(152a) Hydrolysis of Biomass Using a-Hydroxysulfonic Acids

Due to current practices in the petroleum industry, fossil fuel availability is permanently decreasing while their use significantly contributes to the accumulation of greenhouse gasses.  The sustainability and feasibility for the conversion of biomass to hydrocarbon fuels has therefore become an essential research focus.  While fuels are burned for energy and release CO₂ into the atmosphere, replanting previously harvested biomass guarantees that CO₂ will be recycled back through the growth of new foliage. 

Biomass can be converted into valuable chemicals through methods such as acid catalyzed hydrolysis and dehydration.  The cellulose in biomass is hydrolyzed into a few useful chemicals, including levulinic and formic acid, which can be further upgraded to liquid fuels through the relatively simple thermal deoxygenation (TDO) method.  Currently, the preferred method of acid catalyzed hydrolysis of biomass is performed with sulfuric acid.  It is necessary to recover the sulfuric acid for both economical and environmental reasons.  The recovery and recycling of the sulfuric acid has proven to be a significant hurdle with many challenges affecting the scale-up and commercialization of the biomass hydrolysis processes. 

Hydrolysis of biomass using a class of acids called α-hydroxysulfonic acids presents a novel approach to simplifying acid recovery and recyclability.  Until now, little research has gone into hydroxysulfonate formation outside of the chemical pulping field.  We have shown that specific α-hydroxysulfonic acids can be intentionally synthesized to effectively hydrolyze biomass to levulinic and formic acid.  The acid and its constituents exist in equilibrium with each other.  Therefore, the acid can be easily reverted completely to its non-acidic constituents by employing the proper conditions.  The position of equilibrium is subject to the nature of the constituents used to synthesize the acid.  The ability to tune the α-hydroxysulfonic acids in response to desired acid strength and decomposition method becomes a viable approach to process design.  Complications in downstream processing can be minimized as separations, neutralization, and purification steps can be simplified or avoided.  This study presents the results of an investigation into the use of several different α-hydroxysulfonic acids for conversion of cellulose to levulinic and formic acids.