Calorimetric investigations of overcritical behaviour in (TEA)2CuCl4 crystals

The results of experimental investigation of molar heat capacity of [N(C₂H₅)₄]₂CuCl₄ - ferroelasto-ferroelectric crystals in a wide temperature range are presented. The typical anomaly for the first order phase transition of order-disorder type at 258 K and additional anomaly with maximum at 195 K has been observed. We suggest that the low temperature anomalies of physical properties of [N(C₂H₅)₄]₂CuCl₄ crystals can be attributed to over critical traces of isomorphous phase transitions (similar to that observed in liquid-gas system). Results of numerical analysis of phenomenological model of phase transition in [N(C₂H₅)₄]₂CuCl₄ crystals are presented and compared with the experimentally determined temperature dependence of the specific heat and entropy changes.     

TiO2-ZrO2聚合溶胶形成过程的小角X射线散射研究

由金属醇盐（M（OR）₄）水解制备溶胶的方法已广泛应用于溶胶-凝胶法制备纳米孔无机膜。通过控制异丙醇钛[Ti（i-OC₃H₇）₄]和正丙醇锆[Zr（n-OC₃H₇）₄]的混合物在异丙醇（i-C₃H₇OH）中水解制备聚合型TiO₂-ZrO₂溶胶,利用小角X射线散射方法（SAXS）研究了初始反应混合物Ti（i-OC₃H₇）₄：Zr（n-OC₃H₇）₄：H₂O：i-C₃H₇OH=0.9：0.1：m：30（摩尔比,m=1.8,2.0,2.2）形成TiO₂-ZrO₂溶胶的过程,探讨了水与醇盐摩尔比H₂O/M（OR）₄（M=Ti+Zr）、反应温度和正丙醇锆对TiO₂-ZrO₂溶胶形成的影响。研究结果表明,H₂O/M（OR）₄=1.8时,只有少量胶粒形成;H₂O/M（OR）₄=2.0～2.2时,TiO₂-ZrO₂溶胶中胶粒具有质量分形结构,分形维数1.2 ≤ D_m < 1.4;随着H₂O/M（OR）₄增加,胶粒的形成时间缩短,胶粒大小和分形维数均增大,溶胶的稳定性显著下降。升高反应温度有利于胶粒形成。[Ti（i-OC₃H₇）₄+Zr（n-OC₃H₇）₄]混合物比Ti（i-OC₃H₇）₄水解快,H₂O/M（OR）₄相同时,TiO₂-ZrO₂溶胶比TiO₂溶胶稳定性差。     

（NH2）2CO-NH4H2PO4-H2O三元系10 ℃相平衡研究

采用等温溶解平衡法研究了三元系（NH₂）₂CO-NH₄H₂PO₄-H₂O在10 ℃时的相平衡,并采用湿渣法与X射线衍射相结合的方法鉴定了平衡固相的组成与结构。结果表明,该体系为简单共饱和型,无复盐或固溶体生成,共饱点的质量组成（以质量分数计）：尿素,40.03%;磷酸一铵,13.92%;水,46.05%。相图中有2条单变量曲线,相图被划分为4个区域：不饱和区、（NH₂）₂CO结晶区、NH₄H₂PO₄结晶区和（NH₂）₂CO-NH₄H₂PO₄混合结晶区。用Wilson方程与NRTL方程对实验数据关联计算,实验值与计算值吻合度较高,2个热力学模型计算值与实验值的RAD分别为0.37%和0.71%,RMSD分别为0.20和0.29。     

