Investigation Of Catalytic Dehydration And Oxidehydration Of Glycerol Over Sepiolite-Based Catalyst

Glycerol is an unavoidable by-product from biodiesel process and there is also a great potential in producing glycerol from biomass. Glycerol has been considered as one of platform chemical with bioavailability. Catalytic dehydration and oxidehydration of glycerol offers an alternative route to recycle the glycerol and produce acrolein and acrylic acid for commercial applications. Many solid acid catalysts has been used in catalytic dehydration and oxidehydration of glycerol. However, the investigation on the effect of active sites of catalyst on catalytic dehydration and oxidehydration of glycerol is still limited.Clay mineral with adjustable specific surface area and active acid sites has been considered as a low cost solid acid catalyst in many reactions. In this work, I investigated the heterogeneously gas-phase dehydration of glycerol over acid-activated sepiolite catalysts in the concentration range of 0.5-8mol/L to produce acrolein. The structure, porosity and the type and amount of acid sites of sepiolite are changed during acid activation. Catalytic reactions were conducted in a gas-phase fixed-bed reactor at 320 °C with the flow rate of air carrier gas of 20 m L/min. The highest conversion of glycerol was 92.9% and the selectivity of acrolein was 59.4% over 2 mol/L HCl activated sepiolite（SPA-2）. I investigated the oxidehydration of glycerol over V2O5 supported on acid activated sepiolite catalysts with different content and calcination temperature to produce acrylic acid in gas-phase. The content of V2O5 is beneficial for the formation of acrylic acid. The highest conversion of glycerol was 93.0% and the selectivity of acrylic acid was 3.9% over 0.5% V supported on 2 mol/L HCl activated sepiolite calcined at 400°C（0.5%V/SPA-2@400）. The structure, porosity and the type and amount of acidity of hydrochloric acid activated sepiolite are characterized by XRD, XRF, TGA, SEM, N₂ adsorption-desorption, FTIR, NH₃-TPD, and pyridine adsorption of FTIR.The acid activation of sepiolite increased the specific surface area, increased the type and amount of Br?nsted and Lewis acid sites, and changed the strong acid sites to medium and weak acid sites. The presence of V2O5 helped converse acrolein to acrylic aicd. However, the higher amount of V2O5 hindered the formation of acrylic acid. The coke deposit was found on the sepiolite and it deactivated the activity of acidity and adsorpability of sepiolite.My discovery opens up the possibility of the utilization of acid activated clay mineral, and we studied the influence of the active sites of sepiolite catalysts on the catalytic dehydration and oxidehydration of glycerol.