CN107935816B

CN107935816B - A kind of method for catalyzing guaiacol hydrodeoxygenation to prepare cyclohexanol

Info

Publication number: CN107935816B
Application number: CN201711229788.3A
Authority: CN
Inventors: 刘平乐; 龙威; 郝芳; 熊伟; 吕扬; 崔海帅; 吴生焘; 罗和安
Original assignee: Xiangtan University
Current assignee: Xiangtan University
Priority date: 2017-11-29
Filing date: 2017-11-29
Publication date: 2021-03-12
Anticipated expiration: 2037-11-29
Also published as: CN107935816A

Abstract

The invention discloses a method for preparing cyclohexanol by catalyzing the hydrodeoxygenation of guaiacol. In the invention, the supported catalyst x%-Ru-y%-MnO/g-CNTs is used to catalyze the decahydronaphthalene liquid of guaiacol to prepare cyclohexanol by one-step hydrogenolysis, and the catalyst is multi-walled carbon nanotubes treated with mixed acid as The carrier and Ru-MnO are co-loaded and prepared on it. One-step hydrogenolysis of guaiacol in the neutral liquid phase generates cyclohexanol, and the highest selectivity of its main product, cyclohexanol, can reach 85.84%, and the conversion rate at this time is As high as 99.38%, that is, the yield is as high as 85.31%. The process of the invention is short, the reaction equipment and the operation method are simple, the reaction conditions are mild, the reaction time is short, the catalyst is simple and easy to obtain, the cost is low, the stability is good, and the product is pure and easy to use. Separation and purification, the expected economic benefits are very considerable, and it is of great significance in the application of industrial production.

Description

Method for preparing cyclohexanol by catalytic hydrogenation and deoxidation of guaiacol

Technical Field

The invention relates to preparation of cyclohexanol, in particular to an acid-modified carbon nano tube loaded Ru and MnO bimetallic catalyst and a method for catalyzing direct hydrogenolysis of guaiacol to generate cyclohexanol in one step.

Background

Human beings can not survive any more, and the exploration of new energy for sustainable development is always the key point and hot point of the scientific community. Biomass energy has recently been favored by scientific researchers as a green energy source with sustainable development. The plant contains a large amount of lignin, and the degradation of the lignin can produce a large amount of alcohols or phenols, so that the pressure of non-renewable fossil energy can be relieved, and the method has great research value. Guaiacol is one of lignin degradation products, and its content is as high as 60%, and it has typical representativeness. Because the molecule contains functional groups such as benzene ring, phenolic hydroxyl and methoxyl, the catalyst can be used for producing cyclohexanol by liquid phase hydrogenation in a reaction kettle, is a popular technological route in recent years, and the core technology of the catalyst mainly focuses on preparation and modification of the catalyst.

Cyclohexanol is a valuable industrial material which can be widely used in the preparation of resins, paints, ethylcellulose, rubber and other processes, and can also be used in the synthesis of detergents, rubber curing agents, pesticides, herbicides, plasticizers, acid dyes, textile assistants and the like. The cyclohexanol molecule contains unique six-membered carbon ring and alcoholic hydroxyl structure, and can be used as a basic raw material for large-scale production of adipic acid, caprolactam, nylon 66 and the like. At present, the method has brought out unique advantages in the fields of chemical industry, daily chemical industry, building material industry and the like.

The existing method for preparing cyclohexanol mainly comprises two methods, namely phenol hydrogenation and cyclohexane oxidation, wherein the former method has high raw material cost, and the latter method has the defects of complex reaction, more byproducts, low yield and the like. The lignin is used as a renewable resource, a large amount of phenolic substances can be generated in the concentration and purification processes, and valuable industrial material cyclohexanol can be obtained by directly utilizing the cheap phenolic substances through hydrogenation, so that the process has great scientific value and is in the hot research surge at home and abroad. The process relates to a plurality of core technologies in the fields of biology, environmental protection and chemical industry, is the fusion of multidisciplinary technologies, and has no ideal solution at present.

