Methods and catalysts for producing phenolic building blocks from lignin

Abstract

The present invention relates to a process for catalytic decomposition of lignin with high yield and high selectivity to phenolic building blocks with minimal formation of coke fractions, and a catalyst suitable for the process. The catalyst contains a basic support material, 1-10 wt.% platinum, and 0-5 wt.% nickel. The process includes providing a reaction mixture comprising lignin, a catalyst, and a solvent, and heating the reaction mixture to obtain a mixture comprising a product mixture, the catalyst, and the solvent.

Description

[Technical Field]

[0001] Due to the limited global supply of traditional fossil fuels, the production of chemical building blocks from renewable sources is becoming increasingly important. Therefore, the use of biomass from renewable feedstocks as a basis for obtaining a wide range of chemicals has become the subject of intensive research efforts. Lignocellulosic materials, which can be obtained from agricultural and forestry sources such as wood, are available in nearly unlimited renewable supplies. They consist of three main components: cellulose, hemicellulose, and lignin. While the potential use of the first two components for the synthesis of basic chemicals or fuel components has already been relatively well studied, the use of lignin as a feedstock has not yet been established to the same extent.

[0002] Lignin is one of the most abundant biopolymers and the only one composed of aromatic monomeric building blocks. It is an amorphous 3-D polymer found primarily in plant cell walls. The monomeric building blocks, called monolignins, contain primarily phenylpropane alcohols, primarily coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. The aromatic rings can have various substituents, such as hydroxyl, alkoxy, ether, alkyl, aldehyde, or ketone groups. The exact composition and molecular weight vary from plant to plant. The individual building blocks are linked through various types of bonds, including alkyl, aryl, and ether bonds. β-O-4 bonds are the most common. Figure 1 shows an overview of the various types of bonds in lignin.

[0003] The underlying polyphenolic structure makes lignin an ideal candidate to serve as a starting material for the synthesis of high-value aromatic fine chemicals, which can serve as the basis for the synthesis of other chemical products. Figure 2 shows, as an example, a phenolic moiety illustrating the various structural motifs of such desirable phenolic compounds. However, the heterogeneity of lignin structure makes it difficult to develop effective and selective processes to obtain low molecular weight components.

[0004] Lignin can be isolated from wood (e.g., pine, poplar, birch), annual plants (e.g., straw, miscanthus, switchgrass), or agricultural residues (e.g., sugarcane bagasse) by various extraction processes, and the polymeric structure of lignin depends greatly on the plant source, location, season, and isolation process. Many methods already exist for lignin degradation, including pyrolysis, acid or base hydrolysis, more selective catalytic reactions, and biological methods using enzymes. An overview of such processes in the context of biorefinery processes can be found, for example, in "Biorefineries - Industrial Processes and Products" (Kamm et al., in Ullmann's Encyclopedia of Industrial Chemistry, Electronic Release, 7th ed., Wiley-VCH, 2007). It may be necessary to separate lignin prior to depolymerization; for this purpose, for example, organosolv processes have been established to separate lignin from other carbohydrate-containing components of lignocellulosic starting materials.

[0005] Undesirable degradation products in lignin depolymerization can be polymeric components formed by radical rearrangement reactions. These components are commonly referred to as coke fractions, "coke," "char," and / or "tar," and are amorphous, heterogeneous product fractions that cannot be further processed. The formation of this fraction reduces the yield of desired products, especially in uncatalyzed reactions or when catalysts with unsuitable selectivity are used, as described, for example, in "Catalytic Transformation of Lignin for the Production of Chemicals and Fuels" (Li et al. Chem. Rev. 2015, 115, 11559-11624).

[0006] One type of catalytic decomposition reaction is base-catalyzed depolymerization (BCD), in which the lignin to be decomposed is treated with a solution of mineral bases at high temperature and pressure. While this reaction is suitable for at least partially producing desired products such as phenol and catechol derivatives, it produces large amounts of strongly basic solution residue, which precludes large-scale industrial application. An alternative is the use of heterogeneous catalysts, which can be easily separated from the reaction mixture after the reaction and reused.

[0007] Typically, such reactions are carried out in an inert gas and / or hydrogen atmosphere, which significantly increases the requirements of the process technology used compared to processes that can be carried out under atmospheric conditions.

[0008] (Green Chemistry, 2017, 19, 778, 788) describe a series of transition metal-free catalysts suitable for the BCD of lignin, including, for example, zeolites, metal oxides, hydrotalcites, and hydroxylapatite. The reaction conditions described allow for the production of relevant monomeric and oligomeric building blocks, but with low yields and high catalyst usage. Summary of the Invention [Problem to be solved by the invention]

[0009] Support materials with transition metals are a further type of catalyst suitable for the decomposition of lignin. U.S. Pat. No. 9,631,146 (B2) describes, for example, the use of nickel on layered double hydroxides as catalysts. However, studies of such systems have shown that the high proportion of coke fraction in the reaction products leads to relatively low yields of the desired products.

[0010] The object of the present invention was to provide a process for the catalytic decomposition of lignin with high yields and high selectivity to phenolic building blocks, with minimal formation of coke fractions. It was also an object of the present invention to find a process for decomposition under mild reaction conditions, i.e., low temperature, low pressure, and without the use of an inert gas or hydrogen atmosphere. Furthermore, part of the objective was to minimize the amount of catalyst required.

[0011] The aim was also to provide catalysts suitable for use in the processes found.

[0012] According to a first aspect of the present invention, the object is to provide a method for producing a cellular membrane comprising: a) providing a reaction mixture A comprising lignin, a catalyst, and a solvent; b) heating reaction mixture A to obtain mixture B comprising the product mixture, catalyst, and solvent; The catalyst is a basic carrier material; 1 to 10 wt% platinum; This is achieved by a method containing 0 to 5 wt. % nickel.

[0013] In the process according to the invention, a catalyst containing platinum and optionally nickel on a basic support material is used. In the context of the present invention, it has been found that the use of platinum or a combination of these two transition metals results in both a high conversion of the lignin used and selectivity for the formation of low molecular weight components. In this context, conversion should be understood as the total amount of product fractions formed. This also relates to an increase in yield, i.e., an increase in the proportion of reusable oligomeric and monomeric product fractions relative to the lignin used. In this context, selectivity means that the monomeric and oligomeric phenolic building blocks are mainly formed as low molecular weight product fractions, avoiding the formation of the aforementioned coke fractions.

