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45-435: The system reforms natural gas to extract up to 3 normal cubic meters per hour (Nm3/hr) of hydrogen, which is stored in an internal tank . This hydrogen is stored for later use by the vehicle, and can also be supplied to hydrogen appliances or fuel cells within the home. The heat generated by the reforming process can also provide hot water to the home. In addition to providing as much as 5 kilowatts of electrical power to

90-480: A low pressure drop which is advantageous for this application. Steam reforming of natural gas is 65–75% efficient. The United States produces 9–10 million tons of hydrogen per year, mostly with steam reforming of natural gas. The worldwide ammonia production, using hydrogen derived from steam reforming, was 144 million tonnes in 2018. The energy consumption has been reduced from 100 GJ/tonne of ammonia in 1920 to 27 GJ by 2019. Globally, almost 50% of hydrogen

135-401: A method for producing syngas ( hydrogen and carbon monoxide ) by reaction of hydrocarbons with water. Commonly natural gas is the feedstock. The main purpose of this technology is hydrogen production . The reaction is represented by this equilibrium: The reaction is strongly endothermic (Δ H SR = 206 kJ/mol). Hydrogen produced by steam reforming is termed 'grey' hydrogen when

180-470: A range of 200–250 °C. The upper temperature limit is due to the susceptibility of copper to thermal sintering. These lower temperatures also reduce the occurrence of side reactions that are observed in the case of the HTS. Noble metals such as platinum, supported on ceria, have also been used for LTS. The WGSR has been extensively studied for over a hundred years. The kinetically relevant mechanism depends on

225-469: A significant temperature dependence and the equilibrium constant decreases with an increase in temperature, that is, higher hydrogen formation is observed at lower temperatures. With increasing temperature, the reaction rate increases, but hydrogen production becomes less favorable thermodynamically since the water gas shift reaction is moderately exothermic ; this shift in chemical equilibrium can be explained according to Le Chatelier's principle . Over

270-585: A sub-stoichiometric fuel-air mixture is partially combusted in a reformer creating hydrogen-rich syngas. POX is typically much faster than steam reforming and requires a smaller reactor vessel. POX produces less hydrogen per unit of the input fuel than steam reforming of the same fuel. The capital cost of steam reforming plants is considered prohibitive for small to medium size applications. The costs for these elaborate facilities do not scale down well. Conventional steam reforming plants operate at pressures between 200 and 600 psi (14–40 bar) with outlet temperatures in

315-677: Is 2.5:1. The outlet temperature of the syngas is between 950–1100 °C and outlet pressure can be as high as 100 bar. In addition to reactions [1] – [3], ATR introduces the following reaction: [ 4 ] C H 4 + 0.5 O 2 ⇌ C O + 2 H 2 Δ H R = − 24.5   k J / m o l {\displaystyle [4]\qquad \mathrm {CH} _{4}+0.5\,\mathrm {O} _{2}\rightleftharpoons \mathrm {CO} +2\,\mathrm {H} _{2}\qquad \Delta H_{R}=-24.5\ \mathrm {kJ/mol} } The main difference between SMR and ATR

360-481: Is a key criteria for the assessment of catalytic performance in WGS reactions. To date, some of the lowest activation energy values have been found for catalysts consisting of copper nanoparticles on ceria support materials, with values as low as Ea = 34 kJ/mol reported relative to hydrogen generation. Catalysts for the lower temperature WGS reaction are commonly based on copper or copper oxide loaded ceramic phases, While

405-461: Is also pyrophoric in its inactive state and therefore presents safety concerns for consumer applications. Developing a catalyst that can overcome these limitations is relevant to implementation of a hydrogen economy. The WGS reaction is used in combination with the solid adsorption of CO 2 in the sorption enhanced water gas shift (SEWGS) in order to produce a high pressure hydrogen stream from syngas . The equilibrium of this reaction shows

450-491: Is conducted in multitubular packed bed reactors, a subtype of the plug flow reactor category. These reactors consist of an array of long and narrow tubes which are situated within the combustion chamber of a large industrial furnace , providing the necessary energy to keep the reactor at a constant temperature during operation. Furnace designs vary, depending on the burner configuration they are typically categorized into: top-fired, bottom-fired, and side-fired. A notable design

495-653: Is in conjunction with the conversion of carbon monoxide from steam reforming of methane or other hydrocarbons in the production of hydrogen. In the Fischer–Tropsch process , the WGSR is one of the most important reactions used to balance the H 2 /CO ratio. It provides a source of hydrogen at the expense of carbon monoxide, which is important for the production of high purity hydrogen for use in ammonia synthesis. The water–gas shift reaction may be an undesired side reaction in processes involving water and carbon monoxide, e.g.