The cracking process of lignin is complex, and the specific research starts later: in 2008, xujie (CN 101768052 a) of institute of chemico-physical in university of chinese academy of sciences invented that the nickel-based catalyst doped with other metals can catalyze natural lignin or industrial lignin to efficiently hydrogenate to generate aromatic compounds such as phenol group, guaiacol group and lilac, the sum of the contents of both of them accounts for more than 90% of the total products, but the reaction must be carried out at 200 ℃ and 5.0 MPa under continuous reaction for 6 hours, and the conversion rate can only reach 53%. In 2010, a tungsten-based catalyst is invented by Zuo [ CN 102476980A ] of the institute of chemical and physical in the university of Chinese academy of sciences, and can also be efficiently used for the hydro-conversion of natural lignin, phenolic substances are generated by hydrogenation under the hydrothermal condition, the highest yield is only 55.6%, and the conditions are that the hydrogen pressure is set to be 6.0 MPa at the temperature of 235 ℃ and the reaction is continuously carried out for 4 hours. Similarly, Zuo also successfully realizes the hydro-conversion of the jerusalem artichoke in CN 102746117A through a bimetallic catalyst, prepares a great amount of mannitol or sorbitol and other hexahydric alcohols similar to cyclohexanol, and continuously reacts for 12 hours at 80 ℃ and 6.0 MPa of hydrogen pressure by selecting Ru/AC as the catalyst. In 2012, Freund of Zhejiang university also found that the microwave method can promote lignin to be continuously degraded to generate micromolecular phenolic substances, the catalyst is Pd/C, the temperature is 160 ℃, the hydrogen is normal pressure, the continuous reaction is carried out for 40 min, and multiple times of alkaline degradation is carried out under the action of the microwave; in 2013, the foreign professor g.c. combrin found that lignocellulosic biomass can be catalyzed by hydrothermal hydrogenation to generate small molecular substances under the conditions that the pH is controlled within the range of 5.2-7.0, the reaction temperature is 150-300 ℃, and the catalyst is vulcanized CoNiMo; in 2014, the Zhou Cheng of the university in southeast was also tasted in [ CN 104326875A ]Vanadium-based catalyst is used for hydrogenation degradation of lignin under liquid phase condition to form more phenolic compounds, the reaction temperature is 290 ℃, the hydrogen is 3.0 MPa, the reaction is continuously carried out for 60 min, and the conversion rate can reach 85.14%; in 2016, the institute of energy, Guangzhou, China academy of sciences, discloses a MoO-containing material in [ CN 106495974A ]₃The catalyst of (2) can catalyze the hydrogenolysis fracture of C-O bond in monocyclic phenolic compound, improve the intramolecular deoxygenation efficiency, obtain more aromatic hydrocarbon products, and continuously react for 360 min at the reaction temperature of 340 ℃ and the hydrogen pressure of 0.2 MPa. Thus, it is also easier to pyrolyze lignin to phenolics, and to select a suitable active catalyst whose hydrogen pressure and temperature can be selected to achieve higher decomposition and yield.

Guaiacol is a typical representative of phenolic substances in a lignin pyrolysis product, is also a representative of a lignin pyrolysis phenolic product with the simplest molecular structure, is toxic and is not suitable for long-time storage, and therefore, the hydroconversion and utilization process of guaiacol has obvious importance and representativeness. The experiment exploration for directly hydrogenating the catalyst by one step at home and abroad starts late, but the catalyst is always concerned and explored by scholars at home and abroad.

Zhang Ying (CN 102875335A) of China university of science and technology selects SBA-15 as carrier and CeO₂The catalyst with Pd, Pt, Ru and other noble metals as active components is researched as an auxiliary agent, the conversion rate of mixed phenols (phenol: eugenol: guaiacol =1:1: 1) is 100 percent after the catalyst is continuously stirred at the speed of 1000 revolutions per minute for 8 hours at the temperature of 170 ℃, the product is mostly alcohol substances, but the product is various and is not beneficial to effectively separating out main products.

ZrO was selected from the energy institute of Guangzhou, China academy of sciences, Malong (CN 102430409A)₂-SiO₂The binary composite oxide is used as a carrier, a novel catalyst which takes bimetal of Ni and Cu (the content of Ni is 10 percent, the mass ratio of Ni to Cu is 1: 0.5) as an active component and is introduced by an impregnation method is used for carrying out kettle type hydrogenation on guaiacol solution with the mass concentration of 10 percent by taking n-octane as a solvent at the temperature of 300 ℃ and the hydrogen pressure of 5.0 MPa, and the conversion rate can be highThe yield reaches 100 percent, the product is mainly alkane, and the highest yield reaches 62.7 percent.

Wang Yanqi celery (CN 104744204A) of Huadong university of science and technology researches one or more metal active components of ruthenium, platinum, palladium, iridium, iron, cobalt, nickel and copper, loads the metal active components on oxides of transition metal elements niobium, tantalum, zirconium, molybdenum, tungsten, rhenium and the like to form a catalyst with a mixed acid center, aiming at a hydrogenation experiment of guaiacol under the condition of taking water as a solvent, the reaction temperature is 250 ℃, the hydrogen pressure is 1.0 MPa, the reaction is continuously carried out for 24 hours under the stirring speed of 1000 revolutions per minute, the main product is aromatic hydrocarbon, the yield is only 10 percent, and the method proves that the water as the solvent is not suitable for the hydrodeoxygenation conversion of the guaiacol.

