Heterogeneous Having properties

Derivatives of hemicellulose components have properties similar to the ceUulosic equivalents but modified by the effects of thek lower molecular weight, more extensive branching, labile constituents, and more heterogeneous nature. Acetates, ethers, carboxymethylxylan (184), and xylan—poly(sodium acrylate) (185) have been prepared. 

Product-related substances are molecular variants of the desired product formed during manufacture and storage, which are active and have no deleterious effect on the safety and efficacy of the drug product.2 Many recombinant protein products are inherently heterogeneous, mixtures of closely related structures or product variants. These variants possess properties comparable to the desired product and are not considered impurities. It is only when they do not have properties of the desired product that their presence is problematic. 

Holzwarth et al. (51) reported the synthesis and IR thermographic-imaging screening of a 37-member, focused discrete heterogeneous catalyst library L6 for oxidations and reductions. The library was prepared using sol-gel solution synthetic protocols (47, 51) to produce the library individuals as amorphous microporous mixed oxides (AMMs), which have previously shown heterogeneous catalytic properties (54, 55). The scaffolding metal oxides contained either Ti (subset 1, Fig. 11.7) or Si (subset 2), and many active metal components were used. The complete structure of L6 is reported... 

Two or more substances—elements, compounds, or both—can combine physically to produce a mixture. A mixture can be separated into its components by physical means. Mixtures are physical combinations of substances that have properties related to those of their components but that do not have definite compositions. They can be either heten eneons or homc eneons mixtures. In heterogeneous mixtures, two or more different types of matter can be seen to be present with the naked eye or a good optical microscope. Homogeneous mixtures, also called solutions, look alike throughout, even under a microscope. 

The rapid development of catalysis by soluble transition metal complexes and the results of surface science studies afford useful insights into the mechanisms of heterogeneous catalysis. - The surface of a metallic particle presents an array of atoms differing in coordination number which depends on the atom s location on a terrace, step or kink. The spectroscopy of adsorbed reactants and intermediates have properties which suggest structural relationships to organometallic compounds and, presumably, their reactions are analogous. - ... 

It can be seen that there exists a relationship between yf and The very high values of -yf correspond to talc samples treated under moderate conditions. These values and the rather low morphology index clearly indicate, as we already know, that the talc is rather heterogeneous having lateral and base surfaces of totally different adsorption properties. As the treatment conditions become more severe, i. e. as the amount of deposited silica becomes more and more important, the 7 decrease whereas the morphology indexes increase the average talc surface becomes more and more smooth on the molecular level. 

Inherent in the homogeneous system, however, are drawbacks relating to catalyst solubility hmitations and the loss of expensive Rh metal due to precipitation in the separation sections. Therefore, inmiobilization of the Rh complex on a support has been the topic of significant research as its heterogeneous catalyst properties. Moreover, Chiyoda and UOP have jointly developed a heterogeneous Rh catalyst system for the methanol carbonylation process to produce acetic acid [14-16]. 

Citrate-derived monometallic Pt and bimetallic Pt tAujo. colloidal particles have been prepared and adsorbed onto graphitic supports their adsorptive and catalytic properties are considered as is the wider applicability of this preparative route to heterogeneous catalysts. It appears that P Au,(x,.j dispersed bimetallic particles have properties which are very close to those of bulk materials and therefore that colloidal preparative routes to mono- and bi-metallic catalysts are very promising. However, the cleanliness of surfaces needs to be considered as does the extent of surface emiclunent caused by the method of preparation. 

Generally speaking, heterogeneous mixtures themselves do not have distinguishing properties of interest. Only the individual components have properties that define them. Because the components in homogeneous mixtures (solutions) are uniformly mixed together, properties of the mixtures themselves may be important Therefore, most of our discussion of mixtures will deal with solutions. 

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