理论空燃比天然气汽车尾气中H2O和O2对CH4与NO反应的影响

共沉淀法制备CeZrYLa+LaAl 复合氧化物载体, 等体积浸渍法制备了Pt 催化剂, 用于研究理论空燃比天然气汽车(NGVs)尾气净化反应中CH₄与NO的反应规律. 并考察了10% (体积分数, φ)H₂O和计量比O₂对CO₂存在时的CH₄+NO反应的影响. 结果表明: 对于不同条件下的NO+CH₄反应, 主要生成N₂和CO₂, 高温区有CO生成. 低温区无O₂时可以生成N₂O, 有O₂时可以生成NO₂; 添加10% (φ)的H₂O后, CH₄ 转化活性降低, NO转化活性基本不变, 这是由于H₂O减弱了CH₄与CO₂的重整反应, 但是对CH₄与NO的反应基本没有影响; 添加计量比的O₂后, CH₄转化活性提高, 而NO转化活性降低, 这是由于O₂和NO之间存在竞争吸附, CH₄被O₂氧化为主要反应, 从而减弱了NO的转化; 同时添加计量比的O₂和10% (φ) H₂O, CH₄与CO₂的重整反应受到抑制,CH₄与NO的反应、甲烷蒸汽重整反应和甲烷被O₂氧化反应同时发生, CH₄和NO的转化活性均提高.     

A spectroscopic study on the reaction-controlled phase transfer catalyst in the epoxidation of cyclohexene

The epoxidation of cyclohexene with hydrogen peroxide in a biphase medium (H₂O/CHCl₃) was carried out with the reaction-controlled phase transfer catalyst composed of quaternary ammonium heteropolyoxotungstates [π-C₅H₅N(CH₂)₁₅CH₃]₃[PW₄O₁₆]. A conversion of about 90% and a selectivity of over 90% were obtained for epoxidation of cyclohexene on the catalyst. The fresh catalyst, the catalyst under reaction conditions and the used catalysts were characterized by FT-IR, Raman and ³¹P NMR spectroscopy. It appears that the insoluble catalyst could degrade into smaller species, [(PO₄){WO(O₂)₂}₄]³⁻, [(PO₄){WO(O₂)₂}₂{WO(O₂)₂(H₂O)}]³⁻, and [(PO₃(OH)){WO(O₂)₂}₂]²⁻ after the reaction with hydrogen peroxide and becomes soluble in the CHCl₃ solvent. The active oxygen in the [W₂O₂(O₂)₄] structure unit of these soluble species reacts with olefins to form the epoxides and consequently the corresponding W---Ob---W (corner-sharing) and W---Oc---W (edge-sharing) bonds are formed. The peroxo group [W₂O₂(O₂)₄] can be regenerated when the W---Ob---W and W---Oc---W bonds react with hydrogen peroxide again. These soluble species lose active oxygen and then polymerize into larger compounds with the W---Ob---W and W---Oc---W bonds and then precipitate from the reaction solution after the hydrogen peroxide is consumed up. Part of the used catalyst seems to form more stable compounds with Keggin structure under the reaction conditions.     

Investigation of Partial Oxidation of Methane to Syngas on Rh/SiO2-Using 1H-NMR

In our previous work, POM has been investigated by the pulse reaction with CH₄ and CH₄/O₂ respectively, on Rh/SiO₂ catalyst. Kinetic isotopic effect was also studied by using CD₄ and CD₄/O₂. The results suggest that POM may proceed most possibly via a mechanism of surface carbon species reacting with surface oxygen. In the present work, ¹H MAS NMR was utilized to investigate the POM mechanism in aiming of presenting additional evidence.     

La2Zr2O7催化剂结构相变对甲烷氧化偶联反应性能的影响

采用共沉淀法并通过改变焙烧温度制备了一系列具有不同晶相结构的La₂Zr₂O₇催化剂，在微型固定床反应器上评价其甲烷氧化偶联反应性能，并利用XRD、Raman、CO₂-TPD、XPS等表征手段，探究催化剂的物相结构、表面碱性以及表面氧物种的变化规律。结果表明，随着焙烧温度从700℃逐渐升高到1200℃，La₂Zr₂O₇催化剂结晶度不断提高，晶相发生明显变化，从无定形结构逐渐向缺陷萤石结构过渡，最终转变成烧绿石结构。焙烧温度提高促使La₂Zr₂O₇晶相转变过程中，催化剂表面的碱性强度减弱，中等碱性位数量以及具有催化活性的表面氧物种O₂^2-和O₂^-的相对含量不断减少，致使催化剂的CH₄转化率和C₂₊选择性不断降低。其中，无定形LZO-CP-700催化剂表现出最佳的甲烷氧化偶联反应性能。     

