This study source was downloaded by 100000819808907 from CourseHero com on 03 03 2022 01 13 52 GMT 06 00 https www coursehero com file 43022477 Lecture 17 1030 1230docx LECTURE 17 1 Assignment Submitted by ALMES ALLYANNA MARIE R OMBI ON GLEENA RIO N AMMOG AO II RUDYARD NRAMOS KATRHYNE LBALITE TIMMY SRAZON STEPHANIE NICOLE RDOMILIES ALISTER MARC BROLDAN JOHN PATRICKGAMENG YVETHMADULID GELLINNE MICAH17 1 Gaseous reactant A diffuses through a gas film and reacts on the surfaceof a solid according to a reversible first order rate r A k CAS CAe where CAe is the concentration of A in equilibrium with the solid surface Developan expression for the rate of reaction of A accounting for both the mass transferand reaction steps Solution For the mass transfer step rA 1 over S dN rsub A over dt k rsub g C rsub Ag C rsub As 1 For the reversible reaction step rA k rsub S C rsub As C rsub Ae 2 Eliminating CAs gives rA 1 over 1 over k rsub g 1 over k rsub s C rsub Ag C rsub Ae 17 2 Example 17 4 gives the final rate expression for film mass transfer followedby a second order rate expression for reaction on a plane surface Please derivethis expression and show that it is correct Solution rA1 1 over S dN rsub A over dt D over x C rsub Al C rsub As k rsub l C rsub Al C rsub As rA2 kCA2Combining the reaction steps to eliminate CAs giveskl2 4k k rsub l C rsub Al 2k 2kCAl kl rA rA1 rA2 kl This study source was downloaded by 100000819808907 from CourseHero com on 03 03 2022 01 13 52 GMT 06 00 https www coursehero com file 43022477 Lecture 17 1030 1230docx 17 3 In slurry reactors pure reactant gas is bubbled through liquid containingsuspended catalyst particles Let us view these kinetics in terms of the filmtheory as shown in Fig P17 3 Thus to reach the surface of the solid thereactant which enters the liquid must diffuse through the liquid film into the mainbody of the liquid and then through the film surrounding the catalyst particle Atthe surface of the particle reactant yields product according to first orderkinetics Derive an expression for the rate of reaction in terms of theseresistances Required expression for rate of reactionSolution For the interference between gas bubbles and liquid r 1VdNdt kAlai CAi CAl i Where kAl gas liquid mass transfer coefficientai area of gas liquid interface per volume of reactorFor the interface between the solid catalyst particles the surrounding liquid This study source was downloaded by 100000819808907 from CourseHero com on 03 03 2022 01 13 52 GMT 06 00 https www coursehero com file 43022477 Lecture 17 1030 1230docx Powered by TCPDF www tcpdf org r 1VdNdt kAl as CAl CAs ii Where k Al liquid solid mass transfer coefficientas area of liquid solid interface per volume of reactorFor surface reaction r 1VdNdt k1CAsas iii Combining i ii and iii eliminating the intermediate concentrations CAl andCAs gives on manipulation r 1VdNdt 11kAlai 1kAl as 1ksCAiWhere r rate based on unit volume of reactorThis expression is the special case of Eq 22 2 for slurry reactors