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1.
氧化镁负载磷钼钒杂多酸催化剂的结构和催化性能   总被引:2,自引:2,他引:0  
采用乙醇溶液中浸渍的方法制备了氧化镁负载的磷钼钒酸铜(Cu2PMo11VO40)催化剂,考察了正己醇选择氧化生成正己醛的催化反应性能.催化剂的IR,XRD,UV-DRS,NMR,DTA-TG和比表面积等测试结果表明,Cu2PMo11VO40在氧化镁表面单层分散,形成缺位型Keggin结构.反应后催化剂表面分散状态及结构未发生明显改变,Keggin型对称结构有所恢复,形成活化状态的缺位型Keggin结构.  相似文献   

2.
合成了Keggin型缺位取代杂多酸盐(Na5PW11Z(H2O)O39,Z=Mn、Fe、Co、Ni、Cu、Zn,以下简称PW11Z)催化剂.通过ICP、IR、UV等表征手段对催化剂进行了表征.元素分析结果表明,各缺位取代杂多酸盐的计量式为Na5PW11Z(H2O)O39.IR光谱表明,取代型杂多化合物仍保持Keggin型骨架结构.而且,除了Na5PW11Ni(H2O)O39以外,其余化合物的P-O键吸收峰发生劈裂,其劈裂强度为PW11Cu>PW11Zn>PW11Mn>PW11Fe>PW11Co.Mo=O键的振动向低波数位移.UV表征结果表明,由于过渡金属的引入,相对于Keggin型杂多酸H3PW12O40,取代产物的紫外可见吸收峰向紫外方向位移,但位移强度不大,基本有与H3PW12O40中Mo=O键的ππ*跃迁大致相同的吸收.还利用以上催化剂对正己醇氧化生成正己醛的反应活性进行了考察.  相似文献   

3.
再生方法对V2O5/AC催化剂同时脱硫脱硝活性的影响   总被引:12,自引:0,他引:12  
 考察了水洗再生、Ar热再生和5%NH3-95%Ar还原再生对V2O5/AC催化剂同时脱硫脱硝活性的影响. 结果表明,水洗再生虽然可洗去反应过程中沉积在催化剂表面的含硫物质,但也能将部分活性组分V2O5转化生成的VOSO4洗去,使催化剂的脱硫脱硝活性降低. Ar热再生后催化剂的脱硝活性与新鲜样品相同,但脱硫活性很低. 经5%NH3-95%Ar还原再生后,催化剂的脱硫活性可恢复到新制备时的水平,同时脱硝活性大大提高,这是由于催化剂表面除了原有的脱硝活性位V2O5外,又形成了新的活性位NH+4/NH-2. 还原再生过程产生的SO2与NH3在室温下反应生成固体亚硫酸铵盐,可实现硫的资源化,简化了后续处理工艺.  相似文献   

4.
VPO催化剂制备条件对其催化甲苯氨氧化反应性能的影响   总被引:1,自引:0,他引:1  
 用浸渍法制备了负载型钒磷氧(VPO)催化剂,并以甲苯氨氧化合成苯甲腈为探针反应,考察了载体、还原剂、P/V比和V2O5负载量对催化剂性能的影响. 结果表明,大比表面积SiO2负载的VPO催化剂性能稳定,在高温下也具有较好的选择性. 采用不同还原剂制备的催化剂在反应一段时间后活性趋于一致,表明催化剂活性中心是在反应气氛下形成的. P/V比对催化剂活性和结构影响较大,P的加入破坏了V2O5的晶型结构,使磷酸盐物种从催化剂体相向表面聚集,减少了催化剂表面存在的过度氧化物种O-和O-2的数量,选择性氧化物种晶格氧(O2-)起主要氧化作用,提高了催化剂的选择性. V2O5负载量增大,催化剂活性提高,但生成苯甲腈的选择性降低. 表面单分子层覆盖的VOx可能是反应的活性位和选择性位.  相似文献   

5.
合成了磷钨酸铜并利用XRD、FT-IR和UV等对其结构进行了表征,结果表明其具有Keggin结构.在室温无溶剂条件下,考察了磷钨酸铜催化一系列醛和乙酸酐合成相应的乙酰缩醛的反应.结果表明,醛和乙酸酐的物质量比为1∶2,磷钨酸铜用量仅需占醛的0.5%(摩尔比)就能使反应在较短时间内完成,产物产率可达62%~96%.该催化剂在醛和酮同时存在时,可以选择性地与醛基发生反应.  相似文献   

6.
离子液体介质中用Cu/ZrO2-SiO2催化香茅醛加氢合成薄荷醇   总被引:1,自引:0,他引:1  
制备了Cu/ZrO2-SiO2双载体催化剂, 并在离子液体介质中研究了香茅醛催化加氢合成薄荷醇的反应. 研究结果表明, 离子液体中的阳离子与香茅醛分子中的羰基形成氢键, 使香茅醛更容易异构化为胡异薄荷醇, 提高了催化剂的选择性; 特别是可调节酸度的[bmim][AlmCln]离子液体, 有效地提供了香茅醛的异构化所需要的路易斯酸条件, 在竞争性加氢中促进了香茅醛向生成薄荷醇的方向转化. 在0.8 MPa, 90 ℃, 2 h的条件下, 香茅醛一锅反应生成薄荷醇的转化率为100%, 对薄荷醇的选择性为91.3%, 而且, 催化剂和离子液体可回收和重复使用.  相似文献   

