Patent Application
20240239654
The field of this invention is the production of low-carbon methanol, ethanol, or other liquids from low carbon H2 and CO2 at distributed generation sites, and the transport of these low-carbon liquids to chemical and/or fuel production sites, or other locations where low carbon hydrogen or syngas is needed. Improved processes are described for the efficient production of syngas from the low carbon H2 and CO2. The syngas is used for the catalytic production of the alcohols or other liquids which are transported to one or more production sites where low carbon hydrogen or syngas is needed. H2 is produced from the liquids at the production sites by catalytic steam reforming or other reforming or partial oxidation processes. Improved catalysts and processes are described for the efficient production of syngas from the liquids. This syngas is used to produce a variety of low-carbon fuels and chemicals. H2 produced from the liquids may be used in applications including fuel cell vehicles, hydrocracking, green diesel production, ammonia production, chemicals production, and other applications that require low carbon, zero carbon, or negative carbon hydrogen. In some applications, the CO2 produced from the production of H2 from the liquid H2 carrier is sequestered whereby the resulting H2 produced at the production site is carbon negative H2.
CO2 can be generated and captured by several processes generally involving the combustion of fuels, the oxidation of chemicals, gasification processes, petroleum refining, natural gas power production, etc. CO2 can also be produced through other industrial processes including ethanol production and other biological processes. In addition, emerging approaches to capturing CO2 from air (called Direct Air Capture—DAC) allow for CO2 capture from any location globally without being tied to an industrial source (Artz et al, 2018).
Since there are very few locations where suitable geological formations are available to sequester the CO2, it is much more suitable to produce fuels and chemical products from the CO2. Furthermore, CO2 is a valuable feedstock to produce low-carbon fuels and chemicals.
Low carbon electricity can be used to produce H2 using electrolysis (Equation 1). The low-carbon electricity can be generated from renewable power sources such as wind, solar, nuclear, hydroelectric, geothermal, biomass, biogas, or other ways to generate low carbon power.
The electrolysis reaction uses the low carbon electricity to split water into H2 and O2. Electrolyzers consist of an anode and a cathode separated by an electrolyte. Electrolysis for H2 production has been a working technology for many years. However, with decreases in the cost of renewable and low carbon electricity, interest in electrolysis has been increasing (Yan et al, 2019).
There are other forms of low carbon H2 including blue H2 (production of H2 from natural gas or renewable gas reforming) that employs carbon capture and storage, turquoise H2 (pyrolysis of natural gas/methane to produce H2 and carbon black or other products that sequester the carbon), and other methods of production of low-carbon H2.
Because H2 is a useful low carbon fuel source, there has been an increased interest in moving H2 from the generation site to the location of use. To date, H2 has be transported primarily as liquid H2 or compressed H2 (Schwartz, 2011).
More recently Liquid Organic H2 Carriers (LOHC) have been developed that hydrogenate the carrier molecule with H2 resulting in a liquid organic compound that can be easily transported (Hurskainen et al, 2020).
The LOHC hydrogenation is an exothermic reaction (releases heat) and is carried out at elevated pressures (approx. 30-100 bar) at temperatures of approximately 150-250° C. in the presence of a catalyst. The corresponding liquid compound is thereby formed, which can be stored or transported under ambient conditions. The H2 rich form of the LOHC is dehydrogenated, with the H2 being released again from the LOHC. This reaction is endothermic (heat input required) which typically takes place at elevated temperatures (250-320° C.) in the presence of a catalyst. Before the H2 can be used, it usually must be purified. The LOHC must usually be returned to the H2 generation location to complete the cycle (Preuster et al, 2017).
There are also some drawbacks to LOHCs that might limit their economic feasibility in some cases. One distinct feature is the high reaction enthalpies, meaning that a significant amount of heat is required to release the H2 from the LOHC. Considering the inevitable heat transfer losses, an approximate 25-30% of the released H2 needs to be combusted if the heat is provided by H2. Furthermore, as the required temperature level is quite high, it is not possible to use low-value waste-heat sources in most cases. One drawback is also that dehydrogenation must be carried out at close to atmospheric pressure, while hydrogenation in most cases requires some additional pressurizing. Where high-pressure H2 is required by the user, such as bottle filling stations or mobility applications which leads to a high energy demand for compression. Compression of H2 requires energy and adds capital costs.
Furthermore, the depleted LOHC must be delivered back to the H2 generation source. This complicates delivery chains if the same truck needs to deliver H2 to multiple locations in one trip. Lastly, the LOHC concept requires hydrogenation and dehydrogenation reactors, which increase H2 delivery costs.
Low molecular weight alcohols (e.g., methanol, ethanol, and propanol) and low molecular weight acids (e.g., formic, and acetic acid)—are theoretically excellent LOHCs. In addition, naphtha, diesel, kerosene or other light hydrocarbons may also serve as excellent hydrogen carriers. H2 can potentially be produced from these low-molecular weight alcohols and acids and hydrocarbons (Table 1).
