57-55-6Relevant articles and documents
Hydrogenation of lactic acid to propylene glycol over a carbon-supported ruthenium catalyst
Jang, Hyuk,Kim, Sung-Hwan,Lee, Duwon,Shim, Sang Eun,Baeck, Sung-Hyeon,Kim, Beom Sik,Chang, Tae Sun
, p. 57 - 60 (2013)
Catalytic hydrogenation of lactic acid to propylene glycol is performed in a high-pressure batch reactor over ruthenium on various carbon supports (i.e., VulcanXC-72, ketjen black, CNTs, CNFs, and graphite) prepared using the incipient wetness impregnation method. The crystallinity of the synthesized catalyst is investigated via X-ray diffraction, and the particle sizes are determined using transmission electron microscopy. The surface areas of the synthesized catalysts are analyzed using the BET method; the catalytic activity correlates remarkably with the BET surface area. The yield of propylene glycol increases with pressure, and the highest yield is achieved at 130 C. The catalytic activity is strongly dependent on the type of support. Among the catalysts tested, Ru on ketjen black shows the highest yield of propylene glycol.
A significant enhancement of catalytic activities in oxidation with H 2O2 over the TS-1 zeolite by adjusting the catalyst wettability
Wang, Liang,Sun, Jing,Meng, Xiangju,Zhang, Weiping,Zhang, Jian,Pan, Shuxiang,Shen, Zhe,Xiao, Feng-Shou
, p. 2012 - 2014 (2014)
Hydrophilic TS-1 (H-TS-1) with rich hydroxyl groups, which were confirmed by 29Si and 1H NMR techniques, exhibits much higher activities in the oxidation than conventional TS-1. This phenomenon is strongly related to the unique features of high enrichment of H2O2 on H-TS-1.
Robust Iridium Coordination Polymers: Highly Selective, Efficient, and Recyclable Catalysts for Oxidative Conversion of Glycerol to Potassium Lactate with Dihydrogen Liberation
Sun, Zheming,Liu, Yaoqi,Chen, Jiangbo,Huang, Changyu,Tu, Tao
, p. 6573 - 6578 (2015)
Along with the rapid expansion of the biodiesel industry to deal with the world energy crisis, inexpensive glycerol is also produced in large scale as the main byproduct in biodiesel production via transesterification. Much attention has been paid to the development of environmentally benign technologies for the transformation of glycerol to valuable DL-lactic acid and its derivatives. Herein, a series of NHC-Ir coordination polymers were readily synthesized via reaction of some structurally rigid bis-benzimidazolium salts with iridium precursors under alkaline conditions and were successfully applied as robust self-supported catalysts in the oxidative dehydrogenation of glycerol to potassium lactate with dihydrogen liberation. Extremely high activity and selectivity were attained in open air under the mild reaction conditions even with ppm-level loadings of the catalysts, which were readily recovered after reaction by simple filtration and reused for up to 31 runs without obvious loss of activity or selectivity. Probably owing to the effective suppression of inactive binuclear iridium species in a homogeneously catalyzed reaction, the catalysts assembled via self-supported strategy exhibited high selectivity and productivity for potassium lactate, with up to 1.24 × 105 turnover numbers (TON) being attained even in large-scale reactions of neat glycerol at an elevated temperature. The high catalytic activity, recyclability, and scalability of the robust self-supported catalysts highlight their potential toward the development of practical technologies for transformation of glycerol to value-added chemicals.
Kinetics and mechanism of the catalytic hydration of propylene oxide
Shaikhutdinov,Petukhov,Sapunov,Kharlampidi,Petukhov
, p. 50 - 55 (2010)
The kinetics of propylene oxide hydration in the presence of bis(ethane-1,2-diol)molybdate is reported. A mathematical description of PO disappearance and propylene glycol formation is suggested. The most probable scheme for the process is presented. The basic kinetic constants are calculated.
