CN102701898A - Method for directionally preparing benzene by utilizing xylogen - Google Patents

Abstract

The invention relates to a method for directional preparation of benzene by utilizing lignin. It uses a cylindrical fixed-bed catalytic reactor with conductive metal wires in the cavity. The first step is to depolymerize lignin into aromatic monomers. The raw material is lignin, and the catalyst is powdered zeolite catalyst or transition The modified zeolite catalyst of metal nickel element is used so that the weight ratio of catalyst to lignin per hour is 0.3-10, and the product is a liquid aromatic monomer mixture; the second step is to directional convert the aromatic monomer mixture into benzene , the raw material is the aromatic monomer mixture that has been preheated to 200-250 ^o C, the catalyst is a powdered zeolite catalyst containing Re element, and the amount used is to make the aromatic monomer mixture and the zeolite catalyst containing Re element per hour The weight ratio is 0.2-15, and the product is a mixed liquid based on benzene. The method does not require an external hydrogen source, has abundant raw material resources, and can obtain higher benzene yield and benzene selectivity in a medium temperature and normal pressure environment and a green and mild reaction environment.

Description

A method for directional production of benzene by utilizing lignin

technical field

The invention relates to a method for directional production of benzene by utilizing lignin. the

Background technique

Benzene is an important basic chemical raw material in the petrochemical industry. The light tar produced in the coal coking process contains a certain amount of benzene. About 1 kg of benzene can be extracted from 1 ton of coal. At present, most of the benzene in the world comes from non-renewable fossil raw materials. The three most important processes for producing benzene are petroleum catalytic reforming, toluene hydrodealkylation and steam cracking. With the massive consumption of coal and petroleum traditional resources and the emphasis on environmental protection, it is urgent to develop renewable green alternative raw materials. the

The total amount of biomass generated by photosynthesis on the earth exceeds 200 billion tons every year, which is the most abundant renewable resource. Lignin is the second largest natural organic matter after cellulose in plants. It is estimated that lignin is regenerated at a rate of about 50 billion tons per year, and the by-products of lignin produced by the paper industry alone reach 50 million tons per year. Toxin is also a large by-product in the production of second-generation ethanol fuels based on agricultural waste. However, lignin has not been fully and effectively utilized so far. The reported studies on lignin conversion mainly include lignin hydroreduction, catalytic oxidation, pyrolysis, bio-oil refining, lignin gasification, and biochemical conversion. For example literature: (1) Zakzeski J., Bruijnincx P. C. A., Jongerius A. L., Weckhuysen B. M., Chem. Rev., 2010, 110(6): 3552-3599; (2) Pandey M. P., Kim C. S., Chem. Eng. Technol. , 2011, 34 (1): 29-41; (3) Effendi, A.; Gerhauser, H.; Bridgwater, AV, Renewable and Sustainable Energy Reviews, 2008, 12( 8): 2092-2116; (4) Suhas , Carrott, PJM, Ribeiro Carrott MML, Bioresour. Technol., 2007, 98(12): 2301-2312; e) Sena-Martins, G., Almeida-Vara, E., Duarte, JC, Ind. Crops Prod. , 2008, 27(2): 189-195). Catalytic hydrogenation reduction of lignin is through high-pressure hydrogenation to form compounds mainly containing phenols, alkylbenzenes and alkanes. Catalytic oxidation of lignin is to obtain mixed products including aldehydes, acids, aromatic alcohols and quinones under the action of oxidants (such as O ₂ /H ₂ O ₂ ) and catalysts. In addition, the organic liquid produced by pyrolysis of lignin under mild and anaerobic conditions at 400-600 ^o C is called lignin-based bio-oil. This bio-oil has complex components and can have hundreds of types (including phenolic , Benzene, Fu Nan, alcohols, lipids and tar, etc.). The catalytic cracking of lignin is under the action of a catalyst to obtain compounds such as simple aromatic hydrocarbons, naphthalene and phenols, among which the selectivity of benzene is low. In addition, the gasification of lignin and woody biomass produces biomass synthesis gas, which can be used for heating and power generation, as well as for the preparation of chemicals and liquid fuels. Considering the structural characteristics of lignin aromatic polymers, lignin is more suitable as a production The raw materials of aromatic compounds are utilized.

