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Isomerization of Mixed Xylene – Ethylbenzene Feeds over ... Phenol, Bisphenol-A,...

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  • This material is not to be reproduced without the permission of Exxon Mobil Corporation.

    Thomas F. Degnan, Jr., David H. Olson, and B. K. HuhExxonMobil Research and Engineering CompanyAmerican Institute of Chemical Engineers Annual MeetingSan Francisco, CAMonday, November 4, 2013

    Isomerization of Mixed Xylene Ethylbenzene Feeds over ZSM-5:Analysis of Kinetics and Diffusion of C10 Transalkylation ProductsIn Honor of Professor W. Nicholas Delgass 2012 R. H. Wilhelm Award Recipient

  • 2

    Congratulations Nick!

    Great friend, wonderful colleague, and inspirational teacher

    2003 Purdue University Outstanding Undergraduate Teaching Award in memory of Charles B. Murphy.

    Dean A.A. Potter Teaching Award, Purdue, Schools of Engineering, 1990. R.N. Shreve Teaching Award, Purdue School of Chemical Engineering, 1983,

    1986, 1989,1991, 2000 and 2002. Purdue Schools of Engineering Mentoring Excellence Award 2003. New York Catalysis Society Excellence in Catalysis Award, 2006 Inaugural North American Catalysis Society (NACS) Award for Distinguished

    Service in the Advancement of Catalysis, 2010 AIChE R. H. Wilhelm Award, 2012

  • 3

    Manufacture of High Value Alkylaromatics

    Alkylaromatic Major Uses WW Production, lbs/yr Ethylbenzene Styrene, Polystyrene 60 BillionCumene Phenol, Bisphenol-A, Polycarbonate 18 BillionPara-Xylene Terephthalic acid, Polyester 36 Billion

    Reformer

    Fractionation TransalkylationC9+ , C6/C7

    Isomerization

    Disproportionation

    Cumene Synthesis

    EB Synthesis

    Xylene

    Toluene

    Benzene

    C2=

    C3=

    Ethylbenzene

    Cumene

    Para-Xylene

    BenzeneCracker / Separations

    2011

  • 4

    Manufacture of High Value Alkylaromatics

    Alkylaromatic Major Uses WW Production, lbs/yr Ethylbenzene Styrene, Polystyrene 60 BillionCumene Phenol, Bisphenol-A, Polycarbonate 18 BillionPara-Xylene Terephthalic acid, Polyester 36 Billion

    Reformer

    Fractionation TransalkylationC9+ , C6/C7

    Isomerization

    Disproportionation

    Cumene Synthesis

    EB Synthesis

    Xylene

    Toluene

    Benzene

    C2=

    C3=

    Ethylbenzene

    Cumene

    Para-Xylene

    BenzeneCracker / Separations

    2011

  • 5

    Para-Xylene Can be Produced Via Equilibrium or Selective Processes

    +2

    +2

    Xylene Isomerization Toluene Disproportionation

    XylenesAt

    Equilibrium

    SelectiveProcesses

    EquilibriumProcesses

    Transalkylation

    Selective TolueneDisproportionation

    22% Ortho- 54% Meta- 24% Para-

    Para- >> 24%

    Para- ~ 24%

    Para- ~ 24%

    All ProcessesRequire

    Separation

    + 2

  • 6

    ExxonMobils Xylene IsomerizationProcess Development HistoryContinuous Development and Improvement for 35+ Years

    Lower pX Concentration in Isom feeds(e.g. from adsorption)

    Higher pX Concentration in Isom feeds(e.g. from crystallizers)

    MHAI1990

    MHTI1981

    MLPI1978

    MVPI1975

    AdvancedMobilHighActivityIsom.

    MobilHighActivityIsom.

    MobilHighTemperatureIsom.

    MobilLowPressureIsom.

    MobilVaporPhaseIsom.

