光泵甲酸分子远红外激光研究

用波长为10.6μm的连续CO2激光对HCOOH分子进行泵浦产生了743μm的远红外激光。对泵浦源的设计进行了理论分析和实验研究。测定了远红外激光的输出功率、偏振方向和泵浦效率,且输出为高斯光束,输出功率为7.3mW,泵浦效率为3.6×10-4,并对远红外激光输出的稳定性及泵浦效率进行了分析。

理论研究单个水或甲酸分子对乙酰基异构化的影响

在M06-2X、B3LYP、MP2和MC-QCISD水平下,理论研究了大气中的单个水和甲酸分子催化乙酰基异构化的反应机理,发现产物均为CH2COH自由基。研究结果表明,裸反应的活化能为81.2kcal·mol-1,而加上水和甲酸分子活化能分别降低到46.2和29.0kcal·mol-1,表明它们均能与乙酰基通过氢键形成稳定的络合物,以便有效地催化异构化反应。在298K,1标准大气压条件下,通过直接动力学计算发现,裸反应的速率常数为6.49×10-47cm3·molecule-1·s-1,水和甲酸催化反应比其速率常数分别增加24和33个数量级。考虑大气中各物种浓度后,发现裸反应速率为4.96×10-29s-1,水或甲酸催化该反应的速率分别为2.55×107和9.52×109s-1,当大气中水分子或甲酸浓度较高时,乙酰基异构化反应生成CH2COH自由基可能性很大。

对氨基苯甲酸分子在银表面多相吸附及氯离子影响的SERS研究

研究对氨基苯甲酸(PABA)在银表面上的吸附动力学过程以及氯离子对其的影响,发现PABA在银表面上呈多相吸附。与匀相吸附的情况相似,表面形态的差异较大地改变吸附速率常数,而对多相因子的影响不明显。氯离子的竞争吸附改变PABA吸附的多相性质,随着氯离子浓度的增加,PABA分子从多相吸附逐渐转变为匀相吸附。根据吸附等温线估算了PABA的吸附能,U≈-9.6kJ/mol。结果分析进一步证实:化学吸附时多相吸附意味着表面上存在非单一的吸附形式。

低分子质量聚四氢呋喃二苯甲酸酯的合成及其应用

以TiO2/SiO2[n(TiO2)∶n(SiO2)=90∶10]为催化剂,催化合成了低分子质量聚四氢呋喃二苯甲酸酯(PTMGDB)。采用单因素法进行条件筛选,借助响应面分析法建立连续变量曲面模型,优化反应工艺并预测最佳反应工艺条件为:反应时间为4 h、反应温度为202℃、催化剂质量分数为0. 319%(占酸醇总质量)、n(苯甲酸)∶n(聚四氢呋喃)=2. 077∶1。预测的转化率为99. 96%,实验重复3次,酯化率高达99. 91%,相对误差为0. 05%,并通过FT-IR、GPC对产品结构进行表征。结果表明,该模型能成功预测酯化反应结果。加入10%PTMGDB增塑后,PVA水凝膜熔点从183. 5℃降低至116. 9℃,热稳定性提高;拉伸强度由77. 9 MPa降至38. 4 MPa;熔体流动速率由0. 005 g/min升至4. 28 g/min。因此,低分子质量PTMGDB可提高PVA热稳定性、力学性能及熔体流动性,可解决PVA难以热塑性加工的难题。

对羟基苯甲酸六次甲基四胺加合物的晶体结构

用X射线单晶衍射试验方法测定了对羟基苯甲酸六次甲基四胺加合物(CH2)6N4.(p-HOC6H4CO2H)的晶体结构.晶体属单斜晶系,P21/n空间群,a=0.600 1(4)nm,b=1.184 7(9)nm,c=1.890 6(1)nm,β=93.61(5)°,Z=4,V=1.341 6(2)nm3,Dc=1.378 g.cm-3,μ(MoKα)=0.071 mm-1,F(000)=592,对2 341个独立衍射点的最终偏离因子R1=0.040 4.在标题化合物的晶体结构中独立的对羟基苯甲酸分子和六次甲基四胺分子组交错排列,借助多种氢键形式形成三维氢键网络结构,其中弱氢键扮演着重要的角色.

