(576g) Supported Transition Metal Oxide Catalysts at Monolayer Coverage for Natural Gas Upgrading

This presentation will cover the synthesis and characterization of a pool of different supported metal oxide catalysts, highlighting the role of various promoters on the dispersion of metal oxides on SiO₂ and the synergetic effect of mixed transition metal oxides at sub-monolayer and monolayer coverage. Experimentally achieved vanadia dispersion on SiO₂ is only ~3 V/nm², far lower than the vanadia dispersion on all other oxide supports which show ~9 V/nm².¹ We found that the typical, close to the theoretical 9 V/nm² monolayer coverage can also be achieved upon addition of promoters to pure amorphous silica.² Carefully characterization by a variety of techniques such as ICP-OES, BET, in situ Raman, UV spectroscopy and ⁵¹V-NMR evidences a new record for vanadia dispersion on SiO₂. Moreover, we also have used the oxidative dehydrogenation of propane as a complementary characterization technique to confirm the uniquely presence of two-dimensional VO_x species. Indeed, propylene selectivity is drastically reduced by the formation of V₂O₅ nanoparticles above monolayer coverage.³ Our new approach also allows the dispersion of Nb and Ta at loadings higher than the current state-of-the-art.⁴ Interestingly, by using promoted SiO₂, the propane consumption rate is not affected whereas the propylene combustion rate as a function of propane conversion is improved. Moreover, aimed to enhance the productivity toward olefins and following a previously reported study,⁵ several different transition metal oxides were dispersed on promoted SiO₂. We will discuss preliminary data regarding our current work, aimed at i) understanding the role of promoters on the dispersion of different metal oxide catalysts on SiO₂, ii) maximizing the positive synergetic effect between promoter and vanadia in the propylene combustion rate and iii) combine different metal oxides at sub-monolayer and monolayer coverage in order to tune both the (Brønsted and Lewis) acidic and redox properties for different catalytic applications.

References

1. Carrero, C. A.; Schlögl, R.; Wachs, I. E.; Schomäcker, R. ACS Catal., 2014, 4, 3357-3380

2. Grant, J.; Carrero, C. A.; Hermans, I. Patent issued February 2015, United States 62/112, 689

3. Carrero, C. A.; Keturakis, C. J.; Orrego, A.; Schomäcker, R.; Wachs, I. E. Dalton Trans., 2013, 42, 12644-12653 

4. Tian, H.; Roberts; Wachs, I. E. J.Phys.Chem. C 2010,114,14110–14120

5. Carrero, C. A.; Kauer, M.; Dinse, A.; Wolfram, T.; Hamilton, N.; Trunschke, A.; Schlögl, R.; Schomäcker, R. Catal. Sci. Technol., 2014, 4, 786-794