In the prior art, there are mainly two technological approaches for producing benzene from lignin as reported: one is to adopt lignin catalytic hydrogenation method, and the obtained product is an aromatic mixture composed of phenols, benzenes and alkanes, etc., benzene The selectivity of is generally lower than 10%, and the process requires the use of an external source of hydrogen and the reaction under high pressure conditions. Another lignin benzene production process is lignin catalytic cracking process. This method uses lignin to carry out catalytic cracking on zeolite catalysts such as ZSM-5 molecular sieves. The products formed mainly include toluene, xylene, naphthalene, methylnaphthalene, Composed of substances such as benzene and phenols, the selectivity of benzene in the obtained aromatic products is generally not more than 20%. It can be seen that the product distribution of lignin to benzene in the existing process is very wide, but the selectivity of the target product - benzene is very low, and the purpose of directional lignin to benzene cannot be achieved. the

In summary, lignin is the only non-petroleum resource in nature that can provide renewable bulk aromatic compounds. The use of lignin to produce benzene can provide basic chemical raw materials and an important molecule for the development of high-end chemicals for the petrochemical industry. However, there have been no reports on the controllable conversion technology of lignin aimed at the directional production of benzene. the

Contents of the invention

The object of the present invention is to provide a method that can make benzene without external hydrogen source, medium temperature and normal pressure, and green and mild reaction environment, aiming at the technical problem of directional and controllable production of benzene from lignin that has yet to be solved in the prior art. A method for directional preparation of benzene from lignin. the

The purpose of the present invention is achieved through the following technical solutions. the

The method for directional preparation of benzene from lignin according to the present invention comprises selecting a cylindrical fixed-bed catalytic reactor with conductive metal wires in the cavity as a reactor for preparing benzene from lignin, and filling the powdery catalyst in the built-in The periphery of the metal wire is in uniform contact with the surface of the metal wire, and then the reactor is started and the external power supply of the conductive metal wire is connected to make the conversion reaction of the incoming raw material occur. The conductive metal wire is Ni-Cu, or Ni-Cr, or Fe - one of Cr-Al; a heating device is provided on the feed pipe of the reactor and the catalytic reactor; it is characterized in that the conversion reaction is divided into two steps: the first step utilizes a cylindrical fixed bed catalytic reaction The device converts lignin into aromatic monomer by catalytic depolymerization, and the raw material is lignin. The catalyst used is a powdered zeolite catalyst or a modified zeolite catalyst containing transition metal nickel, and the amount used is to make the catalyst per hour The weight ratio to lignin is 0.3-10, and the obtained product is a liquid aromatic monomer mixture. The reaction conditions are: the reactor cavity is under an atmosphere of inert gas (such as _N2 gas), and the temperature is in the range of 450-650 ^o C , the current of the conductive metal wire is between 0A-5A; the second step is to use a cylindrical fixed-bed catalytic reactor to directional convert the aromatic monomer mixture into benzene, and the raw material is preheated to 200-250 ^o The aromatic monomer mixture of C, the catalyst used is a powdery zeolite catalyst containing Re element, and its use amount makes the weight ratio of the aromatic monomer mixture and the zeolite catalyst containing Re element per hour be 0.2-15, and the reaction conditions are: : In the reactor cavity, under the atmosphere of inert gas (such as _N2 gas), the temperature is in the range of 450-650 ^o C, and the current of the conductive metal wire is 0A-5A; the final product is a mixed liquid based on benzene .

In practical applications, in order to achieve continuous production, two cylindrical fixed-bed catalytic reactors can be used to convert the first step reactor for lignin depolymerization and the second step aromatic monomer into benzene The reactors are integrated into a production line in series, that is, the incoming lignin is converted into an aromatic monomer mixture in the first reactor for lignin depolymerization, which is output from the reactor and directly enters the second aromatic monomer A reactor for directional conversion of quasi-monomers into benzene, in which the conversion reaction is completed to obtain a mixed liquid mainly composed of benzene. the

In practical applications, in order to simplify the operation process, the two-step process of catalytic depolymerization of lignin and directional conversion of aromatic monomers into benzene can also be coupled in a catalytic bed reactor, namely:

First, mix the zeolite catalyst or the modified zeolite catalyst containing transition metal nickel element with the zeolite catalyst containing rhenium (Re) element according to the mass ratio of 1:10-5:1, and add a binder and mix evenly to obtain a lignin decomposing agent. A dual-functional mixed catalyst for converting poly-aromatic monomers, wherein the mass content of the binder accounts for 2-40 wt% of the total mass of the dual-functional mixed catalyst; then the dual-functional mixed catalyst is filled in a cylindrical fixed-bed catalyst Around the metal wire in the reactor and in uniform contact with the surface of the metal wire; then start the reactor and connect the external power supply of the conductive wire, so that the temperature in the reactor is in the range of 450-650 ^o C under an atmosphere of inert gas (such as _N2 gas) Inside, the current of the conductive metal wire is 0-5.0A, and the lignin powder raw material that has been preheated to 200-250 ^o C is passed into the reactor, and the amount of the feed is such that the weight ratio of the catalyst to the lignin 0.3-10, so that the lignin depolymerization reaction and the directional conversion reaction of aromatic monomers to prepare benzene occur simultaneously in the one-stage catalytic bed reactor, and a mixed liquid mainly composed of benzene is obtained.

