116-09-6Relevant articles and documents
High-stable CuPd-Cu2O/Ti-powder catalyst for low-temperature gas-phase selective oxidation of alcohols
Liu, Kun,Chen, Zhaoxiang,Zou, Peipei,Wang, Yuanyuan,Dai, Liyi
, p. 54 - 58 (2015)
Abstract The oxidation of alcohols to carbonyl compounds in gas-phase is of great importance in organic chemistry and industrial process. Herein, the catalyst CuPd-Cu2O/Ti-powder is prepared by depositing Cu(NO3)2 and Pd(NO3)2 on Ti powder support followed by in-situ activation in reaction stream, which delivers high-performance for the gas-phase oxidation of alcohols. Compared with Cu/Ti-powder and Pd/Ti-powder, CuPd-Cu2O/Ti-powder exhibits higher stability and activity in alcohol oxidation reaction. The catalyst is characterized by XRD, XPS, TEM and ICP. The results indicate that CuPd(alloy)-Cu2O formed during the reaction contributes to the high activity and stability.
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Baudisch,Bass
, p. 181 (1924)
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Catalytic performance of Pt/AlPO4 catalysts for selective hydrogenolysis of glycerol to 1,3-propanediol in the vapour phase
Priya, Samudrala Shanthi,Kumar, Vanama Pavan,Kantam, Mannepalli Lakshmi,Bhargava, Suresh K.,Chary, Komandur V. R.
, p. 51893 - 51903 (2014)
Hydrogenolysis of glycerol to 1,3-propanediol was investigated in the vapour phase over a series of Pt/AlPO4 catalysts with platinum loadings ranging from 0.5 to 3 wt%. The catalysts were prepared by a wet impregnation method and characterized by various techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), BET surface area, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and CO-chemisorption methods. Ex situ pyridine adsorbed FTIR analysis and temperature programmed desorption (TPD) of NH3 were employed to investigate the acidic properties of the catalysts. Further, the effect of reaction temperature, hydrogen flow rate, glycerol concentration and various contents of platinum (0.5 to 3 wt%) have been investigated to find the optimum reaction conditions. Superior performance with almost 100% conversion of glycerol and above 35% selectivity to 1,3-propanediol was obtained over 2 wt% Pt/AlPO4 at 260 °C and atmospheric pressure. The influence of acidity of the catalyst and its correlation to the catalytic performance (selectivity and conversion) has been studied. The high strength of weak acidic sites and Bronsted acidity of the catalyst measured by NH3-TPD and Pyr-FTIR were concluded to play a key role in selective formation of 1,3-propanediol. XRD, TEM and CO-chemisorption studies revealed that platinum was well dispersed on AlPO4 which further contributed to higher catalytic activity for glycerol hydrogenolysis. This journal is
The selective continuous flow synthesis of lower alcohols from polyols-a mechanistic interpretation of the results
Van Ryneveld, Esti,Mahomed, Abdul S.,Van Heerden, Pieter S.,Green, Mike J.,Holzapfel, Cedric,Friedrich, Holger B.
, p. 832 - 837 (2014)
In an endeavour to understand the hydrogenolysis pathway of glycerol to lower alcohols over Ni on Al2O3 and SiO2 catalysts, the role of the intermediates (1,2-propanediol (1,2-PDO), 1,3-propanediol (1,3-PDO), ethylene glycol (EG) and ethanol) was investigated. Under the reaction conditions employed in this study, it was clear that the hydrogenolysis of the C-C and C-O bonds of glycerol takes place to a lesser extent as compared to dehydrogenation and dehydration which are seen as the dominating initial steps. Ethanol was produced in high selectivities (~67%) with 1,2-propanediol as feed and 1-propanol (1-PO, ~80%) was the main product obtained when 1,3-propanediol was used as feed. Ethylene glycol gave methanol and methane as products, whereas ethanol gave methane and CO2 as major products.