Methanol, ethanol, and propanol have about the same abundance of H2, and the energy required to produce H2 from methanol and ethanol is about the same, but the energy required to produce H2 from propanol is 1.58 times greater than that of methanol. In addition, there is a greater probability of producing side products from ethanol and propanol than from the methanol. Formic acid and acetic acid are also potential LOHC's but the abundance of H2 in these carriers is much lower than that of the alcohols.
The energy required to produce H2 from naphtha, diesel, kerosene or a combination of some or all of these fractions (sometimes called e-crude) is about the same as that for methanol, but side products may be produced and therefore the yield of H2 is lower.
Methanol can be produced from syngas according to Equation 2. Currently, methanol is primarily produced from natural gas and coal. The fossil fuels are first steam reformed to syngas followed by the production of the syngas to methanol (NETL, 2021). The problem is that the methanol produced from fossil fuels is not a low-carbon product.
Syngas can potentially be commercially produced from the catalytic conversion of low-carbon H2 and captured CO2 mixtures. This catalytic process is called the Reverse Water-Gas Shift (RWGS) reaction or CO2 Hydrogenation (Equation 3) (Daza et al, 2016; Vogt et al, 2019; Chen et al, 2020).
This reaction is endothermic at room temperature and requires heat to proceed. Elevated temperatures and efficient catalysts are required for significant CO2 conversion to CO with minimal or no coking (carbon formation) or degradation in catalyst performance with time.
In addition to the production of alcohols, this low-carbon syngas is an excellent feedstock for producing a wide range of other chemical products, including liquid and gaseous hydrocarbon fuels, acetic acid, dimethyl ether, and many other chemical products (Olah et al, 2009; Centi et al, 2009; Jiang et al, 2010; Fischer et al, 2016; Li et al, 2019; NAS, 2019).
H2 is available from the electrolysis of water from low-carbon electricity or from other sources of low-carbon H2 generation at the generation site. CO2 is available from a nearby carbon capture facility, from direct air capture, from a CO2 pipeline, or from other sources. Geological or other conditions at the generation site usually do not allow for the nearby sequestration of the CO2.
At or near the generation site, captured CO2 and low-carbon H2 are processed in an improved two-step process to produce the liquid carrier. The liquid carrier can be any chemical or mixture of chemicals that is a liquid at ambient temperature and ambient pressure. For example, the liquid carrier may be a hydrocarbon or a mixture of hydrocarbons or the liquid carrier can be an alcohol such as methanol or ethanol, an acid, a chemical intermediary or a mixed alcohol or any other type of liquid carrier containing H2 and carbon.
The carrier is produced from the captured CO2 and renewable H2 that are available at the generation site. As described earlier, methanol or ethanol are potentially excellent H2 carriers.
Methanol is commercially produced from the catalytic reaction of H2 and CO in a fixed-bed tubular reactor operating at about 50 bar and 275° C. over a Cu—ZnO-based catalyst (Equation 4). The products are methanol (97%); ethanol (2%); methane (1%) and acetic acid (1%) (Hurley, Schuetzle et al, 2010).
An alternative method is to produce methanol from CO2 and H2 according to Equation 5.
Ethanol can also be produced from the exothermic reaction of H2 and CO at the generation site in a fixed-bed tubular reactor operating at about 50 bar and 275° C. over three catalysts in tandem reactors [#1: Cu—Zn-Alkali; #2: Rh—Y-Alkali; and #3 (Mo—Pd)]. The products are ethanol (72%); methanol (6%); methane (20%) and acetic acid (2%). (Hurley, Schuetzle et al, 2010) (Equation 6).
In addition, as summarized in the next section, no commercial catalysts have been successfully developed to date for the dehydrogenation of methanol or ethanol to produce syngas or H2.
Catalytic Reforming of Methanol—Since methanol is a liquid, it can be easily transported to a second site, the conversion site. If the objective is only to utilize H2 at the conversion site, then the H2 may be produced by catalytic steam reforming of the methanol which is an endothermic process according to Equation 7 (Palo et al, 2007; Iulianelli et al, 2014; Dalena et al, 2018).
The catalysts used for reforming govern the methanol conversion rate and the ratio of products (CO2, H2 and CO). Group VIII-XIII metals (primarily Cu, Pd and Zn) with different promoters have been widely utilized for methanol steam reforming since they produce a higher H2 yield. A semi-empirical model of the kinetics of the catalytic steam reforming of methanol over CuO/ZnO/Al2O3 catalyst has been developed (Amphlett et al, 1994).
A mixture of water and methanol with a molar concentration ratio of 1.0-1.5/1.0 is pressurized to approximately 20 bars, vaporized and heated to a temperature of 250-360° C. The H2 that is created is separated using pressure swing adsorption or a H2-permeable membrane (Dalena et al, 2018; Ranjekar and Yadav, 2021).
With either design, not all the H2 is removed from the product gases (raffinate). Since the remaining gas mixture still contains some chemical energy, it is often mixed with air and burned to provide additional heat for the endothermic reforming reaction.
