BaF2/La2O3催化剂上甲烷氧化偶联反应活性氧物种的原位红外光谱

用原位红外光谱研究了BaF2/La2O3催化剂上甲烷氧化偶联反应的活性氧物种.结果表明,催化剂经O2预吸附后,在1 108~1 118 cm-1处出现超氧物种O2-的O-O键伸缩振动峰.经18O2同位素交换实验后,原1 108~1 118 cm-1处谱峰的强度减弱,同时在1 086和1 051 cm-1处出现(O18O)-物种和18O2-物种的吸收峰.同位素交换实验进一步确证了1 108~1 118cm-1处谱峰确为O2-物种的吸收峰.在700℃下,O2-物种能够活化CH4生成C2H4,而且O2-物种的消耗量和C2H4的生成量呈很好的消长对应关系.超氧物种O2-是BaF2/La2O3催化剂上甲烷氧化偶联反应的活性氧物种.     

PP/PP-g-MAH与铝板粘接界面相的XPS研究

用X射线光电子能谱(XPS)研究铝板/聚丙烯层状复合材料的粘接界面相，提出了粘接界面的化学反应机制.研究发现,聚丙烯(PP)中加入马来酸酐接枝聚丙烯(PP-g-MAH)时，铝板面上Al 2p、O 1s谱线明显向高结合能端移动，表明PP-g-MAH与铝板表面发生了化学反应，形成Al－O－C配位键.配位键的形成使界面粘接强度明显提高. PP中不含PP-g-MAH时，铝板面上Al 2p、O 1s谱线处于低结合能端，聚丙烯未与铝板表面形成化学配位作用.     

聚羧酸型梳状共聚物超分散剂在氟虫腈颗粒界面的吸附性能

采用紫外光谱(UV)、 傅里叶变换红外光谱(FTIR)、 X射线光电子能谱(XPS)和扫描电子显微镜(SEM)对聚羧酸型梳状共聚物超分散剂(TERSPERSE^®2700)在氟虫腈颗粒界面的吸附等温线、 吸附动力学、 吸附作用力、 吸附层厚度以及吸附状态等进行了分析. 实验结果表明, TERSPERSE^®2700分散剂在氟虫腈颗粒界面的吸附模型符合Langmuir吸附等温式, 吸附量随着温度升高而增大, 并计算了ΔG^0-, ΔH^0-和ΔS^0-. 吸附符合准一级动力学模型, 吸附速率常数随着温度升高而增大, 吸附活化能E_a=29.28 kJ/mol. 利用XPS谱图, 估算其吸附厚度约为1 nm, 表明存在吸附作用. 实验发现氟虫腈存在分子间氢键, 同时氢键也是分散剂分子与氟虫腈颗粒表面结合的重要作用力.     

苯乙烯丙烯酸共聚物分散剂在氟铃脲颗粒界面的吸附性能

利用残余质量浓度法、ζ电位测定、红外光谱和XPS法系统地研究了苯乙烯丙烯酸共聚物(MOTAS)分散剂在氟铃脲颗粒界面的吸附量、吸附状态、ζ电位、吸附作用力和吸附层厚度等性能. 实验结果表明, MOTAS分散剂在氟铃脲界面的吸附符合Langmuir吸附等温式, 其饱和吸附量和吸附平衡常数k、ζ电位和吸附层厚度均随MOTAS分散剂相对分子量增加而增大, MOTAS分散剂在氟铃脲界面呈多点吸附, 氢键是分散剂分子与氟铃脲界面结合的重要作用力. 分析实验结果发现, MOTAS分散剂在氟铃脲颗粒界面吸附后具有静电排斥和空间位阻双重作用.     

