Complexity in Complex Mixtures For each process chemistry there will be only O(10):

Transcription

1 Reaction Types Complexity in Complex Mixtures For each process chemistry there will be only O(10): Chemical reactions as mathematical operators Conceptually limited types of bond breaking and bond making events Reactivity Correlations for: log 10 A E* K eq K ads LFER s as Chemical Engineering Correlations For each Reaction Family we seek log k model compound data data base to complex mixture I Quantum Chemical, GA Calculation provides I Correlation provides k 10,000 k's of order 10 parameters 1

2 Linear Free Energy Relationships Geometric Rationalization of LFER Physical picture of hypothetical reaction: Na RCl --> NaCl R Variation of R gives Reaction Family Na, Cl-, R BDEIp-Ae BDE (R-Cl) 2 1 Na, Cl, R E* E*= q ' RI Na RCl q R NaCl 2

3 LFER s as Chemical Engineering Correlations For each Reaction Family we seek log k model compound data data base to complex mixture I Quantum Chemical, GA Calculation provides I Correlation provides k 10,000 k's of order 10 parameters Linear Free Energy Relationships Examples 3

4 Linear Free Energy Relationships Examples ln k / k o Linear Free Energy Relationships Examples: Hammett Plots 4

5 The O(10) Pyrolysis Reaction Families Event Example Activation Energies log 10 A (s -1 ) Bond Fission Hydrogen Abstraction E* = BDE = H o f (R' ) Ho f (R ) - Ho f(r'-r) E * = E * o ( H o rxn ) E * (kcal/mol) = ( H o rxn ) k -Scission CH CH E * (kcal/mol) = ( H o rxn ) CH CHCH b CH CH CH CHCH3 Radical Addition Radical Recombination k I CH CH CH 3 k CH CH CH H CH CH3 CH 2 k CH 3 CH RA 2 CH CHCH3 2 CH CH CH CH CH CH CHCH 3 k T CH 3 CH 2 CH 3 E*(kJ/M) = EA(eV) log k300(m-1s -1 ) = EA(eV) E* (kcal/mol)= Linear Free Energy Relationships Examples in Heterogeneous Catalysis 5

6 Hydrocracking Reaction Families O(10) Reaction Types Rxn Hydrogenation Isomerization Ring Opening Dealkylation Structure LFERs for Isomerization Ring Opening Same slope for both reaction families Isomerization much slower than Ring Opening 10-1 Ring Openings Isomerizations k (1/min) 10-2 T = 320 C H c (kcal/mol) 200 6

7 LFERs for Dealkylation k C i C 4-i k k C i C 6-i C i C 6-i log k Hc from Mochida and Yoneda (1967), J.Catal. 9, Hc of alkyl (kcal/mol) 320 LFERs for Hydrogenation: Heat of Reaction Polanyi relationship : E* = E -0 H, = naphthalenic 10-1 phenanthrenic benzenic k (1/min) H rxn (kcal/mol) 7

8 LFERs for Hydrogenation: Bond Orders BO = electron density between two carbon atoms Indicates unsaturation (1ŠBOŠ2, benzene = 1.38) 10-1 k (1/min) Highest Bond Order 1.8 Two-Index LFER for PNA Hydrogenation k (1/min) Highest Bond Order Heat of Reaction (kcal/mol) 8

9 Hydrogenation Equilibrium Parameters: Comparison with Literature Information T=350 C, P=68.1 atm H2= C Values : Keq * PH2^n = Concentration Ratio at Equilibrium Models: Naphthalene, Phenanthrene Hydrogenation Reactions This Work Frye, J.Chem. Eng. Data, 1962, 1969 Frye et al. Compensation in Hydrogenation Equilibria ln Keq = n (1/RT ) rxn S rxn /R/n Srxn n rxn n H /n (kcal/mol) rxn K eq calc K Frye eq * Frye, J. Chem. Eng. Data, 7, 1962, p.592; Frye and Weitcamp, J. Chem. Eng. Data, 14, 1969 p.372 9

