This invention relates to an apparatus, comprising: at least one process
microchannel having a height, width and length, the height being up to
about 10 mm, the process microchannel having a base wall extending in one
direction along the width of the process microchannel and in another
direction along the length of the process microchannel; at least one fin
projecting into the process microchannel from the base wall and extending
along at least part of the length of the process microchannel; and a
catalyst or sorption medium supported by the fin.