Catalytic processes naphtha reforming

Catalytic Reforming. Worldwide, approximately 30% of commercial benzene is produced by catalytic reforming, a process ia which aromatic molecules are produced from the dehydrogenation of cycloparaffins, dehydroisomerization of alkyl cyclopentanes, and the cycHzation and subsequent dehydrogenation of paraffins (36). The feed to the catalytic reformer may be a straight-mn, hydrocracked, or thermally cracked naphtha fraction ia the... 

Catalytic processes frequently require more than a single chemical function, and these bifunctional or polyfunctional materials innst be prepared in away to assure effective communication among the various constitnents. For example, naphtha reforming requires both an acidic function for isomerization and alkylation and a hydrogenation function for aromati-zation and saturation. The acidic function is often a promoted porous metal oxide (e.g., alumina) with a noble metal (e.g., platinum) deposited on its surface to provide the hydrogenation sites. To avoid separation problems, it is not unusual to attach homogeneous catalysts and even enzymes to solid surfaces for use in flow reactors. Although this technique works well in some environmental catalytic systems, such attachment sometimes modifies the catalytic specifici-... 

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. 

Introduction of zeolites into catalytic cracking improved the quality of the product and the efficiency of the process. It was estimated that this modification in catalyst composition in the United States alone saved over 200 million barrels of crude oil in 1977. The use of bimetallic catalysts in reforming of naphthas, a basic process for the production of high-octane gasoline and petrochemicals, resulted in great improvement in the catalytic performance of the process, and in considerable extension of catalyst life. New catalytic approaches to the development of synthetic fuels are being unveiled. 

Reforming, In refining, a catalytic process in which naphtha molecules are cracked, rearranged, and/or recombined for the purpose of increasing the octane number of the naphtha. Reforming is also the process of converting hydrocarbons and steam to synthesis gas (carbon monoxide and hydrogen). 

Hydrogen production by partial oxidation is similar to production by catalytic steam reforming. The process basically involves the conversion of steam, oxygen and hydrocarbons to hydrogen and carbon oxides. The process proceeds at moderately high pressures with or without a catalyst depending on the feedstock and process selected. The catalytic POX, which occurs at about 865 K, will work with feedstock ranging from methane to naphtha. The non-catalytic POX, which occurs... 

Reforming Both thermal and catalytic processes are utilized to convert naphtha fractions into high-octane aromatic compounds. Thermal reforming is utilized to convert heavy naphthas into gasoline-quality aromatics. Catalytic reforming is utilized to convert straight-run naphtha fractions into aromatics. Catalysts utilized include oxides of aluminum, chromium, cobalt, and molybdenum as well as platinum-based catalysts. 

Catalytic reforming. Catalytic reforming is a process for increasing the octane number of naphthas. It involves isomerisation of alkanes, dehydrogenation of cyclohexanes to aromatic hydrocarbons, isomerisation and dehydrogenation of alkylcyclopentanes, and dehydrocyclisation of alkanes. 

For many years benzene (benzol) was made from coal tar, but new processes that consist of catalytic reforming of naphtha and hydrodealkylation of toluene are more appropriate. Benzene is a natural component of petroleum, but it cannot be separated from crude oil by simple distillation because of azeotrope formation with various other hydrocarbons. Recovery is more economical if the petroleum fraction is subjected to a thermal or catalytic process that increases the concentration of benzene. 

The feed to an aromatics complex is normally a C6+ aromatic naphtha from a catalytic reformer. The feed is split into Cg+ for xylene recovery and C7 for solvent extraction. The extraction unit recovers pure benzene as a product and C7+ aromatics for recycling. A by-product of extraction is a non-aromatic C6+ raffinate stream. The complex contains a catalytic process for disproportionation and transalkylation of toluene and C9+ aromatics, and a catalytic process for isomerization of C8 aromatics. Zeolitic catalysts are used in these processes, and catalyst selectivity is a major performance factor for minimizing ring loss and formation of light and heavy ends. The choice of isomerization catalyst is dependent on whether it is desired to isomerize ethylbenzene plus xylenes to equilibrium or to dealkylate ethylbenzene to benzene while isomerizing the xylenes. Para-selectivity may also be a desired... 

Catalytic reformer feeds are saturated (i.e., not olefinic) materials in the majority of cases that feed may be a straight-run naphtha but in others by-product low-octane naphtha (e.g., coker naphtha) can be processed after treatment to remove olefins and other contaminants. Hydrocracker naphtha that contains substantial quantities of naphthenes is also a suitable feed. 

In the naphtha reforming process, a bifunctional metal-acid catalyst is used. During the coinnercial operation, coke is deposited on both catalytic functions producing their deactivation (refs, 1-3). When activity and selectivity are decreased to values where the operation is not convenient from the economical... 

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

Aitani, A. Reforming processes. In Catalytic Naphtha Reforming, Antos, G. et al., Eds. Marcel Dekker New York, 1995 409. 

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