This study is a starting point for creating a new plastic recycling process. The process consists of two spouted bed reactors. In the first reactor, plastic chips are fed and instantaneously thermally decomposed into lower hydrocarbons (gas or vapor). In the second reactor, the hydrocarbons are further decomposed into carbon and hydrogen. Carbon can be utilized as carbon black, activated carbon and so forth. Hydrogen is a useful and clean fuel (no carbon dioxide evolution) and a raw chemical material. In this study, the decomposition of hydrocarbons (methane, ethane, propane, ethene and propene) was investigated to obtain basic data for the second reactor of the process. The hydrocarbons were decomposed in a fixed bed flow reactor packed with 1-mm-diameter a-alumina balls or 1-mm-diameter nickel-plated a-alumina balls, which were used as a decomposition catalyst. Carbon and hydrogen were the main products. The nickel-plated alpha-alumina balls gave a higher hydrogen production rate than the unplated alpha-alumina balls. This is caused by the dehydrogenation activity of nickel. For alkanes, the higher the carbon number, the greater the hydrogen production rate. For alkenes, a similar tendency was observed. The hydrogen production rate showed positive temperature dependency and positive hydrocarbon partial pressure dependency. The results obtained in this study showed that production of hydrogen and carbon is possible using the second reactor of the process we proposed.