低碳烷烃烯烃在超微孔柔性Cu(Qc)2上的吸附行为

采用实验研究与分子模拟相结合的方法研究了低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附热力学、动力学和吸附分离机理。用常温合成方法制备了超微孔金属-有机骨架材料Cu(Qc)₂,测定了低碳烷烃烯烃（CH₄/C₂H₄/C₂H₆/C₃H₆/C₃H₈）在Cu(Qc)₂上的吸附相平衡和吸附动力学。使用Materials Studio中的Fortcite模块模拟低碳烷烃烯烃在超微孔柔性Cu(Qc)₂上的吸附机理以及材料的结构形变。结果表明Cu(Qc)₂具有优良的C₂H₆ /C₂H₄吸附选择性和吸附动力学,而对C₃H₈ /C₃H₆的吸附选择性很低。273 K和0.1 MPa下,C₂H₆/C₂H₄在Cu(Qc)₂上的IAST选择性达4.6。298 K和0.05 MPa下C₂H₆/C₂H₄在Cu(Qc)₂上的扩散时间常数分别达1.42×10^-3和1.48×10^-3_{s^-1,扩散活化能分别为16.62 和16.43 kJ/mol。应用装填Cu(Qc)2的固定床可在常温条件下实现C2H6 /C2H4二元混合气的完全分离。模拟结果显示Cu(Qc)2为二维堆叠结构,材料会由于吸附不同分子而发生不同程度的结构形变。甲烷易从变大的层间扩散脱附,导致其在材料上的吸附量很低;C2H6/C2H4两者都能稳定吸附在层中的孔道中,其分离推动力主要来源于两种气体在材料上明显的吸附热差异;C3H8/C3H6会分别吸附在两种不同的环境,吸附热差异小导致Cu(Qc)2对C3H8 /C3H6的吸附选择性低。}     

Phase transitions in R2 SnCl6-type crystals (R = NH3 C2H3, NH3C2H5 and N(CH3)4)

The thermal dilatation in (NH₃ ·CH₃) SnCl₆, (NH₃ · C₂H₅) SnCl₆ and [N(CH₃)] SnCl₆ was measured, and as the results it has turned out that (NH₃ ⁶·C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnCl₆ undergo the first order transitions at 128 K and 158 K, respectively. The low temperature phases of (NH · C₂H₅) SnCl₆ and [N(CH₃)₄]₂ SnC1₆ are found to be monoclinic and tetragonal, respectively, No phase transition was observed in (NH₃ ·CH₃)₂ SnCl₆ down to 77 K.     

异丙醇钛控制水解的小角X射线散射研究

由金属醇盐水解制备溶胶的方法已广泛应用于溶胶-凝胶法制备纳米孔无机膜,但对金属醇盐水解机理的认识十分有限。通过控制异丙醇钛[Ti（i-OC₃H₇）₄]在异丙醇（i-C₃H₇OH）中水解制备TiO₂溶胶,利用小角X射线散射（SAXS）方法研究了由不同H₂O/Ti（i-OC₃H₇）₄的反应混合物[Ti（i-OC₃H₇）₄：H₂O：i-C₃H₇OH=1：m：30（摩尔比）]形成TiO₂溶胶的过程,探讨了控制Ti（i-OC₃H₇）₄水解的过程中胶粒形成与长大的规律。研究结果表明,所合成的TiO₂溶胶的胶粒粒径小于10 nm,胶粒的形成和长大与H₂O/Ti（i-OC₃H₇）₄摩尔比密切相关。H₂O/Ti（i-OC₃H₇）₄（摩尔比） ≥ 2.0时,随着H₂O/Ti（i-OC₃H₇）₄增加,溶胶的稳定性下降。     

