RO106395B1 - Integrated process of chemization of isobutene and liniar butenes - Google Patents

Abstract

The present invention relates to a integrated process, concurrent production of methyl-tert-butylester MTBE and isoolefins C8 ... C12 by chewing on these components octane of the entire C4 olefin potential. The invention consists in integrating into a block a MTBE manufacturing technology, using the source of isobutene to either pyrolysis C4 or catalytic cracking, and the resulting isomerization in following isomerization of the linear butene chain at which couples the oligomerization process a of all C4 olefins produced as collateral streams or coming from other sources.

Description

The present invention relates to an integrated process for the chemisorption of linear isobutene and butenes, for the simultaneous production of methyl ierate-butyl ether (MTBE) and isoolefins C _g -C ₁₂ , octane components for non-polluting gasoline.

Particular importance is given to the use of MTBE as a high octane adjuvant in unleaded car petrol, the production of this asymmetrical age having an annual growth rate not found in other petrochemical products. This increase is due primarily to its exceptional qualities in combination with gasoline, which cannot be overlooked the fact that 36% alcohol is involved in its structure, which has become available in appreciable quantities.

However, MTBE production is the availability limit of isobutene which by catalytic addition to methanol leads to the formation of this ether.

For further stimulation ah ₃ c - c = ch ₂ + HO - <5h ₃

The reaction has a high selectivity with respect to the two reactants, when ion exchange resins, of the cross-linked polystyrene type with strongly sulfonated divinylbenzene, with internal necropores, are used (patent RO no. 87238).

The provision of a small excess of methanol, in relation to isobutene, when feeding the etherification reactor and the choice of a thermal regime of compromise between the thermodynamics and the kinetics of the addition reaction, are the two factors that, together with the mentioned catalytic system, lead to some performances. superior to the process.

MTBE synthesis is a balance reaction. In line with the negative growth rate of MTBE production, new pyrolysis and catalytic cracking capacities have been developed, as well as some very large capacity installations, which use as the source of n-butane isobutene.

This last process, although expensive, has become for the areas that have natural gas, the main source that leads to MTBE.

The immediate result of pyrolysis development, in order to obtain ethene, propene, isobutene, etc., was the worldwide record of a major surplus of butadiene, the price of this monomer being constantly decreasing. In this new situation, the production of this monomer was abandoned by oxidative dehydrogenation, thus registering an important availability of linear butenes that can be chemized.

The synthesis of methyl-tertiary-butyl ether is known by the addition of methanol to the double bond with tertiary carbon present in the structure of isobutene:

In its 3 ~ HoC-CO —CHo k ~ ^Λ ι ^J , the thermidinamic equilibrium is strongly displaced as the formation of MTBE at low temperatures, when the inverse reaction rate (k ₂ ) drops sharply. On the other hand, lowering the temperature favors the reaction rate, and at a certain lower limit (45 ° C) the reaction freezes kinetically.

The negative effect of the temperature increase on the thermodynamic efficiency in order to favor the kinetics is partially annihilated by the presence of the excess methanol (EP patent no. 315719).

The trade-off between thermodynamics and kinetics was solved by delimiting two reaction zones in a mixed reactor, muititubular at the top, where there is also the supply with the two reactants and the reaction chamber with cooling coils at the bottom. In the multitubular area where the concentration of isobutene is high, there is a high thermal jump, as a consequence of very high reaction rates, and it is necessary to ensure an effective thermal transfer for the cooling agent to take the developed enthalpy. in this area. an isobutene conversion of over 70% is achieved, the temperature of 75 ... 80 ° C being favorable for the reaction rate (kinetic control) (RO patent no. 73358).

In order to move the balance towards the formation of MTBE, it is necessary to reduce the temperature to 55 ° C in the lower area, concurrently with the increase of the stationary time in order to reach the composition at the thermodynamic equilibrium required by this temperature (thermodynamic control).

The process, according to the invention, removes the disadvantages of the known processes, in that both the C ₄ fraction of pyrolysis pyrolysis concentrated in isobutene together with the isomerate resulting from the isene isomerization process of the linear butenes to which it is coupled and the oligomer process is used as the source of isobutene. of all C ₄ olefins resulting as collateral flows or those from other sources, at a temperature of 75 ... 85 ° C, at a pressure of 12 ... 14 at. and at a voluntary speed LHSV 3 ... 5 m ³ / m ³ cat x h.

The process according to the invention has the following advantages:

- increase of about 50% of the production of

MTBE as a result of isomerization of linear butenes to isobutene; .

- superior use of butenelo to high octane components for lead-free gasoline.

In the following, an embodiment of the invention is shown, in connection with FIG. 1 ... 3, which represents:

FIG. 1 diagram of the MTBE synthesis facility;

FIG. 2, the scheme for the isomerization of n-butenes;

- faith. 3, the scheme of the oligomerization plant.