Stability and regeneration of Cu-ZrO2 catalysts used in glycerol hydrogenolysis to 1,2-propanediol
Durán-Martín,Ojeda,Granados, M. López,Fierro,Mariscal
, p. 98 - 105 (2013)
A series of Cu-ZrO2 catalysts with different copper contents have been prepared by the coprecipitation method. Their catalytic behavior was studied for glycerol hydrogenolysis reaction to obtain 1,2-propanediol (1,2-PDO) joint to deactivation mechanism and regeneration protocols. A number of physical chemical techniques as X-ray diffraction (XRD), evolved gas analysis by mass spectrometry (EGA-MS), temperature programmed reduction (TPR), X-ray photoelectron spectroscopy (XPS) and chemical analysis have been used to characterize the precursors, activated and spent catalysts. Cu-ZrO2 catalysts with higher atomic ratio Cu/Zr showed higher selectivity while glycerol conversion values were not significantly changed. In terms of stability a decreasing of yield to 1,2-PDO due to a decrease of its selectivity was observed with the number of cycles. The main cause of deactivation was associated to the progressive formation of organic deposits on the surface of catalyst. A regeneration process highly efficient, where almost complete recovery of yield to 1,2-PDO shown by the fresh catalyst was reached, has been identified.
Shape effect of ZnO crystals as cocatalyst in combined reforming- hydrogenolysis of glycerol
Hu, Jiye,Fan, Yiqiu,Pei, Yan,Qiao, Minghua,Fan, Kangnian,Zhang, Xiaoxin,Zong, Baoning
, p. 2280 - 2287 (2013)
Disk- and rod-shaped hexagonal ZnO crystals with various length-to-diameter aspect ratios were controllably synthesized via a facile solution route by adjusting the precursor concentration. The shape and the dimension of the synthesized ZnO crystals were observed by scanning electron microscopy (SEM). The wurtzite structure and the growth habit were determined by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) coupled with selected-area electron diffraction (SAED). It is found that with the lowering of the precursor concentrations, the ZnO crystals were elongated along the c-axis, and the diameter of the {001} planes was reduced, leading to shape evolution from hexagonal disk to prismatic rod. As a result, the ZnO crystals were different from each other in the proportion of the {100} nonpolar planes and the {001} polar planes. The well-defined ZnO crystals were used as the cocatalyst with skeletal Ni40Mo10 in the combined reforming-hydrogenolysis (CRH) of glycerol in the absence of adventitious H 2. A remarkable shape-dependent effect on the selectivity to the C3 hydrogenolysis products and the production rate of 1,2-propandiol (1,2-PDO) was identified. ZnO with a larger proportion of the nonpolar planes was more effective in the CRH of glycerol to the C3 products. An excellent linear relationship between the surface area of the {100} nonpolar planes and the production rate of 1,2-PDO was identified. This is attributed to the in situ enhancement of the Lewis acidity of the nonpolar planes of ZnO by chemisorbed CO2 from the reforming of glycerol, which greatly accelerates the dehydration of glycerol to acetol, the intermediate to 1,2-PDO.
Selectively Chemocatalytic Conversion of Fructose to 1,2-Propylene Glycol over Ru-WOx/Hydroxyapatite Catalyst?
Fu, Yao,Li, Chuang,Xu, Guangyue,Zhang, Xiang
, (2020)
The conversion of fructose to 1,2-propylene glycol (PG) is an important process from cellulosic biomass to high-value added chemicals. Herein, Ru-WOx/hydroxyapatite (HAP) catalyst was employed for this reaction and reached up to 91.3% yield of PG at 180 °C, 1 MPa initial hydrogen for 8 h in water. On this catalyst, Ru and WOx were highly dispersed on HAP support and they interacted with each other to form a special catalytic center. The lack of isolated Ru or RuW alloy site led to a moderate activity for hydrogenolysis and hindered the further conversion of PG to propanol. The weak basic HAP support efficiently prevented the humin formation. This precisely controlled catalyst has potential in green PG production.
