Year-end Sale % OFF 
Abstract
The process of dehydrogenation of methyl butenes to isoprene is conducted in the presence of iron oxide catalysts whose composition may include oxides of alkaline metals, alkaline earth metals, and transition metals. Catalysts of latest generation can also contain oxides of rare earth elements, particularly cerium oxide. However there is no any common opinion concerning its effect on catalytic properties of iron oxide catalysts. It is well known that ceric oxide has a positive effect on the quantity and stability of active centers and can play a critical role in a redox cycle of the dehydrogenation process. By means of differential thermal analysis, dispersion analysis and X-ray phase analysis, it was found in present study that introducing of ceric oxide promotes the decrease in hematite crystallite sizes. At the same time, it prevents potassium polyferrites formation, with the equilibrium of topochemical reaction between ferric oxide and po tassium carbonates moving predominantly to the formation of intermediate products–monoferrite systems, having greater catalytic activity. The increase in potassium monoferrite content results in dispersion of particles in the Fe2O3-K2CO3-СеО2 system that is accompanied by modification of texture characteristics. For this catalyst composition, the optimum concentration of ceric oxide (8.7 wt.%), leading to the formation of a certain ratio of mono- and polyferrite phases, was found. If more than 8.7 wt.% of СеО2 is introduced, the modification of texture characteristics of catalyst samples takes place, that negatively affects their selectivity.
Highlights
As known from [1,2,3], the process of olefin hydrocarbons dehydrogenation is performed in presence of iron oxide catalysts where potassium ferrites are the active components that are formed in the process of solid phase interaction between ferric oxide and potassium compounds
Model systems with different ceric oxide content were analyzed by means of differential thermal analysis, particle size analysis, and X-ray phase analysis
That introducing of ceric oxide promotes the decrease in hematite coherent scattering region (CSR)
Summary
As known from [1,2,3], the process of olefin hydrocarbons dehydrogenation is performed in presence of iron oxide catalysts where potassium ferrites are the active components that are formed in the process of solid phase interaction between ferric oxide and potassium compounds. Cerium compound which content varies in the range of 2 to 30 wt% [4,5] is used as a promoter affecting the catalyst activity [6]. In accordance with literature [7], cerium presence in catalyst promotes more intensive electron exchange between Fe2+ and Fe3+ ions which present in the polyferrite structure during dehydrogenation, preventing their complete recovery to Fe3O4. There is a few data in literature about ceric oxide effect on phase composition formation of iron oxide catalysts [6,8,9]. The objective of this study is to define ceric oxide influence on phase composition, iron oxide catalysts activity and to find out the mechanism of its activity
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
