共查询到20条相似文献，搜索用时 31 毫秒
1.
负载Cu,Ag氧化物催化剂的氧化活性和热稳定性 总被引：1，自引：0，他引：1
考究了Ａｌ２Ｏ３，ＣｅＯ２，ＴｉＯ２负载Ｃｕ，Ａｇ氧化物催化剂的氧化活性及ＣｕＯ／ＣｅＯ２，ＣｕＯ／Ａｌ２Ｏ３催化剂的稳定性。结果表明，载体对催化剂的活性有明显影响，对于ＣＯ氧化，Ｃｕ系催化剂中ＣｕＯ／ＣｅＯ２活性最高，Ａｇ系催化剂中，Ａｇ２Ｏ／Ａｌ２Ｏ３活性最好。 相似文献
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氧化物催化剂表面过剩氧与氧化活性 总被引：1，自引：0，他引：1
本文采用肼法测定了金属氧化物催化剂表面过剩氧的浓度，并考察了吡啶的氧化活性。催化剂的氧化活性与表面氧浓度成正比。氧化活性和表面氧浓度的顺序为：Ｃｕ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｍｎ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｃｒ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｆｅ－Ｏ／Ａｌ＿２Ｏ＿３≥Ｃｏ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｎｉ－Ｏ／Ａｌ＿２Ｏ＿３＞Ｃｅ－Ｏ／Ａｌ＿２Ｏ＿３．随着催化剂焙烧温度的提高，催化剂表面氧浓度和氧化活性均下降。Ｃｕ－Ｏ／ＳｉＯ＿２催化剂中添加ＣｅＯ＿２后，催化剂表面氧浓度和氧化活性均有明显提高，同时催化剂的热稳定性也明显增加。 相似文献
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采用X射线衍射（XRD）和程序升温脱附（TPD）考察了Mn／BaCO3、Mn／KCl-BaCO3和Mn／CeO2-BaCO3催化剂的物相及其表面酸碱性;同时考察了乙腈与甲醇选择性合成丙烯腈的催化性能。结果表明,随着Mn负载量的增加,Mn／BaCO3催化剂对乙腈甲基化制丙烯腈的活性呈提高趋势,其中Mn（20％）／BaCO3催化剂对丙烯腈的选择性最高,收率最大。添加CeO2、KCl对催化剂的活性和选择性均起到抑制作用。NH3-TPD、CO2-TPD结果表明,加入CeO2和KCl后,催化剂表面的酸中心数目与碱中心数目都有所减少,表明催化剂的活性与表面酸碱性有着密切的联系。 相似文献
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采用共沉淀法制备催化剂,考察了催化剂制备过程中浆液的pH值和焙烧温度以及反应过程中原料的水蒸气比例和反应压力对复合氧化物催化剂催化异丁烯选择氧化生成甲基丙烯醛反应性能的影响。采用SEM和XPS方法对催化剂的物理化学性质进行了表征。结果表明：在pH=3.0条件下制备的催化剂异丁烯的转化率要明显高于在pH=1.0和pH=6.0条件下制备的催化剂。焙烧温度为400℃的催化剂异丁烯的转化率最高,焙烧温度为500℃的催化剂甲基丙烯醛的选择性最高。加水可以提高异丁烯转化率和甲基丙烯醛选择性,而加压可提高异丁烯转化率,但降低甲基丙烯醛的选择性。 相似文献
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非晶态合金可用作催化新材料．本文用ＸＰＳ方法表征了Ｎｉ－Ｂ和Ｎｉ－Ｃｏ－Ｂ超细非晶态合金，并结合其对ＣＯ加氢的反应性能，初步解释了表面物种及状态与催化活性的关系 相似文献
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探索催化剂的最佳制备条件及合成反应的最佳工艺条件,从而使C02和乙醇反应合成乙酸乙酯具有较高的选择性和收率。结果表明：用氢氧化钠作沉淀剂,采用共沉淀法制备Cu／Zn／A1／Co催化剂,沉淀时PH值为11,Cu、Zn、AI物质的量之比为9：8：15,加入Co的量为Cu、Zn、Al物质量总和的15％时制备所得的催化剂活性最好;在反应温度400℃,反应压力0．6MPa,乙醇与二氧化碳进料体积比为1：150,乙醇进料速度为0．3mL／min时合成反应最佳,此时乙醇的转化率为53．33％,乙酸乙酯的产率为9．77％,乙酸乙酯的选择性为18．33％。 相似文献
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Hao Tian Jinhui Zhao Xinyao Wang Lizhuo Wang Hao Liu Guoxiu Wang Jun Huang Jian Liu G Q Lu 《国家科学评论(英文版)》2020,7(11):1647
It is highly desirable to design hollow structures with multi-scale functions by mimicking cells for the construction of micro/nanoreactors. Herein, we report the construction of hollow-structured submicrometer-photoreactors with bimetallic catalysts loaded within mesoporous silicas. The synthesis parameters are optimized to study the evolution of hollow structure through hydrothermal treatment and an ‘adhesive-contraction’ formation mechanism is proposed. AuPt@HMZS catalysts exhibited a broader absorbance region under visible light and the adsorption edge displayed a red-shift, indicating the strong metal–metal interactions at the alloy interface. The reaction performance of the coupled Au-Pt catalysts can be tuned to achieve excellent catalytic activity in cinnamyl alcohol oxidation to cinnamic acid for 3.1 mmol g−1 with 99% selectivity. The proposed strategy to build hollow structures as multifunctional micro/nanoreactors is promising for the design of high-performance and sustainable catalysts for chemical synthesis. 相似文献
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Yulong Shan Jinpeng Du Yan Zhang Wenpo Shan Xiaoyan Shi Yunbo Yu Runduo Zhang Xiangju Meng Feng-Shou Xiao Hong He 《国家科学评论(英文版)》2021,8(10)
