Petroleum Chemistry (v.57, #2)

Ceramic microfiltration membranes based on natural silica by A. I. Ivanets; V. E. Agabekov (117-126).
The physicochemical features of preparation of macroporous ceramics and multilayer ceramic materials based on natural silica—quartz sand—from the Republic of Belarus, Qatar, Saudi Arabia, Mongolia, Azerbaijan, Turkmenistan, and Vietnam have been studied. It has been shown that the properties and structure of macroporous ceramic substrates are mostly determined by the phase composition of the natural sand and its quartz content. Membrane layers on the macroporous ceramic surface have been formed by the deposition of a suspension of fine natural silica in an aqueous solution of an aluminosilicate binder. The resulting microfiltration membranes with an average pore size of 3–5 μm, an air permeability coefficient of 10–12–10–13 m2, a water permeability of 10–50 m3/(m2 h bar), and a tensile strength of up to 10 bar are promising for wide practical use in the microfiltration of liquid media.
Keywords: porous ceramics; microfiltration membranes; silica; multilayer structure

Study of ionic conductivity of polytriazole and polynaphthalenediimide ion-exchange membranes by S. A. Makulova; Yu. A. Karavanova; I. I. Ponomarev; I. A. Stenina; M. Yu. Zharinova; Yu. A. Volkova; A. B. Yaroslavtsev (127-131).
Transport properties of the new polytriazole and polynaphthalenediimide membrane materials have been observed. According to impedance data, the sulfonated polynaphthalenediimide membrane obtained in dimethylsulfoxide demonstrates the maximum value of ionic conductivity. Modification of a membrane material with silica leads to transport properties improvement.
Keywords: membrane materials; sulfonated polyheteroarylenes; cation-exchange membranes; ionic conductivity

Natural gas drying and cleaning of carbon dioxide by membrane gas separation by N. I. Laguntsov; G. G. Kagramanov; I. M. Kurchatov; M. D. Karaseva (132-138).
To solve the problem of dehydration and CO2 removal in natural gas purification, a membrane process scheme consisting of a two-stage countercurrent recirculation cascade has been proposed. The first stage is an ordinary separator, and the second stage is a two-module separator with recycle. This scheme allows natural gas cleaning to remove highly permeable impurities with any desired level of methane recovery. Optimal values of the main parameters of the given process flowsheet have been determined. Energy efficiency has been evaluated with taking account of the operating costs of interstage compression and methane loss (in energy units).
Keywords: carbon dioxide; natural gas; membrane gas separation; two-stage cascade; energy efficiency; power consumption

Seawater desalination by reverse osmosis is widely used for drinking and utility water supply. But the formation of sparingly soluble salts in membrane devices remains a major problem, complicating the operation of reverse-osmosis (RO) membrane systems. The most effective measure to prevent the calcium carbonate and sulfate scaling of membranes is the technology of dosing inhibitors into feed water. Although a variety of effective scale inhibitors have been developed over the last two to three decades, research in this area is currently focused on the development of new types of reagents, the so-called “green” antiscalants, which do not contain phosphorus and are readily biodegradable. The use of such inhibitors does not cause eutrophication of water bodies by RO desalination concentrates discharged into them. The use of scale inhibitors has become particularly demanded in the case of desalination of seawater, since the water is alkalized and an increase in the pH sharply increases the scale deposition rate. In this study, six new phosphorus-free “green” antiscalants have been tested and compared with conventional inhibitors (Aminat-K). Experimental relationships that made it possible to determine the rate of formation of calcium carbonate in membrane devices and to compare the performance of different scale inhibitors in reducing the rates at different pH values are presented.
Keywords: reverse osmosis; calcium carbonate; green scale inhibitors; crystal growth inhibition; scaling; polyaspartic acid; polyacrylates

