Patent Publication Number: US-2019170046-A1

Title: Conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives

Description:
BACKGROUND 
     Field 
     Embodiments of the present disclosure generally relate to a carbon dioxide conversion system and, more specifically relate to a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives. 
     Technical Background 
     Vehicles driving on roads and in factories throughout the world generate carbon dioxide as part of the exhaust from their propulsion systems. The carbon dioxide is generally formed as a waste product from the combustion of hydrocarbons in an internal combustion utilizing gasoline, diesel, or natural gas for example. The persistent release of carbon dioxide, considered a greenhouse gas, into the atmosphere is considered a contributing factor by scientists to increases in global temperatures. The ability to capture the carbon dioxide from a vehicle&#39;s exhaust and sequester it in an alternative form is considered desirable to reduce the release of carbon dioxide into the environment. 
     Carbon dioxide capture and conversion is a challenging process due to the energy intensity of conversion with carbon dioxide being a stable chemical. Presently the energy used in carbon dioxide conversion processes comes from fossil fuels. Utilization of fossil fuels to convert captured carbon dioxide is counterproductive to the original purpose of a carbon capture process. Specifically, burning carbon dioxide generating fossil fuels to convert captured carbon dioxide does not result in a net reduction in carbon dioxide expelled into the environment because of inefficiencies in the conversion process and the energy required to initially capture the carbon dioxide. 
     Accordingly, ongoing needs exists for efficient carbon capture and utilization where carbon dioxide conversion processes are environmentally green and produce fuels with sufficient thermal efficiency which can be utilized immediately. 
     SUMMARY 
     Embodiments of the present disclosure are directed to a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives. Carbon dioxide captures from vehicle exhaust and stored on-board the emitting vehicle is delivered to a fueling station where it can be converted to a variety of fuel blends like octane enhances such as methanol and cetane enhanced such as dimethyl ether. The system may convert the collected CO 2  to only one type of fuel blend or more than one blend using multiple CO 2  conversion units. The fuels created may also be blended if necessary for optimum use and composition for varying vehicle types. As the conversion of the CO 2  is completed at the same site as refueling of the vehicle the system eliminates the need to transport captured CO 2  from the fueling stations for conversion and minimizes infrastructure needs for the mobile carbon dioxide capture. 
     According to one embodiment, a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives is provided. The system comprises a carbon dioxide collection system, an external power source, an electrolyzer, and a carbon dioxide conversion system. The carbon dioxide collection system interfaces with a mobile carbon dioxide capture system onboard a vehicle to transfer CO 2  captured from vehicle exhaust to a vessel in the carbon dioxide collection system. The external power source provides the energy required for operation of the carbon dioxide conversion system and the electrolyzer. The electrolyzer separates a water feed into hydrogen and oxygen to generate a hydrogen feed and an oxygen feed. The carbon dioxide conversion system converts the CO 2  collected from the exhaust of the vehicles and delivered to the carbon dioxide collection system and the hydrogen feed from the electrolyzer into useful liquid fuels and fuel additives through electrochemical reduction. 
     In a further embodiment, a further system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives is provided. The system comprises a carbon dioxide collection system, an external power source, a carbon dioxide conversion system, and a liquid fuel blending system. The carbon dioxide collection system interfaces with a mobile carbon dioxide capture system onboard a vehicle to transfer CO 2  captured from vehicle exhaust to a vessel in the carbon dioxide collection system. The external power source provides the energy required for operation of the carbon dioxide conversion system. The carbon dioxide conversion system converts the CO 2  collected from the exhaust of the vehicles and delivered to the carbon dioxide collection into useful liquid fuels and fuel additives through electrochemical reduction. The liquid fuel blending system comprising one or more mixing units which combine the liquid fuels and fuel additives produced by the carbon dioxide conversion system in various ratios or combine one or more of the liquid fuels and fuel additives produced by the carbon dioxide conversion system with one or more traditional fossil fuels in various ratios. 
     Additional features and advantages of the embodiments described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawings. 
     It is to be understood that both the foregoing general description and the following detailed description describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying drawings are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification. The drawings illustrate the various embodiments described herein, and together with the description serve to explain the principles and operations of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a flow chart of a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels in accordance with one or more embodiments of the present disclosure. 
         FIG. 2  is a flow chart of a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives in accordance with one or more embodiments of the present disclosure. 
         FIG. 3  is a flow chart of a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives with an oxidation reactor in accordance with one or more embodiments of the present disclosure. 
         FIG. 4  is a reaction scheme illustrating an example series of oxidative chemical reactions to form a cetane boosting additive and octane boosting additive from toluene. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives of the present disclosure. Though the systems for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives of  FIGS. 1, 2, and 3  are provided as exemplary, it should be understood that the present systems encompass other configurations. 
     The system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives aims to convert compressed captured CO 2  from vehicles into fuels and blending components on-site at the location of collection of the captured CO 2  and the fueling station. A synergy is provided where carbon dioxide processed in the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives is captured from mobile sources to reduce the carbon footprint of the mobile sources, but is then also utilized and converted to high value liquid fuels. The system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives can take energy from non-fossil sources such as solar and wind and store the collected energy in the form of high energy liquid fuels. By collecting carbon dioxide from vehicles via mobile collection and converting the carbon dioxide to liquid fuels at a fueling station the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives eliminates the need to secondarily transport captured carbon dioxide to a conversion plant. The carbon dioxide is delivered by the vehicle concurrently with the vehicle filling its fuel tank with liquid fuel generated at the same location. 
