Steam reforming - Citizendia

Steam reforming, hydrogen reforming or catalytic oxidation, is a method of producing hydrogen from hydrocarbons. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. On an industrial scale, it is the dominant method for producing hydrogen. Small-scale steam reforming units are currently subject to scientific research, as way to provide hydrogen to fuel cells. A fuel cell is an electrochemical conversion device It produces electricity from Fuel (on the Anode side and an oxidant (on the

1 Industrial Reforming
2 Fueling fuel cells
3 The process
4 References
5 See also

Industrial Reforming

Steam reforming of natural gas, sometimes referred to as steam methane reforming (SMR) is the most common method of producing commercial bulk hydrogen as well as the hydrogen used in the industrial synthesis of ammonia. Natural gas is a Gaseous Fossil fuel consisting primarily of Methane but including significant quantities of Ethane, Propane, Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Because of its many uses Ammonia is one of the most highly-produced inorganic chemicals It is also the least expensive method. ^[1] At high temperatures (700 – 1100 °C) and in the presence of a metal-based catalyst (nickel), steam reacts with methane to yield carbon monoxide and hydrogen

CH₄ + H₂O → CO + 3 H₂

Additional hydrogen can be recovered by a lower-temperature gas-shift reaction with the carbon monoxide produced. The M acro E xpansion T emplate A ttribute L anguage complements TAL, providing macros which allow the reuse of code across Catalysis is the process in which the rate of a Chemical reaction is increased by means of a Chemical substance known as a catalyst Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. The reaction is summarised by:

CO + H₂O → CO₂ + H₂

The United States produces nine million tons of hydrogen per year, mostly with steam reforming of natural gas. Carbon monoxide, with the chemical formula CO is a colorless odorless tasteless yet highly toxic Gas. Water is a common Chemical substance that is essential for the survival of all known forms of Life. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 The United States of America —commonly referred to as the The worldwide ammonia production, using hydrogen derived from steam reforming, was 109 million metric tonnes in 2004. This article is about the tonne or metric ton For other tons see Ton. ^[2]

This SMR process is quite different from and not to be confused with catalytic reforming of naphtha, an oil refinery process that also produces significant amounts of hydrogen along with high octane gasoline. Catalytic reforming is a chemical process used to convert Petroleum refinery Naphthas typically having low octane ratings, into high-octane liquid products Naphtha normally refers to a number of different flammable liquid mixtures of hydrocarbons i An oil refinery is an industrial Process plant where Crude oil is processed and refined into more useful Petroleum products, such as Gasoline The octane rating is a measure of the resistance of Gasoline and other Fuels to Detonation ( Engine knocking) in spark-ignition

A great deal of ethylene is produced by a non-catalytic process called "steam cracking" which cracks (i. Structure This Hydrocarbon has four Hydrogen Atoms bound to a pair of Carbon atoms that are connected by a Double bond. e. , reforms) large hydrocarbon molecules into smaller molecules). In the year 2003, there was 97,000,000 metric tons of ethylene (used to produce polyethylene and a host of other petrochemicals) manufactured worldwide by the steam cracking of various hydrocarbons (methane, ethane, LPG, naphtha, and fuel oils. ETHANE is a mnemonic indicating a protocol used by Emergency services to report situations which they may be faced with especially as it relates to major incidents where Liquefied petroleum gas (also called LPG, GPL, LP Gas, or Autogas) is a mixture of Hydrocarbon Gases used as a Fuel Fuel oil is a fraction obtained from Petroleum Distillation, either as a distillate or a residue

Fueling fuel cells

Steam reforming of liquid hydrocarbons is seen as a potential way to provide fuel for fuel cells. A fuel cell is an electrochemical conversion device It produces electricity from Fuel (on the Anode side and an oxidant (on the The basic idea is that for example a methanol tank and a steam reforming unit would replace the bulky pressurized hydrogen tanks that would otherwise be necessary. Methanol, also known as methyl alcohol, carbinol, wood alcohol, wood naphtha or wood spirits, is a Chemical compound This might mitigate the distribution problems associated with hydrogen vehicles. A hydrogen vehicle is a Vehicle that uses Hydrogen as its on-board fuel for motive power

However, there are several challenges associated with this technology:

The reforming reaction takes place at high temperatures, making it slow to start up and requiring costly high temperature materials.
Sulfur compounds present in the fuel poison certain catalysts, making it difficult to run this type of system from ordinary gasoline. Sulfur or sulphur (ˈsʌlfɚ see spelling below) is the Chemical element that has the Atomic number 16 Some new technologies have overcome this challenge, however, with sulfur-tolerant catalysts.
The carbon monoxide (CO) produced by the reactor poisons the fuel cell, making it necessary to include complex CO-removal systems.
The thermodynamic efficiency of the process is between 70% and 85% (LHV basis) depending on the purity of the hydrogen product. In Thermodynamics, the thermal efficiency (\eta_{th} \ is a dimensionless performance measure of a thermal device such as an Internal combustion
The biggest problem for reformer based systems remains the fuel cell itself, in terms of both cost and durability. The catalyst used in the common polymer-electrolyte-membrane fuel cell, the device most likely to be used in transportation roles, is very sensitive to any leftover carbon monoxide in the fuel, which some reformers do not completely remove. The membrane is poisoned by the carbon monoxide and its performance degrades. An artificial membrane, also called a synthetic membrane, is a membrane prepared for separation tasks in Laboratory and industry
The catalyst is frequently very expensive.

The reformer–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, but there is an active debate about whether using these fuels to make hydrogen is beneficial, when global warming is such an issue. The overall cost of making, transporting and storing the hydrogen fuel is also a key issue.

The process

The chemical reactions that take place are:

C_nH_m + n H₂O → n CO + (m/2 + n) H₂

CO + H₂O → CO₂ + H₂

The produced carbon monoxide can combine with more steam to produce further hydrogen via the water gas shift reaction. The water gas shift reaction (WGS is a Chemical reaction in which Carbon monoxide reacts with Water to form Carbon dioxide and Hydrogen

The first reaction is endothermic (consumes heat), the second reaction is exothermic (produces heat). In Thermodynamics, the word endothermic "within-heating" describes a process or reaction that absorbs Energy in the form of Heat. In Thermodynamics, the word exothermic "outside heating" describes a process or reaction that releases Energy usually in the form of Heat, but

References

^ George W. Crabtree, Mildred S. Dresselhaus, and Michelle V. Buchanan, The Hydrogen Economy, Physics Today, December, 2004 [1]
^ United States Geological Survey publication

Contents

Industrial Reforming

Fueling fuel cells

The process

References

See also