磷钨磷钼钨Dawson型杂多化合物的合成

Dawson型磷钨杂多化合物(HPC)作为多相或均相催化剂,对烯烃环氧化反应极为有效[1]。在HPC中引入钼原子可以提高它的氧化能力;引入过渡元素如铜可以改善其氧化还原反应的可逆性[2]。目前已合成出Nb、Ti、Mn、Fe、Co等多种过渡元素取代的Dawson型HPC[3],并且证明其具有良好的氧化还原催化性能。本文以Na2WO4·2H2O和Na2HPO4·12H2O为原料合成了K10Na2H2P2W16O60,再以其为反应物合成了过渡元素镍、铜取代的磷钨、磷钼钨共三种Dawson型杂多化合物:K14[Ni2P2W16O62]·24H2O、K15H5[Ni(P2W16MoO61)2]·26H2O和K15H3[Cu(…     

分子筛负载钒配合物催化剂对烃类氧化的择形选择性研究

研究了四价钒配合物VO(pic)2·H2O及其分子筛负载型催化剂VO(pic)2-NaY对芳香烃和正构烷烃的催化氧化性能.实验结果证明,VO(pic)2-NaY催化剂具有与VO(pic)2·H2O配合物催化剂相似的催化氧化活性,而且使对位产物(芳香烃为底物)和伯醇(底物为正构烷烃)的选择性得到提高,显示出均相配合物催化剂所不具有的择形选择性.     

Au/Fe2O3催化剂的制备及其对富氢气体中一氧化碳选择性氧化的催化性能

 采用共沉淀法制备了1.5%Au/Fe2O3催化剂,考察了加料方式对Au/Fe2O3催化剂化学组成及其催化富氢气体中CO选择性氧化性能的影响. 结果表明,正加法制备的Au/Fe2O3催化剂的性能明显好于反加法制备的催化剂,80 ℃时前者对富氢气体中CO选择性氧化反应的转化率为94%,CO2选择性为65%,连续反应10 h,催化剂活性没有变化. XRD,XPS和TEM等的测试结果表明,正加法制备的Au/Fe2O3催化剂中金粒子的平均粒径为2～4 nm,金粒子高度分散在载体上,并与载体之间发生了较强的相互作用,从而表现出较高的催化性能.     

快速测定COD最佳催化消解体系研究

通过正交试验 ,确定了测定环境水样中COD的最佳回流消解条件。以CuSO4作催化剂 ,KAl(SO4) 2 Na2 MoO4作助催化剂 ( 0 1 8gCuSO4·5H2 O 0 1 0gKAl(SO4) 2 ·1 2H2 O 0 1 0gNa2 MoO4·2H2 O) ,在H2 SO4 H3PO4体系中可很好地实现对样品的消解。该体系将回流时间由国标法的 2h缩短至 2 0min ,实现了快速测定的目的且大幅度降低测定成本。样品 1 0次平行测定的相对标准偏差为 1 1 % ;加标回收率为 97 7%～ 1 0 3 3% ,均与国标法无显著性差异     

纳米-微米铁修饰的维氏体氨合成催化剂

我们以商业预还原的维氏体(Fe1-xO)氨合成催化剂为载体,采用Fe(NO)3 ·9H2O和H2C2O4·2H2O进行原位室温固相反应制备纳米铁或微米铁修饰的铁基氨合成催化剂,并通过XRD、SEM、TG-DTG、H2-TPR等进行了表征.结果表明:Fe(NO)3·9H2O和H2C2O4·2H2O室温固相反应完全生成产物Fe2(C2O4)3·5H2O,且产物分散于载体维氏体催化剂表面.通过纳米铁-微米铁的修饰,催化剂的氨合成活性有很大提高且稳定性好.催化剂活性随着Fe负载量的增加先增加后降低,负载量5％时催化活性最好,反应器出口氨浓由450℃(12.4％)、425℃(11.0％)、400℃(9.4％)分别提升至450℃(15.6％)、425℃(14.8％)、400℃(13％).通过一步简单的修饰,维氏体催化剂的氨合成活性提高约25％ ～38％.由于焙烧和还原,生成的Fe1xO或铁粒子与铁催化剂表面发生强相互作用,因此,反应过程中纳米铁或微米铁粒子能稳定存在,催化剂有较高的稳定性.     