     With reference to  FIG. 1 , the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives includes a carbon dioxide collection system  10 , an external power source  20 , an electrolyzer  30 , and a carbon dioxide conversion system  40 . A mobile carbon dioxide capture system captures CO 2  on board a vehicle from an exhaust stream of the vehicle and delivers it to a fuel station and the carbon dioxide collection system  10 . The CO 2  captured in the mobile carbon dioxide capture system is delivered to the carbon dioxide collection system  10  for utilization in the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives. The external power source  20  provides the energy required for operation of the carbon dioxide conversion system  40  and the electrolyzer  30 . The electrolyzer  30  provides the carbon dioxide conversion system  40  with a hydrogen feed  32  from the splitting of water in a water feed  36  to the electrolyzer  30  into its constituent parts of hydrogen and water. Utilizing compressed CO 2  from the carbon dioxide collection system  10 , the hydrogen feed  32  from the electrolyzer  30 , and energy from the external power source  20 , the carbon dioxide conversion system  40  generates useful fuels that can be used in a variety of different vehicles and engine types. 
     The conversion of CO 2  may be done either by unloading it at a fuel station while fueling the vehicle, specifically fueling and unloading CO 2  concurrently or sequentially, then transporting it to a larger centralized conversion plant or by converting it at the fuel station if the area allows for fitting such technology. Converting the CO 2  at the fuel station will reduce transportation costs and emissions resulting from the fuel burned to transport the fuels to a conversion plant. 
     The mobile carbon dioxide capture system may be any system affixed to or integrated with a vehicle&#39;s exhaust system configured to capture CO 2  from the vehicle exhaust stream. The specific configuration and mechanisms for CO 2  capture, collection, and storage on-board the vehicle are outside the scope of this disclosure. Non-limiting examples of mobile carbon dioxide capture systems are provided in U.S. Pat. No. 9,175,591 issued on Nov. 3, 2015 and directed to a Process and System Employing Phase-Changing Absorbents and Magnetically Responsive Sorbent Particles for On-Board Recovery of Carbon Dioxide from Mobile Sources, the contents of which are incorporated by reference. Further non-limiting examples of mobile carbon dioxide capture systems are provided in U.S. Pat. No. 9,180,401 issued on Nov. 10, 2015 and directed to a Liquid, Slurry and Flowable Powder Adsorption/Absorption Method and System Utilizing Waste Heat for On-Board Recovery and Storage of CO 2  from Motor Vehicle Internal Combustion Engine Exhaust Gases, the contents of which are incorporated by reference. 
     In one or more embodiments the carbon dioxide collection system  10  interfaces with the mobile carbon dioxide capture system to transfer CO 2  captured from vehicle exhaust to a vessel in the carbon dioxide collection system  10 . The interface may be any transfer mechanism and configuration known to one skilled in the art. For example, CO 2  may be transferred via a pressurized hose connected to ports on the carbon dioxide collection system  10  and the reservoir of the mobile carbon dioxide capture system. The transfer mechanism for unloading the CO2 to the carbon dioxide collection system  10  from the reservoir of the mobile carbon dioxide capture system may be the same or similar to those utilized for filling natural gas in a compressed natural gas (CNG) engine vehicle as both systems are configured for transfer of compressed gases. Additionally, safety measures utilized for filling natural gas in a CNG engine vehicle may also be implemented in the transfer between the carbon dioxide collection system  10  and the reservoir of the mobile carbon dioxide capture system. 
     In one or more embodiments the carbon dioxide collection system  10  comprises a CO 2  storage vessel for storage of compressed CO 2 . The CO 2  storage vessel may be located at the fueling station, the actual CO 2  conversion plant, or at least one CO 2  storage vessel at each location. It will be appreciated that the CO 2  storage vessel may be sized according to the demands of the carbon dioxide conversion system  40  and the volume of CO 2  deposited by the mobile carbon dioxide capture systems. The CO 2  may be retained in the CO 2  storage vessel at an elevated pressure. In various embodiments, the pressure in the CO 2  storage vessel is sufficiently high to retain the CO 2  in a liquid form. CO 2  forms a liquid at approximately 860 pounds per square inch (psi) or 58.5 atmosphere (atm) at 72° F. (22.2° C.). To ensure the CO 2  maintains its liquid state. In various embodiments the pressure in the CO 2  storage vessel may range from 100 to 300 bar at ambient temperatures. 
     In one or more embodiments, the external power source  20  provides the energy required for operation of the carbon dioxide conversion system  40  and the electrolyzer  30 . The external power source  20  provides the energy to power the conversion of the CO 2  collected in the mobile carbon dioxide capture system and delivered to the carbon dioxide collection system  10  to liquid fuels and fuel additives. In one or more embodiments the external power source  20  comprises non-fossil energy to provide power to the carbon dioxide conversion system  40 , the electrolyzer  30 , or both. Examples of non-fossil energy used on one or more embodiments include wind power from an on-site wind power generator, solar power from an on-site photovoltaic array, or hydroelectric power from an on-site hydroelectric generator. 
     In one or more embodiments the electrolyzer  30  separates a water feed into hydrogen and oxygen to generate a hydrogen feed  32  and an oxygen feed  34  through an electrolysis process. Specifically, electrolysis of water is the decomposition of water into oxygen and hydrogen gas as a result an electric current being passed through the water. In practice in the electrolyzer  30 , a DC current from the external power source  20  is connected to two electrodes, or two plates which are placed in the water. The electrodes or plates are typically made from an inert metal such as platinum, stainless steel or iridium. Hydrogen appears at the cathode electrode or plate where electrons enter the water and oxygen appears at the anode electrode or plate. Assuming ideal faradaic efficiency, the amount of hydrogen generated is twice the amount of oxygen, and both are proportional to the total electrical charge conducted by the solution. The hydrogen feed  32  is provided to the carbon dioxide conversion system  40  for utilization in the conversion CO 2  to useful liquid fuels and fuel additives. 
     In pure water at the negatively charged cathode, a reduction reaction takes place, with electrons (e) from the cathode being given to hydrogen cations to form hydrogen gas. The half reaction at the cathode is in accordance with reaction (1). 
       2H + (aq)+2 e   − →H 2 (g)  (1)
 
