共查询到19条相似文献,搜索用时 684 毫秒
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考察了在具有Pentasil孔道结构的H-Ga-Si与Pt/H-Ga-Si杂原子分子筛及HZSM-5分子筛催化剂上的丙烷芳构化。Pt/H-Ga-Si有较高催化活性和芳烃选择性,用XRD、TEM和TPR等技术对催化剂进行了表征,讨论了Pt与Ga的相互作用。Pt/H-Ga-Si为双功能催化剂,Pt促进烷烃脱氢成为烯烃,还能降低丙烷裂解活性,而且可稳定骨架Ga,使其不易脱除;Ga可以提高中间烯烃转变为芳烃的选择性。H-Ga-Si与HZSM-5上的丙烷芳构化机理不同。H-Ga-Si上为丙烷脱氢机理,Ga脱去H+形成活泼正碳离子,同时由于骨架Ga与分子筛B酸位相邻,所以可提高芳烃选择性;HZSM-5上丙烷活化是经过裂化机理,再通过氢转移步骤形成芳烃。 相似文献
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考察了在具有Pentasil孔道结构的H-Ga-Si杂原子分子筛及HZSM-5分子筛催化剂上的丙烷芳构化,Pt/H-Ga-Si有较高催化活性和芳烃选择性。用XRD、TEM和TPR等于译催化剂进行了表征,讨论了Pt与Ga的相互作用。Pt/H-Ga-Si为双工能催化剂,Pt促进烷烃脱氢成为烯烃,还能降低丙烷裂解活性,而且可稳定骨架Gaw,使其不易脱除;Ga要以提高中间烯烃转变为芳烃的选择性。 相似文献
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采用溶胶-凝胶(Sol-Gel)法制备了微孔结构均匀的“SiO2/陶瓷”膜和“Mo-Co-O/SiO2/陶瓷”催化功能膜,并用XRD、SEM和孔径测定等技术进行了表征。在常压,500~700℃的条件下,在催化膜反应器(CMR)中考察了甲烷氧化制甲醇的反应。在相似的反应条件下(转化率为1.0%),用CMR(甲醇选择性1?.2%)可获得较固定床反应器(甲醇选择性4.5%)高得多的甲醇选择性。 相似文献
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考察了K,V,B等对Ga/HZSM-5催化剂的入性后表面酸性质和Ga组分状态分布的变化以及对甲醇,丙烷芳构化催化作用的异同。结构表明,V,B改性后提高了甲醇转化的芳烃选择性,降低了丙烷的芳构化活性。 相似文献
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Au/HZSM沸石催化剂的正丁烷异构化反应性能的研究 《燃料化学学报》2015,43(8):980-989
采用脉冲微反装置评价了纯正丁烷、含有不同比例异丁烷的混合丁烷在Au改性的纳米HZSM-5催化剂上的反应活性和异构化选择性。结果表明,在300℃时,载金量为1.31%的催化剂上纯正丁烷原料的转化率可达7.0%,异丁烷选择性可达80%以上。相比之下,在纳米HZSM-5载体上正丁烷的转化率只有0.55%,异丁烷选择性仅为11.67%。在Au负载量为0.12%~1.91%,随着Au负载量的增加,正丁烷转化率先增后减,异丁烷选择性在低负载量时增加明显。在反应温度低于400℃时,纯正丁烷在载金催化剂上主要发生异构化反应;高于400℃时,主要发生裂解和芳构化等反应,即400℃是正丁烷在脉冲微反条件下异构化和裂解等反应的分水岭。另外,混合丁烷的组成对正丁烷异构化反应有一定影响,但在适当温度下正丁烷异构化时裂解产物很少,表现出金属-酸双功能催化特征。Au+在反应中发挥了脱氢和加氢作用。 相似文献
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甲醇两步制芳烃反应中低碳烯烃芳构化反应稳定性优异,为分析其内在机制,制备了不同硅铝比(nSiO2/nAl2O3)及Zn负载量的ZSM-5催化剂,以丙烯芳构化为模型反应,分析ZSM-5表面酸性对低碳烯烃芳构化反应性能的影响规律,并探究反应微观特性。发现当硅铝比由150降至75时,增加的酸密度促进了烯烃氢转移芳构化过程,使芳烃选择性由31.0%增至34.4%,但丙烯直接参与的氢转移过程也被强化,使丙烷产物选择性由28.2%增至36.0%。引入Zn助剂可将部分Brønsted酸转变为Zn-Lewis酸,强化烯烃脱氢芳构化过程,使芳烃选择性进一步显著增加到62.4%。丙烯芳构化过程中芳烃烷基化深度比甲醇芳构化过程低,提升总芳烃选择性的同时,也明显抑制了难溶性积碳的形成,使反应稳定性明显提升。由此得出,甲醇两步制芳烃过程中甲醇制低碳烯烃过程对甲醇的预先消耗,抑制了低碳烯烃芳构化反应芳烃产物的深度烷基化,是该反应表现出优异稳定性的重要原因。 相似文献
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Annapurna Jetty Ravichandra Potumarthi A. Gangagni Rao B. Sarva Rao S. V. Ramakrishna 《Applied biochemistry and biotechnology》2009,159(2):579-588
Oxytetracycline (OT) production using glutaraldehyde cross-linked calcium alginate immobilized cells of Streptomyces varsoviensis in continuous fluidized bed reactor (FBR) was investigated. Initially, batch experiments were carried in stirred tank reactor
(STR) and FBR using calcium alginate immobilized cells. Higher OT production of 0.45 gm/L was achieved by FBR when compared
