Simultaneous Carbon Dioxide and Steam Reforming of Methane to Syngas over NiO-CaO Catalyst

摘要

Steam reforming, CO_2 reforming, and simultaneous steam and CO_2 reforming of methane to CO and H_2 over NiO—CaO catalyst (without any prereduction treatment) at different temperatures (700-850℃) and space velocities (5000-70 000 cm~3·g~(-1)·h~(-1)) are investigated. The catalyst is characterized by XRD, XPS, and temperature-programmed reduction (TPR). The catalyst showed high activity/selectivity in both the steam and CO_2 reforming reactions and the simultaneous steam and CO_2 reforming. In the CO_2 reforming, the coke deposition on the catalyst is found to be very fast. However, when the CO_2 reforming is carried out simultaneously with the steam reforming, the coke deposition on the catalyst is drastically reduced. By the simultaneous CO_2 and steam reforming (at ≥800℃ and space velocity of about 20 000—30 000 cm~3·g~(-1)·h~(-1)), methane can be converted almost completely to syngas with 100% selectivity for both CO and H_2. The H_2/CO ratio in products can be varied between 1.5 and 2.5 quite conveniently by manipulating the relative concentration of steam and CO_2 in the feed.