The invention relates to a process for isomeriziny
alkyl aromatic hyclrocarbons. It relates more particularly to
the use of catalysts described and claimed in our U.K. Patent
No.1,464,931 for lsomerizing alkyl aromatic hydrocarbons, the
isomeriæation being performed in at least two steps.
The aforementioned describes and claims a catalyst
for the substantially non-cracking hydro-treatment of hydrocarbons
comprising a substantially non-cracking refractory inorganic
oxide carrier having acid sites, said catalyst having halogen
present in combined form, and having metals on said carrier in
free or combined state comprising:
a) 0.02 to 2% preferably 0.1 to 7% by weight of at
least one platinum metal,
b) 0.02 to 2~ preferably 0.02 to 0.60% by weight
of at least one metal selected from zirconium, titanium and
tungsten,
c) 0.02 to 2% preferably 0.05 to 1.00% by weight of
tin; said weight percentages being based on the total weight of
the catalyst.
Preferably the support of the aforementioned catalyst
has a specific surface greater than 15 m /g. The support can,
for example, be alumina having a specific surface between
100 and 350 m2/mg. It has a specific pore volume greater
than 0.1 cm /g.
The halogen content is preferably between 0.4 and
2% and more preerably between 0.5 and 1.6% referred to the total
weight of the catalyst. The halogen is preferably chlorineO
Desirably the metals consist essentially of platinum
as the only platinum metal and of one other metal.
The aforementioned patent specification also describes
a process for preparing the aforementioned catalysts and their
use for hydro-reforming a batch of hydrocarbons.
. . . . : -. .. - . .
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, : . ~ ~. ~ . . , . , , - . :
, . ~ ~., . . . ,: . . . : ~ . :
Our copending ~application No. 253,010 filed May 20,
1976 describes and claims a process for isomerizing a charge
of alkyl aromatic hydrocarbons comprising bringing together
said hydrocarbon ~harge, hydrogen and a catalyst as claimed
in U.K. Patent No. 1,464,931 under isomerization conditions.
Preferably the halogen content o~ the catalyst is from 1 to 2%
by weight and preferably also the halogen is chlorine.
After continuing their work on the use of the afore-
mentioned isomerization catalysts, the applicants have now found
that the me~ od of isomerization as described in the specification
of copending~Application No. 253,010 is particularly useful when
performed in at least two successive steps.
According to this inven~ion there is prov1ded a process
for isomerizing alkyl aromatic hydrocarbons which process
comprises reacting a batch of said hydrocarbons with hydrogen and
a catalyst as claimed in any one of claims 1 to 9 or 17 of ~.A'.
Patent No. 1,464,931 under isomerising conditions, the process
being performed in at least two successive steps and the reaction
; being carried out in at least one step.
In order to illustrate the invention more clearly,
it will be described with reference to the successive steps,
each comprising only one reactor. However, this is not a
limitation since the method can be worked inbwo successive
steps each comprising more than two reactors, which can be
disposed in parallel or in series in each step~ Similarly,
only two successive steps will be considered but of course the
method accordin~ to the invention could be worked in a
larger number of steps.
The temperature and pressure conditions can be
substantially identical in the two successive steps. Howe~er,
the applicants have observed that very good results are
`~'`' " :
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:
. '``' ~ ' . '. . '. '': .: ' '. . : ' .
~.6~
obtained when the conditions are not the s~ne in both steps.
In each step the conditions may vary within the
following ranges:
Molar ratio of hydrogen to hydrocarbons: from 3 to 15,
~referably from approximately 8 to approximateiy 10.
Temperatures- below approximately 550~C.and above
approximately 250C. in general,
Pressures: f.rom approximately 3 to approximately 40 bars.
The total houxly volumetric speed, i.e. relative to the ~:
total vol~me of catalyst contained in all the reactors, may
vary from 0.4 to 4~ advantageously from 1 to 2.5,
Table I shows the conditions under which it has been
shown it is advantageous to perform each step, in the case of.
two steps only.
