Higher thermal cracking

Alternatively, thermal cracking of acetals or metal-catalyzed transvinylation can be employed. Vinyl acetate or MVE can be employed for transvinylation and several references illustrate the preparation especially of higher vinyl ethers by such laboratory techniques. Special catalysts and conditions are required for the synthesis of the phenol vinyl ethers to avoid resinous condensation products (6,7). Direct reaction of ethylene with alcohols has also been investigated (8). 

Products from catalytic cracking units are also more stable due to a lower olefin content in the liquid products. This reflects a higher hydrogen transfer activity, which leads to more saturated hydrocarbons than in thermally cracked products from delayed coking units, for example. 

An isopropyl carbocation cannot experience a beta fission (no C-C bond beta to the carbon with the positive charge).It may either abstract a hydride ion from another hydrocarbon, yielding propane, or revert back to propene by eliminating a proton. This could explain the relatively higher yield of propene from catalytic cracking units than from thermal cracking units. 

In the thermal cracking methods, the higher-boiling petroleum fractions like heavy oils are subjected to high temperature and pressure by which the bigger hydrocarbon molecules break down to yield lower-boiling lighter fractions ... 

At the lower temperatures (375 and 400 °C), the n-dodecane conversions is higher with a catalyst. Moreover, the products distributions are very different. This is explained by the cracking mechanisms (free radical and carbocation) and maybe by the supercritical conditions. This is no more the case at 425 °C as the catalysts seem to deactivate rapidly by coking. So the formed products come mainly from the thermal cracking. 

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