丁二烯在氧气中的氧化反应特性及产物

采用小型密闭压力容器试验(MCPVT)装置,考察丁二烯的氧化特性,用碘量法测定氧化过程的过氧化值,探讨丁二烯的初期可能氧化反应生成,用顶空(进样)-气相色谱-质谱联用(HS-GC-MS)技术测定反应产物。结果表明,在氮气氛围中,即使到达105℃也未检测到丁二烯发生反应,在氧气氛围中,45℃下能测定过氧化物生成,65℃反应26 h,过氧化值达到9.1 mmol/kg。在70～100℃下,MCPVT能观察到显著的化学反应产生,压力减少。丁二烯在氧气中的反应是复杂的,主要产物有丙烯醛、呋喃、2,5二氢呋喃、2,3二氢呋喃、反式1,2-二乙烯基环丁烷、4-乙烯基环己烯、1,5-环辛二烯等。     

三元硝酸熔盐高温热稳定性实验研究与机理分析

通过熔盐质量损失率和试样中NO2-含量变化状况,以及熔盐材料的热重(TG)曲线,研究了三元硝酸熔盐(53%KNO3-40%NaNO2-7%NaNO3)在空气和氮气气氛中高温条件下的热稳定性性能。结果表明,三元硝酸熔盐空气中的上限使用温度为773K,高温时存在劣化现象;而在氮气气氛中三元熔盐的热分解温度为723K。同时,从热力学和动力学角度分析得到,三元硝酸熔盐在773K以下空气中发生的反应为亚硝酸钠的分解和氧化;而在氮气气氛中三元熔盐723K以下时主要发生的是亚硝酸钠的分解反应。在氧气含量一定的情况下,氧气的扩散和亚硝酸盐的分解反应符合一级反应动力学模型。     

V-Mg-O催化剂上丁烷氧化脱氢动力学研究

制备了V－Mg-O催化剂,并测定了在该催化剂上进行丁烷氧化脱氢的反应动力学。应用BET和X射线衍射技术对催化剂进行了表征,在反应温度793－873K范围内,改变接触时间（W／F）和丁烷与氧气的分压进行了动力学实验。在所有的实验条件下,产物主要有脱氢产物（丁烯、丁二烯）、CO和CO2。提出了一个包括C4烯烃、COx生成反应的反应网络;从所测量的动力学数据中得到了合适的幂率型动力学方程。因为氧化脱氧反应的表观活化能比深度氧化反应的表观活化能大,在相同转化率时,C4烯烃选择性随着反应温度的提高而增加。     

焦炉气非催化部分氧化制合成气数值模拟

基于Curran反应机理,采用Chemkin软件对贫氧条件下的焦炉气非催化部分氧化过程进行了模拟,并考察了反应温度、反应压力和氧气与焦炉气物质的量之比对焦炉气非催化部分氧化制合成气反应的影响。结果表明:该模型能较好地模拟工业操作条件下的焦炉气非催化部分氧化反应;焦炉气非催化部分氧化动力学时间尺度为毫秒级;反应温度越高,动力学时间越短,当温度提高至1373 K后,动力学时间未见明显缩短;反应压力越大,动力学时间越短,当压力提高至3.0MPa后,动力学时间未见明显缩短;氧气和焦炉气物质的量之比越大,动力学时间越短,但得到的合成气摩尔分数以及H_2和CO物质的量之比也相应降低:当氧气和焦炉气物质的量之比增大至0.262后,合成气中H2和CO物质的量之比维持在2.0~2.5。     

低温下2,5-二甲基呋喃的氧化动力学及产物研究

建立了2,5-二甲基呋喃(DMF)的气相色谱(GC)定量分析方法,跟踪测定DMF在低温下的氧化过程及动力学,用碘量法测定了DMF过氧化物的生成,并测定了DMF的氧化产物。结果表明,DMF与氧气在低温下的氧化呈现表观一级反应,温度为323.15,333.15,343.15,353.15,363.15 K时的反应速率常数分别为:0.004 6,0.006 4,0.008 9,0.011 8,0.015 0 h~(-1),反应表观活化能为29.08 k J/mol。在363.15 K反应10 h,主要氧化产物为5-甲基-2-呋喃甲醇(7.3%),反-3-己烯-2,5-二酮(70.8%),5-甲基-2-呋喃甲醛(13.4%),其他(8.5%)。     

