene feed is 2.0 - 4.0 h -1 .

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