ZrO2／SO4^2—超强酸体系形成过程的研究

本文用XRD、TG-DTG-DTA、SEM和化学分析等多种实验手段研究了浸渍H_2SO_4的无定形ZrO_2在不同焙烧温度下的晶化和相变,失水和失硫等过程.实验结果表明,这些过程与超强酸的形成密切相关,在ZrO_2/SO_4~(2-)超强酸体系中不存在水和游离H_(2)SO_(4),体系超强酸强度最高时ZrO_2呈四方晶相,晶体表面约有略少于1/3的Zr原子与SO_4~(2-)根相结合.     

用晶型超细粒子ZrO2制备SO4^2^—／ZrO2超强酸催化剂的研究

用超临界流体干燥法制备了超细粒子晶型ZrO_2,并用稀H_2SO_4溶液对其进行处理,制得了对甲醇转化反应具有高活性的SO_4~(2-)/ZrO_2超强酸催化剂.首次发现,晶型金属氧化物ZrO_2,当它是超细粒子(粒径<0.1μm)时,同样可以用H_2SO_4溶液浸渍的方法制得SO_4~(2-)/ZrO_2固体超强酸.这一事实同时还说明,超细粒子与非超细粒子不仅在某些物理性质上有较大区别,而且在化学性质上也有差别.     

α'-(BEDT-TTF)_2C_6H_4(SO_3)_2的合成、结构与导电性

用恒电流电化学结晶法合成了一种新的基于BEDT-TIF的电荷转移盐α'-(BEDT- TIF)_2C_6H_4(SO_3)_2 [BEDT-TIF = 双亚乙基二硫四硫富瓦烯,C_6H_4(SO_3) _2~(2-) = 对苯二磺酸根]。通过四圆X射线衍射方法测定了α'-(BEDT-TTF) _2C_6H_4-(SO_3)_2的结构。晶体属于单斜晶系,P2/n空间群;晶胞参数：a = 0. 77937(17)nm, b = 0.66989(11) nm, c = 3.4422 (7) nm, β = 91.135(12) °, V = 1.7968(6) nm~3。该晶体中BEDT-TTF~+自由基沿a轴方向形成具有二聚体结构 的交错排列型柱状堆积,沿b轴方向由户并户强分子间相互作用形成一维分子链。 电荷补偿阴离子C_6H_4(SO_3)_2~(2-)则在a方向存在较强的作用。沿c轴方向, BEDT-TTF~+自由基层和阴离子层交替排列形成夹心式结构。α'-(BEDT-TTF) _2C_6H_4-(SO_3)_2在ab面的某方向的室温电导率为0.5913 Ω~(-1)·m~(-1),电 阻率-温度测定曲线表明它具有半导体导电行为。在150K附近,晶体发生了某种相 变。     

气体发生—MIPAES测定溶液中S^2—和SO3^2—的研究

用气体发生-MIPAES法测定了溶液中的S~(2-)和SO_(3)~(2-).样品中S~(2-)和SO_(3)~(2-)同稀H_2SO_4作用,产生H_2S和SO_2,用Ar气将产生的气体带入MIP.在216.9nm处测定硫的发射强度,考察了各实验参数对测定S~(2-)和SO_(3)~(2-)的影响.S~(2-)和SO_3~(2-)的检出限分别为0.08μg和0.25μg.RSD小于5％.     

