CN103664587A - Method for preparing cyclohexyl acetate and method for preparing cyclohexanol ethanol - Google Patents

Abstract

The invention relates to a method for preparing cyclohexyl acetate, which uses pre-esterification and reactive distillation to carry out the addition esterification reaction of acetic acid and cyclohexene, and has a high conversion rate of cyclohexene and cyclohexyl acetate selective. The present invention also relates to a method for preparing cyclohexanol and ethanol. The method first utilizes pre-esterification and reactive distillation to carry out the addition esterification reaction of acetic acid and cyclohexene to prepare cyclohexyl acetate; Esters are hydrogenated to co-produce cyclohexanol and ethanol.

Description

Process for preparing cyclohexyl acetate and process for preparing cyclohexanol and ethanol

technical field

The invention relates to a method for preparing cyclohexyl acetate and a method for preparing cyclohexanol and ethanol.

Background technique

Cyclohexyl acetate is a liquid with banana or apple aroma, and the fruity flavor prepared with it is widely used in food, beverage and cosmetic industries. In addition, cyclohexyl acetate has good solubility for resins, and is often used as an environmentally friendly solvent for high-grade paints and paints.

At present, the synthetic method of cyclohexyl acetate in industry is the esterification reaction of acetic acid and cyclohexanol. The alkyd esterification reaction needs to be carried out smoothly under the action of an acidic catalyst. Song Guijia, Wu Xionggang (Chemical Propellants and Polymer Materials, 2009, V0l.7(2):P31-33), reviewed the progress in the synthesis of cyclohexyl acetate from acetic acid and cyclohexanol esterification, and the catalysts involved Including sulfamic acid, p-toluenesulfonic acid and other sulfonic acid catalyst systems, SO ₄ ^2－ /TiO ₂ , S ₂ O ₈ ^2－ /ZnO ₂ －Fe ₂ O ₃ －SiO ₂ , S ₂ O ₈ ^2－ /Fe ₂ O ₃ -MoO ₃ and other solid superacid catalyst systems, ferrous sulfate, sodium bisulfate, potassium hydrogen sulfate, ferric chloride, copper sulfate and other inorganic salt catalyst systems, phosphotungstic acid and supported heteropolyacid catalyst systems.

CN102060697 proposes a synthesis process of cyclohexyl acetate. First, copper oxide and p-toluenesulfonic acid are reacted to synthesize copper p-toluenesulfonate, then copper p-toluenesulfonate is used as a catalyst, and cyclohexane is used as a water-carrying agent. Acetic acid and cyclohexanol react to synthesize cyclohexyl acetate. Alkylate synthesis of cyclohexyl acetate has problems such as difficulty in separating the catalyst from the product, the need to use a water-carrying agent, and the high price of cyclohexanol, so it is difficult to produce on a large scale.

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 patent 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, JP Ping-313447 discloses a preparation method of cyclohexanol, using ZSM5 or high silica zeolite as a catalyst and in the presence of water, to synthesize cyclohexyl acetate by reacting acetic acid and cyclohexene, reacting at 120°C for 4h, cyclohexanol The yields of hexanol and cyclohexyl acetate were only 12.5% and 65%, respectively.

EP0461580A2 and USP5254721 disclose a method of using a tungsten-containing heteropolyacid catalyst to react acetic acid and cyclohexene to prepare cyclohexyl acetate. This patent proposes that the crystal water content in the heteropolyacid molecule should preferably be 0-3. The best result given by the patent is that the dodecasilicate 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. 0.5MPA, 130°C for 0.5h, the conversion rate of cyclohexene is 95.2%, and the selectivity of cyclohexyl acetate is 99.2%. It can be seen that under the condition of very high acid-to-ene ratio, cyclohexene cannot be completely converted. Since complete conversion of cyclohexene cannot be achieved.

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 and esterification of acetic acid and cyclohexene process reporting.

Both cyclohexanol and ethanol are important chemical raw materials and solvents. Cyclohexanol is mainly used to produce nylon 6, nylon 66, etc., while ethanol is a raw material for synthetic esters and other chemical products, and is also widely used as a fuel additive for gasoline.

