Catalyst supports zirconia

The leaching of catalyst components into the aqueous phase during the reaction represents a possible disadvantage of the process. Therefore, the choice of catalyst support materials has to be limited to those that exhibit long-term hydrothermal stability (e.g. carbon, titania, zirconia). 

Bimetallic Ni-based catalysts were also studied for SR of higher hydrocarbons in order to avoid the carbon formation and sulfur poisoning problems of conventional Ni catalysts.Murata et prepared a series of bimetallic catalysts by adding alkali and alkaline-earth metals to Ni catalyst supported on zirconia and alumina for SR of i-Cg and methylcyclohexane (MCFI). The performance of various bimetallic catalysts for SR of i-Cg and MCH are summarized in Figures 21a and 21b, respectively. It was reported that the stability of Ni/Zr02 is considerably improved by the addition of alkaline-earth metals (M), particularly strontium, to the catalyst with an M/Ni ratio of 0.5 by... 

There is an obvious overlap among various applications categories. An example of the overlap is alumina which is both a structural refractory ceramic as well as a catalyst support. The additives modify the interconversion of various AI2O3 phases and the high surface area of y-Al203 is maintained by the added 3 wt% ceria or lanthana. Additives like yttria stabilize zirconia with respect to inertness and mechanical stability. Addition of yttrium or lanthanide to Fe-Cr-Al alloys reduces the spallation of oxide film. 

High purity binary oxides such as BeO, MgO, AI2O3, Ti02, And stabihzed zirconia are sintered under pressure to produce high density ceramic ware, particularly cracibles and other containers for use in nonferrous metallurgy and other specialized applications where temperature resistance and corrosion are a problem. Titania is also formed in honeycomb arrays for use as catalyst supports. 

Amorphous Ni-(40-x) at% Zr-x at% RE (x = 0, 1, 5 and 10 RE = Y, Ce and Sm) alloy ribbons of about 1 mm width and about 20 pm thickness were prepared by a single-roUer melt spinning method. The structure of the alloys prepared was confirmed by X-ray diffraction with Cu K radiation. The amorphous alloy ribbons were oxidized at 773 K in air for 5 hours and then reduced at 573 K imder flowing hydrogen for 5 hours. During this treatment the amorphous aUoys transformed to nickel catalysts supported on zirconia or zirconia-rare earth element oxides. 

The nano-grained nickel catalysts supported on zdrconia or zirconia-rare earth element oxides are prepared by the oxidation-reduction pretreatment of amorphous Ni-Zr-rare earth element alloys. The conversion of carbon dioxide to methane on the catalyst prepared from amorphous Ni-40Zr alloy is improved by the addition of 5 at% or more rare earth elements (Y, Ce and Sm). 

Enache, D.I., Roy-Auberger, M., and Revel, R. Differences in the characteristics and catalytic properties of cobalt-based Fischer-Tropsch catalysts supported on zirconia and alumina. Applied Catalysis. A, General, 2004, 268, 51. 

Also, Marsh and co-workers [145] showed that gold on cobalt oxide particles, supported on a mechanical mixture of zirconia-stabilised ceria, zirconia and titania remains active in a gas stream containing 15 ppm SO2. Haruta and co-workers [207] found that although the low-temperature CO oxidation activity of Ti02-supported Au can be inhibited by exposure to SO2, the effect on the activity for the oxidation of H2 or propane is quite small. Venezia and co-workers [208] reported that bimetallic Pd-Au catalysts supported on silica/alumina are resistant to sulphur poisoning (up to 113 ppm S in the form of dibenzothiophene) in the simultaneous hydrogenation of toluene and naphthalene at 523 K. 

The support, zirconia (ISA), was supplied by the Norton Company. The oxide was grounded and sieved to a particle size ranged from 0.16 to 0.25 mm, and calcined at 773 K. Its surface properties, 63.3 m g of specific surface and average pore diameter of 8.60 nm, were determined from the nitrogen adsorption isotherms. The catalysts were prepared by adsorption from solution and/or impregnation of precursor(s), ruthenium nitrosyl nitrate (Alfa) and hexachloroplatinic acid (Aldrich), onto the support. Being zirconia isoelectric point 6.5 (determined by electrophoresis [17] using a Malvern Instrument Zetasizer 4) the precursors solution pH value was kept sufficiently low to enable the desired adsorption of complex metal anions. 

