CN103664528A - Method for producing cyclohexanol - Google Patents

Abstract

The invention provides a method for producing cyclohexanol. The method uses benzene as a starting material to produce cyclohexanol through selective hydrogenation of benzene, addition and esterification of cyclohexene, and hydrogenation of cyclohexyl carboxylate. The characteristics of the present invention are: (1) Both the esterification and ester hydrogenation reactions have high selectivity and high atom utilization; (2) The process is environmentally friendly; (3) Reactive distillation is used for addition esterification, Not only can the reaction efficiency be significantly improved, but also the extraction, distillation and separation process can be simplified; (4) primary alcohol is co-produced while producing cyclohexanol.

Description

A kind of method of producing cyclohexanol

technical field

The invention relates to a method for producing cyclohexanol.

Background technique

Cyclohexanol is an important chemical raw material and solvent, which is mainly used in the production of nylon 6, nylon 66 and other products. Industrially, the production methods of cyclohexanol mainly include cyclohexane air oxidation method, phenol hydrogenation method and cyclohexene hydration method, among which cyclohexane oxidation method is the most common application.

Cyclohexane oxidation is currently the most important cyclohexanol production process. The process uses an oxidant (usually air) to oxidize cyclohexane to cyclohexyl hydroperoxide, and cyclohexyl hydroperoxide is decomposed to obtain a mixture of cyclohexanol and cyclohexanone (commonly known as KA oil). The advantages of this process are mild oxidation process conditions, less slagging, and long continuous operation period. The disadvantage is that the process route is long, the energy consumption is high, and the pollution is large. The conversion rate of cyclohexane in this process is only 3-5%; especially in the decomposition process of cyclohexyl hydroperoxide, the selectivity of cyclohexanol is poor, and the yield In addition, this process also produces a large amount of waste lye that is difficult to handle, which is still a worldwide environmental protection problem.

Phenol hydrogenation is a relatively clean technical route for the production of cyclohexanol, and has the advantages of short process flow and high product purity. The hydrogenation of phenol to cyclohexanol mainly adopts the gas phase hydrogenation method. This method usually adopts 3 to 5 reactors connected in series. Under the action of supported Pd catalyst, the yield of cyclohexanone and cyclohexanol can reach 90%-95% at 140-170°C and 0.1MPa. However, this process needs to vaporize phenol (heat of vaporization 69kJ·mol ^-1 ) and methanol (heat of vaporization 35.2kJ·mol ^-1 ), which requires high energy consumption, and the catalyst is prone to carbon deposition during use, resulting in a decrease in activity, and the shortage of phenol , expensive and the use of noble metal catalysts limit the industrial application of this method.

In the 1980s, Asahi Kasei Corporation of Japan developed a process for producing cyclohexene by partial hydrogenation of benzene and hydration of cyclohexene to produce cyclohexanol, and realized industrialization in 1990. Related Chinese patent applications include CN1079727A, CN1414933A and CN101796001A . Cyclohexene hydration is a relatively new production method of cyclohexanol. This method has high reaction selectivity and almost no three wastes in the process. However, there are disadvantages such as low reaction conversion rate and high requirements for cyclohexene purity. If high silicon ZSM-5 catalyst is used, the conversion rate of cyclohexene is only 12.5% after staying in two series slurry reactors for 2 hours.

The traditional methods for producing cyclohexene are dehydration of cyclohexanol and dehydrohalogenation of halocyclohexane. Partial hydrogenation of benzene and oxidative dehydrogenation of cyclohexane are two other methods for preparing cyclohexene. The partial hydrogenation of benzene to prepare cyclohexene mainly includes gas-phase method, liquid-phase method and homogeneous complexation hydrogenation method. The liquid-phase method can adopt a four-phase reaction system of gas (hydrogen), liquid (benzene), liquid (polar solvent), and solid (catalyst), such as the method of feeding benzene and hydrogen into a slurry containing catalyst and water . If a four-phase reaction system is adopted, the amount of water must be at least sufficient to form an oil-water two-phase, and metal salts are usually added to the water, and the preferred metal salts are zinc sulfate or cobalt sulfate. The reaction conditions of the liquid phase method are generally: reaction temperature 25-250°C; hydrogen partial pressure 0.1-20MPa, catalyst dosage 0.001-0.2 times the weight of water. Catalysts for the partial hydrogenation of benzene generally use one or more of metals such as Pt, Pd, Ru, Rh and Ni as the main catalyst component; in order to further improve hydrogenation activity and selectivity, K, One or more of metals such as Zr, Hf, Co, Cu, Ag, Fe, Mo, Cr, Mn, Au, la and Zn are used as additive components. The partial hydrogenation catalyst of benzene can be a supported or non-supported catalyst. The supported method can be ion exchange method, spray method, impregnation method, evaporative drying method, etc. The carrier used can be natural clay, sepiolite, ZrO ₂ , SiO ₂ , TiO ₂ , Al ₂ O ₃ , La ₂ O ₃ , activated carbon, insoluble sulfate, insoluble phosphate or molecular sieve, etc. Taking ruthenium-based catalysts as an example, supported catalysts can be prepared by impregnating ruthenium salts alone or together with other metal salts on the carrier, followed by drying and reducing; unsupported catalysts can be prepared by ruthenium salts alone or together with other metal salts It can be prepared by precipitation, followed by drying and reduction, or by direct reduction of ruthenium compounds or mixtures of ruthenium compounds and other metal compounds. The ruthenium-based catalyst and the method and device for hydrogenation of benzene are described in detail in CN102264471A.

JPA254634/1989 discloses a preparation method of cyclohexanol and cyclohexyl acetate, using a strongly acidic ion exchange resin as a catalyst to synthesize cyclohexanol and cyclohexyl acetate by the reaction of aqueous acetic acid and cyclohexene. The best result mentioned in this literature example is that the conversion rate of cyclohexene is 62.7%, the yield of cyclohexanol is 18.4%, and the yield of cyclohexyl acetate is 43.7%.

