Andrey S. Stoporev

Dependence of the rate of formation and the P-T stability field of methane hydrate suspensions in crude oils upon oil composition

Equilibrium conditions for hydrates obtained from water emulsions in crude oils of the Yurubcheno-Tokhomskoe, Verkhnechonskoe, Gerasimovskoe, and Usinskoe fields have been studied, as well as the relative rates of hydrate formation in these systems. It has been concluded that the presence of oil does not alter the equilibrium conditions of hydrate formation. An increase in the concentration of resin-asphaltene substances and paraffins in crude oil leads to a decrease in the hydrate formation rate.

High-pressure gas hydrates of argon: compositions and equations of state.

Volume changes corresponding to transitions between different phases of high-pressure argon gas hydrates were studied with a piston-cylinder apparatus at room temperature. Combination of these data with the data taken from the literature allowed us to obtain self-consistent set of data concerning the equations of state and compositions of the high-pressure hydrates of argon.

Heterogeneous Nucleation of Methane Hydratein a Water–Decane–Methane Emulsion

Heterogeneous nucleation in disperse systems with metastable disperse phases plays an important role in the mechanisms of environmental and technological processes. The effect the concentration and activity of particles that initiate the formation of a new phase have on nucleation processes in such systems is considered. An approach is proposed that allows construction of a spectrum of particle activity characterizing the features of nucleation in a sample, based on the fraction of crystallized droplets depending on the level of supercooling and the use of Weibull’s distribution. The proposed method is used to describe experimental data on the heterogeneous nucleation of methane hydrate in an emulsion in a water–decane-methane system.

A new method for obtaining fine powders of paracetamol for compression without excipients

Paracetamol (N(phydroxyphenyl)acetamide) is a widely used nonnarcotic analgesic having also anti inflammatory and antipyretic action. Several crystalline polymorphs of paracetamol are known. One of these (monoclinic form I) is thermodynamically stable and is readily prepared but cannot be compressed to tablets without excipients (fillers). Another polymorph (orthorhombic form II) can be readily compressed to tablets without excipients [1, 2] and is better soluble but its formation as a pure phase is not reproducible, and, what is worse, it is metastable and is spontaneously converted to the monoclinic form on storage [1]. The idea of obtaining compressible forms of paracetamol that would be stable on storage attracts considerable attention of the scientific community and pharmaceutical companies. For solving this problem, it has been proposed to use, instead of pure paracetamol, its mixtures with polyvinylpyrrolidone [3], carbohydrates [4], chitosan and sodium alginate [5] or mixed crystals based on oxalic acid, naphthalene and other compounds [6] or the inclusion compounds with hydroxypropylβcyclodextrin [7].