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.     

正丁烷氧化制顺酐流化床催化剂的研究

对正丁烷氧化制顺丁烯二酸酐(以下简称顺酐)流化床催化剂进行了研究。考察了钒-磷-氧系催化剂制备过程及添加不同金属组份对催化剂性能的影响。实验表明,在小试最佳反应条件下,催化剂经长期运转评选,表明F-Ⅳ-Z催化剂具有较好的催化活性和稳定性。     

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．     

钒磷氧合成条件对丁烷选择性氧化催化性能的影响

正丁烷氧化制备顺酐是低碳烷烃高值化利用的典型代表,钒磷氧(VPO)催化剂是该反应唯一的工业催化剂。通过调控有机相法合成过程中还原时间、回流时间和磷钒物质的量比3种实验参数,合成系列VPO催化剂,结合多种分析手段,探索合成条件对催化剂结构的影响规律,获得精细调控催化剂合成的方法和最优条件,催化正丁烷选择性氧化反应,转化率可达93.8%,顺酐收率达62.4%。进而精准构筑VPO催化剂,揭示VPO催化正丁烷选择性氧化制顺酐反应中的构效关系。     

用于丁烷选择氧化制顺酐的铈锆复合钒磷氧催化剂的研究

 在钒磷氧（VPO）催化剂中添加适量铈锆复合氧化物，得到了一\r\n种新型的铈锆复合钒磷氧催化剂．该催化剂对丁烷选择性氧化制顺酐反\r\n应的催化性能比纯VPO催化剂有了显著提高．在丁烷／空气共进料反应\r\n条件下，其顺酐收率比纯VPO催化剂提高了一倍；在无氧反应条件下，\r\n其可参与选择性氧化制顺酐的晶格氧量为纯VPO催化剂的2．2倍．BET比\r\n表面积测试、X射线衍射、钒平均价态测定和程序升温实验等表征结果\r\n表明，混合在催化剂活性相中的少量铈锆复合氧化物参与了VPO体系的\r\n氧化还原过程，并起到了以下两方面的作用：（1）促进了（VO）2P2O\r\n7相的形成，稳定了钒的平均价态，有利于最终形成晶相结构良好和反\r\n应性能稳定的VPO催化剂；（2）显著提高了VPO催化剂的氧化还原性能\r\n，大大增加了催化剂的可逆储氧量．     

氧化钒系催化剂在NH3-SCR脱硝反应中的氧化性能

氧化钒系催化剂已广泛应用于NO x的氨选择性催化还原(NH3-SCR)反应。氧化钒作为催化剂活性成分,具有较强的氧化性,在NO x的NH3-SCR过程中,其强氧化性会造成氨以及烟气中SO2、汞的氧化,从而影响催化剂的SCR性能。本文对氧化钒系催化剂中钒物种的存在形态进行了总结,并重点阐述了脱硝过程中氧化钒系催化剂的氧化性能及其对脱硝性能的影响。     

V-P-O/SiO_2催化剂上苯氧化的ESR研究

用浸渍法制备组成通式为(V_2O_5)_(20)(P_2O_5)_2(SiO_2)_(100)(0相似文献   

超临界流体干燥方法在丁烷选择性氧化制顺酐VPO催化剂制备中的应用

分别用超临界流体干燥方法和传统方法制备了用于丁烷选择性氧化顺酐的VPO催化剂。用超临界流体干燥方法制备的催化剂VPOⅡ的比表面积高达38．8m^2/g,而用传统方法制备的催化剂VPOⅠ的比表面积只有10.7m^2/g。XRD分析表明,除催化剂VPOⅡ中的VOPO4相含量比催化剂VPOⅠ稍多外,这两种催化剂的主要结构均为（VO）2P2O7相。在有氧和无氧条件下进行的丁烷氧化制顺酐的催化反应结果表明,用超临界流体干燥方法制备的催化剂不仅具有较高的顺酐收率,而且含有更多的可在无氧条件下参与选择性氧化反应的晶格氧（催化剂VPOⅡ的可利用选择性晶格氧量比催化剂VPOⅠ增加了1．5倍）。用超临界流体干燥方法可以改善催化剂性能的原因可能与催化剂具有较大的比表面积和较多的V^5 有关。     

超临界流体干燥方法在丁烷选择性氧化制顺酐

分别用超临界流体干燥方法和传统方法制备了用于丁烷选择性氧化制顺酐的VPO催化剂. 用超临界流体干燥方法制备的催化剂VPOⅡ的比表面积高达38.8 m2/g,而用传统方法制备的催化剂VPOⅠ的比表面积只有10.7 m2/g. XRD分析表明,除催化剂VPOⅡ中的VOPO4相含量比催化剂VPOⅠ稍多外,这两种催化剂的主要结构均为(VO)2P2O7相. 在有氧和无氧条件下进行的丁烷氧化制顺酐的催化反应结果表明,用超临界流体干燥方法制备的催化剂不仅具有较高的顺酐收率,而且含有更多的可在无氧条件下参与选择性氧化反应的晶格氧(催化剂VPOⅡ的可利用选择性晶格氧量比催化剂VPOⅠ增加了1.5倍). 用超临界流体干燥方法可以改善催化剂性能的原因可能与催化剂具有较大的比表面积和较多的V5+有关.     

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．     

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%.     

