The staged synthesis of 2-methylimidazole from ethylenediamine and acetic acid in the presence of a bifunctional aluminoplatinum catalyst

An investigation has been conducted into the staged synthesis of 2-methylimidazole from ethylenediamine and acetic acid in the presence of a bifunctional aluminoplatinum catalyst. It has been shown that the formation stage of 2-methylimidazoline occurs more quickly on -Al₂O₃ than its dehydrogenation on the Pt centers. From a comparison of the processes of dehydrogenation of 2-methylimidazoline in the molten phase and in aqueous solution it follows that the water eliminated in the imidazoline formation stage could cause the decrease in activity during the dehydrogenation on the Pt centers. The structures of the secondary and intermediate products have been established for each stage of the process and their formation routes are discussed.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 1997–2002, September, 1992.     

Dehydrogenation of propane on aluminoplatinum catalysts modified with Re,Zr, Sc,and Sn

The effect of addition of Re, Zr, Sc, and Sn on an aluminoplatinum catalyst in the reaction of dehydrogenation of propane was investigated. It was shown that addition of 0.2–0.5% Zr, Sc, or Re virtually does not alter the catalytic properties of the aluminoplatinum catalyst (APC); addition of 0.2% Sn increases the activity, selectivity, and stability of Pt/Al₂O₃. The amount of coke deposited on the APC after the first 5 min of work decreases by three times in the presence of Sn. The coke is more enriched with hydrogen than the other systems formed on the surface of Pt-Sn/Al₂O₃.Deceased.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 765–771, April, 1991.     

Synthesis of hydrocarbons from CO and H2 in the presence of Co-Ru and Co-Pd catalysts containing aluminum oxide

The influence of additions of 0.1–0.5% Pd or Ru in a 10% Co/Al₂O₃ catalyst on its activity and selectivity in the synthesis of liquid hydrocarbons from CO and H₂ has been studied. It has been shown that the bimetallic systems make it possible to carry out the synthesis of hydrocarbons with a higher extent of conversion of CO and a higher yield of C ₅ ⁺ carbons in comparison with the original Co catalyst. Co-Ru catalysts exhibit exceptionally high selectivity (up to 80%) with respect to the formation of liquid products. It has been demonstrated by temperature-programmed reduction (TPR) that the introduction of Pd an dRu promotes the reduction of Co at lower temperatures and the formation of cobalt aluminates.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 1, pp. 60–64, January, 1992.     

The mechanisms of the formation of by-products in the catalytic synthesis of C-alkylimidazoles from diamines and carboxylic acids

The formation of 1-ethyl-2-methylimidazole (1-Et-2-MI) and 1-ethyl-2-methylimidazoline (1-Et-2-MIN), intermediates in the synthesis of 2-methylimidazole (2-MI) from ethylenediamine (EDA) and AcOH in the presence of a platinum-on-alumina catalyst, was studied. Using CH₃ ¹⁴COOH the incorporation of two acetate units into 1-Et-2-MI and 1-Et-2-MIN molecules was demonstrated. The same products were also obtained on dehydrogenation of 2-methylimidazoline (2-MIN) under mild conditions (220–230 °C). A part of the latter is transformed to N-ethyl ethylendiamine (EEDA) and EDA. These facts indicate that both 1-Et-2-MI and 1-Et-2-MIN result from hydrogenolysis of the imidazoline ring with subsequent ethylation. A reverse reaction, the C₅-cyclization of EEDA, was also observed. The formation of 2-MI is favored by increasing temperature.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 937–940, May, 1993.     

Polymerization of vinyl chloride by use of modified Ziegler–Natta catalysts. I. Overall kinetic features

Vinyl chloride has been polymerized by a modified Ziegler-Natta type catalyst VOCl₂ · 2THF–Al(i-Bu)₃–THF, and the kinetics of the polymerization reaction have been investigated in some detail. The present kinetic analysis has demonstrated that the generation of active centers is directly proportional to the catalyst concentration, and that their depletion is by a second-order decay process. Triisobutylaluminum has been found to contribute to the effective removal of active centers through complex formation.     

Catalytic synthesis of C-alkylimidazoles over platinum-alumina catalysts

The synthesis of C-alkylimidazoles from 1,2-diamines and carboxylic acids over bifunctional platinum—alumina catalysts has been studied. It has been shown that this method is effective for the synthesis of 2-alkyl and 2,4-dialkylimidazoles including imidazoles with long-chain alkyls. The effect of the reaction temperature, space velocity of the flow of the raw materials, and dilution by hydrogen on the yield of product has been examined for the example of the synthesis of 2-methylimidazole from ethylenediamine and acetic acid, and the stability of the catalyst in continuous reaction cycles with intermediate oxidative regeneration has been studied. The composition of the accompanying products has been established and a mechanism proposed for their formation.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 4, pp. 932–940, April, 1992.     

