Devices, systems and methods for converting co2 produced by municipal solid waste into fuels and useful products

Abstract

A modular, self-contained system for on-site alcohol production at municipal waste facilities integrates CO2 electrolysis and product separation within a single deployable unit. In some embodiments, the system can utilize a three-compartment CO2 electrolyzer, which in some instance demonstrates high alcohol production rates and reduced CO2 crossover. In some embodiments, the plug-and-play nature of the system can allow for simplified installation and operation at diverse waste management sites. In certain implementations, the integrated design can enhance overall efficiency by combining multiple process steps into a unified system.

Description

DEVICES, SYSTEMS AND METHODSFOR CONVERTING CO2PRODUCED BY MUNICIPAL SOLID WASTE INTO FUELS AND USEFUL PRODUCTSStatement of Government Interest

[0001] The inventions were made, at least in part, with U.S. government support under U.S. Department of Energy Grant No. DE-SC0021472. The government has certain rights in the inventions.Cross-Reference to Related Application(s)

[0002] The present application is related to and claims priority benefits from U.S. Provisional Patent Application Serial No. 63 / 568,185 filed on March 21, 2024, entitled “Devices, Systems And Methods For Converting CO2 Produced By Municipal Solid Waste Into Fuels And Useful Products”. The 63 / 568,185 application is herein incorporated in its entirety.Field of the Invention

[0003] The field of the inventions is electrochemistry. The devices, systems, and methods described involve the process for the electrochemical reduction of CO2 into fuels and useful products.Background of the Invention

[0004] Recycling generated carbon dioxide back to fuels and useful chemicals is beginning to make a difference to the U.S. economy. Presently, fuels and organic chemicals are still usually made from petroleum, coal, and / or natural gas “fossil fuels”. However, increasing the amount of such fuels andchemicals that are made from recycled CO2, will reduce the U.S. dependence on imported oil. Furthermore, emissions of greenhouse gases that contribute to climate change would also be reduced as CO2 produced in power plants would change from a waste product to a useful, economically viable feedstock.

[0005] The United States has made the deployment of systems and facilities to generate renewable fuels a major priority. The economics associated with the production of renewable fuel are also favorable. The US Department of Energy has created a $10,000,000 per year consortium “Reduction and Upgrading for e- Fuels (CCERue)” whose objective is to develop the technology to convert waste CO2 from an ethanol biorefinery into sustainable aviation fuel (SAF).

[0006] If the US is to begin meeting its needs for fuel, including aviation fuel, via recycled CO2, additional sources of renewable CO2 are needed. According to a recent report, there is enough carbon in municipal solid waste to meet the aviation industry's needs many times over. Unfortunately, the sources are distributed. No single source can produce enough CO2 to obtain 25,000,000 gal / yr of SAF needed in the US.

[0007] The field of CO2 conversion to valuable products has seen rapid advancements in recent years, driven by the urgent need to address climate change and develop sustainable energy sources. Researchers have explored various approaches, including electrochemical, thermochemical, and biological methods, to efficiently convert CO2 into fuels and chemicals.

[0008] Electrochemical CO2 reduction, in particular, has garnered significant attention due to its potential for high selectivity and compatibility with renewable electricity sources. This approach typically involves the use of a cathode, where CO2 is reduced to form products such as carbon monoxide, formic acid, ethylene, or alcohols, and an anode, where water is oxidized to produce oxygen and protons. The choice of catalyst materials, electrolyte composition, and operating conditions play crucial roles in determining theproduct distribution and overall efficiency of the process.

[0009] Previous efforts in this field have made significant strides in CO2 conversion technology. For example, U.S. Patent No. 9,181,625, titled “Devices and Processes for Carbon Dioxide Conversion into Useful Fuels and Chemicals” discloses catalyst layers for CO2 conversion in electrochemical cells. The ‘625 patent teaches the use of catalyst layers that demonstrate enhanced CO2 reduction efficiency and selectivity towards desired products like carbon monoxide.