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540-410: Is mildly exothermic), a large amount of heat needs to be added to the reactor to keep a constant temperature. Optimal SMR reactor operating conditions lie within a temperature range of 800 °C to 900 °C at medium pressures of 20-30 bar. High excess of steam is required, expressed by the (molar) steam-to-carbon (S/C) ratio. Typical S/C ratio values lie within the range 2.5:1 - 3:1. The reaction

585-565: Is produced by one-step methane pyrolysis of natural gas. Steam reforming of natural gas produces most of the world's hydrogen. Hydrogen is used in the industrial synthesis of ammonia and other chemicals. Steam reforming reaction kinetics, in particular using nickel - alumina catalysts, have been studied in detail since the 1950s. The purpose of pre-reforming is to break down higher hydrocarbons such as propane , butane or naphtha into methane (CH 4 ), which allows for more efficient reforming downstream. The name-giving reaction

630-453: Is produced via steam reforming. It is currently the least expensive method for hydrogen production available in terms of its capital cost. In an effort to decarbonise hydrogen production, carbon capture and storage (CCS) methods are being implemented within the industry, which have the potential to remove up to 90% of CO 2 produced from the process. Despite this, implementation of this technology remains problematic, costly, and increases

675-478: Is that SMR only uses air for combustion as a heat source to create steam, while ATR uses purified oxygen. The advantage of ATR is that the H 2 :CO ratio can be varied, which can be useful for producing specialty products. Due to the exothermic nature of some of the additional reactions occurring within ATR, the process can essentially be performed at a net enthalpy of zero (Δ H = 0). Partial oxidation (POX) occurs when

720-495: Is the Foster-Wheeler terrace wall reformer. Inside the tubes, a mixture of steam and methane are put into contact with a nickel catalyst. Catalysts with high surface-area-to-volume ratio are preferred because of diffusion limitations due to high operating temperature . Examples of catalyst shapes used are spoked wheels, gear wheels, and rings with holes ( see: Raschig rings ). Additionally, these shapes have

765-508: Is the steam reforming (SR) reaction and is expressed by the equation: [ 1 ] C H 4 + H 2 O ⇌ C O + 3 H 2 Δ H S R = 206   k J / m o l {\displaystyle [1]\qquad \mathrm {CH} _{4}+\mathrm {H} _{2}\mathrm {O} \rightleftharpoons \mathrm {CO} +3\,\mathrm {H} _{2}\qquad \Delta H_{SR}=206\ \mathrm {kJ/mol} } Via

810-409: Is used to produce carbon monoxide from hydrogen and carbon dioxide. This is sometimes called the reverse water–gas shift reaction . Water gas is defined as a fuel gas consisting mainly of carbon monoxide (CO) and hydrogen (H 2 ). The term 'shift' in water–gas shift means changing the water gas composition (CO:H 2 ) ratio. The ratio can be increased by adding CO 2 or reduced by adding steam to

855-700: The water-gas shift reaction (WGSR), additional hydrogen is released by reaction of water with the carbon monoxide generated according to equation [1]: [ 2 ] C O + H 2 O ⇌ C O 2 + H 2 Δ H W G S R = − 41   k J / m o l {\displaystyle [2]\qquad \mathrm {CO} +\mathrm {H} _{2}\mathrm {O} \rightleftharpoons \mathrm {CO} _{2}+\mathrm {H} _{2}\qquad \Delta H_{WGSR}=-41\ \mathrm {kJ/mol} } Some additional reactions occurring within steam reforming processes have been studied. Commonly

900-542: The HTS is the H 2 O/CO ratio where low ratios may lead to side reactions such as the formation of metallic iron, methanation , carbon deposition, and the Fischer–Tropsch reaction. The typical composition of commercial HTS catalyst has been reported as 74.2% Fe 2 O 3 , 10.0% Cr 2 O 3 , 0.2% MgO (remaining percentage attributed to volatile components). The chromium acts to stabilize the iron oxide and prevents sintering . The operation of HTS catalysts occurs within

945-496: The WGSR is proportional to the equilibrium constant of hydroxyl formation, which rationalizes why reducible oxide supports (e.g. CeO 2 ) are more active than irreducible supports (e.g. SiO 2 ) and extended metal surfaces (e.g. Pt). In contrast to the active site for carboxyl formation, formate formation occurs on extended metal surfaces. The formate intermediate can be eliminated during the WGSR by using oxide-supported atomically dispersed transition metal catalysts, further confirming

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990-407: The associative carboxyl mechanism is the predominant low temperature pathway on metal-oxide-supported transition metal catalysts. In 1920 Armstrong and Hilditch first proposed the associative mechanism. In this mechanism CO and H 2 O are adsorbed onto the surface of the catalyst, followed by formation of an intermediate and the desorption of H 2 and CO 2 . In general, H 2 O dissociates onto

