Supported Oxide Catalysts

This reaction is first conducted on a chromium-promoted iron oxide catalyst in the high temperature shift (HTS) reactor at about 370°C at the inlet. This catalyst is usually in the form of 6 x 6-mm or 9.5 x 9.5-mm tablets, SV about 4000 h . Converted gases are cooled outside of the HTS by producing steam or heating boiler feed water and are sent to the low temperature shift (LTS) converter at about 200—215°C to complete the water gas shift reaction. The LTS catalyst is a copper—zinc oxide catalyst supported on alumina. CO content of the effluent gas is usually 0.1—0.25% on a dry gas basis and has a 14°C approach to equihbrium, ie, an equihbrium temperature 14°C higher than actual, and SV about 4000 h . Operating at as low a temperature as possible is advantageous because of the more favorable equihbrium constants. The product gas from this section contains about 77% H2, 18% CO2, 0.30% CO, and 4.7% CH. ... 

High Density Polyethylene. High density polyethylene (HDPE), 0.94—0.97 g/cm, is a thermoplastic prepared commercially by two catalytic methods. In one, coordination catalysts are prepared from an aluminum alkyl and titanium tetrachloride in heptane. The other method uses metal oxide catalysts supported on a carrier (see Catalysis). 

Fig. 1. Examples of the kinetic curves during ethylene polymerization by chromium oxide catalysts. Support—SiOs temperature—80°C polymerization at constant ethylene pressure in perfect mixing reactor. Curve 1—catalyst reduced by CO at 300°C. Curve 2— catalyst activated in vacuum (400°C) polymerization in the case of (1) and (2) in solvent (heptane) ethylene pressure 10 kg/cm2 02 content in ethylene 1 ppm, HsO 3 ppm. Curves 3, 4, 5, 6—catalyst activated in vacuum (400°C) polymerization without solvent ethylene pressure 19 (curve 3), 13 (curve 4), 4 (curve 5), and 2 (curve 6) kg/cm2 02 content in ethylene 1 ppm, HsO = 12 ppm.

Suppose you prepared an iron oxide catalyst supported on an alumina support. Your aim is to use the catalyst in the metallic form, but you want to keep the iron particles as small as possible, with a degree of reduction of at least 50%. Hence, you need to know the particle size of the iron oxide in the unreduced catalyst, as well as the size of the iron particles and their degree of reduction in the metallic state. Refer to Chapters 4 and 5 to devise a strategy to obtain this information. (Unfortunately for you, it appears that electron microscopy and X-ray diffraction do not provide useful data on the unreduced catalyst.)... 

Process Miniaturization Second International Conference, CATTECH, December 1998 Steep progress in microelectronics in the past key players topics of IMRET 2 general advantages of micro flow energy, safety, process development, combinatorial catalyst testing, lab-on-a-chip biological applications anodically oxidized catalyst supports as alternatives to non-porous supports [220]. 

Mikroreaktoren sind so klein wie ein Fingerhut, Handdsblatt, May 1998 Steep progress in microelectronics, sensor and analytical techniques in the past transport intensification for catalysis first catalytic micro reactors available partial oxidation to acrolein partial hydrogenation to cyclododecene anodically oxidized catalyst supports as alternatives to non-porous supports study group on micro reactors at Dechema safety, selectivity, high pressure exclusion of using particle solutions limited experience with lifetime of micro reactors [236],... 

Ataloglou T., Vakros J., Bourikas K., Fountzoula C., Kordulis C., and Lycourghiotis A. 2005. Influence of the preparation method on the structure-activity of cobalt oxide catalysts supported on alumina for complete benzene oxidation. Appl. Catal. B Environ. 57 299-312. 

