A high-temperature and high-pressure optical cell for oil-water separation with porous materials.

Some industrial oil-water separations require in situ separation under high-temperature and high-pressure (HTHP) conditions. Although porous materials are promising for this purpose, dedicated optical cells capable of evaluating their separation performance under controlled HTHP environments remain scarce. Here, an HTHP optical cell was engineered using a 316L stainless-steel framework integrated with quartz-glass windows to enable direct visualization and performance assessment of porous materials under precisely regulated thermal and pressure conditions. The apparatus operates at up to 160 °C and 2 MPa. In representative static-holding and steady-injection validation tests, the system exhibited excellent stability, with maximum recorded deviations of 0.2 °C/0.012 MPa and 0.1 °C/0.003 MPa from the respective mean values, and no anomalous fluctuations were detected. The setup was validated using three distinct porous media, including a sponge, a membrane, and a packed powder bed, to demonstrate its broad applicability. With integrated real-time differential pressure monitoring, the system enables steady-state pressure-drop acquisition across varying flow rates, providing quantitative insight into fluid permeability resistance. It further supports flux-dependent demulsification assessment through continuous collection of the filtrate and subsequent water content analysis. By combining direct optical access with controlled thermophysical extremes, the developed cell offers a practical, robust, and versatile platform for quantitative benchmarking of porous materials in oil-water separation processes under realistic HTHP injection scenarios.