SO2存在下钠、钙、铁及其复合物对NO-半焦反应的催化作用

采用程序升温还原技术,在SO2存在气氛下,对钠、钙、铁及其复合物的NO-半焦催化反应性能进行了研究。结果表明,在相同条件下三种金属对NO-半焦反应的催化活性顺序为：Fe>Ca>Na。SO2可能通过参与氧传递过程来影响金属对NO-半焦反应的催化活性。SO2的浓度对负载三种不同金属半焦催化活性的影响是不同的。SO2浓度对负载钠半焦的催化活性影响最为显著。在SO2存在气氛下,负载2％钠或铁和负载3％钙的半焦具有高的NO转化活性。在SO2存在气氛下,钠－钙和钠－铁二元金属复合催化剂的活性较高,这可能是由于这两种金属间存在协同作用的缘故。     

杂原子修饰的碳纳米管对高级氧化过程的催化性能(英文)

Multi-walled carbon nanotubes (CNTs) were submitted to chemical and thermal treatments in order to incorporate different heteroatoms on the surface. O-, S- and N-containing groups were successfully introduced onto the CNTs without significant changes of the textural properties. The cata-lytic activity of these heteroatom-modified CNTs was studied in two liquid phase oxidation processes: catalytic ozonation and catalytic wet air oxidation (CWAO), using oxalic acid and phenol as model compounds. In both cases, the presence of strongly acidic O-containing groups was found to decrease the catalytic activity of the CNTs. On the other hand, the introduction of S species (mainly sulfonic acids) enhanced the removal rate of the model compounds, particularly in the CWAO of phenol. Additional experiments were performed with a radical scavenger and sodium persulfate, in order to clarify the reaction mechanism. Nitrogen functionalities improve the catalytic performance of the original CNTs, regardless of the process or of the pollutant.     

负载型钙钛矿催化氧化NO及抗SO_2性能研究

采用柠檬酸络合浸渍法制备了负载型钙钛矿氧化物La1-xCexCoO3/CeO2(x=0~0.3)催化剂,考察了不同Ce掺杂量对其催化氧化NO和抗硫性能的影响,并运用X射线衍射(XRD)、傅里叶红外光谱(FT-IR)、氮气物理吸附、程序升温还原(H2-TPR)、氧气程序升温脱附(O2-TPD)等手段对催化剂进行了表征。结果表明,催化剂的活性与其比表面积大小和氧化还原性质密切相关;其中,负载型钙钛矿La0.8Ce0.2CoO3/CeO2催化剂在300℃时催化氧化NO的转化率达78%。在添加CeO2作载体后,不仅改善了非负载性钙钛矿的低温活性,而且抗硫性能也显著提高。     

Enabling continuous-flow chemistry in microstructured devices for pharmaceutical and fine-chemical production

Microstructured devices offer unique transport capabilities for rapid mixing, enhanced heat and mass transfer and can handle small amounts of dangerous or unstable materials. The integration of reaction kinetics into fluid dynamics and transport phenomena is essential for successful application from process design in laboratory to chemical production. Strategies to implement production campaigns up to tons of pharmaceutical chemicals are discussed, based on Lonza projects.     

Effect of SO2 on the catalytic activity of SnO2 and CeO2 in methane oxidation

The variation of the catalytic activity of tin and cerium dioxides in the combustion of SO₂-containing methane has been investigated at SO₂ concentrations of 50 to 1000 ppm in the gas stream. The catalytic activity of SnO₂ decreases dramatically upon the introduction of SO₂, but it returns rapidly to its initial level and then remains invariable (95% conversion, operating temperature of 600°C). Cerium dioxide is much less resistant to poisoning with sulfur dioxide: the higher the SO₂ concentration in the gas stream, the larger the decrease in its activity. After sulfur dioxide is cut off, CeO₂ regains its initial activity at 750°C. The behaviors of SnO₂ and CeO₂ are in agreement with the thermal stabilities of the corresponding sulfates and oxosulfates.     

