乙烷光化学反应体系中有机过氧化物的产生

采用长光路Fourier红外光谱(FT-IR)及高压液相色谱(HPLC)技术对氯原子引发的乙烷光化学反应体系中生成的有机过氧化物进行了研究,证实反应产物中有乙基过氧化氢(CH₃CH₂OOH,EHP)和过氧乙酸(CH₃C(O)OOH,PAA).此外,还发现甲基过氧化氢(CH₃OOH, MHP)、羟甲基过氧化氢(HOCH₂OOH,HMHP)及另外两种未知有机过氧化物.EHP和MHP是这一体系产生的两种主要的有机过氧化物.HMHP的检出表明乙烷光化学氧化过程中可能有Criegee中间体·CH₂OO·产生.模拟实验显示乙烷的光化学氧化可能是大气对流层有机过氧化物的重要来源.     

甲烷-空气-H2O模拟光化学反应体系中CH3OO

在1.013×105 Pa,(298±2)K及O2-N2气氛下,研究了羟基自由基*OH引发的甲烷光化学反应体系中过氧甲基自由基CH3OO*自身复合反应.反应物和产物采用长光路Fourier红外光谱(LP-FTIR)和高效液相色谱(HPLC)测定.证实产物中有甲基过氧化氢(CH3OOH,MHP)和过氧甲醚(CH3OOCH3,DMP)存在并首次在该体系中发现了羟甲基过氧化氢(HOCH2OOH,HMHP).HMHP的检出表明,CH3OO*自身复合的可能途径之一生成了Criegee中间体过氧次甲基双自由基*CH2OO*.采用G2,G2(MP2)和G2(ful)方法对一些反应的标准焓变和标准Gibbs自由能变化进行了理论计算.结果表明CH3OO*自身复合生成*CH2OO*及*CH2OO*与H2O反应生成HMHP的途径在热力学上是可能的.     

甲烷光化学反应体系中有机过氧化物的产生

10 1 32 5Pa ,2 98K ,O2 N2 气氛下 ,采用长光路Fourier变换红外光谱 (FT IR)仪跟踪反应进程 ,高压液相色谱 (HPLC)仪测定反应产物中有机过氧化物的方法研究了氯原子引发的甲烷光化学反应 .实验结果证实反应产物中有过氧化氢(H2 O2 ) ,甲基过氧化氢 (CH3 OOH ,MHP)和过氧甲醚 (CH3 O2 CH3 ) ,并发现还存在羟甲基过氧化氢 (HOCH2 OOH ,HMHP)和一未知有机过氧化物 .HMHP的发现为过氧甲基CH3 OO·自身复合产生Criegee中间体CH2 OO的途径提供了实验证据 .模拟实验显示甲烷光化学氧化产生有机过氧化物的机制比以往认为的要更为复杂 .甲烷的光化学氧化可能是大气对流层有机过氧化物的重要来源     

甲烷-空气-H2O模拟光化学反应体系中CH3OO·自身复合反 应的研究

在1.013×10^5Pa,(298±2)K及O2-N2气氛下,研究了羟基自由基·OH引发的甲烷光化学反应体系中过氧甲基自由基CH3OO·自身复合反应。反应物和产物采用长光路Fourier红外光谱(LP-FTIR)和高效液相色谱(HPLC)测定。证实产物中有甲基过氧化氢(CH3OOH,MHP)和过氧甲醚(CH3OOCH3,DMP)存在并首次在该体系中发现了羟甲基过氧化氢(HOCH2OOH,HMHP).HMHP的检出表明,CH3OO·自身复合的可能途径之一生成了Criegee中间体过氧次甲基双自由基·CH2OO·,采用G2,G2(MP2)和G2(ful)方法对一些反应的标准焓变和标准Gibbs自由能变化进行了理论计算。结果表明CH3OO·自身复合生成·CH2OO·及·CH2OO·与H2O反应生成HMHP的途径在热力学上是可能的。     

Organic peroxide production in the Cl_2-ethane-air photoreaction system

HPLC along with FT-IR technique was used to study the formation of organic peroxides in the CI2-ethane-air photoreaction system. Ethyl hydroperoxide (CH3CH2OOH, EHP) and per-oxyacetic acid ( CH3C(O)OOH, PAA) were conformed to be the peroxide product in the reaction system. In addition, methyl hydroperoxide (CH3OOH, MHP), hydroxymethyl hydroperoxide (HOCH2OOH, HMHP) and two unidentified organic peroxides were detected for the first time. EHP and MHP were the dominant peroxide products. The identification of HMHP showed that Criegee biradical CH2OO may be formed as an intermediate in the oxidation of ethane. Simulation results showed that photooxidation of ethane may make substantial contribution to source of organic peroxides in the atmosphere.     

