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1.
环己烷催化氧化制取顺酐和醋酸的催化剂研究   总被引:3,自引:0,他引:3  
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.  相似文献   

2.
在复合金属氧化物催化剂上丙烷直接氧化制丙烯酸   总被引:3,自引:0,他引:3  
丙烷直接氧化制丙烯酸是近年来催化氧化的热点课题。MoVTe(Sb)NbO复合金属氧化物催化剂是该反应最重要的一类催化剂。本文对该类催化剂的制备化学包括活化方式以及决定催化性能的主要活性相结构等方面的新近认识进行了系统评述;依据丙烷催化转化的反应途径,总结了有关催化剂元素组分在反应中的作用与功能的最新进展,调变催化剂的粒子尺寸与形貌、晶相组成与结构、表面酸碱性与氧化还原性是获得优良催化性能的关键因素。  相似文献   

3.
研究了Fe-P-O催化剂对甲烷氧化偶联(OCM)的低温催化活性,考察了催化剂组分的优化,最适宜的反应温区,反应过程参数,助催化剂组分,催化剂的晶型结构和活性相以及F:元素键合状态的XPS谱.确定了8%LiNO3-0.8Fe/P催化剂在650℃,CH4:O2:Ar=2:1:2及GHSV=3000h-1条件下,可获得甲烷转化率为11.90%和C2烃选择性为69.81%的结果.添加LiNO3为助催成分,可有效改善催化剂表面酸活性中心的分布,防止OCM中深度氧化和表面积炭,提高C2和C2烃选择性.该催化剂为可变价型,是六方形和料方形两种晶型结构的复合磷酸铁,活性相为斜方形FePO4物相.  相似文献   

4.
周凌  李剑锋等 《催化学报》2001,22(5):427-431
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。  相似文献   

5.
肖承庆  黄仲涛 《催化学报》1995,16(4):269-273
研究了Fe-P-O催化剂对甲烷氧化偶联的低温催化活性,考察了催化剂组分的优化,最适宜的反应温区,反应过程参数,助催化剂组分,催化剂的晶型结构和活性相以及Fe元素键合状态的XPS谱。  相似文献   

6.
过渡金属硫化物催化剂上SO2的还原   总被引:4,自引:0,他引:4  
胡大为  秦永宁  马智  韩森 《催化学报》2002,23(5):425-429
 对系列过渡金属硫化物催化剂上CO还原SO2的反应进行了研究.结果表明,FeS的催化性能最好,而MnS的催化性能最差,其他几种催化剂的活性顺序依次为CoS>CuS>NiS.催化剂的活性与硫化物自身的氧化还原能力、所具有的晶相结构及其同SO2的吸附键合作用力有密切的关系.在硫化物催化剂上,SO2还原的反应机理很可能是贫、富含硫化合物的交替作用机理.  相似文献   

7.
李坤兰  周宁  奚祖威 《催化学报》2002,23(2):125-126
 考察了溶剂和催化剂Q3[PO4(WO3)4]中季铵盐阳离子对环己\r\n烯环氧化反应的影响.在环己烯环氧化反应中,以氯仿和叔丁醇为溶剂\r\n时,环氧化反应的结果最好.当催化剂中季铵盐阳离子的碳数合适时,\r\n才能形成反应控制相转移催化过程.催化剂本身不溶于反应体系,但在\r\n过氧化氢的作用下形成可溶于反应体系的活性物种,均相地催化环氧化\r\n反应.当过氧化氢消耗尽时,催化剂又恢复到起始结构并从反应体系中\r\n析出.  相似文献   

8.
在Ba、Cs、Cl促进的Ag/α—Al2O3,催化剂上,考察了丁二烯的环氧化反应,获得较高的丁二烯转化率和乙烯基环氧乙烷选择性.在未添加卤代烃致稳剂条件下,催化剂短期稳定性超过140h.并对反应前后的催化剂进行了XRD、TEM、XPS等晶相和表面分析.XRD结果表明催化剂经短期稳定性试验后,银的平均粒径变化不大,但TEM分析表明在银催化剂的局部有银颗粒的板结;而XPS结果表明催化剂表面Cl有流失,Cs有富集.Cs-Ag的相互作用有可能促进吸附于Cs—Al活性位的氧物种插入吸附于Ag上的丁二烯.  相似文献   

9.
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   总被引:2,自引:2,他引:2  
 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.  相似文献   

10.
采用固体反应.模板剂晶化法合成出纳米介孔二氧化锆,并以其为载体通过浸渍法制备了Ni基催化剂,考察了载体性质对催化剂活性和稳定性的影响.结果表明,以四方晶相纳米二氧化锆为载体的催化剂性能更佳,并对其影响因素进行了分析.  相似文献   

11.
Catalysis is one of the key techniques for people's modern life. It has created numerous essential chemicals such as biomedicines, agricultural chemicals and unique materials. Heterogeneous catalysis is the new emerging method with reusable catalysts. Among heterogenous catalysis patterns developed so far, single crystalline catalysis has become the promising one owing to its high catalytic density and selectivity resulted by the inherent porosity, orderliness of the lattices and permeability. These crystalline catalysts could be used in various reactions such as photo-dimerization, Diels-Alder reaction, CO2 transformation and so on. In this review, we highlighted the reported works about the single crystalline catalysts. Both discrete small molecules and metal-organic frameworks (MOFs) have been used to prepare single crystals for catalysis. For discrete molecules based crystalline catalysts, coordinated and covalent molecules have been used. There were more catalytic modes in crystalline MOF catalysts. Three patterns were identified in this review: single crystalline MOFs i) without catalytic sites, ii) with inherent catalytic features and iii) with introducing catalytic units by post synthetic modification. Based on these examples, this review committed to provide the inspirations for the further design and application of single crystalline materials.  相似文献   

