共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550oC
over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts for
the dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at
10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, the
only by-products were CO and CO2. The reaction rate of propane was found to be first order in propane
and close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with the
activation of the hydrocarbon as the rate determining step. The activation energy of the conversion of
propane was found to be 122±6 kJ/mol. 相似文献
3.
Chuanqing Kang Yihan Zhou Zhijun Du Zheng Bian Jianwei Wang Xuepeng Qiu Lianxun Gao Yuequan Sun 《Journal of mass spectrometry : JMS》2013,48(12):1318-1324
Secondary and tertiary amines have been reported to form [M–H]+ that correspond to dehydrogenation in matrix‐assisted laser desorption ionization time of flight mass spectrometry (MALDI‐TOF MS). In this investigation, we studied the dehydrogenation of amines in MALDI‐TOF MS by isotopic labeling. Aliphatic amines were labeled with deuterium on the methylene of an N‐benzyl group, which resulted in the formation of [M–D]+ and [M–H]+ ions by dedeuteration and dehydrogenation, respectively. This method revealed the proton that was removed. The spectra of most tertiary amines with an N‐benzyl group showed high‐intensity [M–D]+ and [M–H]+ ion peaks, whereas those of secondary amines showed low‐intensity ion peaks. Ratios between the peak intensities of [M–D]+ and [M–H]+ greater than 1 suggested chemoselective dehydrogenation at the N‐benzyl groups. The presence of an electron donor group on the N‐benzyl groups enhanced the selectivity. The dehalogenation of amines with an N‐(4‐halobenzyl) group was also observed alongside dehydrogenation. The amino ions from dehalogenation can undergo second dehydrogenation. These results provide the first direct evidence about the position at which dehydrogenation of an amine occurs and the first example of dehalogenation of haloaromatic compounds in MALDI‐TOF MS. These results should be helpful in the structural identification and elucidation of synthetic and natural molecules. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
4.
L.Late E.A.BlekkanDepartment of Chemical Engineering Norwegian University of Science Technology 《天然气化学杂志》2002,(Z1)
The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550℃ over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts for the dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at 10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, the only by-products were CO and CO2. The reaction rate of propane was found to be first order in propane and close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with the activation of the hydrocarbon as the rate determining step. The activation energy of the conversion of propane was found to be 122±6 kJ/mol. 相似文献
5.
The reaction kinetics of the oxidative dehydrogenation of propane was studied at 475-550℃over a VMgO catalyst. Vanadium-magnesium-oxides are among the most selective and active catalysts forthe dehydrogenation of propane to propylene. Selectivity to propylene up to about 60% was obtained at10% conversion, but the selectivity decreased with increasing conversion. No oxygenates were detected, theonly by-products were CO and CO2. The reaction rate of propane was found to be first order in propaneand close to zero order in oxygen, which is in agreement with a Mars van Krevelen mechanism with theactivation of the hydrocarbon as the rate determining step. The activation energy of the conversion ofpropane was found to be 122±6 kJ/mol. 相似文献
6.
Xinjiang Cui Wu Li Kathrin Junge Zhaofu Fei Matthias Beller Paul J. Dyson 《Angewandte Chemie (International ed. in English)》2020,59(19):7501-7507
Core–shell nanocatalysts are attractive due to their versatility and stability. Here, we describe cobalt nanoparticles encapsulated within graphitic shells prepared via the pyrolysis of a cationic poly‐ionic liquid (PIL) with a cobalt(II) chloride anion. The resulting material has a core–shell structure that displays excellent activity and selectivity in the self‐dehydrogenation and hetero‐dehydrogenation of primary amines to their corresponding imines. Furthermore, the catalyst exhibits excellent activity in the synthesis of secondary imines from substrates with various reducible functional groups (C=C, C≡C and C≡N) and amino acid derivatives. 相似文献
7.
8.
