色谱交点在失活催化剂研究中的应用I. 苯-催化裂化衰化系列催化剂体系

测定了苯在五种积炭量不同的催化裂化衰化系列催化剂上的保留体积, 发现它们的logV~g对1/T直线有一共同交点。这是吸附色谱中同一吸附剂上吸附质为同系物时存在色谱交点的延伸。这是将色谱交点规律应用于失活催化剂研究的新探索。     

色谱交点在失活催化剂研究中的应用 Ⅰ.苯-催化裂化衰化系列催化剂体系

测定了苯在五种积炭量不同的催化裂化衰化系列催化剂上的保留体积,发现它们的logV_g对1/T直线有一共同交点。这是吸附色谱中同一吸附剂上吸附质为同系物时存在色谱交点的延伸。这是将色谱交点规律应用于失活催化剂研究的新探索。     

丁烯氧化脱氢用催化剂的化学吸附特性

用脉冲色谱吸附技术考察了丁烯和丁二烯在六种铁系氧化物、P-Mo-Bi/SiO_2和Sn-P-Li催化剂上的动态化学吸附。所得吸附等温线、吸附速率常数以及计算的相应的吸附热力学参数,揭示了不同类型氧化物催化剂上,丁烯氧化脱氢反应性能存在差异的某些原因。试验结果揭示了铁系氧化物催化剂不同晶相之间的异同和联系,从一个角度解释了工业用H-198尖晶石催化剂和P-Mo-Bi/SiO_2催化剂放大效应不同的内在原因。     

色谱交点在多相催化研究中的应用I. 芳烃在分子筛催化剂上的交点

测定了苯、甲苯、乙苯、二乙苯在四种分子筛催化剂上的保留体积。这些催化剂都被用于研究从苯和乙醇合成乙苯的反应中。发现了苯、甲苯、乙苯的logVg-1/T直线都有共同交点。证明了气相色谱中同系物交点的一般原则, 可以用在催化反应的研究中,从而为该反应提供一些有用的信息。     

色谱交点在多相催化研究中的应用I. 芳烃在分子筛催化剂上的交点

测定了苯、甲苯、乙苯、二乙苯在四种分子筛催化剂上的保留体积。这些催化剂都被用于研究从苯和乙醇合成乙苯的反应中。发现了苯、甲苯、乙苯的logVg-1/T直线都有共同交点。证明了气相色谱中同系物交点的一般原则, 可以用在催化反应的研究中,从而为该反应提供一些有用的信息。     

用色谱技术测定H_2在B204低温变换催化剂上的传递和吸附系数

根据扰动应答原理,应用色谱技术可同时获得物质在多孔性催化剂床层中的传递和吸附系数。这是近十几年发展起来的一种动态分析方法。目前用得较多的数据处理方法是矩量分析法、富里叶分析法和传递函数法。本文用矩量分析法求得了H_2在B-204催化剂上的传递和吸附系数。     

色谱交点在多相催化研究中的应用——Ⅰ.芳烃在分子筛催化剂上的交点

测定了苯、甲苯、乙苯、二乙苯在四种分子筛催化剂上的保留体积.这些催化剂都被用于研究从苯和乙醇合成乙苯的反应中.发现了苯、甲苯、乙苯的 logV_g-1/T 直线都有共同交点.证明了气相色谱中同系物交点的一般原则,可以用在催化反应的研究中,从而为该反应提供一些有用的信息.     

