RAPID PRODUCTION OF HYDROGEN AND CARBON MONOXIDE VIA THE HETEROGENEOUS OXIDATION OF Zn(g)

摘要

The heterogeneous oxidation of Zn(g) is considered as an improved approach to the production of H_2 and CO in the two-step Zn/ZnO solar thermochemical cycle. The rate of Zn(g) oxidation by H_2O and CO_2 is measured gravimetrically in a quartz tubular flow reactor for temperatures between 800 and 1150 K, Zn(g) concentrations up to 36 mol%, and H_2O/CO_2 concentrations up to 45 mol%. The rate of the heterogeneous oxidation of Zn(g) by both H_2O and CO_2 is on the order of 10~(-8)-10~(-5) mol cm~(-2) s~(-1). For similar oxidizing conditions, H_2O oxidizes Zn(g) three times as fast as CO_2, indicative of a lower heterogeneous oxidation activation energy in the H_2O system. Less than one second is required to convert more than 85% of Zn to ZnO for all temperatures in both the H_2O and CO_2 reacting systems.