CeO2负载的PdO与Ce1‒x Pd x O2‒δ 物种的甲烷催化燃烧性能

通过调控Pd前驱物在CeO₂上的沉积方式, 分别制备了以PdO和离子态的Ce_1?x Pd _x O_2?δ 物种为主的 Pd/CeO₂催化剂, 并采用X射线光电子能谱(XPS)和拉曼(Raman)光谱确证了这两种Pd物种的存在. 氧气程序升温脱附(O₂-TPD)和氢气程序升温还原(H₂-TPR)的表征结果显示, 相比于与载体相互作用较弱的PdO物种, 与CeO₂相互作用较强的Ce_1?x Pd _x O_2?δ 物种具有更加稳定的Pd—O键. 催化剂的甲烷燃烧反应起燃活性测试结果显示, 以PdO物种为主的催化剂表现出了良好的低温催化性能, 在原料气配比为1%CH₄/4%O₂-Ar, 空速为60000 mL·{\mathrm{g}}_{\mathrm{c}\mathrm{a}\mathrm{t}}^{-\mathrm{1}}·h^?1的条件下, T₁₀和T₉₀分别为275和367 ℃, 而两种以Ce_1?x Pd _x O_2?δ 物种为主的催化剂的T₁₀均超过420 ℃. 催化剂的甲烷程序升温还原(CH₄-TPR)表征结果表明, 在升温过程中只有当PdO或Ce_1?x Pd _x O_2?δ 物种被CH₄还原后, 催化活性才开始上升. 由于PdO物种的Pd—O键强度较弱, 有利于Pd物种上的晶格氧在较低温度下参与CH₄的氧化过程. 而Ce_1?x Pd _x O_2?δ 物种的Pd—O键较稳定, 且在反应条件下离子态Pd²⁺与反应体系中氧物种的作用较强, 进而抑制了其与CH₄的反应, 因此反应的起燃温度较高. 以γ-Al₂O₃为载体采用相同的方法制备了Pd/γ-Al₂O₃催化剂, 相关的表征结果进一步证实, 与载体相互作用较弱的PdO物种更容易被CH₄还原, 进而具有较高的催化活性. 据此可以认为Pd/CeO₂上氧化态的Pd物种被CH₄的还原性能是决定其甲烷催化燃烧反应活性的重要因素之一.     

CH3CF2O2与HO2自由基反应机理的理论研究

用密度泛函理论(DFT)的B3LYP方法，在6-311G、6-311+G(d)、6-311++G(d, p) 基组水平上研究了CH₃CF₂O₂与HO₂自由基反应机理. 结果表明, CH3CF₂O₂与HO₂自由基反应存在两条可行的通道. 通道CH3CF₂O₂＋HO₂→IM1→TS1→CH₃CF₂OOH＋O₂的活化能为77.21 kJ•mol^－1，活化能较低，为主要反应通道，其产物是O₂和CH₃CF₂OOH. 这与实验结果是一致的；而通道CH₃CF₂O₂＋HO₂→IM2→TS2→IM3→TS3→IM4＋IM5→IM4＋TS4→IM4＋OH＋O₂→TS5＋OH＋O₂→CH₃＋CF₂O＋OH＋O₂→CH₃OH＋CF₂O＋O₂的控制步骤活化能为93.42 kJ•mol^－1，其产物是CH₃OH、CF₂O和O₂. 结果表明这条通道也能发生，这与前人的实验结果一致.     

IN situ Confocal Microprobe Raman Spectroscopic Studies on Defective La-based Complex Oxides

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含氧煤层气流化床催化燃烧脱氧特性研究

利用自制的铜基球形甲烷催化燃烧催化剂,在小型流化床反应器中对模拟含氧煤层气进行了流化床催化燃烧脱氧的实验研究,考察了床层温度、催化剂粒径、空速对脱氧效率和CO₂选择性的影响。结果表明,较高的反应床层温度使催化剂活性增强,进而提高催化脱氧效率。床层温度在450 ℃以上,脱氧效率可稳定保持在95%以上。较小的催化剂粒径降低了内扩散阻力对催化反应的影响,提高催化反应的CO₂选择性。床层温度在450 ℃以下时,降低空速可提高氧气转化率,但温度高于450 ℃时,脱氧反应速率加快,空速变化对脱氧效率影响不明显。此外,通过调节CH₄/Air比例模拟不同含氧量的煤层气,考察流化床反应器及催化剂对含氧煤层气中O₂浓度变化的适应性。模拟含氧煤层气中氧气体积分数在5%~15%,该催化剂均表现出高的脱氧活性和选择性,反应器出口气体中氧气体积分数低于0.2%,CO₂选择性高于98%。     

