US006007636A United States Patent (19) 11 Patent Number: 6,007,636 Lightner (45) Date of Patent: Dec. 28, 1999 54 METHOD TO RECYCLE AN AQUEOUS Concetrated acid Hydrolysis w/Acid Reovery, Prieto, et al. ACIDIC LIQUOR USED FOR 1987 Biochemical/Alcohol Fuels Program Ann. Rpt., p. DEPOLYMERIZATION OF CELLULOSE A-95. 76 Inventor: FederalGene E. Way, Lightner, Wash. 70698023-3549 SW. 296th St., Acid Hydrolysis Research, Wright, J.D., et al., 1987 Bioin chemical/Alcohol Fuels Program Annual Rept. p. A-15. 21 Appl. No.: 09/224,700 22 Filed: Jan. 4, 1999 Primary Examiner David Brunsman 51 Int. Cl. ................................ C07H3/00; C13K 1/02 57 ABSTRACT 52 U.S. Cl. ................................................................ 127/37 58 Field of Search ................................................. 127/37 A method to recycle aqueous acidic liquor used to form 56) References Cited depolymerized cellulose and hemicellulose accompanying cellulose, contained in biomass, by hydrolysis in the aque U.S. PATENT DOCUMENTS ous acidic- - - -liquor. - Cellulose is dissolved- in the aqueous 4,237,226 12/1980 Grethlein .................................. 435/99 acidic liquor and then remains in place to hydrolyze cellu 4,608.245 8/1986 Gaddy et al. ... ... 423/531 1 to f depol ized cellul in th idi 5,188,673 2/1993 Clausen et al. ........................... 127/37 OSe IO IOrm depolymerIZed cellulose In line aqueous acICIIc 5,411,594 5/1995 Brelsford .................................. 127/37 liquor. The depolymerized cellulose, including dextrins, OTHER PUBLICATIONS oligosaccharides, and glucose is Substantially Separated from the aqueous acidic liquor. The Separated aqueous acidic Madison Wood Sugar Proc. Ind. & Eng. Chem Harris, vol. liquor is then recycled to dissolve and hydrolyze additional 38, No. 9, E. E., et al., pp. 890. Ehtanol from Cellolosic Residues & Crops, Moore, M.R., et cellulose to form additional depolymerized cellulose. al, p. A-65, 1987 Biochemical/Alcohol Fuels Program Ann. Rpt., p. A-65. 18 Claims, 3 Drawing Sheets 2O PRECIPITATE FIRST CO'N,ER 14 FORMATION SEPARATOR EXTRACTION N 18 22 LIQUID BOMASS CONTAINING HYDROLYSS A QUEOUS ACDC LIQUOR AND SOLVENT DEPOLYMERIZED POLYMERS SECOND MIXTURE SEPARATOR 34. COUNTER FLOW 42 EXTRACTION A QUEOUS ACDC LOUOR 46 WATER NSOLUBLE SOLIDS U.S. Patent Dec. 28, 1999 Sheet 3 of 3 6,007,636 |NEATJOS 30\/>HOIS 479, ------------> 89 Z6 9/ 6,007,636 1 2 METHOD TO RECYCLE AN AQUEOUS Also, a State of the art process being developed by ACIDIC LIQUOR USED FOR workers at the University of Arkansas, is reported in FY DEPOLYMERIZATION OF CELLULOSE 1997 BIOCHEMICAL conversion/ALCOHOL FUELS BACKGROUND OF THE INVENTION PROGRAM: Annual Report PA.-85. It employs high con centration of Sulfuric acid to convert corn Stover to SugarS. Throughout the World there is increasing interest in con They describe a process Scheme to Separate Sugars contained Verting renewable biomass to usable products Such as etha in the concentrated Sulfuric acid using a heavy boiling nol. Conversion of wood to ethanol has been practiced solvent to dissolve the Sulfuric acid and a low boiling solvent during wartime due to a shortage of liquid fuels. Reported in to dissolve the heavy boiling solvent. They also report that Ind. & Eng. Chem. Vol. 38 No. 9, P. 890 (1946). Because of this method has a loSS of Solvents and a loSS of Sulfuric acid poor yields and consumption of chemicals the conversion which is neutralized with lime. was found not to be economical for peacetime use. Present Reported in the above named report, on page A-15, is a day interest in hydrolysis of biomass is to provide an plan by TVA to develop a high concentration of sulfuric acid alternative fuel Source to avoid dependence on unreliable process. The current focus of TVA is to develop an inex imported petroleum crude oil for liquid fuels. Biomass often 15 contains hemicellulose and lignins accompanying the cel pensive process for recovering the high concentration of lulose contained in the biomass. The hemicellulose and Sulfuric acid. Thus the problem of recovering Sulfuric acid amorphous cellulose of the biomass is easily hydrolyzed, in has not yet been Solved. a process termed pre-hydrolysis, leaving a residue contain It is well known that a high concentration of Sulfuric acid ing lignins and un-hydrolyzed crystalline cellulose. Pre will hydrolyze cellulose and hemicellulose at low tempera hydrolysis consists of reacting water with biomass materials tures to form water soluble depolymerized products which in the presence of a catalyst, usually an acid. Control of can be altered by enzymes to produce Sugars for fermenta tion. The problem with this method is the failure to cost temperature of the hydrolysis and concentration of the acid