Studies on acidity, activity and coke deactivation of ZSM-5 during n-heptane aromatization

Post-steam-treatment of Mo/HZSM-5 Catalysts: An Alternative and Effective Approach for Enhancing Their Catalytic Performances of Methane Dehydroaromatization

“…About 10% N 2 in the feed gas was used as an internal standard for the analysis of all products, including deposited coke, as suggested by Lunsford and co-workers. 16,17 The reaction results were expressed as methane conversions, while the yields of the products and the selectivities toward the products such as C 6 XRD patterns were obtained on a Rigaku diffractometer using Cu KR radiation at room temperature, with instrumental settings of 40 kV and 50 mA. Powder diffractograms of the samples were recorded over a set of 2q values ranging from 5 to 50°at a scanning rate of 5°/min.…”

A novel method for enhancing on-stream stability of fluid catalytic cracking (FCC) gasoline hydro-upgrading catalyst: Post-treatment of HZSM-5 zeolite by combined steaming and citric acid leaching

“…5, the varying trends of isoparaffin and aromatics contents in the products obtained on the corresponding catalysts in the first 39 h TOS are different from each other: in the first 18 h TOS, the contents of isoparaffins and aromatics rapidly increase and decrease, respectively; then, they reach at relatively steady states. It is well known that coking occurs preferentially on the strong acid sites [4,20,21], so the numbers of strong acid sites on the catalysts decrease with the increasing TOS due to coke deposition, leading to the drastically decreased aromatization activity during the initial 18 h TOS. The increasing tendency of the isoparaffin contents in the liquid products indicates that the hydroisomerization of olefins can occur on weak acid sites, and then gradually dominates in the parallel and mutually competitive reactions of hydroisomerization and aromatization due to the decreasing strong acid sites.…”

Hβ/HZSM-5 Composite Carrier Supported Catalysts for Olefins Reduction of FCC Gasoline Via Hydroisomerization and Aromatization

“…Increasing the HZSM-5 content or decreasing the Hb content in the carriers leads to the narrowed pore channels of the catalysts (referring to table 3) and thus confines the diffusion of olefins, and results in the increased acid strength of the catalysts (referring to table 4) and hence strengthens the adsorption of olefins. Consequently, the adsorption of olefins on the catalysts is facilitated and the desorption is restrained, resulting in coke formation on acid sites (especially on those with strong acidity) [22] and poor olefins conversion. Obviously, the increasing temperature unavoidably gives rise to more serious dehydrogenation and carbon deposition on the catalysts, both contributing to the descending slope of the curves in figure 5a.…”