2676-33-7Relevant academic research and scientific papers
Enantioselective hydrogenation of ethyl pyruvate catalyzed by 1,2-diphenyl-ethylenediamine-modified iridium complex: Effect of solvent
Du, You,Li, Chun,Tan, Xiaoyun,Fu, Haiyan,Zheng, Xueli,Li, Ruixiang,Chen, Hua
, p. 319 - 322 (2014)
The enantioselective hydrogenation of ethyl pyruvate was explored by a readily available homogeneous iridium catalysis system. It was found that (1R,2R)-(+)-1,2-diphenyl-ethylenediamine [(1R,2R)-DPEN] modified [Ir(COD)Cl]2 (COD = cis,cis-1,5-cyclooctadiene) was highly active for the enantioselective hydrogenation of ethyl pyruvate, and the moderate enantioselectivity of 29 % was obtained (the best value reported by iridium catalysts was 39 %). NMR spectroscopy proved that hydrogen bond between the solvent and the a-carbonyl of ethyl pyruvate would be favor to the enantioselective hydrogenation.
Synthesis of ethyl lactate from triose sugars on Sn/Al2O3 catalysts
Pighin,Díez,Di Cosimo
, p. 151 - 160 (2016)
Sn-promoted alumina catalysts with different Sn loadings (1-8 wt.%) were prepared by impregnation and characterized by N2 physisorption, X-ray diffraction, UV-vis-DRS, FTIR of pyridine and TPD of NH3. Surface Sn species present Lewis acid properties different from those of the alumina support; the number and strength of the surface Lewis centers increase with the Sn loading. These materials exhibit good catalytic performance for conversion of triose sugars, such as dihydroxyacetone, toward ethyl lactates at mild conditions. The catalyst preparation conditions, Sn content and reaction conditions affect the final ethyl lactate yield. Yields of ≈70% were obtained at 353 K after 7 h of reaction. Surface Sn species participate in the kinetically relevant reaction steps.
Racemization-free monomer: A-hydroxyisobutyric acid from bio-based lactic acid
Watanabe, Kohtaro,Andou, Yoshito,Shirai, Yosihito,Nishida, Haruo
, p. 698 - 699 (2010)
In order to solve the important problem of the racemization of poly(L-lactic acid), a high yield of racemization-free monomer: a-hydroxyisobutyric acid (HIBA) was synthesized from biobased lactic acid by methylation using specific bases with bulky side groups. Obtained HIBA can be converted into poly(tetramethylglycolide), which is racemization-free and has higher melting and glass transition points than poly(L-lactic acid).
Stabilization of Pd, Pt and Ru nanoparticles by optically active CO/styrene copolymers
Favier, Isabelle,Picurelli, David,Pradel, Christian,Durand, Jér?me,Milani, Barbara,Gómez, Montserrat
, p. 766 - 768 (2010)
Fully isotactic, chiral CO/styrene copolymers were used as stabilizers for palladium, platinum and ruthenium nanoparticles synthesis. The tuning of copolymer/metal ratio and metal concentration were found to be key parameters in order to adjust the size and the agglomeration tendency of the metallic nanoclusters. These new materials were fully characterized by elemental analysis, infrared, solid state 13C MASNMRspectroscopies, and transmission electronic microscopy. Platinum and ruthenium nanoparticles were tested as catalysts in the ethyl pyruvate hydrogenation, giving high activities; in this preliminary work, no enantioselectivity induction was observed.
On the implications of hemiketal formation during ethyl pyruvate hydrogenation in alcohol solvents
Bohnen, Frank M.,Gamez, Agnes,Blackmond, Donna G.
, p. 335 - 338 (1998)
Hemiketal formation between alcohol solvents and α-keto esters is shown to be catalyzed not only by the basic cinchonidine modifier but also by the acidic Pt/Al2O3 catalyst. Theoretical considerations and experimental results demonstrate that reaction calorimetry is a valid and accurate measure of the hydrogenation reaction, provided that the substrate and its hemiketal remain in equilibrium over the course of the reaction. The rate of hemiketal formation and, thus, the probability that the preequilibrium step will remain unperturbed during the hydrogenation reaction, is sensitive to the acidic properties of the support.
In situ spectroscopic investigation of heterogeneous catalysts and reaction media at high pressure
Grunwaldt, Jan-Dierk,Baiker, Alfons
, p. 3526 - 3539 (2005)
In situ characterization of catalysts by means of complementary spectroscopic techniques can be regarded as the first step towards rational catalyst design. Spurred by the growing interest of catalytic reactions in supercritical fluids and by several industrial reactions traditionally performed at high pressure (> 10 bar), new demands and challenges are put to in situ spectroscopic characterization of heterogeneous catalytic reactions. In this article, we discuss the development and the use of spectroscopic and related techniques suitable for elucidating such high-pressure reactions. Selected examples from phase behaviour studies with a view cell, investigations with transmission and attenuated total reflection (ATR) infrared spectroscopy as well as X-ray absorption spectroscopy (EXAFS, XANES), are presented to show the strategies, opportunities and limitations of such high pressure in situ studies. Different facets appear to be important to gain insight into catalytic reactions in supercritical fluids: the identification of the phase behaviour of the reaction mixture, the behaviour of the fluid inside the porous catalyst, the processes occurring at the solid fluid interface, the possible dissolution of active species and, similar as in gas-solid reactions, the establishment of structure-activity relationships. The Owner Societies 2005.
