Microalgae residue was efficiently converted into lactic acid with a high yield (33.9%) under mild reaction conditions (210 °C, 2 h) over a Fe-Sn-Beta catalyst. Under the action of homogeneous H 3 O + and distinct Lewis acid sites on the catalyst, the production of lactic acid from microalgae residue underwent three main reaction steps: hydrolysis, isomerization , and retro-aldol condensation. Results demonstrated that the lipid component had a strong inhibitory effect on the production of lactic acid due to the formation of aromatics, esters, and complex nitrogenous heterocyclic compounds , which covered or poisoned the Lewis acid sites of the catalyst. The protein component acted as a chemical buffer that enhanced the production of lactic acid by controlling the release of monosaccharides from the carbohydrate fraction of microalgae and maintaining the catalytic activity of the catalyst. Thus, microalgae residue demonstrated great promise for the production of value-added chemicals.
Bimetallic modified Fe–Sn/Beta was synthesized and examined as a solid acid catalyst for the transformation of glucose into methyl lactate in methanol. The catalysts were characterized by a combined characterization techniques i.e. X-ray fluorescence spectroscopy, N 2 physisorption, powder X-ray diffraction, X-ray photoelectron spectroscopy, NH 3 temperature-programmed desorption, and pyridine adsorption Fourier transform infrared spectroscopy. A high yield of methyl lactate of 67% was achieved upon conversion of 0.3 g glucose in 24 g methanol over 0.15 g catalyst at 220 ℃ under 2 MPa N 2 for 6 h. The recyclability of the catalyst was also investigated, and the conversion of glucose remained constant; conversely, the yield of methyl lactate decreased slightly in five catalytic runs. The excellent catalytic performance of Fe–Sn/Beta was attributed to the presence of large amounts of Lewis acid sites. Besides, the rich mesoporosity in Fe–Sn/Beta improved mass transfer rates in the conversion of glucose to alkyl lactates.
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