U.S. Department of Energy - Energy Efficiency and Renewable Energy

Hydrogen, Fuel Cells and Infrastructure Technologies Program – Hydrogen Production

Natural Gas Reforming

Although today most hydrogen is produced from fossil materials, such as from natural gas at this oil refinery, the Program is exploring a variety of ways to produce hydrogen from renewable resources.

Distributed natural gas reforming is an important pathway for near-term hydrogen production during the transition to a hydrogen economy.

How Does It Work?

Natural gas contains methane (CH₄) that can be used to produce hydrogen via thermal processes, such as steam methane reformation and partial oxidation.

• Steam Methane Reforming

  About 95% of the hydrogen produced today in the United States is made via steam methane reforming, a process in which high-temperature steam (700 - 1000°C) is used to produce hydrogen from a methane source, such as natural gas. In steam methane reforming, methane reacts with steam under 3-25 bar pressure (1 bar = 14.5psi) in the presence of a catalyst to produce hydrogen, carbon monoxide, and a relatively small amount of carbon dioxide. Steam reforming is endothermic - that is, heat must be supplied to the process for the reaction to proceed.

  Subsequently, in what is called the "water-gas shift reaction," the carbon monoxide and steam are reacted using a catalyst to produce carbon dioxide and more hydrogen. In a final process step called "pressure-swing adsorption," carbon dioxide and other impurities are removed from the gas stream, leaving essentially pure hydrogen. Steam reforming can also be used to produce hydrogen from other fuels, such as ethanol, propane, or even gasoline.

  Steam Reforming Reactions
  Methane:
  CH₄ + H₂O (+heat) → CO + 3H₂

  Propane:
  C₃H₈ + 3H₂O (+heat) → 3CO + 7H₂

  Ethanol:
  C₂H₅OH + H₂O (+heat) → 2CO + 4H₂

  Gasoline (using iso-octane and toluene as example compounds from the hundred or more compounds present in gasoline):
  C₈H₁₈ + 8H₂O (+heat) → 8CO + 17H₂
  C₇H₈ + 7H₂O (+heat) → 7CO + 11H₂

  Water-Gas Shift Reaction
  CO + H₂O → CO₂ + H₂ (+small amount of heat)

• Partial Oxidation

  In partial oxidation, the methane and other hydrocarbons in natural gas are reacted with a limited amount of oxygen (typically, from air) that is not enough to completely oxidize the hydrocarbons to carbon dioxide and water. With less than the stoichiometric amount of oxygen available for the reaction, the reaction products contain primarily hydrogen and carbon monoxide (and nitrogen, if the reaction is carried out with air rather than pure oxygen), and a relatively small amount of carbon dioxide and other compounds. Subsequently, in a water-gas shift reaction, the carbon monoxide reacts with water to form carbon dioxide and more hydrogen.

  Partial oxidation is an exothermic process - it gives off heat. It is, typically, a much faster process than steam reforming and requires a smaller reactor vessel. As can be seen from the chemical reactions of partial oxidation (below), this process initially produces less hydrogen per unit of the input fuel than is obtained by steam reforming of the same fuel.

  Partial Oxidation Reactions
  Methane:
  CH₄ + ½O₂ → CO + 2H₂ (+heat)

  Propane:
  C₃H₈ + 1½O₂ → 3CO + 4H₂ (+heat)

  Ethanol:
  C₂H₅OH + ½O₂ → 2CO + 3H₂ (+heat)

  Gasoline (using iso-octane and toluene as example compounds from the hundred or more compounds present in gasoline):
  C₈H₁₈ + 4O₂ → 8CO + 9H₂ (+heat)
  C₇H₈ + 3½O₂ → 7CO + 4H₂ (+heat)

  Water-Gas Shift Reaction
  CO + H₂O → CO₂ + H₂ (+small amount of heat)

Why Is This Technology Being Considered for the Hydrogen Economy?

• Advanced technology and infrastructure (most advanced of all production pathways).

  Natural gas reforming technology is advancing rapidly, and a natural gas pipeline delivery infrastructure already exists. Today, 95% of the hydrogen produced in the U.S. is made via natural gas reforming in large central plants. (The hydrogen produced is used predominantly for petroleum refining and ammonia production for fertilizer).

• Greenhouse gas emissions are lower than gasoline-powered internal combustion engine (ICE) vehicles.

  Producing hydrogen from natural gas does result in some greenhouse gas emissions. When compared to ICE vehicles using gasoline, however, fuel cell vehicles using hydrogen produced from natural gas reduce greenhouse gas emissions by 60%.

It Is Important to Note...

• Current estimates indicate that using natural gas to produce hydrogen during the transition period to a hydrogen economy would increase overall U.S. natural gas consumption by less than five percent.

• DOE is not funding research activities for large-scale central production of hydrogen from natural gas. DOE efforts are focused on distributed natural gas reforming for the transition period only. Large-scale hydrogen production from natural gas reforming is a mature technology, and natural gas resources in the United States are limited—15% of the natural gas we use is imported. Producing large amounts of hydrogen from natural gas in the long term would only trade U.S. dependence on imported oil for U.S. dependence on imported natural gas.

Research Focuses on Overcoming Challenges

Although the technology for distributed natural gas reforming is advancing rapidly, several challenges remain. Capital equipment costs, as well as operation and maintenance costs, must be reduced and process energy efficiency must be improved in order to meet hydrogen cost targets.

In order for hydrogen to be successful in the market place, it must be cost competitive with the available alternatives. In the light-duty vehicle transportation market, this means that hydrogen needs to be available at $2-$3/gge (untaxed). This would result in hydrogen fuel cell vehicles having the same cost to the consumer on a cost per mile driven basis as a comparable conventional internal combustion engine or hybrid vehicle.

Key research areas:

• Intensifying the process (combining steps into fewer operations)
• Developing better designs to lower equipment manufacturing and maintenance costs
• Improving process efficiency by using better catalysts and better heat integration.