Preferential oxidation of carbon monoxide with Pt/Fe monolithic catalysts:interactions between external transport and the reverse water-gas-shift reaction

摘要

A series of Pt/Al_2O_3 catalysts,promoted with Fe and supported on 400 cpsi (cells per square inch) (62 cells/cm~2) ceramic straight-channel monoliths,was synthesized and evaluated for preferential oxidation (PROX) of a low concentration of CO in the presence of a high concentration of H_2.These cartalysts were evaluated in an adiabatic reactor at a total pressure of 0.20 mPa inlet tempratures of 80-170 deg C,and a space velocity of 30,000 h~(-1).The inlet gas composition was-H_2:42%,CO_2:9%,H_2O:12%,CO:0-1.0%,with N_2 as the balance.For a catalyst containing 5 wt.% Pt in the washcoat,the carbon monoxide and oxygen conversions increasd as the iron concentration in the washcoat was increased up to about 0.5 wt.% Fe.The reverse water-gas-shift (r-WGS) reaction played an important role in determining the outlet CO concentration.A catalyst with 1.6 g/in.~3 (0.098 g/cm~3) of an alumina washcoat containing 5 wt.% Pt/Al_2O_3 promotged with 0.5 wt.% Fe was selected for detailed investigation.The effects of both space velocity and linear velocity were studied.External transport was a significant resistance with this catalyst,at the above experimental conditions.The external resistances to heat and mass transfer,coupled with the effect of the r-WGS reaction,reduced the observed CO conversion and selectivity.