[0014] Preferably, a product mixture having a low proportion of coke fraction is obtained by the process according to the invention.

[0015] For the purposes of this invention, coke fractions are understood to be product fractions that are insoluble in neither water nor the organic solvents THF and ethyl acetate. These are primarily polymer fractions formed by radical rearrangement of decomposed lignin. However, they may also contain low-molecular-weight carbon components or short-chain hydrocarbons that may be formed by competing reaction pathways. Because this fraction is insoluble in virtually all common solvents, further characterization is problematic or even impossible. In the context of this invention, insoluble is understood to mean that the substance dissolves in the corresponding solvent at less than 0.1 g / L at 25°C and 1013 hPa.

[0016] The present invention relates to a method for catalytic decomposition of lignin.

[0017] Lignin, as used herein, is understood to mean lignin model components, lignin-containing untreated biomass, lignin-containing fractions from treated biomass, and lignin from treated biomass. The biomass may consist of lignocellulose, although the cellulose and hemicellulose may be completely or partially separated. The biomass may include, for example, wood, straw, bagasse, recycled wood, or grass clippings.

[0018] Treatment can be by chemical pretreatment, by physical methods, or by biological methods.

[0019] In a preferred embodiment, the lignin is derived from biomass, which may be selected from the group comprising wood, straw, bagasse, and turfgrass. The lignin is preferably selected from the group comprising organosolv lignin, kraft lignin, lignin obtained by alkaline degradation, lignin obtained by sulfuric acid process, lignin obtained by sulfite process, lignin obtained by aqueous extraction, lignin obtained by acid hydrolysis, lignin obtained by enzymatic hydrolysis, lignin obtained by wood saccharification, lignin obtained by microbial treatment, lignin from lignin-containing biorefinery process streams, and mixtures thereof.

[0020] The lignin preferably has an average molecular weight in the range of 3,000 g / mol to 20,000 g / mol, more preferably in the range of 4,000 g / mol to 15,000 g / mol.

[0021] "Degradation" is understood to mean the breakdown of polymeric lignin into low molecular weight oligomeric or monomeric building blocks, the bonds between the building blocks being completely or partially destroyed. The term "depolymerization" can also be used synonymously.

[0022] The method according to the present invention comprises providing a reaction mixture A comprising lignin, a catalyst and a solvent.

[0023] The catalyst is preferably a supported catalyst. A supported catalyst is generally understood to mean a catalyst containing a support material on whose surface the catalytically active material is provided in a highly dispersed form. The support material must provide a stable base for the catalytically active material and be stable under the selected reaction conditions.

[0024] The catalyst contains a basic support material suitable for dispersing catalytically active materials in the reaction mixture. A basic support material is understood to mean a support material that has basic sites, i.e., can function as a Bronsted base (proton acceptor) or a Lewis base (electron pair donor). The basic support material is, for example, a metal oxide, a mixed hydroxide, a mixed oxide, a zeolite, or a clay mineral.

[0025] In a preferred embodiment, the basic carrier material is 150 ml 2 / g, preferably less than 100m 2 / g, particularly preferably less than 50m 2 The basic carrier material preferably has a BET specific surface area of ​​5 to 150 m 2 / g, preferably 10 to 100m 2 / g, which is also called specific surface area, and can be determined according to ISO 9277:2010 using nitrogen as the adsorbate.

[0026] Preferred basic carrier materials contain a mixture of divalent and trivalent cations.

[0027] The basic support material is preferably magnesium (Mg 2+ ), Nickel (Ni 2+ ), iron (Fe 2+ ), cobalt (Co 2+ ), copper (Cu 2+ ), zinc (Zn 2+ ), calcium (Ca 2+ ), tin (Sn 2+ ), lead (Pb 2+ ) and combinations thereof. 2+In a preferred embodiment, the divalent cation M 2+ is magnesium (Mg 2+ )

[0028] The basic support material is preferably aluminum (Al 3+ ), iron (Fe 3+ ), chromium (Cr 3+ ), manganese (Mn 3+ ) and combinations thereof. 3+ In a preferred embodiment, the trivalent cation M 3+ is aluminum (Al 3+ )

[0029] The ratio of divalent to trivalent cations can vary, preferably in the range of 1:7 to 7:1, preferably in the range of 1:5 to 5:1, most preferably in the range of 1:3 to 3:1.

[0030] Preferred basic carrier materials are those of the formula [M 2+ 1-w M 3+ w (OH)2] w+ (A n- w / n )·mH2O, A layered double hydroxide (LDH) of the formula: M 2+ represents a divalent cation, M 3+ represents a trivalent cation, A n- represents an anion with charge n, m represents the number of water molecules, and w represents the molar ratio of trivalent cations to the total amount of cations.

[0031] Preferably, the layered double hydroxide is a crystalline material consisting of a lamellar structure.

[0032] In a preferred embodiment, the layered double hydroxide contains exactly one divalent cation.

[0033] In a preferred embodiment, the layered double hydroxide contains exactly one trivalent cation.

[0034] Preferably, the divalent cation is magnesium (Mg 2+ ), and the trivalent cation is aluminum (Al 3+ )

[0035] Layered double hydroxides are hydroxides (OH - ), carbonate (CO3 2- ), nitrate (NO3 - ), sulfate (SO4 2- ) and chloride (Cl - It is preferred that the anion contains at least one anion selected from the group consisting of:

[0036] The basic carrier material may be a hydrotalcite or a hydrotalcite-like compound, where hydrotalcite is understood by those skilled in the art to mean aluminum-magnesium hydroxycarbonate.

[0037] In a preferred embodiment, the basic support material has the formula Mg6AI2(OH) 16 It is hyrotalcite (CO3)·4H2O.

[0038] The catalyst contains platinum and optionally nickel, which are hereinafter referred to individually or collectively as metal species. The metal species form the catalytically active sites of the catalyst. The term "metal species" does not make any statements regarding the oxidation state of platinum or nickel. In other words, it does not indicate the existence of an elemental state with an oxidation state of 0. As used herein and known to those skilled in the art, the term "oxidation state" refers to the formula charge of an atom in a compound or the actual charge of a monatomic ion. By definition, an elemental atom has an oxidation state of 0.

