A New Gas-Phase Method for Formic Acid Production: Tests on a Pilot Plant

摘要

Formic acid is industrially produced from methyl formate by multi-stage liquid-phase methods characterized by high capital intensity and high energy costs. The gas-phase synthesis of formic acid by cat- alytic oxidation of formaldehyde with atmospheric oxygen is developed at the Boreskov Institute of Catalysis. A pilot plant with productivity of up to 3 kg of formic acid per hour is constructed; its flow sheet and the appa- ratus constructions fully reproduce the future industrial process. It includes two catalytic stages: the oxidation of methanol to formaldehyde and the oxidation of formaldehyde to formic acid. Methanol is oxidized over a commercial iron–molybdenum catalyst oxide under conventional conditions. The oxidation of formalde- hyde to acid is performed over titania–vanadia catalyst at temperatures of 120–140°C. Because of the narrow temperature range, a two-reactor flow sheet and the partial dilution of a bed with inert filling in the first of two reactors are used at the second stage. The tests are performed at a methanol concentration in the initial mixture of 6–7 vol % and the temperature is varied in the formaldehyde oxidation reactors. Under optimum conditions, the acid yield is 87–88% relative to the converted formaldehyde and 79–81% based on the con- verted methanol. This is achieved at the complete conversion of methanol and 96.5–98.5% conversion of formaldehyde. The technology meets the requirements of "green" chemistry.