Conversion of methyl halides to hydrocarbons on basic zeolites: a discovery by in situ NMR

Methyl Halide to Olefins and Gasoline over Zeolites and SAPO Catalysts: A New Route of MTO and MTG

“…It was also found that the coexistence of metal species in the synthesis starting gel has effect on the Si substitution into AlPO framework. The 29 Si MAS NMR spectra in Fig. 5 indicated that, with more metal incorporated into the framework, Si island predominant formed and caused lowered acid density of MeAPSO-34 [37].…”

“…Following step for the conversion of methyl halide to higher hydrocarbons has attracted much more research interest from academy and industry due to the significance of C-C bond construction from C 1 -reactant. Intensive studies have shown that the direct conversion of methyl halide to higher hydrocarbons can be carried out on a series of acid zeolites like HZSM-5, HBeta, and HMOR and on cationic zeolites such as faujasites Y and ZSM-5 exchanged with mono or divalent cations [22][23][24][25][26][27][28][29][30][31]. Most of these work presented the product distribution in gasoline range from methyl halide conversion.…”

“…Earlier studies suggested the first C-C bond formation from methyl halide through the methylation of framework bonded CH 2 group [27][28][29][30], while later work over SAPO-34 indicated methyl halide conversion to higher hydrocarbons possibly followed indirect way as methanol conversion [49][50][51].…”

“…Murray and his co-workers studied the conversion of methyl halides to hydrocarbons on basic zeolites, including alkali metal and divalent metal exchanged zeolites [29,30]. In their work of in situ 13 C MAS NMR study, the conversion of methyl iodide on zeolite CsX was proposed to proceed through a framework-bound methoxy intermediate over CsX; and an analogous framework-bound ethoxy species also easily formed upon adsorption of CH 3 CH 2 I.…”

“…At the same time, a second methyl halide was polarized by a Lewis acid-base interaction to form CH 3 + for methylation of the methoxy group. The first species with a C-C bond was proposed to be framework-bound ethoxy group, which quickly eliminated ethylene [29]. In the study of methyl halides reaction on bivalent metal-exchange zeolite catalysts, Murray and their coworker proposed a detailed mechanism for this reaction and also described an explicit role of the metal [30].…”