A reformer device including a reaction chamber for carrying out a reaction having a hydrocarbon stream as a reactant gas and with hydrogen rich synthesis gas as a reaction product. The membrane is provided within the reaction chamber. The reformer device further includes a heating reactor for heating the reaction chamber, where the membrane is a semi-permeable membrane arranged to allow CO2 pass through it; the reaction chamber includes a catalyst material arranged to catalyze a steam methane reforming reaction and to catalyze a water gas shift reaction; and the reformer device is arranged to carry out the steam methane reforming reaction at a pressure between about 15 and about 50 barg within the reaction chamber. A method for carrying out a reaction having a hydrocarbon stream as a reactant gas and with hydrogen rich synthesis gas as reaction product, in a reformer device.