CO2 is emitted (Equation 7) which decreases the life-cycle greenhouse gas value of the H2 produced. If the CO2 can be sequestered or commercially utilized at the conversion site, then the life-cycle greenhouse gas impact can be reduced.
Some of the H2 can be used as fuel for electricity generation or to produce fuels and chemicals. The H2 may also be used for hydrotreating applications in refineries, green diesel facilities, fuel cell vehicles, hydrocracking, ammonia production, chemicals production, and other applications that require low carbon, zero carbon, or negative carbon hydrogen.
It is preferable to convert the methanol to CO and H2 since CO2 is not produced. The H2 and CO can be separated or since the ratio of H2/CO has the ideal stoichiometry (1.5-2.5/1.0) it can be used to produce low-carbon fuels and chemicals (Schuetzle et al, 2010 and 2016). The production of CO and H2 can be catalytically converted from methanol according to the endothermic reaction given by Equation 8. The conversion of methanol to H2 has been typically referred to as methanol dehydrogenation.
The H2 and CO produced from the low-carbon methanol are low-carbon products. Therefore, if the H2 and CO are separated and the CO used as an energy resource for the production processes, then the CO2 is a low-carbon emission.
A few potential catalysts have been synthesized and tested for the reforming of methanol to syngas. It has been found that transition metal catalysts usually suffer from poor coke resistance during the dehydration of hydrocarbons in gas-solid heterogenous systems, including methanol dehydration.
Han et al (2020) synthesized and tested a catalyst comprised of atomically dispersed Ni sites in nitrogen-doped carbon sheets. They synthesized two types of catalysts. The composition of catalyst #1 was 18.3 wt. % Ni on nitrogen-doped carbon and catalyst #2 was produced by acid etching of catalyst #1 which reduced the Ni to 9.3 wt. %. These catalysts were tested for the conversion of methanol to CO and H2 at 15 psig, a space velocity of 16,000 h−1, and a temperature of 350° C. Catalyst #1 and catalyst #2 had losses in activity of 44% and 2%, respectively after 24 hours. In conclusion, these carbon-based catalysts are difficult to synthesize, they are very fragile, and their reductions in performance with time are not acceptable.
Carraro et al (2018) synthesized and tested a 5 wt. % Pd on CeO2 catalysts for the conversion of methanol to syngas at 300° C. The methanol conversion efficiency was 95% for the first five hours of conversion but dropped to about 85% after fifteen hours. Surface analysis of the catalyst demonstrated that the drop in performance was the result of carbon formation on the surface of the catalyst.
Matsumurakoji et al (2000) synthesized a 10 wt. % Ni on silica catalyst and studied its performance for the decomposition of methanol to CO and H2 at 350° C. They found that carbon deposited on the catalyst after 30 hours which significantly reduced the catalyst efficiency.
An improved catalyst and process has been developed and is described herein that contains no or low precious metals and which consists of low-cost, readily abundant metals.
One preferred catalyst is a Pd—Ag catalyst. Another preferred catalyst is a nickel solid solution catalyst. Another catalyst is a metal alumina spinel impregnated with one or more Group I and Group 2 elements.
This catalyst is comprised of a metal alumina spinel substrate or any other alumina substrate that has a surface area greater than about 50 m2/g that has been impregnated with one or more of the following (Cu, Mg, Ni and Zn) elements at a combined concentration of up to 15 parts-by-weight and up to 5 wt. % of La or Ce, and wherein the metal alumina spinel is selected from a group consisting of magnesium aluminate, calcium aluminate, strontium aluminate, potassium aluminate and sodium aluminate. The catalyst consists of one or more substitutional solid solutions on the metal impregnated metal-alumina spinel.
This improved catalyst converts methanol or ethanol to syngas with a per pass efficiency of greater than 60% and 45%, respectively, at 100-450 psig, 400-550° F. and a space velocity of 5,000-25,000 hr−1. The syngas produced from the alcohols have an H2/CO ratio of 1.8-2.2/1.0.
Since methanol and ethanol are acidic in nature, they react readily with basic surfaces of this catalyst that have abundant hydroxy (M-OH) groups to form HCOO-M and H2 as shown in Equation 9 for methanol.
CO is then quickly released at the catalyst operating temperatures from the complex as shown by Equation 10.
Therefore, the combination of processes from Equations 9 and 10 produce syngas with an H2/CO ratio of 2.0/1.0. In addition, the original catalyst surface M-OH is regenerated.
As described, formic acid (HCOOH) is also a possible H2 carrier. It also reacts readily with the catalyst basic surface (M) that have abundant hydroxy (OH) groups to form formates (HCOO-M) as shown in Equation 11.
The CO is quickly released from the complex at the catalyst operating temperature according to Eq. 10. Therefore, the combination of processes from Equations 10 and 11 produce syngas with an H2/CO ratio of 1.0/1.0.
Ethanol reacts with the basic catalyst surface in the same manner as methanol and it produces syngas with an H2/CO ratio of 2.0/1.0. As shown previously in Table 1, methanol and ethanol contain 6.25 and 6.50 mole % H2, respectively. However, the catalytic dehydrogenation of ethanol requires a higher catalyst operating temperature than that of methanol.