含乙醇废水的超临界水氧化反应动力学及反应机理

研究了等温平推流反应器中乙醇的超临界水氧化反应（SCWO）,反应温度475～550 ℃、压力22～30 MPa、停留时间0.6～63.7 s、氧气与乙醇摩尔浓度比4.56～9.09.一氧化碳和二氧化碳分别是反应中间产物和最终产物.随停留时间增大、温度升高,乙醇去除率增大,压力和氧气浓度变化对过程无显著影响.以幂指数方程描述乙醇SCWO动力学,乙醇和氧气的反应级数分别为1和0,计算值和实验值相差基本在10%以内.超临界条件下分别以过氧化氢和氧气为氧化剂时乙醇的氧化反应无明显差别,亚临界条件下过氧化氢氧化速率大于氧气.基于对此现象的分析,作者推测：无论以过氧化氢或氧气作为氧化剂,在超临界水中,它们之间可以通过一系列自由基反应迅速达到平衡,且各物种的平衡分布与初始分布无关,体系的主要氧化过程在平衡分布下进行.     

低温下2,5-二甲基呋喃的氧化动力学及产物研究

建立了2,5-二甲基呋喃(DMF)的气相色谱(GC)定量分析方法,跟踪测定DMF在低温下的氧化过程及动力学,用碘量法测定了DMF过氧化物的生成,并测定了DMF的氧化产物。结果表明,DMF与氧气在低温下的氧化呈现表观一级反应,温度为323.15,333.15,343.15,353.15,363.15 K时的反应速率常数分别为:0.004 6,0.006 4,0.008 9,0.011 8,0.015 0 h^(-1),反应表观活化能为29.08 k J/mol。在363.15 K反应10 h,主要氧化产物为5-甲基-2-呋喃甲醇(7.3%),反-3-己烯-2,5-二酮(70.8%),5-甲基-2-呋喃甲醛(13.4%),其他(8.5%)。     

低阶煤低温氧化过程热力学规律的研究

采用pulse calorimeter仪器,分别研究了低温下低阶煤在湿的氮气气氛下凝结热与蒸发热间的热力学规律,以及在湿的氧气气氛下反应热与蒸发热间的热力学规律;还研究了低阶煤在干燥氧气下经三次低温氧化反应的热力学规律.结果表明,在湿的氮气下,凝结热和蒸发热均随温度的增加而减少,在温度299.15 K～323.15 K范围内,凝结热明显大于蒸发热值,随着温度增加二者差值变小;在湿氧气气氛下,随温度增加,反应热先减少后增加,其蒸发热与湿氮气条件相比,二者的热值及热力学规律基本相同;低阶煤经三次低温氧化反应过程,其中二、三次氧化反应的反应热与第一次相比显著降低.     

超临界水氧化法处理黑索今废水的试验

用超临界水氧化法处理黑索今(RDX)废水进行了试验研究,探讨了反应温度、时间和压力等因素对处理效果的影响。试验结果表明:在氧气过量的条件下,温度是超临界水氧化黑索今废水的主要影响因素,其次是反应压力和反应时间;当反应温度为600℃,反应压力为28MPa,反应时间大于120s时,废水的CODCr去除率高达99.8%。     

Pd-Ag/Al2O3催化剂上丁二烯的加氢反应性能

对Pd-Ag/Al2O3催化剂在裂解混合碳四选择加氢制丁烯反应中的性能进行了研究。实验结果表明,1,3-丁二烯加氢生成1-丁烯的选择性与反应器入口1,3-丁二烯浓度和氢/丁二烯比密切相关,在反应器入口温度40℃、反应压力1.0 MPa、液空速40 h 1的条件下,当入口丁二烯摩尔分数大于2.6%,1-丁烯选择性维持在66%以上;当入口丁二烯摩尔分数降至2.6%以下时,1-丁烯选择性开始下降;当反应器入口1,3-丁二烯摩尔分数小于1.0%时,出口1,3-丁二烯摩尔分数可降至小于1.0×10-5。当反应器入口1,3-丁二烯摩尔分数为0.50%～0.85%时,1-丁烯选择性随着氢/丁二烯摩尔比的增加呈现线性下降趋势,表明过量的氢气是发生丁烯的异构化和加氢反应的重要原因。H2-TPR和XPS表征结果显示,Pd-Ag/Al2O3中的Pd和Ag还原过程中形成了Pd-Ag合金。     