[0010] Additionally, U.S. Patent No. 10,280,378, titled "System and Process for the Production of Renewable Fuels and Chemicals" describes systems and methods for simultaneous CO2 capture and conversion to valuable products. The integrated CO2 capture and conversion approach described in U.S. Patent No. 10,280,378 represents an important direction in process intensification for CO2 utilization. By combining capture and conversion steps, such systems can reduce energy requirements and equipment costs. This concept has been further explored in various configurations, including the use of bipolar membranes, gas diffusion electrodes, and microfluidic devices.

[0011] In addition to the catalysts described in U.S. Patent No. 9,181,625, researchers have investigated a wide range of materials for CO2 electroreduction. These include other transition metals, alloys, metal oxides, and molecularly engineered catalysts. For instance, copper-based catalysts have shown promise for producing multi-carbon products like ethanol, while silver and gold catalysts are often used for selective CO production. Ongoing research aims to develop catalysts with improved activity, selectivity, and stability under industrially relevant conditions.

[0012] The entire contents of U.S. Patent No. 9,181,625 and U.S. Patent No. 10,280,378 are hereby incorporated by reference.

[0013] While significant efforts have been dedicated to developing catalyst for electrochemical CO2 reduction to alcohol, a persistent challenge remains in membrane development with both high ionic conductivity and low alcohol crossover. Many researchers have strived to create membranes that exhibit these desirable properties, but with limited success. This is primarily attributed to the inherent difficulty in decoupling anion transport from alcohol transport, as both species traverse the membrane in the same direction. Consequently, improvements in ionic conductivity often result in a corresponding increase in alcohol crossover, leading to reduced product selectivity and overall system efficiency.

[0014] The challenge of membrane development for CO2 electroreduction systems extends beyond the trade-off between ionic conductivity and alcohol crossover. Researchers are also investigating ways to enhance CO2 transport to the catalyst surface, improve mechanical and chemical stability under operating conditions, and reduce membrane fouling. Novel membrane materials being explored include composite membranes incorporating inorganic fillers, block copolymers with tailored hydrophilic and hydrophobic domains, and chemically modified commercial membranes.

[0015] The utilization of municipal solid waste (MSW) as a CO2 source for fuel production presents unique challenges and opportunities. MSW typically contains a mix of organic and inorganic materials, requiring efficient sorting and processing techniques to isolate the carbon-rich fraction. Technologies for waste gasification and pyrolysis are being developed to convert MSW into syngas (CO and H2), which can then be used as a feedstock for fuel synthesis. Alternatively, anaerobic digestion of organic waste can produce biogas, which contains significant amounts of CO2 that could be captured and converted.

[0016] The distributed nature of MSW sources necessitates the development of modular, scalable CO2 conversion systems that can be deployed at variousscales. Such systems must be robust, easy to operate, and capable of handling the variability in feedstock composition inherent to MSW-derived CO2. Additionally, the integration of these systems with existing waste management infrastructure and local energy grids presents both technical and logistical challenges that need to be addressed.

[0017] As research in CO2 conversion technologies progresses, there is a growing focus on system-level optimization and life cycle assessment to ensure that the developed processes result in net reductions in greenhouse gas emissions and are economically viable. This holistic approach considers factors such as energy inputs, material requirements, and potential environmental impacts across the entire production chain, from CO2 capture to final fuel use.Summary of the Invention

[0018] In some embodiments, a modular, self-contained, plug-and-play system for converting CO2 to alcohol products can include a CO2 electrolyzer, a product separation unit, and a balance of plant.

[0019] In some embodiments, the CO2 electrolyzer can include multiple compartments and membranes. The electrolyzer can comprise a cathode compartment, an anion exchange membrane, a center compartment, a cation exchange membrane, and an anode compartment.

[0020] In some embodiments, the cathode compartment can include a cathode flow field, a cathode gas diffusion layer, and a cathode catalyst layer. In some implementations, the cathode flow field can have serpentine channels machined in stainless steel plate. The cathode catalyst layer can comprise copper-based nanostructures such as nanoparticles, nanosheets, or nanocubes, applied to the cathode gas diffusion layer and configured to convert CO2 to alcohol.

