Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
W O 93/21139 P ~ /GB93/OOX23
~. .
~I1090 i
PROCESS FOR THE PRODUCTION OF OLEFINS
The present invention relates to a process for the production
of olefins by utilising a zeolite catalyst in the conversion of an
oxygenate feed.
Olefins, in particular, branched olefins such as isobutene are
valuable industrial products and are often used as the starting
~aterials for the produczion of other desirable chemicals. Isobutene
may be polymerised to provide polyisobutene which is a valuable
che~ical in the detergents and fuel industry. In particular,
polyisobutene is used as a fuel additive and a lubricant.
Isobutene may be produced via ~arious reaction schemes
including the catalytic conversion of oxygenates such às methanol as
disclo~ed in our European Patent Applications 485145 and 489497.
Additionally, isobutene may be produced from the cracking of the
petroleum additive tertiary butyl alcohol (TBA). This may be
t5 achieved using an alu~ina catalyst.
We have now discovered that a high selectivity to olefins such
as isobutene can be obtained under less severe conditions when a feed
containing an oxy~enate is passed over a zeolite catalyst.
Accordingly, the present invention provides a process for the
production of olefins which comprises passing a feed containing an
oxygenate of the general formula I
R-O-Rl (I)
where R is an alkyl of 4 or 5 carbon atoms and Rl is H or alkyl
optionally substituted with an ether group, over a zeolite catalyst
whose framework includes a lO- or 12- member channel not intersected
'
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by another 10- or 12- member channel with the proviso that when Rl is
H, the zeolite has a framework which includes a 10- member channel
not intersected by another 10- or 12- member channel.
The present invention provides a method of producing olefins
from an oxygenate containing feed which requires a lower operating
temperature than known prior art processes. Furthermore, by-product
yield is minimised,thus providing an improvement in the selectivity
to the desired product.
The process of the present invention provides a method of
cracking an oxygenate to produce an olefin. The oxygenate is of
general formula R-O-Rl.
R of general formula I is an alkyl of 4 or 5 carbon atoms and
is preferably a secondary or tertiary alkyl. It is especially
preferred that R is tertiary butyl.
Rl of general formula I is H or alkyl optionally substituted
with an ether group. Suitably Rl is Cl to C4 alkyl, especially
methyl or ethyl. Where Rl is an alkyl substituted with an ether
group suitably Rl is -(CH2-)n-OR2 where R2 is C2 to C4 alkyl
The process of the present invention is particularly suitable
for the production of isobutene from methyl tertiary butyl ether
(MTBE), 2-methoxy butane, tertiary butyl alcohol (TBA) and secondary
butyl alcohol (SBA).
The feed may be obtained from any suitable source and may be
fed into the reaction chamber either with or without a dilueht. If
it is desired to co-feed a diluent, suitable diluents include steam
or an inert gas, e.g. nitrogen, hydrogen, or an alkane. The mole X
of the diluent gas present may suitably be, for example, up to 50X,
preferably up to 25X, Pspecially from 5 to lOX.
Uhere the feed contains an alcohol, for example TBA, it ls
preferred to co-feed water into the reaction chamber. The percent
weight of water present in the feed will affect the selectivity to
isobutene. Suitably, the feedstream may contain from up to 30Z
weight of water, preferably up to 20X weight and especially up to lOX
weight water.
Zeolites which may be used in the present invention include TON
...WO 93/211~g PCI`/GB93/00823
3 ~lU~
(Theta-1, Nu-10, ZSM-22, K2-2, ISI-l), MTT (ZSM-23, EU-13, ISI-4,
KZ-l), ZSM-48, FER (FU-9, Nu-23, ISI-6, ZSM-35) and EUO (EU-l, TPZ-3,
ZSM-50), all of which contain a 10- membered channel that is not
intersected by another 10- or 12- membered channel. MTW (ZSM-12,
S CZH-S, Theta-3, TPZ-12) and MOR (mordenite) which contain a 12-
membered cbannel that is not intersected by another 10- or 12-
membered channel oay also be used in the present invention where the
feed does not contain an alcohol. The preferred zeolite is TON.
