Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
  • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
  • C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
  • C07D307/38—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
  • C07D307/40—Radicals substituted by oxygen atoms
  • C07D307/46—Doubly bound oxygen atoms, or two oxygen atoms singly bound to the same carbon atom
• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07D—HETEROCYCLIC COMPOUNDS
  • C07D307/00—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom
  • C07D307/02—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings
  • C07D307/34—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members
  • C07D307/38—Heterocyclic compounds containing five-membered rings having one oxygen atom as the only ring hetero atom not condensed with other rings having two or three double bonds between ring members or between ring members and non-ring members with substituted hydrocarbon radicals attached to ring carbon atoms
  • C07D307/40—Radicals substituted by oxygen atoms
  • C07D307/46—Doubly bound oxygen atoms, or two oxygen atoms singly bound to the same carbon atom
  • C07D307/48—Furfural

Definitions

• the present invention relates to a process to produce furfural from pentoses.
• Furfural, OC4H 3 CHO is an important intermediate in the production of chemicals. It can also be used as a solvent.
• Furfural is commonly produced by heating pentoses such as xylose.
• WO2009/030551 relates to the production of stable HMF ethers, and describes the conversion of C5 and C6 sugars to a mixture of furfural and 5-alkoxymethylfurfural to alcohols. Xylose is converted to furfural in the presence of ethanol, but in the absence of water, as water is to be avoided in the production of ethers.
• WO2009/030551 describes that the amount of alcohol is preferably at least equimolar to the amount of hexose, but the amount of alcohol is not defined relative to the amount or the pentose.
• WO2010/130889 relates to the production furfural in an alcohol production unit from lignocellulosic biomass.
• ethanol is removed from the stream, resulting in purified ethanol and a clarified vinasses stream.
• the vinasses stream including xylose, but without the ethanol, which is removed in the preceeding step) is used to produce furfural.
• WO2010/130889 there is no mention of an effect of ethanol on yield, selectivity, or reaction velocity.
• the invention provides a process for the production of furfural comprising subjecting a composition comprising a pentose, an alcohol, an acid catalyst, and balance water, under conditions suitable to produce furfural, wherein the amount of alcohol is between 5 and 95% w/w relative to the total weight of the composition.
• the inventor has surprisingly found that using an alcohol in the conversion of a pentose to furfural may improve the yield of furfural and/or improve the TON and/or improve the selectivity of the reaction and/or improve the reaction velocity.
• WO2009/030551 is silent on a possible effect of ethanol on the yield or selectivity towards furfural, let alone when in the presence of water.
• the alcohol is preferably a lower alcohol.
• Lower alcohols are defined as alcohols having between 1 and 4 C atoms, such as methanol, ethanol, 1 -propanol, 2-propanol, n-butanol, sec-butanol, isobutanol, and tert-butanol.
• a suitable lower alcohol is ethanol.
• the amount of alcohol ranges between 5 and 95% w/w relative to the total weight of the composition.
• the amount of alcohol is between 10 and 95%, 20 and 95%, 30 and 95%, 40 and 90%, 50 and 95%, more preferably between 60 and 90%, even more preferably between 60 and 80%, 70 and 90% w/w relative to the total weight of the composition, even more preferably between 65 and 75& ethanol.
• the ethanol concentration is preferably less than 100%, as xylose may not be soluble at 100% ethanol.
• the amount of the pentose in the composition is not critical, but it typically at least 0.001 mM, at least 0.01 mM, 0.1 mM, more preferably at least 1 mM, more preferably at least 10 mM.
• the upper limit may be 2 M, more preferably 1 M.
• the composition comprises water. In the absence of water the yield and/or TON and/or selectivity may be worse than in the presence of water. However, if the pentose and acid catalyst are dissolved or suspended in water, i.e. without alcohol, the yield and/or TON and/or selectivity may be worse than if the component comprises alcohol.
