CN102476980A - Application of tungsten-based catalyst in preparation of aromatic compound by catalytic hydrogenation of lignin - Google Patents

Abstract

The present invention relates to the hydrocracking of lignin, specifically a method for preparing aromatic compounds by catalyzing the hydrocracking of lignin with a tungsten-based catalyst; the catalyst used in the method uses non-zero-valent tungsten as the main active component, and One or more small amounts of transition metals such as zero-valent nickel, cobalt, ruthenium, iridium, palladium, platinum, iron, copper, etc. are the second metal components. The method uses natural lignin, biomass hydrolysis residue, lignosulfonate, alkali lignin, etc. as raw materials to catalytically hydrogenate under hydrothermal conditions of 120-450 ^o C and hydrogen pressure of 1-20MPa, and high-selectivity cracking is For C6-C9 phenolic compounds, the yield of phenol is as high as 55.6%. Compared with the existing method, the present invention can use renewable natural biomass as raw material, and the raw material is cheap and has a wide range of sources; it does not need to use inorganic acid and alkali, and avoids the production of a large amount of lye catalyzed by traditional lignin; it also has low-cost tungsten-based catalysts. , green reaction process, atom economy and other characteristics.

Description

Application of Tungsten-Based Catalysts in Catalytic Hydrogenation of Lignin to Aromatic Compounds

technical field

The invention relates to the preparation of aromatic compounds, in particular to a method for preparing monophenolic aromatic compounds by catalyzing hydrocracking of lignin resources with a supported tungsten carbide catalyst.

Background technique

The rapid development of the world economy has benefited from the wide application of fossil energy, such as oil, natural gas, and coal. With the continuous consumption of non-recyclable fossil resources, the energy crisis and environmental problems have become increasingly severe. The development of renewable new energy to replace fossil resources has become an inevitable trend of social development.

Biomass resources exist in large quantities in nature, and are the most abundant and cheapest renewable resources that meet the requirements of sustainable development on the earth. In biomass, the content of lignin is second only to cellulose, and it is the most abundant resource of natural aromatic compounds in nature, and it is regenerated at a rate of 50 billion tons every year. The pulp and paper industry separates about 140 million tons of cellulose from plants every year, and at the same time obtains about 50 million tons of lignin by-products. But so far, there is still no effective way to transform and utilize lignin. More than 95% of lignin is discharged into rivers or burned in the form of "black liquor", which not only wastes biomass resources, but also seriously pollutes the environment. Wastewater accounts for 30% of the national industrial wastewater volume, and is the first object of my country's industrial wastewater control.

Aromatic compounds have extremely important applications in the chemical industry, such as phenol and terephthalic acid and their derivatives are not only widely used bulk chemicals, but also important for the production of resins, rubber, pharmaceutical intermediates and other fine chemicals raw material. From a structural point of view, lignin is a three-dimensional network polymer with aromatic rings as the main structure, mainly including three structural units: guaiacyl, syringyl, and p-hydroxyphenyl structures. The structural units are connected by ether bonds or carbon-carbon bonds. By designing a suitable catalyst, selectively hydrogenating and reducing lignin, and cutting off the links between structural units, aromatic phenolic compounds can be prepared from lignin resources, which can be used in various fields as a substitute for fossil resources. To a certain extent, the plight of the world's energy crisis can be alleviated, and at the same time, the discharge of waste "black liquor" can be avoided.

However, due to the complex structure and stubborn physical and chemical properties of lignin, it is very difficult to catalytically crack it. The US patent (US 4,900,873) uses biphenyl or naphthalene as a solvent to pyrolyze lignin to prepare aromatic compounds at 300-400°C, but the yield is less than 20%. U.S. Patent (US5,807,952) prepares phenolic compounds by pyrolyzing lignin under air atmosphere with KOH and other strong bases at 400-600°C. The maximum yield of phenols can reach 60%, but the reaction conditions are harsh and a large amount of spent alkali is produced. liquid. The world patent (WO99/10450) uses alkali-catalyzed hydrogenation of lignin to prepare gasoline components in a hydrogen atmosphere at 260-310°C, but complete hydrogenation of benzene rings requires more hydrogen sources, and the alkali catalyst produces a large amount of waste liquid, polluting the environment . The Canadian patent uses metal sulfide as a catalyst to catalyze the degradation of lignin at 250-450°C and 15-45MPa to obtain phenolic compounds, with a maximum yield of 40% phenol. Chinese patent (CN 101768052A) describes a bimetallic catalyst with zero-valent Ni as the main active component to catalyze the hydrogenation of lignin, and the maximum conversion rate of raw materials reaches 53%. According to the research results of the literature, most of the currently reported lignin hydrogenation catalysts are based on noble metals such as Pd and Pt. There has not been any report using lignin as a raw material. Efficient and selective catalytic degradation to produce aromatic compounds.

