3-甲基-3-丁烯基-1-醇与硫酸/过氧化氢混合溶液的吸收反应研究

应用配置有湿式流动反应管的真空紫外激光单光子电离飞行时间质谱研究了3-甲基-3-丁烯基-1-醇气体在硫酸/过氧化氢混合溶液表面的吸收反应,实验中首次测得了反应的摄取系数,并根据气相产物信息推测了其反应机制.3-甲基-3-丁烯基-1-醇与硫酸/过氧化氢混合溶液的吸收反应速率很快,在ω（H2SO4）为40%～60%范围,摄取系数为2.52×10-4～1.05×10-2.在反应过程的气相收集物中检测出3种气相产物：乙醛、丙酮和3-甲基-3,4-环氧-1-丁醇,由此推测了3-甲基-3-丁烯基-1-醇与H2 SO4/H2 O2混合溶液的非均相反应机制.3-甲基-3,4-环氧-1-丁醇可以经过多步转化形成多羟基化合物,同时生成的醛酮化合物在酸性溶液中可进一步反应,这些对大气二次有机气溶胶的形成起着重要作用.因此,3-甲基-3-丁烯基-1-醇的非均相催化氧化过程可能对二次有机气溶胶的形成有重要贡献.     

Homogeneous and heterogeneous reactions of anthracene with selected atmospheric oxidants

The reactions of gas-phase anthracene and suspended anthracene particles with O3 and O3-NO were conducted in a 200-L reaction chamber, respectively. The secondary organic aerosol (SOA) formations from gas-phase reactions of anthracene with O3 and O3-NO were observed. Meanwhile, the size distributions and mass concentrations of SOA were monitored with a scanning mobility particle sizer (SMPS) during the formation processes. The rapid exponential growths of SOA reveal that the atmospheric lifetimes of gas-phase anthracene towards O3 and O3-NO are less than 20.5 and 4.34 hr, respectively. The particulate oxidation products from homogeneous and heterogeneous reactions were analyzed with a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). Gas chromatograph/mass spectrometer (GC/MS) analyses of oxidation products of anthracene were carried out for assigning the time-of-flight (TOF) mass spectra of products from homogeneous and heterogeneous reactions. Anthrone, anthraquinone, 9,10- dihydroxyanthracene, and 1,9,10-trihydroxyanthracene were the ozonation products of anthracene, while anthrone, anthraquinone, 9-nitroanthracene, and 1,8-dihydroxyanthraquinone were the main products of anthracene with O3-NO.     

Uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide

Multiphase acid-catalyzed oxidation by hydrogen peroxide has been suggested to be a potential route to secondary organic aerosol formation from isoprene and its gas-phase oxidation products, but the lack of kinetics data significantly limited the evaluation of this process in the atmosphere. Here we report the first measurement of the uptake of isoprene, methacrylic acid and methyl methacrylate into aqueous solutions of sulfuric acid and hydrogen peroxide. Isoprene cannot readily partition into the solution because of its high volatility and low solubility, which hinders its further liquid-phase oxidation. Both methacrylic acid and methyl methacrylate can enter the solutions and be oxidized by hydrogen peroxide, and steady-state uptake was observed with the acidity of solution above 30 wt.% and 70 wt.%, respectively. The steady-state uptake coefficient of methacrylic acid is much larger than that of methyl methacrylate for a solution with same acidity. These observations can be explained by the different reactivity of these two compounds caused by the different electron-withdrawing conjugation between carboxyl and ester groups. The atmospheric lifetimes were estimated based on the calculated steady-state uptake coefficients. These results demonstrate that the multiphase acid-catalyzed oxidation of methacrylic acid plays a role in secondary organic aerosol formation, but for isoprene and methyl methacrylate, this process is not important in the troposphere.     

Effect of NOx and SO2 on the photooxidation of methylglyoxal: Implications in secondary aerosol formation

Methylglyoxal(CH₃COCHO,MG),which is one of the most abundant α-dicarbonyl compounds in the atmosphere,has been reported as a major source of secondary organic aerosol(SOA).In this work,the reaction of MG with hydroxyl radicals was studied in a 500 L smog chamber at(293±3) K,atmospheric pressure,(18±2)% relative humidity,and under different NOx and SO₂.Particle size distribution was measured by using a scanning mobility particle sizer(SMPS) and the results showed that the ad...     