CN1023115C and JP Ping-313447 disclose a method for preparing cyclohexanol, using ZSM5 or high silica zeolite as a catalyst to synthesize cyclohexanol and cyclohexyl acetate by reacting acetic acid and cyclohexene in the presence of water. In this document, the yields of cyclohexanol and cyclohexyl acetate were only 12.5% and 65% respectively at 120°C for 4 hours.

EP0461580A2 and USP5254721 disclose a method for preparing cyclohexyl acetate from acetic acid and cyclohexene. The method adopts a tungsten-containing heteropolyacid catalyst, and the crystal water content in the heteropolyacid molecule is preferably 0-3. The best result given in the literature is that the dodecasilic tungstic acid catalyst completely free of crystal water obtained by roasting at 370°C for 3 hours, in a 200mL autoclave, add 61.5g of acetic acid, 13.5g of cyclohexene, and 5g of catalyst, Under the conditions of 0.5MPa and 130℃ for 0.5h, the conversion of cyclohexene was 95.2%, and the selectivity of cyclohexyl acetate was 99.2%. It can be seen that under the condition of very high acid-to-ene ratio, cyclohexene cannot be completely converted.

As can be known from the existing published literature, the existing literature has disclosed various solid acid catalysts for the addition esterification of acetic acid and cyclohexene. The addition esterification reaction generally adopts a tank reactor, and the reaction raw material is pure cyclohexene , even with a high acid-to-ene ratio, it is difficult to achieve complete conversion of cyclohexene.

Reactive distillation has been widely used in processes such as alcohol-ene etherification, alcohol esterification, transesterification, ester hydrolysis, acetal reaction, etc., but so far, no reactive distillation has been used for the addition of carboxylic acid and cyclohexene report on the process.

CN86105765A proposes a method for preparing alcohol by hydrogenation of carboxylic acid ester, which method is to hydrogenate carboxylic acid ester at high temperature, normal pressure or high pressure in the presence of a reduction-activated solid copper-containing catalyst, and the catalyst removes copper In addition, it also contains magnesium, at least one of lanthanide metals or actinide metals. The catalyst is represented by the following general formula before reduction activation: Cu _a M ¹ M ² _b A _c O _x , M ¹ is at least one of magnesium, lanthanide metal or actinide metal, M ² is selected from Ca, Mo, Rh , Pt, Cr, Zn, Al, Ti, V, Ru, Re, Pd, Ag and Au; A is an alkali metal; a is 0.1-4; b is 0-1.0; C is 0-0.5; x is A number that can meet the requirements of other elements for the total valence of oxygen. The alkali metal in the catalyst is an optional component which is introduced into the catalyst in the form of an alkali metal salt. The applicable carboxylate of this method and catalyzer is C1-C24 acyclic monovalent or divalent, saturated or unsaturated, linear or branched chain carboxylate, does not relate to cycloalkanols like cyclohexanol in the literature preparation.

CN1075048C proposes a method and catalyst for direct hydrogenation of carboxylic acid esters, comprising contacting and reacting one or more esters with hydrogen in the presence of a catalyst containing a copper compound, a zinc compound and at least one selected The catalyst is prepared from aluminum, zirconium, magnesium, a compound of a rare earth element or a mixture thereof as its components by calcining these catalyst components at a temperature ranging from 200 to less than 400°C, the method being in a liquid phase , Carried out at 170-250°C and 20.7-138 bar gauge pressure. The carboxylate suitable for the method and catalyst is C6-C22 dimethyl ester obtained by transesterification of natural oil, C6-C66 natural triglyceride or C6-C44 compound obtained by transesterification of natural triglyceride .

US4939307 proposes a process for ester hydrogenation to alcohol. The general formula is R ₁ -CO-OR ₂ or R ₄ O-CO-R ₃ -CO-OR ₂ (wherein R ₁ is H or C ₁ ~ C ₂₀ hydrocarbon group, R ₂ and R ₄ are C ₁ ~ C ₂₀ Hydrocarbon group, R ₃ is -(CH ₂ )n-group, n=1~10) ester mixed with H ₂ and CO, hydrogenation reaction is carried out at 30~150°C, 5~100 bar pressure to form alcohol, which The catalyst is composed of the following components: (a) a group VIII metal ion compound in the periodic table; (b) an alkoxide of an alkali metal or an alkaline earth metal; (c) an alcohol.

US4113662 and USP4149021 disclose a kind of ester hydrogenation catalyst, and this catalyst is made up of the element of cobalt, zinc, copper, oxide, hydroxide or carbonate, and the most suitable carboxylate of this catalyst is polyglycolide, The preparation of cycloalkanols is not mentioned in the literature.

US4611085 discloses a method for gas-phase hydrogenation of C ₁ -C ₂₀ carboxylic acid esters to produce alcohols. The catalyst is composed of a VIII group element, an auxiliary agent and a carbon carrier, wherein the VIII group element includes Ru, Ni, Rh, additives include IA (except Li), IIA group (except Be and Mg), lanthanide and actinide elements, and the BET specific surface area of the carbon support is greater than 100m ₂ /g. The hydrogenation reaction is carried out under the conditions of 100-400°C and gas space velocity of 100-120000h ^-1 . The alkali metals in the catalyst are introduced in the form of alkali metal salts, such as alkali metal nitrates, carbonates or acetates. The method is applicable to carboxylic acid esters that can be vaporized under reaction conditions. The carbon number of the alcohol-derived moiety in the carboxylic acid esters is preferably less than 5 and the carbon connected to oxygen is preferably a primary carbon.

GB2250287A discloses a method for hydrogenating fatty acid esters to produce alcohols. The method is characterized in that a copper-containing catalyst is used for hydrogenation and a certain amount of water is added to the ester raw material to maintain the activity of the catalyst. The applicable carboxylate is C12-C18 fatty acid methyl ester.

