Alcohols dehydration in heterogeneous system – FTIR method development for quantitative determination of catalytic parameters

Abstract

Quantification of the FTIR spectra makes it possible to monitor in situ the catalytic reactions in heterogeneous systems using a batch-mode microreactor. The tested catalysts included a series of solid heteropolyacids (HPAs): H3PW12O40, H3PMo12O40, H6P2W18O62 and H6P2Mo18O62 with Keggin and Wells-Dawson anion structures. The FTIR has been used to monitor the reaction progress in the alcohol dehydrations, by in situ detection of changes in composition of the gas phase over the catalyst surface. This procedure made it possible to evaluate both the degree of conversion and the yields of products as a function of time and temperature. The studied reactions included dehydrations of methanol and of 2-propanol, both processes relying on the catalyst’s acidity. In both the reactions, the HPAs performance turned out to compare well with their acidity determinations carried out by measuring their heats of the NH3 sorption with the gas flow-through microcalorimetry. In case of the 2-propanol dehydration, the catalytic performance of the HPAs in this reaction has also been tested using a more typical setup of the flow-through mode microreactor, combined the gas chromatograph for down-stream detection, and the results have been compared to the batch-mode results for the process. A qualitative agreement between the two microreactor techniques has been found.