Preparation and phase change performance of Na_2HPO_4·12H_2O@poly(lactic acid) capsules for thermal energy storage

Micro-encapsulated phase-change materials(micro PCMs) with Na_2 HPO_4·12 H_2 O encapsulated in poly(lactic acid)(PLA) shell were prepared by a solvent evaporation–precipitation method that involves the use of a coaxial needle. The effects of PLA concentration, stirring speed, injection rate of core and shell solutions, and polyvinyl alcohol(PVA) concentration on phase change properties were investigated. The thermal properties of microP CMs were characterized by differential scanning calorimetry(DSC). The capsules prepared under the optimal conditions are about 2 mm in diameter and show a latent heat of up to 122.2 J·g^(-1).

Methane oxybromination over Rh-based catalysts:Effect of supports

Bromine mediation has been regarded as one of the most efficient ways to activate and convert methane to useful organics.This article reports the effects of active components(Rh,Ru,Pd and Pt)and supports(SiO2,Mg O and Al2O3)on the catalysis of methane oxybromination.Among the prepared catalysts,Rh/SiO2 is the best in performance(CH4 conversion of ca.20%and CH3Br selectivity exceeding 70%).The results reveal that support type has a notable influence on the catalytic performance of Rh,especially on product distribution.The high selectivity to CH3 Br over Rh/SiO2 is attributed to its low propensity for CH3Br oxidation.It was found that Rh small in particle size shows high catalytic activity and CH3Br selectivity.Although silicalite-1 zeolite suffers from a certain degree of structural damage due to the presence of high temperature steam,the use of silicalite-1 as support results in a performance comparable to that of Rh/SiO2.

Dual-template synthesis of HZSM-5 zeolites with tailored activity in toluene methylation with CH3Br

Shape-selective zeolites(UZ-x/y) were synthesized by a one-pot method using TPAOH(y) and/or MeEt3 N^+I^-(x) as templates.The use of MeEt3 N^+I^- affects the crystal growth and the distribution of acid sites on the external surface of the zeolites.The catalysts show excellent catalytic activity towards toluene alkylation with CH3 Br.With toluene conversion of 36.3% and p-xylene selectivity of 66.2%,HZ-40/0 is the most effective among the prepared catalysts,showing a p-xylene yield of 21.2%.The improved para-selectivity is mainly due to the decrease of acid sites on the external surface of the catalysts.

Facile and Green Synthesis of α,β-Unsaturated Ketone Catalyzed by Air-Stable Organobismuth Complex

Air-stable cationic organobismuth complexes (2-5) possessing both acidic and basic characters were synthesized. The catalyst system that comprises an air-stable bifunctional Lewis acidic/basic organobismuth complex and [Bmim]BF4 showed high catalytic activity, diastereoselec-tivity, stability, and reusability in the one-pot synthesis of (E)-α,β-unsaturat-ed ketones through highly selective crossed-condensation of ketones and aldehydes. Through switching the reaction from homogeneous to heterogeneous, the system shows facile separation ability and facile reusability.

Green and efficient cycloaddition of CO2 toward epoxides over thiamine derivatives/GO aerogels under mild and solvent-free conditions

Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-catalyst and solvent. The interaction between thiamine hydrochloride(VB_1-Cl) and substrates(CO_2 and propylene oxide) was proven by ultraviolet-visible spectroscopy and ~1H nuclear magnetic resonance analysis, and it is deduced that the synergistic action among multi-functional groups(hydroxyl, halide anion and amine) is a favorable factor for cycloaddition reaction. A series of VB_1/GO aerogels were facilely prepared through the addition of aqueous VB_1 derivatives to a suspension of GO in ethanol at room temperature. It was found that the aerogel generated through the interaction of VB_1-Cl with GO shows catalytic activity and stability higher than those of VB_1-Cl. It is because the electrostatic interaction between GO and VB_1-Cl enhances the nucleophilicity and leaving ability of anion. The effects of reaction temperature, catalyst loading, CO_2 pressure and reaction time on CO_2 cycloaddition to propylene oxide were thoroughly studied.

A mini review on chemical fixation of CO_(2):Absorption and catalytic conversion into cyclic carbonates

In this article,we present our research results on chemical fixation of CO_(2) using organobismuth compounds.We fabricated bismuth biphenoate complex,Zn-Mg-Al composite oxides,and SBA-15 or Al-SBA-15 immobilized hydroxyl ionic liquid for CO_(2) cycloaddition onto epoxides.The hypervalent bismuth compounds show good ability for association and dissociation with CO_(2).The bismuth biphenolate complexes are catalytically effective for the cycloaddition reaction.The heterogeneous catalysts,viz.Zn-Mg-Al oxides and SBA-15 or Al-SBA-15 immobilized ionic liquid,are efficient for the synthesis of cyclic carbonate from CO_(2) and epoxide.It is found that the presence of a trace amount of water can improve the catalytic activity of the immobilized ionic liquid.

Cationic organobismuth complex as an effective catalyst for conversion of CO_(2) into cyclic carbonates

In order to achieve high-efficiency conversion of CO_(2) into valuable chemicals,and to exploit new applications of organobismuth compounds,cationic organobismuth complex with 5,6,7,12-tetrahydrodibenz[c,f][1,5]azabismocine framework was examined for the first time for the coupling of CO_(2) into cyclic carbonates,using terminal epoxides as substrates and tetrabutylammonium halide as co-catalyst in a solvent-free environment under mild conditions.It is shown that the catalyst exhibited high activity and selectivity for the coupling reaction of CO_(2) with a wide range of terminal epoxide.The selectivity of propylene carbonates could reach 100%,and the maximum turnover frequency was up to 10740 h^(-1) at 120℃ and 3 MPa CO_(2) pressure when tetrabutylammonium iodide was used as co-catalyst.Moreover,the catalyst is environment friendly,resistant to air and water,and can be readily reused and recycled without any loss of activity,demonstrating a potential in industrial application.