• the amount of water in the composition may be expressed as "balance water”. This means that the amount of water in the composition is such that it adds up to 100% w/w after adding the acid catalyst, the pentose, the alcohol, and optionally any other components to the composition. This does, however, not necessarily imply that the acid catalyst, the pentose, the alcohol, and optionally any other components, must be added before the water. Components nay be added to the composition in any particular order.
• Suitable pentoses include arabinose, ribose, ribulose, xylose, xylulose, and lyxose.
• a preferred pentose is xylose.
• the composition may also comprise two or more pentoses.
• the composition may further comprise other components such as salts such as NaCI and other chlorides, sulphates etc).
• the composition may also comprise other saccharides such as hexoses (glucose, galactose).
• the concentration of the pentose may range between 0.001 and 5 M, preferably between 0.01 and 2, more preferably between 0.05 and 1 M, between 0.05 and 0.5 M, between 0.05 and 0.2 M.
• the amount of the pentose may be between 1 and 200 g per liter of composition, preferably between 5 and 50 g per liter of composition, or between 0.1 and 20% w/w relative to the total weight of the composition, preferably between 0.5 and 5 % w/w relative to the total weight of the composition.
• the composition may be a solution or a suspension.
• the acid catalyst may be a solid catalyst.
• Suitable solid catalysts include (strong) acid cation exchangers and zeolytes. These are commercially available. Examples of suitable acid cation exchangers include Smopex 101 and DOWEX-50WX8.
• the acid catalyst may be a soluble catalyst.
• Suitable soluble acid catalysts include Bronsted acids, including organic acids, inorganic acids such hydrochloric acid, sulphuric acid, nitric acid, phosphoric acid, boric acid, and hydrofluoric acid, and triflic acids.
• the acid catalyst can also be a Lewis acid.
• Particularly suitable soluble acid catalysts are hydrochloric acid and/or sulphuric acid.
• the amount of acid catalyst may range between 5 and 200 g per liter of composition, preferably between 10 and 100 g per liter of composition, or between 0.5 and 20% w/w relative to the total weight of the composition, preferably between 1 and 10% w/w relative to the total weight of the composition. If the catalyst is soluble, suitable concentrations of the acid catalyst may range between 0.1 and 5 M, preferably between 0.2 and 2 M, more preferably between 0.5 and 1 M.
• the molratio of pentose : acid catalyst may be between 0.01 and 2, preferably between 0.02 and 1 , more preferably between 0.05 and 0.5.
• the composition may be a biomass-hydrolysate, preferably a hemicellulose-hydrolysate.
• Suitable biomass include hemicellulosic and ligno-cellulosic biomass; cellulose and starch; wood; lumber processing side products such as saw dust, wood chippings and wood shavings; grass; cereal; starch; algae; tree bark; hay; straw; leaves; paper pulp, and dung, particularly herbivore dung.
• Paper pulp, or simply pulp is a lignocellulosic fibrous material obtained by prepared by chemically or mechanically separating cellulose from wood, fibre crops or waste paper. Pulp is rich in cellulose and other carbohydrates.
• Lignocellulosic biomass typically has a fibrous nature and comprises a bran fraction that contains the majority of lignocellulosic (bran) fibers.
• Hemicellulosic biomass is typically rich in pentoses; it usually also comprises hexoses and lignin.
• the biomass-hydrolysate may be obtained by hydrolysis of the biomass, such as acid hydrolysis.
• Suitable acids for the hydrolysis biomass includes sulphuric acid, preferably diluted sulphuric acid, for example at a concentration between 1 .5 - 3%.
• Hydrolysis of a biomass may result in the formation of pentoses and hexoses. The ratio of formation of pentoses and hexoses may depend on the stringency of the hydrolysis reaction in the hydrolysis of the biomass, such as pH, reaction time, and temperature.
• the temperature of the hydrolysis of the biomass may depend on the source of biomass, and may range between 100 - 250°C, preferably between 1 10 - 250°C, 120 - 250°C, 150-250°C, more preferably between 170-240°C, more preferably between 190-230°C, even more preferably between 200 and 220°C.
• the temperature is such that the pentoses remain intact and do not e.g. degrade to form tar of char.
• Said process may comprise one, two, or more stages.
• the pressure of the hydrolysis of the biomass may also depend on the source of biomass as well as on the temperature, and may be anywhere between 1 and 50 bar, preferably between 5 and 40 bar, even more preferably between 10 and 30 bar.
• Suitable reactors include plugflow reactors, backmix reactors, and CSTR reactors and combinations thereof. Different reactors for different stages may be used.