[0021] In some embodiments, the center compartment can be positioned between the anion exchange membrane adjacent to the cathode compartment and the cation exchange membrane adjacent to the anode compartment. In some aspects, the center compartment can comprise an ion exchange media. In some embodiments, the ion exchange media can include a cation exchange resin, anion exchange resin beads, cation exchange fiber felt, and / or anion exchange fiber felt. In certain implementations, the ion exchange media can have a thickness of about 2 mm.

[0022] In some embodiments, the anion exchange membrane can comprise a benzyl group bonded to at least one of: an imidazolium, a pyridinium, a pyrazolium, a pyrrolidinium, a pyrrolium, a pyrimidium, a piperidinium, an indolium, a triazinium, a phosphonium or a quaternary amine. In some embodiments, the anion exchange membrane can include an inorganic filler, an organic filler and / or a barrier layer.

[0023] In some embodiments, the cation exchange membrane can be a Nafion membrane with a thickness of less than 400 pm in some implementations.

[0024] In some embodiments, the anode compartment can comprise an anode flow field, an anode gas diffusion layer, and an anode catalyst layer. In some aspects, the anode flow field can have serpentine channels machined in titanium plate. The anode catalyst layer can include a Pt / C and / or Pt alloy nanoparticle catalyst applied to the anode gas diffusion layer, configured to oxidize H2 and reduce cell voltage.

[0025] In some embodiments, the product separation unit of the system can include a condenser in some embodiments. The condenser can separate alcohol products from unreacted H2 and / or CO2 , which can then be recycled to feed the CO2 electrolyzer.

[0026] In certain aspects, the balance of plant can comprise a safety system that triggers automatic system shutdown in case of operational issues. This can help ensure safe and reliable operation of the modular system.

[0027] In some embodiments, the modular, self-contained nature of the system can allow for easy installation and operation at various locations. The integrated design can combine multiple process steps into a unified system, potentially enhancing overall efficiency of CO2 conversion to alcohol products.

[0028] In some embodiments, the center compartment sits between an anion exchange membrane next to the cathode in cathode compartment and a cation exchange membrane next to the anode in anode compartment.

[0029] In some embodiments, CO2 is reduced to alcohol at a Cu cathode, and reacts with generated OH' to form carbonate / bicarbonate and some of alcohol crossovers to the center compartment through an anion exchange membrane.

[0030] In some embodiments, the anion exchange membrane electrolyzer (AEM) has high conductivity and high alcohol crossover.

[0031] In some embodiments, the center compartment serves to regenerate CO2 from crossovered carbonate / bicarbonate, collect crossovered alcohol, and / or reduces further alcohol crossover to the anode.

[0032] In some embodiments, the cation exchange membrane (CEM) is placed against anode and blocks carbonate / bicarbonate transportation to the anode, instead facilitates proton transportation from anode to the center compartment.

[0033] In some embodiments, hydrogen oxidation at a Pt / C anode replaces oxygen evolution, reducing cell voltage.Brief Description of the Drawings

[0034] FIG. 1 is a schematic diagram of a process to convert CO2 from sources such as municipal waste into a liquid product, which can be converted to SAF.

[0035] FIG. 2 is a schematic diagram of an electrolyzer.

[0036] FIG. 3 is a graph showing properties of various membranes.Detailed Description of Illustrative Embodiments

[0037] It is understood that the process is not limited to the particular methodology, protocols and reagents described herein, as these can vary as persons familiar with the technology involved here will recognize. It is also to be understood that the terminology used herein is used for the purpose of describing particular embodiments only, and is not intended to limit the scope of the process. It also is to be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include the plural reference unless the context clearly dictates otherwise. Thus, for example, a reference to “a linker” is a reference to one or more linkers and equivalents thereof known to those skilled in the art. Similarly, the phrase “and / or” is used to indicate one or both stated cases can occur, for example, A and / or B includes (A and B) and (A or B).

[0038] Unless defined otherwise, technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art to which the process pertains. The embodiments of the process and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and / or detailed in the following description. It should be noted that features of one embodiment can be employed with other embodiments as the skilled artisan would recognize, evenif not explicitly stated herein.