Contents of the invention

The purpose of the present invention is to provide a method for catalyzing the degradation of lignin raw materials to produce aromatic compounds with a tungsten-based catalyst; it can realize the high yield and high selectivity conversion of catalyzed lignin into mono Phenolic aromatic compounds.

In order to achieve the above object, the technical scheme that the present invention takes is:

The catalyst for lignin hydrocracking described in the present invention is a non-zero-valent tungsten-based catalyst, described as follows:

The tungsten-based catalyst can be a supported tungsten carbide catalyst, which is composed of active component tungsten carbide and a carrier. The carrier is one or more of activated carbon, alumina, silica, titania, zirconia, titania, silica-alumina molecular sieve, and phosphorus-aluminum molecular sieve; the loading amount of tungsten in the carrier is 5-80wt%, preferably The amount is 10-50wt%, more preferably the loading amount is 15-40wt%;

The supported tungsten carbide catalyst can also be composed of three parts: the main active component, the carrier and the second metal component. The main active component is tungsten carbide, and the loading amount of tungsten in the carrier is 5-80wt%, preferably 10-50wt%, more preferably 15-40wt%; the carrier is activated carbon , aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, titanium dioxide, silicon aluminum molecular sieve, phosphorus aluminum molecular sieve or one or more; The second metal component is nickel, iridium, platinum, ruthenium, rhodium in metallic state , palladium, iron, cobalt, copper, aluminum, tin, molybdenum, chromium, strontium, preferably one or more of nickel, iridium, ruthenium, palladium, platinum; the second metal component is The loading amount in the carrier is 0.05-30wt%, preferably 0.1-15wt%, more preferably 0.2-5wt%.

The tungsten-based catalyst can be a composite catalyst, including catalyst A and catalyst B, and the active ingredient of catalyst A is the transition metal iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, and platinum of the 8th, 9th, and 10th groups. One or more, the active ingredient of catalyst B is tungsten oxide, tungsten sulfide, tungsten chloride, tungsten hydroxide, tungsten bronze, tungstic acid, tungstate, metatungstic acid, metatungsten one or more of salt, paratungstic acid, paratungstate, peroxytungstic acid, peroxytungstate, tungstic heteropoly acid; the metal active component of catalyst A and the active component of catalyst B (in the form of metal Tungsten weight meter) weight ratio is between 0.02-3000 times.

The catalyst A can be a supported catalyst, and the carrier is a composite carrier of one or more of activated carbon, alumina, silicon oxide, silicon carbide, zirconia, zinc oxide, and titanium dioxide; the content of the active component metal on the catalyst is 0.05-50wt%, preferably 1-30wt%.

The catalyst A can also be an unsupported metal catalyst with an active component as the catalyst skeleton.

The supported catalyst is prepared by a loading method, and the active component salt solution is loaded on the carrier to obtain a catalyst precursor. After drying at 100-160° C., a temperature-programmed reduction reaction is carried out in hydrogen or methane/hydrogen (methane content is 10-100% v/v).

The reduction temperature of the supported tungsten carbide catalyst is between 600-900°C, preferably the reduction temperature is 700-800°C, the reducing atmosphere is hydrogen or methane/hydrogen (methane content is 20% v/v), and the carbonization time is long in 0.5 hours.

The reduction temperature of the supported catalyst A is between 250-800°C, preferably the reduction temperature is 300-500°C, the reducing atmosphere is hydrogen or methane/hydrogen (methane content is 20% v/v), and the carbonization time is not less than 0.5 hours.