The zeolite catalyst used in the above process, the modified zeolite catalyst containing transition metal nickel and the zeolite catalyst containing Re element can be purchased directly from the market, and can also be prepared by the following methods:

Preparation of zeolite catalyst containing transition metal nickel element: prepare a solution of nickel nitrate or nickel acetate with a concentration of 0.05-0.5mol/L; impregnate the selected active component zeolite into the above solution, then dry and sinter to obtain a transition metal catalyst An element-modified zeolite catalyst, wherein the mass content of the transition metal element is 0-40 wt% of the zeolite catalyst mass; the active component zeolite is one of ZSM-5 series zeolite, beta zeolite, HY zeolite, and super-temperature Y zeolite One or several mixtures; Mix and grind the modified zeolite catalyst and binder into powder, wherein the mass content of binder accounts for 2-35wt% of the total mixed powder mass, and the binder is kaolin Or Tianjing powder; the above-mentioned mixed powder is pressed into tablets, dried, crushed and sieved to obtain particle powder with a particle size of 40-80 mesh, which is the finished zeolite catalyst containing transition metal nickel.

Preparation of zeolite catalyst modified with Re element: prepare a rhenium nitrate solution with a concentration of 0.05-0.5mol/L; impregnate the selected active component zeolite into the above solution, then dry and sinter to obtain a zeolite modified with Re element Catalyst, wherein the content of Re is 0-20 wt%, and described active component zeolite is the mixture of one or more of ZSM-5 series zeolite, beta zeolite, HY zeolite, super-temperature Y zeolite; The above-mentioned modified zeolite The catalyst and the binder are mixed and ground into powder, wherein the content of the binder accounts for 2-35wt% of the total mixed powder mass, and the binder is kaolin or Tianjing powder; the above mixed powder is pressed into tablets and dried, Then crush and sieve to obtain particle powder with a particle size of 40-80 mesh, that is, the finished zeolite catalyst containing Re element. the

In the method of the present invention, the current of the conductive metal wire is 0-5.0A, which means that there may be two cases of connecting the external power supply or not connecting the external power supply. When the current fed into the metal wire was zero, the process of depolymerizing the lignin to produce aromatic monomers and the directional conversion of the aromatic monomers into benzene in the second step were all carried out under the action of a catalyst; When the current of the metal wire is not zero, according to the principle of thermionic emission on the metal surface, the energized metal wire provides a large number of hot electrons to the surface of the catalyst, and the process of lignin depolymerization to aromatic monomers and the second step of aromatic monomers The process of directional conversion to benzene is carried out under the synergistic effect of thermal electrons and catalysts. Compared with the two cases, the conversion efficiency when the current is applied is obviously higher than that when the external power supply is not connected. This is because lignin contains a large number of aromatic polymers that are difficult to dissociate, and the synergistic effect of thermal electrons and catalysts can promote the breakage of ether bonds and carbon-carbon bonds in lignin and induce free radical chain chemical reactions; it can also target multiple The characteristics of a complex aromatic monomer mixture and a small amount of oligomers promote the breakage and recombination of functional groups in aromatic monomers, thereby achieving efficient depolymerization of lignin into aromatic monomers and making aromatic monomers efficient Directional conversion to the target product - benzene. the

The actual measurement shows that if 15 wt% Ni/HZSM-5 (HZSM-5 zeolite catalyst loaded with 15% nickel by weight) is used as the catalyst for lignin depolymerization, under the conditions of reaction temperature 600°C and current 0A, lignin The yield of aromatic monomer mixture formed by lignin depolymerization is 0.20 (kg monomer/kg lignin); under the conditions of reaction temperature 550°C and current 4A, the yield of aromatic monomer mixture formed by lignin depolymerization is 0.29 (kg monomer/kg lignin). For the catalytic conversion of aromatic monomers to produce benzene, for example, 10 wt% Re/Y zeolite (a Y-type zeolite catalyst with a weight content of 10% rhenium) is used as the catalyst for the conversion of aromatic monomers, and lignin is used to catalyze The aromatic monomer obtained by pyrolysis is used as a raw material. Under the conditions of reaction temperature 650°C and current 0A, the yield of target product-benzene is 0.10 (kg benzene/kg lignin), and the selectivity of benzene is 96.0%. Under the conditions of temperature 550°C and current 4A, the yield of target product-benzene was 0.13 (kg benzene/kg lignin), and the selectivity of benzene was as high as 95.5%. In addition, if the two-step process of lignin depolymerization and directional conversion of aromatic monomers to benzene is coupled in a one-stage catalytic bed reactor, when 15 wt% Ni/HZSM-5 is used as the lignin depolymerization catalyst, and Mix 10wt% Re/Y type zeolite as aromatic monomer conversion catalyst at a mass ratio of 2:1 to obtain a dual-functional catalyst for lignin depolymerization-aromatic monomer conversion. Lignin is used as a starting material. Under the conditions of temperature 650°C and current 0A, the yield of the target product-benzene was 0.07 (kg benzene/kg lignin), and the selectivity of benzene reached 90.0wt%; under the conditions of reaction temperature 550°C and current 5A, benzene The yield of benzene was 0.08 (kg benzene/kg lignin), and the selectivity of benzene reached 93.0wt%. It can be seen that the purpose of directional preparation of benzene from lignin can be achieved by using lignin catalyzed benzene production without current action (current is zero) and current action lignin catalysis benzene production (current is not zero) operation; When the current is applied, higher benzene yield and benzene selectivity can be obtained at lower reaction temperature. the