     Similarly, at the positively charged anode, an oxidation reaction occurs, generating oxygen gas and giving electrons to the anode to complete the circuit in accordance with reaction (2). 
       2H 2 O(l)→O 2 (g)+4H + (aq)+4 e   −   (2)
 
     The overall reaction when the two half reactions are combined produces 2 molecules of hydrogen gas (H 2 ) and one molecule of oxygen gas (O 2 ) from every two molecules of water (H 2 O) in accordance with reaction (3). 
       2H 2 O(l)→2H 2 (g)+O 2 (g)  (3)
 
     The electrolysis reaction of water into hydrogen and water has a standard potential of −1.23 V, meaning it ideally requires a potential difference of 1.23 volts to split the water. However, electrolysis of pure water requires excess energy in the form of overpotential to overcome various activation barriers. Without the excess energy the electrolysis of pure water occurs very slowly or not at all due to the limited self-ionization of water. The efficiency of the electrolyzer  30  may be increased through the addition of an electrolyte such as a salt, an acid or a base and the use of electrocatalysts. 
     The carbon dioxide conversion system  40  performs the actual conversion of the CO 2  collected from the exhaust of vehicles and delivered to the carbon dioxide collection system  10  into useful liquid fuels and fuel additives  42 . The carbon dioxide conversion system  40  operates in accordance with any known chemical conversion of CO 2  to liquid fuels or fuel additives  42  known to one skilled in the art. In one or more embodiments, the CO 2  is converted to fuels and fuel additives  42  in a 2-step process. Specifically, hydrogen is produced from water through electrolysis in the electrolyzer  30  in a first step, then using the H 2  as a feed to the carbon dioxide conversion system  40  to produce fuels  42  from the CO 2  in the second step. Systems and processes for converting H 2  and CO 2  to useful fuels  42  are known to those skilled in the art. Any known process for converting H 2  and CO 2  to useful fuels  42  may be utilized in the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives of the present disclosure. 
     The carbon dioxide conversion system  40  may utilize a catalyst to drive the electrochemical reduction of CO 2  to liquid fuels and fuel additives  42 . In various embodiments, the catalysts used for the electrochemical reduction of CO 2  include metal macrocycles such as Ni(I) and Ni(II) macrocycles, Co(I) tetraaza macrocycles, Pd complexes, Ru(II) complexes, and Cu(II) complexes. To produce an organic peroxide a catalyst such as N-Hydroxyphthalimide may be utilized. To produce an alcohol or aldehyde a two catalyst system such as N-Hydroxyphthalimide and Cobalt or similar metal may be utilized. 
     The electrochemical reduction of CO 2  may generate a variety of products. Some products are spontaneously generated and other products require input of additional energy to drive the reaction. As a general rule, the Gibbs Free energy (ΔG °) must be negative for the reaction to spontaneously occur at constant temperature and pressure. Similarly, the standard potential (e) must be positive for the reaction to spontaneously occur at constant temperature and pressure. The only CO 2  reactions that are spontaneous are reactions with metal oxides or metal hydroxides to form metal carbonates, and some reactions with high energy molecules such as peroxides. Table 1 provides the Gibbs Free energy and standard potential for various electrochemical reductions of CO 2 . A non-spontaneous reaction requires energy input to increase the Gibbs energy of the product compared to the reactants. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Gibbs Free energy and standard potential 
               
