The first time a catalyst was used in the industry was in 1746 by J. Roebuck in the manufacture of lead chamber sulfuric acid.
Different catalysts are in constant development to fulfil economic, political and environmental demands.
To achieve the best understanding and development of a catalyst it is important that different special fields work together.
Some of the advantages an improved catalyst gives, that affects people's lives, are: cheaper and more effective fuel, new drugs and medications and new polymers.
Today the WGS reaction is used primarily to produce hydrogen that can be used for further production of methanol and ammonia.
The main purpose of the LTS catalyst is to reduce CO content in the reformate which is especially important in the ammonia production for high yield of H2.
Both catalysts are necessary for thermal stability, since using the LTS reactor alone increases exit-stream temperatures to unacceptable levels.
The equilibrium constant is extremely dependent on the reaction temperature, for example is the Kp equal to 228 at 200 °C, but only 11.8 at 400 °C.
As mentioned before, the catalyst is a composition of iron-oxide, Fe2O3(90-95%), and chromium oxides Cr2O3 (5-10%) which have an ideal activity and selectivity at these temperatures.
The redox mechanism is given below: First a CO molecule reduces an O molecule, yielding CO2 and a vacant surface center: The vacant side is then reoxidized by water, and the oxide center is regenerated: The adsorptive mechanism assumes that format species is produced when an adsorbed CO molecule reacts with a surface hydroxyl group: The format decomposes then in the presence of steam: The low temperature process is the second stage in the process, and is designed to take advantage of higher hydrogen equilibrium at low temperatures.
The reduction reaction CuO + H2 →Cu + H2O is highly exothermic and should be conducted in dry gas for an optimal result.
One of the reasons to the fact that the literature is not agreeing on one mechanism can be because of experiments are carried out under different assumptions.
This can be done in different ways from a variety of carbon sources such as: [6] Both the reactions shown above are highly endothermic and can be coupled to an exothermic partial oxidation.
When considering a molecular orbital(MO)-diagram CO can act as an σ-donor via the lone pair of the electrons on C, and a π-acceptor ligand in transition metal complexes.
It can be seen from the figure that Cu(110) shows a faster reaction rate and a lower activation energy.
The process uses syngas as feedstock and for that reason the water gas shift reaction is important for this synthesis.
The most effective catalysts for methanol synthesis are Cu, Ni, Pd and Pt, while the most common metals used for support are Al and Si.
The following mechanism has been proposed over Cu/ZnO/Al2O3: When methanol is almost completely converted CO is being produced as a secondary product via the reverse water-gas shift reaction.
This reaction is the opposite of the methanol synthesis from syngas, and the most effective catalysts seems to be Cu, Ni, Pd and Pt as mentioned before.
Often, a Cu/ZnO-based catalyst is used at temperatures between 200 and 300 °C but by-products of production like dimethyl ether, methyl format, methane and water are common.
The catalyst used is often Cu (Cu/ZnO) or Pd and they differ in qualities such as by-product formation, product distribution and the effect of oxygen partial pressure.
The reaction can be both endothermic and exothermic determined by the conditions, and combine both the advantages of steam reforming and partial oxidation.
The ammonia synthesis advanced between 1909 and 1913, and two important concepts were developed; the benefits of a promoter and the poisoning effect (see catalysis for more details).