Promoter effect of Pd in CuCr2O4 catalysts on the hydrogenolysis of glycerol to 1,2-propanediol
Kim, Nam Dong,Park, Jae Ryul,Park, Dae Sung,Kwak, Byoung Kyu,Yi, Jongheop
, p. 2638 - 2646 (2012)
CuCr2O4 catalysts containing various amounts of Pd (Pd-CuCr) were prepared by a co-precipitation method and examined for use in the conversion of glycerol to 1,2-propanediol (1,2-PDO). Pd was observed to be highly dispersed in a CuCr2O4 spinel structure and conferred unique reduction characteristics of a CuCr2O4 catalyst. After reduction, the amounts of surface exposed Cu0 species and occluded hydrogen species were much larger in the case of added Pd, the Pd-CuCr catalyst, compared to a pure copper chromite catalyst. The Pd-CuCr catalyst utilized hydrogen very efficiently, resulting in an enhancement in the catalytic activity for the conversion of glycerol to 1,2-PDO, even at a relatively low hydrogen pressure. The Pd0.5-CuCr catalyst (containing 0.5 wt% of Pd) showed a total yield of 93.9%, with a selectivity approaching 100% for 1,2-PDO at a hydrogen pressure of 4 MPa. In a kinetic study, the effects of H2 pressure and the concentration of glycerol on the initial rate were examined. Based on the results, the palladium promoter (Pd-CuCr) enhanced the rate constant by about 1.7 times compared with copper chromite. The results provide a basis for the production of 1,2-PDO from glycerol using a process which is both environmentally benign and has improved economics.
Transesterification of propylene carbonate by methanol using KF/Al 2O3 as an efficient base catalyst
Murugan,Bajaj,Jasra
, p. 224 - 231 (2010)
Dimethyl carbonate was synthesized via transesterification of propylene carbonate by methanol using KF/Al2O3 as base catalyst. The catalyst was characterized using FT-IR, XRD, surface area measurement, alkalinity measurement and SEM analysis. The effect of KF loading on Al 2O3, reaction parameters such as reaction temperature, reactant ratio and amount of catalyst on the product yield were investigated. It was found that the catalyst with 20 wt% KF loading on neutral alumina showed 70.9% propylene carbonate conversion with >98% DMC selectivity. Springer Science+Business Media, LLC 2010.
A thermally stable and easily recycled core-shell Fe2O 3@CuMgAl catalyst for hydrogenolysis of glycerol
Xia, Shuixin,Du, Weichen,Zheng, Liping,Chen, Ping,Hou, Zhaoyin
, p. 912 - 916 (2014)
Core-shell structured magnetic Fe2O3@CuMgAl layered double hydroxide (LDH) catalysts were synthesized in a facile route and used in selective hydrogenolysis of glycerol. Characterization disclosed that the thermal stability of the LDH framework, the dispersion of Cu and its activity were enhanced simultaneously in the presence of Fe2O3. This journal is the Partner Organisations 2014.
Electrocatalytic hydrogenation of oxygenates using earth-abundant transition-metal nanoparticles under mild conditions
Carroll, Kyler J.,Burger, Thomas,Langenegger, Lukas,Chavez, Steven,Hunt, Sean T.,Román-Leshkov, Yuriy,Brushett, Fikile R.
, p. 1904 - 1910 (2016)
Electrocatalytic hydrogenation (ECH) is a sustainable pathway for the synthesis of value-added organic compounds, provided affordable catalysts with high activity, selectivity and durability are developed. Here, we synthesize Cu/C, Ni/C, and CuNi/C nanoparticles and compare their performance to Pt/C, Ru/C, PtRu/C for the ECH of hydroxyacetone, a bio-derived feedstock surrogate containing a carbonyl and a hydroxyl functional group. The non-precious metal electrocatalysts show promising conversion-time behavior, product selectivities, and Faradaic efficiencies. Ni/C forms propylene glycol with a selectivity of 89 % (at 80 % conversion), while Cu/C catalyzes ECH (52 % selectivity) and hydrodeoxygenation (HDO, 48 % selectivity, accounting for evaporation). CuNi/C shows increased turnover frequencies but reduced ECH selectivity (80 % at 80% conversion) as compared to the Ni/C catalyst. Importantly, stability studies show that the non-precious metal catalysts do not leach at operating conditions.
