A Novel Radioisotope Method for Studying Catalytic Transformations over Alumina, H-ZSM-5 and H-Beta Zeolite Catalysts: Investigation of Conversion of11C-Labeled Methanol to11C-Labeled Dimethyl Ether and Hydrocarbons

Abstract

A novel radiochemical method for investigating the catalytic transformations of the 11C-radioisotope labeled methanol over H-ZSM-5 and H-Beta zeolite catalysts has been introduced. The catalysis process was monitored by gamma detectors and the 11C-labeled products were analyzed by radio-gas chromatography. The medium pore H-ZSM-5 and H-Beta zeolite catalysts were synthesized and characterized using X-ray powder diffraction, scanning electron microscope, nitrogen adsorption, X-ray fluorescency and FTIR spectroscopy. The investigations of 11C-labeled product distributions and reaction mechanism of the conversion of [11C]methanol over H-ZSM-5 and H-Beta zeolite catalysts have been elaborated in terms of structure and acidity of the catalysts. In microreactors the effect of natural carbon compounds from environment can be a disturbing effect for the detection of inactive carbon products. Applied radio detection method eliminates these disturbing effects and detects only 11C-labeled compounds during the whole catalytic process. In the study of the transformations of carbon compounds, besides the well known 14C tracer technique and 13C MAS NMR spectroscopy investigation, the 11C-method is a new, more sensitive and simple one to monitor the transformation of the starting 11C-labeled compound by radio detectors (gamma detector) and for analyzing the 11C-labeled products by radio-gas chromatography.