Performance Of Mixed Metal Oxide Catalyst In Selective Oxidation Of Isobutene To Methacrolein

In this paper, a detailed study of complex oxide catalyst on selective oxidation of isobutene methyl acrolein reaction. The main catalyst for the composition, preparation methods, pH, and catalyst calcination temperature and redox conditions to deal with a detailed inspection. At the same time combined with XRD, XPS, FTIR, BET and TPR means the composition of the catalyst structure, such as oxidation and reduction were characterized, in-depth study of catalyst structure and the relationship between performance and response. From Co6Mo12Fe4Bi1.5OX found that certain crystallographic phases and phase synergy options to improve the oxidation of isobutene methyl acrolein reaction an important factor in performance. Based on literature research, the complex oxide is only a specific crystalline form, can effectively improve the reactivity and selectivity of target product, and the interaction between the crystal phase is the maintenance of high activity catalyst for an important condition for the essential . We will be a catalyst for the structure, composition and reaction properties of the associated well for the further design and development of a new type of catalyst to provide a theoretical basis.The main research work in this article are as follows:1. System studied the molybdenum-based catalysts in the selective oxidation of isobutene. The use of a catalyst prepared by coprecipitation, followed by adding a system of Bi, Fe, Co, Mn and K on the Mo-based catalysts in the selective oxidation of isobutene influence. Found that Mo, Bi, Fe, Co four elements in the catalyst played a key role in the significant impact of the conversion rate of isobutene and the selectivity of methacrolein. Combination of XRD, FTIR and TPR characterization methods, such as catalysts and catalytic performance evaluation results, the catalyst was found in a new phase Co6Mo12Fe4Bi1.5Ox. Phase of this catalyst lead to the conversion rate of isobutene significantly increased, reaching 99.9%, methacrolein selectivity is also improved, reaching 95.6%.2. A detailed study of the pH on the crystal phase strength Co6Mo12Fe4Bi1.5OX, prepared by coprecipitation through a series of Mo-5-pH catalyst. Combination of literature and the use of XRD and TPR means of a catalyst characterized in detail. The results showed that the catalyst in the pH = 7 the XRD spectrum Co6Mo12Fe4Bi1.5OX a good phase, and 565℃in the TPR spectra of the reduction peak of Service and Co6Mo12Fe4Bi1.5OX crystal phase has a direct correlation. As the pH changes, TPR in 565℃Department to restore the size and the XRD peaks of crystal phase Co6Mo12Fe4Bi1.5OX the strength of diffraction peaks have the same trend of change. The crystal phase and reaction Co6Mo12Fe4Bi1.5OX also has a direct relationship. Further evidence of this phase is the main active site reaction.3. At the same time, we have a detailed study of the calcination temperature on catalyst performance. Will be the catalyst Mo-5-7 at 400-560℃under air atmosphere in three hours roasting. Using XRD, XPS and TPR means of characterization of catalysts and reaction and its associated properties, results showed that the catalyst calcination temperature on the performance of great impact. At 500℃calcination reaction of the catalyst performance is better, at this time Co6Mo12Fe4Bi1.5OX also better. To further prove the role of this phase, we use the catalyst after calcination were restored and in the oxidation process. Found after the catalyst reduction is very low, when the XRD spectrum of the crystal phase Co6Mo12Fe4Bi1.5OX diffraction peak almost disappeared, TPR spectra also no reduction peak of 565℃. Of re-oxidation catalyst, XRD spectra re-emergence Co6Mo12Fe4Bi1.5OX diffraction peak of crystalline phase, TPR spectra also re-emergence of the reduction peak of 565℃, and at this time and the restoration of the original catalyst activity. This result is further evidence of crystalline phase Co6Mo12Fe4Bi1.5OX is the reaction of the active site. At the same time, we also found that the catalyst calcined 400℃without Bi2Mo3O12 crystalline phase diffraction peak, with the catalyst calcination temperature continues to rise slowly phase Bi2Mo3O12 appearance. XPS results show that there is no Bi in the catalyst surface before reaction, Bi found in the catalyst surface after reaction, note the proliferation of Bi phase from the precursor to the catalyst surface, forming a new structure. These new crystal phase and Co6Mo12Fe4Bi1.5OX synergy between the effects of reaction is also an important factor in performance.