The method of industrially synthesizing ethanol is mainly the direct hydration method of ethylene, but in some countries rich in agricultural and sideline products, the fermentation method is still the main method of ethanol production. Due to the large population and insufficient arable land in our country, and the problem of "competing with the mouth for food" in the production of ethanol by fermentation, the fermentation method does not conform to the national conditions of our country. In addition, the pollution of the fermentation method is also relatively serious. my country's oil resources are relatively insufficient, and the price of ethylene is greatly affected by fluctuations in international oil prices. Therefore, the application of ethylene hydration in my country will face certain pressure on raw material costs. In addition, the reaction conditions of the ethylene direct hydration method are relatively harsh and need to be carried out under high temperature and high pressure. In summary, the development of new ethanol synthesis process routes is an inevitable requirement for technological and economic development.

CN102149661A discloses a method for the direct and selective production of ethanol from acetic acid using a platinum/tin catalyst, comprising: a feed stream containing acetic acid and hydrogen is contacted at an elevated temperature with a suitable hydrogenation catalyst comprising a suitable The group of platinum and tin on the catalyst support and optionally a third metal supported on the support, wherein the third metal is selected from the group consisting of palladium, rhodium, ruthenium, rhenium. Iridium, Chromium, Copper, Molybdenum, Tungsten, Vanadium and Zinc.

CN1022228831A discloses a catalyst for preparing ethanol by gas-phase hydrogenation of acetic acid. The catalyst consists of three parts: main active component, auxiliary agent and carrier. The carrier is any one of activated carbon, graphite or multi-walled carbon nanotubes. Its characteristics That is, the main active component is 0.1-30.0% of the weight of the catalyst, the weight of the auxiliary agent is 0.1-10.0% of the weight of the catalyst, and the balance is the carrier. The main active component is any one or both of metal W or Mo. The auxiliary agent is one or more of Pd, Re, Pt, Rh or Ru.

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.

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 catalyst is C1-C24 acyclic monovalent or divalent, saturated or unsaturated, straight chain or branched chain carboxylate, does not relate to the production of cycloalkanol like cyclohexanol.

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 applicable carboxylic acid esters of the method and catalyst are C6～C22 dimethyl esters, C6～C66 natural triglycerides obtained by transesterification of natural oils or C6～C44 compounds obtained by transesterification of natural triglycerides .

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 (where 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 with H ₂ and CO mixed gas, hydrogenation reaction at 30~150°C, 5~100 bar pressure to generate alcohol, The catalyst is composed of the following components: (a) a metal ion compound of group VIII 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, which is characterized in that 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), group IIA (except Be and Mg), lanthanides and actinides, 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 (Eduard Karek Poles, Dirk Ryk Evert Polman, Johanned Joesphus Vreeswijk. Unichema Chemie BV) discloses a method for the hydrogenation of fatty acid esters to alcohols, which is characterized in that a copper-containing catalyst is used for hydrogenation and a certain water to maintain the activity of the catalyst.

US5334779 discloses a catalyst composition and its use in the hydrogenation of carboxylic acid esters. The catalyst consists of copper oxide, zinc oxide and a third component (oxides of aluminum, magnesium, zirconium or their mixtures). The carboxylic acid ester used in the catalyst and method is dimethyl cycloadipate, lower alkyl ester of C10-C20 carboxylic acid, dilower alkyl ester of adipic acid and dilower alkyl ester of maleic acid.

It can be seen from the published literature that there is no information disclosure about the coproduction of cyclohexanol and ethanol by the hydrogenation of cyclohexyl acetate in the prior art.

Contents of the invention

The invention provides a method for preparing cyclohexyl acetate, which utilizes pre-esterification and reactive distillation to carry out the addition esterification reaction of acetic acid and cyclohexene, and can use the partially hydrogenated product of benzene as a raw material, which has a high The conversion of cyclohexene and the selectivity of cyclohexyl acetate. The present invention also provides a method for preparing cyclohexanol and ethanol, the method first utilizes pre-esterification and reactive distillation to carry out the addition esterification reaction of acetic acid and cyclohexene, and efficiently prepares cyclohexyl acetate; and then Co-produce cyclohexanol and ethanol by hydrogenation of cyclohexyl acetate, hydrogenation process uses the hydrogenation catalyst provided by the invention, can convert cyclohexyl acetate into cyclohexanol and ethanol almost quantitatively under higher space velocity, and almost No side effects occurred.

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.