Zeolites, as efficient and stable catalysts, are widely used in the environmental catalysis field. Typically, Cu-SSZ-13 with small-pore structure shows excellent catalytic activity for selective catalytic reduction of NOx with ammonia (NH3-SCR) as well as high hydrothermal stability. This review summarizes major advances in Cu-SSZ-13 applied to the NH3-SCR reaction, including the state of copper species, standard and fast SCR reaction mechanism, hydrothermal deactivation mechanism, poisoning resistance and synthetic methodology. The review gives a valuable summary of new insights into the matching between SCR catalyst design principles and the characteristics of Cu2+-exchanged zeolitic catalysts, highlighting the significant opportunity presented by zeolite-based catalysts. Principles for designing zeolites with excellent NH3-SCR performance and hydrothermal stability are proposed. On the basis of these principles, more hydrothermally stable Cu-AEI and Cu-LTA zeolites are elaborated as well as other alternative zeolites applied to NH3-SCR. Finally, we call attention to the challenges facing Cu-based small-pore zeolites that still need to be addressed. 相似文献
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催化剂对亚临界水中生物质液化行为的影响 总被引：1，自引：0，他引：1
随着社会经济的发展,人类对燃料的需求量越来越大,所以近年来生物质在亚临界水中的液化反应越来越多的得到国内外科研人员的关注,以求得到石油的替代品——生物油。结合我国废生物质利用的现状,本研究用稻草为原料,以得到高产量高品质的生物油为目的,使用间歇式高温高压反应釜,在反应温度573K,压力18MPa．停留时间5min的条件下,对稻草在加入不同催化剂条件下的反应进行实验研究。实验结果表明加入适量的催化剂ZnCl2可以使生物油的产率显著增加,最高可达到32．90％,加入适量的催化剂Na2S可以使生物油的热值（HHV）显著升高,最高可达34．05MJ／kg.当两种催化剂同时加入时可以使生物油的产率和热值同时达到最大,并且使反应剩余残渣减少,并对生成的生物油进行了观察和分析。同时使用GC—MS（气相色谱一质谱联用）技术对生物油的成分进行了定性、定量分析,进一步确定了生物油的成分以及含量。 相似文献
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Xiaorui Zhao Yueqiang Cao Linlin Duan Ruoou Yang Zheng Jiang Chao Tian Shangjun Chen Xuezhi Duan De Chen Ying Wan 《国家科学评论(英文版)》2021,8(4)
The functionalization of otherwise unreactive C–H bonds adds a new dimension to synthetic chemistry, yielding useful molecules for a range of applications. Arylation has emerged as an increasingly viable strategy for functionalization of heteroarenes which constitute an important class of structural moieties for organic materials. However, direct bisarylation of heteroarenes to enable aryl-heteroaryl-aryl bond formation remains a formidable challenge, due to the strong coordination between heteroatom of N or S and transitional metals. Here we report Pd interstitial nanocatalysts supported on ordered mesoporous carbon as catalysts for a direct and highly efficient bisarylation method for five-membered heteroarenes that allows for green and mild reaction conditions. Notably, in the absence of any base, ligands and phase transfer agents, high activity (turn-over frequency, TOF, up to 107 h−1) and selectivity (>99%) for the 2,5-bisarylation of five-membered heteroarenes are achieved in water. A combination of characterization reveals that the remarkable catalytic reactivity here is attributable to the parallel adsorption of heteroarene over Pd clusters, which breaks the barrier to electron transfer in traditional homogenous catalysis and creates dual electrophilic sites for aryl radicals and adsorbate at C2 and C5 positions. The d-band filling at Pd sites shows a linear relationship with activation entropy and catalytic activity. The ordered mesopores facilitate the absence of a mass transfer effect. These findings suggest alternative synthesis pathways for the design, synthesis and understanding of a large number of organic chemicals by ordered mesoporous carbon supported palladium catalysts. 相似文献
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Huidi Yu Yurui Xue Lan Hui Chao Zhang Yan Fang Yuxin Liu Xi Chen Danyan Zhang Bolong Huang Yuliang Li 《国家科学评论(英文版)》2021,8(8)