In 2015, the Qi of Guangzhou energy research institute of Chinese academy of sciences [ CN 10104923233A ] successfully prepared SiO₂Core-shell structure catalyst Ni @ SiO coated with active metal Ni₂The method is used for preparing cyclohexanol by selective hydrodeoxygenation of guaiacol. In a decahydronaphthalene solution of guaiacol with the mass fraction of 1%, the reaction temperature is 120 ℃, the hydrogen pressure is 2.0 MPa, the conversion rate of reactants and the selectivity of cyclohexanol reach 100% after continuous reaction for 2 h, and the high selectivity is attributed to the unique core-shell pore structure, although the result is excellent, the mass fraction of guaiacol used is only 1%, the concentration is very low, the cost of using a large amount of solvent decahydronaphthalene is high, the tolerance to the amount of solvent is very high, a large amount of solvent is wasted under the condition that the mass fraction of guaiacol is kept very low in each experiment, the industrial cost of the technology is greatly increased, therefore, even if the ideal selectivity can be obtained, the separation cost of the product is very high, even if the selectivity of cyclohexanol is stably kept at 100%, the content of the product cyclohexanol in the reaction solution is still very low (about 1%), this causes a great hindrance to further separation and collection, and the processing cost is more likely to be higher than the purification of a product having a low purity, so that the economic efficiency is not desirable. Professor Boonyasuwat (Catal Letter,2013,143: 783-791) in 2016 and professor Ishikawa (Applied Catalysis B: Environmental, 2016,182:193-203) in Japan both proposed the hydrogenation of guaiacol at moderate concentrations (10% -40%)The most suitable catalytic active metal is Ru instead of Ni, and the by-product is inevitable, so far the maximum yield of the improved technology can not break through 76%.

The inventor of the university of Zhejiang industry, in the phoenix article (CN 105001902A), found that guaiacol and alcohol are mixed, and are injected into a fixed bed reactor at 500-600 ℃ under the catalytic action of HZSM-5 molecular sieve, and the temperature is kept for 1 hour, and the product is continuously condensed, extracted and recycled, the conversion rate of guaiacol can reach 100%, and the product is mainly hydrocarbon substances, and the yield is only 20.68%. Recently, Zhang Zong Chao (CN 106554257A) of the institute of chemistry and physics, the Chinese academy of sciences, invented an Ag/TiO₂The catalyst is prepared by continuously reacting 7.5 percent guaiacol solution for 0.25 h under the conditions of 400 ℃, 3.0 MPa of hydrogen pressure and 700 r/min of stirring under the condition of taking n-decane and n-heptane as solvents, and the highest conversion rate of guaiacol can be 81.53%. The invention discloses a sildenafil (CN 105461498A) of the university of agriculture in south China, wherein an Fe-Ni bimetallic catalyst is loaded on a molecular sieve and used for a gas-phase hydrogenation experiment of guaiacol on a fixed bed, the sum of the yields of BTX (benzene, toluene and xylene) products can reach 19.83% at the normal pressure and at the temperature of 250-400 ℃, and the method reduces the loss of carbon atoms and the consumption of hydrogen, but the yield is too low and the required reaction temperature is too high.

In summary, the hydrogenation of guaiacol can be carried out in both gas phase and liquid phase, the main products of gas phase hydrogenation are hydrocarbons, and the main products of liquid phase hydrogenation are phenols or alcohols. The hydrogenation process of guaiacol depends on a high-activity catalyst, the reaction temperature is usually higher than 160 ℃, the hydrogen pressure is 0-5 MPa, the carrier, the active metal and the auxiliary agent influence the variety and distribution of the product, but the over-hydrogenated product is cyclohexane. The industrialization of the guaiacol hydrogenation process needs to fully consider the complexity of instruments, the rigor degree and safety of reaction conditions, the cost and the preparation difficulty of catalysts, the high and low yield of products and the like.

Recently, the scientific community finds that the high activity of the noble metal Ru is very suitable for the hydrogenation process of guaiacol, decahydronaphthalene is very favorable for the hydrogenation of guaiacol as a solvent which can consume hydrogen to generate hydrogenation, and the liquid phase hydrogenation process under the lower temperature and the lower hydrogen pressure is matched for easy realization, thus becoming a hotspot of biomass hydrogenation conversion research. Regardless of phenols, hydrocarbons or alcohols, the purity degree of the product determines the scientific value of the hydrogenation process, and the improvement of the selectivity of the main product can effectively promote the industrial process of guaiacol hydrogenation. The hydrogenation process of guaiacol can be realized by using a simple instrument under mild conditions, a high-purity main product is obtained, and the method is very favorable for industrial production.

One of the new methods for the hydrogenation of guaiacol is to pursue mild conditions for the reaction at lower temperature and lower pressure; secondly, the by-products are reduced so as to achieve high selectivity or yield of the main product; thirdly, the cost of the catalyst and the using amount of the solvent are reduced, the use of toxic and harmful solvents is avoided as much as possible, and the purposes of environmental protection, no pollution, easy separation of products, energy conservation and high efficiency are realized.

Disclosure of Invention

Aiming at the problems of the existing catalytic method for preparing cyclohexanol by one-step hydrogenolysis of guaiacol, the invention aims to provide a novel catalyst of x% -Ru-y% -MnO/g-CNTs, which meets the requirement of efficient hydrogenolysis reaction of guaiacol in a neutral environment.

The invention also aims to provide the method for preparing cyclohexanol by hydrogenolysis of guaiacol, which has the advantages of mild reaction conditions, short process flow, low raw material cost, simple and easily-obtained catalyst, environmental friendliness, high yield of main products and green and environment-friendly process.

