黑碳颗粒物表面SO2的非均相臭氧氧化

采用漫反射红外傅里叶变换光谱(DRIFTS)结合离子色谱(IC)、 X射线光电子能谱(XPS)研究了常温常压下SO2与O3在黑碳颗粒物(以Printex U为代表, 简称UBC)表面的非均相反应. 研究发现, 在O3和水气存在的情况下, 体系的反应产物主要是SO42-, 反应在一定时间内持续进行. UBC可提供反应活性位点, 促进SO2在其表面的臭氧氧化. O3是关键的氧化剂, 能显著提高SO2非均相氧化生成SO42-的速率. 水气的存在有利于表面活性位点再生, 使反应持续发生. 当SO2和O3的浓度为1014~1015 molecule/cm3、 相对湿度为40%时, SO2在UBC(1: 400, 以NaCl为稀释剂稀释400倍)表面非均相反应生成SO42-的稳态摄取系数(γBET)为1~6×10-6, SO42-的生成速率为1014~1015 ion·s-1·g-1.     

NO_2在MgO颗粒物表面的非均相反应

氧化镁(MgO)是大气中矿物气溶胶的重要组分之一,对二次污染物的形成有着重要影响.本研究采用原位漫反射红外傅里叶变换光谱(DRIFTS)与离子色谱(IC)技术,研究了二氧化氮(NO2)在MgO颗粒表面的非均相反应.探讨了无光照、紫外光照、臭氧(O3)、温度及相对湿度(RH)等对该反应的影响机制,建立了新的测定摄取系数的方法.结果表明,无光照时,NO2在MgO颗粒表面生成的主要产物为硝酸盐和亚硝酸盐;在NO2-MgO-O3和NO2-MgO-hv两种反应体系中主要产物均为硝酸盐,生成的硝酸根峰面积分别是无光照条件下的1.54倍和3.04倍,O3和紫外光照对硝酸盐的生成均具有促进作用;在紫外光照条件下,NO2在MgO颗粒物表面生成硝酸根的初始速率随温度的升高而呈单峰变化,40℃时初始速率最大;影响NO2与MgO颗粒物反应的敏感因素为紫外光照和臭氧,其次为相对湿度和温度.在25℃,RH为5%时,无光照条件和紫外光照条件下反应初始摄取系数分别为9.01×10-4和5.65×10-3.     

NO2在NaCl表面的非均相反应

采用新的样品制备方法和气-固自由扩散的实验方式,使用漫反射傅立叶转换红外光谱原位反应器,结合离子色谱、X-射线光电子能谱、扫描电子显微镜等分析方法,研究了NO2在NaCl表面的非均相反应.研究表明反应不只是发生在颗粒物表面,体相也参与了反应; 颗粒物表面的活性点对反应起决定作用,同时测定了反应级数为二级,反应摄取系数为(1.54±0.70)×10-5.     

过渡金属同晶替换的铁氧化物及其在非均相Fenton反应中的应用

过渡金属同晶替换的铁氧化物因其具有稳定、高效和可重复利用等特点而被广泛应用于催化处理难降解有机物领域。本文综述了这种新型催化剂的制备过程、过渡金属的同晶替换对催化剂物理化学性质(如比表面积、表面羟基数量、铁离子溶出量及热稳定性)的影响以及促进非均相Fenton反应的催化机制(氧化还原电对结构及氧空位理论)。本文还探讨了这种新型铁氧化物在难降解有机物处理中的应用进展,为后续研究提供了新的思路。     

甲醛在TiO_2颗粒物表面的非均相反应

使用漫反射红外傅里叶变换光谱(DRIFTS)原位反应器研究了甲醛在TiO2颗粒物表面的非均相反应,结合离子色谱定量分析了反应的主要产物甲酸盐,甲酸盐是由中间产物二氧亚甲基进一步氧化生成.研究了温度和紫外光照对反应的影响,结果表明升高温度和紫外光照可提高反应速率,推测了暗反应和紫外光照下甲醛在TiO2表面的非均相反应机制.结果表明常温下甲醛在TiO2颗粒物表面的反应级数接近2级,初始反应摄取系数为(0.5～5)×10-8([HCHO]:1×1013～2×1014molecule·cm-3),是甲醛浓度的一次函数,同时测定了表观活化能.     

NO2在矿物颗粒物表面的非均相反应

NO2在矿物颗粒物表面的非均相反应会改变矿物颗粒物的化学组成、粒径、形貌、吸湿性,进而影响矿物颗粒物的散射、反射、吸收等光学性质和成云能力,改变其直接和间接辐射强迫,最终对大气氧化性和气候变化产生重要的影响.本文综述了NO:在矿物颗粒物表面的非均相反应的研究体系和研究方法,阐述N02在氧化物颗粒物表面反应产物、反应机理的实验和推测结果,总结了测定的摄取系数,提出了NO2在矿物颗粒物表面非均相反应待深入研究的科学问题.     

