共查询到18条相似文献,搜索用时 580 毫秒
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微波场对固态氧离子导体上的甲烷氧化偶联的影响 总被引:10,自引:0,他引:10
研究了微波场下甲烷在具有δ-Bi2O3结构的固态氧离子导体上氧化偶联反应行为。与常规加热条件下的反应结果相比较,微波辐射下的反应有上特点:(1)在达到相同甲烷转化率时,微波辐照下所需床层温度要远低于常规加热条件下所需床层温度;(2)微波辐照下,甲烷氧化偶联产物中C2烃的选择性普遍较高,在低温区尤为突出。微波场下甲烷偶联产物乙烷、乙烯的再氧化得到一定程度的抑制,致使微波场下的甲烷氧化偶联反应通常有较 相似文献
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微波辐照引发甲烷部分氧化制合成气Ⅰ.反应条件对Ni/La2O3催化剂催化活性的影响 总被引:3,自引:0,他引:3
甲烷部分氧化可直接制得H2/CO比为2的合成气,该反应具有高活性、高选择性、高时空收率和反应温度较低等特点,有可能替代水煤气变换反应制取F-T合成和甲醇合成原料.因此,近年来甲烷部分氧化(POM)制合成气受到了人们的极大关注[1~7].我们的研究结果[4]表明,在微波场中进行的POM反应与常规加热条件下相比较,前者具有反应速率加快、催化床层温度降低、反应物的转化率和产物的选择性均得到改善等优点.在实验中我们还注意到,当原料气的空速增大到某一值后,一旦用微波辐照将反应引发,即可停止辐照,仅靠反应自身放出的热量就能维持反应的继续进行.显然,这对于降低能耗、节约能源大有益处.为此,本文以Ni/La2O3作催化剂,考察了微波辐照引发甲烷部分氧化制合成气的反应行为. 相似文献
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微波场中甲烷部分氧化制合成气 Ⅱ.Co/ZrO_2催化剂在微波场中的升温行为及催化活性 总被引:4,自引:0,他引:4
近年来,甲烷部分氧化制合成气(POM)的研究一直十分活跃[1,2].前文报道了用于甲烷部分氧化制合成气的镍基催化剂(Ni/La2O3)在微波场中的升温行为和催化活性[3],发现在达到相同的CH4转化率时,微波活化方式下的催化剂床层温度比常规加热低得多... 相似文献
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微波辐照下(Bi_2O_3)_(0.8)(La_2O_3)_(0.2)固熔体对甲烷氧化偶联的催化行为陈长林,洪品杰,戴树珊,阚家德(云南大学化学系,昆明,650091)关键词微波,甲烷氧化偶联,(Bi_2O_3)_(0.8)(La_2O_3)_(0.2)甲烷氧化... 相似文献
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甲烷氧化偶联Na2WO4-Mn/SiO2催化剂热效应的研究 总被引:1,自引:2,他引:1
采用固定床微型反应装置,研究了甲烷氧化偶联反应过程中Na2WO4-Mn/S iO2催化剂床层的热效应和催化性能的关系,考察了反应炉温、CH4/O2比和反应气体空速对催化剂床层热点分布的影响.研究结果表明,甲烷氧化偶联催化剂床层的热效应强烈依赖于反应条件.反应炉温越高,CH4/O2比越低,反应气体空速越大,催化剂床层的热点温度越高.结合催化性能和热效应关系的研究,为优化甲烷氧化偶联的反应操作提供了实验依据. 相似文献
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直接利用甲烷氧化偶联产物中的稀乙烯制环氧乙烷刘育,徐法强,沈师孔(中国科学院兰州化学物理研究所,兰州,730000)关键词乙烯环氧化,甲烷氧化偶联,负载银催化剂1.前言甲烷氧化偶联(OCM)是一个产物较为复杂的反应,从目前研究结果来看,产物中C2烃总... 相似文献
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通过优化设计矩形波导谐振腔微波化学反应器,可以大幅提高微波等离子体下甲烷转化率(最高为93.7%)、C2烃收率(最高为91.0%)和乙炔收率(最高为88.6%).且优化后,在实验的压强范围内,甲烷转化率和C2烃收率较为稳定,C2烃主要是乙炔,其选择性都在90%以上.生成乙炔的能量产率和时空产率也都比较高.利用发射光谱法对微波等离子体下甲烷偶联制乙炔的反应进行了诊断研究,在300nm~750nm波长范围内激发态物种有:CH,C2,H2,Hα-根据反应产物和激发态物种从化学反应热力学和动力学上对反应机理进行了初步探索. 相似文献
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NOx催化的甲烷气相氧化反应 总被引:1,自引:0,他引:1
考察了没有固体催化剂时NOx对甲烷气相氧化的催化作用,并用原位红外光谱研究了CH4-O2-NOx体系随温度的变化.实验结果表明,NOx对甲烷气相氧化有很高的催化活性.在20%CH4-10%O2体系中加入0.05%~0.2%的NO后,反应温度可降低200~300℃,在650~700℃下反应时,CH4转化率和CO选择性可分别达到38%和90%,产物中的n(H2)/n(CO)比为0.4~0.7.反应产物中可观察到有甲醛、甲醇和乙烯等,通过改变反应条件可以控制各组分的相对浓度. 相似文献
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Xian-jun Bi Pin-jie Hong Xiao-guang Xie Shu-shan Dai 《Reaction Kinetics and Catalysis Letters》1999,66(2):381-386
In this paper the results of the partial oxidation of methane over Ni-based and Co-based catalysts activated by two different
heating modes (conventional and microwaves) are reported. Compared with a conventional heating mode, the temperature of the
catalytic bed is much lower and there is a higher selectivity of CO and H2 with microwave irradiation. 相似文献
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MicrowavedielectricheatingisfoundtobeanalternativeproceduretoconventionalconductiveheatingforintroducingenergyintocheInicalreactionsandseemstobeawell-suitedprocessforactivatingsolidcatalystS'-'.TheoriginofthendcrowavecouplingdielectricheatingIiesinthecapacityofanelectricfieldtopolarizechargesinamaterial.TheheatingeffectismoreemphasizedwhentheirradiatedmaterialhasastrongdipoIarcharacter.ThisisparticularlythecasewiththosecatalystswhosesupportisanoxidewithnumerouspoIarOHgroups.Moreover,whenpol… 相似文献
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Chang-lin Chen Pin-jie Hong Shu-shan Dai Cheng-cong Zhang Xiao-yun Yang 《Reaction Kinetics and Catalysis Letters》1997,61(1):175-180
The oxidative coupling of methane over (Bi2O3)1-x(WO3)x (x=0.2, 0.3, 0.4) oxygen ion conductive oxide catalysts irradiated by microwave has been studied. Compared with a conventional
heating mode, the temperature of the catalytic bed is much lower with microwave irradiation and there is a change in selectivity
favoring the production of C2 products. 相似文献
