P. A. Gushchin

Study of the Effect of the Degree of Overcooling During the Formation of Hydrates of a Methane-Propane Gas Mixture on the Equilibrium Conditions of Their Decomposition

A study is made of the effect of the initial degree of supercooling on the equilibrium conditions of decomposition of hydrates of a model gas mixture comprised of 95.66 mol % CH4 + 4.34 mol. % C3H8. To ensure a high degree of conversion of water to hydrate, 0.1 wt. % sodium dodecyl sulfate (SDS) solution was used as the liquid phase in experiments performed in an RCS6 Sapphire Rocking Cell instrument. The hydrates were produced by cooling under isochoric conditions in a GHA350 gas hydrate autoclave and under isochoric-isothermic conditions on the RCS6 instrument. The hydrated samples that were obtained were decomposed by heating under isochoric conditions at the rate of 0.2 K/h. Analysis of the decomposition curves indicates that, depending upon the initial conditions, both mixed methane-propane hydrates of various compositions and methane hydrate are formed when the test gas mixture is hydrated. It is demonstrated that the proportion of the CH4 hydrate which is formed increases with an increase in the initial degree of overcooling during hydrate formation. The curve depicting the equilibrium hydrate decomposition conditions for the gas mixture has a more complex configuration than the simple exponential curve proposed earlier. The data that is obtained points to the existence of a multiplicity of equilibrium conditions for the hydrate decomposition of gas mixtures, with the exact conditions in a specific case depending on the degree of overcooling of the system during hydrate formation.

Antiknock Properties of Blends of 2-Methylfuran and 2,5-Dimethylfuran with Reference Fuel

The antiknock properties of blends of 2-methylfuran and 2,5-dimethylfuran with a reference fuel containing toluene are studied. The octane numbers of blends of these substances in various concentrations and the change in sensitivity of the fuel are calculated. In the research method it is shown that the octane number of the blend reaches a maximum at an additive concentration of 10 vol. %, while the sensitivity of the fuel increases to a smaller degree when 2-methylfuran is used.

Kinetic Inhibition of Hydrate Formation by Polymeric Reagents: Effect of Pressure and Structure of Gas Hydrates

Kinetic inhibition of formation of methane hydrate (CS-I) and methane-propane (CH4 + C3H8 in 95.66 + 4.34 mole %) hydrate (CS-II) by the polymeric reagents Luvicap 55W and Luvicap EG is studied in the 40-120 bar pressure range. Cooling at the constant rate of 1°C/hr was used to assess the effectiveness of kinetic inhibition. It is shown that the kinetic hydrate formation inhibitors (KHI) Luvicap 55W and Luvicap EG in identical proportion of 5000 ppm are capable of inhibiting methane hydrate formation at a supercooling temperature twice as low (6-7°C) as in the case of hydrates of methane-propane mixture (13-14°C). In the presence of KHI, hydrates appear in the system in the form of visually discernible opacity of the initially transparent aqueous solution at a temperature that is 1-2°C higher than the temperature at the point of deviation of the P(T) curve from the straight line, i.e., they appear earlier than appearance of signs of gas absorption. Formation of such trace quantities of hydrate do not cause a marked deviation of the P(T) curve from the straight line and can be discerned only by more sensitive physicochemical methods. The inhibiting properties of Luvicap EG and Luvicap 55W with respect to methane hydrate differ insignificantly, but the former is more effective in inhibiting crystal growth. The experimental data indicate that Luvicap 55W is more effective than Luvicap EG in inhibiting nucleation and growth of methane-propane hydrate crystals.

Inhibiting Gas Hydrate Formation by Polymer–Monoethylene Glycol Mixture

Inhibition of formation of methane hydrate with cubic structure CS-I and methane-propane (95.66 CH4 + 4.34 C3H8 mole %) hydrate with cubic structure CS-II by isothermal method and method of cooling at the constant rate of 2°C/h, using 0.5% of a kinetic inhibitor (KIH) + 20.8% of the thermodynamic inhibitor (TIH) monoethylene glycol (MEG) is studied. It is shown that the synergic effect of increase in inhibiting capacity of a polymeric kinetic inhibitor (KIH) in the presence of 20.8% of MEG (TIH) is observed in the case of both methane hydrate and methane-propane hydrate inhibition. The synergy manifests itself in the form of increase in supercooling degree by 2.5-3°C that is attained in the KIH + TIH system before the initiation of hydrate formation as compared to a system that contains no TIH (MEG). The induction time is shown to depend on the degree of supercooling in the system while inhibiting CS-1 and CS-II hydrates with 0.5% KIH + 20.8% MEG. The obtained data indicate that KIH + MEG antihydrate reagents can be used to inhibit formation of technogenous gas hydrates at < 0C temperatures.

