Hydrogen production from methanol with Cu(Zn)/SiO2 catalysts prepared by means of sol-gel method. Characterization and evaluation in thermal decomposition and partial oxidation

LUIS A. ARRÚA*, ESTHER M. FIXMAN, OSVALDO F. GORRIZ, M. CRISTINA ABELLO

Congreso; H2-age: WWW; 2004

In the past years the interest in the study of catalytic transformations of alcohols like methanol and ethanol, especially as alternative roads of hydrogen production, has increased. Several catalysts containing copper have demonstrated to be active for methanol conversion with a high selectivity to hydrogen. In this work, the preparation, characterization and evaluation in the hydrogen production from methanol on Cu/SiO2 and Cu-Zn/SiO2 catalysts with and without addition of a non-surfactant template are presented.Cu/SiO2 and Cu-Zn/SiO2 containing 10 wt% Cu and 5 wt% Zn were prepared by using the one step sol-gel method, under selected pH conditions in order to obtain different metallic copper dispersions (DCu%). The molar ratio TEOS/H2O/C2H5OH was 1/8/6. Copper and Zinc precursors (Cu(NO3)2.3H2O and Zn(NO3)2. 6H2O) were added during hydrolysis step. The catalysts were characterised by specific surface area (SgBET and SgDR), XRD, TPR and N2O dissociative chemisorption. Catalytic activities in methanol transformation were determined in the absence (TDM) and the presence of oxygen (POM). In the last case, a molar ratio O2/CH3OH = 0,6 was used. The values of Sg and DCu% ranged from 492 m2g-1 to 350 m2g-1 and 80% to 7%, respectively. The TPR profiles showed a single reduction peak with maxima between 251 and 270 ºC. XRD patterns of catalysts did not show any signal indicative of CuO or Cu?, except for those with very low DCu% (7 and 13 %).At 230°C, all the catalysts showed to be active in both TDM and POM. From the catalytic results, several facts should be mentioned: (i) the product distribution corresponding to TDM and to POM is noticeable different, being CO2 the main product in the POM and CO in the TDM; (ii) TDM: the catalyst with DCu%?40% showed the best performance, with conversion (XMe) :70% and hydrogen yield (YH2) in the order of 50%; (iii) POM: the catalyst with DCu%?80%, containing very small copper clusters with an estimated average size of ?11 Å, showed a relevant performance, with XMe ? 50%, YH2 ?54% and hydrogen selectivity in the order of 97%, and (iv) under the explored experimental conditions POM seems to be a better option than TDM to produce hydrogen from methanol. Experimental evaluation of these catalysts in steam reforming and oxidative steam reforming of methanol are currently in progress.