Targeted products from fast-hydropyrolysis and hydrodeoxygenation of biomass

Ian Tad Smith, Purdue University

Abstract

Previously, the H2Bioil process was proposed as a possible way to convert sustainably available intact biomass into liquid fuels. The optimization of this process and possible synergies with other biomass conversion processes are presented in this thesis. The selectivity of the PtMo hydrodeoxygenation catalyst was tuned using two different hydrogen partial pressures: 25 bar, and 2.5 bar. This effect was studied on cellulose and intact biomass samples to determine the effect that hydrogen has upon the retention of aromatic compounds found in intact biomass. These experiments show that it is possible for the hydrogenation activity of the PtMo catalyst to be altered such that aromatic compounds are retained in the products after hydrodeoxygenation. Around 3% of carbon is recovered in aromatic products from cellulose, while 10% of the carbon from intact biomass is recovered as aromatics. The carbon efficiency of the cyclone reactor can be further increased by optimization of the temperatures of both the fast hydropyrolysis stage and hydrodeoxygenation stage. Previous work has been done in this area, but was not exhaustive. Experiments done by previous graduate student, Vinod Venkatakrishnan were performed at FHP temperatures of 300°C for HDO and 480°C for FHP. A proof-of-concept experiment is shown, at the lower HDO and FHP temperatures of 275°C and 460°C, respectively, that provides evidence that systematic optimization will lead to improvements in overall process yields. This experiment shows that it may be able to further lower char formation in the FHP stage of the cyclone reactor by temperature optimization. Char formation decreased from 29% to 23% of the total carbon. The total hydrocarbon yield increases from 54% at the standard conditions to 60% for the low temperature experiment. Also important to note is the formation of aromatic compounds which may be more favorable at lower HDO temperatures. Further experiments need to be done for conclusive optimization. A Catalytic Depolymerization of Lignin (CDL) process was recently developed to extract lignin from intact biomass into valuable chemicals. This process results in high value propylphenol products and a leftover carbohydrate residue. This carbohydrate residue can be used in a process such as the H2Bioil process to produce hydrocarbon fuels. An experiment was performed on a CDL treated poplar sample to show a synergistic effects in a combined CDL/H2Bioil process is used to convert intact biomass to chemical and fuel products. After completing a carbon balance on the combined process, it was determined that the overall carbon yield of the combined process is lower than the H2Bioil yield alone. However, the extraction of lignin unexpectedly has no effect on the char yield of the FHP process.

Degree

M.S.Ch.E.

Advisors

Agrawal, Purdue University.

Subject Area

Alternative Energy|Chemical engineering

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