# CHEMICAL REACTION ENGINEERING 2

16. Effective rate constant

Effective rate constant in case of first order gaseous phase reaction catalyzed by non-porous solid

17. Concentration after temperature and pressure correction

CA, a concentration of A inside reactor with temperature and pressure correction

18. Semi-batch reactor
The rate equation for a semi-batch reactor

19. Packed bed reactor
Rate equations for packed bed reactor

20. Equilibrium constant and gibbs energy
Calculating the equilibrium constant for reaction  given Gibbs energy for the reaction 21. Reaction in series Calculating time

21. Reaction in series
Calculating time for the concentration of B to be maximum

22. Reversible reaction

23. Instantaneous fractional yield
Instantaneous fractional yield in case of pore diffusion

24. Concentration inside and outside catalyst surface
For catalytic reaction, a relationship between concentration inside the catalyst surface and concentration at the catalyst surface

25. Fractional yield
For a reaction, a fractional yield is defined as a ratio of moles of desired a product formed to moles of desired product that would have been formed if there were no side reactions and limiting reactant would have reacted completely

26. Series-parallel reaction
In case of series plus parallel reaction, try to solve by mass balance

27. Selectivity of a reaction

Selectivity of a reaction is defined as a ratio of moles of desired product formed to moles of undesired product formed

28. Fractional conversion of reactant

Fractional conversion of reactant is defined as a ratio of moles of reactant reacted to form desired product to total reactant in the feed

29. Half life of a reactant
A half-life of a reactant in a first-order system is defined as follows

30. Dispersion of PFR and CSTR

Zero dispersion implies reactor is plug flow reactor (PFR) and infinite dispersion implies reactor is CSTR

31. The rate of reaction of species j

For homogenous system rate of reaction for species j is defined as

32. The first moment of RTD function
The first moment of RTD function is mean residence time

33. Mean residence time
In a pulse, tracer experiment mean residence time is given by

34. Recycle ratio
Recycle ratio is defined as a ratio of a volume of liquid returned to the entrance of the reactor to a volume of liquid leaving the reactor

35. A ratio of a volume of reactors
In CSTR ratio of volumes V1 and V2 for different conversion x1 and x2

36. Catalytic reaction rate
Rate of reaction for a catalytic reaction = KCAa; where a = activity coefficient.

37. Second order batch reactor/PFR
For second order batch/Plug flow constant volume reactor, the rate equation is defined such that

38. The time required for conversion F
The time required in a reaction for conversion F (conversion F is the fraction of reactants converted to products)

39. Plug flow reactors in parallel
If two plug flow reactors PFR1 and PFR2 are in parallel then

40. Vapour phase catalytic reaction
Vapour phase catalytic reaction with equimolar reactants and surface a reaction is rate controlling then the rate equation becomes

41. A least square regression method

42. Second order unimolecular reaction rate

43. Rate constant dependency on temperature

44. Second order non-ideal liquid phase reaction
The mean conversion in the exit stream for a second order liquid phase reaction in a non-ideal flow reactor is given by

2. Chemical Reaction Engineering

1.Rate variation with temperature

1. Transition state theory approaches the problem of calculating reaction rates by concentrating on the idea of intermediates and intermediates immediately breaking to product

2.Spacetime and holding time

1. For the same conversion in a constant volume reaction, holding time required in a batch reactor is equal to space-time in the plug flow reactor

2. For constant density system, space-time and holding time are equal. For changing density, they are unequal

3.Rate and rate equation

1. If the reactor volume is changed, the rate will also change as a degree of conversion will change

2. Energy balance equation over a tubular reactor under transient conditions is a linear partial differential equation.

3. When an exothermic reaction is conducted adiabatically, a rate of reaction passes through a maximum (K increases first).

4.Reaction in presence of the catalyst

1.reaction A –> B. If the concentration of A at the center of the pellet is much less than at the external surface, the process is limited by diffusion within the pellet. This is a case of large Thiele modulus which means that the surface reaction is rapid and the reactant is consumed to a major extent close to an external surface of the catalyst pellet. Very little of the reactant gets an opportunity to penetrate inside the catalyst particle. Therefore, the reaction is limited by diffusion within the catalyst particle

2.If for a heterogeneous catalytic reactions A + B –> C, with equimolar A and B, the initial rate –rAo is invariant with total pressure, it means that rate controlling step is desorption of C

3.Examples of trickle bed reactor – hydrogenation, hydrodesulfurization and hydrodenitrogenation in refineries (three phases hydro creator); oxidation of harmful chemical compounds in wastewater streams; in cumene process.

4.At steady state, reactant transport (diffusion) rate = reaction rate

5.When due to the decrease in particle size, conversion increases, the reaction is controlled by pore diffusion in the catalyst.

5.Non-Ideal reactions

1. The E curve for a non-ideal reactor defines the fraction of fluid having age between t and t+dt at the outlet and is given by Edt.

6.The extent of a reaction

1. The extent of a reaction is the same for all reactant and products. It has the dimension of mole or mole/sec and it is independent of stoichiometric coefficients.

2. In exothermic first order reaction, maximum heat generated will be at the beginning of the reaction when CA = Cao

7. Reactors

2. For a packed bed reactor, the presence of a long tail in the residence time distribution curve is an indication of a dead zone

3. Consider a reversible exothermic reaction in a plug flow reactor. Tmax = maximum permissible temperature. Tmin = minimum permissible temperature. To achieve the desired conversion, temp profile that will require the shortest residence time is initially a straight line at Tmax and then a downward parabola which would asymptote the x-axis.