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Enders,Marquardt
, p. 46 (1941)
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Chemoselective aerobic oxidation of unprotected diols catalyzed by Pd-(NHC) (NHC = N-heterocyclic carbene) complexes
Bettucci, Lorenzo,Bianchini, Claudio,Oberhauser, Werner,Hsiao, Tsun-Hung,Lee, Hon Man
, p. 63 - 72 (2010)
Neutral Pd(X)(η3-allyl) (X = Cl, OAc (acetate)) complexes bearing mono-coordinating NHC ligands have been synthesized, characterized and employed to catalyze the aerobic oxidation of unprotected 1,2- and 1,3-diols selectively to hydroxy ketones. A comparison of the catalytic performance of these precursors with a reference system has shown that the precursor with the ligands N,N′-bis(adamantyl)imidazol-2-ylidene and chloride is the most efficient for the chemoselective oxidation of 1,2-diols is concerned. High-pressure 1H NMR (HPNMR) experiments in combination with catalytic batch reactions have provided valuable information on the activation of the precursor as well as on the stability of the catalysts.
Influence of the carrier and composition of active phase on physicochemical and catalytic properties of CuAg/ oxide catalysts for selective hydrogenolysis of glycerol
Samson,Zelazny,Grabowski,Ruggiero-Mikolajczyk,liwa,Pamin,Kornas,Lachowska
, p. 9295 - 9306 (2015)
The aim of the present study is to investigate the influence of the support and composition of the active bimetallic phase on both the physicochemical and catalytic properties of catalysts for use in glycerol hydrogenolysis reaction. Two series of catalysts with different amounts of copper oxide and/or silver supported on Al2O3 or TiO2 oxides were prepared. To determine the physicochemical properties of the catalysts, the following techniques were used: Brunauer-Emmett-Teller, reactive N2O adsorption, X-ray diffraction, and temperature-programmed reduction TPR-H2. Physicochemical characterization revealed that addition of silver modifies the redox properties of the catalysts containing copper oxide and influences their specific surface area. It was found that the type of carrier determines the catalytic activity and selectivities for desired products, strongly influencing their distribution. The Al2O3-supported catalysts were much more selective for 1,2-propanediol, whereas 1-propanol was the main reaction product for the titania-supported catalysts. The best catalysts (6Cu/Al and 2Cu/Ti) achieved 38 % glycerol conversion with 71 % selectivity for 1,2-propanediol and 44 % conversion with 62 % selectivity for 1-propanol, respectively.
Synthesis of different ZnO-supported metal systems through microemulsion technique and application to catalytic transformation of glycerol to acetol and 1,2-propanediol
Montes,Checa,Marinas,Boutonnet,Marinas,Urbano,J?ras,Pinel
, p. 129 - 137 (2014)
Different systems consisting of diverse metals (Au, Pt, Pd, Rh) supported on ZnO (5% by weight) were synthesized through the microemulsion technique (ME) and tested for glycerol hydrogenolysis, the main products being hydroxyacetone (acetol) and 1,2-propanediol (1,2-PDO). The solids synthesized using sodium borohydride as the reducing agent (B series) had smaller particle sizes as compared to the use of hydrazine (H series) which, in turn, resulted in a better catalytic performance. This synthetic method allowed us to obtain similar metal particle sizes (2-4 nm) for Pt, Pd and Rh solids in B series, whereas average gold metal particle was higher (>8 nm) which probably accounts for Au-containing systems being inactive under our experimental conditions. Reactivity order followed the sequence Rh > Pt > Pd. A comparison of the systems synthesized in the present paper through ME technique with those obtained in a previous work through the deposition-precipitation process revealed a higher activity and selectivity to acetol for the former solids which could be related to the presence of surfactant. Moreover, results suggested that metal sites could participate not only in hydrogenation of acetol to 1,2-propanediol but also in the previous dehydration step of glycerol to acetol.
Pyrolysis of some (13)C-labeled glucans: A mechanistic study
Ponder, Glenn R.,Richards, Geoffrey N.
