A novel solid acid nano-catalyst [Ti(SO₄)O] was synthesised and used for the simultaneous esterification and transesterification of free fatty acids in used cooking oil (UCO) to produce biodiesel. The synthesised nano-catalyst was fully characterized by different analytical techniques. The XPS results clearly confirmed that the bidentate sulphate coordinated to the Ti⁴⁺ metal in the nano-catalyst product. Obtained d-spacing values from the experimental data of XRD peaks and the SAED pattern of produced nano-catalyst agreed well with the d-spacing values from the JCPDS-ICDD card numbers 04-011-4951 for titanium sulphate oxide or titanium oxysulfate crystal structures.This confirms the sulphate groups were within the crystalline structure rather than on the surface of titania nanoparticles, which has not been previously reported. It has been demonstrated 97.1% yield for the fatty acid methyl ester can be achieved usign the synthetised catalyst under a reaction time of 3h, catalyst to UCO ration of 1.5wt% and methanol to UCO ratio of 9:1 at 75°C reaction temperature. The nano-catalyst showed a good catalytic activity for the feedstock containing ≤6wt% free fatty acid. Furthermore, the catalytic activity and re-usability of the Ti(SO₄)O for the esterification/transesterification of UCO were investigated. XRD results confirmed that the amount of S O 4 2 − species in the solid acid nano-catalyst slowly decreased with re-use after 8 cycles under optimised conditions, which is higher than the reusability of other functionalised titania reported in the literature. Finally, the biodiesel prodcued from this process satisfied the ASTM and European Norm standards.

中文翻译：

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Ti（SO4）O固体酸纳米催化剂的合成及其在用过的食用油生产生物柴油中的应用

合成了一种新型的固体酸纳米催化剂[Ti（SO ₄）O]，并将其用于废食用油（UCO）中游离脂肪酸的同时酯化和酯交换，以生产生物柴油。通过不同的分析技术对合成的纳米催化剂进行了全面表征。XPS结果清楚地证实，双齿硫酸盐与Ti ^4+配位纳米催化剂产品中的金属。从XRD峰的实验数据获得的d间距值和生产的纳米催化剂的SAED图案与JCPDS-ICDD卡号04-011-4951的d间距值非常吻合，用于硫酸钛氧化物或氧硫酸钛晶体结构。这证实了硫酸根基团是在晶体结构内，而不是在二氧化钛纳米粒子的表面上，这是以前没有报道的。已经证明，在75℃反应温度下，使用合成的催化剂在3小时的反应时间，1.5wt％的催化剂与UCO的比率和9：1的甲醇与UCO的比率下，使用合成的催化剂可以达到97.1％的脂肪酸​​甲酯收率。 。纳米催化剂对包含≤6wt％的游离脂肪酸的原料表现出良好的催化活性。此外，_研究了4）O对UCO的酯化/酯交换反应。XRD结果证实，在优化条件下经过8个循环后，固体酸纳米催化剂中SO 4 2-种类的数量随着重复使用而缓慢降低，这高于文献中报道的其他功能化二氧化钛的可重复使用性。最后，从该过程中生产的生物柴油满足ASTM和欧洲规范标准。