Title : CO2 conversion from flue gas using a catalytic hybrid inorganic membranes
Abstract:
Experiments have been carried out using a catalytic membrane reactor for the tri-reforming of power plant flue gas for CO2 conversion. The experiments were performed at two different temperatures of 800 and 900 oC respectively. The gaseous stream was composed of O2, CH4, CO2 and N2. Two membrane sizes were used for the evaluation (10mm OD and 25 mm OD) with a length of 368 mm in each case. The reaction temperature was monitored by strategically located thermocouples with zonal control achieved using a power controller. At each operating temperature, tests were performed at atmospheric pressure and at four different volumetric flowrates (517, 994, 1,656 and 3,312 mL/min). Rhodium chloride (RhCl3) solution was used as the catalyst precursor which was impregnated on the surface of an α-Al2O3 inorganic membrane having a commercial pore size of 600µm. For each membrane the 0.5 wt.% Rh/gamma-Al2O3 catalyst gave the higher conversions of CH4 and CO2 but the syngas ratio did not change significantly with increasing catalyst loading from 0.1 weight % to 0.5 weight %. The gaseous products were analysed using an Agilent Technologies Model 7890B equipped with an Agilent Technologies 5977A MS detector and a Varian CP – 3800 gas chromatograph equipped FID and TCD detectors respectively. The characterization of the membranes was carried out using scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDAX) and the Brunauer-Emmett and Teller (BET) gas adsorption method using liquid nitrogen. It was found that the calcined and reduced catalysts showed a lower surface area compared to γ-Al2O3 support. The reduction in surface area was attributed to catalytic impregnation. It was observed that for each membrane, the 0.5 wt.% Rh/gamma-Al2O3 catalyst gave the higher conversions of CH4 and CO2 but the syngas ratio did not change significantly with increasing catalyst loading from 0.1 weight % to 0.5 weight %. In conclusion, CO2 reforming is more favourable at high temperatures, it was determined that by raising the temperature to the 900 °C range, a high CO2 conversion was achieved.
