Synthesis of Ti(SO4)O solid acid nano-catalyst and its application for biodiesel production from used cooking oil

- A novel solid acid nanocatalyst, Ti(SO4)O, was synthesised from TiO2 and chlorosulphonic acid.
- The XRD and SAED data confirms the JCPDS-ICDD card № 04-011-4951for Ti(SO4)O.
- We examined the catalytic activity, stability and reusability of Ti(SO4)O.
- The FAME yield from UCO was 97.1% at optimum process conditions using Ti(SO4)O.
- Produced biodiesel from UCO satisfied ASTM D6751and EN 14214 standards.

A novel solid acid nano-catalyst [Ti(SO4)O] was synthesised and used for the simultaneous esterification and transesterification of free fatty acids in used cooking oil (UCO) to produce biodiesel. The synthesised nano-catalyst was fully characterized by different analytical techniques. The XPS results clearly confirmed that the bidentate sulphate coordinated to the Ti4+ metal in the nano-catalyst product. Obtained d-spacing values from the experimental data of XRD peaks and the SAED pattern of produced nano-catalyst agreed well with the d-spacing values from the JCPDS-ICDD card numbers 04-011-4951 for titanium sulphate oxide or titanium oxysulfate crystal structures.This confirms the sulphate groups were within the crystalline structure rather than on the surface of titania nanoparticles, which has not been previously reported. It has been demonstrated 97.1% yield for the fatty acid methyl ester can be achieved usign the synthetised catalyst under a reaction time of 3 h, catalyst to UCO ration of 1.5 wt% and methanol to UCO ratio of 9:1 at 75 °C reaction temperature. The nano-catalyst showed a good catalytic activity for the feedstock containing ≤6 wt% free fatty acid. Furthermore, the catalytic activity and re-usability of the Ti(SO4)O for the esterification/transesterification of UCO were investigated. XRD results confirmed that the amount of SO42− species in the solid acid nano-catalyst slowly decreased with re-use after 8 cycles under optimised conditions, which is higher than the reusability of other functionalised titania reported in the literature. Finally, the biodiesel prodcued from this process satisfied the ASTM and European Norm standards.

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