The quantities and concentrations of the fluxes that are part of the block diagram of the chemistry of olefins C

6

The pyrolysis fraction C ₄ (flux a), in the amount of 9150 kg / h, having a concentration of 45% in the isobutene, is pumped through a pipe 1 on one of the tables of a fractionation column 2, which separates as the basic product , at a pressure of 7 ... 8 at and a temperature of 75 ... 80 ° C, the mixture of 2-butene and «-butane. At the top of the column, having 80 bead plates, it separates, at a temperature of 55 ... 60 ° C and at a pressure of 6.5 ... 7 at, the mixture of isobutene -1butene, containing small quantities and of isobutane. This stream (6850 kg / h) with an isobutene content of about 60 ... 62%, after condensation, meets the fresh methanol flow (3400 kg / h), from a pipe 3, the recycle flow (b) constituted of 500 Kg methanol (from pipeline 4) and 560 kg MTBE and isomerized stream (c) (6375 kg / h) (d) having 30% isobutene from pipeline 5. After homogenization of the stream passing through a pipeline 6, in the amount of 17696 kg / h, constituting the two reactants in concentrations of 35% isobutene and 22% methanol, after preheating at 55 ... 60 ° C, penetrates with a pressure of 14 at the upper part of the multitubular zone of a etherification reactor 7. The exothermic reaction of addition of methanol to the isobutene proceeds by contacting the homogeneous liquid phase with the fixed layer of macroporous cationite in the reactor tubes. In this area, at the upper part, high reaction rates are achieved with significant heat releases, the temperature being maintained at 75 ... 85 ° C, with the coolant nozzle circulating in an equivalent manner with the feed flow through the reactor sheath. In this area, at a volume feed rate of about 3 ... 5 m ³ / m ^{3 and} xh is achieved over 65% of the conversion of isobutene from the multitubular area, the film passes into the lower cooling zone where, by gradually decreasing the temperature up to 50 ... 55C sc defines the resolution efficiency to over 95%, as a result of the thermodynamic balance shift.

Simultaneously with this evolution of the thermal regime, the LMSV volume velocity is reduced to 2 ... 3 m ³ / m ³ cat xh in order to increase the stationary time, in order to reach the equilibrium composition.

The effluent of the etherification reactor, containing about 55% MTBE, which exits through a pipeline 8 (flow e) 3% methanol and the remaining inert C ₄ hydrocarbons also containing unreacted isobutene, is directed to an extraction column 9 of methanol through countercurrent circulation. of water and organic flow. The column with plates (30 ... 35) operates at 8 atm pressure and at ambient temperature, the optimum water ratio: the organic phase being 0.5: 1.

The extract coming out from the bottom of the column containing water, 500 kg methanol and 560 kg MTBE is directed to a distillation column 10, where at the top the thermal azeotrope MeOH - MTBE - water is distilled through a pipe 11 (flow b) at a temperature of - 55 ... 60 ° C, and from its base is drained water that recirculates after cooling, at the top of the extractor.

Continuously separated refining at the top of column 9, with a pressure of 8 at, after preheating at 70 ... 80 ° C enters one of the feed trays of a debutanization column 12.

The debranching column, equipped with 50 plates, separates at the tip, at the temperature of 60 ... 65 ° C and the pressure of 6.5 ... 7 at, the C ₄ hydrocarbons containing the linear butenes intended for isomerization, and from the base, continuously 9857 kg / h MTBE of minimum 98% purity (flow f) are evacuated.

The flow of linear cylinders, in the amount of 7130 kg / h, containing - 50% 1-butene and 40% 2-butene, after vaporization, preheating by heat exchange with the tributary of a reactor 13 is brought to a temperature of 480 ° C , after passing through the two zones of an oven 14. With this time 106395 and at a pressure of 0.5 at, it penetrates to the top of the adiabatic reactor 13, in which is the isomerization catalyst.

For a gas volume speed 5

GHSV located within the limits of 800 ... 1000 m ³ / m ³ cat xh and at a contact time of 8 ... 10 s, a conversion of the buds of about 35 ... 36% is performed, the yield in isobutene being to 30%. 10

The reactor effluent containing: 30% ibutene, 20% 1-butene, 40% 2-butene and 5% i-butane, after cooling to 40 ° C, is condensed by compression at 10 at and further distilled under isobutane 15. in a column 15, after which it is sent to the etherification phase.

Flow 9 containing 2-butenes and butane, after preheating at 50 ° C is sent with the pressure of 30 at the upper part 20 of a multitubular 16.

The oligomerization reaction takes place with heat release, this being taken up by the thermal agent circulating through the manCH ₃ - CH ₂ - CH = ch ₂ 1 - butene and the reactor board. The reaction occurs by contacting the liquid phase with the fixed layer of catalyst in the tubular space. At a volume speed LHSV within the limits of 0.5 ... 1 m ³ / m ³ cat xh and at temperatures between 150 ... 160 ° C, a conversion of about - 70% of the butenes to oligomers occurs ( 66%), C ₁₂ (30%) and heavy polymers.

The mixture is subjected to the removal of n-butane and unreacted butenes that are recirculated, of Cg-C ₁₂ oligomers, which constitutes a gas with COR = 95 ... 97.

One of the basic features of the invention is the use of an impotent amount of linear butene resulting from MTBE technology, in order to increase the production of this ether.