Enhancement of Catalytic Activity in Epoxide Hydration by Increasing the Concentration of Cobalt(III)/Salen in Porous Polymer Catalysts
Dai, Zhifeng,Sun, Qi,Chen, Fang,Pan, Shuxiang,Wang, Liang,Meng, Xiangju,Li, Jixue,Xiao, Feng-Shou
, p. 812 - 817 (2016)
The rational design of catalytic materials from the reaction characteristics is expected to be a useful strategy to create highly efficient catalysts. Herein, according to a well-established reaction pathway of epoxide hydration catalyzed a dual-molecular system of Co3+/salen in which a high concentration of active sites is favorable to enhance the activity, we provide an alternative way to prepare a highly efficient heterogeneous catalyst with a high concentration of Co3+/salen from the polymerization of vinyl-functionalized salen monomers followed by the loading of Co3+ species (Co3+/POL-salen). Co3+/POL-salen has a hierarchical porosity and an extraordinary hydrothermal stability. Importantly, catalytic tests in epoxide hydration demonstrate that Co3+/POL-salen affords excellent high activities, which are even better than those of the homogeneous version. This phenomenon is related to the very high concentration of Co3+/salen in the catalyst. In addition, this catalyst can be recycled readily because of its excellent hydrothermal stability.
Hydrogenation of lactic acid on reduced copper-containing catalysts
Simonov,Simakova,Minyukova,Khassin
, p. 1114 - 1118 (2009)
The copper-containing catalysts were prepared by reduction of various oxide precursor compounds. Their catalytic properties were studied in the hydrogenation of lactic acid to propylene glycol under atmospheric pressure. An efficient catalyst, whose precursor compound is copper hydroxosilicate with the structure close to the natural mineral chrysocolla, was developed. The optimum conditions for the synthesis of propylene glycol were established that make it possible to achieve a conversion of lactic acid of 97% at atmospheric hydrogen pressure and 473 K. ; 2009 Springer Science+Business Media, Inc.
A low-cost method for obtaining high-value bio-based propylene glycol from sugar beet pulp
Berlowska,Binczarski,Dudkiewicz,Kalinowska,Witonska,Stanishevsky
, p. 2299 - 2304 (2015)
A new low-cost pathway for the production of high-value propylene glycol (PG) is proposed. This route of waste biomass utilization employs catalytic reduction of lactic acid obtained from fermented enzymatic digests of sugar beet pulp. This journal is
Effects of the precipitation agents and rare earth additives on the structure and catalytic performance in glycerol hydrogenolysis of Cu/SiO 2 catalysts prepared by precipitation-gel method
Huang, Zhiwei,Liu, Hailong,Cui, Fang,Zuo, Jianliang,Chen, Jing,Xia, Chungu
, p. 223 - 232 (2014)
The effects of the precipitation agents (NaOH, Na2CO 3, NH4OH and NH4HCO3) and rare earth additives (La, Ce, Y, Pr and Sm) were studied on the structure and catalytic performance in glycerol hydrogenolysis of the Cu/SiO2 catalysts prepared by precipitation-gel method. The physical-chemical properties of the catalysts were characterized by means of FTIR, H2-TPR, N2O chemisorption, XRD, XPS, BET and TEM. The results showed that precipitation agents had obvious effects on the phase structure, reduction property and catalytic performances (activity, selectivity and stability) of the catalysts. The Cu/SiO2 catalyst precipitated with NaOH presented the highest activity and stability than those with other precipitants, most likely due to its more even dispersion of Cu particles, higher resistant to sintering during glycerol reaction. The incorporation of rare earth additives to Cu/SiO 2 catalyst could promote the structural stability and inhibit the sintering and leaching of the catalysts, especially noticeable for Y and La, and thus contribute to the long-term stability of the catalysts. Clearly, this study provides directions for the design of more efficient and stable Cu catalysts toward the industrial application of glycerol hydrogenolysis.
