Abstract: The present invention provides a process for preparing polysulfide. More particularly, the process of the present invention allows one to prepare the amount of polysulfide needed using clarified white liquor, and to be used when and where it is needed during the cooking process. The process comprises reacting alkaline digesting liquor after clarification with a catalytic amount of a transition metal oxide catalyst, most preferably manganese dioxide. The reaction is conducted at a temperature of 98° C. or less, and is conducted for a short period of time, e.g., less than five minutes, with no oxygen gas or air being introduced with the catalyst and the main flow of clarified liquor.

Abstract: The present invention provides a process for preparing polysulfide. More particularly, the process of the present invention allows one to prepare the amount of polysulfide needed using clarified white liquor, and to be used when and where it is needed during the cooking process. The process comprises reacting alkaline digesting liquor after clarification with a catalytic amount of a transition metal oxide catalyst, most preferably manganese dioxide. The reaction is conducted at a temperature of 98° C. or less, and is conducted for a short period of time, e.g., less than five minutes, with no oxygen gas or air being introduced with the catalyst and the main flow of clarified liquor.

Abstract: Provided is a process for the preparation of polysulfides which comprises reaching sodium sulfide with oxygen in the presence of a transition metal oxide, preferably MnO2, and with the consumption rate of O2 being at least 1.5×10−4 moles/l/sec. The process of the present invention is preferably conducted in a self-recirculated reactor, which has been found to allow easy control of the O2 consumption rate.