               
                 for electrochemical reduction of CO 2   
               
            
           
           
               
               
               
            
               
                 Reaction 
                 ΔG 0  (kJ/mol) 
                 E 0   
               
               
                   
               
            
           
           
               
               
               
            
               
                 CO 2  + e −  → CO 2   −   
                 183.32 
                 −1.90 
               
               
                 CO 2  + 2H +  + 2e −  → CO + H 2 O 
                 19.88 
                 −0.10 
               
               
                 CO 2  + 2H +  + 2e −  → HCOOH 
                 38.40 
                 −0.20 
               
               
                 CO 2  + 6H +  + 6e −  → CH 3 OH + H 2 O 
                 −17.95 
                 0.03 
               
               
                 CO 2  + 8H +  + 8e −  → CH 4  + 2H 2 O 
                 −130.40 
                 0.17 
               
               
                 2CO 2  + 12H +  + 12e −  → C 2 H 4  + 4H 2 O 
                 −40.52 
                 0.07 
               
               
                 2CO 2  + 12H +  + 12e −  → C 2 H 5 OH + 3H 2 O 
                 −49.21 
                 0.085 
               
               
                 3CO 2  + 18H +  + 18e −  → C 3 H 7 OH + 5H 2 O 
                 −52.1 
                 0.09 
               
               
                   
               
            
           
         
       
     
     In further embodiments, CO 2  can also be converted into liquid fuels  42  in a single step process where water and CO 2  are used directly. That is the electrolyzer  30  is omitted from the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives and water and CO 2  are fed directly to the carbon dioxide conversion system  40 . For example, the electrochemical conversion of CO 2  into ethanol using a copper nanoparticle/n-doped graphene electrode completes the transformation in a single step process. Such a single step process is detailed in Yang Song, et al., “High-Selectivity Electrochemical Conversion of CO 2  to Ethanol using a Copper Nanoparticle/N-Doped Graphene Electrode” ChemistrySelect 2016, 1, 1-8 which is incorporated by reference in its entirety. In this process, CO 2  and water are used as reactants in a fuel cell where an electrochemical reaction takes place to produce ethanol directly. 
     The carbon dioxide conversion system  40  converts H 2  and CO 2  or water and CO 2  to useful fuels and fuel additives  42 . A variety of fuels  42  may be formed with uses as both fuels directly as well as octane or cetane enhancers for mixture with conventional fuels. The Research Octane Number (RON) is used to measure the resistance of fuels to auto-ignition and is an important specification for internal combustion engines. Table 2 provides the properties for a variety of formed liquid fuels as well as the high-level synthesis procedure and use. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Example Liquid Fuels and Fuel Additives 
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                   
                 Boiling 
                   
                   
                   
                   
                   
                   
               
               
                   
                 Point 
                   
                 Δ c H° 
                 Δ f G° 
                 Synthesis 
                 Synthesis 
               
               
                 Product 
                 (° C.) 
                 RON 
                 (MJ/L) 
                 (kJ/mol) 
                 Materials 
                 Conditions 
                 Example Use 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
            
               
                 Dimethyl 
                 −24 
                 35 
                 −23.3 
                 −112.9 
                 Catalyst 
                 Reaction at 
                 Fuel blend 
               
               
                 Ether 
                   
                 (55-60 
                   
                   
                 to reduce 
                 less than 
                 with Diesel 
               
               
                   
                   
                 CN) 
                   
                   
                 CO 2   
                 200° C. 
                 and Cetane 
               
               
                   
                   
                   
                   
                   
                   
                   
                 enhancer 
               
               
                 Methanol 
                 64.7 
                 110-116 
                 −17.9 
                 −166.2 
                 Catalyst 
                 Reaction at 
                 Octane 
               
               
                   
                   
                   
                   
                   
                 and 
                 125-165° C. 
                 enhancer 
               
               
                   
                   
                   
                   
                   
                 Ethereal 
               
               
                   
                   
                   