钕铁硼废料(NH_4)_2SO_4焙烧法回收稀土

将钕铁硼废料与(NH_4)_2SO_4混合后焙烧,选择性回收钕铁硼废料中的稀土成分。采用单因素控制变量的方法对焙烧过程中的焙烧温度、焙烧时间、钕铁硼与(NH_4)_2SO_4混料质量比进行研究,结合稀土、铁等浸出率的影响,结果表明:焙烧温度400℃,焙烧时间120 min,钕铁硼与(NH_4)_2SO_4混料质量比1∶2,该条件下稀土可以获得较高的浸出率,约为92%,而Fe的浸出率仅为3%。通过对原料和焙烧后的产物进行热力学、扫描电镜、 X射线衍射和热重差热分析,综合分析得知钕铁硼废料中的主要成分REFeO_3, Fe_2O_3, RE_2O_3和Al_2O_3等发生硫酸化反应,生成RE_2(SO_4)_3和(NH_4)_3Fe(SO_4)_3及(NH_4)Al(SO_4)_2等。升高温度不利于REFeO_3的反应,从而抑制大部分Fe的硫酸化。经过焙烧,稀土以可溶性硫酸盐的形式存在,铁铝等杂质保持一个低的浸出率大部分留在渣中。     

Li_2SO_4-MgSO_4、Li_2SO_4-Li_4SiO_4体系的研究

本文用X射线衍射(高温、室温)相热分析(DTA、DSC、TGA)等方法测定了Li_2SO_4-MgSO_4和Li_2SO_4-Li_4SiO_4体系相图,并研究了化合物的性能和晶体结构. Mg_4Li_2(SO_4)_5在840℃由包晶反应形成,它在105℃分解为Li_2SO_4为基的固溶体和MgSO_4.在105℃反应时,形成每摩尔的Mg_4Li_2(SO_4)_5吸热2.57kJ,反应激活能为173.5kJ/mol.Mg_4Li_2(SO_4)_5属正交晶系,在180℃的点阵常数α=8.577A,b=8.741A,c=11.918A,可能的空间群为.P222或Pmmm,Z=2. Li_(8-2x)(SiO_4)_(2-x)(SO_4)_x是在953℃由包晶反应形成的新相.随着温度的降低,相区扩大.在室温x=0.96—0.58.该相属正交晶系,空间群为.Pmmm,Z=2.晶体的点阵常数在x=0.8时有一最大值,α=5.002A,b=6.173A,c=10.608A.Li_(8-2x)(SiO_4)_(2-x)(SO_4)_x在空气中能吸收7.6wt％的水蒸气和其他气体.脱水温度高于350℃,水份的吸脱不改变晶体结构,与沸石分子筛具有相似性质,脱水激活能为171.5kJ/mol. 熔化后的Li_2SO_4-MgSO_4和Li_2SO_4-Li_4SiO_4试样以10℃/min速率降温,分别形成亚稳态共晶体系.     

离子色谱法同时测定脱硫海水中的SO_4~(2-)和SO_3~(2-)

采用离子交换色谱法同时定量分析脱硫海水中SO_4~(2-)和SO_3~(2-)。0.01 mol/L EDTA和0.10×10~(-3) mol/L NaOH混合溶液用于除去海水样品中Ca~(2+)、Mg~(2+)干扰,加入0.5%的甲醛溶液防止SO_3~(2-)氧化为SO_4~(2-)。实验采用DINOEX AS-9HC阴离子交换柱作分离柱,以9.00×10~(-3) mol/L Na_2CO_3溶液为淋洗液,电导检测器检测。方法线性范围为5.00~100.00 mg/L,加标回收率为97.85%~103.99%,相对标准偏差(RSD)为0.20%~2.07%。SO_3~(2-)的检出限为0.03mg/L,SO_4~(2-)的检出限为0.04mg/L。结果表明,本方法可以有效消除海水中Ca~(2+)、Mg~(2+)对低浓度SO_3~(2-)、SO_4~(2-)测定的干扰,可同时实现海水脱硫体系中SO_3~(2-)、SO_4~(2-)的定量分析。     

