A New Quaternary Ammonium Heteropolyoxotungstate Catalyst for Propylene Epoxidation to Propylene Oxide

A new quaternary ammonium heteropolyoxotungstant (cat.C) is prepared and characterized. And the cat.C also is an reaction-controlled phase-transfer catalyst. The catalytic system of O2/EAHQ (2-ethylanthrahydroquinone)/cat.c is used for the epoxidation of propylene. Under the optimal conditions, the yield of propylene oxide based on EAHQ is 84.1%, theselectivity for propylene oxide based on propylene is 99.8% and the conversion of propylene based on EAHQ is 84.3%. The cat.c precipitates after the epoxidation reaction for easy separation. The cat. C is stable enough to be recycled three times without any loss in selectivity.     

Synthesis of propylene carbonate from urea and 1,2-propanediol

The production of propylene carbonate(PC)from urea and 1,2-propanediol(PG)was investigated in a batch process.The catalytic performances of zinc chloride and magnesium chloride were investigated for this reaction system.The influences of various operation conditions on the PC yield were explored.In this work,MgCl_2 and ZnCl_2 showed the excellent catalytic activity toward PC synthesis,and the yields of propylene carbonate reached 96.5%and 92.4%,respectively.The optimum reaction conditions were as follows...     

Production of propylene from an unconventional metathesis of ethylene and 2-pentene over Re2O7/SiO2-Al2O3 catalysts

An unconventional metathesis of ethylene and 2-pentene over Re2O7/SiO2-Al2O3 catalysts has been studied as an alternative route for the production of propylene. Complete conversion of 2-pentene and propylene yield as high as 88 wt% were obtained under mild reaction conditions at 35°C and atmospheric pressure. Unlike the conventional metathesis of ethylene and 2-butenes in which isomerization is a competing side reaction, the isomerization of 1-butene product from the unconventional metathesis of ethylene and 2-pentene to 2-butenes can further react with excess ethylene in the feed, resulting in additional increase in propylene yield. The secondary metathesis reaction was found to be favored under ethylene/2-pentene (E/2P) molar ratio 3 and gas hourly space velocity (GHSV) 1000 h-1 at the reaction temperature of 35°C. No catalyst deactivation was observed during the 455 min time-on-stream under the selected reaction conditions.     

Dimethyl carbonate synthesis via transesterification catalyzed by quaternary ammonium salt functionalized chitosan

A quaternary ammonium salt covalently linked to chitosan was first used as a catalyst for dimethyl carbonate （DMC） synthesis by the transesterification of propylene carbonate （PC） with methanol. The effects of various reaction variables like reaction time, temperature and pressure on the catalytic performance were also investigated. 54% DMC yield and 71% PC conversion were obtained under the optimal reaction conditions. Notably, the catalyst was able to be reused with retention of high catalytic activity and selectivity. Consequently, the process presented here has great potential for industrial application due to its advantages such as stability, easy preparation from renewable biopolymer, and simple separation from products.     

Fully Biodegradable Poly(lactic acid)/Poly(propylene carbonate) Shape Memory Materials with Low Recovery Temperature Based on in situ Compatibilization by Dicumyl Peroxide

Fully biodegradable blends with low shape memory recovery temperature were obtained based on poly(lactic acid)(PLA) and poly(propylene carbonate)(PPC). By virtue of their similar chemical structures, in situ cross-linking reaction initiated by dicumyl peroxide(DCP) between PLA and PPC chains was realized in PLA/PPC blends. Therefore, the compatibility between PLA and PPC was increased, which obviously changed the phase structures and increased the elongation at break of the blends. The compatibilized blends had a recovery performance at 45 °C. Combining the changes of phase structures, the mechanism of the shape memory was discussed. It was demonstrated that in situ compatibilization by dicumyl peroxide was effective to obtain eco-friendly PLA/PPC blends with good mechanical and shape memory properties.     