Hydrogenolysis of glycerol over a highly active CuO/ZnO catalyst prepared by an oxalate gel method: Influence of solvent and reaction temperature on catalyst deactivation
Bienholz, Arne,Schwab, Frederick,Claus, Peter
, p. 290 - 295 (2010)
The hydrogenolysis of glycerol was performed in an autoclave at temperatures between 190 and 225 °C and at a H2 pressure of 5 MPa over a CuO/ZnO catalyst prepared by an oxalate gel (OG) method. Compared to a CuO/ZnO catalyst prepared by coprecipitation, much higher conversions of glycerol and space-time yields up to 9.8 gpropylene glycol g Cu-1 h-1 are achieved with CuO/ZnO-OG, whereas both catalysts produced propylene glycol with selectivities of about 90%. Additionally, the influence of the temperature and the solvent was examined. Compared to a conversion of glycerol of only 5% in an aqueous glycerol solution, the use of 1,2-butanediol as a solvent leads to a high conversion of 55%. Moreover, experiments were carried out in pure glycerol and from transmission electron microscopy images of fresh and spent catalysts, it was obvious that the morphology of the catalyst changed during the reaction. By X-ray diffraction and N2O chemisorption, it was proved that a tremendous loss of copper surface area occurred during the hydrogenolysis of glycerol. Taking together the influence of the solvent on the conversion of glycerol and the results of the catalyst characterization, it can be concluded that water, as an unavoidable by-product of the reaction, is responsible for a strong deactivation of the catalyst.
Hydrogenolysis of glycerol on bimetallic Pd-Cu/solid-base catalysts prepared via layered double hydroxides precursors
Xia, Shuixin,Yuan, Zhenle,Wang, Lina,Chen, Ping,Hou, Zhaoyin
, p. 173 - 182 (2011)
A series of bimetallic Pd-Cu/solid-base catalysts were prepared via thermal decomposition of PdxCu0.4Mg5.6-xAl 2(OH)16CO3 layered double hydroxides precursors and used in hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO). X-ray diffraction (XRD), scanning electron microscopy (SEM) and N2O oxidation and followed H2 titration characterizations confirmed that well structured layered double hydroxides PdxCu0.4Mg 5.6-xAl2(OH)16CO3 crystals could be prepared when the amount of added Pd was less than x xCu0.4/Mg 5.6-xAl2O8.6-x and Pd improved the reduction of Cu. Hydrogenolysis of glycerol proceeded easily on bimetallic Pd-Cu/solid-base catalysts than separated Pd and Cu. On Pd0.04Cu0.4/Mg 5.56Al2O8.56, the conversion of glycerol and selectivity of 1,2-PDO reached 88.0 and 99.6%, respectively, at 2.0 MPa H 2, 180 °C, 10 h in ethanol solution. And this catalyst is stable in five recycles. It was concluded that H2-spillover from Pd to Cu increased the activity of PdxCu0.4/Mg 5.6-xAl2O8.6-x in hydrogenolysis of glycerol.
Cu/SiO2 catalysts prepared by hom- and heterogeneous deposition-precipitation methods: Texture, structure, and catalytic performance in the hydrogenolysis of glycerol to 1,2-propanediol
Huang, Zhiwei,Cui, Fang,Xue, Jingjing,Zuo, Jianliang,Chen, Jing,Xia, Chungu
, p. 42 - 51 (2012)
Cu/SiO2 catalysts prepared by homogeneous deposition- precipitation (Hom-DP) and heterogeneous deposition-precipitation (Het-DP) methods have been systematically characterized focusing on the effect of precipitation manner during catalyst preparation. It is found that the texture, structure and composition of the dried, calcined and reduced catalysts were largely affected by the precipitation manner. Based on characterizations and previous findings, the copper species on the dried, calcined, and reduced catalysts as well as on the catalysts after work were assigned. Due to a homogeneous precipitation manner, the catalyst prepared by Hom-DP method presented a much higher dispersion, a smaller copper particle size and thus a larger copper surface area than those of its counterpart prepared by Het-DP method. Unexpectedly, catalytic activity tests in the hydrogenolysis of glycerol showed that the catalyst prepared by Het-DP method inversely surpassed the former catalyst, mainly due to a larger number of copper species in the Het-DP catalyst was prereduced to active Cu0 sites, which also presented remarkably higher stability during aqueous phase glycerol reaction as compared to those in the former catalyst. In addition, the selectivity to 1,2-propanediol product is found to be affected by both the precipitation agent applied and the structure of the catalysts.
