Current Organic Synthesis - Volume 14, Issue 3, 2017

Background: In comparison with these platinum group metal catalysts, supported nano gold catalysts have emerged as a new type of catalysts highly active at low temperature and selective for the aerobic oxidation of alcohols. But catalytic data and detailed characterizations of the Au-Ag bimetal catalytic system are not available up to date. Objective: This work is aimed to develop bimetallic AuAg-based heterogeneous catalysts for liquid phase selective oxidation of n-octanol. Modification of the titania support with transition metal additives were used as tools for transforming active species. Method: Catalytic tests in n-octanol liquid-phase oxidation at 80 °C. Catalyst characterization by Transmission electron microscopy, X-ray diffraction, plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, EXAFS and UV-visible spectroscopy. Results and Conclusion: Bimetallic AuAg catalysts supported on titania are moderately active for liquid phase selective oxidation of n-octanol. Formation of Au-Ag alloy was observed. Their activity may be increased by modification of the support with donor additives (La, Mg), while acceptor additives (Ce, Fe) decreased it. The addition of La, that inhibits the formation of Au-Ag alloy, provides the highest activity and the highest stability of reaction rate with run time in either as prepared and red-ox treated forms, which implies that it stabilizes the active centers in its optimal electronic state.

Background: A new approach for the simulation of branched hydrocarbons synthesis on platinum catalysts is provided. The kinetic and thermodynamic laws of low-temperature pentane-hexane fraction isomerization were established and studied. According to the performed research, development of hydrocarbons conversion mechanism on Pt/SO4-ZrO2 catalyst was provided. Objective: The objective of this work is to design the comprehensive mathematical model of isomerization as a tool for real process optimization. Method: This method is based on reactivity of components while prone to changes in the feedstock composition. Validation of the mathematical model of industrial light naphtha isomerization unit was done with industrial data. The proposed model showed satisfactory prediction ability. Results: Changes in feedstock composition correspond to 1 - 1.5 RON change in product. Temperature rise at the inlet of first isomerization reactor above 150 °C leads to a shift of the equilibrium towards the hydrocracking side reactions. Increasing loading of feedstock for every 2500 m/h reduces RON of isomerate by 0.43-0.5 points depending on the feedstock composition. Conclusion: The formalized reaction scheme was developed on basis of thermodynamic analysis for isomerization of light gasoline fractions. The kinetic parameters for different types of isomerization catalysts: Pt/SO4-ZrO2, Pt/zeolite, Pt/Al2O3-CCl4 were determined by solving reverse kinetic problem. The developed model for isomerization reactor was validated with industrial data and has satisfactory accuracy.

Background: Starting from the mid-20th century, synthetic detergents produced from petrochemical raw materials have become more and more widely used and in many cases have better cleaning characteristics than natural soap. Objective: The purpose of this work was to reveal physical and chemical regularities of C9-C14 hydrocarbons transformations and to increase the selectivity of the steps of synthesis of highly biodegradable linear alkylbenzenes. Method: Based on the thermodynamic analysis performed with use of quantum-chemical modeling, the study has shown how the structure of hydrocarbons affects their properties and reactivity. Results: With use of the results of the mathematical modeling of the main steps of synthesis of linear alkylbenzenes, it was shown that the selectivity of the process can be improved by suppressing the catalyst deactivation by coke during dehydrogenation of alkanes to alkenes. Conclusion: This can be achieved by reducing the hydrogen-rich gas circulation ratio while increasing the H2O supply to the reactor. The stemming decrease in the concentration of dienes in the feedstock allows us to reduce the HF flow rate to benzene alkylation with alkenes.