, p. 27 - 48 (1993)
An isotopic labeling study has been conducted to investigate the chemical mechanisms involved in the formation of certain pyrolysis products of glucans, specifically glycolaldehyde (GA), acetol (hydroxypropanone), acetic acid, and formic acid, which are the major non-aqueous components of the distillate fraction (-60 deg C condensate) of the pyrolyzate. (13)C labels at C-1, C-2, and C-6 of the glucose rings in synthetic glucans were used to reveal the origins of this compounds.In general, the results show that each compound is formed by several different mechanisms, but suggest that only a few mechanisms predominate in each case.Glycolaldehyde derives predominantly from the C-1-C-2 segment of the glucose monomers, with C-5-C-6 also contributing significantly.Evidence is presented supporting heterolytic mechanisms which require a reducing end-group and base catalysis.Acetol derives mostly from three contiguous carbons that include a terminal carbon (C-1 or C-6), most often C-6 and most often appearing as the methyl carbon in the acetol.Acetic acid also arises most often from terminal carbons, the C-5-C-6 segment being the major source, with the methyl carbon usually deriving from C-1 or C-6.About half of the formic acid produced arises from C-1.Mechanisms derived from the chemistry of alkaline degradation and involving acylformylcarbinol intermediates are proposed.
Liquid-phase glycerol hydrogenolysis to 1,2-propanediol under nitrogen pressure using 2-propanol as hydrogen source
Gandarias,Arias,Requies,El Doukkali,Gueemez
, p. 237 - 247 (2011)
2-Propanol was studied as a hydrogen donor molecule in the transfer hydrogenation process to selectively convert glycerol into 1,2-propanediol under N2 pressure and using Ni or/and Cu supported on Al2O 3 catalysts. The results were compared to those obtained under the same operating conditions but under H2 pressure. The results of the activity tests and catalyst characterization techniques (N2- physisorption, H2-chemisorption, TPD of NH3, TPR, TPO and XPS) suggest that glycerol hydrogenolysis to yield 1,2-propanediol occurred through a different mechanism regarding the origin of the hydrogen species. When atomic hydrogen came from dissolved molecular hydrogen dissociation, glycerol was first dehydrated to acetol and then hydrogenated to 1,2-propanediol. On the other hand, when the hydrogen atoms were produced from 2-propanol dehydrogenation, glycerol was directly converted to 1,2-propanediol through intermediate alkoxide formation.
Selective conversion of glycerol into 1,2-propanediol at ambient hydrogen pressure
Sato, Satoshi,Akiyama, Masaki,Inui, Kanichiro,Yokota, Masahiro
, p. 560 - 561 (2009)
The vapor-phase reaction of glycerol was performed over a copper-alumina catalyst at ambient hydrogen pressure. Glycerol was converted into 1,2-propanediol (PDO) through dehydrationhydrogenation via hydroxyacetone (HA). We also found that 1,2-PDO was produced at the selectivity higher than 93 mol % in hydrogen flow at gradient temperatures: the dehydrogenation into HA was catalyzed at around 180-200 °C, while the following hydrogenation into 1,2-PDO was catalyzed by Cu-alumina catalyst at around 145-160°C. Copyright
Synergetic effect between Cu0 and Cu+ in the Cu-Cr catalysts for hydrogenolysis of glycerol
Xiao, Zihui,Wang, Xinkui,Xiu, Jinghai,Wang, Yuemin,Williams, Christopher T.,Liang, Changhai
, p. 200 - 207 (2014)
Active species of Cu-Cr catalysts, prepared by an epoxide-assisted sol-gel route, were investigated for the hydrogenolysis of glycerol to 1,2-propanediol. Structural characterization of the catalysts was performed by means of N 2 physisorption, X-ray diffraction, H2-temperature programmed reduction, high-resolution X-ray photoelectron spectroscopy, NH 3-temperature programmed desorption, and N2O titration. On the basis of the characterizations, the copper species on the calcined Cu-Cr catalysts and the reduced Cu-Cr catalysts were assigned. Combined with reaction results, it was found that there was not similar trend in copper metal surface area and glycerol conversion, indicating that a two-site (Cu0 and Cu+) mechanism existed in the hydrogenolysis of glycerol over Cu-Cr catalysts. Besides, the maximum conversion of glycerol was obtained when the surface Cu0/Cu+ ratio increased from 3.1 to 6.6, whereas decreased with increasing sequentially to 15.7, demonstrating that the appropriate surface Cu0/Cu+ ratio was required for optimum hydrogenation activity. Thus, the synergetic effect between the Cu0 and Cu+ was considered to be responsible for the high catalytic activity in the hydrogenolysis of glycerol, and that CuCr2O 4 played a critical role in the glycerol hydrogenolysis reaction since it could function as a "hydrogen delivery bridge".