15 TABLE I
. Operating Operating
conditions conditionq
First sten ~econd.step
Volumetric speed per From 1 to 4 From 1 to 6
hour (partial)
Molar ratio of hydrogen 3 to 15 3 to 15
to.hydrocarbons
Temperature 100 to 450 , 300 to 550C.,
preferably 240 preferably 350 : ::
to 450 ~o 500 .~ .
Pressure 10 to 40 bars, 3 to 30 bars, :
preferably 20 to preferably
10 to 25
The applicants have found that the performance of the
30 catalysts aacording to the aforementioned patent specification :~
:
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31~167~
in the reaction of isomerl~ing alkyl aromatlc hydrocarbons
is improved when the method according to the lnven~ion i~
- worked under the conditions deflned hereinbafore.
The two~step method is particularly suitable when
batches of hydrocarbons are treated under the aforementioned
conditions and consist mainly of hydrocarbons containing 8
carbon atoms, the aim being to increase the production of
paraxylenes by converting the other hydrocarbons in the
batchO The method ~s particularly applicable to batches
1~ containing from approximately 5 to approximately 50~ of ethyl-
benezene.
In the two steps the catalysts used may have the same
composition or a different composition. In the first step,
the proportion of halogen (usually chlorine) in the catalyst
is greater than in the catalyst used ln the second step, lf
the condltlons in the two steps are as in the preceding
Table. The reason is that the equilibrium between chlorine
and water (in the batch injected into the reactor) is dependent
on the aforementioned c~ndition.
In~addition to the chlorine content, the composition
of the catalysts may vary with regard to the nature of the
àctive metals or promoters deposited on the support For
Example, when the isomerization process is performed in two
steps only, the first reactor can have a catalyst containing
only platinum as the metal, whereas the second reactor can
contain a catalyst according to the parent patent.
Alternatively, the following catalyst combinations can be used:
In the first reactor a catalyst according to Yrench
; Patent SpecificatLon No. 2031984, containing a metal from
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5.
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-
36~
crude platin~n and tin as the active metals; alternatively
- the first reactor can comprise a catalyst containing at
least one metal from crude platinum on a refractory oxide
support, together if required with one or more promoters
adapted to improve a particular property of the catalyst
(e.g. its service life, activity, stability or inhibition of.
cracking activity.).
The second reactor can contaln a catalyst according
to the parent patent.
The various catalyst formulae can be used in any desired
manner in the two steps. For example, the catalyst
according to the parent patent can be used in the first step
or the second step or both. The applicant~, however, have ~ ;
found that it is more advantageous to dispose the catalyst
more particularly in the ~econd step, when there axe only two
steps in the isomerization process, and good results have
been obtained with a pl~tinum/alumina formula in the first
step and platinum ~ tin + zirconium/alumina in the second
step. As explained hereinbefore, the platinum/alumina
formula i.n the flrst step may, without greatly changing the
result, be replaced by platinum ~ tin on alumina.
As previously stated~ the proportion of haloger. (usually
chlorine~ in the formulae of the catalysts in the different
steps will vary from one step to another, due to the
difference between the operating conditions of the steps.
Thus, the proportion of halogen will usually be from
1 to 2~ in each step. However, the proportion of halogen
in the catalyst ln the first step wlll be greater than in the ~-
second step, the di~ference varying e.g. rom approximately
6.
~ . . . ..
. ~; :
i779
0.05 to approximately 0.50~, relative to the weight o~
catalyst.
As is known, the purpose o the halogen is to confer
some acidity to the refractory oxide support. Other elements
having the same proI>erty may likewise be added to the various
catàlyst formulae in each step. For example, the a~plicants
have successfully used added silicon, in the proportion of
approximately 0.5 to approximately 2~, relative to the total
weight of catalyst, in the aforementioned catalyst formulae.