7.
CO2氧化异丁烷制异丁烯用Pd/V2O5-SiO2催化剂   总被引:4,自引:0,他引:4  
王茂功  钟顺和 《催化学报》2007,28(2):124-130
 利用表面化学反应改性法制备了不同V2O5负载量的V2O5-SiO2表面复合物载体,进而采用等体积浸渍法制备了负载型Pd催化剂. 用N2吸附、 X射线衍射、透射电镜、 X射线光电子能谱、程序升温脱附、化学吸附-红外光谱和微反技术对系列Pd/V2O5-SiO2催化剂的比表面积、晶相结构、价态、异丁烷的化学吸附性能和CO2部分氧化异丁烷制异丁烯的催化性能进行了研究. 结果表明, Pd/V2O5-SiO2催化剂中的钒以V5+形式存在, V5+在催化剂表面形成活性位V=O, 其中 V=O 晶格氧与 i-C4H10分子的-CH3 和-CH 中的H产生化学吸附作用; 催化剂中金属Pd与V4+协同作用使CO2在催化剂上产生了卧式吸附态; 晶格氧参加了催化氧化反应,催化剂中 V5+←→V4+ 的变化构成了催化反应的氧化还原过程. 在525 ℃, CO2/i-C4H10体积比为1和空速为 1200 h-1的条件下,以Pd/25%V2O5-SiO2为催化剂时异丁烷转化率为22.8%, 异丁烯选择性为89.1%.  相似文献   

8.
在乙醇溶液中采用不同的浸渍方法制备了氧化镁负载的钼钒磷酸铜催化剂,利用XRD、IR和BET比表面测定等测试手段对催化剂进行了表征.XRD和IR表征结果表明,负载的钼钒磷酸铜在载体表面均匀分散,而且能够保持Keggin型结构.XRD和BET比表面测定结果说明,经12h浸渍制备的催化剂(H4PMo11VO40-CuO/MgO12H)化学和结构性能发生变化;其它两种方法制备的催化剂(H4PMo11VO40-CuO/MgO和Cu2PMo11VO40/MgO)没有化学和结构性能的变化,而且这两种催化剂具有相近的表征结果,说明两种催化剂具有相似的结构特征,以正己醇氧化脱氢生成正己醛反应评价了催化剂的催化反应性能,结果表明,H4PMo11VO40-CuO/MgO和Cu2PMO11VO40/MgO催化剂显示出比H4PM011VO40-CuO/MgO12H更高的催化反应活性。  相似文献   

9.
以S iO2为载体用浸渍法制备了Cu3/2PMo12O40/S iO2催化剂,用于碳酸二甲酯和苯酚酯交换合成碳酸二苯酯,并用DTA-TG、IR和XRD等对催化剂进行了表征.煅烧温度低于400℃时,催化剂仍然保持了Keggin结构;高于450℃时,催化剂Keggin结构分解,分解产物为α-MoO3等.活性随煅烧温度升高而增加,在400℃达到最大值,甲基苯基碳酸酯和碳酸二苯酯总收率为25.0%,选择性99.2%;高于500℃催化剂活性降低,表明Keggin结构在催化剂活性中起到了重要作用.  相似文献   

10.
在介质阻挡等离子体放电(DBD)辅助催化剂(6%CuO/15%TiO2/γ-Al2O3,6%CuO/5%CeO2/15%TiO2/γ-Al2O3)反应装置上,研究了4种不同反应条件下(NO+CH4,NO+CH4+O2,NO+CH4+NTP,NO+CH4+O2+NTP)NO和CH4反应,采用BET、XRD、H2-TPR和XPS等手段对催化剂进行了表征.结果表明在上述4种反应条件下,对于NO+CH4的反应,O2的存在有利于NO脱除,在等离子体条件下,O2的加入对NO的转化有所抑制;而等离子体的活化极大增强了NO的低温脱除活性.在等离子体存在条件下,6%CuO/5%CeO2/15%TiO2/γ-Al2O3(6Cu5Ce15TA)对NO的转化率都优于6%CuO/15%TiO2/γ-Al2O3(6Cu15TA).BET结果显示添加TiO2和CeO2于γ-Al2O3表面后,比表面积都有少量降低;而各载体负载6%CuO后比表面积也有所下降.XRD结果表明6Cu15TA和6Cu5Ce15TA催化剂由锐钛矿相TiO2组成,CuO在各催化剂表面呈现高度分散.H2-TPR数据和XPS实验结果显示负载CuO后,催化剂表面的铜物种由高度分散的CuO和嵌入到CeO2或TiO2晶格中Cu2+所组成.6Cu5Ce15TA表面含有较6Cu15TA多的Cu+,从而增强了NO的脱除活性.  相似文献   

11.
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.  相似文献   

12.
KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.  相似文献   

13.
The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.  相似文献   

14.
Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.  相似文献   

15.
16.
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.  相似文献   

17.
The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion.  相似文献   

18.
Quercetin, the polyphenolic compound, which has the highest daily intake, is well known for its protective effects against aging diseases and has received a lot of attention for this reason. Both quercetin 3-O-β-d-glucuronide and quercetin 3′-O-β-d-glucuronide are human metabolites, which, together with their regioisomers, are required for biological as well as physical chemistry studies. We present here a novel synthetic route based on the sequential and selective protections of the hydroxyl functions of quercetin allowing selective glycosylation, followed by TEMPO-mediated oxidation to the glucuronide. This methodology enabled us to synthesize the five O-β-d-glucosides and four O-β-d-glucuronides of quercetin, including the major human metabolite, quercetin 3-O-β-d-glucuronide.  相似文献   

19.
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.  相似文献   

20.
An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.  相似文献   

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