异丁烯两段催化氧化制甲基丙烯酸催化剂研究 Ⅰ．异丁烯气相氧化制甲基丙烯醛多元复合氧化物催化剂的研究

本文报导用于异丁烯（叔丁醇）选择氧化制ＭＡＬ（甲基丙烯醛）的多元复合氧化物催化剂的研究结果。同共沉淀法制备的催化剂的活性主要决定于其化学组成，同时受到制备条件的影响。最佳催化剂的主要物相组成为ＰｂＯ３，Ｂｉ２ＭｏＯ３．３、ＮｉＭｏＯ４、Ｓｂ２Ｏ３及ａ－Ｆｅ２Ｏ３小颗粒。在３５５℃，１０００～２５００ｈ－１空速范围，叔丁醇：水：空气＝１：３．３：７（摩尔比）的条件下可获得异丁烯转化率达９６％，ＭＡＬ选择性达８９％的结果。     

Partial oxidation of isobutene to methacrolein on Bi-W/Fe-Co-Mo-K catalysts

The partial oxidation of isobutene to methacrolein and methacrylic acid was studied on oxidic catalysts containing mainly a mixture of bismuth tungstate and iron-cobalt-potassium molybdate. Catalyst shaping was done by extrusion. The kinetic measurements were performed by monitoring the gas-phase composition along the length of a fixed bed of catalyst. The reactor was treated as an isothermal plug-flow system. The network of parallel and consecutive reactions taking place in this system can be described by a simplified scheme. It is possible to predict the gas-phase composition prevailing in the reactor using five different kinetic parameters. In the temperature range 380<<420°C grain selectivities as high as 85% combined with yields of methacrolein and methacrylic acid about 72% at 92% conversion were obtained.     

异丁烯两段法制甲基丙烯酸甲酯

将异丁烯三步法制甲基丙烯酸甲酯简化为两段法,异丁烯首先被氧化到甲基丙烯醛(MAL),再将甲基丙烯醛氧化到甲基丙烯酸和酯化为甲基丙烯酸甲酯(MMA)的反应合并为一步进行,缩短了工艺流程,提高了产率。第一段用共沉淀法制备含有镧系元素La的MoBiFeCoSbLaCsO催化剂,氧化反应在固定床反应器中进行。反应温度365℃,原料气n〔i(C4H8)〕∶n(O2)∶n(N2)=6∶19∶75,空速1800h-1。异丁烯转化率为93 8%;生成MAL的选择性为88 9%。第二段反应的催化剂为Pd5Pb2FeLa,反应温度为70℃,空气流速为100mL min。MAL转化率为89 2%;生成MMA的选择性为92 3%。     

Interaction of isobutene and methacrolein with silica-supported uranium and molybdenum oxide catalysts

The adsorption of isobutene (in the temperature range 309–341K) and methacrolein (in the temperature range 296–336 K) on a Mo/(Mo+U)=0.89 catalyst were studied. The equilibrium data were analysed according to Freundlich's model. The high coverages observed at lower temperatures suggest some participation of physical adsorption in the reversible adsorption. Entropy calculations showed that these adsorbed species are best described by a mobile model which assumes bidimensional translation and two rotational degrees of freedom. Isobutene is weakly chemisorbed, producing reversible species which were identified as a π-complex formed by interaction with surface OH groups through π-electrons (infrared bands at 1655, 1615, 1470 and 1375 cm^?1), and only a small fraction of isobutene interacts strongly via lattice oxygen forming intermediate species in the oxidation reaction. However, in the presence of oxygen at 523 K a majority of the surface species are strongly held by the surface (infrared bands at 1775, 1723, 1610, 1460 and 1350 cm^?1 associated to a methacrylic complex and bands at 1590 and 1538 cm^?1 of carbonate-carboxylate species).     

Selective Oxidation of Isobutane to Methacrolein over Mo–V–Te–Sb Mixed Oxide Catalysts with Different Antimony Contents

A series of MoV_0.3Te_0.23Sb_x (x=0–0.6) mixed oxides were prepared and investigated for the selective oxidation of isobutane. Among them, MoV_0.3Te_0.23Sb_0.5 showed the best methacrolein selectivity (as high as 39%), and the yield to methacrolein reached 7.8% at 20.0% isobutane conversion at 470 °C.     