The following examples illustrate the invention, both
in the case where the cataIysts according to the parent
patent are disposed in both steps and in the case where the
catalysts are disposed in only the last step of the method.
These examples, however, are non-limitative.
EXAMPLE I
As previously stated, a batch of alkyl aromatic
hydrocarbons was isomerized and had the followLng
composition:
Toluene 1~07%
Ethylbenzene27.44%
Paraxylene 1.44%)
Metaxy4lene 68.67%) Total: 71.42%
Orthoxylene 1.31~)
and an attempt was made to obtain a maximum yield of
paraxylene by this reaction~
The followlng catalyst formulae were used:
, .
.
7.
.. . .
~ ~ 7".
... . ~. .. . .. . .
7~
CATALYST ACCORDING TO THE PARENT PATENT (A)
Platinum 0.35~ by weight
Tin 0.20~ ~y weight
Zirconium 0.15% by weight
S GONTROL CATALYST (B)
Platinum 0.35% by weight ~:
The catalyst supports were alumina having
conventional properties, as follows~
Specific surface: 185 m2/g
Pore volume: 0.48 cm3/g
Average pore radium: 40 R
The chlorine content of the catalyst, indicated
in Table II hereinafter, was kept substantially constant
by injecting 184 ppm of chlorine in the for~ of
dichloropropane into the non-dehydrated batch of alkyl
aromatic hydrocarbons, so as to compensate dechlorination
due to the molsture content of the batch.
A number of tests were made, under the conditiolls
set out in Table II~
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cn ~,-1 1_ ,-1 N rl r~l N ~1 ~ rd .
r-l _ (~
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r~ a) I~ r-l . ~D ~3 O ~ (~
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0 ~\ P:; ~ H UO E-l ~ 111 ~ rl
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r-l ~ E-l ~ .~~C ~¢F 1 ~ O ~ r-l (I) ~
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The results of these various tests are shown
in Table III.
The Table gives:
,
. The yield by weight of the various products in
the effluent;
` The total percentage yield Rl in hydrocarbons . -
containing 8 carbon atoms;
The rat:io R - incomin~ xylenes
; 2 xylenes in the effluent ::
.
, 10 ~he percentage conversion of ethylbenzene (CEB).
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- 11 -
The following notes refer to the results shown in
this Table:
(1) In a single ste~, the best result for the
formula Pt - Sn - Zr was obtained at 15 bars at
475C. (Test No. 3; see the values for the paraxylene
yield, ratio R2 and yield Rl).
(2) A comparison between test 3 and test l
shows that, in two steps:
The total yield Rl is higher,
The R2 ratio is higher, and
The paraxylQne yield is higher.
It is ther~fore more advantageous to produce
paraxylene in two steps rather ~han in a single step.
; (3) In a single step, the best result for formula Pt
~was obtained at 22.5 bars at 447.5~C. (Test No. 12;
: see the paraxylene yield).
~4~ A comparison between tests 12 and 7 shows
that it is advantageous to work in two steps (Test
No. 7) since this increases the paraxylene yleld.
However, the paraxylene pro~uction level is lower than
with the Pt - Sn - Zr formulae according to the
parent patent, and the advantage of going from one to
two steps i9 greater in the case of the aforementioned
Pt - Sn - Zr formulae.
EXAMPLE 2
In this example, a batch of hydrocarbons was
isomerized, the batch having a substantially constant
.
compositiont consisting mainly of metaxylene and
.
12.
_
;'77~
ethylbenzene. Isomerization was performed according
to the invention in two reactors under the following
conditions;
First reactor:
Pressure: 20 bars
Temperature: 280C.
25 cm3 catalyst containing 0.35% by weight of
platinum and l.6% chlorine on alumina,
Second reactor:
Pressure: 15 bars
Temperature: variable between 490 and 530Cy
15 cm3 catalyst (alumina support) having a composition
which varied from one test to another (tests 13 - 18;
see Table IV hereinafter).