Reforming Catalysts of the PR Family: Scientific Foundations and Technological Advancement

Results of investigations of the state of active sites in aluminoplatinum reforming catalysts (RCs) are summarized. Laws governing the formation and the role of platinum ionic species in the adsorption and catalytic conversion of hydrocarbons are presented. Strategies for the design of highly efficient catalysts, the development of catalyst manufacturing technologies, and operation in the production of motor fuels and aromatic hydrocarbons are formulated. Data are reported on the full-scale operation of catalyst PR-51/04 (PR-71), a new RC, and full-scale tests of the Biforming process, a new process for motor fuel production by coprocessing C₃-C₄ hydrocarbon gases and gasoline fractions.     

Anionic SO3H-functionalized ionic liquid: An efficient and recyclable catalyst for the Pechmann reaction of phenols with ethyl acetoacetate

This paper has reported an anionic SO₃H-functionalized ionic liquid N-methylimidazolium sulfomethylsulfonate ([Hmim][HO₃SCH₂SO₃]) for the synthesis of coumarins by Pechmann reaction. The [Hmim][HO₃SCH₂SO₃] is easier to prepare by one-step neutralization reaction of N-methylimidazole with methanedisulfonic acid and show high catalytic performance for Pechmann reaction. Besides, the catalyst can simply be separated from the reaction mixture and recycled ten times without noticeable loss of activity.     

Kinetic analysis of the melt acidolytic (Co) polycondensation of fully aromatic polyesters

Experiments to determine the initial reaction rate constants of acidolytic (co)polycondensations of fully aromatic polyesters were conducted in the melt. The initial reaction rate was determined by constant monitoring of the evolution of acetic acid. Both homo-polycondensation of p-acetoxybenzoic acid (pAcBA) and copolycondensation of 2 parts pAcBA, 1 part p,p'-bisacetoxybiphenyl (BAcBP), and 1 part terephthalic acid (TPA) were studied in a batch reactor under nonisothermal conditions. Next to this, the effect of the presence of the catalyst N-methylimidazole (NMI) on the (co)polycondensations was checked. From the series of experiments it was concluded that the reactivities of acetoxy groups of pAcBA and BAcBP were equal. Furthermore, it was found that the catalyst NMI showed an accelerating effect in the homo- and copolycondensations, thereby acting as a “conventional catalyst.” The postulated reaction mechanism for the (co)polycondensations is in accordance with the reaction mechanism for acidolysis of esters by carboxylic acids as suggested by Loncrini. The reactivity of TPA could not be determined by the method used because of the poor solubility of TPA in the reaction mixture. © 1992 John Wiley & Sons, Inc.     

Effect of preliminaey heating on the physicochemical properties of 10% Co/Al2O3 catalyst and its behavior in hydrocarbon synthesis from CO and H2

The effect of preliminary heating of 10% Co/Al₂O₃ in air at 20–600°C on its surface composition, reducibility, and adsorption properties has been studied by programmed thermal reduction (PTR), IR spectroscopy, and DTA. It has been shown that increasing the pretreatment temperature strengthens the interaction between cobalt and the carrier, resulting in an increase in the fraction of weakly bound adsorbed CO on the surface of the reduced catalyst. The activity of Co/Al₂O₃ has been studied in the Fischer-Tropsch synthesis and it has been proposed that the centers of weakly bound linear forms of CO adsorption are involved in the formation of C₂ ⁺ hydrocarbons from CO and H₂.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2444–2450, November, 1991.     

不同方法合成的沸石咪唑酯骨架结构材料(ZIF-8)的表征和催化性能

以二甲基咪唑为有机连接体和以Zn(OH)2或Zn(NO3)2·6H2O为Zn源,在甲醇与氨水的混合溶液、甲醇和DMF 3种不同的合成体系中合成了沸石咪唑酯骨架结构材料ZIF-8(分别记为ZIF-8(NH4OH)、ZIF-8(MeOH)和ZIF-8(DMF),并采用XRD、FTIR、N2吸附、SEM、TPD及Knoevenagel缩合反应等手段对所合成材料进行了表征。结果表明,采用这3种不同的合成方法均可成功制备出ZIF-8,所合成的ZIF-8的形貌基本一致,但其晶粒大小和酸碱性能有较大区别,同ZIF-8(NH4OH)和ZIF-8(DMF)相比,ZIF-8(MeOH)晶粒分布集中、平均粒径较小且具有较大的外比表面积和较多的酸碱位。不同方法合成的ZIF-8在苯甲醛和丙二腈的Knoevenagel缩合反应中的催化性能有很大差异,ZIF-8(MeOH)催化活性明显高于ZIF-8(DMF)和ZIF-8(NH4OH),其较高的催化活性,同其较大的外比表面积和酸碱性能密切相关。     