The method described in the present invention can convert lignin into benzene directional and efficiently without external hydrogen source, medium temperature and normal pressure and green mild reaction environment, and all raw materials used are various renewable biomass, for example, can be used The lignin obtained by separating sawdust, straw, rice husk, etc. or various lignins from the pulping process of the paper industry has the advantages of rich resources, environmental friendliness and regeneration. The industry provides basic chemical raw materials and is also an important part of the development of high-end chemicals, which is conducive to the sustainable recycling of resources and the environment. the

Detailed ways

Further description is given below by way of examples. the

Example 1 Depolymerization of lignin into aromatic monomers

In the process of this example, the lignin raw material was purchased from Hefei Lanxu Biotechnology Co., Ltd. The main elements in the lignin raw material are carbon, hydrogen and oxygen (the element ratio is C:H:O=62.55:5.83:31.62). The catalyst for lignin depolymerization is 15 wt%Ni/HZSM-5 modified zeolite catalyst. The preparation steps of the catalyst are: weighing 37.5 g of nickel nitrate hexahydrate, adding 100 mL of deionized water to form a nickel nitrate solution; , Shake the solution to cover the powder of ZSM-5, let it soak for 24 hours, then evaporate the water in the solution in an 80-degree water bath, then dry it in an oven at 120 degrees, and then sinter it in a muffle furnace at 550 degrees for 6 hours . Then the prepared 15 wt%Ni/HZSM-5 catalyst and binder (kaolin or Tianjing powder) are mixed and ground to obtain mixed powder, wherein the binder accounts for 10 wt% of the total mixed powder mass, and the above mixed powder After tableting, dry at a temperature of 110 ^o C for 8 hours, and sieve to obtain microparticles with a particle size of 40-80 mesh, that is, a modified zeolite catalyst containing transition metal nickel for lignin depolymerization 15 wt%Ni /HZSM-5 finished product.

The lignin depolymerization catalytic reactor used is a cylindrical fixed-bed catalytic reactor with external heating and insulation layer, and the inlet pipes of reaction raw materials (lignin) and carrier gas and the output of reaction products are connected at both ends. The pipeline, the lignin storage tank is connected with the feeder, the carrier gas pipeline is connected with the reactant inlet pipeline, and the gas control valve and the reactant flow controller are respectively provided, and the outer wall of the inlet pipeline is provided with an external heater for preheating device; the reaction product output pipeline is sequentially connected with a double condenser, a liquid product collector, a solid product collector and an exhaust gas collector; a ceramic insulating layer and an external power supply are arranged in the inner cavity of the cylindrical reactor Metal wire, the power of the metal wire is selected by the required reaction temperature and reactor volume, and the built-in metal wire is a Ni-Cu metal wire. the

In this example, firstly, the 15 wt% Ni/HZSM-5 zeolite catalyst used for lignin depolymerization was filled around the metal wire built in the reactor and evenly contacted with the surface of the metal wire, the amount of catalyst was 10g, and the carrier gas nitrogen For the valve of the cylinder, adjust the flow rate of the carrier gas to 1000ml/min. After the air in the reactor is discharged, adjust the flow rate of the carrier gas to 450 ml/min. Then turn on the power supply for providing thermal electrons and internal heating wires, so that the currents passing through the wires are set at 0, 2, and 4A respectively, and by adjusting the power of the external heating furnace of the reactor, the inner cavity of the reactor The temperature is regulated in the range of 450-650 ^o C. After the temperature in the reactor is stabilized, open the valve of the feeder on the outlet pipe of the lignin raw material storage tank, the lignin feed amount is 10g, and the lignin and carrier gas enter the catalytic reactor inner cavity through the inlet pipe, so that the lignin Depolymerization to a liquid intermediate product - aromatic monomer mixture. The results are shown in Table 1. As can be seen from this table: when the reaction temperature is 550 ^o C and the current is 2A, the yield of aromatic monomers (calculated according to the ratio of the yield of aromatic monomers actually obtained to the amount of lignin injected) is 0.25 ( kg monomer/kg lignin); when the reaction temperature is 550 ^o C and the current is 4A, the yield of aromatic monomer is 0.29 (kg monomer/kg lignin).

