RU2789516C1 - Method for complex processing of lignocellulose biomass - Google Patents

Abstract

FIELD: complex processing of lignocellulose biomass.

SUBSTANCE: invention relates to a method for complex processing of lignocellulose biomass, including hydrolytic treatment of crushed biomass in an autoclave at 180 °C to obtain aqueous hemicellulose hydrolysate and solid lignocellulose residue, oxidative hydrolysis of aqueous hemicellulose hydrolysate in an autoclave at 150 °C in the presence of a catalyst, which uses vanadium, iron or iron ore concentrate deposited on zeolite of the "pentasil" type, followed by extraction from an aqueous solution of formic acid on a distillation column, fractionation of solid lignocellulose residue in an autoclave with concentrated formic acid, including isolated from the solution at the second stage of the process, at its boiling point, in the presence of a catalyst zeolite of the "pentasil" type, to obtain a solution of lignin in formic acid hydrodeoxygenation of a lignin solution in formic acid in a reactor at a temperature of 250 °C on a Pd catalyst/With and in a zeolite type "pentasil" co-catalyst, with the production of cycloalkanes and cycloalkanols.

EFFECT: invention provides a method for complex processing of lignocellulose biomass that meets environmental requirements and provides the production of liquid organic hydrogen carriers and valuable chemical products.

2 cl, 1 tbl, 5 ex

Description

The invention relates to technical chemistry, namely to methods for processing biomass to obtain liquid organic hydrogen carriers and valuable chemical products.

Lignocellulosic biomass is considered as a rich renewable source of fuel and chemical compounds. The advantages of biomass also lie in the possibility of overcoming the problem of the greenhouse effect caused by the emission of CO ₂ when using petrochemical and chemical technologies, due to the fixation of carbon dioxide during the cultivation of biomass [Murzin, D., Salmi, T. Catalysis for Lignocellulosic Biomass Processing: Methodological Aspects // Catalysis letters. - 2012. - V. 142. - N 6. - P. 676-689; Van Putten, R.-J., Van der Waal, JC, De Jong, E., et al. Hydroxymethylfurfural. A Versatile Platform Chemical Made from Renewable Resources // Chemical Reviews. - 2013. - V. 113. - N 3. - P. 1499-1597; Besson, M., Gallezot, P., Pinel, C. Conversion of Biomass into Chemicals over Metal Catalysts // Chemical Reviews. - 2014. - V. 114. - N 3. - P. 1827-1870].

Of particular interest is the search for catalytic technologies for the one-stage, so-called "one-pot", production of valuable substances directly from lignocellulosic raw materials, excluding the technological stages of isolation and purification of intermediate products. The one-stage organization of the process makes it possible to obtain formic acid and other valuable chemical products from plant raw materials by hydrolysis - oxidation.

Formic acid is used as a preservative and antibacterial agent in the pharmaceutical and fodder industries, as a solvent in some chemical reactions, in addition, it can be used either directly as a reducing agent or as a source of hydrogen used as a reducing agent in various chemical processes, in including the production of biofuels. The future use of formic acid as the so-called liquid organic hydrogen carriers (LHOHC) seems to be very promising. One of the main challenges in the development of hydrogen energy, including the replacement of gasoline and diesel engines with engines operating on hydrogen fuel cells, is the search for efficient ways to store hydrogen. After all, when hydrogen is pumped into steel cylinders at a pressure of 350 atmospheres, hydrogen in the cylinder will be only 1.5% by weight, and the rest will be steel. Formic acid as a storage method is attractive in that it is a non-explosive, non-poisonous liquid that can be safely transported to any place where, at room temperature and on catalysts, it will release 4.4% of hydrogen from its composition [Li, J., Ding, D.-J., Deng, L., et al. Catalytic Air Oxidation of Biomass-Derived Carbohydrates to Formic Acid // ChemSusChem. - 2012. - V. 5. - N 7. - P. 1313-1318; Serrano-Ruiz, J.C., Braden, D.J., West, R.M., et al. Conversion of cellulose to hydrocarbon fuels by progressive removal of oxygen // Applied Catalysis B: Environmental. - 2010. - V. 100. - P. 184-189].

