Kinetic Modeling of Hardwood Prehydrolysis. Part III. Water and Dilute Acetic Acid Prehydrolysis of Southern Red OAK


  • Anthony H. Conner
  • Linda F. Lorenz


Prehydrolysis, autohydrolysis, water prehydrolysis, acetic acid prehydrolysis, kinetics, modeling, southern red oak, Quercus falcata Michx


The hemicelluloses in wood are more readily hydrolyzed than is cellulose. Because it is advantageous to process the hemicellulose sugars separately from the glucose obtained from the cellulose, most processes for utilizing wood as a source of chemicals and liquid fuels include a prehydrolysis step to remove the hemicellulose prior to the main hydrolysis of the cellulose to glucose. Kinetic data are required to model the reactions that occur during prehydrolysis so that optimum conditions and product mixes can be predicted. Two promising prehydrolysis methods, the Iotech steam explosion process and the Stake process, are based on water prehydrolysis (autohydrolysis). The kinetics of water and of dilute (5%) acetic acid prehydrolysis of southern red oak wood over the temperature range of 170 to 240 C were investigated. Kinetic parameters were determined that permitted modeling not only of xylan removal from the wood but also of the occurrence of xylan oligosaccharides, free xylose, furfural, and further degradation products in the prehydrolyzate. At lower temperatures (approximately 170 to 200 C), xylan removal could be modeled as the sum of two parallel reactions (one for an easily hydrolyzed portion and one for a more resistant portion of xylan) using the equation derived in Part I. At the highest temperature studied (236.9 C), the removal of xylan from the wood was best modeled as a single reaction with a small fraction of the xylan being essentially nonreactive. The occurrence of xylan oligosaccharides, xylose, furfural, and further degradation products in the prehydrolyzate was modeled as consecutive, irreversible pseudo first-order reactions. A timelag associated with the de-polymerization of the xylan oligosaccharides to xylose was accounted for in the model by allowing the apparent rate constant for the formation of xylose to increase exponentially with time to a maximum value. Increasing the temperature decreased the time required for the overall reactions to occur, increased the portion of xylan removed from the wood, and increased the yield of total anhydroxylose units (xylose + xylan oligosaccharides) that were recovered in the prehydrolyzate. Prehydrolysis with dilute acetic acid does not greatly affect the maximum yields of products in the prehydrolyzate over those observed with water prehydrolysis; however, the time to maximum yield decreased. The data presented in this report indicate that, at higher temperatures, water or dilute acetic acid prehydrolysis gives yields comparable to those for dilute sulfuric acid prehydrolysis at 170 C recently reported in the literature. Preliminary results with lignin isolated from the water and acetic acid prehydrolysis residues confirm recent reports that lignins of this type are useful as phenol substitutes in phenol-formaldehyde adhesives.