The influence of H/D kinetic isotope effect on radiation-induced transformations of hydroxyl-containing compounds in aqueous solutions
Bekish, Andrei V.,Nepachalovich, Palina S.,Shadyro, Oleg I.,Shmanai, Vadim V.
, p. 732 - 744 (2020)
Vicinal diols and its derivatives can be exploited as model compounds for the investigation of radiation-induced free-radical transformations of hydroxyl-containing biomolecules such as carbohydrates, phospholipids, ribonucleotides, amino acids, and peptides. In this paper, for the first time, the prospects of isotope reinforcement approach in inhibiting free-radical transformations of hydroxyl-containing compounds in aqueous solutions are investigated on the example of radiolysis of 1,2-propanediol and 1,2-propanediol-2-d1 aqueous solutions. At an absorbed dose rate of 0.110 ± 0.003 Gy·s?1 a profound kinetic isotope effect (KIE) is observed for the non-branched chain formation of acetone, which is a final dehydration product of predominant carbon-centred radicals CH3·C(OH)CH2OH. In 0.1 and 1 M deaerated solutions at pH 7.00 ± 0.01, the values of KIE are 8.9 ± 1.7 and 15.3 ± 3.1, respectively. A rationale for the fact that a strong KIE takes place only in the case of chain processes, which may occur during free-radical transformations of vicinal diols, is also provided herein based on the results of 2-propanol and 2-propanol-2-d1 indirect radiolysis. Lastly, the lack of KIE is shown in the case of 2-butanone formation from 2,3-butanediol or 2,3-butanediol-2,3-d2. This indicates that the type (primary, secondary) of the β-carbonyl radicals formed as a result of CH3·C(OH)CH(OH)R (R = H, CH3) dehydration determines the manifestation of the effect.
Studies on continuous selective hydrogenolysis of glycerol over supported Cu-Co bimetallic catalysts
Raju, Narsinga,Rekha, Voggu,Abhishek, Burri,Kumar, Peddagolla Mahesh,Sumana, Chenna,Lingaiah, Nakka
, p. 3122 - 3128 (2020)
Alumina supported copper-cobalt catalysts were made and screened for continuous hydrogenolysis of glycerol to 1,2-propanediol at atmospheric pressure. BET surface area, temperature-programmed reduction, X-ray diffraction, pulse N2O chemisorption, transmission electron microscopy and X-ray photoelectron spectroscopy techniques were used to derive the characteristics of the catalysts. The presence of Co in Cu/alumina significantly increased the reducibility of CuO species and also the metallic Cu surface area. The catalyst with 10%Cu-7%Co on Al2O3 afforded complete glycerol conversion with 77% selectivity to 1,2-propanediol. The catalysts activity was found to be mainly due to the existence of Cu in a highly dispersed state with a high metal surface area and synergistic interactions between the Cu-Co moieties. The influence of the reaction parameters was investigated and the best possible parameters were determined. The most active catalyst showed high stability during the time on stream analysis.
Schrauzer, G. N.,Sibert, J. W.
, p. 1022 - 1030 (1970)
Catalytic routes and oxidation mechanisms in photoreforming of polyols
Sanwald, Kai E.,Berto, Tobias F.,Eisenreich, Wolfgang,Gutiérrez, Oliver Y.,Lercher, Johannes A.
