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91.
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Br?nsted酸转变为ZnLewis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
92.
通过熔盐法制备TiB2载体,并采用简单的沉淀-沉积法制备了Co/TiB2磁性可回收纳米催化剂,用于室温催化氨硼烷(NH3BH3)溶液产氢及串联降解对硝基苯酚(4-NP)及偶氮染料酸性橙7(AO7)、酸性红1(AR1)和甲基橙(MO)等有机污染物。采用X射线衍射、扫描电子显微镜、透射电子显微镜、X射线光电子能谱、振动样品磁强计等表征方法对催化剂的微观形貌和结构等进行分析。结果表明,Co纳米粒子均匀地分布在TiB2载体表面,晶粒尺寸约为40 nm,并且被TiB2载体包覆,具有典型的金属-载体强相互作用。Co/TiB2表现出优异的室温催化NH3BH3溶液产氢活性,产氢速率为565.8 molH2·molcat-1·h-1。在串联降解有机污染物反应中,Co/TiB2在7 min内催化4-NP氨基化的转化率接近100%,反应速率常数高达0.72 min-1;降解AO7的反应速率常数在3种偶氮染料中最高(0.34 min-1)。通过EPR-DMPO(EPR=电子顺磁共振,DMPO=5,5-二甲基-1-吡咯啉-N-氧化物)自由基捕获实验检测出Co/TiB2+NH3BH3催化体系中产生大量的氢自由基(·H)。得益于·H的强还原性,Co/TiB2+NH3BH3催化体系能够将4-NP氨基化为具有更高价值的对氨基苯酚(4-AP),同时能够还原偶氮染料分子中的显色基团偶氮基(—N=N—)。 相似文献
93.
摘要:常温催化氧化是消除室内HCHO污染最可行的方法之一,其中以过渡金属氧化物为代表的催化剂因性能优异、成本低廉而备受广泛关注。采用柠檬酸络合法和水热法制备了一系列CuMnCeOx催化剂,研究考察制备方法及载体对催化剂氧化性能的影响,并利用XRD、SEM、BET、H2-TPR、XPS和IR等对催化剂进行微观表征与分析。研究发现,制备方法及载体类型对催化剂的表面结构形貌、氧化性能产生显著影响,其中采用柠檬酸络合法所制的CuMnCeOx-C催化剂性能最佳,48h的HCHO去除率达98.6%,完全满足GB50325-2001标准要求,其介孔结构,晶体粒径及所形成的铈基铜锰固溶体均利于形成大量氧空位及催化氧化反应,且展示出良好的抗水蒸气和稳定性能,其在常温催化氧化VOCs方面具有重要应用前景。 相似文献
94.
《Mendeleev Communications》2022,32(4):446-448
A new one-pot two step synthesis of unsymmetrically substituted indenes from available 3,4-diarylbutadiene sulfones involves SO2 thermal extrusion followed by acid- catalyzed cyclization of the diene formed, the cyclization proceeding selectively at the more electron-rich aryl rings. The procedure is efficient for substrates bearing donor, acceptor, as well as bulky substituents. 相似文献
95.
《Mendeleev Communications》2022,32(4):510-513
The influence of textural characteristics on the catalytic performance of supported KCoMoS2 catalysts was explored to provide essential information for the design of better catalysts for the synthesis of higher alcohols (C1–C5) from syngas. Syngas conversion was carried out over KCoMoS2 catalysts supported on various mesoporous (alumina and carbon-coated alumina) and microporous (two types of powdered activated carbons) materials. The experimental results show that catalysts supported over microporous materials exhibit higher catalytic activity in HAS from syngas than catalysts based on mesoporous materials. 相似文献
96.
