正丁烷选择氧化过程中VPO体系的表面物种

用漫反射傅立叶变换红外光谱法,研究了VPO催化剂上正丁烷选择氧化制顺酐的表面物种及催化反应过程。催化剂暴露在1．5％n-C4 21％02＋N2的流动混合气中,流量为50mL/min,温度100－400℃,在催化剂表面上未观察到吸附的正丁烷,但发现了吸附的顺酐和COx。同时,检测到吸附的马来酸和高活性的烯烃物种。     

添加Tm对VPO催化剂性能的影响

八十年代以来，以正丁烷为原料生产顺酐的磷钒系催化剂研究非常活跃．为改进催化剂的性能，可添加Zn、Co、Zr、Ti等过渡元素［1－3］，但有关催化剂的组成、结构及作用机理方面的报导较少．我们在VPO催化剂中分别加入十五种稀土元素并将其应用于正丁烷选择氧化制备顺酐的反应中［4］．实验结果表明，以添加Tm的催化剂活性及选择性均为最高．本文用IR、XRD、XPS、和NH3－TPD等方法研究了VPO和添加Tm后样品的晶相结构、表面组成和酸性，用固定床反应器考察了正丁烷转化率和生成顺酐选择性的变化并探讨了引起这些变化的机理．1实验（…     

正丁烷氧化制顺酐Ce基复合氧化物VPO催化剂研制

在用共沉淀方法制备的Ｃｅ－Ｆｅ复合氧化物中,加入ＶＰＯ化剂制备复合ＶＰＯ催化剂;井测试结构、氧化还原性能以及催化性能。实验结果表明,Ｃｅ－Ｆｅ复合氧化物的组成和数量均对复合ＶＰＯ催化剂的结构产生较大的影响,Ｃｅ－Ｆｅ复合氧化物的加入,提高了复合ＶＰＯ催化剂表面低温氧物种的活性,降低了品格氧物种的ＴＰＲ出峰温度,无论在有无气相氧条件下,复合ＶＰＯ催化剂的晶格氧均有良好的反应催化性能。     

Novel VPO Catalysts for n-Butane Oxidation to Maleic Anhydride:The Effects of Combined Moderators,Preparation Procedure and MCM-41 Supports

VPO catalysts are widely used in selective oxidation of n-butane into maleic anhydride (MA)^[1-2]. In the recent years, there is an obvious trend worldwide that the selectivity of a target product is more emphasized than the overall conversion, to decrease the undesired by-products. In this study, different approaches have been tried to generate more environmentally friendly VPO catalysts, with high MA selectivity and improved n-butane conversion. The moderated catalyst was prepared in aqueous phase^[3]. For comparison, the moderators were also introduced by impregnating the VPO precursor synthesized in organic medium. The supported VPO systems on the MCM-41 mesopore materials were prepared by employing the reaction of V₂O₅ with isobutanol in the presence of MCM-41 fine powder with different Si/Al ratios. The catalysts were evaluated at 385-425℃ and characterized by XRD, XPS and TPR etc.     

高比表面积VPO催化剂的制备及其性质研究

利用有机相制备VPO催化剂,在制备过程中加入聚乙二醇(PEG)作为分散剂可有效提高VPO催化剂的比表面积。实验中采用两种不同分子量的聚乙二醇(PEG 6000和PEG 10000),所得VPO催化剂的比表面积分别为52与54m²/g,而不加聚乙二醇的VPO催化剂其比表面积仅为19m²/g.XRD,XPS及FTIR的结果表明,催化剂的主要晶相均为(VO)₂P₂O₇,但两类催化剂的微观结构有所不同。正丁烷选择氧化生成马来酐的催化反应结果表明,385℃时加聚乙二醇制备的VPO催化剂其丁烷的转化率为84%～86%.马来酸酐的选择性为78%,而不加聚乙二醇制备的VPO催化剂其转化率和选择性均为71%.     

