This work is dedicated to the 115th anniversary of the birth of L.S. Polak, an outstanding Russian academician and researcher, a promoter and historian of science, and one of the founding fathers of plasma chemistry. The review summarizes the achievements of his scientific school in the plasma chemistry of hydrocarbons. The reactions that occur during the production of acetylene from methane and other hydrocarbons in thermal plasma—reactions studied comprehensively by L.S. Polak and his co-workers—are discussed in the historical context based on the available publications on industrial acetylene production.

The detonability of polyethylene pyrolysis products (pyrogas) in mixtures with air is determined for the first time in a standard pulsed detonation tube based on the measured values of deflagration-to-detonation transition run-up time. The pyrogas is continuously produced in a gas generator at decomposition temperatures ranging from 650 to 850 °C. Chromatographic analysis shows that at a high decomposition temperature (850 °C) pyrogas consists mainly of hydrogen, methane, ethylene, and ethane, and has a molecular mass of about 10 g/mol, whereas at a low decomposition temperature (650 °C), it mainly consists of ethylene, ethane, methane, hydrogen, propane, and higher hydrocarbons, and has a molecular mass of 24–27 g/mol. In a pulsed detonation mode, the air mixtures of pyrogas with the fuel-to-air equivalence ratio ranging from 0.6 to 1.6 at normal pressure are shown to exhibit the detonability close to that of the homogeneous air mixtures of ethylene and propylene. On the one hand, this indicates a high explosion hazard of pyrogas, which can be formed, e.g., in industrial and household fires. On the other hand, pyrogas can be considered as a promising fuel for advanced propulsion powerplants utilizing the thermodynamic Zel’dovich cycle with detonative combustion, e.g., solid-fuel detonation ramjets. In view of it, the novel conceptual design of the dual-duct detonation ramjet demonstrator intended for operation on pyrogas at the cruising flight speed of Mach 2 at sea level has been developed. The ramjet demonstrator has been manufactured and preliminarily tested in a pulsed wind tunnel at Mach 1.5 and 2 conditions. In the test fires, a short-term onset of continuous detonation of ethylene was registered at both Mach numbers.

The task of CO₂ decomposition is one of the components of the problem associated with global warming. One of the promising directions of its solution is the use of low-temperature plasma. For these purposes, different types of discharges are used. Microwave discharge in liquid hydrocarbons has not been studied before for this problem. This paper presents the results of a study of microwave discharge products in liquid Nefras C2 80/120 (petroleum solvent, a mixture of light hydrocarbons with a boiling point from 33 to 205 °C) when CO₂ is introduced into the discharge zone, as well as the results of a study of the discharge by optical emission spectroscopy and shadow photography methods. The main gas products are H₂, C₂H₂, C₂H₄, CH₄, CO₂, and CO. No oxygen was found in the products. The mechanisms of CO₂ decomposition in the discharge are considered. The formation of H₂ occurs simultaneously with the decomposition of CO₂ in the discharge, with a volumetric rate of up to 475 mL/min and energy consumption of up to 81.4 NL/kWh.

The physical and chemical characteristics of the microwave discharge in petroleum solvent during hydrogen production processes involving Ar, He, and CO₂ barbotage were studied. Gas chromatography, emission spectroscopy, high-speed photography, and shadow photography were used for diagnosis. The results demonstrated the dependence of hydrogen yield on the flow rates of Ar, He, and CO₂. The maximum yield values of hydrogen were 791 mL/min and 811 mL/min, while the maximum energy efficiency reached 135.6 NL/kWh and 162.2 NL/kWh in Nefras with Ar and He barbotage, respectively. The dynamics of discharge structure and the rotational and vibrational temperatures of C₂ molecules were studied.

The effect of hydrogen addition on the partial oxidation of a natural gas/O₂ mixture was studied in a flow reactor with increased calorific intensity. The addition of hydrogen (CH₄/H₂ = 3) to a fuel-rich natural gas/O₂ mixture with the oxidizer excess ratio α = 0.34 leads to an increase in the yields of H₂ and CO and in the H₂/CO ratio and to a decrease in the yields of CO₂, H₂O, C₂H₄, and C₂H₂ and in ∆C. The hydrogen addition at CH₄/H₂ = 3 positively influences the hydrogen production in partial oxidation of natural gas/O₂ mixtures.

During high-temperature pulse pyrolysis of acyclic butanes and pentanes under adiabatic compression conditions, cyclopropane, a stressed cyclic hydrocarbon, was found among the reaction products in small quantities for the first time. The analysis of the reaction products was performed by gas chromatography using three capillary columns of different polarity, selectivity and sufficient efficiency. The identification of reaction products, including cyclopropane, was performed using retention times of individual substances and model mixtures, as well as comparing chromatograms with reference chromatograms from the literature and the ScanView Application Database. It was shown that the chromatographic peak attributed to cyclopropane could not be a ghost peak. Additional confirmation of this conclusion was obtained in a series of experiments on the pyrolysis of n-butane at a reduced initial temperature of the adiabatic compression reactor (from 120 °C to 50 °C) and a modified mode of GC analysis. Cyclopropane yields as a function of maximum temperature have a bell-shaped asymmetric dependence. The maximum value of the yield of cyclopropane increases with the transition from normal alkanes to isoalkanes, and from pentanes to butanes; for n-pentane, 0.009 wt. %, and for isobutene, ≈0.017 wt. %. During the pulse pyrolysis of isobutane, n-butane, isopentane and n-pentane, cyclopropane is not a primary product. Further theoretical and experimental studies are needed to establish the mechanism of cyclopropane formation during pyrolysis of C₄–C₅ acyclic alkanes.