镍铝催化剂吸附动力学参数的非线性动态分析

在推导出适应于甲烷化反应体系非线性动态分析不同吸附物种动力学参数模型的基础上，采用计算优化出工业镍铝甲烷化催化剂上可逆吸附氢和可逆吸附一氧化碳的吸附速率常数和吸附平衡常数。结果表明，镍铝催化剂上吸附可逆氢要比吸附一氧化碳快２．２倍左右。该结果为镍铝催化剂上甲烷化产物的生成主要依赖于一氧化碳的吸附这一判断提供了理论依据。由于镍铝催化剂上甲烷化是可逆吸附氢与不可逆吸附一氧化碳共同作用的结果，且不可逆吸     

用色谱技术测定CO_2在合成甲醇催化剂上的传递和吸附系数

研究吸附质在催化剂固定床反应器上的传递和吸附系数,对研究非均相催化剂的性质,提高催化剂的效能,以及为反应器设计提供基本数据等方面,都是十分重要的。用传统的稳态方法求出传递和吸附系数,外推到工业条件下使用,一般是不太可靠的。如果用色谱技术,就能在比较接近工业操作的条件下获得传递和吸附系数,因而这种方法     

Rh基催化剂上CO加氢制C2含氧化物的原位红外光谱研究

 用原位红外光谱考察了Rh-Mn-Li-Fe/SiO2和Rh/SiO2催化剂表面上CO的吸附态及CO加氢反应过程中吸附物种的变化. 结果表明,CO在Rh/SiO2催化剂上仅有线式吸附态存在,而CO在Rh-Mn-Li-Fe/SiO2催化剂上既有线式吸附态存在,又有孪生吸附态存在. 这说明Rh-Mn-Li-Fe/SiO2催化剂中Rh的分散度较高. 经CO加氢反应(3.0 MPa,593 K)后,在Rh-Mn-Li-Fe/SiO2催化剂上可观测到C2含氧化物前驱物种的吸收谱带,而在Rh/SiO2催化剂上未观测到相应的谱带; CO在这两种催化剂上主要以线式吸附态存在,孪生吸附态基本消失. 结合催化剂对CO加氢的催化性能,可以认为线式吸附的CO对生成C2含氧化物有贡献. Rh-Mn-Li-Fe/SiO2催化剂的高活性是由于助剂的存在削弱了其表面吸附CO的 C-O键,促进了CO的活化,从而有利于C2含氧化物前驱物的生成.     

Superactive and stereospecific catalysts. IV. Influence of structure of esters on MgCl2 supported olefin polymerization catalysts

CH-type catalysts were prepared by reacting MgCl₂ · ROH, where ROH is 2-ethyl hexanol (EH), (R)-2-octanol (R-20), and (S)-2-octanol (S-20), with TiCl₄ in the presence of di-i-butyl phthalate (BP), di-i-butyl terephthalate (BT), (-)-dimenthyl phthalate (MP), or (-)-dimenthyl terephthalate (MT). The MT catalysts were found to incorporate 8.9 to 13% Ti whereas the BP catalysts contain only 1.9 to 2.6% Ti. Comparison of the CH(EH, BP) and CH(EH, MT) catalysts showed that they have about equal number of isospecific active sites per gram of catalyst and the same rate constants of propagation for their nonspecific sites, however, the isospecific sites in the latter are less active by comparison. Consequently, the CH(EH, BP) catalysts is five times more active than the CH(EH, MT) catalysts and produces polypropylene which is 97% isotactic (reflux n-heptane insoluble) as compared to 84.7% for the latter. The catalysts derived from 2-octanols are much less active than the corresponding catalysts prepared with 2-ethyl hexanol due to lack of reactivity with phthalic anhydride which permits excessive incorporation of TiCl₄ to form nonstereospecific catalytic sites as well as inactive Ti species.     

Performance of palladium-containing supported catalysts in the oxidation of 1-butene

Performance of palladium-containing supported catalysts in the oxidation of 1-butene was investigated in a fixed-bed flow microreactor. The Pd-Fe-HCl/Ti-Al catalyst is the best among the five Pd-Fe-HCl/X (A= SiO₂,γ -Al₂O₃, Al-Ti, TiO₂, MCM-22) catalysts for the oxidation of 1-butene to butanone. It is interesting that high propionic acid selectivity can be obtained when V and H₂SO₄ are added to the palladium-containing supported catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Renaissance of immobilized catalysts. New types of polymer-supported catalysts, 'microencapsulated catalysts', which enable environmentally benign and powerful high-throughput organic synthesis

