Pilot-scale micro-process technology for heterogeneously catalyzed gas phase reactions is generally highly demanding towards the methods of catalyst coating, flow distribution, reactor manufacturing and assembly, safety issues and other factors. Yet, first cost analysis have shown that economical processes can be developed using micro-technology. For this matter, it is necessary to improve and simplify the laboratory set-up, meaning that the stacked architectures at the meter-scale must be brought down to the micron-scale. This in return calls for specific methods of catalyst coating and a particularly precise assembly of the operation unit.