Deposition and Characteristics of Coke over a H-ZSM5 Zeolite-Based Catalyst in the MTG Process

Abstract

The influence of reaction conditions in the transformation of methanol into gasoline (temperature, time on stream, and contact time) on the deposition and nature of coke (composition, H/C ratio) and on its location in the porous structure of a H-ZSM5 zeolite-based catalyst has been studied in an isothermal fixed-bed integral reactor. The distribution of the coke within the porous structure of the catalyst is similar to that proposed for other reactions on H-ZSM5 zeolites, and the highly hydrogenated character of coke and its instability is noteworthy. Coke deposition has been related to catalyst acidic site deterioration and to a kinetic model for catalyst deactivation in an integral reactor.

Olefin production by cofeeding methanol and n‐butane: Kinetic modeling considering the deactivation of HZSM‐5 zeolite

“…These results are similar to those obtained in methanol transformation. 48,49 For a value of space time of 2.3 (g of catalyst) h (mol CH 2 )…”

Reactivation of acidic sites in mordenite used in toluene disproportionation

“…Harder coke has a lower H/C ratio, a higher boiling point and a more condensed structure. Benito et al found that in MTG reaction, coke is pyridine soluble (soft coke) at reaction temperature lower than 670 K; but at higher reaction temperature, more coke becomes pyridine insoluble (hard coke) [31].…”

Dimethyl ether synthesis via methanol dehydration: Effect of zeolite structure

“…In fact, coke formation is one of the most relevant aspects in any MTH process, since the potential presence of alkyl-aromatics may easily lead to the formation of solid deposit even in the temperature range of MTD [22]. An interesting debate is still on-going about the preferential location of the coke deposition: in some cases the solid was detected also within the zeolite structures [23], but a great number of researcher agreed that both size and connections of the channels limit the internal solid deposition and coke is most favourably located outside the pores on the crystal surface [18], according to the hypothesis that the coke precursors can diffuse from the micropores to the external surfaces especially in case of large external surface area and short diffusion path lengths (crystal size and morphology) [24].…”