American Society for Testing and Materials. 1977. Standard test method for lignin in wood. ASTM Designation D 1106-56.nAmerican Society for Testing and Materials. 1978. Standard test method for ash in wood. ASTM Designation D 1102-56.nAmerican Society for Testing and Materials. 1979. Standard method for chromatographic analysis of chemically refined cellulose. ASTM Designation D 1915-63.nBender, R. 1979. U.S. Patent 4,136,297.nBrice, R. E., and I. M. Morrison. 1982. The degradation of isolated hemicelluloses and lignin-hemicellulose complex by cell-free, rumen hemicellulases. Carbohyd. Res. 301:93-100.nCasebier, R. L., J. K. Hamilton, and H. L. Hergert. 1969. Chemistry and mechanism of water prehydrolysis of southern pine wood. Tappi 52(12):2369-2377.nCasebier, R. L., J. K. Hamilton, and H. L. Hergert. 1973. (a) The chemistry and mechanism of water prehydrolysis on black gum wood. Effect of temperature at constant time. Tappi 56(3): 135-139. (b) Chemistry and mechanism of water prehydrolysis on black gumwood. Effect of time at constant temperature. Tappi 56(11):150-152.nConner, A. H. 1984. Kinetic modeling of hardwood prehydrolysis. Part I. Xylan removal by water prehydrolysis. Wood Fiber Sci. 16(2):268-277.nConner, A. H., K. L. Libkie, and E. L. Springer. 1985. Kinetic modeling of hardwood prehydrolysis. Part II. Xylan removal by dilute hydrochloric acid prehydrolysis. Wood Fiber Sci. (in press).nDietricks, H. H., M. Sinner, and J. Puls. 1978. Potential of steaming hardwoods and straw for feed and food production. Holzforschung 32(6): 193-199.nEffland, M. J. 1977. Modified procedure to determine acid-insoluble lignin in wood and pulp. Tappi 60:143-144.nFoody et al. 1980. Optimization of steam explosion pretreatment: Final report. DOE/ET/23050-1. Submitted to U.S. Department of Energy, Fuels from Biomass Program by Iotech Corp., Ottawa, Ontario.nForintek Canada Corp. 1982. Development of lignin adhesives. ENFOR Project C-209, Eastern Laboratory. Ottawa, Ontario, Canada.nHammig, R. W. 1959. Stable predictor-corrector method for ordinary differential equations. J. Assoc. Computing Machinery 6:37-48.nHarris, J. F., A. J. Baker, A. H. Conner, T. W. Jeffries, J. L. Minor, R. C. Pettersen, R. W. Scott, E. L. Springer, T. H. Wegner, and J. I. Zerbe. 1985. Two-stage, dilute acid hydrolysis of wood: An investigation of fundamentals. USDA Forest Serv. Gen. Tech. Rep. FPL Forest Prod. Lab., Madison, WI.nHarris, J. F., J. R. Saeman, and E. G. Locke. 1963. Wood as a chemical raw material. In B. L. Browning, ed., The chemistry of wood. Interscience.nHelwig, J. T., and K. A. Council, eds. 1979. SAS user's guide, 1979 edition. SAS Institute, Inc., Cary, NC.nIMSL, Inc. 1982. IMSL Library Reference Manual, edition 9. IMSL, Inc., Houston, TX.nKang, Y., and M. Yoo. 1976. Saccharification of sawdust. Part I. Hydrolysis of Lauan wood xylan. Hwahak Konghak 14(2):97-103.nKlemola, A., and G. A. Nyman. 1966. Steam hydrolysis of birchwood. Papper och Trä 10:595-603.nKobayashi, T., and Y. Sakai. 1956. Hydrolysis rate of pentosan of hardwood in dilute sulfuric acid. Bull. Agric. Chem. Soc. Japan 20:1-7.nLee, Y., C. M. Lin, T. Johnson, and R. P. Chambers. 1979. Selective hydrolysis of hardwood hemicellulose by acids. Biotechnol. Bioeng. Symp. 8:75-88.nMadison Academic Computing Center. 1972. Numerical methods series. Differential equations. Reference manual for the 1108. University of Wisconsin, Madison, WI.nMadison Academic Computing Center. 1982. Numerical methods series. NREG 77: Fortran 77 nonlinear regression routine. User manual for the 1100 and the Wires/Vax 11/780. University of Wisconsin, Madison, WI.nMaloney, M. T., T. W. Chapman, and A. J. Baker. 1985. Dilute acid hydrolysis of paper birch: Kinetic studies of xylan and acetyl-group hydrolysis. Biotechnol. Bioeng. (in press).nMarchessault, R. H., and J. St.-Pierre. 1978. A new understanding of the carbohydrate system. CHEMRAWN Conf., Toronto, Canada.nMarchessault, R. H., S. Coulombe, T. Hanai, and H. Morikawa. 1979. Monomers and oligmers from wood. Can. Wood. Chem. Symp., Harrison Hot Springs, B.C., Canada.nMason, W. H. 1921. U.S. Patent 1,399,976.nPettersen, R. C., V. H. Schwandt, and M. J. Effland. 1984. An analysis of the wood sugar assay using high pressure liquid chromatography (HPLC): A comparison with paper chromatography (PC). J. Chrom. Sci. 22:478-434.nRichter, G. A. 1956. Some aspects of prehydrolysis pulping. Tappi 39(4):193-210.nRoot, D. F., J. F. Saeman, and J. F. Harris. 1959. Kinetics of the acid-catalyzed conversion of xylose to furfural. For. Prod. J. 9:158-165.nScott, R. W. 1979. Colorimetric determination of hexuronic acids in plant materials. Anal. Chem. 51:936-941.nSears, K. D., A. Beelik, R. L. Casebier, R. J. Engen, J. K. Hamilton, and H. L. Hergert. 1971. Southern pine prehydrolyzates: Characterization of polysaccharides and lignin fragments. J. Polym. Sci. (Part C) 36:425-443.nSimmonds, F. A., R. M. Kingsburg, and J. S. Martin. 1955. Purified hardwood pulps for chemical conversion. II. Sweetgum prehydrolysis—sulfate pulps. Tappi 38(3):178-186.nSpringer, E. L. 1966. Hydrolysis of aspenwood xylan with aqueous solutions of hydrochloric acid. Tappi 49(3):102-106.nSpringer, E. L., and J. F. Harris. 1982. Prehydrolysis of aspen wood with water and with dilute aqueous sulfuric acid. Svensk. Papperstidn. 85:R152-154.nSpringer, E. L., and K. A. Libkie. 1980. Prehydrolysis of birch wood with sulfur dioxide. Tappi 63(7):119-120.nSpringer, E. L., and L. L. Zoch. 1968. Hydrolysis of xylan in different species of hardwoods. Tappi 51(5):214-218.nSpringer, E. L., J. F. Harris, and W. K. Neill. 1963. Rate studies of the hydrotropic delignification of aspenwood. Tappi 46(9):551-555.nVeeraraghavan, S., R. P. Chambers, M. Mylers, and Y. Y. Lee. 1982. Kinetic modeling and reactor development for hemicellulose hydrolysis. AICHE Meeting, Orlando Florida. February 28-March 3.nWayman, J., and J. H. Lora. 1980. Simulated autohydrolysis of aspen milled wood lignin in the presence of aromatic additives: Structural modifications. J. Appl. Polym. Sci. 25:2187-2194.nWiesenberger, E. 1947. The microanalytical determination of C-methyl and acetyl groups. Makrochem. 33:51-69.n






Research Contributions