                   
                   
                 solvent 
               
               
                 Ethanol 
                 78.37 
                 113 
                 −22.3 
                 −174.1 
                 Catalyst 
                 Reaction at 
                 Octane 
               
               
                   
                   
                   
                   
                   
                 and water 
                 Room 
                 enhancer 
               
               
                   
                   
                   
                   
                   
                 (2-step 
                 Temperature 
               
               
                   
                   
                   
                   
                   
                 process) 
               
               
                 Propanol 
                 97 
                 109-118 
                 −24 
                 −170.7 
                 Catalyst, 
                 Reaction at 
                 Octane 
               
               
                   
                   
                   
                   
                   
                 C 2 H 4 , 
                 approximately 
                 enhance 
               
               
                   
                   
                   
                   
                   
                 and H 2   
                 200° C. 
               
               
                 Ethylene 
                 −103.7 
                 N/A 
                 −28.576 
                 68.1 
                 Catalyst 
                 Reaction at 
                 Compressed 
               
               
                   
                   
                   
                   
                   
                 to reduce 
                 Room 
                 Natural Gas 
               
               
                   
                   
                   
                   
                   
                 CO 2   
                 temperature 
                 Fuel and 
               
               
                   
                   
                   
                   
                   
                   
                   
                 energy 
               
               
                   
                   
                   
                   
                   
                   
                   
                 Carrier 
               
               
                 Methane 
                 −161.5 
                 N/A 
                 −23.5 
                 50.6 
                 Catalyst 
                 Reaction at 
                 Compressed 
               
               
                   
                   
                   
                   
                   
                 to reduce 
                 less than 
                 Natural Gas 
               
               
                   
                   
                   
                   
                   
                 CO 2   
                 160° C. 
                 Fuel 
               
               
                   
               
            
           
         
       
     
     Which specific liquid fuels and fuel additives  42  are formed from the collected CO 2  may be determined at the fuel station level. For example, the options for producing dimethyl ether, methanol, or both may be made at the fuel depot which collects the CO 2  and generates the liquid fuel and fuel additives  42 . A given catalyst generally produces a single species out of all the potential liquid fuels and fuel additives capable of being produced with the carbon dioxide conversion system  40 . In one or more embodiments, the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives may include a single carbon dioxide conversion system  40  with a single catalyst capable of producing a single fuel or fuel additive  42 . In further embodiments, the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives may include a multiple carbon dioxide conversion systems  40 , each with a single catalyst capable of producing a single fuel or fuel additive  42 , to allow for the production of multiple liquid fuels and fuel additives concurrently. It will be appreciated that a single carbon dioxide conversion system  40  may also include multiple catalysts which are selectable to generate different liquid fuels and fuel additives  42   a / 42   b  based on present demand and supply available at the fueling station. 
     With reference to  FIG. 2 , in one or more embodiments, the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives further includes a liquid fuel blending system  50 . The liquid fuel blending system  50  comprises one or more mixing units  52  which combine the products of the carbon dioxide conversion system  40  in various ratios or combine one or more of the products of the carbon dioxide conversion system  40  with one or more traditional fossil fuels in various ratios. The products of the carbon dioxide conversion system  40  are the liquid fuels and fuel additives  42 . For example, in one or more embodiments, one or more products of the carbon dioxide conversion system  40  are mixed with diesel fuel from a diesel fuel reservoir  60  to produce a high-cetane diesel  54 . Specifically, dimethyl ether from the carbon dioxide conversion system  40  may be mixed with the diesel fuel to produce the high-cetane diesel  54 . Further, in one or more embodiments, one or more products of the carbon dioxide conversion system  40  are mixed with gasoline from a gasoline reservoir  70  to produce a high-octane gasoline  56 . Specifically, methanol from the carbon dioxide conversion system  40  may be mixed with the gasoline to produce the high-octane gasoline  56 . A mid-octane liquid fuel  58  may also be formed by mixing the dimethyl ether and the methanol from the carbon dioxide conversion system  40  in various ratios. The ratios of dimethyl ether and methanol included in the final blend may vary based on the standards and specifications specific to the region where the blend is used. For example, in Europe, the current maximum oxygen content in the blend should not exceed 3.7 wt % (11 wt % dimethyl ether or 7.4 wt % methanol) assuming the blend contains only one of the components. Similarly, the current oxygen specification in the United States is 2.7 wt % (8 wt % dimethyl ether and 5.4% methanol). So the range can be anywhere between 0% and the max specification wt % set by the regulatory authorities in that region. 
     In one or more embodiments, the oxygen feed  34  produced by the electrolyzer  30  from the electrolysis of water to generate the hydrogen feed  32  for the carbon dioxide conversion system  40  is utilized to convert low octane components into high octane components for mixture with the liquid fuels. For example, low octane components such as paraffins may be converted into high octane components such as alcohols, ketones, and aldehydes using partial oxidation. Similarly, high cetane components may be formed such as peroxides. 
     With reference to  FIG. 3 , the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives may include an oxidation reactor  80  to oxidize original fuels  90 , liquid fuels generated by the carbon dioxide conversion system  40 , or a mixture of both into products with a greater octane or greater cetane. For purposes of this disclosure the term “original fuels” means hydrocarbons introduced directly into the system and not the products of the carbon dioxide conversion system  40 . The original fuels may be provided from a refinery or similar plant outside the carbon dioxide conversion system  40 . The oxidation reactor  80  may receive oxygen in the oxygen feed  34  from the electrolyzer  30  to oxidize feed streams of fuel to alcohols, aldehydes, ketones, peroxides, and other converted products which would be known to those skilled in the art. The hydrocarbons fed to the oxidation reactor  80  may comprise original fuels  90  such as naptha provided as a raw feed source, a mixture of one or more liquid fuels generated by the carbon dioxide conversion system  40 , or a mixture of both. 
     Table 3 provides some examples of generic Octane and Cetane enhancers which may be formed from the oxidation of fuel streams. The oxidation reactor  80  provides the added benefit of utilizing the waste oxygen produced by the electrolyzer  30  in generating the hydrogen feed  32  from water for the carbon dioxide conversion system  40  and in the process generating increased octane or increased cetane enhanced quality fuels. The enhanced quality fuels generated in the oxidation reactor  80  may be stored and utilized separately from the liquid fuels generated by the carbon dioxide conversion system  40  or may be mixed and combined in various ratios to generate a multitude of fuel products to meet fueling demands of various engine types. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Octane and Cetane enhancers formed from oxidizing fuels 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Synthesis 
                   
