of structure of new UOP zeolite UZM-5. - UZM-5: Rietveld refinement by XRD was not definitive due to broadening of the peaks due to the morphology of the.
Methanol to Olefins (MTO): Development of a Commercial Catalytic Process Simon R. Bare Advanced Characterization, UOP LLC
Modern Methods in Heterogeneous Catalysis Research FHI Lecture November 30, 2007 1
© 2007 UOP LLC, All Rights Reserved
Polyethylene and Polypropylene • Thousands of uses of polyethylene and polypropylene.
2
Polyethylene and Polypropylene • Main source of the ethylene and propylene (monomer feedstock for polyethylene and polypropylene) is steam cracking of naphtha or other hydrocarbon. Naphtha (C5-C9) Ethane HCBN
3
Steam Cracking >850°C, millisec
C2= + C3= + C3+
Methanol To Olefins (MTO) Reaction • Methanol is an alternate source of light olefins. • Dehydration with shape selective transformation to low molecular weight alkenes.
Methanol
SAPO-34 Catalyst
Ethylene Propylene
Δ
Butenes
4
Other By-Products H2O H2 , COX C1-C5 Paraffins C5+ Coke
UOP/Hydro MTO Process SAPO-34 Catalyst
H 2O
CH3OH
5
Courtesy to Unni Olsbye, University of Oslo
MTO Reaction • High selectivity and yield to light olefins. Material T atom % Selectivities (2 hr) C2-C4 olefins CH4 C2H6 C3H8 Stability hr at >50% conversion Coking carbon on used catalyst
SAPO-34 10% Si (gel) 96 1.4 0.3 0.9 >40 19% after 54 HOS
• Many acid catalysts are active for the methanol dehydration – what makes SAPO-34 the preferred catalyst? Yuen, et al., Microporous Materials, 2 (1994) 105 6
Outline • Zeolites • Zeolites as industrial catalysts • Acid sites in molecular sieves • Aluminum phosphate (AlPO4) molecular sieves • Characterization methods for molecular sieves • SAPO-34 • Methanol conversion using zeolites • Zeolites vs. SAPO’s in methanol conversion • CHA and AEI • MTO mechanism • MTO reactor design • Putting it all together: methanol & natural gas • Discovery to commercialization 7
What is a Zeolite?
• Zeolites occur in nature.
Mordenite 8
Chabazite
Natrolite
Zeolites • Zeolites consist of a framework built of tetrahedra. • Each tetrahedron comprises a T-atom bound to four O atoms. • Oxygen bridges connect the tetrahedra. • T-atoms are Si or Al.
T
O
9
Courtesy to Francesca Bleken, University of Oslo
Zeolites • Alumino-silicate framework • Crystalline, microporous (pore diameter 3-14Å) • Framework density 12-ring >8A
Acid Sites in Zeolites • Substitute Al3+ for Si4+: charge imbalance – need additional cation to compensate. O Si
H Al
13
• No total charge.
• One extra charge per Al atom introduced into the lattice. • Cations compensate for total charge. • Protons as cations give Brønsted acid properties. Courtesy to Francesca Bleken, University of Oslo
Evolution of Molecular Sieve Compositions
Time of Initial Discovery
14
Composition
Late 40's to Early 50's
Low Si/Al Ratio Zeolites
Mid 50's to late 60's
High Si/Al Ratio Zeolites
Early 70's
Pure SiO2 Molecular Sieves
Late 70's
