CONTINUOUS CO-CURRENT ELECTROCHEMICAL REDUCTION OF CARBON DIOXIDE

摘要

In various embodiments, the invention provides electro-chemical processes for reduction of carbon dioxide, for example converting carbon dioxide to formate salts or formic acid. In selected embodiments, operation of a continuous reactor with a three dimensional cathode and a two-phase (gas/liquid) catholyte flow provides advantageous conditions for electro-reduction of carbon dioxide. In these embodiments, the continuous two-phase flow of catholyte solvent and carbon dioxide containing gas, in selected gas/liquid phase volume flow ratios, provides dynamic conditions that favour the electro-reduction of COs at relatively high effective superficial current densities and gas space velocities, with relatively low reactor (cell) voltages (<10 Volts). In some embodiments, relatively high internal gas hold-up in the cathode chamber (evident in an internal gas to liquid phase volume ratio >0.1) may provide greater than equilibrium CO2 concentrations in the liquid phase, also facilitating relatively high effective superficial current densities. In some embodiments, these characteristics may for example be achieved at catholyte pH>7 and relatively low CO2 partial pressures (<10 bar). In some embodiments, these characteristics may for example be achieved under near adiabatic conditions, with catholyte outlet temperature up to about 80° C.

主权项

1. An electrochemical process for reducing carbon dioxide to produce formic acid or formate salts comprising:
a) continuously feeding a gas stream comprising carbon dioxide gas and a liquid catholyte into an electrochemical reactor, said electrochemical reactor having a porous 3D cathode in a cathode chamber, an anode in an anode chamber, the anode chamber being separated from the cathode chamber by an electrochemical cell membrane, wherein said gas stream and said liquid stream are fed into said 3D cathode, traveling from a cathode inlet into said 3D cathode to a cathode outlet out of said 3D cathode; b) feeding an anolyte through an anolyte inlet into said anode chamber, said anolyte travelling through said anode chamber to an anolyte outlet out of said anode chamber; c) maintaining a gas to liquid ratio in the porous cathode, measured as a ratio of the volume of said gas in the porous 3D cathode to the volume of said liquid in the porous 3D cathode greater than about 0.1 to promote a super-equilibrium concentration of carbon dioxide dissolved in the liquid stream within the porous 3D cathode; and d) passing an electric current between said porous 3D cathode and said anode, to reduce the dissolved carbon dioxide to a formate salt.