共查询到20条相似文献，搜索用时 274 毫秒
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自从Ziegler-Natta催化剂发现以来,人们已对该类催化剂作了许多的研究,以MgCl_2为载体的高效催化剂的巨大成功,引起了人们对载体和过渡金属元素的相互作用的浓厚兴趣,近年来许多文献和专利报道了对复合载体催化剂的大量的研究成果,似有可能出现具有更优特性的高效催化剂. 本文就复合载体催化剂的研究现状作一综述. 相似文献
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综述了主要合成氧催化剂（传统熔铁催化荆、Fel—xO基催化剂钉基合成氨催化剂）的研究和工业应用情况,并展望了其发展的趋势。 相似文献
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用浸渍法,以Hβ催化剂粉末为载体,磷钨酸为活性组分制备负载型杂多酸催化剂,代替硫酸为催化剂,采用间歇反应器,在连续搅拌的条件下催化合成了乳酸正丁酯。并用正丁醇为内标物,气相色谱分析法分析反应产物。对合成产物进行了GC—MS和IR分析。实验表明负载40％的杂多酸成型催化剂催化合成乳酸正丁酯,2个半小时酯化率能达到98.11％： 相似文献
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以二茂铁为催化剂,硫为添加剂,采用化学气相沉积法合成双壁碳纳米管宏观薄膜和长丝。透射电镜照片显示催化剂的浓度对碳纳米管的纯度以及双壁碳纳米管的直径都有所影响。 相似文献
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一氧化碳(CO)与亚硝酸乙酯(C_2H_5ONO)在负载型钯催化剂(1％Pd/α-Al_2O_3,1％Pd/C和1.4％Pd/γ-Al_2O_3)上合成草酸二乙酯(DEO)的反应,其催化剂的催化活性与选用的载体关系甚密。以α-Al_2O_3作载体时,载体比表面小,活性组份钯粒较粗大,催化活性最好;对于CO与亚硝酸甲酯(CH_3ONO)合成碳酸二甲酯(DMC)的反应,2％Pd/C催化剂因活性碳材质差异、孔结构不一所致的负载其上的钯粒分散度不同而表现出催化活性的明显差别。与前一反应相对照,却以分散度大、钯粒细的催化剂在DMC合成反应中有较好的催化活性。其中2％Pd/C(椰子壳制)的催化活性最好,2％Pd/C(木材制)的最差,在上述两类反应中,明显反映出负载型催化剂的载体效应。 相似文献
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以烯丙基聚醚／烯丙基环氧化合物。含氢氨基硅油为主要原料，在铂催化剂的作用下。合成聚醚—环氧／氨基硅油；并对其应用性能进行了测试。结果表明：采用该硅油处理的织物手感柔软、滑爽，具有良好的使用效果。 相似文献
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Homogeneous molecular catalysts and heterogeneous catalysts possess complementary strengths, and are of great importance in laboratory/commercial procedures. While various porous hosts, such as polymers, carbons, silica, metal oxides and zeolites, have been used in an attempt to heterogenize homogeneous catalysts, realizing the integration of both functions at the expense of discounting their respective advantages, it remains a significant challenge to truly combine their intrinsic strengths in a single catalyst without compromise. Here, we describe a general template-assisted approach to incorporating soluble molecular catalysts into the hollow porous capsule, which prevents their leaching due to the absence of large intergranular space. In the resultant yolk (soluble)–shell (crystalline) capsules, the soluble yolks can perform their intrinsic activity in a mimetic homogeneous environment, and the crystalline porous shells endow the former with selective permeability, substrate enrichment, size-selective and heterogeneous cascade catalysis, beyond the integration of the respective advantages of homogeneous and heterogeneous catalysts. 相似文献
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Qi Shi Yongjun Ji Wenxin Chen Yongxia Zhu Jing Li Hezhi Liu Zhi Li Shubo Tian Ligen Wang Ziyi Zhong Limin Wang Jianmin Ma Yadong Li Fabing Su 《国家科学评论(英文版)》2020,7(3):600
