Kinetic and Deactivation Differences Among Methanol, Dimethyl Ether and Chloromethane as Stock for Hydrocarbons

Abstract

The conversions into hydrocarbons of methanol, dimethyl ether and chloromethane (MTH, DTH and CTH, respectively) on a H‐ZSM‐5 zeolite catalyst were compared trough ab‐initio calculations and experiments, using a fixed‐bed reactor and in‐situ FTIR spectroscopy. The molecular modelling of the reaction was performed using force field calculations. The nature and location of retained species were assessed by a combination of techniques. The experimental results of activity, product distribution and deactivation match these of the molecular modelling as the three reactions proceed through the dual‐cycle mechanism. However, the initiation, evolution and degradation of hydrocarbon pool species are kinetically different depending on the reactant. The reactions are faster in the order DTH>MTH≫CTH whereas the rate at which coke forms and grows (linked with the rate of deactivation) is in the order CTH≫DTH>MTH.

A Systematic Study of Methylation from Benzene to Hexamethylbenzene in H-SSZ-13 Using Density Functional Theory and Ab Initio Calculations

“…This can be ascribed to the steric effects as the repulsion is larger for DME compared to methanol, as also shown in a comparison of the PBE part of the PBE-D3 energy given in Figure S9. It is not straightforward to predict what this means for the use of either MeOH or DME as a reactant in methylation reactions . Methylation with MeOH produces water as a byproduct, which can in first order only be expected to inhibit the further methylation, although other more indirect effects of water are also discussed. − Methylation with DME, however, yields MeOH as a byproduct that can perform an additional methylation.…”

Quenching the Deactivation in the Methanol-to-Olefin Reaction by Using Tandem Fixed-Beds of ZSM-5 and SAPO-18 Catalysts

“…Despite the current use of coal (nonrenewable resource) as the feedstock, the methanol-to-olefin (MTO) process is constantly claimed to be a prospective alternative for a more sustainable production of light olefins because methanol is obtainable from renewable resources . The MTO reaction needs an acid catalyst to convert oxygenates into hydrocarbons through an autocatalytic dual-cycle mechanism (olefin and aromatic cycles), in which olefins and aromatics are intermediates that act as cocatalysts together with the acid sites for the formation of olefins, aromatics, and paraffins. − The main products are light olefins as long as other products are regarded as side products coming from secondary reactions, such as oligomerization and hydrogen transfer. Furthermore, the degradation of aromatics into large polycyclic aromatics (coke) is intrinsic to the MTO reaction, which leads to a rapid catalyst deactivation .…”

Reactor–Regenerator System for the Dimethyl Ether-to-Olefins Process over HZSM-5 Catalysts: Conceptual Development and Analysis of the Process Variables

“…As a consequence, production of both oxygenates from CO 2 is favored in the DTO process. , DME has been reported as the most reactive intermediate in the direct production of hydrocarbons from syngas . The faster formation rate of olefins from DME than that from methanol using HZSM-5 zeolites , is attributed to its higher proton affinity , and its ability to react easily with the intermediate species yielding propylene . Nevertheless, the shape selectivity of the catalyst and reaction conditions have a strong influence on the reactivity of both oxygenates .…”

“…Nevertheless, the shape selectivity of the catalyst and reaction conditions have a strong influence on the reactivity of both oxygenates . A comparison of both oxygenates indicated a faster deactivation by coking using DME because of the higher extent of the mechanism and lower concentration of water in the reaction medium . Given the slower deactivation of the HZSM-5 zeolite than that of SAPO-34, the zeolite was reported as the most suitable catalyst for the conversion of DME into hydrocarbons …”

“…17 A comparison of both oxygenates indicated a faster deactivation by coking using DME because of the higher extent of the mechanism and lower concentration of water in the reaction medium. 15 Given the slower deactivation of the HZSM-5 zeolite than that of SAPO-34, 18 the zeolite was reported as the most suitable catalyst for the conversion of DME into hydrocarbons. 19 Even though methanol and DME reactivities toward olefins are different, their conversions are widely accepted to follow the same overall mechanism over acid catalysts.…”