Methane to higher hydrocarbons via halogenation V. Degirmenci a , D. Uner a, * , A. Yilmaz b a Chemical Engineering Department, Middle East Technical University, Ankara 06531, Turkey b Chemistry Department, Middle East Technical University, Ankara 06531, Turkey Abstract Activation of methane with a halogen followed by the metathesis of methyl halide is a novel route from methane to higher hydrocarbons or oxygenates. Thermodynamic analysis revealed that bromine is the most suitable halogen for this goal. Analysis of the published data on the reaction kinetics in a CSTR enabled us to judge on the effects of temperature, reactor residence time and the feed concentrations of bromine and methane to the conversion of methane and the selectivity towards mono or dibromomethane. The analysis indicated that high dibromomethane selectivity is attainable (over 90%) accompanied by high methane conversions. The metathesis of dibromomethane can provide an alternative route to the conversion of methane (natural gas) economically with smaller installations than the current syn-gas route. # 2005 Elsevier B.V. All rights reserved. Keywords: Methane; Dibromomethane; Syn-gas 1. Introduction In 1956, M King Hubert proposed a life cycle model for petroleum widely known as ‘‘Hubbert’s Model’’ [1]. His prediction that oil production in U.S. would peak around 1969, actually happened in 1970, which was only off by 1 year. The extension of this model predicts that the rate of world oil production starts to decrease after 2010 and petroleum will be exhausted by about 2060 [2]. The decline in the crude oil reserves increases the importance of alternative hydrocarbon sources. Natural gas is the World’s second largest hydrocarbon reserve, which could be a substitute for crude oil. The typical composition of natural gas consists of 70–90% methane and the rest is higher volatile hydrocarbons. However, the end use of natural gas is almost completely methane, above 99% after some purification. The direct conversion of methane to liquid fuels has been the subject of catalysis community in the past couple of decades. Direct oxidative coupling of methane drew great attention in the previous decade. Although several catalysts were investigated, low yield and low selectivity problems could not be overcome. Any catalyst that could reach yields higher than 25% and selectivity over 80% could not be put into practice for economical reasons [3]. Studies focusing on one- step partial oxidation of methane to methanol or formalde- hyde confronted with the problems of low selectivity accompanied by long residence times [4]. The utilization of HZSM-5 and metal supported HZSM-5 zeolites in the direct conversion of methane to liquid hydrocarbons have not achieved high selectivity values [5]. Pulsed discharge plasma processes also applied to methane conversion with the advantage of low gas phase temperature. But, low energy efficiencies revealed a drawback for this approach [6]. Besides, the photo catalytic reactions managed to activate methane, however, they do not result in high yields [7,8]. High stability of the methane molecule is the biggest obstacle against the way from the smallest hydrocarbon to fuels or petrochemicals. As far as the activation of methane is concerned, breaking the carbon–hydrogen bond in the molecule under either oxidative or non-oxidative condition is revealed to be the necessary step. Halogenation of methane towards higher hydrocarbons has been intensively studied in the past by Weissman and Benson [9,10]. The Benson process required the use of chlorine as a catalyst. But, the corrosive nature of the reactants and the products, www.elsevier.com/locate/cattod Catalysis Today 106 (2005) 252–255 * Corresponding author. E-mail address: uner@metu.edu.tr (D. Uner). 0920-5861/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2005.07.140