               
               
                 Product 
                 Synthesis Materials 
                 Conditions 
                 Example uses 
               
               
                   
               
               
                 Organic 
                 Hydrocarbon, O 2  and 
                 Reaction at 
                 Cetane enhancer 
               
               
                 peroxide 
                 Catalyst (example: N- 
                 less than 
               
               
                   
                 Hydroxyphthalimide) 
                 100° C. 
               
               
                 Alcohols and 
                 Hydrocarbon, O 2  and 
                 Reaction at 
                 Octane enhancer 
               
               
                 Aldehydes 
                 two catalysts (example: 
                 less than 
               
               
                   
                 N-Hydroxyphthalimide 
                 100° C. 
               
               
                   
                 and Cobolt - or similar 
               
               
                   
                 metal) 
               
               
                   
               
            
           
         
       
     
     With reference to  FIG. 4 , and example scheme for generation of octane and cetane enhancers is provided. Specifically,  FIG. 4  provides the scheme for how toluene may be oxidized to generate benzyl hydroperoxide as a cetane boosting additive and subsequently benzoic acid as an octane boosting additive. The scheme also provides example catalysts which may be utilized to accomplish each step of the transformation. 
     The oxidation reaction produced in the oxidation reactor  80  is an exothermic reaction. The thermal energy released by the exothermic reaction in the oxidation reactor  80  may be utilized to reduce the energy demands of the external power source  20 . The thermal energy generated from the exothermic reactions may be utilized directly to heat feed streams to the carbon dioxide conversion system  40  or the electrolyzer  30 . The heat generated from the exothermic reactions in the oxidation reactor  80  can also be used directly in the chemical conversion of CO 2  in reactions that require heat for initiation to avoid the need for alternative supplemental heat. Similarly, the thermal energy generated from the exothermic reactions may be utilized indirectly to operate a generator to generate electrical power to augment the external power source  20 . Electricity may also be generated using devices for waste heat recovery such as thermoelectrics or using the Rankine cycle. 
     In one or more embodiments, the oxygen from the electrolyzer  30  is retained in an oxygen reservoir (not shown) and is provided to vehicles when the vehicles are off-loading collected CO 2  from the mobile carbon dioxide capture system which captured CO 2  on board the vehicle from the exhaust stream of the vehicle, fueling the vehicle with liquid fuels generated in the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives, or both. The vehicle may then oxidize fuels onboard with an on-board oxidation system (not shown) to produce increased cetane or octane fuels. 
     In one or more embodiments, the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives also includes a battery  22  electrically connected to the external power source  20 . The battery  22  may collect surplus electrical energy from the external power source  20  during times when the carbon dioxide conversion system  40  and the electrolyzer  30  do not utilize the entirety of the power generated by the external power source  20 . In one or more embodiments, the battery  22  may directly power the carbon dioxide conversion system  40  and the electrolyzer  30  with the external power source  20  continuously recharging the battery  22 . In further embodiments, the external power source  20  may power the carbon dioxide conversion system  40  and the electrolyzer  30  during times of operation and the battery  22  is only charged during pauses in the operation of the carbon dioxide conversion system  40  and the electrolyzer  30 . The battery  22  for storage of electrical energy is especially advantageous when the external power source  20  has variability or intermittency in the ability to generate power. For example, wind power generation may vary based on time of time, meteorological conditions, or other variables which affect wind speeds and direction and consequently affect power generation. Similarly, solar power generation may vary based on time of day, the solar calendar, meteorological condition, or other variable which affect the strength, position, and duration of solar energy reaching the photovoltaic cells. Even hydroelectric power generation may experience variability in power generation based on variability in flow rates as a result of drought conditions reducing release of water through the hydroelectric generators. 
     Arithmetic Examples 
