RU2070190C1 - Process for preparing c1-c4-alkyl-tert-c4-c5-alkyl ethers - Google Patents

Abstract

FIELD: high-octane additives to motor fuels. SUBSTANCE: said ethers are produced by etherification of C₁-C₄ alcohols with tertiary C₄-C₅ olefins in liquid phase in the presence of homogeneous acid catalyst, e.g. sulfuric or phosphoric acid at starting molar ratio of C₁-C₄ alcohol to tertiary C₄-C₅ olefin of (0.9-1.2):1 in vertical tubular reactor filled with catalyst phase comprising (wt%); 5-50 catalyst; 5-30 water; 2-10 tertiary C₄-C₅ alcohol, and the C₁-C₄ alcohol balance. Tertiary C₄-C₅ olefin is fed into reactor lower portion into tubes through nozzles and the separated hydrocarbon phase is withdrawn from the reactor upper (separation) portion, and the desired ether is recovered by rectification from said phase after washing with water. The claimed process is advantageous in that the resulting products are etherified and separated into hydrocarbon and catalyst phases in one apparatus. This makes it possible considerably simpler than prior art process. EFFECT: more efficient preparation process. 7 cl, 1 tbl

Description

The invention relates to an improved method for producing C ₁ -C ₄ alkyl-tert-C ₄ -C ₅ alkyl ethers, which are used as high-octane additives for motor fuels.

Simple C ₁ -C ₄ alkyl-tert-C ₄ -C ₅ alkyl ethers (hereinafter ethers) are obtained by esterification of C ₁ -C ₄ alcohols such as methanol, ethanol, propanol, isopropanol, butanol, sec-butanol, isobutanol with tertiary olefins C ₄ -C ₅ , such as isobutylene and isoamylene. The esterification products are, respectively, methyl tert-butyl ether, ethyl tert-butyl ether, propyl and isopropyl tert-butyl ethers, butyl, sec-butyl, isobutyl-tert-butyl ethers, methyl tert-butyl ether; ethyl tertamyl ether, propyl and isopropyl tertamyl ethers, butyl, sec-butyl, isobutyl tertamyl ethers.

 It is known to obtain ethers by esterification of alcohols with isobutylene or isoamylenes in the presence of heterogeneous acidic catalysts, for example, activated carbons with functional sulfo and carboxyl groups, zeolites, ion-exchange resins [1] However, heterogeneous catalysts are deactivated during operation, they must be periodically regenerated and replaced , when using them, problems arise associated with the mechanical strength of the catalysts and the hydrodynamic resistance of the layer.

 It is known to obtain ethers using homogeneous acid catalysts, for example sulfuric, hydrochloric acids, Friedel-Crafts type catalysts, sulfonic acids, heteropoly acids [2] However, with homogeneous catalysis, problems arise associated with the separation of the catalyst from the reaction products.

 A known method of producing ethers by esterification of alcohols with tertiary olefins in the presence of a homogeneous acid catalyst, followed by dilution of the reaction product with alcohol and distillation of the alcohol and ether from the resulting mixture of an azeotrope, which is then isolated from the azeotrope by washing with water [3] However, the reaction product is diluted with even a large amount of alcohol does not eliminate the decomposition of ether in the presence of acid during rectification.

The closest in technical essence to the invention is a method for producing methyl tert-butyl ether (MTBE) by etherification of methanol with isobutylene in a homogeneous liquid phase at 70-100 ^° C using sulfuric acid as a catalyst at the initial molar ratio of methanol to isobutylene (1.5-5 ): 1 to obtain a reaction mass, which is cooled to room temperature. Next, the reaction mass is separated in a separator into a catalyst phase, which is recycled for esterification, and a hydrocarbon phase containing the target product. The hydrocarbon phase is washed with water, then the target product and a mixture of unconverted hydrocarbons, which in the amount of 10-80 wt. recycle for separation [4 prototype]
According to the known method, the esterification is carried out in a homogeneous phase with an excess of methanol. However, excess methanol complicates the separation of reaction products; it must be isolated and recycled to the synthesis. For separation, the reaction mass is cooled to room temperature and recycled unconverted hydrocarbons are introduced into it. It also complicates the process and leads to increased energy costs. The known method is characterized by large losses of acid catalyst, because 10-50% of the sulfuric acid fed to the reactor passes to the hydrocarbon phase, which requires alkaline water in the amount of 20-50% by weight of the hydrocarbon phase to be washed. In addition to a large acid consumption, there is a problem of disposal of wastewater containing salts.

The aim of the invention is to simplify the technology by eliminating recycle of the catalyst phase and unconverted hydrocarbons, as well as reducing catalyst losses, reducing the amount of wastewater and reducing the cost of releasing unconverted C ₁ -C ₄ alcohol.

