The Study On H₂O₂Oxidation Of Cellulose Catalyzed By Metalloporphyrins In Alkaline Solution

Recently, biomass conversion has received increasing interest in academic andindustry, and different routs have been developed for the transformation of biomassinto fuels, chemicals and materials. Efficiently utilization of cellulose to generatevaluable compounds effectively is of great importance, and is an important area ingreen chemistry.In this paper, with hydrogen peroxide as oxidant, a system about microcrystallinecellulose oxidation catalyzed by metalloporphyrin has been developed. Many kinds offactors which could influence the reaction of cellulose oxidation in NaOH solutionwere investigated systematically, and the preliminary mechanism for hydrogenperoxide oxidation of cellulose in aqueous alkaline medium over metalloporphyrinwas also discussed.The main work about this paper is as follows:1. The results of qualitative and quantitative analysis of the products aboutcellulose oxidation and hydrolysis by HPLC indicated that the main oxidativeproducts in this reaction system are gluconic acid, glycolic acid and formic acid. Inaddition, there are a few acetic acid, cis-butenedioic acid, trans-butenedioic acid,HMF and trace of oxalic acid and lactic acid. The main hydrolysed product ofcellulose is glucose. The quantitative HPLC methods for analysis of these productshave been established by optimizing the condition of separation.2. Two water soluble iron porphyrins and three water insoluble iron porphyrinshave been synthesized, and their catalytic performance on the oxidation of cellulosewith hydrogen peroxide has been studied. The results showed that the reactionperformance with metalloporphyrins was much better than that without catalyst orwith FeCl3as catalyst. Morever, compared with water insoluble metalloporphyrins,water soluble metalloporphyrins exhibited much better reaction performance.Especially when the catalyst was FeTSPPCl, the highest yield of gluconic acidreached up to26.78%.3. FeTSPPCl was chosen as the best catalyst for a optimized study on reactionparameters including reaction time, reaction temperature, concentration of NaOH andthe amount of hydrogen peroxide. The optimized reaction conditions is shown asfollow: the amount of microcrystalline cellulose was0.5g, the loading of FeTSPPClwas6mg, the concentration of NaOH was1mol/L and the volume of it was4.75mL, the amount of hydrogen peroxide was0.25mL, the reaction time was6h, and thereaction temperature was150oC. Under this optimized condition, the conversion ofmicrocrystalline cellulose was48.73%, and the yields of gluconic acid, glycolic acidand formic acid were26.78%,9.23%and8.22%respectively.4. Combining the relevant literatures and the preliminary studies on the role ofmetalloporphyrin and reaction pathways of oxidative products, we proposed themechanism of metalloporphyrin-catalyzed oxidative degradation of cellulose inalkaline solution using hydrogen peroxide as oxidant.