Benzaldehyde is produced from toluene in the catalytic reaction

Dry air and toluene vapor are mixed and fed to the reactor at 350°F and 1 atm. Air is supplied in 100% excess. Of the toluene fed to the reactor, 13% reacts to form benzaldehyde and 0.5% reacts with oxygen to form CO₂ and H₂O. The product gases leave the reactor at 379°F and 1 atm. Water is circulated through a jacket surrounding the reactor, entering at 80°F and leaving at 105°F. During a four-hour test period, 29.3 lb_m of water is condensed from the product gases. Total condensation may be assumed.

The standard heat of formation of benzaldehyde vapor is 17;200 Btu/lb-mole; the heat capacities of both toluene and benzaldehyde vapors are approximately 31 Btu/(lb-mole °F); and that of liquid benzaldehyde is 46 Btu/(lb-mole °F).

(a) Calculate the volumetric flowrates (ft3/h) of the combined feed streamto the reactor and the product gas.

(b) Calculate the required rate of heat transfer from the reactor (Btu/h) and the flow rate of the cooling water (gal/min).

(c) Suppose the process proceeds as designed for several weeks, but one day the product gas and coolant streams emerge at higher temperatures, and the product contains significantly less benzaldehyde. The coolant flow rate is increased, but the product gas temperature cannot be brought down to its prescribed value, so the process must be shut down for troubleshooting. List and briefly explain several possible causes of the problem.

Transcribed Image Text:

C6H5CH3 + O2 - C6H5CHO + H20