The purpose of the invention can be achieved by the following technical scheme:

a method for preparing cyclohexanol by catalytic hydrogenation and deoxidation of guaiacol is characterized in that acid-modified carbon nano tube loaded Ru and MnO bimetal (called as a loaded Ru catalyst for short, and denoted as x% -Ru-y% -MnO/g-CNTs, wherein x% and y% respectively represent the mass ratio of Ru to MnO in the catalyst) is used as a catalyst, under the condition that decahydronaphthalene is used as a solvent, the guaiacol is subjected to hydrogenation and deoxidation to one-step production to obtain the cyclohexanol, and the mass fraction of a decahydronaphthalene solution (called as a guaiacol solution for short) of the guaiacol is 10-25%.

Further, the catalyst is prepared from the following raw materials in percentage by mass:

3-8% of active component Ru

5 to 10 percent of doping auxiliary agent MnO

82-92% of acid modified carbon nanotubes (g-CNTs)

Wherein:

the metal active component Ru is derived from RuCl₃Or Ru (NO)₃)₃A hydrate;

MnO is derived from decomposition of manganese acetate or manganese nitrate.

Further, the mass ratio of the catalyst to the reaction liquid is 0.05-0.15: 6.

Further, the reaction temperature of the hydrogenation deoxidation of the guaiacol is preferably 160-220 ℃, the reaction time is preferably 30-240 min, and the reaction pressure is preferably 0.5-2.5 MPa.

Further, the mass fraction of guaiacol is 20%.

In the catalyst adopted by the invention, Ru-MnO with different mass proportions is loaded on an acid modified carbon nano tube carrier, the catalytic effect is the best 6% -Ru-8% -MnO/g-CNTs in the loaded catalyst, namely the mass of metal Ru accounts for 6.0% of the mass of the whole catalyst, the mass of MnO accounts for 8% of the mass of the whole catalyst, the conversion rate of corresponding guaiacol can reach 99.38%, the selectivity of a main product cyclohexanol reaches 85.84%, the yield of the main product cyclohexanol can reach 85.31%, the concentration in a reaction solution is higher, the separation and purification of products are facilitated, and the industrial popularization and production of the technology are facilitated. The reaction solution in the invention takes decalin as a solvent, the optimal mass fraction of the guaiacol is 20%, and the corresponding used catalyst has the advantages of less mass, low cost and good economy.

According to the invention, the preferential use of the auxiliary agent MnO is favorable for improving the high selectivity of the cyclohexanol as the main product and the stability of the catalyst, TEM (transverse electric field) representation shows that the auxiliary agent MnO is favorable for uniformly dispersing the metal active component Ru loaded on the carrier, and meanwhile, the auxiliary agent MnO can obviously inhibit the occurrence of byproducts.

The invention has the beneficial effects that:

1. according to the invention, the supported catalyst x-Ru-y-MnO/g-CNTs is used as the catalyst, and the guaiacol is subjected to hydrogenolysis in one step to generate cyclohexanol under a mild condition in a liquid phase, so that higher guaiacol conversion rate and cyclohexanol selectivity can be obtained.

2. The reactant raw materials and the catalyst have low cost and are easy to obtain, and the used catalyst has good stability and cycle performance.

3. The reaction condition is mild, the process is short, the operation is convenient, and the industrial production requirement is met.

4. No pollution, high yield, high product purity, easy separation, environment-friendly synthesis process and accordance with the requirements of green chemical process.

Drawings

FIG. 1 is a TEM representation of a 6% -Ru-8% -MnO/g-CNTs catalyst of the present invention, which is a good indication that the metal Ru and MnO are uniformly dispersed on the acid-modified carbon nanotube support.

Detailed Description

The following examples are intended to further illustrate the present invention and are within the scope of the claims.

The preparation and hydrogenation method of the catalyst comprises the following steps:

1. pretreatment of the carrier: the carbon nanotubes need to be subjected to an acid activation treatment. The method comprises the following steps: firstly, preparing a mixed solution of 30.0 mass percent of dilute sulfuric acid and 40 mass percent of dilute nitric acid, adding the mixed acid solution into multi-wall carbon nanotube powder which is placed in a three-necked bottle and is continuously roasted for 6 hours (impurities are removed) at 700 ℃ according to the liquid-solid mass ratio of 20:1, placing the multi-wall carbon nanotube powder in an oil bath kettle at 95 ℃ for continuous thermal reflux for 6 hours, cooling the multi-wall carbon nanotube powder, taking out the multi-wall carbon nanotube powder, washing the multi-wall carbon nanotube powder for 5 times by using distilled water, carrying out suction filtration, continuously drying the multi-wall carbon nanotube powder in a 110 ℃ oven for 12 hours, taking out the multi-wall carbon nanotube powder, grinding the multi-wall carbon nanotube powder into fine powder, placing the fine powder in a tube furnace under the protection of nitrogen after passing through a 160. The specific surface area of the carbon nano tube carrier before treatment is only 195.49 m as obtained by a BET test²G, treatment by mixing sulfuric acid with nitric acidThe specific surface area of the carbon nano tube carrier is increased to 236.57 m²The color of the carrier is blacker than that of the carrier before treatment, the carrier is in a fine powder shape, and XRD representation shows that the carrier only contains main characteristic peaks of two carbon nano tubes, and the purity is very high. The purpose of treating the carbon nano tube by the mixed acid is to form a plurality of defects on the microscopic surface of the carrier material and increase the specific surface area of the carrier material; on the other hand, the carrier material is shown to generate a plurality of microscopic adsorbed hydroxyl groups to enhance the activity of the carrier material, and the processed carrier is called g-CNTs.

