Large and extra-large pore acidic ITQ-zeotypes: An in-situ spectroscopic study of fundamental properties.

Abstract

The first aim of this thesis was to investigate the fundamental properties in the local environment around Ge in extra-large pore acidic ITQ-33 zeotype and large pore acidic ITQ-7 zeotype with in-situ X-ray absorption spectroscopy (XAS). The second aim of this thesis was to synthesize and investigate the catalytic properties of large pore acidic ITQ-24 zeotype with in-situ Fourier Transform-Infrared Spectroscopy (FT-IR) for the Methanol to hydrocarbons (MTH)-reaction. Of the synthesis experiments, three of the most promising ITQ-24 samples were investigated. The first sample contained Al in its composition, while second contained B. The third also contained Al, but was synthesized with hydrofluoric acid (HF).

The in-situ XAS measurements for ITQ-33 and ITQ-7 were conducted during two separate beamtimes at the Swiss-Norwegian Beamline (SNBL) at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. As-synthesized samples of both zeotypes were submitted to an oxygen-helium (O2/He) atmosphere and heated insitu.The ITQ-33 sample was studied with XAS during heating, while ITQ-7 was studied with a combination of XAS and high resolution powder X-ray diffraction (PXRD). In both samples it was investigated for changes in parameters such as multiplicity andbonding length in the local environment surrounding Ge, during stages such as water desorption and template decomposition in both materials. For the in-situ FT-IR investigation of ITQ-24 species for the MTH-reaction, three different samples of calcined ITQ-24 was compared based on the way they were synthesized and their composition.The FT-IR experiments were conducted in-house at NTNU, Trondheim.

The result of the in-situ XAS analysis of ITQ-33 and the in-situ XAS/PXRD analysis of ITQ-7 revealed that Ge was present in tetravalent coordination and in oxidation state +4at room temperature for both materials. It also revealed that the second shell environment in these zeotypic materials depend on Ge-concentration. The in-situ XAS andXAS/PXRD experiments on Al-ITQ-33 and Al-ITQ-7 respectively revealed that the local environment around Ge behaved differently during stages such as water desorption and template removal for the two zeotypes. These changes were due to how the different templates of Al-ITQ-33 and Al-ITQ-7 affected the zeotype structure during template decomposition. The in-situ FT-IR experiments showed that the Al-containing ITQ-24sample functioned as an active catalyst for the MTH-reaction. The B-containing sampleshowed no presence of acidic sites and was not tested for the MTH-reaction. The Alcontaining ITQ-24 sample synthesized with HF showed signs of acidity and was tested for the MTH-reaction, but showed no catalytic activity.