Chemical Engineering Science 57 (2002) 2519–2529 www.elsevier.com/locate/ces Analysis of deactivation and selectivity pattern in catalytic hydrogenation of a molecule with dierent functional groups: crotonaldehyde hydrogenation on Pt = SnO 2 Katerina Liberkova a , Raymonde Touroude a , Dmitry Yu. Murzin b; * a LERCSI, UMR 7515 du CNRS, ECPM, ULP, 25 rue Becquerel, 67087 Strasbourg Cedex 2, France b Laboratory of Industrial Chemistry, Process Chemistry Group, Faculty of Chemical Engineering,  Abo Akademi, FIN-20500, Biskopsgatan 8, Turku, Finland Received 15 May 2001; received in revised form 16 January 2002; accepted 28 January 2002 Abstract Hydrogenation of crotonaldehyde was studied in the gas phase, at atmospheric pressure and 353 K over 5% Pt= SnO2 catalysts, prepared from Pt(NH3)4(NO3)2 and H2PtCl6. Rapid deactivation during time on stream was observed. Experiments were performed consecutively in a series using a catalyst reduction pretreatment between kinetic runs. Selectivity was found to be dependent on ageing period and on the metal precursor. Selectivity as high as 70% until 40% conversion was observed using Pt(NH3)4(NO3)2 as precursor. Adsorption and hydrogenation of the C!O and C!C groups are supposed to occur on dierent sites, which have dierent deactivation properties. Kinetic model is advanced to describe deactivation and selectivity patterns. ? 2002 Published by Elsevier Science Ltd. Keywords: Platinum; Hydrogenation; Crotonaldehyde; Pt=SnO 2 ; Deactivation; Two-site model 1. Introduction Hydrogenation reactions are used in large scale in chem- ical and petrochemical industry as well as in food process- ing industry, pharmaceutical production and ne chemicals (Augustine, 1995). One of the challenging tasks, from both scientic and industrial points of view, is selective reduction of polyfunctional molecules which have several functional groups. ; unsaturated aldehydes is an example of such molecules, as they contain simultaneously C!O and C!C bonds, forming a conjugated system. Selective hydrogena- tion of C!O is a dicult task to achieve. In this eld of research, monometallic catalysts supported on Al 2 O 3 or SiO 2 lead mostly to the formation of saturated aldehydes (Touroude, 1980), e.g. only C!C bond is hydrogenated. To improve the selectivity towards unsaturated alcohols, the use of additives (promoters), bimetallic catalysts or easily reducible supports has been proposed. Dierent results can be obtained depending on the nature of the metal itself. The ∗ Corresponding author. Tel.: +358-2-215-4985; fax: +358-2-215-4479. E-mail address: dmurzin@abo. (D. Y. Murzin). eects of promotion were recently discussed in detail by Ponec (1997). Promoters are thought to be needed for the activation of the carbonyl group due to the strong interac- tion between the oxygen of this group and the promoter in its cationic state. For crotonaldehyde hydrogenation in the gas phase, much attention has been given to the performance of Pt–Sn catalysts for which the selectivity in unsaturated alcohol was found to depend on the Sn= Pt ratio, the prepa- ration method, and more precisely on the Pt–Sn or Pt–Sn oxide interactions (Margitfalvi, Tompos, Kolosova, & Va- lyon, 1998b). The addition of tin to Ru has been reported to increase greatly the formation of unsaturated alcohol in cinnamaldehyde hydrogenation (Neri, Mercadante, Milone, Pietropaolo, & Galvagno, 1996). Another interesting sys- tem is platinum deposited on titania (Claus et al., 1997; Englisch, Jentys, & Lercher, 1997; Makouangou, Murzin, Dauscher, & Touroude, 1994; Sen & Vannice, 1988). It was speculated that after a high temperature reduction Pt-titania interfacial sites are created, which are responsible for this enhancement. Beside TiO 2 , other reducible oxides such as Nb 2 O 5 , Y 2 O 3 , ZrO 2 , CeO 2 , ZnO 2 used as supports of platinum have been found to contribute to changes in the catalytic activity and selectivity in aldehyde hydrogenation (Consonni, Jokic, 0009-2509/02/$ - see front matter ? 2002 Published by Elsevier Science Ltd. PII:S0009-2509(02)00134-3