Ni-Cu /La2O3催化剂上甲烷部分氧化制合成气

用浸渍法制备了不同Cu质量分数的Ni Cu/La2O3双金属催化剂,考察了金属浸渍顺序和Cu质量分数对催化剂甲烷部分氧化性能的影响,并通过BET、XRD、TPR和SEM等技术对催化剂进行了表征。结果表明,在甲烷部分氧化制合成气反应中,Cu助剂的添加对Ni/La2O3催化剂的活性有一定的改进作用,其中浸渍顺序对催化剂的性能影响很大,共浸渍制备的催化剂活性相对较好;Cu质量分数为5%~7%时催化剂有较好的活性和稳定性;XRD等测试表明,Cu和Ni金属由于相同的晶型结构及离子半径在制备过程中形成了双金属固溶体,提高了活性组分Ni的分散度,减少了Ni晶粒的烧结聚集长大,从而提高了催化剂的活性和稳定性。     

A computational study of the oxidation of SO2 to SO3 by gas-phase organic oxidants

We have studied the oxidation of SO(2) to SO(3) by four peroxyradicals and two carbonyl oxides (Criegee intermediates) using both density functional theory, B3LYP, and explicitly correlated coupled cluster theory, CCSD(T)-F12. All the studied peroxyradicals react very slowly with SO(2) due to energy barriers (activation energies) of around 10 kcal/mol or more. We find that water molecules are not able to catalyze these reactions. The reaction of stabilized Criegee intermediates with SO(2) is predicted to be fast, as the transition states for these oxidation reactions are below the free reactants in energy. The atmospheric relevance of these reactions depends on the lifetimes of the Criegee intermediates, which, at present, is highly uncertain.     

Efficient low-temperature oxidation of carbon-cluster anions by SO2

Carbon-cluster anions, CN-, are very reactive toward SO2 (sticking probability of 0.012 +/- 0.005 for C27- at 25 degrees C), in contrast to their inertness toward other common atmospheric gases and pollutants. In flow reactor experiments at ambient temperature and near atmospheric pressure, primary adsorption of SO2 by the carbon cluster anions, N = 4-60, yields CNSO2- or CN-1S-. The inferred elimination of neutral CO2 is also detected as meta-stable decay in collision-induced dissociation. At higher temperatures, the reaction of SO2 with nascent carbon clusters yields CN-1SO- as well as undetected CO. The size-dependent initial reactivity reflects the previously established structural transitions (i.e., from chain to cyclic to cage structures). Such carbon clusters are formed in sooting flames and may act as nuclei for the formation of primary soot particles and serve as models for the local structural features of active soot particle sites for black-carbon soot. The facile generation of reactive carbon-sulfide and -sulfinate units may therefore have implications for understanding the health and environmental effects attributed to the coincidence of soot and SO2.     

异羟肟酸过渡金属配合物对对氯甲苯催化氧化性能的研究

考察了N-羟基-N-苯基苯甲酰胺的钴、锰和铜配合物在对氯甲苯液相氧化生成对氯苯甲酸反应中的催化性能.考察了反应温度、催化剂浓度、中心金属离子、以及助催化剂对催化氧化反应的影响,发现以钴配合物为催化剂,反应温度为140℃,催化剂浓度为1.0 × 10-3 mol·L-1为最佳反应条件.添加NaBr和四甘醇能促进对氯甲苯的...     

Study on electrochemical performance of activated carbon in aqueous Li2SO4, Na2SO4 and K2SO4 electrolytes

The electrochemical performances of activated carbon (AC) in 0.5 mol/l Li₂SO₄, Na₂SO₄ and K₂SO₄ aqueous electrolytes were investigated. The cyclic voltammetric results at different scan rates show that the rate behaviors of AC in the three electrolytes improve in the order of Li₂SO₄ < Na₂SO₄ < K₂SO₄. This improvement can be mainly ascribed to the following two reasons: (1) the decreasing equivalent series resistance in the order of Li₂SO₄ > Na₂SO₄ > K₂SO₄, which is the main factor influencing the maximum output power, and (2) the increasing migration speed of hydrated ions in the bulk electrolyte and in the inner pores of AC electrode in the order of Li⁺ < Na⁺ < K⁺. Their cycling behaviors do not show any differences in capacitive fading. The above results provide valuable information to explore new hybrid supercapacitors.     