     The formation of the liquid fuels and fuel additives from non-fossil fuel sources may be validated as feasible arithmetically. Specifically, the raw materials and energy required to process CO 2  captured from the exhaust of a vehicle and convert the same to a variety of liquid fuels and fuel additives may be calculated. Assuming 60% of CO 2  is captured on-board the vehicle and is delivered to the carbon dioxide collection system  10 , each vehicle would provide approximately 137 kilograms (kg) or 3113 moles of CO 2  per fueling cycle. Further assuming 100% conversion of the captured CO 2  to liquid fuels where Δ f G ° for CO 2  is −394.39 and for H 2 O is −237.14 kJ/mol, the energy required for conversion to specific liquid fuels and fuel additives may be determined. 
     It should now be understood the various aspects of the system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives are described and such aspects may be utilized in conjunction with various other aspects. 
     In a first aspect, the disclosure provides a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives. The system comprises a carbon dioxide collection system, an external power source, an electrolyzer, and a carbon dioxide conversion system. The carbon dioxide collection system interfaces with a mobile carbon dioxide capture system onboard a vehicle to transfer CO 2  captured from vehicle exhaust to a vessel in the carbon dioxide collection system. The external power source provides the energy required for operation of the carbon dioxide conversion system and the electrolyzer. The electrolyzer separates a water feed into hydrogen and oxygen to generate a hydrogen feed and an oxygen feed. The carbon dioxide conversion system converts the CO 2  collected from the exhaust of the vehicles and delivered to the carbon dioxide collection system and the hydrogen feed from the electrolyzer into useful liquid fuels and fuel additives through electrochemical reduction. 
     In a second aspect, the disclosure provides the system of the first aspect, in which the system further comprises a liquid fuel blending system, the liquid fuel blending system comprising one or more mixing units which combine the liquid fuels and fuel additives produced by the carbon dioxide conversion system in various ratios or combine one or more of the liquid fuels and fuel additives produced by the carbon dioxide conversion system with one or more traditional fossil fuels in various ratios. 
     In a third aspect, the disclosure provides the system of the first or second aspects, in which one or more products of the carbon dioxide conversion system are mixed with diesel fuel to produce a high-cetane diesel. 
     In a fourth aspect, the disclosure provides the system of the third aspect, in which wherein dimethyl ether from the carbon dioxide conversion system is mixed with diesel fuel to produce the high-cetane diesel. 
     In a fifth aspect, the disclosure provides the system of any of the first through fourth aspects, in which one or more products of the carbon dioxide conversion system are mixed with gasoline to produce a high-octane gasoline. 
     In a sixth aspect, the disclosure provides the system of the fifth aspect, in which wherein methanol from the carbon dioxide conversion system is mixed with gasoline to produce the high-octane gasoline. 
     In a seventh aspect, the disclosure provides the system of any of the first through sixth aspects, in which dimethyl ether and methanol from the carbon dioxide conversion system are mixed to form a mid-octane liquid fuel. 
     In an eighth aspect, the disclosure provides the system of any of the first through seventh aspects, in which external power source comprises non-fossil energy. 
     In a ninth aspect, the disclosure provides the system of the eighth aspect, in which the external power source comprises one or more of an on-site wind power generator, an on-site photovoltaic array, or an on-site hydroelectric generator. 
     In a tenth aspect, the disclosure provides the system of any of the first through ninth aspects, in which the carbon dioxide conversion system utilizes a catalyst to drive the electrochemical reduction of CO 2  to liquid fuels and fuel additives. 
     In an eleventh aspect, the disclosure provides the system of the tenth aspect, in which the catalysts used for the electrochemical reduction of CO 2  comprises one or more of metal macrocycles, Pd complexes, Ru(II) complexes, and Cu(II) complexes. 
     In a twelfth aspect, the disclosure provides the system of any of the first through eleventh aspects, in which the system further comprises an oxidation reactor configured to oxidize original fuels, liquid fuels generated by the carbon dioxide conversion system, or a mixture of both into products with a greater octane or greater cetane. 
     In a thirteenth aspect, the disclosure provides the system of any of the twelfth aspect, in which the oxidation reactor utilizes the oxygen feed generated in the electrolyzer as an oxidizing agent to oxidize the original fuels, the liquid fuels and fuel additives generated by the carbon dioxide conversion system, or the mixture of both into products with a greater octane or greater cetane. 
     In a fourteenth aspect, the disclosure provides the system of the twelfth or thirteenth aspects, in which thermal energy released by the oxidation of fuels in the oxidation reactor is utilized to reduce the energy demands of the external power source. 