This is achieved by the fact that C ₁ -C ₄ alkyl-tert-C ₄ -C ₅ alkyl ethers are obtained by esterification of C ₁ -C ₄ alcohols with tertiary C ₄ -C ₅ olefins at 70-100 ^° C in the liquid phase using a homogeneous an acid catalyst, for example sulfuric or phosphoric acid, with an initial molar ratio of C ₁ -C ₄ alcohol to C ₄ -C ₅ tertiary olefin (0.9-1.2): 1 in a vertical tubular reactor filled with a catalyst phase containing a catalyst , water, tertiary alcohol With ₄ -C ₅ and alcohol With ₁ -C ₄ in the following ratio, wt. catalyst 5-50; water 5-30; tertiary alcohol C ₄ -C ₅ 2-10; alcohol C ₁ -C _{4 the} rest.

The C ₄ -C ₅ tertiary olefin is fed into the lower part of the reactor into pipes through nozzles and the separated hydrocarbon phase is removed from the upper separation part, from which the target product (ether) is isolated after washing with water by distillation.

A distinctive feature of the method is the esterification at the initial molar ratio of alcohol C ₁ -C ₄ to tertiary olefin (0.9-1.2): 1. Another difference is that the process is carried out in a vertical tubular reactor filled with a catalyst phase containing C ₁ -C ₄ alcohol, a catalyst, water and C ₄ -C ₅ tertiary alcohol at the stated ratio of components.

The difference also lies in the fact that the tertiary olefin C ₄ -C _{5 is} fed into the lower part of the reactor into the pipes through nozzles, and the hydrocarbon phase is removed from the upper, separation, part of the reactor.

The invention provides selective conversion to ether of a tertiary olefin With ₄ -C ₅ both in pure form and in the presence of n-butenes, n-pentenes, butadiene when using C ₄ -C ₅ fractions of pyrolysis, cracking, dehydrogenation and distillation of petroleum products, and according to the proposed method, the processes of esterification of C ₁ -C ₄ alcohols and separation of the resulting reaction mass into the hydrocarbon and catalyst phases are carried out in one apparatus, which makes the process much simpler than the known one.

As a result of the introduction of C ₄ -C ₅ tertiary olefins into a tubular reactor filled with a "standing" catalyst phase, intensive mass transfer of C ₄ -C ₅ tertiary olefins with a catalyst phase containing C ₁ -C ₄ alcohol, a catalyst, water, and a tertiary is ensured through nozzles alcohol C ₄ -C ₅ .

 The resulting ether and unreacted hydrocarbons (hydrocarbon phase) float at the top of the reactor and can be directed after washing to isolate the desired ether.

Alcohol C ₁ -C _{4 is} fed into the reactor in an amount close to the stoichiometric relative to the tertiary olefin C ₄ -C ₅ . Due to the water in the composition of the catalyst phase, almost the entire amount of C ₁ -C ₄ alcohol supplied is in the catalyst phase and a little C ₁ -C ₄ alcohol is removed from the reactor by the hydrocarbon phase, which reduces the cost of releasing unconverted C ₁ -C ₄ alcohol and also reduces loss of acid catalyst, which is removed from the catalyst phase with alcohol With ₁ -C ₄ .

 The reactor is a system of vertical pipes enclosed in a common casing. The number and size of pipes determine the required plant capacity. In the upper part of the reactor beyond the end of the pipes there is a separation (settling) zone. A coolant is supplied to the annulus of the reactor, which ensures the maintenance of a given temperature. The number of reactors is determined by the required plant capacity. Reactors can be interconnected in series and / or in parallel. The temperature in the reactor may be isothermal and / or adiabatic.

C ₄ -C ₅ tertiary olefins, both in pure form and in the form of C ₄ -C ₅ fractions of pyrolysis, cracking, dehydrogenation and distillation of petroleum products, are fed to the lower part of the reactor through nozzles inside each pipe (at least one pipe in each pipe nozzle). The diameter of the nozzles is selected so that the linear velocity of the tertiary C ₄ -C ₅ olefins inside the nozzles is 3-10 m / s. As a result of contact with the catalyst phase, the hydrocarbon fraction breaks up into small droplets, which, due to their lower specific gravity, float up through the catalyst “standing” phase.

 Small drops are needed for intensive mass transfer between the sparingly soluble catalyst and hydrocarbon phases, since the reaction in this case proceeds in a two-phase system. The reaction products and the catalyst are in two phases, the catalyst being almost completely in the catalyst phase, where the reaction itself proceeds, and the ether formed is in the hydrocarbon phase.

A decrease in the linear velocity below 3 m / s leads to an increase in the diameter of the droplets, a decrease in the mass transfer rate below the value required for a given reaction system, and as a result, the productivity of a unit of the reaction volume decreases. An increase in speed of more than 10 m / s does not affect productivity, however, it increases the energy costs associated with the supply of tertiary C ₄ -C ₅ olefins to the reactor (a higher pressure pump is required).

