Formation of pyrolytic carbon from benzene over nickel and some properties of the carbon formed

Abstract

The rate of carbon formation during the catalytic decomposition of benzene vapor over nickel plates was investigated at temperatures from 600 to 970°C. The rate of carbon deposition on the pure nickel was very slow, whereas the rate became fast upon pretreatment of the nickel surface with air at 760°C. Nickel particles of 200–300 Å in diameter were included within the carbon. The nickel contents were 11, 4, 3, and 2 wt% for the carbons deposited at 700, 760, 800, and 900°C for 6 hr, respectively. Direct observations of the deposition process were performed in a scanning electron microscope. The formation of fibrous carbons was observed at the initial stage of the deposition at 760°C. The catalytic activity of this carbon including nickel particles was examined in the hydrogenation reaction of cyclohexene. A high catalytic activity was observed when the nickel-carbon catalyst was pretreated with hydrogen at a high temperature such as 600°C. This fact suggests that the nickel particles were surrounded by carbon, and the carbon was gasified to methane upon treatment with hydrogen at a high temperature.