The process consists of three steps: liquid-phase decomposition of a biomass slurry with lignin rejection; stabilization in a fixed bed reactor; and deoxygenation in another fixed bed reactor. The finished BioGasoline is then separated from the water, which can be recycled.

BTG stabilizes the biomass deconstruction products to prevent them from reacting further to yield undesirable compounds such as organic acids and insoluble furan-based polymers. The BTG stabilized products are not susceptible to further dehydration and are preserved in high yield. This unique approach greatly enhances selectivity in an energy-efficient way, according to the company.

These stabilized products then undergo selective hydrogenation to reduce the oxygen content and increase the energy density and gasoline-compatibility of the product fuel. This final processing step uses a novel catalyst developed by Exelus that achieves the conversion rapidly and at high selectivity, without generating low-value light alkanes like methane or ethane. The product is the high-octane blend of gasoline-compatible alcohols.

The BTG process can utilize many types of lignocellulosic feedstocks such as wood, grass, agricultural waste, or other forms of solid waste. The process simplifications enabled by the high-performance catalysts and chemistry of the BTG process reduce the capital requirements of this technology relative to both biological and gasification-based routes, according to the company. High conversion efficiency maximizes product yield to reduce feedstock consumption, and energy-efficient process design keeps operating costs low.

The process can also be designed to be self-sustaining, producing all of the required reactants, such as hydrogen and water, internally.

Engineered Catalysts. The core of Exelus’ new process technologies is a new class of reactive systems that incorporate many characteristics associated with a reactor within the catalyst structure. These “Engineered Catalysts” are essentially multifunctional catalysts, which have controlled structure at scales ranging from the nano- (pore level) to the macro-scale (reactor level). This higher level of control creates an ideal reaction “atmosphere” at the catalyst surface, which leads to higher productivity.

By combining elements of micro-reactor technology with advanced catalytic materials, Exelus says that it can create a new generation of “green” process technologies, which reduce the scale of raw material usage over current technologies—decreasing greenhouse gas emissions by an order of magnitude while simultaneously increasing profitability of oil refiners and petrochemical producers worldwide.

In addition to the BTG process, Exelus offers ExSact, a unique solid acid catalyzed isoparaffin alkylation technology that overcomes the environmental concerns, safety hazards and rising costs associated with conventional liquid acid technologies. It also has developed ExSyM, a new low-cost styrene monomer production technology based on new chemistry.

ARPA-E Award. Exelus, in partnership with Zeolyst International and Linde Process Plants, also received one of the 37 first-round ARPA-E awards. (Earlier post.)

Small percentage refining inefficiencies equate to massive real losses of potential fuel and unnecessarily emitted greenhouse gases because of the scale of refining in the US. One such source of loss is the olefin content of refinery off-gas (ROG) generated from fluid catalytic cracking. The $1 million APRA-E grant is to support the development of a technology based on a novel catalyst that will enable dilute olefins from ROG to be converted to high-octane alkylate, resulting in recovery of up to 45 million barrels per year of gasoline.