RU2078793C1 - Method of producing high-antiknock gasoline components - Google Patents

Abstract

FIELD: gasoline production. SUBSTANCE: high-octane ether components are prepared by interaction of methanol with isobutylene in a C₄-C₅-hydrocarbon mix in presence of catalyst followed by further processing nonreacted C₄- hydrocarbons in pyrolysis furnace and combining pyrolysis fractions C₄ and higher with starting C₄-fraction fed into reactor with methanol. EFFECT: enlarged yield and choice of desired products. 3 cl, 2 dwg

Description

 The invention relates to an improved method for producing high-octane organic mixtures involving methyl tert-butyl ether, which are used as sets of high-octane gasolines.

 Methyl tert-butyl ether (MTBE) is the best high-octane component of low- and unleaded gasolines. MTBE is used as an additive to motor gasolines, since it has a high octane mixing ratio, the availability of raw materials, the stability of the product during storage, and the simplicity of production technology.

MTBE is usually obtained by the reaction of methanol with isobutylene contained in a mixed stream of C ₄ hydrocarbons supplied, for example, from catalytic cracking units or ethylene complexes.

 The preparation of mixtures based on MTBE is often combined with the production of methyltretamyl ether (MTAE).

A known method of producing MTBE and MTAE from methanol and a mixture of hydrocarbons containing tertolefins C ₄ -C ₅ in the presence of a catalyst.

 The target products are obtained in the form of a mixture with unreacted hydrocarbons and methanol by distillation of the specified mixture with separation of the target product as a bottom residue, and a mixture of unreacted hydrocarbons and methanol in the form of a distiller, from which methanol is then isolated (see A.S. N 1456006, cl. C 07 C 43/04).

The disadvantage of this method is the low yield of the target product (a large amount of C ₄ raffinate is not used, mainly a mixture of isobutane, butylenes, butane).

A known method of producing MTBE as a result of the interaction of methanol with isobutylene contained in fractions of hydrocarbon C ₄ from catalytic cracking units or ethylene complexes (see E.I. "Oil refining and petrochemicals". M. 1992, N 18). The disadvantage of this method is its complexity due to the presence of a significant amount of equipment and the low yield of the target product.

 The prototype of the alleged invention adopted the method of producing esters by reaction-distillation method. (see. Thematic review "Production of methyl-alkyl ethers of high-octane gasoline components." M. 1988, TsNIITneftekhim. Oil refining and petrochemical industry. Overview. Series: Oil refining. Issue N 9, p. 36, 37, 64, 46-51 )

According to the prototype method, the initial fraction of C ₄ -C ₅ hydrocarbons is fed to the reaction apparatus, where it is mixed with a stream of methanol.

 Methanol is fed from above onto the catalyst bed. In the reactor, MTBE and MTAE are synthesized in the middle zone filled with the catalyst, as well as the separation of reaction products in the upper and lower distillation zones.

Vapors of unreacted C ₄ hydrocarbons mixed with methanol close to azeotropic in methanol are taken from the top of the reactor and sent to the washing of unreacted C ₄ hydrocarbons from methanol, after which C ₄ hydrocarbons are sent to the storage and methanol is returned to the process.

The bottom product of the reactor is a high-octane ether component, which is mainly a mixture of MTBE, MTAE, unreacted C ₅ hydrocarbons and methanol is sent to the warehouse.

 The disadvantage of the described method is the low yield of the target product and a narrow range of products.

 The aim of the invention is to increase the output of high-octane components, including MTBE with the expansion of the range of products.

