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Phosphorus-Containing Mesoporous Carbon Acid Catalyst for Methanol Dehydration to Dimethyl Ether

Catalytic dehydration of methanol on an acid carbon catalyst prepared by chemical activation of olive stone with H3PO4 is reported. This preparation methodology produces carbons with a well-developed porous texture and highly thermally stable phosphorus surface complexes in the forms of C–O–PO3 and C–PO3. These P groups confer the carbon with a high oxidation resistance, surface acid, and redox sites. In the absence of oxygen, the catalyst experiment demonstrated a gradual deactivation due to coke deposition on the strong acid sites (P–OH) and reduction of the moderate-strength acid P-surface groups (from C–O–P to C–P type ones). The novelty of this research concerns the high catalytic stability in air atmosphere of this type of carbon with a steady-state methanol conversion of 20% at 300 °C and selectivity towards dimethyl ether of 95%. The presence of oxygen in the reaction gas avoids coke deposition by continuous (re)oxidation of reduced P-surface groups, without gasification of the carbon catalyst.