Sugar – starch – and carbohydrates – Processes – Carbohydrate manufacture and refining
Patent
1985-05-16
1986-04-01
Schor, Kenneth M.
Sugar, starch, and carbohydrates
Processes
Carbohydrate manufacture and refining
127 1, C13K 102
Patent
active
045795959
DESCRIPTION:
BRIEF SUMMARY
The present invention concerns a method for hydrolyzing cellulose and ligno-cellulosic products (wooden chips, sawdust, chopped straw, various vegetal refuses, etc . . . ) into monomeric sugars by means of hydrochloric acid.
BACKGROUND OF THE INVENTION
There exists already a rather large number of techniques for hydrolyzing cellulose to a minor or larger extent by means of hydrochloric acid in concentrated or diluted solutions. These methods, among which there can be mentioned the BERGIUS, HERENG, PRODOR and other processes are disclosed for instance in the following references. Wood Chemistry, Process Engineering Aspects (1965), NOYES DEVELOPMENT CORP., Park-Ridge, N.J. 07656 USA; U.S. Pat. Nos. 2,951,775; 2,959,500; 9,974,067; 2,752,270; 2,778,751; 2,945,777; 3,212,932; 3,212,933; 3,251,716; 3,266,933 and 3,413,189.
However, when one uses solutions of hydrochloric acid, he must use rather high weight ratios of HCl to cellulose which requires, to ensure that the operation is profitable, that means for recovering and recycling this acid be provided. Now, such means are de facto not economical because of the additional equipment involved and, besides, there is a consecutive increase of the corrosion problems in connection with the use of such acids. Hence, means have been sought to remedy these drawbacks by decreasing the total amount of HCl put into work and, as a consequence, to increase its concentration at sites very close to the fiber to be hydrolyzed. Thus, a method is disclosed in U.S. Pat. No. 1,806,531 (GOGARTEN et al) in which cellulose containing materials are saturated with dry HCl (in compressed or liquid form) below zero degree C under pressure in an autoclave whereby decomposition of the material occurs at a temperature of 0.degree. C. or below. Then, steam is introduced into the mass for raising the temperature to about 60.degree.-75.degree. C. and for effecting the saccharification of the decomposed cellulosic product. This method is economically interesting in some aspects since it uses a relatively low HCl cellulosic product weight ratio and also enables to recover part of this acid in highly concentrated form after saccharification. However, this advantage is offset by the necessity to use pressure equipment which is extremely difficult and costly to operate in the presence of compressed gaseous or liquid anhydrous HCl because of corrosion problems. Another disadvantage is that the addition of steam (i.e. a raise in temperature to relatively high values) is known to cause the decomposition of the sensitive sugars formed from wood, namely the pentoses which then turn into a black resin. Another disadvantage is the requirement that the solid comminuted cellulosic material in the autoclave be cooled to zero degree C. or below which is not easy to achieve in all cases and, more particularly, when using rotating pressure equipment. Finally, operating the decomposition of the cellulosic material at low temperatures such as 0.degree. C. or below is not efficient since then the reaction rate is very slow and mixing is very poor as the cold mixture of HCl and cellulosic material is very stiff.
In another reference, i.e. U.S. Pat. No. 1,677,406 (PERL), there is disclosed a method for the saccharification of cellulose bearing products in which some of the above drawbacks are avoided. In this method, the cellulose product (wood chips) is progressively driven in a helical conveyor while a refrigerated mixture of dry HCl and a carrier gas is fed at counter-current relative to the displacement of the cellulose from the downstream side of the conveyor. The gases continuously travel through the conveyed material whereas the HCl is progressively adsorbed therein and the exhausted gases are then removed from the conveyor, replenished with fresh HCl and recycled in the system. This arrangement enables to have the fresh gases (with high HCl concentration) to first meet the material with the highest HCl saturation which minimizes undesirable local temperature jumps due to the heat produced by the dry HCl i
REFERENCES:
patent: 1511786 (1924-10-01), Terrisse et al.
patent: 1806531 (1931-05-01), Gogarten et al.
patent: 2474669 (1949-06-01), Hereng
patent: 3251716 (1966-05-01), Porter
patent: 4292089 (1981-09-01), Reghault et al.
Chemisches Zentralblath, vol. 139, No. 6, 2-7-68, Kusama et al., Abstracts 3045-3051.
Armet Jean-Michel
Cuccolo Sergio
Johansson Ake A.
Roman Alain
Sachetto Jean-Pierre
Battelle (Memorial Institute)
Schor Kenneth M.
Warburton Kenneth R.
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