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Process for organosolv pulping and use of a gamma lactone in a solvent for organosolv pulpingRelated Patent Categories: Paper Making And Fiber Liberation, Processes Of Chemical Liberation, Recovery Or Purification Of Natural Cellulose Or Fibrous Material, Treatment With Particular Chemical, OrganicProcess for organosolv pulping and use of a gamma lactone in a solvent for organosolv pulping description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070034345, Process for organosolv pulping and use of a gamma lactone in a solvent for organosolv pulping. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority from European Patent Application No. 05105245.4, filed Jun. 15, 2005, which is incorporated herein by reference. FIELD OF THE INVENTION [0002] The present invention provides a process for organosolv pulping and the use of a gamma lactone in a solvent for organosolv pulping. BACKGROUND OF THE INVENTION [0003] The most widely used pulp manufacturing process is the Kraft process. An important drawback of the Kraft pulping process is, however, that a large mineral waste stream comprising harmful components is formed. In order to avoid the formation of mineral waste material, organosolv pulping has been proposed and studied as an alternative for Kraft pulping. In organosolv pulping, lignocellulosic material is heated in a solvent comprising organic compounds and optionally water, in order to dissolve the greater part of the hemicellulose and lignin and to obtain a high-quality, high-molecular weight cellulose that is suitable for paper production. The solvent is separated from the dissolved hemicellulose and lignin by simple distillation for recycling. [0004] Well-known solvents for organosolv pulping comprise organic compounds such as lower aliphatic alcohols, for example methanol or ethanol, lower carboxylic acids, for example formic acid or acetic acid, acetone, polyhydric alcohols, for example ethylene glycol or glycerol, or mixtures thereof. Often water is part of the solvent, typically in an amount up to 50 wt %. A small amount of strong mineral acid, typically in the range of a few tenths to a few percent, may be added as catalyst to the solvent. Oxidants such as hydrogen peroxide or peroxy acids may be added to the solvent to improve bleaching. [0005] Organosolv pulping is typically carried out at a temperature in the range of from 80 to 180.degree. C. The operating pressure mainly depends on the volatility of the solvent. The pressure should be such that the solvent is still in the liquid phase. Typically, organolsolv pulping is performed just below the boiling temperature of the liquor. A drawback of the use of relatively volatile solvents is therefore that relatively high operating pressures are needed. [0006] An extensive overview of prior art organosolv processes is given in E. Muurinen, "Organosolv Pulping--A review and distillation study related to peroxyacid pulping", University of Oulu, Finland, 2000, ISBN 951-42-5661-1. SUMMARY OF THE INVENTION [0007] It has now been found that compounds having a gamma lactone group can very suitably be used as solvent or part of the solvent for organosolv pulping. [0008] Accordingly, the present invention provides a process for organosolv pulping, wherein solid lignocellulosic feed material is heated at a temperature in the range of from 50 to 210.degree. C. in a solvent to obtain a solid cellulosic fraction comprising at least 50 wt % of the cellulose present in the feed material and a liquid fraction, wherein the solvent comprises at least 10 wt % of a compound according to general molecular formula wherein R.sub.1 to R.sub.6 each represent, independently, a hydrogen atom or an organic group connected with a carbon atom to the lactone group. [0009] In a further aspect, the invention provides the use of a compound according to general molecular formula (1) in a solvent for organosolv pulping. [0010] An important advantage of the use of a compound having a gamma lactone group in a solvent for organosolv pulping is that it has a relatively high boiling point and that the organosolv pulping can thus be carried out at a relatively low pressure. [0011] A further advantage of the process and the use according to the invention is that the compound according to general molecular formula (1) is both polar and relatively inert. As a consequence, it is an effective organosolv solvent that does hardly form reaction products with the lignocellulosic feed material or with components formed during the organosolv process. DETAILED DESCRIPTION OF THE INVENTION [0012] The process according to the invention is a process for organosolv pulping wherein a solid lignocellulosic feed material is heated in a solvent comprising at least 10 wt % of a compound having a gamma lactone group to obtain a solid cellulosic fraction and a liquid fraction. The liquid fraction contains the solvent and dissolved hemicellulose and lignin degradation products. The aim of organosolv pulping is to obtain a high-quality solid