Esterification of Lactic Acid by Catalytic Extractive Reaction: An Efficient Way to Produce a Biosolvent Composition
Vu, Thu Ha Thi,Au, Hang Thi,Nguyen, Thuy Ha Thi,Nguyen, Thu Trang Thi,Do, Manh Hung,Bui, Ngoc Quynh,Essayem, Nadine
, p. 950 - 956 (2013)
A biosolvent composition containing ethyl lactate and biodiesel was directly obtained by catalytic extractive esterification of lactic acid. Since the esterification of organic acids with alcohols is a thermodynamically limited reaction, the methodology consists in conducting the esterification and the ester extraction simultaneously thereby shifting the equilibrium towards more esters. The acid catalyzed esterification was performed in a biphasic solvent system composed of (i) a reactive polar phase which contains the esterification constituents, lactic acid, ethanol and an acid catalyst (ii) an extractive solvent selective of the ester, fatty acid methyl ester (biodiesel). This solvents system increases the ethyl lactate yield of more than 30 %. During the reaction progress, the selective solvent, fatty acid methyl ester, is progressively blended with ethyl lactate providing a mixture of esters, which can be directly used as an efficient composition of biosolvents without further purification. The solid acidic potassium salt of 12-phosphotungstic acid, K 2.5H0.5PW12O40, was shown to be more efficient than the conventional esterification catalysts, H2SO 4 or Amberlyst 15. K2.5H0.5PW 12O40 gives a yield in ethyl lactate higher than 80 mol% after 2 h of reaction in the biphasic solvent system, using a molar ratio ethanol/lactic acid of 3.3 only. Moreover, K2.5H0.5PW 12O40 shows a remarkable higher activity per protonic sites (factor 30) and is recyclable at least two times without apparent loss of activity. These excellent properties were ascribed to its low density of strong Bronsted acid sites and its adequate hydrophobicity which would make this acid more water tolerant than the conventional esterification catalysts, H 2SO4 or Amberlyst 15. Graphical Abstract: Acid catalyzed esterification of lactic acid with ethanol was performed in a biphasic system where biodiesel acts as an extractive solvent of ethyl lactate. This extractive reaction produces directly a composition of biosolvent: biodiesel blended with ethyl lactate.[Figure not available: see fulltext.]
Investigation of synthetic pathways of carboxylic acid phthalocyanines from glycolic and lactic acids
do Nascimento, Francisco B.,Ribeiro, Anderson O.
, p. 106 - 116 (2017)
We present the study of synthetic pathways to prepare carboxylic acid substituted phthalocyanines from glycolic and lactic acids. Hydroquinone was used as an alternative catalyst for cyclotetramerization reaction of metal free and zinc phthalocyanines, which were characterized by 1H MR spectroscopy, infrared absorption and mass analysis. The photophysical and photochemical properties in dimethyl sulfoxide (DMSO) were analyzed. We verified that the presence of the methyl radical group, that distinguish both structures, diminish the macrocycle aggregation in solution and promote higher quantum yields of fluorescence and for singlet oxygen generation.
Synthetic and Catalytic Potential of Amorphous Mesoporous Aluminosilicates Prepared by Postsynthetic Aluminations of Silica in Aqueous Media
Locus, Roel,Verboekend, Danny,d'Halluin, Martin,Dusselier, Michiel,Liao, Yuhe,Nuttens, Nicolas,Jaumann, Tony,Oswald, Steffen,Mafra, Luís,Giebeler, Lars,Sels, Bert
, p. 1385 - 1397 (2018)
Amorphous aluminosilicate catalysts have been used industrially on a large scale for almost a century. However, the influence of the pH on the alumination of silica in aqueous solutions has remained largely unclear. Herein, room temperature aluminations of different mesoporous amorphous silicas (fumed silica, dried silica gel, SBA-15, MCM-41, and COK-12) with aqueous solutions of various pH (3–13) are explored. The aqueous solutions are prepared using different aluminum sources (Al(NO3)3 or NaAlO2) and alkaline additives (NaOH or NH4OH). The decoupling of pH and Al source using alkaline additives results in a vast experimental potential to prepare unique aluminosilicates, whereby an important role is played by the pH development during the treatment. The bulk and surface composition, acidity, aluminum coordination, morphology, hydrothermal stability, and porosity of the obtained materials are characterized. Optimal samples possess large surface areas and superior acidities (up to 50 % higher) and outstanding stabilities compared to aluminosilicates prepared with state-of-the-art methods. The obtained materials are evaluated in a series of acid-catalyzed model reactions involving substrates of various chemical reactivity and size, enabling insight in the catalytic functionality of the introduced Br?nsted and Lewis sites. The potential of the obtained materials is emphasized by the similar or superior acidity and catalytic performance compared to several benchmark industrial silica–alumina-based catalysts.
Titanosilicate beads as versatile catalysts for the conversion of trioses to lactates and for the epoxidation of alkenes
Lin, Kaifeng,Li, Li,Sels, Bert F.,Jacobs, Pierre A.,Pescarmona, Paolo P.
, p. 89 - 94 (2011)
Titanosilicate beads with hierarchical porosity (TiSil-HPB-60) were prepared from an anion-exchange resin and proved to be a versatile heterogeneous catalyst displaying activity both in the conversion of trioses to ethyl lactate and in the epoxidation of alkenes. In the former reaction, TiSil-HPB-60 showed higher catalytic activity compared to two well-known titanosilicate catalysts: the crystalline microporous TS-1 and the ordered mesoporous Ti-MCM-41. Notably, TiSil-HPB-60 displayed significantly high selectivity towards ethyl lactate due to the absence of strong Br?nsted acid sites. In the epoxidation of alkenes with aqueous H2O2, TiSil-HPB-60 displayed improved epoxide yield compared to TS-1 and Ti-MCM-41 when the bulky cyclohexene was used as substrate, while TS-1 was the most active catalyst with the linear 1-octene. In both reactions, the separation of TiSil-HPB-60 from the reaction mixture is very straightforward, thanks to its bead format, and the catalyst can be reused in successive catalytic cycles without significant loss of activity.
