The catalytic activities of the samples were studied in a U-shaped fixed-bed quartz reactor. A Bruker gas chromatograph (model 450-CG) was used for analysis. Catalytic activity tests were carried out with step heating from 200 to 550 ºC with steps every 50 ºC. The temperature was maintained at each step for 30 min at a heating ramp of 5ºC/min.