CATalyst transformations and LIFEtime by in-situ techniques and modelling (CATLIFE)

Microporous materials with nanometer pores, called zeolites, have found many applications within catalysis and separation processes, and with the discovery of the related silicoaluminophosphate (SAPO) molecular sieve materials in the eighties further new possibilities opened up. Some important examples of applications for these materials are: Conversion of methanol to ethene and propene (a process now being commercialized in China at large scales), various hydrocarbon transformation reactions, and as catalysts for the reduction of NOx emissions. With the many possible structures and modifications, more applications of SAPO catalysts are likely to emerge in the future. However, even with a good performance in many reactions the catalysts deactivate with time by coking and/or structural degeneration. Improvement and understanding of long-term performance is therefore an important research topic that can influence large scale operations. In this project we have studied microporous crystalline catalyst's transformations, dynamics and stability by using several highly complementary approaches. On the experimental side, we have prepared model catalyst systems and used new and specially designed X-ray and NMR equipment at UiO and SINTEF together with the large scale X-ray synchrotron facility in Grenoble. Together with various modelling approaches, we have been able to understand crystal growth and detrimental structural changes that take place during use. Among the catalysts we have studied, there are large differences in stability. Initially when water molecules enters the catalyst pores they strongly interact through hydrogen bonds with the framework walls and/or the catalytic active site. However, for one catalyst system, we observed that at a certain water loading level the structure stretches out before bonds are ruptured. Through comparisons with other chemical similar catalysts we suggest that the topology of the actual framework is determining the stability. For those catalysts with more robust topologies we observe subtle changes with use. However, at a certain point the catalytic active site starts to decompose in these materials. This results in fewer active sites as well as extensive pore blocking, thus deactivating the catalyst over time.

Microporous materials have many applications within catalysis and separation processes and with the discovery of the related silicoaluminophosphate (SAPO) molecular sieve materials in the eighties new possibilities opened up as e.g. olefins could be produ ced efficiently from methanol using the SAPO version of the chabazite mineral. In the nineties UOP and Norsk Hydro (now INEOS) developed the H-SAPO-34 based MTO process. The MTO process is probably the most known process using a SAPO catalyst system, but e.g. the SAPO-37 catalyst has been used for many different reactions where isomerization of n-decane and isobutene/2-butene alkylation are two examples. In addition to various conversion routes for hydrocarbons by SAPO catalysts, the SAPO-34 catalyst has also been investigated as a deNOx catalyst and more applications of SAPO catalysts are likely to emerge in the future. However, in all industrial catalytic processes catalysts deactivate and microporous materials typically do that by coking and/or structu ral degeneration and large efforts have been put in to improve and understand long term performance. Along this line, the CATLIFE project has catalyst performance and long term stability as key topics. The CATLIFE project will apply in-situ XRD and in-sit u NMR together with long term deactivation studies in a parallel fixed bed reactor unit and modelling studies to improve the understanding of the chemical processes taking place when the SAPO catalysts degrade during reactive conditions. A successful proj ect will reveal structure-activity relationships throughout the lifetime of the catalysts resulting in possible improved catalyst formulations and more realistic material deactivation models.