Process benzene alkylation

MBR [Mobil benzene reduction] A catalytic process for reducing the benzene content of gasoline. It combines features of three earlier processes benzene alkylation with tight olefins, olefin equilibration with aromatization, and selective paraffin cracking. The olefins are obtained from FCC offgas. The catalyst is a modified ZSM-5 zeolite. Developed by Mobil Research Development Corporation in 1993. 

Ethjlben ne Synthesis. The synthesis of ethylbenzene for styrene production is another process in which ZSM-5 catalysts are employed. Although some ethylbenzene is obtained direcdy from petroleum, about 90% is synthetic. In earlier processes, benzene was alkylated with high purity ethylene in liquid-phase slurry reactors with promoted AlCl catalysts or the vapor-phase reaction of benzene with a dilute ethylene-containing feedstock with a BF catalyst supported on alumina. Both of these catalysts are corrosive and their handling presents problems. 

Fig. 3. Unocal—Lummus—UOP ethylbenzene process AR = alkylation reactor TR = transalkylation reactor BC = benzene column ...

Catalysts. Nearly aU. of the industrially significant aromatic alkylation processes of the past have been carried out in the Hquid phase with unsupported acid catalysts. For example, AlCl HF have been used commercially for at least one of the benzene alkylation processes to produce ethylbenzene (104), cumene (105), and detergent alkylates (80). Exceptions to this historical trend have been the use of a supported boron trifluoride for the production of ethylbenzene and of a soHd phosphoric acid (SPA) catalyst for the production of cumene (59,106). 

ABB Lummus Crest Inc. and Unocal Corp. have Hcensed a benzene alkylation process usiag a proprietary zeoHte catalyst. Unlike the Mobil-Badger process, the Unocal-Lummus process is suitable for either ethylbenzene or cumene manufacture (27,28). 

The principal use of the alkylation process is the production of high octane aviation and motor gasoline blending stocks by the chemical addition of C2, C3, C4, or C5 olefins or mixtures of these olefins to an iso-paraffin, usually isobutane. Alkylation of benzene with olefins to produce styrene, cumene, and detergent alkylate are petrochemical processes. The alkylation reaction can be promoted by concentrated sulfuric acid, hydrofluoric acid, aluminum chloride, or boron fluoride at low temperatures. Thermal alkylation is possible at high temperatures and very high pressures. 

Should pure olefin be used for alkylation (Shell process), the organic phase consists of benzene, LAB, and heavy alkylate and is fractionally distilled, after which the remaining HF is usually removed by stripping. When using olefin as a solution in paraffin (Pacol and Hiils process) for alkylation, the organic phase contains additional large quantities of paraffin which have to be separated out by distillation and used again in the production of olefin. 

Continuous benzene alkylation was conducted in a reactive distillation column of the type illustrated in Figure 1. The process unit comprises the following principal elements a double column of solid catalyst 32, packing columns above and below the catalyst bed, a liquid reboiler 42 fitted with a liquid bottoms product takeoff 44, a condenser 21 fitted with a water collection and takeoff, and a feed inlet... 

Alkymax A process for removing benzene from petroleum fractions. They are mixed with light olefin fractions (containing mainly propylene) and passed over a fixed-bed catalyst, which promotes benzene alkylation. The catalyst is solid phosphoric acid (SPA), made by mixing a phosphoric acid with a siliceous solid carrier, and calcining. Invented in 1980 by UOP... 

Tphe rate-limiting processes in catalytic reaction over zeolites remain A largely undefined, mainly because of the lack of information on counterdiffusion rates at reaction conditions. Thomas and Barmby (7), Chen et al. (2, 3), and Nace (4) speculate on possible diffusional limitations in catalytic cracking over zeolites, and Katzer (5) has shown that intracrystalline diffusional limitations do not exist in liquid-phase benzene alkylation with propene. Tan and Fuller (6) propose internal mass transfer limitations and rapid fouling in benzene alkylation with cyclohexene over Y zeolite, based on the occurrence of a maximum in the reaction rate at about 100 min in flow reaction studies. Venuto et al (7, 8, 9) report similar rate maxima for vapor- and liquid-phase alkylation of benzene and dehydro-... 

Benzene alkylation over Y zeolites has been studied as a function of olefin, olefin aromatic ratio, temperature, and zeolite cation form. The rate has been modeled, and the rate-limiting process has been quantified as product desorption. 

