Waste-Derived Green Nanocatalyst for Biodiesel Production: Kinetic-Mechanism Deduction and Optimization Studies

Abstract

This research focuses on deducing the kinetic mechanism for biodiesel production catalyzed by a CaO nanocatalyst derived from waste cockle shells via thermal hydration–dehydration treatment. In addition, the CaO nanocatalyst preparation method via thermal hydration–dehydration-related parameters (hydration duration, recalcination temperature, and recalcination duration) was studied and optimized. The transesterification reaction catalyzed by the CaO nanocatalyst followed the Langmuir–Hinshelwood kinetic mechanism with surface reaction as the rate-limiting step. The relatively low activation energy (3786.7 J/mol) for a transesterification reaction offered by the CaO nanocatalyst enhanced the reaction rate to 27.3% FAME yield/hr. The optimal conditions for the thermal hydration–dehydration treatment used to develop the nano CaO catalyst were 6 h of hydration duration, 650 °C of recalcination temperature, and 3 h of recalcination duration. Of biodiesel yield, 94.13% was obtained at a moderate temperature of 60 °C and 3 h reaction time during the transesterification of palm oil catalyzed by the nano-CaO. SEM, BET, and TPD results proved that the CaO nanocatalyst had a large surface area (13.9113 m2/g) and high pore volume (0.0318 cm3/g) that were rich in active sites (1046.46 μmol CO2/g), and the pore diameter (33.17 nm) was accessible to reactants and products.

Synthesis and Characterization of Calcium Oxide Impregnated on Silica from Duck Egg Shells and Rice Husks as Heterogeneous Catalysts for Biodiesel Synthesis

“…Impregnation of CaO on silica is expected to increase the activity of the catalyst by increasing the accessibility of the active site and providing sufficient attachment area 23 . In comparison, the pore diameter of CaO as catalyst 33-41 nm, is slightly larger than that of the molecular reaction, where the dimensions of glycerol and biodiesel product are about 0.10 nm and 0.64 to 1.52 nm 24 , respectively. The larger average pore diameter and the interconnection between the catalyst pores will limit the molecular diffusion of the reactants, so that the molecular reactants can easily infiltrate the interior of the catalyst, and most of the active sites will be used during the transesterification reaction 25 .…”

Biomass Waste-Derived Catalysts for Biodiesel Production: Recent Advances and Key Challenges

“…Hence, attempts have been made to increase the basicity, stability and activity of waste shellderived CaO by doping with active metals [37][38] [39], by catalyst support [40] (Fig. 3b), and by hydration-dehydration [41][42] [43][44] (Fig. 3c).…”

“…Of particular appeal, this performance could be achieved at room temperature [42]. Cockle shell [43] was converted into nano-CaOC-H-D and was utilized in the transesterification of palm oil in 96.43 % yield.…”

Biomass‐based heterogeneous catalysts for biodiesel production: A comprehensive review

“…This corresponds to the results published by Viriya‐empikul et al 50 and Roschat et al 61 They demonstrated in their research that 0.5 hours is not enough calcination time to activate a catalyst. The optimal calcination time was between 2 and 4 hours since the catalytic activity decreases when the calcination time exceeds 4 hours due to a decrease in the surface area related to catalyst sintering when isothermal treatment is applied at prolonged time 50,70,71 . However, in some studies, a calcination time between 6 and 8 hours has been effective for the preparation of solid catalysts, achieving adequate catalytic activity, with a biodiesel yield between 85 and 97% 43,54,66 …”

“…The optimal calcination time was between 2 and 4 hours since the catalytic activity decreases when the calcination time exceeds 4 hours due to a decrease in the surface area related to catalyst sintering when isothermal treatment is applied at prolonged time. 50,70,71 However, in some studies, a calcination time between 6 and 8 hours has been effective for the preparation of solid catalysts, achieving adequate catalytic activity, with a biodiesel yield between 85 and 97%. 43,54,66 Some studies used the impregnation method for the preparation of supported solid base catalyst (see Figure 3).…”