M. GUISNET University of Poitiers Instituto Superior Técnico (F. Gulbenkian)
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Transcript of M. GUISNET University of Poitiers Instituto Superior Técnico (F. Gulbenkian)
M. GUISNET
University of Poitiers
Instituto Superior Técnico(F. Gulbenkian)
Petrochemical ProcessesAromatics
Lisbon December 2005
Petrochemicals : a) Benzene, Paraxylene
Naphtha reforming Steam cracking Aromatization
BTX (+ EB)Excess of toluene, meta and ortho xylenes
Selective Toluene disproportionation (modified MFI)
Isomerization (I) of the C8 aromatic cut and p xylene separation (S)
Aromatization of light naphtha (Pt(K, Ba) LTL)
+2
nC6 + 4 H2
pX
Aromatic loopEB, X
S ((K, Ba)X)
I (PtHMOR)
EB mX oX
Petrochemicals : b) Alkylaromatics
Ethylbenzene Styrene
Cumene Phenol
Linear Alkylbenzene (LAB) Biodegradable detergents
+ C C
+ C CC
+
MFI (gaz phase) MCM22, BEA (Liq phase)
MCM22, BEA
MOR MCM22
Selective toluene disproportionation (STDP)
+2
How to obtain selectively paraxylene (p : 5.5 Å/ o : 5.8 Å)
1) Choice of MFI (ZSM5)
10 5.1 x 5.5 10 5.3 x 5.6 Å
2) Large Crystal size
- Chemical treatment (B, P, Mg…)
- Coking at high temperature
Pore structure of MFI
[ 10 5.1 x 5.5 10 5.3 x 5.6]***
5.3 x 5.6 Å
5.1 x 5.7 Å
8.5 Å
Beneficial « coke »
Increase of the shape selective properties :
High selectivity to paraxylene with ZSM5 zeolite coked at high temperature
Sieving effect Elimination of non selective outer sites
Coke on surface
Internal pore volume
View of surface on molecular scale
+2e.g
Para xylene Manufacturing
Demand : 70% of xylenes films, fibers, resins
Production 25% (Reforming – Steam cracking)
Xylene isomerization
Th Eq 75% (ortho + meta) + 25% (para)
Separation + Recycle
Ethylbenzene produced with xylenes. (17% reforming, 50% steam cracking)
Too high cost of separation
Isomerization Dealkylation
Bifunctional Zeolite Catalysts
PtHMOR (Na), Others (IFP, UOP)
Xylene isomerization with ethylbenzene isomerization
Xylene isomerization Acid mechanism
Ethylbenzene isomerization Bifunctional mechanismEB
ECHE DMCHE
X
+2 H2 -2 H2H+
Pt/Al2O3 – HMOR mixtures under H2 pressure
Secondary reactions : Disproportionation and transalkylation e.g. 2X T + TMB
Dealkylation e.g. EB B + C2
Hydrocracking
Pt Pt
H2
Ethylbenzene isomerizationInfluence of the balance between hydrogenating and acid functions
on selectivity at 35% conversion
0
20
40
60
80
100
0 2 4 6 8 10 12nPt/nH+
Sele
ctiv
ity (%
)
0
10
20
30
40
50
60
0.00 0.50 1.00 1.50 2.00nPt/nH+
Sele
ctiv
ity (%
)
Disproportionation
Dealkylation
Cracking
Isomerization Disproportionation Dealkylation
Cracking
0
20
40
60
80
100
0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5nPt/nH+
Séle
ctiv
ity %
Ethylbenzene isomerizationInfluence of the Na exchange of the HMOR component on selectivity
at 35% conversion
Isomerization
NaHMOR
HMOR
Isomerization of the C8 aromatic cut Recent advances
New processes based on zeolites more efficient than mordenite UOP (I 210), IFP (Oparis)
p Xylene yield of 93% instead of 88-89%
Most likely pore mouth catalysis
Separation of C8 aromatics
p-xylene
Crystallization (Chevron-Amoco) high cost of equipment, high energy consumption
Adsorption : Parex (UOP), Aromax (Toray), Eluxyl (IFP)
m-xylene Complexation with HF/BF3
Mitsubishi
o-xylene Fractional distillation
Separation of p-xylene by selective adsorption
* adsorbent : X (K,Ba)
* 120 - 180°C ; 20 bar
* Desorbent : toluene or p-diethylbenzene (low adsorption capacity)
p-xylene (99.5%)
a : p-xylene; b : other C8; c desorbent
p-xylene
L N Aromatization
RC DH
Pt Pt
Confinement model (Derouane)
Aromax Catalyst Performance
Relative Feed Aromatization Rate Selectivity (%)n-hexane 1.00 90n-heptane 0.80 90-94n-octane 0.70 86-94n-nonane 0.70 90-942-methylhexane - 97methylcyclopentane 0.75 892-methylpentane 0.60 833-methylpentane 0.60 83
LTL (Linde Type L): [001] 12 7.1x7.1*
Petrochemicals : b) Alkylaromatics
Ethylbenzene Styrene
Cumene Phenol
Linear Alkylbenzene (LAB) Biodegradable detergents
+ C C
+ C CC
+