[0039] Any numerical value ranges recited herein include all values from the lower value to the upper value in increments of one unit, provided that there is a separation of at least two units between any lower value and any higher value. As an example, if it is stated that the concentration of a component or value of a process variable such as, for example, size, angle size, pressure, time and the like, is, for example, from 1 to 98, specifically from 20 to 80, more specifically from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32, and the like, are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of numerical values between the lowest value and the highest value are to be treated in a similar manner.

[0040] Moreover, provided immediately below is a “Definitions” section, where certain terms related to the process are defined specifically. Particular methods, devices, and materials are described, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the process.Definitions

[0041] The term “polymer electrolyte membrane” as used here refers to both cation exchange membranes, which generally comprise polymers having multiple covalently attached negatively charged groups, and anion exchange membranes, which generally comprise polymers having multiple covalently attached positively charged groups. Typical cation exchange membranes include proton conducting membranes, such as the perfluorosulfonic acid polymer available under the trade designation NAFION® from E. I. du Pont de Nemours and Company (DuPont) of Wilmington, DE.

[0042] The term “anion exchange membrane electrolyzer” or “AEM electrolyzer” as used here refers to an electrolyzer with an anion-conducting polymer electrolyte membrane separating the anode from the cathode.

[0043] The term “MEA” as used here refers to a membrane electrode assembly.Specific Description

[0044] A distributed system for sustainable aviation fuel (SAF) production can include on-site conversion of CO2 derived from municipal waste into an alcohol solution, such as ethanol or isopropanol; and subsequent transport of the alcohol solution to a centralized facility for conversion into SAF.

[0045] FIG. 1 shows a flow diagram for an exemplary on-site conversion system 1000 used to produce alcohol from CO2. In some embodiments, the source of the CO2 is municipal waste facility. In at least some embodiments, conversion system 1000 can be self-contained and plug-and-play so that operators not used to running chemical processes can operate conversion system 1000.

[0046] In at least some embodiments, conversion system 1000 removes the need for a distillation system that takes hours to come on stream and is subject to process disruptions. In some embodiments, a single unit can handle both electrolysis to form the alcohol and separation to concentrate the alcohol. In at least some embodiments, an automated skid with a safety system around the device can shut down the system automatically if needed, such as during a system failure.

[0047] Conversion system 1000 can incorporate multiple components to facilitate an efficient and controlled conversion process:

[0048] FIG. 1 illustrates conversion system 1000 for processing and converting CO2 and H2 feeds.

[0049] In some embodiments, conversion system 1000 comprises electrolyzer 150 having anode 152 and cathode 154, configured to process the input feeds. In at least some embodiments, electrolyzer 150 is where the primary electrochemical conversion of CO2 takes place. In some embodiments at cathode 154, CCEis reduced to form alcohol products, while anode 152 facilitates the oxidation of water or hydrogen to provide the necessary electrons for the reduction reaction. In some embodiments electrolyzer 150 employs specialized catalysts and membrane technology to enhance conversion efficiency and selectivity.

[0050] In some embodiments, conversion system 1000 incorporates humidifier 122 and / or humidifier 124. In some embodiments, humidifier 122 and / or humidifier 124 can be used to control moisture levels in the gas feeds D and E. In some embodiments, such as the one shown in FIG. 1, humidifier 122 can be responsible for adjusting the humidity of the incoming H2 stream. In some embodiments, such as the one shown in FIG. 1, humidifier 124 could be used for adjusting the humidity of the incoming CO2 feed and / or for conditioning recycled gases.

[0051] In some embodiments, conversion system 1000 includes condenser 112, condenser 114, and / or condenser 116 arranged in different portions of the process flow. In at least some embodiments, these condensers play a role in product separation and purification. For example, in some embodiments, condenser 112 can be responsible for cooling and condensation of product stream A exiting electrolyzer 150. In some embodiments, this product stream can include isopropanol that can be separated in condenser 112. In at least some embodiments, product stream A includes isopropanol and unreacted H2.

[0052] In some embodiments, condenser 114 can be utilized for cooling and condensation of product stream B exiting electrolyzer 150. In some embodiments, product stream B can include isopropanol that can be separated incondenser 114. In at least some embodiments, product stream B includes isopropanol and unreacted CO2.

