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Reforming CatalystsThe catalysts generally used in catalytic reforming are dual functional to provide two types of catalytic sites, hydrogenation-dehydrogenation sites and acid sites.. T

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Catalytic Reforming

*Increasing the octane number of a low-octane naphtha fraction

* the key process for obtaining benzene, toluene, and xylenes (BTX)

Reformer Feeds

•heavy naphtha fraction

•naphtha from other sources

Reforming Catalysts

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

Aromatization

Isomerisation

Hydrocracking is a hydrogen-consuming reaction

that leads to higher gas production and lower liquid yield This reaction is favored at high temperatures and high hydrogen partial pressure The following represents a hydrocracking reaction:

Bond breaking can occur at any position along the hydrocarbon chain

Hydrocracking long-chain molecules can produce

C6, C7, and C8 hydrocarbons that are suitable for

dehydro-cyclization to aromatics

Hydrodealkylation is a cracking reaction of an

aromatic side chain in presence of hydrogen Like hydrocracking, the reaction consumes hydrogen and is favored at a higher hydrogen partial pressure This

reaction is particularly important for increasing benzene yield when methylbenzenes and ethylbenzene are

dealkylated

Catalytic Cracking

Catalytic cracking (Cat-cracking) is a remarkably versatile and flexible process Its principal aim is to crack lower-value stocks and produce higher-value light and middle distillates The

process also produces light hydrocarbon gases, which are

important feedstocks for petrochemicals

Feeds

The feeds to catalytic cracking units vary from gas

oils to crude residues

FCC (fluid catalytic cracking) feedstocks are often pretreated to decrease the metallic and asphaltene contents

Residium fluid catalytic cracking (RFCC) has gained wide acceptance due to a larger production of gasoline with only small amounts of low-value products

Cracking Catalysts

Acid-treated clays were the first catalysts used in catalytic cracking processes, but have been replaced by

synthetic amorphous silica-alumina, which is more active and stable Incorporating zeolites (crystalline alumina-silica) with the silica/alumina catalyst improves selectivity towards

aromatics These catalysts have both Lewis and Bronsted acid sites that promote carbonium ion formation.

Bronsted acid sites

Cracking Reactions

The most important cracking reaction, is the carbon-carbon beta bond scission A bond at a position beta to the positively-charged carbon breaks heterolytically, yielding an olefin and another carbocation.This can be represented by the following example:

Cracking Reactions

Hydrotreatment Catalysts and Reactions

Hydrodesulfurization, HDS

The catalysts should be sulfur-resistant The cobalt-molybdenum system supported on alumina was found to be an effective catalyst NiO/MoO3

and NiO/WO3

Hydrotreatment Catalysts and Reactions

Alkylation Process