Single-atom catalysts are of great interest because they can maximize the atom-utilization efficiency and generate unique catalytic properties; however, much attention has been paid to single-site active components, rarely to catalyst promoters. Promoters can significantly affect the activity and selectivity of a catalyst, even at their low concentrations in catalysts. In this work, we designed and synthesized CuO catalysts with atomically dispersed co-promoters of Sn and Zn. When used as the catalyst in the Rochow reaction for the synthesis of dimethyldichlorosilane, this catalyst exhibited much-enhanced activity, selectivity and stability compared with the conventional CuO catalysts with promoters in the form of nanoparticles. Density functional theory calculations demonstrate that single-atomic Sn substitution in the CuO surface can enrich surface Cu vacancies and promote dispersion of Zn to its atomic levels. Sn and Zn single sites as the co-promoters cooperatively generate electronic interaction with the CuO support, which further facilitates the adsorption of the reactant molecules on the surface, thereby leading to the superior catalytic performance. 相似文献
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为对我国矿产资源空间分布的不均衡性进行定量化的测度和比较,进一步明晰不同种类的矿产资源的空间分布特征,进而为政府进行差别化管理和精细化管理提供支撑,本文采用基尼系数和洛仑兹曲线相结合的方法,以矿种在省域空间的地均查明资源储量作为指标,对我国28种重要矿产资源的空间分布状况进行定量分析,并按不均衡程度将28种矿产划分为4类,结论显示：总体上看,我国矿产资源的空间分布均具有明显的不均衡性,有15种矿产的空间分布不均衡程度相对较高,而不均衡程度相对较低和极高的矿种较少,共6种,不均衡程度相对中等的矿种有7种。从矿类上看,3种能源矿产的空间分布不均衡程度都相对较高,金属矿产基本属于相对中等和相对较高,共有13种,所选取的10种非金属矿产在四种分类中均有,根据分析结论,进一步提出将矿种的空间分布不均衡性作为矿产资源分类管理的空间要素。 相似文献
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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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用化学还原法制备了非晶态合金催化剂Ｎｉ－Ｂ、Ｃｏ－Ｂ和Ｃｏ－Ｎｉ－Ｂ．合金的非晶性质由Ｘ射线衍射（ＸＲＤ）及透射电子显微镜（ＴＥＭ）鉴定．组成用电感耦合等离子发射光谱（ＩＣＰ）分析．在高真空程序升温脱附质谱（ＴＰＤ－ＭＳ）装置上研究了ＣＯ、Ｈ２在三种催化剂上的吸附及ＣＯ和Ｈ２的表面反应（ＴＰＳＲ）．发现ＣＯ和Ｈ２在三种催化剂上分别有二种和一种吸附态，吸附强度和二种吸附态的数目在不同合金上有较大差异．ＣＯ加氢反应的主要产物是ＣＨ４、ＣＯ２和Ｈ２Ｏ，其中ＣＯ在催化剂表面上的解离是反应的控制步骤． 相似文献
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煤基固废的大规模循环利用,对于中国西北大型能源基地的可持续发展和生态环境保护具有重要现实意义。本文以中国典型能源基地为研究对象,采用区域内固废、产业协同配置的思路,通过煤基固废制备化学品、环保材料、建材等关键技术开发,构建电石渣、气化渣、废催化剂等典型煤基固废循环利用关键产品链。结果表明：①电石渣、气化渣、废催化剂等煤基固废可通过杂质快速分离、矿相调控和载体重构等技术的耦合集成,制备性能良好的脱硫剂、水玻璃、催化剂等系列产品,直接用于区域内煤-电-化企业生产过程;②煤基固废中90%以上的钙、硅、铝得到有效利用,废催化剂中钒、钨、钛金属循环利用率超过90%,气化渣中残碳被有效分离利用。以上构建的循环产品链将煤炭、水资源利用效益分别提升36%和27%,3类典型固废综合利用率由28%提升至85%左右,为煤炭固废的大规模利用提供了新路径,从而可实现煤炭及其伴生/二次资源区域内的高效循环。 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