سنتز و شناسايي نانو‌‌¬كامپوزيت‌هاي مزوحفره اكسيد فلزي مختلط با استفاده از ساختارهاي MOFو بررسي عملكرد كاتاليستي آن‌ها در واكنش توليد بيوديزل

Synthesis an‎d Characterization of Mixed Metal Oxide Mesoporous Nanocomposites Using MOF Structures an‎d eva‎luation of their Catalytic Performance in Biodiesel Production Reaction

شيمي معدني

Biodiesel is a sustainable alternative to fossil fuels; however, traditional homogeneous catalysts such as sodium hydroxide an‎d potassium hydroxide face challenges related to separation an‎d reusability. Calcium oxide (CaO) is an effective heterogeneous catalyst for biodiesel production, yet its chemical instability under reaction conditions limits its long-term performance. This study introduces MOF-mediated synthesis (MOFMS) of heterogeneous catalysts, specifically CaO@ZnO an‎d ZnO@CaO nanocomposites, utilizing inexpensive an‎d non-toxic metal salts with water-based binders. Comprehensive characterization techniques, including XRD, FT-IR, BET, FE-SEM, ICP, an‎d CO₂-TPD, were employed to analyze these catalysts. When applied for biodiesel production from soybean oil under ambient temperature an‎d pressure conditions, CaO@ZnO an‎d ZnO@CaO achieved remarkable biodiesel conversion rates of 99% an‎d 92%, respectively, within just 25 minutes. Both catalysts retained their activity over six cycles of use, with Ca2+ leaching remaining below 4% (2% for CaO@ZnO an‎d 4% for ZnO@CaO) after the sixth cycle. These results provide valuable insights into catalyst preparation, leaching control, an‎d reusability, enhancing the prospects for sustainable biodiesel production. In the second part of this study, biodiesel was synthesized using industrial steel slag waste as a low-cost catalyst through a calcination process, eliminating the need for initial chemical treatments. Repurposing industrial waste materials as catalysts presents an economically viable an‎d sustainable strategy for biodiesel production. Steel slag, a byproduct of the metallurgical industry, is abundantly available but remains underutilized in many developing countries, where improper disposal poses environmental challenges. This study explores the promising application of steel slag as a heterogeneous catalyst for biodiesel production from various vegetable oils, including waste cooking oils, thereby promoting waste valorization an‎d resource efficiency. The catalyst was derived from steel slag sourced from Esfahan Steel Company (Esfahan Steel Co.), comprising primarily catalytically active metal oxides, including CaO (42.9%), Fe₂O₃ (14.54%), an‎d MgO (8.53%). Characterization techniques such as XRF, XRD, FT-IR, FE-SEM, an‎d TGA confirmed its physicochemical properties an‎d catalytic potential. Optimal reaction conditions (40°C, 2 hours) enabled near-complete biodiesel conversion (99.99%) across all tested feedstocks, including soybean oil, sunflower oil, corn oil, castor oil, olive oil, an‎d waste cooking oil. Compared to conventional biomass-derived catalysts, this process significantly reduces reaction temperature an‎d time, improving energy efficiency. Furthermore, the catalyst demonstrated excellent reusability, maintaining high performance over five cycles with minimal loss of activity. Finally, to mitigate environmental pollution an‎d reduce greenhouse gas emissions, a catalyst model inspired by the enzyme carbonic anhydrase was employed for CO₂ capture. Various characterization techniques an‎d optimization parameters were applied to refine this enzyme-mimetic catalyst, aiming to enhance its efficacy in environmental applications.

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