Mechanism of Methane Partial Oxidation over SiO2-Supported Nickel Catalyst

The partial oxidation reaction of mathane over reduced 10wt%Ni/SiO₂ catalyst was studied at 600, 650, 700℃ by means of pulse and bond-order conservation Morse-potential (BOC-MP) methods. In the oxidation reaction of surface carbon deposited on the catalyst, it was observed that the product selectivity was subject to the reaction temperature and the selectivity of CO was increased with rasing temperature of CH₄/O₂, the same trend between CO selectivity and reaction temperature was also observed, implying that the partial oxidation of methane to syngas follows the pyrolysis mechanism under the reaction conditions. The BOC-MP calculation on the elementary reaction steps over Ni(111) surface indicates that the direct dissociation of CH₄ without the involvement of surface oxygen is more likely to occur and the formation of CO from CH(s) occurs more readily than from C(s).     

负载型铼催化剂体系与甲醇选择氧化性能的关系

以铼酸铵为前驱体,制备了氧化物负载型铼催化剂并研究其甲醇选择氧化反应的催化性能.结果表明,Fe₂O₃和V₂O₅等氧化物负载型铼催化剂表现出很高的甲醇选择氧化制备二甲氧基甲烷的催化性能,选择性可达90%～94%(摩尔分数).选择氧化反应活性与铼担载量有关.在α－Fe₂O₃担载的铼催化剂中,以担载质量分数为1%～3%铼的催化剂活性最高[450mmol/(h·gRe)],而高于3%的铼担载量,单位铼催化活性逐渐下降.XRD,XPS和脉冲反应等结果表明,铼酸铰负载于α-Fe₂O₃载体上,并于He气氛中焙烧后,所得表面铼物种与担载量有关,当低于单层担载量时以Re⁶⁺占主导,而高于单层担载量时则Re⁶⁺与Re⁴⁺物种共存.     

不同气氛下煤连续热解产物的分配规律及产品品质分析

在连续进出料的流化床中研究了热解温度为850 ℃时,含有O₂、H₂、CO、CO₂、CH₄的反应气氛对热解产物分配规律及产品组成的影响。采用Raman、BET等测试方法对不同热解气氛下制得半焦的品质进行了评价,结合热重分析了影响半焦反应活性的因素。结果表明,无O₂气氛下,H₂与CO₂存在时降低了焦油产率,而CO与CH₄促进了焦油的生成。CH₄的裂解析碳使半焦产率上升。O₂的加入使CO₂、CO含量明显增加,半焦及焦油产率降低。N₂中引入O₂时,PAHs含量降低。CH₄促进了烷基萘与苯类的生成,CO则抑制酚类裂解生成苯类。CO₂的气化作用促进了微孔的生成,相应地,半焦的比表面积快速增加,半焦的反应活性也最高。CO歧化与CH₄热裂解产生的析碳堵塞了部分孔道,降低了比表面积。H₂与CH₄所产生的氢自由基能渗透到半焦内部,引起半焦结构的缩聚,进而影响氧化反应活性。     

助剂CuO和La2O3对NiO/α-Al2O3甲烷催化部分氧化制合成气引发过程的影响

采用分步浸渍法制备了NiO/α-Al₂O₃、NiO-CuO/α-Al₂O₃和NiO-La₂O₃/α-Al₂O₃三种催化剂,运用程序升温表面反应（TPSR）技术考察了助剂CuO和La₂O₃对NiO/α-Al₂O₃甲烷催化部分氧化（CPOM）反应引发过程的影响。结果表明,无论是否经过预还原处理,NiO/α-Al₂O₃催化剂在CH₄/O₂混合气氛下进行程序升温表面反应（CH₄/O₂-TPSR）时,即使升高到910℃也不能引发CPOM反应。添加助剂CuO或La₂O₃后,NiO-CuO/α-Al₂O₃和NiO-La₂O₃/α-Al₂O₃催化剂在CH₄/O₂-TPSR过程中均可以引发CPOM反应。原因分别是CuO促进了CH₄对NiO的还原以及抑制了O₂对Ni0的再氧化,La₂O₃减小了Ni晶粒粒径和还原时扩散阻力促进NiO的还原。     

New heterometallic copper zinc alkoxides: synthesis, structure properties and pyrolysis to Cu/ZnO composites

