Direct valorization of cellulose and glucose to glycolic acid through green catalytic process

The current work reports the catalytic conversion of α-cellulose to glycolic acid using molecular oxygen as an oxidant. A series of copper and cobalt molybdophosphoric acid catalysts (Cu-H3PMo12O40 and Co-H3PMo12O40) were synthesized via impregnation and ion-exchange techniques. Then the synthesized catalysts are thoroughly tested for effective conversion of α-cellulose and glucose into glycolic acid and value-added chemicals. The physicochemical characterization of as prepared catalysts was carried out using X-ray diffraction (XRD) and a scanning electron microscope-energy dispersive spectrometer (SEM–EDS). Fourier-transform infrared spectroscopy (FT-IR), N2-Physisorption and the Hammett test, on the other hand, were used to determine the quantitative relationship between catalyst structure and catalyst activity. Under mild reaction conditions, glycolic acid was discovered to be the primary product with 99.8% selectivity and 99% yield over a Cu-impregnated H3PMo12O40 catalyst. It was also revealed that the catalytic activity was directly related to the catalyst surface area, degree of crystallization, and surface acidic strength. Moreover, synergic interactions of active metals with support materials, Bronsted and Lewis acid properties possessed by catalysts are major determinants of better catalytic activity. Graphic Abstract: (Figure presented.)

Synthesis of glycerol carbonate from industrial by-products by alcoholysis of urea: Crude glycerol and red gypsum

In this study, a heterogeneous catalyst was developed from red gypsum for the synthesis of glycerol carbonate through a glycerolysis reaction with urea. Under optimum reaction conditions, a simple heat treatment on bare red gypsum in a static air environment produces an 87% yield of the targeted glycerol carbonate product. The higher catalytic activity of the calcined catalyst is due to its basic characteristics and the presence of different phases of anhydrite CaSO4 with additional elements, especially an active hematite (Fe2O3) phase. The catalytic process was also found to be insensitive to the type of flowing gas that was used to remove the evolved ammonia gas, whereby, either inert nitrogen gas or reactive air containing oxygen did not significantly impact the glycerol carbonate yield. Indeed, with a promising yield, the developed catalytic system was able to directly synthesise glycerol carbonate from industrial crude glycerol from a biodiesel plant. The red gypsum-based catalytic system seems resistant to the presence of a certain level of moisture and other impurities in crude glycerol. The catalyst efficiency is being retained for consecutive reaction cycles, which are subsequently reused for the next batch reaction without requiring any pre-treatment

Unique Lewis and Bronsted acidic sites texture in the selective production of tetrahydropyran and oxepanefrom1,5-pentanediol and 1,6-hexanediol over sustainable red brick clay catalyst

Activated red brick (ARB) clay material proved superb catalyst for selective conversion of 1,5-pentanediol (1,5-PDO) to tetrahydropyran (THP) and 1,6-hexanediol (1,6-HDO) to oxepane (OP) via dehydration under vapor phase conditions in a continuous flow reactor. As per scanning electron microscopy (SEM), SEM-EDX and X-ray fluorescence (XRF) techniques, ARB clay catalyst majorly possessed silica (quartz), and iron oxide (hematite) species, and synergistic texture contributed to the catalytic efficiency for prolonged time-on-stream (TOS). The combination of active Lewis and Bronsted acidic sites with weak to mild acidic nature in the ARB clay obviously facilitates the dehydration reaction with high selectivity, tetrahydropyran (82%) and oxepane (89%). ARB clay displayed superior catalytic properties in the dehydration of alcohols compared with activities of commercial silica and α-Fe2O3 as catalysts. Commercial silica and α-Fe2O3 catalysts possessing the Lewis acidic sites only did not facilitate synchronous dehydration mechanism