CHEMICALS FROM HIGH MOLECULAR WEIGHT n-PARAFFINS

High molecular weight n-paraffins are obtained from different petroleum fractions through physical separation processes. Those in the range of C₈-C₁₄ are usually recovered from kerosines having a high ratio of these compounds. Vapor phase adsorption using molecular sieve 5A is used to achieve the separation. The n-paraffins are then desorbed by the action of ammonia. Continuous operation is possible by using two adsorption sieve columns, one bed on stream while the other bed is being desorbed. n- Paraffins could also be separated by forming an adduct with urea. For a paraffinic hydrocarbon to form an adduct under ambient temperature and atmospheric pressure, the compound must contain a long unbranched chain of at least six carbon atoms. Ease of adduct formation and adduct stability increases with increase of chain length. Table 1.1 shows some physical properties of C₅-C₁₆ n-paraffins. As with shorter-chain n-paraffins, the longer chain compounds are not highly reactive. However, they may be oxidized, chlorinated, dehydrogenated, sulfonated, and fermented under special conditions. The C₉-C₁₇ paraffins are used to produce olefins or monochlorinated paraffins for the production of detergents. The 1996 capacity for the U.S., Europe, and Japan was 3.0 billion pounds.

Table 1.1 : Selected properties of n-paraffins from C₅-C₁₆