Catalyst Screening through Quantum Chemical Calculations and Microkinetic Modeling: Hydrolysis of Carbon Dioxide

Quantum chemical calculations are emerging as an effective way to screen catalysts for particular applications. In this contribution, we demonstrate the power of density functional theory to study CO₂ hydrolysisby six carbonic anhydrase mimics, evaluating thermodynamic and kinetic parameters at the mechanistic level. A microkinetic model was then built based on the kinetics and thermodynamics calculated from first principles. The intrinsic reaction rate constant was calculated from the results of the microkinetic model and compared with experimental data. Overall, the rate constants were in good agreement with experimental values, except for zinc-tri and complex b, which were overestimated. This was ascribed to their ineffective complexation with Zn²⁺. How the reaction rate constants vary with time was also investigated. From 0 to 12 ms, the rate constants of complexes a and d decreased to 50 and 67% of their initial values, respectively; the rate constants of complexes b and f2 were almost invariant with time; the rate constant of complex f1 showed an unusual double sigmoidal shape. The pK_a values of these six carbonic anhydrase mimics as well as three additional mimics were calculated. A correlation between pK_a values and the binding free energy of OH-was obtained by fitting data from five zinc(II) aza-macrocyclic complexes. The reaction rate constants were found to increase linearly with the pK_a value, indicating CO₂ adsorption is the rate-limiting step.     

High Loading Fe-supported Fischer–Tropsch Catalysts: Optimization of the Catalyst Performance

The iron loading of catalysts, supported on SiO₂, was investigated between 10 and 75 wt%, with and without the addition of promoters (K and Cu), in order to highlight the different catalytic performances of the samples in the Fischer–Tropsch synthesis. An optimization study of the prepared catalysts (active metal/promoters ratio, catalysts’ activation procedure before the Fischer–Tropsch runs, influence of the feeding gas composition) is reported. The mechanical resistance of the catalysts was also evaluated using a suitable method involving ultrasound.     

Effect of Catalyst Preparation on Catalytic Activity: V. Chemical Structures on Nickel/Alumina Catalysts

In situ X-ray photoelectron spectroscopy (XPS or ESCA) was used to identify the nickel species on Ni/Al₂O₃ catalyst surfaces as a function of nickel weight loading. The ESCA results show that the only nickel species on the reduced catalyst surface is NiAl₂O₄ for low weight loading catalysts (< 1 wt.%) whereas both nickel and NiAl₂O₄ are present on high weight loading catalysts. The carbon monoxide temperature-programmed reduction (CO-TPR) results, after reduction of the catalysts in hydrogen, confirm that each type of nickel species acts as a different reaction center for methane production. The high-temperature methane peak observed only from CO-TPR spectra of low weight loading catalysts is due to NiAl₂O₄; a low-temperature peak, which appears as the weight loading is increased, is due to nickel. Steady-state reaction kinetics for methane production yields activation energies that increase with increasing weight loading of the catalyst. The apparent activation energies for catalysts with a single methane peak in their CO-TPR spectra were normally distributed. The apparent activation energies for catalysts with two methane peaks in their CO-TPR spectra were also normally distributed when the method of the catalysts' preparation was considered in testing the statistical nature of the distribution. This study suggests that the spread in the distribution of the apparent activation energies can be related to the structure of the reaction centers on the catalyst surface. The catalysts with a single methane peak in their CO-TPR spectra have uniformly dispersed NiAl₂O₄ species and result in the lowest spread (±0.2 kcal/mol, 0.84 kJ/mol). Catalysts prepared by incipient wetness with two methane peaks in their CO-TPR spectra have more uniform and larger “particle-like” nickel present on the surface than catalysts prepared by wet impregnation; the result is a spread of ±1.0 kcal/mol (4.2 kJ/mol) in the normal distribution in apparent activation energies. Catalysts prepared by wet impregnation have smaller nickel particle sizes and greater heterogeneity in reactive centers; the spread in the distribution of activation energies of catalysts prepared by this method is ±2.6 kcal/mol (10.9 kJ/mol).     

The Innovative Russian Approaches to Catalysts Design: New Generation of Fiberglass Catalysts

Deep understanding of catalysis fundamentals allows the development of highly efficient catalysts of the newest generation. In this paper, the attention is given to studies of novel inorganic materials, like fiber glass textiles of silicate origin. In this case the nanostructured catalysts were prepared which reveal high performance in different catalytic reactions. Some applications of these materials in the production of petrochemicals are presented.     

