Industry University Cooperative Research on High Yield Syntheses of Activated Carbons

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Abstract - Antal - 9521423 A new method for manufacturing charcoal from biomass by operating at elevated pressures doubles the yield of charcoal ordinarily realized by industry, and is able to convert wood logs to charcoal after only one hour of reaction time. This research is aimed at employing this new knowledge to triple the usual industrial yields of activated carbons from biomass feedstocks. Technical barriers to the synthesis of high yield (HY) activated carbons include: (1) What rate laws describe the gasification of HY charcoal by oxygen and steam? (2) Can these rate laws be included in a Thiele modulus analysis to define conditions which produce activated carbons with high surface areas or other desirable properties? (3) Can activated carbons be synthesized at low temperatures? (4) Can impregnants be used to synthesize valuable carbons with peculiarly desirable properties? (5) What reaction conditions maximize the yields of desirable carbons? To overcome the above barriers, this work will focus on the following objectives: (i) Produce various HY charcoals from raw and pretreated biomass feedstocks. (ii) Determine the rate laws governing gasification of these HY charcoals by oxygen and water. (ii) Use Thiele modulus analysis to identify favorable conditions for activation. (iv) Activate the NY charcoals by oxygen (air) in steam (or supercritical water) at moderate to high temperatures and elevated pressures, and by steam (or supercritical water) at moderate to high temperatures over a very large range in pressures, (v) Determine the chemical, physical, and adsorptive properties of the HY activated carbons. (vi) Based on a synthesis of the foregoing results, identify conditions and pretreatments which produce desirable activated carbons with yields of 20% or more. Two experimental testbeds will be used to measure kinetics and activate the charcoals: a large, pressurized, packed bed reactor combined with a high pressure steam generator, both designed to satisfy ASME cod e requirements, and a small diameter, packed bed, supercritical flow reactor. Collaborators with the Hungarian Academy of Sciences will also measure HY charcoal gasifications rates at low pressures by thermogravimetric analysis. This work represents a partnership between the University of Hawaii, two companies concerned with recycling and biomass utilization, and a commercial source of activated carbons. These linkages to private industry will ensure the rapid dissemination and employment of new knowledge generated by this research.