Background: The work performed constituted thermodynamic kinetic analysis of the chemical transformations of C13-C40 hydrocarbons during the catalytic cracking process. Objective: The objective of the work was to increase the yield of light fractions during the catalytic cracking of C13-C40 hydrocarbons. Method: Laboratory research to determine the structural grouped and individual composition of feedstock and products of catalytic cracking using liquid-adsorption and gas-liquid chromatography, chromato-mass spectrometry, n-d-m- and Hazelwood methods allowed a list to be made of catalytic cracking process reactions. Using Density Functional Theory, the thermodynamic parameters of the process reactions were determined and a formalized scheme of hydrocarbons transformations compiled based upon which the kinetic model of the process was documented and implemented programmatically. The determination of kinetic parameters of the reactions was carried out by solving the inverse kinetic problem using experimental data from an industrial plant and laboratory studies. Results: Using the kinetic model of the process, a study was conducted to determine the temperature in the catalytic cracking reactor aimed at achieving a process that yields gasoline fraction and light gas oil fraction. To achieve an optimum yield of high-octane (94.8) gasoline from catalytic cracking (59.30%), it is necessary to maintain the temperature at the exit of the ballistic separator at 530 °C. To achieve an optimum yield of light gas oil from catalytic cracking (12.09%), it is necessary to maintain the temperature at the outlet from the ballistic separator at the level of 520 °C. Conclusion: The use of a kinetic model of catalytic cracking allowed changes in the concentration of the reactants to be calculated as well as the yield and composition of the catalytic cracking products and ensured the selection of optimum conditions for increasing the yield of gasoline and light gas oil fractions based on group composition of raw material for catalytic cracking.

Background: Physical-chemical regularities of diesel fuel catalytic hydrodewaxing process were studied. Objective: The objective of this work is to develop mathematical model of hydrodewaxing for numerical studying patterns of the process. Methods: The method of mathematical modelling was used in the current research. Results: In summer regime, when the required target product is summer grade diesel fuel, the temperature in the reactor should be at the lowest value of 345 ºC in order to prevent catalyst deactivation and expand its service life, the feedstock flow rate should be the highest at 290 m3/h to increase the productivity of the plant. In winter regime, when high conversion of high molecular weight n-paraffins is needed to achieve required loetemperature characteristics, the process is to be carried out at high temperature. So, the temperature 355 ºC is optimal for studied feedstock composition as it allows achieving required selectivity towards high molecular weight n-paraffins. The feedstock flow rate is to be maintained at low level (210 m3/h) to provide high residence time in the reactor. Conclusion: On the base of thermodynamic analysis, which was performed using the method of quantum chemistry, the influence of hydrocarbon structure and length of the carbon chain on the reactiveness was investigated. By solving the reverse kinetic problem, using the experimental data from the industrial plant, kinetic dependences of stages of diesel fuel synthesis were established. Using the developed model, the effect of process parameters on the composition of the product was investigated.

Background: The foam materials have a number of interesting properties which may be used in processes of high temperature alcohol partial oxidation to aldehydes and ketones. Foam materials have uniform cellular structure with isotropy of mechanical and fluidodynamic properties: an average diameter of the elementary cell - 0.5-5.0m; porosity - 80-98%; volume density - 0.1-0.5 g/cm3. Objective: The aim of the present paper is comparative investigation of physicochemical and catalytic properties of Cu, Ag and Au catalysts supported on foam ceramics in the process of partial oxidation of methanol to formaldehyde. Method: Catalytic tests in methanol oxidation at T=550-650 °C. Transmission electron microscopy, adsorption measurements for m testing specific surface area. Results and Conclusion: Catalysts based on Ag, Cu and Au supported on foam ceramics are promising for usage in the processes of alcohol selective oxidation due to their high catalytic, mechanical and gas-dynamic properties. Among these metals Ag catalysts are the most effective; the catalytic characteristics of the Cu samples are much worse. This is caused by the formation of some numbers of Cu2+ ions favoring deep oxidation of alcohols. The activity of gold catalysts (methanol conversion, formaldehyde yield) is substantially lower than those of Ag and Cu samples because of poor oxidizability of gold. However, the selectivity of Au catalysts exceeds the one of Cu samples due to higher stability of active M+ ions.