The total volumetric speed per hour was 1.5; the
molar ratio of hydrogen to hydrocarbon was 7.5. In
addition, dichloropropane was added to the hydrocarbon
batch, in a proportion of 180 ppm/200 ppm of water
present in the batch.
At the beginning of the reaction, the catalyst in
the reactors were given reducing treatment with
hydrogen tat 20 bars) at 500C. for 2 hours.
. .
The catalysts used in the second reactor are
described in Table IV hereinafter.
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TABLE IV
Test 13 14 15 16 17 18
Catalyst \ Control Control
in second
reactor \ _ _
Platinum content 0.35 0.35 0.34 0.38 0.37 0.36
(wt. %)
. - _
Lead content _ 0.20 0.21 0.22 0.220.20
...... _ ..
Z rcon ~m con-. _ _ 0.15 0.14 0.15 O. 79
Chlorine con-1.6 61.69 1.80 1.68 1.73 1.67
Batch:content
(wt. %) ` :
- Toluene 0 0 0. 03 0.070O 18 0
- Ethylbenzene27.5627.26 27.45 27.3827.47 27.56
- Paraxylene 2.30 2.11 2.09 2.10 2.29 2.30 .:
- Metaxylene 68.0768.82 62.42 62.6463.91 68.07
- orthoxylene2.07 1.81 8.01 7.81 6.15 2.07
- Total xylenes 72.44 72.74 72.5272.55 72.35 72.44
-
Table V to X herelnafter show the results obtained
in Tests 13 to 18 respectivelyO
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- 14 -
.. .. .. .. . .. ... ... .. ..
More particularly we have shown the ratio
R = paraxylene in the effluen-t
paraxylene in the effluent + losses.
The losses consisted of benzene, toluene,
light hydrocarbons (containing fewer than 7 carbon
atoms, except for benzene and toluene~ and heavy
hydrocarbons (containing 9 or more carbon atoms).
R represents the paraxylene yield with respect
to the fresh batch, if the hydrocarbons co~taining
8 carbon atoms are recycled after separation
of paraxylene and the losses.
C~ denot s ~e con.erqlo~ o E ethylbenze~e.
;'
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! 11
I I f TABLE V TEST 13
,,
, I!
~emperature ~f ~ ~
~Yiel ~ ond reactor ~ 490 s S 1 510 ~ 520 ~ 53C~5 in weight ~ ' s ~I s s
2 S ~
~.s-light products s o,gls 1~16 t 1~05 ~ 1,43 t 1,74 ;
s J J J
'; t ~ . 8 ~ ~ :
. 1- benzene - I 0,43 : 1,05 : 1,11 s 1,29 ~ 1,52 s
s s
s
s- toluene ~ 1,80 s 2,28 s 3,16 8 3,70 s 4,24 :
s ~ 2
tI t t
saturatéd hydrocarbon6 7~ 4,44 t3, 10 .2,17 s 1,42
containing 8 c~rbon t t
.l atoms s ~ ~s
- I t I 7~ ~ s
5~ I
t~ethyl~enzene ~ 15,0 ~ 15,58 ~ 16~58 ~ 1S,25 l 16,0t
s . t
~~~ paraxylene ~ 16~73 s 17~05 : 16,43 ~ 16~81 s 16,32 :
t s ~
t ~ s ~ s s s
t- metaxylene . 2 39~14 s 39,38 : 39,28 ~ 38,30 s 37,78 s
t ~ ~ s ~ s ~
~ s s s ~ t
orthoxylene t 14,96 1 15,46 ~ 14~83 s 1S,67 ~ 15,04 s
S I ~ ' ~ t I
S
I I- heavy products ~ 0,31 : 0,43 ~ o,66 1 0,90 s 0~70 ~
t S t ~ I
0;~29 : o,776 ~ 0~733 5 0,697 1 o~666 ,
I I t I : s
'~ s ~ t I ~ :
. ! CEEI . ~ 43~4 5 43,5 : 39,8 s 44,6 s 41,9 s
! t t t t t ~
t~ 5 s 2 1 ~ :
11 ~ . .
