MgO-containing porous carbon spheres derived from magnesium lignosulfonate as sustainable basic catalysts

The presence of alkalis in lignosulfonate allows an easy preparation of sustainable MgO-containing carbon catalysts with surface basicity by carbonization of magnesium lignosulfonate and/or further partial gasification of the produced char with CO2. Carbon spheres with different chemical and physical properties were obtained from lignosulfonate treated at temperatures ranging from 500 to 900 oC. Carbonization at 900 degrees C generates hollow porous carbon spheres (pore volume of 0.20 cm3/g and apparent surface area of 465 m2/g) with magnesium content of 12%. A kinetic study of CO2 gasification of the carbon spheres obtained at 900 degrees C at temperatures in the range of 700 - 800 degrees C revealed that the gasification rate can be accurately described by the random pore model up to conversion values of 0.5. Based on this study, in order to develop additional porosity on the carbon spheres obtained at 900 degrees C, a partial gasification with CO2 at 750 degrees C for 30 min was carried out, reaching surface areas higher than 700 m2/g and 15.3% of Mg loading, with an overall preparation yield of 30%. All the obtained carbon materials were tested as catalyst for 2-propanol decomposition, showing a high selectivity to acetone, evidencing the basic character of these carbon catalysts. The highest activity and selectivity were shown by the CO2-activated carbon spheres (conversion and acetone selectivity higher than 90% at 420 degrees C), indicating that magnesium lignosulfonate is an attractive raw material for the preparation of sustainable carbon catalysts for biorefinery applications.

Automated summary

Alkalis in lignosulfonate enable the easy preparation of sustainable MgO-containing carbon catalysts by carbonization and gasification. Different carbon spheres with varied properties were obtained through different temperatures of treatment. The carbon spheres showed high selectivity to acetone as a catalyst for 2-propanol decomposition, and CO2-activated carbon spheres exhibited the highest activity and selectivity.