PA6/5-SSIPA复合材料的微观结构及性能研究

用双螺杆挤出机制备了尼龙6(PA6)/5-(钠代磺基)间苯二甲酸(5-SSIPA)复合材料。变温红外光谱(FTIR)研究结果显示,5-SSIPA能与酰胺基团形成分子间氢键,其强度、热稳定性均好于PA6中原有的分子间氢键。新的分子间氢键的形成使分子链间的作用力增大,有利于分子链排列整齐,提高了复合材料的结晶温度与结晶度。同时材料的拉伸性能和弯曲性能也有明显提高,且随着5-SSIPA用量的增加而提高。

基于DES-RAFT反应技术的邻苯二甲酸二甲酯分子印迹聚合物制备及表征

本研究基于低共熔溶剂(DES)体系的基本性质,采用可逆加成-断裂链转移(RAFT)沉淀聚合法制备一种新型分子印迹聚合物,并对其进行结构表征和性能评价。结果表明:选择四丁基溴化铵-月桂酸作为低共熔溶剂(DES)体系,邻苯二甲酸二甲酯(DMP)为分子模板,α-甲基丙烯酸(MAA)为功能单体,乙二醇二甲基丙烯酸酯(EGDMA)为交联剂,偶氮二异丁腈(AIBN)为链引发剂,三硫代碳酸二苄基酯(DBTTC)为链转移剂,以模板∶功能单体∶交联剂摩尔比为1∶4∶16进行聚合反应,制备而成的邻苯二甲酸二甲酯分子印迹聚合物(DMP-MIPs)对目标物具有良好的特异选择性。同时,由于低共熔溶剂特有的氢键作用,不仅改善了聚合物微球的尺寸和形貌,而且增强了分子印迹聚合物对邻苯二甲酸二甲酯的吸附能力,印迹因子IF可达1.122。将DES-MIPs应用于实际水样检测,并进行3个浓度(0.05 mg/L、0.5 mg/L、1.0 mg/L)加标实验,平均回收率为86.8%~94.3%,相对标准偏差(RSD)在2.41%~3.21%之间。由此可见,基于DESRAFT反应技术制备的分子印迹聚合材料对水质中DMP有良好的选择性吸附,有望应用于环境等领域的有毒有害物质检测。

Alkylation of toluene with tert-butyl alcohol over HPW-modified Hβ zeolite

An Hβ-supported heteropoly acid （H3PW12O40 （HPW）/Hβ） catalyst was successfully prepared by wetness impregnation, and investigated in the alkylation of toluene with tert-butyl alcohol for the synthesis of 4-tert-butyltoluene （PTBT）. X-ray diffraction, scanning electron microscopy, transmis- sion electron microscopy, fourier-transform infrared spectroscopy, inductively coupled plas- ma-optical emission spectrometry, the brunauer emmett teller （BET） method, tempera- ture-programmed NH3 desorption, and pyridine adsorption infrared spectroscopy were used to characterize the catalyst. The results showed that loading HPW on Hβ effectively increased the B acidity and decreased the pore size of Hβ. The B acidity of HPW/Hβ was 142.97 μmol/g, which is 69.74% higher than that of Hβ （84.23 μmol/g）. The catalytic activity of the HPW/Hβ catalyst was much better than that of the parent Hβ zeolite because of its high B acidity. The toluene conversion over HPW/Hβ reached 73.1%, which is much higher than that achieved with Hβ （54.0%）. When HPW was loaded on Hβ, the BET surface area of Hβ decreased from 492.5 to 379.6 m2/g, accompa- nied by a significant decrease in the pore size from 3.90 to 3.17 nm. Shape selectivity can therefore play an important role and increase the product selectivity of the HPW/Hβ catalyst compared with that of the parent Hβ. PTBT （kinetic diameter 0.58 nm） can easily diffuse through the narrowed pores of HPW/Hβ, but 3-tert-butyltoluene （kinetic diameter 0.65 nm） diffusion is restricted because of steric hindrance in these narrow pores. This results in high PTBT selectivity over HPW/Hβ （around 81%）. The HPW/Hβ catalyst gave a stable catalytic performance in reusability tests.