It can be known from the published literature that there is no information disclosure about the co-production of cyclohexanol and primary alcohol by the hydrogenation of cyclohexyl carboxylate in the prior art, and there is no selective hydrogenation of benzene, cyclohexene addition esterification, carboxylate Information on the hydrogenation of cyclohexyl esters to produce cyclohexanols and primary alcohols.

Contents of the invention

The invention provides a method for producing cyclohexanol, which uses benzene as a starting material to co-produce cyclohexanol and primary alcohol.

In the present invention, for stream, "A/B" represents the mixture of A and B; for catalyst, "A/B" represents "active component/carrier".

A method for producing cyclohexanol, comprising:

(1) Under the conditions of hydrogenation of benzene to cyclohexene, benzene and hydrogen undergo a hydrogenation reaction to obtain a stream containing cyclohexene;

(2) contacting the cyclohexene-containing stream obtained in step (1) with carboxylic acid, and an addition esterification reaction occurs under the action of the first catalyst; separating the reaction product to obtain a cyclohexyl carboxylate stream; The carboxylic acid is one or a mixture of two or more acyclic carboxylic acids with 1 to 24 carbon atoms;

(3) The cyclohexyl carboxylate stream obtained in step (2) is contacted with hydrogen, and an ester hydrogenation reaction occurs under the action of a second catalyst; the reaction product is separated to obtain cyclohexanol.

The above three steps will be described respectively below.

1. Benzene hydrogenation to cyclohexene

The method and catalyst for hydrogenation of benzene to cyclohexene are not particularly limited in the present invention, and the existing process of hydrogenation of benzene to cyclohexene and the catalyst for hydrogenation of benzene can be used in the present invention. The present invention preferably adopts liquid phase process. The benzene hydrogenation catalyst is preferably a ruthenium-based catalyst, more preferably a ruthenium-based catalyst containing cobalt and/or zinc. Ruthenium-based catalysts containing cobalt and/or zinc can be prepared by co-precipitation or impregnation of the same carrier.

In step (1), the cyclohexene-containing stream is a benzene hydrogenation product stream or a benzene hydrogenation product stream separated from cyclohexane and/or benzene; preferably a benzene hydrogenation product stream.

The existing separation methods of cyclohexane, cyclohexene and benzene can be used in the present invention, such as extractive distillation or azeotropic distillation. The present invention preferably adopts extraction and rectification to separate the benzene hydrogenation reaction product, and the extractant can use N-methyl-2-pyrrolidone, N,N-dimethylacetamide, adiponitrile, dimethyl malonate, succinic acid Dimethyl ester, ethylene glycol or sulfolane.

2. Addition and esterification of cyclohexene

In the present invention, "addition esterification reaction" refers to a reaction in which a carboxylic acid is added to an olefin double bond to form an ester.

The carbon number of the carboxylic acid is preferably 1-10; more preferably 1-4. Specifically, the carboxylic acid may be one of formic acid, acetic acid, propionic acid and n-butyric acid or a mixture of two or more of formic acid, acetic acid, propionic acid and n-butyric acid.

In step (2), the catalyst is an acid catalyst, either a liquid acid catalyst or a solid acid catalyst. The liquid acid catalyst can be an inorganic acid, such as sulfuric acid, phosphoric acid, etc.; it can also be an organic acid, such as toluenesulfonic acid, sulfamic acid, etc. The present invention preferably uses a solid acid catalyst. The solid acid catalyst can be selected from one or more of strong acid ion exchange resin catalysts, heteropolyacid catalysts and molecular sieve catalysts.

The strong acid ion exchange resin catalyst includes not only ordinary macroporous sulfonic acid polystyrene-divinylbenzene resin, but also sulfonic acid resin modified by halogen atoms. This kind of resin is easy to buy from the market, and can also be prepared according to the methods recorded in classic literature. The preparation method of macroporous sulfonic acid polystyrene-divinylbenzene resin is usually to drop the mixture of styrene and divinylbenzene into the water phase containing dispersant, initiator and porogen under the condition of high-speed stirring. Carry out suspension copolymerization in the system, separate the obtained polymer balls (white balls) from the system, use a solvent to remove the porogen, and then use dichloroethane as a solvent and concentrated sulfuric acid as a sulfonating agent to carry out Sulfonation reaction, and finally through filtration, washing and other processes, the final product is obtained. Introducing halogen atoms, such as fluorine, chlorine, bromine, etc., into the skeleton of ordinary strong acid ion exchange resin can further improve the temperature resistance and acid strength of the resin. This halogen-containing strongly acidic high-temperature resistant resin can be obtained at least through the following two ways. One way is to introduce a halogen atom, such as a chlorine atom, into the benzene ring of the sulfonated styrene resin skeleton. Due to the strong electron-withdrawing effect of the halogen element It can not only stabilize the benzene ring, but also increase the acidity of the sulfonic acid group on the benzene ring, so that the acid strength function (Hammett function) of the resin catalyst can be H0≤-8, and it can be used for a long time above 150°C. Resins can be easily purchased from the market, such as Amber lyst45 resin produced by foreign ROHM & HASS companies, D008 resin produced by Hebei Jizhong Chemical Factory in China, etc.; another way is to replace all the hydrogen on the resin skeleton with fluorine. Electron-absorbing properties make it super acidic and super thermally stable. The acid strength function (Hammett function) H0 can be less than -12, and the heat-resistant temperature can reach above 250 ° C. This type of high-temperature-resistant strong acid resin is typical An example is Nafion resin produced by DuPont Corporation.