含硫液体烃燃料水蒸气重整制氢II. Pt/Ce0.8Gd0.2O1.9 催化剂的原位DRIFTS表征

利用原位红外漫反射技术(DRIFTS)对抗硫中毒催化剂Pt/Ce0.8Gd0.2 O1.9(Pt/CGO)上CO吸附、CO/噻吩共吸附以及CO/H2S顺序吸附进行了研究,并与 Pt/Al2O3催化剂进行了比较. CO吸附实验表明, 1.6%Pt/CGO-800(800 ℃焙烧)上CO的红外特征吸收峰在 2 104 cm-1, 与1.6%Pt/Al2O3-500上CO的红外特征吸收峰(2 070 cm-1)相比,向高波数方向移动了34 cm-1. 1.6%Pt/CGO-600上出现两个CO特征吸收峰,主峰位于 2 108 cm-1, 肩峰位于 2 085 cm-1. C O/噻吩共吸附实验表明,噻吩导致1.6%Pt/CGO-800上CO吸附的红外特征吸收峰红移至 2 090 cm-1, 峰强度略有降低;1.6%Pt/CGO-600上CO的红外特征吸收峰红移至 2 096 cm -1 且强度有所降低,同时肩峰消失. 而1.6%Pt/Al2O3-500上CO的红外特征吸收峰明显减弱并红移至 2 040 cm-1. CO/H2S顺序吸附实验表明, H2S导致Pt/CGO 催化剂在 2 104 和 2 108 cm-1 处的CO特征吸收峰轻微红移,峰强度略有降低,而H2S导致Pt/Al2O3完全丧失CO的吸附能力. 原位DRI FTS表征结果表明, Pt/CGO催化剂上生成的强缺电子特性Pt颗粒具有很强的抗硫中毒能力, 8 00 ℃焙烧有利于生成单一的抗硫中毒的强缺电子Pt金属位,使得1.6%Pt/CGO-800具有最佳的抗硫中毒性能.     

梳状共聚物水泥分散剂构效关系研究进展

梳状共聚物水泥分散剂(由聚电解质主链和非离子型聚乙二醇侧链组成)是建筑化学外加剂领域的研究热点。关于梳状共聚物分子结构-吸附-分散及分散保持的构效关系已经基本明晰,而从梳状共聚物构象和水泥早期水化的研究才刚刚起步。本文结合课题组在梳状共聚物方面的最新研究成果,详细总结了梳状共聚物溶液构象、界面吸附构象、分散及分散保持性能、早期水化历程等构效关系方面的最新研究进展,并提出了今后在基础和产品开发方面的重点研究方向。     

La(Ⅲ),Y(Ⅲ)与多甘醇醛缩氨基酸Schiff碱配合物的合成及其固体高分辨13C NMR波谱

合成了直链醚 氨基酸型的二甘醇醛缩双精氨酸Schiff碱 (H2 DAAR)与镧配合物和四甘醇醛缩双赖氨酸Schiff碱 (H2 TALY)与钇配合物 ,经元素分析确定其组成分别为 :La(H2 DAAR) (NO3 ) 3 ·6H2 O和Y(H2 TALY) (NO3 ) 3 ·5H2 O .采用交叉极化结合魔角旋转技术 (CPMAS)及消除旋转边带技术 (TOSS) ,获得高分辨固体 (HRSS) 13 CNMR谱 ,并与液体 2D1H 13 CNMRCOSY谱作了比较 ,得到相互支持的结果 ;而且在固体高分辨13 CNMR波谱中发现\/ C ——N—的13 C谱峰分裂和烯烃上13 C峰等新信息 .     

酮洛芬的伏安行为及吸附缔合平行极谱催化波研究

采用线性扫描极谱法、循环伏安法及恒电位电解法在NH4Cl-NH3.H2O(pH9.5)缓冲液中研究了酮洛芬(KPF)的伏安行为和极谱催化波的产生机理。结果表明,KPF的羰基首先发生1e-和1H 还原,产生中间体质子化羰基自由基,该自由基再以同样方式进一步还原生成相应的羟基化合物,并伴随有化学反应;引入K2S2O8后,S2O82-作为配位体与吸附在电极表面质子化的KPF形成缔合物,引起峰电位负移,S2O82-及其还原中间产物SO4.-氧化经1e-和1H 还原的KPF羰基自由基,使峰电流显著增加,从而产生了KPF的吸附缔合平行极谱催化波。测得S2O82-氧化KPF质子化羰基自由基的表观速率常数Kf=1.2×104/s。     