One‐step aldol condensation reaction of dimethoxymethane and methyl acetate over supported Cs/ZSM‐35 zeolite catalysts

This study was performed for the development of a green and promising approach for the synthesis of methyl acrylate and acrylic acid by a one‐step aldol condensation reaction of dimethoxymethane and methyl acetate over cesium oxide‐supported on ZSM‐35 zeolite catalysts; the effect of base sites as well as acid sites on the aldol condensation reaction was studied in detail. It was found that base sites were harmful for aldol condensation due to their failure in catalyzing the decomposition of dimethoxymethane precursor into formaldehyde, whereas the acid site was indispensable for the reaction to proceed. This reaction cannot take place without an acid site. Although acid sites in H‐form of the zeolite（HZSM‐35） are indispensable for the aldol condensation reaction, not all of them tend to favor this reaction. A strong acid catalyzes methanol‐to‐olefin‐like reactions resulting in hydrocarbon byproducts, which are finally transferred to hard coke. Medium strong acids and weak acids are great candidates for the target aldol condensation reaction with high activity and selectivity. A γ‐Al2O3 sample with abundant weak‐strength Lewis acid sites, together with a few medium‐strong‐strength acid sites, performs well with a high activity and considerable stability during the synthesis of methyl acrylate and acrylic acid.

HZSM-35 zeolite catalyzed aldol condensation reaction to prepare acrylic acid and its ester:Effect of its acidic property

Acrylic acid(AA)and its ester,methyl acrylate(MA),were produced by a green one‐step aldol condensation reaction of dimethoxymethane and methyl acetate.The reaction was conducted over ZSM‐35 zeolites with different concentrations of Bronsted acid,which were prepared by the sodium ion‐exchange process with H‐form zeolite.The acidic property of HZSM‐35 was studied in detail through infrared experiments.About 51%of all bridging OH groups were distributed in cages,while 23%and 26%,respectively,were distributed in 10‐and 8‐ring channels.The catalytic performance was enhanced by a high concentration of Bronsted acid,indicating that Bronsted acid is an active site for the aldol condensation reaction.The ZSM‐35 zeolite possessing a concentration of Bronsted acid as high as 0.049 mmol/g demonstrated excellent performance with a MA+AA selectivity of up to 73%.

Exclusively catalytic oxidation of toluene to benzaldehyde in an O/W emulsion stabilized by hexadecylphosphate acid terminated mixed-oxide nanoparticles

A series of hexadecylphosphate acid(HDPA) terminated mixed-oxide nanoparticles have been investigated to catalyze the oxidation of toluene exclusive to benzaldehyde under mild conditions in an emulsion of toluene/water with the catalysts as stabilizers. With the HDPA-Fe2 O3/Al2 O3 as the basic catalyst, a series of transition metals, such as Mn, Co, Ni, Cu, Cr, Mo, V, and Ti, was respectively doped to the basic catalyst to modify the performance of the catalytic system, in expectation of influencing the mobility of the lattice oxygen species in the oxide catalysts. Under normally working conditions of the catalytic system, the nanoparticles of catalysts located themselves at the interface between the oil and water phases, constituting the Pickering emulsion. Both the doped iron oxide and its surface adsorbed hexadecylphosphate molecules were essential to the catalytic system for excellent performances with high toluene conversions as well as the exclusive selectivity to benzaldehyde. Under optimal conditions, ~83% of toluene conversion and >99% selectivity to benzaldehyde were obtained, using molecular oxygen as oxidant and HDPA-(Fe2 O3-Ni O)/Al2 O3 as the catalyst. This process is green and low cost to produce high quality benzaldehyde from O2 oxidation of toluene.