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16. I
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,
.,
~ t~
`
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l TABLE VI TEST 14
: .
.
Temperature ~f : I t I . S
econd reactor: 490 t 500 s 510 t 520 s 530
, s Yield ~`~_ (C) s s t I t
in weight ~ _ : 2 ~ ~ ~ I
l l ~; t ~ S
~ t - light products s 0,50 s 0,50 : 0~85 t 0, 76 ~ 0, 93 s
I t I S S
t 8 I S
: t- benzene 1 0,76 s0,42 : 0,80 ~ 0,87 s 1,11 1
~ / s
l ~~ toluene ~ 0,94 ~. 1917 ~ 1956 ~ 2,07 a 2,67 :
l l ~ S St S S , :
~ saturated hydro~arbo~s4~32 3~57 t 2,20 11,20 s 0774
t containing 8 carbon : : 2 ~ ~ .
: atoms s ~ t ~~ :
i t t s I t~ . ; :
, ~ ethy~benzene 1S,37 16,04 s 16,20 15~93 s 16,31
1 ¦ t s~ a t
1- purBxylbne ~ 17$62 t 17,52 s 17,62 ~ 17~80 s 17,60 s
.1 ~ 1 s s s i ~ ':î ~ s ~ ~ ~ t
' 1- mdtnxyl~no 1 40~38 s 40~64 t 40~47 ~ 4,3 t 39D78 S
I S t I ~ ~.
_ orth~xyl~ne 1 16,88 s 16~78 t 16,88 s 17,28 17,08
s s t . 1 5 :
t ~ t t 8
- heavy produc~s ~ 0~22 0,34 0,42 s 0,81 . 0,80
~ s ~ s
~ t : : 0
,j I R s 0~879: 0,878; 07846 s 0,798 t 0,762 :
s ~ ~ :
3 I s
E13 43$6 S41,2 s40,6 41~6 40,2 ~
: ~ ~
~' ` , . ..
l '
. .
; ' , .
., , .
17.
... . ._ ... .. _._ .. ......... , ., .. ~.. ._.. _ _ .__ __ _.. _. _ .. _
~.
il ; , .
TEST VII TEST 15
';' j 11
~... l .
, .
Temperature of ~ t
second reactor 1 500 t ~10 y 520 8 53 ~
~ Yield in ~ (~`C) t ~ ~ t s
.-~, t weight . ~ s t t
! ,
t ~ 2 1~ s
, ~ - light products t 0,S8 s o,68 ~0~77 t 0,98
'j t ~ ~ s. s I
~ ~ - benzene ~ - ~ 0,45 t 0~61 s1 ,o6 :
: : . t t t~ t
l s t t t8 ~
I ~ - toluene t OD~5 ~ S~ 1 ~59 a 2~ 12
t . t t t ~ - s
. ' ~ ' ~ s~: S
t - saturated hydrocarbons s 7,62 : 3,98 s 2362 t 2J58 s
s containing 8 carbon ' t I . 3~ s
î atoms t ~ t s
i ~ t
. ~ t ~
ethylbonz~ne ~ 16~23 ~ 17,02 s16,80s 16~56 s
I ~ t
' 8 S ~ ~ ~
- par~xyleno a 16~46 s 16~51 116,62t 16~79 s
s ~ t t 3
~ t 5
j! ~ - metaxylene ~ 39,20 s 40,18 s40,30~ 39,14 2 . .
:
t
I ~ ¦ t -- orthoxyl~no ~15~69 S 16~78 : 17~29~ 17,01 :
I I t ~ t ~ I
t
i ~ ~ heavy products ~ 0~35 s 0~25 1o,40t ~:0,74 s
s . ~ ~ ! t
,
R : 0,902 s o,867 s 0~83~.0,774 ~
.l, ~ .. ~3 ~ ~ :
s t : Y
EB ~4~9 38~0 t 38~8 39~7 s
,, , _ _~ _ _ _ :
:'
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18. -:.