The heteropolyacid catalyst can be heteropolyacid and/or heteropolyacid acid salt, or a catalyst supporting heteropolyacid and/or heteropolyacid acid salt. The acid strength function H0 of the heteropoly acid and its acid salt can be less than -13.15, and can be used for a long time up to 300°C. The heteropolyacid and its acid salt include Keggin structure, Dawson, Anderson structure, Silverton structure heteropoly acid and its acid salt. Heteropolyacids with keggin structure and their acid salts are preferred, such as dodecaphosphotungstic acid (H ₃ PW ₁₂ O ₄₀ ·xH ₂ O), dodecasilicatetungstic acid (H ₄ SiW ₁₂ O ₄₀ ·xH ₂ O), Dodecaphosphomolybdic acid (H ₃ PMo ₁₂ O ₄₀ ·xH ₂ O), dodecaphosphomolybdovanadate (H ₃ PMo _12- yV _y O ₄₀ ·xH ₂ O), etc. The heteropolyacid acid salt is preferably cesium phosphotungstate (Cs _2.5 H _0.5 P ₁₂ WO ₄₀ ), whose acid strength function H0 is less than -13.15, and the specific surface area can reach more than 100 m ² /g. The heteropolyacid catalyst can be selected from one or more of the above-mentioned preferred heteropolyacids and heteropolyacid acid salts. In the catalyst supporting heteropolyacid and/or heteropolyacid acid salt, the carrier is generally _SiO2 and/or activated carbon.

The solid acid catalyst can also be a molecular sieve catalyst. The molecular sieve can be one or more of Hβ, HY and HZSM-5, preferably one or more of Hβ, HY and HZSM-5 modified with fluorine or phosphorus. After these molecular sieves are modified by fluorine and phosphorus, the acidity and catalytic performance of the molecular sieve can be further improved.

Two implementations of step (2) are described in detail below.

The first implementation mode:

The catalyst adopts solid acid catalyst. In step (2), one or more parallel reactors can be used, and the reactor type can be selected from one or more of tank reactors, fixed bed reactors, ebullating bed reactors and fluidized bed reactors . Preference is given to using one or more parallel tubular fixed-bed reactors. More preferably one or more shell-and-tube reactors connected in parallel are used. The operation mode of the reactor can be a batch mode or a continuous mode, preferably a continuous operation mode. Fixed bed reactors can be operated adiabatically or isothermally. The adiabatic reactor can be a cylinder reactor, the catalyst is fixed in the reactor, and the outer wall of the reactor is kept insulated. Since the addition esterification reaction is an exothermic reaction, it is necessary to control the concentration of the reactants to control the temperature rise of the reactor bed. Or use part of the reaction product to cool and then circulate to the reactor inlet to dilute the reactant concentration. The isothermal reactor can be a shell-and-tube reactor. The catalyst is fixed in the tube, and cooling water is passed through the shell to remove the heat released by the reaction.

The reaction temperature is generally 50-200°C, and the optimal reaction temperature is 60-120°C.

The pressure of the addition esterification reaction is related to the reaction temperature. Since the addition esterification reaction is carried out in the liquid phase, the reaction pressure should ensure that the reaction is in the liquid phase state. Generally speaking, the reaction pressure is normal pressure ~ 10MPa, and the optimal pressure is normal pressure ~ 1MPa.

The acid-to-ene molar ratio of the addition esterification reaction is generally 0.2-20:1, and the optimal condition is 1.2-3:1.

In the above-mentioned addition esterification reaction, the liquid feed space velocity is generally 0.5-20h ^-1 , and the optimum condition is 0.5-5h ^-1 .

Under the above conditions, the conversion of cyclohexene in the addition esterification reaction can generally reach more than 80%, while the selectivity of the esterification reaction can reach more than 99%.

The reaction product of step (2) contains a certain amount of unreacted cyclohexene, carboxylic acid and cyclohexyl carboxylate, and may also contain cyclohexane and/or benzene. The specific composition depends on which cyclohexene-containing stream is used Relevant as the reaction raw material of step (2). The separation of the product can be carried out in an addition esterification product separation unit equipped with a rectification separation part and/or an extractive distillation separation part. The specific separation scheme is also related to which cyclohexene-containing stream is used as the step (2) related to the reaction raw materials. The general principle is to separate the carboxylic acid stream, cyclohexyl carboxylate stream and C6 hydrocarbon stream (containing cyclohexene and possibly cyclohexane and/or benzene) from the reaction product by rectification. The carboxylic acid stream is used as a step (2) A part of the reaction feed, the cyclohexyl carboxylate stream is used as the raw material for the step (3) reaction; if the C6 hydrocarbon stream is a mixture, it can be hydrogenated to prepare cyclohexane, and extractive distillation can also be used for its to separate. Among the separated streams, the benzene stream can be used as a part of the reaction feed in step (1), the cyclohexene stream can be used as a part of the reaction feed in step (2), and the cyclohexane stream can be taken out of the device as a by-product.

The second implementation mode:

The catalyst adopts solid acid catalyst. In step (2), one or more parallel reactive distillation columns are used.

When the reactive distillation tower is used as the reactor, the reaction product can be separated while carrying out the addition esterification reaction. When the carboxylic acid is one of formic acid, acetic acid, propionic acid and n-butyric acid or a mixture of two or more of formic acid, acetic acid, propionic acid and n-butyric acid, the carboxylic acid ring can be obtained from the bottom of the reactive distillation column Hexyl ester stream.

The reactive distillation column is the same in form as an ordinary distillation column, and generally consists of a column body, a top condenser, a reflux tank, a reflux pump, a column kettle, and a reboiler. The type of column can be a tray column, a packed column, or a combination of both. The types of tray columns that can be used include valve columns, sieve tray columns, bubble cap columns, etc. The packing used in the packed tower can be random packing, such as Pall ring, θ ring, saddle packing, stepped ring packing, etc.; it can also be structured packing, such as corrugated plate packing, corrugated wire mesh packing, etc.

