Thermodynamics and Kinetics Research of the Fluorination Process of the Concentrate Rutile

The growth in the production of titanium metal and its compounds leads to an increase in the amount of toxic waste. As a result, at the legislative level, emissions of such wastes are limited, which leads to a drop in the production of titanium-containing products and a shortage of titanium in the international market. This paper presents the results of the process of fluorination of rutile concentrate from the Tarsky deposit (Russia, Omsk region) with elemental fluorine using a laboratory setup of a special design. For fluorination, samples of rutile concentrate weighing 0.1–1.0 g were used. The particle size distribution of particles varied from 2 × 10−6 to 2 × 10−5 m. To determine the possibility of carrying out the process, the calculation of the change in the logarithm of the equilibrium constant versus temperature was performed. The influence of the following operating parameters on the fluorination process has been studied: various concentrations of F2 in a fluorinating mixture of fluorine with nitrogen; process time from 0 to 9 min; different ratios of the initial solid phase to fluorine (10 and 50% excess of fluorine and 10 and 50% of its deficiency); fluorination temperature in the range of 300–1800 K. A kinetic equation is selected that most accurately describes the fluorination process. The values of the activation energy and the preexponential factor in the kinetic equation are determined. The obtained results show that with an increase in the fluorine content in the fluorinating gas mixture and the temperature of the process, the fluorination rate increases. Optimal conditions for fluorination: temperature—680 K; time—5 min excess fluorine in the fluorinating mixture—20–25%. The obtained results allow to propose and consider the conditions of process execution on industrial equipment.

Thermodynamic Studies and Optimization of the Method for Obtaining Neodymium Fluoride for the Production of Magnetic Sensors’ Sensitive Elements

Rare earth metals (REM) with magnetic properties find application in the recently developed high-tech industries. Sensor magnetic systems based on neodymium are increasingly in demand in modern engineering and geological surveys due to their favorable combination of properties of magnetic materials based on rare earth metals. One of the problems is to obtain high-quality materials for the production of such magnetic sensors. It should be noted that the high activity of REM does not allow obtaining master alloys and REM-based alloys from metallic materials; it is advisable to use halide compounds. This work discusses a method for producing neodymium fluoride from its oxide. REM fluorides can be obtained by fluorinating the oxides of these metals. Various fluorine-containing compounds or elemental fluorine are usually used as fluorinating reagents, which have their own advantages and disadvantages. The thermodynamic and technological analysis of neodymium fluoride production processes has shown the most acceptable fluorinating agent is ammonium hydrofluoride, which was used in this work. In order to increase the productivity and degree of chemical transformation, it was proposed to perform heating stepwise; i.e., at the initial stage, heat at a speed of 3 degrees per minute, after which the heating speed was reduced to 2 degrees per minute, and finally the speed was reduced to 1 degree per minute. Due to proposed heating mode, the same productivity and yield of chemical transformation were achieved, with an increased efficiency up to 30%, which can significantly reduce the cost of production. The obtained product is used in the production of neodymium-based alloys by metallothermic reduction of a mixture of fluorides. The sensor material obtained in this way is characterized by a low (less than 0.05%) oxygen content.

Effect of Direct Fluorination on the Transport Properties and Swelling of Polymeric Materials: A Review

Fluorine-containing polymers occupy a peculiar niche among conventional polymers due to the unique combination of physicochemical properties. Direct surface fluorination of the polymeric materials is one of the approaches for the introduction of fluorine into the chemical structure that allows one to implement advantages of fluorinated polymers in a thin layer. Current review considers the influence of the surface interaction of the polymeric materials and membranes with elemental fluorine on gas, vapor and liquid transport as well as swelling and related phenomena. The increase in direct fluorination duration and concentration of fluorine in the fluorination mixture is shown to result mostly in a reduction of all penetrants permeability to a different extent, whereas selectivity of the selected gas pairs (He-H2, H2-CH4, He-CH4, CO2-CH4, O2-N2, etc.) increases. Separation parameters for the treated polymeric films approach Robeson’s upper bounds or overcome them. The most promising results were obtained for highly permeable polymer, polytrimethylsilylpropyne (PTMSP). The surface fluorination of rubbers in printing equipment leads to an improved chemical resistance of the materials towards organic solvents, moisturizing solutions and reduce diffusion of plasticizers, photosensitizers and other components of the polymeric blends. The direct fluorination technique can be also considered one of the approaches of fabrication of fuel cell membranes from non-fluorinated polymeric precursors that improves their methanol permeability, proton conductivity and oxidative stability.

Recent Development of Trifluoromethyl Reagents: A Review

Organic molecules having fluorine atom are very important since it increases the lipophilicity that is essential for drug development and additionally strong carbon-fluorine (C-F) bond makes the material unique, especially for material chemistry. Instead of elemental fluorine, recently trifluoromethylated materials (CF3) have drawn considerable attention in the agrochemical and pharmaceutical industries. In the continuous development of the trifluoromethylated reagents, over the last few decades, some trifluoromethylated reagents have been well developed and the efficiency of these reagents for incorporating CF3 group on different types of substrates are also studied. In this article, all types of available trifluoromethylated reagents and their effectiveness on suitable substrates are summarized. Additionally, the methods of synthesizing trifluoromethylated substrates are discussed. Finally, the scopes of the development of new reagents after focusing on the shortcomings of the current reagents are also discussed.

Richard Dickinson Chambers. 16 March 1935 — 18 April 2019

Richard (Dick) Chambers was one of the most creative and distinguished organofluorine chemists of his generation. He synthesized a range of perfluorinated heteroaromatic systems, including pentafluoropyridine and tetrafluoropyrimidine, by halogen exchange processes, and established their chemistry and associated reaction mechanisms. Notably, ‘mirror image’ negative Friedel–Crafts reactions led to perfluoroalkyl heteroaromatic derivatives that could be transformed into unusual valence bond isomers by irradiation. New ranges of stable, observable perfluorinated carbanions, alkenes and dienes were synthesized and their fundamental chemistry established. Dick was an excellent experimental scientist whose career was marked by his unique skill-set in being able to perform reactions at high pressure under vacuum, using γ-ray irradiation, photochemistry, continuous flow processes and a variety of fluorinating reagents. His research into the use of elemental fluorine gas, which established the key role of solvent in reaction control, established fluorine as a viable reagent for organic synthesis. Several of his new synthetic processes, including syntheses of perfluorocarbon iodides, highly fluorinated heteroaromatic derivatives and α-fluoro-β-ketoester systems, were adopted for scale-up by industry. But Dick was more than a talented and innovative scientist. He was also an outgoing and fun-loving man, who always made time to offer support, guidance and advice to all his colleagues, research group members and scores of scientific friends within the fluorine science community around the world. As a result, he forged strong personal bonds throughout his life and a legacy that has lasted through generations of chemists.