1035-433: The burning of conventional fuels due to increased efficiency and fuel cell characteristics. However, by turning the release of carbon dioxide into a point source rather than distributed release, carbon capture and storage becomes a possibility, which would prevent the release of carbon dioxide to the atmosphere, while adding to the cost of the process. The cost of hydrogen production by reforming fossil fuels depends on

1080-452: The catalyst composition and the temperature. Two mechanisms have been proposed: an associative Langmuir–Hinshelwood mechanism and a redox mechanism. The redox mechanism is generally regarded as kinetically relevant during the high-temperature WGSR (> 350 °C) over the industrial iron-chromia catalyst. Historically, there has been much more controversy surrounding the mechanism at low temperatures. Recent experimental studies confirm that

1125-439: The catalyst to yield adsorbed OH and H. The dissociated water reacts with CO to form a carboxyl or formate intermediate. The intermediate subsequently dehydrogenates to yield CO 2 and adsorbed H. Two adsorbed H atoms recombine to form H 2 . There has been significant controversy surrounding the kinetically relevant intermediate during the associative mechanism. Experimental studies indicate that both intermediates contribute to

1170-424: The catalytic surface back to its pre-reaction state. The mechanism entails nucleophilic attack of water or hydroxide on a M-CO center, generating a metallacarboxylic acid . The WGSR is exergonic , with the following thermodynamic parameters at room temperature (298 K): In aqueous solution, the reaction is less exergonic. In the conversion of carbon dioxide to useful materials, the water–gas shift reaction

1215-522: The development of industrial processes that required hydrogen, such as the Haber–Bosch ammonia synthesis, a less expensive and more efficient method of hydrogen production was needed. As a resolution to this problem, the WGSR was combined with the gasification of coal to produce hydrogen. The WGSR is a highly valuable industrial reaction that is used in the manufacture of ammonia, hydrocarbons , methanol , and hydrogen . Its most important application

1260-483: The development of water gas shift catalysts for the application in fuel cell technology is an area of current research interest. Catalysts for fuel cell application would need to operate at low temperatures. Since the WGSR is slow at lower temperatures where equilibrium favors hydrogen production, WGS reactors require large amounts of catalysts, which increases their cost and size beyond practical application. The commercial LTS catalyst used in large scale industrial plants

1305-606: The direct steam reforming (DSR) reaction is also included: [ 3 ] C H 4 + 2 H 2 O ⇌ C O 2 + 4 H 2 Δ H D S R = 165   k J / m o l {\displaystyle [3]\qquad \mathrm {CH} _{4}+2\,\mathrm {H} _{2}\mathrm {O} \rightleftharpoons \mathrm {CO} _{2}+4\,\mathrm {H} _{2}\qquad \Delta H_{DSR}=165\ \mathrm {kJ/mol} } As these reactions by themselves are highly endothermic (apart from WGSR, which

1350-488: The fuel gas quality (methane number). There is also interest in the development of much smaller units based on similar technology to produce hydrogen as a feedstock for fuel cells . Small-scale steam reforming units to supply fuel cells are currently the subject of research and development, typically involving the reforming of methanol , but other fuels are also being considered such as propane , gasoline , autogas , diesel fuel , and ethanol . The reformer–

1395-482: The fuel-cell system is still being researched but in the near term, systems would continue to run on existing fuels, such as natural gas or gasoline or diesel. However, there is an active debate about whether using these fuels to make hydrogen is beneficial while global warming is an issue. Fossil fuel reforming does not eliminate carbon dioxide release into the atmosphere but reduces the carbon dioxide emissions and nearly eliminates carbon monoxide emissions as compared to

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1440-486: The high reaction rates, but results in incomplete conversion of carbon monoxide. A subsequent low temperature shift reactor lowers the carbon monoxide content to <1%. Commercial HTS catalysts are based on iron oxide – chromium oxide and the LTS catalyst is a copper-based. The copper catalyst is susceptible to poisoning by sulfur . Sulfur compounds are removed prior to the LTS reactor by a guard bed. An important limitation for

1485-537: The home, the Home Energy Station is also able to function as a backup power generation system during power outages. 2005 - The Home Energy Station III underwent testing at Honda R&D Americas Torrance, California . 2007 - The Home Energy Station IV underwent testing for use with the Honda FCX Clarity . Steam reforming Steam reforming or steam methane reforming (SMR) is

1530-416: The kinetic dominance of the carboxyl pathway. The redox mechanism involves a change in the oxidation state of the catalytic material. In this mechanism, CO is oxidized by an O-atom intrinsically belonging to the catalytic material to form CO 2 . A water molecule undergoes dissociative adsorption at the newly formed O-vacancy to yield two hydroxyls. The hydroxyls disproportionate to yield H 2 and return