A method for preparing cyclohexyl acetate, comprising:

(1) Input acetic acid and cyclohexene raw materials into the pre-esterification reactor, and react in the presence of a solid acid catalyst; the cyclohexene raw materials are cyclohexene or cyclohexene and cyclohexane and/or benzene the composition of the mixture;

(2) Input the output of step (1) into the reactive distillation tower, contact with a solid acid catalyst, react, and simultaneously separate the reaction product to obtain cyclohexyl acetate from the bottom of the tower.

The cyclohexene raw material is a mixture of cyclohexene, cyclohexane and/or benzene, and the cyclohexene content is preferably 20m%-80m%, more preferably 20m%-60m%. Industrially, cyclohexene is generally produced by selective hydrogenation of benzene, and the product stream is a mixture of cyclohexene, cyclohexane and benzene, and the content of cyclohexene is generally 20m% to 60m%. Extraction and separation can obtain streams whose cyclohexene content is generally 40m% to 80m%. The present invention preferably uses these streams as cyclohexene raw materials, which can avoid or simplify the separation process with high investment and operating costs.

The cyclohexene raw material is a mixture of cyclohexene, cyclohexane and/or benzene, and a mixture of acetic acid, cyclohexane and/or benzene is obtained from the top of the reactive distillation column.

The pre-esterification reactor can be a tank reactor, a fixed bed reactor, a fluidized bed reactor or an ebullated bed reactor. The fixed-bed reactor is preferably a tubular fixed-bed reactor, more preferably a shell-and-tube reactor. The operation mode of the pre-esterification reaction system can be carried out in a batch mode or in a continuous mode, preferably in a continuous mode. Since the tubular fixed-bed reactor has the advantages of low manufacturing cost and simple operation, it is the preferred reactor of the present invention. 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 heat-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 concentration of the reactants. 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 pre-esterification reaction needs to be carried out at a certain temperature. If the temperature is too low, the reaction rate will be low, and if the temperature is too high, although the reaction rate will be greatly accelerated, side reactions will easily occur, which is unfavorable to the equilibrium conversion rate of the esterification reaction. The selected reaction temperature is related to the catalyst, generally 50-200°C, preferably 60-120°C.

The pressure of the pre-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, the reaction pressure is from normal pressure to 10 MPa, preferably from normal pressure to 1 MPa.

The acid-to-ene molar ratio of the pre-esterification reaction is 0.2-20:1, preferably 1.2-4:1.

The liquid feeding space velocity of the pre-esterification reaction is 0.5-20h ^-1 , and the optimal condition is 1-5h ^-1 .

The output of step (1) contains unreacted acetic acid, cyclohexene and esterification product cyclohexyl acetate, if the mixture of cyclohexene and cyclohexane and/or benzene is used as raw material, the output of step (1) The feed also contains cyclohexane and/or benzene.

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

In step (2), 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 reactive distillation column must have enough theoretical plate numbers and reaction plate numbers to meet the reaction and separation requirements. The number of theoretical plates of the reactive distillation tower is 10 to 150, among which 5 to 30 plates are selected to arrange catalysts among 10 to 120 plates, and the more preferred solution is that the number of theoretical plates of the reaction tower is 30 to 100 , wherein 8 to 20 plates are selected among 10 to 80 plates to arrange the catalyst.

In the present invention, it is necessary to ensure that the reactants have sufficient residence time to realize the complete conversion of cyclohexene. Relative to the total loading volume of the catalyst, the liquid feed space velocity is 0.1 to 20 h ^-1 , preferably 0.2 to

2h ^-1 .

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 tower is -0.0099MPa to 5MPa, preferably normal pressure to 1MPa.

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 area is between 40°C and 200°C, preferably between 60°C and 150°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.

In the present invention, if pure cyclohexene and acetic acid are used as reaction raw materials, total reflux can be realized theoretically. When there is a small amount of light component impurities in the reaction raw materials, it is necessary to lead a small amount of overhead stream out of the reactive distillation column. In the present invention, the reflux ratio is 0.1-100:1, preferably 0.5-10:1.

The solid acid catalyst in step (1) and the solid acid catalyst in step (2) can be the same or different, and are selected from one or more of strong acid ion exchange resin catalysts, heteropolyacid catalysts and molecular sieve catalysts.

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. Resin can be easily purchased from the market, such as Amberlyst45 resin produced by foreign ROHM & HASS company, 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, due to the strong absorption of fluorine Electronic properties make it super acidic and super high thermal stability, the acid strength function (Hammett function) H0 can be less than -12, and the heat resistance temperature can reach above 250 ℃, a typical example of this kind of high temperature resistant strong acid resin It is Nafion resin produced by DuPont Company.

