Kinetic Model and Simulation Analysis for Toluene Disproportionation and C9-Aromatics Transalkylation

A new kinetic model for commercial unit of toluene disproportionation and C9-armatiocs transalkylation is developed based on the reported reaction scheme.A time based catalyst deactivation function taking weight hourly space velocity(WHSV)into account is incorporated into the model,which reasonably accounts for the loss in activity because of coke deposition on the surface of catalyst during long-term operation.The kinetic parameters are benchmarked with several sets of balanced plant data and estimated by the differential variable metric optimiza- tion method.Sets of plant data at different operating conditions are applied to make sure validation of the model and the results show a good agreement between the model predictions and plant observations.The simulation analysis of key variables such as temperature and WHSV affecting process performance is discussed in detail,giv- ing the guidance to select suitable operating conditions.

Intermolecular Transalkylation of Isopropylnaphthalene and Its Application in the Production of 2,6-Diisopropylnaphthalene

Isopropylation of naphthalene with propene resulted in a variety of isomers having different alkylation levels.The most important isomer is 2,6-DIPN,which is the precursor of important monomer 2,6-naphthalene di- carboxylic acid used for making liquid crystal polymers.In order to increase the yield of 2,6-DIPN,the intermo- lecular transalkylation with naphthalene was applied to the mixture of other DIPNs and PIPN to obtain MIPN en- riched product,which underwent isopropylation with propene to produce 2,6-DIPN in a higher yield.The experi- mental study showed that the preferable conditions for transalkylation were reaction temperature of 325℃,the mo- lar ratio of isopropyl group to naphthyl group(IP/N)of 0.8︰1—0.9︰1,reaction time of 4h and 5%of amorphous silica-alumina by mass.The conversions of DIPN and PIPN in its mixture were 62%—69%and 87%—88%respec- tively and the yield of MIPN was greater than 40%.The mixture of MIPN enriched product and recovered MIPN from rectification was subject to isopropylation with propene at 275℃over a shape-selective catalyst to produce 2,6-DIPN in a yield up to 38%.A recycled process of recovered components was established,through one cycle the yield of 2,6-DIPN based on naphthalene may be 2.8 times higher than before,and the utilization ratio of raw naph- thalene was increased by 46%.

Transalkylation of Multi-secbutylbenzenes with Benzene over Hierarchical Beta Zeolite

A hierarchical beta zeolite synthesized by quasi-solid phase conversion method was characterized by BET, scanning electron microscope （SEM）, transmission electron microscope （TEM）, X-ray diffraction （XRD）, temperature-programmed desorption of ammonia （NH3-TPD）, 27A1 and 295i magic angle spinning nuclear magnetic resonance （27A1 and 29Si MAS NMR）, and its catalytic performance was compared with that of conventional microporous beta zeolite for liquid phase transalkylation of multi-secbutylbenzenes （MSBBs） with benzene. The results indicate that the hierarchical beta zeolite consists of nanosized crystals with a meso/ microporous structure and has stronger acid strength than the microporous beta zeolite. The higher conversion oftri-secbutylbenzene （TSBB） and selectivity ofsec-butylbenzene （SBB） are achieved on hierarchical beta zeolite than microporous beta zeolite, while the conversion of di-secbutylbenzene （DSBB） is slightly higher. The improvement of catalytic performance over hierarchical beta zeolite can be ascribed to the presence of mesopores, nanosized crystals and stronger acidity.

Synthesis of ZSM-5 with the silica source from industrial hexafluorosilicic acid as transalkylation catalyst

A new effective process to improve the utilization of industrial fluorosilicic acid of phosphate fertilizer by-product has been investigated to comprehensive application of the silicon and fluorine source. Two-step ammoniation was applied to recover high-quality silica. The recovered silica can be used to hydrothermal synthesize ZSM-5 zeolite without impurity phase contamination, which was confirmed by XRD, TG, SEM, BET and EDS characteristic techniques. It was found that with the increase of SiO_2/Al_2O_3 ratio and the extension of reaction time, the crystal type transform from the orthorhombic to the monoclinic phase. The impurity fluorine content of the recovered SiO_2 from H_2SiF_6 has great influence on the hydrothermal process for ZSM-5 crystal structure formation.Moreover, the increase of fluorine ions content in the hydrothermal process can control the crystal morphology and size of synthesized ZSM-5. Catalytic properties of synthesized HZSM-5 with different SiO_2/Al_2O_3 ratio in transalkylation of toluene and 1,2,4-trimethylbenzene show good and stable catalytic performance. The ZSM-5 synthesized with recovered silica source exhibits similar catalyst life as the performance of small particle size HZSM-5, because the ZSM-5 synthesized with the silica source from industrial hexafluorosilicic acid prefers a thin disk crystal along the b axis direction, which shortens the diffusion distance of generated products.