湿式催化氧化法中催化剂的选择和实验条件的优化

本文研究了湿式催化氧化法(Catalytic Wet Oxidation,CWO)处理高浓度有机水中催化剂的选择和实验条件的优化.在优选催化剂中共计制备十四种催化剂并进行实验,得出Ce、Cu复合催化剂活性最高.在实验条件优化中根据对正交实验数据结果进行的极差分析发现CWO法处理废水时的各影响因素的主次关系是H2O2用量＞Ce、Cu复合催化剂用量＞反应时间.     

湿式催化氧化法废水处理中催化剂和实验条件的优选

研究了湿式催化氧化法在处理难降解有机废水中催化剂的选择和实验条件的优化。在催化剂选择实验中以分子筛为载体共制备一元催化剂、二元催化剂和三元催化剂共计 16种 ,并以之分别处理分散黄、分散蓝、分散红、活性红和活性黑 5种染料以及甲基橙 ,得出了Ce系列和Cu系列的催化剂活性最高 ,COD和浊度的去除率最高可达 90 0 %以上。在以活性红染料为处理对象进行了条件的优化实验中 ,得到了最佳的条件是每 10 0mL活性红染料废水应加入H2 O2 溶液1 0mL ,催化剂 1 0g ,处理时间为 2 0h。     

Fine Chemical Synthesis with Homogeneous Palladium Catalysts: Examples,Status and Trends

During the last decade several palladium-catalyzed reactions have been developed and optimized to a stage that enables application on an industrial scale. The importance of these reactions as novel key steps for fine chemical synthesis is shown. Examples include palladium-catalyzed Heck, Suzuki and Sonogashira coupling reactions, telomerization of 1,3-butadiene with nucleophiles, and carbonylation of aromatic and benzylic halides.     

Hydroformylation Catalysis at Eastman Chemical: Generations of Catalysts

Eastman Chemical has a long term hydroformylation research program that has resulted in several successful low pressure rhodium catalyst technologies. The history of the bidentate ligand, BISBI, and the more recent development of halophosphite ligands will be discussed. The BISBI ligand is well known for high selectivity to the normal isomer and has been widely discussed in the literature. The relatively unknown halophosphite ligands exhibit a unique ability to produce aldehyde products with a variable range of linear to branched ratios by manipulating reaction variables such as reaction temperature, ligand concentration or carbon monoxide partial pressure. The halophosphite catalysts have been found to be resistant to poisoning by traditional hydroformylation poisons such as acetylene.     

Twelve-Nitrogen-Atom Cyclic Structure Stabilized by 3d-Element Atoms: Quantum Chemical Modeling

Using various versions of density functional theory (DFT), DFT M06/TZVP, DFT B3PW91/TZVP, DFT OPBE/TZVP, and, partially, the MP2 method, the possibility of the existence of 3d-element (M) compounds with nitrogen having unusual M: nitrogen ratio 1:12, unknown for these elements at the present, was shown. Structural parameter data were presented. It was shown that all MN4 groupings have tetragonal-pyramidal structure. It was noted that the bond lengths formed by nitrogen atoms and an M atom were equal to each other only in the case of M = Ti, V, Cr and Co, whereas for other Ms, they were slightly different; moreover, the bond angles formed by nitrogen atoms and an M atom were equal to 90.0°, or practically did not differ from this value. Thermodynamic parameters, NBO analysis data and HOMO/LUMO images for this compound were also presented. Good agreement between the calculated data obtained using the above three quantum chemical methods was also noted.     

The Pyrolysis of 3-Picoline: Ab Initio Quantum Chemical and Experimental (Shock Tube) Kinetic Studies

The pyrolysis of 3-picoline dilute in argon was investigated using a single-pulse shock tube over the temperature range of 1400–1650 K and total pressures of 12–13 atm. The principal products observed were HCN, acetylene, benzene, cyanoacetylene, methane, and pyridine. Assuming that 3-picoline decomposes according to first-order kinetics, the rate constant for its overall disappearance was determined to be k_dis = 10^{16.9 (±0.8)} exp[–99 (±6) kcal mol⁻¹/RT] s⁻¹. The principal initial decomposition routes were found to be via the formation of the 3-picolyl and m-pyridyl radicals whose subsequent ring-opening led to the observed products. A 68-step kinetic model was developed that successfully fits the experimental data. The dominant reactions, i.e., the formation of picolyl and pyridyl radicals and their subsequent chain-opening reactions, were studied using ab initio quantum chemical techniques. The ab initio data were also incorporated into the kinetic model in the form of energies and A-factors for reactions for which no kinetic or thermochemical data were previously available. Optimization of the kinetic model yields a value of 64 ± (3) kcal mol⁻¹ for the heat of formation of 3-picolyl, a value lower than that for 2-picolyl, suggesting that the decomposition of 3-picoline more closely resembles that of toluene, rather than its isomer 2-picoline.     