Back in the USSR, copyright certificates were obtained for the production of formic acid from plant materials [SU 188953, 302332, 303315, 742423, 1223840, 1286590]. However, all of these inventions used alkaline solutions, required regeneration of the alkali, the provision of neutralization of waste water and the complex separation of the main product from the by-products resulting from hydrolysis. Important for the further development of methods for obtaining formic acid from biomass work was done more than 40 years ago at the University of California [Gary D., McGinnls Biomass Pretreatment with Water and High-pressure Oxygen. The Wet-Oxidation Process // Ind. Eng. Chem. Prod. Res. Dev., 1983, 22, 352-357]. The process was called wet oxidation, and it was shown that one of the three main components of biomass - hemicellulose - is hydrolyzed, ester bonds are cleaved and acetate and formate groups are released, which are oxidized to the corresponding acids, the concentration of acids increases, the pH falls, and the reactions of further hydrolytic cleavage become predominant. More and more hemicelluloses are broken down, allowing the growth of low molecular weight fragments that are water soluble. The process of wet oxidation includes the transformation of wood under air pressure (up to 30 atm.) in water at a temperature of 120°C and above in the presence of homogeneous catalysts.

In the works of recent years on the complex processing of lignocellulosic biomass into formic acid and the production of hydrogen from it, sulfuric, hydrochloric, heteropoly acids were used as catalysts for hydrolytic splitting, and hydrogen peroxide was used for effective oxidation. In products - levulinic acid and formic with acetic. The authors, analyzing their results, declare the need to replace acids and hydrogen peroxide with heterogeneous catalysts to improve the process and move to its industrial implementation [patents RU 2713659, 2713660, 2509778; EP 2928856; KR 102274756, 102363816; Ju-Hyoung Park, Min-Ho Jin, Dong-Wook Lee et al. Sustainable Low-Temperature Hydrogen Production from Lignocellulosic Biomass Passing through Formic Acid: Combination of Biomass Hydrolysis/Oxidation and Formic Acid Dehydrogenation // Environ.Sci.Technol., 2019, 53, 14041-14053; Ju-Hyoung Park, Min-Ho Jin, Dong-Wook Lee et al. Biomass-formic acid-hydrogen conversion process with improved sustainability and formic acid yield: Combination of citric acid and mechanocatalytic depolymerization // Chemical engineering journal, 421, 2021, 127-827].

The purpose of this invention is to develop a method for the complex processing of lignocellulosic biomass that meets environmental requirements and provides for the production of liquid organic hydrogen carriers and valuable chemical products.

As lignocellulosic biomass, coniferous and deciduous wood, as well as plant waste from agricultural crops, is used.

The method of complex processing of lignocellulosic biomass includes four successive stages.

Stage 1. Hydrolytic treatment of crushed biomass.

A sample of biomass with a dispersion of 1-2 mm is dried to constant weight in an oven, placed in an autoclave reactor, and distilled water is added. The reactor is pressurized, heated to a temperature of 180°C and maintained for 5-60 minutes with constant stirring at 100 rpm. Then the reactor is cooled to room temperature, the contents are discharged and filtered in a Buchner funnel with a water jet pump. The solid lignocellulosic residue is washed until colorless water is obtained and dried in an oven to constant weight. The resulting aqueous hydrolyzate, containing predominantly hemicellulose sugars, is combined with washings. Determine the mass of the solid residue and water-soluble substances in the hydrolyzate.

Stage 2. Oxidative hydrolysis of aqueous hemicellulose hydrolyzate.

The aqueous hydrolyzate obtained in the first stage and the solid catalyst are placed in an autoclave at a ratio of the mass of water-soluble substances: the mass of the catalyst = 1:0.5. The autoclave is filled with high pressure air (3.0 MPa), sealed and heated to 150°C. At a given temperature, the reaction mixture is kept for 3 hours. Next, the autoclave is cooled to room temperature and unloaded. An aliquot sample is taken, in which the content of formic acid is determined by liquid chromatography on a HPLC - chromatograph of the Millichrome A-02 brand (EkoNova, Russia), equipped with a UV detector (registration at λ = 210 nm) and a chromatographic column "Diasfer- 250-PA", 5 µm, 2×75 mm (EkoNova, Russia), eluent (85% 0.075MLiClO4, 15% ACN), _H2O .

Formic acid is extracted from the resulting aqueous solution in a distillation column and used in the next step.