The essence of the proposed method lies in the fact that in the known method for producing high-octane ether components, comprising reacting a mixture of hydrocarbons containing isobutylene or isobutylene and isoamylene, for example, fractions of C ₄ , C ₅ catalytic cracking, with methanol in the presence of a catalyst in an esterification reactor with the selection of the target the product in the form of a bottoms residue, and a mixture of unreacted C ₄ hydrocarbons and methanol discharged from the reactor in the form of a distillate with the possible washing of these C ₄ hydrocarbons from methanol, unreacted C ₄ hydrocarbons are pyrolyzed and the resulting pyrogas fractions containing isobutylene are mixed with the starting fraction fed to the methanol co-processing reactor. With another design of the method, when the distillation is carried out after the esterification reactor, it is possible to isolate both the C ₄ fraction and the C ₄ , C ₅ fraction as a distillate. Moreover, with a significant content of butadiene and divinyl in the C ₄ fraction, it is advisable to isolate them by extraction (before or after the reactor) or by hydrogenation.

The pyrolysis of the entire fraction of C ₄ (including n-butane and trans and cis-butenes-2), as a rule, is advisable when combining this process with the progase treatment process at the pyrolysis unit (if the latter is available at the enterprise).

To improve the pyrolysis process of the spent C ₄ fraction, it is desirable to isolate pyrolysis feedstocks with the highest possible isobutane content from it.

However, due to the close boiling points of isobutane and butylene-1 (n-butylene), their separation at the current level of technology is quite difficult. Therefore, in cases where there is no need for significant amounts of ethylene and propylene, as well as with a significant content of the n-butane fraction and higher in the pyrolysis feed, the n-butane fraction and the fraction of heavier C ₄ hydrocarbons are preliminarily extracted from it. Butylene-1 in this case, depending on the clarity of the distillation, is distributed between the distillate and the bottom residue. The distillation distillation still can also be pyrolyzed with the pyrogas directed to the existing pyrolysis plant.

If the C ₄ -C ₅ fraction of the catalytic cracking process is used as a raw material, in order to simplify the technological scheme of the process, it is advisable to send the pyrogas to the absorption and gas fractionation unit of the cracking unit for the joint gas separation of the cracking products for the joint gas separation of the cracking products and the proposed method. Also, if there is a pyrolysis unit for producing olefins by the pyrolysis method at the enterprise, the pyrolysis products of the spent fraction C ₄ can be mixed with pyrolysis of the pyrolysis unit, and pyrolysis separation can be carried out together with pyrolysis separation of the olefin production unit by pyrolysis, which simplifies the process flow chart.

In order to exclude the methanol water washing unit from the technological scheme, it is possible to direct the C ₄ fraction to pyrolysis in a mixture with unreacted methanol.

 Distinctive features of the proposed method can increase the output of high-octane components, including MTBE, and expand the range of products due to, for example, additional production of ethylene and propylene, which are valuable petrochemical products.

 In FIG. 1 shows a simplified process flow diagram with the location of the separation unit of the pyrogas in front of the esterification reactor; in FIG. 2 is a simplified process flow diagram with the location of the pyrogas separation unit after the esterification reactor.

According to FIG. 1 the initial fraction containing isobutylene, for example, the fraction of C ₄ or C ₄ , C ₅ catcracking through a pipe 1 is fed to a contact reactive distillation apparatus 2 esterification reactor). The apparatus 2 is divided into three distillation zones, the upper and lower of which are filled with mass transfer devices, and the middle is an ion-exchange molded catalyst. Pipeline 3 serves fresh methanol to the top of the middle zone. In the middle zone, isobutylene (isoamylene), the C ₄ (and C ₅ ) fraction react with methanol, resulting in the synthesis of MTBE (or MTBE and MTAE).

 The upper and lower distillation zones are designed to separate the reaction products.

 From the bottom of the apparatus 2, the target product containing MTBE and MTAE esters is withdrawn through pipeline 4.

At the top of the apparatus 2, pairs of unreacted C ₄ hydrocarbons in a mixture with methanol are discharged, which are sent to a methanol separation unit 5 (methanol water washing unit) discharged through a pipeline 6, and C ₄ hydrocarbons via a pipeline 7 are sent to a separation unit 8, where heavy boiling hydrocarbons C ₄ (n-butane, butylene-2, part of butylene-1) are withdrawn via pipeline 9, and the remaining fraction of C ₄ through pipeline 10 is sent to the pyrolysis unit II.

