共查询到19条相似文献,搜索用时 46 毫秒
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铁络合物/八面沸石催化剂中沸石主体的纳米效应 总被引:4,自引:0,他引:4
采用自由配体法制备了Fephen/nano-X和Fephen/nano-Y两种\r\n不同粒度的Fephen/八面沸石纳米复合材料(简称为Fephen/FAU),\r\n并采用X射线衍射、傅里叶变换红外光谱、漫反射紫外-可见光谱、热\r\n重-差热分析和催化反应等手段对其进行了表征.研究结果发现,采用\r\n纳米沸石作主体是自由配体法制备金属络合物/分子筛复合材料中提高\r\n络合物负载量的有效方法.催化反应结果表明,与普通粒度的Fephen/\r\nY复合材料相比,两种不同粒度的Fephen/nano-X和Fephen/nano-Y\r\n纳米复合材料对环己烷氧化反应的催化活性有很大的提高.由于两种纳\r\n米沸石主体的差异,两种纳米复合材料的催化性能也明显不同,不仅对\r\n环己烷的转化能力不同,对氧化产物的选择性也不同. 相似文献
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钒催化剂选择性氧化乳酸乙酯制丙酮酸乙酯 总被引:6,自引:1,他引:6
The structure and surface acidity of vanadium oxide supported on α-Al2O3、TiO2、SiO2 have been studied by XRD、IR、TPR and adsorption microcalorimetry. The catalytic performance of the catalysts for selective oxidation of ethyl lactate to ethyl pyruvate was determined in a continuous flow fix-bed reactor. The results showed that the dispersion of vanadium oxide on the supports weakened the V=O bond and actived the terminal oxygen, which increased the reaction activity. On the otherhand, The surface acidity is harmful to the selectivity of ethyl pyruvate. V/α-Al2O3 exhibited a lower conversion since its dispersion is low. The low selectivity on V/SiO2 is due to its fairly strong surface acidity. Addition of K+ weakened the surface acidty and enhanced selectivity of V/SiO2. V/TiO2 exhibited the best activity and selectivity among the catalysts studied because of its weak surface activity. The conversion of ethyl lactate and selectivity to ethyl pyruvate are 97% and 81%, respectively, over the V/TiO2 catalyst at 473K. 相似文献
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在溴化钾存在下, 大型海洋藻类珊瑚藻的钒-溴过氧化物酶 (V-BPO) 可在常温下催化 H2O2 环氧化环己烯生成环氧环己烷. 通过用含 1.0 mmol/L 钒离子和 1.0 mmol/L 钙离子的缓冲溶液透析 V-BPO, 用恒流泵向反应体系中连续添加 H2O2, 并优化其它反应条件, 可提高该催化反应时空收率. 在优化的反应条件下, 产物环氧环己烷的时空收率为 4.79 g/(h•L), 对 H2O2 的收率为 74%, 均比文献最高值提高了 78%. 相似文献
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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
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醇在钒基催化剂上的氧化 总被引:1,自引:0,他引:1
Wimonrat TRAKARNPRUK Piyanoot HOONSART 《催化学报》2007,28(4):290-292
以过氧化叔丁醇作为氧化剂,研究了醇类(苯甲醇、1-苯基乙醇和环己醇)在钒基催化剂上的氧化反应.制备了含苯磷二酚配体或吡嗪-2-羧酸酯配体的钒配合物,并运用傅里叶变换红外光谱、核磁共振谱、紫外-可见光谱及元素分析对其进行了表征.考察了溶剂对该类反应的影响.发现在甲苯溶剂中进行氧化反应时,苯甲醇被氧化成苯甲醛而不会被深度氧化为苯甲酸;而在乙腈溶剂中,苯甲醛和苯甲酸均有生成.此外,对不同钒磷氧化物的催化活性进行了比较,结果表明,在乙腈溶剂中的产品收率比在甲苯溶剂中高. 相似文献
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Rice husk silica catalyst loaded with 10 wt% vanadium was synthesized from agricultural biomass via a sol-gel synthetic route at pH = 9. The catalyst was characterized by different physico-chemical methods. The FTIR spectra showed the formation of Si–O–V and V=O stretching bands. The presence of vanadium was confirmed by EDX elemental analysis. RH-10V possessed a high specific surface area of 276 m2/g and pore volume of 0.83 ml/g. The prepared catalyst possessed a narrow pore size distribution centered around 7.9 nm. The catalytic performance of RH-10V was tested in the oxidation of acetophenone at 70 ℃. RH-10V was found to be an active catalyst in the oxidation of acetophenone, producing 36.28% conversion efficiency. The products identified were benzoic acid, 2-hydroxyacetophenone, phenol, acetic acid, and 3-hydroxyacetophenone. 相似文献
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《化学:亚洲杂志》2017,12(15):1915-1919
