CS243834B1 - Method of increasing target production. amyl methyl ether from a selectively hydrogenated Covan fraction and from methanol - Google Patents

Abstract

The solution describes a process by which the yield of tert. amyl methyl ether is increased from the selectively hydrogenated Cs-fraction and from methanol in the presence of a strongly acidic cation exchange. The Cs-fraction containing 20 to 50 wt. % of reactive isoamylenes is combined with 0.9 to 1.5 parts by molar methanol per 1 part by molar Cs-fraction, a two to fivefold amount of the Cs-fraction with a reduced content of methylbutenes and unreacted methanol from the previous reaction cycle is added to the mixture, the resulting mixture is introduced into the reaction space with the cation exchange in the H-form at a temperature of 30 to 90 C and a reaction rate of 0.5 to 5 h"1, fraction A containing unreacted starting materials, further tert. amyl methyl ether and a higher-boiling residue are separated from the reaction mixture. Fraction A is divided in a ratio of 2 to 5:1 and the larger part is recycled to the reaction.

Description

The invention relates to a method for increasing the production of target amyl methyl ether (TAME) from a selectively hydrogenated Cg-fraction and from methanol in the presence of a strongly acidic cation exchange resin by returning a portion of unreacted hydrocarbons and azeotropically passed excess methanol.

Tertiary amyl methyl ether /TAME/ is the second homologue in the series of ethers RCH^O, where R is tert. alkyl. Like methyl tert. butyl ether, MTBE has the same use in motor gasolines for its high octane number.

The production also starts from isoolefins with a target carbon at the double bond, to which methanol can be added under mild reaction conditions in the presence of a heterogeneous acid catalyst, usually a cation exchange resin in the H-form.

With increasing size of the target alkyl, the reaction proceeds more slowly and its yield is limited by thermodynamic equilibrium. In TAME, under optimal conditions, the conversion of reactive isoamylenes /RIA/ /2-methyl-1.-butene and 2/methyl-2-butene/ is 40 to 50%. Excess methanol increases the conversion, but not significantly, and more methanol remains in the product, which tends to separate into water when mixed into gasoline.

Cg-fraction comes from catalytic cracking or thermal cracking of hydrocarbons and its diene content causes the formation of resins and polymers which foul the catalyst.

The invention solves a method of increasing the production of tertiary amyl methyl ether from selectively hydrogenated Cg-fraction and from methanol in the presence of a strongly acidic macroporous organic ion exchange resin and consists in that the Cg-fraction containing 20 to 50% by weight of reactive isoamylenes, namely 2-methyl-1-butene and 2-methyl-2-butene, is combined and 0.9 to 1.5 parts by molar methanol per 1 part by molar Cg-fraction, a double to fivefold mass amount of the Cg-fraction is added to the mixture, the concentration of both of the aforementioned methylbutenes having been reduced by 30 to 60% relative to the original content in the Cg-fraction, and unreacted methanol from the previous passage of the raw material mixture through the cation exchange resin, the resulting mixture of fresh raw materials and recyclate freed from the target. amyl methyl ether and any higher-boiling components formed or present are introduced into the reaction space, where a macroporous organic cation exchange resin in H-form with a specific surface area of 20 to 55 m/g and a titration exchange capacity of 3 to 5 milliequivalents of H ⁺ /g is placed, at a temperature of 30 to 90 °C, a space velocity of 0.5 to 5 h" ¹ , the reaction mixture is separated in a distillation column into unreacted Cg-hydrocarbons and azeotropically transferred methanol as fraction A, target amyl methyl ether with a purity of 80 to 99% and a higher-boiling residue, with fraction A being divided in a ratio of 1:2 to 1:5 and the larger part is returned back to the reaction space.

The reaction is preferably carried out at a molar ratio of reactive isoamylenes to methanol of 1 to

AND*

1.1. As a strongly acidic macroporous organic ion exchange, an ion exchange with a specific surface area of 45 m2/g and a titration exchange capacity of 4.8 m2/g is preferably used.

The reaction is preferably carried out at 75 to 90°C and a space velocity of the entire mixture, fresh and recycled, of 1.5 to 2.5 h~1 in a reaction space divided into two parts with a volume ratio of 2:1 to 1:3.

The starting Cg-fraction can come from the thermal cracking of hydrocarbons or from the catalytic cracking of hydrocarbons and is freed from dienes and acetylenes by hydrogenation.

The analysis of the process according to the invention provides an explanation of the most important new features that make TAME production productive. The analysis also better demonstrates the advantages of the new process.