Nonisocyanate based polyurethane/silica nanocomposites and their coating performance

A series of silica nano-particles with different size were prepared by sol–gel technique, then surface modification by using cyclic carbonate functional organoalkoxysilane (CPS) was performed. Various amounts of carbonated silica particles directly added into carbonated soybean oil (CSBO) and carbonated polypropylene glycol (CPPG) resin mixture to prepare polyurethane–silica nanocomposite coating compositions by nonisocyanate route using an aliphatic diamine as a curing agent. Cupping, gloss, impact, and taber abrasion tests were performed on aluminum panels coated with those nano-composite formulations and tensile tests, thermogravimetric and SEM analyses were conducted on the free films prepared from the same coating formulations. An increase in abrasion resistance of CSBO-CPPG resin combination with the addition of silica was observed. In addition, the maximum weight loss of CSBO-CPPG resin combination was shifted to higher temperatures with incorporation of silica nano-particles The positive effect of modified silica particles on thermal stability of CSBO-CPPG system could be explained in such a way that PPG chains are able to disperse particles in the medium throughout the interactions between ether linkages and silanol groups.     

稀土-铁催化剂催化还原烟气中SO2制硫磺

以煤气为还原气,以Fe为主活性金属,稀土为助剂催化还原冶炼烟气中SO2制取硫磺,研究了不同稀土、不同稀土含量及不同催化剂制备方式对稀土-过渡金属催化剂催化还原SO2制硫磺活性的影响,并考察了其反应机制.结果表明:不同稀土对Fe/Al2O3催化剂有不同的改性作用,Sm和Dy的加人大大提高了催化剂的活性,在360 ℃时,smFe/Al2O3的硫产率增大到86.62%,比同温度下Fe/Al2O3的提高了40.5%;在400℃时,DyFe/Al2O3的硫产率增大到91.62%.比同温度下Fe/Al2O3的提高了26.4%;REFe/Al2O3催化剂的活性与稀土含量有一定的关系,对SmFe/Al2O3催化剂,稀土Sm的最佳含量为1.0%;不同方式制备的稀土催化剂活性不同,对硫产率来说其大小顺序为:钐铁溶液混浸>先浸钐后浸铁>先浸铁后浸钐;煤气还原SO2的反应机制为中间产物机制.     

Electron paramagnetic resonance study of V2O5 deactivation in the course of catalytic oxidation of SO2 to SO3

The influence of reagents interactions with V2O5 catalyst on its activity in the reaction of SO2 oxidation has been investigated by electron paramagnetic resonance (EPR) method. It was found that the deactivation of V2O5 is caused by the diminishing of the number of adsorption centers able to interact with reagent molecules and with the creation of elements of the VOSO4 phase.     

固体超强酸催化剂SO2-4/TiO2-WO3的制备及其催化性能研究

制备了固体超强酸催化剂SO2-4/TiO2-WO3,并以丁酸丁酯的合成作为探针反应,系统考察了WO3的含量、硫酸浸渍浓度、焙烧温度等制备条件对SO2-4/TiO2-WO3催化活性的影响.实验表明:制备催化剂的适宜条件为m(H2WO4)=12.5%,硫酸浸渍浓度为1.0 mol·L-1,焙烧温度为580℃,活化时间3 h.利用优化条件下制备的催化剂SO2-4/TiO2-WO3催化合成缩醛(酮),在醛/酮与二元醇(乙二醇,1,2-丙二醇)的投料摩尔比为1:1.5,催化剂的用量占反应物总投料质量的0.5%,反应时间为l h条件下,2-甲基-2-乙氧羰甲基-1,3-二氧环戊烷的收率为78.7%,2,4-二甲基-2-乙氧羰甲基-1,3-二氧环戊烷的收率为83.0%,环己酮-乙二醇缩酮的收率为85.9%,环己酮-1,2-丙二醇缩酮的收率为84.6%,丁酮-乙二醇缩酮的收率为70.7%,丁酮-1,2-丙二醇缩酮的收率为88.3%,2-丙基-1,3-二氧环戊烷的收率为80.6%,4-甲基-2-丙基-1,3-二氧环戊烷的收率为79.6%,2-异丙基-1,3-二氧环戊烷的收率为64.2%,4-甲基-2-异丙基-1,3-二氧环戊烷的收率为83.3%,2-苯基-l,3-二氧环戊烷的收率为75.3%,4-甲基-2-苯基-1,3-二氧环戊烷的收率为95.1%.     

