Hydrodynamics of gas–liquid flow in a capillary at elevated pressure: Implications for the fixation of CO2 into propylene carbonate in microreaction systems

•Gas-liquid two-phase flow characteristic in a capillary microreactor at elevated pressure is observed.•Transition lines of the flow pattern shift to higher WeG and lower WeL at elevated pressure.•The effects of pressure on gas bubble sizes, liquid film thickness, and gas bubble frequency are studied.