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 Kegin structure, Dawson, Anderson structure, Silverton structure heteropoly acid and its acid salt. Heteropoly acids with keggin structure are preferred, such as dodecaphosphotungstic acid (H ₃ PW ₁₂ O ₄₀ xH ₂ O), dodecasilicon tungstic 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. In the catalyst supporting heteropolyacid and/or heteropolyacid acid salt, the carrier is _SiO2 and/or activated carbon.

In the present invention, the solid acid catalyst can also be a molecular sieve catalyst. The molecular sieve can be one or more of Hβ, HY and HSZM-5, preferably one or more of Hβ, HY and HSZM-5 modified with fluorine and/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.

Preferably, the number of theoretical plates of the reactive distillation column is 30 to 100, and 8 to 20 plates are selected between 10 to 80 plates to arrange the solid acid catalyst; the solid acid catalyst is macroporous strong acid Hydrogen type ion exchange resin or cesium phosphotungstate salt; relative to the total loading volume of the catalyst, the liquid feed space velocity is 0.2~2h ^-1 ; the operating pressure of the reactive distillation tower is from normal pressure to 1MPa; the catalyst loading area The temperature is between 120～180℃; the reflux ratio is 0.5～10:1.

The above-mentioned method is characterized in that: the combination of pre-esterification and reactive distillation esterification is adopted, and most of the cyclohexene conversion is realized through pre-esterification, and then a small amount of catalyst is arranged in the reactive distillation column to further realize the conversion of cyclohexene complete transformation. Using the combination of reaction and rectification separation, the product stream of partial hydrogenation of benzene or the cyclohexene-containing stream separated by one-step extraction can be used as the raw material for esterification, and the complete conversion of cyclohexene can be realized, thereby avoiding or simplifying investment and operating costs Very high extractive distillation separation process.

The present invention also provides a method for preparing cyclohexanol and ethanol, comprising:

(1) Input acetic acid and cyclohexene raw materials into the pre-esterification reactor, and react in the presence of a solid acid catalyst; the cyclohexene raw materials are cyclohexene or cyclohexene and cyclohexane and/or benzene the composition of the mixture;

(2) inputting the discharge of step (1) into a reactive distillation tower, contacting with a solid acid catalyst, reacting, and simultaneously separating the reaction product to obtain cyclohexyl acetate from the bottom of the tower;

(3) In the presence of a hydrogenation catalyst, the cyclohexyl acetate obtained in step (2) is contacted with hydrogen to react; the hydrogenation catalyst includes: (a) copper oxide, (b) zinc oxide, (c) Oxides of one or more metals selected from the group consisting of aluminium, gallium, tin, titanium, zirconium, chromium, molybdenum, tungsten, manganese, rhenium, lanthanides and actinides, (d) alkali hydrogen One or more of oxides and alkaline earth metal hydroxides; in the catalyst, in terms of parts by mass, component (a) is 5-60 parts, component (b) is 10-50 parts, The component (c) is 5-30 parts, and the component (d) is 0.2-2 parts.

Steps (1) and (2) are the same as the aforementioned method for preparing cyclohexyl acetate, and will not be repeated here.

The reactor used in step (3) is one or more, and the reactor type can be selected from one or more of tank reactors, tubular fixed bed reactors, ebullating bed reactors and fluidized bed reactors .

Step (3) can be implemented either in a batch manner or in a continuous manner. The batch hydrogenation reaction generally uses a reactor as a reactor, puts cyclohexyl acetate and a hydrogenation catalyst into the reactor, feeds hydrogen to react at a certain temperature and pressure, and takes the reaction product from the reactor after the reaction is completed. Unload, separate the product, and then put in the next batch of materials for reaction. Continuous hydrogenation reaction can adopt shell-and-tube shell-and-tube reactor. The hydrogenation catalyst is fixed in the shell tube, and the heat released by the reaction is removed by cooling water at the shell side.

In step (3), the hydrogenation reaction temperature is 150-400°C, preferably 200-300°C; the reaction pressure is normal pressure-20MPa, preferably 4-10MPa; the hydrogen ester molar ratio is 1-1000:1, preferably 5-100:1; the liquid feeding space velocity of cyclohexyl acetate is 0.1-20h ^-1 , preferably 0.2-2h ^-1 .

