Synthesis and Characterisation of Hierarchically Structured Titanium Silicalite‐1 Zeolites with Large Intracrystalline Macropores

Abstract

The successfuls ynthesis of hierarchically structured titaniums ilicalite-1 (TS-1) with large intracrystalline macroporesb ys team-assisted crystallisation of mesoporous silica particlesi sr eported. The macropore topologyw as imaged in 3D by using electron tomographya nd synchrotron radiation-based ptychographic X-ray computed tomography,r evealing interconnected macropores within the crystals accounting for about3 0% of the particle volume. The study of the macropore formation mechanism revealed that the mesoporous silica particles act as as acrificial macropore template during the synthesis. Silicon-to-titanium ratio of the macroporous TS-1 samples was successfully tuned from 100 to 44. The hierarchically structured TS-1 exhibited high activity in the liquid phase epoxidation of 2-octene with hydrogen peroxide.T he hierarchically structured TS-1 surpassed ac onventional nano-sized TS-1 sample in terms of alkene conversion and showed comparable selectivity to the epoxide. The flexible synthesis route described herec an be used to prepare hierarchical zeolites with improved mass transport properties for other selective oxidation reactions.

First ptychographic X-ray computed tomography experiment on the NanoMAX beamline

“…Comparison of published PXCT experiments (Dierolf et al, 2010;Guizar-Sicairos et al, 2011Diaz et al, 2012Diaz et al, , 2014Esmaeili et al, 2013;Trtik et al, 2013;Holler et al, 2014Holler et al, , 2017Donnelly et al, 2015;Fløystad et al, 2015;Dam et al, 2015;Fam et al, 2018;Polo et al, 2018;Kahnt et al, 2018;Sala et al, 2019;Becher et al, 2019;Weissenberger et al, 2019; in magenta, cyan and yellow with the present data in red. (Left) The average achieved 2D translational scanning speed (scan dimensions for a single projection divided by the time it took to record one projection) plotted against the imaged volume.…”

Micron‐Sized Zeolite Beta Single Crystals Featuring Intracrystal Interconnected Ordered Macro‐Meso‐Microporosity Displaying Superior Catalytic Performance

“…[12] Jacobsen et al performed the pioneering work using commercial carbon nanoparticles [13] or carbon fibers [14] for preparing mesoporous MFI-type zeolite single crystals (ZSM-5 [13a, b, 14] and TS-1 [13c] ), which were significantly more active in the catalytic cracking and isomerization of n-hexadecane [13a] and the epoxidation of cyclohexene [13c] than their microporous counterparts.Tsapatsis and co-workers demonstrated the ingenious synthesis of size-tunable zeolite nanocrystals (MFI, [10c] Beta, [15] LTA, [15] FAU [15] and LTL [15] )w ith aw ide range of intercrystalline mesoporosities using mesoporous carbon templates through either steam-assisted crystallization [10c] or hydrothermal synthesis [15] for improved applications in ethanol dehydration. [16] Schwieger and co-workers nicely synthesized afamily of MFItype zeolites (Silicalite-1, [11c] ZSM-5, [17] TS-1 [18] )w ith large intracrystalline macropores by steam-assisted crystallization of mesoporous silica particles.T he additional intracrystalline macropores,which were connected to the micropores and the crystal external surface,c an drastically enhance the catalyst lifetime of ZSM-5 catalysts in the methanol to olefins (MTO) reaction [17] and increase both the alkene conversion and epoxide selectivity of TS-1 catalysts in the liquid phase epoxidation of 2-octene with hydrogen peroxide. [18] Xiaos group used either ad esigned cationic amphiphilic copolymer [12f] or ac ommercial cationic polymer [12g] to synthesize zeolite ZSM-5 single crystals with b-axis-aligned mesoporous channels [12f] or zeolite Beta single crystal with interconnected mesopores.…”

“…[16] Schwieger and co-workers nicely synthesized afamily of MFItype zeolites (Silicalite-1, [11c] ZSM-5, [17] TS-1 [18] )w ith large intracrystalline macropores by steam-assisted crystallization of mesoporous silica particles.T he additional intracrystalline macropores,which were connected to the micropores and the crystal external surface,c an drastically enhance the catalyst lifetime of ZSM-5 catalysts in the methanol to olefins (MTO) reaction [17] and increase both the alkene conversion and epoxide selectivity of TS-1 catalysts in the liquid phase epoxidation of 2-octene with hydrogen peroxide. [18] Xiaos group used either ad esigned cationic amphiphilic copolymer [12f] or ac ommercial cationic polymer [12g] to synthesize zeolite ZSM-5 single crystals with b-axis-aligned mesoporous channels [12f] or zeolite Beta single crystal with interconnected mesopores. [12g] Theb -axis-aligned mesoporous ZSM-5 showed highly improved catalytic conversions in the condensation reactions of benzaldehyde with hydroxyacetophenone or 1-pentanol compared to ZSM-5 with randomly oriented mesopores and conventional ZSM-5.…”

Hierarchical ZSM‐5 Catalysts: The Effect of Different Intracrystalline Pore Dimensions on Catalyst Deactivation Behaviour in the MTO Reaction

“…We could successfully prepare hierarchical ZSM‐5 catalysts with different types of additional, intracrystalline pore systems (mesopores, macropores and a combination of both) while keeping the bulk properties constant and use this set of catalysts to study the effect of additional pore systems on the catalytic performance in the MTO reaction. For the first time we could prepare a novel type of macro/mesopore system by a combination of invers crystallisation and post synthetic alkaline treatment.…”