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After conventional oil recovery operations, more than half of the crude oil still remains in a form, which is difficult to extract. Therefore, exploring and developing new enhanced oil recovery (EOR) technologies have always been priority research in oilfield development. Microbial enhanced oil recovery (MEOR) is a promising tertiary oil recovery technology that has received widespread attention from the global oil industry in recent years due to its environmental friendliness, simplicity of operation, and cost-effectiveness. This review presents the: principle, characteristics, classification, recent development, and applications of MEOR technology. Based on hundreds of field trials conducted worldwide, the microbial strains, nutrient systems, and actual effects used in these technologies are summarized, with an emphasis on the achievements made in the development and application of MEOR in China in recent years. These technical classifications involve: microbial huff and puff recovery (MHPR), microbial flooding recovery (MFR), microbial selective plugging recovery (MSPR), and microbial wax removal and control (MWRC). Most of them have achieved good results, with a success rate of approximately 80%. These successful cases have accumulated into rich experiential indications for the popularization and application of MEOR technology, but there are still important yet uncertain factors that hinder the industrialization of this technology. Finally, based on the extensive research and development of MEOR by the authors, especially in both laboratory and industrial large scales, the main challenges and future perspectives of the industrial application for MEOR are presented. [ABSTRACT FROM AUTHOR]

Monodisperse composite microspheres were prepared of zirconia and urea formaldehyde resin having an average particle size of 2.2 μm. Their surface was modified by silane coupling agent and styrene, and then sulfuric acid assisted with silver sulfate to form solid sulfonic acid based ion‐exchange catalyst (namely, ZrO2‐SIEC) for the alkylation of 2,4/2,5‐xylenol mixture. The selectivities of catalyst ZrO2‐SIEC to produce 6‐2,4‐xylenol and 4‐2,5‐xylenol were found to be 98.9% and 97.9%, with yields of 98.6% and 80.9%, respectively. The optimized reaction conditions were identified including temperature (80°C), catalyst dosage (9%) and reaction time (180 min). In addition, catalyst ZrO2‐SIEC showed good reusability for maintaining stable catalytic performance over 25 cycles of reuse, attributed to its stable mechanical, thermal and chemical properties. Comparison with other four catalysts demonstrated good performance of ZrO2‐SIEC in terms of catalytic activity, operating conditions, separation from products, and environmental friendliness. [ABSTRACT FROM AUTHOR]

The title compound, [Mn(C7H3NO4)(C12H6N2O2)(H2O)2]·2H2O, is a neutral mononuclear MnII complex. The Mn—N bond to the pyridine-2,6-dicarboxylate ligand lies along a crystallographic twofold rotation axis. The Mn2+ cation has a distorted pentagonal–bipyramidal configuration, coordinated by three N atoms, one from the pyridine-2,6-dicarboxylate ligand and two from the chelating 1,10-phenanthroline-5,6-dione ligand. The remaining four coordination sites are occupied by O atoms, two from the pyridine-2,6-dicarboxylate ligand and two from water molecules. The asymmetric unit also contains a solvent water molecule. The crystal structure is stabilized by a network of O—H...O hydrogen-bonding interactions in a three-dimensional supramolecular structure. [ABSTRACT FROM AUTHOR]