KINETIC STUDY OF SYNTHESIZING UNSYMMETRIC ACETALS UNDER PHASE TRANSFER CONDITIONS

An effective method was proposed to determine the two organic-phase rate constants of the primary and secondary reactions which have differences in rates. The goal was achieved by employing the reaction of two mixed l-alcohols and dibromomethane in an alkaline solution of KOH/chlorobenzene two-phase medium under phase transfer catalysis. A new product of unsymmetric acetal was obtained in this work. The intermediate ROCH₂Br (a-haloalkyl ether) was not detected during or after the reaction when using high reactive alcohols. This result indicated that ROCH2Br was more reactive than the organic reactant CH₂Br₂. This high reactive a-haloalkyl ether implied that the rate constants of secondary reactions are larger than those of the primary reactions. The resistance of mass transfer of the catalyst ((C₄H₉)₄NBr, QBr) and the active catalyst, ((C₄H₉ )₄NOR, QOR R: c₄h₉and C₈h₁₇) transferring from the aqueous phase to the organic-phase and vice versa were found to be negligible. The organic-phase reaction is a rate-determining step of the phase transfer catalytic reaction, A measured constant concentration of tetrabutylammonium alkoxide (QOR) during the reaction leads to the application of pseudo-first order rate law. The reaction rate constant of ROCh₂Br acts 10⁴ larger than that of CH₂Br₂.     

Preparation of catalyst precursors for selective oxidation of n-butane by exfoliation–reduction of VOPO4·2H2O in primary alcohol

A new method through intercalation and exfoliation of VOPO₄·2H₂O crystallites in primary alcohol (1-propanol or 1-butanol), followed by reduction with the alcohol, have been investigated for the preparation of catalyst precursor. Lamellar compounds, consisting of V⁴⁺, P⁵⁺ and alkyl group with thin film-like morphology, were formed and was characterized by means of XRD, IR, TG/DTA, and elemental analysis. The chemical formula of the precursor obtained by exfoliation–reduction in 1-butanol was shown to be VO{(n-C₄H₉)_0.16H_0.84}PO₄·0.8H₂O. On the other hand, a direct reduction of VOPO₄·2H₂O in the alcohol gave a mixed phase shown by (VOHPO₄·0.5H₂O)_0.3(VO{(n-C₄H₉)_0.3H_0.7}PO₄·3H₂O)_0.7 comprising plate-like microcrystallites. These precursors transformed to (VO)₂P₂O₇ phase during an activation process at 703 K in the presence of a mixture of n-butane 1.5% and O₂ 17% in He balance. The obtained (VO)₂P₂O₇ through the exfoliation–reduction was well crystallized and consisted of thin flaky crystallites. It was found that (VO)₂P₂O₇ thus prepared through the exfoliation–reduction was highly active and selective for oxidation of n-butane.     

水力喷射-空气旋流器用于湿法烟气脱硫及其传质机理

在一种新型高效的气液传质设备--水力喷射-空气旋流器(WSA)中,以Ca(OH)₂料浆为吸收剂进行了模拟烟气湿法脱硫的实验研究。结果表明:脱硫率随进口气速增加而增加;随液体喷射速度增加先增加,增加到一定程度后几乎不变;随烟气中SO₂的进口浓度增加而减小,存在一适宜的Ca(OH)₂浓度和回流比。在气体流量24～72 m³·h^-1、循环液体量0.4～0.8 m³·h^-1、料浆中Ca(OH)₂浓度7500 g·m^-3时,对SO₂浓度为1891～6373 mg·m^-3的烟气进行湿法脱硫,脱硫率达88.9%～97.7%,且WSA的旋流气体和喷射液体在湿法脱硫中具有自清洁能力,未发现内部结垢和喷孔堵塞现象。总体积传质系数K_Ga、有效相界面积a均随进口气速u_G增大而增大,而总传质系数K_G随u_G增加变化较小;当液体喷射速度 u_L≤0.26 m·s^-1时,K_Ga和K_G随u_L增加快速增大,之后增加缓慢,而a随u_L几乎线性增加,K_Ga和K_G随吸收剂中Ca(OH)₂浓度c_L增加有一最大值。结合实验数据拟合得到了相关的经验公式,这些关联式能较好地预测WSA的湿法脱硫传质性能。气体旋流场强度对总体积传质系数K_Ga和有效相界面积a起支配作用,脱硫传质过程同时受气膜和液膜阻力控制,但以液膜控制为主。     