Depending on various reasons, for example, with a relatively low content of n-butane fraction and higher in the spent mixture C ₄ , block 8 may not be installed. In this case, the entire mixture of C ₄ hydrocarbons is sent to the pyrolysis unit II immediately after block 5. It is also possible to pyrolyze the C ₄ fraction together with the methanol contained in it, excluding the methanol washing unit 5.

From the pyrolysis compartment II, the resulting pyrogas is sent via line 12 to a deethanizer 13, from above which a mixture of hydrocarbons H ₂ , C ₁ , C _{2 is} withdrawn, and the bottom product of the deethanizer is sent through a pipe 15 to a depropanizer 16, on top of which the propane-propylene is taken through a pipe 17 fraction, and below the fraction of C ₄ and above, which is sent through line 18 to line 1 for mixing with the original hydrocarbon fraction C ₄ (C ₄ , C ₅ ).

If there is a pyrolysis unit at the refinery, gas separation in apparatuses 13 and 16 can be replaced by the joint processing of the pyrogas of the proposed process and pyrolysis of the pyrolysis unit at the gas separation unit of the pyrolysis unit. It is possible to carry out gas separation on the absorption and gas fractionation unit of the catcracking unit together with the gases of the catcracking unit. If the company has a straight-run isobutane fraction, it is advisable to supply it to the pyrolysis apparatus 11 in a mixture with the spent fraction C _{4 of the} proposed process.

 The circuit of FIG. 2 differs from the above scheme in FIG. 1 in that the pyrogas is fed without synthesis for synthesis into reactor 2. For this scheme, it is necessary that reactor 2 operate at elevated pressure and have large dimensions due to an increase in the amount of gases. At the same time, the scheme makes it possible to combine gas separation for this scheme with the separation of straight-run gases in a gas fractionation unit.

 According to the circuit of FIG. 2, the initial fraction through pipeline 1 enters the contact apparatus 2. Methanol is also supplied through pipeline 3. The unreacted mixture of hydrocarbons with methanol enters through pipeline 4 and deethanizer 5. Washing of the mixture from methanol is not conventionally shown in this scheme.

Dry gas is discharged from the top of the apparatus 5 through a pipeline 6 (mixture of H ₂ , C ₁ , C _2. The fraction C ₃ and higher passes through a pipe 7 to a depropanizer 8, on top of which a C ₃ fraction is discharged through a pipeline 9. Hydrocarbons C ₄ and more come through pipeline 10 into the distillation apparatus 11, on top of which mixture of isobutane and butylene-1 leaves through pipeline 12, and a fraction of n-butane and higher from below, through pipe 13. In this case, C ₅ hydrocarbons do not enter reactor 2. If necessary it is necessary to supplement the scheme debutanizer bottom fraction which C ₅ bude supplied to the mixing with the feed unit 2 (in the diagram not shown).

Fraction C ₄ enters the pyrolysis unit 14, and the pyrogas is mixed with the raw materials of apparatus 2 via pipeline 15.

 The bottom of the reactor 2 through line 16 output the target product.

 Example 1 (prototype method).

For the synthesis of esters, a mixture of the C ₄ -C ₅ fraction of catalytic cracking of vacuum gas oil and the C ₅ fraction of the EP-300 pyrolysis unit of the following composition is fed into reactor 2: C ₃ -23 kg / h, isobutane 9048 kg / h, isobutylene 3448 kg / h, butylene 1 9127 kg / h, butadiene 46 kg / h, n-butane 3193 kg / h, butene-2-trans 3998 kg / h, butene-2-cis 1951 kg / h, 3-methylbutene-1 141 kg / h , isopentane 9320 kg / h, penten-1 2155 kg / h, 1-methylbutene-1 2095 kg / h, n-pentane 1311 kg / h, penten-2-trans - 2511 kg / h, penten-2-cis 2184 kg / h, 2-methylbutene-2 2419 kg / h, pentadiene + C ₆ 470 kg / h.

