Real-time regeneration of a working zeolite monitored X-ray diffraction and crystallographic imaging: how coke flees the MFI framework.

We have monitored the regeneration of H-ZSM-5 time-resolved powder X-Ray diffraction (PXRD) coupled with mass spectroscopy (MS). Parametric Rietveld refinements and calculation of the extra-framework electronic density by differential Fourier maps analysis provide details on the mode of coke removal combined with the corresponding sub-unit cell changes of the zeolite structure. It is clear that the coke removal is a complex process that occurs in at least two steps; a thermal decomposition followed by oxidation.

Topology-dependent hydrocarbon transformations in the methanol-to-hydrocarbons reaction studied by operando UV-Raman spectroscopy.

The methanol-to-hydrocarbons (MTH) reaction represents a versatile, industrially viable alternative to crude-oil based processes for the production of chemicals and fuels. In the MTH reaction, the shape selectivity of acidic zeolites is exploited to direct the synthesis towards the desired product. However, due to unavoidable side reactions occurring under processing conditions, all MTH catalysts suffer deactivation due to coke formation.

Deactivation of Zeolite Catalyst H-ZSM-5 during Conversion of Methanol to Gasoline: Operando Time- and Space-Resolved X-ray Diffraction.

The deactivation of zeolite catalyst H-ZSM-5 by coking during the conversion of methanol to hydrocarbons was monitored by high-energy space- and time-resolved operando X-ray diffraction (XRD) . Space resolution was achieved by continuous scanning along the axial length of a capillary fixed bed reactor with a time resolution of 10 s per scan. Using real structural parameters obtained from XRD, we can track the development of coke at different points in the reactor and link this to a kinetic model to correlate catalyst deactivation with structural changes occurring in the material.

Conversion of methanol to hydrocarbons over zeolite ZSM-23 (MTT): exceptional effects of particle size on catalyst lifetime.

A variety of synthetic procedures have been used to obtain zeolite ZSM-23 (MTT) catalysts with crystallite sizes ranging from the micrometer to nanometer scale. When the acidic zeolite is used as a catalyst for the methanol to hydrocarbon (MTH) reaction, the catalytic lifetime is dramatically influenced by the crystallite shape and size.

Time- and space-resolved study of the methanol to hydrocarbons (MTH) reaction - influence of zeolite topology on axial deactivation patterns.

Zeolites representing seven different topologies were subjected to life-time assessment studies as methanol to hydrocarbons (MTH) catalysts at 400 °C, P(MeOH) = 13 kPa and P(tot) = 100 kPa. The following topologies were studied: ZSM-22 (TON), ZSM-23 (MTT), IM-5 (IMF), ITQ-13 (ITH), ZSM-5 (MFI), mordenite (MOR) and beta (BEA). Two experimental approaches were used.