Production of Bio-Hydrogenated Diesel by Hydrotreatment of High-Acid-Value Waste Cooking Oil over Ruthenium Catalyst Supported on Al-Polyoxocation-Pillared Montmorillonite

Abstract

Waste cooking oil with a high-acid-value (28.7 mg-KOH/g-oil) was converted to bio-hydrogenated diesel by a hydrotreatment process over supported Ru catalysts. The standard reaction temperature, H 2 pressure, liquid hourly space velocity (LHSV), and H 2 /oil ratio were 350 °C, 2 MPa, 15.2 h -1 , and 400 mL/mL, respectively. Both the free fatty acids and the triglycerides in the waste cooking oil were deoxygenated at the same time to form hydrocarbons in the hydrotreatment process. The predominant liquid hydrocarbon products (98.9 wt%) were n-C 18 H 38 , n-C 17 H 36 , n-C 16 H 34 , and n-C 15 H 32 when a Ru/SiO 2 catalyst was used. These long chain normal hydrocarbons had high melting points and gave the liquid hydrocarbon product over Ru/SiO 2 a high pour point of 20 °C. Ru/H-Y was not suitable for producing diesel from waste cooking oil because it formed a large amount of C 5 -C 10 gasoline-ranged paraffins on the strong acid sites of HY. When Al-polyoxocation-pillared montmorillonite (Al 13 -Mont) was used as a support for the Ru catalyst, the pour point of the liquid hydrocarbon product decreased to −15 °C with the conversion of a significant amount of C 15 -C 18 n-paraffins to iso-paraffins and light paraffins on the weak acid sites of Al 13 -Mont. The liquid product over Ru/Al 13 -Mont can be expected to give a green diesel for current diesel engines because its chemical composition and physical properties are similar to those of commercial petro-diesel. A relatively large amount of H 2 was consumed OPEN ACCESSCatalysts 2012, 2 172 in the hydrogenation of unsaturated C=C bonds and the deoxygenation of C=O bonds in the hydrotreatment process. A sulfided Ni-Mo/Al 13 -Mont catalyst also produced bio-hydrogenated diesel by the hydrotreatment process but it showed slow deactivation during the reaction due to loss of sulfur. In contrast, Ru/Al 13 -Mont did not show catalyst deactivation in the hydrotreatment of waste cooking oil after 72 h on-stream because the waste cooking oil was not found to contain sulfur-containing compounds.

Catalytic Deoxygenation of Hexadecyl Palmitate as a Model Compound of Euglena Oil in H2 and N2 Atmospheres

“…The yield of C 10 -C 16 hydrocarbons is important as they can be used as aviation fuel [16]. As shown in Figure 7 [6,7]. The amounts of formed CO and CO 2 almost kept constant after reaction for 2 h. A small amount of C 1 -C 4 gaseous hydrocarbons was also formed during the reaction in H 2 atmosphere, and the amount of C 1 -C 4 gaseous hydrocarbons increased with prolonging the reaction time.…”

“…C15H31COOC16H33 + H2 = C15H32 + C16H34 + CO2 Decarboxylation (6) As shown in Reactions (4)- (6), the reduction of one C15H31COOC16H33 molecule produces two C16H34 molecules. On the other hand, either decarbonylation or decarboxylation of one C15H31COOC16H33 molecule produces one C16H34 molecule and one C15H32 molecule.…”

“…For deoxygenation of C15H31COOC16H33 in H2 atmosphere, the metal site alone could achieve a high activity, because deoxygenation was carried out via three routes: reduction, decarbonylation, and decarboxylation. We used an acid support for the metal in order to adjust the selectivity of the hydrocarbon products during deoxygenation in H2 atmosphere [6,7]. In this study, we used a base support (Mg(Al)O) for the metal (Pd) in order to suppress the hydrocracking of n-C15H32 and n-C16H34 products (to light hydrocarbons) during deoxygenation of C15H31COOC16H33 in H2 atmosphere.…”

“…We used an acid support for the metal in order to adjust the selectivity of the hydrocarbon products during deoxygenation in H 2 atmosphere [6,7]. In this study, we used a base support (Mg(Al)O) for the metal (Pd) (6)) occurred during the reaction.…”

“…Vegetable oils can be converted to fatty acid methyl esters (FAME, known as biodiesel) by transesterification with methanol [4]. Recently, the hydrotreatment of vegetable oils to produce hydrocarbon 'drop-in' fuels has attracted global research interest [5][6][7].…”