Kinetics of high-temperature water-gas shift reaction over two iron-based commercial catalysts using simulated coal-derived syngases

摘要

The kinetics of the water-gas shift (WGS) reaction over two iron-chromium based commercial catalysts has been studied. The experiments were performed in a differential reactor at a constant temperature of 450 °C and a space velocity of 1.9 m~3 g_(cat)~(-1) h~(-1) at approximately atmospheric pressure. The effects of CO, CO2, H2O and H2 concentration on WGS reaction rate were determined over both catalysts using selected gas compositions that might be encountered in coal based gasification system of the dry-feed and slurry-feed types and at the backend of conventional fixed-bed and catalytic membrane reactors. It was found that the rates of the WGS reaction (in mol g_(cat)~(-1) s~(-1)) over two commercial catalysts (referred to as HTC1 and HTC2) at a reaction temperature of 450 °C can be expressed by the following power-law rate models: For HTC1 R= 10~(2.845±0.03) exp ((-111 ±2.63)/(R'T))P_(CO)~(1.0±0.031) P_(CO2)~(-0.36±0.043) P_(H2)~(-0.09±0.007) (1-1/K (P_(CO2)P_(H2))/P_(CO)P_(H2O))) For HTC2 R=10~(0.659±0.0125) exp ( (-88 ±2.18)/R'T) P_(CO)~(0.9±0.041) P_(H2O)~(0.31±0.056)P_(CO2)~(-0.156±0.078) P_(H2)~(0.05±0.006) (1-1/K(P_(CO2)P_(H2))/P_(CO)P_(H2O))). It was observed that HTC1 promotes the rate of WGS reaction when the inlet gas consists of higher CO concentration, and lower CO2 and H2 concentration. Due to the less-negative reaction order with respect to CO2, HTC2 was found to be more applicable to the gas streams with higher CO2 levels, which are likely to be found on the retentate side at the backend of a catalytic membrane reactor.