• the skilled person will understand that the reaction time in the hydrolysis of the biomass depends on the reaction temperature, the pressure, as well as the source of biomass and the concentration of the acid. At higher reaction temperatures the reaction time may be shorter in order to obtain the biomass-hydrolysate, whereas at lower reaction temperatures the reaction time may be longer in order to obtain the biomass- hydrolysate. Likewise, at lower pressure, the reaction time may be longer whereas at higher pressure the reaction time may be shorter. The skilled person may therefore, without undue burden, establish suitable conditions with respect to temperature, reaction time, and pressure in order to obtain the biomass-hydrolysate.
• the reaction time in the hydrolysis of the biomass may vary between one second and one day, preferably between 10 seconds and one hour.
• a biomass-hydrolysate in the process of the invention has the advantage that it is renewable.
• the furfural produced can also be considered to be renewable.
• the process is also beneficial in view of energy conservation.
• the conditions of the process are such that they are suitable to produce furfural.
• the temperature may range between 50 and 250°C, preferably between 100 and 200°C, more preferably between 125 and 175°C.
• the reaction time may vary between 30 seconds and 24 hours. Preferably the reaction time ranges between 1 minute and 3 hours, more preferably between 5 minutes and 2 hours.
• the skilled person will understand that the reaction time in the process depends on the reaction temperature, the pressure, as well as the pentose and the type and amount of the acid catalyst.
• the reaction time may be longer for solid acid catalysts than for soluble acid catalysts. At higher temperatures the reaction time may be shorter in order to produce the furfural, whereas at lower reaction temperatures the reaction time may be longer in order to produce the furfural.
• reaction time may be longer whereas at lower amounts of acid catalyst the reaction time may be shorter.
• the skilled person may therefore, without undue burden, establish suitable conditions with respect to temperature, reaction time, and type and amount of acid catalyst in order to produce the furfural.
• the components may be added to the composition in any order.
• the composition may be stirred.
• the composition may be heated under stirring.
• the process may be a continuous process.
• the invention further provides the use of an alcohol to improve the TON and/or selectivity and/or yield and/or the reaction velocity in a process to produce furfural from a pentose.
• Experiments 1 -5 were done with using the same microwave setting, i.e. in one series without intermittent re-setting of the parameters: for every time point, a microwave vial (10 ml) was filled with 2 ml of a pentose (always xylose, 0.1 M), ethanol (if present), and an acid. Each vial was closed and placed in a microwave device and heated under stirring (800 rpm) with a 10 mm Teflon stirring bar to 150°C for a certain time. The vial was cooled to 40°C by air inside the microwave.
• the liquid content was then filtered using a PTFE syringe filter (0.45 ⁇ ) and diluted 6-7 times with distilled water prior to the analysis by HPLC (organic acid column, Aminex HPX-87H). Settings in Table 1 .
• Vials were withdrawn at certain times after the start of the reaction. After withdrawal from the microwave, the furfural yield of every sample was determined (in mol% relative to the pentose). The furfural yield was found to vary over the course of the reaction time; first the yield increases then decreases, possibly due to degradation of furfural, so that at a certain time point a maximum yield can be determined. Such maximum yield is shown in Table 1 for Examples 2, 3, and 5.
• Examples 6-14 were also done in one series, without intermittent re-setting of the parameters, however this was a separate series as compared to Examples 1 -5.
• the pentose was always xylose, 0.1 M.
• the acid was always HCI, 1 M.
• the heating was always 15 min at 150°C.
• Results are shown in Table 4. Shown is the furfural yield as function of the reaction time. The maximum yield can be easily determined. For Example 14, the maximum yield is shown only (59 mol%). Table 3.

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• Furan Compounds (AREA)

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Citations (5)

• 2013
  • 2013-07-12 WO PCT/EP2013/064783 patent/WO2014009522A1/fr not_active Ceased

Patent Citations (5)

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