正丁烷在金属钼酸盐催化剂上的氧化脱氢

 用柠檬酸盐法合成了第一系列过渡金属(Cr,Mn,Fe,Co,Ni,Cu和Zn)及Mg的钼酸盐催化剂,研究 了它们对正丁烷氧化脱氢反应的催化作用. 结果表明,这些钼酸盐催化剂的催化性能受阳离子的影响较大. CoMoO4催化剂具有最高的催化活性和较高的选择性,其催化性能与文献报道的对正丁烷氧化脱氢反应催化性能最好的ZrP2O7和Mg3V2O8催化剂大致相当; MgMoO4催化剂虽然选择性较高,但活性较低; Cr2(MoO4)3上基本没有C4烯烃生成; 其它钼酸盐催化剂对正丁烷氧化脱氢反应的催化活性和对烯烃的选择性都较低. XRD,NH3-TPD和H2-TPR的研究结果表明,催化剂为单一的钼酸盐晶相,催化剂的性能由其氧化还原性决定而与其表面酸量没有直接关系. 通过对产物分布的分析,提出了正丁烷在CoMoO4催化剂上的氧化脱氢反应途径. 在558 ℃,正丁烷发生氧化脱氢生成正丁烯和丁二烯以及氧化燃烧生成CO2三个平行竞争反应的竞争分率分别约为75%,10%和15%. 在正丁烷转化率较高的条件下,产物中的CO2主要来自C4烯烃的再氧化反应,而CO则完全来自C4烯烃的再氧化.     

助剂Fe和反应修饰剂修饰的Ru催化剂上苯选择加氢制环己烯

共沉淀法制备了Ru-Fe(x)催化剂,并利用X射线衍射(XRD)、X射线荧光光谱(XRF)、N2物理吸附和透射电镜等手段对催化剂进行了表征.结果表明,Ru-Fe(x)催化剂中助剂Fe以Fe3O4形式存在.单独Fe3O4并不能提高Ru催化剂的环己烯选择性.但在加氢过程中Fe3O4可与反应修饰剂ZnSO4反应生成(Zn(OH)2)3(ZnSO4)(H2O)x(x=1 or 3).化学吸附的(Zn(OH)2)3(ZnSO4)(H2O)x(x=1 or 3)在提高Ru催化剂环己烯选择性中起着关键作用.此外,Ru-Fe(x)催化剂的性能还与浆液中的Zn2+浓度和pH值有关.在0.61 mol/L ZnSO4溶液中Ru-Fe(0.47)催化剂不但给出了56.7%的环己烯收率,而且具有良好的稳定性和重复使用性能.化学吸附在Ru表面的Fe2+同样能提高Ru催化剂的环己烯选择性.在0.29 mol/L和0.61 mol/L FeSO4溶液中Ru-Fe(0.47)催化剂上化学吸附Fe2+量近似,性能近似.因为Fe2+和Zn2+性质的差异,在0.29 mol/L和0.61 mol/L FeSO4溶液中Ru-Fe(0.47)催化剂的环己烯选择性分别低于在同浓度的ZnSO4溶液中的.     

MCM-41分子筛固载BF3·X固体酸催化剂的合成及其催化性能的研究

以BF3·X(X=Et2O, H2O, H3PO4, HOAc, HOEt)对MCM-41分子筛进行表面改性, 具体合成了BF3·X/MCM-41固体酸催化剂, 同时采用XRD和原位FT-IR技术对BF3·X/MCM-41催化剂进行表征, 并探讨了催化剂的制备条件对环氧氯丙烷与异丁醇的缩合反应性能的影响.     

