Kinetics

1. Kinetics Patrick Cable, Dat Huynh, Greg Kalinyak, Ryan Leech, Wright Makambi, Ronak Ujla

2. Batch Reactor • No inlet or outlet flow • Reactants are placed inside the reactor and allowed to react over a set period of time • Advantages • High Conversion can be achieved if allowed a long reaction time • Versatile, and can be quickly adapted for different products • Disadvantages • Difficult to use for large scale production • High cost of labor per unit of production https://www.researchgate.net/figure/Schematic-diagram-of-batch-reactor_fig9_259169382

3. Batch Reactor Design Equations Input - Output + Generation = Accumulation Input = Output = 0 https://www.researchgate.net/figure/Schematic-diagram-of-batch-reactor_fig9_259169382

4. Semi-Batch Reactor • In between a CSTR and a Batch reactor • No outlet flow, only an inlet flow • Reactants are fed in at a set rate in either a two phase reaction or to prevent unwanted side reactions • Advantages • Minimize side reactions • Good temperature control • Disadvantages • Not good for large scale production • High Cost • Reactor operation can be difficult to analyze https://www.safaribooksonline.com/library/view/essentials-of-chemical/9780132317191/h4_699.html?orpq

5. Semi-Batch Reactor Design Equations Input - Output + Generation = Accumulation • Due to the change in both Volume over time and Concentration with time, solving the equations needs the use of a computer • Need to set up an equation for each component using the mass balance and another for the volume and solve simultaneously https://www.safaribooksonline.com/library/view/essentials-of-chemical/9780132317191/h4_699.html?orpq

6. Continuous Stir Tank Reactor (CSTR) • A constant inlet and outlet flow that is continuously mixed • The concentration inside the reactor is the same as the outlet • Advantages • Cheap to construct • Large amounts of product • Temperature Control is easy • Disadvantages • Conversion of reactor to product is small compared to other reactors • Deadzones can occur if mixing isn’t done well. https://www.researchgate.net/figure/Schematic-representation-of-the-continuous-stirred-tank-reactor-CSTR

7. CSTR Design Equation Input - Output + Generation = Accumulation https://www.researchgate.net/figure/Schematic-representation-of-the-continuous-stirred-tank-reactor-CSTR

8. Slurry Reactors • Multiphase reactor where gas is bubbled through a solvent containing catalyst particles • Can be operated in batch or continuously • Advantages • Good temperature control • Large heat capacity • Good catalyst control and extended life • Common Applications - Hydrogenation, Oxidation, Hydroformylation, Polymers Elements of Chemical Reaction Engineering, 5th Edition

9. Steps in Slurry Reactor • Adsorption from gas phase to bubble surface • Diffusion from bubble surface to bulk • Diffusion from bulk to catalyst surface • Diffusion from catalyst surface into porous catalyst • Reaction with catalyst Elements of Chemical Reaction Engineering, 5th Edition

10. Design Equation Derivation Rearranging... Elements of Chemical Reaction Engineering, 5th Edition

11. Fluidized Bed Reactors (FBR) • Similar flow pattern to slurry reactors • Bed of solid catalyst, liquid or gas pumped/forced up thru the bed, suspending catalyst particles • “Fluidized” catalyst particles • Useful for: • Catalytic cracking of petroleum naphthas for gasoline • Advantages: • Excellent mixing/contact of catalyst and reactants • Uniform temperature • Continuous regeneration of catalyst • Disadvantages: • Fluid mechanics not well known • Need to overcome gravity to suspend the catalyst/move the fluid • Increased size requirements due to expansion Elements of Chemical Reaction Engineering, 5th Edition

12. FBR Considerations • Velocity/flow rate of fluid/gas must be great enough to suspend solid catalyst, but slow enough that the solid catalyst is not carried out of the reactor with the fluid/gas • Porosity of catalytic bed prior to (and post) fluidization • Mass transfer rates must be taken into account Elements of Chemical Reaction Engineering, 5th Edition

13. Bubbling Bed Model by Kunii & Levenspiel • Reactant gas bubbles up through the reactor • MT of reactant occurs, through the wall of the bubble, onto the solid catalyst particles, which convert to product • MT of product occurs, back through the wall of the bubble, and the resultant reactant/product mixture is carried out of the reactor Conversion depends on rate of MT in/out of bubbles, rate of reaction, as well as on the residence time of reactant in the reactor. Elements of Chemical Reaction Engineering, 5th Edition

14. FBR Design Parameters • Porosity of bed at minimum fluidization • Minimum fluidization velocity • Maximum fluidization velocity • Bubble size • Velocity of bubble rise • Fraction of total bed occupied by bubbles • Fraction of the bed consisting as wakes • Volume of catalyst in bubbles, clouds and emulsion • Mass of solid catalyst

15. Packed Bed Reactor (PBR) • Similar to the previous reactors. • Contains a compartment for the catalyst. • Heterogeneous reactions. • Considerations • Pressure drop • Catalyst size • Most common found in industry • Applications: • Methanol synthesis/oxidation • Styrene production • Wastewater treatment https://www.comsol.com/blogs/packed-bed-reactor/

16. PBR cont... • Advantages • High Conversion per weight of catalyst. • Easy to build. • More contact between reactant and catalyst. • More effective at high temperatures and pressures. • Disadvantages • No temperature control. • Difficulty in replacing catalyst. • Channeling of gas stream. https://www.comsol.com/blogs/packed-bed-reactor/

17. PBR Design equations • Unlike a PFR the volume of the reactor is no longer relevant. • Catalyst weight and density https://www.comsol.com/blogs/packed-bed-reactor/

18. Plug Flow Reactor (PFR) • Reactors that consist of a cylindrical pipe where reactants flow in and products flow out • Plug flow means no radial changes in velocity, temperature, or concentration • Good for various applications in gas and liquid systems • Gasoline Production • Ammonia Synthesis • Advantages • Mechanically simple and easy to maintain • High conversion rate per reactor volume • Disadvantages • Reactor temperature difficult to control • Undesirable thermal gradients Sourced from: https://homes.nano.aau.dk Elements of Chemical Reaction Engineering, 5th Edition

19. PFR Design Equations Elements of Chemical Reaction Engineering, 5th Edition

20. Laminar Flow Reactor (LFR) • Very similar to PFR except it is a tube with laminar flow which means radial changes in velocity • Generally been used in research for multiphase reactions Sourced from: https://www.researchgate.net

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