Methanol is a better H2 carrier than formic acid since it produces twice as much H2 for every carrier molecule. An advantage is that liquid H2 carriers such as methanol and ethanol are completely utilized at the generation site and the solid materials, typically used in LOHC, do not need to be returned to the generation site.
The transport of H2 carriers such as methanol, ethanol, naphtha, diesel and other liquid carriers is well known since they can use existing transportation infrastructure including truck, rail, barge, and other forms of transporting liquid fuels that are in widespread use today. The cost of the liquid H2 carrier transportation is significantly lower than the cost of transporting compressed H2 in tube trailers or liquid H2 in specialized trucks equipped to handle liquid H2.
In
Stream 2 is a stream comprising high-purity water. The water can be from any source that meets the water quality specifications required for different electrolysis systems or may be recycled water from the production system.
Stream 3 is a stream comprising CO2. CO2 is available from a nearby carbon capture facility, from a carbon dioxide pipeline, or captured from ambient air. CO2 can be generated and be captured by several processes generally involving the combustion of fuels, the oxidation of chemicals, gasification processes, petroleum refining, cement production, etc. For example, industrial manufacturing plants that produce ammonia for fertilizer produce large amounts of CO2. Ethanol plants that convert corn or wheat into ethanol produce large amounts of CO2 via fermentation. Power plants that generate electricity from various carbonaceous resources produce large amounts of CO2. Municipal sewage treatment systems using aerobic and anaerobic digestion of sludge produce large amounts of CO2. All these sources of CO2 can be used in the current invention.
The CO2 in stream 3 (
In
At least a portion of the liquid carrier, stream 4, is transported to another location called the conversion site of the invention shown in
Several combinations of transition metals, such as Pt2Mo, Hf2Fe, and TiPt, have been used as cathode materials and have shown significantly higher electrocatalytic activity than state-of-the-art electrodes.
Water at the anode combines with electrons from the external circuit to form oxygen gas, positively charged H2 ions, and electrons. The H2 ions pass through the membrane and combine with the electrons from the external circuit at the cathode to form H2 gas. In this way, both H2 and O2 are produced in the electrolyzer. In one embodiment of the invention, multiple electrolyzers are operated in parallel.
The electrolyzer produces at least two product streams, a H2 stream 21 (
Block 102 in
The RWGS reactor feed streams, stream 21 and stream 3, are blended in Block 102. The ratio of H2/CO2 in the RWGS feed stream is between 2.0 mol/mol to 5.0 mol/mol or more preferably between 3.0 mol/mol and 4.0 mol/mol. The mixed RWGS reactor feedstock must be heated to RWGS operating conditions. In one embodiment, the RWGS feed stream is heated to reaction temperature of greater than 1450° F. (e.g., between 1,450 and 1,800° F.), or preferably greater than 1,550° F. (e.g., between 1,550 and 1,750° F.) using a RWGS feed heater. In one embodiment, the RWGS feed heater is a fired heater that uses the combustion of H2 taken from stream 21 as the fuel gas that combusts with air to produce water and heat. This heat is used to raise the temperature of the RWGS feed stream.
In another embodiment, low carbon electricity is used in an electrical heater to raise the RWGS feed temperature. The heater is electrically heated and raises the temperature of the feed gas through indirect heat exchange to greater than 1,550° F. (e.g., between 1,550 and 1,750° F.).
The heated RWGS reactor feed gas is supplied to a main RWGS reactor. The main reactor vessel is adiabatic or nearly adiabatic and is designed to minimize heat loss. No heat is added to the main reactor vessel.
The product stream leaving the main RWGS reactor vessel (102) are comprised of CO, unreacted H2, unreacted CO2, and H2O. Additionally, the product stream may also comprise a small amount of methane (CH4) that was produced as a side reaction.
The product stream is shown in
In other embodiments, where CO is not used in the conversion block, 103, block 102 does not act as a RWGS reactor system but only acts only to mix and heat the feeds for block 103 listed as stream 22 in
Block 103 of
At least a portion of the RWGS product gas is used as the Liquid Fuel Production (LFP) reactor feed. Also, because the operating pressure of the RWGS reactor may be lower than that of the LFP operating pressure, the produced syngas may require compression to the LFP inlet pressure. The LFP is also known as the hydrocarbon synthesis step. The LFP reactor converts CO and H2 into C5-C24 hydrocarbons that can be used as liquid fuels and chemicals and, in this case, produces the liquid carrier, stream 4. Ideally the H2 to CO ratio in the feed to the LFP reaction is between 1.9 and 2.2 mol/mol but it may be below 1.9 or above 2.2 as necessary to modify the composition of the liquid stream. The LFP reactor is a multi-tubular fixed bed reactor system. The LFP reactor tube profile can be round, oval, flattened, twisted, or other variations. The LFP reactors are generally vertically oriented with LFP reactor feed entering at the top of the LFP reactor. However, horizontal reactor orientation is possible in some circumstances and setting the reactor at an angle may also be advantageous in some circumstances where there are height limitations. Most of the length of the LFP reactor tube is filled with LFP catalyst. The LFP catalyst may also be blended with diluent such as silica or alumina to aid in the distribution of the LFP reactor feed into and through the LFP reactor tube.