C‐Scorpionate vanadium(IV) [VOxCl3−x {κ3‐RC(pz)3}] [pz=pyrazol‐1‐yl; x= 0, R=SO3 ( 1 ); x= 1, R=CH2OH ( 2 ) or CH2OSO2Me ( 3 )] complexes supported on functionalized carbon nanotubes (CNTs) are the first V‐scorpionate catalysts used so far for the neat oxidation of o ‐, m ‐ or p ‐xylene, with TBHP (70 % aqueous solution), to the corresponding toluic acids (main products), tolualdehydes and methylbenzyl alcohols. Remarkably, a p ‐toluic acid yield of 43 % (73 % selectivity, TON=1.34×103) was obtained with 2 @CNT in a simple microwave‐assisted mild oxidation procedure, using a very low catalyst charge (3.2×10−2 mol % vs. substrate). Further, this occurred in the absence of any bromine source, what is significant towards the development of a greener and more sustainable process for oxidation of xylenes. Moreover, reuse of catalysts with preservation of their activity was found for up to six consecutive cycles. The effects of reaction parameters, such as reaction time, temperature, amount of catalyst or type of heating source, on the performance of the above catalytic systems are reported and discussed. 相似文献
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Chun JIN Yin Juan JIA Bin Bin FAN Jing Hong MA Rui Feng LI 《中国化学快报》2006,17(3):419-422
In the last decade, encapsulation of transition metal complexes in zeolites and related materials has been paid much attention, because this type of materials could serve as functional mimic enzymes, possessing both homogeneous-catalysis and heterogeneous… 相似文献
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用等体积浸渍法制备了SBA-15担载的钒基氧化物催化剂,使用X射线衍射(XRD)分析、氮气吸附、紫外激光拉曼、傅里叶变换红外(FTIR)光谱和紫外-可见漫反射(UV-Vis DRS)光谱对催化剂的结构进行了表征,并评价了催化剂对丙烷选择氧化的活性与选择性.实验结果表明SBA-15载体对丙烷选择氧化的活性优于常规的SiO2载体.SBA-15担载的低载量催化剂是高分散的催化剂体系,在低钒载量(n(V)/n(Si)<2.5%)时,催化剂具有规则的六方介孔结构.低钒载量(n(V)/n(Si)<0.1%)时,隔离四配位的钒氧化物是丙烷选择氧化生成醛类化合物的活性物种;高钒载量(n(V)/n(Si)>2.5%)时,聚合六配位的钒氧化物和微晶钒氧化物是丙烷脱氢或深度氧化的活性物种. 相似文献
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通过溶剂热法制备Ce掺杂的TiO2,利用等体积浸渍法制得一系列V2O5/Ce-TiO2催化剂,并用于甲醇选择性氧化制二甲氧基甲烷(DMM)。 采用XRD、UV-Vis、 H2-TPR、NH3-TPD等技术手段对催化剂进行了表征。 结果表明,Ce掺杂改性后的TiO2负载V2O5更有利于催化剂表面钒氧物种的分散,且钒氧物种主要以孤立的和聚合态的形式存在,没有形成V2O5晶相结构。 Ce掺杂改性后,改变了TiO2载体与钒氧物种间的作用力,Ce掺杂量越大,钒氧物种的还原温度逐渐向高温移动,使得催化剂的氧化还原能力减弱。 Ce改性的TiO2负载V2O5,Ce的改性量对催化剂的酸性质几乎没有影响,但是催化剂的酸性却随着V2O5负载量的增大而逐渐减弱。 当Ce和Ti的摩尔比为0.01,V2O5的负载量为10%所得催化剂10V/1Ce-TiO2具有较为适宜的氧化还原性和酸性,在反应温度160 ℃时,甲醇的转化率为39.6%,DMM的选择性高达99.9%。 相似文献
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eljka Soldin Boris-Marko Kukovec Dubravka Matkovi-alogovi Zora Popovi 《Molecules (Basel, Switzerland)》2021,26(16)
Three new mercury(II) coordination compounds, {[HgCl(pic)]}n (1), [HgCl(pic)(picH)] (2), and [HgBr(pic)(picH)] (3) (picH = pyridine-2-carboxylic acid, picolinic acid) were prepared by reactions of the corresponding mercury(II) halides and picolinic acid in an aqueous (1) or alcohol–methanol or ethanol (2 and 3) solutions. Two different types of coordination compounds were obtained depending on the solvent used. The crystal structures were determined by the single-crystal X-ray structural analysis. Compound 1 is a one-dimensional (1-D) coordination polymer with mercury(II) ions bridged by chelating and bridging N,O,O′-picolinate ions. Each mercury(II) ion is four-coordinated with a bidentate picolinate ion, a carboxylate O atom from the symmetry-related picolinate ion and with a chloride ion; the resulting coordination environment can be described as a highly distorted tetrahedron. Compounds 2 and 3 are isostructural mononuclear coordination compounds, each mercury(II) ion being coordinated with the respective halide ion, N,O-bidentate picolinate ion, and N,O-bidentate picolinic acid in a highly distorted square-pyramidal coordination environment. Compounds 1–3 were characterized by IR spectroscopy, PXRD, and thermal methods (TGA/DSC) in the solid state and by 1H and 13C NMR spectroscopy in the DMSO solution. 相似文献
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由廉价的手性氨基醇与3,5-二溴或3,5-二碘水杨醛缩合得到配体,配体与VO(acac)2按一定比例络合形成络合物催化剂,考察了室温下该催化剂对芳基甲基硫醚不对称氧化反应的催化性能. 结果表明,当VO(acac)2/配体摩尔比为1/2, 并且以H2O2作为氧源时,催化剂具有较高的活性和中等至很高的对映选择性. 与(S)-苯丙氨醇和(R)-亮氨醇衍生得到的配体相比,由(S)-缬氨醇得到的配体具有更高的对映选择性. 在缓慢滴加H2O2的条件下,以3,5-二碘水杨醛和(S)-缬氨醇缩合得到的Schiff碱为配体,以苯甲硫醚和对溴苯甲硫醚为底物时,产物的ee值分别为88%和92%. 研究表明,与Fe(acac)3/Schiff碱体系不同,向VO(acac)2/Schiff碱催化体系中加入羧酸或羧酸盐类化合物并不能改善催化剂的催化性能. 相似文献