The lignin precursors of coniferin and syringin were synthesised, and guaiacyl-type and guaiacyl-syringyl-type oligomeric lignin dehydrogenation polymers (DHP and DHP-GS) were prepared with the bulk method. The carbon-13 nuclear magnetic resonance spectroscopy showed that both DHP-G and DHP-GS contained β-O-4, β-5, β-β, β-1, and 5-5 substructures. Extraction with petroleum ether, ether, ethanol, and acetone resulted in four fractions for each of DHP-G (C11–C14) and DHP-GS (C21–C24). The antibacterial experiments showed that the fractions with lower molecular weight had relatively strong antibacterial activity. The ether-soluble fractions (C12 of DHP-G and C22 of DHP-GS) had strong antibacterial activities against E. coli and S. aureus. The C12 and C22 fractions were further separated by preparative chromatography, and 10 bioactive compounds (G1–G5 and GS1–GS5) were obtained. The overall antibacterial activities of these 10 compounds was stronger against E. coli than S. aureus. Compounds G1, G2, G3, and GS1, which had the most significant antibacterial activities, contained β-5 substructures. Of these, G1 had the best antibacterial activity. Its inhibition zone diameter was 19.81 ± 0.82 mm, and the minimum inhibition concentration was 56.3 ± 6.20 μg/mL. Atmospheric pressure chemical ionisation mass spectrometry (APCI-MS) showed that the antibacterial activity of G1 was attributable to a phenylcoumarin dimer, while the introduction of syringyl units reduced antibacterial activity. 相似文献
9.
掺杂钛酸盐对乙烷氧化脱氢催化性能的研究 总被引:2,自引:0,他引:2
在700 ̄850℃范围内研究了掺杂CaTiO3、SrTiO3催化剂用于乙烷氧化脱氢(ODHE)的催化行为,发现这类催化剂对ODHE均有一定的催化活性。适量的Li^+取代Ti^4+后不仅提高了催化活性,而且改善了催化剂对乙烯的选择性。催化剂CaTi0.9Li0.1O3-δ在850℃时乙烷转化率和乙烯选择性分别为87.8%和71.7%。Sr对Ca部分取代后制得的催化剂可在极宽的温度范围内(700 ̄85 相似文献
10.
Benjamin S. Nehls Frank Galbrecht David J. Brauer Christian W. Lehmann Ullrich Scherf Tony Farrell 《Journal of polymer science. Part A, Polymer chemistry》2006,44(19):5533-5545
A helical step‐ladder polyarylene incorporating chiral (R)‐2,2′‐dioctoxy‐1,1′‐binaphthyl units was synthesized for the first time. The first step involved the preparation of a precursor poly(arylene ketone) via a palladium‐mediated Suzuki‐type cross‐coupling reaction with the aid of microwave heating. Two polymer‐analog reaction steps, the reduction of the keto groups to tertiary alcohol functionalities and subsequent intramolecular Friedel–Crafts cyclization, gave a step‐ladder polymer ( 6 ) in good yields with reasonable mean average molecular weights greater than 13,000. The regioselective cyclization pattern in the α position of the naphthalene core was confirmed by a comparison of the NMR data of the polymer with those of the corresponding model ladder oligomers, 12 and 13 , and also a single‐crystal structure of 13 . The optical spectra of the oligomers and polymers indicated that there was little electronic interaction across the binaphthyl units. The circular dichroism spectrum of 6 exhibited a strong bisignate Cotton effect in the π–π* absorption region of the planar chromophores, which reflected the strong exciton coupling within the helical polymer chain. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5533–5545, 2006 相似文献
11.
Surman J. Majda D. Rafalska-Łasocha A. Kuśtrowski P. Chmielarz L. Dziembaj R. 《Journal of Thermal Analysis and Calorimetry》2001,65(2):445-450
K-promoted hematite catalysts for ethylbenzene dehydrogenation were studied by thermal analysis (TG/DTG) and high-temperature
XRD. The formation of potassium ferrite (K2Fe2O4), considered to be a catalytically active phase, was observed during calcination of the Ce-promoted catalysts. A linear correlation
of the catalytic activity and the temperature of potassium ferrites formation was found.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
12.
环己醇脱氢催化反应本征动力学研究 总被引:3,自引:0,他引:3
采用管式连续流动固定床积分反应器,对环己醇在Cu-Co/MgO催化剂上的脱氢反应本征动力学进行了研究,求出幂式速率模型各项参数,得到反应的表观活化能为44.28kJ/mol.将上述实验数据与由似平衡浓度法导出的速控步骤的数学模型相关联,求出各有关参数和物种的吸附烙.结果表明,以环己醇吸附和表面反应为速控步骤的模型可较好地进行关联.对上述模型进行了方差和残差分析,误差在宏观动力学研究允许范围内,实验无系统误差.方差分析表明,表面反应为速控步骤的模型对描述反应具有相对最小误差. 相似文献
13.
CatalyticOxidativeDehydrogenationandO2┐FreeDehydrogenationofIsobutaneonSomeMolybdates*HUANGYan,WANGGuo-jia**,YANGHong-maoandW... 相似文献
14.
15.
