DE102007058394A1 - Process for the production of fuels from biomass - Google Patents

Abstract

The invention relates to a process for the production of fuels from biomass in a heterogeneously catalyzed reaction using ionic liquids.

Description

The The invention relates to a process for the production of fuels from biomass in a heterogeneously catalyzed reaction using of ionic liquids.

continuous Rising oil prices will lead to Fuels from natural sources, in particular polysaccharides comprehensive sources, such as wood for energy supply, become increasingly important. Hydrotreating and catalytic Cracking of raw materials, such as cellulose, starch and sugar or even vegetable oils, offer promising Perspectives for the future production of such Biofuels.

cellulose is due to the high availability and high carbon content (40-60 wt .-%) currently the most significant renewable resource for the textile, paper and nonwovens industry. From the same It has a considerable potential as a starting material for the production of fuels.

A Possibility of producing fuels includes the fermentative conversion of z. B. cellulose to ethanol of z. B. can be used directly in suitable internal combustion engines. Generally, products from such manufacturing processes are under the Term bioethanol known.

Another possibility is disclosed by Bridgewater et al. [ AV Bridgwater, Applied Catalysis A: General 116 (1994) ]. A process is disclosed which comprises the catalytic conversion of solid starting materials (e.g., cellulose) to intermediates which can be used after refining steps as fuels for use in auto-ignition internal combustion engines. Catalytic conversion to produce fuels herein involves catalytic cracking to reduce the degree of polymerization of the reactant in the absence of air using a heterogeneous catalyst. The catalytic cracking disclosed may be carried out under normal pressure and at temperatures of 250 ° C to 400 ° C. The process results in a gaseous, a solid and a liquid product. The liquid product comprises a hydrophilic and a hydrophobic phase and forms the intermediate which can be used as fuel after working up steps. In order to be able to contact the disclosed heterogeneous catalyst with the starting material, the disclosed method comprises suspending the starting material in a liquid comprising hydrocarbons (for example a heat transfer oil) which is unable to dissolve the starting material. According to the disclosure, the liquid comprising hydrocarbons at the same time serves as a hydrogen donor for the likewise disclosed reduction of the starting material.

The disclosed method is disadvantageous because the starting material in the Hydrocarbons containing liquid not dissolved can be, so that an intense contact between heterogeneous Catalyst can not be achieved. It is assumed, that catalytic cracking in the disclosed method preceded by at least partial thermal cracking, its products then further catalytically reduced in their degree of polymerization become. A consequence of this is a low turnover and the uneconomical Use of energy. Basically unfavorable is the Fact that the starting material (especially cellulose) for suspending in a liquid first must be crushed. If crushing is not planned, this prevents the technical feasibility of the disclosed method.

In WO 2003/029329 discloses a method according to which the dissolution of cellulose in a molten ionic liquid, optionally with the aid of microwave radiation and heating, up to mass fractions of 35 wt .-% is possible. Apparently, the ionic liquid must be largely free of water, so that the process is feasible. The restriction makes the process unsuitable for the production of fuels from biomass, since in particular the important starting material wood comprises a significant residual water content. Extensive drying of the starting materials, which would require the disclosed process, makes such processes economically unfavorable. Furthermore, thereby the possibility of a reaction in the sense of a catalytic cracking and optionally a reduction by a hydrogen donor to produce a fuel from z. B. prevents dried wood, because in the course of the reactions water would occur, which makes the inventive method impracticable.

In WO 2007/101811 discloses a process in which polysaccharides (eg cellulose) are dissolved in at least one ionic liquid and subsequently treated with at least one acid, thereby reducing the polysaccharides in their degree of polymerization. The acid may comprise an inorganic, an organic or a mixture thereof. It is therefore a homogeneous, acid-catalyzed hydrolysis. The disclosed process is not subject to the restriction that no water may be present in the ionic liquid, as according to the disclosure the addition of water is permissible. There may be a proportion of up to 50% by weight of the polysaccharide dissolved in the ionic liquid. The dissolved cellulose and / or its in The disclosed process is disadvantageous in that it is a homogeneously catalyzed process Such processes have disadvantages well known to those skilled in the art, for example, such processes are economically disadvantageous because of ease of separation Catalyst (the acid) and solvent (the ionic liquid) is not possible, where thermal separation processes with high energy input are necessary.