According to the method provided by the present invention, a solid acid catalyst is arranged in the reactive distillation column. Those skilled in the art know clearly that the catalyst arrangement in the reactive distillation column should meet the following two requirements: (1) It should be able to provide enough channels for the passage of vapor-liquid two-phase, or have a relatively large bed gap rate (generally at least 50%) to ensure that the gas-liquid two-phase can flow through without causing flooding; (2) to have good mass transfer performance, the reactant should be transferred from the fluid phase to the catalyst for reaction, At the same time, the reaction product is transferred from the catalyst. Various arrangements of catalysts in the reactive distillation column have been disclosed in the existing literature, and all of these arrangements can be adopted in the present invention. The arrangement of existing catalysts in the reaction tower can be divided into the following three types: (1) The catalyst is directly arranged in the tower in the form of rectification packing. The main method is to mechanically mix catalyst particles of a certain size and shape with rectification packing , or the catalyst is sandwiched between the structured packing and the structured packing to form an integral packing, or the catalyst is directly made into the shape of the rectification packing; (2) The catalyst is placed in a small gas-liquid permeable container and placed in the reaction The catalyst is placed on the tray of the tower, or the catalyst is arranged in the downcomer of the reaction tower; (3) The catalyst is directly loaded into the reaction tower in the form of a fixed bed, and the liquid phase flows directly through the catalyst bed layer, and a dedicated gas phase is set up. In this way, the catalyst bed and the rectification tray are alternately arranged at the position where the catalyst is installed. The liquid on the tray enters the next catalyst bed through the downcomer and the redistributor, and is carried out in the bed. Addition reaction, the liquid in the lower part of the catalyst bed enters the next tray through the liquid collector.

The theoretical plate number of the reactive distillation column is 10-150, and the addition esterification solid acid catalyst is arranged between 1/3 to 2/3 of the theoretical plate number; relative to the total loading volume of the catalyst, the liquid The feed space velocity is 0.2-20h ^-1 ; the operating pressure of the reactive distillation tower is -0.0099MPa to 5MPa; the temperature of the catalyst loading area is between 50-200°C; the reflux ratio is 0.1-100:1.

The reactive distillation column must have enough theoretical plate numbers and reaction plate numbers to meet the reaction and separation requirements. The theoretical plate number of the reactive distillation column is preferably 30-100, and the solid acid catalyst is arranged between 1/3 to 2/3 of the theoretical plate number.

In the present invention, it is necessary to ensure that the reactants have sufficient residence time to realize the complete conversion of cyclohexene. The space velocity of the liquid feed is preferably 0.5 to 5 h ^-1 relative to the total loading volume of the catalyst.

In the present invention, the operating pressure of the reactive distillation column can be operated under negative pressure, normal pressure and pressurized conditions. The operating pressure of the reactive distillation column is preferably from normal pressure to 1 MPa.

The operating temperature of the reactive distillation tower is related to the pressure of the reactive distillation tower. The temperature distribution of the reaction tower can be adjusted by adjusting the operating pressure of the reaction tower so that the temperature of the catalyst loading area is within the active temperature range of the catalyst. The temperature of the catalyst loading zone is preferably between 60°C and 120°C.

The reflux ratio of the reactive distillation column should meet the requirements of separation and reaction at the same time. In general, increasing the reflux ratio is conducive to improving the separation ability and reaction conversion rate, but at the same time it will increase the energy consumption of the process. The reflux ratio is preferably 0.5˜10:1.

The separation principle of the esterification product is the same as that of the first embodiment, and the specific separation scheme is related to which cyclohexene-containing stream is used as the reaction raw material of step (2), and the present invention will not repeat it here.

For the above two implementations, any separation scheme that conforms to the separation principle of the present invention should be considered as disclosed by the present invention.

3. Hydrogenation of cyclohexyl carboxylate

According to the method provided by the present invention, the cyclohexyl carboxylate stream separated from the addition esterification product is sent to the ester hydrogenation reactor for hydrogenation reaction to generate the corresponding primary alcohol and cyclohexyl carboxylic acid described in step (2). Hexanol.

In step (3), one or more parallel reactors can be set, and the reactor type is selected from one or more of tank reactors, fixed bed reactors, ebullating bed reactors and fluidized bed reactors. In step (3), one or more parallel tubular fixed-bed reactors are preferably set up. In step (3), it is more preferable to set up one or more parallel shell-and-tube reactors, the ester hydrogenation catalyst is fixed in the tubes, and the heat released by the reaction is removed through the cooling medium at the shell side.

The second catalyst is an ester hydrogenation catalyst. Although the existing published literature is mainly about the hydrogenation of methyl carboxylate or ethyl carboxylate, as usual, hydrogenation of fatty acid methyl esters is used to produce higher alcohols, and methyl maleate is hydrogenated to produce 1,4 -butanediol, 1,6-hexanedioic acid dimethyl ester hydrogenation produces 1,6-hexanediol etc., do not see any report about the carboxylic acid ester hydrogenation reaction of naphthenic alcohol derivation, but the present invention It has been found that existing ester hydrogenation catalysts can be used for the hydrogenation of cyclohexyl carboxylates. The hydrogenation of esters generally uses copper-based catalysts, ruthenium-based catalysts and noble metal-based catalysts, with copper-based catalysts being the most commonly used. Copper-based ester hydrogenation catalysts use copper as the main catalyst, and add chromium, aluminum, zinc, calcium, magnesium, nickel, titanium, zirconium, tungsten, molybdenum, ruthenium, platinum, palladium, rhenium, lanthanum, thorium, gold, etc. One or more components are used as co-catalysts or additive components. Copper-based ester hydrogenation catalysts can be easily purchased from the market, and can also be prepared by co-precipitation. The usual preparation method is to put the soluble salt solution of each metal into the neutralization kettle, and add alkali solution (sodium hydroxide, sodium carbonate, ammonia water, urea, etc.) at a certain temperature and stirring speed to neutralize to pH8~ 12 Growth and precipitation, the precipitation is formed through aging, filtration, washing, drying, roasting, molding and other processes, and finally reduced in a hydrogen atmosphere to make the final ester hydrogenation catalyst. The general composition of ruthenium catalysts: Ru/Al ₂ O ₃ or Ru-Sn/Al ₂ O ₃ . The general composition of noble metal catalysts: Pt/Al ₂ O ₃ , Pd-Pt/Al ₂ O ₃ or Pd/C.