2. Preparing an x% -Ru/g-CNTs supported catalyst by an impregnation method: weighing a certain mass of ruthenium chloride trihydrate (RuCl)₃•3H₂O) is dissolved in 20.00 mL of high-purity deionized water, stirred for 10 min at room temperature to be completely dissolved, g-CNTs powder subjected to acid activation treatment is carefully added after a uniform and stable black solution is formed, the solution is soaked for 8 hours under continuous stirring at room temperature to be in a slurry state, taken out and subjected to microwave ultrasonic treatment for 30 min, then aged for 2 hours, dried for one night at the temperature of 110 ℃, taken out and ground into fine powder, screened by a 100-mesh screen, sent into a tubular furnace under the protection of nitrogen, continuously roasted for 3 hours at the temperature of 400 ℃, then transferred to a hydrogen environment for 3 hours, and the catalyst is fully reduced and then transferred to nitrogen to be cooled to room temperature. If the catalyst is placed for a long time, the catalyst is placed in a tubular furnace at the temperature of 400 ℃ again and reduced by hydrogen for 3 hours to form a catalyst A, B, C, D, E, F, the supported mass fractions of Ru are 3%, 4%, 5%, 6%, 7% and 8%, respectively, and the catalyst is stored in a closed and air-isolated manner.

3. The tests for carrying out the guaiacol hydrogenolysis reaction over different catalysts and under different reaction conditions were as follows:

example 1: the hydrogenation device is a 20 ml stainless steel high-pressure electric heating reaction kettle, firstly 1.2 g of guaiacol is added into 4.8 g of decahydronaphthalene, the mixture is stirred by a magnet for 30 min to form a uniform guaiacol solution with the mass fraction of 20%, then 0.1 g of catalyst A is added, the high-pressure kettle is closed rapidly, air in the kettle is replaced by hydrogen for 3-4 times, stirring is started, the pressure of introduced hydrogen is adjusted to 2.0 MPa, the temperature is increased to 200 ℃, the mixture is continuously reacted for 200 min at the temperature and then cooled to room temperature, products are taken out and weighed after careful pressure release, an upper layer liquid is taken out, the centrifugal liquid is detected by using a gas chromatography internal standard method, ethylbenzene is used as an internal standard substance, and conversion rate and selectivity data of related species are obtained by calculation and are shown in table 1.

Example 2: catalyst B was selected, the reaction feeds and hydrogenolysis conditions were the same as in example 1, and the conversion and selectivity data for the relevant species calculated are shown in table 1.

Example 3: catalyst C was selected, the reaction feeds and hydrogenolysis conditions were the same as in example 1, and the conversion and selectivity data for the relevant species calculated are shown in table 1.

Example 4: catalyst D was selected, the reaction feeds and hydrogenolysis conditions were as in example 1, and the conversion and selectivity data for the relevant species calculated are shown in table 1.

Example 5: catalyst E was selected, the reaction feeds and hydrogenolysis conditions were as in example 1, and the conversion and selectivity data for the relevant species calculated are shown in table 1.

Example 6: catalyst F was selected, the reaction feeds and hydrogenolysis conditions were as in example 1, and the conversion and selectivity data for the relevant species calculated are shown in table 1.

TABLE 1

Analysis and comparison of six groups of data show that when the content of the transition metal Ru is lower than 6%, the conversion rate of the guaiacol is increased along with the increase of the loading amount of the metal Ru, but the selectivity of each product is basically unchanged; when the content of the transition metal Ru is higher than 6%, the conversion rate is basically unchanged along with the increase of the loading amount of the metal Ru, the selectivity of cyclohexane is increased, and the selectivity of other products is basically kept unchanged. Therefore, the selectivity of the cyclohexanol as the main product does not depend on the loading of the transition metal Ru, but in the subsequent catalyst modification exploration, the loading of the transition metal Ru is selected to be 6% in order to save cost.

