(437f) Modeling Methods for Concentrating a Formic Acid Product Generated from a Novel Electrochemical Reduction of CO2 Cell Design

Formic acid is a commercial industrial chemical product that has various applications such as a chemical used in leather tanning, a preservative in silage (animal feed), non-salt deicer chemicals, oil field stimulation chemicals (replacing HCl), and as a chemical feedstock for producing various chemical derivatives. Annual worldwide production is currently about 900,000 tonnes/year.

One of the biggest potential markets is in the use of formic acid as a hydrogen storage chemical, It can be easily stored as a solution and can be readily converted to hydrogen using decomposition catalysts. A number of researchers are investigating formic acid for energy storage and in fuel cells. Alternatively, formic acid can also be converted to CO, which can then be used for producing renewable fuels if the CO₂ feed source is from biomass, power plants, or air.

Dioxide Materials has recently developed a novel cell design for producing a pure formic acid product from the electrochemical reduction of CO₂. The electrochemical cell utilizes a 3-compartment design, consisting of an anode compartment, center flow compartment, and a cathode compartment. The center flow compartment is bounded by a cation exchange membrane on the anode side and a PSTMIM based Sustainionâ„¢ X-37 anion membrane on the cathode side. A nanoparticle Sn-based GDE cathode in combination with a PSTMIM imidazolium-based ionomer are used in efficiently reducing the CO₂ feed to formate ions, which migrate into the center flow compartment. A pure formic acid product is recovered from the center flow compartment using a DI water carrier stream. A cation ion exchange media is employed as an efficient conductive electrolyte media in the center flow compartment. DI water is also used as an anolyte in the anode compartment. The electrochemical cell operates at a current density of 140 mA/cm² at a cell voltage of 3.50 V, with Faradaic efficiencies near 90%.

The pure formic acid product from the electrochemical system can range from 10 to 25 wt%. The next step in commercializing the technology is determining the best economic methods for concentrating the formic acid to a commercial product concentration of 85 to 99 wt%. Process modeling software, such as ChemCad and Aspen, is being used to model various distillation configurations to determine the most economically effective design. The results of the modeling will be discussed in the presentation.