Irreducible supports

In the catalysis community, it is generally accepted that there are two types of support materials for heterogeneous oxidation catalysts [84]. One variety is the reducible supports such as iron, titanium, and nickel oxide. These materials have the capacity to adsorb and store large quantities of molecules. The adsorbed molecules diffuse across the surface of the support to the catalyst particle where they are activated to a superoxide or atomically bound state. The catalytic reaction then takes place between the reactant molecules and the activated on the catalyst particle. Irreducible supports, in contrast, have a very low ability to adsorb O. Therefore, can only become available for reaction through direct adsorption onto the catalyst particle. For this reason, catalysts deposited on irreducible supports generally exhibit turnover frequencies that are much lower than those deposited on reducible supports [84]. More recent efforts in our laboratory are focused on characterizing catalyst support materials that are commonly used in industry. These studies are aimed at deciphering how specific catalyst and support material combinations result in superior catalytic activity and selectivity. 

Strength and resistance to thermal degradation [86]. Aluminum oxides, however, are generally regarded to be irreducible supports that do not contribute directly to the reactivity of the catalyst. Our experiments were aimed at determining whether or not aluminum oxides, in the absence of gold, are active for the oxidation of CO. 

Jim Griesemer That is Sober s argument for parsimony that there are irreducible assumptions, process assumptions, that you have to put in to construct a cladogram in the first place. Unless he s wrong about that, I don t see that it supports your argument. 

Several factors must be taken into account when the dispersion of iron catalysts prepared by carbonyl complexes is compared to that of conventionally prepared catalysts. The iron loading and the possible formation of irreducible iron phases (by the interaction of Fe or Fe with the support) can determine a low reduction degree for conventionally prepared catalysts with low iron content and a support with high ability to react with the iron cations. In contrast, when catalysts prepared from carbonyl complexes are considered, for a given support the temperature of pre treatment which defines the hydroxyl population of the surface is a main aspect to be taken into account. For Fe/Al203 catalysts prepared from iron carbonyls and reduced after impregnation at a moderate temperature (573 K), the extent of... 

In the following example, we examine the role of different gases and metal-support interactions in metal-particle catalysts supported on the so-called nonwetting or irreducible ceramic oxides by dynamic EM. The direct observations provide powerful insights into the role of gas environments in catalytic reactions and in the regeneration of supported metallic catalyst particles. 

In situ ETEM studies of metal-irreducible ceramic support interactions... 

In situ ETEM permits direct probing of particle sintering mechanisms and the effect of gas environments on supported metal-particle catalysts under reaction conditions. Here we present some examples of metals supported on non-wetting or irreducible ceramic supports, such as alumina and silica. The experiments are important in understanding metal-support interactions on irreducibe ceramics. 

In a more technical vein, Miller excitedly announced that some components of IC biochemical systems I discuss have other roles in the cell, such as the ciliary proteins tubulin and dynein.11 But I myself pointed that out when I first wrote Darwin s Black Box ten years ago For example, in Chapter 3 I wrote that microtubules occur in many cells and are usually used as mere structural supports, like girders, to prop up cell shape.12 Furthermore, motor proteins also are involved in other cell functions, such as transporting cargo from one end of the cell to another. Nonetheless, I emphasized that such other roles don t help with the irreducible complexity of the cilium an evolutionary story for the cilium must envision a circuitous route, perhaps adapting parts that were originally used for other purposes to build a cilium. And I went on to show why indirect routes are quite implausible.13 Toothpicks do not... 

From this, we may conclude that while reducible supports perform best, gold on irreducible ceramic oxides still shows a modicum of activity providing that the particles are small enough the reaction then proceeds solely on the gold without any assistance from the support. 

Ette (9) introduced the concept of model stability that allows the pharmacometri-cian to ensure that the covariates retained in the final irreducible model are those supported by the data. The steps in this process are as follows ... 

Let us now consider the diagrams which contribute to 2( q, — q f) they consist of a series of [-irreducible sub-diagrams supporting the wave vector q, and of side branches. These side branches dress the I-irreducible sub-diagram constituting the diagram axis. Thus, l( q, -q,f) can be written in the form... 

These are of two kinds (i) those of moderate character, experienced by very small metal particles on ceramic (i.e. irreducible) oxides having various acid/base characters, and (ii) strong interactions (SMSI) where the support is partially reduced, or a reducible component has been added, and the metal is decorated by species of indeterminate type, stemming from the support. These effects have been outlined in Section 2.6 their consequences for the reactions of higher alkanes will now be considered. The last shall be first. 

Regarding the increased deactivation rates and irreversible nature of the deactivation [26,27] at higher vol % added H2O levels, the cause may be due to cobalt surface reoxidation effects [25,28], oxidation involving the formation of irreducible cobalt support complexes (e.g., cobalt silicates) [29], or pore collapse or breakdown leading to encapsulation of cobalt clusters [9], or a combination of phenomena. As pointed out by Krishnamoorthy et al. [5] and... 

---