Thermogravimetric Analysis of Vanadium Phosphorus Oxide Catalysts Doped with Cobalt and Iron

The transformation of VOHPO4·0.5H2O (VPO) precursor doped with cobalt or iron for n-butane oxidation to maleic anhydride was investigated by thermogravimetric analysis under air and nitrogen, with and without n-butane in the flow. While almost no effect was observed in nitrogen or air, a strong influence of the doping was observed when n-butane was added to the nitrogen or air. This resulted in a delay of the decomposition of the precursor and a further reoxidation of the VPO catalyst, particularly for doping with cobalt at low percentage (1%). This shows that doping can change the oxidation state of vanadium phosphorus oxide catalysts, which can explain differences in their catalytic performances and the favourable effect of doping by cobalt. This revised version was published online in July 2006 with corrections to the Cover Date.     

掺杂Pr对VPO催化剂性质的影响

在ＶＰＯ催化剂中添加Ｐｒ，用ＸＲＤ，ＬＲＳ，ＸＰＳ，ＥＳＲ和＾３１Ｐ固体核磁共振考察了催化剂的相组成和钒的氧化态，用ＮＨ３－ＴＰＤ和吡啶吸会原位红外光谱表征了催化剂表面的酸量。将催化剂应用于正丁烷选择氧化生成顺酐的反应中，实验结果表明，当Ｐｒ／Ｖ原子比＝０．０５时，活性相（ＶＯ）２Ｐ２Ｏ７的量增加，表面酸性增强，正丁烷转化率和生成顺酐的选择性都有所提高，而Ｐｒ／Ｖ≥０．１０时，（ＶＯ）２Ｐ２Ｏ７的     

Effect of Cr and Co Promoters Addition on Vanadium Phosphate Catalysts for Mild Oxidation of n-Butane

In this study, Cr and Co promoted, as well as unpromoted vanadium phosphate (VPO) catalysts were synthesized by the reaction of V2O5 and o-H3PO4 in organic medium followed by calcination in n-butane/air environment at 673 K. The physico-chemical properties and the catalytic behavior were affected by the addition of Cr and Co dopants. H2-TPR was used to investigate the nature of oxidants in the unpromoted and promoted catalysts. The results showed that both the Cr and Co promoters remarkably lowered the temperature of the reduction peak associated with V5 . The amount of oxygen species originated from the active phase, V4 , removed was significantly increased for Co and Cr-promoted catalysts. Both Cr and Co dopants improve strongly the n-butane conversion without sacrificing the MA selectivity. A good correlation was observed between the amount of oxygen species removed from V4 phase and the activity for n-butane oxidation to maleic anhydride. This suggested that V4 -O was the center for the activation of n-butane.     

Mechanism of phthalic anhydride formation in the oxidation of n-pentane on a vanadium-phosphorus oxide catalyst

The reaction paths of product formation in the partial oxidation of n-pentane on vanadium-phosphorus oxide (VPO) and VPO-Bi catalysts are considered. The condensed products of n-pentane oxidation were analyzed by chromatography-mass spectrometry, and the presence of C₄ rather than C₅ unsaturated hydrocarbons was detected. It was found that the concentration of phthalic anhydride in the products increased upon the addition of C₄ olefins and butadiene to the n-pentane-air reaction mixture. With the use of a system with two in-series reactors, it was found that the addition of butadiene to a flow of n-butane oxidation products (maleic anhydride, CO, and CO₂) resulted in the formation of phthalic anhydride. The oxidation of 1-butanol was studied, and butene and butadiene were found to be the primary products of reaction; at a higher temperature, maleic anhydride and then phthalic anhydride were formed. The experimental results supported the reaction scheme according to which the activation of n-pentane occurred with the elimination of a methyl group and the formation of C₄ unsaturated hydrocarbons. The oxidation of these latter led to the formation of maleic anhydride. The Diels-Alder reaction between maleic anhydride and C₄ unsaturated hydrocarbons is the main path of phthalic anhydride formation.     

On the mechanism of the Skraup-Doebner-Von Miller quinoline synthesis

The mechanism of the formation of substituted quinolines from anilines and alpha,beta-unsaturated ketones has been studied by the use of 13C-labeled ketones in cross-over experiments. In the reaction of doubly labeled 13C(2,4) mesityl oxide, a 100% scrambling of the label in the quinoline product was observed, whereas only a small (5-10%) amount of the starting mesityl oxide showed scrambling of the label. Similarly, the reaction of triply labeled pulegone clearly shows that the label in the product is 100% scrambled, whereas the label in the starting pulegone is retained. On the basis of these studies, a mechanistic pathway for the Skraup quinoline synthesis is proposed that involves a fragmentation-recombination mechanism. The aniline component condenses with the alpha,beta-unsaturated ketone initially in a conjugate fashion, followed by a fragmentation to the corresponding imine and the ketone itself. These fragments recombine to form the quinoline product.     

