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Two-Stage, Dilute Sulfuric Acid Hydrolysis of Wood: an Investigation of Fundamentals

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Two-Stage, Dilute Sulfuric Acid Hydrolysis of Wood: an Investigation of Fundamentals United States Department of Agriculture Two-Stage, Dilute Forest Service Forest Sulfuric Acid Products Laboratory General Hydrolysis of Wood: Technical Report FPL-45 An Investigation of Fundamentals John F. Harris James L. Minor Edward L. Springer Andrew J. Baker Roger C. Pettersen Theodore H. Wegner Anthony H. Conner Ralph W. Scott John I. Zerbe Thomas W. Jeffries Abstract Conversion of Units This paper presents a fundamental analysis of the Multiply By To obtain processing steps in the production of methanol from southern red oak (Quercus falcata Michx.) by two-stage 1 kilogram (kg) 2.205 pounds dilute sulfuric acid hydrolysis. Data for hemicellulose and cellulose hydrolysis are correlated using models. 1 tonne = 1,000 kg 1.102 tons (U.S.) This information is used to develop and evaluate a process design. 1 joule (J) 0.2388 calories Keywords: Southern red oak hemicellulose, cellulose 1 kilojule (kJ) 0.9478 Btu acid hydrolysis, reaction kinetics, yields, process, xylose, glucose, ethanol, furfural 1 kilopascal (kPa) 0.1450 psi 1 kilojoule/kilogram (kJ/kg) 0.4299 Btu/pound 1 millimeter 0.03937 inches October 1985 Harris, John F.; Baker, Andrew J.; Conner, Anthony H.; Jeffries, Thomas W.; Minor, James L.; Pettersen, Roger C.; Scott, Ralph W.; Springer Edward L; Wegner, Theodore H.; Zerbe, John I. Two-stage, dilute sulfuric acid hydrolysis of wood: An investigation of fundamentals. Gen. Tech. Rep. FPL-45. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory; 1985. 73 p. A limited number of free copies of this publication is available to the public from the Forest Products Laboratory, P.O. Box 5130, Madison, WI 53705. Laboratory publications are sent to over 1,000 libraries in the United States and elsewhere. The Laboratory is maintained in cooperation with the University of Wisconsin. Table of contents Page Page Introduction . 1 Research Recommendations. 57 Mechanisms and Data Sources. 3 Process Research and Development .......... 57 First Stage (Prehydrolysis). 3 Wood Chemistry Research. 58 Hemicellulose Removal ................... 3 Summary and Conclusions. 58 Xylan removal .......................... 3 Literature Cited .............................. 60 Glucan removal. 4 Appendix A: Acidity Calculations Prehydrolysis data. 4 I. Calculations of Hydrogen Ion + Catalyst concentration. 4 Concentration [H ]. 62 II. Calculation of Necessary Concentration of Removal of other components ............. 6 + Added Acid to Obtain a Particular [H ]. 62 Xylose and Furfural Yields. 7 Appendix B: Calculation of Furfural Yields During Steaming Acid-impregnated Chips .......... 9 Xylan Hydrolysis. 63 Digester ........................... 9 Appendix C: Analysis of Glucose Reversion Data. 64 Hydrolysis of impregnated chips. 10 Appendix D: Relationships Between Liquid movement and its effect on acidity. 11 Disappearance Rates of Reducing Power, Free Glucose, and Total Glucose. 65 Data correlation ....................... 16 Appendix E: Calculation of Glucose Yields (From Prehydrolysis of rapidly impregnated chips. 18 Fig. 16). 66 Furfural yields ......................... 19 Appendix F: Comparison of Ethanol Yields From Second Stage (Hydrolysis). 20 Percolation and Two-Stage Processes .......... 68 Glucose Reversion. 20 Appendix G: Experimental and Chemical Analysis Procedures; ................................ 72 Glucose Decomposition. 22 Kinetics of Cellulose Hydrolysis. 24 Glucose and Reversion Products from Cellulose ............................... 25 Organic lmpurities Other Than Reversion Material ................................ 30 Impurity load from mass balance. 30 Impurities from glucose decomposition .... 33 impurities in the cellulose hydrolysate. 35 Process Concepts. 42 First Stage ............................... 42 Hydrolyzer Type .......................... 42 Processing Alternatives. 42 First-Stage Process Description. 45 Furfural Recovery ........................ 46 Acetic Acid Recovery and Molasses Quality. 47 Second Stage ............................. 48 Hydrolyzer Type .......................... 48 Processing Alternatives. 49 Second-Stage Process Description .......... 50 Material and Energy Balances. ................ 52 Comparison with the Percolation Process ....... 