The regulation of ferrocene-based catalysts on heat transfer in highpressure combustion of ammonium perchlorate/hydroxyl-terminated polybutadiene/aluminum composite propellants

The regulation of the burning rate pressure exponent for the ammonium perchlorate/hydroxylterminated polybutadiene/aluminum(AP/HTPB/Al)composite propellants under high pressures is a crucial step for its application in high-pressure solid rocket motors.In this work,the combustion characteristics of AP/HTPB/Al composite propellants containing ferrocene-based catalysts were investigated,including the burning rate,thermal behavior,the local heat transfer,and temperature profile in the range of 7-28 MPa.The results showed that the exponent breaks were still observed in the propellants after the addition of positive catalysts(Ce-Fc-MOF),the burning rate inhibitor((Ferrocenylmethyl)trimethylammonium bromide,Fc Br)and the mixture of Fc Br/catocene(GFP).However,the characteristic pressure has increased,and the exponent decreased from 1.14 to 0.66,0.55,and 0.48 when the addition of Ce-FcMOF,Fc Br and Fc Br/GFP in the propellants.In addition,the temperature in the first decomposition stage was increased by 7.50℃ and 11.40℃ for the AP/Fc Br mixture and the AP/Fc Br/GFP mixture,respectively,compared to the pure AP.On the other hand,the temperature in the second decomposition stage decreased by 48.30℃ and 81.70℃ for AP/Fc Br and AP/Fc Br/GFP mixtures,respectively.It was also found that Fc Br might generate ammonia to cover the AP surface.In this case,a reaction between the methyl in Fc Br and perchloric acid caused more ammonia to appear at the AP surface,resulting in the suppression of ammonia desorption.In addition,the coarse AP particles on the quenched surface were of a concave shape relative to the binder matrix under low and high pressures when the catalysts were added.In the process,the decline at the AP/HTPB interface was only exhibited in the propellant with the addition of Ce-Fc-MOF.The ratio of the gas-phase temperature gradient of the propellants containing catalysts was reduced significantly below and above the characteristic pressure,rather than 3.6 times of the difference in the blank propellant.Overall,the obtained results demonstrated that the pressure exponent could be effectively regulated and controlled by adjusting the propellant local heat and mass transfer under high and low pressures.

Chemoselective Transfer Hydrogenation of Cinnamaldehyde over Activated Charcoal Supported Pt/Fe3O4 Catalyst

A variety of spherical and structured activated charcoal supported Pt/Fe3O4 composites with an average particle size of ~100 nm have been synthesized by a self-assembly method using the difference of reduction potential between Pt （Ⅳ） and Fe （Ⅱ） precursors as driving force. The formed Fe3O4 nanoparticles （NPs） effectively prevent the aggregation of Pt nanocrystallites and promote the dispersion of Pt NPs on the surface of catalyst, which will be favorable for the exposure of Pt active sites for high-efficient adsorption and contact of substrate and hydrogen donor. The electron-enrichment state of Pt NPs donated by Fe304 nanocrystallites is corroborated by XPS measurement, which is responsible for promoting and activating the terminal C=O bond of adsorbed substrate via a vertical configuration. The experimental results show that the activated charcoal supported Pt/Fe3O4 catalyst exhibits 94.8% selectivity towards cinnamyl alcohol by the transfer hydrogenation of einnamaldehyde with Pt loading of 2.46% under the optimum conditions of 120 ℃ for 6 h, and 2-propanol as a hydrogen donor. Additionally, the present study demonstrates that a high-efficient and recyclable catalyst can be rapidly separated from the mixture due to its natural magnetism upon the application of magnetic field.

Preparation and characterization of Mn/MgAlFe as transfer catalyst for SO_x abatement

A series of manganese-promoted MgAlFe mixed oxides, used as sulfur transfer catalysts, were prepared by acid-processed gelatin method and characterized by TGA-DTA, XRD, N2 adsorption-desorption and FT-IR techniques. It was found that the sulfur transfer catalysts with 0.5？3.0 wt% manganese showed its good dispersion in the precursor. The novel Mn/MgAlFe catalysts with 0.5？5.0 wt% manganese oxide showed a high oxidative adsorption rate and sulfur adsorption capacity, and 5.0 wt% Mn/MgAlFe sample was superior to the others for SO2 removal. Moreover, the presence of CO had no obvious effect on the adsorption activity of sulfur transfer catalysts for SO2 uptake.

PVP-Supported Palladium-Cadmium Bimetallic Catalyst for the Hydrogen Transfer Dechlorination of Aryl Chlorides

PVP-supported bimetallic catalyst, PVP-PdCl2-CdCl2, exhibits extremely high catalytic activity for the hydrogen transfer dechlorination of aryl chlorides in neutral environment. The yields of dechlorination products are high under mild reaction conditions and the operation is simple.