1575-496: The most common supports include alumina or alumina with zinc oxide, other supports may include rare earth oxides, spinels or perovskites. A typical composition of a commercial LTS catalyst has been reported as 32-33% CuO, 34-53% ZnO, 15-33% Al 2 O 3 . The active catalytic species is CuO. The function of ZnO is to provide structural support as well as prevent the poisoning of copper by sulfur. The Al 2 O 3 prevents dispersion and pellet shrinkage. The LTS shift reactor operates at

1620-405: The price of the produced hydrogen significantly. Autothermal reforming (ATR) uses oxygen and carbon dioxide or steam in a reaction with methane to form syngas . The reaction takes place in a single chamber where the methane is partially oxidized. The reaction is exothermic. When the ATR uses carbon dioxide, the H 2 :CO ratio produced is 1:1; when the ATR uses steam, the H 2 :CO ratio produced

1665-640: The range of 815 to 925 °C. Flared gas and vented volatile organic compounds (VOCs) are known problems in the offshore industry and in the on-shore oil and gas industry, since both release greenhouse gases into the atmosphere. Reforming for combustion engines utilizes steam reforming technology for converting waste gases into a source of energy. Reforming for combustion engines is based on steam reforming, where non-methane hydrocarbons ( NMHCs ) of low quality gases are converted to synthesis gas (H 2 + CO) and finally to methane (CH 4 ), carbon dioxide (CO 2 ) and hydrogen (H 2 ) - thereby improving

1710-416: The reaction of carbon monoxide and water vapor to form carbon dioxide and hydrogen : The water gas shift reaction was discovered by Italian physicist Felice Fontana in 1780. It was not until much later that the industrial value of this reaction was realized. Before the early 20th century, hydrogen was obtained by reacting steam under high pressure with iron to produce iron oxide and hydrogen. With

1755-524: The reaction rate over metal oxide supported transition metal catalysts. However, the carboxyl pathway accounts for about 90% of the total rate owing to the thermodynamic stability of adsorbed formate on the oxide support. The active site for carboxyl formation consists of a metal atom adjacent to an adsorbed hydroxyl. This ensemble is readily formed at the metal-oxide interface and explains the much higher activity of oxide-supported transition metals relative to extended metal surfaces. The turn-over-frequency for

1800-482: The rhodium-based Monsanto process . The iridium-based Cativa process uses less water, which suppresses this reaction. The WGSR can aid in the efficiency of fuel cells by increasing hydrogen production. The WGSR is considered a critical component in the reduction of carbon monoxide concentrations in cells that are susceptible to carbon monoxide poisoning such as the proton-exchange membrane (PEM) fuel cell . The benefits of this application are two-fold: not only would

1845-412: The scale at which it is done, the capital cost of the reformer, and the efficiency of the unit, so that whilst it may cost only a few dollars per kilogram of hydrogen at an industrial scale, it could be more expensive at the smaller scale needed for fuel cells. There are several challenges associated with this technology: Water-gas shift reaction The water–gas shift reaction (WGSR) describes

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1890-521: The temperature range of 310 °C to 450 °C. The temperature increases along the length of the reactor due to the exothermic nature of the reaction. As such, the inlet temperature is maintained at 350 °C to prevent the exit temperature from exceeding 550 °C. Industrial reactors operate at a range from atmospheric pressure to 8375 kPa (82.7 atm). The search for high performance HT WGS catalysts remains an intensive topic of research in fields of chemistry and materials science. Activation energy

1935-445: The temperature range of 600–2000 K, the equilibrium constant for the WGSR has the following relationship: In order to take advantage of both the thermodynamics and kinetics of the reaction, the industrial scale water gas shift reaction is conducted in multiple adiabatic stages consisting of a high temperature shift (HTS) followed by a low temperature shift (LTS) with intersystem cooling. The initial HTS takes advantage of

1980-429: The waste carbon dioxide is released to the atmosphere and 'blue' hydrogen when the carbon dioxide is (mostly) captured and stored geologically—see carbon capture and storage . Zero carbon 'green' hydrogen is produced by thermochemical water splitting , using solar thermal, low- or zero-carbon electricity or waste heat, or electrolysis , using low- or zero-carbon electricity. Zero carbon emissions 'turquoise' hydrogen

2025-442: The water gas shift reaction effectively reduce the concentration of carbon monoxide, but it would also increase the efficiency of the fuel cells by increasing hydrogen production. Unfortunately, current commercial catalysts that are used in industrial water gas shift processes are not compatible with fuel cell applications. With the high demand for clean fuel and the critical role of the water gas shift reaction in hydrogen fuel cells,

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