Preparation Of Novel Alkali Catalyst And Its Catalytic Transesterification Of Castor Oil For Biodiesel Production

Biodiesel is regarded as a good substitute for petroleum diesel due to the fact that it has the properties of no-toxicity,biodegradable,etc.At present,the biodiesel is commonly prepared by transesterification method,and the heterogeneous base catalyst has gained a lot of attention in catalytic transesterification because it has high catalytic efficiency and excellent catalytic performance,etc.This study focused on the biodiesel production from castor oil through the heterogeneous alkali catalyst catalyzed transesterification.The carbon-doped,red mud-based potassium and carbon-based calcium catalysts were synthesized,respectively.The effect of catalyst preparation condition on catalytic activity were investigated.The catalysts were characterized by X-ray diffraction（XRD）,Scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XPS）and N₂ adsorption-desorption,etc.,respectively.The effect of different conditions for the transesterification of castor oil were studied.The main contents and results of the study were as follows:（1）Using urea as carbon source,the carbon-doped catalyst was successfully synthesized via co-precipitation method.The optimal preparation conditions of catalyst were as follows:urea amount 6 wt%,calcium-to-magnesium molar ratio 1:1,calcination temperature 800 ^oC and calcination time 5 h.The characterization results suggested that the optimum catalyst（1Ca1Mg-6UREA-800-5）had good crystallinity,high basicity（1.55 mol/g）,surface area（358.93 m²/g）and pore volume（0.34 cm³/g）.Based on the XPS analysis,the structure defect of catalyst was formed due to doping carbon,improving the electron transfer between catalyst and reactant.91.1%of biodiesel conversion ratio was obtained under the conditions of molar ratio of methanol to oil 21:1,catalyst dosage 8 wt%,reaction temperature 70℃and reaction time 4 h.The thermo-kinetic results indicated that the transesterification of castor oil catalyzed by 1Ca1Mg-6UREA-800-5 catalyst was a non-spontaneous,endothermic reaction.The comparison results revealed that the catalytic activity of 1Ca1Mg-6UREA-800-5 was obviously higher the Ca O-Mg O-800-5,Ca O,Mg O,Mg O-6UREA-800-5 catalysts.Furthermore,the1Ca1Mg-6UREA-800-5 catalyst had excellent reusability.The results of turnover frequency（TOF）,environmental factor（E-factor）and process mass index（PMI）manifested that 1Ca1Mg-6UREA-800-5 was a high-efficiency catalyst,and the transesterification followed green reaction pathway.（2）Using red mud（RM）and potassium carbonate（K₂CO₃）as raw material.The red mud-based potassium composite catalyst was synthesized via solid method.The optimal preparation conditions of catalyst were:K₂CO₃/RM mass ratio 2:1,calcination temperature 900 ^oC and calcination time 4 h.The following inference can be drawn from the characterization results of catalyst:（1）the optimal catalyst（KRM-2-900-4）contained a lot of active components;（2）the KRM-2-900-4 had more basic sites,large surface area（414.14 m²/g）and pore volume（0.37 cm³/g）.The biodiesel conversion ratio was 94.52%under the optimum reaction condition of methanol to oil molar ratio 18:1,reaction temperature 65 ^oC,reaction time 2.5 h and catalyst dosage 5 wt%.According to the results of thermo-kinetic of reaction,it could be concluded that the transesterification catalyzed by KRM-2-900-4 was a non-spontaneous,endothermic reaction.The conversion ratio reached to 82%when the KRM-2-900-4 catalyst was reused four times.The results of TOF,E-factor and PMI indicated that the KRM-2-900-4 was a high-efficiency catalyst and reaction process was green,eco-friendly.（3）Using bagasse and CaO as raw material,the carbon-based calcium catalyst was prepared by impregnation-calcination method.The optimum preparation parameters of catalyst were as follows:carbonization temperature500 ^oC and carbonization time 3 h.The characterization analysis of catalyst revealed that the optimal catalyst（Ca/C-500-3）had good morphology,high basicity（1.61 mmol/g）,surface area（453.85 m²/g）and proper pore structure.The maximum conversion from castor oil to biodiesel（95.44%）was acquired with methanol to oil molar ratio 18:1,catalyst dosage 5 wt%,reaction temperature 65 ^oC and reaction time 2.5 h.The conversion ratio reached to 85%when the Ca/C-500-3 catalyst was reused four times.TOF,E-factor and PMI suggested that the Ca/C-500-3 catalyst had high catalytic efficiency,and the reaction had negligible effect for the environment.