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A new concept in zeolite catalysis: Morphology induced shape selectivity

Final Report Summary - ZEOMORPH (A new concept in zeolite catalysis: Morphology induced shape selectivity)

ZeoMorph - FP7-ITN-EID

ZeoMorph is a European Industrial Doctorate project comprising 5 PhD candidates. The Danish company Haldor Topsøe A/S and the University of Oslo, Norway are full network partners. Groups at the University of Torino, Italy, Århus University, Denmark, and Ghent University, Belgium, are associated partners in the project.

About the project

Zeolites are crystalline aluminosilicates and have been used as catalysts within refining and hydrocarbon conversion processes since the 1960s. In addition to possessing strong Brønsted acidity, zeolites are microporous materials, having regular pores channels and cavities of molecular dimensions. These materials therefore possess shape selectivity for chemical reactions. Nevertheless, insufficiently shape selective catalyst, leading to rapid deactivation and unselective production, is a major obstacle for improved and new zeolite based industrial processes. Within the ZeoMorph project, these challenges will be overcome by bringing together leading European groups within physical and inorganic chemistry.

The ZeoMorph objective

The scientific vision of ZeoMorph is to establish a new concept within zeolite catalysis: Morphology induced shape selectivity

Major successes

As indicated by the overall ZeoMorph objective, the emphasis has been to determine if the performance of zeolite catalyst can be governed by tuning the particle morphology. This has indeed been found to be the case, and this has been demonstrated for three cases:

First, a series of offretite zeolite catalyst have been prepared. Offretite strongly prefers to crystallize into hexagonal prisms, where the 8MR and 12MR channels are accessed from the side and the end of the crystals, respectively. For some catalysts, the small 8MR channel openings are abundant and dominate, giving rise to a typical 8MR product spectrum, despite the presence of accessible 12MR channels. However, unlike all previous reports, the product distribution (product shape selectivity) seen for one of the catalysts is controlled by the 12-ring channels and reflects the actual offretite topology, in contrast to the other catalysts and previous reports. These results constitute a new example of morphology induced shape selectivity for zeolite catalysts.

Second, in another work, a variety of synthetic procedures were used to obtain zeolite ZSM-23 (MTT) catalysts with crystallite sizes ranging from the micrometer to nanometer scale. When this 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, by nearly two orders of magnitude. The results indicate that the catalyst lifetime can be explained by the length of the unidirectional channels, which tend to be parallel to the longest crystal dimension, leading to long diffusion pathways and rapid coke accumulation for large crystals.

Third, a series of ZSM-5 zeolite catalysts having very different particle morphologies have been prepared and carefully characterized. These catalysts (micron sized crystals, nanometer sized crystals, and sub nanometer unit cell thick layers of catalysts) have been tested as catalysts in the methanol to hydrocarbons reaction, n-hexane cracking, and as methylation catalysts. Again, a profound and complex impact is seen of morphology on performance, both with respect to catalyst activity and deactivation resistance.

At the time of writing this report, 10 journal publications have been accepted. 40 lectures or posters have been presented at various conferences and seminars directed towards different audiences.

Impact of the project

ZeoMorph has gathered leading European groups within the field of zeolite science, and has been strengthened by the complementary nature of expertise offered by the individual participants. Student exchange between the partners has been a key characteristic of the project and this has contributed to a strengthening of the competitive edge of the training network.

Within the project, 5 PhD candidates with unique multi-faceted emphasis on world leading basic research, industrial innovation and entrepreneurship, and outreach/dissemination will be educated. PhD candidates educated in the field of catalysis are very attractive and competitive for a broad range of jobs and end up in industry, research and administration, consulting companies, research institutes, academia, and as civil servants at a high level. The candidates that have completed their degrees at the time when this report is written have indeed found employment in relevant industry.

The primary users of the new knowledge generated in ZeoMorph will be refinery operators (oil companies) and the global suppliers of catalysts and technology for refinery and petrochemical processes.

The scientific output of ZeoMorph may, in a long term perspective, lead to substantial European impacts. The catalytic processes that will be investigated are strongly related to the key strategic European issues of a secure supply of fuels and petrochemicals, and process improvements derived from ZeoMorph outputs may have substantial implications.

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