[0039] In the case of base-catalyzed depolymerization of lignin, the basic support material can also act catalytically alone. However, this reaction is not selective as defined in the present invention and does not result in high yields of the desired phenolic components. Surprisingly, by providing the basic support material with platinum and optionally nickel, it is possible to achieve the desired selectivity of the catalytic depolymerization of lignin, increasing the yield of the desired product fraction.

[0040] Preferably, the catalyst contains at most 15% by weight, particularly preferably at most 12% by weight, in particular at most 9% by weight, of metal species, based on the total weight of support material and metal species.

[0041] In a preferred embodiment, the catalyst contains in the range of 1 to 15 wt% metal species, for example, 15 wt% metal species, 10 wt% metal species, 9 wt% metal species, 8 wt% metal species, 7 wt% metal species, 6 wt% metal species, 5 wt% metal species, 4 wt% metal species, 3 wt% metal species, 2 wt% metal species, or 1 wt% metal species.

[0042] The catalyst may contain 1 to 10 wt. % platinum, for example, 1 wt. %, 2 wt. %, 3 wt. %, 4 wt. %, 5 wt. %, 6 wt. %, 7 wt. %, 8 wt. %, 9 wt. %, 10 wt. %, or any intermediate weight percentages therebetween. This means that 1 to 10% of the total weight of the catalyst, including the support material and the metal species, is made up of platinum species. In a preferred embodiment, the catalyst contains 2 to 8 wt. % platinum, more preferably 3 to 7 wt. % platinum.

[0043] The platinum is preferably present as metallic platinum, ie in the zero oxidation state.

[0044] The catalyst can contain 0 to 5 wt. % nickel, for example, 0 wt. %, 1 wt. %, 2 wt. %, 3 wt. %, 4 wt. %, 5 wt. %, or any intermediate weight percentage therebetween. This means that 0 to 5% of the total weight of the catalyst, including the support material and the metal species, is made up of nickel species. In a preferred embodiment, the catalyst contains 0.1 to 5 wt. % nickel, more preferably 1 to 4 wt. % nickel.

[0045] In a preferred embodiment, the catalyst contains 5% by weight platinum and 1% by weight nickel.

[0046] In a more preferred embodiment, the catalyst contains 5% by weight of platinum and 2% by weight of nickel.

[0047] In a more preferred embodiment, the catalyst contains 5% by weight of platinum and no nickel.

[0048] Preferably, the metal species are present in particulate form on the basic support material.

[0049] Preferably, the surface area of ​​the platinum-containing particulate metal species is at least 1 m 2 / g, more preferably at least 2m 2 / g, and even more preferably at least 4m 2 The surface area of ​​the platinum-containing fine particles as a metal species can be determined using the CO adsorption method described below, which includes a reduction step.

[0050] In a preferred embodiment, the catalyst is 50 ml 2 / g, preferably less than 40m 2 / g, particularly preferably less than 20m 2 The basic carrier material preferably has a BET specific surface area of ​​3 to 50 m 2 / g, preferably 4 to 40 m 2 / g。 The BET surface area of ​​the catalyst can be determined similarly according to ISO 9277:2010 using nitrogen as the adsorbate.

[0051] Suitable catalysts can be prepared by a number of methods known to those skilled in the art, such as precipitation, impregnation, adsorption or ion exchange.

[0052] Suitable catalysts are preferably obtained by impregnating a basic support material with a solution of at least one compound of at least one metal of the metallic species, followed by reduction, optionally followed by a heat treatment.

[0053] Suitable catalysts are, for example: I) impregnating a basic support material with a solution containing at least one compound of at least one metal of the metallic species and a solvent; II) a reduction step.

[0054] In step I), the basic support material is impregnated with a solution of at least one compound of at least one metal of the metallic species. In this step, the material to be impregnated, in this case the basic support material, is contacted with a solution of one or more compounds of at least one metal of the metallic species.

[0055] The impregnation step results in a basic support material that is impregnated (i.e., supported with at least one compound of one or more metals of the metallic species). A preferred result is that the basic support material is homogeneously or uniformly provided with at least one compound of at least one metal of the metallic species.

[0056] Various impregnation methods are known to those skilled in the art, such as capillary-controlled impregnation (the so-called "incipient wetness" method) and diffusion-controlled impregnation (the so-called "adsorption-controlled" method). In principle, both techniques are suitable for producing catalysts suitable for the present invention.

[0057] Impregnation is generally understood to mean the association of a compound with a support material, so that the compound is adsorbed on the surface of the support material. In the case of porous support materials, the surface is in particular also the inner surface, i.e. the surface located within the pores.

[0058] This bonding is carried out, for example, by adding a solution of at least one compound of at least one metal of the metal species to a suspension of a basic carrier material in a solvent and mixing the mixture.However, it is also possible to spray such a solution onto the basic carrier material, or to add the basic carrier material to such a solution, and then mix the mixture.Methods for mixing such systems are known to those skilled in the art and include, for example, stirring or kneading, and can use a forced mixer, a free-fall mixer, a stirrer, a kneader, a flow mixer, or a mixing pump.

[0059] Preferably, the composition containing the basic carrier material and the solution are mixed continuously during the impregnation step.

[0060] In a preferred embodiment, the basic carrier material is present in suspended form in the solution during the impregnation step. For the purposes of the present invention, a suspension is a mixture of solids and liquid, in which the solids are uniformly dispersed in the liquid in the form of finely divided solid matter.

[0061] In an alternative embodiment, the basic carrier material and the solution are present in the form of an impregnated powder during the impregnation step, which means that the solution is added only to the extent that the basic carrier material is wetted.

[0062] When the basic support material is simultaneously impregnated with several compounds of at least one metal of the metal species, it may be preferable to provide the relevant compounds in one solution. However, it may also be preferable to provide the relevant compounds in separate solutions. Both variants are suitable for providing the basic support material simultaneously with, for example, platinum and nickel.

