Carbon dioxide reforming (also known as dry reforming) is a method of producing

synthesis gas Syngas, or synthesis gas, is a mixture of hydrogen and carbon monoxide, in various ratios. The gas often contains some carbon dioxide and methane. It is principly used for producing ammonia or methanol. Syngas is combustible and can be used ...

(mixtures of hydrogen and carbon monoxide) from the reaction of

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

with hydrocarbons such as

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...

with the aid of noble metal catalysts (typically Ni or Ni alloys). Synthesis gas is conventionally produced via the

steam reforming Steam reforming or steam methane reforming (SMR) is 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 product ...

reaction or coal gasification. In recent years, increased concerns on the contribution of greenhouse gases to

global warming In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...

have increased interest in the replacement of steam as reactant with carbon dioxide. The dry reforming reaction may be represented by: :CH4 + CO2 <=> 75^oC2CO + 2H2 Thus, two greenhouse gases are consumed and useful chemical building blocks, hydrogen and carbon monoxide, are produced. A challenge to the commercialization of this process is that the hydrogen that is produced tends to react with carbon dioxide. For example, the following reaction typically proceeds with lower

activation energy In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (''E''a) of a reaction is measured in joules per mole (J/mol), kilojoules p ...

than the dry reforming reaction itself: :CO + H2O <=> 00^oCCO2 + H2 Another issue with dry reforming is situated in the fact that it operates at conditions that produces water. As a result, this water can lead to unwanted back-reaction to CO₂ via the

water-gas shift reaction Water gas is a kind of fuel gas, a mixture of carbon monoxide and hydrogen. It is produced by "alternately hot blowing a fuel layer okewith air and gasifying it with steam". The caloric yield of this is about 10% of a modern syngas plant. F ...

. To prevent CO₂ from being formed, and consequently losses in CO yield, CO₂ can be adsorbed onto calcium oxide. Consequently, the process forms only CO and H₂O, increasing the utilization efficiency of the feedstocks. This process is better known as super-dry reforming. CO₂ can be dry reformed in to CO gas at 800-850 °C by reacting with

petcoke Petroleum coke, abbreviated coke or petcoke, is a final carbon-rich solid material that derives from oil refining, and is one type of the group of fuels referred to as cokes. Petcoke is the coke that, in particular, derives from a final cracki ...

biochar Biochar is the lightweight black residue, made of carbon and ashes, remaining after the pyrolysis of biomass. Biochar is defined by the International Biochar Initiative as "the solid material obtained from the thermochemical conversion of ...

, coal, etc. using low cost iron based catalysts. Using cheaper renewable electricity like solar or wind energy, this cheaper method converts petcoke and green house gas CO₂ in to useful fuel like methanol achieving

carbon capture and utilization Carbon capture and utilization (CCU) is the process of capturing carbon dioxide ( C O2) to be recycled for further usage. Carbon capture and utilization may offer a response to the global challenge of significantly reducing greenhouse gas emissions ...

. Some CO gas is converted in to hydrogen via water-gas shift reaction.

References

{{Reflist Hydrogen production Chemical processes reforming Industrial gases