Design and development of catalysts & adsorbents for COx free H2 production

Abstract

The overall purpose of this research study is to produce, characterize and investigate the performance of catalysts and adsorbents which will play a role in COx-free hydrogen production via fuel processing for fuel cell applications. In the first three parts of the study; the purpose was to design and develop Pt-Ni/Al2O3 and Au-Re/CeO2 bimetallic catalysts for water gas shift (WGS) reaction. Results showed that Pt-Ni/Al2O3 catalysts were not suitable for fuel processors since methanation was observed under real feed conditions, although Pt-Ni/Al2O3 catalysts were found highly active and stable for WGS reaction with ideal feed including only main reactants. Gold addition by deposition precipitation technique on impregnated Re/Ceria catalysts led to higher dispersion and stronger interaction between Au and Re particles. 1%Au-0.5%Re/Ceria (imp+dp) catalyst was found highly active for WGS reaction, especially at high H2O/CO feed ratios. DRIFT profiles indicated that the reaction took place between the OH groups present on the catalyst and linearly adsorbed CO to produce surface formate along with surface carbonate and bicarbonate species. In the fourth section, DRIFTS and CO/CO2 adsorption studies were conducted on Pt-Sn and Pt catalysts supported on HNO3-oxidized activated carbon (AC3) with the aim of understanding the reasons behind the superior PROX performance of Pt-Sn/AC3. Studies revealed that Pt3Sn alloy formation on AC3 support has led to CO adsorption in higher amounts, and faster surface reaction involving intermediate OH groups which bring along increase in CO conversion and selectivity as the temperature decreases within the range 110-135oC. The last part consisted of SEM, DRIFTS and CO2 adsorption studies over activated carbon (AC) adsorbents prepared by subjecting a commercial sample to oxidative, alkali and thermal treatments aiming to develop an efficient AC based CO2 adsorbent. With Na2CO3 impregnation the CO2 mass uptakes at 20 bars and 25ºC were improved by ca. 8 and 7 folds and at 1 bar were increased ca. 15 and 16 folds, on the average, for air and HNO3 oxidized samples, respectively.