Alkane Activation Initiated by Hydride Transfer: Co‐conversion of Propane and Methanol over H‐ZSM‐5 Zeolite

Abstract

Co-conversion of alkane with another reactant over zeolite catalysts has emerged as a new approach to the long-standing challenge of alkane transformation. With the aid of solid-state NMR spectroscopy and GC-MS analysis, it was found that the co-conversion of propane and methanol can be readily initiated by hydride transfer at temperatures of ≥449 K over the acidic zeolite H-ZSM-5. The formation of (13)C-labeled methane and singly (13)C-labeled n-butanes in selective labeling experiments provided the first evidence for the initial hydride transfer from propane to surface methoxy intermediates. The results not only provide new insight into carbocation chemistry of solid acids, but also shed light on the low-temperature transformation of alkanes for industrial applications.

Characterizing the First and Second 27Al Neighbors of Brønsted and Lewis Acid Protons in Zeolites and the Distribution of 27Al Quadrupolar Couplings by 1H{27Al} Offset REAPDOR

“…The two cosine terms in eq are responsible for two or four zero crossings of the quadrupolar interaction within a full rotor period. By virtue of sample rotation, spin packets move through the resonance position at different time points, and it depends on η Q and the efg tensor orientation in the rotor frame, when this happens and whether a spin has two or four zero crossings per rotor period . Thus, the crystallite orientations are time-dependent for a rotating sample, which helps spin packets of different crystallite orientations to move into resonance position for systems with large quadrupolar interactions.…”

Catalytic Upgrading of Light Naphtha to Gasoline Blending Components: A Mini Review

“…Intermediate products (methoxy or ethoxy groups) from the conversion of methanol or ethanol activated n -hexane conversion via a bimolecular hydride transfer. A similar reaction pathway was proposed by Yu et al for the coupling of propane and labeled methanol ( 13 CH 3 OH) over MFI zeolite using NMR and gas chromatography–mass spectrometry (GC–MS). Scheme presents the reaction for producing value-added gasoline components from the activation of a C–H bond via hydride transfer and the formation of methoxy groups.…”

“…The transformation of light naphtha has been hindered by inertness of carbon–carbon and carbon–hydrogen bonds, which results in an elevated temperature and, therefore, unfavorable thermodynamics, low selectivity and yields, and high cost for commercial applications . As refiners continue to process lighter feeds, such as shale oil and condenstates, a process that cost effectively converts excess C 5 –C 6 components is highly desirable …”

Roles of ethanol in coke formation and HZSM-5 deactivation during n-heptane catalytic cracking

“…It was attributed to the easy formation of methoxy and olefin intermediates from methanol, which worked as the active sites and triggered the hydride transfer of n -pentane and n -hexane. Via NMR, GC–MS, and isotope labeling analysis, Yu et al 18 confirmed the ready initiation of coupled methanol and propane cracking over HZSM-5 zeolites at 176 °C, as well as the direct activation of propane by the hydride transfer of surface methoxy intermediates.…”