, p. 806 - 816 (2016)
Photocatalytic reforming of biomass-derived oxygenates leads to H2 generation and evolution of CO2 via parallel formation of organic intermediates through anodic oxidations on a Rh/TiO2 photocatalyst. The reaction pathways and kinetics in the photoreforming of C3–C6 polyols were explored. Polyols are converted via direct and indirect hole transfer pathways resulting in (i) oxidative rupture of C–C bonds, (ii) oxidation to α-oxygen functionalized aldoses and ketoses (carbonyl group formation) and (iii) light-driven dehydration. Direct hole transfer to chemisorbed oxygenates on terminal Ti(IV)-OH groups, generating alkoxy-radicals that undergo ?-C–C-cleavage, is proposed for the oxidative C–C rupture. Carbonyl group formation and dehydration are attributed to indirect hole transfer at surface lattice oxygen sites [Ti?O?Ti] followed by the generation of carbon-centered radicals. Polyol chain length impacts the contribution of the oxidation mechanisms favoring the C–C bond cleavage (internal preferred over terminal) as the dominant pathway with higher polyol carbon number.
Enhancement of glycerol conversion to acetol in high-temperature liquid water by high-pressure carbon dioxide
Yamaguchi, Aritomo,Hiyoshi, Norihito,Sato, Osamu,Rode, Chandrashekhar V.,Shirai, Masayuki
, p. 926 - 927 (2008)
Dehydration of glycerol to acetol proceeded in high-temperature liquid water at 573 K in a batch reactor. The acetol formation rate increased with an addition of high-pressure carbon dioxide. Copyright
OH-initiated photooxidations of 1-pentene and 2-methyl-2-propen-1-ol: Mechanism and yields of the primary carbonyl products
Peirone, Silvina A.,Cometto, Pablo M.,Lane, Silvia I.
, p. 3848 - 3854 (2014)
The products of the gas-phase reactions of OH radicals with 1- pentene and 2-methyl-2-propen-1-ol (221MPO) at T=298±2 K and atmospheric pressure were investigated by using a 4500 L atmospheric simulation chamber that was built especially for this work. The molar yield of butyraldehyde was 0.74± 0.12 mol for the reaction of 1-pentene. This work provides the first product molar yield determination of formaldehyde (0.82±0.12 mol), 1-hydroxypropan-2-one (0.84±0.13 mol), and methacrolein (0.078±0.012 mol) from the reaction of 221MPO with OH radicals. The mechanism of this reaction is discussed in relation to the experimental results. Additionally, taking into consideration the complex mechanism, the rate coefficients of the reactions of OH with formaldehyde, 1-hydroxypropan-2- one, and methacrolein were derived at atmospheric pressure and T=298±2 K.; the obtained values were (8.9±1.6)×10-12, (2.4±1.4)×10-12, and (22.9±2.3)×10-12 cm3 molecule-1 s-1, respectively.
1-tert-Butoxypropan-2-one as direct reaction product of acetone with tert-butyl hydroperoxide
Grebenshchikov,Dykman,Pinson
, p. 617 - 618 (2008)
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Active sites in modified copper catalysts for selective liquid phase dehydration of aqueous glycerol to acetol
Mane, Rasika B.,Yamaguchi, Aritomo,Malawadkar, Atul,Shirai, Masayuki,Rode, Chandrashekhar V.
, p. 16499 - 16508 (2013)
We report here the influence of oxides of various metals viz. Ba, Mg, Zr, Zn, Al, and Cr in modified copper catalysts, on the formation of different copper species and acid sites responsible for dehydration of aqueous glycerol to acetol. These catalysts were prepared by a co-precipitation method, among which the catalysts having higher acid strength and predominant Bronsted acidity (Cu-Mg, Cu-Zr and Cu-Al) gave the highest acetol selectivity (76-92%), while the catalysts with lower acidity such as Cu-Zn showed very poor (25%) selectivity to acetol in spite of the highest conversion of 68%. Nevertheless, catalysts exhibiting higher activity and acetol selectivity also showed the presence of metallic Cu confirmed by XRD and XANES-EXAFS characterization. Based on these results, two different catalytic pathways have been proposed highlighting the role of Lewis and Bronsted acidity along with the metal sites in individual steps of glycerol dehydration reaction. The Royal Society of Chemistry 2013.