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Microwave heating is not the same as conventional heating, and it is believed that this difference, the "microwave effect," may be interpreted to be due to selective, local heating. The temperature at the surface where sorption occurs is "effectively" greater than the measured solid or gas temperature. In these studies, measurements of the amounts of adsorption as functions of the partial pressures of a specific adsorbate in the presence of microwave irradiation were related to the conventional adsorption isotherms. Equating the adsorbate pressure required to achieve a specific coverage (an isostere) in the presence of microwave irradiation to the amount adsorbed for a conventional isotherm allowed for an estimate of the "effective" surface temperature in the presence of microwaves. It was found that the effective surface temperature increased when using adsorbates having a higher permittivity or when increasing the microwave power. The implication of this change in the surface energy for specific species in the presence of microwaves is discussed. 相似文献
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常规加热或微波照射下, 含氮杂环1与多聚甲醛反应以良好的产率生成含氮杂环基甲醇3, 反应物物质的量的比、反应温度等对反应产率有影响, 微波条件下的反应时间比常规加热下大大缩短. 化合物3和异氰酸酯4在常规加热或微波照射下生成相应的氨基甲酸含氮杂环甲基酯5a~5m. 反应温度、反应物物质的量的比、反应时间、微波辐射功率等对反应产率都有一定的影响, 与常规加热相比微波条件下的反应时间大大缩短. 化合物5的结构经过IR, 1H NMR, MS, 元素分析测定, 部分化合物经过13C NMR测定. 测定了化合物5的杀虫和除草活性, 结果表明其杀虫活性较低, 除草活性高于杀虫活性, 5a, 5d, 5e和5m对苋菜和黄瓜的防除率高达100%. 相似文献
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Despite the advances of solid phase peptide synthesis (SPPS) the synthesis of long peptides is still challenging. Microwave irradiation and conventional heating are considered to improve the efficiency of SPPS. It has been shown that conventional heating and heating by microwave irradiation improves the efficiency of solid phase synthesis of peptides that are prone to aggregation as compared to the synthesis at room temperature. In this Letter, the influence of elevated temperature and microwave irradiation on the homogeneity of the synthesis product of a 58-mer peptide affibody has been compared. A detailed analysis by high resolution HPLC and LC-MS mass spectrometry using a high-mass resolution Orbitrap Exactive mass spectrometer was performed. This study revealed that neither thermal heating nor microwave heating improves the yield and purity of the crude product as compared to the synthesis at room temperature. In contrast, the formation of undesirable side products rather increased by microwave irradiation. These results indicate that neither heating nor microwave enhancement of solid phase synthesis does allow a significant improvement of peptide sequences with a low aggregation potential. 相似文献
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For the first time, N-(2-hydroxyl) propyl-3-trimethyl ammonium chitosan chloride (HTCC) was prepared through a fast, easy and efficient method with the assistance of microwave irradiation, and the quaternized chitosan was also degraded via the microwave irradiation. A comparative study was performed by using the conventional heating method to prepare HTCC. The structure and property of the quaternized chitosan obtained by these two methods were characterized by GPC, XRD, FTIR, NMR, TG and elemental analysis. It was shown that quaternized chitosan was successfully prepared within 50 min via microwave irradiation method, while a much longer time of 6–7 h was needed with the conventional heating method. The substitutions both occurred on the C2 position of chitosan with the two different methods, and their HTCC products had weight average similar molecular weight (Mw), structure and thermal stability. The HTCC prepared by the microwave irradiation method had a little lower degree of substitution (DS) than those prepared via conventional heating with the same mole ratio (6:1) of the intermediate to chitosan. The degradation study showed that the Mw of HTCC decreased rapidly from 4.6 × 105 to 1.1 × 105 in 1 h under microwave irradiation, while it only decreased from 4.6 × 105 to 2.1 × 105in 1 h through conventional heating degradation. These results revealed that microwave irradiation is a more efficient and environment-friendly way to obtain the water-soluble chitosan derivatives and their degraded products. 相似文献