含硫液体烃燃料水蒸气重整制氢 Ⅱ. Pt/Ce_(0.8)Gd_(0.2)O_(1.9)催化剂的原位DRIFTS表征

利用原位红外漫反射技术(DRIFTS)对抗硫中毒催化剂Pt/Ce0.8Gd0.2O1.9(Pt/CGO)上CO吸附、CO/噻吩共吸附以及CO/H2S顺序吸附进行了研究,并与Pt/Al2O3催化剂进行了比较.CO吸附实验表明,1.6%Pt/CGO-800(800℃焙烧)上CO的红外特征吸收峰在2104cm-1,与1.6%Pt/Al2O3-500上CO的红外特征吸收峰(2070cm-1)相比,向高波数方向移动了34cm-1.1.6%Pt/CGO-600上出现两个CO特征吸收峰,主峰位于2108cm-1,肩峰位于2085cm-1.CO/噻吩共吸附实验表明,噻吩导致1.6%Pt/CGO-800上CO吸附的红外特征吸收峰红移至2090cm-1,峰强度略有降低;1.6%Pt/CGO-600上CO的红外特征吸收峰红移至2096cm-1且强度有所降低,同时肩峰消失.而1.6%Pt/Al2O3-500上CO的红外特征吸收峰明显减弱并红移至2040cm-1.CO/H2S顺序吸附实验表明,H2S导致Pt/CGO催化剂在2104和2108cm-1处的CO特征吸收峰轻微红移,峰强度略有降低,而H2S导致Pt/Al2O3完全丧失CO的吸附能力.原位DRIFTS表征结果表明,Pt/CGO催化剂上生成的强缺电子特性Pt颗粒具有很强的抗硫中毒能力,800℃焙烧有利于生成单一的抗硫中毒的强缺电子Pt金属位,使得1.6%Pt/CGO-800具有最佳的抗硫中毒性能.     

利用原位红外光谱确证Ru/SBA-15的加氢活性位点

Ru/SBA-15催化剂具有高的氢气活化能力,因此被广泛应用在加氢和氢解反应中.一般认为Ru/SBA-15催化剂的高活性与金属Ru的高分散有关,然而有研究发现在氧化硅载体上还存在溢流的氢,这部分溢流氢也很可能参与加氢和氢解反应.这就产生了两个关键性的问题:(1)Ru/SBA-15的催化加氢活性中心是什么,是金属Ru还是载体SBA-15;(2)在金属Ru上解离的H是如何迁移到载体上的.因此,加氢活性位点及其形成机理的确认对理解Ru/SBA-15催化剂的高活性至关重要.原位红外光谱可从分子层面研究在工作状态的催化剂表面活性位点的状态,进而推测可能的反应机理.通过与催化剂Pd/SBA-15,Ru/Al2O3和SBA-15比较发现,在氢气氛围中Ru/SBA-15催化剂的原位红外谱图中存在一个独特的位于1996 cm?1的峰.由于在Pd/SBA-15,Ru/Al2O3和SBA-15上都不存在这个峰,因此该峰的形成是金属Ru和SBA-15相互作用的结果.此外,Si–O键在位于1866 cm?1的合频峰不随氢气氛围变化而变化,因此可排除这个峰属于Si–O键振动的倍频峰.为了排除该峰的产生是由于CO的吸附,我们采用脉冲引入CO的方法,发现在低的CO覆盖率下,红外谱图中位于2068 cm?1处出现了一个CO在Ruδ+上的线性吸附峰.随着CO覆盖率增加,该峰逐渐蓝移至2075 cm?1,同时位于2132 cm?1处的峰强度增强了,这两个峰都归属于Run+(CO)x物种的振动峰.这些CO的化学吸附强度都很高,即使在He气中吹扫1 h后仍然存在,而1996 cm?1峰的形成是可逆的.此外,低CO覆盖率下生成的吸附峰(2068 cm?1)的强度低于1996 cm?1峰的强度,因此可以排除1996 cm?1峰属于CO吸附峰的可能.既然1996 cm?1峰的形成是可逆的,将这个峰归属于载体上氢的可能性也可排除,因为形成载体上氢的过程是不可逆的.另外,形成1996 cm?1峰的速率还证明了这个峰不属于金属Ru上吸附的氢,因为金属Ru上氢的吸附是很快的.通过以上分析,我们推断1996 cm?1峰应该指认为在Ru和SBA-15界面处位点的红外峰.为了证明这一点,我们制备了不同Ru负载量的Ru/SBA-15催化剂,发现这个界面处位点峰的峰面积与金属Ru颗粒在载体上形成交界面的周长成正比,而峰达到稳态所需时间与Ru颗粒大小成反比.这说明H2在金属Ru上发生解离吸附后迁移到Ru和SBA-15界面处,形成了Ru–H–Si物种.当金属Ru的颗粒比较小时,与载体形成交界面的周长小,Ru–H–Si物种的数量少,体现在红外谱图上峰的峰面积小,但解离的氢迁移到该界面所需时间变短了.当金属Ru的颗粒比较大时,与载体形成交界面的周长大,Ru–H–Si物种的数量多,1996 cm?1峰的峰面积大,但解离氢的迁移慢了.此外,H-D交换实验还证明这个界面处的位点具有加氢活性.与文献报道的孤立Si–H物种的红外峰位置比较发现,Ru–H–Si物种具有明显的峰红移现象,说明该物种中的Si–H键活性很高,这可能是由于金属Ru将电子转移至Si–H键的结果.总之,以上结果清晰地表明这个1996 cm?1峰归属为结构是Ru–H–Si的活性位点.     