过渡金属二取代三元杂多酸盐的制备和表征

在水中由Na2 WO4 ·2H2 O ,Na2 MoO4 ·2H2 O和KH2 PO4 ·2H2 O反应生成具有半Dawson结构的钨钼混配杂多阴离子Na9PW6Mo3O34 ·1 0H2 O。以阴离子和过渡金属硝酸盐为原料在水溶液中合成了一系列过渡金属二取代的具有Keggin结构的杂多酸四丁基铵盐 [TBA]4 Hn[PW7Mo3M2 O38(H2 O) 2 ]·C3H6O(n =1 ,M =Fe3+;n =3,M =Mn2 +,Co2 +,Ni2 +,Cu2 +) ,用元素分析和波谱进行了表征。     

Cr2O3催化剂上甲烷部分氧化制备合成气

分别采用柠檬酸络合法和直接分解法制备了Cr2O3催化剂, 采用XRD, BET, TPR, XPS, TEM和TGA表征了催化剂的物理化学性质, 在常压固定床石英管(内径5 mm)反应器中考察了Cr2O3催化剂对甲烷部分氧化反应的催化性能. 在500~750 ℃, V(CH4)∶V(O2)=2, 空速12×104 h-1的条件下, O2几乎完全转化, CH4转化率及H2和CO选择性随着温度的升高而增加. 700 ℃下CH4转化率及H2, CO选择性随着空速(6.0×104~24×104 h-1)的升高而增加. 在500 h稳定性实验中, 随着反应时间的延长, CH4转化率及H2, CO选择性缓慢下降, XRD, TEM和BET结果表明, 催化剂的活性下降与烧结和团聚有关, TGA分析表明催化剂具有良好的抗积炭性. 通过CH4脉冲反应, 推测在反应过程中CO, H2, CO2和H2O是直接生成的.     

间接电解氧化法合成正丁醛

提出了一种合成正丁醛的新方法———间接电解氧化法 .在陶瓷隔膜电解槽中 ,用Pb/PbO2 作阳极 ,石墨作阴极 ,将Mn2 + 氧化成Mn3 + ,然后用Mn3 + 作氧化剂对正丁醇进行氧化获得正丁醛 ,还原所得的Mn2 + 可循环利用 .电解的优选条件为 :C硫酸 =4 .0mol/L ,电流密度 80 0A/m2 ,CMn(II) =0 .5mol/L ,温度t=2 0℃ .     

Fe(III)EDTA作为氧化羰化苯酚合成碳酸二苯酯一种有效的氧化还原催化助剂

研究了氧化羰化苯酚合成碳酸二苯酯反应。发现了Fe(III)EDTA 在PdCl2/Fe(III)EDTA/1,4 苯醌/ 四丁基溴化铵催化体系中具有很好的助催化效果。讨论了上述催化体系中的每一组分的作用，并提出了一个催化反应机理。氧化羰化苯酚合成碳酸二苯酯反应的最佳温度为100℃～120℃。当反应在100℃、PCO=2.0MPa、PO2=0.5MPa、苯酚 0.5mol、 PdCl2 0.28mmol、n(PdCl2)∶n(Fe(III)EDTA)∶n(苯醌)∶n(四丁基溴化铵)=1∶1∶10∶40、 4A 分子筛 5.0g、 4h进行时，碳酸二苯酯的产率和选择性分别为8.35%和97.5%。压力越高对生成碳酸二苯酯越有利。     

Investigation of spherical oil agglomeration properties of celestite

In this study, concentration of celestite particles was investigated by using oil agglomeration. For this purpose, effects of operating parameters were investigated, and zeta potential measurements and Fourier transform infrared spectrophotometry (FTIR) analyses have also been carried out. In the experiments, effects of operating parameters such as pH, stirring speed, amount of Na oleate as a anionic type collector and kerosene as a bridging liquid, solid ratio, agglomeration time, collector stirring time, conditioning time, and amount of EDTA were investigated to obtain optimum conditions. Zeta potential measurements were carried out for various pH values and amounts of Na oleate. FTIR analyses were investigated to determine the adsorption type of Na oleate on celestite surface. By evaluation of the experimental results, optimum oil agglomeration conditions of celestite were determined as follows: pH 7, stirring speed 1500 rpm, amount of kerosene 100 l/t, amount of Na oleate 10 kg/t, solid ratio 5 wt%, conditioning time 5 min, collector stirring time 1 min, agglomeration time 5 min, and amount of EDTA 1.0 kg/t. In the optimum conditions, celestite was concentrated with recovery of 89.47 wt%.     