As a catalyst for oxidative hydrolysis, heterogeneous catalysts are used: vanadium nitrate, iron ore concentrate, deposited on a zeolite of the "pentasil" type.

Stage 3. Fractionation of lignocellulosic residue.

The solid lignocellulosic residue is placed in an autoclave and filled with concentrated formic acid, including that isolated from the solution at the second stage of the process. A Pentasil-type zeolite catalyst is added to the reactor, the reaction mixture is heated to the boiling point of the formic acid solution and boiled for 2 hours. The main part of lignin (more than 80 wt. % of the weight of lignin in the sample) passes into solution during boiling, which is separated by filtration from the cellulose product. In the resulting solid cellulose product, the content of residual lignin did not exceed 10.5 wt. %. Determination of the content of residual lignin in the cellulose product was carried out according to the Klason method modified by Komarov.

Stage 4. Hydrodeoxygenation (HDO) of dissolved lignin.

Pd/C catalyst and Pentasil type zeolite cocatalyst are added to the resulting solution of lignin in formic acid and placed in a reactor. The reactor is purged with nitrogen to remove air, heated to 250°C and incubated for 2 hours. In the reaction mixture, an aqueous solution of formic acid simultaneously acts as a solvent for the HDO products of lignin and as a hydrogen donor. Depolymerization of lignin macromolecules occurs on the acidic sites of the catalyst, and on the palladium sites of the Pd/C catalyst, the intermediate intermediates of depolymerization and HDO of lignin are stabilized by hydrogen. As a result of catalytic depolymerization and HDO from 76 to 89 wt. % lignin is converted into monomeric products. Of these, 65-73 wt. % are cycloalkanes and cycloalkanols. The composition of monomeric lignin conversion products was analyzed in an aliquot taken from a mixture of filtrate and ethanol extract by GC-MS using an Agilent 7890A chromatograph equipped with an Agilent 7000A Triple Quad selective mass detector, while recording the total ion current. Separation of products was carried out on a capillary column HP-5MS 30 m long with an inner diameter of 0.25 mm, with temperature programming in the range of 40-250°C. Identification was performed using the NIST MS Search 2.0 instrument database and literature data.

As a Pd/C catalyst carrier, carbon obtained from a polyconjugated polymer, or carbon in the form of nanodiamonds, or carbon obtained by decomposition of organic compounds in plasma or by destruction of hydrocarbon gases in an electric arc, or by growing carbon nanotubes on nickel, can be used. deposited on alumina or solid acids, and the amount of palladium is from 0.1 to 1.0% by weight of the catalyst.

All the above stages of the process are carried out in aqueous media and at low temperatures. The developed method complies with environmental requirements, since it completely eliminates the effluents of third-party mineral acids and alkalis, and does not require the use of acid-resistant equipment. In addition, for the fractionation of the lignocellulose residue and the hydrodeoxygenation of the dissolved lignin, the formic acid obtained in the process is used as both a solvent and a hydrogen donor, rather than the pressurized molecular hydrogen usually used, which greatly simplifies the implementation of the method.

The obtained products - formic acid, cycloalkanes and cycloalkanols can be used to solve the problem of hydrogen storage, which is the most important for hydrogen energy. Formic acid under the action of a catalyst (palladium deposited on a carbon carrier) decomposes at room temperature into molecular hydrogen and carbon dioxide.

Cycloalkanes and cycloalkanols containing a high proportion of hydrogen in their composition during catalytic dehydrogenation on a palladium catalyst release up to 2-3 moles of molecular hydrogen in terms of a mole of cyclic hydrocarbon or cyclic alcohol

The method is confirmed by specific examples.

Example 1

Stage 1 Hydrolytic treatment of crushed biomass.

A sample of aspen wood with a dispersion of 1-2 mm and a weight of 100 g is dried to a constant weight in an oven at 105°C for 3 hours, placed in a 3-liter stainless steel autoclave reactor, and 2000 ml of distilled water are added. The reactor is pressurized, heated to a temperature of 180°C and maintained for 30 minutes with constant stirring at 100 rpm. Then the reactor is cooled to room temperature, the contents are discharged and filtered in a Buchner funnel with a water jet pump. The solid lignocellulosic residue is washed until colorless water is obtained and dried in an oven to constant weight at 105°C. The weight of the solid residue after drying is 66 g. The resulting aqueous hemicellulose hydrolyzate is combined with washings. The total volume of the hydrolyzate was 2200 ml, the amount of water-soluble substances was 34 g.