  • 7

    ExxonMobil MHAIXylene Isomerization Process

    p-Xylene recovery

    Unit

    C9+ Aromatics

    Make-up Hydrogen

    Separator

    Compressor Hydrogen Recycle

    Gas

    Benzene &Toluene

    Isomerate

    CW

    Stabilizer

    Reactor

    Furnace

    XyleneColumn

    Para-xylene

    C8AromaticHeart-cut

    EBConversion

    Xylene Isomerization

    Catalysts

    +

  • 8

    ExxonMobil MHAIXylene Isomerization Process

    p-Xylene recovery

    Unit

    C9+ Aromatics

    Make-up Hydrogen

    Separator

    Compressor Hydrogen Recycle

    Gas

    Benzene &Toluene

    Isomerate

    CW

    Stabilizer

    Reactor

    Furnace

    XyleneColumn

    Para-xylene

    C8AromaticHeart-cut

    EBConversion

    Xylene Isomerization

    Catalysts

    +

  • 9

    Transalkylation Reactions inthe Ethylbenzene Xylene System

    +

    +

    E , E

    E , X+

    X , E++

    X , X+ +

    Ref: D. H. Olson and W. O. Haag, ACS Symp.Ser. 248, pp. 275 307 (1984)

    +

  • 10

    Xylene EB TransalkylationProduces C9 and C10 Aromatics

    ZSM-5 Crystal

    + +

    +

    + +

    +

    + +

    DEB

    DMEB

    kE,E

    kX,E kE,X

    kX,X

  • 11

    Xylene EB TransalkylationProduces C9 and C10 Aromatics

    ZSM-5 Crystal

    + +

    +

    + +

    +

    + +

    DEB

    DMEB

    kE,E

    kX,E kE,X

    kX,X

    Changes in DEB/DMEBRatio are indicators ofIntracrystallinediffusivity

  • 12

    Transalkylation Kinetic Parametersin EB Xylene System

    Relative Rate ConstantsReaction ZSM-4 Mordenite ZSM-5

    E, E 10.4 20.8 125.0E, X 2.2 3.6 16.8X, E 1.3 1.5 3.6X, X 1.0 1.0 1.0

    Ethyl vs. Methyl TransferkE,E / kX,E 8.0 13.9 34.7kE,X / kX,X 2.2 3.6 16.8

    Ethylbenzene vs. XylenekE,E / kE,X 4.7 5.8 7.4kX,E / kX,X 1.3 1.5 3.6Memo: Conditions: 250 280oC, 2800 kPa, WHSV = 2 to 20 hr-1

    Ref: D. H. Olson and W. O. Haag, ACS Symp.Ser. 248, pp. 275 307 (1984)

  • 13

    Aromatic Kinetic Diameters areClose to Pore Diameters of ZSM-5

    Straight Channel5.4 x 5.6

    Sinusoidal Channel5.1 x 5.5

    Kinetic Diameter of Aromatics Close to the Pore Size of ZSM-56.8 6.8 5.8 5.8 5.8 5.8

    ~ ~ ~ ~

    Ortho-Xylene Meta-Xylene Para-Xylene Ethylbenzene

    >

    Toluene Benzene

  • 14

    The Role of Shape Selective Zeolites in C8 C10 Aromatic Reactions

    Reactant Selectivity (Hydrodealkylation)

    Product or Isomer Selectivity (Selective Toluene Disproportionation)

    + H 2 +

    +2

    Csicsery, J Catal 1971, 23, 124

    5.8 6.8 6.8

    Metal

    Transition State Selectivity (C8 Aromatics Disproportionation)

    +very low

    yields+ +Bulky

  • 15

    Study Objectives

    Examine the diffusional characteristics of C10 transalkylation products (DMEB and DEB) in ZSM-5 catalyzed Isomerization of Xylene: Ethylbenzene Feeds

    ZSM-5 catalyzed isomerization of a mixed Xylene: EB feed Mixed Xylenes (86 wt%) : Ethylbenzene (14 wt%) Temperatures: 350o 390oC WHSV = 2 to 150 hr-1