AlPO4 Molecular Sieves
Late 70's to Early 80's
SAPO and MeAPO Molecular Sieves
Late 70's
Metallo-silicates, -aluminosilicates
Early to Mid 90's
Mesoporous Molecular Sieves Octahedral-tetrahedral Frameworks
Framework Types • 176 framework types recognized by the International Zeolite Association (IZA) (http://www.iza-online.org/). • IZA Structure Commission assigns framework type codes to all unique and confirmed framework topologies. ABW AFT ATT CAS DFO EUO ISV LOS MFS NES PON SAT SOD UOZ
15
ACO AFX ATV CDO DFT FAU ITE LOV MON NON RHO SAV SOS USI
AEI AFY AWO CFI DOH FER ITH LTA MOR NPO -RON SBE SSY UTL
AEL AHT AWW CGF DON FRA ITW LTL MOZ NSI RRO SBS STF VET
AEN ANA BCT CGS EAB GIS IWR LTN MSO OBW RSN SBT STI VFI
AET APC *BEA CHA EDI GIU IWW MAR MTF OFF RTE SFE STT VNI
AFG APD BEC -CHI EMT GME JBW MAZ MTN OSI RTH SFF TER VSV
AFI AST BIK -CLO EON GON KFI MEI MTT OSO RUT SFG THO WEI
AFN ASV BOG CON EPI GOO LAU MEL MTW OWE RWR SFH TON -WEN
AFO ATN BPH CZP ERI HEU LEV MEP MWW -PAR RWY SFN TSC YUG
AFR ATO BRE DAC ESV IFR LIO MER NAB PAU SAO SFO UEI ZON
AFS ATS CAN DDR ETR IHW -LIT MFI NAT PHI SAS SGT UFI
Zeolites as Industrial Catalysts • But only ~18 framework types have seen commercial utility. ABW AFT ATT CAS DFO EUO ISV LOS MFS NES PON SAT SOD UOZ
ACO AFX ATV CDO DFT FAU ITE LOV MON NON RHO SAV SOS USI
AEI AFY AWO CFI DOH FER ITH LTA MOR NPO -RON SBE SSY UTL
AEL AEL AEN AHT AWW CGF DON FRA ITW LTL MOZ NSI RRO SBS STF VET
ANA BCT CGS EAB GIS IWR LTN MSO OBW RSN SBT STI VFI
AET APC *BEA CHA EDI GIU IWW MAR MTF OFF RTE SFE STT VNI
BEA CHA EUO FAU FER GIS LTA LTL MOR RHO
16
AFG APD BEC -CHI EMT GME JBW MAZ MTN OSI RTH SFF TER VSV
AFI AST BIK -CLO EON GON KFI MEI MTT OSO RUT SFG THO WEI
AFN ASV BOG CON EPI GOO LAU MEL MTW OWE RWR SFH TON -WEN
AFO ATN BPH CZP ERI HEU LEV MEP MWW -PAR RWY SFN TSC YUG
ERI HEU
AFR ATO BRE DAC ESV IFR LIO MER NAB PAU SAO SFO UEI ZON
MTW MWW
AFS ATS CAN DDR ETR IHW -LIT MFI NAT PHI SAS SGT UFI
MFI
Commercial Catalytic Uses of Zeolites (Refining & Petrochemicals) Process Ethylbenzene Cumene Other aromatics Xylene isom C4 isom C4= isom C5= isom Iso-dewaxing Amination C3,C4 arom Naphtha arom FCC Dewaxing Hydrocracking MTG MTO Toluene trans-alkylation
FAU = Y, USY MWW = MCM-22 RHO = zeolite RHO 17
FAU LTL MOR BEA MWW MFI AEL FER RHO CHA ??? x
x
x
x x
x x x x
x x
x x x
x
x x
x x
x x
x
x
x x x
x x x x x x
x x
LTL = Linde L, K-L MOR = mordenite BEA = beta MFI = ZSM-5 AEL = SAPO-11, SM-3 FER = ferrierite CHA = chabazite, SAPO-34 K. Tanabe and W. Holderich, Appl. Catal. A, 399 (1999) 181
Alumino-phosphate (AlPO4) Molecular Sieves • Microporous solids similar to silico-aluminate zeolites – but composed of interlinked tetrahedra of AlO4 and PO4 vs. AlO4 and SiO4. • Alternating Al-O-P bonds • Almost never Al-O-Al, and never P-O-P (due to charge and lack of hydrothermal stability). O Al
18
P
Idealized 2D Connectivity of tetrahedral AlPO4 framework • Al and P strictly alternating. • Neutral framework.