Xianghao Luo Anqi Tian Mengyu Pei Dr. Jiaying Yan Dr. Xiang Liu Prof. Long Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(3):e202103361
With the development of green chemistry, it is still a challenge to maintain the unstable valence state of the metal in heterogeneous catalysts and realize new catalytic synthesis methods. In this paper, it is reported that an univalent copper nanocomposite (Cu@Al/SBA-15) can efficiently catalyze the formation of novel amino-containing benzotriazoles with great fluorescence properties in a new synthetic strategy. Subsequently, its application is further verified by an acylation reaction to produce a series of novel benzotriazoles derivatives with high yield. It is worth noting that the Cu@Al/SBA-15 nanocomposites not only enable the reaction completed with high yield in a short time, but can also be recycled many times without a significant reduction in activity, and the leaching of copper and aluminum species in reaction system is negligible. Finally, the detailed and feasible reaction mechanism is also provided. 相似文献
97.
Dr. Josep Mas-Roselló Prof. Dr. Nicolai Cramer 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(10):e202103683
Catalytic reduction of oximes represents a direct efficient approach to synthesize valuable hydroxylamine derivatives. However this transformation presents significant challenges: oximes are hard to reduce and, if reactive, reductive cleavage of the weak N−O bond often leads to primary amine side products. The first suitable systems involved the use of platinum-based heterogeneous catalysts with hydrogen as reductant and stoichiometric amounts of a strong Brønsted acid. More recently metal-free and transition-metal-based homogeneous catalysts have been developed, which display the highest turnovers (up to 4000). In the asymmetric variants, the E/Z-geometry of the oxime double bond affects significantly the stereoselectivity, sometimes requiring extra synthetic efforts in substrate preparation. This minireview provides an overview of the advances and limitations in catalytic oxime to hydroxylamine reduction. Emphasis is put on highlighting and comparing the practical aspects of the existing methods, such as their reaction conditions and substrate scope. Additionally, future directions for improving this young research area are suggested. 相似文献
98.
Dr. Andreas A. Bastian Dr. Maria Bastian Dr. Manuel Jäger Mark Loznik Dr. Eliza M. Warszawik Xintong Yang Dr. Nabil Tahiri Dr. Peter Fodran Prof. Dr. Martin D. Witte Anne Thoma Dr. Jens Köhler Prof. Dr. Adriaan J. Minnaard Prof. Dr. Andreas Herrmann 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(36):e202200883
The continuous emergence of antimicrobial resistance is causing a threat to patients infected by multidrug-resistant pathogens. In particular, the clinical use of aminoglycoside antibiotics, broad-spectrum antibacterials of last resort, is limited due to rising bacterial resistance. One of the major resistance mechanisms in Gram-positive and Gram-negative bacteria is phosphorylation of these amino sugars at the 3’-position by O-phosphotransferases [APH(3’)s]. Structural alteration of these antibiotics at the 3’-position would be an obvious strategy to tackle this resistance mechanism. However, the access to such derivatives requires cumbersome multi-step synthesis, which is not appealing for pharma industry in this low-return-on-investment market. To overcome this obstacle and combat bacterial resistance mediated by APH(3’)s, we introduce a novel regioselective modification of aminoglycosides in the 3’-position via palladium-catalyzed oxidation. To underline the effectiveness of our method for structural modification of aminoglycosides, we have developed two novel antibiotic candidates overcoming APH(3’)s-mediated resistance employing only four synthetic steps. 相似文献
99.
Prof. Christopher Batchelor-McAuley Dr. Minjun Yang Prof. Rosalind E. M. Rickaby Prof. Richard G. Compton 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(68):e202202290
The ultimate fate, over the course of millennia, of nearly all of the carbon dioxide formed by humankind is for it to react with calcium carbonate in the world's oceans. Although, this reaction is of global relevance, aspects of the calcite dissolution reaction remain poorly described with apparent contradictions present throughout the expansive literature. In this perspective we aim to evidence how a lack of appreciation of the role of mass-transport may have hampered developments in this area. These insights have important implications for both idealised experiments performed under laboratory conditions and for the measurement and modelling of oceanic calcite sediment dissolution. 相似文献
100.