V.I. Anikeev

Transformations of several monoterpenoids in the presence of aldehydes in supercritical solvents

The reactivity of verbenol epoxide and isopulegol in supercritical solvents in the presence of aromatic aldehydes was studied using a flow type reactor and a heterogeneous catalyst (Al2O3) or no catalyst. The intramolecular transformations or interactions of reagents with the solvent prevailed in all cases; the yield of the products of intermolecular reactions of terpenoids with aldehydes was up to 1%. The aldehydes did not interact with verbenol epoxide but produced a considerable effect on the distribution of its isomerization products.

Reduction of nitrotoluenes in supercritical isopropanol over Al2O3 in a flow reactor

The reduction of o-, m-, and p-nitrotoluenes in supercritical isopropanol over Al2O3 in a flow reactor is studied. It is shown that corresponding toluidines are major reaction products. Aromatic ring alkoxylation and N-alkylation products make a considerable contribution to the composition of reaction mixtures.

Stepwise Selective Reduction of Polynitroarenes Using Isopropanol as a Source of Hydrogen in a Flow-Type Reactor in the Presence of Alumina

Reduction of several polynitroarenes with isopropanol in a flow-type reactor in the presence of Al2O3 catalyst was studied. Temperature-controlled highly selective reduction of one, two, or three nitro groups in all the studied polynitroarenes proved to be feasible. N-alkylation of the reaction products was the predominant side reaction at high temperatures, except for the reduction of 2,7-dinitronaphthalene: in this case, a considerable amount of alkoxylated product was obtained. Benzo[c]cinnoline was the main product of reduction of 2,2′-dinitrobiphenyl.

Cyclization of citronellal in a supercritical solvent in a flow reactor in the presence of Al2O3

The reactivity of citronellal under supercritical solvent conditions in a flow reactor in the presence of Al2O3 is examined. It is shown that at 160°C, the main transformation product of citronellal is isopulegol, and when the temperature is increased to 190°C, they are monoterpenes with a para-menthane framework and myrcene.

Transformations of α- and β-ionones in the presence of Al2O3 in a supercritical solvent in a flow reactor

The reactivity of α- and β-ionones under the supercritical conditions in a flow type reactor in the presence of Al2O3 at 200–230°C was studied. α-Ionone was reduced to α-ionol, while β-ionol was unstable already at 200°C and underwent dehydration. The secondary reaction products were the corresponding megastigmatrienes.

Environmentally Benign Transformations of Monoterpenes and Monoterpenoids in Supercritical Fluids

The use of supercritical fluids (SCFs) to perform transformations of monoterpenes and their oxygen-containing derivatives enables one to obtain a broad range of valuable products using renewable raw materials under green conditions. The advantages of SCFs are most vividly manifested when they are used in combination with heterogeneous catalysts and/or flow-type reactors. The review covers all types of transformations of monoterpenes and monoterpenoids in SCFs published in literature up to early 2012, including the results obtained by the authors and literature data.

Synthesis of Biodiesel Fuel in Supercritical Lower Alcohols with and without Heterogeneous Catalysts (Thermodynamics, Phase and Chemical Equilibriums, Experimental Studies)

Abstract Thermodynamic data (critical parameters, enthalpy, entropy) were calculated for mono-, di-, and triglycerides of fatty acids (palmitic, oleic, and linoleic), free fatty acids, and methyl esters of fatty acids, which are involved in transesterification of vegetable oils with lower alcohols. Phase diagrams of the reaction mixtures were calculated and reaction conditions providing supercritical state of the reaction mixture were selected for transesterification of triglycerides in various lower alcohols. The chemical equilibria of the methanol transesterification of simple and mixed fatty acid triglycerides were studied in a wide range of temperatures, pressures, and ratios of initial components, including the region of the supercritical state of the reaction mixture. Calculation of the phase equilibrium and equilibrium composition of the reaction products obtained by transesterification of triglycerides and vegetable oils with lower alcohols allowed selection of the optimal reaction conditions for practical applications. Transesterification reactions of rapeseed oil in supercritical methanol in a flow reactor over a wide range of variation of the methanol/oil ratio, pressure, and contact time were studied. Conditions ensuring selectivity and a high degree of rapeseed oil conversion were found. Experiments to study this reaction in the presence of zeolite heterogeneous catalyst were performed.