Mechanochemically synthesized LiAlOx catalyst for aqueous aldol condensation of furfural with acetone

Abstract

Abstract:In the present study, the mechanochemical method is proposed for synthesis of LiAl-layered double hydroxides (LDHs). This method is eco-friendly and allows obtaining LiAl-LDH under relatively mild conditions (centripetal acceleration of milling bodies 300 m s -2 ) and in a short period of time (15 minutes). The structures of as-prepared LiAl-LDH, LiAl-mixed oxide (calcined LDH) and "activated" LiAl-LDH obtained after rehydration of the corresponding mixed oxide were confirmed by X-ray diffraction. The basicity of LiAlO x was measured by temperature-programmed desorption of CO 2 and double isotherm technique. According to data obtained, LiAl-mixed oxide has a significant higher carbon dioxide adsorption capacity compared to MgAlmixed oxides prepared by conventional co-precipitation method. This indicates a large amount of basic surface sites with different strength (strong, medium and weak) for Li-containing systems. The formation of "activated" LiAl-LDH having Brønsted basic sites (OH groups in the interlayer space) provides an increased catalytic activity of LiAlO x in the reaction of aqueous-phase aldol condensation between furfural and acetone.

Catalytic applications of layered double hydroxides in biomass valorisation

“…55 Calcined LiAl-LDHs (Li:Al of 0.5) synthesised by mechanochemical methods have been explored for aldol condensation of acetone and furfural, and exhibit higher base site loadings and reaction rates than Mg3Al-LDH. 56 Calcined MgFe-LDH (Mg:Fe of 1 to 10) are also active for acetone and furfural condensation, with a balance of acid and base sites necessary to achieve both condensation and dehydration steps to form the stable enone; while increasing Mg content enhanced furfural conversion, dehydration was favoured over acidic materials with Mg:Fe≤ 5. 57 The versatility of LDHs in condensation reactions is further demonstrated in the coupling of furfural and levulinic acid over Mg3Al-LDH, 58 isobutyraldehyde and formaldehyde to produce hydroxypivaldehyde over CaAl-LDH, 59 and the Guerbet reaction of ethanol to 1-butanol over calcined Mg3Al-LDH.…”

Развитие Подходов К Формированию Платиновых Центров С Заданными Свойствами С Использованием Носителей Со Слоистой Структурой

“…Для получения каталитически активных смешанных оксидов, обладающих высокой удельной поверхностью, СДГ, как правило, прокаливают в диапазоне температур 400-600 °C, а необходимая температура определяется типом интеркалированных анионов, катионным составом и степенью кристалличности материала [71,72]. Данные о пористой структуре СДГ и соответствующих оксидов получают при анализе изотерм адсорбции-десорбции азота, а традиционными методами исследования их оснóвных свойств являются динамический метод температурно-программируемой десорбции диоксида углерода (ТПД-СО 2 ) и статический метод, основанный на анализе изотерм адсорбции СО 2 [73]. Оснóвные свойства и, соответственно, прочность адсорбции СО 2 определяются составом гидроксидных слоев, природой промоторов и межслоевых анионов [74][75][76].…”