Catalyst examples

There is an enormous volume of Hterature available on the appHcations for supported catalysts. Examples are compiled here based on important synthesis methods and industrial uses. The organization is according to specific reactions and appHcations rather than according to catalyst type. 

The above described experiments over atomically clean single crystal catalysts have been extended to studies of the kinetics of various catalytic reactions over chemically modified catalysts. Examples are recent studies Into the nature of poisoning by sulfur of the catalytic activity of nickel, ruthenium, and rhodium toward methana-tlon of CO (11,12) and CO2 (15). ethane (12) and cyclopropane (20) hydrogenolysls, and ethylene hydrogenation (21). 

But not only the (in)activity can suggest the identity of the catalyst. Examples reported recently point to a distinction taking into account the selectivity behaviour. 

An important synthesis method of organogermanes is the hydrogermylation of olefinic and acetylenic derivatives in the presence of a catalyst. Examples of such reactions are listed below38 ... 

As mentioned above, MPVO catalysts are very selective towards carbonyl compounds. Alkenes, alkynes or other heteroatom-containing double bonds are not affected by these catalysts, while they can be reduced by transition-metal catalysts. Examples of the reduction of a,/ -unsaturated ketones and other multifunctional group compounds are compiled in Table 20.3. 

So far, no reference has been made to the presence of more than one phase in the reactor. Many important chemicals are manufactured by processes in which gases react on the surface of solid catalysts. Examples include ammonia synthesis, the oxidation of sulphur dioxide to sulphur trioxide, the oxidation of naphthalene to phthalic anhydride and the manufacture of methanol from carbon monoxide and hydrogen. These reactions, and many others, are carried out in tubular reactors containing a fixed bed of catalyst which may be either a single deep bed or a number of parallel tubes packed with catalyst pellets. The latter arrangement is used, for exjimple, in the oxidation of ethene to oxiran (ethylene oxide)... 

Symmetrical a-diketones can be prepared in comparable yields by reaction of the acyl halide with hexabutylditin in the presence of the Pd(II) catalyst. Example ... 

Homoallyl methyl ethers.4 Trityl perchlorate catalyzes a reaction of allyltri-methylsilanes with dimethyl acetals or ketals to form homoallyl methyl ethers in 60-90% yield. Diphenylboryl triflate is a somewhat less efficient catalyst. Example ... 

An important group of surface-active nonionic synthetic polymers (nonionic emulsifiers) are ethylene oxide (block) (co)polymers. They have been widely researched and some interesting results on their behavior in water have been obtained [33]. Amphiphilic PEO copolymers are currently of interest in such applications as polymer emulsifiers, rheology modifiers, drug carriers, polymer blend compatibilizers, and phase transfer catalysts. Examples are block copolymers of EO and styrene, graft or block copolymers with PEO branches anchored to a hydrophilic backbone, and star-shaped macromolecules with PEO arms attached to a hydrophobic core. One of the most interesting findings is that some block micelle systems in fact exists in two populations, i.e., a bimodal size distribution. 

Alkylation and animation ofallylie phosphates.6 Allyl diethyl phosphates undergo efficient allylie alkylation and animation in the presence of this Pd(0) catalyst. Examples ... 

If correlations do exist for simple metals, predictions are much more difficult for composite materials. On the other hand, cathode activation has two aims (i) to replace active but expensive materials with cheaper ones, and (ii) to enhance the activity of cheaper materials so as to approach or even surpass that of the more expensive catalysts. In the case of pure metals there is little hope to find a new material satisfying the above requirements since in the volcano curve each metal has a fixed position which cannot be changed. Therefore, activation of pure metals can only be achieved by modifying its structure so as to enhance the surface area (which has nothing to do with electrocatalysis in a strict sense), and possibly to influence the mechanism and the energetic state of the intermediate in the wanted direction. This includes the preparation of rough surfaces but also of dispersed catalysts. Examples will be discussed later. 

Zapf A, Beller M (2002) Fine chemical synthesis with homogeneous palladium catalysts examples, status and trends. Top Catal 19 101-109... 

Cas in the catalyst volume. Some systems require derivation of several balances. For example, the balance of bulk or lattice oxygen Cas.v can be included into consideration along with the balance of surface species for the oxide catalyst (Example 4). 

XRD is valuable because it provides unambiguous determinations of phases, their dynamics, and evidence of their structures at the nanoscale, even at high pressures and temperatures. This technique is still not frequently applied for characterization of functioning catalysts, but the advent of ultra-high-brilliance radiation sources such as free-electron lasers and improved synchrotron sources will open new possibilities for determination of time-resolved XRD patterns to establish details of the temporal evolution of structural dynamics and of the nanostructures of functioning catalysts. Examples in this chapter illustrate the value of the method for characterization of mixed oxide catalysts, such as those containing molybdenum oxide structures. 

By contrast, the sulfonation of anthraquinone requires oleum and no more than two sulfonic acid groups can be introduced. In this system, sulfonation in the a-position requires the use of HgO as a catalyst. Examples of the... 

This chapter is concerned with the improvement of catalyst performance through a better pellet design. This design relates to the physical properties of the catalyst pellets for given kinetics and does not involve the chemical composition of the catalyst. Examples are given to illustrate the influence of structural parameters on catalyst performance. 

Polymerisation reactions in ionic liquids have so far focused on processes that do not involve a transition metal catalyst. Examples include acid-catalysed/34"361 free-radical,[37 50] electrochemical19,51"551 and laser1561 induced polymerisation reactions and a review is available on the topic.1571... 

Ballester, Vidal-Ferran, and van Leeuwen evaluate concepts and strategies in the field of supramolecular catalysis. The authors describe what characterizes supramolecular catalysts, formulating a definition on the basis of the nature of interactions between catalyst and substrate or between building blocks of the catalyst. Examples are cited that demonstrate how supramolecular catalysts are superior to simple molecular catalysts in a broad range of reactions. Ballester et al. consider supramolecular catalysts as enzyme models, guided in their comparisons by the various mechanisms by which enzymes accelerate chemical transformations such as the binding of a reactant next to the catalytic site, the simultaneous complexation of two reactants, or desolvation. Addressing the synthesis of supramolecular catalysts, the authors describe how... 

As described above, most industrial catalysts are mixed oxides of at least two oxide phases, because catalyst performance is greatly improved by mixing different oxides, according to be following mechanisms (i) stabilization, (ii) control of redox properties, (iii) creation of acidity and basicity, (iv) control of electronic and coordination state of the metal ion, and (v) combination of more than two frinctions to evolve acid-oxidation and acid-base bifrinctional catalysts. Examples are provided in the following sections. 

Although several research groups have been interested in transition metal enolates to use the metal centre as a potential site of asymmetry in the design of chiral catalysts, examples of well defined redox reaction involving middle to late transition elements and lanthanides are scarce in the literatnre. Based on Pearson s theory of hard and soft acids and bases", it has been proposed that combining a hard ligand with a soft late transition metal centre may lead to weak metal-heteroatom links, resnlting in reactive late metal-heteroatom bonds. 

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