In the process of this embodiment, the situation of no current enhancement is also done, that is, the power supply connected to the metal wire is turned off, so that the current passing through the metal wire is 0, and the power in the reactor inner cavity is only adjusted by adjusting the power of the external heating furnace of the reactor. temperature. Then measure the lignin injection amount and the generation amount of lignin depolymerization products respectively, and calculate the yield of aromatic monomers in Table 1, the results show that at the same reaction temperature, the lignin catalytic depolymerization using the current enhancement effect The efficiency of the method will be higher than that of the lignin-catalyzed depolymerization method without current enhancement. the

Table 1 (the data in the table are the average value of three experiments)

Embodiment 2 makes the directional conversion of aromatic monomer into benzene

In the process of this example, the reactant raw material is the aromatic monomer mixture produced by the catalytic depolymerization of lignin in Example 1 at 600 ^o C and a current of 0A. The catalyst is a 10 wt % Re/Y rhenium-containing zeolite catalyst. The preparation steps of the catalyst are as follows: weighing 16g of rhenium nitrate, adding 100mL of deionized water to configure a rhenium nitrate solution; Make the solution submerge the powder of HY zeolite, let it stand for immersion for 24 hours, evaporate the moisture in the solution in an 80-degree water bath, then dry it in an oven at 120 degrees, and then sinter it in a muffle furnace at 550 degrees for 6 hours. Then the prepared 10wt% Re/Y type zeolite catalyst and binding agent (kaolin or Tianjing powder) are mixed and ground in a certain proportion to obtain mixed powder, wherein the binding agent accounts for 20 wt.% of the total mixed powder mass. The above-mentioned mixed powder was compressed into tablets and dried at 110 ^o C for 8 hours, and sieved to obtain particles with a particle size of 40-80 mesh, that is, the catalyst 10wt% Re/Y finished product for the conversion of aromatic monomers.

The selected aromatic monomer catalytic conversion reactor is a cylindrical fixed-bed catalytic reactor with external heating and insulation layer, and its two ends are connected with reactants (aromatic monomer liquid mixture) and carrier gas ( _N2 gas) into the pipeline and the reaction product output pipeline, the aromatic monomer storage tank is connected to the liquid injection pump, the carrier gas is respectively connected to the inlet pipeline, and is respectively equipped with a gas control valve and a reactant flow controller, and the inlet pipeline An external heating device for preheating is provided on the outer wall of the reactor; a double condenser, a liquid product collector and a tail gas collector are sequentially connected to the output pipe of the reaction product; a ceramic insulating layer is provided in the inner cavity of the cylindrical reactor and a Ni-Cu metal wire connected to an external power supply, the power of the metal wire is selected by the required reaction temperature and reactor volume. Open the valve of the carrier gas nitrogen cylinder, and then turn on the power supply for providing thermal electrons and internal heating wires, so that the currents of the wires are respectively set at 0, 2, and 4A. By adjusting the external heating furnace of the reactor Power, so that the temperature in the reactor cavity is adjusted in the range of 550-650 ^o C.

Method for producing benzene by directional conversion of aromatic monomers: First, fill the finished 10wt.% Re/Y catalyst product for the conversion of aromatic monomers around the built-in wire and evenly contact the surface of the wire. The amount of catalyst used is determined by the feed amount of the reaction raw materials per hour. In this embodiment, the amount of catalyst used is 8g, and the flow rate of the carrier gas is adjusted to 1000ml/min. After the air in the reactor is discharged, the flow rate of the adjusted carrier gas is 150 ml /min. Then switch on the power supply of the electric heating belt in the preheating zone, so that the temperature in the preheating zone is within 180-200 ^o C; 0, 2, and 4A remain unchanged, and the temperature in the inner cavity of the reactor can be adjusted within the range of 550-650 ^o C by adjusting the power of the heating furnace outside the reactor. Finally, turn on the sampling pump on the outlet pipe connected to the aromatic monomer raw material storage tank and the valve of the carrier gas to adjust the injection volume of the reaction raw material, and the preheated aromatic monomer mixture and carrier gas are passed through the reactants. The pipeline enters the aromatic monomer conversion reactor, so that the aromatic monomer mixture is converted into the target product - benzene under the synergistic action of thermal electrons and catalysts. In this embodiment, the feed flow rate of the aromatic monomer raw material is 50 g/h, and the carrier gas flow rate is 150 ml/min. Then, under different current and temperature conditions, the reactants (i.e. the liquid mixture of aromatic monomers prepared by depolymerization of lignin) and the amount of benzene were measured, and the yield and selectivity of benzene were calculated. The measured results are shown in Table 2 shown.

