144541-38-8Relevant articles and documents
Continuous synthesis of menthol from citronellal and citral over Ni-beta-zeolite-sepiolite composite catalyst
Er?nen, Kari,M?ki-Arvela, P?ivi,Martinez-Klimov, Mark,Muller, Joseph,Murzin, Dmitry Yu.,Peurla, Markus,Simakova, Irina,Vajglova, Zuzana
, (2022/04/03)
One-pot continuous synthesis of menthols both from citronellal and citral was investigated over 5 wt% Ni supported on H-Beta-38-sepiolite composite catalyst at 60–70 °C under 10–29 bar hydrogen pressure. A relatively high menthols yield of 53% and 49% and stereoselectivity to menthol of 71–76% and 72–74% were obtained from citronellal and citral respectively at the contact time 4.2 min, 70 °C and 20 bar. Citral conversion noticeably decreased with time-on-stream under 10 and 15 bar of hydrogen pressure accompanied by accumulation of citronellal, the primary hydrogenation product of citral, practically not affecting selectivity to menthol. A substantial amount of defuctionalization products observed during citral conversion, especially at the beginning of the reaction (ca. 1 h), indicated that all intermediates could contribute to formation of menthanes. Ni/H-Beta-38-sepiolite composite material prepared by extrusion was characterized by TEM, SEM, XPS, XRD, ICP-OES, N2 physisorption and FTIR techniques to perceive the interrelation between the physico-chemical and catalytic properties.
Nb-doped variants of high surface aluminium fluoride: A very strong bi-acidic solid catalyst
Marshall, Clara Patricia,Scholz, Gudrun,Braun, Thomas,Kemnitz, Erhard
, p. 6834 - 6845 (2019/05/27)
A niobium doped high surface aluminium fluoride (HS-AlF3) catalyst was prepared, using an approach in which niobium doped aluminium hydroxide fluoride obtained via reaction of aqueous HF with the respective metal alkoxides in isopropanol is further fluorinated under flow of CHClF2 at 200 °C. A comparable procedure was used to synthesize a Nb-free variant for comparison. Both catalysts exhibit very strong Lewis acidic surface sites which are capable to activate strong carbon-halogen bonds at room temperature, just as the classical high-surface AlF3 (HS-AlF3), obtained by reacting aluminium isopropoxide with anhydrous HF, does. The catalysts were characterized by elemental analysis, P-XRD, MAS NMR spectroscopy, N2 adsorption, NH3-TPD, and pyridine photoacoustic FT-IR spectroscopy. In contrast to previously reported niobium doped HS-AlF3, which was prepared using anhydrous HF, the doped catalyst obtained via this aqueous HF-route shows excellent performance both in the isomerization of 1,2-dibromohexafluoropropane, a reaction that occurs only in the presence of the strongest Lewis acids, and in the cyclization of citronellal to isopulegol, a reaction which requires both, Lewis and Br?nsted acid sites.
Method for improving optical purity of L-isopulegol through chiral resolution
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Paragraph 0056; 0057; 0058, (2019/02/10)
The invention provides a method for improving the optical purity of L-isopulegol through chiral resolution. The method comprises the following steps: putting D,L-isopulegol and a resolution agent L-linalool into a dispersant and an auxiliary agent and reacting for 3 to 4 hours at 70 to 80 DEG C; after cooling to 10 to 25 DEG C, centrifuging and separating to obtain an intermediate L-isopulegol.L-linalool; carrying out alkali analysis on the intermediate; decomposing the intermediate; then carrying out gel chromatography to obtain the high-purity L-isopulegol. The method has the advantages of low raw material cost and low reaction energy consumption and is applicable to large-scale industrialized production.
