Abstract
New methods in lowering energy consumption costs for evaporation and concentration are needed in many commercial chemical processes. Pervaporation is an underutilized, low-energy processing method that has a potential capability in achieving lower energy processing costs. A recently developed new electrochemical process that can generate a 5–25 wt% pure formic acid (FA) from the electrochemical reduction of CO2 requires a low-energy process for producing a more concentrated FA product for use in both on-site and commercial plant applications. In order to accomplish this, a 25 cm2 membrane area pervaporation test cell was constructed to evaluate the FA-H2O system separation performance of three distinct types of membrane candidates at various FA feed concentrations and temperatures. The selection included one cation ion exchange, two anion ion exchange, and two microporous hydrophobic membranes. The permeation flux rates of FA and H2O were measured for FA feed concentrations of 10, 20, 40, and 60 wt% at corresponding temperatures of 22, 40, and 60 °C. The separation performance results for these particular membranes appeared to follow the vapor liquid equilibrium (VLE) characteristics of the vapor phase in the FA-H2O system as a function of temperature. A Targray microporous hydrophobic high-density polyethylene (HDPE) membrane and a Chemours Nafion® N324 membrane showed the best permeation selectivities and mass flux rates FA feed concentrations, ranging from 10 to 40 wt%. The cation and anion ion exchange membranes evaluated were found not to show any significant enhancements in blocking or promoting the transport of the formate ion or FA through the membranes. An extended permeation cell run concentrated a 10.12% FA solution to 25.38% FA at 40 °C. Azeotropic distillation simulations for the FA-H2O system using ChemCad 6.0 were used to determine the energy requirement using steam costs in processing FA feed concentrations ranging from 5 to 30 wt%. These experimental results indicate that pervaporation is a potentially useful unit process step with the new electrochemical process in producing higher concentration FA product solutions economically and at lower capital costs. One major application identified is in on-site production of FA for bioreactors employing new types of microbes that can assimilate FA in producing various chemicals and bio-products.
Highlights
The conversion of carbon dioxide into sustainable chemicals and fuels provides a pathway in reducing the amount of CO2 released into the atmosphere [1,2,3,4,5,6,7,8,9,10]
The Sustainion® anion membranes did not show any significant anion ion enhancement behavior in increasing the formic acid (FA) transport through the membrane. These results indicate that the pervaporation process separation efficiency with all these membranes is significantly less when operating at FA concentrations above about 40 wt% FA at a temperature of 60 ◦ C
FA is known to deviate from angas, ideal gas, and partreason of the isreason is molecules dimerize in the vapor phases
Summary
The conversion of carbon dioxide into sustainable chemicals and fuels provides a pathway in reducing the amount of CO2 released into the atmosphere [1,2,3,4,5,6,7,8,9,10]. Several new electrochemical technologies have recently been developed by Dioxide Materials Inc. C 2020, 6, 42 technologies have recently been developed by Dioxide Materials Inc. (Boca Raton, FL, USA) that may provide economically viable routes in CO2 conversion to various chemicals and fuels. ® anion®membrane (FA) product a three-compartment novel three-compartment cell design. A Sustainion anion membrane in product using using a novel cell design. One of the technologies developed is direct the direct electrochemical reduction of CO a pure formic acid technologies developed is the electrochemical reduction of CO into into a pure formic acid (FA)
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