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。     

二甲基亚砜对钒磷氧催化剂性能的影响

在制备钒磷氧催化剂前驱体的过程中,加入高沸点溶剂二甲基亚砜（DMSO）,改善了钒磷氧催化剂对正丁烷氧化制顺丁烯二酸酐的催化性能．催化性能评价实验表明,当DMSO／V（摩尔比）=0．1时,用催化剂（D0.1-VPO）制备顺酐的收率达到最大（49．4％）,与没有加入DMSO的催化剂（VPO）相比其选择性由57％提高到76％,转化率达到65％．采用BET,XRD,SEM,FT-IR等方法分析,发现添加DMSO能增大催化剂的比表面积,改变催化剂前驱体择优取向和催化剂的微观形貌,形成了一些具有纳米尺度的催化剂颗粒．     

Effect of Bismuth Additives on the Properties of Vanadium–Phosphorus Oxide Catalyst in the Partial Oxidation of n-Pentane

The selective oxidation of n-pentane on vanadium–phosphorus oxide (VPO) catalysts with bismuth additives (Bi/V = 0–0.30) is studied. The catalysts are characterized by XRD, XPS, and specific surface area measurements using nitrogen adsorption. Their acidic properties are studied (using ammonia TPD and the 2-methyl-3-butyn-2-ol reaction). It was found that the introduction of bismuth insignificantly affects the specific surface area but increases the surface concentration of phosphorus and changes the acidic properties of the catalysts. The specific catalytic activity of samples in n-pentane oxidation correlates with the effective charge of surface oxygen (E _b of O1s electrons). The selectivity to citraconic anhydride increases with an increase in the general surface acidity. The selectivity to maleic anhydride increases with an increase in the Brønsted acidity of the surface. The selectivity to phthalic anhydride increases with an increase in the Lewis acidity. The pathways of product formation in the partial oxidation of n-pentane are proposed.     

Effects of mechanochemical treatment to the vanadium phosphate catalysts derived from VOPO4·2H2O

Modification by using mechanochemical treatment of vanadium phosphate catalysts on the microstructure, morphology, oxygen nature and catalytic performance for n-butane oxidation is described and discussed. In this work, the precursor, VOHPO₄·0.5H₂O prepared by reduction of VOPO₄·2H₂O by isobutyl alcohol was subjected to a high energy planetary ball mill for 30, 60 and 120 min in ethanol. The ball milling process reduced the crystallite size of the catalysts and consequently increased their surface area. The morphologies of the milled catalysts are dependent on milling time. The highest reactivity and mobility of the lattice oxygen species has been achieved by the catalyst milled for 60 min with lower reduction peak temperature and higher amount of oxygen atoms removed. The oxygen species removed from the active V⁴⁺ phase was shown to be correlated with the rate of reaction. A good relationship was also found between the oxygen species associated with V⁵⁺ and maleic anhydride selectivity. However, a larger amount of this oxygen species will give a deleterious effect on the conversion rate. The present study demonstrate that the mechanochemical method (with an appropriate duration) effectively enhanced the catalytic activity by increasing the surface area and controlling the reactivity, and that the amount of oxygen species contributed to the partial oxidation of n-butane to maleic anhydride.     

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     

分数维法对V系催化剂表面的纹理及催化性质的表征

应用计算机纹理分析技术,以分形理论及萘氧化制邻苯二甲酸酐钒系催化剂为样本,通过改变K_2SO_4、P_2O_5助剂含量,研究了多相催化剂的表面形貌.结果表明,催化剂表面分数维D随助剂的含量发生变化,D在极大值时邻苯二甲酸酐的收率最高。     

Reaction mechanism-based design of efficient VPO catalysts for <Emphasis Type="Italic">n</Emphasis>-C<Subscript>5</Subscript>H<Subscript>12</Subscript> oxidation into phthalic,maleic, and citraconic anhydrides

Hypotheses as to possible ways of enhancing the selectivity of partial n-pentane oxidation with respect to phthalic, maleic, and citraconic anhydrides are suggested based on the mechanistic concepts of the formation of these products. The hypotheses are checked by studying the properties of vanadium-phosphorus oxide (VPO) catalysts upon the introduction of different concentrations of La, Bi, Fe, W, Te, Ti, Zr, or Mo. It is shown by various physicochemical methods (x-ray diffraction, IR spectroscopy, X-ray photoelectron spectroscopy, and pyridine and 2,6-dimethylpyridine adsorption) that the phase composition of the VPO catalyst and the oxidation states of its elements on the surface are not changed in most cases upon the introduction of these additives. The additives mainly affect the number of Lewis acid sites, whereas the Brønsted acidity changes only slightly. The existence of a correlation between the citraconic anhydride selectivity and the total acidity of the modified catalyst surface is confirmed. In agreement with the assumptions as to the process selectivity, it was discovered that the phthalic anhydride selectivity increases with an increase in the number of Lewis acid sites. The observed regularities open up the way to the purposeful synthesis of catalysts with enhanced selectivity with respect to these products.     

Product oriented oxidative bromination of methane over Rh/SiO_2 catalysts

Rh/SiO2 was prepared for the oxidative bromination of methane. The catalyst was prepared by calcination at different temperatures and for different times to obtain catalysts with different specific surface areas for the purposes of producing either CH3Br or CH3Br and CO. It was found that the catalyst having a low specific surface area (calcined at relatively high temperature) favors the selective oxidation of methane to prepare CH3Br, while the catalyst having a high specific surface area favors the deeper partial oxidation of methane, which is good for CH3Br and CO preparation.The 650 h on stream life-time test revealed that the catalytic performance of the 0.4Rh/SiO2-900-10 catalyst was excellent.Both methane conversion and CH3Br selectivity kept increasing trends during the life-time test.No matter how serious was the Rh leaching during the reaction,the 0.4Rh/SiO2-900-10 catalyst did not deactivate at all.