V5+物种对钒磷氧化物催化性能的影响

采用有机相法制备钒磷氧化物催化剂，通过空气或氧气气氛中不同时间的原位预处理以系统调变样品中V⁵⁺物种的含量及其状态，并考察对催化正丁烷选择氧化制马来酐的反应性能的影响。理化表征手段的结果表明，空气或氧气预处理改变了V物种的价态及V⁵⁺/V⁴⁺的相对含量，但对催化剂的比表面积和表面P/V比没有显著影响。表面V⁵⁺/V⁴⁺的合适比例及相应的结构状态可能在V⁵⁺-V⁴⁺物种之间产生较好的协同作用，从而获得较为理想的催化反应性能。     

钒磷复合氧化物催化剂再氧化的在线动态质谱研究

 采用在线质谱动态响应技术，研究了钒磷复合氧化物（VPO）催化剂再氧化条件（氧浓度、温度和时间）对正丁烷选择氧化制顺酐反应的影响．结果表明，催化剂再氧化条件对正丁烷选择氧化反应性能有明显的影响，其中再氧化温度是主要影响因素．当正丁烷选择氧化和VPO催化剂再氧化在反应器（循环流化床和固定床）内序贯、交替进行时，可以通过改变再氧化条件使催化剂再氧化反应与正丁烷选择氧化反应恰当地匹配以改善时均反应性能．     

Selective Oxidation of n-Butane over VPO Catalyst Modified by Different Additives

A series of vanadyl pyrophosphate catalyst （VPO） modified by different additives have been prepared with the aim to study the performance for selective conversion of n-butane to maleic anhydride（MA）. The addition of various promoters improved the catalytic performance remarkably on both activity and selectivity. The correlation of activity and selectivity of the catalysts with their structure has been discussed. The increase in BET surface areas and surface redox sites leads to an enhanced activity. However, good selectivity can only be obtained on those surfaces with suitable surface acid sites.     

Mechanism studies of the conversion of 13C-labeled n-butane on zeolite H-ZSM-5 by using 13C magic angle spinning NMR spectroscopy and GC-MS analysis

By using 13C MAS NMR spectroscopy (MAS = magic angle spinning), the conversion of selectively 13C-labeled n-butane on zeolite H-ZSM-5 at 430-470 K has been demonstrated to proceed through two pathways: 1) scrambling of the selective 13C-label in the n-butane molecule, and 2) oligomerization-cracking and conjunct polymerization. The latter processes (2) produce isobutane and propane simultaneously with alkyl-substituted cyclopentenyl cations and condensed aromatic compounds. In situ 13C MAS NMR and complementary ex situ GC-MS data provided evidence for a monomolecular mechanism of the 13C-label scrambling, whereas both isobutane and propane are formed through intermolecular pathways. According to 13C MAS NMR kinetic measurements, both pathways proceed with nearly the same activation energies (E(a) = 75 kJ mol(-1) for the scrambling and 71 kJ mol(-1) for isobutane and propane formation). This can be rationalized by considering the intermolecular hydride transfer between a primarily initiated carbenium ion and n-butane as being the rate-determining stage of the n-butane conversion on zeolite H-ZSM-5.     

表征固体超强酸性的新方法-正丁烷异构化反应的原位~(13)CMASNMR谱

室温下SO_4~(2-)/ZrO_2催化剂（SZ）上~(13)C标记的丁烷异构化反应的原位 ~(13)C MAS NMR谱研究结果表明：其反应动力学符合Langmuir-Hinshelwood一级可 逆表面反应动力学公式，由该动力学公式计算得到的反应速率常数可以用于衡量固 体催化剂的表面超强酸性。这种新的表征方法显示采用一步-醇热-超临界干燥综合 技术合成的SZ催化剂不仅比表面和硫酸根含量高，而且其超强酸性和异构化反应活 性均明显优于常规法合成的催化剂，具有良好的应用前景。     