In the present invention, the ester hydrogenation catalyst can be selected from one or more of copper-based catalysts, ruthenium-based catalysts and noble metal-based catalysts, preferably copper-based catalysts, more preferably copper-based catalysts containing zinc and/or chromium.

The ester hydrogenation reaction unit can be operated either batchwise or continuously. The batch reaction generally uses a reactor as a reactor, puts cyclohexyl carboxylate and a hydrogenation catalyst into the reactor, feeds hydrogen to react at a certain temperature and pressure, and removes the reaction product from the reactor after the reaction is completed. Out, the product is separated, and then put into the next batch of materials for reaction. The shell-and-tube reactor can be used for the continuous hydrogenation reaction. The hydrogenation catalyst is fixed in the tube, and cooling water is passed through the shell to remove the heat released by the reaction.

The hydrogenation reaction temperature of cyclohexyl carboxylate is related to the selected hydrogenation catalyst. For copper-based hydrogenation catalysts, the general hydrogenation reaction temperature is 150-400°C, and the optimal reaction temperature is 200-300°C. The reaction pressure is from normal pressure to 20MPa, and the optimal pressure is from 4 to 10MPa.

The control of the hydrogen ester molar ratio in the hydrogenation reaction of cyclohexyl carboxylate is very important. A high hydrogen-to-ester ratio is beneficial to the hydrogenation of esters, but too high a hydrogen-to-ester ratio will increase the energy consumption of the hydrogen compression cycle. Generally, the ratio of hydrogen to ester is 1-1000:1, and the optimal condition is 5-100:1.

In the hydrogenation reaction, the feed space velocity of the ester is related to the activity of the selected catalyst. Higher activity catalysts can use higher space velocities. For the selected catalyst, the reaction conversion decreases with the increase of the reaction space velocity. In order to meet a certain conversion rate, the space velocity must be limited within a certain range. Generally, the liquid feeding space velocity of the ester is 0.1-20h ^-1 , and the optimum condition is 0.2-2h ^-1 . If a batch reaction is adopted, the reaction time is 0.5-20 h, preferably 1-5 h.

The ester hydrogenation reaction product mainly contains primary alcohol and cyclohexanol, and may also contain a certain amount of unreacted cyclohexyl carboxylate, and may also contain a certain amount of other carboxylic acid esters and cyclohexanone, and a small amount of high boilers ( dimer ketones), these mixtures can be separated by rectification and/or extractive distillation, preferably by rectification. Distillation and separation can adopt a batch scheme or a continuous process scheme. The present invention preferably adopts continuous rectification to separate ester hydrogenation products. Continuous distillation requires the separation of the various components using a series of distillation columns. Various separation processes can be designed according to the order of the boiling points of each component. The present invention prefers the process scheme of sequential separation, that is, the separation is carried out in the order of boiling points from low to high. In step (3), after the reaction product is separated, the obtained cyclohexyl carboxylate stream can be used as a part of the reaction feed in step (3).

The invention provides a high-efficiency, low-cost new technology route for producing cyclohexanol. The characteristics of the present invention are: (1) Both esterification and ester hydrogenation have high selectivity, so the utilization rate of atoms is high; (2) The process is environmentally friendly; (3) Reactive distillation is used for addition esterification , not only can significantly improve the reaction efficiency, but also simplify the extraction, distillation and separation process, greatly reducing investment and operating costs; (4) Co-production of primary alcohol while producing cyclohexanol.

Detailed ways

The present invention is further illustrated by the following examples, but the present invention is not limited thereto.

Example 1

This example illustrates the method for the selective hydrogenation of benzene to cyclohexene.

Benzene and hydrogen are injected into the hydrogenation reactor filled with ruthenium particle catalyst at a molar ratio of 1:3, and the benzene hydrogenation reaction is carried out under the conditions of a reaction temperature of 135°C, a pressure of 4.5MPa, and a residence time of 15min. After the reaction product is separated from the hydrogen , Collect the liquid product and run continuously for 1000h. After the test, the collected liquid product was analyzed by gas chromatography, and its composition was: 53.3% benzene, 35.4% cyclohexene, and 11.3% cyclohexane.

Example 2

100mL of macroporous strongly acidic hydrogen-type ion exchange resin (synthesized in the laboratory according to the classic literature method, suspension copolymerization of styrene solution containing 15% divinylbenzene to make white balls, and then sulfonated with concentrated sulfuric acid, measured Its exchange capacity is 5.2mmolH ⁺ /g dry basis) into the middle part of a stainless steel tube reactor with a jacket of φ32×4×1000mm, and a certain amount of quartz sand is filled at both ends. The raw materials of acetic acid and cyclohexene (composition: 75m% cyclohexene, 25m% cyclohexane; obtained by extracting and rectifying the reaction product of Example 1, using N,N-dimethylacetamide as the extractant) according to a certain The flow rate is pumped into the reactor by the metering pump for reaction, hot water is passed into the outer jacket of the reaction tube to control the reaction temperature, and the reactor pressure is controlled by the back pressure valve at the outlet of the reactor. The outlet product of the reactor was sampled by an online sampling valve for online chromatographic analysis, and the conversion of cyclohexene and the selectivity of cyclohexyl acetate were calculated from the composition of the product. The reaction conditions and results are shown in Table 1.

It can be seen from Table 1 that the reaction between cyclohexene and acetic acid using a strong acid type ion exchange resin catalyst, the conversion rate of cyclohexene is greater than 90%, the selectivity of ester products is greater than 99%, and the catalyst activity and selectivity are stable after 600 hours of operation.

Example 3

The test device and method are the same as in Example 2, except that the catalyst is a phosphorus-modified Hβ molecular sieve catalyst (the Hβ molecular sieve with a silicon-aluminum ratio of 50 is modified with 85% phosphoric acid, then kneaded with alumina and extruded to shape, after Drying at 120°C, roasting at 500°C, the phosphorus content is 2%); cyclohexene raw material (composed of: benzene 60m%, cyclohexene 40m%; the reaction product of Example 1 was obtained by extraction and rectification, the extraction agent using N,N-dimethylacetamide). The reaction conditions and results are shown in Table 2. It can be seen from Table 2 that the reaction conversion rate of cyclohexene and acetic acid is greater than 80%, the selectivity of ester product is greater than 99%, and the catalyst activity and selectivity are stable after running for 480 hours.