In order to achieve the purpose of the present invention, the present invention first provides a carboxylic acid ester hydrogenation catalyst, including: (a) copper oxide, (b) zinc oxide, (c) one or more metals selected from the following groups Oxides of aluminium, gallium, tin, titanium, zirconium, chromium, molybdenum, tungsten, manganese, rhenium, lanthanides and actinides, (d) hydroxides of alkali metals and hydroxides of alkaline earth metals or several; in the catalyst, in parts by mass, component (a) is 5-60 parts, component (b) is 10-50 parts, component (c) is 5-60 parts, and component Point (d) is 0.2 to 2 parts.

Preferably, in the catalyst, in terms of parts by mass, component (a) is 10-50 parts, component (b) is 15-45 parts, and component (c) is 15-55 parts, Component (d) is 0.2 to 2 parts.

More preferably, in the catalyst, in parts by mass, component (a) is 30-45 parts, component (b) is 20-35 parts, and component (c) is 20-50 parts , component (d) is 0.5 to 1.5 parts.

Considering the availability of raw materials, cost and use effect, component (d) is preferably one or more of potassium hydroxide, sodium hydroxide and barium hydroxide.

It should be understood that catalysts are generally traded and stored in the form of precursors (or called precursors). Although catalyst precursors cannot directly catalyze reactions, catalyst precursors are customarily called "catalysts". The catalyst precursor becomes catalytically active after being reduced, which is usually done by the operator of an industrial device, and those skilled in the art are familiar with the reduction process, so the present invention will not repeat it here. The catalyst precursor can be made into various shapes according to the needs of users, such as shaped pellets, or it can be in a state before molding, such as powder.

The present invention also provides a kind of preparation method of carboxylic acid ester hydrogenation catalyst, comprising:

(1) Composite metal oxides are prepared by co-precipitation; the composite metal oxides include (a) copper oxide, (b) zinc oxide, (c) oxidation of one or more metals selected from the following groups substances, aluminum, gallium, tin, titanium, zirconium, chromium, molybdenum, tungsten, manganese, rhenium, lanthanide metals and actinide metals; in the composite metal oxide, component (a) 5-60 parts, component (b) 10-50 parts, component (c) 5-60 parts;

(2) impregnating the composite metal oxide obtained in step (1) with an aqueous alkali metal hydroxide and/or alkaline earth metal hydroxide solution with a mass fraction of 0.5-5%, and then filtering, drying, and roasting to obtain the product.

Preferably, in step (2), the impregnation temperature is 30°C-80°C, and the impregnation time is 1-48h; the drying temperature is 100°C-200°C, and the drying time is 3-48h; the roasting temperature is 250°C-400 ℃, the roasting time is 3~48h.

The co-precipitation method refers to the reaction of two or more metal cations in the solution in a homogeneous phase with the precipitant, so that the metal cations in the solution are precipitated to obtain a uniform precipitation of various components, and the resulting precipitation mixture or solid solution precursor, A method of obtaining composite metal oxides by filtering, washing, and roasting (thermally decomposing the precipitated mixture or solid solution precursor). The co-precipitation method can be realized in different ways, both the solution containing metal cations can be added to the precipitant solution, the precipitant solution can also be added to the solution containing metal cations, and the solution containing metal cations can also be added The solution and the precipitant solution are simultaneously added to the solvent. The solvent used in the co-precipitation method may be water or a mixed solvent of ethanol and water.

In more detail, the co-precipitation method in step (1) includes:

(I) Prepare mixed soluble metal salt solution, the metals include (a) copper, (b) zinc and (c) one or more metals selected from the following group, aluminum, gallium, tin, titanium, zirconium , chromium, molybdenum, tungsten, manganese, rhenium, lanthanides and actinides;

(II) At 15°C to 80°C, add a precipitating agent aqueous solution to the aqueous solution in step (I) until the pH is 6 to 9 to generate mixed precipitation of the metal elements described in step (I), and the precipitating agent makes The resulting precipitate can be pyrolyzed into metal oxides;

(Ⅲ) Keep the precipitation system obtained in step (II) at 30°C to 80°C for 1 to 48 hours, then filter and wash until the metal cations in the filtrate are less than 100ug/g, at 100°C to 200°C Drying for 3-48 hours, calcination at 250° C. to 400° C. for 3-48 hours to obtain composite metal oxide powder.

