Date of Award
Master of Engineering Science
Chemical and Biochemical Engineering
Prof. Paul A. Charpentier
Application of biomass and waste for renewable energy sources is gaining an important role in the world’s future energy policy as we are facing a tremendous challenges related to energy and the environment, in particular energy sustainability while reducing carbon emissions from fossil fuels. Supercritical water gasification (SCWG) presents an innovative technology for complete and efficient destruction of biomass or wastes without formation of harmful by-products. The major products formed during supercritical water gasification of biomass are hydrogen, carbon monoxide, methane and carbon dioxide with clean water effluents. Catalysts enhance the overall gasification efficiency as well as the organic carbon destruction in the liquid effluents to enable drinking quality water as the effluent. Since SCWG is a hydrothermal process and catalyst deactivation always occurs in high temperature processes due to coke deposition on the catalyst surface, the aim of this study is to prepare noble and non-noble metal based catalyst on alumina support to reduce the graphitic coke formation during supercritical water gasification. Usually non-noble metal based catalysts are used in high temperature gasification because of their ready availability and low cost but this study showed that introduction of a small amount of noble metal onto non-noble based catalysts greatly influenced the catalyst performance while reducing the graphitic coke formation. In this research, supercritical water gasification (SCWG) of a model biomass compound was studied to produce hydrogen rich gas at moderate temperatures (400-500°C). The catalysts were synthesized by different procedures, evaluated and characterized (fresh and spent) to study the catalyst role in SCWG. The catalysts studied were synthesized by
incipient wetness impregnation and a sol-gel method with and without various templates, respectively to compare the catalytic performance based on their synthetic procedures. It was found that the templating synthesis of catalysts increased the surface area as well as pore volume & strong metal support interactions in the catalysts which play an important role in SCWG. The aerogel catalyst prepared from sol-gel synthesis with supercritical CO2 drying also enabled a catalyst to be produced with a large surface area and strong metal support interaction. The most important finding of this study was to reduce graphitic coke formation during gasification because of the presence of ruthenium metal in the catalyst structure.
To the best of our knowledge, the resulting hydrogen yield, total organic carbon (TOC) destruction and gasification efficiency were significantly higher using the novel aerogel and templated Ru-Ni-Al203 catalysts than any other reported results for SCWG of any biomass compound at moderate temperatures (~500 °C) and pressures (~25 MPa).
A global kinetic model for TOC destruction in supercritical water was developed using non-linear regression, which convincingly fit the experimental results showing the significant effect of water in SCWG of model biomass compound.
Hossain, Md. Zakir, "Ru-Ni-Al20 3 CATALYSTS FOR SUPERCRITICAL WATER GASIFICATION OF GLUCOSE" (2011). Digitized Theses. 3491.