Low-temperature Activation Of The Solid Base Catalyst CaO For Biodiesel Production

Development of alternative energy is becoming a trend currently all over the world attributed to the exhausted oil resource and increasing energy demand. The biodiesel, which has a excellent combustion performance, environment -friendly and renewable, is a perfect alternation for petroleum baesd biodiesel. Homogeneous catalysts, such as NaOH, KOH, which were used usually in the production of biodiesel, could lead to discharge of acid or alkaline waste water, and were not recycled. Many researchers had developed heterogeneous process for the production of biodiesel.CaO , as a heterogeneous solid base catalyst, was a promising catalyst in the industrial production of biodiesel because of its low cost, wide source, low soloubility and high catalytical activity. But CaO could be carbonated and hydrated gradually during the storage, attributed to moisture and CO2 in the air, and cause to reduce its catalytical activity for transesterification. So the CaO has to be reactivated in a 800℃temperature before reaction, which limit the range of application, and could not keep high activity in the storage, since CaO could has a chemical reaction with supporter in high temperature. In this paper, influences of methanol, glycerol and water on the activation of the solid base catalyst CaO in the biodiesel production were investigated respectively, in addition, the activation time, catalyst amount, air tolerance and activation mechanism were also studied and discussed. The results showed that glycerol and water had better activation than methanol, and the water had excellent activity on CaO even without pre-activation; the catalyst CaO didn't have any activity loss even exposed in air for 15 days after the process of glycerol, but the more practical storage method was that CaO should be immersed into methanol. The activation mechanism was that the activation agents, such as methanol, glycerol or water, accelerated the transesterification in biodiesel production by methyloxyl ion or propyltrioxyl ion from activation process, and the surface of CaO was decarbonated after the process of methanol or water, whereas the surface of CaO were dehydrated and decarbonated after the process of glycerol. The possible mechanism of warer activation without pre-activation was that it help the proton to dissociate from the methanol as a lewis base.