Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C3/00—Pulping cellulose-containing materials
  • D21C3/20—Pulping cellulose-containing materials with organic solvents or in solvent environment

Definitions

• the invention relates to a method for the digestion of lignocellulose material which comprises cooking the fragmented lignocellulose material with an aqueous methyl or ethyl alcohol containing dissolved therein an alkaline earth metal salt, namely a chloride or nitrate of magnesium, calcium or barium or magnesium sulfate or a soluble mixture thereof in a concentration of less than 1.0 molar and, optionally, an acid reacting substance in a concentration of Less than 0.008 normal for not more than two hours at a temperature above 130°C, the amount of cooking liquor being at least 4 parts by weight per part by weight of the lignocellulose material, recovering the fibres liberated thereby from the cooking liquor, and separating the remaining spent cooking liquor into solvent, lignin and sugars.
• an alkaline earth metal salt namely a chloride or nitrate of magnesium, calcium or barium or magnesium sulfate or a soluble mixture thereof in a concentration of less than 1.0 molar and, optional
• the problem to be solved by the invention is to improve deligniflcation specificity for all lignocellulose species and thereby to increase the yield of cellulose pulp, to reduce viscosity losses in cellulose due to carbohydrate degradation, improve the quality and stability of dissolved lignin in solution and increase the uniformity of digestion at reduced cooking times of air-dry softwood chips and increase temperature stability of lignocellulose materials during high temperature digestion.
• Great Britain patent No. 357 821 (Kleinert) describes a process for the decomposition of vegetable fibrous matter for the purpose of obtaining the cellulose and the incrusting materials which uses as the decomposing agent mixtures of alcohol and water with a water content of 20 to 75 percent by weight and states on page 1, lines 74 to 77, that with 96 percent alcohol a dark brown residue amounting to 92 percent of the raw material is obtained.
• angewandte Chemie 44 (1931), pages 788 to 791, states on page 789 that absolute alcohol solves only little lignin and nearly no carbohydrates, and on same page, lines 4 to 2 from the bottom with reference to figure 1 that maximum digestion results with an alcohol content of 45 to 50 percent, and United States patent No. 3 585 104 (Kleinert) states in lines 42 to 44 of c.2 that methanol or ethanol in the medium concentration range between about 20 per cent and 75 percent by weight alcohol content have a stronger delignifying effect upon fibrous plant materials than the water-free alcohols.
• methanol is the preferred alcohol, bute where methanol is not available in sufficient amount ethanol can be used as well.
• the preferred alcohol content of the cooking liquor is 80 to 98 pe rc e n t by volume, but the higher percentages within this range are relatively difficult to achieve because of the moisture contained in the lignocellulose starting material.
• the preferred ratio of lignocellulose material to cooking liquor is 1:6 to 1:20.
• Wood chips in both air-dry and green conditions were conditioned to a uniform moisture content before the pulping trials.
• Batch quantities of commercial size chips were charged into the digester with ten times their weight of cooking liquor containing predetermined quantities of the salt catalysts.
• the volume ratio of methanol to water ranged between 90:10.
• the sealed stationary vessel was quickly brought to cooking temperature in a thermostatically controlled glycerine bath and the temperature held constant for the cooking interval required.
• the reported cooks are those which at the end of the stated period produced a free pulp when slurried in a disintegrator at slow stirred speed.
• the process also appeals to be quite tolerant to extended cooking times wherein the parameter most affected is residual lignin content.
• the pulping liquor when subjected to vacuum distillation at low temperature yields a flocculated lignin precipitate.
• a sugar solution having a solids concentration up to 25 percent is obtained.
• Charcoal filtration removes most of the yellow color due to the water soluble lignin depolymerisation products.
• the molecular weight distribution of the lignin shows one major and 2 to 3 minor peaks with the maximum being under 3800. Purification of the crude lingin is most effectively done by redissolution in acetone and spray drying in vacuum at low temperature to avoid melting and resinification. A dried solid filter cake is easily broken up into a free flowing tan-colored powder.

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Citations (4)

• 1980
  • 1980-07-25 CA CA000359443A patent/CA1150012A/en not_active Expired
• 1981
  • 1981-07-24 DE DE8181902305T patent/DE3177195D1/de not_active Expired - Fee Related
  • 1981-07-24 BR BR8108706A patent/BR8108706A/pt unknown
  • 1981-07-24 EP EP19810902305 patent/EP0056409B1/en not_active Expired
  • 1981-07-24 WO PCT/EP1981/000105 patent/WO1982000483A1/en active IP Right Grant
  • 1981-07-24 JP JP50258981A patent/JPH0329917B2/ja not_active Expired
• 1982
  • 1982-03-17 FI FI820927A patent/FI71781C/sv not_active IP Right Cessation
  • 1982-03-24 RU SU823411783A patent/RU1830091C/ru active

Patent Citations (4)

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