10 Adsorption Parameters LFER Kinetic Measurement of KA over Ni/Mo/Al2O3 MNDO calculations of Proton Affinity K (l/mol) NH N This work (Ni/W) This work (USY) PA MNDO (kcal/mol) La Vopa et al. (Ni/Mo) 210 N 215 Data from LaVopa / Satterfield, J.Catal. 110:375 (1988), MNDO Calculations M. Neurock Adsorption Constants for Hydrogenation Sites - Regress Ring Number Lumps (0,1,2,3,4 aromatic Rings) - Denominator exponent did not significantly alter numerators: Kads(n=1) 2*Kads(n=2) K (l/mol) 4-rings/Pyrene rings/Chrysene ring lump ring lump ring lump 7.4 Saturates lump

11 Adsorption LFER: Metal Sites ln Ki (l/mol) = NAR NSC NAR = Number of aromatic rings Activity: Catalyst/PNA acid-base interaction NSC = Number of saturated carbons Availability: Size of the molecule 28 adsorption constants ----> 3 QS/RC parameters LFER s for Metal Center Transformations HYDROGENATION REACTION FAMILY: Regressed Variables QS/RC Parameters Rate: 80 Hrxn, n, T 3 Equilibrium: 80 Hrxn, n, T 2 Adsorption: 136 NAR, NSC, T 3 ln k = -( n) H 0 rxn RT 1 lnk eq = -7.02n ( RT ) H 0 rxn lnk H ads = N AR 0.123N SC RT 11

12 LFER s for Acid Center Transformations ACID CENTER TRANSFORMATIONS REACTION FAMILY: Regressed Variables QS/RC Parameters Rate: 72 Hc, T 5 Equilibrium: 72 Hrxn, T 2 Adsorption 136 NAR, NSC, T 3 ln k = A - B( RT )( RT ) H f c Isomerizations: A=-2.89, B=-305. lnk eq = ( lnk A ads 1 RT ) H 0 rxn = N AR 0.187N SC RT Ring Openings: A=lnPH2-4.64, B=-271. LFER s as a Diagnostic of Alkylbenzenes Intrinsic Chemistry Ring Dealkylation ln(k) y = x R^2 = C7 C9 C5 C15 C19 C12 C4 C2 ²Hrxn of rate determining step: H R 1 R 1 Correlation holds for C2 C7 alkylbenzenes ²Hrxn of Rate-Determining Step (kcal/mol) Departure of intrinsic chemistry beyond C7 alkylbenzene 12

13 LFERs for Hydrogenation -4 y = x R^2 = y = x R^2 = C 8 H 17 C 12 H 25 ln(k) C 10 H 21 C 10 H 21 C 10 H 21 C 12 H 25 C 8 H 17 C 8 H 17 C 12 H 25 C 12 H 25 Polanyi Relationship E*=Eo a H slope Semenov Value) ln(k) a slope for phenanthrenic slope for naphthalenic ²Hrxn of hydrogenation (kcal/mol) 45 LFERs for Ring Closure -4 Tetralin as Example R R H R 1 R 1 R = 1 H (A 1 ) (A 2 ) Step 2 Step 3 y = e-2x R^2 = y = e-2x R^2 = ln(k) C19 C15 C12 C9 C7 C Hf(Tetralin Carbenium Ion) (kcal/mol) C4 200 ln(k) C12 C15 C19 Successful reactivity indices for ring closure: Heat of formation of ring closure carbenium ion ²Hrxn of dealkylation after ring closure Intrinsic correlation fails beyond C9 alkylbenzene C9 C ²Hrxn of Step 3 for Tetralin (kcal/mol) C

14 LFERs for Ring Closure R Indan as Example R H R 1 R 1 (B 1 ) (B 2 ) step 2 step 3 R 1 = H ln(k) y = e-2x R^2 = C9 C7 C15 C19 C12 C5 C4 ln(k) y = x R^2 = C12 C15 C19 C9 C7 C Hf(Indan Carbenium Ion) Successful reactivity indices for ring closure: Heat of formation of ring closure carbenium ion ²Hrxn of dealkylation after ring closure Intrinsic correlation fails beyond C9 alkylbenzene ²Hrxn of Step 3 for Indan (kcal/mol) 70 HC Parameter Reduction via LFER Correlation LFER dependence on temperature accounted Reduce parameters by 90% (122 12) 10-1 k LFER (12 ) k regressed (122 ).1 14

