Progress on Modified Calcium Oxide Derived Waste-Shell Catalysts for Biodiesel Production

Experimental and Quantum Chemical Calculations on the High-Efficiency Transesterification of Dimethyl Carbonate with Alcohol Catalyzed by Calcium Oxide

Typical catalysts used in dimethyl carbonate (DMC) transesterification encounter challenges in terms of environmental sustainability and economic viability. Calcium oxide (CaO), being an environmentally friendly and cost-effective catalyst, exhibits favorable compatibility with the criteria above. It has been conclusively demonstrated that CaO performs high efficiency as a catalyst for the transesterification between alcohols and DMC. The optimal conditions for the CaO-catalyzed transesterification of DMC and 1-octanol were determined (90 °C, 17 h, and CaO/1-octanol/DMC molar ratio = 0.3:1.0:40.0), under which the conversion of 1-octanol reaches 98.3%, while the yield and selectivity of methyl octyl carbonate are 98.1 and 99.9%, and CaO has been proven to have the efficient ability to be recycled three times. Meanwhile, the CaO-catalyzed reaction mechanism of the transesterification of DMC with alcohol is illustrated in the quantum chemical method based on the M06-2X functional, and the structures of the corresponding transition states are simultaneously derived. The activation energy barrier is proven to be effectively decreased by the catalytic effect of CaO. In addition, the electrostatic potential diagram verifies the proposed reaction sites. This research constructs the theoretical basis for CaO-based DMC chemistry and expands the green catalysts available for the synthesis of dialkyl carbonates.

Microwave-Assisted Biodiesel Production Using UiO-66 MOF Derived Nanocatalyst: Process Optimization Using Response Surface Methodology

The present work is on the transesterification of soybean oil to biodiesel under microwave irradiation using a biomass and MOF−derived CaO−ZrO2 heterogeneous catalyst. The optimisation of different parameters was processed by adopting a central composite design for a response−surface methodology (RSM). The experimental data were fitted to a quadratic equation employing multiple regressions and investigated by analysis of variance (ANOVA). The catalyst was exhaustively characterised by XRD, TGA, FTIR BET, SEM, TEM, CO2 TPD and XPS. In addition, the synthesized biodiesel was characterized by 1H and 13C NMR, GCMS. The physicochemical properties of the biodiesel were also reported and compared with the ASTM standards. The maximum yield that was obtained after optimization using RSM was 97.22 ± 0.4% with reaction time of 66.2 min, at reaction temperature of 73.2 °C, catalyst loading of 6.5 wt.%, and methanol−to−oil ratio of 9.7 wt.%.

Trends in Widely Used Catalysts for Fatty Acid Methyl Esters (FAME) Production: A Review

The effective transesterification process to produce fatty acid methyl esters (FAME) requires the use of low-cost, less corrosive, environmentally friendly and effective catalysts. Currently, worldwide biodiesel production revolves around the use of alkaline and acidic catalysts employed in heterogeneous and homogeneous phases. Homogeneous catalysts (soluble catalysts) for FAME production have been widespread for a while, but solid catalysts (heterogeneous catalysts) are a newer development for FAME production. The rate of reaction is much increased when homogeneous basic catalysts are used, but the main drawback is the cost of the process which arises due to the separation of catalysts from the reaction media after product formation. A promising field for catalytic biodiesel production is the use of heteropoly acids (HPAs) and polyoxometalate compounds. The flexibility of their structures and super acidic properties can be enhanced by incorporation of polyoxometalate anions into the complex proton acids. This pseudo liquid phase makes it possible for nearly all mobile protons to take part in the catalysis process. Carbonaceous materials which are obtained after sulfonation show promising catalytic activity towards the transesterification process. Another promising heterogeneous acid catalyst used for FAME production is vanadium phosphate. Furthermore, biocatalysts are receiving attention for large-scale FAME production in which lipase is the most common one used successfully This review critically describes the most important homogeneous and heterogeneous catalysts used in the current FAME production, with future directions for their use.