Promoting effect of boron oxide on Cu/SiO2 catalyst for glycerol hydrogenolysis to 1,2-propanediol
Zhu, Shanhui,Gao, Xiaoqing,Zhu, Yulei,Zhu, Yifeng,Zheng, Hongyan,Li, Yongwang
, p. 70 - 79 (2013)
Cu/SiO2 catalyst has been extensively applied in glycerol hydrogenolysis for its high selectivity to 1,2-propanediol, while suffering from severe deactivation easily. B2O3 is frequently used as an additive for stabilizing active species. Thus, a series of Cu/SiO2 catalysts with various B2O3 loadings for glycerol hydrogenolysis were prepared via precipitation-gel method followed by impregnation with boric acid. These catalysts were fully characterized by ICP, BET, XRD (in situ XRD), N2O chemisorption, H2-TPR, NH 3-TPD, IR, Raman, XPS, and TEM. Addition of B2O 3 to Cu/SiO2 can greatly restrain the growth of copper particles and promote the dispersion of copper species upon calcination, reduction and reaction, which resulted in the enhanced catalytic activity and stability. The optimal 3CuB/SiO2 reached complete conversion with 98.0% 1,2-propanediol selectivity. The strong correlation between 1,2-propanediol yield and Cu surface area gave direct evidence that the active Cu species were the primary active sites for glycerol hydrogenolysis.
Formation of furans upon electron-beam heating of cellulose
Kholodkova,Ponomarev
, p. 18 - 24 (2011)
Similarity between cotton cellulose and sulfate and sulfite pine celluloses in degradation during electron-beam distillation has been shown. The yield of the distillate liquid slightly depends on the type of cellulose and makes up ~60 wt %. The product liquid contains organic compounds with molecular masses of 32 to 128, of which furfural and its derivatives prevail. Electron-beam distillation can be used as an effective method for the manufacturing of furfural and other furan derivatives from cellulose (along with the traditional pentosan conversion processes). It has been shown that grinding and preheating of cellulose lead to an increase in the proportion of furfural and other furans in the condensates. Pleiades Publishing, Inc., 2011.
Gas phase reaction of the hydroxyl radical with the unsaturated peroxyacyl nitrate CH2 = C(CH3)C(O)OONO2
Grosjean,Williams,Grosjean
, p. 921 - 929 (1993)
The gas phase reaction of the hydroxyl radical with the unsaturated peroxyacyl nitrate CH2C(CH3)C(O)OONO2 (MPAN) has been studied at 298 ± 2 K and atmospheric pressure. The OH-MPAN reaction rate constant relative to that of OH+ n-butyl nitrate is 2. 08 ± 0.25. This ratio, together with a literature rate constant of 1.74 ×10-12cm3molecule-1s-1 for the OH+ n-butyl nitrate reaction at 298 K, yields a rate constant of (3.6 ± 0.4) × 10-12cm3 molecule-1S-1 for the OH-MPAN reaction at 298 ± 2 K. Hydroxyacetone and formaldehyde are the major carbonyl products. The yield of hydroxyacetone, 0.59 ± 0.12, is consistent with preferential addition of OH at the unsubstituted carbon atom. Atmospheric persistence and removal processes for MPAN are briefly discussed.
Palladium-Catalyzed (3+3) Annulation of Allenylethylene Carbonates with Nitrile Oxides
Pan, Ting,Gao, Xing,Yang, Sen,Wang, Lan,Hu, Yimin,Liu, Min,Wang, Wei,Wu, Yongjun,Zheng, Bing,Guo, Hongchao
, p. 5750 - 5754 (2021)
In this paper, we designed and synthesized a new type of cyclic carbonates, allenylethylene carbonates (AECs). With AECs as reactive precursors, we developed palladium-catalyzed (3+3) annulation of AECs with nitrile oxides. Various AECs worked well in this reaction under mild reaction conditions. A variety of 5,6-dihydro-1,4,2-dioxazine derivatives with allenyl quaternary stereocenters can be accessed in a facile manner in high yields (≤98%).
