Hydrothermal Decarboxylation of Corn Distillers Oil for Fuel‐Grade Hydrocarbons

Abstract

Catalytic hydrothermal conversion of non‐edible corn distillers oil (CDO), a low‐value by‐product of the ethanol industries, into high value fuel‐grade hydrocarbons was investigated in near‐supercritical water. The decarboxylation experiments were conducted using activated carbon in a 300 mL batch stirred tank reactor at reaction temperatures of 300–400 °C with pressure ranges from 2200–2500 psi (≈15–17 MPa), water/CDO (v/v) ratios of 2:1 to 5:1, and reaction times of 0.5 to 4 h at constant stirring speed (800 rpm). For the first time, complete removal of the −COO− group from CDO was achieved at 400 °C with 4 h of reaction time and a water/CDO (v/v) ratio of 4:1. The liquid products obtained were a mixture of saturated hydrocarbons, mainly C8–C16 (selectivity 49.7 %) and heptadecane (48.9 %) which have similar specific gravity, higher heating value (HHV), cloud points, and pour points to those of commercial fuels. 65 % liquid yield was obtained under optimal reaction conditions. The reaction mechanism was found to follow pseudo‐first‐order kinetics with an activation energy 66.1±3 kJ mol−1, which is much lower than similar reported literature values for the decarboxylation process.

The Effect of Activated Carbon Pellet on Hydrothermal Decarboxylation of Palm Olein into Renewable Diesel

“…It was comparable to the highest yield of heptadecane. However, compared with temperatures of 300 °C and 330 °C, there is a decrease in CO2 19) . It is consistent with this study's findings that there is an increase and decrease in CO2 gas production.…”

“…In an autoclave with a 500 mL volume, palm olein was deoxygenated hydrothermally at various temperatures of 330 -400 °C) with pressure range from 52-230 bar. Reactants are palm olein oil (30 grams), deionized water (120 grams), and activated carbon pellets (21 grams) were loaded for a typical reaction 19). After purging and filling with N2 gas under static conditions, the autoclave's temperature was adjusted to the reaction condition.…”

“…Hossain used powder-activated carbon, while this study used activated carbon pellets with a larger pore size than powder form. The Hossain research's optimum conditions were adopted in this work: the water to oleic acid ratio of 4:1 (w/w), the catalyst to total feed ratio (0.7), and the residence time of 4 h 19) .…”

“…According to Hossain's research, the -COO group from CDO could be thoroughly eliminated at 400 °C within 4 hours and water to CDO ratio of 4:1. The main products were C8 to C16 (49.7% selectivity) and heptadecane (48.9%) saturated hydrocarbons 19) . So, this work used optimum conditions based on Hossain's study.…”

Recent advances in the catalytic deoxygenation of plant oils and prototypical fatty acid models compounds: Catalysis, process, and kinetics

“…They showed that deoxygenation of saturated and unsaturated fatty acids can be conducted at near supercritical water temperature with a selectivity over 90% towards HCO 2 products, but the molar yield of HCO 2 products obtained was only 6 %. Other than supercritical water, Hossain et al [189,199] and Edeh et al [186] exploited the diffusivity of subcritical water in the deoxygenation of fatty acid derivatives and corn oil into diesel-like hydrocarbons, both demonstrated excellent n-alkanes selectivity and liquid yield. In the same theme, both Vardon et al [198] and Hollak et al [200] employed hydrothermal aqueous phase reforming of glycerol for in-situ hydrogen production and the catalytic HCO 2 of triglycerides.…”