Study on the reaction of 3-methyl-2-butenal and 3-methylbutanal with Cl atoms: kinetics and reaction mechanism

The reaction of Cl atoms with two C₅ aldehydes (3-methyl-2-butenal and 3-methylbutanal) were investigated by proton-transfer-reaction mass spectrum (PTR-MS) using smog chamber at 298 ± 1 K and 760 Torr. A relative rate method was used to determine the rate constants of the title reactions with m-xylene and trans-2-butene as reference compounds: (3.04 ± 0.18)  ×  10⁻¹⁰ and (2.07 ± 0.14)  ×  10⁻¹⁰ cm³/(molecule⋅sec) for 3-methyl-2-butenal and 3-methylbutanal, respectively. Additionally, the gas-phase products were also identified by PTR-MS, and the possible reaction mechanisms were proposed basing on the identified products. The detected gas-phase products are similar for two C₅ aldehydes reactions, mainly including small molecules of aldehydes, ketones and chlorinated aldehyde compounds. The atmospheric lifetimes (τ) calculated for 3-methyl-2-butenal (τ = 7.0 hr, marine boundary layer (MBL)) and 3-methylbutanal (τ = 10.3 hr, MBL) according to the obtained rate constants. The results indicate that Cl atoms at MBL are competitive with OH radicals for the degradation contribution of C₅ aldehyde compounds.     

Observations of N2O5 and NO3 at a suburban environment in Yangtze river delta in China: Estimating heterogeneous N2O5 uptake coefficients

The nitrate radical(NO₃) and dinitrogen pentoxide(N_2.5) play an important role in the nocturnal atmosphere chemistry.Observations of N03 radicals and N₂ O₅ were performed in a semirural ground site at Tai’Zhou in polluted southern China using cavity ring down spectroscopy(CRDS) from 23 May to 15 June 2018.The observed N03 and N₂ O₅ concentrations were relatively low,with 1 min average value of 4.4±2.2 and 26.0±35.7 pptV,respective...     

位阻胺混合甘氨酸盐溶液吸收CO2的研究

在双搅拌反应釜中研究了位阻胺2-氨基-2-甲基-1-丙醇(AMP)与甘氨酸钠(SG)混合溶液吸收CO2的性能.实验温度293~313K,混合溶液的浓度为AMP(1.5kmol/m3)+SG (0.2,0.4,0.6,0.8kmol/m3),SG浓度每增加0.2kmol/m3,200min内的平均吸收速率分别提高11.47%,10.07%,9.18%和5.33%.与AMP单一溶液相比,混合溶液在200 min时的吸收容量增加了11.5%~41.1%.在293~313K,吸收速率随温度上升而提高.使用加热的方法进行再生实验,得到1.5 kmol/m3 AMP + 0.6 kmol/m3 SG混合液的最适再生温度为378K.AMP + SG混合溶液的再生效率高于单一SG溶液及AMP + MEA/DEA混合溶液.     

Morphology-dependent interfacial interactions of Fe2O3 with Ag nanoparticles for determining the catalytic reduction of p-nitrophenol

In this work,we fabricated three kinds of Ag/Fe₂O₃ model catalysts with different morphologies to study the interfacial interactions between Ag and Fe₂O₃,and how they affected the catalytic activity in hydrogenation of p-nitrophenol was explored.The hydrothermal method was used to synthesize the metal oxide supported silver catalyst,with various morphologies including nanoplates(NPs),nanospheres(NSs),and nanocubes(NCs).The crystal structure,morphology ...     

