The Continuous-Flow Solid Acid Catalyst Hydrothermal Biorefinery

The Continuous-Flow Solid Acid Catalyst Hydrothermal Biorefinery

An Abstract for the RCN Conference on Pan American Biofuels and Bioenergy Sustainability

Michael T. Timko and Geoffrey Tompsett

Worcester Polytechnic Institute

A major challenges for sustainable biorefineries include adoption of continuous flow processing of whole biomasses and development of new technologies to catalyze selective biomass conversion reactions at mild conditions. Solving these problems will reduce biorefinery capital and operating costs, improve energy balances, and reduce water use. In this talk, I will share recent developments on continuous biomass processing in a hydrothermal reactor and synthesis of hydrothermally stable solid acid catalysts.

In terms of continuous hydrothermal processing, many engineering challenges remain unsolved, including how to deal with reactor plugging, whole biomass utilization, and high-pressure slurry pumping. Here, we have focused our efforts on developing a continuous flow reactor to achieve rapid heating rates in a turbulent mixer to break-up the lignocellulosic matrix, followed by reaction in a secondary zone to maximize simple carbohydrate production. We present time-on-stream data for the prototype reactor with different model feeds.

Solid acid catalysts can play important roles in economically competitive biorefineries, ranging from upstream biomass pre-treatment, to carbohydrate conversion, to bio-ethanol upgrading. A key feature of all these applications is the need for both activity and stability in water-rich aqueous environments. In this talk, I will highlight some early work to develop solid catalysts that retain activity and stability in biorefinery applications. I will describe research to synthesize and characterize bio-char catalyst supports, a class of materials that can be functionalized into strong Bronsted acids. Specifically, my lab has used a two-step hydrothermal-mechanochemical method to synthesize bio-chars for catalytic applications and characterized them using Raman spectroscopy. In a second line of work, I will share research on organic functionalized zeolites. Recent work elsewhere has shown that organic coatings can increase hydrothermal stability of zeolites; however, less work has been performed to characterize diffusion limitations associated with the organic coating. In my lab, we have synthesized several organic functionalized zeolites, characterized them using a suite of standard techniques, and performed dynamic uptake measurements to investigate molecular diffusion rates. These two catalyst vignettes showcase the range of strategies being adopted to develop solid acid catalysts suitable for biorefinery applications.