Preparation And Properties Of Solid Ca-waste Derived Catalyst For Biodiesel Production

Biodiesel,which is regarded as a non-toxic and biodegradable fuel produced from plant/algal oils or animal fats,has gained extensive attention in the past few decades.Conventionally,biodiesel can be synthesized via transesterification of triacylglyceride?C14^C20?with C1^C2 alcohols in the presence of homogeneous base catalysts.Unfortunately,the homogeneous catalysis strategy usually possesses several disadvantages,such as occurrence of saponification and reactor corrosion,difficulty in catalyst reuse,and generation of a large amount of waste water.To address these problems,the utilization of solid base catalysts for biodiesel production has been widely described in previous literatures,wherein the authors summarized the following outstanding advantages,e.g.,ease of separation,no toxicity,no corrosion,and less environmental pollution.The aim of our work was to improve the catalytic activity and the stability of solid waste derived CaO catalyst.The details of this study were summarized as follows:Waste ostrich eggshell-derived calcium oxide?CaO?OE??particles were synthesized and explored as cost-effective catalysts for the ultrasonic-assisted transesterification of palm oil.More specifically,the CaO?OE?showed comparable catalytic activity to the one derived from commercial calcium carbonate?CaO?Lab??.Moreover,under ultrasonic conditions,the catalytic activity of CaO?OE?could be enhanced significantly.The maximum yield of fatty acid methyl esters could reach 93.7%?87.2% for MS-CaO?OE??under the optimal condition of reaction time of 60 min with ultrasonic power of 60%?120W?,methanol-to-oil ratio of 9:1,and catalyst loading of 8 wt.%.The reusability test results indicated that after recycling for eight cycles,the US-CaO?OE?catalysts still showed good catalytic performance.A porous CaO-based catalyst was synthesized using a fast mineralization process induced by sodium poly?styrenesulfonate??PSS?followed by calcination.The solid base catalyst was tested in palm oil transesterification to determine its viability in biodiesel production.The CaO-based catalysts synthesized with the incorporation of PSS exhibited an enhanced catalytic activity in the transesterification of palm oil when compared to the CaO catalyst without the assistance of PSS?0-CaO catalyst?.The enhanced activity was mainly due to the enlarged pore size/volume and increased active site density of the PSS catalyst.A maximum yield of biodiesel,at 97.2%?89.5% for the 0-CaO catalyst?,was reached when the PSS concentration was fixed at 10 g/L.Moreover,this 10-CaO catalyst exhibited excellent reusability?71.8%?,having superior catalytic activity than the commercial CaO?C-CaO?catalyst?59.5%?after being recycled 10 times.A highly efficient CaO-based catalyst was synthesized by using abalone shell as a precursor and ethanol as a modification agent for biodiesel production.Once utilized for transesterification of palm oil,the modified CaO?M-CaO?catalyst exhibited an increased catalytic activity mainly due to the high surface area,increased total basicity and decreased crystalline size compared to the unmodified CaO?U-CaO?catalyst.Particularly,when the ethanol treatment temperature was 100 oC,the maximum biodiesel yield for the M-CaO catalyst could reach 95.5%?86.7% for the U-CaO catalyst?.Furthermore,the M-CaO catalyst exhibited excellent reusability,having a superior catalytic activity compared to the U-CaO catalyst after recycling for more than five cycles.Rice husk ash?RHA,solid waste from agriculture?was served as the support for loading calcined eggshell?another material derived from waste source?to prepare stable solid base catalysts.This catalyst was then applied for catalytically converting palm oil into biodiesel.The experimental results revealed that 30%RHA800-800 catalyst?CE loading of 30 wt.%,calcination temperature of 800 oC and RH treatment temperature of 800 oC?exhibited the highest catalytic activity.More specifically,when the reaction was carried out with a reaction time of 4 h,methanol-to-oil molar ratio of 9:1,and catalyst loading of 7 wt.%,the biodiesel yield can reach 89.5%.Besides,after reused for more than 8 cycles,the catalyst could still possess a rather high biodiesel yield?above 82%?.CaO-SiO₂ catalysts were successfully synthesized through a biomimetic silicification approach by using eggshell and Na₂SiO₃ as raw materials.The powdered egg shells,where lysozyme?the inducer?was located,were dispersed into Na₂SiO₃ aqueous solution to implement the biomimetic silicification under ambient conditions to form CaCO₃-SiO₂ compound.After calcination,when utilized in the catalytic transesterification of palm oil,the CaO-SiO₂ catalysts exhibited decreased catalytic activity and increased reusability as the amount of Si compounds increased.Particularly,when the Na₂SiO₃ concentration was below 0.4 M,a slight decrease in the catalytic activity could be observed,whereas the reusability of the catalyst was significantly improved?little deactivation?9% of biodiesel yield?was found after 12 cycles on the 2Si5 Ca catalyst during the transesterification reaction?.Hopefully,this biomimetic silicification approach can be applied for the synthesis of a wide range of efficient and stable solid base catalysts for transesterification/esterification reactions.