Chromatography Forum

Hi,
I want to analyse the yield and conversion of a reaction. i have calibrated the GC. I have done two types of calibrations for the prodcuts and by products , one against a standart (mesytylene) and one calibartion against a reagent.
What sould i do to calculate the conversion and yield of the reaction? One of the by products(biphenyl) it is a reaction of a reagent with itself, and i also would like to know how to calculate the amount present in the reaction.

Thank you for the help.

You must pass the reactants by pass (without passing of the reactor) and take measures of the peak area in gc. I suppose that you have a loop on gc that trap an amount of the gas stream (1ml perhaps). From your standards you have a coefficient (moles of the reactant in the loop)/(peak area). Or (concentration of the reactant/peak area).
So, measuring, by pass, the peak area of the reactants you will have the moles (and calculate the concentration) of the reactands to the entry of the reactor. If you don't know all your products or you can;t measure them I think you must follow this procedure:
If a reactant i, the convesion of i will be (Fi-Fo)/Fi *100% Fi: moles/s to the inlet of the reactor and Fo to the exit. Selectivity of a specific product j will will be: (moles of the reactant that reacted and gave j)/(total moles of the reactant that reacted )*100%. If a conversion of 20% and selectivity of 50% the yield of a product will be: yield = conversion * selectivity= 0,2 * 0,5 *100%=10%.
if you have a large change of volume during the reaction (from stoichiometry of the reaction) you must take into consideration this change. If you have a polymerization reaction for example 5C -> C-C-C-C-C you have large decrease of the gas volume between inlet and outlet of the reactor. (because 5 moles in the inlet give 1mole in the outlet).