The new process is suitable for a plant with sufficient reaction space and distillation capacity to recycle a portion of the unreacted reactive isoamylenes. A two-reactor system is advantageous, in which temperatures can also be optimized for high conversion.

The choice of cation exchange resin and the purity of the raw material are closely related. The appropriate porosity limits the desac...

243833 resins. On the contrary, the porous system tolerates certain residual concentrations of dienes without being affected. Also, diluting the raw material with the product /actually its parts/ reduces the deactivation of the cation exchange resin.

The presented example shows how the new process improves the production of TAME, although the conditions are not exhaustive, but only illustrative.

Example

To prepare TAME, the Cg-fraction from thermal cleavage containing 25 wt. % RIA and methanol with 0.5 wt. % water was used. The catalyst used was a cation exchange resin in the H-form with a specific surface area of 45 m/g and a titration exchange capacity of 4.8 meq/g, the Cg-fraction was freed from dienes to a residual value of 0.5 wt. %.

This Cg-fraction was mixed with methanol in a ratio of 1.1 mol/mol RIA. In the case of direct passage, the product shown in Table 1 was obtained. According to the invention, this fresh feed was mixed with a portion of the distillate to give the mixed feed shown in column 2 of Table 1.

A reaction product was formed, from which 90% of TAME suitable as an additive to motor gasoline was isolated by distillation, and a distillate boiling up to 55 °C, the composition of which is given in the table. The irreversible part of the distillate, which constituted one third of the total amount, combined with the isolated TAME and formed the product shown in column 4.

It is evident that the TAME concentration increased by 50% relative using the process according to the invention and both RIA and methanol decreased in the product.

The results in the table are selected from several sets of experiments in which the individual effects of reaction parameters on TAME yields were measured.

In the temperature range of 30 to 90 °C, the maximum TAME yield was between 65 to 80 °C at a space velocity range of 1 to 3 h” ¹ . The TAME concentration in the product increased in the range of ratios of the returned fraction A from 1:2 to 1:5 from 20 to 30 wt. %.

Table

Properties of the products of the reaction of the Cg-fraction with methanol. /

/1.5 MPa, 75 °C, 1.5 vol. raw material/vol. . cation exchange resin . hour/ sample no. 1 2 3 4 characteristic product mixture 3 and distillate product sample from direct fresh up to 55°C of 2 without passage raw materials from product 2 recyclate composition % wt. RIA . 11.1 13.2 7.3 5.6 methanol 6.1 7.2 4.7 3.6 THERE 16.2 <1.0 <1.0 24.3

Claims (4)

A process for increasing the production of tert-amyl methyl ether from a selectively hydrogenated Cg-fraction and methanol in the presence of a strongly acidic macroporous organic ion exchange resin, characterized in that the Cg-fraction contains 20 to 50% by weight of a mixture. of reactive isoamylenes, namely 2-methyl-1-butene and 2-methyl-2-butene, are combined with 0.9-1.5 parts by molar methanol per 1 molar Cg-fraction, two to five times by weight added to the mixture amount of Cg fraction whose concentration of both methylbutenes was reduced by 30 to 60% relative to the original content in the C _g fraction and unreacted methanol from the previous passage of the feedstock mixture through the cation exchange resin, the resulting mixture of fresh feedstocks and recycled de-target, amylmethylether; The resulting high-boiling components are introduced into a reaction space where a macro-5 porous organic cation exchanger is placed in an H-form with a specific surface area of 20 to 55 m / g and a titration exchange capacity of 3 to 5 milliequal H ⁺ / g at 30 to 90 ° C. from a flow rate of 0.5 to 5 h ^-1 , the reaction mixture is separated on the distillation column into unreacted C 8 hydrocarbons and azeotropes with methanol passed through fraction A tert-amyl methyl ether in a purity of 80 to 99%; and a higher boiling residue, fraction A being split at a ratio of 1: 2 to 1: 5 and the greater part being returned to the reaction space. 2. The process according to claim 1, wherein the reaction is carried out at a molar ratio of reactive isoamylenes to methanol of 1 to 1.1. 3. A process according to claim 1, characterized in that an ion exchanger having a specific surface area of 45 m / g and a titration exchange capacity of 4.8 meq is used. H / g. 4. Process according to claim 1, characterized in that the reaction is carried out at 75 to 90 [deg.] C. and the volumetric velocity of the whole mixture, fresh and recycled, from 1.5 to 2.5 h &^lt; ^-1 &gt; a volume ratio of 2: 1 to 1: 3.