Wax gelation obstructs the flow of oil and the hindrance is dependent upon the size, shape, number of wax crystals - paraffin composition parameters - as well as the total wax concentration. In other words, the basestocks with the same physical properties can have different wax compositions hence their pumpability characteristics may not be equal.

The latter, however, can make themselves known in having unequal low temperature engine oil pumpability properties. The basestocks produced by these divergent pathways may have the same physical properties - i.e., viscosity at 40☌, viscosity index, and pour point - and yet be different mixtures of desirable hydrocarbons.

The refinery unit operations can be combined to manufacture basestocks by four pathways. This hydrocarbon molecular selectivity is predicated upon vapor pressure or molecular weight/structure, i.e., vacuum pipestill, chemical bond strengths, i.e., hydrocracking, solubility, i.e., solvent dewaxing/extraction, and molecular shape/chemical bond strengths, i.e., catalytic dewaxing. The refinery unit operations take into account the chemical and physical properties of the hydrocarbons that are present in the crude oil. Basestocks are desirable mixtures of hydrocarbons in which the undesirable components are weeded out by refinery separation and conversion sciences. The wax composition is determined by the basestocks used in the formulation and its impediment to oil flow is reduced by additives. Octane is increased by the cracking and isomerization of olefins produced by the base cracking catalyst.A key element in low temperature engine oil pumpability is wax, and in particular its composition and behavior. FCC additives of the ZSM-5-type are effective for increasing gasoline octane due to their low activity for hydrogen transfer. Also discussed are improvements in processing schemes, including hydrodesulfurization before or after MDDW, and MDDW of cycle oils from catalytic = molar ratio greater than 500. 84 with the original catalyst produces a constant-octane gasoline, since it operates at an almost constant temperature and produces, rather than consumes, hydrogen in most applications. The improved catalyst gives a higher gasoline yield, at the expense of C/sub 3/'s and C/sub 4/'s produces 88-91 research octane number clear gasoline, compared with approx. The improved MDDW catalyst requires frequent temperature adjustments during the first few weeks on stream, after which an equilibrium temperature is reached and only small temperature increases are needed to compensate for slow coking of the catalyst. Improvements in the Mobil distillate dewaxing (MDDW) process which involves selective cracking of wax inside the pores of a ZSM-5 catalyst, greatly reduce the reactivation requirements and increase the yield of more valuable products.

Dewaxing process of light gas oil