[0063] According to the present invention, the amount of metal species in the solution can vary widely. "Amount of metal species" refers to the content of platinum and optionally nickel in the solution. Particularly good results are obtained when the solution contains metal species in an amount of at least 1% by weight, in particular at least 2% by weight, preferably at least 5% by weight, and more preferably at least 10% by weight, based on the amount of solvent. In particular, the solution can contain metal species in an amount ranging from 1% to 80% by weight, in particular from 2% to 70% by weight, preferably from 5% to 60% by weight, and more preferably from 10% to 50% by weight.

[0064] The impregnation step can be carried out at room temperature. However, the impregnation step can also be carried out at a temperature lower or higher than room temperature. During the impregnation step, the temperature of the mixture containing the basic carrier material and the solution can be, for example, 10°C to 90°C, more preferably 20°C to 80°C.

[0065] The duration of the impregnation step is selected so that at least one compound of at least one metal of the metal species can be precipitated in sufficient amounts on the basic support material, and suitable durations can be determined by those skilled in the art based on routine experimentation.

[0066] Preferably, at least one compound of at least one metal of the metal species is completely precipitated from the solution onto the basic support material. Thus, after the impregnation step, the solvent does not contain compounds of at least one metal of the metal species. Those skilled in the art will understand that "free of compounds" means a concentration that can no longer be detected by precious metal detection using tin chloride in a hydrochloric acid environment, a method that is generally known to those skilled in the art.

[0067] The amount of basic support material used during production depends on the desired amount of metal species to be deposited on the basic support material and therefore also on the concentration of the use solution of at least one compound of at least one metal of the metal species.

[0068] During the impregnation step, the basic support material is present, for example, in the range of 5% to 95% by weight, more preferably in the range of 10% to 90% by weight, based on the total amount of solution and basic support material.

[0069] At least one compound of at least one metal of the metallic species can preferably be converted to the elemental state via thermal decomposition or by wet chemical reduction.

[0070] Suitable compounds of at least one metal of the metal species are, for example, salts, complex compounds or organometallic compounds.

[0071] Platinum compounds that can be used for impregnating the basic carrier material are known to those skilled in the art. For example, the platinum compound is a Pt(II) or platinum(IV) compound, such as a salt of Pt(II) or Pt(IV), a complex compound of Pt(II) or Pt(IV), or an organometallic compound of Pt. Examples of platinum compounds include platinum halides or their acids, hexachloroplatinic acid or its salts, potassium tetrachloroplatinate, platinum nitrate, platinum acetylacetonate, platinum oxalate, or a mixture of at least two of these compounds.

[0072] Nickel compounds that can be used for impregnating the basic support material are also known to those skilled in the art. For example, the nickel compound is a Ni(II) compound, such as a Ni(II) salt, a Ni(II) complex compound, or a Ni organometallic compound. Examples of nickel compounds include nickel nitrate, nickel hydroxide, nickel halide, or a mixture of at least two of these compounds.

[0073] The solution further comprises at least one solvent.

[0074] The solution may also contain additional components such as an acid.

[0075] The at least one solvent may be selected from the group consisting of water and an organic solvent, which may be, for example, an alcohol such as methanol or ethanol.

[0076] Optionally, the impregnated basic support material obtained according to step I) may first be dried to partially or completely remove the solvent before carrying out the reduction of step II).

[0077] It may be preferable to filter off the impregnated basic support material and dry it.

[0078] The impregnated support material is dried, for example, at a temperature below 250°C, more preferably below 200°C, and even more preferably below 150°C.

[0079] In particular, drying can be carried out under reduced pressure, preferably at a pressure of less than 300 mbar.

[0080] Preferably, the drying is carried out for 0.5 to 24 hours, more preferably 2 to 20 hours.

[0081] Optionally, the method can also include a heat treatment of the impregnated support material after step I) and before step II), such a heat treatment also known to those skilled in the art as calcination.

[0082] In a preferred embodiment, the heat treatment of the impregnated basic support material decomposes at least one compound of at least one metal of the metallic species.

[0083] The heat treatment is preferably carried out in the presence of oxygen.

[0084] In one embodiment, if drying has not been performed, an optional heat treatment will evaporate the solvent, which in one embodiment will evaporate the solvent and completely decompose at least one compound of at least one metal of the metallic species.

[0085] The heat treatment can be carried out at a temperature of less than 1000° C., less than 900° C., less than 800° C., less than 700° C., less than 600° C., less than 500° C., less than 400° C., or less than 300° C. In one embodiment, the impregnated basic support material is heat treated at a temperature of from 150° C. to 250° C.

[0086] Preferably, the impregnated basic support material is heat-treated in multiple stages. This should be understood to mean that the impregnated basic support material is first heat-treated at a first temperature and then heat-treated at at least one further temperature. Preferably, the first temperature is lower than the at least one further temperature. Preferably, the first temperature is in the range of 100 to 200°C. Preferably, the at least one further temperature is in the range of 200 to 300°C.

[0087] In a further preferred embodiment, the temperature is increased during the heat treatment. The increase in temperature may be stepwise or continuous, or a combination of stepwise and continuous increases.

[0088] Preferably, the heat treatment is carried out for 0.5 hours to 24 hours, more preferably 2 hours to 18 hours.

[0089] In step II) of the method for preparing a suitable catalyst, a reduction is carried out, which should be understood to mean that at least one compound of at least one metal of the metal species present on the basic support material after impregnation is converted into a lower oxidation state.

[0090] In the case of platinum compounds, for example, it may be desirable to convert platinum from the Pt(II) or Pt(IV) oxidation state to the Pt(0) oxidation state.

[0091] In the case of compounds of nickel, for example, it may be desirable to convert the nickel from the Ni(II) oxidation state to the Ni(0) oxidation state.

[0092] The reduction method and suitable reducing agents are known in principle to those skilled in the art. The reduction step can be carried out, for example, under a reducing atmosphere or wet chemically. In particular, the reduction step can be carried out under a forming gas atmosphere using a reducing acid, its salt or a reduced boron compound. Those skilled in the art will understand that forming gas is a gas mixture containing nitrogen and hydrogen, for example, 95% by volume of nitrogen and 5% by volume of hydrogen. In the case of wet chemical reduction, preferably, formic acid or a salt of formic acid, for example, sodium formate, is used as the reducing agent.

[0093] In the case of wet chemical reduction, the reduction step can be carried out directly in the impregnation solution, i.e. the impregnated support material obtained after step I) is not separated from the solvent, in other words it may be preferable to add the reducing agent immediately after step I).