A facile and convenient method for synthesis of alkyl thiocyanates under homogeneous phase transfer catalyst conditions

A simple and environmentally friendly method is described for the efficient conversion of alkyl halide to alkyl thiocyanate using tetrabutylammonium bromide （TBAB） as a phase transfer catalyst. The reactions occur in water and furnish the corresponding alkyl thiocyanate in high yields. No evidence for the formation of isothiocyanates as by-product of the reaction was observed and the products were obtained in pure form without further purification.

Transfer and Reaction Performances of Selective Catalytic Reduction of NzO with CO over Monolith Catalysts

This work tries to identify the relationship between geometric configuration of monolith catalysts, and transfer and reaction performances for selective catalytic reduction of N2O with CO. Monolith catalysts with five different channel shapes (circle, regular triangle, rectangle, square and hexagon), was investigated to make a comprehensive comparison of their pressure drop, heat transfer Nu number, mass transfer Sh number and N2O conversion. It was found that monolith catalysts have a much lower pressure drop than that of traditional packed bed, and for monolith catalysts with different channel shapes, pressure drop decreases in the order of regular triangle > rectangle > square > hexagon > circle. The order of Nu is in regular triangle > rectangle ≈ square > hexagon > circle, similar to that of Sh. N2O conversion follows the order of regular triangle > rectangular ≈ square ≈ circle > hexagon. The results indicate that chemical reaction including internal diffusion is the controlling step in the selective catalytic reduction of N2O removal with CO. In addition, channel size and gas velocity also have influence on N2O conversion and pressure drop.

Interphase Mass Transfer in G-L-S Magnetically Stabilized Bed with Amorphous Alloy SRNA-4 Catalyst

Gas-liquid (G-L) and liquid-solid (L-S) mass transfer coefficients were characterized in a gas-liquid-solid (G-L-S) three-phase magnetically stabilized bed (MSB) using amorphous alloy SRNA-4 as the solid phase. Effects such as superficial liquid velocity, superficial gas velocity, magnetic strength, liquid viscosity, and particle size were investigated. Experimental results indicated that the G-L volumetric mass transfer coefficients (KLa) increased along with the magnetic strength, superficial gas and liquid velocities. Proper increase of liquid viscosity promoted KLa only in the range of lower liquid viscosity. The external magnetic field made L-S mass transfer coefficients (Ks) in the G-L-S MSB lower than those of conventional fluidized beds. Ks in the MSB almost kept constant as the su- perficial liquid velocity and superficial gas velocity increased and decreased with the liquid viscosity and surface tension, while increased with the particle size Ks showed uniform axial and radial distributions except of small de- creases close to the wall. Dimensionless correlations were established to estimate KLa and Ks of the MSB with SRNA-4 catalysts , which showed the average error of 5.4% and 2.5% respectively.

Effect of mass transfer limitations on catalyst performance during reduction and carburization of iron based Fischer-Tropsch synthesis catalysts

Existence of intraparticle mass transfer limitations under typical Fischer-Tropsch synthesis has been reported previously,but there is no suitable study on the existence of intraparticle diffusion limitations under pretreatment steps (reduction and activation) and their effect on catalytic performance for iron based catalysts.In this study,Fe-Cu-La-SiO2 catalysts were prepared by co-precipitation method.To investigate the intraparticle mass transfer limitation under reduction,activation and reaction steps,and its effect on catalytic performance,catalyst pellets with different sizes of 6,3,1 and 0.5 mm have been prepared.All catalysts were calcined,pretreated and tested under similar conditions.The catalysts were activated in hydrogen (5%H2in N2) at 450℃ for 3 h and exposed to syngas (H2/CO=1) at 270℃ and atmospheric pressure for 40 h.Afterwards,FTS reaction tests were performed for approximately 120 h to reach steady state conditions at 290℃,17 bar and a feed flow (syngas H2/CO=1) rate of 3 L/h (STP).Using small pellets resulted in higher CO conversion,FT reaction rate and C5+ productivity as compared with larger pellets.The small pellets reached steady state conditions just 20 h after starting the reaction.Whereas for larger pellets,CO conversion,FT reaction rate and C5+ productivity increased gradually,and reached steady state and maximum values after 120 h of operation.The results illustrate that mass transfer limitations exist not only for FTS reaction but also for the reduction and carburization steps which lead to various phase formation through catalyst activation.Also the results indicate that some effects of mass transfer limitations in activation step,can be compensated in the reaction step.The results can be used for better design of iron based catalyst to improve the process economy.

