Catalysts alumina/zirconia

In the mid-1950s, alumina-silica catalysts, containing 25 percent alumina, came into use because of their higher stability. These synthetic catalysts were amorphous their structure consisted of a random array of silica and alumina, tetrahedrally connected. Some minor improvements in yields and selectivity were achieved by switching to catalysts such as magnesia-silica and alumina-zirconia-silica. 

Together with the fast oxidation (at low temperatures) of NO to N02, the plasma causes the partial HC oxidation (using propylene, the formation of CO, C02, acetaldehyde and formaldehyde was observed). Both the effects cause a large promotion in activity of the downstream catalyst [86]. For example, a "/-alumina catalyst which is essentially inactive in the SCR of NO with propene at temperatures 200°C allows the conversion of NO of about 80% (in the presence of NTP). Formation of aldehydes follows the trend of NO concentration suggesting their role in the reaction mechanism. Metal oxides such as alumina, zirconia or metal-containing zeolites (Ba/Y, for example) have been used [84-87], but a systematic screening of the catalysts to be used together with NTP was not carried out. Therefore, considerable improvements may still be expected. 

As already published in the literature, sol-gel associated to supercritical drying always gives highly developed and divided materials which can have many applications in heterogeneous catalysis. Addition of a small part of Y2O3 to silica, alumina, zirconia, and titania revealed a beneficial effect on the thermal resistance of these materials. However, it is difficult to compare our results to those already published because in our work, the volumetric ratio of precursor to solvent (1/1) was much higher than the one generally used by other authors on the one hand, and on the other hand, we never added any catalyst, either acidic or basic, contrary to most of the works recently described in the literature. 

Conversion of Isophorone to Metaxylenol is a well documented reaction in the patent literature. Activity and life-time of three eatalytic systems Alumina, Zirconia and Thoria with or without variable level of Chromia doping have been studied in the present work. For Zirconia and Thoria doping with Chromia results in remarkable enhancements in catalytic activities, but for alumina, the effect is less pronounced. In all these cases, there is cin optimum level of Chromia doping theat results in maximum efficiency. Although high initial activities are obsereved with all these catalysts, the rates of deactivation are fast in all cases. Spectroscopic and other physico-chemical measurements have been carried out on these catlysts. A nationalisation of the observed activities is offered on the basis of such physico-chemical data... 

Here we describe the effect of chromia doping on three different catalysts viz. alumina, zirconia and thoria. The basis for choosing these catalysts and using chromia as a doping are two fold. First literature references clearly indicate that the first two materials when doped with chromia are active for the above mentioned reaction. Thoria whose thermal stability, high selectivity in dehydration reactions are well documented, was tried to compare the activities of acidic catalysts with that of an amphoteric one.(7 8)... 

Initial conversion is very high in all the cases, but conversion at the 24th hour are different for different catalyst. Obviously this is due to the difference in deactivation rate of each sample. Fig.l shows difference in activity for each of the carrier viz. Alumina, Zirconia and Thoria. 

Similarly 5% chromia was doped on Zirconia and Thoria. After doping chromia it was found that the catalyst activity has been enhanced. The Fig.2 shows the results effect of addition of chromia doping on all the carriers viz. Alumina, Zirconia and Thoria. 

Solid catalysts active in MPVO reactions have surface basicity or Lewis acidity. They include, amongst others, alumina, zirconia, magnesium oxide, and magnesium phosphates. More recent developments include the chemical anchoring of catalytically active co-ordination complexes, and the application of hydrotalcites, mesoporous materials (MCM-41), and zeolites. Anchoring of co-ordination compounds might open the route to true heterogeneous enantioselective MPVO reactions. As a result of their inherent shape-selectivity zeolites uniquely afford remarkable stereoselectivity in MPVO reactions. 

A double metal oxide sulfate solid superacid (alumina-zirconia/ persulfate, SA-SZ) can be prepared by treatment of a mixture of aluminum hydroxide and zirconium(IV) hydroxide with an aqueous solution of ammonium persulfate, followed by calcination at 650°C. This catalyst can be efficiently utilized in the benzoylation of arenes with benzoyl and parfl-nitrobenzoyl chloride (Table 4.22), giving BPs in interesting yields. Even if 1 g of catalyst is needed for 40 mmol of chloride, the process seems to be quite useful because the catalyst can be readily regenerated by heating after washing with acetone and diethyl ether and reused four times. 

Titania with alumina, zirconia, or stannic oxide produces a steady increase in the yield of sodium sulfate with increasing time of reaction. Stannic oxide with either zirconia, alumina, or thoria has fairly high initial activity but is quickly quenched with very little conversion occurring after a few hours. Thoria with zirconia shows a definite initial inhibition with a fair increase in activity after the induction period. Zinc oxide inhibits the activity of titania. Likewise, the combination of thoria with alumina shows very little promise as a catalyst towards the Hargreaves reaction. 