Continuous catalytic process for the selective dehydration of glycerol over Cu-based mixed oxide
Concepción, Patricia,Domine, Marcelo E.,Mazarío, Jaime,Ventura, María
, p. 160 - 175 (2020)
The selective dehydration of glycerol to hydroxyacetone (acetol) was studied with Cu-based mixed oxides derived from hydrotalcite as catalysts in a continuous flow fix-bed reactor. Catalysts were prepared by co-precipitation and characterized by ICP, N2 adsorption, XRD, NH3-TPD, CO2-TPD, TPR and TEM. Different parameters were investigated to develop the most appropriate material as well as to determine the function of every metallic species. The optimized Cu-Mg-AlOx offered ≈60% acetol selectivity at >90% glycerol conversion (≈80% liquid yield, up to TOS = 9 h). The catalyst could be regenerated by calcination, achieving full activity recovery after five re-cycles. “In-situ” FTIR and XPS measurements evidenced that the presence of Cu, specially the most active Cu1+ species, was essential to carry out the dehydration to acetol with high reaction rates, and to form the preferred intermediate (with C[dbnd]O group); although a minor contribution from Cu0 and Cu2+ species could not be discarded.
Selectivity Switch in the Aerobic 1,2-Propandiol Oxidation Catalyzed by Diamine-Stabilized Palladium Nanoparticles
Oberhauser, Werner,Evangelisti, Claudio,Capozzoli, Laura,Manca, Gabriele,Casaletto, Maria Pia,Vizza, Francesco
, p. 2896 - 2906 (2021/05/06)
Palladium nanoparticles stabilized by a sterically demanding secondary diamine ligand have been synthesized by hydrogen reduction of a palladium acetate complex bearing the corresponding diimine ligand. The obtained nanoparticles were used to catalyze the aerobic oxidation of 1,2-propandiol in n-hexane, and after their heterogenization onto a high surface area carbon, in water. In n-hexane (2,4-dimethyl-1,3-dioxolan-2-yl) methanol has been obtained as major product, whereas in water acetic acid with a selectivity of >85 % has been achieved. The selectivity switch observed was a clear induced by water. The robustness of diamine-stabilized palladium nanoparticles under real aerobic oxidation conditions has been proved by recycling experiments, TEM measurements of the recovered catalysts and by comparison of its performance with that of palladium nanoparticles generated by the metal vapor synthesis technique and supported onto the same carbon in the absence of the stabilizing diamine ligand.
Mesoporous silica supported phosphotungstic acid catalyst for glycerol dehydration to acrolein
Wang, Zhiheng,Liu, Licheng
, p. 55 - 64 (2020/10/20)
Conversion of glycerol to acrolein is a useful reaction for value-added application of biodiesel-derived glycerol and bioenergy development. The high-performance solid acid catalyst is essential to this dehydration reaction. In this paper, tungsten-based heteropolyacids (HPA) were supported on non-ordered mesoporous silica (MSU-x) to increase their dispersion and used as catalysts for glycerol dehydration to acrolein. Aiming to reveal the surface structure of HPA and resulting acidic properties, as well as the relationship between acidic properties and dehydration activity, different loadings of H3PW12O40 were supported on MSU-x (10–50 wt%) and the catalysts were characterized by X-ray diffraction (XRD), BET, SEM/TEM, UV–vis diffuse reflectance spectra (DRS), Raman and FT-IR techniques. Their acidic properties were studied by NH3-Temperature Programmed Desorption (NH3-TPD) and Pyridine adsorption methods. The molecular structure and dispersion of H3PW12O40 supported on the catalysts was revealed. The Keggin unit preserved well but with different hydration level for various loadings. The total acid concentration and respective Br?nsted/Lewis acid identification were calculated. The acrolein yield increased with H3PW12O40 loading until 30 wt% and showed less change with higher loadings. Based on the correlation of acrolein formation rate with acidic properties, the active role of Br?nsted acid and the cooperative role of Br?nsted/Lewis acid sites for glycerol dehydration to acrolein were discussed. This work provides new insight into the structure evolution of heteropolyacids and the catalyst design for the glycerol to acrolein.