Background: Materials containing supported gold nanoparticles are considered as the most favorable for liquid-phase alcohol oxidation. Our previous studies showed that MgAl2O4 spinel can be an effective support for gold catalysts in liquid-phase alcohol oxidation. Objective: The aim of the present paper a comparative study of gold supported on different metal oxides (Al2O3, MgO, MgAl2O4 spinel) in liquid phase oxidation of glycerol. Also we highlighted the influence of the precursor protective layer in mediating the support effect on catalytic activity and comparing MgAl2O4 spinel with individual oxide supports. Method: Catalytic tests in glycerol liquid-phase oxidation at 50 °C. Catalyst characterization by Transmission electron microscopy, X-ray diffraction, adsorption measurements, plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy. Results and Conclusion: It was shown that, depending on the preparation method, the activity of Au supported on oxide supports can become reversed. For deposition-precipitation method Au/Al2O3 is more active than Au/MgO while for sol immobilization, the contrary occurs and Au/MgO is more active than Au/Al2O3. Activities of Au catalysts supported on MgAl2O4 spinel are high and close to each other for catalysts prepared by both methods. It is suggested that Au particle size and interaction of Au with support are activity determining parameters, while gold content do not play a significant role. This study gets an insight on the importance of the direct contact between the support and the gold particle.

Background: Ring Opening Metathesis Polymerization (ROMP) can provide a wide range of possibilities for polymers and copolymers synthesis. Norbornene and its derivatives can serve as monomers for the synthesis of highly molecular mass polymers with widely varying structure. Objective: In this paper a new polymers based on dimethyl ether norbornenedicarboxylic acids were prepared by ring-opening metathesis polymerization in the presence of a catalyst of Hoveyda-Grubbs II. Method: The resulting polymers and monomers were characterized by NMR, IR, GCMS, TGA, DSC. Results: Chemical yield of investigated processes was more than 95 %, molecular mass of the obtained polymers was also relatively high (more than 4.5•106 g/mol). The research findings have shown that polymers obtained with bi- and tri-functional comonomers are more heat resistant and are stable up to the 370 °C. Also it was shown that the addition of bi-and tri-functional comonomers facilitates the significant improving of mechanical and physical properties. Polymer obtained with 3 wt.% of tri-functional comonomer possesses the biggest values of modulus of elasticity in flexure, breaking elongation and breaking strength. Conclusion: New polymers based of exo,exo and endo,endo-dimethyl esters of 5-norbornen-2,3-dicarbonic acid (DME) with addition of bi-functional and tri-functional comonomers were synthesized via metathesis polymerization. The addition of 3 wt.% of bi-functional and tri-functional comonomers resulted in polymers having a higher crosslinking degree and glass transition temperature. The synthesized polymers demonstrated a higher application temperature and better mechanical and physical properties than poly-DME.

Background: Double metal phosphates, such as silver- and copper-zirconium phosphates, are considered promising materials for alcohol transformation to high-value chemicals (aldehydes, esters, olefins) due to high functional properties. Objective: The work was aimed to synthesize AgZr2(PO4)3 and Zr2.25(PO4)3 and study the influence of reduction conditions on their chemical and phase composition as well as catalytic properties under aerobic and anaerobic ethanol transformation. Methods: The structure of the catalysts was characterized by the XRD and HR TEM methods. The gas-phase ethanol conversion was studied in the temperature-programmed mode with online chromatographic analysis of reaction products. Results: The treatment of silver-zirconium phosphate with hydrogen leads to formation of 5-10 nm Ag0 particles along with partial destruction of initial AgZr2(PO4)3 phase. The products of the acidic route are eliminated under oxygen-free conditions for both catalysts, while the acetaldehyde is mainly formed in the oxygen-containing reaction mixtures. The formation of acetaldehyde over zirconium phosphate involves formation of Zr4+Oads oxidized sites. The highest yield of acetaldehyde is 74% at 330 oC and 93% ethanol conversion over Ag-containing catalyst in aerobic conditions. Conclusion: The ethanol dehydration is the main reaction pathway under anaerobic conditions regardless of the presence of Ag. In contrast, the presence of oxygen in the feed favors ethanol conversion to acetaldehyde.