Towards a Sustainable Synthesis of Formate Salts: Combined Catalytic Methanol Dehydrogenation and Bicarbonate Hydrogenation 下载免费PDF全文
Dr. Qiang Liu Lipeng Wu Dr. Samet Gülak Dr. Nils Rockstroh Dr. Ralf Jackstell Prof. Dr. Matthias Beller 《Angewandte Chemie (International ed. in English)》2014,53(27):7085-7088
Formate salts are important chemicals widely used in everyday products. The current industrial‐scale manufacture of formates requires CO at high pressure and harsh reaction conditions. Herein, we describe a new process for these products without the utilization of hazardous gases and chemicals. By application of ruthenium pincer complexes, a simultaneous methanol dehydrogenation and bicarbonate hydrogenation reaction proceeds, which provides a green synthesis of formate salts with excellent TON (>18 000), TOF (>1300 h?1), and yield (>90 %). 相似文献
16.
17.
异丁烷在Cr2(MOO4)3,Fe2(MoO4)3催化剂上的无氧脱氢与氧化脱氢 总被引:1,自引:0,他引:1
研究了Cr2(MoO4)3、Fe2(mO4)3、对异丁烷无氧脱氢与氧化氢的催化性能,在无氧脱氧反应中,催化剂的表面酸性既有利于异丁烷活性生成异丁烯,又易引起裂和异构化等副反应,在氧化脱氢反应中,异丁烯选择性较低,催化剂的表面酸中心对反应中间体的吸附将导致深度氧化。 相似文献
18.
以自制的四丙基氢氧化铵为模板剂,通过改进经典的水热晶化操作步骤,快速合成出TS-1分子筛,并对其合成过程进行了结晶动力学研究.结果表明,在所考察的晶化温度下,TS-1的成核诱导期均很短,且晶体的成核及生长速率随晶化温度的升高而增大;其表观成核活化能和表观生长活化能分别为33.60和36.73kJ/mol,比经典的水热合成体系所得数值略小.晶化温度越高,晶化液的pH值变化越显著;分子筛结构的迅速形成与晶化液pH值的快速上升过程相一致.高温下合成的TS-1分子筛对苯酚羟基化反应的催化活性更高.导致TS-1分子筛催化活性差异的主要原因是进入分子筛骨架中钛的含量不同,以及样品的结晶度不同.在不同晶化温度下所合成的TS-1分子筛颗粒尺寸稍有差别,但均为100nm左右. 相似文献
19.
Davood Nori-Shargh Abolfazl Shiroudi Reza Naeem-Abyaneh Maryam Nozari 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):435-442
Abstract The nature of the transition state structures of the decomposition of 3-pyrroline (1), 2,5-dihydrofuran (2) and 2,5-dihydrothiophene (3) were investigated usingab initio Molecular Orbital (MO) and Density Factional Theory (DFT) methods. The energy barrierof the decomposition of compound 1 is smaller than compound 2 and compound 2 is smaller than compound 3. The energy barriers for the decomposition of compounds 1–3 are 46.20, 50.17, and 61.34 kcal mol?1, respectively, which is calculated by B3LYP/6-31G*//HF/6-31G* level of theory. Which is ingood agreement with reported experimental data. Contrary to the previously reported data, the distance between the cis-2-and-5-hydrogen atoms in compound 1 is greater than compound 2. The transition-state structures of the decomposition of compounds 1–3 are formed by interaction of the cis-2-and-5-hydrogen atoms. Also, the rings of compounds 1–3 in the transition state structures are puckered. 相似文献
20.
以十二烷基硫酸钠(SDS)和三嵌段共聚物P123为混合模板剂,尿素为沉淀剂,采用均匀沉淀法制备了具有介孔结构的NiO和CeNiO催化剂.考察了催化剂的丙烷氧化脱氧反应性能,并利用用N2吸附-脱附、透射电镜(TEM)、X射线粉末衍射(XRD)和H2程序升温还原(H2-TPR)等技术对催化剂进行了表征.活性测试结果表明,在400-450℃范围内NiO和CeNiO催化剂有相似的催化性能,但后者表现出较高的低温(<400℃)催化活性.325℃反应时,纯NiO上丙烯收率仅为3.1%,而5CeNiO(nCe/nNi=5%)催化剂上丙烯收率高达12.2%.N2吸附-脱附和TEM结果表明,制备的NiO和CeNiO催化剂均有较大的比表面积且具有虫孔状介孔结构.H2-TPR结果表明,CeNiO催化剂中由于Ce的存在使得得一部分氧物种的可还原性能明显增强,这可能是该催化剂具有较高催化活性的重要原因. 相似文献