Multivariate optimization of solvent extraction with 1,1,1-trifluoroacetylacetonates for the determination of total and labile Cu and Fe in river surface water by flame atomic absorption spectrometry

A procedure for simultaneous solvent extraction of Cu(II) and Fe(III) from river surface waters as diethyldithiocarbamates (DDC) 1,1,1-trifluoroacetylacetonates into isobutyl methyl ketone (IBMK) has been developed prior to their determination by flame atomic absorption spectrometry. Experimental design approaches were used in order to obtain the best compromise conditions for simultaneous solvent extraction. Variables such as pH, sodium DDC or 1,1,1-trifluoro-2,4-pentanodione (H(TFA)) concentrations, reaction time, IBMK volume and extraction time have been optimized. First, Plackett–Burman designs involving 13 experiments and 2 replicates were used as screening designs to determine which variables were significant. DDC or H(TFA) concentration, as well as pH and IBMK volume were found statistically significant and they were finally optimized by applying a central composite design (15 experiments and 2 replicates). Optimum values for these variables were selected for compromise extraction conditions of Cu(II) and Fe(III) species. An optimum pH of 5.3 was chosen for Cu–H(TFA) and Fe–H(TFA) formation with an optimum H(TFA) concentration of 0.20% (m/v). The optimum IBMK volume for extraction was 8 ml, allowing a pre-concentration factor of 10. A microwave-assisted peroxydisulfate oxidation was used to break down the metal–organic matter complexes in river surface waters in order to assess the total Cu and Fe contents. Applying the experimental design approach, optimum conditions was an irradiation for 5.0 min at a microwave power of 500 W using 0.5 g of ammonium peroxydisulfate. The method was applied to determine total Cu and Fe contents and also labile Cu(II) and Fe(III) contents in several river surface water samples.     

Complexometric catalytic titrations using the indicator reaction periodate-triethanolamine

The possibility of applying a new indicator reaction, i.e., periodate-triethanolamine, as the indicator in titrations of ethylenediamine-N,N,N′,N′-tetracetic acid (EDTA), 1,2-diaminocyclohexanetetraacetic acid (DCTA), and diethylenetriaminepentaacetic acid (DTPA) with standard manganese(II) sulfate solution (phosphate buffer pH 6.84) has been investigated. The titration course was followed potentiometrically using a perchlorate ion-selective electrode. The optimum conditions for determinations in relation to concentration of the indicator reaction components have been established. Furthermore, the influence of some ions on the possibility of EDTA determination was considered and maximally tolerable concentrations under these conditions were established. The amounts of 0.170–18.00 mg of EDTA, 0.150–16.00 mg of DCTA, and 0.180–19.00 mg of DTPA were determined with a maximal relative standard deviation less than 1.0%. Results are in good agreement with those of comparable methods. Finally, the experimental catalytic titration curves obtained in this way are compared to the simulated ones.     

新型磁性Fe3O4/EDTA复合纳米粒子的制备及性能研究

采用氨羧络合剂EDTA对纳米磁性Fe3O4粒子进行表面改性,制备出能够螯合金属离子和放射性核素离子的磁性Fe3O4/EDTA复合纳米粒子.用X射线衍射、红外光谱、透射电子显微镜、光电子能谱、振动样品磁强计和原子吸收光谱对复合粒子进行了表观形貌、结构、磁学及螯合性能表征.结果表明,纳米磁性Fe3O4和EDTA之间能够有效地以化学键合方式进行复合.改性后,Fe3O4/EDTA纳米复合粒子可以对包括放射性金属离子在内的多种金属离子具有良好的络合效果.     