Syntheses of α-Hydroxyarylacetic Acids in the Presence of Different Phase Transfer Catalysts Under Sonication

The syntheses of α-hydroxyarylacetic acids with a good yield in the presence of different phase transfer catalysts (PTC) under sonication were studied. The results obtained are superior to those by other similar methods. The data show that β-cyclodextrin (β-CD) is more efficient than other PTC. The preliminary reaction conditions are also discussed.

Nuclephilic ring opening of epoxides promoted by multi-site phase-transfer catalyst:An efficient and eco-friendly route to synthesis of β-hydroxythiocyanate

A highly effective and mild protocol for ring opening of epoxides with NH4SCN in the presence of catalytic amount of a multi- site phase-transfer catalyst, α,α＇,α＂-N-hexakis（triethylammoniummethylene chloride）-melamine, is developed. A variety of ^-hydroxy thiocyanates as important intermediates in agricultural and pharmaceutical chemistry were obtained in high yields with excellent regioselectivity and in short reaction times. 2009 Ali Reza Kiasat. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.

A New Reaction-controlled Phase-transfer Catalyst System

A new reaction-controlled phase-transfer catalyst system was designed and synthesized. In this system, heteropolytungstate [C7H7N(CH3)3]9PW9O34 was used for catalytic epoxidation of cyclohexene with H2O2 as the oxidant. The conversion of H2O2 was 100% and the yield of cyclohexene oxide was 87.1% based on cyclohexene. Infrared spectra showed that both fresh catalyst and the recovered catalyst do have completely same absorption peak, indicating the structure of catalyst is very stability and can be recycled.

Mechanically mixing copper and silver into self-supporting electrocatalyst for hydrogen evolution

Commercial hydrogen production involves the development of efficient hydrogen evolution reaction catalysts.Herein,we adopted a friction stir processing(FSP)technique to mix immiscible metals homogenously and obtain a self-supporting copper-silver(CuAg)catalyst.The gust of Ag atoms with larger atomic sizes caused a tensile strain in the Cu matrix.Meanwhile,the chemical-potential difference induced electron transfer from Cu to Ag,and the two factors jointly led to the upshift of Cu d-band and improved the catalytic activity.Consequently,the CuAg electrode exhibited a high turnover frequency(12 times that of pure Cu),a low overpotential at high current density(superior to platinum foil),and high durability(1.57%decay over 180 h).Our work demonstrates that FSP is a powerful method for preparing self-supporting catalysts of immiscible alloys with high catalytic performance.

Long-range electron synergy over Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst in enhancing charge separation for photocatalytic hydrogen production

The development of novel single-atom catalysts with optimal electron configuration and economical noble-metal cocatalyst for efficient photocatalytic hydrogen production is of great importance,but still challenging.Herein,we fabricate Pt and Co single-atom sites successively on polymeric carbon nitride(CN).In this Pt_(1)-Co_(1)/CN bimetallic single-atom catalyst,the noble-metal active sites are maximized,and the single-atomic Co_(1)N_4sites are tuned to Co_(1)N_3sites by photogenerated electrons arising from the introduced single-atomic Pt_(1)N_4sites.Mechanism studies and density functional theory(DFT)calculations reveal that the 3d orbitals of Co_(1)N_3single sites are filled with unpaired d-electrons,which lead to the improved visible-light response,carrier separation and charge migration for CN photocatalysts.Thereafter,the protons adsorption and activation are promoted.Taking this advantage of long-range electron synergy in bimetallic single atomic sites,the photocatalytic hydrogen evolution activity over Pt_(1)-Co_(1)/CN achieves 915.8 mmol g^(-1)Pt h^(-1),which is 19.8 times higher than Co_(1)/CN and 3.5 times higher to Pt_(1)/CN.While this electron-synergistic effect is not so efficient for Pt nanoclusters.These results demonstrate the synergistic effect at electron-level and provide electron-level guidance for the design of efficient photocatalysts.

The Reactions Between Halides and Alcohols in the Presence of Phase Transfer Catalysts Without Any Base

ＴｈｅＲｅａｃｔｉｏｎｓＢｅｔｗｅｅｎＨａｌｉｄｅｓａｎｄＡｌｃｏｈｏｌｓｉｎｔｈｅＰｒｅｓｅｎｃｅｏｆＰｈａｓｅＴｒａｎｓｆｅｒＣａｔａｌｙｓｔｓＷｉｔｈｏｕｔＡｎｙＢａｓｅＪＩＡＮＧＹｕ－ｌｉｎ；ＹＵＡＮＹｕｎ－ｃｈｅｎｇ；ａｎｄＷＵＢａｏ－ｑｉ...

