Mesoporous Porphyrin-Silica Nanocomposite as Solid Acid Catalyst for High Yield Synthesis of HMF in Water

Synthesis of Hollow Mesoporous Silica Nanospheroids with O/W Emulsion and Al(III) Incorporation and Its Catalytic Activity for the Synthesis of 5-HMF from Carbohydrates

Controlling the particle size as well as porosity and shape of silica nanoparticles is always a big challenge while tuning their properties. Here, we designed a cost-effective, novel, green synthetic method for the preparation of perforated hollow mesoporous silica nanoparticles (PHMS-1) using a very minute amount of cationic surfactant in o/w-type (castor oil in water) emulsion at room temperature. The grafting of Al(III) through post-synthetic modification onto this silica framework (PHMS-2, Si/Al ~20 atomic percentage) makes this a very efficient solid acid catalyst for the conversion of monosaccharides to 5-HMF. Brunauer–Emmett–Teller (BET) surface area for the pure silica and Al-doped mesoporous silica nanoparticles (MSNs) were found to be 866 and 660 m2g−1, respectively. Powder XRD, BET and TEM images confirm the mesoporosity of these materials. Again, the perforated hollow morphology was investigated using scanning electron microscopic analysis. Al-doped hollow MSNs were tested for acid catalytic-biomass conversion reactions. Our results show that PHMS-2 has much higher catalytic efficiency than contemporary aluminosilicate frameworks (83.7% of 5-HMF yield in 25 min at 160 °C for fructose under microwave irradiation).

Microwave-assisted extraction of lignin from coconut coir using deep eutectic solvents and its valorization to aromatics

Lignin is a rich renewable source of aromatics present in lignocellulosic biomass (LCB). The extraction of lignin from the intricate LCB network is a challenging task for successful commercialization of sustainable biorefineries. In the present study, a series of choline chloride (ChCl)-carboxylic acid based deep eutectic solvents (DESs) were used for the extraction of lignin from coconut coir under microwave irradiation. Among the synthesized DESs, ChCl: lactic acid (LA) (1:4) gave the highest lignin yield of 82% with >95% purity. Interestingly, the severity factor (H factor) for the pretreatment process was found to be a significantly lower (55.5) as compared to reported studies due to efficient microwave heating. Moreover, the DES showed good recyclability for four recycle runs thus making it a promising candidate for the delignification of LCB. Finally, the extracted lignin was converted to aromatics via catalytic transfer hydrogenation (CTH) using Ru/C and isopropanol as in-situ hydrogen donor.