多核NMR在相图研究中的应用——Na_2SO_4-Al_2(SO_4)_3-H_2O体系的~(23)Na、~(27)Al NMR研究

前文报道了多核NMR方法研究NaCl-NH_4Cl-H_2O体系相图,表明具有不受其它离子干扰和快速、简便等优点。本文用~(23)Na、~(27)Al NMR方法研究了Na_2SO_4-Al_2(SO_4)_3-H_2O体系,指出20℃时平衡固相中有Na_2SO_4·10H_2O,Al_2(SO_4)_3·18H_O及NaAl(SO_4)_2·12H_2O等水合物和复盐存在,与其它方法所得结果吻合。实验部分分析纯Na_2SO_4于120℃干燥8小时,保存在干燥箱中备用。对分析纯Al_2(SO_4)_3·18H_2O用EDTA-Zn经典返滴方法分析,证实其组成为Al_2(SO_4)_3·18H_2O,符合NMR定量分析     

(NH_4)_2SO_4-Na_2SO_4-NH_4Cl-NaCl-H_2O体系在35℃的溶解度相图

为了降低生产成本,有的化工厂直接利用含硫酸盐的卤水为原料生产化工产品。但在生产的循环过程中,将使SO_4~(2-)离子富集。本文就是研究富集SO_4~(2-)离子后的母液跟铵盐的溶解度关系。A、Seidell曾测定过NaCl—Na_2SO_4—H_2O体系的溶解度相图,报道过NH_4Cl—NaCl—H_2O体系的溶解度相图,H.Dawson等也发表过Na_2SO_4-(NH_4)_2SO_4     

五元体系Li~+,K~+//CO_3~(2-),SO_4~(2-),B_4O_7~(2-) -H_2O在288 K时的介稳相平衡研究

采用等温蒸发法研究了五元体系Li~+,K~+//CO_3~(2-),SO_4~(2-),B_4O_7~(2-) -H_2O在288 K时的介稳相平衡关系,测定了该五元体系在288 K条件下的介稳平衡的溶解度和溶液密度,根据实验数据绘制了相应的介稳平衡相图和水图,相平衡研究结果表明该五元体系介稳相平衡中有复盐K_2SO_4·Li_2SO_4生成,其介稳相图(Li_2CO_3饱和)有4个共饱和点,9条单变量曲线,6个Li_2CO_3饱和的结晶区分别为LiBO_2·8H_2O,K_28_4O_7·4H_2O,K_2CO_3·3/2H_2O,K_2SO_4,Li_2SO_4·H_2O和复盐K_2SO_4·Li_2SO_4.     

Oxidation of NO over cobalt oxide supported on esoporous silica

Cobalt oxide catalysts supported on mesoporous silica (Co3O4/MPS) were prepared, characterized and applied for catalytic oxidation of NO. Effects of catalyst supports, calcination temperatures, H2O and SO2 on NO conversion were investigated. The samples were also characterized by BET, XRD, FTIR and TG/DTG. The results suggested that Co3O4/MPS catalyst calcined at 573 K had the smallest crystal particles and the best surface dispersion. This catalyst had the highest activity and yielded 82% NO conversion at 573 K, at a space velocity of 12000 h−1. Although the conversion of NO decreased with the introduction of H2O, it could be restored completely after removing residual H2O from Co3O4/MPS catalyst by heating at 573 K. In the presence of SO2, the oxidation activity decreased and CoSO4 was detected on the catalyst. The NO conversion decreased to 30.2% in the presence of SO2 and H2O. It could not be restored completely after cutting off H2O and SO2. The deactivation of the catalyst in the presence of SO2 and H2O was attributed to the formation of cobalt sulfate species.     

稀土Pr6O11上CO和表面羟基反应的原位FT-IR研究

利用FT-IR原位考察了稀土氧化镨上CO和表面羟基的反应。在473K以下,未检测到CO和氧化镨表面反应的吸附物种;在CO气氛中,升温到473K,观察到甲酸根吸附物种的红外特征峰1578,1371和1367cm~(-1)。用同位素D_2部分还原的氧化镨吸附CO以及甲酸吸附证实了CO与氧化镨表面的羟基反应可生成表面甲酸根吸附物种。讨论了CO在氧化镨表面的反应机理及甲酸根的氧化过程。     

