The advantages of the monolith structure over the packed bed, namely, low pressure drop, large geometric surface area to volume ratio, simple flow pattern and modular structure, make the monolith an attractive tool for the conductance of fast reactions and for construction of reactor-heat exchanger units. Several autothermal designs employing adiabatic and cross-flow units are considered for the oxidation of SO2. The study is aimed at optimizing the design parameters and operating conditions in order to minimize expenses on energy and catalyst required to achieve 97% conversion. The analysis reveals that an adiabatic-crossflow-adiabatic design may be superior to a design of two monoliths with interstage cooling. The advantage gained by the former design is limited by the low conversion over the heat exchanging unit due to overcooling and the cross-flow structure and strategies for improving design are suggested.