Hydroconversion of Waste Cooking Oil into Bio‐Jet Fuel over a Hierarchical NiMo/USY@Al‐SBA‐15 Zeolite

Abstract

The direct conversion of waste cooking oil (WCO) into bio-jet fuel was investigated over a core-shell hierarchical USY@Al-SBA-15 zeolite-supported NiMo catalyst. The core-shell structure showed better acid and pore size distributions. The synergetic effect of the core-shell micropore and mesopore structure significantly contributed to enhancing the selectivity for the jet fuel (C 9-15 hydrocarbons) from 9.3 % over NiMo/USY up to 35.7 % over NiMo/USY@Al-SBA-15, with high isomerization (iso-/n-paraffins ratio = 2.7) and moderate aromatic fraction (18.7 %). The decarboxylation reaction was selectively enhanced. Optimal selectivity for jet fuel (39.7 %) was obtained at 380°C and a high H 2 /oil ratio would decrease the yield of jet fuel. This catalyst showed excellent stability for the hydroconversion of WCO to hydrocarbons.

Influence of Impurities and Oxidation on Hydroconversion of Waste Cooking Oil into Bio‐jet Fuel

“…Generally, the triglycerides are converted into alkanes through three reaction pathways: HDO, decarbonylation (DCO), and decarboxylation (DCO 2 ). In previous works, the selectivity for DCO x /HDO could be identified by the C 17 /C 18 ratio , , . As illustrated in Fig.…”

“…However, the conversion also declined to some extent after the coke formed. The conversion of WCO on NiMo/USY@Al‐SBA‐15 was reported to be almost 100 % for a long time (at least 14 h) because the formed suitable pore channel reduced the chance of coke formation (Tab. S2).…”

“…The selectivities of polycyclic aromatic hydrocarbons, long‐chain cycloalkanes, and long‐chain cyclanes was low (below 0.4 %), while the selectivities of these materials using NiMo/USY were above 3 %. This can be attributed to the fact that the core‐shell of NiMo/USY@Al‐SBA‐15 contained a rational acid gradient with a strong acid inside and a weak acid outside, leading to a hierarchical porous structure .…”

“…USY, ZSM‐5, and Al 2 O 3 served as catalyst supports. Two composite supports, namely, USY and mesoporous materials (MCM‐41, SBA‐15), were also used , . The support was loaded with 4.0 wt % Ni and 12 wt % Mo by incipient wetness impregnation with an aqueous solution containing (NH 4 ) 6 Mo 7 O 24 and Ni(NO 3 ) 2 .…”

“…WCO is two to three times cheaper than vegetable oils and has become a promising feedstock in biofuel production , . However, compared with vegetable oils, WCO contains many different impurities.…”