In WO 2007/101813 discloses a process in which polysaccharides (eg cellulose) are dissolved in at least one ionic liquid and subsequently treated with at least one nucleophile, thereby reducing the polysaccharides in their degree of polymerization. The process is largely identical to that used in WO 2007/101811 is disclosed. A distinguishing feature is the use of a nucleophile to reduce the degree of polymerization of the cellulose (the degradation). It is also disclosed that the nucleophile is homogeneously present in the same phase of the ionic liquid or is even already supplied in dissolved form to the process. It is therefore again a homogeneously catalyzed process with the already explained disadvantages.

task So it's a procedure to provide that does not have the respective disadvantages of the prior art and advantageously a production of fuels Starting materials, such as. B. cellulose allows.

Especially It is therefore an object to provide a method the degradation of starting materials such. As cellulose in ionic liquids without the disadvantages of the homogeneous used in the prior art Catalysis includes.

• a) Lösen der Ausgangsstoffe in mindestens einer ionischen Flüssigkeit,
• b) Umsatz des gelösten Ausgangsstoffes mit mindestens einer Wasserstoffquelle in Anwesenheit mindestens eines heterogenen Katalysators zu einem Reaktionsprodukt,
• c) Abtrennen des aus Schritt b) erhaltenen Reaktionsproduktes,

umfasst, gelöst werden.Surprisingly, the object can be achieved by a process for producing fuels or their precursors from starting materials, characterized in that it comprises at least the steps:

• a) dissolving the starting materials in at least one ionic liquid,
• b) conversion of the dissolved starting material with at least one hydrogen source in the presence of at least one heterogeneous catalyst into a reaction product,
• c) separating the reaction product obtained from step b),

includes, be solved.

The Inventive materials can all substances comprising polysaccharides. Preference is given to substances from natural sources containing a high proportion of polysaccharides include, for example, wood and plant remains. Especially preferred are polysaccharides themselves, such as cellulose, hemicellulose, Starch, sugar or lignin. Very particular preference is given to cellulose, Hemicellulose and lignin.

As ionic liquids according to the invention, all in WO 2007/101811 and WO 2007/101813 disclosed ionic liquids of general formula (I) [A] + / n [Y] ^n- (1) where n is 1, 2, 3 or 4;
[A] ^{+ represents} a quaternary ammonium cation, an oxonium cation, a sulfonium cation or a phosphonium cation, and;
[Y] ^{n- represents} a mono-, di-, tri- or tetravalent anion,
or the general formula (II) [A ¹ ] ⁺ [A ² ] ⁺ [Y] ^n- (IIa), where n = 2; [A ¹ ] ⁺ [A ² ] ⁺ [A ³ ] ⁺ [Y] ^{n -} (IIb), where n = 3; or [A ¹ ] ⁺ [A ² ] ⁺ [A ³ ] ⁺ [A ⁴ ] ⁺ [Y] ^{n -} (IIc) where n = 4 and wherein [A ¹ ] ⁺ , [A ² ] ⁺ , [A ³ ] ⁺ and [A ⁴ ] ^{+ are} independently selected from the groups mentioned for [A] ⁺ ; and [Y] ^{n- has} the meaning just mentioned.

Preferred are ionic liquids, characterized in that [A] ⁺ [A ¹ ] ⁺ , [A ² ] ⁺ , [A ³ ] ⁺ or [A ⁴ ] ^{+ is} ammonium. Also preferred are ionic liquids, characterized in that [Y] ^{n- is} an anion comprising at least one halogen.

