Subject catalyst support

Poisoning of deNOx catalysts by SO2 could also be a problem since diesel fuels contain small amounts of sulfur compounds. Only a few studies deal with this subject [11-13]. It appears from the literature that for Cu catalysts the use of MFI as a support reduces the inhibition by SO2. Support effects also appear in the case of Co since Co/MFI is much less sensitive to SO2 than Co/ferrierite [13]. Since this support effect may be related to acidity, it becomes important, to investigate the influence of SO2 on the properties of Cu catalysts supported on Si02, AI2O3, MFI, BEA and unpromoted or sulfate promot Ti02 and Zr02- These latter have been reported active for deNOx [14]. 

In this study we examine the generalities in reductive alkylation however, since the subject is vast, we limited ourselves to the interaction of aromatic and aliphatic primary amines and diamines with ketones. The ketones examined include the cyclic ketone, cyclohexanone, and aliphatic ketones such as acetone, and methyl isobutyl ketone (MIBK). We limited our study to sulfided and unsulfided Pt and Pd catalysts supported on activated carbon that were commercially available from Evonik Degussa Corporation. 

Concerning the Fischer-Tropsch synthesis, carbon nanomaterials have already been successfully employed as catalyst support media on a laboratory scale. The main attention in literature has been paid so far to subjects such as the comparison of functionalization techniques,9-11 the influence of promoters on the catalytic performance,1 12 and the investigations of metal particle size effects7,8 as well as of metal-support interactions.14,15 However, research was focused on one nanomaterial type only in each of these studies. Yu et al.16 compared the performance of two different kinds of nanofibers (herringbones and platelets) in the Fischer-Tropsch synthesis. A direct comparison between nanotubes and nanofibers as catalyst support media has not yet been an issue of discussion in Fischer-Tropsch investigations. In addition, a comparison with commercially used FT catalysts has up to now not been published. 

Another gemstone in the portfolio of rational carbon synthesis is nitrogen-doped carbons. Recently, they became the subject of particular interest to researchers due to their remarkable performance in applications such as C02 sequestration [22], removals of contaminants from gas and liquid phases [23], environmental protection [24], catalysts and catalysts supports [25], or in electrochemistry as supercapacitors [26], cells and batteries to improve stability and the loading capacity of carbon. 

The development of mesoporous materials with more or less ordered and different connected pore systems has opened new access to large pore high surface area zeotype molecular sieves. These silicate materials could be attractive catalysts and catalyst supports provided that they are stable and can be modified with catalytic active sites [1]. The incorporation of aluminum into framework sites of the walls is necessary for the establishment of Bronsted acidity [2] which is an essential precondition for a variety of catalytic hydrocarbon reactions [3], Furthermore, ion exchange positions allow anchoring of cationic transition metal complexes and catalyst precursors which are attractive redox catalytic systems for fine chemicals [4]. The subject of this paper is the examination of the influence of calcination procedures, of soft hydrothermal treatment and of the Al content on the stability of the framework aluminum in substituted MCM-41. The impact on the Bronsted acidity is studied. 

Figure 13 Schematic of ceramic catalyst support subjected to inertia, back pressure, and frictional forces. (From Ref. 44, courtesy of SAE.)...

The catalyst support is subjected to mechanical loads dunng manufacture, during canning, and in service. It must have sufficient strength to sustain these stresses without the onset... 

In the earliest catalysts, two basic support configurations were used. The first was thermally stable alumina in the form of cylindrical pellets or spheres, typically 3 mm in diameter, that had for several decades been used in the chemical processes industry, such as petroleum refining. The second type of catalyst support was the so-called monolith, made from metal, as described in this chapter, or a ceramic material such as cordierite (2MgO 2Al203 5Si02) the subject of the previous chapter. The monolith has strong thin... 

In certain cases the surface of the support may be pre-modified to either increase or decrease its absorptive capacity. Techniques for the former have been thoroughly explored in the area of anchoring homogeneous catalyst complexes and metal clusters. Since this subject has been amply reviewed we will not discuss it further. These techniques primarily involve pre-treatment of the support surface with a compound that can serve as a bridging ligand. Techniques for decreasing the absorptive capacity are also of importance and these will be covered later in greater detail when we come to consider metal location on a catalyst support. 