19
Al
P
Al
P
Al
P
Al
P
P
Al
P
Al
P
Al
P
Al
Al
P
Al
P
Al
P
Al
P
P
Al
P
Al
P
Al
P
Al
Al
P
Al
P
Al
P
Al
P
P
Al
P
Al
P
Al
P
Al
Al
P
Al
P
Al
P
Al
P
P
Al
P
Al
P
Al
P
Al
Si Substitution for P in AlPO4 to give SAPO • Si substitution for P in AlPO4 yields negative framework charge and Brønsted acid sites. Isolated Si: Si+4 →P+5
Al
P
Al
P
Al
P
Al
P
P
Al
P
Al
P
Al
P
Al
Al
Si
Al
P
Al
P
Al
P
P
Al
P
Al
P
Al
P
Al
Al
P
Al
P
Al
P
Al
P
No Si-O-P
P
Al
P
Al
P
Al
P
Al
No P-O-P
Al
P
Al
P
Al
P
Al
P
P
Al
P
Al
P
Al
P
Al
Negative framework charge Template decomposition →H+
20
H
Si Substitution Produces Brønsted Acid Sties Si island Isolated Si
Al
P
Al
P
Al
P
Al
P
1 Si = 1P
P
Al
P
Al
P
Al
P
Al
1 Si = 1 H+
Al
Si
Al
P
Al
Si
Al
P
P Al
H
Al
P
P
Al
Si
Si
H
H
Si
5 Si = 4P + 1 Al 5 Si = 3 H+
Al
Yes
Al
P
Al
Si H Al
P
Al-O-P
Si
Al
P
Al
Al
Si-O-Al
Adjacent isolated Si
P
2 Si = 2P
Al
Si
Al
P
Al
P
Al
P
No
2 Si = 2 H+
P
Al
P
Al
P
Al
P
Al
Al-O-Al
H Al
H
P
Si-O-Si
P-O-P Si-O-P 21
Outline • Zeolites • Zeolites as industrial catalysts • Acid sites in molecular sieves • Aluminum phosphate (AlPO4) molecular sieves • Characterization methods for molecular sieves • SAPO-34 • Methanol conversion using zeolites • Zeolites vs. SAPO’s in methanol conversion • CHA and AEI • MTO mechanism • MTO reactor design • Putting it all together: methanol & natural gas • Discovery to commercialization 22
Characterization Methods for Zeolites • NH3 TPD • Hydroxyl FTIR • Pyridine FTIR • Framework FTIR • Low temperature CO FTIR • Solid State NMR • Electron microscopy: SEM/TEM • XPS • XRD • EXAFS • Many others….. 23
Acidic Sites: Use of Base for Characterization • Acidic catalyst surface may expose both protic (Brønsted) and aprotic (Lewis) sites. • Protic sites in a zeolite are surface hydroxyl groups OH. • Aprotic sites in zeolite are typically extraframework Al surface cations. • Basic probe molecule will interact with OH via hydrogen bonding: OHs + B ⇔ OHs…Β • If OH is sufficiently acidic then proton transfer: OHs…Β ⇔ Os−…Η+Β • For aprotic sites the base will form a Lewis acidbase adduct: L + B ⇔ L←B
24
Ammonia Temperature Programmed Desorption • NH3 TPD is used to measure the amount and relative strength of the acid sites. • NH3 small molecule but not very specific. H
H H
H
H
N N
H Ammonia
Al Lewis acid (electron acceptor)
Al Brønsted acid (proton donor)
25
N H+ O
oo
H H
H
Ammonia Temperature Programmed Desorption
Linear temperature ramp. Amount of ammonia desorbed as a function of temperature recorded and quantified. 700
18
14
Temperature (°C)
500
12
400
10
300
8 6
200
4 100
2
0
0 0
10
20
30
40
Time (minutes) 26
50
60
70
80
Rate of NH3 Desorption
16
600
Hydroxyl FTIR • Use FTIR to measure the infra red spectrum of the zeolite. • The vibrational frequency of the hydroxyl species in the sample is dependent on the type of hydroxyl species present. • Can differentiate between framework and extraframework species. Terminal Si-OH
BEA
Terminal Si-OH
Absorbance
.4
.3
Extra-framework Al-OH
.2
Non-framework Al-OH
Bridging Si-OH-Al
3Bridging OH
.1
Extra-framework Al-OH Terminal Al-OH
0 3900
3800
3700
3600 3500 3400 Wavenumber (cm-1)
3300
3200
3100
3000
Normalized
27
H. Knözinger in Handbook of Heterogeneous Catalysis, Vol 2, p. 707
Hydroxyl FTIR • Transformation of IR spectrum on steaming of zeolite BEA. • Dealumination of framework Al species. Starting Material Steamed 5%; 550C; 24hrs Steamed 10%; 600C; 24hrs
Terminal Si-OH Terminal Si-OH
Absorbance
.4
.3
Extra-framework Al-OH
.2
Non-framework Al-OH
Bridging Si-OH-Al Bridging OH
.1
Extra-framework Terminal Al-OH Al-OH
0 3900
3800
3700
3600 3500 3400 Wavenumber (cm-1) Normalized
28
3300
3200
3100
3000
Pyridine FTIR: Basics • Pyridine is a weak base which coordinates with both Brønsted and Lewis acid sites. • Distinct FTIR-active bands are observed for each type of acid site. • The integrated intensity provides a relative measure of the number of each site. • The desorption temperature provides a relative measure of the acid site strength. • Most useful when comparing a series of samples.