 Only 53400 kg / hour.

Reactor 2 receives methanol in the amount of 3771 kg / h. At the bottom of reactor 2, a high-octane gasoline component comes out in an amount of 29480 kg / h, including MTBE 4938 kg / h and MTAE 4506 kg / h. The spent fraction C ₄ in the amount of 27386 kg / h, including C ₃ 23 kg / h, isobutane 9048 kg / h, butylene-1 9127 kg / h, butadiene 46 kg / h, n-butane 3193 kg also leaves the installation. / hour, butene-2-trans 3998 kg / hour, butene-2-cis 1951 kg / hour, 3-methylbutene-1 100 kg / hour.

The process is carried out on a sulfonated ion catalyst KIF at a pressure of 7.5-8 kgf / cm ² , the temperature in the upper distillation zone 60 ^o C, in the reaction zone 65-75 ^o C in the lower distillation zone 115-120 ^o C.

 Example 2 (the proposed method).

Under the feed conditions of Example 1, the spent C ₄ fraction is separated into an n-butane fraction and higher and a fraction lighter than normal butane. The spent fraction of n-butane and higher in the amount of 9188 kg / h leaves the installation, and a mixture of isobutane and butylene -1 in the amount of 18198 kg / h is subjected to pyrolysis at a pressure of 8-9 kgf / cm ² and a temperature of 720-750 ^o C. pyrogas of the following composition: H ₂ 264 kg / h, CH ₄ 3106 kg / h, C ₂ H ₄ 1519 kg / h, C ₂ H ₆ 4458 kg / h, C ₃ H ₈ 573 kg / h, i C ₄ H ₈ 3367 kg / h, C ₅ and> 4383 kg / h are gas-separated.

Gas up to C ₂ inclusive is directed for joint gas separation to the pyrolysis unit, C ₃ fraction to concentrate propylene, and C ₄ and> fraction to produce high-octane ether components in apparatus 2. The operating conditions of the reaction-distillation apparatus 2 are similar to Example 1.

 This method additionally yields (estimated amounts, losses taken into account) 1450 kg / h of ethylene, 4300 kg / h of propylene and 7400 kg / h of the high-octane gasoline component, including 4750 kg / h of MTBE. In addition, 1425 kg / h of methanol is consumed.

 The octane number of the ether component and its quality improves due to the increase in the content of MTBE.

Claims (5)

1. A method of producing a high-octane component of gasolines by reacting hydrocarbons of a C ₄ or C ₄ C ₅ fraction containing isobutylene or isobutylene and isoamylene with methanol in the presence of an esterification catalyst in a reactor, followed by separation of unreacted C ₄ or C ₄ C ₅ hydrocarbons from the obtained product and methanol, characterized in that the unreacted C ₄ or C ₄ C ₅ hydrocarbons are directed to pyrolysis and the resulting pyrolysis products or a fraction thereof containing C ₄ and higher hydrocarbons, under they are mixed with the initial fraction fed to the reactor. 2. The method according to p. 1, characterized in that hydrocarbons having a boiling point of n-butane and higher are separated from the mixture of unreacted C ₄ or C ₄ C ₅ hydrocarbons before being sent to the pyrolysis. 3. The method according to claim 1, characterized in that a fraction containing C ₄ C ₅ hydrocarbons is isolated from the pyrolysis products and the separation is carried out on the absorption and gas fractionation unit of the catalytic cracking unit together with the separation of the C ₄ C ₅ fraction from the catalytic cracking products. 4. The method according to p. 1, characterized in that the separation of the fraction containing hydrocarbons With ₄ and above, from the pyrolysis products is carried out by separating it together with the separation of the pyrogas of the plant for the production of olefins by pyrolysis. 5. The method according to p. 1 characterized in that the unreacted C ₄ hydrocarbons are sent for pyrolysis in a mixture with methanol.

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