Linking Zeolite Porosity to Molecular Diffusion at the Single Crystal Level

Project Information

ZeoPoreDiff

Grant agreement ID: 748563

DOI

10.3030/748563

Project closed

EC signature date 27 February 2017

Start date 1 July 2017

End date 30 June 2019

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 177 598,80

EU contribution

€ 177 598,80

Coordinated by

UNIVERSITEIT UTRECHT
Netherlands

Periodic Reporting for period 1 - ZeoPoreDiff (Linking Zeolite Porosity to Molecular Diffusion at the Single Crystal Level)

Reporting period: 2017-07-01 to 2019-06-30

Summary of the context and overall objectives of the project

Zeolites are porous materials, containing small channels in which molecules bounce back and forth untill they are converted into valuable products. However, due to the molecular size of these zeolite channels, molecules cannot travel inside the material, hindering reaction and the efficient use of the zeolite’s volume. Trial-and-error experimentation have learned that the access of molecules into the zeolite can be improved by generating highway inside the zeolite structure which can transport molecules through the zeolite framework. Yet, a fundamental understanding of this highway generation is still missing and impedes the rational design of the next generation of tailored zeolites. The goal of this project is to apply novel advanced microscopic techniques. A first microscopy-type develloped in this project relies on the scattering of X-rays by zeolite channels. By shining X-ray through the material with a microscope, the highway’s properties can be derived by catching the X-ray which have changed direction. As a second complementary technique, channel formation is monitored live in real-time by watching the highways being formed by placing molecules in the zeolite which lighten up at the channel contours. By applying this powerful combo, new vistas could open up on zeolite highway formation and the dynamics of their generation.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

First, X-ray scattering (SAXS) microscopy has been applied for the first time on heterogeneous catalysts, here zeolites in specific. Advanced data analysis protocols have been develloped for extracting the highway properties, hereafter termed ‘pore’ properties. Pores are only formed in selected parts of the zeolite. Particularly, in pore-rich zones, smaller pores of a few nanometers are observed at all locations in the zone, whereas larger pores only appear in selected hotspots. At these hotspots, a high concentration of needle-shaped pores occur. The application of X-ray scattering microscopy allowed to classify several types of pore zones, ranging from zone where no pores occur to regions where spherical and needle-type pores are formed.

Second, confocal fluorescence microscopy has been employing for capturing the dynamics of pore formation in real-time during the process. By staining the pores with fluorescent molecules, the pores could be visualized and their evolution monitored in live. Pore formation starts at the crystal surface and propagates towards the crystal core. The mechanism of pore formation can thus be defined as a initiation-propagation mechanism, triggered at the crystal edges. Finally, a clear structural correlation in the position of pore formation is observed between X-ray scattering and fluorescence microscopy, corroborating the results with both techniques.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

X-ray scattering microscopy has not been applied on heterogeneous catalysts and could potentially impact the field since it can visualize nanometer-sized pores over relatively large material volume. Strong electron microscopes can also visualize pores but only scan small volumes while other characterization techniques can screen larger material volume but are not sensitive enough to detect small pores. In this sense, X-ray scattering microscopy has been develloped as a novel tool for mapping porosity in heterogeneous materials, which provides strong opportunities for novel materials understanding and development. In addition, fluorescence microscopy has never been applied during the formation of nanometer-sized pores. Uncovering the formation mechanisms of this live monitoring can provide mechanistic knowledge, complementary to X-ray scattering microscopy, which can aid in generating next-level zeolites and heterogeneous catalysts.

While this is a fundamental science project aimed at further understanding the underlying mechanisms of nanopore formation in zeolites, the materials studied are of high value to society, and especially for developing more sustainable technologies. Specifically, the catalysts are essential for the methanol to hydrocarbons process, which can use renewable or non-renewable feedstocks to produce high demand chemical feedstocks, as well as automotive emissions reduction catalysts, vital to clean air. This is therefore directly in line with European policy objectives and strategies and will be essential for the competitiveness of the European chemical industry and economy.

Project overview