Gas permeability of carborane-containing polyamides by Yu. P. Yampolskii; S. A. Legkov; B. F. Shklyaruk; A. L. Rusanov; V. I. Bregadze (153-158).
The gas permeation properties of two novel polyamides comprising m-carborane groups in the backbone have been first studied. The polymers have been synthesized by the polycondensation of m-carboranedicarboxylic acids and two diamines. It has been found that the synthesized polyamides exhibit unexpectedly low glass transition temperatures (140 and 173°C). For a number of light gases, permeability (P) and diffusion (D) coefficients have been measured and solubility coefficients as the S = P/D ratio have been determined. The parameters found have been compared with the P, D, and S values of other aromatic polyamides. It has been shown that according to these transport parameters, the novel polyamides are similar to many of the previously studied aromatic polyamides.
Keywords: carborane-containing polyamides; permeability; selectivity; diffusion coefficients; solubility coefficients

Intensification of separation of oil-in-water emulsions using polysulfonamide membranes modified with low-pressure radiofrequency plasma by A. V. Fedotova; I. G. Shaikhiev; V. O. Dryakhlov; I. R. Nizameev; I. Sh. Abdullin (159-164).
Effect of low-pressure radiofrequency capacitively-coupled plasma parameters on the separation of model “oil-in-water” emulsions using UPM-20 polysulfonamide membranes with a pore size of 0.01 μm has been studied. Atmospheric air has been used as a plasma gas. The plasma treatment time is 1, 5, 4, and 7 min at a plasma torch anode voltage of U a = 1.5–7.5 kV. The separated medium is a 3% emulsion based on the industrial oil I-20A; the stabilizer is the surfactant Kosintol-242. The highest performance is observed in the case of membranes treated with plasma for 7 min. It is found that plasma treatment leads to an increase in the emulsion separation efficiency from 90 to 99%. It has been shown that the plasma treatment contributes to the surface hydrophilization of the membranes owing to the formation of oxygen-containing functional groups. The membrane exhibits a contact angle of water of α = 59.6° before treatment and α = 19.5° after a 4-min plasma treatment at U a = 7.5 kV. Atomic force microscopy reveals that the plasma treatment leads to a change in the surface structure of the membranes, namely, to a decrease in their roughness. The internal structure of the membranes also undergoes changes which result in an increase in their crystallinity.
Keywords: polysulfonamide membranes; plasma treatment; oil-in-water emulsion; separation

Modified PTFE–PANI membranes for the recovery of oil products from aqueous oil emulsions by D. D. Fazullin; G. V. Mavrin; I. G. Shaikhiev (165-171).
Composite membranes have been prepared by modifying a polytetrafluoroethylene membrane with aniline hydrochloride, and the effect of polymerization time on the efficiency of the recovery of petroleum products from aqueous oil emulsions was studied. It has been found that the modification leads to an increase in the degree of oil removal from oil-in-water emulsions by 29%. The specific productivity of the original and modified membranes has been determined with distilled water and water–oil emulsions. It has been found that the specific productivity of the membranes decreases with the time of membrane treatment with ammonium persulfate. The surface of the modified membranes has been studied with the aid of a scanning electron microscope, and the elemental composition of composite membrane surfaces has been examined by X-ray fluorescence analysis. It has been determined that the modification of a polytetrafluoroethylene membrane with aniline hydrochloride leads to an increase in the carbon content and the appearance of nitrogen, oxygen, and sulfur atoms.
Keywords: emulsion; oil products; membranes; polyaniline; PTFE

Separation of ammonia-containing gas mixtures in a one-compressor multistage membrane apparatus by I. V. Vorotyntsev; D. N. Shablykin; P. N. Drozdov; M. M. Trubyanov; A. N. Petukhov; S. V. Battalov (172-181).
Separation of the gas mixtures 7.7 vol % nitrogen in ammonia and 5.5% carbon monoxide in ammonia in one-compressor multistage membrane devices with one and two separation steps has been compared. The apparent values of selectivity have been determined for these gas mixtures. Expressions relating the degree of separation to the stage cut and the degree of purification to the product loss have been experimentally obtained. The degree of purification has been shown to increase with the number of stages despite of the fact that the degree of separation at individual stages is lower than in a single membrane module.
Keywords: membrane gas separation; ammonia; one-compressor multistage membrane apparatus; cascade