Studies on the Formation of Catalytically Active PGM Nanoparticles from Model Solutions as a Basis for the Recycling of Spent Catalysts

The paper presents basic studies on the precipitation of platinum, palladium, rhodium, and ruthenium nanoparticles from model acidic solutions using sodium borohydride, ascorbic acid, and sodium formate as reducing agents and polyvinylpyrrolidone as a stabilizing agent. The size of the obtained PGM particles after precipitation with NaBH4 solution does not exceed 55 nm. NaBH4 is an efficient reducer; the precipitation yields for Pt, Pd, Ru, Rh are 75, 90, 65 and 85%, respectively. By precipitation with ascorbic acid, it is possible to efficiently separate Pt, Rh, and Ru from Pd from the two-component mixtures. The obtained Pt, Pd, and Rh precipitates have the catalytic ability of the catalytic reaction of p-nitrophenol to p-aminophenol. The morphological characteristic of the PGM precipitates was analyzed by AFM, SEM-EDS, and TEM.

Plug and Abandonment for Gas Wells: A Case Study from Baghjan Oilfield, India

The economic end of the life-cycle of a well is dynamic and it varies with the oil & gas market conditions and advances in extraction technologies. If production declines or the need for a workover arises, plugging and abandonment operations are followed. In case the wellsite has encountered accidental releases, systematic abandonment and remediation becomes even more crucial to avoid further environmental damage and capital investment. This paper analyzes the Baghjan oilfield blowout of the Assam-Arakan basin and provides abandonment practices for gas wells. The mobile workover rig was stationed at the Baghjan Well-5 with the aim to plug the lower producing zone at 3871 m and complete the well in the upper Lakadong+Therria sand at a depth of 3739 m. Baghjan Gas Well No.5 blew during the temporary abandonment which was planned to mitigate the leakage in the wellhead. Improper depth for the placement of cement plug, failure to check the plug integrity, and shortcomings in the regular inspection of annular casing pressure led to the well control situation at the Baghjan gas well. While pulling out the tubing conveyed perforation gun after perforating the Lakadong+Therria I+II sand, Shut-In Tubing Pressure of 4400 psi and 3900 psi Shut-In Casing Pressure was observed which indicated a leak in the Tubing Seal Assembly. The well was killed with a 9.76 lbm/gal sodium formate brine and in the middle of pulling the tubing, leakage in the W.F. Spool was identified which changed the priority of the operations. Therefore, a temporary abandonment operation was planned to mitigate the leakage problem in the primary and secondary seals, during which the well started flowing gas profusely after nipple-down of the blowout preventer. The shortcomings of the abandonment process can be conquered by the selection of an appropriate isolation material such as resin-based sealants or bismuth and thermite, which shall act as a primary barrier and provide enhanced zonal isolation. The isolation material should mitigate micro-fractures, minimize treatment volume and fluid loss, provide ample pumping time, and not degrade in the presence of wellbore fluids. The study discusses resin-based sealants, cement slurry designs, advances in conventional, unconventional, and rigless abandonment techniques, and suggests the most efficient method for the temporary and permanent abandonment operations to avoid further such incidents in the oil and gas industry.

Processing of formate solutions obtained from red mud leaching

The paper determines the indicators of the developed process flow for the complex processing of red sludge via the formate method: recovery of components; yield and composition of products when processing a sample of formate solution obtained from red mud leaching. The conducted experiments used red mud generated in the production of alumina at the Urals Aluminium Smelter. The samples of formate solution obtained in the course of red mud leaching were analyzed using an Optima 8000 ICP-OES Spectrometer, a Sartorius MA-30 Moisture Analyzer to measure moisture content, as well as an ARL 9800 XRF Spectrometer to ascertain the mass fraction of elements in metal and nonmetal specimens found in one of three states (solid, liquid, or powder). These experiments were performed while continuously measuring and monitoring pH values by means of a pH meter having a thermal compensation function. The performed experiments involved the total recovery of valuable elements from formate solutions produced during red mud leaching. A concentrate containing Al, Sc, and rare earth elements (REEs) was processed to produce scandium oxide and rare earth metal concentrate (after dissolving aluminum in an alkali). Rare earth metals and scandium were shown to concentrate in the solid phase; scandium was then selectively leached with a sodium bicarbonate solution to form water-soluble carbonate complexes [Sc(CO3)4]5- having carbonate ions СО32- and НСО3-. When using the proposed technology, the overall recovery of scandium and REEs amounts to 98–99%, whereas that of aluminum, calcium formate, and sodium formate from the produced solution reaches 99%. The processing of formate solution yields the following end products: scandium oxide (99 wt% Sc2O3) and REE concentrate (content of 56.1%). The paper demonstrates the possibility in pri nciple to process solutions obtained from the flow-through leaching of red mud via the formate method.

Non-Innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides

We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated <i>in situ</i>. The combination of isophthalonitrile and sodium formate promotes diverse aryl radical coupling reactions from abundant but difficult to reduce aryl chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled by a key terminal reductant byproduct, carbon dioxide radical anion.

Non-Innocent Radical Ion Intermediates in Photoredox Catalysis: Parallel Reduction Modes Enable Coupling of Diverse Aryl Chlorides

We describe a photocatalytic system that elicits potent photoreductant activity from conventional photocatalysts by leveraging radical anion intermediates generated <i>in situ</i>. The combination of isophthalonitrile and sodium formate promotes diverse aryl radical coupling reactions from abundant but difficult to reduce aryl chloride substrates. Mechanistic studies reveal two parallel pathways for substrate reduction both enabled by a key terminal reductant byproduct, carbon dioxide radical anion.

Organophotocatalytic selective deuterodehalogenation of aryl or alkyl chlorides

Development of practical deuteration reactions is highly valuable for organic synthesis, analytic chemistry and pharmaceutic chemistry. Deuterodehalogenation of organic chlorides tends to be an attractive strategy but remains a challenging task. We here develop a photocatalytic system consisting of an aryl-amine photocatalyst and a disulfide co-catalyst in the presence of sodium formate as an electron and hydrogen donor. Accordingly, many aryl chlorides, alkyl chlorides, and other halides are converted to deuterated products at room temperature in air (>90 examples, up to 99% D-incorporation). The mechanistic studies reveal that the aryl amine serves as reducing photoredox catalyst to initiate cleavage of the C-Cl bond, at the same time as energy transfer catalyst to induce homolysis of the disulfide for consequent deuterium transfer process. This economic and environmentally-friendly method can be used for site-selective D-labeling of a number of bioactive molecules and direct H/D exchange of some drug molecules.