Solid Acid Catalysts: Roles in Chemical Industries and New Concepts

Extensive studies of the cracking catalyst used in the largest process in chemical industries established the research field of solid acid catalysis. Solid acid catalysts are also utilized in various industrial processes. A new concept for acid site generation, Molecular hydrogen-originated protonic acid site, and its characteristics in alkane isomerization are described.     

Activated Carbon Monolith Catalysts (ACMC): A New and Novel Catalyst System

Monolithic catalysts have been widely used in gas–solid phase systems for a variety of environmental applications. More recently they are being investigated for use in three phase systems however there are few catalysts available commercially for these applications. Monoliths offer several advantages over traditional three phase slurry and trickle bed systems, in that they can be easily separated from the system, offer low pressure drop and high rates of adiabatic cooling, and are mostly linear when scaling up. In this chapter, we present a new and novel three phase catalyst, Activated Carbon Monolith Catalyst (ACMC), utilizing a newly developed integrated activated carbon monolith as an alternative to granular catalysts.     

改进铜基甲醇催化剂升温还原方法及优化使用

对甲醇合成系统的铜基甲醇催化剂的升温还原方法进行了改进,提出了生产过程中的优化措施,从而达到了延长催化剂使用寿命的目的。     

汽车尾气净化催化剂及载体的研究进展

汽车尾气是大气污染的主要来源之一,汽车尾气净化器催化是控制汽车污染的重要手段。因此本文综述了汽车尾气净化催化剂及其载体的研究进展,包括催化剂及其载体的分类及研究进展。并对金属型催化剂及稀土复合型催化剂进行了优缺点的比较,提出了汽车尾气净化催化剂的研究发展方向。     

新型环己醇脱氢催化剂的制备及其与工业催化剂性能比较

以硝酸铜和高氯酸锆为原料,氢氧化钠为沉淀剂,采用共沉淀法制备了环己醇脱氢生产环己酮的新型Cu/ZrO2催化剂。通过正交试验确定了较优的催化剂制备条件为锆铜原子比为2,焙烧温度为500℃,焙烧时间为5 h,锆盐初始浓度为0.2 mol.L-1,滴定终点pH为12。优化条件下制得的催化剂在实验室中用于环己醇脱氢,环己醇收率达85%,选择性高于98%,优于目前该反应过程工业上所用的同类催化剂。     

Realistic Surface Science Models of Supported Catalysts: The Chromium Oxide Ethylene Polymerization Catalyst

Depositing catalytically active particles onto flat, thin oxide films which have electric conductivity forms an attractive way to make supported catalysts suitable for surface science investigations. Here we describe the development of a model system for the chromium oxide on silica catalyst used in industry for the polymerization of ethylene, the so-called Phillips catalyst. The model system, consisting of molecularly dispersed chromium ions, deposited by wet chemical impregnation on a thin silica film and anchored to it by treating it in oxygen, displays a representative activity for polyethylene formation.     

Methanol Oxidation over Iron-Molybdate Catalysts: Optimization of the Process

This research aims to shed more light on the possibilities to optimize the process of selective oxidation of methanol over oxide catalysts using an adiabatic layer by determining border values of basic parameters of the process in the adiabatic layer that ensure a maximum rate of methanol oxidation at high selectivity. Laboratory experiments were performed to clarify the influence of the most important parameters of the process (temperature, space velocity and methanol concentration) on the efficiency of the adiabatic layer. An industrial experiment was carried out to verify the results obtained.     

Reusability, Durability and Treatability of Palladium Catalyst on a Semiconductor Plate: Comparison with Commercially Available Solid-Supported Palladium Catalysts

A palladium catalyst supported on a semiconductor plate underwent the Heck reaction effectively to afford a coupling product. The catalytic plate was easily recovered from the reaction mixture with tweezers and reused several times without any special treatment. Comparison of reusability, durability, and treatability of seven kinds of commercially available solid-supported palladium catalysts and the semiconductor-supported catalyst plate was studied.