The LFP reactor in one embodiment is operated at pressures between 150 to 450 psig. The reactor is operated over a temperature range from 350° F. to 460° F. and more typically at around 410° F. The LFP reaction is exothermic in which the temperature of the reactor is maintained inside the LFP reactor tubes by the reactor tube bundle being placed into a heat exchanger where boiling water is present on the outside of the LFP reactor tubes. The boiler water temperature is at a lower temperature than the LFP reaction temperature so that heat flows from the LFP reactor tube to the lower temperature water. The shell water temperature is maintained by controlling the pressure of the produced steam. The steam is generally saturated steam. In alternate embodiments, the catalytic LFP reactor can be a slurry reactor, microchannel reactor, fluidized bed reactor, or other reactor types known in the art.
The CO conversion in the LFP reactor is maintained at between 30 to 80 mole % CO conversion per pass. Unconverted gas can be recycled for extra conversion or sent downstream to an additional LFP reactor. Multiple LFP reactors may also be used in series or in parallel.
In one embodiment, a series of fractionators are used to create a high cetane diesel fuel with an adjustable flash point, and a stabilized naphtha (potentially a gasoline blend stock or chemical feedstock) or a blended e-crude. The high cetane diesel fuel can be used as a liquid carrier (
In another embodiment, an alcohol synthesis reactor is used as the conversion device of Block 103 (
The CO2 separation block (Block 201) comprises a means in which, at a minimum, a stream comprising CO2 (Stream 7), and a means to produce electricity, shown as stream 23, are produced from the chemical conversion of the liquid carrier, stream 4. Optionally, a stream comprising H2 shown as stream 6 can be produced in Block 201. Block 201 may comprise multiple steps or processes for the conversion.
The CO2 separation block can be accomplished by several means that include steam reforming. In one embodiment, the liquid carrier comprises a system where the liquid carrier, 4, is reacted with steam to produce a product mixture of H2 and CO2 that can be separated into streams 6 and 7, respectively. In another embodiment, the liquid carrier can be steam reformed to produce a mixture of H2 and CO as shown by Equation 7. The H2 in the steam reformer product can be separated to become stream 6.
A mixture of water and methanol with a molar concentration ratio (water/methanol) of 1.0-1.5 is pressurized to approximately 300 psig, vaporized, and heated to a temperature of 250-360° C. The H2 that is created is separated using pressure swing adsorption (PSA), an H2-permeable membrane, or a palladium alloy. There are two basic methods of conducting this process.
The water-methanol mixture is introduced into a tube-shaped reactor where it contacts the catalyst. H2 is then separated from the other reactants and products in a later chamber, either by PSA or through use of a membrane where the majority of the H2 passes through.
The other process features an integrated reaction chamber and separation membrane, a membrane reactor. The reaction chamber is made to contain high-temperature, H2-permeable membranes that can be formed of refractory metals, palladium alloys, or a Pd/Ag-coated ceramic. The H2 is thereby separated out of the reaction chamber as the reaction proceeds. This purifies the H2 and, as the reaction continues, increases both the reaction rate and the amount of H2 extracted.
With either design, not all the H2 is removed from the product gases. Since the remaining gas mixture still contains a significant amount of chemical energy, it can be mixed with air and burned to provide heat for the endothermic reforming reaction.
In one embodiment, the steam reforming system comprises an adiabatic reactor with limited heat loss. The steam reformer feed is heated in a steam reformer heater. In one embodiment, the steam reformer heater is heated to temperature by low carbon electricity through an electrical heater. In another embodiment, the steam reformer heater is heated to temperature by the combustion of H2 or a combination of H2, CO, and unconverted vaporized liquid carrier. In another embodiment, the steam reformer is operated at nearly isothermal conditions and the steam reformer feed is fed through multiple tubes that are in a heater fire box. In another embodiment, the steam reforming is performed using waste heat from an industrial facility or co-location facility at the conversion site. The combustion of H2 or a combination of H2, CO, and unconverted vaporized liquid carrier provides the heat of reaction. In one embodiment, the steam reformer feed is heated by cross exchange with the steam reformer product and additional heat from the electricity generation block, block 202.
In another embodiment, the CO2 conversion block, 201, comprises an oxy-combustion system in which the liquid carrier, stream 4, is reacted with nearly pure oxygen to produce a stream comprising CO2 and H2O. The oxy-combustor product stream can be separated such that a CO2 rich stream, stream 7, is produced. The oxygen is produced by an air separation unit or is available by pipeline.
