Adsorbents rejuvenation

IR spectroscopy is the most widely used technique to characterize catalysts and molecules adsorbed on them. It has been successfully applied to dispersed catalysts as well as to planar model catalyst. Comprehensive reviews by Sheppard and De la Cruz (18,19), Hoffmann (17), Chabal (161), and others (162) describe the basics, technical aspects, and applications of the technique to a variety of catalysts (considering, for example, catalyst preparation, activation and rejuvenation, and the state of the catalyst during the course of a catalytic reaction). The reader is referred to these reviews for details here, we focus on recent developments and high-pressure applications. 

In this study it was found that dissociation of CO2 and CH4 is an elementary step in the CO2 reforming of methane and that an active site for the dissociation of CO2 and CH4 (eqns. (1) and (2)) is metallic Ni on the KNiCa catalyst. Ni surface of KNiCa/ZSI catalyst was mostly occupied by adsorbed C and O species as intermediates during the reaction. Surface reaction of these species produced carbon monoxide and simultaneously rejuvenated nickel species (eqn. (5)), which was considered to be rate-determining step under the following reaction scheme. 

The catalyst s life in industrial processes may extend from a month to a year of more i.e., the catalyst is active for this period, after which it becomes necessary to remove it from the reactor and replace it with fresh material or otherwise to recondition it chemically. However, it is relatively common practice to rejuvenate catalysts periodically by removing deposits, piHsons, or other adsorbed and undesirable materials. This is usually accomplished by passing air, steam, or other reactivating gas over the... 

John Gyann in his US Patent (4,764,384, 1988) proposed a blend of amorphous silica, synthetic amorphous magnesium silicate, diatomaceous earth and synthetic silica alumina for rejuvenating spent frying oil. In this invention, the inventor claims that the adsorbent would remove some free fatty acids and other oil breakdown products. It does not clearly specify if the adsorbent also removes the soap that is formed during adsorption due... 

The surface of the ZnO adsorbs an H2S molecule, an S atom exchanges with an O atom, and H2O desorbs from the surface. The surface is rejuvenated by reaction with oxygen. 

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