The production and the properties of the liquid organic hydrogen carrier (LOHC) obtained from the light cycle oil (LCO)

Abstract

A technological concept of production of a hydrocarbon LOHC prototype from the light cycle oil (LCO) has been proposed with the estimate of the key features through an experimental study. It has been shown that an alkylnaphthalene-rich LCO could be converted into a narrow alkyldecalin fraction (T5%/T95% = 206/231 °C) via a combined distillation‑hydrogenation approach. The obtained product has been characterized as a potential LOHC. Upon the dehydrogenation over a commercial Pd/C catalyst in a flow reactor at 320–400 °C the release of pure H2 (99.3–99.8 vol%) was observed; the estimated H2 yield did not exceed 26% due to a severe catalyst deactivation. A multistep dehydrogenation in a batch reactor (T = 380 °C, Pd/C) allowed a conversion of 87.9% be obtained. Both the starting and the dehydrogenated carriers were found to be diesel fuel-like liquids with high flash points (87 and 101 °C), low viscosities (2.63 and 2.89 mm2 s−1) and excellent low-temperature properties (freezing points < −60/−26 °C; melting points < −60/−36 °C). The GCxGC/MS technique was applied to characterize the chemical composition of the LOHC; the calculation of the hydrogen capacity by means of the “virtual (de)hydrogenation” protocol has been shown. The hydrogen capacity for the LCO-derived LOHC prototype was found to be 5.97 wt% or 66.9 nl H2 per 1 kg of the LOHC, and the hydrogen content in the H2-rich and H2-lean carriers amounted to 13.27 and 7.77 wt%, respectively.