Catalytic conversion of lactic acid into propylene glycol over various metals supported on silica
Jang, Tae Young,Chung, Ku Bong,Eom, Hye Ri,Noh, Dong Kyun,Song, In Kyu,Yi, Jongheop,Baeck, Sung-Hyeon
, p. 1275 - 1282 (2011)
Catalytic hydrogenation of lactic acid to propylene glycol was performed over various metals (Ag, Co, Cu, Ni, Pt, and Ru) supported on silica prepared by an incipient wetness impregnation method. The loading amount of each metal was 5 wt%. Crystallinity of the synthesized catalysts was investigated by X-ray diffraction (XRD), and the BET method was utilized to examine the surface area. Pore volume and pore size of catalysts were determined using BJH analysis of the N2 adsorption isotherm. Particle sizes of various metals were determined from transmission electron microscopy (TEM) images. The catalytic activity was found to be strongly dependent on the supported metal. Among catalysts tested, Ru/SiO2 showed the highest propylene glycol yield. The yield of propylene glycol increased with pressure, and the highest yield was achieved at 130 °C.
A Nuclear Magnetic Resonance Kinetic and Product Study of the Ring Opening of Propylene Oxide. Nucleophilic and General Catalysis by Phosphate
Pocker, Y.,Ronald, B. P.,Ferrin, L.
, p. 7725 - 7732 (1980)
Systematic kinetic and product studies have been performed in an examination of the ring opening of propylene oxide over the entire pH region.The NMR kinetic method, which involves the integration of reactant and product resonances as a function of time, provided the rate data.The plots of log (areat - areainfinite) vs. time were linear to better than three half-life times of reactiom.Reproducibility error for rate measurements run under identical conditions wes less than 5percent.Products were identified by 1H and 13C NMR spectroscopy and with gated decoupler techniques.The latter was used to quantitatively determine the product composition.The validity of this method of product analysis was carefully established with a series of control experiments.The error in these determinations was shown to be less than 4percent.Emphasis was placed on the search for general and nucleophilic mechanisms of catalysis.Kinetic and product analyses were performed on reaction solutions in both aqueous formate and aqueous phosphate buffers.The glycol monoformate esters proved to be labile under kinetic conditions.By contrast the glycol monophosphate esters permitted a complete dissection of the buffer catalytic components into nucleophilic and general modes.Thus careful analysis of the reaction species present in the buffer matrix shows that glycol monophosphate esters are always produced in amounts less than the buffer contribution to the overall rate and furthermore arise almost exclusively from HPO42- attack upon neutral epoxide.This nucleophilic catalysis accounts for 80 +/- 6percent of kHPO42- and leads to almost equal amounts of 1,2-propanediol-1-phosphate and 1,2-propanediol-2-phosphate.The remaining 20 +/- 6percent of kHPO42- and the total kH2PO4- represent general catalysis.These contributions arise mechanistically though hydrogen bonding which operates to increase the nucleophilic capacity of rear side water molecules or to enhance the electrophilic character of the epoxide ring, respectively.
One-pot Fixation of CO2 into Glycerol Carbonate using Ion-Exchanged Amberlite Resin Beads as Efficient Metal-free Heterogeneous Catalysts
Alassmy, Yasser A.,Paalman, Patrick J.,Pescarmona, Paolo P.