Stage 2. Oxidative hydrolysis of aqueous hemicellulose hydrolyzate.

The aqueous hemicellulose hydrolyzate obtained in the first stage, in an amount of 2200 ml and 15.5 g of solid catalyst, is placed in a 3000 ml Rexo Engineering autoclave. The ratio of the mass of water-soluble substances: the mass of the catalyst is 1:0.5. The V ₂ O ₅ /ZSM-5 catalyst is prepared by impregnating a Pentasil (KN-30) type zeolite with an aqueous solution of vanadium nitrate, followed by drying and calcination at a temperature of 500°C. The content of vanadium in the catalyst 7 wt. % (in terms of the weight of the substrate). The autoclave is filled with high pressure air (3.0 MPa), sealed and heated to 150°C. At a given temperature, the reaction mixture is kept for 3 hours. Next, the autoclave is cooled to room temperature, unloaded, and formic acid is extracted from the resulting aqueous solution in a distillation column. The content of formic acid is 138 mmol/l or 45 wt. % in terms of the weight of water-soluble substances in 2200 ml of loaded hydrolyzate.

Stage 3. Fractionation of lignocellulosic residue.

The solid lignocellulosic residue after hydrolytic treatment in the amount of 66 grams is placed in an autoclave reactor with a volume of 3000 ml and 2800 ml of concentrated formic acid is poured, including that isolated from the solution at the second stage of the process, and the catalyst zeolite KN-30 is added in the amount of 15 wt. % by weight of the substrate. The reaction mixture is heated to the boiling point of a formic acid solution and boiled for 2 hours. The main part of lignin (88.6 wt. % of the weight of the sample) passes into solution during boiling, which is separated by filtration from the cellulose product. In the resulting solid cellulose product, the content of residual lignin 9.4 wt. %.

Stage 4. Hydrodeoxygenation of dissolved lignin.

Pd/C catalyst and KH-30 co-catalyst are added to the resulting solution of lignin in formic acid in an amount of 2800 ml and placed in a 3000 ml reactor. The ratio of catalyst : cocatalyst is 1:1, the weight of the catalysts is 15 wt. % by weight of dissolved lignin (22.3 g). The reactor is purged with nitrogen to remove air, heated to 250°C, and GDT of the dissolved lignin is carried out for 3 hours. As a result of catalytic depolymerization and HDO 79.4 wt. % lignin is converted into monomeric products. Of these, 68.2 wt. % are cycloalkanes and cycloalkanols .

Example 2

Similar to example 1, differs in that they use a sample of fir wood.

Stage 1. The mass of the solid residue after drying is 68 g. The total volume of the hydrolyzate is 2200 ml, the amount of water-soluble substances is 32 g.

Stage 2. The content of formic acid is 110 mmol/l or 36 wt. % in terms of the weight of water-soluble substances in 2200 ml of loaded hydrolyzate.

Stage 3. 82.4 wt. % by weight of lignin in the sample goes into solution, the content of residual lignin in the cellulose product is 10.2 wt. %.

Stage 4. 76.3 wt. % lignin is converted into monomeric products, of which 65.2 wt. % are cycloalkanes and cycloalkanols.

Example 3

It is similar to example 1, differs in that a sample of the Jerusalem artichoke plant, dried to a constant weight, ground to a fraction of 0.1-0.2 mm, is used.

Stage 1. The mass of the solid residue after drying is 50 g. The total volume of the hydrolyzate is 2200 ml, the amount of water-soluble substances is 50 g.

Stage 2. The content of formic acid is 130 mmol/l or 32 wt. % in terms of the weight of water-soluble substances in 2200 ml of loaded hydrolyzate.

Stage 3. 92.4 wt. % by weight of lignin in the sample goes into solution, the content of residual lignin in the cellulosic product is 6.2 wt. %.

Stage 4. 89.2 wt. % lignin is converted into monomeric products, of which 73.0 wt. % are cycloalkanes and cycloalkanols.