Kinetics of the reaction of aqueous iron(vi) (FeVIO42-) with ethylenediaminetetraacetic acid

The reaction of aqueous iron(vi) (FeVIO42-, Fe(vi)) with ethylenediaminetetraacetic acid (EDTA) was studied kinetically as a function of pH (1.98-12.40) and temperature (15-45 degrees C) using a stopped flow kinetic technique. The rate law for the reaction of Fe(vi) with EDTA was found to be first-order with respect to each reactant over the entire studied pH range. The observed rate constants, k, decrease with an increase in pH, varying from 4.19 x 10(4) to 8.60 x 10(-2) M(-1) s(-1) over the pH range. The speciation of Fevi (H3FeO4+, H2FeO4, HFeO4-, and FeO42-) and EDTA (H4Y, H3Y-, H2Y2-, HY3-, and Y4-, Y = EDTA) species was used to explain the pH dependence of the k values. From the temperature effect on k at pH 5.4, 7.1, and 9.2, activation parameters, DeltaS(double dagger) and DeltaH(double dagger), were obtained for the reactions of Fe(VI) with EDTA. The values of DeltaS(double dagger) for the reactions were found to be negative, implying a highly ordered transition state in the reaction. The DeltaH(double dagger) for the reaction at pH 7.1 and 9.2 showed similar values within experimental error. Using the observed enthalpy parameters and the enthalpy of deprotonation of HFeO4- and EDTA species (HEDTA3- and H2EDTA2-), the enthalpy of deprotonation of H2FeO4 (DeltaH0H2FeO4) was determined as 5.7 +/- 3.0 kJ mol(-1). The reactivity of Fe(VI) with aminopolycarboxylates (APCs) was also studied in alkaline medium. The order of reactivity was determined as primary > secondary > tertiary, which suggests that FeVIO42- attacks at the nitrogen atom sites of APCs.     

微波等离子体炬原子发射光谱法测定米粉中微量元素——一个大学化学仪器分析实验的设计与实践

设计了一个科研参与型的大学化学仪器分析实验。本实验应用MPT原子发射光谱仪对米粉中的金属元素(Ca,Cu,Fe,Mn)进行了检测分析。对影响金属元素检测性能的实验条件,如微波等离子体炬的微波功率和维持气流量进行了系统的考查及优化。最后,通过对样品进行测定,证实与标准含量相符,结果比较满意。学生在实验过程中,可以学习和掌握样品的前处理方法、原子发射光谱的机理和仪器测试条件的优化。     

Spectrophotometric determination of macroquantities of iron and titanium in real-world objects

The conditions of formation of Fe(III) and Ti(IV) ethylenediaminetetraacetate chelates were optimized. A new rapid spectrophotometric procedure for determination of iron and titanium as EDTA complexes in real-world objects was developed.     

A new method of evaluation of element pollutant mobility in sediments

The application of a strong chelating agent for the screening test of element mobility in sedimentary systems was investigated. Single-step and sequential extraction procedures were applied to four sediment samples collected from an industrially polluted region of Eastern Slovakia. A sequential extraction procedure (SEP), recommended by the Institute for Reference Materials and Measurements (IRMM), was applied and used as a reference extraction method. A single-step extraction with 0.05 mol dm⁻³ ethylenediaminetetraacetic acid (EDTA) was adapted for sediments when extraction conditions were optimised. The extraction efficiency of the single-step procedure was compared with that of SEP. The contents of elements extracted by Na2EDTA were in good agreement with the sum of the first three steps of the SEP for Fe, Mn, and Co. Na₂EDTA can therefore be considered capable to extract the majority of elements associated with the reducible sedimentary phase — bound to Fe and Mn oxides in the regional geological conditions of the monitored region. Thus, Na₂EDTA extraction of Fe and Mn can serve as an economical, time-saving supplementary test for the IRMM procedure. This paper is dedicated to the memory of Erika Krakovská Presented at the XVIIIth Slovak Spectroscopic Conference, Spišská Nová Ves, 15–18 October 2006.