Oxy-CO_2 reforming of methane to syngas over CoO_x/MgO/SA-5205 catalyst

摘要

The oxy-CO_2 methane reforming reaction (OCRM) has been investigated over CoO_x supported on a MgO precoated highly macroporous silica-alumina catalyst carrier (SA-5205) at different reaction temperatures (700-900 deg C), O_2/CH4 ratios (0.3-0.45) and space velocites (20,000-100,000 cc/g/h). The reaction temperature had a profound influence on the OCRM performance over the CoO/MgO/SA-5205 catalyst; the methane conversion, CO_2 conversion and H_2 selectivity increased while the H_2/CO ratio decreased markedly with increasing reaction temperature. While the O_2/CH_4 ratio did not strongly affect the CH_4 and CO_2 conversion and H_2 selectivity, it had an intense influence on the H_2/CO ratio. The CH_4 and CO_2 conversion and the H_2 selectivity decreased while the H_2/CO increased with increasing space velocity. The O_2/CH_4 ratio and the reaction temperature could be used to manipulate the heat of the reaction for the OCRM process. Depending on the O_2/CH_4 ratio and temperature the OCRM process could be operated in a mildly exothermic, thermal neutral or mildly endothermic mode. The OCRM reaction became almost thermoneutral at an OCRM reaction temperature of 850 deg C, O_2/CH_4 ratio of 0.45 and space velocity of 46,000 cc/g/h. The CH_4 conversion and H_2 selectivity over the CoO/MgO/SA-5205 catalyst corresponding to thermoneutral conditions were excellent: 95 percent and 97 percent, respectively with a H_2/CO ratio of 1.8.