COMPOSITES BASED ON CALCIUM PHOSPHATES AND COPPER NANOPARTICLES

Боргидридным методом с использованием полимерных стабилизаторов (полиэтиленгликоля, поливинилпирролидона) синтезированы наночастицы меди. Методом оптической спектроскопии установлено, что наибольшей стабильностью (до 1,5 месяца) обладают наночастицы меди, полученные при мольном соотношении Cu /полимер 1:3 - 6. Показано, что в отсутствии полимера либо при его небольшом содержании (мольное соотношение Cu /полимер 1:1) происходит агрегирование образующихся наночастиц и выпадение осадка, содержащего медь и ее оксиды (CuO, CuO). Механическим смешиванием аморфизированных фосфатов кальция (в порошковой и гелевой форме) и наночастиц меди (в виде коллоидного раствора) получен порошковый композит, содержащий фазы CaCuH(PO) и CuPOOH . Выявлено, что при совместном осаждении фосфатов кальция и наночастиц меди происходит встраивание ионов меди в кристаллическую решетку фосфатов кальция с образованием смешанных кислых и средних солей. Copper nanoparticles were synthesized by the borohydride method using polymer stabilizers (polyethylene glycol, polyvinylpyrrolidone). It was found by optical spectroscopy that copper nanoparticles obtained at a molar ratio Cu / polymer of 1: (3 - 6) have the highest stability (up to 1.5 months). It was shown that in the absence of polymer or at its low content (molar ratio Cu / polymer 1:1), the resulting nanoparticles aggregate and a precipitate forms containing copper and its oxides (CuO, CuO). By mechanical mixing of amorphized calcium phosphates (in powder and gel form) and copper nanoparticles (in the form of a colloidal solution), a powder composite containing CaCuH(PO) and CuPOOH phases was obtained. It was shown that during the coprecipitation of calcium phosphates and copper nanoparticles, copper ions are incorporated into the crystal lattice of calcium phosphates with the formation of mixed acidic and medium salts.

Laboratory Studies For Design of a Foam Pilot For Reducing Gas Channeling From Gas Cap in Production Well in Messoyakhskoye Field

Messoyakhskoye field, operated by Gazprom Neft, is currently experiencing gas channeling from gas cap in production wells because of strong heterogeneity. Foam for a long has been considered as a good candidate for gas blocking, (Svorstol I. et al., 1996), (Hanssen, J. E., & Dalland, M. 1994), (Aarra, M. G. et al., 1996). However, foam injection for gas blocking in injection well is different from that in production well, where it is necessary to selectively and long-term impact on gas-saturated highly permeable areas without affecting the phase permeability of oil in the reservoir. This paper provides detailed laboratory studies that show how to determine suitable foam systems for gas blocking in production well. For gas blocking in production well, a long half-life time is required to sustain stable foam because a continuous shear of surfactant solution/gas can't be achieved like in injection well. Therefore, reinforced foam by polymer is chosen. Four polymer stabilizers and five foam agents were evaluated using bulk test to determine foaming ability, foam stability, and effect of oil by comparing foam rate and half-life time to determine the suitable foam system. Furthermore, filtration experiments were conducted at reservoir conditions to determine the optimal injection mode by evaluating apparent viscosity, breakthrough pressure gradient, resistance factor, and residual resistance factor. Polymer can significantly improve half-life time (increase foam stability), and the higher the polymer concentration, the longer the half-life time. But simultaneously, a high polymer concentration will increase the initial viscosity of solution, which not only decreases the foam rate, but also increases difficulties in injection. Therefore, an optimal polymer concentration of about 0.15-0.2 wt% is determined considering all these influences. Filtration experiments showed that the apparent viscosity in core first increased and then deceased with foam quality (the ratio of gas volume to foam volume (gas + liquid). The optimal injection mode is co-injection of surfactant/polymer solution and gas to in-situ generate foam at the optimal foam quality of about 0.65. Filtration experiments on the different permeability cores showed that gas-blocking ability of polymer reinforced foam is better in high-permeability cores, which is beneficial for blocking high permeability zone. It should be also noted that under a certain ratio of oil to foam solution (about lower than 1 to 1), the presence of oil slowly decreased foam rate with increasing oil volume, but significantly increased half -life time, which is favorable for foam treatment in production well. This work highlights the difference between foam injection for gas blocking in production well and injection well, and emphasizes the use of polymer reinforced foam. Moreover, this work shows systematic experimental methods for choosing suitable foam systems for gas blocking in production well considering different factors, which provides a guide regarding what kinds of foaming agents and polymer stabilizers should be used and how to evaluate them for designing a pilot application.