+
Ring vibrational modes
1450 cm-1
N N
L Lewis (aprotic) 29
H O-
1550 cm-1
B Brønsted (protic)
Pyridine FTIR: Spectrum Hydroxyl Region Pyridine Adsorption
Absorbance
1.5
Pyridine adsorption attenuates bridging OH groups; bands are restored upon pyridine desorption
Bridging OH
1
N-H bands .5
Si-OH 0 3900
3800
3700
3600
3500 3400 3300 Wavenumber (cm-1)
3200
File # 1 : Y-64PRTC
3000
Pyridine Adsorption Spectral Region
Key: Pretreated After 150C After 300C After 450C
Brønsted/Lewis 1.5
Absorbance
Pyridine adsorption yields distinct Brønsted and Lewis acid site absorbance bands in this region
30
3100
1
Brønsted/Lewis
Brønsted
.5
0
1650
File # 1 : Y-64PRTC
1600
Lewis
1550 1500 1450 Wavenumber (cm-1)
1400
1350
1300
Pyridine FTIR: Acid Site Distribution Pyridine Adsorption IR
Integrated area of pyridine adsorbed on Brønsted acid site; ~ 1550 cm-1
Brönsted Acid Site Distribution Integrated Area/mg
1.2 1 0.8 0.6 0.4
Integrated area of pyridine adsorbed on Lewis acid site; ~1450 cm -1.
0.2 0 Sample 1
Weak
Moderate
Strong
Total
Pyridine Adsorption IR
Moderate site: pyridine desorbed between 300ºC and 450ºC Strong site: pyridine remaining after 450 ºC desorption 31
Lewis Acid Site Distribution 0.6
Integrated Area/mg
Weak Site: pyridine desorbed between 150ºC and 300ºC
0.5 0.4 0.3 0.2 0.1 0 Sample 1
Weak
Moderate
Strong
Total
Framework FTIR
Absorbance
• Framework region (1400 - 400 cm-1) contains information on T-O-T modes, ring modes of zeolites • T-O-T(asym) frequency shifts with Si/Al2 ratio.
2 1.5
Before calcination – 1091.4 cm -1 325C Steamed - 1095.6 cm -1 550C Steamed - 1098.9 cm -1 610C steamed - 1100.8 cm -1
T-O-T stretch Loss of framework aluminum from higher temp steaming results in shift of T-O-T stretch
1 .5 0
1600
1400
1200
1000
Wavenumber(cm-1) Wavenumber
32
800
600
Low Temperature CO FTIR • CO is a small, very weak, soft base - Accessible to small pores • Reversible adsorption at 11
Usually < 9
Temperature
25 – 200°C
100 – 200°C
Time
Hours – weeks
Usually < 3 days
Template Packing in SAPO-34 • >30 templates make SAPO CHA framework type. - Most not well studied - TEAOH is most common
N-Mebutylamine
46
Morpholine
Cyclam
Calculating Acid Site Density of CHA Framework • Elemental analysis of SAPO best expressed as mole fraction:
- SixAlyPzO2 where x + y + z = 1.00 • Framework charge = [Al – P] = [Si] if Si is isolated
• Each cage bounded by 36 TO2 • Each TO2 is shared by 3 cages • 1 acid site per cage = 0.03 Si
47
Acid Site Location: Dehydrated D-SAPO-34 • Neutron diffraction used to locate the actual position of the acid sites in CHA cage. Protons attached to O4 (4.0% occupancy) More acidic 3630 cm-1
8-ring
8-ring
Protons attached to O2 (3.4% occupancy) Less acidic 3601 cm-1
L. Smith et al, Catal. Lett. 1996, 41, 13 48
Discovery of ALPO and SAPO Materials • In late 70’s Edith Flanigen’s group at Union Carbide given the challenge:
“Discover the next generation of molecular sieve materials” • Words of Edith Flanigen ……
49
Discovery of ALPO and SAPO Materials • A commitment on part of management to support long-range innovative discovery with no guarantee for commercial success. • Willingness to take that risk and to assign significant resources to back up that commitment. • Patience to allow major discoveries to find their place in the commercial world. • Creating an environment and culture that fostered innovation and that attracted the best scientists and challenged them to their limits. • Allowing them freedom to dream, and trusting that they would succeed. • Recognizing and rewarding them when they did succeed. 50
Outline • Zeolites • Zeolites as industrial catalysts • Acid sites in molecular sieves • Aluminum phosphate (AlPO4) molecular sieves • Characterization methods for molecular sieves • SAPO-34 • Methanol conversion using zeolites • Zeolites vs. SAPO’s in methanol conversion • CHA and AEI • MTO mechanism • MTO reactor design • Putting it all together: methanol & natural gas • Discovery to commercialization 51