NO2在黑碳表面的非均相反应

HONO是大气中OH自由基的重要来源,NO2在黑碳表面可反应生成HONO,因此NO2在黑碳表面的非均相反应引起了人们的关注。目前不同研究小组测量的摄取系数可相差7个数量级,选择不同的摄取系数去评估非均相反应的重要性将得到完全不同的结果。本文在深入分析NO2在黑碳表面反应机理的基础上,从反应体系、黑碳表面性质、反应条件等角度对不同小组测量的摄取系数存在差异的原因进行了分析,为模式中摄取系数的选取提供了依据。     

层状钠锰氧化物的制备及离子交换反应动力学

层状钠锰氧化物的制备及离子交换反应动力学     

羰基氧化物环化反应动力学的计算研究

用密度泛函（DFT）方法计算了羰基氧化物（H2COO、HFCOO、F2COO和Me2COO）环化反应的动力学信息，优化了反应物和产物的几何构型，优化搜索了各反应的过渡态结构，并用频率分析和内禀坐标法(IRC)验证了各鞍点构型和反应路径.计算了不同温度下经零点能校正的活化热力学量、反应过程热力学改变量，反应速率常数及频率因子.计算表明，电负性较大的取代基对环化反应有促进作用.     

铁铈复合氧化物催化剂SCR脱硝反应动力学研究

利用共沉淀法制备了铁铈复合氧化物催化剂,在积分实验系统上考察了NO初始浓度、NH₃/NO比及O₂浓度对其SCR脱硝活性的影响;并借助微分系统探讨了其SCR脱硝的催化反应动力学,构建了铁铈复合氧化物催化剂的催化脱硝反应动力学模型.实验结果表明,NO初始浓度越高,每克催化剂的NO转化率越高;随着NH₃/NO比的增加,NO转化率先迅速增加后趋势减缓,最终趋于稳定;O₂在NH₃-SCR反应中起着重要的作用;在175~225 ℃下,Fe_0.95Ce_0.05O_z催化剂的NO和NH₃反应级数分别为1级和0级,O₂的反应级数接近0.5级,该反应的表观活化能为42.6 kJ/mol.     

Acetylation and Formylation of Alcohols in the Presence of Silica Sulfuric Acid

Alcohols are converted to esters in a mild, clean, and efficient reaction with acetic and formic acids in the presence of silica sulfuric acid. All reactions were performed under mild and completely heterogeneous conditions in refluxing n-hexane.     

对硝基苯酚在酸性介质中的电化学还原反应机理

采用电化学原位红外光谱技术研究了对硝基苯酚在铜电极表面及硫酸介质中的电化学反应机理. 对硝基苯酚首先经电还原反应生成对亚硝基苯酚和对羟胺苯酚, 对亚硝基苯酚可发生缔合生成反式二聚体, 最后在较低的电位下, 对羟胺苯酚经电还原生成了对氨基苯酚.     

Heterogeneous Uptake of Hydrogen Peroxide on Mineral Oxides

The interaction of mineral oxides (α-Al₂O₃, MgO, Fe₂O₃, and SiO₂) with hydrogen peroxide was investigated using the Knudsen cell reactor. The initial reactive uptake coefficients for the commercially available powders are measured as (1.00±0.11)×10^-4 for α-Al₂O₃, (1.66±0.23)×10^-4 for MgO, (9.70±1.95)×10^-5 for Fe₂O₃, and (5.22±0.9)×10^-5 for SiO₂. These metal oxide powders exhibit some catalytic behavior toward the decomposition of hydrogen peroxide excluding SiO₂. H₂O₂ can be destroyed on Fe₂O₃ surface and O₂ is formed. The experimental results suggest that the heterogeneous loss on mineral surface can represent an important sink of hydrogen peroxide.     

Kinetics and Substrate Selectivity of the Oxidation of Saturated Hydrocarbons by Adamantyl Cations in Sulfuric Acid

It was shown that at 70 °C sulfuric acid ([H₂SO₄] > 85 wt.%) solutions of 1-hydroxyadamantane and the solutions obtained in the reaction of adamantane with concentrated sulfuric acid oxidize saturated hydrocarbons (RH). Data on the kinetics, selectivity, kinetic isotope effect, and the effect of the acidity of the medium on the oxidation rate of RH indicate cleavage of the C—H bond in the substrate at the rate-determining stage and the direct participation of adamantyl carbocations.     

Application of the Sulfuric Acid-Halide Salt Reaction to the Analysis of Sulfuric Acid Containing Aerosols

Abstract

A new X-ray fluorescence method for the determination of sulfuric acid in sulfuric acid containing aerosols is presented. The technique makes use of the reaction between sulfuric acid and potassium chloride yielding volatile hydrogen chloride and thus changing the C1/K ratio. Nuclepore^R membrane filters are first loaded with potassium chloride and then used for the collection of the aerosol under study. The chlorine and potassium X-ray signals are measured before and after the sampling of the acid aerosol, and the decrease in the Cl/K intensity ratio is taken as a measure for the amount of sulfuric acid collected.     

