Vapor-phase alkylation

Vapor-Phase Processes. Although vapor-phase alkylation has been practiced since the early 1940s, it could not compete with Hquid-phase processes until the 1970s when the Mobil—Badger vapor-phase ethylbenzene process was introduced (Eig. 4). The process is based on Mobil s ZSM-5 zeohte catalyst (38,52,53). The nonpoUuting and noncorrosive nature of the process is one of its major advantages over the AlCl hquid-phase system. 

Ethyltoluene is manufactured by aluminum chloride-cataly2ed alkylation similar to that used for ethylbenzene production. All three isomers are formed. A typical analysis of the reactor effluent is shown in Table 9. After the unconverted toluene and light by-products are removed, the mixture of ethyltoluene isomers and polyethyltoluenes is fractionated to recover the meta and para isomers (bp 161.3 and 162.0°C, respectively) as the overhead product, which typically contains 0.2% or less ortho isomer (bp 165.1°C). This isomer separation is difficult but essential because (9-ethyltoluene undergoes ring closure to form indan and indene in the subsequent dehydrogenation process. These compounds are even more difficult to remove from vinyltoluene, and their presence in the monomer results in inferior polymers. The o-ethyltoluene and polyethyltoluenes are recovered and recycled to the reactor for isomerization and transalkylation to produce more ethyltoluenes. Fina uses a zeoHte-catalyzed vapor-phase alkylation process to produce ethyltoluenes. 

Alkylation. Ethylbenzene [100-41 -4] the precursor of styrene, is produced from benzene and ethylene. The ethylation of benzene is conducted either ia the Hquid phase ia the preseace of a Eriedel-Crafts catalyst (AlCl, BE, EeCl ) or ia the vapor phase with a suitable catalyst. The Moasanto/Lummus process uses an aluminum chloride catalyst that yields more than 99% ethylbenzene (13). More recently, Lummus and Union Oil commercialized a zeoHte catalyst process for Hquid-phase alkylation (14). Badger and Mobil also have a vapor-phase alkylation process usiag zeoHte catalysts (15). Almost all ethylbenzene produced is used for the manufacture of styrene [100-42-5] which is obtained by dehydrogenation ia the preseace of a suitable catalyst at 550—640°C and relatively low pressure, <0.1 MPa (<1 atm). 

The reachon of benzene with ethylene or propylene to form ethylbenzene or isopropylbenzene (cumene) is an industrially important transformahon, with ethylbenzene as the key building block for polystyrene and cumene as the feedstock for phenol produchon [55]. Fthylbenzene was originally produced with a Lewis acid catalyst consishng of AlCfi or a Bronsted acidic solid phosphoric acid (SPA) catalyst [56]. Both catalyst systems suffered from equipment corrosion so, in the 1980s the Mobil-Badger vapor phase alkylation process was introduced, which... 

Vapor-phase alkylation of benzene by ethene and propene over HY, LaY, and REHY has been studied in a tubular flow reactor. Transient data were obtained. The observed rate of reaction passes through a maximum with time, which results from build-up of product concentration in the zeolite pores coupled with catalyst deactivation. The rate decay is related to aromatic olefin ratio temperature, and olefin type. The observed rate fits a model involving desorption of product from the zeolite crystallites into the gas phase as a rate-limiting step. The activation energy for the desorption term is 16.5 heal/mole, approximately equivalent to the heat of adsorption of ethylbenzene. For low molecular weight alkylates intracrystalline diffusion limitations do not exist. 

It is proposed3 that in this vapor-phase alkylation an alkyl of zinc or aluminum first is formed and that this reacts immediately with the silicon halide ... 

Although these liquid-phase and vapor-phase alkylations serve well to attach aliphatic groups to silicon, they are not so satisfactory for the substitution of aromatic groups. Very early in the history of organosilicon chemistry, Ladenburg found that the aryl compounds of mercury were more effective reagents than those of zinc. For example, mercury diphenyl reacted with silicon tetrachloride in a sealed tube at 300° to form phenyltrichlorosilane ... 

Vapor phase alkylation techniques A. Different types of catalyst employed... 

The earlie industrial developments of vapor phase alkylation processes involved the use of alumina base catalyst systems. They include the Koppers technique industrialized in the Second World War, which operates around 310°C and between 6 and 6. 10 Pa absolute, but does not allow the transalkylation of polyethylbenzenes. 