Information on zeolite structures is given in the Atlas of
Zeolite Structure Types by Meier WH and Olsen DH, 1987, distributed
by Polycrystal Book Service, Pietsburgh, VSA. All of these known
zeolite structure types can be prepared by published literature
methods. Typical general methods are given, for example, in
~Synthesis of High Silica Aluminosilicate Zeolites~ by PA Jacobs and
JA Martens; ~Studies in Surface Science and Catalysis~ vol. 33,
Elsevier, 1987; and ~Zeolite Molecular Sieves~ by DW Breck, John
Wiley, 1974.
The synthetic zeolite immediately after synthesis contains
cations which, depending upon the precise synthesis method used, may
be hydrogen, aluminium, alkali metals, organic nitrogen containing
cations or any combination thereof.
Tha zeolite is preferably used in the present process in the
hydrog~n form. The hydrogen form may be achieved by, in the case of
organic containing zeolite, calcination to remove the organ~s
followed by either a ronium ion exchange followed by calcination,
proton exchange with an acid solution or a combination of both. In
the case of the zeolite synthesised in the absence of organic
nitrogen containing compound, the hydrogen fonm could, if desired, be
prepared by either direct a onium exchange followed by calcination
or proton exchange with acid solution or a combination of both. If
so desired, the hydrogen form of the zeolite also may be partially
exchanged or impregnated with a metal such as Ga or Mg and used in
the present process.
The zeolite may be modified to alter its acidity or shape
selectivity in such a way to improve the catalytic performance. The
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motifications may include a calcination regime, stea~ treatment,
chemical treatment, e.g. with a dealuminating agent such as SiC14,
EDTA, etc or an aluminating agent such as sodium aluminate, AlC13
inclusion of phosphorus compound, Lewis base, HF etc. A combination
of treatments may also be carried out. The treatment step may be
carried out during ehe preparation of the H-form or be carried out
after preparation of the H-form.
The zeolite, if desired, may be bound in a suitable binding
~aterial. The binder may suitably be one of the conventional
0 aluoina, silica, clay or alu~inophosphate binders or a coobination of
binders.
The process according to the invention may suitably be carried
out at a teoperature of from 100 to 400-C, preferably 150 to 300-C,
especially 150 - 200-C, and is preferably carried out at atmospheric
pressure, although other pressures may be used if desired, eg up to
15 barg.
The oxygenate feed may be fed into the reaction chamber either
with or without diluents at a rate of suitably 0~1 to 50, preferably
0.9 to 10, especially 0.9 to 4.5 liquid hourly space velocity (LHSV).
`~ 20 For the purposes of the present invention, it is understood that
liquid hourly space velocity is defined as the volume of feed fed per
volu~e of catalyst per hour.
The process of the present invention may be carried out in any
suitable reactor, for example a fixed bed, fluid bed, a reactive
distillation column, a slurry reactor or a continuous catalyst
regeneration reactor. The preferred reactor is a fixed bed reactor.
The reactor may be made from any suitable material, e.g. steel or
quartz.
The product of the process of the present invention will, of
course, be dependent upon the feed. Where R is butyl, the product
comprises butenes, e.g. n-butene and iso-butene. Where R is pentyl,
the product comprises pentenes, e.g. n-pentene and iso-pentene. The
product stream will also comprise water. Additionally, small amounts
of othor alkenes such as ethene, propene, hexene, octene, and the
corresponding alcohols may also be present.
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5 211~~
The process will now be described with reerence to the
following examples.
ExamDle 1 - Svnthesis of Theta-l Zeolite
Theta-l was synthesised using ammonia as the templating agent.
Sodium aluminate (19.67g, 61wtX A1203, 38wtX Na20) and sodium
hydroxide (17.58g ex BDH) were dissolved in distilled water (240g).
