Synthesis of methyl formate via two-step methane partial oxidation A. Parmaliana a,b,* , F. Frusteri b , F. Arena a , A. Mezzapica b , V. Sokolovskii c a Dipartimento di Chimica Industriale, Universita Á di Messina, Salita Sperone 31, c.p. 29, I-98166 S. Agata, Messina, Italy b Istituto CNR-TAE, Salita S. Lucia 39, I-98126 S. Lucia, Messina, Italy c Department of Chemistry, University of Witwatersrand, P.O. Wits 2050, Johannesburg, South Africa Abstract Using a two reactor system the direct catalytic conversion of methane to methyl formate is achieved. The two-step reaction sequence consists of the partial oxidation of methane to HCHO at 600±7008C on a SiO 2 -based catalyst and the dimerisation of HCHO to methyl formate at 130±1708C on amphoteric oxides such as TiO 2 , ZrO 2 and Al 2 O 3 . By adopting a continuous ¯ow recycle reactor mode methyl formate yield up to 12% has been attained. A preliminary analysis of the factors controlling activity and reaction pattern of oxide catalysts in the dimerisation of formaldehyde is given. # 1998 Elsevier Science B.V. All rights reserved. Keywords: Methyl formate; Methane partial oxidation; Catalyst; Formaldehyde dimerisation; Oxide 1. Introduction The direct conversion of natural gas to higher hydrocarbons, easily transportable fuels and chemi- cals is still one of the hottest and challenging research topics in catalysis. However, in spite of the efforts and resources devoted to this subject, due to the limited yield none of the catalytic processes proposed so far, such as oxidative coupling, partial oxidation to metha- nol or formaldehyde, thermal pyrolysis, electrophylic activation etc., is yet mature for industrial exploitation [1]. The lack of success of such direct catalytic methods for natural gas conversion has stimulated the interest toward indirect routes via syngas. Recently, a renewed interest in the direct conversion of methane to oxygenates and higher hydrocarbons of higher added value [2±5] has been associated with the disclosure of more effective operating strategies and reactor con®gurations [6±9]. Indeed, Klier and his group have reported how the yield of CH 3 OH and HCHO in the methane partial oxidation can be max- imised by using a double bed reactor system, one for the abstraction of hydrogen from methane and the other for the formation and hydrolysis of the methox- ide species [2]. Even a sequence of three catalysts for the synthesis of propanol from methane and air through a parallel/series reactor con®guration invol- ving the methane oxidative coupling to ethylene, the methane partial oxidation to syngas and the hydro- formylation of ethylene, has been proposed [3]. In order to overcome the expensive cryogenic separation step for C 2 H 4 recovering in the oxidative coupling of methane, Liu and Shen have studied the direct epox- idation of C 2 H 4 in the dilute reaction stream realising the direct conversion of methane into ethylene oxide [4]. Exxon has also patented a method for producing a mixture of methanol and ethanol by contacting methane, water and an acidic aqueous solution of Catalysis Today 46 (1998) 117±125 *Corresponding author. 0920-5861/98/$ ± see front matter # 1998 Elsevier Science B.V. All rights reserved. PII: S0920-5861(98)00333-2