1. From Model Component Behaviour to Industrial Reactor Simulation: Aromatic Hydrogenation in Hydrocracking J. W. Thybaut and G. B. Marin Laboratorium voor Petrochemische Techniek, Ghent University Eurokin Workshop, Dow Terneuzen, November 25, 2002

2. (hydro)cracking as refinery process gasses diesel heavy gasoil residu medium gasoil kerosine LPG naphtha reforming alkylation cracking coking LPG gasoline kerosine diesel LPG/gasoline kerosine diesel industrial fuel bitumen destillation tower end products hydrocracking catalytic cracking

3. detailed refinery scheme

5. catalytic versus hydrocracking catalytic cracking carbon rejection riser-regenerator- configuration LPG/gasoline product rich in unsaturated components hydrocracking hydrogen addition downflow packed bed kerosine/diesel few aromatics, low S- en N-content in product choice is nuanciated and depends on local conditions

6. hydrocracking: reaction mechanism fluidum phase physisorption (de)-hydrogenation (de)-protonation alkyl-shift PCP-branching ß-scission zeolite metal sites acid sites + + + + + +

7. overview single-event model carbon number and acid strength effects in hydrocracking toluene hydrogenation in the vapor phase toluene hydrogenation in the liquid phase simulation of an industrial reactor

8. single event alkyl-shift, PCP-branching,  -scission rate coefficient depends on reaction type and type of the carbenium ions involved (s,t) forward and backward reaction are one elemenatry step forward step consists of 2x more single events than the backward step + +

9. building blocks rate equation alkyl-shift PCP-branching  -scission (de)-protonation (de)-hydrogenation physisorption

10. detailed rate equation via physisorption experiments carbon number dependent zeolite dependent (geometry) via thermodynamics via NH 3 -TPD: zeolite dependent (number of sites) via operating conditions parameters to be estimated: carbon number dependent zeolite dependent (acid strength) via reaction network

11. net rates of formation summation over all elementary steps number of terms increases with carbon number  ‘re’lumping: fast & fundamental

12. overview single-event model carbon number and acid strength effects in hydrocracking toluene hydrogenation in the vapor phase toluene hydrogenation in the liquid phase simulation of an industrial reactor

13. carbon number effect (i) physisorption effects, (ii) extent reaction network, (iii) carbenium ion stability

14. single-event model does account for nearest neighbour effects but not for next-nearest neighbour effects important for low carbon numbers single-event model does account for nearest neighbour effects carbenium ion stability + + + +

15. standard protonation enthalpy same effect on reacting carbenium ion and activated complex + + n-nonanen-octane + +

16. quantitative important for lower carbon numbers levelling out for higher carbon numbers

17. catalyst effect (i) physisorption, (ii) number of sites, (iii) acid strength

18. standard protonation enthalpy same effect of acid strength on stability of reacting carbenium ion and activated complex + zeolite Izeolite II + + +

19. quantitative Y-zeolite: weakest acid sites intermediate dealumination degree  strongest acid sites

20. overview single-event model carbon number and acid strength effects in hydrocracking toluene hydrogenation in the vapor phase toluene hydrogenation in the liquid phase simulation of an industrial reactor

21. microkinetic model model construction literature quantumchemical calculations experiments

22. experimental inlet partial pressure effects negative for toluene m  -0.2 positive for hydrogen n  0.6 tot 1.8

23. quantumchemistry & literature + 3 H 2 + 6 H + 2 H 2 + 4 H + H 2 + 2 H gas phase catalyst surface

24. model assumptions Competitive H 2 and toluene chemisorption (E) 1 st & 2 nd H-addition not rate determining (Q) 5 th & 6 th H-addition quasi equilibrated (L) reactant chemisorption quasi equilibrated product desorption fast and irreversible equal rate coefficients 1 st to 4 th H-addition (no rate-determining step) 3 rd of 4 th H-addition rate determining

25. reaction scheme desorption surface reactions chemisorption

26. rate equation equal rate coefficients rate-determining step i=3,4

27. calculation preexponential factors = 10 -12 immobile surface species = 10 -10 mobile surface species = 10 15 mobility in transition state = 10 -2 2 reactants  1 product with

28. estimation enthalpies/energies chemisorption enthalpies: toluene: -70 kJ mol -1 hydrogen: -42 kJ mol -1 activation energies: similar behaviour of ‘no RDS’ and ‘4H RDS’  ‘no RDS’ because of its more general character no RDS3H RDS4H RDS E act (kJ mol -1 ) 3880 35 F-value10 4 5 10 2 10 4

29. agreement model - experiments surface concentrations –toluene: high (60%) –hydrogen: low (20%) –free sites: low (20%)

30. overview single-event model carbon number and acid strength effects in hydrocracking toluene hydrogenation in the vapor phase toluene hydrogenation in the liquid phase simulation of an industrial reactor

31. gas versus liquid industrial: –3-phase reactor (gas/liquid/solid) laboratory : –gas phase reactor (Berty): reaction mechanism –3-phase reactor (Robinson- Mahoney): liquid phase effects Berty reactor Robinson Mahoney reactor

32. model construction kinetic scheme: identical thermodynamic ideality: –gas phase: ideal (fugacities > 0.95, even >0.99) –liquid:non ideal –chemisorbed state: ideal mixture liquid: –deviation from ideality with respect to ideal gas state (comparison with gas phase results) chemisorbed state: –only interaction with catalyst surface, independent from surface concentrations  ideal mixture

33. rate equation liquid phase gas phase

34. simulation & regression simulation results in too high toluene conversions  adjust via regression

35. model describes liquid phase aspects in chemisorption regression results model describes liquid phase aspects in chemisorption surface reaction steps are affected by the aggregation state of the reactants, higher activation energies are observed in the liquid phase

36. overview single-event model carbon number and acid strength effects in hydrocracking toluene hydrogenation in the vapor phase toluene hydrogenation in the liquid phase simulation of an industrial reactor

37. simulation model reactor model –mass, energy and momentum balance –geometry reaction model (kinetics) –relumped single-event model for isomerization and cracking of (cyclo)- alkanes –microkinetic model for the hydrogenation of aromatic components

38. reactor equations geometry –cocurrent downflow packed bed reactor mass & heat transfer limitations –gas liquid interface: mass & heat –liquid solid interface: none –internal: mass

39. geometry & operating conditions

40. temperature profiles

41. aromatic profile

42. hydrogen profiles

43. aromatic content - temperature profile

44. aromatic content - aromatic profile

45. aromatic content - hydrogen profile

46. conclusions standard protonation enthalpy in hydrocracking –describes the carbon number dependence –describes acid strength effects hydrogenation of aromatics –effect aromatic resonance stabilization disappears upon chemisorption on Pt-surface –equal rate coefficients for first 4 H-additions

47. conclusions liquid phase –fugacities adequately describe liquid phase effects in chemisorption –surface reaction steps are affected by the aggregation state of the reactants simulation of an industrial reactor –hydrogenation of aromatics leads to ‘hot spot’ –mass transfer limitations between gas and liquid phase for high aromatic content in the feed

48. acknowledgement IAP-PAI programme funded by the Belgian Government, financial support Mark Saeys, quantumchemical calculations