Ammonia solution (1400g, SG 0.90- containing 25X ammonia) was added
with gentle mixing. Ludox AS40 (Trade Mark) (1200g) silica gel which
contained 40wtX silica was added over 20 minutes with stirring to
maintain a homogeneous hydrogel. The molar composition of the
hydrogel was:
2.9 Na20 : 175 NH3 : 1.0 A1203 : 68 SiO2 : 950 H20
The d xture was then loaded into a 5 litre Parr autoclave and
crystallised at l75-C for 29 hours under autogeneous pressure whilst
mixing by a -echanical stirring action at 150 revs/min. The total
ti e included time for the autoclave to reach the reaction
~; temperature from ambient (about 3 hours). At the end of the
crystallisation period, the autoclave was cooled and the product
filtered, washed and dried in an air oven at lOO-C.
The crystallinity and the purity of the zeolite were determined
by X-ray powter diffraction (XRD). The sample contained Theta-l
zeolite with esti~ated amount of cristobalite of less than 5X.
ExamDle 2- Pre~sration of the H-Form Theta-l Zeolite
The Thota-l as synthesised in Example 1 which contained both
Na+ and NH4~ ions was directly ion exchanged in order to remove the
Na+ ions. The zeolite was mixed for 1 hour at room te~perature with
an aqueous ammonium nitrate solution (LM, zeolite to solution weight
ratio of 1:20). The zeolite was filtered, washed and the ion
exchange treatment repeatet twice. The ammonium form of the zeolite
was then dried at lOO-C and calcined overnight in air at 550'C to
convert it to the hydrogen form. The X-ray diffraction pattern of
the H-form is shown in Table 1.
ExamDle 3
The zeolite powder (H-form) was pressed into tablets at 10
tonnes. The tablets were broken and sieved into granules to pass
W O 93/2l139 PC~r/GB93/00823
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through 850 micron but not 600 micron sieves. An 7.8ml volume of the
catalyst weight 3.15g was loaded into a quartz reactor with a 35ml
preheater zone in an isothermal Carbolite furnace, activated in air
at a rate of 60~ml per hour following the temperature profile:
room temperature 1C/minute~ 120C (2 hours) 1C/minute~ 500C (14-
hours)-10C/minute> lSOC initial test temperature
Tertiary butyl alcohol (TBA) was pumped into the reactor using
a perfusor syringe triver fitted with a 50ml syringe. On entering
the reactor, the TBA was vapourised and mixed with nitrogen (gas flow
of 590ml per hour). The products were identified using gas
chromatography. Table 2 provides the product stream analysis
obtained for the reaction.
Examnle 4
The zeolite powder (H-form) was pressed into tablets at 10
tonnes. The tablets were broken and sieved into granules to pass
through 850 micron but not 600 micron sieves. An 8.2ml volume of the
~; catalyst weight 4.34g was loaded into a quartz reactor with a 25ml
preheater zone in an isothermal Carbolite furnace, activated in air
at a rate of 600ml per hour following the temperature profile:
room temperature 2C~minute~ 300-C (12 hours)-10C/hour ~ 175-C.
Methyl tertiary butyl ether was pumped into the reactor using a
perfusor syringe driver fitted witb a 50~1 syringe. On entering the
reactor, the MTBE was vapourised and mixed with nitrogen (gas flow of
680ml per hour). Table 3 provides the product stream analysas
obtained for the reaction.
Comparative Example 1
The process of Example 3 was repeated using a commercial
alumina catalyst of surface area 184 ~ 4m2/g and mean pore volume of
l9nm. A 7.8ml volume of the catalyst (weight 5.13g) was used. The
catalyst was purchased from ARCO under the trade name of UOP CAB 2L
and ca~e in the form of 3mm spheres Table 3 provides the product
stream analysis obtained for the reaction. It can be seen that
conversion of tertiary butyl alcohol is considerably less when an
alumina catalyst is used in the process. Selectivity to isobutene is
also less than in the corresponding process using the zeolite
W O 93~2l139 PC~r/GB93/00823
7 2 ~ J o l~
catalyst.
Comnarative Example 2
The process of Comparative Example l was repeated using methyl
tertiary butyl ether as the feed. The product stream analysis is
given in Table 4. It can be seen that conversion of MTBE is
considerably less when an alumina catalyst is used in the process.
