This project aims to synthesize several novel heterogeneous catalysts for transesterification of oils to biodiesel. Unlike the common homogeneous catalysts, such as NaOH and KOH, the heterogeneous catalysts can be recycled and reused in the reaction several times. Employing these catalysts also removes the water washing stage and the resultant wastewater as they can be separated from the products by simple filtration. However, they form a third phase in the reaction mixture which significantly increases mass transfer resistance. The higher mass transfer resistance reduces the reaction rate and lengthens the reaction time, dictating more vigorous mixing and harsher reaction conditions in ST reactors. In order to overcome these drawbacks, a hydrodynamic cavitation (HC) reactor will be designed and constructed in this work. The HC reactor is a cutting-edge technology which substantially improves the contact surface area and mixing of the reactants by the cavitation phenomenon. The intensification produced by cavitation is expected to reduce mass transfer resistance in the three-phase system (oil, alcohol and solid catalyst), thus increasing the reaction rate and shortening the reaction time. Utilizing the HC reactor may also lead to higher conversion along with lower feedstock and energy consumption.
Methods. This step of the project is the use of calcium carbide residue (CCR) as a catalyst for biodiesel production (Scheme, A). After the hydrolysis of calcium carbide, the carbide residue will be collected and analyzed. The composition of the residue and its morphology will be studied. Alkalinity, solubility in water, oils and biodiesel fraction will be determined. Of course, the recyclability of CCR will not be high, but the use of waste even once is a step forward in the field of green chemistry. After obtaining biodiesel (Scheme, B), the remained catalyst will be examined by various methods: SEM/TEM, XRD analysis, porosity, FT-IR, etc., in order to reveal the sorption of organic compounds on the catalyst surface, which is also prevent further catalytic processes. CCR use as a catalyst will be carried out for the first time. The dependence of CCR structure on the conditions of calcium carbide hydrolysis will be determined. Hydrolysis of calcium carbide is usually carried out in two ways: by adding water to carbide and by adding carbide to water. Various approaches to hydrolysis have previously been investigated only for a more complete release of acetylene. The structure of CCR was not investigated. These studies will also be carried out for the first time. The main objective of this step is to show whether CCR can be used as a catalyst for biodiesel production.

Scheme. Using calcium carbide residue as a catalyst for biodiesel production

Testing the catalysts in biodiesel production under cavitation conditions
All the resulting catalysts will be investigated in the production of biodiesel with the determination of activity and recyclability. The most efficient catalysts obtained at all stages will be investigated under cavitation conditions. This part of the project will test the scalability of the reaction using the selected catalysts. The effect of ultrasound on the structure and properties of the resulting catalysts was also investigated.

The additional funding will be requested from RSF as a joint proposal this or next year.