56 Two-Stage, Dilute Sulfuric Acid Hydrolysis of Wood: An Investigation of Fundamentals1 John F. Harris, Chemical Engineer Andrew J. Baker, Chemical Engineer Anthony H. Conner, Chemist Thomas W. Jeffries, Microbiologist James L. Minor, Chemist Roger C. Pettersen, Chemist Ralph W. Scott, Chemist Edward L. Springer, Chemical Engineer Theodore H. Wegner, Chemical Engineer John I. Zerbe, Technologist Forest Products Laboratory, Madison, Wis. Introduction Of the various methods by which wood can be reimpregnated with acid and charged to the second converted to energy, the simplest and most efficient is stage. As with the first stage, the liquid content of the direct combustion. However, because of the continuing second-stage charge is kept to a minimum. Conditions need to reduce liquid petroleum imports, there has here are sufficient to hydrolyze the resistant cellulose. evolved a strong national cummitment to produce The resulting mixture is discharged to washers where energy from wood in the farm of ethanol. In keeping the glucose solution is separated from the lignin with its historical role in researching the production of residue. chemicals and energy from wood, the Forest Products Laboratory has undertaken selecting, describing, and improving the most promising process from among those that can conceivably be commercialized in the near future. We believe that process is two-stage dilute-acid hydrolysis. The process, in its simplest outline, is shown in figure 1. Wood chips, impregnated with a dilute sulfuric acid solution and drained of all interstitial liquid, are charged to the first stage. Here they are heated with direct steam, resulting in the hydrolysis of most of the hemicelluloses, and then discharged to washers. After being washed free of the material Figure 1.—Simple schematic of the two-stage solubilized in the first stage, the lignocellulose is hydrolysis process. (ML84 5484) 1This report was written as a result of research undertaken by various projects at the Forest Products Laboratory (FPL) through a cooperative agreement with the Tennessee Valley Authority, Muscle Shoals, Ala. The research team was led by John F. Harris and received administrative advice and guidance from John I. Zerbe, Program Manager, and Andrew J. Baker, Chemical Engineer, of the Energy Research, Development, and Application Program at the FPL. This process was selected for investigation because it the lignocellulose hydrolysis, no fermentation studies was thought that: (1) The process could be carried with it were done, but the known contaminants of the rapidly to commercial operation, on the basis of the hydrolysate are being tested for toxicity in yeast amount of information available on the use of dilute fermentation. sulfuric acid as a hydrolysis medium. (2) The separate stages for hydrolyzing the hemicelluloses and cellulose The project has spawned several related fundamental would result in high yields and high-purity products. studies not essential to the current process design. Because much of the liquid is removed before each of They include investigations of xylose metabolism, the hydrolysis steps, (3) the energy consumption would cellulose hydrolysis, sugar-degradation and be minimized, and (4) the resulting sugar solutions deacetylation kinetics. We plan to continue these would be more concentrated. studies and release the results through technical journals. Some developmental work on a similar process was carried out in Sweden during World War ll and a short This report presents information currently available to description of the results presented at a United Nations help carry the process into pilot-plant development. It conference in 1952 (Cederquist 1954). Although the also contains facts needed to evaluate the process at results were encouraging, the process was clearly its present state of development and to select areas for considered to have been a wartime expedient, and work study that would lead to improvement. Considerable was discontinued when the war ended. No attempt had attention is given to a discussion and analysis of the been made to deal with effluents, to complete the underlying physical and chemical mechanisms. This is design, or to optimize the process. The wood used was important in obtaining an appreciation of the many spruce (Picea excelsa Link) rather than the problems and the possibilities for future development. hardwoods-southern red oak (Quercus falcata Michx.), in particular-that are of greater importance in the American economy. The approach taken in this research was shaped by the large amount of fundamental data available from previous research at the Forest Products Laboratory. Existing information was believed sufficient to permit a fairly accurate design of the, process-that is, the more important components could be modeled and brought info a harmonious whole. We also did experimental work to validate or modify the assumptions and data used in modeling. Our purpose was to recommend processing conditions pertaining to each element, and to estimate yields, energy requirements, and other pertinent process information. The major process elements are the first-stage prehydrolysis and second-stage hydrolysis. Since these are within the area of our expertise, the report deals mainly with these two
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