Experimental and modelling study of propane aromatization over H‐ZSM‐5 catalysts prepared by different silica sources

Abstract

The catalytic performance of H‐ZSM‐5 samples prepared from different silica sources, namely, Ludox (sample A), waterglass (sample B) and tetraethyl orthosilicate (sample C) in aromatization of propane was studied. The catalysts were characterized by BET, SEM, XRD and NH3‐TPD techniques to analyze the structure and acidity of the active sites. The performance tests were carried out in fixed‐bed reactor at 550 °C. For a quantitative assessment, the long‐term propane conversion data were fitted with a second order kinetics for the main reaction and a second order independent kinetics for deactivation using integral method of analysis. Fair fits were observed. According to silica source, the order for activity and stability were A>B>C and B>C>A, respectively. The incorporation of Zn (0.4 wt. %) as a promoter showed beneficial effect on aromatic selectivity at the expense of propane conversion and catalyst stability. The introduction of Zn decreased the rate constant of aromatization from 9.4 to 8.7 m6·kg−1·mol−1·h−1 at 550 °C, while the rate constant of deactivation increased by a factor of five, that is, from 0.0056 to 0.025 h−1.

Kinetic study of propane aromatization over Zn/HZSM-5 zeolite under conditions of catalyst deactivation using genetic algorithm

“…% Zn over HZSM-5 catalyst in the propane aromatization led to an increase in the deactivation constant from 0.0056 to 0.025 h -1 . By comparing the obtained deactivation constant value (Table IV) with Baradaran et al 35 results, it can be concluded that the increasing of deactivation constant is due to the increase of Zn load from 0.4 to 3 wt. %.…”

“…In comparison with the values of the reported activation energies for the propane aromatization, 23 the results obtained from this work are acceptable. It has been shown by Baradaran et al 35 that introducing of 0.4 wt. % Zn over HZSM-5 catalyst in the propane aromatization led to an increase in the deactivation constant from 0.0056 to 0.025 h -1 .…”

“…As the product components can bring about coke formation, the independent deactivation equation could be used and the deactivation order equals 1 was assumed. 35,36 Therefore, the following equation is obtained:…”

Highly Selective Hierarchical ZnO/ZSM-5 Catalysts for Propane Aromatization

“…However, recent research efforts are focused on catalyst development for BTX production from alternative feedstocks such as light alkanes. 4 Moreover, rapid progress has been made recently in utilizing stranded natural gas reserves for converting gas to liquid using a non-oxidative methane dehydroaromatization (DHA) catalytic route whereby the conventional gas-to-liquid (GTL) technologies become economically unaffordable. 5 The major challenges experienced so far in its implementation are the thermodynamic barrier, which limits the benzene yield to 12−13% at 700 °C, and rapid catalyst deactivation as a result of coke accumulation on the surface of the catalyst, which accounts for 10−20% methane conversion when the Mo/H-ZSM-5 catalyst is employed.…”

An overview on the effects of metal promoters and acidity of ZSM-5 in performance of the aromatization of liquid hydrocarbons

“…As it was alluded in many papers, the good operation of zeolites is under different factors, some of which are metals as promoter and acidity of the zeolites. The aromatization of some alkanes were studied meticulously by the authors of this manuscript [9][10][11]. The first aim of this work is scrutinizing the influence of the factors mentioned above over aromatization processes in order to comprehend how various catalysts conditions can make a change in the production of aromatic components.…”