MMA preparation method with isobutene including saturated hydrocarbon

Abstract

Disclosed is a method for preparing methyl methacrylate (MMA), the method including: (1) separating isobutene containing saturated hydrocarbon (n-butane and iso-butane), via a catalytic distillation process from a stream of C.sub.4 hydrocarbons containing butadiene, n-butene, and isobutene; (2) producing methacrolein via a first oxidation reaction of the separated isobutene; (3) producing methacrylic acid via a second oxidation reaction of the produced methacrolein; and (4) esterifying the produced methacrylic acid with methanol. By having a high heat capacity, the amount of nitrogen added is minimized to reduce the size of the reactor and the amount of gas production at a rear end, which has a high economic feasibility due to the effect of reducing investment and investment cost.

Claims

1. A method for preparing methyl methacrylate (MMA), the method comprising: (1) concentrating isobutene comprising n-butane and iso-butane by a catalytic distillation process including an extractive distillation step of removing butadiene and a reactive distillation step of removing n-butene from a feedstock, wherein the feedstock is a stream of C.sub.4 hydrocarbons containing butadiene, n-butene, isobutene, n-butane, and iso-butane; (2) removing light gas, between a first oxidation reaction and a second oxidation reaction; (3) producing methacrolein by the first oxidation reaction of the concentrated isobutene; (4) producing methacrylic acid via the secondary oxidation reaction of the produced methacrolein; and (5) esterifying the produced methacrylic acid with methanol.

2. The method of claim 1, wherein a catalyst in the catalytic distillation process is a Pd/alumina catalyst.

3. The method of claim 1, wherein a catalyst for the first oxidation reaction is an oxide catalyst.

4. The method of claim 1, wherein a catalyst for the second oxidation reaction is an oxide catalyst.

5. The method of claim 1, wherein the light gas comprises CO, CO.sub.2N.sub.2 and/or O.sub.2.

Description

BRIEF DESCRIPTIONS OF DRAWINGS

(1) The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

(2) FIG. 1 is a flow diagram of an embodiment of the prior art.

(3) FIG. 2 is a flow diagram of a preferred embodiment of the present disclosure.

DETAILED DESCRIPTION

(4) Example embodiments will now be described more fully with reference to the accompanying drawings.

(5) The present disclosure will be described in more detail. The present disclosure relates to a novel MMA preparation process using isobutene containing saturated hydrocarbon (n & iso-butane) in which MMA may be prepared without an additional isobutene purification process by utilizing isobutene at a top of the reactive distillation column (CD-DeIB overhead) of an olefin conversion process.

(6) The MMA preparation process of the present disclosure includes reactive distillation to increase isobutene concentration and MMA preparation process (isobutene oxidation reaction, and esterification reaction).

(7) The MMA preparation process of the present disclosure includes a butadiene extraction distillation step in which butadiene is removed from a C.sub.4 mixture of NCC containing butadiene, 1-butene, 2-butene, isobutene, n-butane and iso-butane, and a trace amount of C.sub.3 gas; and, subsequently, a reactive distillation step of converting 1-butene to 2-butene and removing 2-butene using a boiling point difference. In this connection, 1-butene is completely converted to 2-butene, and 2-butene having a high boiling point is removed from a bottom of the reactive distillation column, such that a mixture containing isobutene, iso-butane and n-butane is produced.

(8) Further, the MMA preparation process of the present disclosure may further include a step of removing light gas between the first oxidation reaction (isobutene.fwdarw.methacrolein) and the second oxidation reaction (methacrolein.fwdarw.methacrylic acid).

(9) In one implementation, Pd/alumina catalyst is used as a catalyst for the reactive distillation process to increase the isobutene concentration in the C.sub.4 olefin. An MMA preparation process catalyst employs an oxide catalyst in the first step, an oxide catalyst in the second step, and an ion exchange resin in the third step.

(10) Hereinafter, the present disclosure will be described in more detail based on examples, but the present disclosure is not limited to the examples.

Preparation Example 1

(11) The first oxidation reaction (isobutene methacrolein) was performed using only high-purity isobutene (99% or greater) as a raw material. A composition of reactants as added during the reaction is shown in Table 1 below.

