Note: Descriptions are shown in the official language in which they were submitted.
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- 1 - CASE 1ll73
DESCRIPTION
This invention relates to a process for producins tert~butyl
alkyl ethers in the presenee of butadiene.
The reaction of addition oE alcohols to tertiary olefins æuch as
isobutene to produce tert.butyl alkyl ethers is an exothermic
reaction t~ich is acid-catalysed~
In the presence of suitable catalysts such as macroporous ion
exchange resins, the reaction proceeds to equilibrium in times
which are of industrial interest, even at relati~ely low temper_
atures t40-50c).
It is kno~m that it is not neeessary to operate with high purity
isobutene, and instead any cut which contains it is suitable, as
the alcohol addition takes place selectively to the double bonds
which engage a tertiary carbon atom. Those cuts originating from
eatalytic cracking and those originating from steam cracking,
these latter either before or after eYtracting the buiadiene~ are
particularly suitable.
When usin~ as olefin feedstock the C4 fraetion from catalytic
eracking or that fro~ steam cracking after extractirlg the butadiene~
and using methanol or ethanol as the alcohol an~ a sulpnonie
maeroporous resin type Amberlyst l5 or Lewatit SPC 108 as the
eatalystl tne reaetion can be used industrially within a wide
range of reactor designs and operating conditions direeted towards
optimisir.g the conversio~ of one or other o~ the reactants~ I~
these cases, high selectivity is alwa~s obtained, together wtith
good perf~rmance of the catalyst both in terms of catalytie
aetivity a~d life.
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~ihen o~eratin~ with an olefin cut with a high butadiene
content~ such as the C4 cut from steam crackin~ before extractin~
the butadiene~ the operating conditions must be accurately defined
in order to allow a butadiene recovery exceeding ~8 ~. In
particular7 it is necessary to maintain a strict relationship
between the temperature and spacial velocity as described in USA
Patent 4,039,590.
- It has howsver been noted that when carrying out the isobutene
etheri~ication reaction in the presence of butadiene in a tu~ular
reactor containinO a macroporous resin7 and feeding the reactants
from the top downwards in the nor~nal manner, an increase in pressure
drops takes place with time~ even 1.rhen operating ~lnder conditions
which allow a high butadiene recovery of ~ 99%, and in addition
a slight conversion fall-off~
t 15 However, an identical test carried out with a butadiene~free cut
shows neither pressure drop increases nor conversion reductions.
It has been surprisingly found, and constitutes the subject matter
of the present invention9 that by feeding the butadiene containing
~ feedstocks so that they flow from the bottom upward6~ under slight
`~ - 20 bed expansion conditions, the pressure drops remain constant with
timeO
The process according to the present invention consists of producing
tert.butyl alkyl ethers by reacting the isobutylene o~ a hydro-
carbon feedstock which also contains butadiene at concentrations
of between 10 clnd 70% by weiOnt~ with one or more aliphatic
alcohols~ preferably methanol or ethanol~ in one~ two or more
reactors~ preferably in series, and is characterised in that the
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reactants (hydrocarbon feedstock containing butadiene and
alcohol or alcohols) and the reaction products flow through
the reactor or reactors from the bottom upwards.
The reactors may be provided with a macroporous
acid ion exchange resin catalyst.
In addition to the ascendl~g direction of flow of the
reactants and reaction products, the linear velocity of the
reactants through the reactor or reactors may vary from
0.5 to 2 cm/sec. and the temperature in the reactors may
range from 50 to 60C, preferably from 50 to 55C. Some
examples are described hereinafter for the purpose of better
illustrating the invention, but these must in no way be con-
sidered as limitative thereof.
EXAMPLE 1
A C4 cut having the following composition:
Propylene0.46 % by weight
Isobutane6.87 % by weight
n-butane11.80 ~.by weight
Butene-l11.39 % by weight
Isobutene30.19 % by weight
Butene-2+3.25 % by weight
Cis butene-21.55 % by weight
Butadiene34.43 % by weight
in mixed with methanol such that the molar isvbutene/methanol
ratio is equal to 0.85, and the mixture is fed at a through-
put of 14 l/h and a temperature of 50C through two reactors
connected ln series, having a total capacity of 4~5 litres
and filled with 4 litres of catalyst. The catalyst is a
macroporous sulphonic resin with an
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exchange capacity of 4~8 meq H+/g dry.
The reactants flow from the botto~ up~ards~
The linear veloclty is 1 cm/sec.
The conrersion and pressure drops with respect to time are as
~ollo~ls
- Time hours 24 5002000
- ~ P 1st reactor kg/cm2 0.2 0.2 0.2
- ~ P 2nd reactor kg/cm 0.2 002 0.2
- % ~rEE by weight 38.1 38 38
- ,' dimers and codimers by weight 0.05 0.05 0.0
- % butenyl ethers by weight 0.2 0~150.2
- isobutene conversion 9606 96~496.4
- butadiene recovery ~ 99 ~ 9g ~ 99
- ~ P represents pressure drop.
15 EXA~LE 2 (comparative)
The feedstock described in the preceding example is fed under the
same temperature and spacial ~elocity conditions to the two
reactor~ connected in series, but in such a manner that the flow
direction of the reactants is from the top downwards.
At the beginning o~ the test, the results are analogous to those
of the preceding example, but ~s time passes a progressiv~ pressure
drop increase and a slight con~ersion fall-o~ are obser~ed.
_ Time hours 24 500 2000
- ~ P 1st reactor k ~cm2 o ~ ~.4 1.5
- ~ P 2nd reactor kg/c~2 0.3 005 1~8
_ 76 ~rBE by weight 38 37-9 36
_ % dimers and codimers by wei~ht 0~1 0,1 0.05
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51~2~
_ ~ butenyl ethers by weisht 0.2 0~2 0.2
- isobutene conversion 96.4 96.1 91.3
butadiene recovery ~99 >99 ~ 99
:~ EXAMPLE 3 (comparative)
; 5 Methanol i.s added to an olefin cut containing 35% of isobutene and
O.ZY of butadiene by weight, such that the molar isobutene~methanol
ratio.is o.8s.
` Tha mixture is fed at a throughput of 14 l/h and a temperature of
-- 50C to the two reactors connected in series, the flow dlrectio:
being from the top downwards. In the absence of butadiene~ no
. pres.sure drop increase or conversion fal].-off with time are
observed.
Time hours 24 500 2000
- . P 1st reactor kg/cm2 0.3 0.3 0.3
:; 15 - L~ P 2nd reactor kg/crn o,3 o.3 o,3
- % ~TBE by weight 43.1 42.9 43
- ~ dimers and codimers by weight 0.3 0.3 0.2
_ isobutene conversi.on 96.8 9606 9606
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