JPS60106532A - Regeneration of adsorbent for boron trichloride - Google Patents

Abstract

PURPOSE:To regenerate used active carbon and to recover simultaneously adsorbed BCl3 with almost same amt. of impurity as BC3 used in the starting stage by heating the active carbon in the first stage to recover gas consisting essentially of BCl3 and then heating said active carbon at higher specified temp. in the second stage to regenerate the active carbon. CONSTITUTION:For the regeneration of active carbon used for removal of Si compd., phosgen, and chlorinated hydrocarbons contained in BCl3 gas, the active carbon is first heated at 40-120 deg.C, and the gas consisting essentially of BCl3 eliminated from said active carbon is recovered, then the active carbon is heated at 200-700 deg.C. By this method, the active carbon is regenerated, and major portion of adsorbed BCl3 is recovered as BCl3 having almost same degree of the content of impurities as high as the BCl3 used in the starting stage. The regenerated active carbon is not deteriorated and is usable repeatedly. Therefore, the consumption of raw materials and adsorbent per unit weight of final product are remarkably reduced. The process contributes to cost reduction of purified BCl3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an adsorbent regeneration method for regenerating activated carbon used to adsorb and remove impurities in boron chloride and recovering adsorbed boron trichloride.

Boron trichloride (acza) has established uses as a cationic polymerization catalyst, but in recent years, as the demand for miniaturization of integrated circuits has increased, it has been used for dry etching of aluminum used as wiring for semiconductor devices. Its use as a source of chlorine in the world is rapidly increasing.

Bcll is produced by a known method such as chlorinating boron oxide (B*Oa) with C1*, alkali metal chloride, silicon tetrachloride (8iCJ+), etc., but in the produced crude BCJa, N, % o, , phosgene (C
'OC11), halogenated hydrocarbons (hereinafter referred to as TOO), 8i compounds, various metals, and BOA!
, for dry etching of aluminum, etc., it is desirable to remove various metals, COCJffi, Si compounds, and TOC from among the impurities to tppm or less.

Each lump metal can be removed by simply gasifying crude BC, but CUC/m, Si compounds, TOC, etc.
It is difficult to reduce the amount to less than ppm. Conventional purification methods do not target BC1 for dry elatin, which requires high purity, or are impractical due to complicated operations and low yields even if they can be purified to high purity. There was a drawback.

In order to solve the above-mentioned problem, the present inventor conducted 11 investigations and first determined crude B(J, (for example, Si component (as Si) in liquid phase analysis value: 1901) l) In, COCl1: 240
ppln%TOC: 130. BC containing about ppm
We proposed a method for distilling high-purity BCla by contacting activated carbon with BCl1s gas, which is the vaporized BClIm').

This method uses vaporized BClm as shown in Figure 1.
Even if the impurities are saturated adsorbed (initial adsorption) on the activated carbon and begin to distill, the impurities are still adsorbed on the activated carbon, and the above distillate B C4
, the Si component, COCl2, etc. (■: 3i component is shown as
When s is vaporized, a considerable portion remains unvaporized, but it nevertheless breaks through first and becomes an indicator of impurity breakthrough, and impurities (TOC breaks through even later than COCl1) break through. This is a purification method that collects the previous high-purity distillate BC1. That is, it is necessary to stop feeding the vaporized BCls and regenerate the activated carbon for repeated use before impurities penetrate the activated carbon layer.

By the way, in the above-mentioned initial adsorption, BCl is adsorbed in an amount of about 1/2 of the weight of the activated carbon, so releasing expensive CJs during the regeneration of the activated carbon is an extremely large economic loss. In addition, if the amount of impurities in BCl recovered by regeneration is too high compared to the impurity concentration in crude UCL, which is the raw material for purification, it is not possible to use the recovered B'(J) as a raw material for the above purification method. , resulting in disadvantages that rapidly reduce the silk-making efficiency.

In view of the above circumstances, the present invention provides a method for regenerating activated carbon and recovering most of the adsorbed BCl as B(J), which has the same impurity content as crude BCl. The purpose is to regenerate activated carbon used to adsorb and remove silicon compounds, phosgene, and chlorinated hydrocarbons in boron trichloride gas. The present invention provides a method for regenerating a boron trichloride adsorbent, which comprises heating the activated carbon to a temperature of 200 to 700°C, recovering the gas mainly composed of boron trichloride desorbed from the activated carbon, and then heating the activated carbon to a temperature of 200 to 700°C.

The present invention will be explained in detail below.

The method of the present invention is used to purify the above B CJl,
Activated carbon that has adsorbed BCJs and various impurities is subjected to a first stage treatment at a relatively low temperature and a second stage treatment at a relatively low temperature.

In the @1-stage treatment, activated carbon is maintained at a temperature of 40 to 120°C, preferably 80 to 100°C, and a small amount of inert gas (for example, Nl) is passed through to desorb adsorbed BCl. At this time, BCAs are released first, and the Si compounds, CO Cl, TO
Only a portion of C is desorbed, and the recovered BCl is crude BCJ.
, it will contain the same amount of impurities from storage, and as it is,
Can be used as a refining raw material. Due to this first stage processing, ゛C
The recovered BCI is the B that was adsorbed on activated carbon during adsorption.
It is about 80 sections of C1s.

