A tubular reactor and method for producing a product mixture in a tubular reactor where the tubular reactor comprises an internal catalytic insert having orifices for forming fluid jets for impinging the fluid on the tube wall. Jet impingement is used to improve heat transfer between the fluid in the tube and the tube wall in a non-adiabatic reactor. The tubular reactor and method may be used for endothermic reactions such as steam methane reforming and for exothermic reactions such as methanation.