[0053] In some embodiments, evaporator 140 can be utilized for separating CCh and alcohol from electrolyte stream C. In some embodiments, product stream C can include isopropanol that can be separated in condenser 116. In at least some embodiments, product stream C includes CO2 and isopropanol.

[0054] In some embodiments, condenser 112, condenser 114, and / or condenser 116 are positioned to process different portions of the flow stream, with cooling water connections shown for temperature management.

[0055] In some embodiments, conversion system 1000 includes several pumps 160 positioned at various points to facilitate fluid movement through the system and / or maintain proper circulation of reactants and products. In some embodiments, these pumps ensure consistent flow rates, which can be critical for maintaining optimal reaction conditions and separation efficiencies.

[0056] In some embodiments, conversion system 1000 includes heat exchanger 132 that is integrated into the process flow, taking waste heat generated from the electrolyzer 150 and allowing for temperature control and energy recovery within the system. In some embodiments, heat exchanger 132 can help in preheating incoming feeds D and E using the heat from outgoing product streams, improving overall energy efficiency.

[0057] In some embodiments, conversion system 1000 includes cooling water circuits connected to the condensers, providing temperature control for efficient separation and purification. In some embodiments, temperature management of the condensers is critical for achieving the desired product specifications and / or maximizing recovery rates. In some embodiments, conversion system 1000 has CO2 feed stream D and H2 feed stream E entering the system. In some embodiments, purge streams are provided at certain points.In some embodiments, the electrolyte is recirculated. In some embodiments, this ensures a consistent supply of water to support the ion conduction within the membrane and redox reactions occurring at the electrodes.

[0058] In some embodiments, CO2 and H2, serve as the primary reactants for conversion system 1000. In some embodiments, the CChis sourced from municipal waste facilities, while H2 is produced on-site via water electrolysis and / or sourced externally.

[0059] In some embodiments, conversion system 1000 includes purge streams F at various points. In some embodiments, purge streams F remove unwanted byproducts or maintain system purity by preventing the accumulation of inert gases or contaminants.

[0060] In some embodiments, the system allows for integrated processing of the feed materials through the electrolyzer components (anode 152 and cathode 154) while maintaining appropriate temperature and flow control via heat exchanger 132 and pumps 160. In some embodiments, the system includes separation capabilities for processing the output streams into desired products.

[0061] In some embodiments, conversion system 1000 is powered by power source 180. In some embodiments, power source 180 is a source of renewable energy such as a solar panel or wind turbine. Use of renewable resources to power conversion system 1000 aligns the system’s goal of creating a sustainable process for converting waste CO2 into valuable products, potentially allowing for carbon-neutral or even carbon-negative fuel production when considering the full lifecycle of the process.

[0062] In some embodiments, conversion system 1000 can be configured to produce, among other products, either ethanol or isopropanol depending on the specific catalysts and operating conditions employed.

[0063] Processes utilizing electrochemical cells for chemical conversionshave been known for years. Generally, an electrochemical cell contains an anode, a cathode and an electrolyte. Catalysts can be placed on the anode, the cathode, and / or in the electrolyte to promote the desired chemical reactions. During operation, reactants or a solution containing reactants are fed into the cell. Voltage is then applied between the anode and the cathode, to promote the desired electrochemical reaction.

[0064] When an electrochemical cell is used as a CO2 conversion system, a reactant comprising CO2, carbonate or bicarbonate is fed into the cell. A voltage is applied to the cell, and the CO2 reacts to form new chemical compounds.

[0065] FIG. 2 illustrates an embodiment of electrolyzer 2000 to convert CO2 to alcohol. In some embodiments, electrolyzer 2000 includes cathode compartment 220 comprising cathode flow field 200, gas diffusion layer 201, and cathode catalyst layer 202, anion exchange membrane 203, center compartment 204 comprising a porous ion exchange media, cation exchange membrane 205, and anode compartment 230 comprising anode catalyst layer 206, gas diffusion layer 207 and anode flow field 208.

