Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-I-12MECHANISTIC ASPECTS OF STEAM REFORMING OF METHANOLOVER COPPER-BASED CATALYSTSJ. Papavasiliou, G. Avgouropoulos, T. IoannidesFoundation for Research and Technology-Hellas (FORTH), Institute of ChemicalEngineering and High Temperature Chemical Processes (ICE-HT), P.O. Box 1414, Patras,Greece. Fax:+30-2610-965223, e-mail: geoavg@iceht.forth.gr1. IntroductionSteam reforming of methanol (SRM) is a simple and efficient way of producing H 2 . Whenone designs methanol reformers, the kinetics and mechanism of the reforming reaction isimportant in sizing the reactor. A number of different mechanisms for the SRM over Cubasedcatalysts have been proposed in the literature and disagreements exist about themechanism of CO by-product formation and the methyl formate reaction route [1]. Steadystateisotopic transient kinetic analysis (SSITKA) has long been documented and widelyaccepted as one of the most powerful techniques to elucidate in a precise way mechanisms ofheterogeneous reactions [2]. Many studies have been reported on application of SSITKAtechniques over a wide range of surface-catalyzed reactions including ammonia and methanolsynthesis, ammonia oxidation, CO oxidation, NO-CO reduction, methane activation e.t.c.In the present study, SSITKA-Mass Spectrometry experiments were performed in order tostudy mechanistic aspects of the steam reforming of methanol over three Cu-based catalysts,namely: CuMnO and CuCeO catalysts and a commercial CuZnAl 2 O 3 catalyst.2. ExperimentalThe isotopes used in the experiments were 13 CH 3 OH (99atom% 13 C, Isotec) and H 18 2 O(97atom% 18 O, Isotec). SSITKA experiments performed in order to follow the «C-path» ofreaction, involved the switch: 12 CH 3 OH/H 2 O/He/Ar → 13 CH 3 OH/H 2 O/He, while those tofollow the «O-path» of the reaction, involved the switch: CH 16 3 OH/H 16 2 O/He/Ar →CH 16 3 OH/H 16 2 O/ H 18 2 O/He. All experiments were performed at 190°C, ensuring methanolconversions below 20%. Cu 0.30 Mn 0.70 and Cu 0.15 Ce 0.85 samples were prepared with thecombustion method, as reported elsewhere [3].3. Results and discussionThe quantitative results obtained from the SSITKA experiments are summarized in Table1. It is observed, that in the case of CuCeO catalyst, the total steady-state amount ofintermediate species present on the catalyst surface that leads to CO 2 , is more than three timeslower than that of CuMnO or CuZnAl 2 O 3 catalysts, while the rate of CO 2 formation is one233