Three aspects of the performance of supported catalysts are also discussed in this Chapter. With the development of techniques, as outlined above, for the characterization of supported metal catalysts, it seems timely to survey studies of crystallite size effect/structure sensitivity with special reference to the possible intrusion of adventitious factors (Section 5). Recently there has been considerable interest in the existence of (chemical) metal-support interactions and their significance for chemisorption and catalytic activity/ selectivity (Section 6). Finally, supported bimetallic catalysts are discussed for various reactions not involving hydrocarbons (hydrocarbon reactions over alloys and bimetallic catalysts have already been reviewed in this Series with respect to both basic research and technical applications ). References to earlier reviews (including some on techniques) that complement material in this Chapter are given in the appropriate sections. It might be useful, however, to note here some topics not discussed that also form part of the vast subject of supported metal and bimetallic catalysts and for which recent reviews are available, viz, spillover, catalyst deactivation, the growth and... 

The distributions of cis and trans structures in the array of products are subject to wide variations that are characteristic of each of the transition metal catalysts. The nature of the catalyst support is of minor concern as long as the support is not an active catalyst in its own right. A single sequence of reaction steps common to all transition metals is envisaged. Product variability is associated with significant differences in the relative rates of successive steps in the reaction path. Productcontrolling steps may occur early or late. 

Other and quite noticeable effects are also obtained in the activity of the catalyst by the use of certain supporting materials. Tims, a nickel catalyst supported on alumina is subjected to an effect similar to that of a protective colloid or a colloidal sol in that the reduced nickel is able to withstand higher temperatures without sintering or loss in activity and... 

The specific surface area and pore volume of the catalyst support was determined by nitrogen adsorption using a Sorptomatic 1900 (Carlo Erba Instruments). Increase in the calcination temperature fi-om 973 to 1173 K resulted in a decreased surface area fi-om 184 to 81 m /g (Figure 2). The pore volume was also decreased fi-om 0.41 to 0.18 mVg. The support sintering was studied by subjecting the support prepared at 1173 K to steam (12 vol% water in nitrogen) at 1073 K for 8 h. The N2-physisorption data indicated that the water vapor treatment resulted in a decrease of the BET specific surface area of ca. 9% as well as in closure of the pores smaller than 5 nm in diameter. The alkali content of the silica is probably the main contributor to the loss of surface during the hydrothermal treatment [6]. 

Many studies report the effect of porosity and surface area on metal dispersion and catalytic activity. Linares-Solano et al. [10] prepared platinum catalysts supported on a graphitized carbon black (V3G), which was subjected to various degrees of activation in air to increase the surface area. They observed that as the surface area of the parent sample increased from 62 m /g to 136 m /g,... 

In addition to its use as a catalyst support (see Chapter 4), carbon can find applications as a catalyst on its own. Activated carbon catalysts have long been used in the production of phosgene [1,2] and sulfur hahdes [3], The corresponding technologies seem to be well established, although the mechanistic details are not known in detail [4], The only recent pubhcation on this subject concerns the reduction of the by-product carbon tetrachloride using Sibunit (a carbon material developed at the Boreskov Institute of Catalysis) instead of the coconut shell-based activated carbon catalyst [5],... 

The subject of soluble polymers as supports in catalysis has been discussed in a number of recent reviews [ 1-5]. These other reviews each focused on a particular polymer or groups of polymers or on some aspect of catalysis (e.g., organic catalysis or asymmetric synthesis) [2, 3, 6-8]. Soluble polymers use as supports in synthesis has also been reviewed, but this topic is not covered below because in synthesis the polymer is used in a stoichiometric amount and is generally not recyclable [5,9-11]. This review takes a general approach, focusing on soluble polymers used as catalyst supports. It discusses these supports within a context of the separation strategies that could be or were used to separate or recover the soluble polymer-bound catalyst from the products. This review emphasizes examples from the last few years where soluble polymers are used but includes, for completeness, earlier examples if a particular... 

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