In another embodiment, the CO2 conversion block, 201, comprises a partial oxidation system in which the liquid carrier, stream 4, is reacted with nearly pure O2 at a rate to accomplish the partial oxidation to a partial oxidation product comprising H2 and CO. The O2 to C ratio is controlled to approximately 0.50 to 0.55 on a molar basis to allow the partial oxidation instead of full combustion. This partial oxidation stream can be separated by PSA or other means to produce a nearly pure stream comprising H2, stream 6. The CO can be converted to CO2 through water gas shift or through further oxidation such that a stream comprising CO2 is produced, stream 7.
Both the oxy-combustion and the partial oxidation embodiments are exothermal under normal operation and require no additional external heat to heat the feed gas to full operating temperature, unlike the steam reforming embodiments.
The CO2 conversion reactors often result with product streams that are at elevated temperature. In one embodiment, a heat recovery system can be used to reduce the product gas temperature. Steam is generated in the cooling of the gas. The steam so generated in this embodiment is stream 23 and provides the motive force for the generation of electricity in electricity generating block, 202. In other embodiments, the high temperature heat and some portion of the product gas that is conveyed from the CO2 conversion reactors can be stream 23 that acts as a feed gas to a solid oxide fuel cell as one embodiment of the electricity generation block, 202.
The electricity generating block, 202, can be any number of electricity generation systems. These systems may include but are not limited to steam turbine systems, fuel cell systems, gas turbine systems, organic Rankine cycle systems, or Stirling engines systems.
A stream comprising CO2 is produced by an industrial process or captured from ambient air. This CO2 stream is fed to a CO2 capture facility. The CO2 capture facility uses methyl diethanolamine (MDEA) in an absorber tower to capture the CO2. Relatively pure CO2 (
Low-carbon electricity from a wind farm, a solar farm, a nuclear power plant, or other low-carbon power sources is available at the site of the carbon capture facility. High-purity water is produced from locally available water. Low-carbon H2 is produced from the purified water via electrolysis.
This reaction uses the low-carbon electricity to split the water into H2 and O2. The electrolyzer in this example is a PEM Electrolyzer, block 101 in
At the generation site, 100, the improved catalyst and catalytic reactor (
The product stream, stream 22 (
At least a portion of the methanol produced in the syngas-to-methanol reactor is the liquid carrier, stream 4, and is transported to a second site by rail, truck or by other suitable means, 200 (
At the conversion site, the transported methanol is converted to a stream of H2 and CO2 by a steam reforming process, 201 (
In this example, the catalyst in the reformer is a Pd—Ag catalyst. In another embodiment, the catalyst is a nickel solid solution catalyst, and in yet another embodiment the catalyst is a metal alumina spinel impregnated with one or more Group I and Group 2 elements.
The reactor is an adiabatic fixed bed reactor with a pressure drop of less than 25 psig across the reactor and catalyst bed. Over 95% (i.e., between 95% and 100%) of the methanol in the reformer feed is converted to CO2 and H2.
Some water and carbon monoxide are also present in the methanol reformer product. The methanol reformer product is cooled via cross exchange with the reformer feed stream. The methanol reformer product in this example is further processed in a pressure swing adsorption (PSA) unit to recover the H2. Before the PSA unit, most of the water in the reformer product stream is removed in a knock-out vessel. The knock-out vessel overheads become the feed to the PSA unit. The knock-out vessel bottoms which are predominantly water are recycled and used as a portion of the water that is blended with the methanol stream to produce the methanol reformer feed stream. The pressure swing adsorption unit comprises beds of solid adsorbent to separate impurities from the H2-rich methanol reformer product stream. The higher-pressure H2 in the reformer product and PSA feed stream is absorbed on the adsorbent. The adsorbent beds “swing” between impurity adsorbing and desorbing operations. This leads to a high-pressure PSA product stream that has a composition of over 95 volume % H2 at a pressure of 176 psig. The low-pressure PSA product is called tail-gas and has a pressure of 20 psig, a molar composition of approximately 22% H2, 71% CO2, 5% CO, and 2% water. Overall, through the PSA Unit, 90% of the H2 in the reformer product stream ends up in the high-pressure PSA product stream, stream 6.
The low-pressure PSA product stream still has H2, CO, and a small volume of unconverted vaporized liquid carrier that can be used to produce electricity, stream 23.
A stream comprising CO2 is produced by an industrial process or captured from ambient air. This CO2 stream is fed to a CO2 capture facility. The CO2 capture facility uses methyl diethanolamine (MDEA) in an absorber tower to capture the CO2. Relatively pure CO2 (
Low-carbon electricity from a wind farm, a solar farm, a nuclear power plant, or other low-carbon power sources is available at the site of the carbon capture facility. High-purity water is produced from locally available water. Low-carbon H2 is produced from the purified water via electrolysis.
