Biofuels/Biomass Conversion

The Conn Center is focused on developing technologies for converting biomass to useful fuels and chemicals. Specifically, the center is interested in lipid and cellulosic biomass conversions to transportation fuels and chemicals. Such capabilities will bring Kentucky new private investors to build plants that process biofuels utilizing our research expertise and innovations.

Biomass raw material for transportation fuels, such as gasoline, diesel, and jet fuels, can be broadly divided into two categories: 1) lignocelluloses containing carbohydrates, i.e., wood, switchgrass, leaves, rice and wheat husks, etc.; and 2) lipids containing (mainly) triglyceride esters, i.e., vegetable and animal fats and greases, waste oils, algae oils, etc. Lignocelluloses can be converted to gasoline, diesels, and jet fuels. Due to their chemical structure of long chain fatty acids, the lipid triglyceride esters are well suited for processing into fuels such as fatty acid methyl ester (FAME) biodiesels, "green" diesels, which are a mixture of hydrocarbons boiling in the diesel range, and bio jet fuels.

Cellulosic Biomass Conversion

Several technical and economic obstacles currently hinder the development of biofuels from biomass. A key bottleneck is the difficulty in breaking down and converting the raw cellulose substrate into simple fermentable sugars, where conversion does not reach or often even approach 100%, even after several days of reaction time. The process is further complicated by the desire to work with high solids content to maximize the product concentration in the fermentable sugar stream, minimize water and energy use, and minimize capital expenditures for larger reactors. Like many industrial applications, working with solids suspensions creates challenges associated with maintaining those solids in suspension as well as other mass and heat transfer issues. Also, power consumption in conventional reactors can become prohibitive on an industrial scale.

By integrating state-of-the-art experimental and computational techniques, we are working to:

  1. better understand limitations in regard to mass transfer and kinetics of the biomass processing environment;
  2. comprehend the impact of solids loading on mixing and associated power requirements;
  3. develop processing strategies to overcome these current limitations; and
  4. partner with industry to facilitate biofuels and associated economic development in the region.

Accomplishments to date are associated with the development and/or improvement of bioprocessing where existing techniques are limited due to complexities with working media, such as multi-phases, high solids content, and complex flow fields. By 2011, 3 PhD students and 8 Masters students will have completed training in this type of biomass processing.

Lipids to Fuels and Chemicals

The conversion of lipid sources into diesels, jet fuels, and chemicals involves the development of suitable, competitive, and heterogeneous catalysts that can be utilized for Fischer-Tropsch synthesis reactions or hydrotreatment. Key considerations for these conversions involve determining the fatty acid compositions of various lipid sources, testing the effectiveness of basic and acidic catalysts, and resolving post-production quality issues and distribution challenges. In the US, FAME biodiesels must conform to the ASTM D6751-09 specifications; however, FAME biodiesels have NOx cold flow and oxidation/storage stability issues that have not been fully addressed. Similarly, bio jet fuels must adhere to a very low maximum freezing point of -47 degrees C, which has also not yet been resolved. In contrast, "green" diesels possess the advantage of being "drop-in" fuels, as they do not require any change in the existing petrofuels industry infrastructure, such as storage, pipeline transport, or delivery.

Researchers at the Conn Center are working to overcome these challenges. We have developed a process for the production of FAME biodiesels with superior cold flow properties and innovations in the production of biodiesels, green diesels, and jet fuels.

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