     In a fifteenth aspect, the disclosure provides the system of the fourteenth aspect, in which the thermal energy released by the oxidation of fuels in the oxidation reactor is utilized directly in the carbon dioxide conversion system for the chemical conversion of CO 2  in reactions that require heat for initiation to reduce or eliminate the need for alternative supplemental heat. 
     In a sixteenth aspect, the disclosure provides the system of the fourteenth or fifteenth aspects, in which the thermal energy released by the oxidation of fuels in the oxidation reactor is utilized indirectly to operate a generator to generate electrical power to augment the external power source. 
     In a seventeenth aspect, the disclosure provides a system for on-site conversion of carbon dioxide from vehicle exhaust to liquid fuels and fuel additives. The system comprises a carbon dioxide collection system, an external power source, a carbon dioxide conversion system, and a liquid fuel blending system. The carbon dioxide collection system interfaces with a mobile carbon dioxide capture system onboard a vehicle to transfer CO 2  captured from vehicle exhaust to a vessel in the carbon dioxide collection system. The external power source provides the energy required for operation of the carbon dioxide conversion system. The carbon dioxide conversion system converts the CO 2  collected from the exhaust of the vehicles and delivered to the carbon dioxide collection into useful liquid fuels and fuel additives through electrochemical reduction. The liquid fuel blending system comprising one or more mixing units which combine the liquid fuels and fuel additives produced by the carbon dioxide conversion system in various ratios or combine one or more of the liquid fuels and fuel additives produced by the carbon dioxide conversion system with one or more traditional fossil fuels in various ratios. 
     In an eighteenth aspect, the disclosure provides the system of the seventeenth aspect, in which one or more products of the carbon dioxide conversion system are mixed with diesel fuel to produce a high-cetane diesel. 
     In a nineteenth aspect, the disclosure provides the system of the eighteenth aspect, in which dimethyl ether from the carbon dioxide conversion system is mixed with diesel fuel to produce the high-cetane diesel. 
     In a twentieth aspect, the disclosure provides the system of any of the seventeenth through nineteenth aspects, in which one or more products of the carbon dioxide conversion system are mixed with gasoline to produce a high-octane gasoline. 
     In a twenty-first aspect, the disclosure provides the system of the twentieth aspect, in which methanol from the carbon dioxide conversion system is mixed with gasoline to produce the high-octane gasoline. 
     In a twenty-second aspect, the disclosure provides the system of the any of the seventeenth through twenty-first aspects, in which dimethyl ether and methanol from the carbon dioxide conversion system are mixed to form a mid-octane liquid fuel. 
     In a twenty-third aspect, the disclosure provides the system of any of the seventeenth through twenty-second aspects, in which the external power source comprises non-fossil energy. 
     In a twenty-fourth aspect, the disclosure provides the system of the twenty-third aspect, in which the external power source comprises one or more of an on-site wind power generator, an on-site photovoltaic array, or an on-site hydroelectric generator. 
     In a twenty-fifth aspect, the disclosure provides the method of any of the seventeenth through twenty-fourth aspects, in which the system further comprises an oxidation reactor configured to oxidize original fuels, liquid fuels and fuel additives generated by the carbon dioxide conversion system, or a mixture of both into products with a greater octane or greater cetane. 
     In a twenty-sixth aspect, the disclosure provides the method of the twenty-fifth aspect, in which thermal energy released by the oxidation of fuels in the oxidation reactor is utilized to reduce the energy demands of the external power source. 
     In a twenty-seventh aspect, the disclosure provides the method of the twenty-sixth aspect, in which the thermal energy is utilized directly in the carbon dioxide conversion system for the chemical conversion of CO 2  in reactions that require heat for initiation to reduce or eliminate the need for alternative supplemental heat. 
     In a twenty-eighth aspect, the disclosure provides the method of the twenty-sixth or twenty-seventh aspects, in which the thermal energy is utilized indirectly to operate a generator to generate electrical power to augment the external power source. 
     It should be apparent to those skilled in the art that various modifications and variations can be made to the embodiments described herein without departing from the spirit and scope of the claimed subject matter. Thus it is intended that the specification cover the modifications and variations of the various embodiments described herein provided such modification and variations come within the scope of the appended claims and their equivalents. 
     It is noted that one or more of the following claims utilize the term “wherein” as a transitional phrase. For the purposes of defining the present invention, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure of the claimed subject matter and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.”