Example 4

Similar to example 1, it differs in that iron ore concentrate (magnetite content 80 wt.%) GOK is used as a catalyst for the oxidation of the hydrolyzate, and zeolite of the ZSM-5 type (KN-30 brand) is used as a cocatalyst in a ratio of 5:1.

Stage 1. The weight of the solid residue after drying is 66 g. The resulting aqueous hemicellulose hydrolyzate is combined with washings. The total volume of the hydrolyzate was 2250 ml, the amount of water-soluble substances was 34 g.

Stage 2. The content of formic acid is 95.7 mmol/l or 31.2 wt. % in terms of the weight of water-soluble substances in 2200 ml of loaded hydrolyzate.

Stage 3. 88.6 wt. % by weight of lignin in the sample goes into solution, the content of residual lignin in the cellulose product is 9.4 wt. %.

Stage 4. 79.4 wt. % lignin is converted into monomeric products, of which 68.2 wt. % are cycloalkanes and cycloalkanols.

Example 5

Similar to example 1, differs in that for the oxidation of the hydrolyzate, a catalyst based on iron deposited on a hierarchical zeolite of the ZSM-5 type is used.

Stage 1. The mass of the solid residue after drying is 66 g. The total volume of the hydrolyzate was 2250 ml, the amount of water-soluble substances was 34 g.

Stage 2. The content of formic acid is 86.2 mmol/l or 28.1 wt. % in terms of the weight of water-soluble substances in 2200 ml of loaded hydrolyzate.

Stage 3. 88.6 wt. % by weight of lignin in the sample, the content of residual lignin in the pulp product of 9.4 wt. %.

Stage 4. 79.4 wt. % lignin is converted into monomeric products, of which 68.2 wt. % are cycloalkanes and cycloalkanols.

As follows from the examples and the table, the integration of these four successive stages allows for the complex processing of lignocellulosic biomass, which meets environmental requirements and ensures the production of liquid organic hydrogen carriers and valuable chemical products.

Table Indicators of the process of complex processing of lignocellulosic biomass Example No. Stage 1
hydrolytic treatment
crushed biomass Stage 2
oxidative hydrolysis
aqueous hydrolyzate of hemicellulose Stage 3 fractionation of lignocellulosic residue
(catalyst ZSM-5) Stage 4
hydrodeoxygenation of a solution of lignin in formic acid (catalyst Pd/C + ZSM-5) type of biomass amount of water-soluble substances, g mass of solid residue, g catalyst (carrier ZSM-5) formic acid concentration,
mmol/l yield of formic acid,
wt. % lignin content in solution, wt. % content remains
th lignin, wt. % the amount of converted lignin, wt. % number of cycloalkanes, cycloalkano
catch, wt. % 1 aspen wood 34 66 Vanadium 138 45 88.6 9.4 79.4 68.2 2 fir wood 32 68 Vanadium 110 36 82.4 10.2 76.3 65.2 3 Jerusalem artichokes
Boer 50 50 Vanadium 130 32 92.4 6.2 89.2 73.0 4 aspen wood 34 66 iron ore concentrate* 95.7 31.2 88.6 9.4 79.4 68.2 5 aspen wood 34 66 iron 86.2 28.1 88.6 9.4 79.4 68.2 * - magnetite content 80 wt. %

Claims (2)

1. A method for the complex processing of lignocellulosic biomass, including hydrolytic treatment of crushed biomass in an autoclave at a temperature of 180 °C to obtain an aqueous hemicellulose hydrolyzate and a solid lignocellulosic residue, oxidative hydrolysis of an aqueous hemicellulose hydrolyzate in an autoclave at a temperature of 150 °C in the presence of a catalyst, which is used as vanadium, iron or iron ore concentrate deposited on a zeolite of the "pentasil" type, followed by extraction of formic acid from an aqueous solution in a distillation column, fractionation of the solid lignocellulosic residue in an autoclave with concentrated formic acid, including that isolated from the solution at the second stage of the process, with its boiling point, in the presence of a Pentasil zeolite catalyst, to obtain a solution of lignin in formic acid, hydrodeoxygenation of a solution of lignin in formic acid in a reactor at a temperature of 250 °C on a Pd/C catalyst and cocatalyst eolite type "pentasil", with the production of cycloalkanes and cycloalkanols. 2. The method according to claim 1, characterized in that the biomass is coniferous and hardwood, as well as plant waste from crops.