- The cooperative effect of Lewis and Br?nsted acid sites on Sn-MCM-41 catalysts for the conversion of 1,3-dihydroxyacetone to ethyl lactate
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Lactic acid and alkyl lactates are widely applied in the production of food, cosmetics, pharmaceuticals, organic synthesis and biodegradable polymers. They can be prepared via one-pot synthesis from renewable trioses, such as dihydroxyacetone (DHA). Br?nsted-Lewis bifunctional solid acids (BAS & LAS) can promote the reaction via a two-step cascade reaction mechanism. BAS catalyses the dehydration of DHA, resulting in the formation of pyruvaldehyde (PA) via the rearrangement of the enol form. Upon alcohol addition, PA can be converted to the desired alkyl lactates at LAS or to pyruvaldehyde hemiacetal (PAHA) at strong BAS. The density and strength control of Br?nsted acid sites (BAS) and Lewis acid sites (LAS) and the optimization of their cooperation are essential for the efficient conversion of trioses to the target products. Here, we prepared a series of Sn-containing mesoporous MCM-41 catalysts with various BAS/LAS ratios by room temperature techniques. Sn-doped [Si]MCM-41 having a lower BAS/LAS ratio in this research shows a high initial selectivity to ethyl lactate (EL) and similar EL yield in 6 hours as the reported best Sn catalyst Sn-grafted [Si]MCM-41/carbon network materials in DHA conversion. A relatively large density of LAS in Sn-doped [Si]MCM-41 causes a fast conversion of PA to EL, while the overall yield has been limited by the BAS density for the DHA conversion. New H-form [Sn]MCM-41, having a suitable density of LAS and weak BAS and an optimized BAS/LAS ratio, provides a 100% yield of ethyl lactate in the catalytic conversion of DHA in ethanol within 30 min, showing a superior performance hitherto.
- Kim, Kyung Duk,Wang, Zichun,Jiang, Yijiao,Hunger, Michael,Huang, Jun
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supporting information
p. 3383 - 3393
(2019/06/24)
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- Kinetic study of the ethyl lactate synthesis from triose sugars on Sn/Al2O3 catalysts
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The reaction kinetics of the liquid-phase synthesis of ethyl lactate from dihydroxyacetone and ethanol was studied on Sn-promoted alumina catalysts. Yields of ≈70% were obtained at 353?K after 7?h of reaction. The effect of the catalyst Sn loading (1–8?wt.%) and reaction temperature (343–373?K) on the reaction kinetics was investigated. The reaction is promoted by Lewis acid sites provided by surface Sn species. A kinetic model based on a pseudohomogeneous mechanism was postulated to describe the reaction network comprising a sequence of consecutive and parallel reaction steps. The kinetic rate constant associated to ethyl lactate formation increases with the number of Lewis acid sites confirming that surface Sn species participate in the kinetically relevant reaction steps. Catalysts were prepared by impregnation and characterized by N2 physisorption, X-ray diffraction, UV-vis-DRS, FTIR of pyridine and TPD of NH3.
- Pighin,Díez,Di Cosimo
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- High-Yield Synthesis of Ethyl Lactate with Mesoporous Tin Silicate Catalysts Prepared by an Aerosol-Assisted Sol–Gel Process
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An aerosol-assisted sol–gel method is used to prepare mesoporous tin silicate catalysts that exhibit a record activity in the synthesis of ethyl lactate from dihydroxyacetone and ethanol. The method is based on the formation of an aerosol from a solution of precursors and surfactant. During the fast drying of the droplets, the surfactant self-assembles and the Sn-silica matrix is formed by polycondensation reactions. After calcination, the resulting material is composed of a true tin-silicon mixed oxide in the form of spherical microparticles with calibrated mesopores of 5–6 nm. Sn species are incorporated in the silica network, mainly in the form of single sites. This makes these catalysts highly active for the targeted reaction, as shown by record turnover numbers. The catalyst is recyclable and truly heterogeneous as it can be reused for several cycles and it does not leach.
- Godard, Nicolas,Vivian, Alvise,Fusaro, Luca,Cannavicci, Lorenzo,Aprile, Carmela,Debecker, Damien P.
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p. 2211 - 2218
(2017/06/27)
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- Synthesis of ethyl lactate from triose sugars on Sn/Al2O3 catalysts
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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.
