Hydrotalcite-Derived Mixed Oxides for the Synthesis of a Key Vitamin A Intermediate Reducing Waste
| Autor: | Javier Pérez-Ramírez, Sharon Mitchell, Jan Schütz, Ferdy J. A. G. Coumans, Jonathan Medlock |
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| Jazyk: | angličtina |
| Rok vydání: | 2018 |
| Předmět: |
Vitamin
Hydrotalcite Organic base 010405 organic chemistry Chemistry General Chemical Engineering General Chemistry 010402 general chemistry 01 natural sciences Article 0104 chemical sciences lcsh:Chemistry chemistry.chemical_compound lcsh:QD1-999 Pyridine Hydroxenin monoacetate Organic chemistry Stoichiometry |
| Zdroj: | ACS Omega, Vol 3, Iss 11, Pp 15293-15301 (2018) ACS Omega, 3 (11) ACS Omega |
| ISSN: | 2470-1343 |
| Popis: | The synthesis of hydroxenin monoacetate, a key intermediate in the manufacture of vitamin A, relies on the undesirable use of stoichiometric amounts of organic bases such as pyridine. Although the final product (vitamin A acetate) can be produced from hydroxenin diacetate, using the monoacetylated intermediate improves the overall process yield. Aiming to identify more efficient, environmentally benign alternatives, this work first studies the homogeneous acetylation reaction using pyridine. The addition of the base is found to enhance the rate of hydroxenin monoacetate formation, confirming its catalytic role, but also yields non-negligible amounts of hydroxenin diacetate. On the basis of these insights, Mg- and Al-containing hydrotalcites are explored because of their broad scope as base catalysts and the ability to finely tune their properties. The reaction kinetics are greatly enhanced via controlled thermal activation, forming high surface area mixed metal oxides displaying Lewis basic sites. In contrast, a Brønsted basic material synthesized by the reconstruction of a mixed oxide performs similarly to the as-synthesized hydrotalcite. Variation of the Mg/Al ratio from 1 to 3 has no significant impact, but activity losses are observed at higher values because of a reduced number of basic sites. After optimizing the reaction conditions, hydroxenin monoacetate yields >60% are obtained in five consecutive cycles without the need for any intermediate treatment. The findings confirm the potential of hydrotalcite-derived materials as highly selective catalysts for the production of vitamins with reduced levels of organic waste. ACS Omega, 3 (11) ISSN:2470-1343 |
| Databáze: | OpenAIRE |
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