KOH/CaO/C supported catalyst was prepared via incipient wetness impregnation and used in synthesis of biodiesel. First, the effects of carrier/active components mass ratio, calcination temperature and calcination time on catalytic activity were investigated aiming at biodiesel yield, and the optimal process conditions for preparation of KOH/CaO/C catalysts were: mass ratio of C/CaO was 4:6; KOH solution (mass concentration) was 25%; impregnation time was 24 h; drying temperature was 105°C and time was 4 h; calcination temperature was 500°C and time was 5 h. Then the complex catalysts prepared under the optimal conditions were applied to synthesize biodiesel, and the effects of dose of catalyst, reaction temperature, and reaction time on the yield of biodiesel were investigated. At last, the optimal process conditions for synthesis of biodiesel were concluded: methanol-oil ratio was 10:1; catalyst dose was 2% of that of soybean oil; reaction temperature was 65°C; reaction time was 5 h. The yield of as-prepared biodiesel could be 98%.
Hydrogenation energy consumption has been intensified along with the rapid economic development worldwide. The reduction of oil resources and the increasing demands for oil have subjected economic development to severe pressures. The resulting energy shortage diverts people to seeking renewable and environmental fuels and replacing petroleum resources. Biomass energy, solar energy and other renewable energy will substitute petroleum and coals and thus gradually become the major energy sources. Biodiesel deserves special attention owing to the high combustion performance, heat value, combustion stability, low-temperature start-up lubrication, renewability and environmental friendliness [
In this paper, KOH/CaO/C supported biodiesel catalyst was prepared using blending impregnation. First, CaO was supported on activated carbon and then impregnated with KOH. The catalyst of CaO impregnated with KOH was highly active and renewable. Besides, the activated carbon as the carrier was featured by large specific surface area, easy separation from the products, and high intensity after calcination.
The materials were anhydrous methanol, KOH, CaO, anhydrous NaCO3, HCl, anhydrous ethanol, and 95% ethanol, which were all chemically pure.
Acid value (AV) of raw oil was measured using the hot ethanol method as per Animal and Vegetable Fats and Oils-Determination of Acid Value and Acidity (GB/T5530-2005). Saponification value (SV) of raw oil was measured as per Animal and Vegetable Fats and Oils-Determination of Saponification Value (GB/T5534-2008). The average molar mass of raw oil was computed as follows:
where, SV is saponification value [mg KOH/g oil]; AV is acid value [mg KOH/g oil].
KOH/CaO/C supported catalyst was prepared via incipient wetness impregnation: the ground CaO powder and activated carbon at a preset ratio were fully mixed and then impregnated with KOH solution at room temperature, dried and calcinated at last.
With methanol and soybean oil as raw materials, biodiesel was prepared in a 3-neck flask via transesterification, the hot crude products were filtered immediately, and then the catalyst was removed. The liquid phase was transferred to a separating funnel, and put still until it was separated. The upper layer in the funnel was collected and the lower layer of glycerol phase was discharged. 1/2 volume of water at 50˚C was added into the biodiesel, and then it was shaken, and put still for separation. Then the lower layer of glycerol-water phase was discharged. The remaining solution was washed 3 times. The biodiesel phase was reserved and added with anhydrous CaCl2 for 24 h of drying. The drying agent was filtered out to obtain biodiesel, which was weighed. The yield y of biodiesel was computed as follows:
where, mB0 is the weight of biodiesel [g]; m0 is the weight of the raw oil [g].
C/CaO at different mass ratios were mixed, and then impregnated for 20 h in a 25% KOH solution (mass percentage concentration), followed by drying at 105˚C for 3 h and calcination at 500˚C for 5 h. Catalysts were prepared under different conditions and applied to synthesize biodiesel. The synthesis conditions were: methanol-oil ratio was 9:1, catalyst dose was 1% of that of soybean oil, reaction temperature was 60˚C, reaction time was 4 h. The effects of C/CaO mass ratio on biodiesel yield were investigated and the results were listed in
Activated carbon and CaO (4:6) were mixed and impregnated at room temperature in KOH solutions with varying concentration for 20 h, followed by drying at 105˚C for 3 h and calcination at 500˚C for 5 h. The effects of impregnated amounts of active components on reactivity were investigated and the results were listed in
At C/CaO ratio 4:6, KOH concentration 25%, drying at 105˚C for 3 h, and calcination at 500˚C for 5 h, the impregnation time was changed and its effects on reactivity were investigated. The results were listed in
At C/CaO ratio 4:6, KOH concentration 25%, impregnation at room temperature for 24 h, drying at 105˚C for 3 h, and calcination for 5 h, the calcination temperature was changed and its effects on reactivity were investigated. The results were listed in
At C/CaO ratio 4:6, KOH concentration 25%, impregnation at room temperature for 24 h, drying at 105˚C for 3 h, and calcination temperature 500˚C, the calcination time was changed and its effects on reactivity were investigated. The results were listed in
The as-prepared KOH/CaO/C supported catalysts were applied into synthesis of biodiesel and the optimal conditions were determined at last.
At methanol-oil molar ratio 9:1, catalyst dose 1% of that of soybean oil, and reaction time 4 h, the reaction temperature was changed and its effects on biodiesel yield were explored. The results were showed in
At methanol-oil molar ratio 9:1, reaction temperature 65˚C, and reaction time 4 h, we changed the dosage of catalyst and explored its effects on biodiesel yield. The results were showed in
At methanol-oil molar ratio 9:1, catalyst dose 2% of that of soybean oil, and reaction temperature at 65˚C, we changed the reaction time and explored its effects on biodiesel yield. The results were showed in
At catalyst dose 2% of that of soybean oil, reaction temperature 65˚C, and reaction time 5 h, we changed the methanol/bean oil ratio and explored its effects on the yield. The results were showed in
tio is too small, little fatty acid methyl ester is generated, indicating low yield. But if the methanol-oil ratio is too large or exceeds the normal level in transesterification, the volume of reaction solution becomes larger, which slightly dilutes the concentrations of reactants, and the amount of catalyst is relatively smaller, leading to less opportunity for contact between catalyst and fatty glyceride. These changes less promote the reaction and enhance the polarity of the solution, which leads to slower reaction and lower biodiesel yield.
KOH/CaO/C supported catalysts via blending impregnation were prepared and then were applied to synthesis of biodiesel. The best optimum synthesis conditions were identified according to the biodiesel yield. The conclusions are summarized as follows:
The optimal prepared conditions of KOH/CaO/C supported catalysts are: C/CaO mass ratio is 4:6, mass concentration of KOH solution is 25%, impregnation time is 24 h, drying temperature is 105˚C and drying time is 4 h, calcination temperature is 500˚C and calcination time is 5 h.
Catalysts are prepared under above conditions with methanol and soybean oil as raw materials and then applied to synthesize biodiesel. The optimum synthesis conditions for biodiesel are: alcohol-oil ratio is 10:1, catalyst dose is 2% of that of soybean oil, reaction temperature is 65˚C and reaction time is 5 h. The yield of as- prepared biodiesel could be 98%.
The authors are grateful to the Provincial Key Laboratory of Oil and Gas Chemical Technology of Northeast Petroleum University in China for financial support.