- Pighin,Díez,Di Cosimo
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p. 151 - 160
(2016/03/22)
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- Extra-small porous Sn-silicate nanoparticles as catalysts for the synthesis of lactates
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A series of Sn-MCM-41 nanoparticles (XS-Sn-MCM-41) with a diameter ranging from 20 to 140 nm and very high specific surface area were successfully prepared and tested as heterogeneous catalysts for the conversion of the triose sugar dihydroxyacetone to ethyl lactate. Characterization of the materials indicated that the physicochemical properties of the nanoparticles can be significantly affected by different synthesis parameters, including the metal loading, the sequence of adding the Si and Sn precursors into the synthesis mixture, the preparation time and temperature. Most of the XS-Sn-MCM-41 catalysts displayed higher activity compared to conventional Sn-MCM-41 with large particle size in the conversion of dihydroxyacetone into ethyl lactate. The superiority of the best XS-Sn-MCM-41 catalyst in terms of conversion and turnover number is correlated to its high amount of accessible acid sites, which in turn is ascribed to a combination of different physicochemical features such as high surface area, particles morphology and coordination of the tin atoms in tetrahedral framework sites. The best catalyst can be reused in consecutive runs without loss of activity.
- Li, Li,Collard, Xavier,Bertrand, Arnaud,Sels, Bert F.,Pescarmona, Paolo P.,Aprile, Carmela
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- Selective conversion of dihydroxyacetone-ethanol mixture into ethyl lactate over amphoteric ZrO2-TiO2 catalyst
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The conversion of dihydroxyacetone in ethanol solution into ethyl lactate over several acidic and amphoteric oxides at 100-160 C was studied. The formation of ethyl lactate with 80-90% selectivity was observed on amphoteric ZrO2-TiO2
- Mylin, Artur M.,Levytska, Svitlana. I.,Sharanda, Mykhailo E.,Brei, Volodymyr V.
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- Zeolite-catalysed conversion of C3 sugars to alkyl lactates
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The direct conversion of C3 sugars (or trioses) to alkyl lactates was achieved using zeolite catalysts. This reaction represents a key step towards the efficient conversion of bio-glycerol or formaldehyde to added-value chemicals such as lactate derivatives. The highest yields and selectivities towards the desired lactate product were obtained with Ultrastable zeolite Y materials having a low Si/Al ratio and a high content of extra-framework aluminium. Correlating the types and amounts of acid sites present in the different zeolites reveals that two acid functions are required to achieve excellent catalysis. Bronsted acid sites catalyse the conversion of trioses to the reaction intermediate pyruvic aldehyde, while Lewis acid sites further assist in the intramolecular rearrangement of the aldehyde into the desired lactate ester product. The presence of strong zeolitic Bronsted acid sites should be avoided as much as possible, since they convert the intermediate pyruvic aldehyde into alkyl acetals instead of lactate esters. A tentative mechanism for the acid catalysis is proposed based on reference reactions and isotopically labelled experiments. Reusability of the USY catalyst is demonstrated for the title reaction.
- Pescarmona, Paolo P.,Janssen, Kris P. F.,Delaet, Chloe,Stroobants, Christophe,Houthoofd, Kristof,Philippaerts, An,De Jonghe, Chantal,Paul, Johan S.,Jacobs, Pierre A.,Sels, Bert F.
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experimental part
p. 1083 - 1089
(2010/08/20)
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- Tin-catalyzed conversion of trioses to alkyl lactates in alcohol solution
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Tin chlorides, SnCl2 and SnCl4·5H2O are excellent catalysts for the reactions of trioses, dihydroxyacetone and glyceraldehyde with alcohols (MeOH, EtOH and nBuOH) to give alkyl lactates, whose reaction mechanism involves the intermediary formation of pyruvic aldehyde followed by its esterification, which is distinctively promoted by tin halides. The Royal Society of Chemistry 2005.
- Hayashi, Yukiko,Sasaki, Yoshiyuki
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p. 2716 - 2718
(2007/10/03)
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- Reactions of 2-alkoxypropenals with thiols in neutral and acid media
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Addition of thiols to 2-alkoxypropenal in neutral medium at 20°C in the absence of a catalyst occurs regioselectively, following the Markownikoff pattern. The resulting 2-alkoxy-2-R-thiopropanals are capable of undergoing spontaneous isomerization to 1-al
- Keiko,Funtikova,Stepanova,Chuvashev,Larina
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p. 970 - 976
(2007/10/03)
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- Kinetic and thermodynamic control in the synthesis of methylglyoxal thioacetals from 2-ethoxypropenal
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Under kinetically controlled conditions, the addition of organylthiols to 2-ethoxypropenal follows the Markovnikov rule to give 2-ethoxy-2-organylthiopropanals which spontaneously isomerize to 1-ethoxy- 1-organylthiopropanones in storage or in the presenc
- Keiko,Funtikova,Stepanova,Chuvashev,Larina,Voronkov
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p. 110 - 112
(2007/10/03)
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