Sulfonated porous carbon catalysts for biodiesel production: Clear effect of the carbon particle size on the catalyst synthesis and properties

• An easy synthesis and low cost of catalysts for the biodiesel synthesis is depicted.
• The catalyst shows high performance for biodiesel production.
• The catalyst can be recycled several times without significant loss of activity.
• The Higher amount of sulfonic groups is obtained for smaller particles.
• Due to the easy synthesis and low cost are promising materials for biodiesel synthesis.

Sulfonated porous carbons (PCs-SO3H) are prepared by the sol-gel reaction of resorcinol and formaldehyde. The porosity is maintained during drying using a cationic polyelectrolyte as pore stabilizer. It was found that varying the Resorcinol/Na2CO3 molar rate, different resins are produced which, after pyrolysis, give carbonaceous materials with different textural properties. It seems that a Resorcinol/Na2CO3 molar ratio of 200:1 was the optimal condition to produce a well-developed porous structure. Both resins and carbon materials are sulfonated by treatment with sulphuric acid. The relation between the carbon particles size, the sulfonation efficiency and its performance as a catalyst is studied. The higher amount of sulfonic groups, and thermal stability, as well as better catalytic performance, was obtained when smaller porous carbon particles were chosen by sieving. PCs-SO3H exhibited high efficiency for the esterification reaction and high performance for biodiesel production. The catalysts can be recycled several times with a minimal loss of activity. Thermal analysis evidenced stability up to ca. 200 °C, allowing the use of this catalyst at high temperature. The simple synthesis and low cost of the PCs-SO3Hs make them promising catalysts for the synthesis of biodiesel.

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