STRUCTURE SENSITIVITY OF CO2 HYDROGENATION REACTION CATALYZED BY PT CARBON CATALYSTS

Structure sensitivity of CO2 hydrogenation reaction catalyzed by Pt/ca rbon and Pt-M/carbon (M = Ca, Mg) catalysts has been studied. Catalyti c activity experiments have been carried out by TPR (temperature progr ammed reaction). Various techniques like H-2-TPD (hydrogen temperature programmed desorption), TEM (transmission electron microscopy), and X RD (X-ray diffraction) have been used to study the evolution of platin um particles structure. The effects of a heat treatment at high temper ature (1200 K) under different atmospheres and the catalyst reduction conditions on the catalytic activity and on the catalyst structure hav e been analyzed. The results of catalytic activity in relation to part icle size have been analyzed with the concept of reaction dimension. T he results show that CO2 hydrogenation catalyzed by carbon-supported p latinum catalysts is highly sensitive to the structure of the platinum particles. The reaction dimension obtained is close to 0.06. A heat t reatment to high temperature (1200 K) produces a large increase in act ivity. This behavior has been explained considering that at these temp eratures, carbon atoms can dissolve in platinum producing a change in the structure, as a result of which the number of active sites increas es noticeably.