One-Pot Transformation of Citronellal to Menthol Over H-Beta Zeolite Supported Ni Catalyst: Effect of Catalyst Support Acidity and Ni Loading

Abstract

Citronellal was converted to menthol in a one-pot approach using H-Beta zeolite-based Ni catalyst in a batch reactor at 80 °C, under 20 bar of total pressure. The effects of H-Beta acidity (H-Beta-25 with the molar ratio SiO2/Al2O3 = 25 and H-Beta-300 with SiO2/Al2O3 = 300) and Ni loading (5, 10 and 15 wt %) on the catalytic performance were investigated. Ni was impregnated on H-Beta support using the evaporation-impregnation method. The physico-chemical properties of the catalysts were characterized by XRD, SEM, TEM, ICP-OES, N2 physisorption, TPR, and pyridine adsorption–desorption FTIR techniques. Activity and selectivity of catalysts were strongly affected by the Brønsted and Lewis acid sites concentration and strength, Ni loading, its particle size and dispersion. A synergetic effect of appropriate acidity and suitable Ni loading in 15 wt.% Ni/H-Beta-25 catalyst led to the best performance giving 36% yield of menthols and 77% stereoselectivity to ( ±)-menthol isomer at 93% citronellal conversion. Moreover, the catalyst was successfully regenerated and reused giving similar activity, selectivity and stereoselectivity to the desired ( ±)-menthol isomer as the fresh one. Graphical Abstract

Supported Ni Catalysts: Simple Vapor Deposition Preparation Method and Improved Catalytic Performance for Oxidative Dehydrogenation of Ethane

“…Inspection of Figure 1 for the preparation device shows that each unit of this device is a commonly used one, and the whole set up is suitable for magnification. It is known that ALE/ALD-based methods 30,31 require very expensive setup. In contrast, our method is obviously cheaper.…”

“…More ALE cycles led to an increase of Ni content and the size of the Ni cluster, improving the catalytic activity. Medlin and co-workers 31 The ALD catalyst gave an obvious improvement in the selectivity to propylene hydrogenolysis instead of propylene hydrogenation compared with the impregnation catalyst. However, as is known, the cost of preparation for ALD/ALE is quite high.…”

“…Taghavi et al used the evaporation impregnation method to impregnate Ni on the H-Beta support. First, the Ni precursor was dissolved in distilled water in the flask, and the H-Beta support was added to the solution.…”