[0094] The reduction step is carried out, for example, at a temperature of less than 400° C., more preferably less than 350° C., particularly preferably less than 300° C. In the case of wet chemical reduction, it may be preferable to carry out the reduction at a temperature of less than 100° C.

[0095] Preferably, the reduction step is carried out for 0.5 to 24 hours, more preferably 2 to 15 hours.

[0096] It may be preferable to subject the material obtained in step II) to further process steps.

[0097] For example, it may be preferable to dry the material obtained after step II) to partially or completely remove the solvent.

[0098] In a preferred embodiment, the material obtained in step II) is filtered off and dried.

[0099] Drying is carried out, for example, at a temperature below 250°C, more preferably below 200°C, even more preferably below 150°C.

[0100] In particular, drying can be carried out under reduced pressure, preferably at a pressure of less than 300 mbar.

[0101] Preferably, drying is carried out in the absence of oxygen.

[0102] Preferably, the drying is carried out for 0.5 to 24 hours, more preferably 2 to 20 hours.

[0103] In the process according to the invention, the reaction mixture A in process step a) comprises, in addition to lignin and catalyst, a solvent.

[0104] The solvent may contain multiple chemicals, i.e., the solvent may be a solvent mixture. The solvent may contain water and / or an organic solvent. The organic solvent may be an alcohol, such as methanol, ethanol, propanol, isopropanol, or a ketone, such as acetone.

[0105] Reaction mixture A may comprise solvent in an amount of at least 60% by weight, more preferably at least 70% by weight, and even more preferably at least 80% by weight.

[0106] The solvent preferably contains at least 10 wt %, more preferably at least 20 wt %, and most preferably at least 30 wt % of water, based on the total weight of the solvent. For example, the solvent contains water in the range of 10 to 80 wt %, more preferably in the range of 20 to 70 wt %, and even more preferably in the range of 30 to 60 wt %.

[0107] The solvent preferably contains water and an alcohol, preferably water and methanol, water and ethanol, water and propanol, or water and isopropanol. The solvent preferably contains 5 to 95% by weight of alcohol, more preferably 15 to 85% by weight, even more preferably 25 to 75% by weight, and most preferably 30 to 60% by weight.

[0108] The use of the catalysts described herein allows for the selective catalytic depolymerization of lignin using smaller amounts of catalyst than described in the prior art. In a preferred embodiment, the catalyst is present in reaction mixture A in an amount of less than 30 wt.%, preferably less than 20 wt.%, more preferably less than 10 wt.%, and particularly preferably less than 5 wt.%, based on the total amount of catalyst and lignin. In a preferred embodiment, the catalyst is present in reaction mixture A in an amount ranging from 0.1 to 30 wt.%, preferably in the range of 0.5 to 20 wt.%, and more preferably in the range of 1 to 15 wt.%, based on the total amount of catalyst and lignin.

[0109] In process step b), the process according to the invention comprises heating reaction mixture A.

[0110] The exact cracking conditions will depend on the lignin used, the catalyst used and the desired product composition.

[0111] Reaction mixture A can be stirred during the process.

[0112] The reaction mixture A is heated to the reaction temperature, which is understood to mean the temperature reached after the heating step of the reaction mixture, which is preferably reached after a heating step of not more than 90 minutes, more preferably not more than 60 minutes.

[0113] Preferably, reaction mixture A is heated to a reaction temperature of less than 400° C., more preferably less than 300° C., and most preferably less than 250° C. Preferably, reaction mixture A is heated to a reaction temperature in the range of 50° C. to 400° C., preferably in the range of 100° C. to 300° C., and more preferably in the range of 150° C. to 250° C.

[0114] In a preferred embodiment, the reaction temperature in process step b) is maintained for less than 240 minutes, more preferably less than 180 minutes, in particular less than 150 minutes. Preferably, the reaction temperature is maintained for 5 to 240 minutes, particularly preferably 20 to 180 minutes, in particular 30 to 150 minutes.

[0115] Methods for heating the reaction mixture are known in principle. In a preferred embodiment, the heating is carried out by jacket heating.

[0116] The method according to the present invention makes it possible to decompose lignin without applying high pressure.

[0117] In a preferred embodiment, the method is carried out in a closed vessel.

[0118] During the thermal treatment of reaction mixture A, gaseous products may also be formed, which may increase the pressure in the vessel in which the thermal treatment is carried out. The pressure during step b) may be less than 150 bar, preferably less than 100 bar, particularly preferably less than 50 bar. The pressure during step b) is preferably between 0.1 bar and 35 bar, more preferably between 1 bar and 10 bar, in particular between 1 bar and 5 bar.

[0119] A further advantage of the method according to the invention is that it does not have to operate in a hydrogen or inert gas atmosphere.

[0120] The process according to the invention gives a mixture B comprising the product mixture, the catalyst and the solvent.

[0121] The product mixture contains monomeric and oligomeric products that are soluble in the organic solvent. The product mixture may also contain additional products, such as polymeric lignin rearrangement products or gaseous products. The gaseous products typically contain CO and H. Additionally, the product mixture may contain products that are water soluble, referred to as the water soluble product fraction.

[0122] For the definition of the terms "monomer product", "oligomeric product" and "polymer", reference is made in principle to the IUPAC definition. "Oligomer" is understood to mean a molecule of medium molecular weight consisting of several smaller repeating units. Medium molecular weight means that the properties of the molecule do not change when one or several smaller units are removed. The term "oligomer" preferably includes compounds having at least 3 and / or up to 20 monomer units.

[0123] In the context of the present invention, such products are called monomeric or oligomeric components obtained from lignin by the process according to the invention.

[0124] The monomeric product is preferably soluble in ethyl acetate, and the oligomeric product is preferably soluble in THF.

[0125] The monomeric and oligomeric products preferably contain building blocks containing at least one aromatic ring with at least one oxygen-containing substituent. In other words, the monomeric and oligomeric products preferably contain mainly phenolic building blocks. The presence of phenolic building blocks can preferably be determined by Folin-Ciocalteu titration of OH groups.

[0126] Preferably, the monomeric and oligomeric products comprise at least 40% by weight, more preferably at least 50% by weight, of phenolic building blocks, based on the total weight of the monomeric and oligomeric components.