The copper compound [(THF)KCu(O^tBu)₃]_∞ 1 was obtained by interaction of a 1:1 mixture of ZnCl₂/CuCl₂ with KO^tBu. Bi- and trifunctional aminoalcohols were used to synthesize the intramolecularly donor stabilized Cu(II) alkoxides Cu(OCH(R)CH₂NMe₂)₂ (3: R=Me, 4: =CH₂NMe₂) where 4 was structurally characterized. Lewis acid–base adduct formation with (Me₃Si)₃CZnCl gave the heterodinuclear compounds (Me₃Si)₃CZnCl · Cu(OCH(R)CH₂NMe₂)₂ (5: R=Me, 6: R=CH₂NMe₂), which were characterized by X-ray single-crystal structure analysis. The two metal centers Cu and Zn of 5 and 6 are bridged by two oxygen atoms to form a Cu–O–Zn core. Pyrolysis of compounds 5 and 6 in dry argon or a H₂/N₂ mixture at atmospheric pressure forms metallic copper and zinc oxide, whereas pyrolysis under O₂/Ar forms additionally oxidized copper species. Elemental analysis of the pyrolysis products showed carbon and nitrogen contamination. Scanning electron microscopy and energy dispersive X-ray analysis were performed to get information on the morphology and the chemical composition of the pyrolysis products.     

不同载体Ni基催化剂生物质热解气甲烷化反应性能

采用浸渍法制备了Ni金属负载在不同载体(SiO2、ZrO2、CeO2、Al2O3和Al2O3-CeO2)表面形成的催化剂,研究了水蒸气和载体对生物质热解气甲烷化反应性能的影响。结果表明,随着水蒸气量的增加CO转化率逐渐增大,而甲烷选择性呈现先增加后降低的变化趋势,当nw ater/ngas比值为0.26时达到最大。载体Al2O3相比SiO2、ZrO2和CeO2具有更大的比表面积和Ni金属分散度,促进了生物质热解气甲烷化反应活性和选择性。相比于Ni-Al2O3催化剂,Al2O3-CeO2复合载体具有更多的镍金属负载量活性金属分散度,以及最好的低温甲烷化反应性能。在300℃的低温条件下,Ni-Al2O3-CeO2催化剂的CO转化率达到97%,CH4增长率达到110%。     

基于程序升温氢化表征的Ni-Al2O3催化剂上CO2-CH4重整反应积炭研究

采用水热沉积法制备Ni-Al₂O₃催化剂,用于CO₂-CH₄重整反应;基于程序升温氢化（TPH）表征,研究了反应时间、温度、原料气CO₂/CH₄比例和空速等因素对CO₂-CH₄重整反应过程中Ni-Al₂O₃催化剂上表面积炭行为的影响。结果表明,表面积炭是导致催化剂重整反应失活的重要原因。随反应时间的延长,催化剂表面积炭量增多,虽未成比例增加,但其TPH峰温有向高温方向移动的趋势,表明所积之炭的石墨化程度增加。反应温度和空速对催化剂表面积炭也有一定影响,且空速的影响更大。另外,由于CO₂消炭反应（CO₂+C=2CO）的存在,CO₂/CH₄比例对表面积炭的影响也很大。CO₂/CH₄比例太低,不能明显抑制积炭;随着CO₂/CH₄比例增加,积炭将得到有效抑制,但CO₂/CH₄比例过高,CO₂在产物中的分离和回收再利用将使成本增加。     

Characteristics of a zirconia composite membrane fabricated by a laser firing method

By a method of laser firing, a high zirconia containing (70%) composite membrane on porous ceramic tubing was successfully fabricated. The laser sintered composite membrane was characterized by gas separation/permeation experiments. In the separation experiment of a CO₂---CH₄ gaseous mixture, it was found that the separation factor of CH₄ over CO₂ was 1.15. In the pure gases permeation experiment, it was found that Knudsen diffusion is considered to be predominant in the permeation mechanism for pure gases H₂, He, CH₄, N₂, O₂, and CO₂, and the permeation mechanism of H₂O at lower temperature depends mainly on surface diffusion and on Knudsen diffusion at higher temperature.     

叔丁醇在H5PMo10V2O40/SiO2催化剂上吸附的红外光谱研究

用FTIR研究了叔丁醇在H₅PMo₁₀V₂O₄₀/SiO₂上的化学吸附和转化,叔丁醇在15℃质子酸的作用下形成(CH₃)₃C^*吸附态,进而转化为类似π-烯丙基结构的吸附态H₂C^*=C(CH₃)=C^*H₂和σ-烯丙基吸附态C^*H₂C(CH₃)=CH₂.     