Textural mesoporosity is a feature that is quite frequently found in materials consisting of particles with sizes on the nanometer scale. For such materials, the voids in between the particles form a quasi-pore system. The dimensions of the voids are in the nanometer range. However, the particles themselves are typically dense bodies without an intrinsic porosity. This type of material is quite frequently found in catalysis, e.g., oxidic catalyst supports, but will not be dealt with in the present chapter. Here, we will learn that some materials possess a structural porosity with pore sizes in the mesopore range (2 to 50 nm). The pore sizes of these materials are tunable and the pore size distribution of a given material is typically uniform and very narrow. The dimensions of the pores and the easy control of their pore sizes make these materials very promising candidates for catalytic applications. The present chapter will describe these rather novel classes of mesoporous silica and carbon materials, and discuss their structural and catalytic properties. 

The degradation of the B02 was conducted by using iron oxide catalyst supported on cerium oxide as a heterogeneous Fenton catalyst in the presenee of H2O2. The effect of the... 

The focus of these studies has been on identifying mild activation conditions to prevent nanoparticle agglomeration. Infrared spectroscopy indicated that titania plays an active role in dendrimer adsorption and decomposition in contrast, adsorption of DENs on silica is dominated by metal-support interactions. Relatively mild (150° C) activation conditions were identified and optimized for Pt and Au catalysts. Comparable conditions yield clean nanoparticles that are active CO oxidation catalysts. Supported Pt catalysts are also active in toluene hydrogenation test reactions. 

Waugh et al.131 discussed the selective oxidation of benzene to maleic anhydride on the basis of a detailed study of maleic anhydride and benzene adsorption on a V-Mo oxide catalyst supported on a-Al203. Hydroquinone is found to be an intermediate in this reaction and p-benzoquinone, formed from the hydroquinone, is the main intermediate in the non-selective pathway. The maleic anhydride is observed to be immobile adsorbed and the surface oxidation reaction has a relatively low activation energy. From this the authors conclude that it is not lattice oxygen but weakly bound molecular 02 which is responsible for the selective oxidation and a detailed mechanism, in which use is made of orbital symmetry arguments, is presented. 

A recent in situ Mossbauer study (124) of a mixed tin-platinum oxide catalyst supported on zinc aluminate at 500°-600°C indicated the presence of tin(IV), tin(II), and an alloy of tin and platinum in the active catalyst. Changes in the nature of the tin species with time and temperature were correlated with the catalytic activity of the material. 

Fig. 24. Phololuminescence speclrum and its excitation spectrum of the vanadium oxide catalyst supported on AI2O3 (vanadium oxide/Al20i) at 4.2 K. Excitation wavelength, 300 nm emission monitored at 520 nm [reproduced with permission from Hazenkamp (130)].

I lG. 27. Yields of the photoluniinescciice (phosphorescence) spectra of molybdenum oxide catalysts supported on SiOj (molybdenum oxide/SiO,) (O) and the rate of the metathesis reaction of QH6 ( ) on the catalysts at 473 K (pressure of QH6, 4 kPa) [reproduced with permission from Ono el al. (75S)]. 

Fig. 41. Sterii-Volmer plots of o/4> values for the quenching by various molecules of the phosphorescence of the vanadium oxide catalyst supported on SiO (vanadium oxide/ SiO 0.03 V wt%) prepared by an impregnation method data taken at 298 K [reproduced with permission from Anpo et at (//6)].

Strength (FLS) empirical approach are discussed in Section 3 as methods for determining the molecular structures of metal-oxide species from their Raman spectra. The state-of-the-art in Raman instrumentation as well as new instrumental developments are discussed in Section 4. Sampling techniques typically employed in Raman spectroscopy experiments, ambient as well as in situ, are reviewed in Section S. The application of Raman spectroscopy to problems in heterogeneous catalysis (bulk mixed-oxide catalysts, supported metal-oxide catalysts, zeolites, and chemisorption studies) is discussed in depth in Section 6 by selecting a few recent examples from the literature. The future potential of Raman spectroscopy in heterogeneous catalysis is discussed in the fmal section. 

Thermostable yttria-doped inorganic oxide catalyst supports for high temperature reactions... 

It has been found that lead oxide catalysts supported on basic carriers such as MgO or B -AloOj exhibit excellent activity and selectivity for the oxidative coupling of methane. Lattice oxygen is proved to be responsible for the formation of C hydrocarbon. 

