Aromatics from short-chain alkanes

1 Fixed-bed reactors 2 Separator for light-boiling compounds 3 Hydrogen recovery 4 Propane/butane recovery 5 Stripping column 

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Several new pathways of zeolite catalysis are offered by ZSM-5 based catalysts [1]. One of their applications is production of aromatics from short-chain alkanes [2]. The presence of metals such as platinum (partly as Pt " ") has been foimd to promote conversion of propane to aromatics [3, 4], although Pt was not the best additive for this purpose. Alkanes with longer carbon chain have also been foimd to form aromatics [5] or skeletal isomers [6] on various Pt-ZSM catalysts. 

Since zeolite catalysts are successfully introduced in the refining and petrochemical industries, it is not surprising that most of the recent advances concern incremental improvements of existing processes with the development of new generations of catalysts (e.g., dewaxing, ethylbenzene and cumene synthesis). The number of newer applications is much more limited, for example, direct synthesis of phenol from benzene and aromatization of short-chain alkanes, etc. However, both the improvement and development of processes contribute significantly to environmental advances. 

While olehos can be obtained industrially by synthesis from shorter molecules, or from functional molecules, aromadc hydrocarbons are not yet produced individually by th two methods. They are produced in a mixture by dehydrocydizadon as part of naphtha catalyuc reforming, and are likely to be produced shortly by the aromatization of short-chain alkanes. 

By contrast, the specific components of crude oil that have been most closely associated with foam behavior reveal radically different chemistry to these simple hydrocarbon chain surfactants. As exemplified by the work of Poindexter et al. [4, 20], those components can be listed as asphaltenes, resins, and waxes. Of these, arguably asphaltenes are the most important. These components are derivatives of polycyclic aromatics, which are distinguished from other crude oil components by insolubility in short-chain n-alkanes such as n-heptane. They are, however, soluble in toluene. Resins are soluble in short-chain alkanes and are therefore usually extracted from crude oil by adsorption onto silica from solution. Both asphaltenes and resins can even each be present in crude oil at concentrations in excess of 15 wt.%. Such extremely high concentrations usually lead to crude oils of high density and high viscosity—so-called heavy crudes (see, e.g., reference [4]). 

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