Separation technologies/processes zeolite applications

Zeolites are used massively in industrial catalysis, ion-exchange processes, separation technologies, and as desiccants. Summarize briefly the attributes allowing these different applications. 

As documented in Chapter 5, zeolites are very powerful adsorbents used to separate many products from industrial process steams. In many cases, adsorption is the only separation tool when other conventional separation techniques such as distillation, extraction, membranes, crystallization and absorption are not applicable. For example, adsorption is the only process that can separate a mixture of C10-C14 olefins from a mixture of C10-C14 hydrocarbons. It has also been found that in certain processes, adsorption has many technological and economical advantages over conventional processes. This was seen, for example, when the separation of m-xylene from other Cg-aromatics by the HF-BF3 extraction process was replaced by adsorption using the UOP MX Sorbex process. Although zeolite separations have many advantages, there are some disadvantages such as complexity in the separation chemistry and the need to recover and recycle desorbents. 

Chapter 7 gives a review of the technology and applications of zeolites in liquid adsorptive separation of petrochemical aromatic hydrocarbons. The application of zeolites to petrochemical aromatic production may be the area where zeolites have had their largest positive economic impact, accounting for the production of tens of millions of tonnes of high-value aromatic petrochemicals annually. The nonaromatic hydrocarbon liquid phase adsorption review in Chapter 8 contains both general process concepts as well as sufficient individual process details for one to understand both commercially practiced and academic non-aromatic separations. 

Today the melt crystallization can be advantageously replaced by a more challenging separation method known as simulated moving bed (SMB) technology. The method exploits the differences in affinity of zeolitic adsorbents for p-xylene with respect to other A8 components. Despite the name, the adsorbent phase is stationary and only fluid phase is distributed in a cyclic manner by a multivalve system. Operation parameters are temperatures of 125 to 200 °C and pressures up to 15 bar. Lighter (toluene) or heavier solvents (p-diethylbenzene) may be used as a desorbent. The Parex process working on this principle today has many applications. 

Changing economic scenarios and available processing options often compel a refiner to pursue resid processing. Due to the varied properties of resid feeds, the refiner must carefully consider the choice of available FCC catalyst technology. This paper reviews novel matrix and zeolite technologies for resid processing applications to obtain better coke selectivity, gas selectivity and bottoms upgrading. Commercial experience and mechanism of separate particle vanadium traps to control vanadium deactivation is also reviewed. 

Thus, Volume 7 of the series Molecular Sieves - Science and Technology presents descriptions, critical analyses, and illustrative examples of applications of the most important methods for investigations of sorption and sorption kinetics in zeolite systems and related materials. The editors hope that the volume will be helpful for researchers as well as technologists who are confronted with the important phenomena of adsorption and diffusion in microporous materials as they occur, for instance, in separation processes and catalysis. 

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