Adsorption of atrazine on soils: model study

The adsorption of the widely used herbicide atrazine onto three model inorganic soil components (silica gel, gamma-alumina, and calcite (CaCO(3)) was investigated in a series of batch experiments in which the aqueous phase equilibrated with the solid, under different solution conditions. Atrazine did not show discernible adsorption on gamma-alumina (theta=25 degrees C, 3.8相似文献   

α-Al2O3与Co-Ni合金电化学共沉积动力学模型

在经典复合电沉积机理基础上,考虑到粒子与电极表面之间的多种作用力,以吸附强度来表征粒子与电极表面的作用力大小,根据粒子在电极表面的临界吸附强度,把粒子的吸附分为有效吸附和非有效吸附.当吸附强度大于临界吸附强度时,粒子能被有效吸附嵌入到沉积层中,粒子被有效吸附的概率和平均吸附强度有关.建立了相应的复合电沉积动力学模型.该模型在α-Al2O3与Co-Ni合金的复合共沉积体系中,在电流密度为1～20 A•dm2范围内得到了验证.通过数学模型和实验结果研究了电流密度对粒子沉积量φc、吸脱附常数K、有效吸附概率P和平均吸附强度的影响规律.     

Adsorption of atrazine from aqueous electrolyte solutions on humic acid and silica

The adsorption of, the still widely used, herbicide atrazine on model soil components, such as humic acid and humic acid-silica gel mixtures, was investigated in a series of batch experiments, under different experimental conditions (ionic strength, temperature, and pH). The investigation aimed at obtaining an estimate of the contribution of each of the soil components on the adsorption of atrazine from aqueous solutions. The kinetics of atrazine adsorption on humic acid showed two steps: a fast step, of a few hours duration, and a second slow step, which continued for weeks. The kinetics of adsorption data gave a satisfactory fit to the Elovich equation. Τhe adsorption of atrazine on the test substrates was found to be reversible in all cases. The atrazine uptake data on the test substrates were fitted best with the Freundlich adsorption isotherm. The ionic strength of the atrazine aqueous solutions did affect the amount of the atrazine adsorbed on the test substrates, suggesting that electrostatic forces between atrazine molecules and soil play a significant role in the adsorption process. An increase of temperature resulted in a decrease of atrazine adsorption on humic acid at low atrazine equilibrium concentrations. However, for higher levels of equilibrium concentrations (≥3 mg/L) the amount of atrazine adsorbed onto the test substrate increased as temperature increased. The calculated isosteric enthalpies of adsorption ranged between slightly exothermic at low atrazine uptake and slightly endothermic at high atrazine uptake, all values being in the range of physisorption.     