CH3OOH和CH3CH2OOH的表征和活性：光电子能谱的研究

The ionization energies of MHP （CH3OOH） and EHP（CH3CH2OOH） nave been determined by Hel photoelectron spectroscopy （PES） measurement and both Gaussian-2 （G2） calculation and Hartree-Fock （HF） method on the basis of Koopmans theorem at 6.311＋G^＊ basis set level for the first time. The assignment and characterization of PE spectra of MHP and EHP were also supported by the G2 and HF calculations. The first ionization energies of MHP and EHP are 9.87 and 9.65 eV, respectively. Higher solubility of EHP in the atmosphere was attributed to their lower ionization energy values.     

铁(Ⅲ)的氮杂环配合物的合成、结构及对环己烷氧化的催化性能

制备了铁氮杂环配合物[Fe(H2L)2]·(CH3COO)2·(OH)·H2O(H2L=2,6-二(5-甲基-1H-吡唑-3-基)吡啶),通过元素分析、X射线粉末衍射和X射线单晶结构分析等技术手段表征了它的结构。 将其用于液相环己烷的催化氧化,系统研究了H2O2用量、HNO3用量、水量、反应时间和温度等对中间活性物种环己基过氧化氢(C6H11OOH) 的生成和分解的影响,探讨了反应机理。 结果表明,H2O2是氧化环己烷为C6H11OOH的主要氧化剂;硝酸对此过程没有氧化作用,但能大幅度提高C6H11OOH分解成环己醇(酮)的分解速率。 H2O会抑制中间物种C6H11OOH的生成和分解,而降低催化剂的比活性。 在不同反应阶段,C6H11OOH和环己醇(酮)的生成速率不同。 升温能促进C6H11OOH的分解速率,而有利于环己醇(酮)的生成。     

过渡金属离子掺杂Zn3(OH)2V2O7·2H2O的合成及其光催化性质

利用水热法合成了3d过渡金属离子掺杂Zn3(OH)2V2O7·2H2O的微米花结构,其分子式可表达为Zn3-3xM3x(OH)2V2O7·2H2O(其中M=Cu,Co,Ni,Mn;0.001≤x≤0.20)。应用XRD、SEM、TEM、UV-Vis DRS、EDX和BET等分析测试技术对产物进行了表征。结构和形貌分析结果显示过渡金属离子掺杂后产物仍保持Zn3(OH)2V2O7·2H2O的六方晶体结构,微米花由主晶面为(0001)的纳米片组装而成。紫外-可见漫反射光谱显示过渡金属离子掺杂后带边吸收红移,其中以Cu的掺杂产物Zn3-3xCu3x(OH)2V2O7·2H2O最为明显,带边吸收扩展到可见光区。首次对Zn3(OH)2V2O7·2H2O及其不同金属离子掺杂产物Zn3-3xM3x(OH)2V2O7·2H2O进行了可见光催化降解有机污染物的研究,结果显示与其它产物相比掺0.1at%Cu的Zn2.997Cu0.003(OH)2V2O7·2H2O对亚甲基蓝(MB)的可见光催化降解效果最好。对掺杂离子种类、掺杂离子浓度对产物可见光催化性质的影响也进行了考察。     

Pd促进ZnO/Al2O3催化乙醇水蒸气重整制氢

采用浸渍法制备了Pd促进ZnO/Al2O3催化剂, 考察了该催化剂作用时, 在水醇摩尔比为3, 常压和450 °C工作条件下乙醇水蒸气重整(SRE)制氢反应性能. 研究结果表明, 在该催化剂体系作用下的SRE反应过程中, H2、CH3CHO为主要产物, 与ZnO/Al2O3催化剂不同, Pd能促使CH3CHO发生C-C键断裂反应, 显著提高C2H5OH转化率及H2选择性, 分别达65%、55%. 还利用BET比表面积、透射电子显微镜(TEM)、热重-差示扫描量热-质谱(TG-DSC-MS)等表征手段考察了催化剂失活以及表面积炭情况, 发现Pd的加入对催化剂总积炭量并无明显影响.     

