CO2 currently is used as a very useful material for human life. One of the major uses of CO2 in large scale industry is in the synthesis of urea. Urea is the widely used type of nitrogen fertilizer among the farmers. Urea has the highest nitrogen content of all solid nitrogenous fertilizers in common use. The synthesis of urea and the production of salicylic acid by Kolbe-Schmitt reaction have been exploited at the industrial level for more than a century. Urea, CO(NH2)2, synthesis currently utilizes the largest amount of CO2 in organic synthesis. Urea is the most important nitrogen fertilizer in the world. It is also an intermediate in production of melamine and urea resins which are used as adhesives and bonding agents. Urea is currently produced by the synthesis of ammonia, synthesized mainly from low cost natural gas and CO2 recovered from the offgas of the ammonia- synthesizing process. However, when urea is synthesized using natural gas as a feed stock through steam reforming, there is a shortage in the balance of CO2 to ammonia. Accordingly, in order to improve the balance of CO2 to ammonia, CO2 recovered from the offgas of a steam reformer producing hydrogen and CO from natural gas is fed into the urea synthesis process so that the volume of urea produced is maximized.
Urea is produced from ammonia and CO2 in two equilibrium reactions:
Global urea production according to International Fertilizer Industry Association (IFA) has reached 146 million tonnes in 2008 and is expected to grow at the rate of 3.7% per year to reach around 175 tonnes in 2013. For every one tonne of urea produced 1 tonne of CO2 is used in the production process. Hence to produce around 150 million tonnes per year of urea globally 150 Mt of CO2 is required which is a meagre amount when compared to the amount of CO2 released into atmosphere (which is roughly 35 giga tonne per year).