PNNL

Abstract

The use of heterogeneous catalysts in near-critical water processing provides many challenges of material stability in addition to the normal questions of chemical activity. Conventional catalyst materials developed in traditional organic chemistry or petroleum chemistry applications provide a source of information of materials with the required activities but often without the required stability when used in hot liquid water. The importance of the use of catalysts in near-critical water processing plays a particularly crucial role for the development of renewable fuels and chemicals based on biomass feedstocks. Stability issues include both those related to the catalytic metal and also to the catalyst support material. In fact, the stability of the support is the most likely concern when using conventional catalyst formulations in near-critical water processing. Processing test results are used to show important design parameters for catalyst formulations for use in wet biomass gasification in high-pressure water and in catalytic hydrogenations in water for production of value-added chemical products from biomass in the biorefinery concept. Analytical methods including powder x-ray diffraction for crystallite size and composition determination, surface area and porosity measurements, and elemental analysis have all been used to quantify differences in catalyst materials before and after use. By these methods both the chemical and physical stability of heterogeneous catalysts can be verified.