GROUP TRANSFER POLYMERIZATION OF ETHYL ACRYLATE WITH LEWIS ACID CATALYST

This paper reports the kinetics of group transfer polymerization (GTP)of ethyl acrylate (EA)with zinc iodide catalyst in 1,2-dichloroethane using dimethyl ketene methyl trimethylsilyl acetal (MTS) as initiator at 0℃ and above 0℃. The amount of catalyst used was studied. When zinc iodide catalyst used is more than 10mol% relative to monomer, the rate of polymerization is proportional to the concentration of monomer, whereas zinc iodide catalyst used is less than 10 mol% of the monomer, the rate of polymerization is independent of the monomer concentration.In the GTP of EA an induction period was observed when the zinc iodide contents are less than l0mol%. If the reaction temperature is over 0℃, living species become unstable and diminish, leading to incomplete monomer conversion. The reaction curves equations are obtained. The polymers have narrow molecular weight distributions which are not changed as decreasing zinc iodide contents. The polydispersity is about 1.2.

The Action Mechanism of Phase Transfer Catalyst in the Oxidation of Toluene by Mn^（3＋） in 40％ H_2SO_4

ＴｈｅＡｃｔｉｏｎＭｅｃｈａｎｉｓｍｏｆＰｈａｓｅＴｒａｎｓｆｅｒＣａｔａｌｙｓｔｉｎｔｈｅＯｘｉｄａｔｉｏｎｏｆＴｏｌｕｅｎｅｂｙＭｎ^（３＋）ｉｎ４０％Ｈ_２ＳＯ_４￥（胡万里）（周定）ＨＵＷａｎｌｉ；ＺＨＯＵＤｉｎｇ（Ｄｅｐｔ．ｏｆＡｐｐｌｉｅｄ?..

Synthesis of α-Aminoarylacetic Acids in the Presence of Phase Transfer Catalysts

Synthesis of aminoarylacetic acids with good yield in the presence of phase transfercatalyst (PTC) under sonication has been studied. Results obtained are superior to those by othersimilar methods. The data show that cyclodextrin (5 -CD) is a more efficient catalyst thanother PTC. Optimum reaction conditions and a preliminary mechanism are also discussed.

Regulating the interfacial charge transfer and constructing symmetry-breaking sites for the enhanced N_(2) electroreduction activity

The Haber-Bosch process for industrial NH_(3) production is energy-intensive with heavy CO_(2) emissions.Electrochemical N_(2) reduction reaction(NRR)is an attractive carbon-neutral alternative for NH_(3) synthesis,while the challenge associated with N_(2) activation highlights the demand for efficient electrocatalysts.Herein,we demonstrate that PdCu nanoparticles with different Pd/Cu ratios anchored on boron nanosheet(PdCu/B)behave as efficient NRR electrocatalysts toward NH_(3) synthesis.Theoretical and experimental results confirm that the highly efficient NH_(3) synthesis can be achieved by regulating the charge transfer between interfaces and forming a symmetry-breaking site,which not only alleviates the hydrogen evolution but also changes the adsorption configuration of N_(2) and thus optimizes the reaction pathway of NRR over the separated Pd sites.Compared with monometallic Pd/B and Cu/B,the PdCu/B with the optimized Pd/Cu ratio of 1 exhibits superior activity and selectivity for NH_(3) synthesis.This study provides new insight into developing efficient catalysts for small energy molecule catalytic conversion via regulating the charge transfer between interfaces and constructing symmetry-breaking sites.

Gold/Mg-Al mixed oxides catalysts for oxidative esterification of methacrolein:Effects of support size and composition on gold loading

Gold catalysts supported on Mg-Al mixed oxides for oxidative esterification of methacrolein are prepared by impregnation.Effects of the support particle size,concentration of HAuCl4 solution and Mg/Al ratio on gold loading and catalytic properties are investigated.The catalysts are characterized by CO_(2)-TPD,EDS,XPS,STEM and XRD techniques.Catalysts with smaller support particle size show more uniform gold distribution and higher gold dispersion,resulting in a higher catalytic performance,and the uniformity of gold and the activity of the catalysts with larger support particle size can be improved by decreasing the concentration of HAuCl4 solution.The Mg/Al molar ratio has significant effect on the uniformity of gold and the activity of the catalyst,and the optimum Mg/Al molar ratio is 0.1–0.2.This study underlines the importance of engineering support particle size,concentration of HAuCl4 solution and density of adsorption sites for efficient gold loading on support by impregnation.