Development and characterization of a microfluidic glucose sensing system based on an enzymatic microreactor and chemiluminescence detection

Chemiluminescence detection was developed as an alternative to amperometric detection for glucose analysis in a portable, microfluidics-based continuous glucose monitoring system. Amperometric detection allows easy determination of hydrogen peroxide, a product of the glucose oxidase-catalyzed reaction of glucose with oxygen, by oxidation at a microelectrode. However, (micro)electrodes in direct contact with physiological sample are subject to electrode fouling, which leads to signal drift, decreased reproducibility and shortened detector lifetimes. Moreover, there are a few species present in the body (e.g. ascorbic acid, uric acid) which can undergo oxidation at the same applied potential as hydrogen peroxide. These species can thus interfere with the glucose measurement, reducing detection specificity. The rationale for exploring chemiluminescence as opposed to amperometric detection is thus to attempt to improve the lifetime and reproducibility of glucose analysis for monitoring purposes, while reducing interference caused by other chemicals in the body. The study reported here represents a first step in this direction, namely the realization of a microfluidic device with integrated silicon photodiode for chemiluminescence detection of glucose. This microflow device uses a chaotic mixing approach to perform enzymatic conversion of glucose, followed by reaction of the hydrogen peroxide produced with luminol to produce light at 425 nm. The chemiluminescence reaction is catalyzed by horseradish peroxidase in the presence of iodophenol. The performance of the fabricated chip was characterized to establish optimal reaction conditions with respect to sample and reagent flow rates, pH, and concentrations. A linear calibration curve was obtained for current response as a function of glucose concentration in the clinically relevant range between 2 and 10 mM, with a sensitivity of 39 pA/mM (R = 0.9963, one device, n = 3) and a limit of detection of 230 μM (S/N = 3).     

无溶剂条件下锰 (Ⅲ)-席夫碱配合物催化过氧化氢氧化醇

 Aliphatic and aromatic alcohols are efficiently oxidized to ketones or carboxylic acids using aqueous hydrogen peroxide as an oxidant in the presence of a Mn(III) Schiff-base complex as a catalyst under solvent-free conditions. The oxidation of alcohols occurred at 50 °C to give the corresponding ketones or carboxylic acids with a yield higher than 60%.     

POLYMER—SUPPORTED SINGLE AND MIXED AMMONIUM AND PHOSPHONIUM SALTS AS CATALYSTS FOR PHASE—TRANSFER REACTIONS

In this study was to investigate,by phase-transfer catalysis,the activity of single and mixed ammonium and phosphonium salts grafted on a “gel-type“ stryene-7% divinylbenzene copolymer in the oxidation of benzyl alcohol with hydrogen peroxide.A wide variety of catalysts with different quaternary groups and different quaternary chain length substitutents were examined.The activity of single“onium“salts increases as a consequence of the association of ammonium and phosphonium salts grafted onn the same polymeric support.The activity of polymer-supported ammonium and phosphonium salts increases with the number of carbon atoms contained in the alkyl radicals of the -onium and of the functionalization degree with phosphonium groups.     

Effects of Temperature and Catalyst to Oil Weight Ratio on the Catalytic Conversion of Heavy Oil to Propylene Using ZSM-5 and USY Catalysts

It is useful for practical operation to study the rules of production of propylene by the catalytic conversion of heavy oil in FCC (fluid catalytic cracking). The effects of temperature and C/O ratio (catalyst to oil weight ratio) on the distribution of the product and the yield of propylene were investigated on a micro reactor unit with two model catalysts, namely ZSM-5/Al2O3 and USY/Al2O3, and Fushun vacuum gas oil (VGO) was used as the feedstock. The conversion of heavy oil over ZSM-5 catalyst can be comparable to that of USY catalyst at high temperature and high C/O ratio. The rate of conversion of heavy oil using the ZSM-5 equilibrium catalyst is lower compared with the USY equilibrium catalyst under the general FCC conditions and this can be attributed to the poor steam ability of the ZSM-5 equilibrium catalyst. The difference in pore topologies of USY and ZSM-5 is the reason why the principal products for the above two catalysts is different, namely gasoline and liquid petroleum gas (LPG), repspectively. So the LPG selectivity, especially the propylene selectivity, may decline if USY is added into the FCC catalyst for maximizing the production of propylene. Increasing the C/O ratio is the most economical method for the increase of LPG yield than the increase of the temperature of the two model catalysts, because the loss of light oil is less in the former case. There is an inverse correlation between HTC (hydrogen transfer coefficient) and the yield of propylene, and restricting the hydrogen transfer reaction is the more important measure in increasing the yield of propylene of the ZSM-5 catalyst. The ethylene yield of ZSM-5/Al2O3 is higher, but the gaseous side products with low value are not enhanced when ZSM-5 catalyst is used. Moreover, for LPG and the end products, dry gas and coke, their ranges of reaction conditions to which their yields are dependent are different, and that of end products is more severe than that of LPG. So it is clear that maximizing LPG and propylene and restricting dry gas and coke can be both achieved via increasing the severity of reaction conditions among the range of reaction conditions which LPG yield is sensitive to.     

