| 1. |
- Andersson, Arne, et al.
(author)
-
Direct Propane Ammoxidation to Acrylonitrile: Kinetics and Nature of the Active Phase
- 1993
-
In: New Frontiers in Catalysis (Studies in Surface Science and Catalysis ). - 0167-2991. ; 75, s. 691-705
-
Conference paper (peer-reviewed)abstract
- The kinetics of the direct synthesis of acrylonitrile from propane on V-Sb-Al-(W) mixed oxides indicate that acrylonitrile (ACN) forms by two parallel pathways, one directly from propane and the second, which is the prevalent path, through the intermediate formation of propylene (C3=). The limiting factor in the formation of ACN is the relative slowness of the step of allylic oxidation to ACN of the intermediate C3=, and the higher rate of C3= oxidation to carbon oxides as compared to that of ACN to COx. The step of C3= oxidation to ACN is controlled by the surface availability of NH3 which, in turn, depends considerably on the side reaction of NH3 oxidation to N2. The catalytic behavior of different modified V-Sb-(Al)-O systems and their characterization by X-ray diffraction analysis and Raman, Infrared and X-ray Photoelectron spectroscopies indicate that i) a reduction of both V and Sb occurs during the catalytic reaction, ii) the presence of vanadium not stabilized in the rutile-like phase is responsible for the side reaction of NH3 oxidation and lowering of the selectivity, iii) alumina reacts with antimony forming an AlSbO4 rutile phase which could be epitaxially intergrown or in solid solution with the VSbO4/Sb2O4 system, which, in turn, limits the presence of not stabilized (unselective) vanadium species, and iv) antimony oxide supported on alumina is also selective in propane ammoxidation, but forming acetonitrile as the main product. The doping with vanadium of this sample increases slightly the activity, but especially gives rise to the formation of acrylonitrile instead of acetonitrile.
|
|
| 2. |
- Andersson, Arne, et al.
(author)
-
Surface Characterization and Reactivity in Ammoxidation Reactions of Vanadium Antimonate Catalysts
- 1994
-
In: Applied Catalysis A: General. - 0926-860X. ; 113:1, s. 43-57
-
Journal article (peer-reviewed)abstract
- Unsupported vanadium antimonate catalysts with Sb/V ratios of 1 and 5 and samples with the latter ratio supported on alumina were studied in toluene and propane ammoxidation to benzonitrile and acrylonitrile, respectively, and were characterized by X-ray photoelectron spectroscopy (XPS) analysis before and after catalytic tests. Activity data for toluene ammoxidation suggest that excess antimony with respect to the stoichiometric amount required for forming the VSbO4 rutile phase affects the dispersion of the latter phase giving smaller particles. Vanadium sites are involved both in the activation of toluene and in the insertion of nitrogen in this reaction, whereas antimony does not play a specific role in the reaction mechanism. In propane ammoxidation, on the other hand, due to a higher reaction temperature with respect to toluene (500°C vs. 370°C), free vanadia on the surface of the catalyst has a negative influence on the selectivity because it promotes the conversion of ammonia to nitrogen, decreasing the surface nitrogenous species required for the selective formation of acrylonitrile. Excess antimony is thus necessary for completing the reaction between antimony and vanadium oxides, but antimony also participates in the reaction mechanism. In propane ammoxidation, in fact, XPS data show that both vanadium and antimony sites are reduced. Tentatively, vanadium sites are involved in the activation of propane, while antimony sites insert nitrogen. The differences between the toluene and propane ammoxidation mechanisms are interpreted to be primarily related to the different reaction temperatures.
|
|
| 3. |
- Beller, M., et al.
(author)
-
Chemistry Future : Priorities and Opportunities from the Sustainability Perspective
- 2017
-
In: ChemSusChem. - : John Wiley & Sons. - 1864-5631 .- 1864-564X. ; 10:1, s. 6-13
-
Journal article (peer-reviewed)abstract
- To celebrate the 10 year anniversary of ChemSusChem, we as the chairmen of the editorial board are writing this Essay to summarize important scientific contributions to our journal during the past decade in terms of sustainable science and technology. Bibliometric analysis of published papers show that biorefinery, solar energy conversion, energy-storage materials, and carbon dioxide utilizations attracted most attention in this area. According to our own knowledge and understanding and from the sustainability point of view, we are also pointing out those research directions that we believe can play key roles in the future chemistry to meet the grand challenges in energy and environment. Hopefully, these perspective aspects will provide the readers with new angles to look at the chemistry in the coming decades and inspire the development of new technologies to make our society sustainable.
|
|