Example 7: the co-leaching method is used for preparing the x-Ru-y-MnO/g-CNTs supported catalyst: weighing RuCl with a certain mass₃•3H₂O dissolved in 20.00 mL of high purityStirring for 10 min at room temperature in deionized water to completely dissolve the components until a uniform and stable black solution is formed. Carefully weighing a certain mass of manganese acetate Mn (CH)₃COO)₂•4H₂Adding the O solid into a beaker, continuously stirring at room temperature to obtain uniform and stable liquid, adding a g-CNTs carrier with a certain mass after acid activation treatment, continuously stirring and soaking for 8 hours, taking out, performing ultrasonic treatment for 30 min, then aging for 2 hours, drying at 110 ℃ overnight, taking out, grinding into fine powder, sieving with a 100-mesh sieve, sending into a tubular furnace under nitrogen protection, continuously roasting at 400 ℃ for 3 hours, then continuing for 3 hours in a hydrogen environment, fully reducing the catalyst, and cooling to room temperature under nitrogen. If the catalyst is placed for a long time, the catalyst is placed in a tubular furnace at the temperature of 400 ℃ again and is reduced for 3 hours by hydrogen to form a catalyst G, the corresponding load mass fractions of Ru and MnO are respectively 6% and 5%, and the catalyst G is sealed, isolated from air and well stored. The mass of the feeds and the hydrogenolysis conditions were the same as in example 1 and the conversion and selectivity data for the relevant species were calculated and shown in table 2.

Example 8: the same catalyst preparation method as that of example 7 was used to prepare a catalyst H of 6% -Ru-6% -MnO/g-CNTs, and the conversion and selectivity data of the relevant species obtained under the same feeding quality and hydrogenolysis reaction conditions are shown in Table 2.

Example 9: the same catalyst preparation method as in example 7 was used to prepare a catalyst I of 6% -Ru-7% -MnO/g-CNTs, and the conversion and selectivity data of the relevant species obtained under the same feeding quality and hydrogenolysis conditions are shown in Table 2.

Example 10: the same catalyst preparation method as in example 7 was used to prepare catalyst J of 6% -Ru-8% -MnO/g-CNTs, and the conversion and selectivity data of the relevant species obtained under the same feeding quality and hydrogenolysis conditions are shown in Table 2.

Example 11: the same catalyst preparation method as that of example 7 was adopted to prepare a catalyst K of 6% -Ru-9% -MnO/g-CNTs, and the conversion and selectivity data of the related species obtained under the same feeding quality and hydrogenolysis reaction conditions are shown in Table 2.

Example 12: the catalyst L prepared by the same method as that of example 7 was 6% -Ru-10% -MnO/g-CNTs, and the conversion and selectivity data of the related species obtained under the same feeding quality and hydrogenolysis reaction conditions are shown in Table 2.

TABLE 2

The above experimental results show that: when the mass ratio of the supported metal Ru in the total catalyst is 6% and the mass ratio of the auxiliary agent MnO in the total catalyst is 8%, the conversion rate of guaiacol and the selectivity of the main product cyclohexanol are highest. The characterization of XRD and XPS shows that Mn in the catalyst exists in the form of MnO, and the TEM shows that Ru has high dispersion, which shows that the introduction of MnO can effectively promote the dispersion of transition metal Ru, thereby promoting the exertion of hydrogenation activity, and simultaneously, the catalyst can also inhibit the generation of byproducts such as cyclohexanone, benzene and the like, so that the selectivity of the main product cyclohexanol is greatly improved.

Example 13: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction temperature was 160 ℃, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 3.

Example 14: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction temperature was 180 ℃, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 3.

Example 15: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction temperature was 220 ℃, the charge mass and other conditions were the same as those described in example 1, and the conversion and selectivity data of the relevant species were obtained through experiments as shown in Table 3.

TABLE 3

Comparing the data at different reaction temperatures shows that: the temperature is too low, the conversion rate of guaiacol is not ideal, the required reaction time is too long, the content of intermediate products is also high, and the selectivity of the main product cyclohexanol is not ideal; although the conversion can be increased, the cyclohexanol in the hydrogenation process can be shifted toward cyclohexane, resulting in a selectivity of cyclohexanol as a main product which is not as high as that obtained at 200 ℃ (corresponding to the data of example 10), and a suitable increase in cyclohexane selectivity, therefore, it is desirable to select the reaction temperature at 200 ℃.

Example 16: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the pressure of hydrogen gas introduction was 0.5 MPa, the feeding quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 4.

Example 17: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the pressure of hydrogen gas introduction was 1.0 MPa, the charging quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 4.

Example 18: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the pressure of hydrogen gas introduction was 1.5 MPa, the charging quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 4.

Example 19: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the pressure of hydrogen gas introduction was 2.5MPa, the feeding quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 4.

TABLE 4

Comparison of the reaction data at different hydrogen pressures shows that: the hydrogenation of guaiacol requires a certain hydrogen pressure, if the pressure of the introduced hydrogen is too low, the conversion and the selectivity of the main product are not ideal, while the pressure of the introduced hydrogen is too high, which also results in the conversion of cyclohexanol into cyclohexane, so that the suitable hydrogen pressure is 2 MPa (corresponding to the data of example 10).

Example 20: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction time was set to 30 min, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 5.

Example 21: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction time was set to 60 min, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 5.

Example 22: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction time was set to 90 min, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 5.