    H2 : Hydrocarbon molar ratios = 2 to 4 Pressure = 1480 kPa

  • 16

    ZSM-5 Catalysts

    Designation Relative Activity (C6 cracking)

    D/r2 , sec-1(p-Xylene uptake

    method)SCLA 1.5 3.2 x 10-4

    MCLA 1.0 4.7 x 10-5

    LCLA 1.3 6.3 x 10-6

    SCMA 13.3 3.4 x 10-4

    MCMA 17.5 4.5 x 10-5

    LCMA 6.7 5.7 x 10-6

    SCHA 70.0 3.1 x 10-4

    MCHA 58.3 3.3 x 10-5

    LCHA 54.7 5.0 x 10-6

    Memo: SC - Small Crystal; MC - Midsize Crystal; LC - Large Crystal; LA Low Activity; MA Moderate Activity; HA High Activity

  • 17

    Effect of ZSM-5 Acidity onDiethylbenzene (DEB) Yield

    EB Conversion, mole pct.

    DE

    B Y

    ield

    , mol

    e pc

    t.

    Temperature: 370oCWHSV = 2 to 150 hr-1H2 : Hydrocarbon molar ratios = 2 to 4Pressure = 1480 kPa

    Large Crystal

    Low activityModerate activityHigh activity

  • 18

    Small Crystal

    Medium Crystal

    Large Crystal

    Effect of Crystal Size onDiethylbenzene (DEB) Yield

    Temperature: 370oCWHSV = 2 to 150 hr-1H2 : Hydrocarbon molar ratios = 2 to 4Pressure = 1480 kPa

    EB Conversion, mole pct.

    DE

    B Y

    ield

    , mol

    e pc

    t.

  • 19

    Small Crystal

    Medium Crystal

    Large Crystal

    Effect of Crystal Size onDimethylethylbenzene (DMEB) Yield

    Temperature: 370oCWHSV = 2 to 150 hr-1H2 : Hydrocarbon molar ratios = 2 to 4Pressure = 1480 kPa

    EB Conversion, mole pct.

    DM

    EB

    Yie

    ld, m

    ole

    pct.

  • 20

    Small Crystal

    Medium Crystal

    Large Crystal

    Effect of Crystal Size onDEB / DMEB Ratio

    Temperature: 370oCWHSV = 2 to 150 hr-1H2 : Hydrocarbon molar ratios = 2 to 4Pressure = 1480 kPa

    EB Conversion, mole pct.

    DE

    B /

    DM

    EB

    Rat

    io, m

    olar

  • 21

    Summary: Effects of ZSM-5 Crystal Size

    DEB yield is a direct function of the zeolite acidity, or number of acid sites.

    DEB yield is a strong function of EB conversion and a mild function of crystal size.

    Conversely, DMEB yield is a strong function of crystal size, indicating that it is more strongly influenced by intracrystalline diffusivity and crystal size.

    DEB/DMEB Ratio increases with ZSM-5 crystal size and activity which is consistent with differences in the intracrystalline diffusivities of DEB and DMEB

  • 22

    0.1

    1

    10

    0 0.02 0.04 0.06 0.08

    DEB and DMEB:First Order Kinetics

    1/WHSV

    kDEB = 60 hr-1

    Small Crystal; Low Activity ZSM-5370oC1515 kPa

    kDEB = k E E kDMEB= k X E

    1/WHSV

    DMEB

    Production of Diethylbenzene andDimethylethylbenzene are both governed by First Order Kinetics

    DEB

    No diffusion limitation expected - withlow crystal activities and small crystal

    0.01

    0.1

    1

    0 0.02 0.04 0.06 0.08

    kDMEB = 6 hr-1

    Olson and Haag This (1984) Study

    kDEB / kDMEB 7.4 10.0

    Frac

    tion

    DM

    EB

    in P

    rodu

    ct, m

    olar

    Frac

    tion

    DM

    EB

    in P

    rodu

    ct, m

    olar

    Ref: D. H. Olson and W. O. Haag, ACS Symp.Ser. 248, pp.

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