..
.,~ ~ .
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.: . , ' : ' -
:, . . ' ` . ,, . : ~ . '
.' ,: ' ~. : ' . ~ ' '
i i
i
. ! ~ABLE VIII TEST 16
lil ' '
, i . _ . _ _ , .
: 1 ~ Temperature of
second reacto~ 490 ~ 500 s 510 s 520 ~ 530 ~
~Yield i ~ ( C) s s t~ s s
. ' weight ' s I s s
I li t _ ~ ~ J S ~ ~ t
S I t
! so light products s O.S1 s o9~6 s o,64 s 0,57 ~ o,84
I I t t S 5 ~ t S
I ~ ~ ~ t S ~ ~ .
I ; I b~nzon~ 0,45 s 0~78 ~ 0~70 :
1 ~ s s s t :
; I ~
l s- tolueno : 0~91 t 1,13 2~ p41 s 1 ,41 . 1 j78 ,
2 t ' S J t 2 ~
I I ~ 8 S ~ : ..
S-saturated hydrocarbon~ 8~69 : 6~37 : 3~78 s 2~92s 2,33 :
: containing 8 carbon t S S S :
s atoms : s : ~ ~ s
. t ~ I ~ t ~ . ~
s ~ : s ~ :
s- ~thylbenzane t15~54 16~02 . 17~49 17~76 ~ 17,67 .
~ `; 2 ~ : ~ I . s
i ! I- p~ra~tylene . sl6,31 tl6,49 s 16,43t16,Sl : 16,73 :
l l ~ t ~ S 8 ~ t
j ! , met~xyl~ne s3~,35 s38,95 s 39,60 s39,72 s 39,41 s :
I t S t ~ S '-1' ~:
s- orthoxylone t 16~49 :16,95 2 16,92 :16,98 s 17,14 :
: : s s : s :
t s : t ~ ~ :
I ~ h d s 0~23 0~35 s 0,29 0,35 0~40 . -
~ I I s ~
! 1 ~ R ~0~908 sO,8~1 s 0,855 :0,842 ~ ~818 :
~' ~ . s :, s s ~ ~
I I t I : t s ~ ' :
CEB s43,2 s41~5 s 36D6 s35, 1 ~ ~594 ~ ~ :
` ~t~v _ s ~ t
i . . . ~:
. . ~:~
~ . . .
., 19.
:~:
.~ .
. ~
. ,,. , ~..... . . , - .
l !
1l .
I I TABLE IX TEST 17
i I .
: I
i !
I . ~ . . . ,, . _
~ ~ ~ Temperature of ~ 3 ~ I
¦ ' ~ second reactor ~490 2 500 ~ S10 s S20 S3
Yield i~ .(C) : . : 8 t ~
, weight ~ '` ~ ' J ~ ~ .
'I I :s I I t s
I ~
~: :z : s ~ :
It~ light products s 0~45 s o,63 t o,86 t o,as s Oa96 t : ~
3 s 8 s :
t - bonzbne t -- s -- s 0~ 46 t 0~ 94 s 1 ~ 09 s
S ~ ~ ~ s
jt t ~ t ~ ~ :
- ~ tolueno . 1,02 ~ 1,26 : 1"59 s2,28 s 2r73 :
s ~ ' :
': : : I I z t
:- saturated hydrocarbons 8,57 t 5,82 s 4320 s 2,65 ~ 1j88 s
: containing 8 carbon : t s s ~ :
atoms . : : s i t :
t ~ ~ S 2 8 ~
s- ethylbenzene : 15,~8 s 16,13 : 16~41 s 15,59 ~15,65 :
S t ~ S ~
t ~ S : ' : t I
:- paraxylene s 16,32 1 16,74 s 16,84 ~ 17~33 s17,23 s
t ~ I t
s ' s . s : t s :
t- metaxylene s 38,51 ~ 39,20 : 39,33 ~ 39,33 s39,09 :
` S ~ ~ 2 t
t : , S ' t
:- orthoxylene s 16,28 ~ 16,85 2 17,01 ~ 17,50 ~17,45:
, t s~ S ~
t s~ : ~ s ~ :
s- heavy products 10~18 ~o,39 10,30 10,54 8 0,74 s
t ~z 2 1 ~ 8
. tt t I ~ ~
t R . s0~908 s 0,880 t o,840 1 0~79 ~ 0~757 :
- s ~
:
CE~ ~ 42,9 2 41,3 t 40~3 s 43,~ t 43,0 :
t ~
s _ , ~ ~, t : .
