Advances in Sulfonation Using Sulfur Trioxide

Advances in applications and technology for sulfonation using sulfur trioxide in manufacturing dye intermediates are reviewed. The main areas of progress are as follows: 1) by optimization of conditions for sulfonation, the yield was increased and the amount of waste acid reduced; 2) by optimization of equipment and apparatus design, higher mass and heat transmission in the reactor were achieved; 3) use of new metal complexes or catalysts achieved higher selectivity of the product. Some typical sulfonation processes and equipments are introduced.