First chemistry problem
A few years ago, I taught organic chemistry at the local community college for one term as an adjunct professor. I thought I'd inject some chemical engineering into the course, especially since many of the students told me they were headed for engineering courses when they got to a four-year college or university. Below is the first problem on the second test of the term. Tests were take-home, and students were given about a week to finish them. The chemistry curriculum had supposedly included ideal gas laws and behavior, chemical equation balancing, states of matter, and yield calculations in previous terms. If you want to take a crack at this problem, use the comments section. I'll post the solution soon. Good luck!
The Fischer-Tropsch process for producing diesel fuel from carbon monoxide and hydrogen (synthesis gas or syngas) was discussed in the context of reactions involving alkanes. In recent times, natural gas has been used as feedstock as its price has gone down. In the first step of the process, natural gas (mostly methane) is converted into syngas by steam reforming:
H2O + CH4 → CO + H2
The syngas thus produced is fed into the main reactor, where at 150-300°C over iron or cobalt catalysts, alkanes in the 16-20 carbon range are produced:
H2 + CO → CnH2n+2 + H2O
The water can be recycled back into the steam reforming stage.
Using n = 16 in the main reaction above, and making sure to balance the equations, calculate the yield of hexadecane product if doing these reactions in a 1 L “bomb” reactor (that tolerates high pressures) at 230°C and an initial pressure of methane of 100 psi, assuming a conversion of methane of 97% and 100% conversion of syngas in the main reaction. Give your answer in milliliters.
Hint: Use the ideal gas law to calculate the initial moles of methane in the steam reforming reaction, then calculate the yields of CO and H2, adjust for conversion and then use these values for the initial amounts of CO and H2 in the main reaction. Assume hexadecane is the only product of the main reaction (yield is 100%).
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