Development of novel catalysts for nitrogen reduction at ambient pressures and temperatures with ultrahigh ammonia (NH3) yield and selectivity is challenging. In this work, an atomic catalyst with separated Pd atoms on graphdiyne (Pd-GDY) was synthesized, which shows fascinating electrocatalytic properties for nitrogen reduction. The catalyst has the highest average NH3 yield of 4.45 ± 0.30 mgNH3 mgPd−1 h−1, almost tens of orders larger than for previously reported catalysts, and 100% reaction selectivity in neutral media. Pd-GDY exhibits almost no decreases in NH3 yield and Faradaic efficiency. Density functional theory calculations show that the reaction pathway prefers to perform at the (Pd, C1, C2) active area because of the strongly coupled (Pd, C1, C2), which elevates the selectivity via enhanced electron transfer. By adjusting the p–d coupling accurately, reduction of self-activated nitrogen is promoted by anchoring atom selection, and side effects are minimized. 相似文献
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纳米酶代表了一类新型人工酶和生物催化剂,打破了无机与有机生命的界限。它既有纳米材料的理化特性,也有独特的类酶催化活性。同时,这些理化特性有可能会调控催化活性,使得纳米酶跟天然酶、传统的模拟酶和化学催化剂区别开来。纳米酶有比较好的稳定性、耐高温、低温、耐酸碱、活性可调且多功能,目前受到了广泛关注,在生物医药、环境治理、绿色农业、新能源等领域展现出巨大的应用前景,并初步形成了相应的学科框架。为了更好地推动纳米酶的发展,拓展对纳米酶的认识,文章回顾了纳米酶发现,分析凝练了纳米酶的学科特点及其结构,综述了纳米酶的应用,并展望了未来的发展趋势。 相似文献
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硅钨酸催化合成水杨酸甲酯的研究 总被引：10，自引：0，他引：10
报道了以硅钨酸作催化剂合成水杨酸甲酯,提出了反应时间,酸醇比,催化剂用量等合适的酯化条件。结果表明,硅钨酸具有较高的催化活性和较好的催化选择性。 相似文献
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N-heterocyclic phosphines (NHPs) have recently emerged as a new group of promising catalysts for metal-free reductions, owing to their unique hydridic reactivity. The excellent hydricity of NHPs, which rivals or even exceeds those of many metal-based hydrides, is the result of hyperconjugative interactions between the lone-pair electrons on N atoms and the adjacent σ*(P–H) orbital. Compared with the conventional protic reactivity of phosphines, this umpolung P–H reactivity leads to hydridic selectivity in NHP-mediated reductions. This reactivity has therefore found many applications in the catalytic reduction of polar unsaturated bonds and in the hydroboration of pyridines. This review summarizes recent progress in studies of the reactivity and synthetic applications of these phosphorus-based hydrides, with the aim of providing practical information to enable exploitation of their synthetically useful chemistry. 相似文献
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金属氧化物及其复合纳米纤维具有独特性能和潜在的应用价值,一直为人们所关注。本文提出了一种简便制备CuO/SiO2纳米复合纤维的新方法。即将静电纺丝技术与溶胶凝胶法结合,得到前驱体纤维;随后在适当的温度下热处理去除有机成分,最终得到直径150～200 nm的质量比为10%CuO/90%SiO2复合纳米纤维。使用SEM、TG-DTG、XRD、FT-IR、BET、UV-Vis技术手段对样品进行表征。SEM、TG-DTG、XRD、FT-IR结果表明该纤维的成分、形貌和晶相很大程度上受到煅烧温度的影响。BET结果表明该纤维的比表面积为141.95 m2/g,是纳米结构。光吸收测量结果发现该纤维的紫外光吸收性能随纤维晶相改变而改变。 相似文献
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Sheng-Nan Sun Ning Li Jiang Liu Wen-Xin Ji Long-Zhang Dong Yi-Rong Wang Ya-Qian Lan 《国家科学评论(英文版)》2021,8(3)
Identification of the real catalytic site in CO2 reduction reaction (CO2RR) is critical for the rational design of catalysts and the understanding of reactive mechanisms. In this study, the catalytic activity of pyridine-containing materials was for the first time structurally demonstrated in CO2RR by crystalline supramolecular coordination compounds model system. The system consists of three stable supramolecular coordination compounds (Ni-TPYP, Ni-TPYP-1 and Ni-TPP) with different numbers (4, 2 and 0) of active pyridine groups (i.e. uncoordinated pyridine nitrogen atoms). The electrocatalytic test results show that with the decrease of the number of active pyridine groups, the CO2RR performance is gradually reduced, mainly showing the reduction of highest FECO (99.8%, 83.7% and 25.6%, respectively). The crystallographic, experimental and theoretical evidences prove that the CO2RR activity is more likely derived from uncoordinated pyridine nitrogen than the electrocatalytic inert metal nickel in porphyrin center. This work serves as an important case study for the identification of electrocatalytic activity of pyridine-containing materials in CO2RR by simple supramolecular model system. 相似文献