K对Mn—Co—O的结构及氧化活性的影响

利用XRD,TPD,TFD-MS及催化氧化反应等实验技术,研究了K对Mn-Co-O的结构及氧化活性的影响。XRD结果表明,Mn-Co-O系已形成反尖晶石型的MnCo_2O_4结构;K-Mn-Co-O系中除MnCo_2O_4型结构外,还有新相KMnO_2存在。根据O_2的TPD-MS及吡啶的TPD结果,Mn-Co-O中添加适量的K能提高供氧活性和增加供氧数目,但酸中心数目减少,强度降低。K对Mn-Co—O催化剂氧化活性的影响随反应物分子结构的不同而异,对乙酸乙脂、苯甲酰氯等极性有机物的完全氧化反应,K能提高氧化活性,但对苯、正己烷等非极性有机物的完全氧化反应,K使其活性降低。     

ZrO2催化剂上吸附甲酸的TPD和IR研究

众多的研究表明甲酸在氧化物催化剂上的吸附分解与催化剂的表面酸碱性质有关。研究吸附相甲酸物种的变化表明甲酸分解反应的选择性除受温度影响外,还与甲酸的表面覆盖度有关。Z_rO_2表现为较典型的弱酸弱碱双功能性催化剂。最近我们的研究表明Z_rO_2表面存在表面键诱导酸-碱相互作用,它的酸-碱双功能催化作用在烷基胺分解转化为腈的反应中得到了较好地体现。本文报导Z_rO_2催化剂上吸附甲酸的程序升温脱附(TPD)和红外光谱(IR)研究结果。     

Influence of lattice interactions on the Jahn-Teller distortion of the [Cu(H2O)6]2+ ion: dependence of the crystal structure of K2[Cu(H2O)6](SO4)(2x)(SeO4)(2-2x) upon the sulfate/selenate ratio

The temperature dependence of the structure of the mixed-anion Tutton salt K2[Cu(H2O)6](SO4)(2x)(SeO4)(2-2x) has been determined for crystals with 0, 17, 25, 68, 78, and 100% sulfate over the temperature range of 85-320 K. In every case, the [Cu(H2O)6]2+ ion adopts a tetragonally elongated coordination geometry with an orthorhombic distortion. However, for the compounds with 0, 17, and 25% sulfate, the long and intermediate bonds occur on a different pair of water molecules from those with 68, 78, and 100% sulfate. A thermal equilibrium between the two forms is observed for each crystal, with this developing more readily as the proportions of the two counterions become more similar. Attempts to prepare a crystal with approximately equal amounts of sulfate and selenate were unsuccessful. The temperature dependence of the bond lengths has been analyzed using a model in which the Jahn-Teller potential surface of the [Cu(H2O)6]2+ ion is perturbed by a lattice-strain interaction. The magnitude and sign of the orthorhombic component of this strain interaction depends on the proportion of sulfate to selenate. Significant deviations from Boltzmann statistics are observed for those crystals exhibiting a large temperature dependence of the average bond lengths, and this may be explained by cooperative interactions between neighboring complexes.     

Ni-P非晶态合金超细微粒的晶化行为

非晶态合金超细微粒因兼具非晶材料和超细微粒材料的特点而表现出优良的催化性能,近年来有关这类催化剂的制备与研究日益引起人们的重视.前文我们已报导Ni-P 非晶态合金超细微粒催化剂的化学制备方法,并初步探讨了制备条件对微粒粒度均匀性的影响.与单元金属超细微粒不同,二元合金超细微粒的表面性质不仅与粒度有关,而且与合金组元的结构状态有关.尤其是非晶态合金一定条件下会发生结构驰豫和晶化,从而可能导致微粒表面性质的变化.为此,本文对Ni-P 非晶态合金超细微粒的晶化行为进行了研究,首次获得Ni-P 超细微粒结构和表面形态的变化规律,为深入研究其结构和催化性能之间的关系提供基本信息.     