Direct Synthesis of Dimethyl Carbonate from CO_2 and CH_3OH Using 0.4nm Molecular Sieve Supported Cu-Ni Bimetal Catalyst

The 0.4 nm molecular sieve supported Cu-Ni bimetal catalysts for direct synthesis of dimethyl carbonate (DMC) from CO 2 and CH 3 OH were prepared and investigated. The synthesized catalysts were fully characterized by BET, XRD (X-ray diffraction), TPR (temperature programmed reduction), IR (infra-red adsorption), NH 3-TPD (temperature programmed desorption) and CO 2-TPD (temperature programmed desorption) techniques. The results showed that the surface area of catalysts decreased with increasing metal content, and the metals as well as Cu-Ni alloy co-existed on the reduced catalyst surface. There existed interaction between metal and carrier, and moreover, metal particles affected obviously the acidity and basicity of carrier. The large amount of basic sites facilitated the activation of methanol to methoxyl species and their subsequent reaction with activated carbon dioxide. The catalysts were evaluated in a continuous tubular fixed-bed micro-gaseous reactor and the catalyst with bimetal loading of 20% (by mass) had best catalytic activities. Under the conditions of 393 K, 1.1 MPa, 5 h and gas space velocity of 510 h 1 , the selectivity and yield of DMC were higher than 86.0 % and 5.0 %, respectively.

Hydrous manganese dioxide adsorbing humic acid： controlling trihalomethane formation

Effectiveness of hydrous manganese dioxide （δMnO2） adsorbing humic acid under different conditions and its subsequent effects on trihalomethane （THMs） formation have been studied. Humicacid removal increases with higher pH and residual TOC decreases from 3.63 mg/L to 1.68 mg/L with pH increasing from 5.5 to 8.5 at 3.0 mg/L δMnO2; δMnO2 exhibits good potential of removing humic acid and the adsorbing potential as high as 1 mg TOC/mg δMnO2 is achieved; the fractional reduction of humic acid with higher molecular weight is about 30% higher than that with lower molecular weight. δMnO2 adsorption obviously reduces subsequent THMs formation; more significant THMs formation reduction is observed for humic acid with higher molecular weight. δMnO2 adsorption is an important factor that contributes to humic acid removal and THMs formation reduction in permanganate pre-oxidation process.

Silicoaluminophosphate molecular sieve DNL-6: Synthesis with a novel template, N,N'-dimethylethylenediamine, and its catalytic application

DNL-6, a silicoaluminophosphate（SAPO） molecular sieve with RHO topology, was hydrothermally synthesized using a new structure-directing agent（SDA）, N,N＇-dimethylethylenediamine. The obtained samples were characterized by X-ray diffraction, X-ray fluorescence, X-ray photoelectron spectroscopy, scanning electron microscopy, and N2 adsorption, which indicated that the synthesized DNL-6 s have high crystallinity and relatively high Si content ranging from 20% to 35%. Solid-state magic-angle-spinning（MAS） nuclear magnetic resonance（13 C, 29 Si, 27 Al, 31 P, and 27 Al multiple-quantum（MQ）） was conducted to investigate the status of the SDA and local atomic environment in the as-synthesized DNL-6. Thermal analysis revealed the presence of a large amount of amines in the DNL-6 crystals（about 4.4 SDAs per α-cage）, which was the reason for the formation of DNL-6 with an ultrahigh Si content（36.4% Si per mole）. Interestingly, DNL-6 exhibited excellent catalytic performance for methanol amination. More than 88% methanol conversion and 85% methylamine plus dimethylamine selectivity could be achieved due to the combined contribution of strong acid sites, suitable acid distribution, and narrow pore dimensions of DNL-6.

