In the current research, we report on the synthesis of WO₃/GQD system as a heterogeneous catalyst for the transesterification of waste cooking oil into biodiesel using methanol. The characterization of the prepared catalyst was done by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscope (TEM), energy-dispersive X-ray (EDX), Fourier transform-infrared spectroscopy (FT-IR) techniques, and Brunauer-Emmett-Teller surface area measurement. To study the effect of process variables such as methanol to oil ratio, reaction temperature, and time, we have employed response surface methodology (RSM) based on Box-Behnken design (BBD). The suitability of the predicted model was verified, and the average biodiesel yield of (96.8 ± 0.16%) was reported at optimal reaction condition of 1:6 oil to methanol ratio, 70 °C reaction temperature, 2 wt% catalyst loading, and 3.5 h reaction time. Biodiesel was characterized using proton nuclear magnetic resonance (¹H NMR) and carbon nuclear magnetic resonance (¹³C NMR) techniques, and fatty acid methyl ester composition was determined using gas chromatography-mass spectrometry (GC-MS). Fuel properties of the biodiesel obtained comply with ASTMD6751 biodiesel standards. The kinetics of transesterification was studied and found to follow pseudo-first order. The results showed the rate constant ranging from 0.0028 to 0.007 min⁻¹, activation energy (E_a) of 55.92 kJ mol⁻¹, and frequency factor (A) of 1.72 × 10⁶ min⁻¹.

Graphical abstract

在当前的研究中，我们报告了WO ₃的合成/ GQD系统作为非均相催化剂，用于使用甲醇将废弃的食用油酯交换为生物柴油。通过X射线衍射（XRD），拉曼光谱，透射电子显微镜（TEM），能量色散X射线（EDX），傅立叶变换红外光谱（FT-IR）技术对制备的催化剂进行表征Brunauer-Emmett-Teller表面积测量。为了研究诸如甲醇与油的比例，反应温度和时间等工艺变量的影响，我们采用了基于Box-Behnken设计（BBD）的响应面方法（RSM）。验证了预测模型的适用性，并且在1：6的油/甲醇比，70°C的反应温度，2 wt％的催化剂负载和3.5的最佳反应条件下，报告的平均生物柴油产率为（96.8±0.16％）。 h反应时间。¹ H NMR）和碳核磁共振（¹³ C NMR）技术，并使用气相色谱-质谱（GC-MS）确定脂肪酸甲酯的组成。获得的生物柴油的燃料特性符合ASTMD6751生物柴油标准。对酯交换反应的动力学进行了研究，发现其遵循伪一级。结果表明，速率常数为0.0028至0.007 min ^-1，活化能（E _a）为55.92 kJ mol ^-1，频率因子（A）为1.72×10 ⁶  min ^-1。

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