Platinum catalytic reforming

Hydrofining is applied to virgin naphthas mainly in the form of a pretreatment step for the feed to catalytic reformers (Powerforming). Sulfur levels of 5 parts per million (ppm) or less are required to avoid deactivation of the platinum reforming catalyst. 

Powerforming is one tecnique used for aromatics chemical production. Powerforming uses a platinum catalyst to reform virgin naphthas. The principal reaction is the conversion of naphthenes in virgin naphthas to aromatics e.g., isomerization and dehydrocyclization reactions also occur in catalytic reforming. 

The catalysts generally used in catalytic reforming are dual functional to provide two types of catalytic sites, hydrogenation-dehydrogenation sites and acid sites. The former sites are provided by platinum, which is the best known hydrogenation-dehydrogenation catalyst and the latter (acid sites) promote carbonium ion formation and are provided by an alumina carrier. The two types of sites are necessary for aromatization and isomerization reactions. 

Catalytic reformers take linear alkanes, e.g., -pentane, and produce branched alkanes, e.g., i-pentane. The catalyst is finely divided platinum on Si203. 

Catforming [Catalytic reforming] A catalytic reforming process using a platinum catalyst on a silica/alumina support. Developed by the Atlantic Refining Company and first operated in 1952. 

Hon (Informing A continuous catalytic reforming process for producing aromatic concentrates and high-octane gasoline. It used a fixed bed of a platinum catalyst. Developed in the 1950s by the Houdiy Process Corporation. 

Powerforming A catalytic reforming process, based on a platinum catalyst. Developed by Esso Research Engineering Company. First commercialized in Baltimore in 1955, and now widely licensed. 

Sovaforming [Socony Vacuum reforming] A catalytic reforming process, using a platinum catalyst in a fixed bed. Developed by the Socony-Vacuum Oil Company in 1954. Subsequently renamed Platinum Reforming, or PR. 

Ultraforming A catalytic reforming process developed by Standard Oil of Indiana and licensed by Amoco Oil Company. The catalyst contains platinum and rhenium, contained in a swing reactor - one that can be isolated from the rest of the equipment so that the catalyst can be regenerated while the unit is operating. The first unit was commissioned in 1954. 

Figure 7.10 An aerial view of a catalytic reforming processing plant. The reactors are the 21-ft spherical objects in the middle. These contain platinum and are in a series so that the octane is increased a little more in each reactor. (Courtesy of BP Amoco, Texas City, TX)...

There are two methods of manufacture of the xylenes. The major one is from petroleum by catalytic reforming with a platinum-alumina catalyst. The second method (which has been developed recently) is by processes involving the disproportionation of toluene or the transalkylation of toluene... 

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. 

A number of refinery processes require the use of a fixed-bed catalyst These processes include catalytic reforming, hydrodesulfurization, hydrotreating, hydro-cracking, and others. These catalysts become inactive in six months to three years and are eventually replaced in the reactors with fresh catalyst during a unit shutdown. Many of these catalysts contain valuable metals which can be recovered economically. Some of these metals, such as platinum and palladium, represent the active catalytic component other metals such as nickel and vanadium are contaminants in the feed which are deposited on the catalyst during use. After valuable metals are recovered (a service usually performed by the outside companies), the residuals are expected to be disposed of as solid waste. 

The conversion of cyclohexanes to aromatics is a highly endothermic reaction (AH 50 kcal./mole) and occurs very readily over platinum-alumina catalyst at temperatures above about 350°C. At temperatures in the range 450-500°C., common in catalytic reforming, it is extremely difficult to avoid diffusional limitations and to maintain isothermal conditions. The importance of pore diffusion effects in the dehydrogenation of cyclohexane to benzene at temperatures above about 372°C. has been shown by Barnett et al. (B2). However, at temperatures below 372°C. these investigators concluded that pore diffusion did not limit the rate when using in, catalyst pellets. 

In the catalytic reforming of naphthas there are a number of nonhydrocarbon materials which play an important part in the performance of the catalyst. Sulfur is a poison for the reforming catalyst. There appears to be evidence developing that the platinum-rhenium catalysts may be more sensitive to sulfur than the conventional catalysts. Effective pretreatment of the feed stock to maintain sulfur at low levels is desirable. 

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