(12) TABLE-US-00001 TABLE 1 Composition of reactants (molar ratio) Isobutene Oxygen Water Nitrogen 1 2.0 1.6 11.9

Preparation Example 2

(13) A stream of C.sub.4 hydrocarbon containing butadiene, n-butene and isobutene was used as a raw material. Isomerization of 1-butene contained in the C.sub.4 hydrocarbon into 2-butene was carried out using a catalyst. Then, the 2-butene was removed from the bottom of the distillation column. A rest of the distillation column contained an isobutene-rich stream containing saturated hydrocarbon. The stream of the isobutene-rich saturated hydrocarbons was subjected to the first oxidation reaction (isobutene methacrolein) such that the isobutene was converted to methacrolein. The composition of the reactants injected during the reaction is shown in Table 2 below.

(14) TABLE-US-00002 TABLE 2 Composition of reactants (molar ratio) Isobutene Isobutane Oxygen Water Nitrogen 1 0.266 2.0 1.6 11.63

Preparation Example 3

(15) As in the preparation example 2, the isobutene-rich stream containing saturated hydrocarbon was separated from the raw material stream. The isobutene contained in the stream was subjected to the first oxidation reaction (isobutene methacrolein) such that the isobutene was converted to methacrolein. Table 3 shows the composition of the reactants injected during the reaction.

(16) TABLE-US-00003 TABLE 3 Composition of reactants (molar ratio) Isobutene Isobutane Oxygen Water Nitrogen 1 0.266 2.2 1.6 11.43

(17) A conversion rate of isobutene, and methacrylic acid selectivity and yield as shown in Examples and Comparative Example are calculated as follows:
Conversion rate of isobutene (mol %)=[added isobutene (mol)−isobutene after reaction (mol)]/added isobutene (mol)×100
Methacrylic acid selectivity (mol %)=produced methacrylic acid (mol)/[added isobutene (mol)−isobutene after reaction (mol)]×100
Methacrylic acid yield (mol %)=produced methacrylic acid (mol)/added isobutene (mol)×100

Comparative Example

(18) According to the method of the present disclosure, isobutene oxidation was carried out while using the Preparation Example 1 as a feed. A reaction condition is shown in Table 4 below.

(19) TABLE-US-00004 TABLE 4 First reaction Second reaction (Isobutene .fwdarw. (methacrolein .fwdarw. methacrolein) methacrylic acid) Reaction 340° C. 280° C. temperature Reaction 0.5 barg 0.3 barg pressure Space 1,000 h.sup.−1 800 h.sup.−1 velocity Catalyst 40 ml 75 ml amount

(20) The isobutene conversion rate obtained under the above oxidation reaction conditions was 99.0 mol %, the methacrylic acid selectivity obtained under the above oxidation reaction conditions was 86.0 mol %, and the methacrylic acid yield obtained under the above oxidation reaction conditions was 56.0 mol %.

Example 1

(21) According to the method of the present disclosure, an isobutene oxidation reaction was performed while using the Preparation Example 2 as a feed. The isobutene conversion rate and the methacrylic acid selectivity and yield as obtained via an oxidation reaction under the same reaction conditions as those of the Comparative Example are as follows.

(22) The isobutene conversion rate was 99.0 mol %, the methacrylic acid selectivity was 87.0 mol %, and the methacrylic acid yield was 57.0 mol %.

Example 2

(23) According to the method of the present disclosure, an isobutene oxidation reaction was performed while using the Preparation Example 3 as a feed. The isobutene conversion rate and the methacrylic acid selectivity and yield as obtained via an oxidation reaction under the same reaction conditions as those of the Comparative Example are as follows.

(24) The isobutene conversion rate was 99.5 mol %, the methacrylic acid selectivity was 87.0 mol %, and the methacrylic acid yield was 57.5 mol %.

(25) As described above, when the isobutene containing the saturated hydrocarbon is used as the raw material, the methacrylic acid selectivity and yield may be improved too.

(26) The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.