In step (I), the "soluble" means that the solubility of each metal salt in water can meet the composition requirements of the prepared composite metal oxide.

In step (I), suitable soluble metal salts can be selected from: nitrates, sulfates, hydrochlorides, acetates of the metals or their hydrates.

In step (II), it is preferable to add an aqueous solution of precipitating agent to the aqueous solution in step (I) under stirring, which will help to improve the homogeneity of the catalyst.

In step (II), the precipitant is preferably one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, ammonia, urea, sodium oxalate, potassium oxalate and ammonium oxalate.

Detailed ways

Embodiment 1～4 are used to illustrate the method for preparing cyclohexyl acetate.

The tests carried out in Examples 1 to 4 were all carried out in a cyclohexyl acetate model test device. The model device consists of a fixed-bed pre-esterification reactor and a reactive distillation esterification tower. The pre-esterification reactor is a 316L stainless steel tube of φ48×4×1200mm. The reaction tube has a hot water jacket outside, and hot water can be passed into the jacket to control the reaction temperature. The reactive distillation esterification tower is a titanium steel (TA2) tower with a diameter (inner diameter) of 50mm and a height of 3m. The lower part of the tower is connected to a tower kettle with a volume of 5L, and a 10KW electric heating rod is installed in the kettle. The heating rod is controlled by an intelligent controller through a silicon controlled rectifier (SCR) to control the heating capacity of the tower kettle. The top of the tower is connected with a condenser with a heat exchange area of 0.5 m and a reflux tank with a volume of 2 L. The raw materials acetic acid and cyclohexene are respectively loaded into a 30L storage tank, and pumped into a pre-esterification reactor through a metering pump for reaction, and the pre-esterification product enters a reactive distillation tower for further reaction. The heating capacity of the reaction tower is adjusted by adjusting the heating power of the tower kettle. Adjust the reflux ratio of the column through the top reflux ratio regulator. Light components are withdrawn from the top of the column. The cyclohexyl acetate product is withdrawn from the bottom of the column.

Example 1

500mL 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, then sulfonated with concentrated sulfuric acid, measured Its exchange capacity is 5.2mmolH ⁺ /g dry basis) is loaded into the middle part of the pre-reactor, and a certain amount of quartz sand is filled at both ends. In addition, the high-temperature-resistant sulfonic acid ion exchange resin (the brand name is Amberlyst45, produced by Rhom&Hass Company) was 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 were 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 put 1950mL of glass spring packing with a diameter of 3mm and a length of 6mm in the upper and lower parts (the filling height is 1m, equivalent to 10 theoretical trays). plate). The cyclohexene and acetic acid are pumped into the pre-reactor by the metering pump for reaction, and the pre-reaction product enters the reaction tower for further reaction. The pre-reaction temperature was adjusted by adjusting the temperature of the hot water in the jacket of the pre-reactor. Adjust the heating capacity of the tower kettle and the reflux flow at the top of the tower to continuously react, and the reaction conditions and reaction results of the stable operating conditions are shown in Table 1.

Example 2

The configuration of reaction tower and catalyst is identical with embodiment 1. Only cyclohexene, cyclohexane and benzene mixture were used instead of cyclohexene for testing, and the pressure of the pre-reactor was 2.0MPa, and the reaction tower was operated under normal pressure. Adjust the heating capacity of the tower kettle and the top reflux flow to continuously react, and the reaction conditions and reaction results of the stable operating conditions are shown in Table 2 below.

Example 3

Put 500mL φ3～4 spherical H _0.5 Cs _2.5 PW ₁₂ O ₄₀ /SiO ₂ catalyst into the middle of the pre-reactor, and fill a certain amount of quartz sand at both ends. In addition, the spherical H _0.5 Cs _2.5 PW ₁₂ O ₄₀ /S iO ₂ catalyst of φ3～4 (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 the mixer , in the sugar coating machine, the silica sol is used as the bonding machine to roll the ball, and then dried and roasted) sandwiched into the titanium wire mesh wave plate to make a cylindrical structured packing with a diameter of 50mm and a height of 50mm. Put this packing type catalyst L into the middle part of the model reaction tower (1m high, equivalent to 12 theoretical trays), and put 1950mL glass spring packing with a diameter of 4mm and a height of 4mm at the top and bottom (the filling height is 1m, equivalent to 12 theoretical plates). 15 theoretical plates). The cyclohexene and acetic acid are pumped into the pre-reactor by the metering pump for reaction, and the pre-reaction product enters the reaction tower for further reaction. The pre-reaction temperature was adjusted by adjusting the temperature of the hot water in the jacket of the pre-reactor. Adjust the heating capacity of the tower kettle and the reflux flow at the top of the tower to continuously react, and the reaction conditions and reaction results of the stable operating conditions are shown in Table 3.

