Figure : Raman maps of the inner reactor surface of both reactors before use and after reaction in the catalyst zone and the inlet zone; each map is 100 x 100 µm 2 ; Raman maps were taken from planes depicted in Figure ; red channel: PTFE/PFA, green channel: inorganic oxides like titanates (for PTFE) and no match for PFA, blue channel: no match for both polymers.