12.
利用电场作用通过交流和直流等离子体在低温、常压和低功率下催化反应将甲烷直接转化为碳二烃(乙烷、乙烯、乙炔)。考察了在对称电场作用下催化剂的催化性能。实验结果表明,在交流电场作用下,碳二烃选择性差别不大;甲烷转化率的大小顺序为: MnO_2/Al2O3>Ni/Al2O3>MoO_3/Al2O3>Al2O3>Ni/Al2O3>MoO_3/Al2O3>Ni/NaY>Pd/ZSM-5>Ni/H4Mg2Si3O4>Ni/ZSM-5>Co/ZSM-5>无催化剂:在直流电场作用下,碳二烃选择性差别也不大(除Ni/NaY外),甲烷转化率的大小顺序为: Ni/A12O3>Ni/H4Mg2Si3O4>Ni/ZSM-5>Co/ZSM-5>MnO2/A12O3>MoO3/A12O3>Ni/NaY>无催化剂>Pd/ZSM-5。  相似文献   

13.
采用以溶剂热方法合成的CdS纳米棒与酞菁氧钛复合制备的复合光导体,在570nm光照下其光电导性能明显提高,将质量分数为5%的CdS纳米棒与TiOPc复合使光敏性能提高32%.电子结构的数据和表面光电压谱分析结果表明,复合体系中存在从CdS纳米棒到TiOPc的光致空穴转移,TiOPc因被CdS纳米棒敏化而表现出高的光电导性能.  相似文献   

14.
Dry reforming of methane by CO2 using nickel ferrite as precursor of catalysts was investigated.Nickel ferrite crystalline particles were prepared by coprecipitation of nitrates with NaOH or ammonia followed by calcination,or by hydrothermal synthesis without calcination step.The textural and structural properties were determined by a number of analysis methods,including X-ray diffraction (XRD),Raman spectroscopy and X-ray photoelectron spectroscopy (XPS),among which X-ray diffraction (XRD) was at room and variable temperatures.All synthesized oxides showed the presence of micro or nanoparticles of NiFe2O4 inverse spinel,but Fe2O3 (hematite) was also present when ammonia was used for coprecipitation.The reducibility by hydrogen was studied by temperature-programmed reduction (TPR) and in situ XRD,which showed the influence of the preparation method.The surface area (BET),particle size (Rietveld refinement),as well as surface Ni/Fe atomic ratio (XPS) and the behavior upon reduction varied according to the synthesis method.The catalytic reactivity was investigated using isopropanol decomposition to determine the acid/base properties.The catalytic performance of methane reforming with CO2 was measured with and without the pre-treatment of catalysts under H2 in 650-800 C range.The catalytic conversions of methane and CO2 were quite low but they increased when the catalysts were pre-reduced.A significant contribution of reverse water gas shift reaction accounted for the low values of H2 /CO ratio.No coking was observed as shown by the reoxidation step performed after the catalytic reactions.The possible formation of nickel-iron alloy observed during the study of reducibility by hydrogen was invoked to account for the catalytic behavior.  相似文献   

15.
刘海超 《分子催化》2006,20(5):470-472
烃类选择氧化在石油化工中极其重要.近二十多年来,随着石油化工原料逐步从烯烃、芳烃等不饱和烃向资源丰富和价格相对低廉的烷烃的转化,研究烷烃的氧化活化和定向转化来取代相应的烯烃和芳烃工艺具有非常重要的学术意义和工业价值.因而,烷烃的选择活化和氧化得到了世界范围内的  相似文献   

16.
在固定床反应器上,以甲苯为生物质气化焦油的模型化合物,对橄榄石以及其负载镍催化剂对甲苯裂解反应和甲苯/水蒸气重整反应的催化性能进行了研究,并对催化剂进行了SEM、BET、XRD、H2-TPR等表征。结果表明,煅烧使原矿的物化特性发生改变,橄榄石对甲苯裂解反应和重整反应有一定的催化活性。而Ni的引入,使催化剂对甲苯裂解反应的活性有所降低,甲苯的转化率降低2.2%~9.8%;但催化剂对甲苯/水蒸气重整反应的活性升高,甲苯的转化率可高达97.0%,并且载镍橄榄石催化剂对甲苯/水蒸气重整反应有较强的稳定性。  相似文献   

17.
Covalent organic frameworks (COFs) as an emerging type of crystalline porous materials, have obtained considerable attention recently. They have exhibited diverse structure and attractive performance in various catalytic reactions. It is highly expected to have a systematic and comprehensive review summing up COFs‐derived catalysts in homogeneous and heterogeneous catalysis, which is favorable to the judicious design of an efficient catalyst for targeted reaction. Herein, we focus on summarizing recent and significant developments in COFs materials, with an emphasis on both the synthetic strategies and targeted functionalization, and categorize it in accordance with the different types of catalytic reactions. Their potential catalysis applications are reviewed thoroughly. Moreover, a personal view about the future development of COFs catalysts with respect to the large‐scale production is also discussed.  相似文献   

18.
19.
We demonstrated a catalytic cascade inverse electron demand hetero-Diels-Alder reaction (Povarov reaction) and hydrogen-transfer process. The reaction of electron-rich olefins and excess amount of imines in the presence of acid catalysts under appropriate conditions affords substituted quinolines in a single operation. In the cascade process, the catalysts, such as Tf2NH, TfOH, and Lewis acids, catalyze two mechanistically distinct reactions (auto-tandem catalysis). We also describe the synthetic utility of the prepared quinolines.  相似文献   

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