Oxidative pyrolysis of methane to higher hydrocarbons: effects of water in feed

Abstract

Direct conversion of methane into higher hydrocarbons (ethane, ethylene, and to small extent C_3-4 hydrocarbons) by its partial oxidation with oxygen in the absence of catalyst has been investigated. It was carried out in a quartz flow reactor at atmospheric pressure under nonflame conditions at different temperatures (1,123-1,273 K), CH₄/O₂ ratios (1.7-9.0), space velocities (500-5,000 h^-1), and water concentrations (0.0-80 mol %) in the feed. No coke deposition was observed in the reactor, but there was a formation of small amounts of tarry matter in the reaction at ≥ 1,223 K, particularly for the lower CH₄/O₂ ratios (≤3.5). The product distribution in the process was strongly influenced by the dilution of feed with N₂ or water. Addition of water in the feed was highly beneficial to obtaining higher yield and/or to selectivity for the higher hydrocarbons and suppressing almost completely the formation of tarry matter.