Showing papers by "Zi Gao published in 1998"

New catalyst of SO 4 2− /Al2O3–ZrO2 for n-butane isomerization

Abstract: The catalytic behavior of Al-promoted sulfated zirconia for n-butane isomerization at low temperature in the absence of H2 and at high temperature in the presence of H2 was studied. The addition of Al enhances the activity and stability of the catalysts for reaction at 250°C and in the presence of H2 significantly. After on stream for 120 h, the n-butane conversion of the catalyst containing 3 mol% Al2O3 keeps steadily at 88% of its equilibrium conversion and no observable trend of further deactivation has been observed. The difference in behavior of the promoted and unpromoted catalysts at low and high temperature is associated with a change of reaction mechanism from bimolecular to monomolecular. Experimental evidence is presented to show that the promoting effect of Al is different from that of the transition metals. Microcalorimetric measurements of NH3 adsorption on catalysts reveal that the remarkable activity and stability of the Al-promoted catalysts are caused by an enhancement in the number of acid sites effective for the isomerization reaction.

Benzoylation of toluene with benzoyl chloride on Al‐promoted sulfated solid superacids

Abstract: The catalytic performance of Al‐promoted sulfated zirconia and sulfated titania for benzoylation of toluene with benzoyl chloride has been investigated The incorporation of Al enhances the catalytic activity of the sulfated oxide catalysts prominently owing to an increase in superacidity of the catalysts Al‐promoted sulfated zirconia catalysts are more active than the analogous sulfated titania catalysts because of their higher superacidity In particular, SO42-–/3%Al2O3–ZrO2 is a good clean catalyst for the benzoylation reaction, which gives 100% yield of methylbenzophenones after on stream for 12 h at 110 °C

Catalytic combustion of n-pentane on Pt supported on solid superacids

Abstract: The combustion of n-pentane on Pt supported on sulfated zirconia-based solid superacids has been studied. The combustion activity is related with the Pt dispersion of the catalyst and the acid strength of the support. Chemisorption of n-pentane on the catalysts has been investigated by means of infrared spectroscopy. The formation of alkane carbocations on the surface sulfates during reaction may account for the enhancement of the combustion activity by the strong acidity of the supports.

Catalytic activities and properties of AlHMS mesoporous molecular sieves

Abstract: AlHMS with Si/Al ratio in the range 4.6–31.0 were synthesized by the neutral templating route using hexadecylamine as template. Similar to AlMCM-41, AlHMS molecular sieves have high surface area, uniform mesopores and high thermal stability. Acid sites are generated directly by calcining the as-synthesized materials. The acid strengths of the weak and strong acid sites on AlHMS are close to those on HY zeolite, but the number of acid sites is less. AlHMS catalysts are active for acid-catalyzed reactions, such as cumene cracking and isopropanol dehydration. They are more catalytically active than HY for 1,3,5-tri-tert-butylbenzene dealkylation due to facilitation of the diffusion of the bulky reactant and product molecules. AlHMS-supported NiO catalysts show good activities for thiophene hydrodesulfurization.