Styrene, one of the world s major organic chemicals, is derived from ethylene via ethylbenzene. Several recent developments have occurred with respect to this use for ethylene. One is the production of styrene as a co-product of the propylene oxide process developed by Halcon International (12). In this process, benzene is alkylated with ethylene to ethylbenzene, and the latter is oxidized to ethylbenzene hydroperoxide. This hydroperoxide, in the presence of suitable catalysts, can convert a broad range of olefins to their corresponding oxirane compounds, of which propylene oxide presently has the greatest industrial importance. The ethylbenzene hydroperoxide is converted simultaneously to methylphenyl-carbinol which, upon dehydration, yields styrene. Commercial application of this new development in the use of ethylene will be demonstrated in a plant in Spain in the near future. 

Branched paraffins react somewhat differently to the normal paraffins during cracking processes and produce substantially higher yields of olefins having one fewer carbon atom that the parent hydrocarbon. Cycloparaffins (naphthenes) react differently to their noncyclic counterparts and are somewhat more stable. For example, cyclohexane produces hydrogen, ethylene, butadiene, and benzene Alkyl-substituted cycloparaffins decompose by means of scission of the alkyl chain to produce an olefin and a methyl or ethyl cyclohexane. 

In 1945 Mamedaliev published a book in Baku (213) reporting the research carried out in his laboratory on the alkylation of aromatics and isoparaffins with olefins in the presence of a number of catalysts. Subsequent information indicates that Mamedaliev has developed a continuous process of alkylation of benzene with olefins. He also described alkylation of benzene with propylene in the presence of activated clay (214). 

Some excellent reviews exist on benzene alkylation.52 Comparison of Beta with other zeolites (USY 53 or MCM-22 and ZSM-5)54 shows that Beta seems to be the most active catalyst whereas MCM-22 shows the best overall properties combining a good activity with an excellent stability. Similar results are found for the zeolite-based cumene processes where zeolite Beta is used in the process developed by Enichem.52... 

Application To produce linear alkylbenzene (LAB) from C10 to C14 linear paraffins by alkylating benzene with olefins made by the Pacol dehydrogenation and the DeFine selective hydrogenation processes. The alkylation reaction is carried out over a solid, heterogeneous catalyst in the Detal process unit. 

Thus, in ammonia synthesis, mixed oxide base catalysts allowed new progress towards operating conditions (lower pressure) approaching optimal thermodynamic conditions. Catalytic systems of the same type, with high weight productivity, achieved a decrease of up to 35 per cent in the size of the reactor for the synthesis of acrylonitrile by ammoxidation. Also worth mentioning is the vast development enjoyed as catalysis by artificial zeolites (molecular sieves). Their use as a precious metal support, or as a substitute for conventional silico-aluminaies. led to catalytic systems with much higher activity and selectivity in aromatic hydrocarbon conversion processes (xylene isomerization, toluene dismutation), in benzene alkylation, and even in the oxychlorination of ethane to vinyl chloride. 

The phenomenological Horiuti Boreskov Onsager equations allow in some cases a first approximation to be made for the kinetic description of catalytic transformations in systems that involve numerous parallel trans formation channels. Consider how these equations can be applied with the process of benzene alkylation with ethylene as an example. 

Branched dodecylbenzene is produced by alkylation of polymer tetramer and benzene. The polymer tetramer feedstock is produced in a propylene oligomerization plant using a process such as the UOP catalytic condensation process. Benzene feedstock is typically produced by solvent extraction of reformate or pygas by means of an aromatics extraction process. There is no detailed discussion of DDB production in this entry, as the production of SDBS has been almost entirely phased out. A complete discussion is presented in Ref.. ... 

Because the liquid phase process is predominantly used for new EB plants, the critical operating and design parameters for liquid phase benzene alkylation are discussed below. 

Figure 2.29 (a) Mobil/Badger s EBMax and (b) CDTECH EB processes for ethylbenzene (EB) production by benzene alkylation. Source adapted from Woodle [226]. 

Notably, benzene conversion is quite similar to that usually achieved in cumene process over the benzene alkylation and cumene oxidation stages. 

In the Xiao s laboratory [27], the pyridinium-based ionic liquids as the suitable media were used for the Friedel-Crafts alkylation of benzene, which was carried out at a better rate but at relatively lower temperature with high product conversion. They found that the [EtPyKCFjCOO] (i-ethyl-pyridinium trifluoroacetatel-FeClj was an enviromnental friendly, recyclable, and reusable solvent-catalyst system to replace the traditional aluminum catalysis system. During the process, the alkylation... 

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