CO Hydrogenation over functionalized AlMCM-41 materials and ZSM-11/5 zeolites as catalysts

We studied the reaction in which carbon monoxide is converted to hydrocarbons, and investigated the behaviors and the combination system of catalysts exchanged with platinum and ammonium ions. Experiments were conducted at 1.2 MPa, 523K, and CO/H2=1 ratio. The structure and the texture of the catalysts, assessed by XRD, BET/BJH, and SEM, exhibited a microporosity for ZSM-5/11 and a micro/mesoporosity for AlMCM-41, which implies a direct effect on the catalytic properties of these materials. The conversions obtained were 60%, 55%, and 50% for Ptn+/H+-catalysts, Ptn+-catalysts, and H+-catalysts respectively. Such conversions could be attributed to the good acidity resulting from the simultaneous presence of Ptn+/H+ at different oxidation states of platinum, which was revealed by XANES PtLIII analysis, and their uniform dispersion within the inner surface and its grain size average conducted by the titration of adsorbed H2-O2. FTIR analysis showed a better distribution of acid sites for bi-exchanged catalysts over mono-exchanged ones, which resulted in a good catalytic activity. These results suggest a strong correlation between the high selectivity of light hydrocarbon products, the ions, and the catalyst types. These differences depended mainly on the facility of forming different products, such as n/iso-alkanes and alkenes. Skeletal isomerization was the main transformation observed on exchanged catalysts, particularly those with Ptn+/H+ ions. A deactivation process of catalysts, versus time-on-stream, begins after 70 minutes, especially for combined exchanged materials.