Controllable wettability on Ni foam with PDA coatings and gas–liquid mass transfer enhancement in micropacked bed reactors

A micro-nano coating with controllable wettability is constructed on Ni foam using the dipping coating method, incorporating organic polydopamine (PDA) and 1H,1H,2H,2H-perfluorodecyltriethoxysilane, and inorganic SiO₂ nanoparticles. PDA has the properties of controlling wettability, strong adhesion, and abundant grafting sites. The water contact angle (WCA) of modified Ni foam is controlled in the range of 0–151.5°. The stability measurement displays that modified Ni foam packings exhibit excellent acid and alkali resistance as well as mechanical stability to fluid erosion under microenvironment. Compared with non-modified (131.5°) and superhydrophilic (0°) Ni foam packings, the maximum ratios of mass transfer enhancement for the superhydrophobic (151.5°) Ni foam packing are 35.6 % and 160.2 %, respectively. Empirical correlations of the gas–liquid mass transfer coefficient and friction factor are established considering the effect of the WCA, and errors between predicted values and experimental values are within ± 15 % and ± 10 %, respectively.