Solvolysis of 4-acyloxy-3-nitrobenzoic acid substrates catalyzed by polyethylenimine derivatives

The solvolytic reactions of anionic activated esters (S_n^?) catalyzed by dodecane-block-poly[ethylenimine-graft-4(5)-methylimidazole] and related model compounds were investigated. Hydrolysis of 4-acetyl-3-nitrobenzoic acid (S₂^?) as a function of pH suggested that electrostatic interactions are operative only in the higher molecular weight polymers. Apolar interactions were evident from the greater catalytic rates observed for the hydrolysis of a series of 4-acetoxy-3-nitrobenzoic acid substrates (S_n^?). The largest rate enhancements were reflected by catalysts that make effective use of the electrostatic interaction and also provide an apolar binding site. Dodecane-block-poly[ethylenimine-graft-4(5)-methylimidazole], with a DP = 85, catalyzed hydrolysis of S_n^?(n = 2, 4, and 7), in excess substrate, exhibited saturation kinetics and followed a simple Michaelis-Menten-type mechanism. Inhibition of the catalyst in the hydrolysis of S₁₂^? was observed and can be rationalized by analogy to certain multisite enzymatic reactions.     

不同方法合成的沸石咪唑酯骨架结构材料(ZIF-8)的表征和催化性能

以二甲基咪唑为有机连接体和以Zn(OH)₂或Zn(NO₃)₂·6H₂O为Zn源,在甲醇与氨水的混合溶液、甲醇和DMF₃种不同的合成体系中合成了沸石咪唑酯骨架结构材料ZIF-8(分别记为ZIF-8(NH₄OH)、ZIF-8(MeOH)和ZIF-8(DMF),并采用XRD、FTIR、N₂吸附、SEM、TPD及Knoevenagel缩合反应等手段对所合成材料进行了表征。结果表明,采用这3种不同的合成方法均可成功制备出ZIF-8,所合成的ZIF-8的形貌基本一致,但其晶粒大小和酸碱性能有较大区别,同ZIF-8(NH₄OH)和ZIF-8(DMF)相比,ZIF-8(MeOH)晶粒分布集中、平均粒径较小且具有较大的外比表面积和较多的酸碱位。不同方法合成的ZIF-8在苯甲醛和丙二腈的Knoevenagel缩合反应中的催化性能有很大差异,ZIF-8(MeOH)催化活性明显高于ZIF-8(DMF)和ZIF-8(NH₄OH),其较高的催化活性,同其较大的外比表面积和酸碱性能密切相关。     

Recent advances in the synthetic and mechanistic aspects of the ruthenium-catalyzed carbon-heteroatom bond forming reactions of alkenes and alkynes

The group’s recent advances in catalytic carbon-to-heteroatom bond forming reactions of alkenes and alkynes are described. For the C-O bond formation reaction, a well-defined bifunctional ruthenium-amido catalyst has been successfully employed for the conjugate addition of alcohols to acrylic compounds. The ruthenium-hydride complex (PCy₃)₂(CO)RuHCl was found to be a highly effective catalyst for the regioselective alkyne-to-carboxylic acid coupling reaction in yielding synthetically useful enol ester products. Cationic ruthenium-hydride catalyst generated in-situ from (PCy₃)₂(CO)RuHCl/HBF₄·OEt₂ was successfully utilized for both the hydroamination and related C-N bond forming reactions of alkenes. For the C-Si bond formation reaction, regio- and stereoselective dehydrosilylation of alkenes and hydrosilylation of alkynes have been developed by using a well-defined ruthenium-hydride catalyst. Scope and mechanistic aspects of these carbon-to-heteroatom bond forming reactions are discussed.     

The number of active centers and propagation rate constant in ethylene polymerization with a homogeneous catalyst based on cobalt 2,6-bis[imino]pyridyl complex with methylaluminoxane activator

The number of active centers C _p and propagation rate constant k _p upon ethylene polymerization with a homogeneous catalyst based on a cobalt complex with bis[imino]pyridyl ligands (LCoCl₂, where L is 2,6-(2,6-(Me)₂C₆H₃N=CMe)₂C₅H₃N) using methylaluminoxane as an activator was determined by quenching by radioactive carbon monoxide (¹⁴CO). It was found that the drop in activity during polymerization on the above catalyst is due to the decreasing number of active centers (from 0.23 to 0.14 mol/mol Co within 15 min of polymerization); the propagation rate constant remained unchanged, 3.5 × 10³ l/(mol s) at 35°C, which is substantially lower than for a catalyst based on an iron complex with analogous bis[imino]pyridyl ligands. It follows from the data on molecular mass characteristics of the produced polymer that the homogeneous catalyst LCoCl₂/methylaluminoxane is of monocenter type, and the obtained value of the propagation rate constant reflects the true reactivity of its active centers.     