[0066] In some embodiments, electrolyzer 2000 is formed, at least in part, by using Dioxide Materials' 5 cm2formic acid electrolyzer hardware, which has a three-compartment design. A typical three-compartment design includes a cathode compartment, a central compartment, and an anode compartment.

[0067] In some embodiments, cathode flow field 200 is a serpentine flow field. In some embodiments, anode flow field 208 is a serpentine flow field.

[0068] In some embodiments, catalyst layer 201 is a copper-based catalyst for CO2 conversion to alcohol.

[0069] In some embodiments, a copper-based catalyst layer is prepared by using products such as. but not limited to. copper and copper alloys nanoparticles, nanocubes or nanosheets as catalysts.

[0070] In some embodiments, catalyst layer 206 is a Pt / C catalyst layer for hydrogen oxidation to lower the cell voltage and avoid oxidation of crossovered alcohol if any.

[0071] In some embodiments, anion exchange membrane 203 is a Sustainion ® anion membrane made by Dioxide Materials, PiperlON® made by Versogen or Aemion® made by lonomr, etc.

[0072] In some embodiments cation exchange membrane 205 is a perfluorosulfonic acid (PF SA) membrane or hydrocarbon-based sulfonic acid (PFSA-free) membrane, such as but not limited to, Nafion® or Pemion® membrane made by lonomr.

[0073] In some embodiments, the cathode flow field has a feed of humidified CO2 gas which is electrochemically reduced to alcohol at the gas diffusion electrode (GDE) cathode catalyst layer 202, generating OH' which reacts with CO2to form carbonate / bicarbonate. In some embodiments, alcohol is separated from cathode exhaust and collected for SAF production.

[0074] In at least some embodiments, ion exchange media comprises a cation ion exchange media and / or anion exchange resin beads. In at least some embodiments, the ion exchange media is a strong acid cation media that is constantly acidified from a flow of hydrogen ions (H+) that is formed at and transported from the anode through the cation exchange membrane. In some embodiments, ion exchange media includes an ion exchange resin fill such as but not limited to AmberLite™ resin and / or Dowex® resin.

[0075] In at least some embodiments, the carbonate / bicarbonate produced at the cathode and transported through the anion exchange membrane 203 is prevented from further transport to the anode by a cation exchange membrane. Instead, in at least some embodiments, it is decompose within the acidified ion exchange media, generating CO2. In some embodiments, this CO2, along withany alcohol transported through the anion exchange membrane, is separated and recycled to the feed cathode. In some embodiments, alcohol is collected as a product for further conversion to SAF. In at least some embodiments, ion exchange media reduces, if not eliminates, the CO2 and alcohol crossover.

[0076] In some embodiments, the CEM with a thickness of preferably 400um, more preferably less than 200um, even more preferably less than lOOum is used to reduce the total cell resistance, improving energy efficiency.

[0077] In at least some embodiments, the cation ion exchange media with a thickness of preferably less than 2mm, more preferably less than 1mm, even more preferably less than 0.5mm, is used to reduce the total cell resistance.

[0078] FIG 3 illustrates key properties of the various membranes used in electrolyzer 150. In some embodiments, the membrane comprises a benzyl group bonded to at least one of: an imidazolium, a pyridinium, a pyrazolium, a pyrrolidinium, a pyrrolium, a pyrimidium, a piperidinium, an indolium, a triazinium, a phosphonium or a quaternary amine.

[0079] In some embodiments, the membrane was crosslinked with such as but not limited to tetramethylhexanediamine (TMHDA).

[0080] In at least some embodiments, the membrane comprises a filler either inorganic or organic filler, such as but not limited to TiCh, ZrO2, graphene, graphene oxide, PTFE, or polyvinyl chloride “PVC”.

[0081] In at least some embodiments, the membrane includes a barrier layer sandwiched in the middle of the membrane, such as but not limited to, clay, TiO2, ZrO2, or MCM-41.Specific Examples 1

[0082] In specific Example 1 , anion exchange membranes with different ligands such as but not limited to, tetramethyl imidazole (TMIM), trimethylamine (TMA), methyl -piperidine (MPi), 3,5 Dimethylpyridine (DMP),N-methylpyrrolidine (MPy), were synthesized using same procedure disclosed in patent U.S. Patent No. 9,849,450 which is hereby incorporated by reference. Tetramethyhexanediamine (TMHDA) was used to crosslink the membrane. The polymer solution was cast onto a polyethylene terephthalate (PET) liner. All membranes prepared above were activated by soaking in the IM KOH solution.