Hydrogenation of 1,3-butadiene on platinum surfaces of different structures

1,3-butadiene hydrogenation is studied on platinum foil and Pt(111), Pt(100), Pt(755) single-crystal surfaces at 300--375 K. The results are compared with the data of alkene hydrogenation reactions. Similar to the hydrogenation kinetics of butenes, 1,3-butadiene hydrogenation exhibits near zeroth-order dependence on hydrocarbon and near first-order dependence on hydrogen pressure. With the same hydrocarbon (3.5-70 Torr) and hydrogen (14-140 Torr) pressure, the rate of 1,3-butadiene hydrogenation is one order of magnitude lower than for the rates for n-butenes. The hydrogenation products include 1-butene, trans- and cis-2-butene, and n-butane. The reaction selectivity is independent of reactant mixture and platinum surface structure, but changes slightly as a function of reaction temperature. The butene product distribution is determined by surface reaction kinetics. While 1-butene is thermodynamically less stable than trans- and cis-2-butene, it is the major butene product in 1,3-butadiene hydrogenation. This revised version was published online in July 2006 with corrections to the Cover Date.     

中高温下SiAlON-SiC和Si3N4-SiC材料的氧化行为

通过研究SiAlON-SiC和Si3N4-SiC制品在1073K、1123K、1173K和1223K空气中氧化100h后的动态质量变化及氧化前后显气孔率、体积密度和孔径分布的改变来反映制品的抗氧化性能。结果表明,浇注成型SiAlON-SiC(简称CS)试样抗氧化性能最好,压力成型SiAlON-SiC(简称PS)试样次之,压力成型Si3N4-SiC(简称PN)试样最差。动力学分析发现,制品氧化前期符合界面反应控速模型,氧化后期符合扩散控速模型,且前后期的反应速度常数k都符合关系:kPN>kPS>kCS,k1223K>k1173K>k1123K>k1073K。     

Formation of C4 species in the deactivation of a Pd/SiO2 catalyst during the selective hydrogenation of acetylene

The deactivation characteristics of Pd/SiO₂ in the selective hydrogenation of acetylene were correlated with changes in the amount of the C4 species produced. The amounts of butenes produced changed in parallel with the catalyst activity, indicating that the rate limiting step for butene production was the same as that for acetylene hydrogenation. On the other hand, the amount of 1,3-butadiene produced changed, showing a maximum with catalyst deactivation because 1,3-butadiene is an intermediate in the sequential reaction process which involves both the production and consumption of 1,3-butadiene. This was verified by a simultaneous TG/reaction experiment showing that 1,3-butadiene was a precursor of green oil. The catalyst showed a self-regenerative behavior in its activity and the amounts of C4 species produced during the early stage of deactivation because two opposite factors, which contributed to either the lowering or the promotion of activity, were involved in the process. A specific type of polymer species, produced during the initial period of deactivation, is proposed to be responsible for the promotion of catalyst activity.     

Combined UHV and ambient pressure studies of 1,3-butadiene adsorption and reaction on Pd(1 1 1) by GC,IRAS and XPS

The hydrogenation of 1,3-butadiene on Pd(1 1 1) at 300 K was studied at atmospheric pressure by infrared reflection absorption spectroscopy (IRAS) and gas chromatography (GC). Kinetic measurements showed 1-butene, trans-2-butene and cis-2-butene as primary products. Once 1,3-butadiene had been completely consumed, 1-butene was re-adsorbed on the surface producing trans-/cis-2-butene through isomerization and n-butane through hydrogenation. These results were corroborated by in situ IRAS spectroscopy. Post-reaction analysis by X-ray photoelectron spectroscopy (XPS) in the C1s region revealed a band at 284.2 eV, corresponding to adsorbed butadiene and/or carbonaceous deposits. Quantification of this peak revealed a total carbon coverage of 0.3 ML. Nevertheless, deactivation due to carbon deposition was a minor effect under our reaction conditions, as indicated by the kinetics of the subsequent butene hydrogenation reaction. Temperature-dependent XPS experiments after butadiene adsorption at 100 K indicated a high stability of the diene molecule with hardly any desorption and/or decomposition up to 500 K. Above this temperature, butadiene decomposed to carbon species that eventually dissolved in the Pd bulk above 700 K.     