NOx和/或NH3气氛下SO2在高岭土表面非均相转化的实验研究

利用自制气溶胶反应器研究了NO_x和/或NH_3气氛下SO_2在高岭土表面的非均相转化过程,应用扫描电镜(SEM)对高岭土颗粒物形貌进行了表征.结果表明:高岭土颗粒表面的SO_2非均相转化致使其成分和形貌产生了较大变化.相同实验条件下,SO_2转化的协同作用程度由高到低依次为NH_3、NO_x/NH_3和NO_x气氛,相对湿度40%、有光照条件下,SO_2转化量增幅最高可分别达125%、75%和50%.所有气氛下,协同作用在无光照时在高相对湿度(40%~70%)区间更为突出,有光照时其显著性则体现在低相对湿度(20%~40%)区间.SO_2、NO_x、NH_3三者共存时,在高岭土颗粒表面发生的非均相反应过程既有协同作用又存在竞争反应.     

ZnMnxCo2-xO4活化过一硫酸盐降解有机污染物

分别以Zn（CH₃COO）₂·2H₂O、Mn（CH₃COO）₃·2H₂O和Co（CH₃COO）₂·4H₂O为锌源、锰源和钴源,采用溶胶-凝胶自燃烧法成功制备了ZnMn_xCo_2-xO₄（x=0~2）复合物,并用X射线衍射和X射线光电子能谱对其进行表征.同时,还研究了Mn/Co物质的量比、催化剂用量及PMS用量对目标污染物降解的影响.结果表明,该复合物可催化活化过一硫酸钾（PMS）降解有机污染物,当催化剂中x=0.8,催化剂投加量为0.2 g·L^-1,PMS用量为0.4 mmol·L^-1（0.25 g·L^-1）时,20 μmol·L^-1（10 mg·L^-1）罗丹明B（RhB）可在15 min内完全降解.ZnMn_0.8Co_1.2O₄的高催化活性主要归功于Mn³⁺和Co²⁺的协同效应.将ZnMn_xCo_2-xO₄-PMS体系用于亚甲基蓝、结晶紫、金橙、双酚A、4-氯酚等其他污染物的降解,也取得了较好的效果.基于电子自旋共振ESR和自由基猝灭实验的结果,可以推测该反应体系中活性物种为硫酸根自由基和羟基自由基.     

Fe2O3(1-12)作用下CO化学链燃烧反应机理研究

在化学链燃烧(CLC)过程中,载氧体表面的原子结构和电子特性决定了其化学反应活性.本文以Fe_2O_3为载氧体,探讨了其自然条件下主要裸露的高米勒数指表面(1-1 2)的结构性质,研究发现表面不同配位数的氧和铁原子(包括O2f、O3f、O4f、Fe4f和Fe5f)的键参数、电子态密度及电荷布居等存在明显差异.为探究这种差异对Fe_2O_3反应活性的影响,对比分析了CO在表面5种氧和铁原子位生成CO_2的吸附-反应机理.CO在表面低配位O原子O2f和O3f首先形成物理吸附,然后被晶格氧氧化生成CO_2,反应需要克服能垒分别为3.657 e V和3.401 e V;然而,CO在O4f位吸附时,首先克服1.864 e V能垒形成二齿形碳酸盐物种,之后克服1.097 e V的能垒形成CO_2.当CO在Fe4f和Fe5f位吸附时,CO与Fe原子成键,后经过活化与表面O原子成键,形成二齿形碳酸盐物种,能垒分别为0.416和0.219 e V,最终碳酸盐物种分别克服0.500和1.462e V的能垒生成CO_2.因此,可以推断表面高配位数的O4f、Fe4f和Fe5f原子,由于其较高的氧化态,在化学链燃烧过程中充当活性位的作用.本研究有助于了解铁基载氧体表面化学链燃烧反应的微观机理,并为载氧体表面结构性能调控制备提供理论借鉴.     

Preparation of MnO2 decorated Co3Fe1Ox powder/monolithic catalyst with improved catalytic activity for toluene oxidation

In this paper, KMnO₄ was used to pre-treat Co₃ Fe-layered double hydroxides(LDH) precursor to prepare MnO₂ decorated Co₃Fe₁O_x catalyst. The toluene oxidation performance of the catalyst was investigated systematically. The optimized 0.1 Mn CF-LDO catalyst exhibited the best catalytic performance, and the temperatures of 50% and 90% toluene conversion( T₅₀ and T₉₀) were 218 and 243 ℃, respectively. The apparen...