Improved processes for producing high purity acesulfame potassium. In one embodiment, the process comprises the steps of contacting a solvent, e.g., dichloromethane, and a cyclizing agent, e.g., sulfur trioxide, to form a cyclizing agent composition and reacting an acetoacetamide salt with the cyclizing agent in the composition to form a cyclic sulfur trioxide adduct. The contact time is less than 60 minutes. The process also comprises forming from the cyclic sulfur trioxide adduct composition a finished acesulfame potassium composition comprising non-chlorinated, e.g., non-chlorinated, acesulfame potassium and less than 35 wppm 5-halo acesulfame potassium, preferably less than 5 wppm.