Example 23: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction time was set to 120 min, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 5.

Example 24: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction time was set to 150 min, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 5.

Example 25: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction time was set to 180 min, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 5.

Example 26: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the reaction time was set to 240 min, the charge quality and other conditions were the same as those described in example 1, and conversion and selectivity data of related species were obtained through experiments as shown in Table 5.

TABLE 5

By comparing the data of examples 20-26, we can easily find that the optimal reaction time is 200 min (corresponding to the data of example 7), the too long hydrogenation time results in the increase of the content of cyclohexane as a byproduct, the too short reaction time results in the cyclohexanone as a byproduct, and the content of other intermediate products also increases.

To analyze and explore the effect of catalyst reduction temperature, we also made relevant comparative experiments:

example 27: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the temperature for calcining the catalyst in a tube furnace and reducing the catalyst with hydrogen was 200 ℃, the other steps were the same as before, the charge quality and other reaction conditions were the same as those described in example 1, and the conversion and selectivity data of the relevant species were obtained through experiments as shown in Table 6.

Example 28: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the temperature for calcining the catalyst in a tube furnace and reducing the catalyst with hydrogen was 300 ℃, the other steps were the same as before, the charge quality and other reaction conditions were the same as those described in example 1, and the conversion and selectivity data of the relevant species were obtained through experiments as shown in Table 6.

Example 29: a6% -Ru-8% -MnO/g-CNTs catalyst was prepared according to the same catalyst preparation method as in example 10, the temperature for calcining the catalyst in a tube furnace and hydrogen reduction was 500 ℃, the other steps were the same as before, the charge quality and other reaction conditions were the same as those described in example 1, and the conversion and selectivity data of the relevant species were obtained through experiments as shown in Table 6.

TABLE 6

The influence of the roasting temperature and the hydrogen reduction temperature of the catalyst on the catalyst is large, and manganese-containing species (mainly containing Mn) obtained by reducing manganese acetate at different temperatures by hydrogen are different₃O₄、Mn₂O₃MnO and Mn). Species Mn reduced at 200 deg.C₃O₄The doping influence of Mn of a species reduced at 500 ℃ is not great, the selectivity of a main product cyclohexanol is not ideal, and the species reduced at 300 ℃ simultaneously contains Mn₃O₄、Mn₂O₃MnO, the species reduced at 400 ℃ is mainly MnO. The morphology of the Mn-containing promoter was clearly discernible in combination with XRD and XPS characterization of the catalyst, and we found that the addition of MnO was the most effective in increasing the activity of the catalyst and the selectivity of the main product, with an optimum calcination and hydrogen reduction temperature of 400 ℃ (corresponding to the data of example 10).

In order to compare the influence of other metal additives, a part of bimetallic catalyst is selected through a large amount of experiments, and the catalytic performance of the bimetallic catalyst is compared and analyzed.

Example 30: in the same way as the catalyst preparation method of example 10, a 6% -Ru-8% -Ni/g-CNTs catalyst (certain mass of nickel acetate is selected to be added) is prepared, the temperature of roasting the catalyst in a tube furnace and reducing hydrogen is 400 ℃, other reaction conditions are the same as those in example 1, and conversion rate and selectivity data of related species are obtained through experiments and are shown in Table 7.

Example 31: in the same way as the catalyst preparation method of example 10, a 6% -Ru-8% -Ag/g-CNTs catalyst (a certain mass of silver nitrate is selected to be added) is prepared, the temperature of roasting the catalyst in a tube furnace and reducing hydrogen is 400 ℃, other reaction conditions are the same as those in example 1, and conversion rate and selectivity data of related species are obtained through experiments and are shown in Table 7.

Example 32: in the same way as the catalyst preparation method of example 10, a 6% -Ru-8% -Zn/g-CNTs catalyst (a certain mass of zinc acetate is selected to be added) is prepared, the temperature of roasting the catalyst in a tube furnace and reducing hydrogen is 400 ℃, other reaction conditions are the same as those in example 1, and conversion rate and selectivity data of related species are obtained through experiments and are shown in Table 7.

TABLE 7

Comparing the above results shows that: the invention relates to a novel supported catalyst of 6% -Ru-8% -MnO/g-CNTs (the mass fraction of Ru is 6% and the mass fraction of MnO is 8%), which has more ideal catalytic effect compared with the addition of Ni, Ag and Zn to prepare cyclohexanol by the hydrogenolysis of decalin liquid of guaiacol.

The prepared 6% -Ru-8% -MnO/g-CNTs catalyst is reacted once, centrifugally collected and dried overnight, then placed in a tube furnace to be continuously roasted for 3 h at 400 ℃ under the protection of nitrogen, then transferred into a hydrogen atmosphere to be reduced for 3 h, then transferred into a nitrogen atmosphere to be cooled to room temperature for continuously carrying out hydrogenation experiments to investigate the stability of the catalyst, the experiments are repeatedly carried out for 5 times, other reaction conditions are the same as those in example 1, and the obtained experimental data are shown in Table 8.