Ni-Fe催化剂乙醇部分氧化制氢的研究

研究了Ni Fe催化剂对乙醇部分氧化制氢反应,系统地考察了不同O2/C2H5OH摩尔比及反应温度下催化剂的性能.发现Ni Fe催化剂对乙醇部分氧化制氢具有较好的催化活性,其中组成为Ni50Fe50催化剂最好,最佳的反应条件是O2/C2H5OH=1.0,T=573 K.XRD谱图表明催化剂主要由尖晶石结构的铁酸盐和FeNi3合金相组成. XPS结果说明,催化剂体相以还原态FeNi3合金相为主,表面以氧化态的铁酸盐为主.稳定性考察的结果表明,催化剂经40 h反应后,对氢的选择性明显下降,此时对应的FeNi3物相衍射峰强度也明显降低,表明催化剂对H2选择性的下降与FeNi3物相的转变有关.     

ELECTROCHEMICAL POLYMERIZATION OF ANILINE IN PHOSPHORIC ACID AND THE PROPERTIES OF POLYANILINE

The behavior of the electrochemical polymerization of aniline in a weak acid, phosphoric acid, is very similar to that in strong acids, i.e. its polymerization rate increases quickly with the electrolysis time. The FTIR spectra of polyaniline samples synthesized in phosphoric acid indicate that the counter ion H2PO4^- is present in both the oxidized form and the reduced form of polyaniline. The counter ion plays an important role in adjusting the pH value at the electrode surface of polyaniline during the oxidation and reduction processes. As a result, a pair of redox peaks still appear in cyclic voltammograms of polyaniline in a solution of sodium sulfate of pH 5.5 and in a solution of NaH2PO4 of pH 7.0,respectively, at low potential scan rate; and the color of polyaniline film also changes with applied potential at pH 7.0. Thus,the pH region for the electrochemical activity and the electrochromism of polyaniline is extended to pH 5.5 for a solution of sodium sulfate and to pH 7.0 for a solution of NaH2PO4. The conductivity of polyaniline is 3.3 S cm^-1, depending on the concentration of phosphoric acid used in the stage of polymerization of aniline. The result of elemental analysis of polyaniline is presented here.     

Theoretical study of the first acid dissociation of H2SO4 at a model aqueous surface

Electronic structure calculations on the H2SO4.(H2O)(4,6) model system embedded at the surface of an aqueous layer have been performed to examine the feasibility of the first acid dissociation of H2SO4 to an H2SO4-.H3O+ contact ion pair over a wide temperature range, with a special focus on the 190-250 K range relevant for atmospheric sulfate aerosols. The results indicate that the acid dissociation can be either thermodynamically favored or disfavored depending on the degree of solvation of the acid and the produced ions, as well as on the temperature.     

On the characterization of surface VOx-species by XPS: layered oxidic systems as model catalysts

Summary The influence of the support on vanadia, immobilized on Au, SiO₂, Al₂O₃ and TiO₂, suitable for the selective catalytic reduction (SCR) of nitric oxide by ammonia has been investigated. The layered oxidic substrates, which are deposited onto gold coated silicon wafers, represent model systems for the surfaces of technical SCR catalysts, that are suitable for surface science investigations. The oxidation states of the surface vanadia species immobilized on these samples have been studied by XPS after well-defined sample treatment in both oxygen and hydrogen atmospheres at 573 K and 723 K. From the observed shifts of the V 2p_3/2 binding energies, and from peak deconvolution, vanadia layers on gold, silica and alumina are found to exhibit characteristics similar to those of bulk vanadia. This behavior is characterized by the relative stability against a reductive atmosphere at 573 K. Changes in the oxidation states of the surface vanadia species are prominent only after treatment at 723 K. Titania exhibits a unique support interaction with vanadia which allows the reduction of vanadia at temperatures as low as 573 K. This fact may contribute to the outstanding performance of VO_x/TiO₂ in the selective reduction of nitric oxide by ammonia in waste gases.