scholarly journals The preparation of large surface area lanthanum based perovskite supports for AuPt nanoparticles: tuning the glycerol oxidation reaction pathway by switching the perovskite B site

2016 ◽  
Vol 188 ◽  
pp. 427-450 ◽  
Author(s):  
Christopher D. Evans ◽  
Simon A. Kondrat ◽  
Paul J. Smith ◽  
Troy D. Manning ◽  
Peter J. Miedziak ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Surface Area ◽  
Reaction Pathway ◽  
Large Surface Area ◽  
Oxidation Catalyst ◽  
Small Surface ◽  
Acid Yield ◽  
Tartronic Acid ◽  
Supercritical Carbon

Gold and gold alloys, in the form of supported nanoparticles, have been shown over the last three decades to be highly effective oxidation catalysts. Mixed metal oxide perovskites, with their high structural tolerance, are ideal for investigating how changes in the chemical composition of supports affect the catalysts' properties, while retaining similar surface areas, morphologies and metal co-ordinations. However, a significant disadvantage of using perovskites as supports is their high crystallinity and small surface area. We report the use of a supercritical carbon dioxide anti-solvent precipitation methodology to prepare large surface area lanthanum based perovskites, making the deposition of 1 wt% AuPt nanoparticles feasible. These catalysts were used for the selective oxidation of glycerol. By changing the elemental composition of the perovskite B site, we dramatically altered the reaction pathway between a sequential oxidation route to glyceric or tartronic acid and a dehydration reaction pathway to lactic acid. Selectivity profiles were correlated to reported oxygen adsorption capacities of the perovskite supports and also to changes in the AuPt nanoparticle morphologies. Extended time on line analysis using the best oxidation catalyst (AuPt/LaMnO3) produced an exceptionally high tartronic acid yield. LaMnO3 produced from alternative preparation methods was found to have lower activities, but gave comparable selectivity profiles to that produced using the supercritical carbon dioxide anti-solvent precipitation methodology.

One-Pot Procedure to Synthesize High Surface Area Alumina Nanofibers Using Supercritical Carbon Dioxide

Langmuir ◽  
2010 ◽  
Vol 26 (4) ◽  
pp. 2707-2713 ◽  
Author(s):  
Muhammad B. I. Chowdhury ◽  
Rouhong Sui ◽  
Rahima A. Lucky ◽  
Paul A. Charpentier
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
One Pot ◽  
Alumina Nanofibers ◽  
Supercritical Carbon

scholarly journals Influences of supercritical carbon dioxide fluid on pore morphology of various rank coals: A review

2020 ◽  
Vol 38 (5) ◽  
pp. 1267-1294
Author(s):  
Zichao Hu ◽  
Dengfeng Zhang ◽  
Man Wang ◽  
Shilin Liu
Keyword(s):  
Carbon Dioxide ◽  
Supercritical Carbon Dioxide ◽  
Pore Structure ◽  
Surface Area ◽  
Carbon Dioxide Sequestration ◽  
Mineral Dissolution ◽  
Pore Morphology ◽  
Coal Matrix ◽  
Area And Volume ◽  
Supercritical Carbon

Supercritical carbon dioxide is known to change the pore structure of coals and thus affect their carbon dioxide sequestration capacity. In this study, supercritical carbon dioxide dependence of pore morphology of coals was reviewed. Results indicated that the micropore surface area and volume of dry coals varied between –20% and 20% after exposure to supercritical carbon dioxide. Changes in the micropore size distribution of dry coals after supercritical carbon dioxide exposure were not found to be significant; however, the change in meso- and macropores with diameter of 2–8 nm was observed to be significant. Supercritical carbon dioxide and H2O exposure mainly influenced pores with diameters of 0.4–0.7, 0.7–0.9 and 2–8 nm. The variation in the pore fractal dimensions of the coals ranged from –0.5% to 0.5% after supercritical carbon dioxide exposure. Furthermore, the dependence of supercritical carbon dioxide on the pore structure of coals relies on the coal rank. The change in the pore structure of the coals after supercritical carbon dioxide exposure was observed to be related to the following aspects. First, supercritical carbon dioxide induced swelling in coal matrix, thus reducing the pore surface area and volume of the coal matrix and compressing the cleat system. Next, the extraction of supercritical carbon dioxide mobilised the small organic molecules dispersed in the coal matrix; this increased the pore volume, particularly of micropores. Finally, the mineral dissolution/precipitation also changed the pore structure of the coals. To further examine supercritical carbon dioxide dependence of coal pore morphology, the following studies should be performed. The characterisation of the chemical and pore structure of coals should be combined with existing coal structure models to account for the mechanism of supercritical carbon dioxide changing the pore structure of coals. Combination of physical experiments and numerical simulations is recommended to predict the changes in porosity and permeability of coals due to long-term carbon dioxide sequestration.

Sign in / Sign up

Export Citation Format

Share Document