Investigation on gold dispersion of Au/ZrO2 catalysts and activity in the low-temperature WGS reaction

Au/ZrO2 catalysts for LT-WGSR: Active role of sulfates during gold deposition

“…In fact we have recently demonstrated that CO chemisorption performed by a pulse flow system at 157 K on suitably pre-treated samples can be taken as a method for the quantitative determination of the gold sites on Au/ZrO 2 catalysts [7]. Moreover we have recently verified [13] the close connection between chemisorption data and catalytic results in the LT-WGSR, pointing out that Au dispersion in zirconia catalysts is a very important parameter for their preliminary evaluation. Results of pulse flow CO chemisorption measurements for the catalysts object of the present work are reported in Table 2.…”

“…In conclusion, we can remark that the effect of sulfates on zirconium oxide is to increase its surface area and reduce the mean pore size, shifting crystallization processes towards higher temperatures during calcination treatment. Table 2 shows the gold content of the catalysts, while the sulfates amount in the final samples are not reported because no sulfates are present in the final catalysts as previously verified [6,13]. This is not unexpected, as the detachment of sulfate groups occurs during the dp as a consequence of the basic conditions.…”

“…It has been shown that the amount of low coordinated gold sites exposed at the surface of some Au/ZrO 2 systems [7] is up to 10 times higher than the one observed for standard Au/TiO 2 by WGC (World Gold Council). In fact, a very good relationship between catalytic activity and chemisorption data has been evidenced [13], indicating that the chemisorption test is suitable for a preliminary evaluation of the Au/ZrO 2 systems used for the LT-WGSR. We have recently demonstrated [13] that gold supported on sulfated zirconia is more active than the samples on plain zirconia in the LT-WGSR.…”

“…In fact, a very good relationship between catalytic activity and chemisorption data has been evidenced [13], indicating that the chemisorption test is suitable for a preliminary evaluation of the Au/ZrO 2 systems used for the LT-WGSR. We have recently demonstrated [13] that gold supported on sulfated zirconia is more active than the samples on plain zirconia in the LT-WGSR. This higher activity is probably due to a larger surface area of sulfated zirconia that leads to a better dispersion of gold on the surface.…”

“…Then the catalysts were heated again (180 K/h) in a 2% hydrogen/nitrogen mixture (50 mL/min) up to 453 K; once this temperature was reached, the gas feed composition was slowly changed to pure hydrogen (50 mL/min) and after 1 h changed to the feed mixture: [6,13]. The progress of the reaction was followed by gas-chromatographic analysis of the converted mixture at the reactor outlet (packed column Carbosphere, TCD detector, V loop = 1 mL).…”