effectively recover the Sulfuric acid. Recovery of the Sulfuric is adjusted to control the kinetic rate of hydrolysis. Con acid is reported as an unsolved problem. Thus it is believed ventional processes center around acidic hydrolysis of bio 25 mass to produce glucose and pentoses. Pentoses, by contin that no Satisfactory recovery method has yet been devel ued hydrolysis conditions, may be reacted to form furfural. oped. Biomass is a term used to describe material containing The present concern is about recovering aqueous acidic cellulose including: paper, pulp, wood waste, Sawdust, liquor used to produce depolymerized cellulose and hemi municipal solid waste (MSW), agricultural wastes, fabrics, cellulose. This invention relates to a method of recycling and cotton. aqueous acidic liquor used to produce depolymerized cel A state of the art hydrolysis process, described in U.S. Pat. lulose and hemicellulose contained in a biomass. No. 5,411,594, uses two stages to hydrolyze biomass mate Therefore an object of this invention is to obviate many of rials. The first Stage is operated at low temperature and low the limitations and disadvantages of the prior art to hydro preSSure where both hemicelulose and amorphous cellulose 35 lyze cellulose and to ultimately produce glucose. are readily hydrolyzed. Residue from the first stage, con Depolymerized cellulose formed from aqueous acidic taining lignins and difficult to hydrolyze cellulose, is liquor may be hydrolyzed at low temperature to form removed and Sent to a Second Stage operating at high glucose rapidly and therefore will not have time to form preSSure and high temperature for hydrolysis of crystalline significant quantities of HMFs so as to reduce the lost yield cellulose. The hydrolyZate from the high pressure and high 40 of glucose. temperature Stage contains acid and glucose and glucose Another object of this invention is to avoid use of costly degradradation products, 5-hydroxymethylfurfural (HMF). and Slow acting enzymes for hydrolysis of cellulose. HMF is formed rapidly from glucose at high temperatures Still another object of this invention is to produce a yield thus limiting the yield of glucose. Kinetic reaction rate of of hydrolysis of cellulose and hemicellulose nearing 100%. HMF is dependent on concentration of glucose and tem 45 Yet another object of this invention is to operate and perature. accomplish low energy consumption. Another process for converting biomass to glucose, An additional object of this invention is to provide described in U.S. Pat. No. 4,237,226, uses two stages. The recycling of aqueous acidic liquor used to produce depoly first Stage operating at low temperature and dilute acid will merized cellulose and hemicellulose contained in a biomass. pre-hydrolyze hemicellulose and amorphous cellulose con 50 With the above and other objects in view, this invention tained in biomass. Residue, containing crystalline cellulose relates to the novel features and alternatives and combina and acid, from the first Stage is neutralized then added to a tions presently described in the brief description of the Second Stage to hydrolyze the cellulose with added enzymes. This slow-acting hydrolysis proceSS requires use of Steril invention. ized biomass residue in Sterilized reactors. The cost of the 55 BRIEF DESCRIPTION OF THE INVENTION enzymes is much more than that for acids. The present invention, in its broadest aspect, will provide A State of the art process being developed at TVA, a method to convert biomass into water insoluble Solids and reported in FY 1997 BIOCHEMICAL conversion/ desirable water soluble depolymerized products by dissolv ALCOHOL FUELS PROGRAM: Annual Report PA-65. ing cellulose in an aqueous acidic liquor and then forming Upon pre-hydrolysis of corn Stover, with dilute acid in a first 60 depolymerized cellulose in place in the aqueous acidic Stage, residue from the first Stage is treated with additional liquor. Key features are: Substantially freeing depolymerized acid and then the residue is dried at low temperature to cellulose from the aqueous acidic liquor and recycling to concentrate the acid contained in the residue. The resulting reuse recovered aqueous acidic liquor, hemicellulose residue contains concentrated acid and crystalline cellulose accompanying cellulose and will also be depolymerized, which is rapidly hydrolyzed in a Second Stage reactor 65 recycling to reuse components integral to the method, and operating at low temperature. Un-hydrolyzed crystalline removing water insoluble Solids containing water Substan cellulose is contained in a residue with lignins. tially free of components integral to the method. 6,007,636 3 4 The cellulose molecule is a polymer composed of a heretofore precipitate with a Supplementary