Thursday, April 26, 2012

Recycling Carbon emissions to Gasoline production


Nature has a wonderful way of capturing Carbon and recycling it through a process called ‘carbon cycle’ for millions of years. The greenhouse gases in the atmosphere were restricted within certain limits when it was left to Nature. But when human being started burning fossil fuels to generate power or to run cars, the GHG emission surpassed the limit beyond a point where global warming became an issue. The GHG level has increased to 392 ppm level for the first in our long history. Many Governments and companies are exploring various ways and means to reduce greenhouse emissions to avoid global warming. Some Governments are imposing taxes on carbon emission in order to reduce or discourage such emissions. Others are offering incentives to promote alternative energy sources such as wind and solar. Some companies are trying to capture Carbon emission for sequestration. While we try to capture Carbon and store them underground, there are many potential commercial opportunities to recycle them. This means the Carbon emission is captured and converted into a commercial fuel such as Gasoline or Diesel or Methane so that future sources of fossil fuels are not burnt anymore. But this is possible only by using ‘Renewable Hydrogen’. Hydrogen is the key to reduce carbon emission by binding carbon molecules with Hydrogen molecule, similar to what Nature does. When NASA plans to send a man to Mars they have to overcome certain basic issues. Mars has an atmosphere with 95% Carbon dioxide, 3% Nitrogen, 1.6% Argon and traces of oxygen, water and methane.Nasa is planning to use Carbon dioxide to generate Methane gas to be used as a fuel and also generate water by using the following reaction. CO2 + 4H2-----CH4 + 2 H2O, 2H2O-------2H2 + O2 The water is electrolyzed to split water into Hydrogen and Oxygen using solar power. The resulting Hydrogen is reacted with Carbon dioxide from Mars to generate Methane gas and water using a solid catalyst. This methanation reaction is exothermic and self sustaining. How this can be achieved practically in Mars in those conditions are not discussed here. But this is a classical example on how the Carbon emission can be tackled to our advantages, without increasing the emissions into the atmosphere. There are several methods available to convert Carbon emission in to valuable products including gasoline. The reaction of the methane with water vapor will result in Methanol. 2H2 + CO-------- CH3OH On Dehydration, 2CH3OH ----- CH3COCH3 + H2O.Further dehydration with ZSM-5 Catalyst gives Gasoline 80% C5+ Hydrocarbon. Gas to liquid by Fischer-tropic reaction is a known process. Carbon dioxide is also a potential refrigerant to substitute CFC refrigerants that causes Ozone depletion. Carbon recycling is a temporary solution to mitigate Greenhouse gas emission till Hydrogen becomes an affordable fuel of the future. It depends upon individual Governments and their policies to make Hydrogen affordable. Technologies are available and only a political will and leadership can make Hydrogen a reality.