Regeneration And Recycling Of Wasted Manganese Oxides By Oxidation And Activation

A large amount of waste solid of manganese oxides, whose major conponents are MnO2that has not been consumered and low-valence manganese oxides of which MnO is dominant, is generated in the synthesis of perillaldehyde when MnO2is ofren used as an oxidant. Currently, most of the domestic manufacturers deal the waste solid of manganese oxides as hazardous industrial waste residue, such as landfill, pile and dumping directly, which have caused tremendous pressure on the environment. In this paper, waste solid of manganese oxides produced in the synthesis of perillaldehyde at a perfumery company in Hunan, was used as original material to prepare activated MnO2, then activated MnO2could be reused in oxidizing perilla alcohol to produce perillaldehyde, thereby, recycling of MnO2in the process of perillaldehyde production can be achieved.Firstly, the content of MnO2and MnO in waste solid of manganese oxides was analyzed in this paper, it obtained that MnO2occupies about49.68%of the waste solid, while MnO is about41.72%. Secondly, the optimum method of preparing MnO2was studied, in the first place, five methods as acid washing, MNCO3pyrogenation, H2O2oxidation, NaC103oxidation, KMnO4oxidation, were singly used to produce MnO2, then two complex methods as NaC103oxidation&acid washing and NaClO3oxidation&KMnO4oxidation were taken further to prepare MnO2. Through comparing the productivity and oxidizing capability of the MnO2, the economical efficiency of those method, the optimum method of preparing MnO2that NaC103oxidation&KMnO4oxidation was obtained.The best conditions of producing initial MnO2, studied in the process of recycling and producing MnO2, were obtained by using single factor experiments and orthogonal experiments, the results showed as:reaction time is about5h, reaction temperature is85℃, NaClO3dosage is130%of theoretical dosage, and the molar concentration of H2SO4is1.5mol/L. In the purifying&activate process of initial MnO2with KMnO4, it was discovered that activating speed can be accelerated and reaction time can be shortened by raising reaction temperature, but it has no significant effect on increasing the purity of activated MnO2.Perilla alcohol was oxidized by three kinds of MnO2as initial MnO2, activated MnO2and Electrolytic MnO2, on the same conditions. Results showed that, initial MnO2has the worst oxidation capacity, When perilly alcohol was oxidized by initial MnO2, the productivity of perillaldehyde was only14.9%, while the productivity of perillaldehyde can reach52.8%, which is nearly equal to that of electrolytic manganese dioxide, when activated MnO2is used. Furthermore, microstructure analysis of the three kinds of MnO2were taken by SEM and XRD experiments. SEM experiments showed that particles of activated MnO2is smaller than that of initial MnO2, also the Surface porosity of the former is bigger than the latter, that makes activated MnO2has a better oxidation capacity than initial MnO2.Crystal types as α, β, γ,ε were found among the three kinds of MnO2by XRD, β and s are the majority Crystal types, and there is a decreasing trend of a Crystal type in activated MnO2Compared with initial MnO2.The cost of regenerating activated MnO2using waste solid of manganese oxides is obtained by economic evaluation, which is less than RMB5000per ton, lower than that of the raw oxidizer Electrolytic Manganese Dioxide. that is to illustrate that NaClO3oxidation&KMnO4oxidation method used to prepare activated MnO2is economically viable.The optimum conditions of producing perillaldehyde using activated MnO2were discussed in Recycling of MnO2, through single factor experiments&orthogonal experiments, the optimal conditions were concluded that ethyl acetate was selected as solvent, dosage of solvent is15mL, mass ratio between perilla alcohol and MnO2is1:4, reaction time is4hours, reaction temperature is85℃.