A process for the preparation of linear alkylbenzenes

Abstract

The application relates to a preparation method of straight-chain alkylbenzene, characterized in that, under the conditions of an alkylation reaction and in the presence of an auxiliary agent, an alkylation reaction is caused by contacting an aromatic hydrocarbon and a long-chain alkene with a catalyst in a reactor, the auxiliary agent is a low-carbon alkane, and the catalyst is concentrated sulfuric acid or a mixed acid mainly composed of concentrated sulfuric acid. The preparation method solves the technical problem that benzene and concentrated sulfuric acid contact to generate benzene sulfonic acid, reduces acid consumption, has high long-chain alkene conversion rate and high selectivity of the target product, and has industrial practicability.

Description

Technical Field

[0001] This invention relates to a method for preparing alkylbenzenes, and more specifically to a method for preparing linear alkylbenzenes. Background Technology

[0002] Linear alkylbenzenes (LABs) are important aromatic organic chemical raw materials. Further sulfonation and neutralization yield linear alkylbenzene sulfonates (LAS), which are excellent anionic surfactants and are key raw materials in household and industrial detergents. LABs are produced by the alkylation reaction of benzene and linear olefins in the liquid phase. This reaction is a typical Friedel-Crafts reaction, where, under the action of an acidic catalyst, the olefin reacts with H₂O. + A carbocation is formed, which then undergoes electrophilic addition with the conjugated π electrons of the benzene ring to form an alkylbenzene; since the stability of the carbocation increases with the degree of substitution: (CH3)3C + >(CH3)2CH + >CH3CH2 + CH3 + Therefore, double bond shifts occur, resulting in a mixture of various alkylbenzene isomers in the final product. The properties of the LAS obtained by sulfonation vary depending on the position of the benzene ring on the alkylbenzene carbon chain: for example, an increase in 2-LAB in the product can improve the biodegradability of the detergent; while an increase in 3-LAB can improve the detergency of the detergent. Industrially, straight-chain alkylbenzenes are obtained from benzene and long-chain olefins through alkylation reactions, often using aluminum trichloride, liquid hydrofluoric acid, or solid acid processes.

[0003] US5386072A discloses an improved aluminum trichloride process, characterized by using powdered aluminum trichloride and aluminum as catalysts, with a molar ratio of n-olefins containing 7-20 carbon atoms to chlorinated paraffins containing 7-20 carbon atoms of 70:30-99:1. Aluminum trichloride catalysts readily form flocculent precipitates, leading to difficulties in product separation and catalyst recovery, low equipment efficiency, and high energy consumption.

[0004] The liquid acid process for hydrofluoric acid has relatively low reaction temperature and pressure, and the technology is mature, highly practical, and has low material and energy consumption. However, hydrofluoric acid is toxic and highly corrosive. Once leaked, it can easily vaporize and spread, causing major public safety and environmental incidents. As people's requirements for public safety and environmental protection continue to increase, hydrofluoric acid plants need to undergo multiple modifications to reduce safety and environmental risks before they can continue to operate.

[0005] UOP's Delta process is a solid acid process, which has advantages such as low corrosivity and safety and environmental friendliness. However, due to the more stringent reaction conditions compared to liquid acid processes, the catalyst has a shorter lifespan and faster deactivation during the reaction, requiring periodic regeneration, which is quite troublesome, and resulting in high raw material consumption and high energy consumption. In the alkylation method disclosed in CN1210509A, the activity duration of the mordenite zeolite catalyst after hydrogen fluoride treatment is less than 500 hours.

[0006] Sulfuric acid is a commonly used catalyst for liquid acid-catalyzed alkylation reactions, possessing advantages such as high activity, good product quality, and strong raw material applicability. It is safer than hydrofluoric acid, and the waste acid problem has been effectively resolved. In recent years, sulfuric acid alkylation units have been applied to the production of alkylated gasoline, and their quantity and processing capacity have developed rapidly. However, if concentrated sulfuric acid is used as a catalyst for the alkylation reaction of benzene with long-chain olefins, the high freezing point of benzene (freezing below 6°C) limits the reaction temperature, affecting reaction efficiency and the selectivity of the target product. Furthermore, at higher reaction temperatures, concentrated sulfuric acid reacts with benzene to form benzenesulfonic acid, increasing acid consumption and reducing the selectivity of the target product, making the sulfuric acid process for benzene alkylation with long-chain olefins difficult to truly apply industrially. Summary of the Invention

[0007] The purpose of this invention is to address the problems encountered in the alkylation of benzene with long-chain olefins using the sulfuric acid process, and to provide a method for preparing linear alkylbenzenes by alkylation of benzene with long-chain olefins that can reduce acid consumption, has high selectivity for the target product, and is industrially practical.

