Visible light assisted sulfonic acid-functionalized porphyrin comprising benzimidazolium moiety for photocatalytic transesterification of castor oil

• Published in: Fuel (Guildford) Vol. 304; p. 121490
• Main Authors: Bhansali, Karan J., Balinge, Kamlesh R., Raut, Subodh U., Deshmukh, Shubham A., Senthil Kumar, M., Ramesh Kumar, C., Bhagat, Pundlik R.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 15.11.2021; Elsevier BV
• Subjects: Acidity; Alcohols; Ambient temperature; Biodiesel; Biodiesel fuels; Biofuels; Castor oil; Catalytic activity; Heterogeneous photocatalyst; High-performance liquid chromatography; Hydrogen; Imidazole; Liquid chromatography; Methyl ricinoleate; NMR; Nuclear magnetic resonance; Photocatalysis; Photocatalysts; Porphyrin; Porphyrins; Reaction mechanisms; Recyclability; Room temperature; Sulfonic acid; Transesterification; Vegetable oils; Visible light; Heterogeneous photocatalyst; Visible light; Methyl ricinoleate; Transesterification; Porphyrin; Biodiesel
• ISSN: 0016-2361; 1873-7153
• DOI: 10.1016/j.fuel.2021.121490

[Display omitted] •(SAFPBM) as heterogeneous photocatalyst was synthesized and characterized.•The transesterification of castor oil performed with was with methanol ethanol in presence of visible light irradiations (5W/9W/12W LED).•Maximum yield of the methyl biodiesel achieved of 94% (18 h, 15 mg photocatalyst under visible light at ambient conditions).•The heterogeneous photocatalyst (SAFPBM) was recycled up to 7th cycle without declined its activity.•The possible mechanism is through formation of H+, CH3O* and RCOOH* on the surface of catalyst. A novel sulfonic acid-functionalized porphyrin comprising benzimidazolium moiety (SAFPBM) was prepared using 1-(3-formyl-2-hydroxybenzyl)-3-(4-sulfobutyl) (3a), dihydro-1H-benzo[d] imidazole-3-ium(oxidosulfinyl)bis(I1-oxy) (7a) and pyrrole in stoichiometric proportions. The synthesized photocatalyst was confirmed by various characterizations and assessed as a potential photocatalyst for the conversion of castor oil to biodiesel component by reaction with alcohols in presence of visible light irradiations (5 W/9W/12 W LED). The photocatalyst with 0.70 Hammett acidity, achieved 94% methyl ricinoleate in 18 h using 15 mg under visible light at ambient temperature and 6:1 methanol: castor oil ratio. SAFPBM displayed admirable photocatalytic activity with recyclability for 7 runs, towards the transesterification of castor oil and other vegetable oils at room temperature. The formation of methyl recinoleate was confirmed by NMR, DEPT, HRMS, HPLC and successfully hydrogenated to methyl 12-hydroxyoctadecanoate using HCOOH as a hydrogen source. A plausible reaction mechanism for the formation of methyl ricinoleate is projected via formation of H+, CH3O* and unstable tetrahedral intermediate on Photocatalytic surface.