This was possible by implementing in the technological flow for obtaining MTBE the isomerization process at the linear butene chain with obtaining isobutene.

(1) h ₃ cc = ch ₂ ch ₃ h ₃ c / ^h =

CH = CH oar - butene - 2

H ₃ CC = CH ₂ ch ₃ (2)

H ₃ C

CH trans - butene - 2 / CH,

CH H ₃ CC = CH ₂ ch ₃ (3)

These chain isomerizations result from acceptable speeds, from a practical point of view, in the presence of active alumina, having a certain Bronsted acidity or in the presence of alumino-silicates.

The main feature of this isomerization process is the participation of the three linear butenes, irrespective of their concentrations, in the isomerization reaction to isobutene.

Table 2 presents the composition of the three isomers obtained on a modified alumina, using the three butene at purities of over 98%. The working conditions were: temperature = 450 ° C and feed 0.92 g / g cat x h.

Component isomerized 1-butene isomerized 2-butene (cis) isomerized 2-butene (trans) C _r C3 (£ 53 033 (ξ32 iC ₄ 5.57 4.50 3.54 n C ₄ 1.00 0.52 0.29 ic ₄ 19.92 22.36 20.80 iC ₄ 27.26 25.33 20.08 tr.C ^ 27.05 ' 27.05 29.34 cis (¾ 17,30 18.80 23.07 2C _{S +} 0.84 1.03 2.45 1.3 C ₄ 0.15 0.08 0.11

From the data presented, the chemistry is complex, coking reactions occur, with hydrogen release reacting with olefin. It also results in a decrease in the yield in isobutene of the order 1 C ₄ '> cis C ₄ ² > tr C4 ² ' while the concentrations of trans - and 1C4 'remain approximately constant.

Of the three linear cylinders, 1-butene is the least thermodynamically stable, converting more easily into isobutene, followed by cis-butene. On the other hand, the double bond isomerization enters the competition:

.1cis C

^ .2- -— tf Q and thus the chain isomerization process probably proceeds via 1-butene.

Following a high activation energy, the chain isomerization takes place at high temperatures (450 ... 470 ° C), and in case of "5-butene-2" even higher temperatures are required. The yield per passage is around 30%, between the by-products that are formed being the isobutane in a larger quantity and the coke.

The catalytic system is a modified alumina, having a certain specific surface and a certain volume of pores, both of which are specific to this process. Also important is the absence of metal impurities as well as the value of Bronsted acidity.

The invention is also characterized by the fact that in the etherification phase which is common to both isobutene sources, a constant concentration in isobutene is maintained, thus eliminating the difficulties in maintaining a process-specific thermal regime as well as maintaining the performance in terms of yield and selectivity.

The process according to the invention also allows the C ₈ -C _I2 oligomers to be obtained by oligomerizing the secondary fluxes containing C ₄ olefins, along with / zC ₄ and iC ₄ . These flows, due to the accumulations of saturated by recirculation, cannot be directed to isomerization. The oligomerization reaction is exothermic (-1.5 kcal / mol) and proceeds in a multitubular reactor with cooling, in the presence of polyphospheric acid deposited on a suitable support.

The concentration of these technologies in a block presents a good flexibility regarding the existence of the sources of raw materials and of the requirements, being possible to direct the production according to them.

Claim

Claims (4)

1. An integrated process for the chemization of linear isobutene and butenes, by the methanol addition reaction, characterized in that, for the concomitant production of methyl-tert -butylether and C ₈ -C ₁₂ isoolefins, 5 isobutene is used as the source. the C ₄ fraction of pyrolysis concentrated in isobutene, together with the isomerization resulting from the chain isomerization of the linear butenes to which it is coupled and the oligomerization process of all the C ₄ olefins resulting as collateral flows or those from other sources, at a temperature. of 75 ... 85 ° C, at the pressure of 12 ... 14 at and at a volume speed LHSV 3 ... 5 m ³ / m ³ cat xh, at the upper part of the reaction zone with the decrease of the temperature to 50 ... 60 ° C and LHSV volume speed at 1 ... 2 m ³ / m ^{3 and} xh at the bottom. Process according to Claim 1, characterized in that, in a first step, the reaction of adding methanol to the isobutene present in the flow resulting by combining the C ₄ fraction of pyrolysis with the isomerate resulting from the catalytic isomerization process of linear butenes is carried out. . Process according to Claims 1 and 2, characterized in that the linear butenes resulting from the separation of methyl-hierbutyl ether or other sources of linear butenes are converted to isobutene by their chain isomerization reaction in the presence of an aluminum catalytic system. modified, at temperatures of 460 ... 470 ° C and has a contact time within 4 ... 7 s which corresponds to a GHSV volume speed of 800 ... 1000 m ³ / m ³ cat.x h. Process according to Claim 1, characterized in that the collateral flows containing C ₄ olefins and saturated C ₄ hydrocarbons are oligomerized to C ₈ ... C ₁₂ isooolefins at temperatures of 130 ... 140 ° C and pressures of 20. 30 atmospheres in the presence of a solid polyphosphoric acid catalyst.