Naphtha reforming, catalytic process type

Catalytic conversion processes include naphtha catalytic reforming, catalytic cracking, hydrocracking, hydrodealkylation, isomerization, alkylation, and polymerization. In these processes, one or more catalyst is used. A common factor among these processes is that most of the reactions are initiated hy an acid-type catalyst that promotes carhonium ion formation. 

Table 1 Worldwide distribution of naphtha reforming by capacity and process type Catalytic Naphtha Reforming... 

By 1950 a reforming process was introduced using a catalyst to improve the yield loline components while minimizing the formation of unwanted material. In catalytic as in thermal reforming, a naphtha-type material serves as the feedstock, but the reactions are carried out in the presence of... 

Selecting the naphtha type can be an important processing procedure. For example, a paraffinic-base naphtha is a better feedstock for steam cracking units because paraffins are cracked at relatively lower temperatures than cycloparaffins. Alternately, a naphtha rich in cycloparaffins would be a better feedstock to catalytic reforming units because cyclo-paraffins are easily dehydrogenated to aromatic compounds. Table 2-5 is a typical analysis of naphtha from two crude oil types. 

When naphtha or naphthenic gasoline fractions are catalytically reformed, they usually yield a Cx aromatics stream that is comprised of mixed xylenes and ethylbenzene. It is possible to separate the ethylbenzene and o-xylene by fractionation. It is uneconomic to separate the m- and p-xylenes in this manner because of the closeness of their boiling points. To accomplish the separation, a Werner-type complex for selective absoiption of p-xylene from the feed mixture may be used. Or, because of the widely different freezing points of the two xylene isomers, a process of fractional crystallization may be used. To boost the p-xylene yield, die filtrate from the crystallization step can be catalytically isomerized. 

There are situations where support acidity has a positive influence, influencing the main reaction. The support adds dual functionality to the overall catalysis, as best demonstrated with catalytic reforming/ The objective in this process is to convert low octane components of naphtha, typically normal paraffins and naphthenes, into high-octane iso-parafHns and aromatics. Low loadings of Pt type metals on AljOj are used for this purpose. Metallic Pt dehydrogenates naphthenes to aromatics but cannot isomerize or cyclize normal paraffins. This is accomplished through the acidic function of the support, as shown for n-hexane ... 

Hydrotreating is being employed extensively in the petroleum industry for processing a variety of feedstocks. Both straight-run and cracked petroleum products such as naphthas, kerosenes, middle distillates, gas oils (atmospheric and heavy vacuum types), cycle stocks, residues, asphalts, crudes, and shale oils may be so treated. The process primarily is employed as a pretreat previous to catalytic reforming or catal3d ic cracking. 

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