[0008] To achieve the objective of this invention, the present invention provides a method for preparing linear alkylbenzenes, characterized in that, under alkylation reaction conditions and in the presence of an auxiliary agent, the method includes contacting an aromatic hydrocarbon and a mixed alkene feedstock containing long-chain olefins with a catalyst in a reactor to undergo an alkylation reaction, wherein the auxiliary agent is a low-carbon alkane, and the catalyst is concentrated sulfuric acid or a mixed acid mainly composed of concentrated sulfuric acid.

[0009] In the preparation method described above, the aromatic hydrocarbon is a monocyclic aromatic hydrocarbon; the aromatic hydrocarbon has a side chain with 0 to 8 carbon atoms, preferably 0 to 4 carbon atoms. It includes, but is not limited to, one or a mixture of several of benzene, toluene, and o-xylene.

[0010] In the preparation method described above, the long-chain olefin includes C 10 ~C 14 A mixture of one or more of the long-chain olefins, including but not limited to one or more of decene, undecene, dodecene, tridecene, and tetradecene.

[0011] In the preparation method described above, the volume ratio of the aromatic hydrocarbon to the mixed olefin feedstock containing long-chain olefins is 4 to 20:1, preferably 12 to 20:1, and the mixed olefin feedstock is expressed as a mole fraction.

[0012] In the preparation method described above, the catalyst is concentrated sulfuric acid or a mixed acid with concentrated sulfuric acid as the main component, preferably concentrated sulfuric acid with a concentration of 90% to 99.2% or a mixed acid with concentrated sulfuric acid of that concentration as the main component. The volume ratio of the concentrated sulfuric acid to the aromatic hydrocarbon is 0.9 to 1.2:1, preferably 1.0 to 1.1.

[0013] In this invention, low-carbon alkanes are added as alkylation reaction promoters. The low-carbon alkanes are preferably one or more C3-C5 alkanes, such as propane, n-butane, isobutane, n-pentane, isopentane, neopentane, etc. Since isobutane reacts with the mixed dilute solution under these reaction conditions, the separation of C5 alkanes is difficult, and propane is less effective than n-butane; therefore, n-butane is preferred as the low-carbon alkanes used as reaction promoters.

[0014] In the alkylation reaction conditions described, the reaction temperature is -10 to 10°C, preferably -5 to 5°C.

[0015] This invention solves the technical problem of benzenesulfonic acid being generated when benzene and concentrated sulfuric acid react, by adding low-carbon alkanes as alkylation reaction promoters and controlling the alkylation reaction conditions at -10 to 10°C, preferably below the freezing point of benzene (6°C). This makes the reaction no longer limited by the reaction temperature, improves the reaction efficiency and target product selectivity, reduces sulfuric acid consumption, and has high conversion rate of long-chain olefins and high selectivity of target products, making it industrially practical. Detailed Implementation

[0016] The present invention will be further illustrated by the following examples, but these examples are not intended to limit the invention.

[0017] Experimental methods not specified in the examples are generally performed under standard conditions.

[0018] Example 1

[0019] Add 38.5 mL of benzene and 80.0 mL of concentrated sulfuric acid (98.0% wt) to a batch reactor. Pressurize the reactor with N2 to 0.2 MPa and then introduce low-carbon alkane (butane, chemically pure) as an auxiliary agent. Control the reaction temperature at -4℃ and the stirring speed at 800 rpm.

[0020] The raw material dodecene (experimental grade, dodecene content of 94.8%, and 2.3% C10, 2.4% C11, and 0.5% C12 alkanes) was premixed with 30.0 mL of benzene in a raw material tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0021] The volume ratio of benzene to n-butane is 8:1, and the molar ratio of benzene to dodecene is 18:1.