MFI (gaz phase) MCM22, BEA (Liq phase)
MCM22, BEA
MOR MCM22
+ C C
Old catalyst (1950) AlCl3+HCl
AlCl3 corrosivity and problems associated with safe handling and disposal
For 1 tonne of EB, use of 2-4 kg catalyst, 1kg of HCl, 5 kg of caustic solution, production of salts
Zeolite catalysts
- 1980 Mobil Badger vapour phase process MFI (ZSM5) 370-420°C, 7-27 bar, B/C2
= 5-20, WHSV 300-400 h-1, recycling of DEB, yield > 99.5%, life time : 1 year
- 1995 EB Max liquid phase process MWW (MCM22) 200°C , B/C2
= 3.5, Yield > 99.9%, life time > 3 years, more energy efficient
Pore structure of MCM-22 (MWW)
Supercages(7.1 x 18.4 Å)
Sinusoidal Channels(4.0 x 5.0 Å)
(A)
(B)
External Cups(7.1 x 7.0 Å)
Sinusoidal channels openings
(C)
Channel(4.0 x 5.5 Å)
Alkylation over MCM-22. Location
N Effect of collidine ( )
A) Eb synthesis (B/C2= = 3.5, 220°C)
C2= conversion
•Undoped sample 95.6 %
•Collidine doped sample 1.4 %
B) No effect on ethylbenzene adsorption (no pore mouth blocking)
Benzene alkylation occurs in the external cupsH. Du and D.H. Olson, J. Phys. Chem. B 2002
Initial significant « coke » deposition within the supercages
Method for determining the catalytic role of the three MCM-22 pore systems
Deactivation by « coke »
Activity (A) of supercages and product distribution
Trap cages: large (7.1 x 18.2 Å h) with small apertures (4.0 x 5.5 Å)
Poisoning of the large external cups (7.1 x 7.0 Å) with a bulky
basic molecule: (2,4-DMQ)N
A of external cups and product distribution
A of sinusoidal channels = A Total – A supercages – A cups
Product distributions are those expected from the size and shape of pores and apertures.
S. Laforge et al, Micropor. Mesopor. Mater. 2004
0
5
10
15
0 5 10 15 20 25TOS (h)
Con
vers
ion
(%) D = 10 %
D = 0.3 %
Method for determining the acid site distribution in the three MCM-22 pore systems
00 200 400
2,4-DMQ (µmol.g-1)
1
2
3
4
X (%
)
Q
CCup sites
1450 1500 1550 Wavenumber (cm-1)
0.1Fresh Coked 24 h
CPyH+ = CSupercage sites
CSinusoidal channel sites
=Ctotal – Csupercages - Ccups
Comparison of MCM-22 samples with different crystallite sizes
SupercagesSinusoidal channelsCups
Sext = 38 m².g-1 Sext = 114 m².g-1
0
20
40
60 48 %
%
18 %
0
20
40
60
25 %%
10 %
A B
A : m-Xylene conversionB : Brönsted sites
A B
How to increase the external surface ?
Calcination
MCM-22
Swollen MCM-22
CTMA +
Pillaring
MCM-36
Delamination
ITQ-2
Corma et al, (1999)
Synthesis of cumene over HBEA zeolitesEniricerche process
+ C C C
CCC
Bellussi 1995
Comparison of HBEA with the usual catalysts PA (H3PO4/kieselguhr)
HBEA PAT 150°C 200°C
C3= conversion 90 % 90 %Oligomers (wt %) 0.3 1.1
Cumene (wt %) 94.3 95.1n propylbenzene 175 400
(ppm)DIPB (wt%) 4.5 3.2
Selectivity C 9/C6 (%) 95.7 97IPBS/C3 98.3 96.4
HBEA a very particular zeolite Tridimensional channel system 12 6.6 x 6.7** 12 5.6 x 5.6*
Intergrowth hybrid of two distinct structures (polymorphs A and B)
many internal local defects (T atoms not fully coordinated to the framework Lewis acid sites)
Generally synthesized under the form of small crystallites ( 20-50 nm large external suface diffusion limitations)
Acid treatment of BEA (12) % dealumination (total, framework). Acidity (H+, Lewis)
EFAL species : monomeric (360), polymeric (290)
µmol.g-1 Structure defects (120)
Bridging OH (470)
Shape selectivity
Adaptability
Remarkable Acid Properties
CONCLUSIONS
Efficient adsorbents and catalysts
Refining Petrochemicals
Depollution Fine Chemicals
GREEN CHEMISTRYGREEN CHEMISTRY
CONCLUSIONS
Recent advances New industrial processes
Isodewaxing SAPO11, TON
Methanol to olefins SAPO 34
Ethylbenzene and cumene synthesis MWW, BEA etc.
Isomerisation of the C8 arom cut IFP OPARIS process
Aromatization KL, Ga/MFI
NEW CONCEPTS
New Concepts
Shape Selectivity of the external surface
External cups (MCM 22)
Pore mouth (SAPO 11, TON, FER …) and key lock catalysis
Coke molecules as active species
Synthesis of zeolites with large external surface (nanocrystalline, delaminated zeolites…)
Synthesis of zeolites with cups on the outer surface…