La2O3对Ni-Cu/MgSiO催化剂的甲烷部分氧化制氢反应性能的影响

 用等体积浸渍法制备了MgO-SiO2(MgSiO)复合氧化物负载的Ni-Cu双金属催化剂,采用程序升温还原(TPR),X光电子能谱(XPS),红外光谱(IR),程序升温脱附(TPD)及微反技术考察了稀土La2O3的加入对CH4和H2O在Ni-Cu/MgSiO催化剂表面上的吸附及甲烷部分氧化制氢反应性能的影响. 结果表明,加入La2O3使催化剂表面Ni和Cu原子的电子云密度增加,CH4和H2O在催化剂表面上的吸附增强. CH4与O2和H2O在Ni-Cu/MgSiO催化剂上反应的主要产物为H2和CO2. La2O3的加入有利于提高CH4转化率及H2的选择性,并可提高催化剂稳定性及抗积炭能力. 讨论了La2O3的助催化作用机理.     

Organic peroxide production in the Cl2-ethane-air photoreaction system

HPLC along with FT-IR technique was used to study the formation of organic peroxides in the Cl₂-ethane-air photoreaction system. Ethyl hydroperoxide (CH₃CH₂₁OOH, EHP) and peroxyacetic acid ( CH₃C(O)OOH, PAA) were conformed to be the peroxide product in the reaction system. In addition, methyl hydroperoxide (CH₃OOH, hydroxymethyl hydroperoxide (HOCH₂OOH, HMHP) and two unidentified organic peroxides were detected for the first time. EHP and were the dominant peroxide products. The identification of HMHP showed that Criegee biradical CH₂OO may be formed as an intermediate in the oxidation of ethane. Simulation results showed that photooxidation of ethane may make substantial contribution to source of organic peroxides in the atmosphere.     

Organic peroxide production in the Cl2-ethane-air photoreaction system

HPLC along with FT-IR technique was used to study the formation of organic peroxides in the Cl₂-ethane-air photoreaction system. Ethyl hydroperoxide (CH₃CH₂₁OOH, EHP) and peroxyacetic acid ( CH₃C(O)OOH, PAA) were conformed to be the peroxide product in the reaction system. In addition, methyl hydroperoxide (CH₃OOH, hydroxymethyl hydroperoxide (HOCH₂OOH, HMHP) and two unidentified organic peroxides were detected for the first time. EHP and were the dominant peroxide products. The identification of HMHP showed that Criegee biradical CH₂OO may be formed as an intermediate in the oxidation of ethane. Simulation results showed that photooxidation of ethane may make substantial contribution to source of organic peroxides in the atmosphere.     

高效液相色谱-荧光检测法测定环境样品中的过氧化物

对高效液相色谱-荧光检测法测定过氧化氢和有机过氧化物的方法进行了改进,从而提高了方法的检测灵敏度。以氯化血红素(hemin)作催化剂进行柱后衍生反应,过氧化物将对羟基苯乙酸氧化生成能吸收荧光的二聚物,然后用荧光检测器检测。实验确定了最佳反应管温度和荧光检测波长。应用该法测定了大气和雨水样品中过氧化物的浓度。     

Formation of organic peroxides in the photooxidation of CH4

The formation of organic peroxides in the Cl-atom-initiated photooxidation of CH₄ in O₂-N₂ mixtures at 101 325 Pa and 298 K was studied with HPLC and FT-IR methods. Four peroxidic products were detected, which were H₂O₂, hydroxymethyl hydroperoxide (HOCH₂OOH; HMHP), methyl peroxide (CH300H; MHP) and dimethyl peroxide (CH₃00CH₃). A chromatogram peak at retention time of 8.08 min was assigned tentatively to peroxyformic acid (HC(O)OOH). The identification of HMHP in the reaction system showed that one of the reaction paths for the self-reaction of CH₃00. led to producing Criegee intermediate CH₂OO. The formation mechanism of organic peroxide in the photooxidation of CH₄ is more complicated than it was assumed before. Photooxidation of CH₄ is probably an important source of organic peroxides in the troposphere. Project supported by the State Scientific and Technological Commission of China (Grant No. E96-05)     

