Ruthenium-doped (5 wt%) acidic heteropoly salt Cs2.5H0.5[PW12O40] (CsPW) is an active bifunctional catalyst for the one-pot hydrogenolysis of glycerol to 1,2-propanediol (1,2-PDO) in liquid
phase, providing 96% selectivity to 1,2-PDO at 21% glycerol conversion at 150 °C and an unprecedented low hydrogen pressure
of 5 bar. Rhodium catalyst, 5%Rh/CsPW, although less active, shows considerable selectivity to 1,3-PDO (7.1%), with 1,2-PDO
being the main product (65%). 相似文献
The influence of technological parameters like hydrogen pressure, temperature, glycerol concentration in aqueous solution, amount of catalyst, stirring speed, and reaction time on glycerol hydrogenolysis to 1,2‐propanediol over a Cu/Al2O3 catalyst prepared by coprecipitation was investigated. Functions describing the process were glycerol conversion as well as selectivity to 1,2‐propanediol and to by‐products in the liquid and gas phase. The structure and properties of synthesized Cu/Al2O3 were characterized by X‐ray diffraction, energy dispersive X‐ray microanalysis, BET surface area, average pore volume, and pore diameter. Catalyst recycle studies were also performed. 相似文献
The effect of preparation methods on the Cu/ZnO/Al2O3 catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH3-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al2O3 catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol. 相似文献
The effect of preparation methods on the Cu/ZnO/Al2O3 catalyst structure and catalytic activity on liquid glycerol hydrogenolysis to 1,2-propanediol has been investigated. The physicochemical properties of the catalysts were characterized by BET, XRD, TG/DTA, NH3-TPD and TPR. The experimental results showed that the catalyst prepared by an oxalate gel–coprecipitation had the highest activity. At 200 °C and 400 psi hydrogen pressure, the glycerol conversion and 1,2-propanediol selectivity catalyzed by the Cu/ZnO/Al2O3 catalyst prepared via oxalate gel–coprecipitation were 92.3 and 94.5 % respectively. It was found that the 1,2-propanediol selectivity was dependent on hydrogen pressure and the un-desired by-products were mainly due to the side reactions caused by the presence of the intermediate acetol.
The concept of supported ionic liquid phase (SILP) catalysis has been extended to 1‐butene hydroformylation. A rhodium‐sulfoxantphos complex was dissolved in [BMIM][n‐C8H17OSO3] and this solution was highly dispersed on silica. Continuous gas‐phase experiments in a fixed‐bed reactor revealed these SILP catalysts to be highly active, selective and long‐term stable. Kinetic data have been acquired by variation of temperature, pressure, syngas composition, substrate and catalyst concentration. A linear dependency in rhodium concentration could be established over a large concentration range giving another excellent hint for truly homogeneous catalysis in the SILP system. Compared to former studies using propene, the SILP system showed significantly higher activity and selectivity with 1‐butene as feedstock. These findings could be elucidated by solubility measurements using a magnetic microbalance. 相似文献
Phosphotungstic acid (H3PW12O40 6H2O) was immobilized within a hierarchically structured silica matrix by sol–gel inclusion using polyethylene oxide as a phase separation initiator (one‐pot synthesis). The macropore size of the SiO2‐HPW composites was controlled by the polymer content. The hierarchically structured catalysts with different HPW loadings were tested against their counterparts with monomodal pore size distribution, applying the dehydration of glycerol as a test reaction. The catalysts with bimodal pore size distribution showed a significantly better long‐term stability. The improved performance was attributed to their balanced acidity, excellent leaching stability, and enhanced mass transfer within the hierarchically structured pore system. 相似文献
An oxidative cross‐coupling reaction between aldehydes and sulfoximines involving dual C H/N H functionalization has been developed. This reaction process is facilitated by a simple copper catalyst (1 mol% loading) and tert‐butyl hydroperoxide (TBHP) as the oxidant and proceeds under mild reaction conditions to afford a series of valuable N‐acylated sulfoximine derivatives in excellent yields. 相似文献
Glycerol trioleate‐based ionic liquid microemulsions are promising biolubricant alternatives. This study presents the formation and the phase behavior of glycerol trioleate‐based ionic liquid microemulsions. Areas of the single‐phase domain were calculated to illustrate the phase‐forming capacities of the designed systems. The effects of ionic liquid anions and cations, oxyethylene groups’ number of surfactant, mass ratio of surfactant to co‐surfactant, chain length of co‐surfactant, and temperature on the phase behavior and phase‐forming capacities of glycerol trioleate‐based ionic liquid microemulsions were investigated using pseudo‐ternary phase diagrams. The results showed that the phase‐forming capacities of glycerol trioleate‐based ionic liquid microemulsions with different ionic liquids were Tf2N?‐based > PF6?‐based > BF4?‐based, OMIM+‐based > HMIM+‐based > BMIM+‐based > EMIM+‐based. The designed systems contained ionic liquid‐glycerol trioleate amphiphilic balance; thus, glycerol trioleate‐surfactant micelles achieved the maximum solubilization capacity for the ionic liquid when the surfactant had approximately five oxyethylene groups with a surfactant to co‐surfactant mass ratio of 4:1. Moreover, increasing the temperature and the aliphatic chain length of co‐surfactant from C2 to C6 enhanced the ability of glycerol trioleate and ionic liquids to form microemulsions. 相似文献
The kinetic model originally developed for quicklime‐catalyzed methanolysis of sunflower oil was tested for another three calcium‐based catalysts, namely, neat CaO, Ca(OH)2, and CaO·ZnO. This model includes the changing reaction mechanism and the triacylglycerol (TAG) mass transfer. The applicability and generalization capability of this model for heterogeneous methanolysis reaction catalyzed by calcium‐based catalysts was evaluated. As indicated by the high coefficient of determination and the relatively small mean relative percentage deviation, the model was a reliable predictor of the time variation of TAG conversion degree in the sunflower oil methanolysis over all four calcium‐based catalysts within the ranges of the reaction conditions applied. This model is recommended in general for describing the kinetics of sunflower oil methanolysis over calcium‐based catalysts. 相似文献
