A simultaneous transesterification and esterification process was applied for production of biodiesel from high acidic waste cooking oil containing 18 wt% FFA using a range of heterogeneous bifunctional strontium–zinc–aluminium catalyst. The influence of the molar ratio of metal oxide, the ethanol to waste oil molar ratio, temperature and time of reaction, catalyst dosage, and free fatty acids in the feedstock on the conversion of biodiesel were studied. High interaction between Sr, Al and Zn metal was recognised to promote catalyst performance. A high interaction and mixing of strontium, aluminium and zinc oxides enhanced and increased the active sites on the surface of acid and base. The catalyst with a 2.6:1 M ratio of strontium to zinc was found to perform the best to transesterify the glycerides and esterify the fatty acid in the used oil simultaneously. The catalyst exhibited higher catalytic activity with high acidity waste cooking oil, with 95.7% reaction conversion at the optimum conditions 10:1 ethanol to waste oil molar ratio, 15 wt% catalyst dosage, and 5 h reaction time at 75 °C reaction temperature. The used catalyst showed low reusability due to high leaching of strontium.

同时酯交换和酯化工艺被用于使用一系列异质双功能锶-锌-铝催化剂，从含18％（重量）FFA的高酸性废食用油中生产生物柴油。研究了金属氧化物的摩尔比，乙醇与废油的摩尔比，反应温度和时间，催化剂用量以及原料中的游离脂肪酸对生物柴油转化率的影响。Sr，Al和Zn金属之间的高相互作用被认为可以促进催化剂性能。锶，铝和锌的氧化物的高相互作用和混合增强并增加了酸和碱表面上的活性位。具有2.6的催化剂：发现1 M的锶与锌的比例在用过的油中同时酯交换甘油酯和脂肪酸酯方面表现最佳。该催化剂在高酸度废食用油中具有较高的催化活性，在最佳条件下乙醇与废油的摩尔比为10：1，催化剂用量为15 wt％，在75°C反应温度下反应5小时，在最佳条件下的反应转化率为95.7％。所用的催化剂由于锶的高浸出而显示出低的可重复使用性。