Au/TS-1选择性催化氧化NO性能研究

制备了负载型Au/TS-1催化剂,采用XRD、SEM、TEM等方法进行了表征,并将其应用于选择性催化氧化NO反应,考察了各工艺条件对NO催化氧化效率的影响。结果表明,Au/TS-1催化剂具有良好的结晶度,Au粒子成功地负载在TS-1上。该催化剂在选择性催化氧化NO反应中具有优异的低温催化氧化活性,在NO体积分数为1×10-3,O2含量为10%,空速为5 000 h-1,Au的负载量为1.0%,180℃时,NO的氧化率高于55%(此时最适宜吸收处理);260℃时,氧化率可达到78%。     

Drop size effect on the rate and mechanism of SO2 oxidation in tropospheric clouds

The drop size effect on the rate and mechanism of sulfur dioxide oxidation in tropospheric clouds is analyzed. In the daytime, the oxidation rate decreases as the drops grow. This effect is due to the fact that the liquid-phase reactions slow down because of a decreasing influx of oxidizing species, namely, H₂O₂, OH^., HO^. ₂, and O₃. The effect of the nonuniformity of OH^. and O₃ distribution in the drop bulk on the reaction rate is discovered.     

SO2对NO催化氧化过程的影响(Ⅱ)载体γ-Al2O3与SO2的相互作用

考察了423K时SO2在γ-Al2O3上反复作用对NO氧化过程的影响。结果显示，SO2的存在在一段时间内促进了γ-Al2O3对NO的催化氧化。用TPD，FTIR，XRD，BET及固体酸度测定等多种表征讨论了γ-Al2O3和SO2之间的相互作用。研究表明，SO2在γ-Al2O3表面与NO等吸附物结合形成活性吸附物种是γ-Al2O3在SO2气氛中显示氧化活性的重要原因，但当其表面被强吸附的SO2逐步覆盖后，则活性下降。     

2-Sulfiliminopyridines and their oxidation to 2-nitropyridines

Sulfilimines of the pyridine series with electron-acceptor substituents in the ring were synthesized. It was shown that their oxidation with trifluoroperacetic acid results in the corresponding nitropyridines. The limitations of the methods were indicated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1536–1538, November, 1990.The authors with to express their gratitude to Yu. A. Strelenko for his help in interpretation of the ¹³C NMR spectra.     

Catalytic wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene

The rates of wet air oxidation of 2-nitrotoluidine and 2,4-dinitrotoluene in the presence of excess oxygen and at different temperatures and oxygen pressures was investigated. Oxidation experiments were carried out at temperatures between 180 and 225^oC and oxygen partial pressures of 1,0-3,0 MPa, in a 280 mL glass vessel-inserted stainless steel reactor. Copper sulfate (CuSO₄ .5H₂O) was used as a catalyst, and the effect of catalyst loading was studied by varying the concentration: 0.75, 2.5 and 25 mg/L as Cu²⁺. Addition of Cu²⁺ ions in the reaction media accelerated 2-nitrotoluidine oxidation nearly ten times even if it exists in trace amount in the reaction medium (0.75 ppm Cu²⁺). Unfortunately copper did not show catalytic effect for the oxidation of 2,4-dinitrotoluene. This revised version was published online in August 2006 with corrections to the Cover Date.     

Size effects in the catalysis of atmospheric oxidation of SO2 by iron ions

The oxidation of SO₂ catalyzed by iron ions in cloud drops of various sizes is analyzed in terms of the reduced model of atmospheric processes. It is demonstrated for the first time that iron ions exert a catalytic effect only in the smallest (<5 μm) and the largest (>100 μm) drops. This behavior of iron ions is due to the variation of the concentration ratio between the active form Fe(III) and the inactive form Fe(II) in the drops. SO₂ oxidation in drops of intermediate sizes is slower, because most of the iron in these drops is in the Fe(II) state.