Catalytic isomerization dewaxing

Catalytic isomerization dewaxing on the other hand preferentially isomerizes the paraffins, reducing the diesel pour point and cloud point while keeping the high-cetane components in the diesel product. It also favourably decreases the boiling range of the fuel (T95) and produces a higher mid distillate yield. 

Shell has produced group HI base stocks with Vis greater than 145 at their Petit Couronne, France, refinery since the 1970s. The feed used was slack wax which was catalytically isomerized and then dewaxed, and presumably finished if that last step was part of the process—no details appear to have been published. 

Catalytic isomerization and dewaxing is a special kind of hydrocracking used to make high-quality lube base stocks. This topic is well-covered elsewhere, so we won t elaborate here. 

Catalysis. As of mid-1995, zeoHte-based catalysts are employed in catalytic cracking, hydrocracking, isomerization of paraffins and substituted aromatics, disproportionation and alkylation of aromatics, dewaxing of distillate fuels and lube basestocks, and in a process for converting methanol to hydrocarbons (54). 

Detergent manufacturing Catalytic cracking and hydrocracking Xylene isomerization, benzene alkylation, catalytic cracking, catalyst dewaxing, and methanol conversion. 

Iso-CDW [Isomerization and catalytic dewaxing] A general term for dewaxing processes which include these two processes. Exemplified by Isodewaxing, MSDW. 

Isodewaxing A catalytic dewaxing process developed by Chevron Research Technology. It incorporates catalysts that achieve both wax isomerization and shape-selective cracking. 

Chevron s wax isomerization process uses Pt-SAPO-11 [46,47], Wax isomerization is far superior than previous catalytic dewaxing processes because it reduces the pour point of lubes and fuels with minimum hydrocracking, and because it makes very high VI products Multiple branching, which decreases the viscosity index, is limited. Low selectivity for cyclic coke precursors makes long catalyst life possible. 

The two lighter streams were catalytically dewaxed by a ZSM-5-type catalyst, while the heavy stream was solvent dewaxed (in a later modification, all streams were dewaxed by Chevron s Isodewaxing process, which isomerizes wax rather than hydrocracking it). 

Hydroisomerization is the catalytic process for dewaxing waxy lubes and conversion of waxes to high VI base stocks by isomerization of n-paraffin structures to isoparaffins with one or more branches. These branches are usually methyl branches. We have already seen in Chapters 2 and 3 that iso-paraffins have lower pour points than n-paraffins and can have quite high Vis if the branches are close to the chain ends. Hydroisomerization is distinguished from catalytic dewaxing via ZSM-5-type catalysts in that the latter cracks n-paraffin structures to C3 to C8 molecules (Figure 10.18), whereas the former causes isomerization and has... 

Source S. J. Miller, New Molecular Sieve Process for Lube Dewaxing by Wax Isomerization, Paper presented at the Symposium on New Catalytic Chemistry Utilizing Molecular Sieves, 206th National Meeting of the American Chemical Society, Aug 23-27, 1993. Table copyrighted by the Chevron Corporation and used with permission. 

An inspection of the industrial use of zeolites as catalysts shows, however, that only a rather limited number of zeolite topologies are currently used in major industrial processes. Among the more important ones are ultrastable Y (USY) (FAU), rare-earth-exchanged faujasite-type (X, Y) (FAU) andZSM-5-type (MFI) zeolites in fluid catalytic cracking (FCC) of oil fractions [4] noble-metal-loaded U SY for hydroisomerization and hydrocracking of naphtha feedstocks [5] mordenite (MOR) and zeolite Omega (MAZ) -based catalysts for C4-C6 alkane isomerization [6] zeolites ZSM-23 (MTT), ZSM-35 (FER), ZSM-5 for selective oil dewaxing [7] ZSM-5, silicalite (MFI), MCM-22 (MWW), Beta-type (BEA) zeolites for aromatics alkylation to yield ethylbenzene, p-xylene. 

In catalytic dewaxing, linear alkanes are separated from branched hydrocarbons by cracking the molecules over zeolites with micropores that access linear alkanes only, but not branched molecules. Branched alkanes are desired as high octane gasoline components. A low reaction temperature (200° C) is preferred for the isomerization reaction because isomerization is an exothermic reaction. In this reaction linear paraffins are isomerized and more branched molecules are produced. 

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