If the temperature of the first stage treatment is 40° C. or lower, BCA'3 is not substantially desorbed, and if the temperature is 120° C. or higher, the impurity concentration in the recovered BC increases.

In the second stage treatment, the activated carbon treated in the first stage is maintained at 200 to 700 °C, preferably 230 to 300 °C, and a small amount of inert gas is passed through to remove the remaining BCl.
, and completely remove impurities.

If the temperature of the second stage treatment is 200° C. or lower, it will take a long time (more than 3 hours) to remove the adsorbate, which is not practical.

Particularly at around 160°C, impurities cannot be completely removed even if the second stage treatment is carried out for a long time, and when BCi is purified using this activated carbon, the initial 8i is detected in the BCI distilled out.

This 8i disappears soon after continuing distillation of BCIa, indicating that it was distilled due to poor regeneration. The above phenomenon also appears when processing at 190° C. for a relatively short time. That is, it is extremely important to completely remove adsorbed impurities through the second stage treatment. Moreover, since the upper limit of the temperature is heating in an inert gas, the punch capacity limit is 10,000, but if it exceeds 700° C., it will have an adverse effect on the activated carbon and the equipment, and is also economically disadvantageous.

The activated carbon regenerated by the upper dB(J) regeneration method does not reduce the refining ability of B(J) even after repeated use, and the B(J, contains the same level of impurities as crude BCJ, and can be used as a refined raw material as is.

The method of heating the activated carbon to be regenerated is not particularly limited, and may be either external heating of the adsorption tube filled with activated carbon or heating of the inert gas introduced into the adsorption tube in advance.

Next, the method of the present invention will be specifically explained with reference to Examples.

Example 1 A jacketed absorption tube with an inner diameter of 28 tm was filled with 110 g (215 cc) of sufficiently dried activated carbon of 8 to 32 meshes, and cold water was passed through the jacket to form a layer of activated carbon of 13 to 32 mm.
Maintained at 15℃, liquid phase analysis value: 8i: 190ppm, C
OCl, :240ppm, TOC:iaoppm (7
) fflB C1s is vaporized and flowed at 8V:50h-1
A breakthrough curve of impurities shown in the AM1 diagram was obtained. When the impurities broke through and the amount of distilled BCJ was 2.5 times the amount of activated carbon, the supply of BCJ was stopped, and B(J) and the activated carbon adsorbed with impurities were used as samples for the regeneration test. The activated carbon contained approximately 1/2 (557) of the amount of BC during adsorption.
II, is adsorbed, and the supplied BCJ is about three times the weight of activated carbon.

Next, as a first treatment, the activated carbon was treated with SV:2Qh-1.
Flow the islets with water and hold at 80°C for 1 hour to release BCJs.
was collected by a cold trap.

Furthermore, as a secondary treatment, the activated carbon was kept flowing as it was, and the activated carbon was heated to 250'Q and held for 3 hours, during which time the desorbed B(J) was collected.

BCA' obtained by the above first and second treatments.

The impurity and impurity concentrations are shown in Table 1.

In Table 1, the amount of B(J, cock) recovered in the secondary treatment is small because COCl1 decomposes into co and ch due to the catalytic action of activated carbon at this temperature.

Example 2 Using the above regenerated activated carbon, BCI was distilled under the same operation and conditions as in Example 1.

The above regeneration and BC1a Sei'JR were alternately repeated 10 times to obtain breakthrough curves for impurities, and all breakthrough curves were almost the same as in Figure 1, indicating that the activated carbon deteriorated due to repeated regeneration. I was not able to admit. In addition, BCJI collected in the first treatment
', the impurity concentration in it was almost constant, and it could be used as crude Bcl as a sufficiently purified raw material.

As described above, the BCII and adsorbent regeneration method according to the present invention removes most of the BCJ8 adsorbed during purification.
The recovered and regenerated activated carbon as BCII, which has approximately the same impurity a degree as crude B (J), can be used repeatedly without deterioration, so the basic unit of raw material and adsorbent in the adsorption purification method is significantly reduced. This greatly contributes to reducing the cost of purified BC1.

[Brief explanation of drawings]

Figure 1 shows the case where B(J) is made of r4 using activated carbon.
Figure 2, which shows the breakthrough state of impurities, is a diagram showing the behavior of 81 when B (J) is purified with activated carbon that is insufficiently regenerated. ■...Si (Si compound), ■・・・・・・c
ockl. Applicant Showa Denko Co., Ltd.

Claims (1)

[Claims] When regenerating the activated carbon used to adsorb and remove silicon compounds, phosgene, and chlorinated hydrocarbons in boron trichloride gas, first heat the activated carbon to 40 to 120 ° C.
A method for regenerating a boron trichloride adsorbent, which comprises recovering a gas mainly composed of boron trichloride desorbed from the activated carbon, and then heating the activated carbon to 200 to 700°C.