ULTRAFINECOPPER AND NICKEL POWDERS INTHE ELECTRO-CATALYTICHYDROGENATIONOF ORGANIC COMPOUNDS

Ultrafine copper and nickel powders are synthesized by a chemical reduction of the metal cations from their salts in an aqueous ethanol solution without and with the addition of a polymer stabilizer (polyvinylpyrrolidone and polyvinyl alcohol). The structure and morphological features of the prepared metal powders were investigated by X-ray phase analysis and electron microscopy. The electrocatalytic properties of the Cu and Ni powders have been studied in the electrohydrogenation of acetophenone, nitrobenzene, p-nitroaniline, and cyclohexanone. A higher electrocatalytic activity of Cu powders, as well as skeletal copper, was established in the electrohydrogenation of the first three of the listed compounds in comparison with nickel powders, which is explained by the ability of copper cations to be reduced from its oxides in the electrochemical system under investigation. It is shown that the use of polymer stabilizers in the synthesis of Cu and Ni powders contributes to reducing metal particle sizes, but does not increase the electrocatalytic activity of the corresponding metal powders.

Schiff Bases: Interesting Scaffolds with Promising Antitumoral Properties

Schiff bases, named after Hugo Schiff, are highly reactive organic compounds broadly used as pigments and dyes, catalysts, intermediates in organic synthesis, and polymer stabilizers. Lots of Schiff bases are described in the literature for various biological activities, including antimalarial, antibacterial, antifungal, anti-inflammatory, and antiviral. Schiff bases are also known for their ability to form complexes with several metals. Very often, complexes of Schiff bases with metals and Schiff bases alone have demonstrated interesting antitumor activity. Given the innumerable vastness of data regarding antitumor activity of all these compounds, we focused our attention on mono- and bis-Schiff bases alone as antitumor agents. We will highlight the most significant examples of compounds belonging to this class reported in the literature.

Stability and Dynamic Aggregation of Bare and Stabilized Zero-Valent Iron Nanoparticles under Variable Solution Chemistry

Surface modification of nanoscale zero-valent iron (nZVI) using polymer stabilizers (e.g., sodium carboxymethyl cellulose, CMC) is usually used to minimize aggregation, increase stability, and enhance transport of nZVI. We investigated the stability and dynamic aggregation of bare and CMC–nZVI as affected by variations in pH, ionic strength (IS), and nZVI particle concentration. CMC coating of nZVI resulted in smaller hydrodynamic size and larger zeta potential. The largest hydrodynamic size of nZVI was associated with bare nZVI at high IS (100 mM), pH close to the point of zero charge (PZC, 7.3–7.6), and larger particle concentration (1.0 g L−1). The increase in the zeta potential of CMC–nZVI reached one- to four-fold of that for bare nZVI, and was greater at pH values close to PZC, high IS, and larger particle concentration. The stability of CMC–nZVI was increased by 61.8, 93.1, and 57.5% as compared to that of bare nZVI at IS of 1, 50 and 100 mM, respectively. Calculations of Derjaguin, Landau, Verwey and Overbeek (DLVO) interaction energy were in agreement with stability results, and showed the formation of substantial energy barriers at low IS indicating greater nZVI stability. Our results suggest that at IS above 50 mM and nZVI particle concentration larger than 0.1 g L−1, the likelihood of nZVI aggregation is high. Nevertheless, CMC polymer stabilizer would enhance the stability and transport of nZVI even under these unfavorable solution chemistry conditions.

TETRAACETYLGLYCOLURIL AND ITS DERIVATIVES: SYNTHESIS, PROPERTIES AND APPLICATION

Due to high multi-functionality, bicyclic ureas of octoic type (also known as glycolurils) are used in many applications, including the manufacturing of slow-release nitrogen fertilizers, additives for paints and coatings, polymer stabilizers, psychoactive drugs, intermediates for synthesize supramolecular compounds such as cucurbiturils and bambusurils and other practically important products. Among the glycoluril derivatives, N,N,N,N-tetraacetic derivative named as tetraacetylglycoluril occupies a special place and is produced as a fine chemical and used as a bleaching activator (as an example for perborates) in detergents. Tetraacetylglycoluril as a parent compound of acylated glycolurils finds its application as a bleaching activator in detergents and successfully competes with its counterpart tetraacetylethylenediamine. The chemistry of tetraacetylglycoluril presented in the literature is fragmentary and unsystematized, and does not allow receiving a deep understanding on the chemical properties and fields of application of this available compound. We suppose that the availability and multi-functionality of the tetraacetylglycoluril makes it possible to realize its synthetic potential. In the present article the main processes to produce tetraacetylglycoluril, its chemical properties and application fields are discussed in details. Chemical properties of tetraacetylglycoluril are described in details for reactions of hydrolysis, nucleophilic substitution, N- and O-acylation of amines and alcohols. It is noteworthy that tetraacetylglycoluril can be successfully used as a soft acylating agent for biogenic organic substrates and as a building block to synthesize new supramolecular compounds.