蛇纹石与绿矾耦合提取富镁溶液矿化二氧化碳并回收镍

蛇纹石与绿矾耦合提取镁用于矿化二氧化碳,并富集回收蛇纹石中的镍,这为处理蛇纹石和绿矾提供了一条新的路径。为得到富镁溶液,同时从溶液中分离镍,以蛇纹石与绿矾混合焙烧-浸出后得到的溶液为研究对象,采用水解沉淀法除铁,二乙基二硫代氨基甲酸钠(DDTC)络合法分离镍镁,得到镍的产物和富镁溶液并将其用于二氧化碳矿化。结果表明,该方法能够高效地去除杂质、分离镍镁。在30℃、p H为5.0条件下,铁的去除率达97.36%,而镍、镁的损失率较低。在最佳络合条件下,镍的络合率达到99.50%,而镁的损失率仅为3.03%。此外,对络合机理进行了研究,DDTC中的特征官能团是—SH,络合之后镍和铁分别以Ni[(C₂H₅)₂NCS₂]₂,Fe[(C₂H₅)₂NCS₂]₃的形式存在,而镁不会被络合。富镁溶液在80℃下矿化率达92.63%。每1 000 kg蛇纹石可固定227.38 kg的二氧化碳...     

L-精氨酸衍生物的合成及其性质研究

以L-精氨酸(L-Arginine)和香兰素(Vanillin)为原料,首先合成新型的具有手性的希夫碱配体L(C_(14)H_(14)KN_3O_4),其次配体L分别与金属盐(CH_3COO)_2Ni·2H_2O、BaCl_2、(CH_3COO)_2Zn·2H_2O进行配位反应,得到3种新型的金属配合物(C_(16)H_(19)ZnKN_3O_7、C_(14)H_(14)BaClKN_3O_4和C_(18)H_(20)KN_3NiO_8),目标产物用IR、荧光分光光度计和元素分析仪等表征其结构,并用紫外漫反射光谱在可见光照射下,考察了配体L和3种新型的金属配位化合物的催化性能。实验结果推测配体L和L金属配合物均具有光催化性质,L金属配合物的催化性能更强。     

茂金属/有机硼化物催化1-癸烯均相聚合反应动力学

以茂金属体系rac-Et（1-Ind）₂ZrCl₂/C₆H₅NH（CH₃）₂B（C₆H₅）₄/Al（i-Bu）₃催化1-癸烯聚合,对不同反应条件下（如温度,铝锆摩尔比）聚合反应动力学进行了研究。通过中间取样并利用GC测定单体浓度、GPC测定聚合物相对分子质量,获取动态的变化数据;结合聚合反应机理和物料平衡,对烯烃聚合反应做了一些假设,建立了聚合反应的动力学模型,该模型包括链引发、链增长、链转移至单体、链转移至活性中心和链终止几个反应。借助Levenberg-Marquardt算法对模型参数进行优化,通过该模型可以预测聚合反应速率、数均分子量和重均分子量等参数,验证实验结果表明模型预测值与实验数据相接近。模型显示链引发过程在几秒内完成,链增长反应相对于链转移反应具有较低的活化能,温度升高有利于链转移反应的进行。     

Epoxidation of propylene by using [π-C5H5NC16H33]3[PW4O16] as catalyst and with hydrogen peroxide generated by 2-ethylanthrahydroquinone and molecular oxygen

The epoxidation of propylene catalyzed by a reaction-controlled phase transfer catalyst [π-C₅H₅NC₁₆H₃₃]₃[PW₄O₁₆] is investigated. The H₂O₂ is generated by the oxidation of 2-ethylanthrahydroquinone (EAHQ) with molecular oxygen in the organic solvent. Under mild conditions, the selectivity for propylene oxide, based on propylene, is 95%, and the yield, based on 2-ethylanthrahydroquinone, is 85%. During the epoxidation, the catalytic system is homogeneous. However, after the H₂O₂ is used up, the catalyst can be recovered as a precipitate and can be reused. After the epoxidation reaction, 2-ethylanthraquinone can be regenerated to 2-ethylanthrahydroquinone by catalytic hydrogenation, and no coproduct is produced.     

