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Chemicals from Aromatic Hydrocarbons
Published in James G. Speight, Handbook of Petrochemical Processes, 2019
In the same vein as dealkylation, transalkylation is a chemical reaction involving the transfer of an alkyl group from one organic compound to another. For example, the reaction is used for the transfer of methyl and ethyl groups between benzene rings which is of considerable value to the petrochemical industry for the manufacture of p-xylene and styrene as well as other aromatic compounds. Motivation for using transalkylation reactions is based on a difference in production and demand for benzene, toluene, and the xylene isomers. Transalkylation can convert toluene, which is overproduced, into benzene and xylene, which are underproduced. Zeolite catalysts are often used as transalkylation reactions.
Study on efficient utilization of light cycle oil with combined process
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Fourth, LCO is utilized by the combined process of hydrocracking and solvent extraction. The LCO-X process (Johnson, Frey, and Thakkar 2007) was developed by the UOP company for the production of benzene and xylene by combining the LCO-Unicracking process with selective transalkylation technology. The LCO-Unicracking process converts naphtha fractions into benzene and xylene by hydrocracking, but some alkylbenzene may still be saturated to form the corresponding alkyl cyclohexane. To maximize the production of the aromatic, part of the hydrogenated alkyl cyclohexane is converted into aromatics and then treated by solvent extraction. The process has a high conversion rate, and the mass fraction of unconverted LCO is less than 5%, but the process also has the problem of excessive hydrogen consumption.
Hydrodeoxygenation of bio-oil and model compounds for production of chemical materials at atmospheric pressure over nickel-based zeolite catalysts
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2020
Zhiyu Li, Weiming Yi, Zhihe Li, Xueyuan Bai, Peng Fu, Chunyan Tian, Yuchun Zhang
As shown in a product distribution analysis in Figure 6, the reaction pathway of the HDO of GUA is as follows: most GUA produced phenol and CH4 by HDO (GUA+H2→Ph+CH3O−). o-Xylene was primarily produced from the transalkylation, HDO and hydrogenation (or dehydrogenation) of phenol (Ph+CH3O−+H2→methylphenol+H2O; methylphenol+H2→Tol+H2O; Tol+H2+ CH3O−→O-xy+H2O). Anisole was primarily produced from the HDO of GUA (GUA+H2→An+H2O). Benzene was primarily produced by the demethoxylation of anisole (An+H2→Ben+CH3O–). Styrene was formed by combining transalkylation and HDO (Ben+H2+ CH3O–→Sty+H2). Benzene in phenol HDO can be ignored because this rarely occurs under environmental pressure (Saidi et al. 2013). Additionally, benzene derivatives were prepared by transferring methyl or methoxy groups of GUA and anisole into benzene rings. Methoxyl or methyl groups were also transferred to phenol rings to produce phenol derivatives and other oxygen compounds. Methylphenol was formed by the HDO of GUA (Nimmanwudipong et al. 2011). (An: anisole, Ph: phenol, Tol: toluene, O-xy: o-xylene, Ben: benzene, Sty: styrene)
Alkyl transfer reactions on solid acids. The disproportionation of ethylbenzene and toluene on H-mordenite and HY zeolites
Published in Petroleum Science and Technology, 2018
Toluene disproportionation proved to be more difficult than ethylbenzene disproportionation because of the higher number of carbon atoms on the alkyl substituent made it easier for the alkyl group to be cleave off from ethylbenzene as an alkene rather than as a radical like from toluene. Comparable reaction rates are found for H-MOR at 180 and 300°C for ethylbenzene and toluene disproportionation, respectively. Benzene studies earlier showed some conversions but in the presence of toluene in the system benzene (produced in the system) did not show any conversion evidence even at high temperatures on both catalysts, the same was the case during ethylbenzene disproportion though the later was performed at lower temperatures. Toluene proved to be active in the system and might interfere strongly during transalkylation reactions in which it is used as an alkyl group recipient, but then the presence of the methyl group on the ring facilitates also the addition of other alkyl groups on the ring; thus, toluene may presumably be the alkyl-acceptor of choice depending on the type of reaction involved and reaction conditions.