Processes Mobil selective dewaxing

MSDW [Mobil selective dewaxing] A catalytic dewaxing process which uses a catalyst containing a shape-selective molecular sieve and a noble metal. 

MIDW [Mobil isomerization dewaxing] A petroleum refining process which improves yield and quality by isomerizing and selectively cracking paraffins in waxy oils. The catalyst is a noble metal, supported on a zeolite. Developed by Mobil Corporation from 1991 to 1996. 

The cracking of paraffins over ZSM-5 catalysts is described above. The selective cracking of long chain and slightly branched paraffins over ZSM-5 has been used by Mobil in a commerical process for the dewaxing of distillate oils. 

The Mobil process for catalytic dewaxing by selective hydrocracking of wax molecules arose from that company s development work on zeolites and the discovery of the remarkable selectivity exhibited by these catalysts some 20 years prior to first commercialization. In 1960 Weise and Frilette, of the then Socony Mobil Research and Development Laboratories,1 reported that n-decane cracked readily to lighter paraffins over the sodium form of a zeolite known as 13X, whereas the bulkier molecules, a-pinene and isopropylbenzene, underwent no reaction (Figure 10.1). 

The state of the art, today, is based on an all catalytic lube plant, which does not rely on solvent processing. An example of such a plant is Mobil s Jurong plant located in Singapore (11). The configuration of the plant relies on the use of a lube hydrocracker, coupled with a selective catalytic dewaxing unit (Fig. 8.2). 

Mobil invents ZSM-5. During the next three decades, this shape-selective catalyst finds uses in numerous processes, including FCC, catalytic dewaxing, and the conversion of methanol to gasoline. 

Catalytic dewaxing (CDW) was developed by Exxon Mobil in the 1980s. The process employs a shape-selective zeolite called ZSM-5, which selectively converts waxy n-paraffms into lighter hydrocarbons. 

Dewaxing is the process aimed at the conversion of linear long-chain hydrocarbons while leaving intact the branched isomers. The different options of the technology were developed by Mobil, Chevron, and Akzo and are based on the shape-selectivity effects of ZSM-5 zeolite. Other types of medium-pore size zeolites (ZSM-23, B-ZSM-5) have been also used. 

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