Embodiment 4～5 are used to illustrate adopting the method for preparing cyclohexyl acetate by reactive distillation.

The tests carried out in Examples 4 to 5 are all carried out in the reactive distillation model test device of the following specifications: the main body of the model device is a stainless steel tower with a diameter (inner diameter) of 50mm and a height of 3m, and the lower connecting volume of the tower is The 5L tower kettle is equipped with a 10KW electric heating rod in the kettle. The heating rod is controlled by an intelligent controller through a silicon controlled rectifier (SCR). A condenser with a heat exchange area of ^0.5m2 is connected to the top of the tower, and the steam at the top of the tower is condensed into a liquid by the condenser and then enters a reflux tank with a volume of 2L. The liquid in the reflux tank is partially refluxed to the reaction tower through the reflux pump, and part of it is extracted as light components. The operating parameters of the tower are displayed and controlled by intelligent automatic control instruments. The reflux flow of the tower is controlled by the reflux regulating valve, and the output at the top of the tower is controlled by the liquid level controller of the reflux tank. The production volume of the tower kettle is controlled by adjusting the tower kettle discharge valve by the tower kettle liquid level controller. The raw materials of acetic acid and cyclohexene are put into 30L storage tanks respectively, and are pumped into corresponding preheaters through metering pumps to preheat to a certain temperature before entering the reaction tower. The feeding speed is controlled by metering pumps and accurately measured by electronic scales.

Example 4

The high-temperature-resistant sulfonic acid ion exchange resin (the brand name is Amber lyst45, produced by Rhom&Hass Company) is crushed into a powder with a particle size of less than 200 mesh (0.074mm) with a multi-stage high-speed pulverizer, and pore-forming agents, lubricants, and antioxidants are added. The agent and adhesive are mixed evenly on a high-speed mixer, and then internally kneaded on an internal mixer at 180°C for 10 minutes to make the material completely plasticized, and then injected into a mold to make a Raschig ring with a diameter of 5mm, a height of 5mm, and a wall thickness of 1mm. type resin catalyst filler. Put 1950mL of this packing into the middle of the model reaction tower (1m in height, equivalent to 8 theoretical trays) and 1950mL of glass spring packing with a diameter of 3mm and a length of 6mm (filling height is 1m, equivalent to 10 theoretical trays). plate). The cyclohexene raw material and acetic acid were pumped into the preheater by the metering pump to preheat and enter the reaction tower, and the heating capacity of the tower kettle and the reflux flow at the top of the tower were adjusted for continuous reaction. The reaction conditions and reaction results under stable operation are shown in Table 3.

Example 5

Spherical H _0.5 Cs _2.5 PW ₁₂ O ₄₀ /SiO ₂ catalyst with a diameter of 3-4 (composed of H _0.5 Cs _2.5 PW ₁₂ O ₄₀ powder and coarse-pore silica gel powder with a particle size of less than 200 meshes is fully mixed in a mixer, then In the sugar coating machine, silica sol is used as a bonding machine to roll the ball into shape, and then dried and roasted) sandwiched into a titanium wire mesh wave plate to make a cylindrical structured packing with a diameter of 50mm and a height of 50mm. Put this packed catalyst L into the middle of the model reaction tower (1m in height, equivalent to 12 theoretical trays), and put 1950mL glass spring packing with a diameter of 4mm and a height of 4mm in the upper and lower parts (the packing height is 1m, equivalent to 15 block theoretical plate). The cyclohexene raw material and acetic acid were pumped into the preheater by the metering pump to preheat and enter the reaction tower, and the heating capacity of the tower reactor and the reflux flow at the top of the tower were adjusted for continuous reaction. The reaction conditions and reaction results under stable operation are shown in Table 5.

Embodiments 6-7 are used to illustrate the hydrogenation method of cyclohexyl acetate.

Example 6

The raw material for hydrogenation is cyclohexyl acetate with a purity of 99.6%.

40g copper zinc aluminum ester hydrogenation catalyst (laboratory synthesis, composition is CuO40.5%, ZnO29.6%, _Al2O330.4 %. By the nitrate solution _of copper, zinc, chromium, add in the sodium hydroxide solution and to PH=9.0, centrifuged, washed, dried, pressed into tablets, and roasted) into the middle of a stainless steel tube reactor with a jacket of φ20×2.5×800mm, and a certain amount of quartz sand is filled at both ends . Pass in hydrogen (500mL/min) and reduce for 24h under the conditions of 280°C and 6MPa, then drop to the temperature and pressure of hydrogenation reaction. The cyclohexyl acetate is pumped into the reactor by the metering pump, the hydrogen gas enters the reaction system through the mass flow controller for hydrogenation reaction, the reaction temperature is controlled by introducing heat transfer oil into the outer jacket of the reaction tube, and the reaction temperature is controlled by the back pressure valve at the outlet of the reactor. Control the reactor pressure. The reaction product is sampled through the linear sampling valve at the rear of the reactor for online chromatographic analysis. The reaction conditions and results are shown in Table 5. The results in Table 5 show that, using the copper-zinc-aluminum catalyst, the conversion rate of cyclohexyl acetate hydrogenation reaction can reach more than 99.0%, and the selectivity of cyclohexanol is greater than 99.9%. After 1000 hours of operation, the conversion rate and selectivity have not decreased.

Example 7

The raw material for hydrogenation is cyclohexyl acetate with a purity of 99.6%.