As can be seen from Table 2: when the reaction temperature is 550 ^o C and the current is 2A, the benzene yield (calculated according to the ratio of the actual benzene yield to the starting material lignin usage) and the benzene selectivity (according to the actual The ratio of benzene yield to the mass of all liquid products) was 0.09 (kg benzene/kg lignin) and 82.5 wt %; when the reaction temperature was 550 ^o C and the current was 4A, the benzene yield and benzene selectivity increased respectively to 0.13 (kg benzene/kg lignin) and 95.5 wt %.

In the process of this embodiment, a comparative example of catalytic conversion of aromatic monomers without current enhancement was also made. That is, turn off the power supply connected to the Ni-Cu metal wire, so that the current passing through the Ni-Cu metal wire is 0, and by adjusting the power of the external heating furnace of the reactor, the temperature in the inner cavity of the reactor is in the range of 550-650 ^o C adjust. When the current of the Ni-Cu wire was 0 and the reaction temperature was 550 ^o C, the benzene yield and benzene selectivity were 0.06 (kg benzene/kg lignin) and 71.6 wt%, respectively. In addition, when there is no current enhancement effect, increasing the temperature is beneficial to improve the yield and selectivity of benzene. For example, when the temperature is increased to 650 ^o C, the yield and selectivity of benzene increase to 0.10 (kg benzene/kg lignin ) and 96.0 wt%.

Table 2 (the benzene yield in the table, the benzene selectivity data are the average value of three experiments)

Example 3 Coupling method for depolymerization of lignin and directional conversion of aromatic monomers into benzene

In the process of this example, the lignin raw material is derived from the lignin sample of Hefei Lanxu Biotechnology Co., Ltd., and the main elements in the lignin raw material are carbon, hydrogen and oxygen elements (the element ratio is C:H:O=62.55:5.13 :32.30). The lignin depolymerization catalyst was a commercially available HZSM-5 zeolite with a silicon-aluminum ratio of 100, and the aromatic monomer conversion catalyst was a commercially available 16% ReY catalyst. The two catalysts were mixed in a ratio of 1:1, and 10wt% kaolin was added as a binder. That is, a finished bifunctional catalyst product with lignin depolymerization and directional conversion of monomers into benzene is obtained.

The catalytic conversion reactor used is a cylindrical fixed-bed catalytic reactor with external heating and insulation layer. Its two ends are connected with reactant (lignin) and carrier gas ( _N2 gas) reactant inlet pipe and reaction product output pipe, the lignin storage tank is connected with the feeder, and the carrier gas pipe is connected with the reactant inlet pipe. and a gas control valve and a reactant flow controller are respectively provided, and an external heating device for preheating is provided on the outer wall of the inlet pipe; a double condenser and a liquid product collector are sequentially connected to the reaction product output pipe , a solid product collector and a tail gas collector; a ceramic insulating layer and a metal wire connected to an external power supply are arranged in the inner cavity of the cylindrical reactor, and the power of the metal wire is selected by the required reaction temperature and the volume of the reactor. This implementation The built-in wire used in the example process is a Fe-Cr-Al wire.

Process-coupled lignin benzene production method: firstly, the finished bifunctional catalyst is filled around the built-in metal wire of the reactor and evenly contacts with the surface of the metal wire. The amount of catalyst used is determined by the amount of lignin fed per hour. In this example, the amount of catalyst used is 25g, then turn on the power supply of the electric heating belt in the preheating zone, so that the temperature of the preheating zone is 200 ^o C; turn on the power supply for providing the thermal electrons and the metal wire for internal heating, so that the current passing through the metal wire is 0 A respectively , 2 A and 5A remain unchanged, and the temperature in the reactor cavity is adjusted to 550-650 ^o C by adjusting the power of the heating furnace outside the reactor. Finally, open the sampling pump connected to the outlet pipe of the lignin raw material storage tank and the valve of the carrier gas to adjust the sample amount of lignin and the flow rate of the carrier gas. The preheated lignin and carrier gas are passed into the pipeline through the reactant Entering the reactor, the lignin depolymerization reaction and the directional conversion of aromatic monomers into benzene are simultaneously catalyzed under the synergistic action of thermal electrons and catalysts. The liquid product containing a large amount of benzene is collected with a condensation tank. In this embodiment, the lignin flow rate is 100 g/h, and the carrier gas flow rate is 220 ml/min.

When the reaction temperature is 550 ^o C and the electric current is 2A, the benzene yield (calculated according to the ratio of the actual benzene yield to the amount of raw material lignin used) and benzene selectivity (according to the ratio of the actual benzene yield to the quality of all liquid products Ratio calculation) were 0.07(kg benzene/kg lignin) and 77.5wt% respectively; when the reaction temperature was 550 ^o C, when the current increased to 5A, the benzene yield and benzene selectivity were 0.08(kg benzene/kg lignin ) and 93.0 wt%. It can be seen that increasing the current has a great effect on the selectivity of benzene in the product.

