643-01-6Relevant articles and documents
TOWARDS UNDERSTANDING (13)C-N.M.R. CHEMICAL SHIFTS OF CARBOHYDRATES IN THE SOLID STATE. THE SPECTRA OF D-MANNITOL POLYMORPHS AND OF DL-MANNITOL
Grindley, T. Bruce,McKinnon, Michael S.,Wasylishen, Roderick E.
, p. 41 - 52 (1990)
The cross-polarization, magic-angle spinning (13)C-n.m.r. spectra of solid DL-mannitol and of three polymorphs of D-mannitol have been recorded and assigned.Recrystallization of D-mannitol from several solvents under different conditions gave either one of the three known pure polymorphs or mixtures containing two or more of these polymorphs.The (13)C-chemical shifts from the four species in the solid state were all less than the solution values.Conformations in deuterium oxide and di((2)H3)methyl sulfoxide solutions were obtained from the vicinal proton coupling constants that resulted from analysis of the (1)H-n.m.r. spectra.The major cause of the differences between solid-state and solution chemical shifts is that there are significant populations of one of the gauche rotamers and the anti O-C-C-C rotamer about the terminal C-C bonds in solution.Other effects on solid-state (13)C-chemical shifts are discussed.
Direct conversion of cellulose into isosorbide over Ni doped NbOPO4catalysts in water
Guo, Jiaxing,He, Minyao,Li, Cuiqing,Liu, ShanShan,Song, Yongji,Wang, Hong,Wang, Xincheng
supporting information, p. 10292 - 10299 (2020/07/14)
Isosorbide is a versatile chemical intermediate for the production of a variety of drugs, chemicals, and polymers, and its efficient production from natural cellulose is of great significance. In this study, bifunctional catalysts based on niobium phosphates were prepared by a facile hydrothermal method and used for the direct conversion of cellulose to isosorbide under aqueous conditions. NH3-TPD analysis showed that a high acid content existed on the catalyst surface, and pyridine infrared spectroscopic analysis confirmed the presence of both Lewis acid and Br?nsted acid sites, both of which played an important role in the process of carbohydrate conversion. XRD and H2-TPR characterization determined the composition and the hydrogenation centers of the catalyst. An isosorbide yield of 47% could be obtained at 200 °C for 24 h under 3 MPa H2 pressure. The Ni/NbOPO4 bifunctional catalyst retains most of its activity after five consecutive runs with slightly decreased isosorbide yield of 44%. In addition, a possible reaction mechanism was proposed that the synergistic effect of surface acid sites and hydrogenation sites was favorable to enhancing the cascade dehydration and hydrogenation reactions during the conversion of cellulose to isosorbide. This study provides as an efficient strategy for the development of novel multifunctional heterogeneous catalysts for the one-pot valorisation of cellulose. This journal is
Hydrothermally Stable Ruthenium–Zirconium–Tungsten Catalyst for Cellulose Hydrogenolysis to Polyols
Lucas, Martin,Fabi?ovicová, Katarina,Claus, Peter
, p. 612 - 618 (2017/12/28)
In this work, we describe a catalytic material based on a zirconium–tungsten oxide with ruthenium for the hydrogenolysis of microcrystalline cellulose under hydrothermal conditions. With these catalysts, polyols can be produced with high yields. High and stable polyol yields were also achieved in recycling tests. A catalyst with 4.5 wt % ruthenium in total achieved a carbon efficiency of almost 100 %. The prepared Zr-W oxide is mesoporous and largely stable under hydrothermal conditions (493 K and 65 bar hydrogen). Decomposition into the components ZrO2 and WO3 could be observed at temperatures of 1050 K in air.