Particular preference is given to ionic liquids, characterized in that [A] ⁺ [A ¹ ] ⁺ , [A ² ] ⁺ , [A ³ ] ⁺ or [A ⁴ ] ^{+ is} ammonium and [Y] ^{n- is} an anion which comprises at least one halogen.

It can also mixtures of several ionic liquids be used.

The preferred and particularly preferred ionic liquids are particularly advantageous because they provide a quick release allow the starting materials and a high dissolving power possess the starting materials. Furthermore, you own at the later Step b) of the inventive method advantageous physical properties, such as comparatively low viscosity and high diffusion coefficients for the hydrogen sources according to the invention.

The hydrogen sources according to the invention However, hydrogen may also be other substances which, under the conditions of step b) of the process according to the invention, have a reduction potential due to the release of hydrogen onto the starting material.

preferred Hydrogen sources are hydrogen and other substances called hydrocarbons are. Preferred other substances that are hydrocarbons are Vacuum oils, lubricating oils, gear oils, naphthalene, Naphthen, tetralin, tetracontane, lower alcohols, ketones and aldehydes.

hydrogen is particularly advantageous because it has a very high reduction potential has opposite to the starting materials.

Especially preferred other substances which are hydrocarbons are low Alcohols, ketones and aldehydes, containing not more than five carbon atoms, such as methanol, ethanol, acetone, acetaldehyde, butenol Etc.

These Hydrocarbons are particularly advantageous because they have a high Have reduction potential compared to the starting materials.

Also particularly preferred other substances which are hydrocarbons, are vacuum oils and lubricating oils.

These Hydrocarbons are particularly advantageous because they are waste products are available in large quantities and acceptable Have reduction potential compared to the starting materials.

Of the heterogeneous catalyst, which in the inventive Usually involves an acidic, heterogeneous catalyst.

preferred acidic, heterogeneous catalysts include silicates, aluminosilicates, acidic ion exchangers, zeolites, Lewis acids and / or Mixtures of these.

Especially preferred are zeolites.

All particularly preferred are the zeolites Y, X, MOR, BEW, ZSM-5, MCM-41 and / or mixtures of these.

Also Preferred acidic heterogeneous catalysts comprise at least one Metal component selected from the list Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os, Cu, Zn, Mo, W.

The Use of acidic, heterogeneous catalysts with metal component is particularly advantageous because in this way the hydrogen transfer greatly facilitated by the hydrogen source on the starting material and thus the necessary energy (eg in the form of a necessary energy) Operating temperature) is reduced.

The Reaction product referred to in the context of the present Invention hydrocarbon compounds, as in similar Form are found in diesel fuels.

The Solving according to step a) of the invention Process is usually carried out at opposite Room temperature (25 ° C) elevated temperature. Prefers is dissolving at a temperature of 30 ° C to 450 ° C. Particularly preferred is the release in a Temperature from 200 ° C to 400 ° C.

The Dissolving at elevated temperature is particularly advantageous because it increases the speed of release while preheating the reaction in step b) of the method according to the invention can be carried out.

Regarding the pressure at which the release according to step a) carried out the process of the invention will, there are no special requirements, so it out purely economic reasons advantageous and preferred is, the release according to step a) at ambient pressure (1013 hPa).

The Solving according to step a) of the invention Process is preferably carried out with stirring.

The Solving according to step a) of the invention Process can be carried out batchwise or continuously.

Prefers the dissolution according to step a) of the invention Procedure carried out continuously.

Especially the release according to step is preferred a) the process of the invention in a continuous operated stirred tank performed.

In an alternative embodiment of the invention Step a) a screw reactor is used in which the starting material is intensively kneaded with the ionic liquid.

The Reaction according to step b) of the invention Process is usually wise at room temperature (25 ° C) elevated temperature. The temperature is preferably when carried out the reaction according to step b) of 200 ° C. up to 450 ° C. Particularly preferably from 280 ° C to 350 ° C.

The Reaction according to step b) of the invention Process is usually at a partial pressure of oxygen equal to that in the ambient air (~ 20% by volume).