[0022] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0023] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0024] The conversion rate of dodecene was 100%, and the selectivity of dodecylbenzene was 98.6%, of which the selectivity of 2-LAB was 19.4%.

[0025] Comparative Example 1

[0026] This comparative example illustrates the reaction without the addition of any additives.

[0027] Add 38.2 mL of benzene and 79.0 mL of concentrated sulfuric acid (98.0% wt) to a batch reactor, and pressurize with N2 to 0.2 MPa. Control the reaction temperature at -4℃ and the stirring speed at 800 rpm.

[0028] Crystals appeared in the reactor. Based on the freezing point of benzene being 6°C, it is presumed to be benzene crystals.

[0029] The raw material dodecene (experimental grade, dodecene content of 94.8%, and 2.3% C10, 2.4% C11, and 0.5% C12 alkanes) was premixed with 30.0 mL of benzene in a raw material tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0030] The molar ratio of benzene to dodecene is 18:1.

[0031] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0032] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0033] The dodecene conversion rate was 92.7%, the dodecylbenzene selectivity was 74.6%, and the 2-LAB selectivity was 10.3%.

[0034] Comparative Example 2

[0035] This comparative example illustrates the reaction using hydrofluoric acid as a catalyst.

[0036] Add 37.6 mL of benzene and 79.0 mL of hydrofluoric acid (commercially available, concentration 99.0% (wt)) to a batch reactor, and pressurize with N2 to 0.2 MPa. Control the reaction temperature at 20℃ and the stirring speed at 800 rpm.

[0037] The raw material dodecene (experimental grade, dodecene content of 94.8%, and 2.3% C10, 2.4% C11, and 0.5% C12 alkanes) was premixed with 30.0 mL of benzene in a raw material tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0038] The molar ratio of benzene to dodecene is 18:1.

[0039] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0040] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0041] The conversion rate of dodecene was 100%, and the selectivity of dodecylbenzene was 97.1%, of which the selectivity of 2-LAB was 15.5%.

[0042] Example 2

[0043] Add 38.0 mL of benzene and 79.1 mL of concentrated sulfuric acid (98.0% wt) to a batch reactor. Pressurize the reactor with N2 to 1.5 MPa and then introduce low-carbon alkane (propane, chemically pure) as an auxiliary agent. Control the reaction temperature at 0°C and the stirring speed at 1000 rpm.

[0044] Long-chain mixed olefins were used as raw materials, and the composition and content of the raw materials are shown in Table 1.

[0045] Table 1

[0046] decene 0.6 decane 7.2 Undecane 29.6 Undecene 3.7 Dodecene 3.5 dodecane 23.8 Tridecene 4.3 Tridecane 25.3 1,2,3,5-Tetramethylbenzene 0.3 1,4-Dimethyl-2-(2-methylpropyl)-benzene 0.6 Pentylbenzene 0.2 Hexylbenzene 0.3 tert-butylbenzene 0.4 1-Methylbutylbenzene 0.2

[0047] The above-mentioned long-chain mixed olefins were premixed with 30.0 mL of benzene in a feed tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0048] The volume ratio of benzene to propane is 5:1. The molar ratio of benzene to the mixed olefin feedstock of long-chain olefins is 12:1 (calculated based on the amount of benzene added and the content of each component in the mixed dilute).

[0049] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0050] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0051] The olefin conversion rate was 100%, the alkylbenzene selectivity was 97.4%, and the 2-LAB selectivity was 18.7%.

[0052] Comparative Example 3

[0053] Add 38.2 mL of benzene and 79.5 mL of concentrated sulfuric acid (98.0% wt) to a batch reactor, and pressurize with N2 to 1.5 MPa. Control the reaction temperature at 0℃ and the stirring speed at 1000 rpm.

[0054] Crystals appeared in the reactor. Based on the freezing point of benzene being 6°C, it is presumed to be benzene crystals.

[0055] Long-chain mixed olefins were used as raw materials, and the composition and content of the raw materials are shown in Table 1.

[0056] The above-mentioned long-chain mixed olefins were premixed with 30.0 mL of benzene in a feed tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0057] The molar ratio of benzene to long-chain olefins in the mixed olefin feedstock is 12:1.

[0058] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0059] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0060] The olefin conversion rate was 99.7%, the alkylbenzene selectivity was 95.9%, and the 2-LAB selectivity was 15.2%.