Example 4

The configuration of reaction tower and catalyst is identical with example 3. Only cyclohexene, cyclohexane and benzene mixture were used instead of cyclohexene for testing, and the pre-reaction pressure of 2.0MPa reaction tower was operated under the condition of 0.2MPa. Adjust the heating capacity of the tower kettle and the reflux flow at the top of the tower to continuously react, and the reaction conditions and reaction results of the stable operating conditions are shown in Table 4.

Embodiment 5～10 (preparation of catalyst)

The catalysts of Examples 5-10 were prepared according to the following procedure: weigh a certain amount of soluble metal salt according to the formula in Table 1, place in a 2000mL three-neck flask, add water to dissolve and prepare about 1000mL solution, and install a stirrer and a pH meter on the flask and a thermometer, and place the flask in a temperature-adjustable constant temperature water bath, start stirring, adjust the temperature of the constant temperature water bath, gradually drop a certain concentration of precipitant solution into the flask, control the drop rate of the precipitant aqueous solution, and increase the temperature of the solution. The high temperature is controlled within 1°C. As the pH of the solution increases, precipitation occurs in the solution, and gradually increases as the pH increases. When the pH of the solution reaches the specified value, the dropwise addition of the precipitant aqueous solution is stopped. Then keep a certain temperature and age for a certain period of time under the condition of continuing to stir. Stop stirring, cool down to room temperature naturally, centrifugally filter the precipitate on a high-speed centrifuge, wash 5 times with deionized water, dry the obtained precipitate in an oven, transfer to a muffle furnace for roasting, and obtain mixed metal oxides. The metal oxide is impregnated with a certain concentration of alkali solution at room temperature, vacuum filtered to remove the impregnation solution, the mixture is dried in an oven, transferred to a muffle furnace for roasting, and finally mixed metal oxides are obtained. The composition of the obtained samples was analyzed by ICP method. The specific preparation conditions and results are shown in Table 5.

Examples 11-19 (catalyst evaluation in autoclave)

Embodiments 11 to 19 are the cyclohexyl acetate hydrogenation tests of the catalysts obtained in examples 5 to 10 in an autoclave. The test procedure is as follows: get a certain amount of catalyst powder and place it in a 500mL autoclave, add 250g of cyclohexyl acetate Hexyl ester, the reaction kettle was closed, replaced with nitrogen three times, hydrogen gas was introduced to a certain pressure, and the temperature was gradually raised. At about 80°C, the pressure in the kettle began to drop, indicating that the catalyst in the kettle began to reduce, and the ester hydrogenation reaction began. Timely Supplement hydrogen to maintain a certain pressure in the reactor, and finally raise the temperature to a given temperature, and maintain the pressure at this temperature for a certain period of time, then stop the reaction, cool down to room temperature, and unload the reaction product and catalyst. Analyze the product composition with gas chromatography, and calculate the cyclohexyl acetate conversion rate and the selectivity of cyclohexanol according to the analysis results by the following formula.

Conversion rate of cyclohexyl acetate=[1-moles of unreacted cyclohexyl acetate/(moles of unreacted cyclohexyl acetate+moles of cyclohexane+moles of cyclohexanol+moles of ethyl cyclohexyl ether]× 100%

Cyclohexanol selectivity=[moles of cyclohexanol/(moles of cyclohexanol+moles of cyclohexane+moles of ethyl cyclohexyl ether)]×100%

The experimental results are shown in Table 6.

Table 1

According to the experimental data, the conversion rate of cyclohexene is calculated to be 99.76%, and the selectivity of cyclohexyl acetate is 99.03%.

Table 2

According to the experimental data, the conversion rate of cyclohexene is calculated to be 98.38%, and the selectivity of cyclohexyl acetate is 99.11%.

table 3

According to the test data, the conversion rate of cyclohexene is calculated as 99.9%, and the selectivity of cyclohexyl acetate is 99.35%.