Methanol Conversion using Zeolites • 1975 – Mobil Oil discloses ZSM-5 catalyst for conversion of methanol to gasoline (MTG)
2 CH3OH
-H2O +H2O
CH3-O-CH3 -H2O
Isoparaffins Aromatics C6+ olefins
C2 - C5 olefins
Chang, Silvestri, and Smith, US 3894103 and 3928483 52
Methanol Conversion over Zeolites • Several zeolites with Brønsted acid sites show activity for methanol conversion. Pore Size Examples Performance (low conversion) Small ERI Light olefins ERI/OFF KFI Medium MFI Olefins FER MTT Large MOR FAU
53
Performance (high conversion) Paraffins Paraffins Aromatics Olefins Aromatics Paraffins
G.F. Froment et al, Catalysis (London), 9, 1 (1992)
Methanol to Hydrocarbons CHA, SAPO-34
MTO
MTG
Methanol to Hydrocarbon Catalysis, J. F.Haw, et al., Acc. Chem. Res. 2003, 36, 317 54
MTO Catalysts • Medium-pore zeolites (ZSM-5) - Major olefin product is Propylene - Significant C5+/aromatics by-products - Slow deactivation
• Small-pore molecular sieves (SAPO-34) - Major olefin products are Ethylene and Propylene - Fast deactivation by aromatic coke - SAPO molecular sieves more stable than corresponding
zeolite structure
Shape Selectivity 55
Structural Comparison
5.5 Ă
3.8 Ă
H O
H O (Al-O)3Si
Al(O-P)3
Small Pore Weak Acid Sites 56
(Si/Al-O)3Si
Al(O-Si)3
Medium Pore Strong Acid Sites
Small, Medium & Large Pore • Small, medium and large pore SAPO’s show MTO activity – but distinct selectivity differences.
SAPO-34
SAPO-11
Large
Medium
Small
C7+
SAPO-5
C6 C5 C2-C4= C1-C4 CO 0
20
40
60
80
0
20
40
60
80
0
20
40
60
80
Wt% selectivity 57
350C, WHSV = 0.3 h-1, MeOH = 0.02 bar, N2 = 0.98 bar
S.M. Yang et al, Stud. Surf. Sci. Catal., 61, 429 (1991)
SAPO-34 vs. SSZ-13 • SSZ-13 has same structure (CHA) as SAPO-34 but is an aluminosilicate zeolite. • Selectivity to olefins substantially less in SSZ-13. Material T atom % Selectivities (2 hr) C2-C4 olefins CH4 C2H6 C3H8 Stability hr at >50% conversion Coking carbon on used catalyst
SAPO-34
SSZ-13 SSZ-13 SSZ-13 (Chabazite) (Chabazite) (Chabazite) 10% Si (gel) 18% Al 10% Al 3.3% Al 96 1.4 0.3 0.9
69 3.9 5.4 18.9
75
87
>40
6
13
7
19% after 54 HOS
16.6% after 18 HOS
19.3% after 18 HOS
15.0% after 18 HOS
Yuen, et al., Microporous Materials, 2 (1994) 105 58
Another Twist in the Story……. • SAPO-34 has CHA topology. Related framework type is AEI.
Structures depicted as layers of D6R
CHA
AEI
Layers of a, a, a 59
Alternating layers of b, a, b, a
AEI and CHA • Exxon and Hydro patents teach that intergrowth of AEI and CHA topology are readily formed and are also active in MTO. AEI cage AEI
CHA
CHA cage
AEI 60
WO 02 70407 (2002); WO 98/15496 and US 6334994 (2002)
AEI and CHA Intergrowths
%CHA 85 75 70 70 70 80 60 10 20
ExxonMobil PCT WO 02/070407 61
Outline • Zeolites • Zeolites as industrial catalysts • Acid sites in molecular sieves • Aluminum phosphate (AlPO4) molecular sieves • Characterization methods for molecular sieves • SAPO-34 • Methanol conversion using zeolites • Zeolites vs. SAPO’s in methanol conversion • CHA and AEI • MTO mechanism • MTO reactor design • Putting it all together: methanol & natural gas • Discovery to commercialization 62
MTO Mechanism • More than 20 proposed mechanisms during the past 30 years (Involving intermediates such as radicals, carbenes, oxonium ions, carbocations)
H2O
H2O 2CH3OH
CH3OCH3
Hydrogen transfers
Alkanes
Alkenes Aromatics
• How can two or more C1-entities react so that C-C bonds are formed? • No simple β-hydride elimination so no straightforward mechanism to olefins from methanol. • Don’t have time to go into great detail on some of the elegant mechanistic work performed. 63
Hydrocarbon Pool Mechanism
C2 H4 nCH3OH
-nH2O
(CH2)n
C3 H6 saturated hydrocarbons aromatics
C4 H8 • What is the identity of the hydrocarbon pool? • How does it operate?