Vapor-phase alkylation of phenol with ferf-butyl alcohol in the presence of trivalent iron-substituted molecular sieve catalysts (FeMCM-41) gives para-fert-butylphenol with high regioselectivity . Supported heteropoly acid catalysts have been used in the heterogeneous alkylation reactions of 1-octene or nonene with phenol at 80-100°C. The catalyst H4SiWi204o/Si02 gives 90% para-alkylphenol and 10% orf/zo-alkylphenol. 

The effects of various parameters on the ferf-butylation of phenol on the ZeoUte-H-beta have been studied". Alkylation of phenol in the vapor phase using Zeolite SAP-11 and ferf-butyl alcohol gives the ortho- and para-ferf-butylphenols, together with the 2, 6-di-ferf-butylphenol (equation 22). Vapor-phase alkylation of phenol with tert-butyl alcohol over solid superacid catalysts, such as sulfated zirconia" and mesoporous H-AMCM-41, gives para-fert-butylphenol as a major product in high regioselectivity. 

The CDTECH EB process is based on a mixed liquid-vapor phase alkylation reactor section. The design of a commercial plant is similar to the liquid phase technologies except for the design of the alkylation reactor, which combines catalytic reaction with distillation into a single operation. ... 

The mechanism of burning for polymers is believed to take place through thermal pyrolysis of the solid plastic to produce gases that act as fuel for the fire (45). Fire retardants work in both the condensed and the vapor phase to interrupt melting of the polymer and burning of the gases. Triaryl phosphates function well in the vapor phase. Alkyl aryl phosphates are believed to decompose in the flame front to form polyphosphoric acid, which stays in the condensed phase to form char, which reduces flammability and smoke evolution (46. 47). 

Triethylamine. N,N-Diethyiethanamine. C4H,N mol wt 10119. C 7[,2I%, H 14.94%, N [3.84%. (CjHJjN. Prepd by reaction of, V. V-dielhylacelarrude with lithium aluminum hydride Uffer, Schlittler, Helv. Chim. Acta 31, 1397 (1948). Manuf by vapor phase alkylation of ammonia with ethanol Lemon, Myerly, U.S. pat, 3,022,349 (1962 to Union Carbide). 

Mechanisms of Vapor-phase Alkylations of Hydrocarbons. Paraffins can be alkylated in the absence of catalysts at sufficiently high temperatures, about 500°C, so that a small amount of the paraffins will decompose into free radicals. A free-radical mechanism for the alkylation seems probable, as is shown below for the reaction between propane and ethylene ... 

Vapor Phase Alkylation. Weisz-Prater analysis, with an assumed value of 10- ... 

Preliminary vapor phase alkylation experiments have verified that the effect of diffusion is drastically reduced by switching from a liquid to a vapor phase feed. However, the vapor phase alkylation does not appear to be a viable process due to the unfavorable product selectivities observed. 

This reaction also occurs between the solid LDH and vapor-phase alkyl halides. The substitution takes place mainly on the external surface of LDH, with rapid moving out of internal chloride and formation of LDH-Br. 

In 1945, Hurd reported the vapor-phase alkylation of silicon halides by the use of zinc and alkyl halides [2]. 

With the introduction of faujasite zeolite into petroleum cracking, interest in vapor phase alkylation was renewed. There were several reported studies on the use of faujasite or mordenite to ethylate benzene.They were very active, but associated with rapid aging attributed to coke formation. Therefore, a feasible commercial alkylation using faujasite as a catalyst never evolved. 

Vapor-phase alkylation of benzene, toluene, 0-, m-, p-xylenes and fluorobenzene with alkyl halides was studied with Nafion-H as a catalyst.Conversion of as high as 87% (based on isopropyl halide) was obtained at 353 K from a 5 2 mixture of benzene tmd the chloride. The catalyst showed no deactivation. Alkylation ability follows the order RF > RCl > RBr and secondary > primary. The only product obtained in the alkylation of toluene with propyl chloride was cymenes (isopropyltoluenes) no propyl-toluenes were detected. This indicates the intermediacy of the isopropyl cation in the alkylation reaction. 

Narayanan and Sultana [208] as well as Narayanan and Deshpande [209] admixed V2O5 to H,Na-X, H-Y, H-ZSM-5 and H-MOR and subsequently conducted solid-state reaction. Compared to the parent hydrogen zeolites, considerably enhanced activity of the catalysts prepared via SSIE was observed in vapor-phase alkylation of aniline. 

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