Table 4

According to the experimental data, the conversion rate of cyclohexene is calculated as 99.02%, and the selectivity of cyclohexyl acetate is 99.19%.

Table 5 Summary of Catalyst Preparation Results

Table 6 Summary of autoclave catalyst evaluation results

Claims (13)

1. A method for preparing cyclohexyl acetate, comprising: (1) Input acetic acid and cyclohexene raw materials into the pre-esterification reactor, and react in the presence of a solid acid catalyst; the cyclohexene raw materials are cyclohexene or cyclohexene and cyclohexane and/or benzene the composition of the mixture; (2) Input the output of step (1) into the reactive distillation tower, contact with a solid acid catalyst, react, and simultaneously separate the reaction product to obtain cyclohexyl acetate from the bottom of the tower. 2. The method according to claim 1, wherein the cyclohexene raw material is a mixture of cyclohexene, cyclohexane and/or benzene, and the cyclohexene content is 20m%-80m%. 3. according to the described method of claim 2, it is characterized in that, cyclohexene content is 20m%～60m%. 4. according to the described method of claim 1, it is characterized in that, described pre-esterification reactor is tank reactor, tubular fixed bed reactor, fluidized bed reactor or ebullating bed reactor. 5. according to the described method of claim 1, it is characterized in that, pre-esterification reaction temperature is 50～200 ℃, reaction pressure is normal pressure～10Mpa, the acid-ene mol ratio of pre-esterification reaction is 0.2～20:1, The liquid feed space velocity is 0.5-20h ^-1 . 6. according to the described method of claim 1, it is characterized in that, the theoretical plate number of described reactive distillation tower is 10～150, select 5～30 plates between 10～120 plates in theoretical plate number The solid acid catalyst is arranged; relative to the total loading volume of the catalyst, the liquid feed space velocity is 0.1~20h ^-1 ; the operating pressure of the reactive distillation column is -0.0099MPa to 5MPa; the temperature of the catalyst bed loading area is 40~200 ℃; the reflux ratio is 0.1～100:1. 7. according to the described method of claim 1, it is characterized in that, the solid acid catalyst of step (1) and the solid acid catalyst of step (2) are selected from strong acid type ion exchange resin catalyst, heteropolyacid catalyst and molecular sieve catalyst respectively one or more of. 8. according to the described method of claim 7, it is characterized in that, described strong acid type ion exchange resin catalyst is macroporous sulfonic acid type polystyrene-divinylbenzene resin or the sulfonic acid type after halogen atom modification resin. 9. 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 heteropoly of load keggin structure Catalyst for heteropolyacid acid salt of acid and/or keggin structure. 10. according to the described method of claim 9, it is characterized in that, described heteropolyacid acid salt is acid cesium phosphotungstic acid salt. 11. The method according to claim 7, characterized in that, the molecular sieve catalyst is one or more of Hβ, HY and HZSM-5. 12. A process for preparing cyclohexanol and ethanol comprising: (1) Input acetic acid and cyclohexene raw materials into the pre-esterification reactor, and react in the presence of a solid acid catalyst; the cyclohexene raw materials are cyclohexene or cyclohexene and cyclohexane and/or benzene the composition of the mixture; (2) inputting the discharge of step (1) into a reactive distillation tower, contacting with a solid acid catalyst, reacting, and simultaneously separating the reaction product to obtain cyclohexyl acetate from the bottom of the tower; (3) In the presence of a hydrogenation catalyst, the cyclohexyl acetate obtained in step (2) is contacted with hydrogen to react; the hydrogenation catalyst includes: (a) copper oxide, (b) zinc oxide, (c) Oxides of one or more metals selected from the group consisting of aluminium, gallium, tin, titanium, zirconium, chromium, molybdenum, tungsten, manganese, rhenium, lanthanides and actinides, (d) alkali hydrogen One or more of oxides and alkaline earth metal hydroxides; in the catalyst, in parts by mass, component (a) is 5-60 parts, component (b) is 10-50 parts, The component (c) is 5-30 parts, and the component (d) is 0.2-2 parts. 13. The method according to claim 12, characterized in that in step (3), the temperature is 150-400°C, the reaction pressure is 1-20MPa, the hydrogen ester molar ratio is 1-1000:1; the cyclohexyl acetate liquid feed The space velocity is 0.1～20h ^-1 .