Polymerization of methyl methacrylate catalyzed by mono-/bis-salicylaldiminato nickel(II) complexes and methylaluminoxane

Two types of salicylaldiminato-based nickel complexes, mono-ligated Ni(II) complexes ([O-C₆H₄-o- C(H)=N-Ar]Ni(PPh₃)(Ph) (5), [O-(3,5-Br₂)C₆H₂-o-C(H)=N-Ar]Ni(PPh₃)(Ph) (6), [O-(3-t-Bu)C₆H₃-o-C(H)=N-Ar]Ni(PPh₃)(Ph) (7)) and bis-ligated Ni(II) complexes ([O-(3,5-Br₂)C₆H₂-o-C(H)=N-Ar]₂Ni (8), [O-(3,5-Br₂)C₆H₂-o-C(H)=N-2-C₆H₄(PhO)]₂Ni (9), Ar=2,6-C₆H₃(i-Pr)₂) were synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), mass spectrography (MS) and elemental analysis (EA). In the presence of methylaluminoxane (MAO) as cocatalyst, all the nickel complexes exhibited high activities for the polymerization of methyl methacrylate (MMA) and syndiotactic-rich poly(methyl methacrylate) (PMMA) was obtained. The complexes with less bulky substituents on salicylaldiminato framework possessed higher activities, while with the same salicylaldiminato, the mono-ligated nickel complexes showed higher catalytic activity than bis-ligated ones.     

Raman spectra of (NH4)4H2(SeO4)3 superionic single crystal

Raman spectra of (NH₄)₄H₂(SeO₄)₃ protonic conductor were studied at room temperature using a 1064 nm - excited Fourier transform (FT) - Raman spectroscopy. A tentative assignment of the external and internal vibrations is proposed.     

氨法烟气脱硫SO2吸收传质系数研究

喷淋塔氨法脱硫技术被广泛应用于净化烟气的SO₂,传质系数是喷淋吸收塔重要的设计和运行参数,但目前文献中有关氨法脱硫传质系数的报道很少,还有待进一步研究。在喷淋塔中对氨法脱硫SO₂吸收传质过程进行了实验研究,结合对液滴和塔壁液膜运动的计算,得到不同实验条件下SO₂的吸收传质速率,并建立了氨法脱硫SO₂吸收传质系数表达式。该传质系数包含浆液pH、烟气流速u_g和液气比L/G等主要参数,能够反映不同pH、u_g和L/G条件下SO₂在单位气液接触面积上的传质速率。对比验证结果表明,该传质系数计算得到的SO₂吸收传质速率与实验值之间的相对误差小于±12%,二者能够较好地吻合。建立的传质系数表达式能够为喷淋塔氨法脱硫的优化设计和运行提供理论参考。     

水力喷射-空气旋流器中气液传质特性及其机理

对一种新型高效的气液传质设备--水力喷射-空气旋流器(WSA)的传质机理进行了研究。分别采用化学吸收法(CO₂-空气-NaOH体系)和物理吸收法(CO₂-空气-H₂O体系)测定了不同进口气速、不同液体喷射速度下的有效相界面积a和液膜传质系数k_L,并由此得到体积传质系数k_La。结果表明,由于WSA中气液间的强交互作用,a、k_L以及k_La均随进口气速和液体喷射速度增大而增大。采用量纲分析法对实验数据进行了归纳,拟合出了a、k_L和k_La随气相Reynolds数Re_g、液相Weber数We_L之间的经验公式:a=0.0024Re_g^1.25We_L^0.079,Sh_L=35.31Re_g^0.2303We_L^0.13,k_La=6.52×10^-8Re_g^1.48We_L^0.21,这些关联式能较好地预测WSA的传质性能。研究还表明,在WSA中的气液射-旋流传质体系中,传质过程符合双膜理论、表面更新理论和溶质渗透理论,但以表面更新机理为主。     