The reaction process for realizing the catalytic hydrocracking of lignin to produce phenolic compounds is as follows: the hydrogenation degradation reaction of the lignin raw material is carried out in a closed high-pressure reactor, and the mass ratio of the reaction raw material to the solvent is 1:500-1:1, preferably 1:100-1:5; the amount of the catalyst is the amount of the catalyst. In order to speed up the reaction, the mass ratio of lignin to the catalyst is usually 1:2-100:1, and the preferred ratio is 2:1-20:1; The initial pressure of hydrogen filling in the reactor at room temperature is 1-20MPa, preferably 3-10MPa; the reaction temperature is 120-450°C, preferably 150-300°C; the reaction time is 10min-24h.

Compared with prior art, the present invention has following advantage:

1. The raw material lignin of the present invention is the most abundant natural renewable aromatic compound resource in nature, with wide sources and low cost. Compared with the preparation of aromatic compounds by existing petroleum-based industrial synthesis routes, the invention does not consume fossil resources, has the advantage of renewable raw materials, and meets the requirements of sustainable development.

2. The invention provides a new approach for the utilization of industrial lignin, and reduces the pollution caused by industrial lignin discharge and incineration.

3. The catalyst uses non-zero-valent tungsten as the main active component, which is low in cost and high in activity, and the yield of monophenolic compounds is as high as 55.6%.

4. When water is used as the solvent, the reaction system is environmentally friendly and pollution-free; no inorganic acid or alkali is used in the reaction process, which avoids the common environmental pollution problems in the lignin degradation process.

Further detailed description will be given below through specific examples.

Detailed ways

Example 1

Preparation of activated carbon-supported nickel-tungsten carbide catalyst (Ni-W ₂ C/AC): Ammonium metatungstate and nickel nitrate are prepared into a mixed solution according to the ratio of tungsten/nickel weight ratio of 15:1, wherein metatungstate The mass concentration of ammonia is 0.4g/ml. Then, the mixed solution was impregnated with activated carbon support (AC) by equal volume impregnation method. After being dried in an oven at 120°C for 12 hours, the catalyst precursor was placed in an H2 atmosphere for a temperature-programmed carbothermal reaction. The specific reaction process was: 1.0 g of the precursor was heated from room temperature to 400°C in a quartz reaction tube for 1 hour, and then heated at 1°C. /min to raise the temperature to 700°C and keep it for 1h for carbonization, and the hydrogen flow rate is 60ml/min. A Ni-W ₂ C/AC catalyst with a tungsten loading of 30 wt % and a nickel loading of 2 wt % was obtained, expressed as Ni-W ₂ C/AC (2 wt % Ni-30 wt % W ₂ C).

Other conditions remain the same, only changing the concentrations of ammonium metatungstate and nickel nitrate in the impregnating solution, or through multiple impregnations, catalysts with different loadings of active components can be obtained; the composition is as follows: Ni loading is 2wt%, tungsten Ni-W ₂ C/AC catalysts with loadings of 5wt%, 10wt%, 15wt%, 60wt%, and 80wt%, and tungsten loadings of 30wt%, nickel loadings of 0.05wt%, 0.2wt% %, 5wt%, 10wt%, 30wt% Ni-W ₂ C/AC catalyst.

Example 2

Preparation of Ni-WxC/AC catalyst: The preparation process is similar to Example 1, except that the carbonization temperature is 850°C, and a Ni-WxC/AC catalyst with a tungsten loading of 30wt% and a nickel loading of 2wt% is obtained , wherein, WxC is a mixed crystal phase of W ₂ C and WC, 1<x<2. Expressed as Ni-WxC/AC (2wt%Ni-30wt%WxC).

Example 3

Preparation of WxC/AC catalyst: The preparation process is similar to Example 1, except that only ammonium metatungstate is used in the precursor without adding nickel nitrate, and the carbonization temperature is 800°C, thus obtaining W ₂ C/AC catalyst ; or carbonized at 850° C. to obtain a WxC/AC catalyst, which is a mixed crystal phase of W ₂ C and WC, 1<x<2.

