The three-way catalyst system (“catalytic converter”) plays a vital role in decreasing the pollution from automotive exhaust. The catalytic converter promotes three desired reactions that convert the pollutants CO, NOx (such as NO) and hydrocarbons (such as CH4) into less harmful compounds

.(1) CO + ½ O2 ->CO2

(2) CH4 + 2O2->CO2 + 2H2O

(3) 2NO + 2CO -> N2 + 2CO2

However, an undesired reaction can also occur. This reaction produces NH3

(4) 5CO + 3H2O + 2NO ->2NH3 + 5CO2

The combustion product from a typical internal combustion engine is sent to a catalytic converter. Assume that this combustion product consists of 47 mol/s N2, 8.0 mol/s CO2, 9.0 mol/s H2O, 1.0 mol/s CO, 0.25 mol/s NO and 0.25 mol/s CH4. The oxygen content varies, depending on the fuel/air blend of the engine. For now, treat this as an unknown.

(a) Draw and fully label a flowchart for this process

(b) Write the extent of reaction equation for each species involved in this system (yes, this is a lot of work, but it is good practice). Also, perform a DoF analysis according to the extent of reaction method. It is suggested, but not required, that you also practice modeling this system with the atomic balance approach.

(c) When the fuel blend fed to the engine is “rich”, the combustion product contains no oxygen (O2). Thus, no O2 enters the catalytic converter. What is the expected molar flowrate of CH4 in the stream leaving the catalytic converter?

(d) When the fuel blend fed to the engine is “lean”, the combustion product contains oxygen (O2). Here we will assume that the engine exhaust contains 2.0 mol/s O2. Imagine that we have a monitoring system in place to measure the mol% of CO, NO, CH4 and NH3 in the stream leaving the catalytic converter. Determine if you have enough information to solve for all of the unknowns. If you find that the system is solvable, explain how you would solve for all unknowns, including the extent of reaction values, and for the selectivity for NO conversion to N2, relative to NH3. If you prefer to solve using actual numerical values, you are welcome to do so. You can use 0.67 mol% CO, 0.045 mol% NO, 0.074 mol% CH4 and 0.21 mol% NH3.

Answer rating: 100% (QA)

Answer Catalytic converters widely used since its introduction in the US In the fall of 1974 it was ... View the full answer