A new gas-phase method for formic acid production: Tests on a pilot plant

Abstract

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 catalytic 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 apparatus 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 formaldehyde 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 converted 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.