Selectoforming process

Reactant shape selectivity was the basis of the Selectoforming process previously mentioned. The n-alkanes of light gasoline (essentially n-pentane, n-hexane) enter the pores of the erionite catalysts and are transformed into propane and n-butane, whereas the branched alkanes are excluded from the pores and do not react (Figure 1.5a). 

N. Y. Chen (Mobil Research Development Corp., Princeton, N. J. 08540) It might be of interest to the audience, particularly to those who are not familiar with the application of zeolites in industrial catalytic processes, to mention that since the discovery of catalysis over shape-selective zeolite first published by Weisz and Frilette in I960, a commercial process based on selective hydrocracking reactions similar to that reported in this paper has been in operation on a large scale in more than four of our refineries since 1967. A technical paper describing this process, known as the Selectoforming process, was published in 1968. 

The efficiency of the catalytic reforming process is determined by the relationship between the octane number (ON) and the liquid yield. For improvement of the ON of reformates the n-alkanes can be hydrocracked shape-selectively on narrow-pores zeolites, i.e. in case of the Selectoforming process (ref. 1) on metal containing H-erionite. During the past 15 years efforts were directed towards the integration of the shape-selective catalyst into the reforming unit (ref. 2). 

Thus erionite, with the smallest pore opening of 0.38-0.52 nm, has the highest shape selectivity. It was found that with certain zeolites, the linear alkane n-hexane is cracked 40-100 times faster than the branched isomer 3-methylpentane. This is exploited industrially in the Selectoforming process, in which erionite is added to the reforming catalyst. 

Shape-selective zeolite catalysts were first used in the Selectoforming process by Mobil in 1968. Hydrogen-exchanged natural erionite, containing some nickel,... 

Selectoforming A process for increasing the octane rating of a petroleum fraction by selectively cracking the n-pcntanc and n-hcxanc in it. The catalyst is a metal-loaded synthetic zeolite. Developed by Mobil Corporation and first commercialized in the mid-1960s. 

Another key step was the demonstration by P.B. Weisz and coworkers (3-5) of the shape selectivity of zeolite catalysts related to molecular sieving (1960). This initiated further research in the synthesis of new zeolites as well as industrial applications based on this property. The first commercial shape-selective process, Selectoforming, was developed by Mobil (1968) and allowed the selective cracking of the low octane (n-alkane) components of light gasoline over a natural zeolite (erionite) (6). 

First commercial process selectoforming (natural erionite, Weisz, Chen)... 

One of the first success of zeolites as catalysts, and the first commercial molecular shape selective catalytic process, was the use of erionite in a post-reforming process named selectoforming (39). Ihis 8 MR zeolite was able, based on the principle of size exclusion, to selectively crack the short chain n-parafiins to produce LPG. To avoid the deactivation by coke NiS was deposited on the zeolite. The erionite based catalyst is generally located at the bottom of the last reactor of the reformer unit and operates then at the reformer pressure, and at the temperature of the last reformer reactor. When more flexibility was to be achieved from the selectoforming, the catalyst is introduced... 

ZSM-5 zeolites were shown to perform shape-selective cracking (called Selectoforming with a later improved M-forming process by Mobil) [8]. 

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