Pack 40g of copper chromium ester hydrogenation catalyst (commercially available, produced by Taiyuan Xinjida Chemical Co., Ltd., brand name is C1-XH-1, CuO content is 55%, diameter 5mm tablet, crushed into 10-20 mesh particles) Enter the middle part of the φ20×2.5×800mm jacketed stainless steel tube reactor, and fill a certain amount of quartz sand at both ends. Pass in hydrogen (500mL/min) and reduce for 24h under the conditions of 280°C and 6MPa, then drop to the reaction temperature and pressure. The cyclohexyl acetate is pumped into the reactor by the metering pump, the hydrogen gas enters the reaction system through the mass flow controller for hydrogenation reaction, the reaction temperature is controlled by introducing heat transfer oil into the outer jacket of the reaction tube, and the reaction temperature is controlled by the back pressure valve at the outlet of the reactor. Control the reactor pressure. The reaction product is sampled through the linear sampling valve at the rear of the reactor for online chromatographic analysis. The reaction conditions and results are shown in Table 6. The results in Table 6 show that, using the copper-zinc-aluminum catalyst, the conversion rate of cyclohexyl acetate hydrogenation reaction can reach more than 98.0%, and the selectivity of cyclohexanol is greater than 99.9%. After 500 hours of operation, the conversion rate and selectivity have not decreased. Table 1 Test data of strongly acidic ion exchange resin catalyzed esterification of acetic acid and cyclohexane/cyclohexene

Table 2 Hβ molecular sieve catalyst catalyzed acetic acid and cyclohexene/benzene for esterification test data

Table 3 Reactive distillation test data of high temperature resistant sulfonic acid type ion exchange resin catalyst

According to the experimental data, the conversion rate of cyclohexene is calculated as 98.8%, and the selectivity of cyclohexyl acetate is 98.0%.

Table 4 Reactive distillation test data of H _0.5 Cs _2.5 PW ₁₂ O ₄₀ /SiO ₂ catalyst

According to the experimental data, the conversion rate of cyclohexene is calculated to be 99.35%, and the selectivity of cyclohexyl acetate is 99.6%.

The cyclohexyl acetate hydrogenation test data of table 5 copper zinc aluminum ester hydrogenation catalyst

The cyclohexyl acetate hydrogenation test data of copper chromium ester hydrogenation catalyst of table 6

Claims (19)

1. A method for producing cyclohexanol, comprising: (1) Under the conditions of hydrogenation of benzene to cyclohexene, benzene and hydrogen undergo a hydrogenation reaction to obtain a stream containing cyclohexene; (2) contacting the cyclohexene-containing stream obtained in step (1) with carboxylic acid, and an addition esterification reaction occurs under the action of the first catalyst; separating the reaction product to obtain a cyclohexyl carboxylate stream; The carboxylic acid is one or a mixture of two or more acyclic carboxylic acids with 1 to 24 carbon atoms; (3) The cyclohexyl carboxylate stream obtained in step (2) is contacted with hydrogen, and an ester hydrogenation reaction occurs under the action of a second catalyst; the reaction product is separated to obtain cyclohexanol. 2. The method according to claim 1, characterized in that, in step (1), the benzene hydrogenation catalyst used is a ruthenium-based catalyst. 3. The method according to claim 2, characterized in that, in step (1), the benzene hydrogenation catalyst used is a ruthenium-based catalyst containing cobalt and/or zinc. 4. The method according to claim 1, characterized in that, in step (2), the first catalyst is a solid acid catalyst. 5. according to the described method of claim 4, it is characterized in that, described solid acid catalyst is selected from one or more in strong acid type ion exchange resin catalyst, heteropolyacid catalyst and molecular sieve catalyst. 6. according to the described method of claim 5, it is characterized in that, described strong acid type ion exchange resin is macroporous sulfonic acid type polystyrene-divinylbenzene resin or the sulfonic acid type resin after halogen atom modification . 7. according to the described method of claim 5, it is characterized in that, described heteropolyacid catalyst is heteropolyacid and/or heteropolyacid acid salt, or load heteropolyacid and/or heteropolyacid acid formula salt catalyst. 8. according to the described method of claim 7, it is characterized in that, described heteropolyacid catalyst is the heteropolyacid of keggin structure and/or the heteropolyacid acid salt of keggin structure, or is the heteropolyacid of load keggin structure Catalyst for heteropolyacid acid salt of acid and/or keggin structure. 9. The method according to claim 5, characterized in that, the molecular sieve is one or more of Hβ, HY and HZSM-5. 10. The method according to claim 9, characterized in that the molecular sieve is one or more of Hβ, HY and HZSM-5 modified with fluorine or phosphorus. 11. The method according to claim 4, characterized in that, in step (2), one or more parallel reactors are used, and the reactor type is selected from tank reactors, fixed bed reactors, and ebullating bed reactors And one or more of the fluidized bed reactors. 12. The method according to claim 11, characterized in that in step (2), the reaction temperature is 50-200°C, the acid-to-ene molar ratio is 0.2-20:1, and the liquid feed space velocity is 0.5-20h ^{- 1} . 13. The method according to claim 4, characterized in that, in step (2), one or more parallel reactive distillation columns are used. 14. The method according to claim 1, characterized in that, in step (3), the second catalyst is an ester hydrogenation catalyst. 15. The method according to claim 14, wherein the ester hydrogenation catalyst is selected from one or more of copper-based catalysts, ruthenium-based catalysts and noble metal-based catalysts. 16. The method according to claim 15, characterized in that in step (3), the ester hydrogenation catalyst is a copper-based catalyst, the hydrogenation reaction temperature is 150-400°C, and the reaction pressure is normal pressure-20MPa , the hydrogen ester molar ratio is 1-1000:1, and the liquid feed space velocity is 0.1-20h ^-1 . 17. The method according to claim 15, characterized in that, in step (3), the copper-based catalyst is a copper-based catalyst containing zinc and/or chromium. 18. The method according to claim 1 or 13, characterized in that the carbon number of the carboxylic acid is 1-4. 19. The method according to claim 1, characterized in that, in step (1), the cyclohexene-containing stream is a benzene hydrogenation product stream or a benzene hydrogenation product stream to separate cyclohexane and/or benzene logistics.