微通道内单乙醇胺水溶液吸收CO2/N2混合气的传质特性

采用高速摄像仪对400 μm×400 μm T形微通道内单乙醇胺（MEA）水溶液吸收混合气中CO₂过程的气液两相流及传质特性进行了实验研究,微通道内的压力降采用压力传感器进行测量。考察了弹状流型下气液两相流量及MEA浓度对压力降、比表面积和传质性能的影响。结果表明,当MEA浓度不变,气液两相流量增大时,压力降、比表面积、传质系数、体积传质系数和增强因子均增大,并逐渐趋于恒定。当气液流量不变,MEA浓度增大时,压力降、传质系数、体积传质系数和增强因子增大,但比表面积减小。实验条件下,压力降范围为2.00~5.23 kPa,化学吸收过程的传质系数范围为7.74×10^-4~2.97×10^-3 m·s^-1。对于伴有快速化学反应的传质过程,以Sherwood数、Reynolds数、Schmidt数及增强因子为变量建立了体积传质系数的预测关联式,平均偏差为5.09%,具有良好的预测性能。     

Structural and Optical Properties of Barium Strontium Titanate (Ba0.5Sr0.5TiO3) Thin Films

Ferroelectric Barium Strontium Titanate (Ba_0.5Sr_0.5TiO₃) or BST thin films on quartz substrates have been prepared by using a modified sol gel processing technique. The starting materials are Barium 2-ethylhexanoate Ba[CH₃(CH₂)₃CH(C₂H₅)CO₂]_2, Strontium 2-ethylhexanoate Sr[CH₃(CH₂)₃CH(C₂H₅)CO₂]₂ and Titanium(IV) isopropoxide [TiOCH(CH₃)₂]₄. The precursors except [TiOCH(CH₃)₂]₄ were synthesized in the laboratory. Transparent and crack-free films were fabricated on quartz substrates by spin coating. The as-fired films were found to be amorphous, which crystallized to cubic phase after annealing at 550°C in air for 1 hr. In this paper we report the structural and optical properties of BST films prepared by the modified sol-gel process.

Communicated by Prof. E. C. Subbarao     

The effect of oxygen concentration on the reduction of NO with propylene over CuO/γ-Al2O3

The effect of oxygen concentration on the pulse and steady-state selective catalytic reduction (SCR) of NO with C₃H₆ over CuO/γ-Al₂O₃ has been studied by infrared spectroscopy (IR) coupled with mass spectroscopy studies. IR studies revealed that the pulse SCR occurred via (i) the oxidation of Cu⁰/Cu⁺ to Cu²⁺ by NO and O₂, (ii) the co-adsorption of NO/NO₂/O₂ to produce Cu²⁺(NO₃⁻)₂, and (iii) the reaction of Cu²⁺(NO₃⁻)₂ with C₃H₆ to produce N₂, CO₂, and H₂O. Increasing the O₂/NO ratio from 25.0 to 83.4 promotes the formation of NO₂ from gas phase oxidation of NO, resulting in a reactant mixture of NO/NO₂/O₂. This reactant mixture allows the formation of Cu²⁺(NO₃⁻)₂ and its reaction with the C₃H₆ to occur at a higher rate with a higher selectivity toward N₂ than the low O₂/NO flow. Both the high and low O₂/NO steady-state SCR reactions follow the same pathway, proceeding via adsorbed C₃H₇---NO₂, C₃H₇---ONO, CH₃COO⁻, Cu⁰---CN, and Cu⁺---NCO intermediates toward N₂, CO₂, and H₂O products. High O₂ concentration in the high O₂/NO SCR accelerates both the formation and destruction of adsorbates, resulting in their intensities similar to the low O₂/NO SCR at 523–698 K. High O₂ concentration in the reactant mixture resulted in a higher rate of destruction of the intermediates than low O₂ concentration at temperatures above 723 K.