This reaction uses the low-carbon electricity to split the water into H2 and O2. The electrolyzer in this example is a PEM Electrolyzer, block 101 in
At the generation site, 100, the improved catalyst #1 and catalytic reactor (
The product stream, stream 22 (
At least a portion of the ethanol produced in the syngas-to-ethanol reactor is the liquid carrier, stream 4 (
The transported ethanol is first stored in a storage tank. The ethanol is pumped from the storage tank at 200 psig, mixed with water, and heated to 260° C. by indirect heat exchange (where at least one of the reformer heat exchangers is a reformer feed and product cross-exchange heat exchanger in this case). The steam to carbon ratio in the water-ethanol mix is controlled to 1.5 on a molar basis. The heated ethanol-water mixture is fed to a catalytic reactor where the ethanol is converted to a stream of H2 and CO2, 201 (
In this example, the catalyst in the reformer is a Pd—Ag catalyst. In another embodiment, the catalyst is a nickel solid solution catalyst and in yet another embodiment the catalyst is a metal spinel impregnated with one or more Group I and Group 2 elements.
The reactor is an adiabatic fixed bed reactor with a pressure drop of 14 psi across the reactor and catalyst bed. Over 99% (i.e., between 99% and 100%) of the ethanol in the reformer feed is converted to H2 and CO2. Some H2O and CO are also present in the ethanol reformer product. The ethanol reformer product is cooled via cross exchange with the reformer feed stream. The ethanol reformer product in this example is further processed in a pressure swing adsorption (PSA) unit to recover the H2. Before the PSA unit, most of the H2O in the reformer product stream is removed in a knock-out vessel. The knock-out vessel overheads become the feed to the PSA unit. The knock-out vessel bottoms which are predominantly water are recycled and used as a portion of the water that is blended with the methanol stream to produce the methanol reformer feed stream. The pressure swing adsorption unit comprises beds of solid adsorbent to separate impurities from the H2 rich methanol reformer product stream. The higher-pressure H2 in the reformer product and PSA feed stream is absorbed on the adsorbent. The adsorbent beds “swing” between impurity adsorbing and desorbing operations. This leads to a high-pressure PSA product stream that has a composition of over 99 volume % H2 at a pressure of 176 psig. The low-pressure PSA product is called tail-gas and has a pressure of 20 psig, a composition by mole of about 22% H2, 71% CO2, 5% CO, and 2% H2O. Overall, through the PSA Unit, 90% of the H2 in the reformer product stream ends up in the high-pressure PSA product stream, stream 6.
The low-pressure PSA product stream still has H2, CO, and a small amount of unconverted vaporized liquid carrier that can be used to produce electricity, stream 23.
The present invention provides various processes and catalysts. In one aspect, the present invention provides a process “A” for utilizing captured carbon dioxide at a generation site. The process A involves: producing a hydrogen stream from water using an electrolyzer powered by low carbon electricity; utilizing a carbon dioxide stream from a carbon capture facility or a carbon dioxide pipeline; catalytically converting the hydrogen stream with the carbon dioxide stream to produce a low carbon syngas (e.g., H2 and CO mixture); catalytically converting the low carbon syngas to a liquid, low carbon H2 carrier; transporting at least a portion of the liquid (e.g., 10% to 100%) to a production site; catalytically converting the liquid low carbon H2 carrier to H2 or syngas.
The H2 produced from the liquid H2 carriers from process A can be used: as a fuel for vehicles; for the production of chemicals; for the production of power; for the production of green diesel; directly to produce low-carbon liquid fuels; directly to produce low-carbon chemicals; in the production of low carbon diesel, naphtha and jet fuel; for the production of low carbon, high-value chemical products; for the production of power.
The liquid hydrogen carrier produced in process A can be any suitable carrier, including: methanol, ethanol, propanol, a methanol/ethanol mixture, a methanol/propanol mixture, an ethanol/propanol mixture, a methanol/ethanol/propanol mixture, a hydrocarbon naphtha.
In another aspect, the present invention provides a process “B” for producing a hydrogen carrier and transporting it to a site where the hydrogen carrier is converted to hydrogen and carbon dioxide or syngas. The process B involves: producing an H2 stream; producing or obtaining CO2 that is converted to a CO2 stream; catalytically converting the H2 and CO2 streams to low carbon syngas; catalytically converting the low carbon syngas to a liquid, low carbon H2 carrier; transporting the low carbon H2 carrier, or a portion thereof, to a site; catalytically converting the low carbon H2 carrier at the site to hydrogen and carbon dioxide or syngas.
The H2 stream of process B is typically produced from water using an electrolyzer powered by low carbon electricity. In certain cases, the H2 stream is produced by splitting natural gas into hydrogen and carbon dioxide by steam methane reforming or auto thermal reforming. In other cases, the H2 stream is produced by pyrolyzing methane using electricity generated heat.
The low carbon electricity referenced in process B can be produced in any suitable way. It can, for instance be produced from: a wind farm, a solar farm, a nuclear power plant, a hydroelectric power plant, a geothermal power plant, or battery storage cells charged with intermittent electricity from wind farms or solar farms.
The carbon dioxide converted to a CO2 stream in process B can be produced and/or captured in a variety of ways, such as: production of CO2 by and industrial process; capture of CO2 from ambient air. Nonlimiting examples of industrial processes include: the combustion of fuels, the oxidation of chemicals, a gasification process, petroleum refining, cement production, fertilizer production, ethanol production, power production, or sewage treatment. Capture of CO2 from ambient air can involve reaction of CO2 with one or more amine solvents; chemisorption or physisorption of CO2 with one or more Metal Organic Framework materials; reaction of CO2 with a metal oxide material; direct air capture.