Adsorption and photophysics of fullerene C60 at liquid-zeolite particle interfaces: unusually high affinity for hydrophobic, ultrastabilized zeolite Y

Adsorption of fullerene C60 from solution to the external surface of zeolite particles has been investigated. The most intriguing result of this study was the nature of C60 adsorption to ultrastablized zeolite Y (or USY). Two commercial samples of USY were tested: CBV780 (Y780) and CBV901 (Y901). Y901 was shown in previous reports to be more hydrophobic than Y780. Higher affinity of C60 for Y901 was found relative to Y780 in a variety of hydrocarbon solvents, including toluene and cyclohexane. In these same solvents, weak or no affinity for Y901 of typical arenes such as naphthalene or pyrene was observed. In toluene, adsorption isotherms for C60 gave dissociation constants (and values of saturation binding) = 0.5 microM (5.8 micromol g(-1)) and 8 microM (1.4 micromol g(-1)) for Y901 and Y780, respectively. C60 was estimated to cover nearly one-half of the estimated external surface area of Y901 particles at saturation. Significant adsorption of C60 to the ionic zeolites NaX, NaY, and KL was observed in cyclohexane but not in toluene, consistent with the pi-cation effect as a driving force for adsorption to these materials. The main driving force for C60 adsorption to Y901 is postulated to involve the interaction of C60 with lone pair electrons of framework oxygen atoms of the 12-ring entry aperture to the supercage. In the 12-ring site, C60 is located in half-supercage bowls on the exterior particle surface. The adsorptive interaction on Y901 relies on the spherical shape of C60 and the hydrophobicity of the zeolite surface. On ionic zeolites, the presence of specific adsorption sites such as exchangeable cations and hydroxyl groups hinder the special positioning necessary for C60 interaction with the 12-ring site. The ground-state and triplet-state absorption spectrum of adsorbed C60 was solution-like on all zeolites. Quenching of the C60 triplet state was examined by using transient absorption spectroscopy. Rate constants for quenching by rubrene, ferrocene, and O2 at the Y901-toluene interface were 18, 9, and 3 times lower, respectively, relative to rate constants in solution. These differences point out that the approach of molecular quenchers to C60 at the interface is more hindered for larger molecules, an expected result for C60 located in half-supercage bowls. The high affinity of fullerenes for hydrophobic zeolite Y provides a strategy for organizing fullerenes at interfaces and for studies of fullerene photochemistry.     

Removal of endocrine‐disrupting compounds from water using macroporous molecularly imprinted cryogels in a moving‐bed reactor

Highly efficient removal of endocrine‐disrupting compounds (EDCs) such as 17β‐estradiol (E2), 4‐nonylphenol (NP) and atrazine from water was achieved using a novel macroporous adsorption medium. The medium consisted of a macroporous poly(vinyl alcohol) (PVA) cryogel with molecularly imprinted polymer (MIP) particles embedded in it. The MIP was prepared using E2, NP and atrazine as templates. The macroporous composite molecularly imprinted cryogels were formed inside the open‐ended protective shells, known as Kaldnes carriers. These adsorbents (defined as Macroporous Gel Particles, MGPs) were evaluated on the removal of E2, NP and atrazine from water using different column configurations, namely column filled with the MGPs (packed‐bed column) and in moving‐bed reactors (defined here as moving‐bed MGPs reactor). Complete binding (> 99%) of E2 from a spiked aqueous solution (1 mg/L) was achieved using E2‐MIP/MGPs in a moving‐bed MGPs reactor at the retention time in the reactor of 4 min, while only 77% was bound to the nonimprinted medium (NIP/MGPs). Similar results were also obtained for the adsorption medium imprinted with atrazine. All contaminants studied (E2, atrazine and NP) were effectively removed from water at low (environmentally relevant) concentrations by the respective adsorption medium.     

Atmospheric chemistry of propionaldehyde: kinetics and mechanisms of reactions with OH radicals and Cl atoms, UV spectrum, and self-reaction kinetics of CH3CH2C(O)O2 radicals at 298 K