[0127] Preferably, the process according to the invention results in a product mixture in which at least 50% by weight, more preferably at least 60% by weight, of the lignin used in reaction mixture A is converted into monomeric and oligomeric products. In other words, in the process according to the invention, a yield of at least 50% by weight of the target product is obtained, and the proportion of undesired by-products is minimized. For the purposes of the present invention, undesired by-products are understood to be the coke fraction, the water-soluble product fraction and the gaseous product fraction.

[0128] The yield is determined using the following formula: Yield (wt%) = (weight of monomer product + weight of oligomer product / weight of lignin used) × 100.

[0129] Preferably, a product mixture containing less than 30% by weight of a coke fraction is obtained by the process according to the invention. This means that less than 30% by weight of the resulting product mixture, which contains polymeric, monomeric and oligomeric components, and optionally a water-soluble fraction and gaseous products, consists of this insoluble fraction. More preferably, a coke fraction of less than 25% by weight, even more preferably less than 20% by weight, and most preferably less than 10% by weight is obtained.

[0130] Preferably, a product mixture containing at least 5 wt. %, more preferably at least 10 wt. % of the monomer product is obtained by the process according to the invention. Preferably, a product mixture containing 1 to 30 wt. %, more preferably 5 to 20 wt. % of the monomer product is obtained by the process according to the invention.

[0131] Preferably, a product mixture containing less than 20 wt. %, more preferably less than 15 wt. %, even more preferably less than 10 wt. % of monomer products having no aromatic moieties is obtained by the process according to the invention.

[0132] Preferably, the monomer product contains 20 or fewer carbon atoms, preferably 15 or fewer carbon atoms.

[0133] The average molecular weight of the monomer product is preferably less than 1500 g / mol, more preferably less than 1000 g / mol. The average molecular weight can be measured by gel permeation chromatography (GPC).

[0134] The product mixture preferably contains at least one monomeric product containing a phenolic building block. The presence of such products with phenolic OH groups can be determined by the Folin-Ciocalteu method.

[0135] Preferably, the total weight of the monomer products comprises at least 40 wt.%, more preferably at least 50 wt.%, and even more preferably at least 60 wt.% of the monomer products comprising an aromatic system having at least one oxygen-containing substituent, as can be determined by gas chromatography-mass spectrometry (GC-MS).

[0136] The monomer product preferably comprises at least one product from the group comprising alkylated phenol, alkylated alkoxyphenol, catechol, alkylated catechol and alkylated alkoxycatechol. The monomer product can be characterized by GC-MS.

[0137] Preferably, a product mixture containing at least 40 wt. %, more preferably at least 50 wt. %, even more preferably at least 60 wt. % of oligomeric product is obtained by the process according to the invention.

[0138] The average molecular weight of the oligomeric product is preferably less than 10,000 g / mol, more preferably less than 8,000 g / mol.

[0139] Preferably, the average molecular weight of the oligomeric product is no more than 70%, more preferably no more than 60%, and even more preferably no more than 55% of the average molecular weight of the lignin originally used.

[0140] The product mixture preferably comprises at least one oligomeric product whose monomer building blocks comprise a phenolic building block. The presence of such products with phenolic OH groups can be determined by the Folin-Ciocalteu method.

[0141] The oligomeric product preferably comprises at least one oligomer containing a monomer selected from the group including alkylated phenol, alkylated alkoxyphenol, catechol, alkylated catechol, and alkylated alkoxycatechol.

[0142] In a preferred embodiment, the catalyst is separated from mixture B after carrying out the process according to the invention. This separation may be carried out, for example, by filtration.

[0143] The method may also include a process step of separating the product mixture from mixture B. The entire product mixture or a portion of the product mixture can be separated, for example, by filtration, evaporation, distillation, centrifugation, decantation, sedimentation, or other methods known to those skilled in the art.

[0144] In a preferred embodiment, the method according to the present invention may comprise a step of fractionating, isolating or purifying mixture B.

[0145] In a preferred embodiment, the method according to the invention is part of a process to split biomass into various streams and to decompose the lignin moieties.

[0146] In a preferred embodiment, the method includes the further step of producing a phenolic resin from at least one product mixture component.

[0147] The present invention also relates to a product mixture obtainable by the process according to the invention, comprising monomeric and oligomeric products. For preferred embodiments, see the above description.

[0148] The present invention also relates to catalysts suitable for use in the process according to the invention. For preferred embodiments, see the above description. [Brief explanation of the drawings]

[0149] [Figure 1] Figure 1 shows an overview of the different types of bonds in lignin. [Figure 2] FIG. 2 is an illustration of phenolics illustrating various structural motifs of desirable phenolics. [Figure 3]FIG. 3 shows the composition of a representative depolymerization product mixture using four catalysts (IE1 to IE4) in comparison with that of a non-metal-supported hydrotalcite (CE1). (IE1 to IE5 correspond to EB1 to EB5 in the figure, and CE1 corresponds to VB1.) [Figure 4] FIG. 4 shows a comparison of exemplary GPC chromatograms used to analyze the average molecular weight of the lignin used and the monomeric and oligomeric product fractions of the depolymerization with IE3. [Figure 5] FIG. 5 shows the chromatographic results of the example and the comparative example (IE1 to IE5 correspond to EB1 to EB5 in the figure, and CE1 corresponds to VB1). [Example]

[0150] DETAILED DESCRIPTION OF THE INVENTION The present invention will now be described by way of illustrative embodiments and in specific terms which are not to be construed as limiting.

[0151] Measurement method Platinum and nickel content of the catalyst The platinum and nickel contents were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0152] BET surface area The BET surface area was measured according to ISO 9277:2010 according to the BET theory (multipoint method) at 77 K using nitrogen as adsorbate.

