Most technological development in the ethylbenzene (EB) and styrene area in recent years has centered on EB production, with the technology now converging on liquid phase operation for both alkylation and transalkylation. Such processes are licensed by the major licensors: ABB Lummus Global (Lummus) with its EB One process and Raytheon Engineers and Constructors (Raytheon) with its EB Max process. These processes are generally quite similar, the main distinguishing factors being the catalysts used in the alkylation and transalkylation reactions and the specific operating conditions throughout the processes. Interest continues in schemes to utilize dilute ethylene and dilute benzene as means of reducing feedstock costs. Such schemes usually tap the ethylene content of fluid catalytic cracker (FCC) offgas streams. The CDTECH reactive distillation process operates with benzene in the liquid phase, whereas the 3rd generation Raytheon technology operates with benzene in the vapor phase. Integration of ethylbenzene production with an olefins plant can permit dilute ethylene and dilute benzene (from pyrolysis gasoline) to be used in the EB plant. Aluminum-chloride catalyzed alkylation remains in use in numerous existing plants where suitable means of disposing of spent catalyst are available. However, this disposal can represent a cost disadvantage. Dehydrogenation of EB to styrene is a mature technology with continuing refinement of catalysts and reactor designs in an attempt to increase EB conversion without losing selectivity to styrene. Flameless Distributed Combustion developed by Shell is being applied in the "Styrene 7.0" process being jointly developed by Shell Technology Ventures and Raytheon. This technique provides continuous heat input to the endothermic reaction and permits operation at lower temperatures. Heat transfer is primarily by convection, as opposed to conduction as in conventional heat exchangers. Oxidative dehydrogenation is used primarily for revamp projects where capacity increase at nominal capital cost is desired. In this approach, heat needed for the dehydrogenation reaction is generated by controlled combustion of hydrogen. By removing hydrogen from the reaction mixture, the reaction equilibrium is shifted towards higher EB conversion. The propylene oxide coproduct process is a mature technology which represents an important source of styrene. Most propylene oxide is now made by coproduct routes (styrene or tertiary butyl alcohol) rather than the environmentally disadvantaged chlorohydrin route. Propylene oxide demand controls the siting and capacity of these coproduct plants, but the primary output is styrene by a weight ratio of 2.4 to 1 - 2.2 to 1. Another approach to take advantage of a lower cost, available feedstock is the dimerization of butadiene to an intermediate which can be dehydrogenated to styrene. Butadiene is generated in significant quantities by olefins plants which feed naphtha, while much lesser quantities arise from cracking lighter feedstocks such as ethane and propane. Dow has developed an oxidative dehydrogenation process which takes the intermediate all the way to styrene, minimizing the number of process steps. DSM, on the other hand, has developed a process wherein the intermediate is dehydrogenated to ethylbenzene, which must then be fed to a conventional EB dehydrogenation step. Updated economics are compared for commercial EB and styrene processes. Speculative economics are presented for Dow's process starting from butadiene. Sensitivity analyses show the effect of variations in economic parameters such as feed prices, capacities, investments, etc. Supply and demand estimates are updated for the United States, Western Europe, Japan and East Asia. | 
