JPS5959202A - Fractionating method - Google Patents

Abstract

PURPOSE:To increase the removal efficiency of gaseous components, by using a fractionating column consisting of a rectification plates section and a packing column section. CONSTITUTION:Rectification plates such as bubble-cap trays valve trays, perforated plates or the like are used. As a packing material, Raschig rings, Lessing rings, saddles or the like are used. Which of the two types of the column should the upper is optionally decided and fractionation may be performed batchwise or continuously. The height of the packing part is 5-50% of the sum of the height of the plate column part and the height of the packing column part. Especially, high purity trioxane is separated and recovered from a mixture containing trioxane as the main component having high b.p. components, benzene as the main component having low b.p. components and formaldehyde as a dissolved gas component.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention also relates to a method for separating and recovering high-boiling components by rectifying a raw material containing high-boiling components, low-boiling components, and dissolved gas components. Generally, a rectification method is used to separate high-boiling components and low-boiling components.

The rectification columns used in the rectification method can be roughly divided into shelf type and packed type. In general, plate rectification columns are advantageously used for large-scale implementation.

Now, when the raw material contains dissolved gas components in addition to high-boiling components and low-boiling components, the situation becomes somewhat complicated.

Industrially, there are surprisingly many such systems, such as porumamide.
There are too many to list, including the methano/reimmonium system, the N,N-dimethylpolamide-methanol-dimethylamine system, and the trioxanobenzene-formaldehyde system. When high-boiling components are separated and recovered as a target product in such a system, rectification using a plate rectification column results in unexpectedly large amounts of gas components contaminating the target product, resulting in undesirable quality. There are cases where you can only get one. Even though the boiling point of the gas component is much lower than the boiling point of the low-boiling component in terms of boiling point, and even though the low-boiling component is sufficiently removed from the high-boiling component by the rectification effect, the desired high-boiling component cannot be achieved. Gas components may not be removed from boiling components.

For example, trioxane (high boiling component)-benzene (low boiling component)-formaldehyde (gas component) system is one such system.

The present inventors discovered that in the rectification of such a system, if a part of the plate rectification column is made into a packed type, the removal efficiency of gas components increases dramatically. Completed the invention.

The present invention utilizes only rectification without using separate means such as degassing or extraction, and utilizes the industrial advantages of a plate rectification column, while achieving high purity in the above system. This is a method of separating and recovering boiling components.

That is, the present invention provides a tray-type section for separating a mixture containing one or more of each of high-boiling components, low-boiling components, and dissolved gas components into high-boiling components, low-boiling components, and dissolved gas components by distillation. This is a rectification method characterized by using a rectification column consisting of a packed section and a rectification column.

There are no particular restrictions on the diameter and overall height of the rectification column, as well as the height and number of plates of the plated portion, and are selected in accordance with the raw material and the purpose of rectification. There are no particular restrictions on the format of the shelves or the type of filling.

Commonly used types of shelves include bubble bells, bulk trays, and perforated plates. Fillings include Raschig ring, Reshin ring, <, R-shaped, stained banking,
There are many different types such as Dixon Ring and McBuhon Banking. The mode of rectification operation may be either batch type or continuous type. Continuous systems are generally adopted for large-scale industrial implementation. Rectification operating conditions such as pressure, temperature, i-flow ratio, etc. are appropriately selected depending on the raw material and the purpose of rectification.

The height of the packed section of the rectification column to fully exhibit the effects of the present invention varies depending on the raw material and the purpose of rectification, but is generally 596 or more of the sum of the height of the tray section, and is usually 1.
0 to 5096 is sufficient. When the ratio exceeds 50%, the advantage of the tiered type in terms of design, construction, operability, etc. decreases.

Now, in systems where it is difficult to remove gas components from high-boiling components, the affinity between the gas component and the high-water component is generally lower than the gas component 2.
It is a system that has a stronger affinity with low-boiling components. In order to separate and recover high-purity high-boiling components from which the residue components have been sufficiently removed in such a system, it is generally preferable that the packed section of the rectification column is located at the bottom of the column; It is preferably located below the mouth. In such a case, the combination of the tiered part and the filling part may be either a combination of the filling part below the tiered part or a tiered part above and below the filling part. .

As mentioned above, there are many possible systems from which high-purity high-boiling components can be obtained according to the present invention. For example, highly purified trioxane with a sufficiently low formaldehyde content can be separated and recovered from raw materials containing trioxane, benzene, and formaldehyde. Further examples of this will be described below.

Example 1, Comparative Example 1 A batch rectification operation was performed using a rectification column with a column diameter of 50 mm. The terraced part is a so-called Oldershaw tower with perforated plates with a stage spacing of 50n+M.

For the filling type part, a packed tower with a height of 5 DD mm and filled with one stainless steel Raschig ring with a diameter of 6 wn and a length of 6 rings was used. Yong at the bottom of the tower! 2.13 flasks were connected to form an evaporator. In the evaporator, trioxane 74.8% by weight, benzene 25.0% by weight, formaldehyde 0.16%
Raw materials containing % by weight and trace amounts of low boiling components such as methanol were charged. When the tower was a combination of an Oldershaw tower and a packed tower, and when it was only an Oldershaw tower, the same raw materials were operated at normal pressure and a reflux ratio of 5, and benzene and formaldehyde were recovered from the top of the tower. Table 1 shows the results when the temperature inside the evaporator reached 116°C 45 minutes after the start of heating.

Formaldehyde in trioxane was determined using the sulfite addition method. The same applies to the following Examples and Comparative Examples.

Examples 2 to 5, Comparative Examples 2 to 5 A raw material supply port was provided in the same rectification column as in Example 1 or Comparative Example 1, and continuous rectification operation was performed at normal pressure and a reflux ratio of 2. A packed column filled with 6rrml x 7FD of McMahon Panogi/g was used for the packed part. Trioxa 729-
Raw materials containing low-boiling components such as 5"llA%, benzene 70.0% by weight, formaldehyde 0.45% by weight, and a trace amount of methanol were continuously fed from the raw material supply port at a feeding rate of 5'00 g/hr. A distillate containing benzene and formaldehyde was taken out from the top of the column. 16 hours after the start of operation, the liquid concentration in the evaporator reached 2-e. Thereafter, trioxane was taken out from the evaporator as a bottom liquid at a rate of 147 g/ hr
was collected continuously at a speed of Table 2 shows the results under stable conditions 24 hours after the start of operation.

Table 2 ―I

Claims (1)

[Claims] (1) A mixture containing one or more of each of a high boiling component, a low boiling component, and a dissolved gas component is distilled to remove the high boiling component,
When separating into low-boiling components and dissolved gas components, a rectification column consisting of a tray section and a packed section is used. (2) A rectification method characterized by k. Rectification method according to claim 1 using a rectification column having a height of 5% to 50% of the sum of the height of the plated section and the height of the packed section (6) Height of the packed section Rectification method according to claim 1 (4) using a rectification column in which the height of the tray type part is in the range of 10% to 60% of the sum of the height of the packed type part (4) the packed type part Rectification method according to claim 1 (5) using a rectification column in which the column is located in the lower half of the column A rectification method according to claim 1. (61) The rectification method according to claim 1, wherein the raw material contains trioxane as a main component of high-boiling components, benzene as a main component of low-boiling components, and formaldehyde as a dissolved gas component.