[0153] CO adsorption (precious metal surface) The precious metal surface of the catalyst was measured by CO adsorption. For this purpose, the catalyst was first reduced in a sealed vessel in forming gas consisting of 95% argon and 5% hydrogen at 400 °C for 20 minutes. Subsequently, carbon monoxide (CO using helium as a carrier gas) was pulsed into the vessel containing the catalyst. This was continued until a consistent CO peak was detected downstream of the catalyst. The amount of CO absorbed by the catalyst was determined by measuring the area of ​​the peak for the administered CO and the area of ​​the peak for the reacted CO. For this purpose, the integral of the area for the administered CO was subtracted from the integral of the area for the reacted CO. The amount of CO absorbed was used to calculate how much CO was stored per amount of catalytically active composition used. Using conversion, the surface area of ​​the active precious metal sites (often referred to as CO surface area or precious metal surface area) could be determined from the measured amount of CO stored on the active sites.

[0154] Gel Permeation Chromatography (GPC) The molecular weights of the various components were determined by gel permeation chromatography (GPC, Dionex ICS-5000+ from Thermo Scientific and PSS MCX analytical 100A+1000A+100 000A columns, 8 mm x 300 mm, also from Thermo Fisher). Characterization was carried out using 0.1 mol / L NaOH as eluent at a flow rate of 0.5 mL / min at 30 °C. Detection was performed at 280 nm.

[0155] Before injection, the samples were dissolved in 0.1 mol / L NaOH and filtered through a 0.45 μm filter. Size-exclusion chromatography (SEC) calibration was performed using PSS standards (Polymer Standard Service, Mp: 976 000, 679 000, 470 000, 258 000, 194 000, 152 000, 78 400, 29 500, 10 200, 3 420, 891) and vanillin. The standards were similarly dissolved in NaOH (1 mg / mL in 0.1 mol / L NaOH).

[0156] Gas chromatography-mass spectrometry (GC-MS) Qualitative and quantitative analyses were performed using gas chromatography-mass spectrometry (GC-MS, Shimadzu GC-MS-QP 2020, HP-SM5 capillary column, 60 m × 0.25 mm × 0.25 μm). The system temperature was increased from 50 °C to 300 °C at a heating rate of 10 °C / min. A holding time of 5 min at 120 °C and 8 min at 280 °C was selected. Helium was used as the carrier gas. The injection temperature was 250 °C. Five mg of sample was dissolved in 1 mL of ethyl acetate, mixed with 100 μL of toluene (containing an internal standard), and directly injected. Forty-one monomer components were used as standards for external calibration, with concentrations ranging from 300 mg / L to 0.3 mg / L. Toluene containing the internal standard was also used.

[0157] Measurement of phenolic groups The phenolic groups were measured by the Folin-Ciocalteu method, in which hydroxyl groups were titrated with a colored indicator. The indicator system used was a complex system consisting of molybditol phosphate and tungstophosphate (3H2O·P2O5·13WO3·5MoO3·10H3O or 3H2O·P2O5·14WO3·4MoO3·10H2O). The intensity of the blue complex after reduction is proportional to the concentration of phenolic OH groups, which was quantified by UV-VIS spectroscopy. The calibration substance used was vanillin, a substance with a known percentage of OH groups.

[0158] Inventive Example 1 (IE1) Hydrotalcite (Sasol, BET surface area 19 m 2 145.5 g of Pt (Pt / g) was suspended in 800 mL of deionized water, and 4.5 g of Pt was added as hexachloroplatinic acid (H2PtCl6 solution containing 33% Pt, manufactured by Heraeus). The suspension was stirred at 80 °C for 2 days. Subsequently, 22.5 g of sodium formate was dissolved in 30 mL of water at 70 °C and added to the suspension. The suspension was stirred overnight at 70 °C. The suspension was then diluted with 1 L of deionized water and filtered after cooling to room temperature. The residue was washed and finally dried at 120 °C. The precious metal surface area of ​​the catalyst was 7 m 2 / g.

[0159] Inventive Example 2 (IE2) Five grams of platinum (II) nitrate (Pt(NO) solution containing 15.2% Pt, manufactured by Heraeus) was diluted to 30 mL and homogenized. This solution was then homogenized with hydrotalcite (manufactured by Sasol, BET surface area 19 m). 2 The mixture was added to 95 g of ZnO (95% by volume, 95% by volume) and the mixture was homogenized. The mixture was dried overnight at 110 °C in a nitrogen atmosphere under vacuum. It was then heat-treated in an oxygen-containing atmosphere for 14 hours, during which the temperature was increased stepwise up to 250 °C. Finally, the material was treated with forming gas (95% by volume nitrogen, 5% by volume hydrogen) up to 250 °C for 16 hours. The precious metal surface area of ​​the catalyst was 10 m 2 / g.

[0160] Inventive Example 3 (IE3) The preparation was carried out as in IE2. In addition, 1 g of Ni was added as nickel(II) nitrate hexahydrate (Ni(NO3)2*6H2O containing 20% ​​Ni, Merck) to the platinum(II) nitrate solution, which were then diluted together and homogenized. This solution was added to 94 g of hydrotalcite, and the mixture was homogenized. The precious metal surface area of ​​the catalyst was 5 m 2 / g.

[0161] Inventive Example 4 (IE4) The preparation was carried out as in IE2. In addition, 2 g of Ni was added as nickel(II) nitrate hexahydrate (Ni(NO3)2*6H2O containing 20% ​​Ni, Merck) to the platinum(II) nitrate solution, which were then diluted together and homogenized. This solution was added to 93 g of hydrotalcite, and the mixture was homogenized. The precious metal surface area of ​​the catalyst was 11 m 2 / g.

[0162] Depolymerization The standard conditions for depolymerization are described below: 20 g of organosolv lignin (manufactured by Chemical Point, average molecular weight 6,200 Da) was mixed with a catalyst and suspended in 200 mL of solvent (45.9 vol% ethanol in water).

[0163] Lignin was decomposed in an autoclave (PARR, 4871 Process Controller, software: SpecView3) at a stirring speed of 300 rpm. The reaction mixture was heated to the target temperature and maintained at this temperature for the desired time.

[0164] After the mixture was cooled to room temperature, the catalyst was separated, and then the product fractions were separated from each other. To this end, the mixture was adjusted to pH 2 using concentrated hydrochloric acid (HCl 37% by weight), and the lignin tar fraction (containing the oligomeric products) was precipitated. The solid components were then separated by vacuum filtration. The solids were washed three times with dilute hydrochloric acid. The aqueous phase was extracted three times with ethyl acetate, and the organic phases were combined, dried over sodium sulfate, and filtered. The ethyl acetate was removed using a rotary evaporator, and the resulting solid was the lignin-oil fraction (containing the monomeric products). The solid obtained after vacuum filtration was slurried in THF to dissolve the oligomeric products, and the remaining solid components (a coke fraction containing polymeric rearrangement products of lignin and additional solid insoluble products) were again separated by vacuum filtration. The organic phase was evaporated using a rotary evaporator to obtain the oligomeric product fraction.