In certain cases, the H2 and CO2 streams referenced in process B are converted into low carbon syngas in a RWGS reactor. The ration of H2 to CO2 fed into the RWGS reactor is between 2.0 ml/mol and 5.0 mol/mol heated to a temperature between 1,450° F. and 1,800° F.
Oftentimes, the low carbon H2 carrier of process B is methanol or ethanol. The low carbon gas can be converted into methanol, for example, using a Cu—ZnO-based catalyst; the low carbon gas can be converted into ethanol, for example, using three catalysts in tandem reactors. The three catalysts are Cu—Zn-Alkali, Rh—Y-Alkali and Mo—Pd. It can be transported to another site using any suitable means including, without limitation: rail, truck, barge, boat, or pipeline.
In certain cases, the low carbon H2 carrier of process B is catalytically converted to a mixture containing hydrogen and carbon dioxide using a steam reforming process. The steam reforming process uses a catalyst selected from a Pd—Ag catalyst, a nickel solid solution catalyst or a metal alumina spinel impregnated with one or more Group 1 and Group 2 elements.
In other cases, the low carbon H2 carrier of process B is catalytically converted to syngas using a catalyst. The catalyst comprises a metal alumina spinel substrate that has a surface area between 50 m2/g and 150 m2/g and that is impregnated with one or more of Cu, Mg, Ni, and Zn at a concentration between 1 part-by-weight and 15 parts-by-weight. The catalyst further includes between 0.1 wt. % and 5 wt. % of La or Ce. The metal alumina spinel substrate is selected from a group of substrates consisting of magnesium aluminate, calcium aluminate, strontium aluminate, potassium aluminate and sodium aluminate. The catalyst typically includes one or two substitutional solid solutions on the metal impregnated metal-alumina spinel. Where the H2 carrier is methanol, it is oftentimes converted to syngas with a per pass efficiency between 60% and 95% at 100-450 psig; 400-550° F. and a space velocity of 5,000-25,000 hr−1. Where the H2 carrier is ethanol, it is oftentimes converted to syngas with a per pass efficiency between 45% and 95% at 100-450 psig, 400-550° F. and a space velocity of 5,000-25,000 hr−1.
In certain cases, the H2 carrier in process B is catalytically converted to syngas, which is then used as an LFP reactor feed. The LFP reactor can be a multi-tubular fixed bed reactor system that is vertically oriented with the LFP reactor feed entering at the top of the LFP reactor.
In another aspect, the present invention provides a catalyst “C” for the conversion of methanol or ethanol to syngas. The catalyst is bound to methanol or ethanol and comprises a metal alumina spinel substrate that has a surface area between 50 m2/g and 150 m2/g. The metal alumina spinel substrate is impregnated with one or two of Cu, Mg, Ni, and Zn at a concentration between 1 part-by-weight and 15 parts-by-weight. The catalyst further includes between 0.1 wt. % and 5 wt. % of La or Ce, and the metal alumina spinel substrate is selected from a group of substrates consisting of magnesium aluminate, calcium aluminate, strontium aluminate, potassium aluminate and sodium aluminate.
In certain cases, the metal alumina spinel substrate of catalyst C is magnesium aluminate or calcium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Cu, Mg or both, and wherein the catalyst further includes La. In other cases, the metal alumina spinel substrate of catalyst C is magnesium aluminate or calcium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Cu, Mg, or both, and wherein the catalyst further includes Ce. In other cases, the metal alumina spinel substrate of catalyst C is strontium aluminate, potassium aluminate or sodium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Cu, Mg, or both, and wherein the catalyst further includes La. In other cases, the metal alumina spinel substrate of catalyst C is strontium aluminate, potassium aluminate or sodium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Cu, Mg, or both, and wherein the catalyst further includes Ce. In other cases, the metal alumina spinel substrate of catalyst C is magnesium aluminate or calcium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Ni, Zn, or both, and wherein the catalyst further includes La. In other cases, the metal alumina spinel substrate of catalyst C is magnesium aluminate or calcium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Ni, Zn, or both, and wherein the catalyst further includes Ce. In other cases, the metal alumina spinel substrate of catalyst C is strontium aluminate, potassium aluminate or sodium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Ni, Zn, or both, and wherein the catalyst further includes La. In other cases, the metal alumina spinel substrate of catalyst C is strontium aluminate, potassium aluminate or sodium aluminate, and wherein the metal alumina spinel substrate is impregnated with either Ni, Zn, or both, and wherein the catalyst further includes Ce. Catalyst C can include one or two substitutional solid solutions on the metal impregnated metal-alumina spinel. Hydrogen can also be bound to the catalyst.
This application is a division of U.S. patent application Ser. No. 17/300,538, filed Aug. 5, 2021, which is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 17300538 | Aug 2021 | US |
| Child | 18445228 | US |