I.M. Dahl and S. Kolboe, J. Catal. 149 (1994) 329, 64
I.M. Dahl and S. Kolboe, J. Catal. 161 (1996) 304.
Zeolite Beta as a Model System • The beta zeolite is a wide pore zeolite allowing direct introduction of rather large molecules. • It is not interesting as a commercial catalyst for MTO/MTH chemistry. Model: Beta, BEA-topology Cages = Windows
12-ring window, substituted aromatic hydrocarbons can enter. 65
7.7 x 6.6 Å
Methanol over H-Beta at 400°C
4
5
Pentamethyl benzene
2-methyl-2-butane
6 7 Retention time (minutes)
Hexamethyl benzene
Aromatics cis-2-butene
trans-2-butene
n-butane
Isobutane Methanol 1/i-butene
Dimethylether
Propane/propene
Methane
Ethane/ethene
Aliphatics
8
26
28
Hexamethylbenzene is a dominant gas phase product Bjørgen, M. and Kolboe, S. Appl. Catal. A 2002, 225, 285-290. 66
Courtesy Unni Olsbye, Univ. Oslo
Hydrocarbon Pool
He
Methanol
Hydrocarbon pool
Alkenes H2O
H-zeolite
The olefin production goes on for several minutes after the methanol feeding has been terminated What is the active pool contained inside the zeolite?
67
Courtesy Unni Olsbye, Univ. Oslo
Hydrocarbons Retained in Zeolite Pores
Analysis (GC-MS, HRMS, NMR)
9 Analyzed
68
ex-situ by: 9 Quenching the reaction (after a set time, few mins) 9 Dissolving the zeolite (15% HF) 9 Extracting the organic material from the water phase 9 Trapped organic species are liberated and can be analyzed Courtesy Unni Olsbye, Univ. Oslo
Trapped Hydrocarbons • Methanol reacted over the H-beta zeolite (GC-MS)
8
69
10
12
Hexamethylnaphthalene
Hexamethylbenzene
Pentamethylbenzene
Tetramethylbenzene
The trapped material nearly exclusively composed of Stability of the retainedis hydrocarbons was probed by stopping the Hexamethylbenzene is a dominant retained species polymethylated feed and flushingaromatics the catalyst with carrier gas for 1 minute
Among the trapped hydrocarbons, hexaMB shows the fastest decomposition
14
Retention time (minutes)
16
18
20
Courtesy Unni Olsbye, Univ. Oslo
Hexamethylbenzene over H-Beta
24 22
4 .4
4 .6
4 .8
Aromatics
14 12
5 .0
5 .2
5 .4
2-methylbutane 6 .4
6 .6
HexaMB
4 .2
PentaMB
4 .0
n-butane
10
TriMB
Detector response (mV)
11
Aliphatics
TetraMB
12
Isobutane
Ethane/ethene
13
Propane/propene
• The same gas phase products as observed when methanol was reacted • The retained compounds were the same as those obtained from methanol
10 19
20
21
22
23
24
25
28
29
R e te n tio n tim e (m in u te s )
Bjørgen, M.; Olsbye, U.; Kolboe, S. J. Catal. 2003, 215, 30-44. 70
Courtesy Unni Olsbye, Univ. Oslo
Initial formation of HMB and heptaMP+ 13
CH3 13
13
13
H3 C
CH3
6 CH3OH H-Zeolite
13
H313C 13
6H2O
13
H313C 13
CH3OH
CH3
H313C
13
CH3
13
CH3
+
H-Zeolite
CH3
CH3
H313C 13
H2O
Hexamethylbenzene: Six labelled atoms
CH3 Zeolite
-
Heptamethylbenzenium: Seven labelled atoms
Hexamethylbenzene in zeolite pore can take up another CH3 to form heptamethylbenzenium ion
71
M. Bjørgen, U. Olsbye, D. Petersen and S. Kolboe, J. Catal. (2004), 221, 1-10.
Exocyclic Mechanism
• Deprotonation of heptaMB+ • Exocyclic double bond reacts with incoming CH3OH resulting in ethyl group on benzene ring • Subsequent dealkylation to ethylene • Essential intermediate in cycle is formation of two gem-methyl groups attached to benzene ring. 72
M. Bjørgen, U. Olsbye, D. Petersen and S. Kolboe, J. Catal. (2004), 221, 1-10.
Paring Mechanism *
*
Alkyl side chain growth by ring contraction/expansion
Zeolite * *
*
Leads predominantly to propylene and isobutene
Methanol
*
*
*
*
*
*
*
+
*
*
*
*
*
+
*
*
* +
Leads to carbon atom interchange between ring and substituents
*
*
*
*
+
*
Iso-butene
*
*
*
*
* *
*
Propene * *
* *
*
*
*
*
+
* *
73
*
*
M. Bjørgen, U. Olsbye, D. Petersen and S. Kolboe, J. Catal. (2004), 221, 1-10.
MTO Site – Organic-Inorganic Hybrid
74
Courtesy Unni Olsbye, Univ. Oslo
SAPO-34 • SAPO-34 (CHA) has large cages connected with small windows. • Large aromatics are accumulated in these cages during the reaction. • An array of nanoreactors!