Catalytic roles of the acid sites in different pore channels of H‐ZSM‐5 zeolite for methanol‐to‐olefins conversion

H‐ZSM‐5 zeolite is a typical catalyst for methanol‐to‐olefins(MTO)conversion.Although the performance of zeolite catalysts for MTO conversion is related to the actual location of acid sites in the zeolite framework,the catalytic roles of the acid sites in different pore channels of the H‐ZSM‐5 zeolite are not well understood.In this study,the MTO reaction network,involving the aromatic cycle,alkene cycle,and aromatization process,and also the diffusion behavior of methanol feedstock and olefin and aromatic products at different acid sites in the straight channel,sinusoidal channel,and intersection cavity of H‐ZSM‐5 zeolite was comparatively investigated using density functional theory calculations and molecular dynamic simulations.The results indicated that the aromatic cycle and aromatization process occurred preferentially at the acid sites in the intersection cavities with a much lower energy barrier than that at the acid sites in the straight and sinusoidal channels.In contrast,the formation of polymethylbenzenes was significantly suppressed at the acid sites in the sinusoidal and straight channels,whereas the alkene cycle can occur at all three types of acid sites with similar energy barriers and probabilities.Consequently,the catalytic performance of H‐ZSM‐5 zeolite for MTO conversion,including activity and product selectivity,can be regulated properly through the purposive alteration of the acid site distribution,viz.,the location of Al in the zeolite framework.This study helps to elucidate the relation between the catalytic performance of different acid sites in the H‐ZSM‐5 zeolite framework for MTO conversion,which should greatly benefit the design of efficient catalyst for methanol conversion.

Unveiling the decomposition mechanism of formic acid on Pd/WC(0001) surface by using density function theory

In pursuit of low-cost direct formic acid fuel cells,tungsten carbide(WC)supported Pd catalyst is considered as an ideal candidate for efficient decomposition of formic acid due to low Pd utilization and excellent performance.Herein,different adsorption configurations and active sites of the intermediates,involved in the HCOOH decomposition,on WC(0001)-supported Pd monolayer(Pd/WC(0001))surface investigated by using density functional theory.The results reveal that trans-HCOOH,HCOO,cis-COOH,trans-COOH,HCO,CO,H2 O,OH and H exhibit chemisorption on Pd/WC(0001)surface,whereas cis-HCOOH and CO2 exhibit weak interactions with Pd/WC(0001)surface.In addition,the minimum energy pathways of HCOOH decomposition are analyzed to generate CO and CO2 due to the fracture of C–H,H–O and C–O bonds.The adsorbed HCOOH,HCOO,mH COO,cis-COOH and trans-COOH configurations exhibit dissociation rather than desorption.CO formation occurs through the decomposition of cis-COOH,trans-COOH and HCO,whereas the CO2 formation happens due to the decomposition of HCOO.It is found that the most favorable pathway for HCOOH decomposition on Pd/WC(0001)surface is HCOOH→HCOO→CO2,where the formation of CO2 from HCOO dehydrogenation determines the reaction rate.Overall,CO2 is the most dominant product of HCOOH decomposition on Pd/WC(0001)surface.The presence of WC,as monolayer Pd carrier,does not alter the catalytic behavior of Pd and significantly reduces the Pd utilization.

