HPLC chromatograms of four representative hydrolysates. Source: NABC. Click to enlarge.

Virent’s Catalysis of Lignocellulosic Sugars (CLS) is one of six different process strategies represented in the DOE’s grant program with the NABC. In Stage I for the CLS process strategy, Washington State University (WSU) chose a wet oxidation pretreatment and enzymatic hydrolysis process to digest the hemicellulose and cellulose to create several hydrolysates from both feedstocks.

The National Renewable Energy Laboratory (NREL) has also supplied several hydrolysates using a dilute sulfuric acid pretreatment and enzymatic hydrolysis process. Virent then processed the four hydrolysate samples using its patented BioForming (earlier post) process.

Chromatograms show some differences in the hydrolysates relative to each other. However, in addition to generating significant amounts of glucose, the hydrolysates contain significant amounts of pentoses (e.g., xylose) and other carbon-containing species including organic acids and furanic materials.

Schematic illustration of the catalytic conversion of lignocellulosic sugars (CLS). Source: NABC. Click to enlarge.

Virent’s catalytic BioForming process converts all of these materials to desirable products, significantly increasing the overall process and liquid fuel yield; this shows that a range of feedstocks and process techniques can be employed. This flexibility means that technical, economic, and sustainability factors can be optimized to select the most attractive deconstruction process and feedstock.

BioForming—based on the company’s Aqueous Phase Reforming (APR) Process—is a catalytic method using moderate temperatures and pressures (ca. 175°–300°C and 150–1,300 psi) for the production of hydrogen or alkanes from oxygenated compounds. BioForming combines APR technology with conventional catalytic processing technologies such as catalytic hydrotreating and catalytic condensation processes, including ZSM-5 acid condensation, base catalyzed condensation, acid catalyzed dehydration, and alkylation.

Virent fed each of the four hydrolysate samples into its Aqueous Phase Reforming (APR) catalyst reactor system, removing most of the oxygen from the biomass sugar mixtures, producing monoxygenates such as alcohols, aldehydes and ketones, plus the reforming products of hydrogen and carbon dioxide. Virent says that its APR process, unlike other pathways, is well suited to handle mixed sugars from cellulosic streams with minimal processing.

The liquids were then fed into Virent’s Catalytic Oxygenates to Aromatics (COTA) process to produce a high octane biogasoline material, which the company has trademarked BioFormate.

In addition to being able to be uses as a refinery stream in commercial gasoline production, Virent’s renewable aromatic hydrocarbons will serve as several key platform chemicals historically sourced from petroleum reformate.

Moving forward in Stage I, the CLS team will produce larger volumes of BioFormate material to enable evaluation by BP and Tesoro, the refinery integration team that will be giving recommendations back to the NABC regarding the quality of fuel blendstocks or intermediate products from all of the process pathways.

Pall Corporation has been studying methods for improved hydrolysate purification and will be contributing to the commercial scale economics. Pacific Northwest National Laboratory (PNNL) is characterizing fresh and used catalyst samples. NREL and Argonne National Laboratory (ANL) will be completing techno-economic and life cycle analysis work for the CLS process strategy as well as for the other process strategies within NABC.