Immobilized catalysts have been reinvestigated from two aspects; as keys to environmentally benign chemical processes and high-throughput organic synthesis for combinatorial chemistry. While most known polymer-supported catalysts are less active than the corresponding original catalysts, new types of polymer-supported catalysts, microencapsulated catalysts, have been developed. The catalysts were immobilized on to polymers using physical envelopment by polymer backbones and interaction between pi electrons of benzene rings of the polystyrenes used as polymer backbones and vacant orbitals of the catalysts. Microencapsulated Sc, Os, Pd and Ru catalysts have been successfully prepared and high activities have been attained. In all cases, no leaching of the catalysts occurred, and the immobilized catalysts were recovered quantitatively by simple filtration and reused without loss of activity. It is noted that this method enables direct immobilization of metals onto polymers, and that normally unstable species such as Pd(0)(PPh3) can be kept stable by this immobilization technique. It is expected that other metal catalysts can be immobilized using this microencapsulation technique.     

Stereospecific polymerization of methacrylonitrile. IV. Polymerization by ate complex-type catalysts

Methacrylonitrile was polymerized by a number of ate-complex catalysts. The catalysts used were NaAlR₄, LiAlR₄, LiZnR₃, Li₂ZnR₄, RMg[AlR₄], and Mg[AlR₄]₂. It was found that the ate-complex catalysts in which one of the alkyls is replaced by a diphenylamino group are capable of producing polymers with higher degrees of crystallinity than those of polymers obtained by unmodified catalysts. It was shown that the diphenylamide linkage in these catalytic systems must play an important role in the steric control in the propagation steps of this type of polymerization, although the mechanism is not clear at present. The crystallinity index used in this research gave a linear relation against I measured by NMR, and can be used as a measure of the stereo-regularity of the polymer.     

Copper-cerium oxide catalysts for the selective oxidation of carbon monoxide in hydrogen-containing mixtures: II. Physicochemical characterization of the catalysts

The copper-cerium oxide catalysts were characterized using a set of physicochemical techniques including in situ FTIR spectroscopy, XPS, and XRD. It was found that copper segregated on the surface of cerium oxide and its states were labile and dependent on catalyst pretreatment conditions. Copper in a dispersed state was responsible for the reaction of CO oxidation in the presence of H₂ on the copper-cerium oxide catalysts. It is likely that this state of copper was composed of two-dimensional or three-dimensional surface clusters containing Cu⁺ ions.     

离子液体催化甘油和尿素合成甘油碳酸酯

将一系列酸性、碱性和中性的功能化离子液体用于催化甘油和尿素合成甘油碳酸酯。结果表明,中性离子液体表现出更高的催化活性。离子液体阳离子和阴离子的协同效应促进了反应的进行,离子液体阳离子的正电性活化尿素,阴离子的负电性活化甘油,并且催化剂酸碱位点的平衡对催化反应过程也有一定的影响。此外,离子液体可以实现回收利用至少五次,且催化活性基本不变。采用功能化离子液体替代传统金属催化剂,减少了不可再生资源的利用,且所用原料为廉价易得的生物基原料,过程中也不使用有机溶剂,环境友好。     

Immobilized organometallic catalysts in the catalytic polymerization of olefins

Studies in the field of supported Ziegler-Natta catalysts employed for the polymerization of olefins that were begun by works performed under the guidance of Prof. Chirkov are reviewed in brief. The development of immobilization procedure for metallocene catalysts including the synthesis of alkylaluminoxanes heterogenized on the support surface via the partial hydrolysis of AlR₃ by water contained in the support and subsequent supporting of a metallocene is described. It is revealed how the immobilization of various metallocenes on the solid surface affects the activity of the catalysts and the structure and molecular mass of the polymers. The use of immobilized organometallic catalysts for the polymerization filling of polyolefin matrices aimed at the design of new polymer composites with special characteristics and preparation of polyolefin nanocomposites is considered.     