cellulose fraction or cellulose pulp that is suitable for paper production. Therefore, the exact process conditions in terms of temperature, pressure, heating time and the solvent used are chosen such that the greater part of the cellulose remains intact, i.e. is not depolymerised and dissolved in the liquid fraction. In the process according to the invention at least 50 wt % of the cellulose present in the feed material is recovered in the solid cellulosic fraction, preferably at least 60 wt %, more preferably at least 80 wt %. The cellulose content of the feed material and of the solid cellulose fraction obtained may for example be determined by hydrolysing a sample of the material followed by identification and quantification of sugars by means of gas chromatography according to TAPPI method T 249 cm-00. After correction of the glucose value by subtracting the glucose portion derived from the glucomannan present in the sample, the cellulose content is calculated from the corrected glucose value. [0013] Preferably, the solid cellulosic fraction obtained has an average degree of polymerisation of at least 300. Reference herein to the average degree of polymerisation of the cellulose is to the weight-average degree of polymerisation. The degree of polymerisation may be determined by measuring the viscosity of a solution of the cellulosic fraction of known concentration, for example according to TAPPI method T 230 om-04. [0014] Preferably, at least 50 wt % of the lignin in the lignocellulosic feed material is removed from the feed material during the organosolv process according to the invention, more preferably at least 80 wt %. [0015] The lignocellulosic feed material is heated in the solvent at a temperature that is typical for organosolv processes, i.e. in the range of from 50 to 210.degree. C., preferably of from 100 to 200.degree. C., more preferably of from 80 to 180.degree. C. [0016] The solvent used in the process according to the invention comprises at least 10 wt % of a compound having a gamma lactone group, i.e. a compound according to general molecular formula (1). Preferably, the solvent comprises at least 20 wt % of such compound, more preferably at least 50 wt %, even more preferably at least 80 wt %, based on the total weight of the solvent. [0017] Reference herein to the solvent is to the total liquid phase in which the solid feed material is heated. Apart from one or more compounds according to general molecular formula (1), the solvent may comprise further organic compounds that are known solvents for organosolv pulping. Examples of such known compounds are lower aliphatic alcohols such as methanol or ethanol, polyhydric alcohols, in particular diols with the hydroxyl groups on adjacent carbon atoms such as ethylene glycol, glycerol, 1,2-propanediol or 2,3-butanediol, lower carboxylic acids such as formic acid or acetic acid, and acetone. The solvent may also comprise water, preferably in an amount up to 50 wt %, more preferably up to 20 wt %. [0018] The solvent may comprise an acid catalyst. Any acid known to be suitable as catalyst in organosolv pulping may be used. In particular strong mineral acids such as phosphoric acid, sulphuric acid, hydrochloric acid and nitric acid, are known to be very effective catalysts for organosolv pulping. The catalyst preferably is a strong mineral or organic acid with a pKa below 2.5. Preferred strong mineral acids are phosphoric acid and sulphuric acid, more preferably phosphoric acid. Preferred strong organic acids are oxalic acid, 2-oxopropanoic acid, maleic acid, and 2,4,6-trihydroxibenzoic acid. Combinations of acids may also be used. [0019] It is preferred to keep the concentration of mineral compounds in the solvent as low as possible in order to avoid mineral waste streams. The acid catalyst, in particular in case of a mineral catalyst, is therefore preferably present in a concentration of below 5 wt % of the solvent, more preferably in a concentration in the range of from 0.01 to 3.0 wt %, even more preferably of from 0.05 to 1.0 wt %. For a heating temperature in the range of from 100 to 210.degree. C., it is preferred to use a solvent that is free of mineral acid. Therefore, in a preferred embodiment of the process according to the invention, the feed material is heated at a temperature in the range of from 100 to 210.degree. C., more preferably of from 120 to 180.degree. C., in a solvent that is free of mineral acid. For lower heating temperatures, i.e. below 100.degree. C., the presence of an acid catalyst in the solvent is preferred. Continue reading about Process for organosolv pulping and use of a gamma lactone in a solvent for organosolv pulping... Full patent description for Process for organosolv pulping and use of a gamma lactone in a solvent for organosolv pulping Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Process for organosolv pulping and use of a gamma lactone in a solvent for organosolv pulping patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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