In this paper, the reservoir characteristics and fluid properties of a reservoir of the Bohai Sea oil field were taken as the research platform. It was confirmed that there exists compatibility between hydrophobically-associating-polymer (HAP) molecular aggregation and pore-throat size. The experiment for oil displacement in heterogeneous cores indicated that there exists applicability of HAP for a heterogeneous reservoir and the applicability can be influenced by polymer concentration. The experiment for oil displacement of parallel cores demonstrated the effect of polymer concentration on the applicability of HAP for reservoir heterogeneity from two aspects of the dynamic behavior of oil displacement and the effectiveness of oil displacement. The results show that with the increase of HAP concentration, the association degree between polymer molecules increases, molecular-clew dimension enlarges, and the compatible size of pore throats of the core increases. The change of HAP concentration not only has an effect on the amount of liquid suctioned by different permeability layers and on the time of profile inversion, but also has an effect on the displacement ability of polymer solution within different layers. As polymer concentration changes, the adaptability of HAP for reservoir heterogeneity changes and the oil-recovery efficiency also changes.
Development of a simple and efficient strategy for improving the catalytic activity of cobalt-based catalysts toward hydrogen evolution from sodium borohydride (NaBH 4 ) is paramount but remains challenging. Here, we reported a facile and efficient approach to tune the catalytic performance for NaBH 4 hydrolysis with Co-based catalysts prepared by using cobalt sulfate as a precursor or a mixture of sulfur-containing sodium salts/cobalt salts as a raw material. With the use of cobalt sulfate as the precursor, the CoSO 4 -doped Co 3 O 4 sample was formed and it exhibited excellent activity with the generation of ∼500 mL of hydrogen gas from NaBH 4 hydrolysis under mild conditions. In terms of sulfur-free cobalt salts (e.g., cobalt chloride, cobalt nitrate, and cobalt acetate) as precursors, the obtained Co-based samples were found to be entirely ineffective for hydrogen production. Interestingly, during the cobalt-based catalyst preparation, the introduction of sodium sulfate or sodium sulfide can considerably accelerate hydrogen production. On the contrary, adding sulfur-bearing salts did not inspire any activity improvement only during the hydrogen generation reaction. Control experiments indicate that during catalyst preparation, the presence of Na 2 SO 4 and Na 2 S is beneficial for the in situ transformation of Co 3 O 4 into catalytically active Co−B alloys, accompanying a positive change in surface morphology during the NaBH 4 hydrolysis, thereby inducing an excellent hydrogen generation rate of up to 4425 mL•min −1 •g cat −1
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