The early type of catalytic cracking units involved the use of a fixed-bed operation and this type of processing has been largely supplanted by the fluid- and moving-bed types of operation. The catalysts are used in the form of powder, microspheres, spheres, and other preformed shapes. The catalysts employed are either synthetic silica-alumina composites or natural aluminosilicates. Other catalysts, such as silica-magnesia, alumina-boria, silica-zirconia, and silica-alumina-zirconia have found limited commercial application and, at present, the synthetic silica-alumina and natural clay catalysts dominate the field. 

Catalytic Cracking of Hexadecane Temperature 500°C. Catalyst silica-alumina-zirconia Pressure atmospheric Process Period 1 Hour... 

The topic of ionic Hquids, however, has been limited to ionic liquids on silica and titania surfaces and more research work is necessary to gain more insight into ionic liquids on other type of surfaces. Surfaces that serve as catalyst supports, such as alumina, zirconia, in addition to silica and titania, may be of further interest. 

Apart from the degree of reduction affecting overall performance, the nature of the support is also crucial in determining final activity. For supported molyb-dena catalyst, alumina and titania support materials provide best performance. Silica, zirconia, chromia, and zinc oxide are also good support materials, although they produce less active catalysts. Inactive catalysts can be readily synthesized by supporting molybdena upon cobalt oxide, nickel oxide, magnesium oxide, or tin oxide. To date, no correlation between the acidity of the support material and cataljdic activity has been found (304). 

Our research conducted at Cincinnati have been primarily focused on sol-gel synthesis of alumina, zirconia, titania and silica. These metal oxides not only are commonly used as adsorbent or catalyst support but also have recently emerged as excellent materials for ceramic membranes. The objective of this article is to report synthesis and properties of these sol-gel derived adsorbent materials with emphasis on development of a sol-gel granulation method and the properties of the sol-gel derived granular adsorbents. 

Platinum catalysts are superior for hydrocarbon oxidation [350]. Platinum is usually present as metaDic platinum at temperatures exceeding 400 °C [351]. Besides alumina, zirconia, molecular sieves and metal oxides are applied as supports, amongst others. However, an inhibition effect of oxygen was observed over platinum/alumina for light hydrocarbons [350,352] and other platinum-containing catalysts for methane [353] and propane oxidation [354]. This effect becomes problematic, in particular because full hydrocarbon conversion is usually required for a catalytic burner. The temperature control of catalytic burners also becomes difficult, because this is frequently carried out by regulation of the air feed flow rate to suprastoichiometric values. 

Another catalyst system found in the patent literature involves the deposition of halides such as zirconium tetrachloride, vanadium tetrachloride, titanium tetraiodide, or oxyhalides such as chromium oxychloride or vanadium oxychloride on a finely divided particulate inorganic substrate having surface hydroxyl groups. Among such solids are alumina, zirconia, silica (particularly a pyrogenic silica such as Cab-O-SiF ), or a carbon black such as channel black or furnace black. A toluene slurry of this material is added, under dry nitrogen, to a toluene solution of A -vinyl-pyrrolidone containing a small amount of triisobutylaluminum. After 24 hr at 80°C, a 25% yield of polymer is produced [73]. 

Yan XM, Kwon S, Contreras AM, Koebel MM, Bokor J, Somoijai GA (2005) Fabrication of dense arrays of platinum nanowires on silica, alumina, zirconia and ceria surfaces as 2-D model catalysts. Catal Lett 105 127-132... 

The oxygen content of automotive exhaust gases is measured by zirconia. Alumina is the carrier for combustion catalysts. Alumina also insulates the electrodes of a hot spark plug. Chromia prevents superalloys from burning up in an aircraft turbojet. 

Studied [269,272,273], Both ZSM-5 catalysts emerge as the best catalysts with the highest yields of hydrocarbon products and lowest coke formation [269], The aromatics yield tends to decrease in the order ZSM-5 >H-beta>H-mordenite>H-ferrierite/HY [273], Stefanidis et al. demonstrated that, in comparison to a range of amorphous catalysts such as alumina, zirconia/ titania, and magnesium oxide, ZSM-5 is more suitable for the reduction of undesirable compounds and production of aromatics in the upgrading of pyrolysis vapors from beech wood [274], The excellent performance of ZSM-5 is attributed to the important role of its medium pore size [269], Besides, Park et al. pointed out that ZSM-5 is more efficient than Y zeolites due to the proper distribution of strong acid sites [275],... 

Kaewpengkrow, P., Atong, D., Sricharoenchaikul, V., 2014. Catalytic upgrading of pyrolysis vapors from Jatropha wastes using alumina, zirconia and titania based catalysts. Bioresource Technology 163, 262—269. 

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