 Due to the water in the composition of the catalyst phase, the floating hydrocarbon phase is easily separated from the catalyst in the upper separation zone and removed from the reactor as a single stream.

 The pressure in the reactor is maintained so that the reaction mixture is in a liquid state, which in this case is achieved at 5-22 atm.

In the conditions of the method of esterification is highly selective, because using water and a tertiary alcohol With ₄ -C _{5 the} formation of dimers and polymers of these tertiary olefins is suppressed. The presence of tertiary alcohols in the catalyst phase in an amount of more than 2% also prevents the consumption of tertiary C ₄ -C ₅ olefin and water for the formation of C ₄ -C ₅ tertiary alcohol.

When the water content decreases below 5%, the reaction mixture becomes homogeneous, which makes it impossible to separate it in the reactor. An increase in the amount of water more than 30% and the tertiary alcohol C ₄ -C ₅ more than 10% leads to a decrease in the conversion of tertiary olefin C ₄ -C ₅ .

The initial ratio of C ₁ -C ₄ alcohol to the C ₄ -C ₅ tertiary olefin affects both the selectivity of esterification (with a decrease in the amount of C ₁ -C ₄ alcohol below 0.9 mol per mol of the tertiary C ₄ -C ₅ olefin, dimers are formed and trimers of the indicated olefin), as well as on the content of the catalyst in the hydrocarbon phase, which increases with an increase in the declared amount of C ₁ -C ₄ alcohol.

 The catalyst used is mineral acids, for example, sulfuric, phosphoric, organic sulfonic acids, for example, propanesulfonic acid, benzenesulfonic acid, heteropoly acids, for example, molybdenum phosphoric, carboxylic acids, for example, oxalic.

More preferably, as a catalyst, the use of sulfuric acid in an amount of 5-20% or phosphoric acid in an amount of 20-50%
Due to the water in the composition of the catalyst phase, the hydrocarbon phase leaving the reactor contains 0.5-1.5% of the catalyst in the reactor. The hydrocarbon phase containing the target product, a portion of the unconverted C ₁ -C ₄ alcohol and C ₄ -C ₅ tertiary alcohol, are washed with water, which requires 4-6% by weight of the hydrocarbon phase, to wash the catalyst and the C ₁ -C ₄ alcohol. Moreover, due to the insignificant content of the catalyst in the hydrocarbon phase, alkali does not need to be added to the water supplied to the washing, which allows further disposal of the acid contained in the washing water by known methods.

Rinse water, in addition to acids, contains the unconverted C ₁ -C ₄ alcohol, which is usually distilled off further on a distillation column and returned to esterification. Together with C ₁ -C ₄ alcohol, a small amount of C ₄ -C ₅ tertiary alcohol is distilled off and returned for synthesis, which is washed from the hydrocarbon phase together with C ₁ -C ₄ alcohol.

After washing, the hydrocarbon phase is sent to a distillation column, where unconverted hydrocarbons are distilled off, then fed to the next distillation column, where the target ether is distilled off from C ₄ -C ₅ tertiary alcohol, taken to a warehouse, and then directly used as a component of motor fuels. The distillation residue is returned to the synthesis reactor.

The proposed method is easier to implement due to the absence of recycling of the catalyst phase and unconverted hydrocarbons. Another advantage is to reduce catalyst losses, reduce the amount of wastewater and the cost of releasing unconverted C ₁ -C ₄ alcohol.

 The possibility of carrying out the invention is confirmed by the following examples. The experimental data for the examples are shown in the table.

 Examples 1-5. The synthesis of methyl tert-butyl ether (MTBE) is carried out using a reactor unit of two-tube reactors of the same design. The reactor consists of 199 vertical metal pipes, each with a diameter of 100 mm, a height of 15 m, enclosed in a common casing. In the upper part of the reactor beyond the end of the pipes there is a separation zone. Steam condensate is supplied to the annulus of the reactor, which maintains the set temperature.

 At the bottom of the reactor, under the pipes, there is a switchgear with nozzles that are inside each pipe (there is one nozzle in the pipe). The reactors are filled with a catalyst phase. In the separation zone, the separation level of the two phases of the catalyst and hydrocarbon is maintained, which is removed from the top of the reactor.

The initial C ₄ fraction is fed through nozzles to the first reactor (upstream), then fed from the top of the first reactor together with the reaction products (hydrocarbon phase of the first reactor) to the second reactor through nozzles. Methanol, which dissolves in the catalyst phase, is fed to the bottom of each reactor.

 The predetermined composition of the catalyst phase is kept constant due to the fact that: methanol is fed into the reactor in an amount corresponding to its consumption, for the formation of MTBE and small entrainment with the hydrocarbon phase.