Example 4-9

Preparation of Co-W ₂ C/AC, Fe-W ₂ C/AC, Pt-W ₂ C/AC, Ru-W ₂ C/AC, Ir-W ₂ C/AC, Pd-W ₂ C/AC Catalysts : The preparation process is similar to Example 1, and the difference is that cobalt nitrate, ferric nitrate, chloroplatinic acid, ruthenium chloride, chloroiridic acid and palladium chloride are used instead of nickel nitrate in the precursor, and W is loaded in the catalyst The loading amount of Co, Fe, Pt, Ru, Ir, and Pd is 30wt%, respectively, 2wt%, 2wt%, 1wt%, 1wt%, 1wt%, and 1wt%, thus obtaining Co-W ₂ C/A, Fe-W ₂ C/AC, Pt-W ₂ C/AC, Ru-W ₂ C/AC, Ir-W ₂ C/AC and Pd-W ₂ C/AC catalysts.

Examples 10-15

Ni-WC was respectively supported on alumina, silica, titania, zirconia, titania, and silica-alumina molecular sieves to prepare supported Ni-WC catalysts: the preparation process was similar to Example 1, except that the carriers were respectively Alumina, silica, titania, zirconia, titania, silica-alumina molecular sieve instead of activated carbon, at the same time, the carbonization gas is changed from hydrogen to CH ₄ /H ₂ (volume ratio 1:4), and the W loading in the catalyst is 30wt %, the loading amount of Ni is 2wt%, and the crystal phase of tungsten carbide is WC. Thus, Ni-WC is loaded on alumina, silica, titania, zirconia, titania, silicon-aluminum molecular sieve, and phosphorus-aluminum molecular sieve. kind of catalyst.

Example 16

Preparation of supported catalyst Pt/AC: Dissolve 0.279g of chloroplatinic acid in 4ml of water, impregnate an equal volume on 2g of activated carbon support, and dry at 120°C for 12h to obtain a catalyst precursor. The catalyst precursor undergoes a temperature-programmed reduction reaction in a hydrogen atmosphere. The specific reaction process is as follows: the temperature of the precursor is raised from room temperature to 350° C. in a quartz reaction tube for 1 h, and maintained for 2 h, and the hydrogen flow rate is 120 ml/min to obtain a 5 wt % Pt/AC catalyst.

The preparation process of the other supported catalysts A is similar. Co/AC, Ni/AC, Ru/AC, Ni/AC, Ru/ AC, Ir/AC, Pd/AC.

Example 17

Different tungsten carbide catalysts catalyze the hydrogenation reaction of natural lignin in aqueous solution: add 1.0g white birch wood powder containing natural lignin, 0.4g catalyst and 100ml water into a 300ml reaction kettle, replace the gas with hydrogen for three times, and fill with hydrogen to 6MPa, stirred at a speed of 1000 rpm, and heated to 235°C for 4 hours. After the reaction was completed, it was lowered to room temperature, and the supernatant was centrifuged and then sampled for analysis. The catalysts used in Table 1 correspond to: (1) 30wt% W ₂ C/AC, (2) 30wt% WxC/AC (1<x<2), (3) Ni-W ₂ C/AC (4wt %Ni-30wt%W ₂ C), (4) Ni-WxC/AC (4wt%Ni-30wt%WxC, 1<x<2), (5) Pt-W ₂ C/AC (1wt%Pt-30wt %W ₂ C), (6) Ru-W ₂ C/AC (1wt% Ru-30wt% W ₂ C), (7) Ir-W ₂ C/AC (1wt% Ir-30wt% W ₂ C), (8) Pd-W ₂ C/AC (1wt% Pd-30wt% W ₂ C), (9) Ni-W ₂ C/Al ₂ O ₃ , (10) Ni-W ₂ C/SiO ₂ , (11 ) Pd-W ₂ C/Al ₂ O ₃ , (12) 0.05 wt% Ni-80 wt% W ₂ C/AC, (13) 20 wt% Ni-5 wt% W ₂ C/AC. Qualitative analysis of the product was carried out by GC-MS technology and standard sample control, and quantitative analysis was realized by gas chromatography internal standard method. The results are shown in Table 1. In addition to guaiacyl propane, syringyl propane, guaiacyl propanol and syringyl propanol, the products also include phenol, 2-methylphenol, 4-ethylphenol and other C6-C9 phenolic compounds , classified as other phenols in the table.

