Abstract
Several types of solid acid catalysts were prepared based on oxides like (ZrO2, TiO2, HfO2, MCM-41 and SBA-15), using two main preparation methods: the precipitation and the sol-gel methods. Each catalyst was subjected to two types of impregnations: sulfate ions using sulfuric acid as precursor and niobium using niobium oxalate as precursor. These prepared catalysts were tested in the etherification reaction of 2-naphtol, where the catalysts showed both acidic and redox properties. The acidic character was manifested through the formation of 2-butoxynaphtalene (with moderate yields) when oxide is sulfated, and the redox character (when impregnated with niobium) manifested through the formation of the interesting product 2-ethylnaphtofuran (with low yields) and other products that were a result of oxidative coupling of two 2-naphtol molecules (binol and acetal of binol). However despite the effort, several attempts to increase the yield of 2-ethylnaphtofuran did not work. All products prepared were obtained in pure form and characterized by 1H and 13C NMR, GC and MS.
Highlights
Tightening environmental legislation is driving the fine and specialty chemicals industries to consider alternative processes that avoid the use of conventional mineral acids
The acidic character was manifested through the formation of 2-butoxynaphtalene when oxide is sulfated, and the redox character manifested through the formation of the interesting product 2-ethylnaphtofuran and other products that were a result of oxidative coupling of two 2-naphtol molecules
By using these solid acid catalysts, chemical processes become more productive and more environmentally friendly. They are being used in many industrial chemical processes from the largest chemical process of catalytic cracking in petroleum refining to the synthesis of various fine chemicals [1] [2], the preparation of active and selective heterogeneous acid catalysts is a challenge
Summary
Tightening environmental legislation is driving the fine and specialty chemicals industries to consider alternative processes that avoid the use of conventional mineral acids. Research nowadays is focused on the use of heterogeneous acid catalysts By using these solid acid catalysts, chemical processes become more productive and more environmentally friendly. We chose these types of impregnations since both sulfate and niobium doping are reported to induce strong acidity to the oxides on which they are impregnated These prepared catalysts were first screen tested in the etherification reaction of 2-naphtol with butanol to determine which has the highest acidity by comparing butoxynaphtalene (2) yields since the reaction of aromatic ether formation requires strong acids, where the catalyst that gave the highest yield of butoxynaphtalene would be the one with high acidity. The optimization of the reaction conditions (time, temperature and catalyst loading) for this reaction will be discussed and the detailed preparation methods for each catalyst will be given
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