Soutenance de thèse Sara ALMASI

I have the pleasure of inviting you to my thesis defense, which will take place on Wednesday, April 24th at 9:30 a.m . in the salle des thèses in the ENSIACET/INP building.

The thesis is entitled « A Sustainable Catalyst and Vibromixing Process for Enhancing Biodiesel and Biolubricant Production », directed by Joelle AUBIN (LGC) and Barat GHOBADIAN (Tarbiat Modares University, Iran).

The defense will be conducted in English.

The jury will be composed of:

• Ms. Martine POUX, Co-encadrante, Toulouse INP
• Ms. Shaliza IBRAHIM, Rapporteur, University Malaya, Malaysia
• Mr. Lionel ESTEL, Rapporteur, INSA Rouen
• Mr. Pascal FONGARLAND, Examiner, Université Claude Bernard Lyon

Abstract

The environmental impact caused by the use of non-renewable fuel and lubricant resources, coupled with concerns about climate change, has increased the demand for sustainable energy sources. Biobased products, such as biodiesel and bio-lubricants, have emerged as alternatives to mineral fuels and lubricants due to their availability, renewability, lower gas emissions, non-toxicity and biodegradability. Although biodiesel and bio-lubricants are typically produced through the transesterification reaction with homogeneous catalysts in conventional stirred-tank reactors, there are two primary challenges associated with each of these processes. Firstly, the use of homogeneous catalysts requires numerous and costly purification steps. Heterogeneous basic catalysts that have high surface area and that are reusable and easy to separate are a promising solution to mitigate these challenges. Secondly, the transesterification reaction is a slow mass-transfer limited reaction that involves two immiscible liquids, specifically triglyceride and methanol. For biodiesel production in stirred-tank reactors there are many associated challenges such as inadequate mixing, limited interfacial area between liquids and long process times. This results in low biodiesel content and the formation of undesirable secondary products. Alternate mixing equipment that improves liquid-liquid contacting to intensify and enhance the transesterification may be required.

The objective of this study is to explore two different ways to enhance biodiesel and biolubricant production: by developing a new heterogeneous catalyst and by using a vibromixer to enhance mixing. Firstly, a heterogeneous basic catalyst named magnetic activated carbon, derived from almond shell waste and modified by calcium oxide (MAC@CaO), was synthesized. The resulting material underwent comprehensive characterization using various techniques. Subsequently, the potential of the MAC@CaO as a recoverable basic catalyst in transesterification reactions was explored, focusing on the production of fatty acid methyl ester (FAME) and trimethylolpropane triester (TMPTE). Optimal reaction conditions yielded FAME and TMPTE yields of 93.2% and 95.3%, respectively. The recyclability of the MAC@CaO catalyst was also assessed to determine its chemical stability. FAME and TMPTE yields remained consistently above 85% over five consecutive cycles, highlighting the potential of the developed catalyst. In the second part of this thesis, the vibromixer underwent comprehensive testing to evaluate its mixing capabilities for both single-phase and multiphase (solid-liquid and liquid-liquid-solid) mixing operations. The objective of this assessment was to gain a better understanding of the vibromixer device for various mixing processes by quantifying mixing time, cloud height, and Pickering emulsion production before applying it to biodiesel production. The results show that single phase mixing and solid suspensions improve when increasing the vibration amplitude and mixer plate size. Pickering emulsions characterized with small droplet sizes (approximately 2 microns) have a stability exceeding two months. Subsequently, the results from the biodiesel production experiments using the vibromixer demonstrated a similar trend. With an increase in vibration amplitude, plate size and the number of conical holes in the plate, the FAME content also increased. The maximum FAME content achieved was 97.8% after only 30 minutes; this is equivalent or shorter than for stirred tank reactors. It is expected that the enhanced reaction is due to good flow circulation and excellent breakup of droplets, which consequently increases interfacial area and significantly improves the mass transfer processes involved in the transesterification reaction of triglycerides into FAMEs.

Keywords: Magnetic heterogeneous catalyst; Transesterification; Vibromixer; Mixing