Benzene; Ethylene

ethylbenzene

To produce ethylbenzene (EB) by alkylation of benzene with ethylene in the vapor phase, using a fixed-bed reactor.

Description: Ethylene feedstocks as low as 10 mol % purity (such as FCC offgas) can be used economically. The product EB is suitable for making styrene monomer by all known process routes. Additional economies are possible by a union of this EB process with a companion styrene process.
   In the reaction section (1) fresh and recycle benzene are vaporized and preheated and then combined with a polyethylbenzene (PEB) recycle stream and fresh ethylene and fed to a reactor containing a proprietary, fixed bed heterogeneous catalyst developed by Mobil. The benzene is alkylated with ethylene in the vapor phase at moderate pressure. The reactor effluent is fed to the benzene fractionation system (2) for recovery of unreacted benzene for recycle to the reactor. The remainder of the reactor effluent is fractionted in a two-column system. In the EB recovery column (3) EB product is separated from higher boiling components. The bottoms from the EB recovery column are further distilled in the PEB recovery column (4). PEB and other alkylaromtics are recovered overhead and recycled to the reaction section. A small residue stream from the bottom of the column can be used as fuel.
   The process is highly energy efficient: essentially all of the process heat input plus heat of reaction can be recovered as useful medium- and low-pressure steam. Design flexibility allows the use of alternative heating media: steam, hot oil or direct fired reboilers.
   Environmentally, the process is nonpolluting; no process waste streams are produced. The catalyst is noncorrosive, nonhazardous, environmentally inert and requires no special handling. Materials of construction are generally carbon steel throughout.

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