还原-氧化-还原过程对Co-ZrO_2共沉淀催化剂结构及其费托合成反应性能的影响

采用程序升温还原、氮吸附、X射线衍射、Raman、XPS和H2-TPD等方法研究了还原(400℃,氢还原)-氧化(室温,暴露空气中氧化)-还原(250℃或400℃,氢还原)预处理过程对Co-ZrO2共沉淀催化剂结构的影响,考察了催化剂在不同反应器中的费托反应性能。结果表明,催化剂还原氧化前后钴物种均以Co3O4形式存在,颗粒直径无明显变化;还原氧化处理后催化剂表面钴物种含量有所下降,但H2-TPD结果显示催化剂经还原-氧化-还原后氢吸附量增加。另外,还原氧化过程能够降低催化剂表层钴物种的还原温度。反应结果表明,催化剂经还原氧化还原处理后活性明显增加,甲烷选择性降低。     

固体酸WO3/TiO2负载锂锰催化剂组成对其甲烷氧化偶联反应性能的影响

The selective oxidation of methane to basic petrochemicals (ethylene and ethane) is desirable and has attracted extensive research attention. The oxidative coupling of methane (OCM) is considered a promising one-step route for the production of C₂ compounds (ethylene and ethane) from methane, and has been the focus of industrial and fundamental studies. It is widely accepted that the composition is a crucial factor governing the activity of a catalyst system. It was found that the phase structures, basicity, existing status and distribution of the active components, oxygen species, and chemical states of the catalyst were influenced by the composition and ratio, resulting in different catalytic performances for the OCM. In this study, a series of solid acid WO₃/TiO₂-supported lithium-manganese oxide catalysts for OCM were synthesized via the impregnation method. The impacts of diverse compositions, such as the individual contents (Li and Mn) and dual contents (Li-Mn), on the OCM were investigated in detail, using inductively coupled plasma optical emission spectrometry, X-ray diffraction, high-resolution transmission electron microscopy, CO₂-temperature-programmed desorption, O₂-temperature-programmed desorption, H₂-temperature-programmed reduction, Raman spectroscopy, X-ray photoelectron spectroscopy, and CH₄-temperature-programmed surface reaction. The addition of Li content to the catalyst not only led to the anatase-to-rutile crystal structure transformation of TiO₂, and the reduction of the high-valence-state Mn species to low-valence-state Mn, but also increased the content of surface lattice oxygen and decreased the surface basicity. The observed effects on the structures and catalytic performance suggest that the Li content is helpful in suppressing the formation of completely oxidized CO₂, and increases the C₂ selectivity. Moreover, increasing the Li content of the catalyst facilitated the mobility of the lattice oxygen, which triggered the promotion of CH₄ activation, thereby enhancing the OCM catalytic performance. The Mn content acted as the active sites for OCM; therefore, the performance of the catalyst was closely related to the Mn concentration and valence state. However, the WO₃/TiO₂-supported catalyst with excessive Mn content exhibited a high surface basicity, high valence state of Mn, and low abundant lattice oxygen, which was unfavorable for C₂ selectivity. The Raman spectroscopy results revealed that MnTiO₃ was formed due to the co-existence of Li and Mn on WO₃/TiO₂, and played an essential role in improving the low-temperature OCM performance. There was a synergic effect of the Li and Mn components on the OCM. The optimal performance (16.3% C₂ yield) was achieved over the WO₃/TiO₂-supported lithium-manganese catalyst with n(Li) : n(Mn) = 2 : 1 at 750 ℃.     

醋酸钯和四氯对苯醌催化氧化低浓度煤矿瓦斯制甲醇

利用自制的实验系统进行了醋酸溶液中低浓度瓦斯催化氧化制甲醇研究。实验结果表明,以Pd(OAc)₂为催化剂,反应体系中添加对苯醌或四氯对苯醌可改善甲烷活化环境,四氯对苯醌对瓦斯催化氧化过程的作用效果好于对苯醌。四氯对苯醌用量、反应压力和反应温度对瓦斯催化氧化具有重要影响。甲醇生成量随四氯对苯醌用量、反应压力和反应温度升高而增加。CH₃OH是通过反应过程中产生的H₂O₂与CH₄相互作用形成的。CH₃COOCH₃一部分是由Pd²⁺直接氧化CH₄得到的;另一部分是由CH₃OH与反应溶剂CH₃COOH通过酯化反应形成的。