Theoretical Studies on Mechanism and Rate Constant of Gas Phase Hydrolysis of Glyoxal Catalyzed by Sulfuric Acid

The gas phase hydration of glyoxal (HCOCHO) in the presence of sulfuric acid (H2SO4) were studied by the high-level quantum chemical calculations with M06-2X and CCSD(T) theoretical methods and the conventional transition state theory (CTST). The mechanism and rate constant of the ve di erent reaction paths are consid-ered corresponding to HCOCHO+H₂O, HCOCHO+H₂O H₂O, HCOCHO H₂O+H₂O, HCOCHO+H₂O H₂SO₄ and HCOCHO H₂O+H₂SO₄. Results show that H₂SO₄ has a strong catalytic ability, which can signi cantly reduce the energy barrier for the hydration reaction of glyoxal. The energy barrier of hydrolysis of glyoxal in gas phase is lowered to 7.08 kcal/mol from 37.15 kcal/mol relative to pre-reactive complexes at the CCSD(T)/6-311++G(3df, 3pd)//M06-2X/6-311++G(3df, 3pd) level of theory. The rate constant of the H₂SO₄ catalyzed hydrolysis of glyoxal is 1.34×10^-11cm³/(molecule s), about 10¹³ higher than that involving catalysis by an equal number of water molecules, and is greater than the reaction rate of glyoxal reaction with OH radicals of 1.10×10^-11cm³/(molecule s) at the room temperature, indicating that the gas phase hydrolysis of glyoxal of H₂SO₄ catalyst is feasible and could compete with the reaction glyoxal+OH under certain atmospheric condi-tions. This study may provide useful information on understanding the mechanistic features of inorganic acid-catalyzed hydration of glyoxal for the formation of oligomer     

Efficient One-Pot Synthesis of Polyhydroquinoline Derivatives Using Silica Sulfuric Acid as a Heterogeneous and Reusable Catalyst Under Conventional Heating and Energy-Saving Microwave Irradiation

An efficient Hantzsch four-component condensation reaction for the synthesis of polyhydroquinoline derivatives was reported under two conditions: solvent-free conventional heating and energy-saving microwave irradiation. The process is simple and environmentally benign, and the use of a heterogeneous and reusable catalyst, high yields, and short reaction times are the key features of this protocol.     

铌酸/氧化铌在多相催化反应中的应用

介绍了铌酸，氧化铌的结构、性质及其在多相催化反应中的研究现状及应用前景。作为一种新型的催化材料，铌酸，氧化铌由于其独特的酸性和氧化还原性正受到越来越多人的关注。它可以作为催化剂的活性组分、助剂或载体使用，在烃类转化、选择性氧化、水解、水合、缩合、加氢，脱氢等若干酸碱和氧化还原反应中得到广泛的应用。     

Alternating Copolymers of Limonene with Methyl Methacrylate: Kinetics and Mechanism

The radical copolymerization of limonene (optically active) with methyl methacrylate in xylene at 80±0.1°C for 1 hr, initiated by benzoyl peroxide (BPO) yield alternating copolymer(s), under the inert atmosphere of nitrogen, as evidenced by reactivity ratios r₁ (MMA)=0.07 and r₂ (limonene)=0.012 using the Kelen–Tüdos method. The kinetic expression is Rα[I]^0.5[MMA]^1.0[Lim.]^?1.0. The decrease in the rate of polymerization with increase in concentration of limonene is due to penultimate unit effect. The overall energy of activation is calculated as 49 kJ/mole. FTIR of the copolymer(s) shows the characteristic frequencies at 1732.40 and 2951.40 cm^?1 due to –OCH₃ of MMA and aromatic C–H stretching of limonene, respectively. ¹H NMR spectra shows peak at 3.8–4.1 δ and 5.3–5.6 δ due to –OCH₃ of MMA and trisubstituted olefinic protons [–CH=CH–CH₂–] of limonene, respectively.     

环氧乙烷环氧丙烷开环聚合反应动力学研究

环氧乙烷和环氧丙烷由于具有较高的环张力,因而容易发生开环聚合。本文综述了环氧乙烷合环氧丙烷开环聚合反应的动力学研究进展,考察了环氧乙烷和环氧丙烷开环聚合反应的机理,分别讨论了各类催化剂体系中环氧乙烷和环氧丙烷开环聚合的动力学常数、两者的竞聚率及开环聚合产物的分子量分布,并指出了开环聚合反应动力学研究对于环氧乙烷和环氧丙烷的开环聚合研究及工业应用的重要性。