M.M. Tsyba

Functionalization of Carbon and Silica Gel by Phosphoric Acid

Functionalization of polymer-based carbon (SCS-3) and silica gel (SG60) by phosphoric acid at 800°C was investigated. It was shown that heat treatment of carbon and silica gel in the presence of phosphoric acid at 800°C provides a way of functionalizing materials with phosphorus-containing surface groups. Functionalization of the finished carbon occurs as a surface reaction while destruction of the silica gel structure was observed. Functionalization with phosphoric acid creates new acid surface groups — phosphorus-containing and oxygen-containing in the case of carbon and only phosphorus-containing in the case of silica gel. Enhancement of the amount of acid surface groups by functionalization improves the metal-ion binding properties of both carbon and silica gel.

Ethyl tert-butyl ether synthesis using carbon catalysts from lignocellulose

Porous structure, surface chemistry and catalytic properties of carbon catalysts with various acid groups in ethyl tert-butyl ether synthesis were studied. Carbon catalysts were obtained by phosphoric acid activation followed by sulphonation of lignocellulosic feedstocks of different origin. Porous structure of carbon catalysts was characterized by nitrogen adsorption. Surface chemistry was investigated by potentiometric titration. Carbon catalysts obtained from lignosulphonate and sucrose showed the highest catalytic activity in ethyl tert-butyl ether synthesis (reaction rate at 120℃ is 4.3–5.2 × 10−6 mol·g−1·s−1), is comparable to activity of Amberlyst-15 (5.0 ×10−6 mol·g−1·s−1). Calculated turnover frequency (TOF) of sulphonic groups (pKa = −2.5) equals 0.00116 s−1, polyphosphate groups (pKa = 1.9) 0.01019 s−1, strong carboxylic (pKa = 3.6) 0.00202 s−1 and 0 s−1 for weak carboxylic (pKa = 6) groups. The activity of acid groups with pKa lower than 3.6 is higher than the activity of sulphonic groups of Amberlyst-15 (TOF 0.00115 s−1).