TABLE 8

The same catalyst hydrogenation experimental data after 5 times of comparative circulation can be known as follows: the 6% -Ru-8% -MnO/g-CNTs catalyst has very good stability, the catalytic effect of the catalyst is not reduced basically after the catalyst is continuously circulated for 4 times, and the activity of the catalyst is reduced only when the catalyst is circulated for 5 times because the loss of part of species in the catalytic reaction causes the reduction of the activity, so the catalyst has potential for novel industrial popularization and application. The stability and the recycling of the catalyst are the embodiment of the superior performance of the catalyst, and the catalyst designed by the invention has the very superior recycling and high-efficiency utilization performance after simple recovery, drying, roasting and activation.

To investigate the effect of the mass fraction of guaiacol on the performance of this technique, we selected 6% -Ru-8% -MnO/g-CNTs catalyst and performed the same experiment at different guaiacol concentrations, and other reaction conditions were the same as those described in example 1, and the experimental data obtained are shown in table 9.

TABLE 9

When the concentration of guaiacol is too low, economic benefits are poor, and industrial application is severely limited, the investigation of the invention starts from the time when the concentration is 10%. When the concentration of the guaiacol reactant reaches 25%, cyclohexanone as a byproduct appears, and when the concentration of the guaiacol reactant reaches 30%, benzene as a byproduct also appears, which indicates that the increase of the reactant concentration will increase the types of the byproducts, thus being inconvenient for the purification of the product; when the concentration of the reaction product of the guaiacol reaches 100 percent (namely, decahydronaphthalene is not added), the conversion rate is lower, the selectivity of the main product cyclohexanol is not high, the content of the intermediate product 1, 2-cyclohexanediol reaches 24.56 percent, and the reaction degree is incomplete, a plurality of byproducts are produced, and the effect is poor. Therefore, it is desirable to control the initial mass concentration of the reactant guaiacol to be 20%, and a solvent therefor is also indispensable.

To investigate the effect of the healing solvent on the technology, we selected 6% -Ru-8% -MnO/g-CNTs catalyst and performed the same experiment under different common solvents (guaiacol mass fraction is kept at 20%), and other reaction conditions were the same as those in example 1, and the obtained experimental data are shown in table 10.

Watch 10

Comparing the hydrogenation experimental performance of guaiacol in different solvents with the same catalyst, it can be found that the polarity of the solvent has a certain influence on the distribution of the reaction product, but the catalytic performance in 8 solvents is not as good as that of decalin as the solvent.

In conclusion, the multi-walled carbon nanotube treated by mixed acid is used as a carrier, the Ru-MnO is commonly loaded on the carrier to prepare the bimetallic catalyst, the guaiacol is subjected to hydrogenolysis in one step in a neutral liquid phase to generate cyclohexanol, the highest selectivity of the main product cyclohexanol can reach 85.84%, the conversion rate can reach 99.38%, the yield of the main product cyclohexanol can reach 85.31%, the catalyst is low in cost, the process conditions are appropriate, the expected economic benefit is considerable, and the application of the catalyst in industrial production is of great significance. The method has the advantages of short process route, simple reaction equipment and operation method, mild reaction conditions, short reaction time, simple and easily obtained catalyst, good stability, pure product, easy separation and purification, environmental protection and suitability for industrial popularization.

Claims

1. a method for catalyzing guaiacol hydrodeoxygenation to prepare cyclohexanol, it is characterized in that, with acid-modified carbon nanotube load Ru and MnO bimetal as catalyzer, this catalyzer is the supported Ru catalyst, is marked as x %-Ru-y%-MnO/g-CNTs, x% and y% represent the mass ratio of Ru and MnO in the catalyst, respectively. Under the condition that decalin is the solvent, guaiacol hydrodeoxygenation is produced in one step. To obtain cyclohexanol, the mass fraction of the decalin solution of guaiacol is 10-25%;

The catalyst is made from the following raw material components in mass percent:

Active ingredient Ru 6%

Doping additive MnO 8%

Acid-modified carbon nanotubes are g-CNTs 86%.

2. the method for catalyzing guaiacol hydrodeoxygenation to prepare cyclohexanol according to claim 1, is characterized in that, active component Ru is derived from RuCl ₃ or Ru(NO)(NO ₃ ₎ hydrate, MnO From the decomposition of manganese acetate or manganese nitrate.

3. the method for preparing cyclohexanol by catalyzing guaiacol hydrodeoxygenation according to claim 1, is characterized in that, the mass ratio of catalyst and reaction solution is 0.05～0.15:6.

4. the method for preparing cyclohexanol by catalyzing the hydrodeoxygenation of guaiacol according to claim 1, is characterized in that, the hydrodeoxygenation of guaiacol, the reaction temperature is 160～220 ℃, and the reaction times is 30～ 240 min, the reaction pressure was 0.5~2.5MPa.

5. the method for catalyzing guaiacol hydrodeoxygenation to prepare cyclohexanol according to claim 1, is characterized in that, the mass fraction of guaiacol is 20%.