Salen-Cu(Ⅱ)@MIL-101(Cr) as an efficient heterogeneous catalyst for cycloaddition of CO_2 to epoxides under mild conditions

A double active center system, namely Salen-Cu(Ⅱ)@MIL-101(Cr), was successfully synthesized via the"ship in a bottle" approach, which acted as a bifunctional material for both capture and conversion of CO_2 in a single process. For the first time, Salen-Cu(Ⅱ)@MIL-101(Cr) catalyst was developed for the synthesis of propylene carbonate from CO_2 and propylene oxide under room temperature and ambient pressure with a yield of 87.8% over 60 h. Furthermore, the reaction mechanism was also discussed.     

Propylene Dimerization by（η^5—C9H7）2 Nickel（Ⅱ）Catalytic System

The catalytic performance of Ni(η^5-Ind)2 complex in the dimerization of propylene was studied in combimation with an organoaluminum co-catalyst,eventually in the presence of a phosphine ligand.The effects of the type of aluminum co-catalyst and its relative amount,the nature of phosphine ligand and P/Ni ratio as well as the reaction temperature were examined.The results indicated that the nickel precatalyst exhibited high productivity for the propylene dimerization together with organoaluminum.It was likely to strongly modify the reactivity in the catalytic sytem when using phosphine ligand as additives,especially at the reaction temperature below 0℃.The catalytic system based on Ni(η^5-Ind)2 complex displaed an extremely high productivity(TOF up to 16900h^-1)and a good regioselectivity to 2,3-dimethylbutenes (2,3-DMB) in dimers(66.4%)under proper reaction parameters.     

Metal-free synthesis of substituted phenols from arylboronic acids in water at room temperature

A convenient,efficient and practical metal-free method for the synthesis of substituted phenols from arylboronic acids has been developed.The protocol uses hydrogen peroxide as a hydroxylating agent ammonium bicarbonate as an additive,and the reactions were conveniently performed in water at room temperature.The method shows an excellent tolerance of functional groups,so it will find a wide variety of applications in academic and industrial research.     

硅胶键合的N-丙基三亚乙基四胺氨基磺酸作为可回收固体酸催化剂催化合成2-氨基-4,6-二芳基烟腈(英文)

A simple and efficient procedure for the preparation of silica-bound N-propyl triethylenetetramine sulfamic acid(SBPTETSA) by the reaction of silica-bound N-propyl triethylenetetramine(SBPTET) with chlorosulfonic acid in chloroform is described.Silica-bound N-propyl triethylenetetramine sulfamic acid was employed as a recyclable catalyst for the synthesis of 2-amino-4,6-diarylnicotinonitriles from the multi-component reaction of an acetophenone derivative,an aromatic aldehyde,malononitrile,and ammonium acetate under solvent-free conditions at 100 °C.The heterogeneous catalyst was recycled for five consecutive runs in the optimized multi-component reaction of 4-chloroacetophenone,4-chloroenzaldehyde,malononitrile,and ammonium acetate without significant loses to its catalytic activity.     

A facile synthesis of ω-aminoalkyl ammonium hydrogen phosphates

A series of v-aminoalkyl ammonium hydrogen phosphates were synthesized through a simple and efficient three-step method.The starting materials,v-aminoalkyl alcohols(AC-n,with carbon number n = 3,4,5,6),were amino-protected with 9fluorenylmethyl chloroformate(Fmoc-Cl),followed by phosphorylation with POCl 3 and deprotection in piperidine/DMF.The structures of each intermediate and final product were confirmed by 1 H NMR,FTIR and mass spectrum.The yield of each step was about 77-92%,with a total yield higher than 56%.This new method was superior in low-cost raw materials,mild reaction temperatures(0-25 8C) and easy purification methods.     

Synthesis and properties of long-chain quaternary ammonium hydroxides

A series of long-chain quaternary ammonium hydroxides were synthesized from tertiary amines and confirmed by ~1H NMR and FTIR.Surface properties and pH of these surfactants were investigated.The critical micelle concentrations(CMC) of the synthesized quaternary ammonium hydroxides are lower than the conventional quaternary ammonium surfactants.The micelles shapes of these long-chain quaternary ammonium hydroxides in aqueous solution are spherical at a concentration of 0.1 mol/L.The pH values of the synthesized quaternary ammonium hydroxides are 12.25-12.51.     