Table 1 Comparison of catalytic hydrogenation performance of natural lignin over different tungsten carbide catalysts

It can be seen from the table that the tungsten carbide catalysts promoted by different metals can catalyze the hydrogenation of lignin to obtain aromatic phenol compounds, and the tungsten carbide catalysts supported by different supports have excellent catalytic activity.

Example 18

Different composite catalysts A-B (the mass ratio of A to B is 1:3) catalyze the hydrogenation reaction of natural lignin in aqueous solution: add 1.0g white birch wood powder containing natural lignin, 0.4g catalyst and 100ml water into a 300ml reaction kettle In the process, after replacing the gas with hydrogen for three times, fill the mixture with hydrogen to 6 MPa, stir at a speed of 1000 rpm, and raise the temperature to 235°C for 4 hours. After the reaction was completed, it was lowered to room temperature, and the supernatant was centrifuged and then sampled for analysis. The product analysis method is the same as in Example 17. The results are shown in Table 2.

Table 2 Composite Catalyst A-B Catalytic Performance Comparison of Natural Lignin Hydrogenation

Example 19

Catalytic conversion reaction of natural lignin in small molecule solution: 1.0g white birch wood powder containing natural lignin, 0.4g Ni-W ₂ C/AC (4wt%Ni-30wt%W ₂ C) catalyst and 100ml small molecule solvent Add it into a 300ml reactor, replace the gas with hydrogen for three times, fill it with hydrogen to 6MPa, stir at a speed of 1000 rpm, and raise the temperature to 235°C for 4 hours. After the reaction was completed, it was lowered to room temperature, and the supernatant was centrifuged and then sampled for analysis. The product analysis method is the same as in Example 17. The results are shown in Table 3.

It can be seen from the table that the hydrogenation reaction of lignin is easier to proceed in small molecular solvents capable of forming hydrogen bonds. When ethylene glycol is used as solvent, the yield of aromatic phenol on Ni-W ₂ C/AC catalyst is Up to 50.6%. The reason is that the solubility of lignin increases through the hydrogen bond between lignin and small molecule solvent, thereby increasing the contact surface between lignin and catalyst, making the catalytic reaction easier to proceed.

Table 3 Hydrogenation results of natural lignin catalyzed by Ni-W ₂ C/AC in different solvents

Example 20

Catalytic hydrogenation reaction of different lignin raw materials: 1.0g lignin raw materials (40 mesh particles) from different sources, 0.4g Ni-W ₂ C/AC (4wt%Ni-30wt%W ₂ C) catalyst and 100ml water were added to In a 300ml reactor, after passing through hydrogen to replace the gas three times, fill it with hydrogen to 6MPa, stir at a speed of 1000 rpm, and raise the temperature to 235°C for 4 hours. After the reaction was completed, it was lowered to room temperature, and the supernatant was centrifuged and then sampled for analysis. The product analysis method is the same as in Example 17. The results are shown in Table 4.

Table 4 Ni-W ₂ C/AC catalyzed hydrogenation results of different lignin raw materials

Example 21

Catalytic hydrogenation reaction of natural lignin under different reaction conditions: mix different qualities of white birch powder (40 mesh) and catalyst (4wt%Ni-30wt%W ₂ C/AC) with 100ml water, add to 300ml reactor In the process, after replacing the gas with hydrogen for three times, fill it with hydrogen to the specified pressure, stir at a speed of 1000 rpm, and at the same time raise the temperature to the specified temperature for a certain period of time. Other processes are the same as in Example 17. The results are shown in Table 5.

Table 5 Catalytic hydrocracking results of natural lignin under different reaction conditions

Claims (13)

1. the application of tungsten-based catalyst in xylogen shortening system aromatics; It is characterized in that: tungsten-based catalyst with have under the polar solvent effect that forms the hydrogen bond ability, xylogen highly effective hydrogenation cracking in airtight autoclave prepares phenylol, Syringa oblata Lindl. base and pockwood phenolic group aromatics.

2. according to the described application of claim 1, it is characterized in that: said xylogen is one or more in biomass, biomass by hydrolyzation residue and the industrial lignin that contains xylogen.