 Also due to the fact that the entrainment of tert-butyl alcohol (TBS) is fully compensated by the recycle of TBS from the hydrocarbon phase.

 And also due to the fact that a small amount of water and a catalyst are supplied to the reactor to compensate for entrainment with the hydrocarbon phase.

 The hydrocarbon phase from the top of the second reactor is fed to the bottom of the wash column, filled with a nozzle Rashig rings. Water is supplied to the top of the column.

 From the bottom of the wash column, the wash water is then distilled off at atmospheric pressure to distill off methanol (methanol-recycle), which is mixed with fresh methanol and fed for synthesis.

The hydrocarbon phase leaving the top of the wash column is fed to a distillation column, where the spent C ₄ fraction is distilled off at a pressure of 5 atm. The bottom liquid of this column is fed to the next distillation column, where MTBE is distilled off at atmospheric pressure. The residue after distillation of MTBE is TBS, which is recycled to the synthesis.

As isobutylene-containing raw materials in examples 1-3, a C ₄ fraction of isobutane dehydrogenation of the following composition is used, wt. propane 0.3; isobutylene 47.1; n-butane 2.1; isobutane 47.9; n-butenes 2,3; divinyl 0.2; pentanes 0.1.

As isobutylene-containing raw materials in examples 4,5 using C ₄ -fraction pyrolysis of gasoline of the following composition, wt. propane 0.7; isobutylene 25.7; n-butane 9.6; isobutane 2.0; n-butenes 19.5; divinyl 41.7; pentanes 0.8.

As follows from the data in the table, the synthesis of MTBE in a vertical tubular reactor filled with a “standing” catalyst phase containing the declared amounts of water and TBS allowed us to exclude the recycling of the catalyst phase and carry out the process not only selectively, but also with less loss of acid catalyst. The supply of C ₄ fractions through nozzles with the indicated linear velocity made it possible to achieve high isobutylene conversion without special methods of mixing a two-phase reaction system.

Example 6. The synthesis is carried out analogously to example 1, however, as a tertiary olefin using C ₅ -fraction of dehydrogenation of isopentane, containing: propane 1,1; butane 3,5; isopentane 59.6; isoamylene 29.8; isoprene 1.3; n-pentane 1,2; n-amylenes 2.9; piperylene 0.6.

The degree of conversion of isoamylene to methyltretamyl ether is 71.5%
Example 7. The synthesis is carried out analogously to example 1, however, ethanol is used as C ₁ -C ₄ alcohol. The conversion of isobutylene to ethyl tert-butyl ether is 72.3%
Example 8. The synthesis is carried out analogously to example 1, however, isopropyl alcohol is used as C ₁ -C ₄ alcohol. The conversion of isobutylene to isopropyl tert-butyl ether is 86.2%

Claims (7)

1. The method of obtaining C ₁ -C ₄ -alkyl-tert-C ₄ -C ₅ -alkyl ethers by esterification of alcohols C ₁ -C _{4 with} tertiary olefins C ₄ -C ₅ at 70-100 ^o C in the liquid phase in the presence of a homogeneous acid catalyst separation from the catalyst phase of the hydrocarbon phase containing the target product, washing with water the hydrocarbon phase and isolating the target product from it by distillation, characterized in that the esterification is carried out at the initial molar ratio of alcohol C ₁ -C ₄ to the tertiary olefin C ₄ -C ₅ (0 , 9 1.2): 1 in a vertical tubular reactor filled with a catalyst phase containing a catalyst, water, a C ₄ -C ₅ tertiary alcohol and a C ₁ -C ₄ alcohol in the following ratio of components, wt. Catalyst 5 50
Water 5 30
Tertiary alcohol C ₄ -C ₅ 2 10
Alcohol C ₁ -C ₄ to 100
with the supply of a tertiary olefin C ₄ -C ₅ into the lower part of the reactor into the pipes through nozzles and the withdrawal of the hydrocarbon phase from the upper separation part. 2. The method according to claim 1, characterized in that the tertiary olefin C ₄ -C _{5 is} fed into the pipes through nozzles with a linear velocity of 3 10 m / s.  3. The method according to claim 1, characterized in that as a catalyst use sulfuric acid in an amount of 5 to 20 wt. in the catalyst phase.  4. The method according to claim 1, characterized in that the catalyst used is phosphoric acid in an amount of 20 to 50 wt. in the catalyst phase. 5. The method according to claim 1, characterized in that methanol is used as the alcohol C ₁ -C ₄ . 6. The method according to claim 1, characterized in that as the tertiary olefin C ₄ -C ₅ use isobutylene or the C ₄ isobutane dehydrogenation fraction. 7. The method according to claim 1, characterized in that as the tertiary olefin C ₄ -C ₅ use isoamylenes or the C ₅ fraction of isopentane dehydrogenation.

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