The alkaline, kraft pulping process which uses sodium hydroxide and sodium sulfide is the predominant chemical pulping method in the United States, and is currently used to produce 45 million tons of pulp per year. The technology is very efficient with respect to both energy and chemical recovery, but is capital intensive, has yield losses due to degradation of non-cellulosic polysaccharides and results in the generation of hazardous air pollutants (HAPs) includingmalodorous mercaptans, requiring additional unit operations for their removal. Catalytic methods offer a viable alternative to increase cellulose fiber yield by improving selectivity, reducing energy use and eliminating the formation of odor-causing mercaptans and other volatile organic compounds (VOCs) associated with kraft pulping. The current work represents a coupled experimental and computational effort for the development and optimization of catalysts for the pulping of wood. While numerous oxidative catalysts have been proposed, this work is concentrated on cobalt-Schiff bases, e.g. Co(salen), that can oxidize lignin model compounds using mild O2 pressures and temperature in non-aqueous or basic, aqueous solutions. Co(salen) catalysts also favor lignin over carbohydrates. Results from computational quantum chemistry are reported that are being used to design improved cobalt catalysts by identifying chemical factors (e.g., ligand bite angle, electronic or electrostatic stabilization, and steric control) that directly affect the rate-determining step(s) and therefore the product yield and distribution. Modifications to the native reactivity, selectivity, or both, are explored computationally to rationally design optimized catalysts.

Catalytic pulping of wood

253rd National Meeting (2017)

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