[0083] Ethanol crossover was conducted using H-cells. A candidate membrane was placed between the two chambers, and then IM ethanol and DI water were loaded into each chamber of the H-cell. Ethanol buildup in the water chamber was measured as a function of time using nuclear magnetic resonance “NMR”. The ethanol permeability was tabulated in Table 1

[0084] Area Specific Resistance (ASR) measurements were conducted in an electrochemical cell by using Potentiostat (Solartron, 1276) coupled with a frequency response analyzer (FRA, Solartron 1255). A piece of membrane is sandwiched between a Pt cathode and IrO anode supported on carbon fiber paper and mounted in 5cm2Dioxide Materials’ electrolyzer hardware. IM K2CO3 was fed to the cathode and anode. The cell was kept at room temperature. The electrochemical impedance spectrum (EIS) was measured by scanning frequencies from 100kHz to 1Hz with amplitude of lOmV at open circuit potential. The membrane resistance (R, assuming the negligible contribution of cell hardware and electrodes) was determined by the intercept of EIS at the real axis. The ASR was calculated by the equation:Area Specific Resistance = R x A where R is the membrane resistance, and A is the geometric area of the membrane in contact with the electrodes.

[0085] To evaluate the effectiveness of crosslinker on the membrane properties, the impact factor (IF) of crosslinker on the membrane properties with respect to area specific resistance (ASR) and permeability (p) wasintroduced and defined as the following:ASRQ x p0IF = -ASRXX pxWhere ASRo and po are the area specific resistance and permeability of a pristineSustainion® membrane functionalized with ligand of tetramethyl imidazole (TMIM) respectively, and x refers to the membrane with other ligands.Table 1: Properties of the membranes with different ligands.

[0086] Table 1 shows the properties of the membranes with different ligands X-TMIM and X-MPy membranes showed IFs of 2 and 1.5, respectively, which are higher than 1 , so crosslinker had a positive effect on these two membranes.X-TMA and X-DMP membranes had IFs close to 1, so there was no significant effect of crosslinker. However, X-MPi showed much smaller IF of 0.4, so the crosslinker had a negative effect.Specific Examples 2

[0087] In Specific Examples 2, a number of ligands with different pKa were selected to replace TMIM in a Sustainion® anion exchange membrane to tune the conductivity and alcohol crossover. The polymer solution was cast onto PET liner. All membranes prepared above were activated by soaking in the IM KOH solution.

[0088] Area specific resistance and permeability were measured. Table 2 shows the ethanol permeability and ASR of the membrane with different ligands. Table 2: Ethanol permeability and ASR of the membrane with different ligands.Specific Examples 3

[0089] In Specific Example 3, the inorganic fillers were introduced to the pristine Sustainion® X-37 to tune the ethanol crossover. TiO (18nm), ZrO(<100nm) powders, graphene oxide and graphene nano pallets were mixed with the polymer solution. The fillers content varied from 0-20%. The mixture was cast onto PET liner. All membranes prepared above were activated by soaking in the IM KOH solution. Area specific resistance and permeability were measured. The addition of both graphene oxide and graphene nano pallets not only reduced the ethanol permeability from 1.5x1 O'7to 4.16xl0'8mol / cm2 / sec, but also reduced the ASR from 0.26 to 0.1 Qcm2.Specific Examples 4

[0090] In Specific Example 4, a hydrophobic polyvinyl chloride (PVC) polymer was blended into a Sustainion® membrane. PVC was first dissolved in Dimethylacetamide (DMAC) and a certain amount of PVC solution was mixed with polymer solution using homogenizer to get homogeneous solution. The solution was then cast on PET liner and dried in oven to form a membrane. The membrane was activated in IM KOH before test.