Polymer–Methanol Combines Inhibition of Gas Hydrate Formation

A study was carried out on combined inhibition by a solution containing 0.5% polymer kinetic inhibitor (KI) + 10.0% methanol as a thermodynamic inhibitor (TI) in the formation of methane hydrate (Class I) and the hydrate of 95.66 mol. % CH4 + 4.34 mol.% C3H8 (methanepropane mixture) (Class II). This combined inhibition was studied by an isothermal method and a method entailing cooling at a constant rate using a GHA350 autoclave. Methane was shown to have an adverse effect on the inhibiting properties of the polymer KI both relative to formation of methane hydrate and hydrates of C1–C3 hydrocarbons. The loss of inhibition by the polymer KI in the presence of methanol is expressed as the decrease in the extent of supercooling attainable in the system without adsorption of the hydrate-forming gas (1.5–2.5°C in comparison with the system without TI). The induction time is shown to depend on the extent of supercooling in the system during inhibition of formation of the Class I and Class II hydrates by the solution containing 0.5% KI + 10.0% TI.

Performance of Reformers with Different Catalyst Distributions in the Reactors. Parametric Equations for Calculating the Octane Number of the Reformate

We present production data on operation of reactor blocks in reformers. We identify the typical behavior of the change in temperature differential in the reactors as the reactor run time and the ratio of the catalyst volumes in the reactors are varied. It is shown that the n-paraffin content in the reformate corresponds to the temperature differential in the reactors. We propose parametric equations for calculating the octane number of the reformate for known aromatic hydrocarbon content in the reformate and known density.

Core-shell composite metal catalysts incased into natural ceramic nanotubes

The bimetallic halloysite nanotubes were prepared by the injection of halloysite- containing aerosols into the microwave plasma reactor. Nanotubes contain metal nanoparticles formed from the metal salt solution in the lumen of nanotubes and the iron oxide nanoparticles at the outer surface of nanotubes. Such halloysite composites may be sputtered onto the surface of the porous carrier forming the nanostructured catalyst, as was shown by the pure halloysite sputtering onto the model porous ceramic surface.

Physicochemical Mechanisms of Light Oil Oxidation During Extraction from High-Temperature Low-Permeability Oil Reservoirs

Use of a combination of multistage hydrofracking and high-pressure air injection is proposed for developing low-permeability oil deposits of the Tyumen Suite (Upper Jurassic). An effective inert gaseous agent is formed during intrastratal transformation of the air due to oxidation of the oil. The oil autooxidation mechanism is studied. A weak dependence of the oxidation rate on the oil properties is observed.

Thermodynamic Calculations to Determine the Optimal Composition of Oxide Catalysts

Thermodynamic calculations of the optimal compositions of oxide catalysts with different natures are performed based on the theory of catalysis by polyhedra. The obtained compositions of the active catalysts agree with experimental data. The electrostatic potential generated by polyhedra of metal-oxide catalysts in a variety of directions is calculated. The dependence of the sign and magnitude of the potential on the distance from the central metal ion towards the vertex of the polyhedron, the middle of its edge or the centre of the face is estimated. It is assumed that the magnitude of the potential can serve as a reference point for determining active centres, which produce adsorption complexes and intermediate compounds.

Effect of Pressure on the Effectiveness of the Kinetic Inhibition of Hydrate Formation by Polymer Reagents

We have studied the inhibiting properties of the reagents Luvicap 55W and Luvicap EG in the process of KC-I methane hydrate formation in the pressure range 60-120 bar. In order to evaluate the effectiveness of the kinetic inhibition, we used the method of cooling at a constant rate of 1 degree/hour. We established that both in a system containing the kinetic inhibitor and in a system without the inhibitor, the initial pressure does not affect the maximum degree of supercooling at which methane hydrate is still not formed. The reagents Luvicap 55W and Luvicap EG at a concentration of 0.5 wt.% can effectively inhibit methane hydrate formation for a degree of supercooling no greater than 6°C-7°C. For inhibition of KC-I hydrate formation for a greater degree of supercooling, the reagents Luvicap 55W and Luvicap EG should be used in a higher concentration or combined with appropriate thermodynamic inhibitors.