75
(001) projection
Courtesy Unni Olsbye, Univ. Oslo
Outline • Zeolites • Zeolites as industrial catalysts • Acid sites in molecular sieves • Aluminum phosphate (AlPO4) molecular sieves • Characterization methods for molecular sieves • SAPO-34 • Methanol conversion using zeolites • Zeolites vs. SAPO’s in methanol conversion • CHA and AEI • MTO mechanism • MTO reactor design • Putting it all together: methanol & natural gas • Discovery to commercialization 76
Fixed Bed MTO Performance
C o n versio n /S electivity, %
• SAPO-34 catalyst highly active with good selectivity then conversion drops rapidly. 100 Total Olefins
80 60
Conversion Ethylene
40 Propylene
20 Propane
0
Time 77
Molecular View of Initial Deactivation • Hexamethylbenzene in CHA cage • With increasing TOS some methylbenzenes age into methylnaphthalenes. • Further aging to phenanthrene causes loss of activity • Largest ring system to form in SAPO-34 is pyrene.
78
Haw, Accts. Chem. Res. 36 (2003) 317
MTO Reactor Design
• Fixed Bed Reactor
- rapid deactivation due to coke formation - reactor would have to swing between process & regeneration - product composition varies with time - expensive high-temperature valves required
• Fluidized-Bed Reactor
- transport reactor, internal catalyst circulation - continuous movement of portion of used catalyst to separate regenerator - reduced catalyst inventory, increased capacity - uniform product distribution with time
79
Fluidized Bed Reactor Fast Fluidized-Bed
80
Regenerator
Product
Offgas
MeOH
Air
Fluidized Bed Reactor Results
Conversion or Selectivity, %
• Conversion and selectivity remain high over months of operation. Conversion
100 80 60
Selectivity to C2=
40
Selectivitychemical to C3= Often in catalysis some clever engineering 20 required to make the catalytic process commercially 0 viable. 0
10
20
30
40
50
60
Time on-stream, days 81
70
80
90
UOP/HYDRO MTO Process Flow Scheme • The catalytic reactor is only one small part of the overall process! Reactor
Regenerator
Quench Tower
Caustic Wash
DeDe-C1
DeDe-C2
C2 Splitter
DeDe-C3
C3 Splitter
DeDe-C4
Tail Gas Ethylene
Regen Gas
Propylene Dryer Mixed C4
DME Recovery
Air
Water
C2H2 Reactor C5+ Propane
Methanol
82
Ethane
Olefin Cracking Technology • Another piece of the process….. • Production of propylene and ethylene from C4 to C8 olefins.
C4 to C8 Olefins C4H8 to C8H16
83
Catalyst
Olefin Cracking −Δ T
Propylene & Ethylene C3H6 & C2H4
Olefin Cracking integration with MTO • Upgrade C4+ MTO product to C2= and C3=. MeOH
MTO Unit
C3= Light Olefins
C4-C5 Olefins
OCP Unit
84
C2=
C4+
•
20% increase in light olefin yields
•
Nearly 80% reduction in C4+ by-products
•
Can achieve 2:1 propylene/ethylene product ratio
MTO Reaction with Olefin Cracking
Methanol
SAPO-34 Catalyst Δ
Ethylene Propylene
X
Butenes
Other By-Products H2O H2 , COX C1-C5 Paraffins C5+ Coke 85
Outline • Zeolites • Zeolites as industrial catalysts • Acid sites in molecular sieves • Aluminum phosphate (AlPO4) molecular sieves • Characterization methods for molecular sieves • SAPO-34 • Methanol conversion using zeolites • Zeolites vs. SAPO’s in methanol conversion • CHA and AEI • MTO mechanism • MTO reactor design • Putting it all together: methanol & natural gas • Discovery to commercialization 86
Why Natural Gas Conversion? • Large reserves of remote natural gas. • Environmental need to minimize venting or flaring of associated gas from oil fields. • Existing technologies for methane conversion limited by market size or marginal economics.