[0165] The percentage yield of the various product fractions was calculated as follows: Monomer component yield (wt%) = (weight of lignin-oil fraction / weight of lignin used) × 100; Oligomer yield (wt%) = (weight of lignin-tar fraction / weight of lignin used) × 100; Coke ratio (wt%) = (weight of coke fraction / weight of lignin used) × 100.

[0166] Figure 3 shows the composition of a representative product mixture from depolymerizations using four catalysts according to the present invention (IE1-IE4) compared to a non-metal-loaded hydrotalcite (CE1). The lignin to catalyst ratio used was constant (20 wt. % catalyst), and all reactions were carried out at 200 °C for 30 min. Figure 4 also compares exemplary GPC chromatograms used to analyze the average molecular weights of the lignin used and the monomer and oligomer product fractions from the depolymerization using IE3. [Table 1]

[0167] Table 1 summarizes the average molecular weights of the monomeric and oligomeric product fractions. The results show that the use of the catalyst according to the invention allows a significant increase in the conversion of the lignin used. The phenolic OH groups were titrated by the Folin-Ciocalteu method on both the lignin used and the product fractions. Table 1 also includes these results. For all catalyst systems shown here, the concentration of OH groups, which indicates the presence of phenolic building blocks, was comparable to that of the lignin used (3.7 mmol / g), suggesting that these building blocks were retained during the degradation reaction.

[0168] In IE5, the same catalyst as in IE3 was used, except that only 1.2 wt. % of catalyst was used relative to the weight of lignin being reacted. The depolymerization was carried out at 230° C. for 90 minutes. IE5 shows that it is possible to achieve high yields and desired selectivities in the reaction using small amounts of the catalyst according to the invention and under mild reaction conditions.

Claims

1. 1. A method for catalytic decomposition of lignin, comprising: a) providing a reaction mixture A comprising lignin, a catalyst, and a solvent; b) heating the reaction mixture A to obtain a mixture B comprising a product mixture, the catalyst, and the solvent; The catalyst is a basic carrier material; 1 to 10 wt % platinum; 0 to 5 wt. % nickel; Contains the catalyst is present in reaction mixture A in an amount of less than 30 wt.%, based on the total amount of catalyst and lignin; The basic carrier material has the formula: [M ２＋ １－ｗ M ３＋ ｗ (OH) ２ ] ｗ＋ (A ｎ－ ｗ／ｎ )・mH ２ O (In the formula, M ２＋ represents a divalent cation, M ３＋ represents a trivalent cation, and A ｎ－ represents an anion having a charge n, m represents the number of water molecules, and w represents the molar ratio of trivalent cations to the total amount of cations. It is a layered double hydroxide (LDH) represented by The method of claim 1, wherein said reaction mixture A is heated to a reaction temperature of less than 400°C.

2. 2. The method of claim 1, wherein the lignin is selected from the group comprising organosolv lignin, kraft lignin, lignin obtained by alkaline degradation, lignin obtained by sulfuric acid process, lignin obtained by sulfite process, lignin obtained by aqueous extraction, lignin obtained by acid hydrolysis, lignin obtained by enzymatic hydrolysis, lignin obtained by wood saccharification, lignin obtained by microbial treatment, lignin from lignin-containing biorefinery process streams, and mixtures thereof.

3. 3. The method of claim 1 or 2, wherein the lignin has an average molecular weight in the range of 3,000 g / mol to 20,000 g / mol.

4. The basic carrier material is 5 to 150 m ２ / g, 4. The method according to any one of claims 1 to 3, wherein the BET surface area is determined according to ISO 9277:2010 using nitrogen as the adsorbate.

5. The method of any one of claims 1 to 4, wherein the solvent comprises water and an alcohol.

6. 6. The method according to any one of claims 1 to 5, wherein the reaction temperature in method step b) is maintained for less than 240 minutes.

7. 7. The process of any one of claims 1 to 6, wherein the product mixture contains less than 30 wt% of a coke fraction.

8. 8. The method of any one of claims 1 to 7, wherein at least 50 wt% of the lignin used in reaction mixture A is converted into monomeric and oligomeric products.

9. 9. The method of any one of claims 1 to 8, wherein the product mixture comprises at least one monomer product containing a phenolic building block.

10. 10. The method of any one of claims 1 to 9, wherein the product mixture comprises at least one oligomeric product, and the monomer building blocks of the oligomeric product comprise phenolic building blocks.

11. The basic support material is magnesium (Mg ２＋ ), nickel (Ni ２＋ ), iron (Fe ２＋ ), cobalt (Co ２＋ ), copper (Cu ２＋ ), zinc (Zn ２＋ ), calcium (Ca ２＋ ), tin (Sn ２＋ ), lead (Pb ２＋ ) and combinations thereof. ２＋ The method according to any one of claims 1 to 10, comprising:

12. The basic support material is aluminum (Al ３＋ ), iron (Fe ３＋ ), chromium (Cr ３＋ ), manganese (Mn ３＋ ) and combinations thereof. ３＋ The method according to any one of claims 1 to 11, comprising:

13. 1. A method for producing a product mixture comprising a monomeric product and an oligomeric product, comprising:

10. A method of manufacturing wherein the product mixture is obtained by the method of claim 1.

14. A catalyst that can be used in the process of claim 1, a basic carrier material; 1 to 10 wt % platinum; 0 to 5 wt. % nickel; Contains The basic carrier material has the formula: [M ２＋ １－ｗ M ３＋ ｗ (OH) ２ ] ｗ＋ (A ｎ－ ｗ／ｎ )・mH ２ O (In the formula, M ２＋ represents a divalent cation, M ３＋ represents a trivalent cation, and A ｎ－ represents an anion having a charge n, m represents the number of water molecules, and w represents the molar ratio of trivalent cations to the total amount of cations. The catalyst is a layered double hydroxide (LDH) represented by the formula:

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