Development of Novel Pyrolysis Technology Involving Chromium for the Measurement of D/H Ratios in n-Alkanes

Abstract

A new pyrolysis technology involving chromium is proposed for the determination of δD in alkanes based on the systematic analysis of reaction temperature, conversion rate, and reaction mechanism. Compared with the traditional high-temperature conversion (HTC) method, our findings suggest that chromium/high-temperature conversion (Cr/HTC) can improve the conversion rate of hydrocarbons and reduce the required pyrolysis temperature by up to 175 °C; meanwhile, the pyrolysis conversion rate of hydrocarbons increased by an average of 2.42% across the entire analyzed temperature range using the Cr/HTC method. Changes in the chromium wire itself were analyzed using X-ray photoelectron spectroscopy (XPS); this facilitated an understanding of the interaction mechanism between chromium and hydrocarbons and possible pathways of the catalytic pyrolysis process. The results show that chromium reacts with hydrocarbons, capturing carbon as chromium carbide (Cr2C3 and CrC3) and releasing hydrogen in the form of H2. As the reaction progresses, the resulting free carbon accumulates on the surface of the chromium wire or chromium carbide, resulting in a marked reduction in the Cr/C ratio; these findings provide reliable evidence for the further application of Cr/HTC technology.