The chemical composition of the different catalysts investigated are collected in Table 1. Also the sulfur contents calculated for complete conversion to Zr(S04)2 are indicated. The experimental sulfur contents are lower than the calculated values. The reaction of the silica-supported zirconia with gaseous sulfur trioxide is therefore not complete and the reaction of zirconium hydroxide and zirconia with sulfuric acid involves only a limited fraction of the zirconia. As to be expected, the specific surface area of the catalyst prepared from zirconium hydroxide is much larger than that of the other catalysts. The catalyst based on calcined zirconia exhibited the X-ray diffraction pattern of zirconia and the catalyst based on zirconium hydroxide showed broadened reflection of zirconia. The bulk water-free zirconium sulfate did not display an X-ray diffraction pattern after exposure to ambient air (relative humidity 50 to 60%) for two weeks the sharp X-ray diffraction pattern of Zr(S04)2-4H20 appeared [1]. 

Thermogravimetry indicated a continuous weight loss of the sulfated sihca supported zirconia of only about 3 %. The thermogravimetric data on the catafysts prepared by reaction of zirconia with suUuric acid were more informative (see also ref. [12]). When the temperature was raised with 10 K/min, the catalyst prepared by reaction with calcined zirconia showed a much more smooth weight loss, which set on already at about 350 K. Apparently, it is much more difficuh to remove the constituents of sulfuric acid out of the much more porous structure of the zirconium hydroxide. 

In the present work, the performance of different palladium catalysts supported on cerium-modified zirconia has been studied for the oxidation of methaiK in air, alone and in the presence of SO2. This conqwund has been chosen because it is very commonly present in gaseous emissions. On the other hand, in previous works it was found the effect of other reduced sulphur compounds on Pd catalysts was very similar [6]. 

Synthesis and characterization of nanostructured mesoporous zirconia catalyst supports using non-ionic surfactants as templating agents... 

A synthesis protocol of porous zirconia catalyst support, through a neutral Ci3(EO)6-Zr(OC3H7)4 assembly pathway has been developed. Our studies evidenced the role played by the surfactant. It has also been observed that the increase of hydrothermal treatment time and temperature have a benefical effect on tailoring the pore sizes. The synthesized materials will be used in preparation of Au / ZrOz, Au / VO / ZrOz catalysts, which will be tested in the benzene oxidation reaction. Thermogravimetric analysis shows that the recovered zirconia present a relatively low thermal stability. Then the structure collapses due to the crystallization to more stable tetragonal and monoclinic phase. 

Pure zirconia itself can also serve as a catalyst support, although it yields catalysts with very low activity, in part because of low porosity. Amorphous zirconia can stabilize a small amount of Cr(VI) during calcination, which produces polymer when exposed to ethylene. Figure 130 shows the MW distributions of polymers obtained with Cr/zirconia activated at 500 °C, and tested under the same reaction conditions as the Cr/Zr-silica examples described above. Cr/zirconia produces very high-MW polymer, quite different from Cr/silica-zirconia. This... 

It can be concluded that the modification of SBA-15 supports with Z1O2 species results in high-performance NiMo catalysts for hydrodesulfurization of hindered dibenzothiophenes. Zirconia loading in the catalyst support leads to an increase in the dispersion of oxidic Mo species and promotes the HYD pathway of 4,6-DMDBT hydrodesulfurization. 

A NOVEL THRIFTED PALLADIUM-ZINC CATALYST SUPPORTED ON CERIA STABILISED ZIRCONIA FOR USE IN THREE-WAY VEHICLE EXHAUST CATALYSIS... 

The preparation of sulphated zirconia designed for catalyst supports was studied by Boutonnet et al. . Zirconia prepared in microemulsion showed a pure tetragonal structure compared with zirconia prepared by an impregnation -precipitation procedure which also contained monoclinic phase. Platinum-promoted sulphated zirconia catalysts were prepared both in anionic and non-ionic microemulsions. Furthermore, the catalytic activity and selectivity for the isomerization of hexanes were tested. The catalysts produced by the microemulsion method showed a higher selectivity towards isomers but a lower activity when compared to catalysts prepared by impregnation technique. More recently, a study of zirconia synthesis from micro and macroemulsion systems has been conducted . Spherical ZrOa particles ranging from tens of nanometers to a few micrometers were produced. 

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