[0091] The permeability decreased to 5.18xl0'8mol / cm2 / sec with the increase of PVC concentrations in the membrane, while the ASR was very close to the original membrane up to 20% of PVC. However, the ASR increased significantly to 0.584 Qcm2when 50% PVC was added.Specific Examples 5

[0092] In Specific Examples 5, a barrier layer was introduced. The barrier layer comprised molecular sieve, clay layer, graphene, graphene oxide and polytetrafluoroethylene (PTFE) particles. The sandwich-type barrier layer was prepared as follows: A suspension with different fillers is prepared by mixing fillers via sonication in 10 ml of the polymer solution to make a 5% by weight suspension. A thin film of Sustainion® 37 solution is cast on polypropylene backing and dried at room temperature for 30min to yield a 15um thick membrane. Then, a 20pm of suspension containing filler is cast on top of theSustainion® 37 membrane and dried for 30min at room temperature. Finally, another 20pm thick Sustainion® 37 is cast on top of the film.

[0093] Area specific resistance and permeability were measured. The permeability was decreased by one order of magnitude to 4-7><10'8mol / cm2 / sec.

[0094] While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, that the invention is not limited thereto since modifications can be made by those skilled in the art without departing from the scope of the present disclosure, particularly in light of the foregoing teachings.

Claims

What is claimed is:Claim 1. A system comprising: an CO2 electrolyzer; and a product separation unit.Claim 2. The system of claim 1, wherein the CO2 electrolyzer comprises: a cathode compartment; an anion exchange membrane; a center compartment; a cation exchange membrane; and an anode compartment.Claim 3. The system of claim 2, wherein the cathode compartment comprises: a cathode flow field; a cathode gas diffusion layer; and a cathode catalyst layer.Claim 4. The system of claim 3, wherein the cathode flow field has serpentine channels machined in stainless steel plate.Claim 5. The system of claim 3, wherein the cathode catalyst layer comprises copper-based nanostructures selected from the group consisting of nanoparticles, nanosheets, and nanocubes, applied to said cathode gas diffusion layer, and configured to convert CO2 to alcohol.Claim 6. The system of claim 2, wherein the center compartment is positioned between:said anion exchange membrane adjacent to the cathode compartment; and said cation exchange membrane adjacent to the anode compartment.Claim 7. The system of claim 2 wherein said anion exchange membrane comprises a benzyl group bonded to at least one of: an imidazolium, a pyridinium, a pyrazolium, a pyrrolidinium, a pyrrolium, a pyrimidium, a piperidinium, an indolium, a triazinium, a phosphonium or a quaternary amine.Claim 8. The system of claim 2 wherein said anion exchange membrane comprises an inorganic filler, an organic filler and / or a barrier layer.Claim 9. The system of claim 2 wherein said the center compartment comprises an ion exchange media.Claim 10. The system of claim 9 wherein said ion exchange media comprise a cation exchange resin, an anion exchange resin beads, a cation exchange fiber felt, and / or anion exchange fiber felt.Claim 11. The system of claim 9 wherein said ion exchange media has a thickness of 2mm.Claim 12. The system of claim 2 wherein said cation exchange membrane is a Nafion membrane with a thickness of less than 400um.Claim 13. The system of claim 2, wherein said the anode compartment comprises: an anode flow field;an anode gas diffusion layer; and an anode catalyst layer.Claim 14. The system of claim 13, wherein said the anode flow field has serpentine channels machined in titanium plate.Claim 15. The system of claim 13, wherein the anode catalyst layer comprises a Pt / C and / or Pt alloy nanoparticle catalyst applied to said anode gas diffusion layer, configured to oxidize H2 and reduce cell voltage.Claim 16. The system of claim 1, wherein the product separation unit comprises a condenser.Claim 17. The system of claim 16, wherein the condenser separates alcohol products from unreacted H2 and / or CO2 that is then recycled to feed said CO2 electrolyzer.Claim 18. The system of claim 1, wherein said system is modular.Claim 19. A method of using an electrolyzer to produce alcohol from CO2.Claim 20. A system comprising an electrolyzer to produce fuel from CO2.Claim 21. An electrolyzer.

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