15 O(10) FCC Elementary Step Reaction Families Protolytic Cracking R CH 2 CH 2 R' H R CH 3 CH 2 R' ß-Scission CH 3 (CH 2 ) 2 CH CH 2 CH 3 CH 3 CH 2 CH 2 CH Hydride Transfer CH 2 CH 3 R C H R' R'' CH 2 R''' R CH 2 R' R'' C H R''' Hydride/Methyl Shift R C H CH R' R CH C H R' X X Protonation/ Deprotonation CH 2 R H _ H H CH 2 R PCP Isomerization CH 3 CH 3 CH 2 C H CH 3 CH 3 C CH 3 Summary of Mechanistic Models: Heptane, Hexadecane and Phenyloctane n C 7 n C 16 PO No. of Reaction Families No. of Reactions No. of Species No. of Equations No. of Adjustable Parameters

16 Heptane Model Results Model Regression of Data at T=500 C, Si/Al= n-heptane Conversion WHSV -1, hr Heptane Model Results Model Regression of Data at T=500 C, Si/Al= Predicted Molar Yield Experimental Molar Yield Hydrogen Methane Ethane Ethene Propane Propene n-butane Isobutane 1-Butene 2-Butene Isobutene n-pentane Isopentane Pentenes 16

17 Heptane Model Predictions Temperature Effects 1 n-heptane Conversion WHSV -1, hr 450 C 450 C 500 C 500 C 550 C 550 C Heptane Model Predictions Product Yields T=550 C, Si/Al= Predicted Molar Yield Experimental Molar Yield Hydrogen Methane Ethane Ethene Propane Propene n-butane Isobutane 1-Butene 2-Butene Isobutene n-pentane Isopentane Pentenes 17

18 Heptane Model Predictions Catalyst Effects 1 n-heptane Conversion WHSV -1, hr Si/Al = Si/Al = Si/Al = Si/Al = Si/Al = 63.5 Si/Al = 63.5 Heptane Model Predictions Product Yields T=500 C, Si/Al= Predicted Molar Yield Experimental Molar Yield Hydrogen Methane Ethane Ethene Propane Propene n-butane Isobutane 1-Butene 2-Butene Isobutene n-pentane Isopentane Pentenes 18

19 Linear Free Energy Relationship (LFER) as a Semi Empirical Chemical Engineering Correlation Field Mass Transfer Momentum Transfer Heat Transfer Colburn Analogy Chemistry and Kinetics (LFER) Classic Correlation Sh = 2 0.6Re 1/2 Sc 1/3 f = 16 Re f = Re 025. Nu = 2 0.6Re 1/2 Pr 1/3 Laminar regime Turbulent regime j = j = 1 f f (Re) D, loc H, loc 2 loc log k = a bi H H o R Underlying Basis Mass transfer equation (Continuity) Equation of motion (Navier Stokes) Energy balance equation Similarity in governing eqns. Transition State Theory (Hammett, Evans Polyani, Dewar and Schrodinger) Conclusions Detailed quantitative information on rate, equilibrium and adsorption constants during hydrogenation and hydrocracking of PNAs HYDROGENATION: Pathways and kinetics for PNAs with 1-4 aromatic rings QS/RCs for rate, equilibrium and adsorption constants Reactivity Indices: Bond Order, Reaction Enthalpy Summarize 85 constants representing 1700 concentrations in 10 QS/RC parameters HYDROCRACKING: Pathways and kinetics for PNAs with 1-4 aromatic rings Effect of hydrocarbon and heteroatom inhibition Effect of temperature: Arrhenius and van't'hoff factors 19

20 Linear Free Energy Relationships Examples 20