Study On The Removal Of Sulfur From By-product Hydrogen Chloride Of Monochloroacetic Acid And Its High Value Utilization

Monochloroacetic acid(MAC)is widely used in chemical engineering,medicine,pesticides,dyes,organic synthesis,etc.The overwhelming majority of domestic manufacturer of monochloroacetic acid adopt the chlorination of acetic acid which use sulfur as catalyst.It inevitably produces a large amount of hydrogen chloride containing impurities such as sulfur dioxide.The conventional treatment for this type of gas is absorbed the hydrogen chloride with water to sale as by-product hydrochloric acid.Due to the existence of sulfur dioxide in the by-product hydrochloric acid,its application scope is quiet limited and its economic efficiency is not well.It also leads to serious environmental pollution and considerable waste of resources,thus the development of the monochloroacetic acid industry is restricted.Therefore,it is necessary to study a new process in order to get high value and effective utilization of hydrogen chloride and sulfur dioxide in tail gas.In this paper,the removal of sulfur in by-product hydrogen chloride in the process of the preparation of monochloroacetic acid and the process of its high value utilization was studied.The study on desulfurization for sulfur dioxide in hydrogen chloride has been done through chemisorption-oxidation coupling based on the precise and simple method for the determination of sulfur dioxide.Micron-scale barium sulfate with low oil absorption has been prepared by using the obtained mixed acid containing saturated hydrogen chloride in the desulfurization process and barium chloride as raw materials.The effective purification of by-product hydrogen chloride and high value utilization of sulfur in the process of the preparation of monochloroacetic acid has been realized.In the desulfurization process of hydrogen chloride,the effects of oxidants,molar ratio of sulfur dioxide to oxidants,sulfuric acid content in the absorption solution,reaction temperature,reaction pressure on desulfurization ratio has been investigated.Result showed that the optimum reaction conditions as follows: mole ratio of hydrogen peroxide to chlorine of 1:14 as oxidants,mole ratio of sulfur dioxide to oxidants of 1:1.1,sulfuric acid content in the absorption solution of less than 30%,reaction temperature of50 ℃,reaction pressure of 0.3 MPa.The desulfurization rate of sulfur dioxide could reach 99% under the optimum reaction conditions.The content of sulfur dioxide content in hydrogen chloride is less than 0.08% and meet the requirement of sulfur dioxidecontent in hydrogen chloride in the synthesis process of methyl chloride after the desulfurization of by-product hydrogen chloride.In the process of the preparation of barium sulfate the influence of sulfuric acid content in the mixed acid,reaction temperature,reaction time,stirred up condition on the particle size of barium sulfate has been studied.The obtained barium sulfate under different conditions were characterized by whiteness,surface area,oil absorption value and SEM.Then the optimum reaction conditions have been obtained.Result showed the optimum reaction conditions as follows: stir condition,sulfuric acid content of 20%,reaction temperature of 100 ℃,reaction time of 16 h.Under the optimum reaction conditions,the whiteness of barium sufate was 94.7,particle size of 3 μm,oil absorption value of 11.4.There is no impurity peak in the XRD diagram,and the crystal is complete.The indicators meet the requirements for superior product in GB/T 2899-2008.