The kinetics and mechanism of the reactions of Cl atoms and OH radicals with CH3CH2CHO were investigated at room temperature using two complementary techniques: flash photolysis/UV absorption and continuous photolysis/FTIR smog chamber. Reaction with Cl atoms proceeds predominantly by abstraction of the aldehydic hydrogen atom to form acyl radicals. FTIR measurements indicated that the acyl forming channel accounts for (88 +/- 5)%, while UV measurements indicated that the acyl forming channel accounts for (88 +/- 3)%. Relative rate methods were used to measure: k(Cl + CH3CH2CHO) = (1.20 +/- 0.23) x 10(-10); k(OH + CH3CH2CHO) = (1.82 +/- 0.23) x 10(-11); and k(Cl + CH3CH2C(O)Cl) = (1.64 +/- 0.22) x 10(-12) cm3 molecule(-1) s(-1). The UV spectrum of CH3CH2C(O)O2, rate constant for self-reaction, and rate constant for cross-reaction with CH3CH2O2 were determined: sigma(207 nm) = (6.71 +/- 0.19) x 10(-18) cm2 molecule(-1), k(CH3CH2C(O)O2 + CH3CH2C(O)O2) = (1.68 +/- 0.08) x 10(-11), and k(CH3CH2C(O)O2 + CH3CH2O2) = (1.20 +/- 0.06) x 10(-11) cm3 molecule(-1) s(-1), where quoted uncertainties only represent 2sigma statistical errors. The infrared spectrum of C2H5C(O)O2NO2 was recorded, and products of the Cl-initiated oxidation of CH3CH2CHO in the presence of O2 with, and without, NO(x) were identified. Results are discussed with respect to the atmospheric chemistry of propionaldehyde.     

Pickering emulsions stabilized solely by layered double hydroxides particles: the effect of salt on emulsion formation and stability

The formation and stability of liquid paraffin-in-water emulsions stabilized solely by positively charged plate-like layered double hydroxides (LDHs) particles were described here. The effects of adding salt into LDHs dispersions on particle zeta potential, particle contact angle, particle adsorption at the oil-water interface and the structure strength of dispersions were studied. It was found that the zeta potential of particles gradually decreased with the increase of salt concentration, but the variation of contact angle with salt concentration was very small. The adsorption of particles at the oil-water interface occurred due to the reduction of particle zeta potential. The structural strength of LDHs dispersions was strengthened with the increase of salt and particle concentrations. The effects of particle concentration, salt concentration and oil phase volume fraction on the formation, stability and type of emulsions were investigated and discussed in relation to the adsorption of particles at the oil-water interface and the structural strength of LDHs dispersions. Finally, the possible stabilization mechanisms of emulsions were put forward: the decrease of particle zeta potential leads to particle adsorption at the oil-water interface and the formation of a network of particles at the interface, both of which are crucial for emulsion formation and stability; the structural strength of LDHs dispersions is responsible for emulsion stability, but is not necessary for emulsion formation.     

Kinetics studies of aqueous phase reactions of Cl atoms and Cl2(-) radicals with organic sulfur compounds of atmospheric interest

A laser flash photolysis-long path UV-visible absorption technique has been employed to investigate the kinetics of aqueous phase reactions of chlorine atoms (Cl) and dichloride radicals (Cl2(-)) with four organic sulfur compounds of atmospheric interest, dimethyl sulfoxide (DMSO; CH3S(O)CH3), dimethyl sulfone (DMSO2; CH3(O)S(O)CH3), methanesulfinate (MSI; CH3S(O)O-), and methanesulfonate (MS; CH3(O)S(O)O-). Measured rate coefficients at T = 295 +/- 1 K (in units of M(-1) s(-1)) are as follows: Cl + DMSO, (6.3 +/- 0.6) x 10(9); Cl2(-) + DMSO, (1.6 +/- 0.8) x 10(7); Cl + DMSO2, (8.2 +/- 1.6) x 10(5); Cl2(-) + DMSO2, (8.2 +/- 5.5) x 10(3); Cl2(-) + MSI, (8.0 +/- 1.0) x 10(8); Cl + MS, (4.9 +/- 0.6) x 10(5); Cl2(-) + MS, (3.9 +/- 0.7) x 10(3). Reported uncertainties are estimates of accuracy at the 95% confidence level and the rate coefficients for MSI and MS reactions with Cl2(-) are corrected to the zero ionic strength limit. The absorption spectrum of the DMSO-Cl adduct is reported; peak absorbance is observed at 390 nm and the peak extinction coefficient is found to be 5760 M(-1) cm(-1) with a 2sigma uncertainty of +/-30%. Some implications of the new kinetics results for understanding the atmospheric sulfur cycle are discussed.