Oxidative steam reforming of ethanol over Rh based catalysts in a micro-channel reactor

摘要

Oxidative steam reforming of ethanol (OSRE) was studied over Rh/CeO_2/Al_2O_3 catalysts in a micro-channel reactor. First, the catalyst support, A1_2O_3, was deposited on to the metallic substrate by washcoating and then the CeO_2 and active metal were sequentially impregnated. The effect of support composition as well as active metal composition on oxidative steam reforming of ethanol in a micro-channel reactor was studied at atmospheric pressure, with water to ethanol molar ratio of 6 and oxygen to ethanol molar ratio ranging from 0.5 to 1.5, over a temperature range of 350-550 ~°C. Ceria added to l%Rh/Al_2O_3 showed higher activity and selectivity than l%Rh/Al_2O_3 alone. Out of the various catalysts tested, 2%Rh/20%CeO_2/Al_2O_3 performed well in terms of activity, selectivity and stability. The OSRE performance was compared with that of SRE over 2%Rh/20%CeO_2/Al_2O_3 catalyst at identical operating conditions. Compared to SRE, the activity in OSRE was higher;however the selectivity to desired products was slightly lower. The H_2 yield obtained in OSRE was ~ 112 m~3 kg~(-1) h~(-1), as compared to ~ 128 m~3 kg~(-1) h~(-1) in SRE. The stability test performed on 2%Rh/20%CeO_2/Al_2O_3 at 500 ~°C for OSRE showed that the catalyst was stable for ~40 h and then started to deactivate slowly. The comparison between packed bed reactor and micro-channel reactor showed that the micro-channel reactor can be used for OSRE to produce hydrogen without any diffusional effects in the catalyst layer.