Studies on Ziegler-Natta catalysts. Part V. Stereospecificity of the active center

Experimental results on Ziegler-Natta catalysts, based on observations made with the electron microscope, and a qualitative comparison of the stereospecificity of various catalyst combinations are given. The polymerization of olefin in these experiments is performed in the gas phase on dry catalysts in the absence of solvent or excess aluminium alkyl. The crystallographic structure of the lateral faces of α-TiCl₃ is established by electron microscopy and electron diffraction. The electron micrographs of α-TiCl₃–AlMe₃ catalysts show that the active centers, which are revealed by the dotwise formation of polymer, are located along the growth spirals, on lateral faces, and on surface defects. These regions of the surface are the only regions in which the surface titanium atoms are incompletely coordinated. The presence of chlorine vacancies and exposed titanium atoms is therefore an essential condition for the formation of active centers. However, the number of active centers is small in comparison to the number of incompletely coordinated titanium atoms, and hence it is concluded that the normally occurring α-TiCl₃ sites with one vacancy do not yield active centers on reaction with aluminum alkyl. It is proposed that the reaction with aluminum alkyl on such sites leads ultimately to a bimetallic complex which fills the original vacancy on the titanium atom. That the complexation is reversible and that the deblocked alkylated site, which is of the type proposed by Cossee, is an active center is not excluded. Such a center would, however, give atactic polymer. Similar complex formation on a TiCl₃ site having originally two vacancies would leave one vacancy on the titanium atom. This is believed to be the center of stereospecific polymerization. A model of this active center and a mechanism of polymer growth on it are proposed.     

Advanced electron microscopy characterization of nanostructured heterogeneous catalysts.

Heterogeneous catalysis is one of the oldest nanosciences. Although model catalysts can be designed, synthesized, and, to a certain degree, characterized, industrial heterogeneous catalysts are often chemically and physically complex systems that have been developed through many years of catalytic art, technology, and science. The preparation of commercial catalysts is generally not well controlled and is often based on accumulated experiences. Catalyst characterization is thus critical to developing new catalysts with better activity, selectivity, and/or stability. Advanced electron microscopy, among many characterization techniques, can provide useful information for the fundamental understanding of heterogeneous catalysis and for guiding the development of industrial catalysts. In this article, we discuss the recent developments in applying advanced electron microscopy techniques to characterizing model and industrial heterogeneous catalysts. The importance of understanding the catalyst nanostructure and the challenges and opportunities of advanced electron microscopy in developing nanostructured catalysts are also discussed.     

New selectivities from old catalysts. Occlusion of Grubbs’ catalysts in PDMS to change their reactions

This article describes new selectivities for Grubbs’ first and second generation catalysts when occluded in a hydrophobic matrix of polydimethylsiloxane (PDMS). Occlusion of catalysts in mm-sized slabs of PDMS is accomplished by swelling with methylene chloride then removing the solvent under vacuum. The catalysts are homogenously dissolved in PDMS yet remain catalytically active. Many substrates that react by olefin metathesis with Grubbs’ catalysts freely dissolved in methylene chloride also react by olefin isomerization with occluded catalysts. Eleven examples of substrates that exhibit dual reactivity by undergoing olefin isomerization with occluded catalysts and olefin metathesis with catalysts dissolved in methylene chloride are reported. Most of these substrates have olefins with allylic phosphine oxides, carbonyls, or ethers. Control experiments demonstrate that isomerization is occurring in the solvent by decomposition of the catalyst from a ruthenium carbene to a proposed ruthenium hydride. This work was extended by heating occluded Grubbs’ first generation catalyst to 100 °C in 90% MeOH in H₂O in the presence of various alkenes to transform the Grubbs’ catalyst into an isomerization catalyst for unfunctionalized olefins. This work demonstrates that occlusion of organometallic catalysts in PDMS has important implications for their reactions and can be used as a method to control which reactions they catalyze.