III International Conference

PP-I-25EFFECT OF THE PRESSURE ON THE MECHANISMS OF THE CO 2 /H 2REACTION ON A CO-PRECIPITATED CuO/ZnO/Al 2 O 3 CATALYSTHocine S., Cherifi O. 1 , Bettahar M.M. 2Laboratoire de Chimie Appliquée et de Génie Chimique Université M. Mammeri de Tizi-Ouzou BP .17 R.P 1500 Tizi-Ouzou Algérie .1 Laboratoire de Chimie du Gaz Naturel, Institut de Chimie , BP32, El-Alia,16111Bab-Ezzouar, Alger, Algérie2 Laboratoire de Catalyse Hétérogène, UMR CNRS 7565, Université Henri Poincarré- Nancy 1,BP 239, 54506 Vandoeuvre-lès-Nancy, Cedex, FranceThe influence of the working pressure on the mechanisms of the CO 2 /H 2 reaction on a coprecipitatedCuO/ZnO/Al 2 O 3 catalyst has been studied. Methanol and carbon monoxide arecompetitively formed. The former is produced directly from CO 2 whatever the pressurewhereas carbon monoxide stems either from decomposition of methanol at low pressure orfrom CO 2 directly at high pressure.1- Introduction:The synthesis of methanol from CO/CO 2 /H 2 mixtures using CuO/ZnO/Al 2 O 3 catalysts iscurrently attracting much interest due to its economical importance (1). On the other hand, therole of each oxide in the mechanism of formation of methanol (reactions I and II) is still amatter of debate (1,2) since occurs the reaction of conversion (reaction III) also:CO 2 + 3 H 2 CH 3 OH + H 2 O (I)CO + H 2 O CO 2 + H 2 (II)CO + 2H 2 CH 3 OH (III)According to Klier (3) carbon monoxide is the principal source of methanol production(reaction I) whereas for Chinchen (4), methanol is directly formed from carbon dioxide.Rosovskii (5) as wall as Trambouze (6) concluded that the products are formed by parallelreactions (scheme I) rather than by successive reactions (scheme II):CH 3 OHCO 2(schemeI)COCO 2CO CH 3 OH (schemeII)However, the results obtained by Denise (7) and Baussart (8) show contradictorily that asecond type of successive reactions occurs in the CO 2 /H 2 in which methanol is the primaryproduct (scheme III): CO CO (schemeIII)2CH 3 OH52