Selective Synthesis of 2,6-Dimethylnaphthalene by Transalkylation in the Presence of Acid Ionic Liquids [C_nmim]Cl-AlCl_3

A highly selective synthesis of 2,6-dimethylnaphthanlene（2,6-DMN） by transalkylation between 2-methylnaphthanlene（2-MN） and 1,2,4,5-tetramethylbenzene（TeMB） was performed with 1-alkyl-3-methylimidazo- lium aluminum chloride（[Cnmim]Cl-AlCl3） ionic liquids（ILs） as catalysts. The influences of the alkyl group as the organic cation, the acidic strength of [C4mim]Cl-AlCl3 ILs as well as the reaction conditions on the catalytic performance were investigated. [C4mim]Cl-AlCl3 ILs[x（AlCl3）=71%] exhibited high activity and selectivity toward 2,6-DMN. The selectivity to 2,6-DMN and the 2,6-DMN/2,7-DMN ratio reached up to 68.2% and 3.7：1, respectively. The UV-Vis spectrum of TeMB treated by different ILs shows that the protonated degree of TeMB dependeds on the acidity strength of ILs, which has a significant impact on the reaction results. The high protonated degree of TeMB is advantageous to enhancing the conversion of transalkylation and the large stereo-hindrance effect of TeMB is favorable to improving the selecivity to 2,6-DMN.

Transalkylation of N-methyl tertiary amines with 3,4-dibromobutenolides

The selective transalkylation of N-methyl tertiary amines with 3,4-dibromobutenolides is described. The N-methyl group of the parent tertiary amines was replaced by alkenyl units of the butenolides; and a series of butenolide-containing tertiary enamines were obtained in moderate to good yields. Interestingly, the product 2b has shown a promising anticancer activity against HeLa cell lines （IC50 = 0.19μmol/L）.

Advances in development and industrial applications of ethylbenzene processes

The benzene alkylation process for the production of ethylbenzene has undergone significant improvements during recent decades.Various environmentally benign zeolite-catalyzed ethylbenzene processes,including ZSM-5-zeolite-based vapor-phase ethylbenzene processes and Y-,β-,and MCM-22-zeolite-based liquid-phase processes,have been developed and commercialized.Pure ethylene,ethanol,and dilute ethylene have been used as ethylation agents.Here,the development and industrial application of alkylation catalysts and benzene ethylation techniques are summarized,and some other promising innovations are discussed.Recent advances in benzene alkylation over hierarchical zeolites with improved access to active sites and molecular transport are also covered.Zeolites with short diffusion lengths are promising candidates as better alkylation catalysts.The key point is how to obtain such materials easily and economically.The structure-activity relationships of commercial zeolites in these processes are discussed.Liquid-phase processes catalyzed by β and MCM-22 are more profitable than vapor-phase processes catalyzed by ZSM-5.

Preparation of 2,6-diisopropylnaphthalene with recycled process of isomers

2,6-Diisopropylnaphthalene（2,6-DIPN）,as the precursor of important monomer 2,6-naphthalene dicarboxylic acid,was prepared by hydroisopropylation of refined naphthalene with propene over shape-selective catalyst.Naphthalene conversion of 92% and 2,6-DIPN selectivity of 64% were obtained.Static melt crystallization was applied to separate and purify 2,6-DIPN from its isomers,resulted in a product purity of≥99%.The other isomers were converted into monoisopropylnaphthalene,which also reacted with propene to form 2,6-DIPN.A recycled process including hydroisopropylation,separation and transalkylation was established,the yield of 2,6-DIPN based on naphthalene could be doubled by one cycle operation.