Prefers the reaction according to step b) of the invention Process at a reduced relative to ambient air Proportion of oxygen (<20 Vol .-%) performed. Particularly preferred is the atmospheric oxygen by hydrogen or an inert gas, such as. As nitrogen or a Inert gas replaced, so that the oxygen partial pressure fraction ~ 0 vol .-% is.

The Reduction of the oxygen content in the reaction is advantageous because this promotes the reduction of the starting material is because oxidative back reactions are prevented.

simultaneously can the total pressure at which the step b) of the invention Procedure is carried out between 1 bar and 100 bar be. Preference is given to a pressure of 1 bar to 50 bar.

Of the at least one heterogeneous catalyst, in the presence of which Reaction according to step b) of the invention The procedure is usually done in a ratio of 1: 1000 to 1:10, based on the Mass of the dissolved starting material fed in step b), used. Preferred is a ratio of 1: 100 to 1:10.

Of the heterogeneous catalyst can be immobilized in the device, in the reaction is carried out, are present, for. In Form of a fixed bed or a monolith, or may take the form of a Powder or a bed of particles of heterogeneous Catalyst can be added to the solution.

Prefers if the reaction is carried out in a fixed bed reactor, the one immobilized bed of heterogeneous catalyst particles includes.

A such procedure is particularly advantageous, because thereby separating heterogeneous catalyst from reaction solution does not have to be performed.

The Reaction according to step b) of the invention Process can also be carried out in a screw reactor in which the catalyst with the starting material in the ionic liquid is kneaded intensively.

The Reaction according to step b) of the invention Process can be carried out continuously or discontinuously become. The reaction is preferably according to step b) carried out continuously.

Especially Step b) of the invention is preferred Process in a continuous flow through fixed bed reactor carried out an immobilized bed of heterogeneous catalyst particles.

methods immobilized beds of heterogeneous catalyst particles can be obtained in the form of a fixed bed in the sense of the reaction technique the skilled person without the need for further inventive step well known.

The Separating according to step c) of the invention Process can be carried out by means of a distillation / rectification or by other methods generally known to those skilled in the art for the separation of Liquids, such. B. membrane method, extraction method etc., or by displacement of the reaction product with a suitable anti-solvent.

One suitable anti-solvent in the latter case is for Example water.

Prefers is a separation according to step c) of the invention Process by distillation / rectification. Especially preferred is a distillation / rectification with further use of a stripping gas or distillation / rectification at ambient pressure (1013 hPa) reduced pressure.

The Separation by means of stripping gas or under reduced pressure is special advantageous because the ionic liquids used and the under Circumstances not yet reacted starting material very low Have vapor pressures and thus a selective separation of the reaction product, which has a significantly higher vapor pressure owns, is possible.

The Separation may as well as the steps a) and b) of the invention Method be operated continuously or discontinuously. Preference is given to continuous operation.

In a preferred development of the invention Process is the ionic liquid optionally reused with the suspended catalyst. This evolution is beneficial because it leads to economic operation of the Process contributes.

By the inventive method and its preferred Embodiments and developments is an advantageous one Methods have been found that to higher yields Hydrocarbon compounds in the sense of the invention Reaction product leads.

These Hydrocarbon compounds are preferably used as fuels in self-igniting internal combustion engines or at least as precursors for such fuels.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• WO 2003/029329 [0007]
• - WO 2007/101811 [0008, 0009, 0014]
• - WO 2007/101813 [0009, 0014]

Cited non-patent literature

• AV Bridgwater, Applied Catalysis A: General 116 (1994) [0005]

Claims (15)