Crystal Structure and Molecular Structure of Binuclear Copper(Ⅱ) Complex, [Cu (C_5H_5NO) (C_6H_5COO)_2]_2

At room temperature, dibenzoyl peroxide and pyridine N-oxide reacted with metallic copper powder in a mixed solvent(dichloromethane, trichloromethane and tetrahydrofuran), resulting in a binuclear copper(Ⅱ) complex. [Cu (C_5H_5NO)-(C_6H_5COO)_2]_2. The structure of the complex was characterized by elemental analyses.IR spectra and X-ray single crystal analysis. The crystal is triclinic, space group P1,with cell parameters . a= 9. 262(4) ,b= 10. 697(2) , c=10. 881 (3 )A , a=59. 60( 2 ),β= 74. 83 ( 3 ) .Y = 72. 80 ( 2 )°. V= 880. 0 A￣3 . D_c = 1 . 5 20 g/cm￣3 . Z = 1 . μ= 1 2. 7 cm-1, R=0. 044 ,R_w=0. 048 for 3477 reflections with I>3σ(I), M_r=805. 78. Each copper(Ⅱ) atom is coordinated by four bridging bidentate benzoate ligands and one pyridine M-oxide.

In-situ IR Monitoring the Synthesis of Amphiphilic Copolymery P(HEMA-co-tBMA) via ARGET ATRP

The amphiphilic copolymer poly（hydroxyethyl methacrylate-co-tert-butyl methacrylate） [P（HEMA-co-tBMA）] was synthesized by activators regenerated by electron transfer atom transfer radical polymerization （ARGET ATRP）, with the synthesis process monitored by in-situ infrared spectroscopy （IR）. The molecular weight, chem- ical structure and characteristics of the copolymer were determined by 1H NMR, gas chromatography and gel permeation chromatography. The influences of various parameters on the living polymerization were explored. The molecular weight of the copolymer with narrow molecular weight distribution （Mw/Mn 〈 1.50） increases ap- proximately linearly with the monomer conversion, indicating a good control of polymerization. In the reaction temperature range from 50 ℃ to 90 ℃, the monomer conversion is higher at 60 ℃. The tBMA conversion rate decreases gradually with the increase of tBMA content, while the HEMA conversion is hardly affected by HEMA content. Weak polar solvent is more favorable to the polymerization compared to polar solvent. The molar ratio of reducing agent to catalyst has significant effect on the polymerization and increasing the amount of reducing agent will accelerate the reaction rate but causes wider molecular weight distribution. It is indicated that in-situ IR monitoring contributes to a more in-depth understanding of the mechanism of methacrylate monomer copolymerization.

Molecular modeling study of the effect of base methylation on internal interactions and motions in DNA and implication to B-Z conformation change

Methylation in the bases of DNA is known to induce B-Z conformation change. In this work, molecular mechanics and normal mode analysis are used to probe how certain methylation affects the internal interactions and thermodynamic motions in the DNA double helixes in both B and Z conformations, and its implication to B-Z conformation change. By molecular modeling with Insight II, two cases involving cytosine C5 and guanine C8 methylation on both B and Z-form DNA duplex d(CGCGCG)2 are studied in comparison with the corresponding unmethylated duplexes. The internal interaction energies computed based on a molecular mechanics force field and the entropies due to internal motions computed according to a normal mode analysis are in fare agreement with respective observed thermodynamic quantities. The analysis on the computed individual energy terms suggests that the observed B-Z conformation change induced by methylation is primarily driven by enthalpic factors. A combination of changes in Van der Waals interaction, electrostatic interaction and hydrogen bonding likely contributes to the change of enthalpy that favors Z-conformation in the methylated states.

DFT Calculation of Glycine with Methanols Clusters

Density functional theory （DFT） calculations are reported for the structures of neutral and zwitterionic glycine-（CHaOH）n where n=1-6. Initial geometries of the clusters of neutral and zwitterionic glycine with 1-6 methanol molecules are fully optimized at B3LYP/6-31＋G^＊ level of theory. The lowest energy configurations are located and their hydrogen bond structures are analyzed. Theoretical prediction reveals that the methanols prefer to locate near the carboxylic acid group for the small clusters （n_〈3） with the neutral form while the configurations with the methanols bridging the acid and the amino group are favorite in the zwitterionic form clusters. When the number of the methanol molecules in the clusters reaches five and six, the two forms tend to be isoenergetic.