, I , .
20 .
~,
. ~'.' '` ' :'' - '` .
.. . . . . .. .. : . . .- . -
~ ¢~;7~7~
~p . . .. .. . _ . .. ... . . .. . , . . _ .. ..... _ __ _ _ _
TABLE X TEST.18
second reactor ' 490 ' 5 ~ 510 t 520 s 530 ~
i SYield i ~ (C) ~ s s I s s
¦ 2 weight -- ~ S ~ ~ t
: 5 ~ S ~
S ,: . :
; s ; t S g ~ ;
s- light products ois6 . 0,94 s 0,93 C,86 ~ 0~92 .
j : S : S t Z :
,:-- benz~n~ . s -- s o,3o , o,67 , o,76 s 0,~?2
:
I t S S ~ ~ t
, I t- toluon~ s o,g6 s 1,25 ~ 1,70 s l~9B s 2,54 ~
' ' ~ I t ~ I t 3
t ~ ~ ~ 3 ~
! j t- saturated hydrocarbo~s6,08 s 4,43 s 2,53 ~ 1,71 : 0,99 t
il ~ containing 8 carbon ~ ~ ~ t ~ S
il ~ atoms
t S t t
2 t s
thylbenzan~ s 15,56 t 15983s 16~20 t 16,18 s 15,95 ~
s s
: t ~ t 8 :
P~raXY1~ne : 17~32 ~ 17~44t 17~S8 S 17"68 : 17D68 S
;' . S ~
t ~ S ~ ~ t
;- m~taxylon~ s 39~14 s 39~292 39~64 s 39~86 s 39~41 :
s : s s .....
s- orthoxylollo s 16~99 s 17~27s 17~48 s l7t49 s 17~6~
t ~ s ~ ~
t ~ ~ . .,
:- heavy products I0,38 s0,24 s0,27 s0,49 t 0,93
s ~ ~ s ~ .
s
s : ~ s ~ . .
2 .. S 0,901 : o,86S~ 0,831 2 0,812 : o~769 t
S t ~ 2 ~ :
t : S S S ~ ' : : '
~ EB s 43,5 : 42,6 : 41,2 s 41,3 t 42,1 .
2 t ~ S : : :
j, .. ,~
., . .
., ' . .
21. ~ ~:
.
.: ~.~ .
, ' , ' . ' .' .'
;7~5~
The results in ~he Tablesshow that the process
. according to the invention is very suitable ~or
isomerizing aromatic hydrocarbons containing 8
carbon atoms. More particularly, lt is very advantageous
compared with a method using catalysts containing only
platinum. Comparison with the platinum-tin fonmulae
used ~n the second reactor is to the advantage of the
platinum + tin + zirconium formulae for Tests 15 and 16,
whereas the results are substantially equivalent
in Tests 17, 18 and 14.
In order to facllitate this comparison, the
single accompanying Figure shows curves whic~, in
dependence on the temperature T, give the values of
the ratio R for each of the catalyst combinations
used in Tests 13 to 18. ~.
:.
~'.
22.
.
,
' C~.
~ 3
.. .. ~ ` ., , .. ., . - . .. . . .