[0061] Comparative Example 4

[0062] This comparative example illustrates the reaction using hydrofluoric acid as a catalyst.

[0063] Add 37.9 mL of benzene and 79.0 mL of hydrofluoric acid (commercially available, concentration 99.0% (wt)) to a batch reactor, and pressurize with N2 to 0.2 MPa. Control the reaction temperature at 20℃ and the stirring speed at 1000 rpm.

[0064] The above-mentioned long-chain mixed olefins were used as raw materials, and the composition and content of the raw materials are shown in Table 1.

[0065] The above-mentioned long-chain mixed olefins were premixed with 30.0 mL of benzene in a feed tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0066] The molar ratio of benzene to long-chain olefins in the mixed olefin feedstock is 12:1.

[0067] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0068] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0069] The olefin conversion rate was 100%, the alkylbenzene selectivity was 97.1%, and the 2-LAB selectivity was 14.5%.

[0070] Example 3

[0071] Add 37.5 mL of toluene and 79.4 mL of catalyst to a batch reactor, pressurize with N2 to 0.2 MPa, and then introduce low-carbon alkanes as an auxiliary agent. Control the reaction temperature at -2℃ and the stirring speed at 1000 rpm.

[0072] The raw material dodecene (experimental grade, dodecene content of 94.8%, and 2.3% C10, 2.4% C11, and 0.5% C12 alkanes) was premixed with 30.0 mL of toluene in a raw material tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0073] The molar ratio of toluene to dodecene is 15:1. The volume ratio of toluene to n-butane is 12:1.

[0074] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0075] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0076] The dodecene conversion rate was 98.2%, the dodecylbenzene selectivity was 61.9%, and the 2-LAB selectivity was 7.6%.

[0077] Example 4

[0078] Add 38.0 mL of benzene and 80.0 mL of concentrated sulfuric acid (98.0% wt) to a batch reactor. Pressurize the reactor with N2 to 0.2 MPa and then introduce low-carbon alkane (propane, chemically pure) as an auxiliary agent. Control the reaction temperature at -4℃ and the stirring speed at 800 rpm.

[0079] The raw material dodecene (experimental grade, dodecene content of 94.8%, and 2.3% C10, 2.4% C11, and 0.5% C12 alkanes) was premixed with 30.0 mL of benzene in a raw material tank and fed into the reactor at a feed rate of 0.05 mL / min.

[0080] The volume ratio of benzene to propane is 8:1, and the molar ratio of benzene to dodecene is 18:1.

[0081] After the reaction is complete, turn off the stirring; take the reaction mixture after the reaction and let it stand to separate into two phases. The lower phase is the catalyst phase, and the upper phase is a mixture including alkylbenzene products and unreacted reaction raw materials.

[0082] The content of each component in the mixture of alkylbenzene products and unreacted reactants in the upper phase was determined by GC-MS.

[0083] The dodecene conversion rate was 100%, the dodecylbenzene selectivity was 97.5%, and the 2-LAB selectivity was 18.8%.

Claims

1. A method for preparing a straight-chain alkylbenzene, characterized in that, In the presence of an alkylation reaction condition and an auxiliary agent, benzene and long-chain olefins are brought into contact with a catalyst in a reactor to undergo an alkylation reaction. The auxiliary agent is propane, and the volume ratio of benzene to the auxiliary agent is 4~20:

1. The catalyst is concentrated sulfuric acid or a mixed acid with concentrated sulfuric acid as the main component. In the alkylation reaction condition, the reaction temperature is -10~5℃.

2. The preparation method according to claim 1, characterized in that, The long-chain olefin includes C 10 ~C 14 A mixture of one or more long-chain olefins.

3. The preparation method according to claim 1, characterized in that, The molar ratio of benzene to the long-chain olefin is 4~20:

1.

4. The preparation method according to claim 1, characterized in that, The volume ratio of benzene to the auxiliary is 12~20:

1.

5. The preparation method according to claim 1, characterized in that, The reaction temperature is -5~5℃.

6. The preparation method according to claim 1, characterized in that, The volume ratio of concentrated sulfuric acid to benzene is 0.9~1.2:

1.

7. The preparation method according to claim 6, characterized in that, The volume ratio of concentrated sulfuric acid to benzene is 1.0~1.1:1.