1-hexene aromatization is a promising technology to convert excess olefin in fluid catalytic cracking (FCC) gasoline to high-value benzene (B), toluene (T), and xylene. Besides, the increasing market demand of xylene has put forward higher requirements for new generation of catalyst. For increasing xylene yield in 1-hexene aromatization, the effect of mesopore structure and spatial distribution on product distribution and Zn loading was studied. Catalysts with different mesopore spatial distribution were prepared by post-treatment of parent HZSM-5 zeolite, including NaOH treatment, tetra-propylammonium hydroxide (TPAOH) treatment, and recrystallization. It was found the evenly distributed mesopore mainly prolongs the catalyst lifetime by enhancing diffusion properties but reduces the aromatics selectivity, as a result of damage of micropores close to the catalyst surface. While the selectivity of high-value xylene can be highly promoted when the mesopore is mainly distributed interior the catalyst. Besides, the state of loaded Zn was also affected by mesopores spatial distribution. On the optimized catalyst, the xylene selectivity was enhanced by 12.4% compared with conventional Zn-loaded parent HZSM-5 catalyst at conversion over 99%. It was attributed to the synergy effect of mesopores spatial distribution and optimized acid properties. This work reveals the role of mesopores in different spatial positions of 1-hexene aromatization catalysts in the reaction process and the influence on metal distribution, as well as their synergistic effect two on the improvement of xylene selectivity, which can improve our understanding of catalyst pore structure and be helpful for the rational design of high-efficient catalyst.

Coke formation on n-butene cracking catalyst is the main reason for the reducing of its lifetime. To study the effects of acidity and textural properties on the coke formation process, a series of HY zeolite-type catalysts were prepared by ammonium hexafluorosilicate treatment (AHFS). NH3-TPD and Py-IR-TPD were used to systematically study the change law of zeolite acidity. It was found that with the increase of AHFS concentration, the acid density decreased, whereas the ratio of Brønsted acid to Lewis acid first increased and then decreased. Meanwhile, the percentage of Brønsted acid inside the supper cages increased and the strength of Brønsted acid increased with the degree of dealumination. Combined with in situ IR study on coke formation, the relationship between coking and acid site was revealed. It was found that the rate of coke formation on zeolites was affected by acid density, which is the rate of coke formation decreased with the decline of acid density. When the acid density remains at the same level, it was the acid strength that determined the coke formation rate—the stronger the acid strength, the faster the coke formation rate.

Hydroisomerization of n-alkanes has become an essential route for producing high quality fossil fuels and lu-bricants meeting the state-of-art regulations. The hydroisomerization of light alkanes, i.e., pentane and hexane, has been well developed. However, this process for heavier n-alkanes still has a large room for improvement. Therefore, the purpose of the present work is to review similarities and differences among the hydro-isomerization of n-alkanes with different chain length. Attention has been paid on the effect of metal-acid balance and textual modifications on the bifunctional catalysts. Besides, the mechanism of hydroisomerization was also discussed in detail. At last, conclusions and prospects for the hydroisomerization of long-chain n-alkanes have been made. This review could help to understand difficulties in enhancing isomers yield during the hydroisomerization process and could benefit new researchers in this field by relating the state-of-art researches to the reaction mechanism.

In this study, the mechanism and microkinetics of 1-butenecatalytic cracking were investigated. Based on the calculation results of thefull reaction, the optimal paths for 1-butene isomerization anddimerization-cracking were clarified, and a new aromatization mechanismis proposed. In addition, the effect of reaction temperature variation onthe product distribution was clarified. Limited by the amount of 1-buteneadsorbed, increasing the temperature will gradually change the rate-determining step of the system and have negative effects on the reactionrate. In the temperature range suitable for the production of ethylene andpropylene, this effect becomes very significant. Therefore, appropriatelyincreasing the number of Bronsted acid sites in the catalyst to ensure highadsorption amount of 1-butene at high temperatures is an effective way toimprove the production of ethylene and propylene in catalytic cracking ofbutene

To reveal the effects of Bronsted acid site concentrations on product distribution and reaction pathways of pentene cracking, ZSM-5 zeolites with similar pore structures and different acid concentrations were prepared and evaluated using C-5 distillate of FCC gasoline as feed. Three indexes related to reaction pathways (M/B, P/O, and A/O) were defined. A high strong Bronsted acid sites (SBAS) concentration favored the increase in the M/B index to promote monomolecular cracking pathways. However, the P/O index and the A/O index also increased, resulting from the enhancement of the hydrogen transfer reaction and aromatization. Therefore, an intermediate concentration of SBAS was advantageous to produce more ethylene and propylene. The optimum concentration range of SBAS was 4.4-6.7 mu mol.g(-1) for the maximum total yield of ethylene and propylene (74.7 wt %). The indexes (M/B, P/O, and A/O) provided a new thought to optimize the design of catalysts for intensifying ethylene and propylene by controlling the olefin cracking reaction pathways.