The Influence Of Carboxylic Acid And Carboxylate Radical On The OMS-2 Materials With Tetragonal Morphology And Their Catalytic Activities For Deep Catalytic Oxidation Of O-xylene

Benzene hydrocarbons, including benzene, toluene and xylene, are the major organic volatitle compounds（VOCs）. Catalytic oxidation technology is the most effective methods for VOCs elimination. The key is the selection of catalysts. II-manganese oxide octahedral molecular sieve（OMS-2） is regarded as an important catalysts due to its low-priced. OMS-2 morphology has an influence on its oxidation performance. Therefore preparation of special morphological and high activity OMS-2 catalysts is a meaningful subject. In this paper, OMS-2 materials with tetragonal morphology were prepared, and their catalytic activities were tested for catalytic oxidation of o-xylene. The main results are as follows:（1） OMS-2 was successfully synthesized using KMnO4 and n-butyric acid by changing the molar ratio and calcination temperature. Then, n-butyric acid potassium was added in above system, n-butyric acid and n-butyric acid potassium can form buffer solution to adjust the p H value of the system. The as-prepared materials were donated as MnO₂-potassium permanganate/n-butyric acid molar ratio-calcination temperature-incorporation of n-butyric acid potassium. The results of catalytic activity test showed that the T100（the temperature at which the yield of CO₂ was 100%） of MnO₂-n-1/0.875-500-1 was 210℃, and T50（the temperature at which the yield of CO₂ was 50%） was 180℃.SEM data showed that MnO₂-n-1/0.875-500-1 was tetragonal morphology. IR data showed that MnO₂-n-1/0.875-110-1 catalyst had carboxylic acid and carboxylate radical stretching vibration peak. However, these peaks disapperared at MnO₂-n-1/0.875-500-1 catalyst. Then, MnO₂-n-1/0.5-500-1 catalyst was successfully synthesized by reducing potassium permanganate and n-butyric acid molar ratio. SEM data showed that the samples present uniform nanoparticles. The results of catalytic activity test showed that the T100 of MnO₂-n-1/0.5-500-1 was 220℃, and T50 was 191℃. IR data showed that MnO₂-n-1/0.5-110-1 and MnO₂-n-1/0.5-500-1 catalysts did not have carboxylic acid and carboxylate radical stretching vibration peak. Therefore, n-butyric acid and n-butyric acid potassium can form buffer solution, the p H value of the system in 4-5 and the acid potassium can form buffer solution, the p H value of the system was in the range of 4-5 and the existence of excess n-butyric acid, n-butyric acid and n-butyric acid root may be adsorpted on the surface of the manganese dioxide, which was as the template agent to oriente form tetragonal morphology.（2） For further research in tetragonal morphology, the reaction temperature and reaction time were changed. The results showed that the reaction temperature 30℃and reaction time 24 h was the best conditions of preparation of OMS-2 materials with tetragonal morphology.（3） OMS-2 catalyst was successfully synthesized using potassium permanganate and oleic acid, the different of molar ratio and calcination temperature were studied. The as-prepared materials were donated as MnO₂-potassium permanganate and oleic acid molar ratio-calcination temperature. XRD results showed that manganese oxide were all OMS-2. BET results showed that MnO₂-1/0.375-400 specific surface area was biggest, 125.201m2·g-1. SEM data showed that MnO₂-1/0.375-400 was tetragonal morphology, the morphology of MnO₂-1/0.15-400 was mixed state of nanoparticles and nanorods, the morphology of MnO₂-1/2-400 was aggregation of nanoparticles.The results of catalytic activity test showed that the T100 of MnO₂-1/0.375-400 was 200℃, and T50 was 162℃; the T100 of MnO₂-1/0.15-400 was 200℃, and T50 was 178℃; the T100 of MnO₂-1/2-400 was 250℃. IR data showed that MnO₂-1/0.375-400 catalyst had carboxylic acid and carboxylate radical stretching vibration peak. However, these peaks disapperared at MnO₂-1/0.375-400 catalyst. H2-TPR and O₂-TPD results showed that MnO₂-1/0.375-400 had lower temperature of reduction peak and deoxidation peak.