In the process of this embodiment, the catalytic conversion of aromatic monomers without the effect of current enhancement was also tested. That is, turn off the power supply connected to the Fe-Cr-Al metal wire, so that the current passing through the Fe-Cr-Al metal wire is 0, and by adjusting the power of the external heating furnace of the reactor, the temperature in the inner chamber of the reactor is kept at 550- Adjustable in the range of 650 ^o C. Then, the lignin injection amount and the benzene generation amount were compared at different temperatures, and the yield and selectivity of benzene were calculated. The results are shown in Table 3. As can be seen from the table: when the catalytic conversion method without current action is adopted, at the same reaction temperature of 550 ^o C, the benzene yield and benzene selectivity are lower than the situation with current action; when the reaction temperature is increased to 650 ^o C, the yield and selectivity of benzene will increase accordingly. Can also find out from this embodiment, adopt the method of the present invention, no matter have or not feed electric current, the selectivity of benzene is all higher than adopting the selectivity that lignin is converted into benzene in the prior art (generally lower than 20%) ).

Table 3 (the benzene yield and selectivity data in the table are the average value of three experiments)

Example 4 Two reactors for depolymerization of lignin and directional conversion of aromatic monomers into benzene are integrated in series

This example aims to evaluate the cascade integration method of depolymerization of lignin and directional conversion of aromatic monomers to benzene, that is, the depolymerization of lignin and the conversion of aromatic monomers are performed continuously in two reactors in series.

In the process of this example, the lignin raw material is derived from the lignin sample of Hefei Lanxu Biotechnology Co., Ltd., and the main elements in the lignin raw material are carbon, hydrogen and oxygen elements (the element ratio is C:H:O=62.55:5.13 :32.30). The lignin depolymerization catalyst was a commercially available HZSM-5 zeolite with a silicon-to-aluminum ratio of 100, and the aromatic monomer conversion catalyst was a commercially available 16% ReY catalyst. The first reactor is used as a lignin depolymerization reactor; the second reactor is used as an aromatic monomer conversion reactor, which is filled with 16% ReY catalyst. The reactor used is a cylindrical fixed-bed catalytic reactor with external heating and insulation. Its two ends are connected with reactant (lignin) and carrier gas ( _N2 gas) reactant inlet pipe and reaction product output pipe, the lignin storage tank is connected with the feeder, and the carrier gas pipe is connected with the reactant inlet pipe. and a gas control valve and a reactant flow controller are respectively provided, and an external heating device for preheating is provided on the outer wall of the inlet pipe; a double condenser and a liquid product collector are sequentially connected to the reaction product output pipe , a solid product collector and a tail gas collector; a ceramic insulating layer and a metal wire connected to an external power supply are arranged in the inner cavity of the cylindrical reactor, and the power of the metal wire is selected by the required reaction temperature and the volume of the reactor. This implementation The built-in wire used in the example process is a Fe-Cr wire.

A method for producing benzene from lignin with two reactors integrated in series: firstly, 16% ReY catalyst is filled in the first reactor (lignin depolymerization reactor) with an amount of 5 g. Fill the HZSM-5 catalyst in the second reactor (aromatic monomer conversion reactor) with an amount of 10 g. Then turn on the power supply for providing thermal electrons and internal heating wires, so that the currents passed into the wires are 0A and 4.0A respectively, and by adjusting the power of the external heating furnace of the reactor, the first reactor and the second reactor The temperature in the two reactor chambers is 550 ^o C, respectively. Finally, open the sampling pump connected to the outlet pipe of the lignin raw material storage tank and the valve of the carrier gas to adjust the sample amount of lignin and the flow rate of the carrier gas. The preheated lignin and carrier gas are passed into the pipeline through the reactant Entering the first reactor, the depolymerization reaction of lignin occurs under the synergistic action of thermal electrons and catalysts, and the aromatic monomer mixture output from the first reactor enters the second reactor directly through the pipeline. Under the synergistic action of electrons and catalysts, it is converted into benzene. The liquid product containing a large amount of benzene is collected with a condensation tank. In this embodiment, the lignin flow rate is 100 g/h, and the carrier gas flow rate is 220 ml/min. When the reaction temperature is 550 ^o C and the current is 4.0 A, the benzene yield (calculated according to the ratio of the actual benzene yield to the raw material lignin usage) and benzene selectivity (according to the actual benzene yield to the mass of all liquid products Calculated by the ratio of ) to 0.08 (kg benzene/kg lignin) and 83.0 wt%, respectively.

