Activated alumina

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

Water transfer coefficient in adsorptive porous body

Abstract: Water transport in wet porous materials is expressed as the simultaneous transport of adsorbed water, capillary water and water vapor. The sum of the surface flow coefficient and the liquid water transfer coefficient is defined as the water transfer coefficient in this paper. The water transfer coefficient was measured by a modified method which is a kind of constant-volume method for adsorption equilibrium. An activated alumina whose pores are fine was used as the experimental material. Based on the water transfer model previously proposed by the authors, the observed dependence of the water transfer coefficient on water content and temperature were successfully interpreted.

Preparation of catalyst for purifying exhaust gas

Abstract: PURPOSE:To develop a catalyst excellent in the removal effect of NOx, CH and CO in exhaust gas, by adhering a composition prepared by compounding a ceria powder with an activated alumina powder having Ce preliminarily contained therein to the surface of a monolithic carrier substrate before supporting a noble metal such as Pt, Rh or Pd. CONSTITUTION:A granular carrier comprising activated alumina such as gamma- alumina or delta-alumina immersed in an aqueous cerium nitrate solution and, after drying, the impregnated carrier is baked at 600 deg.C to prepare a carrier containing 1-5% of CeO2 as a metal. In the next step, an alumina sol and a ceria powder are mixed with the obtained powdery carrier in a predetermined ratio and crushed by a ball mill. In this case, the ceria powder is added to the alumina layer in a range of 5-50%. This alumina-containing solution is adhered to a monolithic carrier substrate and baked at 650 deg.C while the obtained baked one is allowed to support at least one noble metal such as Pt, Rh or Pd before baking. By this method, a catalyst excellent in the removal efficiency of NOx, HC and CO in the exhaust gas of an engine is obtained.

Improved catalyst compositions and methods of making same

Abstract: A method of making a catalyst composition comprising an activated alumina coating stabilized against thermal de­gradation includes applying a coating of alumina having one or more platinum group metal catalytic components dispersed thereon onto a carrier substrate and calcining the coating. The calcined coating is then impregnated with a solution of a thermal stabilizer-precursor and calcined again to provide a thermal stabilizer in the alumina. Bulk ceria, optionally an aluminum-stabilized bulk ceria, may also be added to the composition, preferably at specified minimum levels, includ­ing a high purity bulk ceria on which one or more non-rhod­ium platinum group metal catalytic components, e.g., platin­um, optionally, are dispersed. A separate aspect of the in­vention provides for a method of making a catalyst composi­tion including dispersing one or more platinum group metal catalytic components on an activated alumina and calcining the combined alumina and platinum group metal catalytic components. The steps are carried out under limited acidi­fication conditions whereby at least minimum dispersions of the platinum group metal catalytic components are attained. The invention also provides for catalyst compositions re­sulting from either or both the foregoing methods.

Process for producing dimethyl ether

Abstract: A process for producing dimethyl ether, which includes dehydrating methanol in vapor phase in the presence of an activated alumina catalyst having an average pore radius of 2.5 nm to 8.0 nm both inclusive and having a sodium oxide content of 0.07 wt % or less. This invention provides a process for producing DME with an improved conversion ratio using a highly active DME-production catalyst.

Treating gases by pressure swing adsorption - with two superimposed layers of different adsorbent materials

Abstract: A pressure swing method for selectively adsorbing and removing one or more target components from a gas mixt. with alternating regeneration of the adsorbens is performed in two stages, using two layers of different adsorbent materials. The first stage adsorbs the target component at high concn. and reduces the co-adsorption of other components. The residual target component is adsorbed by a second material having lower adsorbing capacity than the first material both for that component and for the other components. Esp. for removing CO2 and water vapour from air, with zeolite as the first material and activated alumina as the second material, forming 25-80 (50) vol.% of the combined total layers. High efficiency is obtd. with a reduced quantity of adsorbent material and a small unit size.