Adsorption technology, commercial

Leadbond is an adsorption technology designed to remove heavy metals, particularly lead, from aqueous streams. This technology is typically used for purification of drinking water to remove lead contamination. The vendor states that it is also useful for the treatment of contaminated waste streams where lead removal is essential and where disposal is costly. Leadbond was developed by NoChar, Inc., and is commercially available. 

Table 1. Key Commercial Applications of Gas Separation and Purification by Adsorption Technology...

Low-temperature process Production of relatively pure CO2 stream Both chemical and physical absorption are mature technologies Commercial polymeric membranes are available (polyimide, polysulfone, polyether-polyamide copolymer, etc.) and can be used with an adsorption liquid (e.g. MEA)... 

Aluminas have been in use for many years as adsorbents. First introduced commercially in 1932 by Alcoa for water adsorption [1], activated aluminas have traditionally been known as desiccants for the chemical process industries. As early as 1901, references can be found for the use of synthetic aluminas in the chromatographic purification of biological compounds [2], In recent years aluminas have found widespread usage in applications as diverse as municipal wastes, polymers, and pharmaceuticals. Novel design of these materials is extending their separations capability into even more nontraditional areas of adsorption technology. 

At present adsorption technology is recognized to be the most common technology applied to reach ultra-low sulfur levels for fuel cells applications. Activated carbon is one of the most versatile adsorbents known with high removal efficiency, low costs reusability, and possible product recovery [16,140-155]. However, there are many other commercial adsorbents used for fuels desulfurization at ambient temperature and pressure, such as silica, alumina, zeolites and some metal oxides [156-166]. 

Although reactive adsorption technologies are well proven at lab scale, they still need to be applied commercially for continuous large-scale applications. It is essential to develop new materials for reactive adsorbents with improved chemical and mechanical properties such that they fulfill necessary requirement of matching of operating conditions for both reaction and adsorption. The reusability of an adsorbent for a longer duration with sustainable adsorption capacity is another crucial parameter, which needs to be improved. Also for the processes where more than one contaminant is present in the effluent stream, it is essential to develop multicomponent reactive adsorption systems however the interaction between adsorbates and adsorbent makes the selectivity in reactive adsorption process more complex. 

Adsorptive separation is a powerful technology in industrial separations. In many cases, adsorption is the only technology available to separate products from industrial process streams when other conventional separation tools fail, such as distillation, absorption, membrane, crystallization and extraction. Itis also demonstrated that zeolites are unique as an adsorbent in adsorptive separation processes. This is because zeolites are crystalline soUds that are composed of many framework structures. Zeolites also have uniform pore openings, ion exchange abiUty and a variety of chemical compositions and crystal particle sizes. With the features mentioned, the degree of zeoUte adsorption is almost infinite. It is also noted that because of the unique characteristics of zeoHtes, such as various pore openings, chemical compositions and structures, many adsorption mechanisms are in existence and are practiced commercially. 

The Parex, Toray Aromax and Axens Eluxyl processes are the three adsorptive liquid technologies for the separation and purification of p-xylene practiced on a large scale today. The MX Sorbex process is the only liquid adsorptive process for the separation and purification of m-xylene practiced on an industrial scale. We now consider a few other liquid adsorptive applications using Sorbex technology for aromatics separation that have commercial promise but have not found wide application. 

Ethylbenzene is a high volume petrochemical used as the feed stock for the production of styrene via dehydrogenation. Ethylbenzene is currently made by ethylene alkylation of benzene and can be purified to 99.9%. Ethylbenzene and styrene plants are usually built in a single location. There is very little merchant sale of ethylbenzene, and styrene production is about 30x10 t/year. For selective adsorption to be economically competitive on this scale, streams with sufficiently high concentration and volume of ethylbenzene would be required. Hence, although technology has been available for ethylbenzene extraction from mixed xylenes, potential commercial opportunities are limited to niche applications. 

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