RESUMO
In this work, we report the design of one-dimensional (1D) metal-organic framework containing Cu(II) and Ni(II) active sites using a N,N'-bis-(4-pyridyl)isophthalamide linker to form MOF 1 [Cu1/2(L1)(NO3-)·DMF] and MOF 2 [Ni1/2L1Cl]. The MOFs were evaluated as heterogeneous catalysts for the hydrogenation of furfural to furfuryl alcohol. MOF 2 catalyst showed impressive performance with conversion of FF (81%) and selectivity towards FA (100%). Post-experimental characterisation showed that the structural integrity of the MOF 2 was not altered after catalysis. The catalyst could also be reused several times without any significant loss in activity and selectivity. Furthermore, a possible plausible reaction mechanism of the reaction over MOF 2 was proposed.
RESUMO
Phytomining is a newly developing alternative green technology. This technology has been applied for recovering precious metals from mine tailings that are low-grade ores. In this study, effective catalytic transfer hydrogenation of furfural to furfural alcohol was investigated using a ruthenium (Ru) bio-based catalyst, Ru@CassCat. The catalyst was prepared from Ru rich bio-ore recovered during laboratory scale phytomining as a model of mining tailing using the cassava plant (Manihot esculenta). Pre-rooted cassava cuttings were propagated and watered with Ru rich solutions for ten weeks before harvest. Harvested cassava roots were calcined to produce the bio-ore used as an in situ bio-based catalyst. The properties of the catalyst were characterized by various techniques, which include transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM-EDS), powder X-ray diffraction (pXRD), ultraviolet-visible (UV-Vis) spectroscopy, thermogravimetric analysis (TGA) and Brunauer-Emmett-Teller (BET) theory. Characterization by FTIR, SEM and TEM revealed that RuCassCat has spherical component particles, loosely arranged around a cellulose/lignin-like matrix of the biocatalyst. It was also found that calcination strengthened the structure and texture of the support carbon matrix to distribute the Ru particles evenly. An ICP-MS analysis showed that up to 295 µg g-1 of Ru was detected in cassava roots. The variation of test conditions, namely, temperature, time, base, catalyst load, and a hydrogen source, was investigated. Optimally, a 0.00295 wt% ruthenium loading on the Ru@CassCat catalyst resulted in 100% furfural conversion with a turnover frequency of 0.0114 million per hour at 160 °C for 24 h using triethylamine as a base and formic acid as a hydrogen source. The catalyst remained active for up to three recycles, consecutively and produced furfural alcohol in high turnover numbers.
RESUMO
A series of water-soluble Rh(i) mononuclear complexes of general formula: [Rh(sulphsal-X-R)(COD)] [sulphsal = sulphonated salicylaldimine, COD = cyclooctadiene; where R = H, Cl, CH3 and X = H, (t)Bu] have been synthesized. All the compounds were characterised using various spectroscopic and analytical techniques such as nuclear magnetic resonance spectroscopy, infrared spectroscopy, single crystal X-ray diffraction (for complex ) and mass spectrometry. All the compounds display excellent water-solubility at room temperature and were tested as catalyst precursors in the aqueous biphasic hydroformylation of 1-octene. The catalysts could be easily recovered by phase separation and were used up to 5 times without any significant loss in activity and 1-octene conversion. Very high yields of the expected aldehydes were obtained without addition of any phase transfer agents, co-solvents or hydrophobic ligands. Excellent aldehyde chemoselectivity is observed for all the catalysts but this varied each time the catalysts were recycled, with the formation of a small amount of internal olefins. ICP-OES and mercury poisoning experiments show that a combination of homogeneous catalysis and catalysis mediated by nanoparticles is taking place in these systems.
