Removal of residual sulfur dioxide from dimethyl sulfate
The present invention relates to a method of removing SO 2 contaminants from dimethyl sulfate (DMS) by treatment with an oxidizing agent, and to a process for the preparation of odor free fatty acid trialkanolamine esters quaternized with DMS which is substantially free of SO 2 contaminants.
1. A process for removing residual SO 2 from dimethyl sulfate that comprises treating said dimethyl sulfate with an SO 2 -removing effective amount of at least one oxidizing agent for a time and at a temperature effective to remove substantially all residual SO 2 from the dimethyl sulfate.
2. The process of claim 1 wherein said oxidizing agent is represented by the formula: ROOR where R═H or R′[O] m [CO] n —, wherein R′=alkyl or aryl and m and n=0 or 1, with m=0 if n=0.
3. The process of claim 2 wherein said oxidizing agent is selected from the group consisting essentially of hydrogen peroxide, hydroperoxides, peroxides, peresters, percarbonates and mixtures thereof.
4. The process of claim 3 wherein said oxidizing agent is selected from the group consisting essentially of O 2 , O 3 , Cl 2 , KMnO 4 , K 2 Cr 2 O 7 , KClO 3 , NaClO 2 , HNO 3 , H 2 O 2 , t-butyl hydroperoxide, and mixtures thereof.
5. The process of claim 1 wherein said oxidizing agent(s) are added to the SO 2 -containing DMS in quantities of from about 5 ppm to about 1000 ppm.
6. The process of claim 5 wherein said oxidizing agent is added to said SO 2 -containing DMS in an amount of from about 10% to about 100% molar excess versus the analyzed molar amount of SO 2 .
7. The process of claim 1 wherein said treatment is conducted at ambient temperature.
8. The process of claim 1 wherein said dimethyl sulfate contains less than 20 ppm sulfur dioxide subsequent to said treatment.
9. The process of claim 8 wherein said dimethyl sulfate contains less than 8 ppm sulfur dioxide subsequent to said treatment.
10. The process of claim 9 wherein said dimethyl sulfate contains less than 5 ppm sulfur dioxide subsequent to said treatment.