Mechanism of methano.pdfVIP

Applied Catalysis, 30 (198’7) 333-338 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 333 MECHANISM OF METHANOL SYNTHESIS FROM CO,/CO/H2 MIXTURES OVER COPPER/ZINC OXIDE/ ALUMINA CATALYSTS: USE OF 14C-LABELLED REACTANTS G.C. CHINCHEN, P.J. DENNY, D.G. PARKERa, M.S. SPENCER*and D.A. NHAN Imperial Chemical Industries, plc, Agricultural Division, Billingham, Cleveland TS23 ILB, England. aImperial Chemical Industries, plc, Advanced Materials Business Group, Hilton, Cleveland, England. (Received 1 September 1986, accepted 20 December 1986) ABSTRACT The addition of 14 CO or14C02 tracers to C02/CO/H2 reactant mixtures for methanol svnthesis over a commercial coooer/zinc oxide/alumina catalvst was used to deter- mine the origin of the carbon in the product.. For pCD2/pCO ratios from 0.02 to 1 the fraction of methanol made from carbon dioxide rises from %0.7 to $1, so carbon dioxide is the major reactant under industrial conditions. There is no carbon-containing surface intermediate common to methanol synthesis and the water- gas shift reaction. INTRODUCTION In much of the discussion [I,21 on the mechanism of methanol synthesis over copper/zinc oxide catalysts it has been tacitly assumed that carbon monoxide is the main source of carbon for the product methanol. However, earlier Russian work [3], some with C tracers, indicated that methanol was made from carbon dioxide only and recent studies [4-71 also indicate that carbon dioxide is the primary reactant. As methanol can be made from CO/H2 and C02/H2 mixtures [8,9], isotope- labelling studies under industrially-relevant conditions are the best method for determining the source of methanol in the reaction of C02/CO/H2 mixtures. In this paper both labelled CO and CO2 were used over a range of feed compositions in a flow system with an industrial copper/zinc oxide/alumina catalyst. EXPERIMENTAL The industrial methanol synthesis catalyst, made by co-precipitation [IO] and