Fully Biodegradable Poly(lactic acid)/Poly(propylene carbonate) Shape Memory Materials with Low Recovery Temperature Based on <Emphasis Type="Italic">in situ</Emphasis> Compatibilization by Dicumyl Peroxide

Fully biodegradable blends with low shape memory recovery temperature were obtained based on poly(lactic acid) (PLA) and poly(propylene carbonate) (PPC).By virtue of their similar chemical structures,in situ cross-linking reaction initiated by dicumyl peroxide (DCP) between PLA and PPC chains was realized in PLA/PPC blends.Therefore,the compatibility between PLA and PPC was increased,which obviously changed the phase structures and increased the elongation at break of the blends.The compatibilized blends had a recovery performance at 45 ℃.Combining the changes of phase structures,the mechanism of the shape memory was discussed.It was demonstrated that in situ compatibilization by dicumyl peroxide was effective to obtain eco-friendly PLA/PPC blends with good mechanical and shape memory properties.     

Chemical Reactions and Kinetics of the Carbon Monoxide Coupling in the Presence of Hydrogen

The chemical reactions and kinetics of the catalytic coupling reaction of carbon monoxide to diethyl oxalate were studied in the presence of hydrogen over a supported palladium catalyst in the gaseous phase at the typical coupling reaction conditions. The experiments were performed in a continuous flow fixed-bed reactor. The results indicated that hydrogen only reacts with ethyl nitrite to form ethanol, and kinetic studies revealed that the rate-determining step is the surface reaction of adsorbed hydrogen and the ethoxy radical (EtO-). A kinetic model is proposed and a comparison of the observed and calculated conversions showed that the rate expressions are of rather high confidence.     

Electrocatalytic Synthesis of Propylene Carbonate from CO_2 and Propylene Oxide

The electrocatalytic synthesis of propylene carbonate(PC) from CO2 and propylene oxide(PO) was studied under mild conditions(PCO2=1.01×105 Pa, t=25 ℃). Influences of solvents, supporting electrolytes, the passed charge, the nature of electrodes and the current density(j) on the yield of PC were investigated to optimize the electrolytic conditions, with the maximal yield to be 46.2%, the selectivity of propylene carbonate is 100%. The reduction of propylene oxide in the absence and presence of CO2 was examin...     

Synthesis of Di-substituted Proazaphosphatrane and Its Application in Carbon-carbon Double-bond Isomerization

Diisopropyltren was synthesized from the reaction of tren with benzaldehyde in toluene, followed by reducing the imine intermediate with NaBH 4 , and debenzylation catalyzed by 10% Pd/C in methanol. It was then converted to its corresponding azaphosphatrane via ring-closing reaction of HMPT and triflic acid. Deprotonation of azaphosphatrane with potassium t-butoxide afforded the target diisopropyl proazaphosphatrane 1d. A comparative study of compound 1d for isomerization of allylic system and methylene-interrupted diene system revealed that compound 1d is more efficient than its tri-substituted analoque(1b). In acetonitrile at 40 °C, allylaromatics were selectively isomerized to 1-arylpropene generally in an isolated yield more than 95% with trans, cis molar ratios in a range of 87/13 to 96/4. Allyl phenylsulfide was converted to 1-phenylthiopropene(molar ratio of Z/E=54/46) in a yield of 93%―95%. Methylene-interrupted dienes were also isomerized in high yield.     

A novel and efficient strategy for the synthesis of various carbamates using carbamoyl chlorides under solvent-free and grinding conditions using microwave irradiation

We present an efficient,fast and simple strategy of generating the intermediate carbamoyl chlorides from secondary amines using stoichiometric amounts of bis(trichloromethyl)carbonate(BTC) in solution and solvent-free conditions with excellent yields.The results obtained showed the yield increasing on whether a base was used.Finally,an efficient and rapid synthesis of variety carbamate derivatives was developed by the reaction with a high variety of different alcohols,phenols,diols and this intermediate at room temperature with grinding and in solvent-free conditions under microwave irradiation.The presence of various safe bases is shown to be effective in reducing the reaction times,increasing the yields and easing purification.The present method does not involve any hazardous phosgene.