The bifunctional Cinchona‐based sulfonamide catalysts showed the highest levels of enantioselectivity reported to date in the alcoholytic desymmetrization of meso‐glutaric anhydrides. Density functional theory (DFT) computational studies provide detailed insight into the observed sense of enantioselectivity. Moreover, detailed experimental studies and single crystal X‐ray analysis confirmed that these bifunctional organocatalysts 3 do not form H‐bonded self‐aggregates in both solution and solid state. The synthetic utility of this methodology was also demonstrated in the synthesis of pharmaceutically important γ‐amino acids, such as (S)‐pregabalin. Of the many asymmetric syntheses of enantiomerically pure (S)‐pregabalin reported to date, our synthesis requires the least number of and the simplest steps. 相似文献
Structured catalysts consisting of metal sheets on which Raney nickel was deposited by the thermal spraying method were tested for the liquid‐phase hydrogenation of glucose to sorbitol and 2‐nitrotoluene to 2‐methylaniline, used as model reactions. Catalytic tests performed in a bench‐scale (1 L) reactor showed that the catalytic activity of Raney Ni sheets is significantly higher than the one of the pellets used for fixed‐bed applications, but lower than the activity of the powder catalyst used in slurry mode. The activity could be significantly improved when applying a two‐phase co‐current flow through a monolith. In this case, the activity was superior to the one obtained with the slurry catalyst. These results confirm the potential of Raney Ni monoliths as structured catalysts. 相似文献
Today, glycerol is mainly a by‐product of fat splitting and biodiesel production. Further growth of the biodiesel market would result in a fall in the price of glycerol. Particularly glycerol‐water from rapeseed oil methyl ester production, for example, would be an interesting raw material if it could be utilised in fermentation without further pretreatment. Under anaerobic conditions, bacteria can transform glycerol into 1,3‐propanediol (PDO), which can be used as a monomer in the chemical industry. PDO can be produced biotechnologically from glycerol with the aid of bacteria. Another way would be the utilization of glucose instead of glycerol, which would provide independence from the fluctuating glycerol market. However, under certain conditions, the classic technique based on glycerol can be quite interesting with regard to technical and economic aspects: A concerted, extensive search for new microorganisms (screening) and improved process design (fed‐batch with pH‐controlled substrate dosage) allowed the product concentrations, which were relatively low at a maximum of 70–80 g/L as a result of product inhibition, to be raised to more than 100 g/L. An additional advantage of the new technique and the newly isolated strains is the utilisation of low‐priced crude glycerol or glycerol‐water. This is a factor which should not be underestimated and has a direct effect on the product costs. Further on, the use of immobilised cells compared to freely suspended cells enables an increase of productivity from about 2 up to 30 g /Lh. 相似文献
The catalytic performance of bifunctional catalysts, MOx‐Al2O3‐PO4, that contain acidic centers and different transition metal oxide components were evaluated in the gas‐phase dehydration of glycerol using the TPD‐TG‐MS technique and a continuous flow reactor experiment. The initial catalytic activity and selectivity to acrolein and acetol significantly depends on the acidity and the type of transition metal oxide. The higher the total acidity, the higher the acrolein selectivity in the order W > Mo > Cu > V~ Fe ~Cr > Ce. On the other hand, Mn‐, Cr‐, and Fe‐containing catalysts favor the formation of products of oxidative C‐C cleavage. TPD‐TG‐MS investigations of catalysts loaded with glycerol are useful tools for fast‐screening of initial activities of catalysts in the gas‐phase dehydration of glycerol. 相似文献
The asymmetric bromohydroxylation of 2‐aryl‐2‐propen‐1‐ols catalyzed by quinine‐derived bifunctional catalyst has been developed. The regioselectivity was controlled by employing a boronate ester as tether which was formed in situ and enantioselectivity was introduced by taking advantage of a quinine‐derived bifunctional catalyst which activated the boronate ester and N‐bromosuccinimide (NBS) at the same time. Chiral bromohydrin, which is a useful feedstock in organic synthesis, was produced in moderate to excellent enantioselectivity in a two‐step reaction sequence. 相似文献
4‐Aryl‐2(1H)‐quinolones were efficiently synthesized via copper‐catalyzed hydroarylation of (o‐aminophenyl)propiolates with arylboronic acid neopentyl glycol esters. The substrate propiolates were prepared from the corresponding silylalkynes with carbon dioxide by Kondo’s carboxylation method using N,N‐dimethylformamide as a solvent. Hydroarylation was performed in the presence of 3 mol% copper(II) acetate in methanol at 28 °C for 12 h and subsequent deprotection using trifluoromethanesulfonic acid (3.0 equiv.) at 65 °C for 2 h in the same pot to afford the desired 4‐aryl‐2(1H)‐quinolones in 39–89% yields.
Aerobic oxidation using a combination of copper salts and 2,2,6,6‐tetramethylpiperidine N‐oxyl (TEMPO) represent useful tools for organic synthesis and several closely related catalyst systems have been reported. To gain further insights, these catalytic systems were evaluated in a gas–liquid segmented flow device. The improvement of oxygen mass transfer has a significant influence on the turnover‐limiting step. Hence, an improved catalytic system using copper(II) as copper source was implemented in a microreactor for the safe and efficient oxidation of primary alcohol.