Title : Oxidative transformation of ethylene into ethyl alcohol and acetaldehyde under the per-FTPhPFe3+OH/Al2O3 bioimitator
Abstract:
For the first time, the investigation of the coherent-synchronized reaction of heterogeneous catalytic ethylene monooxidation with hydrogen peroxide into ethyl alcohol and acetaldehyde was carried out using the new highly efficient bioimitator, per-FTPhPFe3+OH/Al2O3, which is highly resistant to oxidizing agents and high temperatures, as well as a long service life. The process of gas-phase ethylene monooxidation with hydrogen peroxide was carried out at atmospheric pressure, in a flow system, in an integral type reactor with a reaction zone volume of 3.5 cm3. Optimal conditions for maximum yields of target products were determined: a) at a temperature of 120°C, a concentration of an aqueous solution of hydrogen peroxide of 20 wt.%, molar ratio C2H4:H2O2 = 1:1, the highest yield of ethyl alcohol is 15.4 wt.%. The selectivity for monooxygenase products is almost 100%; b) at t = 200°C, concentration of an aqueous solution of hydrogen peroxide 30 wt.%, molar ratio C2H4:H2O2 = 1:1.7, the yield of acetaldehyde is 34.6 wt.%. The selectivity for monooxygenase products is 87%.
The process of biomimetic oxidation of ethylene by hydrogen peroxide is carried out in the bioimitator-H2O2-C2H4 system in a bifurcation mode, in which catalase (decomposition of hydrogen peroxide), monooxygenase (ethylene monooxidation) and peroxidase (peroxidase oxidation of ethyl alcohol) reactions are coherently proceed. The oxidative conversion of ethylene into monooxygenase products occurs in the following sequence: . Each of these transformations is a complex reaction and consists of two coherent-synchronized reactions: 1) primary (catalase) and 2) secondary (monooxygenase and peroxidase) reactions.The mechanisms of ethylene oxidation into ethyl alcohol and acetaldehyde on the surface of a biomimetic catalyst are presented, in which the unity of redox and acid-base mechanisms can be traced within the framework of the bond redistribution chain (BRC) theory.
Kinetic modeling of the process of heterogeneous catalytic ethylene monooxidation with hydrogen peroxide on the per-FTPhPFe3+OH/Al2O3 bioimitator was carried out using various methods: using the Michaelis-Menten equation; using the method of stationary concentrations; based on the determinant equation. A comparative analysis of the results obtained by various modeling methods showed that the kinetic model using the determinant equation adequately describes the processes. It has been established that the kinetic model, based on the determinant equation and the coherence relationship of coherent-synchronized catalase, monooxygenase and peroxidase reactions allows assessing the coherent nature of synchronously flowing reactions qualitatively and quantitatively. Kinetic modeling was also carried out with the aim of further application of the chosen model in the optimization and design of this process.