, p. 475 - 486 (2021)
The one-pot synthesis of glycerol carbonate from carbon dioxide and glycerol was achieved using ion-exchanged Amberlite resin beads as metal-free heterogeneous catalysts. Two commercially available Amberlite resin beads consisting of polystyrene cross-linked with divinylbenzene and functionalized with either trimethyl ammonium chloride (IRA-900) or dimethyl ethanol ammonium chloride (IRA-910) groups were used as starting materials to prepare the catalysts. These polymeric beads were transformed into their iodide (Amb-900-I, Amb-OH-910-I) or hydroxide (Amb-900-OH and Amb-OH-910-OH) counterparts through straightforward ion-exchange reactions. First, the two resin bead catalysts in hydroxide form were tested in the base-catalyzed transcarbonation reaction of glycerol with propylene carbonate. Both resin bead catalysts were more active compared to benchmark basic catalysts as hydrotalcites and attained 80 % yield of glycerol carbonate over Amb-OH-910-OH after 2 h at 115 °C, employing a 4 : 1 ratio between propylene carbonate and glycerol. Then, the one-pot reaction of CO2, glycerol and propylene oxide to produce propylene carbonate, glycerol carbonate and propylene glycol was investigated as the main target of this study. The reaction involves two steps: the reaction of propylene oxide with CO2 yielding propylene carbonate, and the transcarbonation of the formed cyclic carbonate with glycerol. Amb-900-I, Amb-OH-910-I, Amb-OH-910-OH and combinations of the latter two were employed as catalysts. Although Amb-OH-910-I alone is poorly active in the transcarbonation reaction, it showed the highest catalytic activity in the one-pot cascade reaction, surprisingly surpassing the performance of the Amb-OH-910-I/Amb-OH-910-OH mixtures and reaching high yields of glycerol carbonate (81 %, 115 °C, 4 h). These findings led to proposing a mechanism for the one-pot reaction using the Amb-OH-910-I catalyst. The bead format led to easy recovery of the catalyst, which displayed good reusability in consecutive runs.
Well-defined Cp*Co(III)-catalyzed Hydrogenation of Carbonates and Polycarbonates
Dahiya, Pardeep,Gangwar, Manoj Kumar,Sundararaju, Basker
, p. 934 - 939 (2020/12/15)
We herein report the catalytic hydrogenation of carbonates and polycarbonates into their corresponding diols/alcohols using well-defined, air-stable, high-valent cobalt complexes. Several novel Cp*Co(III) complexes bearing N,O-chelation were isolated for the first time and structurally characterized by various spectroscopic techniques including single crystal X-ray crystallography. These novel Co(III) complexes have shown excellent catalytic activity to produce value added diols/alcohols from carbonate and polycarbonates through hydrogenation using molecular hydrogen as sole reductant or iPrOH as transfer hydrogenation source. To demonstrate the developed methodology's practical applicability, we have recycled the bisphenol A monomer from compact disc (CD) through hydrogenation under the established reaction conditions using phosphine-free, earth-abundant, air- and moisture-stable high-valent cobalt catalysts.
Sterically controlling 2-carboxylated imidazolium salts for one-step efficient hydration of epoxides into 1,2-diols
Cheng, Weiguo,Dong, Li,Fu, Mengqian,Su, Qian,Tan, Xin,Yao, Xiaoqian,Ying, Ting,Zhang, Suojiang
, p. 2992 - 3000 (2021/05/07)
In order to overcome the disadvantages of excessive water and many byproducts in the conventional process of epoxide hydration into 1,2-diols, 2-carboxylated imidazolium salts were first adopted as efficient catalysts for one-step hydration of epoxides into 1,2-diols. By regulating the cation chain lengths, different steric structures of 2-carboxylated imidazolium salts with chain lengths from C1 to C4 were prepared. The salt with the shortest substituent chain (DMIC) exhibited better thermal stability and catalytic performance for hydration, achieving nearly 100% ethylene oxide (EO) conversion and 100% ethylene glycol (EG) selectivity at 120 °C, 0.5 h with just 5 times molar ratio of H2O to EO. Such a tendency is further confirmed and explained by both XPS analysis and DFT calculations. Compared with other salts with longer chains, DMIC has stronger interaction of CO2?anions and imidazolium cations, exhibiting a lower tendency to release CO2?and form HO-CO2?, which can nucleophilically attack and synergistically activate ring-opening of epoxides with imidazolium cations. The strong huge sterically dynamic structure ring-opening transition state slows down the side reaction, and both cations and anions stabilized the transition state imidazolium-EG-HO-CO2?, both of which could avoid excessive hydration into byproducts, explaining the high 1,2-diol yield. Based on this, the cation-anion synergistic mechanism is then proposed.
