Lignin fragmentation over magnetically recyclable composite Co@Nb2O5@Fe3O4 catalysts
| Autor: | Nicoleta G. Gheorghe, Frank Krumeich, Vasile I. Parvulescu, Cristina Opris, Madalina Tudorache, Jeroen A. van Bokhoven, Simona M. Coman, Bahir Duraki, Bogdan Cojocaru |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
chemistry.chemical_element
02 engineering and technology 010402 general chemistry 021001 nanoscience & nanotechnology 01 natural sciences Catalysis Oxalate 0104 chemical sciences chemistry.chemical_compound chemistry X-ray photoelectron spectroscopy Hydrogenolysis Mössbauer spectroscopy Organic chemistry Physical and Theoretical Chemistry 0210 nano-technology Brønsted–Lowry acid–base theory Cobalt Nuclear chemistry Magnetite |
| Zdroj: | Journal of Catalysis. 339:209-227 |
| ISSN: | 0021-9517 |
| DOI: | 10.1016/j.jcat.2016.04.002 |
| Popis: | Recoverable catalysts for lignin fragmentation were prepared as X wt%Co@Nb 2 O 5 @Fe 3 O 4 composites having magnetite as an inner core. A shell of niobia covering the magnetic nanoparticles (leading to intermediate Nb 2 O 5 @Fe 3 O 4 composite) was deposed from a solution of ammonium niobate (V) oxalate complex by precipitation with NH 3 . Finally, the deposition of cobalt following the deposition–precipitation method generated the X wt%Co 3 O 4 @Nb 2 O 5 @Fe 3 O 4 composites that were reduced with hydrogen to X wt%Co@Nb 2 O 5 @Fe 3 O 4 . Catalysts with loading of cobalt in the range X = 1–20 were prepared using this procedure. The different steps of the preparation were followed using various techniques such as surface area measurements, XRD, Raman and NH 3 -DRIFT spectroscopy, XPS, Mossbauer and TEM. On this basis it was concluded that the synthesized composites exhibit both Lewis and Bronsted acid sites associated with the niobia shell and contain finely dispersed cobalt nanoparticles. The fragmentation of lignin occurred on the constituent parts of this composite, i.e. Fe 3 O 4 , Nb 2 O 5 , Nb 2 O 5 @Fe 3 O 4 but with lower performances. The addition of cobalt (Co@Nb 2 O 5 @Fe 3 O 4 catalysts) led to a complete fragmentation of lignin where the dominant fragments were those containing C20–C28 molecules. This catalytic behavior is explained on the capability of niobia to catalyze the acidic hydrolysis of the β-O-4′ bounds and of Co to break the C–C bonds via hydrogenolysis. The optimization of the catalyst composition indicated a loading of 4 wt% as optimal. Working at 180 °C and 10 atm H 2 this catalyst allowed a conversion of 53% leading to a mixture containing over 96% in C20–C28 and C29–C37 fragments. The investigated catalysts were completely recyclable as it was showed in six successive cycles. No leaching of the elements included in the composition was determined by ICP-OES. |
| Databáze: | OpenAIRE |
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