6050-51-7Relevant articles and documents
The influence of long-term exposure of Mg–Al mixed oxide at ambient conditions on its transition to hydrotalcite: The long-term aging of Mg–Al mixed oxide
Bábelová, Monika,Hájek, Martin,Kocík, Jaroslav,Strejcová, Kate?ina,Ti?ler, Zdeněk,Velvarská, Romana
, (2021/09/08)
The paper is focused on the study of long-term aging of Mg–Al mixed oxides, which causes the rebuilding of the hydrotalcite layered structure in the presence of humidity. The novelty consists in the description of influence during the long-term aging (6 m
Optimized Cellulose Nanocrystal Organocatalysts Outperform Silica-Supported Analogues: Cooperativity, Selectivity, and Bifunctionality in Acid-Base Aldol Condensation Reactions
Ellebracht, Nathan C.,Jones, Christopher W.
, p. 3266 - 3277 (2019/03/26)
Cellulose nanocrystals (CNCs) are demonstrated as effective, ordered supports for cooperative acid-base heterogeneous organocatalysis, offering an alternative to typical silica supports. CNC catalyst surface chemistry is optimized through quantitative control of the loadings of carboxylic acids, primary amines, and sulfate half-esters, as characterized by elemental analysis, conductometric titration, and FT-IR spectroscopy. Catalysts are evaluated in the liquid phase aldol condensation of 4-nitrobenzaldehyde or furfural with acetone. Carboxylic acids are effective cooperative acid partners in CNC organocatalysts, and site-specific activity is strongly correlated with the COOH:NH2 ratio. Partial sulfate half-ester removal, high acid/base ratios, and use of unprotected diamines in the catalyst synthesis lead to optimized CNC catalyst function (site-time yield = 1.0 × 10-4 s-1). High selectivities to dehydrated aldol products (>80%) are achieved due to the acid content of the CNC catalysts. CNC catalysts outperform analogous SBA-15-supported aminosilica catalysts in regard to both activity and selectivity. Crystalline surface structures and ordered chemical functionalization in CNCs appear advantageous for precise design and control of bifunctional acid-base cooperative catalysts.
Nanosized TiO2—A promising catalyst for the aldol condensation of furfural with acetone in biomass upgrading
Nguyen Thanh, Dong,Kikhtyanin, Oleg,Ramos, Ruben,Kothari, Maadhav,Ulbrich, Pavel,Munshi, Tasnim,Kubi?ka, David
, p. 97 - 107 (2016/09/28)
Nanosized TiO2 catalyst was successfully prepared by a simple green procedure and used in liquid phase aldol condensation of furfural with acetone, a key step in bio-fuel processing. In order to determine the effect of calcination temperature on catalytic properties of TiO2, the as-prepared TiO2 and calcined TiO2 (150–900?°C) were studied by XRD, BET, TPD-CO2/NH3, TGA/DTG and FTIR evaluation. The catalytic performance of TiO2 samples in aldol condensation of furfural with acetone was evaluated and compared with that of Mg–Al hydrotalcites and a BEA zeolite. These experiments showed that uncalcined TiO2 possessed reasonable activity in aldol condensation of furfural to acetone and resulted in commonly produced condensation products. The observed catalytic behavior of TiO2 could be competitive with that reported for other inorganic solids. The calcination of TiO2 resulted, however, in a decrease in its catalytic activity due to extensive dehydration and surface dehydroxylation as well as due to changes of textural properties resulting in a decrease in the amount of accessible active sites. Thanks to its advanced properties, nanosized TiO2 is a promising catalyst for aldol condensation of furfural with acetone and could broaden possibilities for optimizing conditions for bio-fuel production.