Base-induced decomposition of alkyl hydroperoxides in the gas phase. Part 3. Kinetics and dynamics in HO- + CH3OOH, C2H5OOH, and tert-C4H9OOH reactions

The E(CO)2 elimination reactions of alkyl hydroperoxides proceed via abstraction of an alpha-hydrogen by a base: X(-) + R(1)R(2)HCOOH --> HX + R(1)R(2)C=O + HO(-). Efficiencies and product distributions for the reactions of the hydroxide anion with methyl, ethyl, and tert-butyl hydroperoxides are studied in the gas phase. On the basis of experiments using three isotopic analogues, HO(-) + CH3OOH, HO(-) + CD3OOH, and H(18)O(-) + CH3OOH, the overall intrinsic reaction efficiency is determined to be 80% or greater. The E(CO)2 decomposition is facile for these methylperoxide reactions, and predominates over competing proton transfer at the hydroperoxide moiety. The CH3CH2OOH reaction displays a similar E(CO)2 reactivity, whereas proton transfer and the formation of HOO(-) are the exclusive pathways observed for (CH3)3COOH, which has no alpha-hydrogen. All results are consistent with the E(CO)2 mechanism, transition state structure, and reaction energy diagrams calculated using the hybrid density functional B3LYP approach. Isotope labeling for HO(-) + CH3OOH also reveals some interaction between H2O and HO(-) within the E(CO)2 product complex [H2O...CH2=O...HO(-)]. There is little evidence, however, for the formation of the most exothermic products H2O + CH2(OH)O(-), which would arise from nucleophilic condensation of CH2=O and HO(-). The results suggest that the product dynamics are not totally statistical but are rather direct after the E(CO)2 transition state. The larger HO(-) + CH3CH2OOH system displays more statistical behavior during complex dissociation.     

Ground and electronically excited states of methyl hydroperoxide: comparison with hydrogen peroxide

Equilibrium geometries of the ground states of hydrogen peroxide (H(2)O(2)) and methyl hydroperoxide (CH(3)OOH) have been obtained using quadratic configuration interaction methods with correlation-consistent basis sets. These results are compared with experiments and prior calculations. The dipole moments of the ground states of these two molecules have been calculated. The results illustrate the sensitivity of this quantity to molecular geometry. Several excited states of H(2)O(2) and CH(3)OOH were calculated using the equation-of-motion coupled-cluster singles-and-doubles method. Aside from vertical excitation energies, excited state energies along the O-O, O-H, and C-O dissociation pathways were calculated. The results are expected to be of assistance in resolving discrepancies in the experimental interpretation of the UV absorption spectrum and photodissociation of CH(3)OOH.     

Vibrational overtone initiated unimolecular dissociation of HOCH2OOH and HOCD2OOH: evidence for mode selective behavior

The vibrational overtone induced unimolecular dissociation of HMHP (HOCH(2)OOH) and HMHP-d(2) (HOCD(2)OOH) into OH and HOCH(2)O (HOCD(2)O) fragments is investigated in the region of the 4nu(OH) and 5nu(OH) bands. The unimolecular dissociation rates in the threshold region, corresponding to the 4nu(OH) band, exhibit measurable differences associated with excitation of the OH stretch of the alcohol versus the peroxide functional group, with the higher energy alcohol OH stretching state exhibiting a slower dissociation rate compared to the lower energy peroxide OH stretch in both HMHP and HMHP-d(2). Predictions using the Rice-Ramsperger-Kassel-Marcus theory give rates that are in reasonably good agreement with the measured dissociation rate for the alcohol OH stretch but considerably differ from the measured rates for the peroxide OH stretch in both isotopomers. The present results are interpreted as suggesting that the extent of intramolecular vibrational energy redistribution (IVR) is different for the two OH stretching states associated with the two functional groups in HMHP, with IVR being substantially less complete for the peroxide OH stretch. Analysis of the OH fragment product state distributions in conjunction with phase-space theory simulation gives a D(0) value of 38+/-0.7 kcal/mole for breaking the peroxide bond in HMHP.