VPO催化剂上气态环己烷催化氧化制取顺酐及醋酸的研究

为研究气态环己烷催化氧化制取顺酐及醋酸的新反应，采用沉淀法制备了8种相同晶相的VPO固体催化剂．借助XRD、FT-IR技术对催化剂进行主体晶相确定，利用氧化还原滴定方法测定了催化剂中钒的平均氧化数．结合催化反应的活性评价，发现具有适宜结晶度、适宜V^4 ／V^5 比和在反应气氛下活化的催化剂，均可提高实现目标反应的催化活性；添加钼组份并不能改善催化剂的选择性．     

环己烷催化氧化制取顺酐和醋酸的催化剂研究

为研究气态环己烷催化氧化制取顺酐及醋酸的新反应，采取不同的方法制备了系列固体VPO催化剂.借助XRD、FT-IR对催化剂进行了主体晶相确定，用氧化还原滴定方法测定了不同晶相催化剂中钒的平均氧化数.结合催化反应的活性评价，发现催化剂主体晶相、结晶度、活化气氛和催化剂的V4＋/V5＋比均对目标反应的催化活性产生影响，5种催化剂中以(VO)2P2O7晶相催化剂的活性为最高.     

New heterocycles of 2,3‐diaryl‐substituted maleic hydrazides

2,3‐Diaryl‐substituted maleic anhydrides were prepared by a modified one‐pot synthesis of Perkin condensation using mixed sodium salts of arylglyoxylic acid and arylacetic acid with acetic anhydride in 1,4‐dioxane. The treatment of these anhydrides with ammonium bicarbonate, or methanolic hydrazine, offered the corresponding 2,3‐diaryl‐substituted maleimides and maleic hydrazides (4,5‐diaryl‐substituted 1,2‐dihydropyridazine‐3,6‐dione), respectively. Evidence obtained from NMR, UV, and mass spectra suggest that 2,3‐diaryl‐substituted maleic hydrazides do not exhibit monolactim forms. Ring contraction of the diaryl‐substituted maleic hydrazide by nitrosation led to the formation of the corresponding maleimide. Interconversion between the corresponding maleic hydrazide and maleimide was observed following equilibrium reaction. Our experiment proposes that the chemistry of 2,3‐diaryl‐substituted maleic hydrazides rarely involves the function of ethylene moiety and resembles that of succinic hydrazine. J. Heterocyclic Chem.,(2011).     

Mechanism Studies of the Conversion of 13C‐Labeled n‐Butane on Zeolite H‐ZSM‐5 by Using 13C Magic Angle Spinning NMR Spectroscopy and GC–MS Analysis

By using ¹³C MAS NMR spectroscopy (MAS=magic angle spinning), the conversion of selectively ¹³C‐labeled n‐butane on zeolite H‐ZSM‐5 at 430–470 K has been demonstrated to proceed through two pathways: 1) scrambling of the selective ¹³C‐label in the n‐butane molecule, and 2) oligomerization–cracking and conjunct polymerization. The latter processes (2) produce isobutane and propane simultaneously with alkyl‐substituted cyclopentenyl cations and condensed aromatic compounds. In situ ¹³C MAS NMR and complementary ex situ GC–MS data provided evidence for a monomolecular mechanism of the ¹³C‐label scrambling, whereas both isobutane and propane are formed through intermolecular pathways. According to ¹³C MAS NMR kinetic measurements, both pathways proceed with nearly the same activation energies (E_a=75 kJ mol^?1 for the scrambling and 71 kJ mol^?1 for isobutane and propane formation). This can be rationalized by considering the intermolecular hydride transfer between a primarily initiated carbenium ion and n‐butane as being the rate‐determining stage of the n‐butane conversion on zeolite H‐ZSM‐5.     

正丁烷脱氢制正丁烯催化剂

综述了对正丁烷脱氢制备正丁烯的催化剂体系,包括有氧脱氢中钒基催化剂、钼酸盐系列和焦磷酸盐系列催化剂;催化脱氢中贵金属Pt系催化剂、以ZSM-5分子筛为载体的催化剂以及膜反应器。探讨了正丁烷脱氢动力学,并在Mars-van Krevlen和 Eley-Rideal机理模型动力学基础上归纳了正丁烷氧化脱氢及直接脱氢的机理。讨论了正丁烷催化剂的影响因素,比较了各类催化剂的特点并对其进行展望,认为ZSM-5分子筛将可能成为正丁烷脱氢制正丁烯的新的研究热点。