112
aromatics, especially benzene, are saturated to cyclic hydrocarbons to produce MS
pool blendstock. However, keeping in view the ever-increasing pressure on gross
refinery margin (GRM) improvement and high hydrogen production cost, it is of
utmost importance to valorize the aromatics stream, especially benzene, with the
process having an ease of integration with existing refinery operation. Acidcatalyzed aromatic alkylation is such a route that could fetch several valuable petrochemicals or chemical intermediates. Ethyl benzene, styrene, cumene, and xylene
are such valuable monomers/intermediates that come through benzene alkylation.
Thus, the integration of refinery units with petrochemical units with a suitable
choice of advanced catalyst bed has become popular among oil refiners. Accordingly,
several processes and catalyst formulations have been developed and licensed by
technology providers. Today, considering the future outlook of aromatic/benzene
consumption for obtaining valorized products, benzene to cyclohexylbenzene
(CHB) and toluene to styrene are gaining major focus by researchers and technology developers. Benzene and toluene conversion to CHB and styrene, respectively,
would offer a platform for valorization of gasoline-range aromatics.
In view of the above, the present chapter deals with the issues related to the current processes for production of alkylate, cyclohexylbenzene, and styrene and
brings out the advances made in improving these processes in terms of development
of green catalytic processes.
1.1 C 4 -Alkylation
Alkylates were first produced during World War II in the late 1930s and early 1940s
by the collaborative effort of companies in America to produce high-quality and
high-octane gasoline to be used in the warplanes. Since then, various catalysts and
processes have been improved upon as alkylation is becoming an essential unit for
refiners to produce Euro-VI gasoline. Alkylation of isobutane with C 3 -C 5 olefins in
the presence of catalyst results in the production of high RON stream for the gasoline pool [4]. Currently, the contribution of the alkylate to the gasoline pool is
approximately 15%, and research octane numbers (RONs) of about 93–97 are
obtained for the products [5].
Conventionally, alkylation is carried out by employing conventional mineral acid
catalysts; however, such processes are now being avoided due to corrosion issues
related to catalyst nature, toxicity, environmental damage due to production of high
amounts of effluents, and the complexities involved in the process. Thus, environmentally friendly solid acid-catalyzed processes are now being considered, and
research efforts are being carried out in this area. The use of heterogeneous catalysts
serves as a platform to overcome the environmental concerns by reducing the capital and operational expenditures. The desired catalyst systems are being developed
based on the alkylation mechanism as given below.
S. M. Pai et al.
aromatics, especially benzene, are saturated to cyclic hydrocarbons to produce MS
pool blendstock. However, keeping in view the ever-increasing pressure on gross
refinery margin (GRM) improvement and high hydrogen production cost, it is of
utmost importance to valorize the aromatics stream, especially benzene, with the
process having an ease of integration with existing refinery operation. Acidcatalyzed aromatic alkylation is such a route that could fetch several valuable petrochemicals or chemical intermediates. Ethyl benzene, styrene, cumene, and xylene
are such valuable monomers/intermediates that come through benzene alkylation.
Thus, the integration of refinery units with petrochemical units with a suitable
choice of advanced catalyst bed has become popular among oil refiners. Accordingly,
several processes and catalyst formulations have been developed and licensed by
technology providers. Today, considering the future outlook of aromatic/benzene
consumption for obtaining valorized products, benzene to cyclohexylbenzene
(CHB) and toluene to styrene are gaining major focus by researchers and technology developers. Benzene and toluene conversion to CHB and styrene, respectively,
would offer a platform for valorization of gasoline-range aromatics.
In view of the above, the present chapter deals with the issues related to the current processes for production of alkylate, cyclohexylbenzene, and styrene and
brings out the advances made in improving these processes in terms of development
of green catalytic processes.
1.1 C 4 -Alkylation
Alkylates were first produced during World War II in the late 1930s and early 1940s
by the collaborative effort of companies in America to produce high-quality and
high-octane gasoline to be used in the warplanes. Since then, various catalysts and
processes have been improved upon as alkylation is becoming an essential unit for
refiners to produce Euro-VI gasoline. Alkylation of isobutane with C 3 -C 5 olefins in
the presence of catalyst results in the production of high RON stream for the gasoline pool [4]. Currently, the contribution of the alkylate to the gasoline pool is
approximately 15%, and research octane numbers (RONs) of about 93–97 are
obtained for the products [5].
Conventionally, alkylation is carried out by employing conventional mineral acid
catalysts; however, such processes are now being avoided due to corrosion issues
related to catalyst nature, toxicity, environmental damage due to production of high
amounts of effluents, and the complexities involved in the process. Thus, environmentally friendly solid acid-catalyzed processes are now being considered, and
research efforts are being carried out in this area. The use of heterogeneous catalysts
serves as a platform to overcome the environmental concerns by reducing the capital and operational expenditures. The desired catalyst systems are being developed
based on the alkylation mechanism as given below.
S. M. Pai et al.