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methanex plant - THE PRODUCTION OF METHANOL AND GASOLINE...

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VII-Energy-D-Methanol-1 THE PRODUCTION OF METHANOL AND GASOLINE Methanol is made from methane (natural gas) in a series of three reactions: Ni/800 0 C Steam reforming: CH 4 + H 2 O ! CO + 3H 2 r H = +206 kJ mol -1 Ni/800 0 C Water shift reaction CO + H 2 O ! CO 2 + H 2 r H = +206 kJ mol -1 Synthesis 2H 2 + CO ! CH 3 OH r H = -92 kJ mol -1 Cu-Zn Thus overall: CO 2 + CO + 5H 2 2CH 3 OH + H 2 O + heat The methanol thus formed may be converted to gasoline by the Mobil process. First methanol is dehydrated to give dimethyl ether: 2CH 3 OH ! CH 3 OCH 3 + H 2 O This is then further dehydrated over a zeolite catalyst, ZSM-5, to give a gasoline with 80% C 5 + hydrocarbon products. The Methanex plant and sites in Taranaki are described. INTRODUCTION Methanol or methyl alcohol (CH 3 OH) is a colourless liquid with a boiling point of 65 o C. Methanol will mix with a wide variety of organic liquids as well as with with water and accordingly it is often used as a solvent for domestic and industrial applications. It is most familiar in the home as one of the constituents of methylated spirits. Methanol is the raw material for many chemicals, formaldehyde, dimethyl terephphalate, methylamines and methyl halides, methyl methacrylate, acetic acid, gasoline etc. Methanol and gasoline are produced from Kapuni and Maui natural gas (methane) by Methanex New Zealand Ltd around Waitara and New Plymouth in North Taranaki. Methane is steam reformed to make syngas (hydrogen and carbon monoxide), and this in turn is used to make methanol some of which can be used in methanol to gasoline (MTG) production. For economic reasons the MTG plant was taken out of production in late 1996, but could be recommissioned if the economic situation warranted it. In this article the overall layout and production steps at the Methanex plants will be described, followed by sections on the chemistry of methanol and gasoline production. THE METHANEX PLANTS Methanex owns two methanol plants, the stand alone plant at Waitara Valley which came on stream in 1983 and which can produce 1500 tonnes per day of crude methanol and distil 3000 tonnes per
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