Selectivity to dimethyl ether is also greater than in the
corresponding process using the zeolite catalyst.
:
~:~
WO 93/211~9 PC~/G893/00823
21 l 090'~ 8
T~BLE 1
PRODUCT OF E~AHPLE 2
_ _ _
2 THETA D SPACINGS RELATIVE INTENSITIES
(20) (A~) 100 x I/TomAY i
8.17 10.81 100
10.16 8.70 22
12.81 6.91 23
16.36 5.42 11
19.42 4.57 12
20.36 4.36 97
24.22 3.67 82
24.64 3.61 52
25.76 3.46 - 36
Variation in intensities of ~ 20X. Variation in 2 theta positions
of ~ 0.2- with corresponding variations in D spacings. Peak below lOX
of ImaX excluded. Copper alpha 1 wavelength, l.S4060.
X-~ay Diffractometer Philips PW 1820/00
Slits 1/4-, 0.2-, 1/4-
2 Theta Scan 2~ - 32
Step Size 0.025-
2S Time 4 seconds
~yVO 93/21139 P ~ /GB93/00823
~llO'~Oq
TABLE 2
P~ODUCT STRE~M ANALYSIS FROM CRACKING TBA USING H-THET~-l
Temperature Feed rate XH2O Conversion (X) Selectivity(X)
(-C) (ml~h) TBA isobutene
150 12 0 100 99.53
150 30 0 99.99 62.71
225 12 0 99.99 62.71
300 6 0 99.05 73.56
300 30 0 99.84 81.77
150 12 10 99.04 87.14
225 6 10 99.89 81.88
225 12 10 99.54 99.15
225 12 10 99.94 98.80
225 30 10 97.57 94.52
300 12 10 99.78 70.40
150 30 20 99.61 94.75
300 6 20 99.82 48.71
300 12 20 100 76.08
300 30 20 100 76.15
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~1~09o~
T~BLE 3
PRODUCT STREAM ANAL~SIS FRO~ CR~CKING MTBE USING THET~-l
Temperature LHSV Conversion(X) Selectivity (X)
_____~ ____ (h-1) MTBE Isobutene DHE
0.9 99.8 70.3 0.8
175 2.7 99.2 75.7 1.0
~ lO 175 4.5 91.7 74.7 0.1
: 250 0.9 98.9 67.3 3.0
250 2.7 99.8 75.0 3.4
250 4.5 98.5 72.4 1.5
;~ 15 DHE - dimethyl ether
: :
~: .
:; : 35
: ~.
:
~ ,~
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2~109~'~
T~BLE 4
PRODUCT STRE~M AN~LYSIS FROH CRACKI~G TBA USING ~LU~INA C~TALYST
TemperatureFeed rate ZH20 Con~ersion (X) SelectivitytX)
(~C) (ml/h) TBA isobutene
150 6 0 21.17 52.75
150 30 0 5.03 98.10
225 12 0 82.83 92.08
300 6 0 82.34 99.51
300 30 0 93.48 98.~6
150 12 10 9.14 B7.94
225 6 10 99.99 81.88
225 12 10 99.96 99.91
225 12 10 95.50 9g.60
225 30 10 83.07 g4.52
300 12 10 100.00 60.88
150 6 ` 20 15.1~8 44.gg
150 30 20 4.21 36.67
225 12 20 78.18 98.,61
300 6 20 90.90 97.13
300 ~ 30 20 99.93 ~ _95.53
2S
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T~BLE 5
PRODUCT STREA~ ~NALYSIS FRO~ CRACRING ~TBE USING ~LtJ~IN~ CATI~YST
s
Temperature LHSV Conversion(X~ Selectivity (X)
(-C) (h-l) MTBE Isobutene DME
175 0.9 27.4 72.6 1.7
175 2.7 48.4 73.5 3.4
175 4.5 1.0 76.6 0.7
250 0.9 91.0 65.4 11.2
250 2.7 66.4 70.7 7.0
1~ 250 4.5 78.6 72.8 7.7
DME - dimethyl ether
2S
