Activated alumina

About: Activated alumina is a research topic. Over the lifetime, 1430 publications have been published within this topic receiving 31090 citations.

Exhaust gas purification catalyst

Abstract: PURPOSE:To prevent the formation of an alloy with Pd and Rh or Pt when used at high temperature and thereby prevent performance deterioration by forming a layer which does not contain precious metal components between a layer containing Pd and a layer containing Pt and/or Rh. CONSTITUTION:The subject catalyst is composed of the first layer containing Pd and activated alumina, the second layer containing activated alumina which does not contain precious metal, and the third layer containing Rh and/or Pt and activated alumina on monolithic carrier base as a catalyst for exhaust gas purification. Thus, the mutual action between Pd, and Pt and/or Rh is prevented by an intermediate layer which does not contain precious metal, so that the production of an alloy during use at high temperature is restricted. Subsequently, catalytic performance deterioration is minimized.

Catalyst-supported particulate filter

Abstract: In a particulate filter, a catalyst layer containing Pt-carried activated alumina particles, CeZr-based mixed oxide particles and ZrNd-based mixed oxide particles is formed, the proportion of the total amount of the CeZr-based mixed oxide particles and the ZrNd-based mixed oxide particles in the total amount of the Pt-carried activated alumina particles, the CeZr-based mixed oxide particles and the ZrNd-based mixed oxide particles is 10% to 60% by mass, both inclusive, and the mass ratio of the CeZr-based mixed oxide particles to the ZrNd-based mixed oxide particles is 20/80 to 80/20, both inclusive. This configuration enhances the particulate burning property and the low-temperature exhaust gas conversion efficiency.

Removal of cyanide in aqueous solution by oxidation with hydrogen peroxide in presence of activated alumina

Abstract: This work is dedicated to the removal of free cyanide from aqueous solution by oxidation with hydrogen peroxide H2O2 catalyzed by neutral activated alumina. Effects of initial molar ratio [H2O2]0/[CN−]0, catalyst amount, pH, and temperature on cyanide removal have been examined. The presence of activated alumina has increased the reaction rate showing thus, a catalytic activity. The rate of removal of cyanides increases with rising initial molar ratio [H2O2]0/[CN−]0 but decreases at pH 10 to 12. Increasing the alumina amount from 1.0 to 30 g/L has a beneficial effect, and increasing the temperature from 20 °C to 35 °C improves cyanide removal. The kinetics of cyanide removal has been found to be of pseudo-first-order with respect to cyanide and the rate constants have been determined.

Catalytic conversion of C6-alkanes over Pd/Al2O3 catalysts: The effect of support acidity

Abstract: A comparable study of catalytic conversion of two C6-alkanes (n-hexane and 2,2-dimethybutane) has shown several analogies in the catalytic behavior of a series of differently loaded, chlorine-free Pd/Al2O3 catalysts. Different sample pretreatments have been used to modify the catalytic behavior. The catalytic performance of lowly reduced (at 573 K) samples of Pd/Al2O3 catalysts is similar to that exhibited by unsupported or silica-supported palladium, i.e. the predominance of metal-catalyzed reactions is observed with high hydrogenolysis selectivity and a bond-shift mode of isomerization. Highly reduced (at 873 K) samples experience a serious increase in overall activity, and simultaneously, big enhancement of isomerization selectivity (at ≤563 K), in agreement with previous reports [1] , [2] , [3] . At the same time, the activity is strongly correlated with the amount of activated alumina in the catalyst and only insignificantly dependent on Pd content in the catalyst. TPD of ammonia has been employed to confirm expected changes in the acidity generated by various catalyst pretreatments. It is considered that Lewis acidity of alumina, increased upon high temperature reduction (HTR), is a source of enhanced isomerization activity exhibited by Pd/Al2O3 catalysts. However, a palladium-free alumina cannot serve as efficient catalyst in alkane hydroconversion. Metallic function is needed to provide active hydrogen for a hydrogenative desorption of rearranged hydrocarbon species from acid sites of γ-Al2O3.