Cobalt Single-Atom Catalysts with High Stability for Selective Dehydrogenation of Formic Acid

Metal–organic framework (MOF)-derived Co-N-C catalysts with isolated single cobalt atoms have been synthesized and compared with cobalt nanoparticles for formic acid dehydrogenation. The atomically dispersed Co-N-C catalyst achieves superior activity, better acid resistance, and improved long-term stability compared with nanoparticles synthesized by a similar route. High-angle annular dark-field–scanning transmission electron microscopy, X-ray photoelectron spectroscopy, electron paramagnetic resonance, and X-ray absorption fine structure characterizations reveal the formation of Co^IIN_x centers as active sites. The optimal low-cost catalyst is a promising candidate for liquid H₂ generation.     

Kinetics of vanadium (V) catalyzed oxidation of gallic acid by potassium bromate in acid medium

The kinetics of oxidation of gallic acid with potassium bromate in the presence of vanadium(V) catalyst in aqueous acid medium has been studied under varying conditions. The active species of catalyst and oxidant in the reaction were understood to be HBrO₃ and VO₂⁺. The autocatalysis exhibited by one of the products, i.e. Br⁻, was attributed to complex formation between bromide and vanadium(V). A composite scheme and rate law were possible, some reaction constants involved in the mechanism have been evaluated. © 1996 John Wiley & Sons, Inc.     

Solid State Reactions of Hemin with Basic Substances: Formation of bis and Mixed Complexes

The solid state reactions of hemin with KCN, Na₂SxH₂O, arginine, imidazole, 1-methylimidazole, 2-methylimidazole, benzimidazole, and mixtures of these basic reagents were monitored using IR, Mössbauer, and XRD techniques. All these basic substances react at the peripheral propionic acid group of hemin-forming salts. Binary mixtures of KCN, arginine, imidazole, 1-methylimidazole, 2-methylimidazole, and benzimidazole were found to form complexes with mixed ligands at the iron site of hemin. According to the structural information obtained for these mixed complexes, mechanisms for their formation are proposed. The solid state synthesis and the properties of the obtained products reveal the specifities of the involved ligands.     

Studies on Ziegler-Natta catalysts. Part IV. Chemical nature of the active site

The determination of the number of sites active in the polymerization of ethylene on the surface of α-TiCl₃–Al(CH₃)₃ dry catalysts leads to the conclusion that this number is small in comparison to the total surface of the catalyst. Qualitatively this conclusion is also reached by two other independent methods. Infrared spectra of the catalyst before and after polymerization do not show a change in the type of bonds present in the surface. Electron microscopy proves that no active sites are formed on the basal plane of the α-TiCl₃ which constitutes 95% of the total surface. The results strongly favor the lateral faces of α-TiCl₃ as the preferred location of active centers. The lateral faces contain chlorine vacancies and incompletely coordinated titanium atoms. This must then be the essential conditions for the formation of active centers. The propagation of the polymer chain has been repeatedly shown to follow an insertion mechanism. The active site, therefore, necessarily contains a metal–carbon bond. The study of catalysts derived from TiCl₃CH₃ leads to the conclusion that a Ti? C bond on titanium of incomplete coordination is the active species in these cases. The alkylation of surface titanium atoms was proven to be an intermediate step in the catalyst formation from TiCl₃ and AlR₃. Survival of titanium–alkyl bonds on the lateral faces, where titanium atoms are incompletely coordinated explains best, in the light of our data, the activity of Ziegler-Natta catalysts. Coordination of aluminum alkyl compounds in or around the active center probably complicates the structure of the active centers.     

The influence of plasma chemical treatment of a platinum catalyst on its activity in the dehydrogenation of cyclohexane

The influence of plasma chemical treatments on the catalytic activity of 0.64 wt % Pt/SiO₂ and 1.0 wt % Pt/SiO₂ platinum catalysts in the dehydrogenation of cyclohexane was studied. The state of the surface of the catalysts was examined using X-ray photoelectron spectroscopy. Temperature hysteresis caused by the formation of active carbon was observed in flow experiments. It was shown that the reaction on the initial catalysts occurred on neutral and positively charged Pt particles, and that the active centers contained carbon. After catalyst treatment with a high-frequency plasma in H₂, its activity increased by many times because of the formation of a large number of low-activity centers on positively charged platinum particles also containing carbon. Glow discharge plasma in Ar sharply decreased catalytic activity, and the reaction then predominantly occurred on centers localized on neutral Pt particles, whereas centers on positive Pt particles were blocked. The state of the substrate (silica gel) did not change under the action of plasmas of both kinds.