Background: Virgaureoside A is a component of Solidago virgaurea L. (Goldenrod ordinary) which is a well-known remedy in folk Chinese medicine. However, the isolation and, consequently, pharmacological testing of this diglycoside is difficult due to its low content. Objective: To perform the first total synthesis of the diglycoside Virgaureoside A and apply the developed synthetic approach to the synthesis of analogues compound, iso-Virgareoside A, thus allowing the acquisition of these diglycosides in any desired quantity and thereby permit an assessment of their potential biological properties. Results: The first syntheses of Virgaureoside A [2-(β-D-glucopyranosyloxy)benzyl 2-(β-D-glucopyranosyloxy) benzoate], a diglycoside of the Solidago virgaurea L. plant, and iso-Virgaureoside A [2-(β-D-glucopyranosyloxy) benzyl 4-(β-D-glucopyranosyloxy)benzoate], which is not found in nature and has not been described in the literature, have been accomplished. The key step involved selective acid catalyzed cleavage of acetyl esters in the presence of a substituted benzoyl ester and two glycosidic linkages. Conclusion: The desired products Virgaureoside A and iso-Virgaureoside A were synthesized in four steps in 5.6% and 3.0% overall yield, starting from ethyl 2-hydroxybenzoate and ethyl 4-hydroxybenzoate, respectively.

Heterocycles are widely spread in natural products and in many bioactive compounds, as well as in a variety of fine chemicals. Synthesis through catalysis is always an advantageous strategy and today it is difficult to consider an approach to a target molecule without the inclusion of a catalytic step. Moreover, it is indeed almost a required characteristic for all the synthetic transformations in line with the principles of green chemistry and sustainable processes. Chemical transformations via visible light photocatalysis are emerging strategies that meet the increasing demand for more sustainable chemical processes. Up to date, several visible light approaches have been successfully applied to various organic transformations. Moreover, potential advantages are envisaged in this highly active new field. This review gives a brief overview of methods based on visible-light photoredox catalysis that have been developed for the synthesis of heterocycles using transition metal catalysts and organic catalysts. Only works in which at least one heterocycle is constructed are included, leaving the vast area of functionalization of heterocycles for other reviews.

This review deals with the utility of hydrazonoyl halides in synthesis of bioactive heterocylic compounds such as pyrazoles, triazoles and pyrimidines which showed wide range of biological activities. We discussed here the synthesis of heterocyclic ring system derived from hydrazonoyl halides and their significant biological properties as for example, antitumor, antimicrobial, analgesic, anti-inflammatory, anti-H1N1 and anti HCV activity.

Organic synthesis efficiency can take considerable advantage from microwave heating. Compared to conventional heating, it allows to improve the reactions speed and yield through an energy-efficient, clean, and easy-to-use processing tool. Transition-metal catalyzed cross-coupling reactions and in particular the Suzuki- Miyaura cross-coupling is powerful and widely used tool for the formation of carbon-carbon bonds. Crosscoupling reactions are of large interest for the bonding of a broad range of functional groups, in particular biaryl groups, allowing for a strong stereoselectivity. In this paper, recent research results concerning the application of microwave heating in Suzuki-Miyaura cross-coupling reactions are reviewed with particular emphasis on reactions involving supported Pd as a catalyst.

Examples of reactions and physicochemical processes influenced by preferential solvation run in binary liquid solvent mixtures have been reviewed. The catalytic role of solutions of inorganic salts has been discussed. Different methods of classification of pure solvents and binary solvent mixtures have been presented. We have also discussed studies on the preferential solvation of neutral and ionic species. The nature of influence of organic solvents on the surface charge density of silica, solubilities of different organic compounds in binary liquid mixtures, permeation of mixtures of solvents through ceramic membranes, production of polymer nanoparticles by the solvent-displacement method have been discussed. Also examples of different physicochemical studies undertaken to characterize properties and nature of intermolecular interactions in binary solvent mixtures are presented.