Effects of Oxygen Transfer Limitation and Kinetic Control on Biomimetic Catalytic Oxidation of Toluene

Under oxygen transfer limitation and kinetic control, liquid-phase catalytic oxidation of toluene over metalloporphyrin was studied. An improved technique of measuring dissolved oxygen levels for gas-liquid reaction at the elevated temperature and pressure was used to take the sequential data in the oxidation of toluene catalyzed by metalloporphyrin. By this technique the corresponding control step of toluene oxidation could be obtained by varying reaction conditions. When the partial pressure of oxygen in the feed is lower than or equal to 0.070 MPa at 463 K, the oxidation of toluene would be controlled by oxygen transfer, otherwise the reaction would be controlled by kinetics. The effects of both oxygen transfer and kinetic control on the toluene conversion and the selectivity of benzaldehyde and benzyl alcohol in biomimetic catalytic oxidation of toluene were systematically investigated. Three conclusions have been made from the experimental results. Firstly, under the oxygen transfer limitation the toluene conversion is lower than that under kinetic control at the same oxidation conditions. Secondly, under the oxygen transfer limitation the total selectivity of benzaldehyde and benzyl alcohol is lower than that under kinetic control with the same conversion of toluene. Finally, under the kinetics control the oxidation rate of toluene is zero-order with respect to oxygen. The experimental results are identical with the biomimetic catalytic mechanism of toluene oxidation over metalloporphyrins.     

Oxidation Kinetics of Hexagonal-Shaped Single-Crystal Silicon Whiskers

The oxidation kinetics of hexagonal-shaped Si whiskers at high temperature were studied. Si whiskers were oxidized at 1000°C under a partial oxygen pressure of 0.14 atm. Oxide thickness was measured using scanning electron microscopy (SEM). A unique model was developed to describe the oxidation kinetics of hexagonal-shaped fibers. The model takes into account the inward diffusion of oxygen, oxidation reaction at the oxide/Si interface, and the fiber diameter change caused by the molar volume difference between SiO₂ and Si. Comparison of the model with experimental data shows good agreement.     

Effects of monomer impurities on the emulsion polymerization of chloroprene and properties of polychloroprene. IV. Effect of 1-chloro-1,3-butadiene

The influence of small amounts of 1-chloro-1,3-butadiene on the kinetics of the emulsion polymerization of 2-chloro-1,3-butadiene and on properties of the resulting polychloroprene has been studied. Some changes in the properties of the chloroprene polymers were observed at 1-chloro-1,3-butadiene concentrations in monomer as relatively high as about 5%. Polymer prepared in the presence of 5% 1-chloro-1,3-butadiene had decreased tensile strength, and also its crystallization tendency was somewhat lowered. At 1-chloro-1,3-butadiene concentrations near 1% or higher, the polychloroprene obtained had worsened thermo-oxidation stability which resulted in crosslinking during aging. The kinetics of emulsion polymerization of chloroprene are not influenced by 1-chloro-1,3-butadiene up to 5%.     

Effect of reaction conditions on the catalytic performance of Co<Subscript>9</Subscript>Fe<Subscript>3</Subscript>Bi<Subscript>1</Subscript>Mo<Subscript>12</Subscript>O<Subscript>51</Subscript> in the oxidative dehydrogenation of n-butene to 1,3-butadiene

Oxidative dehydrogenation of n-butene to 1,3-butadiene over Co₉Fe₃Bi₁Mo₁₂O₅₁ catalyst was conducted in a continuous flow fixed-bed reactor. The effect of reaction conditions (steam/n-butene ratio, reaction temperature, and space velocity) on the catalytic performance of Co₉Fe₃Bi₁Mo₁₂O₅₁ was investigated. Steam played an important role in decreasing contact time, suppressing total oxidation of n-butene, and removing coke during the reaction. Yield for 1,3-butadiene showed a volcano-shaped curve with respect to steam/n-butene ratio. The compensation between thermodynamic effect and kinetic effect led to a volcano-shaped curve of 1,3-butadiene yield with respect to reaction temperature. The Co₉Fe₃Bi₁Mo₁₂O₅₁ catalyst showed the best catalytic performance at a certain value of space velocity. The optimum steam/n-butene ratio, reaction temperature, and gas hourly space velocity were found to be 15, 420 °C, and 675 h⁻¹, respectively.     

超临界水氧化法处理醇类废水(Ⅰ)处理效果及过程参数的影响

研究了以超临界水氧化法（ ＳＣＷＯ）处理乙醇废水的过程。实验表明,一氧化碳和二氧化碳分别是反应中间产物和最终产物。５５０℃、２５ＭＰａ、停留时间大于１０ｓ时,ＳＣＷＯ能将乙醇完全氧化为二氧化碳,达到彻底处理的目的。随停留时间增大、温度升高,乙醇的去除率增大,而压力和氧气浓度的变化对过程没有显著影响。