Valorization of (Bio)Ethanol over MoO3/(WO3-ZrO2) Sol-Gel-like Catalysts

Reactions Pub Date : 2024-03-20 DOI:10.3390/reactions5010012
A. P. Soares Dias, Bruna Rijo, M. F. Costa Pereira, R. Zăvoianu, O. Pavel
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Abstract

Bioethanol, which is currently produced commercially from a growing variety of renewable biomass and waste sources, is an appealing feedstock for the production of fuels and chemicals. The literature clearly shows that bioethanol is a versatile building block to be used in biorefineries. The ethanol conversion using several catalysts with acidic, basic, and redox characteristics results in a diverse assortment of high-value bioproducts. High-acidity tungsten zirconia-based catalysts are stated to compete with traditional zeolitic catalysts and can be employed in the dehydration of ethanol to ethylene, but for a low reaction temperature acetic acid is formed, which causes corrosion issues. WO3-ZrO2 (W/Zr = 1, atomic) catalysts modified with MoO3 were prepared by a sol-gel-like procedure and tested in a gas phase ethanol conversion in the presence of air. The citrate derived xerogels were annealed at 853 K for 12 h, allowing low surface area (<10 m2/g) materials with a Mo-W mixed-oxide-rich surface over tetragonal nanostructured zirconia. Catalysts with MoO3-loading produced mainly acetaldehyde, instead of ethylene, as a result of the high reducibility of Mo6+ when compared to W6+. During the reaction, the Mo6+ becomes partially reduced, but Mo6+/Mo5+ species are still active for methanol conversion with increased ethylene selectivity due to the high acidity of tetrahedral MOX species formed during the reaction. Adding water to ethanol, to simulate bioethanol, only leads to a slight inhibition in ethanol conversion over the MoO3/(WO3-ZrO2) catalysts. The results show that molybdenum oxide deposited on tungstated zirconia catalyst is active, with low sensitivity to water, for the valorization of bioethanol into high-value chemicals, such as ethylene and acetaldehyde, and whose selectivity can be tuned by changing the amount of MoO3 that is loaded. The MoO3/(WO3-ZrO2) catalysts prepared show catalytic behavior similar to that of noble metal-based catalysts reported in the literature for the dehydrogenation of bioethanol in high-value chemicals.
在 MoO3/(WO3-ZrO2)类溶胶-凝胶催化剂上实现(生物)乙醇的有效化
生物乙醇目前是利用越来越多的可再生生物质和废物资源进行商业化生产的,是生产燃料和化学品的一种极具吸引力的原料。文献清楚地表明,生物乙醇是生物精炼厂中可使用的多功能原料。使用多种具有酸性、碱性和氧化还原特性的催化剂进行乙醇转化,可以生产出多种多样的高价值生物产品。高酸度氧化锆钨催化剂可与传统的沸石催化剂竞争,并可用于乙醇脱水制乙烯,但反应温度较低时,会形成乙酸,从而引起腐蚀问题。采用类似溶胶凝胶的方法制备了用 MoO3 修饰的 WO3-ZrO2(W/Zr = 1,原子)催化剂,并在空气存在下进行了气相乙醇转化测试。柠檬酸盐衍生的异凝胶在 853 K 下退火 12 小时后,在四方纳米结构氧化锆表面形成了富含 Mo-W 混合氧化物的低表面积(<10 m2/g)材料。与 W6+ 相比,Mo6+ 具有较高的还原性,因此添加了 MoO3 的催化剂主要产生乙醛,而不是乙烯。在反应过程中,Mo6+ 会部分还原,但 Mo6+/Mo5+ 物种对甲醇转化仍有活性,由于反应过程中形成的四面体 MOX 物种酸性较高,乙烯选择性增加。在乙醇中加入水以模拟生物乙醇,仅会导致 MoO3/(WO3-ZrO2)催化剂的乙醇转化率受到轻微抑制。结果表明,沉积在钨氧化锆催化剂上的氧化钼具有活性,对水的敏感性低,可将生物乙醇转化为乙烯和乙醛等高价值化学品,其选择性可通过改变 MoO3 的负载量来调整。制备的 MoO3/(WO3-ZrO2) 催化剂在生物乙醇脱氢制取高价值化学品方面的催化行为与文献报道的贵金属基催化剂相似。
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CiteScore
2.70
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