3. according to the described application of claim 2, it is characterized in that: the said biomass that contain xylogen are one or more in birch, poplar, toothed oak wood, linden, beech, maple, dragon spruce, pine, Eucalyptus, bamboo, the agricultural crop straw, but are not limited to this; Said industrial lignin is one or more in sulfonated lignin, alkali lignin or the dealkalize xylogen.

4. according to the described application of claim 1; It is characterized in that: said have a polar solvent that forms the hydrogen bond ability, can be water, dioxane, THF, phenol and short chain saturated fatty alcohol like one or more in methyl alcohol, ethanol, terepthaloyl moietie, butanols, the butyleneglycol.

5. according to the described application of claim 1; It is characterized in that: said tungsten-based catalyst is a loading type carbonization tungsten catalyst, and carrier is one or more in gac, aluminum oxide, silicon oxide, titanium oxide, zirconium white, titanium oxide, Si-Al molecular sieve, the phosphate aluminium molecular sieve.

6. according to the described application of claim 5, it is characterized in that: the loading of tungsten in carrier is 5-80 wt%, and preferred loading is 10-50 wt%, and more preferably loading is 15-40 wt%.

7. according to the described application of claim 1, it is characterized in that: tungsten-based catalyst is a loading type carbonization tungsten catalyst, is made up of main active component, carrier and second metal component, three parts;

Said main active component is a wolfram varbide; Said carrier is one or more in gac, aluminum oxide, silicon oxide, titanium oxide, zirconium white, titanium oxide, Si-Al molecular sieve, the phosphate aluminium molecular sieve; In the nickel that said second metal component is a metallic state, iridium, platinum, ruthenium, rhodium, palladium, iron, cobalt, copper, aluminium, tin, molybdenum, chromium, the strontium one or more.

8. according to the described application of claim 7, it is characterized in that:

The loading of tungsten in carrier is 5-80 wt%, and preferred loading is 10-50 wt%, and more preferably loading is 15-40 wt%;

In the preferred nickel of said second metal component, iridium, ruthenium, palladium, the platinum one or more;

The loading of second metal component in carrier is 0.05-30 wt%, and preferred loading is 0.1-15 wt%, and more preferably loading is 0.2-5 wt%.

9. according to the described application of claim 1; It is characterized in that: said tungsten-based catalyst is a composite catalyst; Comprise catalyst A and catalyst B; The activeconstituents of catalyst A is one or more in the transition metal iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum of the 8th, 9,10 families, and the activeconstituents of catalyst B is one or more in the oxyhydroxide, tungsten bronze(s), wolframic acid, tungstate, metatungstic acid, metatungstate, para-tungstic acid, para-tungstate, peroxide wolframic acid, peroxide tungstate, heteropoly tungstic acid of muriate, the tungsten of sulfide, the tungsten of oxide compound, the tungsten of tungsten;

The metal active composition of catalyst A and the activeconstituents of catalyst B (in tungsten weight) weight ratio are between 0.02-3000 times of scope.

10. according to the described application of claim 9, it is characterized in that: said catalyst A is a loaded catalyst, and said carrier is gac, aluminum oxide, silicon oxide, silit, zirconium white, zinc oxide, titanium oxide is a kind of or the complex carrier more than two kinds; The content of activity component metal on catalyzer is 0.05-50 wt%, preferably at 1-30 wt%.

11., it is characterized in that according to the described application of claim 9: said catalyst A also can be unsupported, with the skeleton metal catalyst of active ingredient as catalyst backbone.

12. according to the described application of claim 1, it is characterized in that: the mass ratio of said xylogen raw material and solvent is 1:500-1:1; Catalyst levels is getting final product of catalytic amount; The original pressure of filling hydrogen under the room temperature in the reaction kettle is 1-20 MPa; Temperature of reaction is 120-450 ^oC; Reaction times is 10 min –, 24 h.

13. according to the described application of claim 12, it is characterized in that: the mass ratio of said xylogen raw material and solvent is 1:100-1:5; For adding fast response, the mass ratio of xylogen and catalyzer is generally 1:2-100:1, and preferred proportion is 2:1-20:1; The original pressure of filling hydrogen under the room temperature in the reaction kettle is 3-10 MPa; Temperature of reaction is 150-300 ^oC.