In the course of this example, the conversion without current enhancement was also tested. That is, turn off the power supply connected to the Fe-Cr metal wire, make the current passing through the Fe-Cr metal wire 0, and adjust the power of the external heating furnace of the reactor to make the temperature in the inner chamber of the reactor 550 ^o C. Then the lignin injection amount and the benzene generation amount were measured, and the yield and selectivity of benzene were calculated. The results are shown in Table 4. It can be seen from the table that when the catalytic conversion method without current action is adopted, the benzene yield and benzene selectivity are lower than those with current enhancement.

Table 4 (benzene yield in the table and selectivity data are the average value of three experiments)

As can be seen from Example 3 and Example 4, when utilizing lignin to produce benzene, the two processes of lignin depolymerization conversion and aromatic monomer directional conversion to produce benzene can be coupled in one reactor, or the The above two preparation processes are sequentially connected in series in two reactors and carried out continuously.

Claims (3)

1. one kind is utilized the directed method for preparing benzene of xylogen; Comprise the reactor drum of selecting for use the tubular fixed bed catalytic reactor that is provided with conductive wire in the chamber to be prepared as benzene as xylogen; Said powder catalyst is filled in around the built-in metal silk and the wire surface uniform contact, starts reactor drum then and connect the external source of conductive wire, make to feed raw material generation conversion reaction; Described conductive wire is Ni-Cu or Ni-Cr, or a kind of among the Fe-Cr-Al; On the feed pipe of reactor drum and catalyticreactor, be provided with heating unit; It is characterized in that; Said conversion reaction be divided into two the step carry out: the first step utilizes the tubular fixed bed catalytic reactor that the xylogen catalytic degradation is converted into the aromatics monomer; The feeding raw material is an xylogen; Catalyst system therefor is pulverous zeolite catalyst or the modified zeolite catalyst that contains the transition metal nickel element, and its usage quantity is that to make the weight ratio of catalyzer hourly and xylogen be 0.3-10, and the product that obtains is an aromatic liquid class monomer mixture; Reaction conditions is: under inert gas atmosphere, temperature is at 450-650 in the reactor cavity ^oIn the C scope, the feeding electric current of conductive wire is between the 0A-5A; Second step was to utilize the tubular fixed bed catalytic reactor to make aromatics monomer mixture orientation be converted into benzene, fed raw material for being preheating to 200-250 ^oThe aromatics monomer mixture of C; Catalyst system therefor is the zeolite catalyst of the pulverous Re of containing element; It is 0.2-15 that its usage quantity per hour makes aromatics monomer mixture and the weight ratio that contains the zeolite catalyst of Re element; Reaction conditions is: under inert gas atmosphere, temperature is at 450-650 in the reactor cavity ^oIn the C scope, the feeding electric current of conductive wire is 0A-5A; The product that finally obtains is to be main mixing liquid with benzene.

2. the directed method for preparing benzene of xylogen of utilizing as claimed in claim 1; It is characterized in that; Said conversion reaction is to use two tubular fixed bed catalytic reactors; With the reactor drum that is used for lignin depolymerization of the first step and the aromatics monomer set in second step to the integrated production line of the reactors in series that is converted into benzene; That is: the xylogen of feeding changes into the aromatics monomer mixture at first reactor drum that is used for lignin depolymerization, and it directly gets into second aromatics monomer set to the reactor drum that is converted into benzene from this reactor drum output back, and accomplishing therein that conversion reaction obtains with benzene is main mixing liquid.

3. the directed method for preparing benzene of xylogen of utilizing as claimed in claim 1; It is characterized in that; Said conversion reaction is that described xylogen catalytic degradation and aromatics monomer set are carried out in a catalytic bed reactor to the two step PROCESS COUPLING that are converted into benzene simultaneously, that is:

Earlier with zeolite catalyst or contain the transition metal nickel element modified zeolite catalyst, mix according to mass ratio 1:10-5:1 with the zeolite catalyst of rhenium-containing element; And add sticker and mix and obtain having lignin depolymerization and the bifunctional mixed catalyst of aromatics conversion of monomer, wherein the mass content of sticker accounts for the 2-40wt% of total difunctional mixed catalyst quality; Again said difunctional mixed catalyst is filled in the tubular fixed bed catalytic reactor around the wire and with the wire surface uniform contact; Start reactor drum then and connect the external source of conductive wire, make in the reactor drum under inert gas atmosphere, temperature is at 450-650 ^oIn the C scope, the feeding electric current of conductive wire is 0-5.0A, will be preheating to 200-250 ^oThe xylogen powder stock of C is passed in the reactor drum; Its feeding amount is to make that the weight ratio of catalyzer and xylogen is 0.3-10; Make xylogen that lignin depolymerization reaction and the conversion reaction of aromatics monomer set to preparation benzene take place in the one-part form catalytic bed reactor simultaneously, obtaining with benzene is the mixing liquid of leading.