In situ pulse diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) mass spectrometry study of the water-gas shift reaction on nickel(II) oxide-zinc(II) oxide catalysts.
The water-gas shift (WGS) reaction has been studied by pulsing carbon monoxide (CO) into a steady-state water (H2O)-Ar flow over nickel(II) oxide-zinc oxide (NiO-ZnO) catalysts using in situ diffuse reflection infrared Fourier transform spectroscopy (DRIFTS) coupled with a mass spectrometer method using the pulse technique (in situ pulse DRIFTS-MS) for different flow rates (gas hourly space velocity [GHSV] of 24,000-72,000 h(-1)) and reaction temperatures (250-350 °C). The results obtained from the in situ pulse DRIFTS-MS revealed that there are two types of water adsorption bands on the surface of the catalyst: (i) molecular adsorption (infrared [IR] bands in the 2500-3600 cm(-1) range and at 1640 cm(-1)), and (ii) dissociative adsorption at 3700 cm(-1), where carboxyl bands are formed at 1461 and 1368 cm(-1) and the gas-phase CO is adsorbed at 2187 and 2111 cm(-1) on the surface of the catalyst. After using a GHSV = 24,000 h(-1) H2O/Ar flow, we probed the existence of two active intermediates via the formation of two hydrogen production peaks. The products of hydrogen gas (H2) and carbon dioxide (CO2) had two pathways: the redox process and the associative process via the intermediate of the carboxyl group. In situ pulse DRIFTS-MS proves to be an effective approach for studying the nature of adsorbed species on the catalyst surface and the nature of the reaction product.
Army Academy ROC, Department of General Education, Taoyuan, 32093 Taiwan, Republic of China.
Chih-Wei
CW
Tang
Steven S C
SS
Chuang