| According to the present disclosure, a composite solid base catalyst includes an aluminum carrier and a plurality of calcium particles. The calcium particles are supported by the aluminum carrier. The beta basic sites of the composite solid base catalyst are 0.58 mmol/g – 3.89 mmol/g. Therefore, the composite solid base catalyst of the present disclosure will go through a heterogeneous catalysis reaction, which is favorable for reducing the purification cost and purification waste, and the goals of environmental friendly and sustainable development can be achieved. |