with 0.33 g/L of OT in STR. All subsequent studies were carried out in continuous mode of operation in FBR. During 21 days
of operation, effect of glucose concentration and different dilution rates were studied. A maximum of 0.75 g/L OT was achieved
in the medium having 10 g/L of glucose concentration. The highest OT concentration of 0.92 g/L and the highest yield of OT
with respect to biomass at 0.1713 g/g were obtained at the dilution rate of 0.25 day−1. 相似文献
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Lihe Zheng Dong Xuan Jianjun Guo Hui Lou Xiaoming Zheng Institute of Catalysis Chemistry Department Zhejiang University Hangzhou China 《天然气化学杂志》2006,15(1)
The non-oxidative aromatization of mixed CH4 with C3H8 over La-promoted Zn/HZSM-5 catalysts was studied in a fixed-bed reactor at 823 K with space velocity 600 h-1 and CH4/C3H8 (mol ratio)=5:1. The propane conversion and the aromatic selectivities were up to 99% and 60% over the catalyst respectively, while methane conversion had an induction period with the highest conversion of 30%. The structure and surface acidity of the catalysts were characterized by XRD, NH3-TPD and TG-DTA. The influences of reaction and regenerative conditions on the activity and selectivity were also investigated. 相似文献
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A Smith and Crystal LCH microreactor was used in n-octane reforming. The useful catalyst volume of the reactor can be changed in the 4-15 cm3 range. At the industrially used space velocity the conversion is close to 100%, therefore, the secondary reactions affect the product composition. In order to suppress these secondary reactions, the space velocity was varied between 1 h-1 to 4 h-1. The optimum space velocity in this microreactor was found to be at 4 h-1. Among these conditions the conversion is appropriate for further investigations. The isomerization selectivity is increased while aromatization selectivity is decreased along with the space velocity increase. 相似文献
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U. Tegtmeyer H. P. Weiss R. Schlögl 《Fresenius' Journal of Analytical Chemistry》1993,347(6-7):263-268
Summary Ionisation of small molecules via ion-molecule reactions (IMR) offers the possibility to reduce fragmentation caused by high energy electron impact ionisation. Widely varying rate constants for the IMR processes allow to introduce additional species selectivity together with the mass selection in a quadrupole system. A comparison between low energy electron impact ionisation and IMR illustrates the potential of this new ionisation method in gas analysis applications. 相似文献