抄録
Utilization of carbon dioxide is one of the most significant subjects in environmental technologies. A common idea is reducing carbon dioxide to carbon monoxide or methane, which are valuable in industry. Though it is rather easy technically, the problem is how hydrogen can be supplied more cheaply. Supplying pure gaseous hydrogen is easiest, but most costly. One solution is to supply hydrogen in the form of hydrocarbons. Even if the reactions work, some remaining questions need to be answered. The first is if the dehydrogenation products from the hydrocarbons used are valuable in industry. The second is how the products will be separated. This study may give an answer to both the questions. A cyclic operation experiment of catalytic cyclohexane dehydrogenation and carbon dioxide hydrogenation was carried out successfully using LaNi5 particles as a catalyst and as a hydrogen reservoir. Five kinds of LaNi5 particles ranging from 10 to 725 μm in mean diameter were used. After a 30-minute activation of LaNi5 using hydrogen at 673 K, carbon dioxide and cyclohexane flowed through the LaNi5 particles bed for each 30 minutes at 673 K alternatively. The cycle was repeated four times. When cyclohexane was fed, cyclohexene, benzene and hydrogen were detected as products. Cyclohexane conversion increased with decrease in the mean diameter of LaNi5, ie., with increase in external surface area per unit mass of alloy. When carbon dioxide was fed, carbon monoxide formed Hydrogen also was detected in the outlet gas. Carbon monoxide yield also increased with decrease in the mean diameter of LaNi5
