共查询到20条相似文献,搜索用时 62 毫秒
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采用脉冲色谱技术、XRD、TPR和XPS等方法研究了在天然气二氧化碳转化制合成气反应中催化剂的抗积炭性能。实验结果表明,在N Al2O3催化剂中添加CeO2和MgO助剂(催化剂记为Ni/ARM)能有效抑制甲烷脱氢反应,提高二氧化碳消炭能力,增加催化剂的抗积炭性能。其主要原因是,添加CeO2和MgO助剂增加了活性组分镍的分散度,加强了活性组分和载体的相互作用。改性后的Ni/ARM催化剂在1023K、二氧化碳/天然气/氧气比为2.4/0.1以及1123K、二氧化碳/天然气/氧气比为1.4/1/0.05的条件下反应800小时后活性不降低,产物中合成气(CO+H2)摩尔百分含量始终保持在94-96%左右。说明该催化剂具有较高的活性、选择性和抗积炭性。 相似文献
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考察了添加在镍基催化剂中的碱金属助剂对甲烷与空气制合成气的催化反应性能的影响。并用TPO、TPR、CO_2程序升温脱附(TPD)、XPS及CO脉冲色谱对催化剂进行了表征。实验结果表明,碱金属助剂对降低催化剂结炭有一定作用;催化剂抗积炭顺序为; Ni-K2O/CaO/Al2O3>Ni-Li2O/CaO-Al2O3>Ni-Na2O/CaO-Al2O3>Ni/CaO/Al2O3。在实验中,我们发现碱金属的添加使催化剂的Ni晶粒变大和吸附CO_2的能力增强,结合能发生不同程度的变化。这些实验结果从不同方面解释了碱金属助剂对催化剂活性和抗积炭性的影响。实验结果表明Ni-Li2O/CaO-Al2O3具有较好的活性和抗积炭性。 相似文献
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La2O3—Ni/SrAl12O19催化剂上甲烷与二氧化碳重整反应的研究 总被引:8,自引:1,他引:8
采用XRD,UV-DRS,H2-O2滴定,TPR,吡啶吸附红外光谱等技术,研究了La2O3助剂对La2O3-Ni/SrAl12O19催化剂的还原性,表面酸性,金属镍的分散度和抗烧结能力,以及对催化甲烷与二氧化碳重整制取合成气反应性能的影响。结果表明,在负载型的镍催化剂中,添加La2O3助剂,能够削弱金属组分与载体之间的相互作用,降低催化剂的还原性,提高金属镍在催化剂表面的分散度和在反应过程中的抗烧 相似文献
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XU Long Ya * WANG Qing Xia LIN Li Wu XU Yi De Dalian Institute of Chemical Physics The Chinese Academy of Sciences Dalian Liaoning 《天然气化学杂志》1998,7(1):7-15
Ni/Si2催化剂具有较好的低碳烷烃与二氧化碳重整制合成气的反应性能,添加La2O3助剂和K2O助剂可提高催化剂活性和合成气收率,从而进一步改善催化剂的低碳烷烃与CO2重整制合成气的反应性能,研制的KLaNi/Si2催化剂,用于天然气与CO2重整反应制合成气可达97%的低碳烷烃转化率和95%以上的合成气收率。 相似文献
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用固定床流动反应装置及TPR、TPD、XRD、XPS、TEM等技术考察了因热处理温度不同而具有不同Ni-γ-Al_2O_3间相互作用的Ni/γ-Al_2O_3催化剂的甲烷、二氧化碳重整活性、还原性能、吸附性能、表面化学形态和抗积炭性能等。结果表明,低温热处理的催化剂具有易于还原、低温活性较高和抗积炭性能差的特性,经高温热处理的催化剂,由于Ni-γ-Al_2O_3间强的相互作用而使催化剂表面几乎全部形成了难以还原的“NiAl_2O_3”表面尖晶石,这虽然在一定程度上降低了催化剂的低温活性,但却使其抗积炭性能大为改观,尤其在反应温度大于750℃时,还可表现出与低温热处理催化剂趋于等同的高活性,实验中还观察到催化剂表面的积炭主要以空心炭丝的形式存在。 相似文献
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采用固定床流动反应器和XRD、TPR等技术对添加了La2O3助剂的Ni/αAl2O3催化剂进行了研究。结果表明,经La2O3改性后,催化剂的活性和稳定性得到提高,La2O3的最佳含量为2%(wt)。脉冲试验结果表明,添加2%(wt)的La2O3助剂,能够有效抑制甲烷脱氢性能,增加二氧化碳消碳活性。TPR结果表明,添加La2O3助剂,能够改变活性组分和载体之间的相互作用,增加镍的分散度,降低氧化镍的还原温度,提高重整反应的活性。 相似文献
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Ni,Pd/Al2O3对丙酮加氢一步合成甲基异丁基酮性能比较 总被引:7,自引:0,他引:7
研究了Al2O3负载Ni、Pd催化剂上丙酮加氢一步合成甲基异丁基酮的反应活性。考察了不同Ni含量和不同Pd含量对活性的影响。结果表明,在载体Al2O3中加入不同含量的SiO2后,会改善载体的性能,Ni/Al2O3催化剂中添加稀土元素La或Ce后可改善催化剂的稳定性。 相似文献
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采用固定床流动反应装置研究了高温焙烧的负载型钴金属催化剂对甲烷与二氧化碳转化制合成气的催化性能,考察了催化剂活性组分、预处理温度及反应条件等对合成气生成量的影响,并用色谱法测定了催化剂上的积炭量.结果表明,钴负载量高于12%时,在1073~1473K焙烧的Co/Al2O3催化剂不仅具有高的催化活性,而且具有独特的抗积炭性能.TPR,XRD和催化反应结果表明,来源于CoAl2O4尖晶石的金属Co以及CoAl2O4尖晶石对催化剂的活性和抗积炭性能起着关键作用,其活性特征在许多方面不同于低温焙烧的Co/Al2O3或Ni/Al2O3催化剂. 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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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
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
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
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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
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A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
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
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A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献