Activated alumina

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

Role of Brønsted acid centres for alkene double bond migration over alumina at temperatures above 450 K

Abstract: Water was added to alumina samples following their activation in vacuo at both 723 and 1023 K. Reactions of [2H0]propene and of CD2CH—CH3 were then studied on these catalysts. Adsorption of water (2.7 × 1018 molecule m–2) at ∼300 K is molecular and serves only slightly to poison catalytic activity at ∼300 K. Adsorption of water at > 453 K occurs dissociatively and completely poisons those sites on the fresh catalyst surface which promote reactions at ∼300 K. Reaction of propene occurs on such a water poisoned catalyst at ∼483 K and proceeds with incorporation of D+(from D2O) through an associative mechanism involving carbonium ions, in contrast to a dissociative mechanism at a reaction temperature of 300 K on an unpoisoned catalyst. Water “added-back” to activated alumina at > 453 K is therefore effective in producing Brϕnsted acid centres on the surface and it is suggested that residual hydroxyls, those left following activation, can also participate in carbonium ion formation from propene at > 453 K. Therefore, not only is the activity of alumina strongly influenced by its activation temperature but it is also determined by the temperature used for subsequent alkene catalysis.

High temperature-resistant activated alumina material and preparation method thereof

Abstract: The present invention provides a high temperature-resistant activated alumina material and a preparation method thereof. The alumina material is prepared by the following steps: mixing macroporous pseudo-boehmite, high viscosity pseudo-boehmite and an additive by using water; uniformly stirring at a rotation speed of 100-1000 r/min; adding dilute nitric acid with a concentration of 30% to carry out a reaction until the pH value is 2.0-5.5 and the solution is at the peptization state, and then aging for 3-6 hours at a temperature of 80-100 DEG C while stirring; adding a pore-forming agent at a room temperature, and carrying out uniform stirring, pulping, spraying and drying; and carrying out calcination at a temperature of 900 DEG C to prepare the alumina. The alumina material of the present invention has advantages of convenient mass production, high specific surface, and the like, wherein the specific surface of the alumina material of the present invention can be maintained more than 110 m /g for a long time at a temperature of 1000-1100 DEG C. In addition, the preparation method of the alumina material has characteristics of simple process and low cost.

Catalyst for redn. of nitrogen oxides in effluent gases - using gaseous ammonia, comprises metal oxide on activated alumina

Abstract: Catalyst for ren. of N oxides is industrial combustion gases with gaseous ammonia is selected from CuO and Fe2O3 and can be combined with an active alumina carrying Cr2O3. The catalyst system is pref. preliminarily treated with N2 or air contg. 50-2000 ppm SO2 at 200-450 degrees C, whereby the redn. of catalytic activity caused by moisture is eliminated (alternatively, the effluent gases may contain 50-1400 ppm SO2). The catalytic activity is stabe even at high temps. This catalyst system is cheaper than prior art systems.

Mode D'elimination de composes organiques polaires par une alumine activee γ‐Al2O3 en milieu aqueux. Comparaison avec le charbon actif.

Abstract: Batch experiments carried out on dilute solutions of organic acids (oxalic, maleic, benzoic and salicylic acids, humic substances) showed that activated alumina γ‐Al2O3 removed these solutes from water. The removal of organic acids was optimum in an acid medium (4 < pH < 6) and was significantly affected by the presence of inorganic anions. Filtration experiments showed competitive fixation of organic acids on γ‐Al2O3. Activated alumina could be regenerated by sodium hydroxide solutions but an important loss of efficiency of the filters was observed for the salicylic acid removal during 5 exhaustion‐regeneration cycles. A comparative study showed clearly that granular activated carbon (F400) had higher adsorptive capacities and was a better support for bacterial growth than activated alumina y‐A12O3.