JPH1087805A - Continuous esterification reactor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermosiphon-type continuous esterification reactor which can prevent the short pass of unreacted substances contained in the esterification reaction product sent to the subsequent step. SOLUTION: This reactor is provided with an external heating heat exchanger 2 so that the reaction product may be circulated within an esterification tank 1 by a thermosiphon effect. In the tank 1, at least two partition plates 3 are provided in the horizontal direction in such a manner that the attachment positions of the adjoining partition plates are opposite to each other, that the adjoining partition plates have parts of overlap, and that they are spaced from each other so that the flow paths of the reaction product may alternate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous esterification reactor capable of preventing a short path of unreacted substances contained in an esterification reactant to be sent to the next step.

[0002]

2. Description of the Related Art In recent years, a thermosiphon type reactor having a heat exchanger for heating outside has been used as a reactor for a reaction requiring a large temperature rise or a reaction having a large heat load such as an endothermic reaction.
It is used in many manufacturing processes and has the following advantages. 1. Since stirring is performed by thermal driving, mechanical stirring is not required, and energy costs can be reduced. 2. Since the heat exchanger is provided outside the reaction tank, the heat transfer area can be freely designed. 3. The structure of the reaction tank can be simplified as compared with a method in which heating is performed by a jacket or an internal coil.

When such a reactor is used as a continuous esterification reactor, for example, when terephthalic acid and ethylene glycol are continuously esterified and then polycondensed to produce polyethylene terephthalate. If the number of complete mixing type reaction tanks is small, a large amount of unreacted raw material is discharged from the reaction product outlet, and there is a problem that the operability of the next process and the quality of the final product are deteriorated.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a thermosyphon type continuous esterification reactor having an external heat exchanger for short-circuiting unreacted substances contained in an esterification reactant sent to the next step. An object of the present invention is to provide a continuous esterification reactor capable of preventing a pass.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems. The gist of the present invention is to provide a heat exchanger for heating outside and circulate the reactants in the esterification reaction tank by the thermosiphon effect. In the continuous esterification reaction device, two or more partition plates are horizontally arranged in the esterification reaction tank, and the mounting positions of the adjacent partition plates are opposite to each other,
In addition, there is provided a continuous esterification reaction apparatus characterized in that adjacent partition plates have portions that overlap in the vertical direction, and are provided at intervals so that the flow paths of the reactants are alternated.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic explanatory view showing an embodiment of the apparatus of the present invention, where 1 is an esterification reaction tank,
2 is a heat exchanger, 3 is a partition plate, 4 is a heat medium supply pipe, 5 is a heat medium discharge pipe, 6 is a raw material supply pipe, 7 and 8 are reactant circulation pipes, 9 is a reactant extraction pump, Reference numeral 10 denotes a distillation column.

The raw material supplied from the raw material supply pipe 6 merges with the reactant circulating in the reactant circulation pipe 7 and is heated in the heat exchanger 2, and then the ester is supplied from the reactant circulation pipe 8. Into the reaction tank 1. In the esterification reaction tank 1, the reactant flows through the flow path formed by the partition plate 3 while reacting, and is sent out to the reactant circulation pipe 7. Then, a part of the reactant is withdrawn by the reactant withdrawal pump 9 and sent to the reactor in the next step. At this time, by setting the position where the reactant is extracted to a position away from the raw material supply position, a short path of the unreacted material can be eliminated.

In the apparatus according to the invention, the circulation of the reactants is
Heating to a temperature higher than that of the esterification reaction tank 1 in the heat exchanger 2 causes a decrease in the density of the reactant, generation of bubbles, and the like, which occurs when the reactant flows upward.

In the esterification reaction tank 1, two or more partition plates are provided in a horizontal direction, and a position where the adjacent partition plates are attached to each other in the opposite direction, and the adjacent partition plates overlap each other in the vertical direction. Reactants are provided at intervals so that the flow paths of the reactants alternate, and the reactants sequentially flow between the partition plates 3, so that the circulation cycle becomes longer.