Process for the production of fuels or their precursors from starting materials, characterized in that it comprises at least the steps: a. Dissolving the starting materials in at least one ionic liquid, b. Turnover of the dissolved starting material with at least one hydrogen source in the presence of at least one heterogeneous catalyst to a reaction product, c. Separating the reaction product obtained from step b). A method according to claim 1, characterized in that an ionic liquid of the general formula [A] + / n [Y] ^n- (I) where n is 1, 2, 3 or 4; [A] ^{+ represents} a quaternary ammonium cation, an oxonium cation, a sulfonium cation or a phosphonium cation, and; [Y] ^{n- is} a mono-, di-, tri- or tetravalent anion comprising at least one halogen; or the general formula (II) [A ¹ ] ⁺ [A ² ] ⁺ [Y] ^n- (IIa), where n = 2; [A ¹ ] ⁺ [A ² ] ⁺ [A ³ ] ⁺ [Y] ^{n -} (IIb), where n = 3; or [A ¹ ] ⁺ [A ² ] ⁺ [A ³ ] ⁺ [A ⁴ ] ⁺ [Y] ^{n -} (IIc) where n = 4 and wherein [A ¹ ] ⁺ , [A ² ] ⁺ , [A ³ ] ⁺ and [A ⁴ ] ^{+ are} independently selected from the groups mentioned for [A] ⁺ and [Y] ^{n- has} the meaning just mentioned becomes. A method according to claim 1, characterized in that an ionic liquid of the general formula [A] + / n [Y] ^n- (I) where n is 1, 2, 3 or 4; [Y] ^{n- is} a mono-, di-, tri- or tetravalent anion, or the general formula (II) [A ¹ ] ⁺ [A ² ] ⁺ [Y] ^n- (IIa), where n = 2; [A ¹ ] ⁺ [A ² ] ⁺ [A ³ ] ⁺ [Y] ^{n -} (IIb), where n = 3; or [A ¹ ] ⁺ [A ² ] ⁺ [A ³ ] ⁺ [A ⁴ ] ⁺ [Y] ^{n -} (IIc) where n = 4 and wherein [A] ⁺ [A ¹ ] ⁺ , [A ² ] ⁺ , [A ³ ] ⁺ or [A ⁴ ] ^{+ is} ammonium and [Y] ^{n- has} the meaning just mentioned is used. Method according to one of the preceding claims, characterized characterized in that the at least one hydrogen source, hydrogen and other substances that are hydrocarbons. Method according to one of the preceding claims, characterized characterized in that the heterogeneous catalyst is an acidic, heterogeneous Catalyst comprises. Method according to claim 5, characterized in that the acid heterogeneous catalyst is a zeolite. Method according to claim 5 or 6, characterized in that the acidic, heterogeneous catalyst comprises at least one metal component selected from the list Ni, Pd, Pt, Co, Rh, Ir, Fe, Ru, Os, Cu, Zn, Mo, W includes. Method according to one of the preceding claims, characterized characterized in that step a) of the process with stirring is carried out. Method according to one of the preceding claims, characterized characterized in that step b) of the method opposite Room temperature (25 ° C) elevated temperature, preferably at temperatures from 200 ° C to 450 ° C, especially preferably from 280 ° C to 350 ° C, performed becomes. Method according to one of the preceding claims, characterized in that in step b) of the method of at least a heterogeneous catalyst in a ratio of 1: 1000 to 1:10, based on the mass of the fed in step b) dissolved starting material, preferably in a ratio from 1: 100 to 1:10 is used. Method according to one of the preceding claims, characterized in that the separation according to step c) by means of a distillation / rectification, a membrane process, an extraction process or by displacement of the Reaction product carried out with a suitable anti-solvent becomes. Method according to claim 11, characterized in that that the separation according to step c) by means of a Distillation / rectification is performed. Method according to claim 12, characterized in that that the distillation / rectification with further use of a Stripping gas or that distillation / rectification at opposite Ambient pressure (1013 hPa) reduced pressure performed becomes. Method according to one of the preceding claims characterized in that the ionic liquid is optionally reused together with the suspended catalyst. Use of the reaction product from the process according to one of claims 1 to 14 as a fuel in self-igniting Internal combustion engines or as precursors for such Fuels.