87
World Natural Gas Reserves Egypt Canada Netherlands Kazakhstan Uzbekistan Turkmenistan Malaysia Norway Australia Indonesia Iraq Nigeria Venezuela Algeria
Others
United States United Arab Saudi Emirates Qatar Arabia
Russia
World Total = 179 x 1012 Cubic Meters Iran
Source Oil & Gas Journal 2003
• Natural gas utilization is desired by many companies and nations
- Monetization of stranded gas reserves - Reduced gas flaring - Less dependence on crude oil 88
Ethylene Supply & Demand • Demand for ethylene predicted to increase: source will have to come from new capacity. 2004 Supply (PG) 103 MM MTA
Others 2%
Naphtha 54%
140,000
Gas Oil 6%
130,000
D
kMTA
(steam crackers)
150,000
em
d an n No
-E
? ne a th
120,000
89
20 14
20 12
20 10
Current Capacity
100,000
20 08
“PG” = polymer-grade
Propane 7%
20 06
Butane 4%
e? n a h Et
110,000
20 04
Ethane 27%
Data Source: CMAI 2005
Propylene Supply & Demand • Propylene demand also predicted to rise. 100,000
2004 Supply 61 mm MTA
90,000
Refinery
80,000 kMTA
D
Steam Naphtha Cracker
d n a em
70,000
Steam Crackers, Refineries PDH, Olefin Conversion, MTO
Dehydro Others
?
60,000
Current Capacity
90
20 14
20 12
20 10
20 08
20 06
20 04
50,000
Data Source: CMAI 2005
Stranded Gas Monetization Processes Production
Liquefaction Shipping
Synthesis gas production CO + H2
Hydrocarbon synthesis Methanol synthesis
Revaporization
Upgrading
MTO Polymers
91
Natural gas
Liquid fuels Ethylene Propylene Polyethylene Polypropylene
LNG GTL GTO GTP
Value of Products Produced from 1 MM BTU of Natural Gas
12
Value of Products, $
10 8 6 4 2 0
Natural Gas
LNG
Gasoline
Methanol
Olefins
Polymers
Polymers are highest value product 92
Large Gas Fields by Size • Substantially more fields economically viable for GTP technology than other technologies.
Size of Fields
50 - 500 Tcf
86 Suitable for LNG & GTL
15
5-50 Tcf
71
320 Suitable for GTP
1 - 5 Tcf
234
0.5 - 1 Tcf
269 0
Total = 589 Large Fields 93
1 Trillion cf = 28.2 BCM
50
100
150
200
250
300
Number of Fields Source: Oil & Gas Journal
Methanol to Olefins Process • MTO process is new viable route to polymer grade ethylene and propylene.
Bio-Mass
Natural Gas
Synthesis Gas Production
Methanol Methanol Synthesis
MTO
Ethylene & Propylene
Coal HCHC +H O 2+ 94
CO→CO +H H2O 2
SAPO-34 Catalyst +C H + CH H23OH → CH3OH → C2CH2H 4 4+ C33H6
MTO Commercial Status • MTO Demo Unit - Started-up in 1995 at Norsk Hydro facilities in Norway - Used commercial methanol feedstock
• UOP and Total Petrochemicals announced in Dec 2005 an integrated demonstration unit consisting of both a UOP/HYDRO Methanol-to-Olefins unit and a Total Petrochemicals/UOP Olefin Cracking unit. • Construction started at Total’s petrochemical complex in Feluy, Belgium. Start-up in 2008. 95
Outline • Zeolites • Zeolites as industrial catalysts • Acid sites in molecular sieves • Aluminum phosphate (AlPO4) molecular sieves • Characterization methods for molecular sieves • SAPO-34 • Methanol conversion using zeolites • Zeolites vs. SAPO’s in methanol conversion • CHA and AEI • MTO mechanism • MTO reactor design • Putting it all together: methanol • Discovery to commercialization 96
SAPO-34 vs UZM’s • For SAPO-34 it took 20+ years from discovery of the material to its use in a commercial process. • In 1998 New Materials Group formed at UOP to discover new zeolites. • UZM-8 discovered in late 2000, patent issued 2004. • Identified as a candidate for ethylbenzene production. C6H6 + C2H4
C6H5CH2CH3
benzene ethylene
ethylbenzene
• Performance of UZM-8 allowed for the design of a more economical process. • New process with new catalyst for EB production offered for sale in late 2006.
6 years to commercialization! 97
Acknowledgements • John Chen • Paul Barger • Steve Wilson • Hayim Abreveya • Edith Flanigen • Wharton Sinkler • Sue Wojnicki • Emmanuelle Siler • Sesh Prabhakar • Prof. Unni Olsbye, University of Oslo. 98