The partition plate 3 needs to be installed so that the flow path extending to the bottom of the esterification reaction tank 1 below the connection portion of the reactant circulation pipe 8 is long. For this reason, the partition plates 3 are alternately installed at intervals so that adjacent partition plates have portions that overlap in the vertical direction. It is preferable that the ratio of the overlapping portion is 60 to 95% of the cross-sectional area of the esterification reactor 1. If this ratio is too small, the effect of prolonging the circulation cycle is poor,
On the other hand, if this ratio is too large, the reactants will not flow smoothly.

The device according to the invention is particularly suitable for terephthalic acid (TP
It is preferably used for a continuous esterification reaction between A) and ethylene glycol (EG).

[0012]

According to the present invention, in a thermosiphon-type esterification reactor having a heat exchanger for heating outside, two or more partition plates are alternately placed in an esterification reaction tank, and adjacent partition plates are vertically aligned. Since it is installed at intervals so as to have an overlapping portion, the circulation cycle, that is, the reaction time can be lengthened, and the short path of the unreacted substance contained in the esterification reactant to be sent to the next step is reduced. Can be prevented.

[0013]

Next, the present invention will be described in detail with reference to examples. In addition, the measuring method of a characteristic value etc. is as follows. (a) Unreacted TPA amount The esterification reaction product was dissolved in hexafluoroisopropanol, the undissolved material was separated, and the weight was measured. (b) Esterification reaction rate An acid value AV and a saponification value SN were determined by the following method, and were calculated by the following formula. Esterification reaction rate (%) = (1-AV / SN) × 100 AV: Esterification reaction product was dissolved in dioxane, and titrated with a methanol solution of sodium hydroxide. SN: The esterification reaction product was saponified with an ethanol solution of sodium hydroxide under reflux for 2 hours, and the excess sodium hydroxide was determined by back titration with hydrochloric acid. (c) Circulation cycle Inject dye at a certain point in the raw material supply pipe during raw material supply,
The time required for the coloring of the extracted reaction product to be visually confirmed was measured.

Examples 1 to 5 and Comparative Examples 1 to 3 In the apparatus shown in FIG. 1, in the esterification reaction tank 1 having a diameter of 60 cm, the number of partition plates 3 shown in Table 1 were alternately arranged in the vertical direction. Are arranged at intervals so that the ratio of the overlapping portion to the cross-sectional area of the reaction tank 1 becomes the ratio shown in Table 1. In the esterification reactor 1 where bis (β-hydroxyethyl) terephthalate and its low polymer are present, TP
A slurry having a ratio of 100 mol / h of A and 120 mol / h of EG was continuously supplied, and an esterification reaction was carried out at a temperature of 260 ° C. and a residence time of 7 hours. At this time, the temperature of the heat medium supplied to the heat exchanger 2 was set to 270 ° C. Table 1 shows the circulation state of the reactants and the characteristic values of the esterification reactants.

[0015]

[Table 1]

[0016]

According to the present invention, in a thermosiphon-type esterification reactor having a heat exchanger for external heating, short paths of unreacted substances contained in the esterification reactant to be sent to the next step are prevented. A continuous esterification reactor is provided.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of the apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Esterification reaction tank 2 Heat exchanger 3 Partition plate 6 Raw material supply pipe 7, 8 Reactant circulation pipe 9 Reactant extraction pump

Claims (1)

[Claims] 1. In a continuous esterification reactor in which a heat exchanger for heating is provided outside and a reactant in an esterification reaction tank is circulated by a thermosiphon effect, two or more partitions are horizontally arranged in the esterification reaction tank. The plates were provided at intervals such that the mounting positions of the adjacent partition plates were facing each other, and the adjacent partition plates had portions that overlapped in the vertical direction, and the flow paths of the reactants were alternated. A continuous esterification reactor characterized by the above-mentioned.