反荷离子及制备方法对Keggin型杂多化合物结构和性质的影响

采用喹啉沉淀法和共沉淀法制备了一系列不同反荷离子的Keggin型杂多化合物(HPCs)催化剂,通过N2吸附-脱附、傅里叶变换红外光谱、X射线衍射、31P固体魔角核磁共振谱、扫描电子显微镜和NH3-程序升温脱附表征,研究了反荷离子和制备方法对HPCs催化剂结构和性能的影响,并考察了该系列催化剂在甲基丙烯醛(MAL)氧化为甲基丙烯酸(MAA)反应中的催化活性。实验结果表明,添加Cs+提高了HPCs催化剂的活性;Cu2+与Cs+的协同作用提高了HPCs催化剂的氧化还原能力和结构稳定性,MAL的转化率达到88.6%,MAA的选择性达到94.9%;含La3+的HPCs催化剂具有较强的酸性,MAA的选择性较高;与共沉淀法相比,喹啉沉淀法制备的HPCs催化剂具有较大的比表面积和较高的MAL氧化活性。     

稀土氧化物对钼-铋催化剂性能的影响

在异丁烯选择氧化制甲基丙烯醛的钼-铋催化剂中加入La2O3等八种稀土氧化物,并在固定床反应器中考查了反应温度、异丁烯浓度、原料气的流速和稀土氧化物的添加量对异丁烯转化率和生成甲基丙烯醛选择性的影响。实验表明,CeO2、Eu2O3及Tb4O7添加后,可明显提高异丁烯转化率和生成甲基丙烯醛的选择性。     

甲基丙烯醛氧化酯化制甲基丙烯酸甲酯

制备了用于甲基丙烯醛(MAL)一步氧化酯化为甲基丙烯酸甲酯(MMA)的新型催化剂;考察了反应温度、催化剂在反应体系中的质量分数对MAL转化率和产物选择性的影响;将离子液体[bmim]PF6用于该反应中,不仅提高了产物的选择性,还能有效防止产物的聚合。反应温度θ=50℃,催化剂在反应体系中质量分数为2 4%,pH=10 5,O2流量6mL/min,反应时间6h时,在反应体系中添加1mL离子液体[bmim]PF6,MAL的转化率为96 2%,MMA单体的选择性可达98 7%。     

Green process for methacrolein separation with ionic liquids in the production of methyl methacrylate

Separation of methacrolein (MAL) is a critical technique for the production of methyl methacrylate, which is an important raw material for the preparation of acrylic resins applied in a variety of end‐uses. In this work, an azeotropic distillation process and an ionic liquid (IL) green process were developed for the separation of MAL with BmimBF₄. The two processes were simulated with Aspen plus. The simulated results are in good agreement with the experimental results which were attained in a pilot plant. Also the economic and green degree analysis of these two processes was investigated. When compared with the azeotropic distillation process, the IL green process exhibits economic superiority and green degree superiority. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Catalytic behaviour of multiphasic oxide catalysts containing lanthanides (La,Ce, Pr,Sm, Tb) in the selective oxidation of isobutene to methacrolein

The catalytic performances of five lanthanide oxides (La₂O₃, Sm₂O₃, CeO₂, Pr₆O₁₁ and Tb₄O₇) for the selective oxidation of isobutene to methacrolein are evaluated within the framework of the remote control mechanism. Mechanical mixtures of these oxides with typical donor (Sb₂O₄) or acceptor (MoO₃) phases of spill-over oxygen were prepared and tested for their activity in the isobutene-to-methacrolein oxidation at 400°C. Amongst the five lanthanide oxides tested, only CeO₂ and Pr₆O₁₁ were found to display significant cooperation effects for the investigated reaction, with enhanced yields and selectivity for partial oxidation and concomitant decrease of CO₂ production. The fresh and used catalysts were characterized by X-ray diffractometry, and the occurrence of solid state reactions between the partner oxides outside the reaction conditions was investigated in parallel in the temperature range 400–500°C. No new phase was observed in the case of the mixtures with La₂O₃, Sm₂O₃, CeO₂ and Tb₄O₇. Account taken of the absence of any new phase in the CeO₂-MoO₃ system, it can be concluded that CeO₂ is a potential donor of spill-over oxygen. The situation in the MoO₃-Pr₆O₁₁ mixtures is more complex, owing to the generation of various praseodymium molybdates, together with the oxocarbonate Pr₂CO₅. The latter phase was shown to have no intrinsic tendency to produce methacrolein, but it seems that some of the praseodymium molybdates present in the working catalysts may exhibit noticeable catalytic properties.