The same reaction was attempted in the presence of oxygen by Wang et al. The reaction is conducted at 350 °C with acetone/methanol/02/N2 feed rates of 1.5/1.5/5.0/15.0 mL/min over various metal oxide catalysts supported on fluoro tetrasilicic mica. Over the Ti02 catalyst, the main products are methyl vinyl ketone, methyl ethyl ketone, and methyl acetate. The yields are 9.8, 0.023, and 1.3 mol%, respectively, at an acetone conversion of 11.6 the selectivity to methyl ethyl ketone is 85 mol% based on acetone. 

In this work the catalytic activity of a series of copper oxide catalysts supported on monolithic honeycomb supports in the reduction of nitrogen oxide with propylene in an oxidising atmosphere was studied. The monoliths were produced from acid washed sepiolite, sepiolite or a mixture of sepiolite and alumina in order to study the effect of the support on the activities and selectivities of the catalysts. Tlie introduction of nickel oxide as a second active species on the overall activity was also detennined. Finally tlie application of an alumina washcoat impregnated with the copper and nickel salts to increase the accessibility of tlie gases to be treated to the active phase was studied. 

Chromium oxide catalysts, supported on AI2O3 and activated by LiAlH4, have been claimed to cause ROMP of cycloalkenes but the yields are low (Eleuterio 1957). Cr(CO)3(mesitylene) initiates the polymerization of alkynes, possibly via a metallacyclobutene intermediate (Farona 1974 Woon 1974) see Ch. 10. 

The stability of chromium oxide catalysts supported on Ti02 and AI2O3 was examined at various feed concentrations of PCE from 30 to 10,000 ppm as shown in Fig. 1. The activity... 

Scheme 2 Perruthenate oxidation catalyst supported on an ion-exchange resin...

In addition to the Wacker oxidation catalysts, supported eutectic molten salt CuCl/KCl-based catalyst systems have also been examined for other processes including, for example, production of synthesis gas from methanol for the use as on-board hydrogen production in vehicles [57] and quantitative combustion of chlorinated hydrocarbons to COx and HCI/CI2 at ambient pressure (200-500 °C) with silica-based systems [58,59]. 

The literature contains many other studies of supported oxides by adsorption microcalorimetry, and in particular oxides used for propane or isobutane dehydrogenation such as chromia supported on Z1O2 [121] or Y-AI2O3 [122], or Ca-doped chromium oxide catalysts supported on Y-AI2O3 [123]. 

Biomimetic oxidation catalysts supported on inorganic matrices. 

Alex Zletz of Standard Oil of Indiana (later, Amoco) was actually the first to disclose (patent filed 28 April 1951) the use of a transition metal catalyst for the production of highly linear (what came to be called high density) polyethylene HDPE, using a molybdenum oxide catalyst supported on alumina. The polymer density was 0.96. 

Tetrahydrofuran is obtained as byproduct of the hydrogenation of succinic anhydride on nickel-rhenium catalyst. The hydrogenation of y-butyrolactone to 1,U-butanediol is conducted at 250°C and 100 bar the presence of a nickel-cobalt-thorium oxide catalyst supported on silica. Slurry reactors have been used up to now for these hydrogenations, as it is often the case when new processes are extrapolated from small pilot plant or laboratory data, the more so as the actual capacities (a few thousands tons per year)are rather small. 

In the synthesizer (fig. 1), the water sample is reacted with calcium carbide in a steel chamber under vacuum conditions to produce acetylene. Any water vapor associated with the evolved acetylene is eliminated by trapping in an iso-propyl alcohol and dry ice bath. Further purification in the acetylene is accomplished by a phosphorous pentoxide-ascarite column. The acetylene is collected as a solid in a liquid nitrogen cooled trap and sublimed directly onto a vanadium oxide catalyst supported by an alumina substrate where polymerization to pure benzene is accomplished. The pure benzene is isolated from the catalyst column by heating at 90 degrees Celsius under vacuum and trapping the pure benzene as a solid in a dry-ice... 

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