JP2011085566A - Method for facilitating recovery of uranium from catalyst containing uranium-antimony complex oxide - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate recovery of uranium from a catalyst supporting an uranium-antimony complex oxide. <P>SOLUTION: Recovery of uranium is facilitated by performing a chloriding treatment on a catalyst having an uranium-antimony complex supported on a porous carrier; volatilizing and separating antimony from the complex oxide as antimony chloride; and converting remaining uranium into an uranium oxide. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates generally to a method for recovering uranium, and more specifically to a method for facilitating recovery of uranium from a catalyst supporting a composite oxide of uranium and antimony.

  Acrylic nitrile (AN) is widely used as a basic chemical such as acrylic fibers and resin raw materials. In the past, composite oxides of antimony and uranium have been used as a synthesis reaction catalyst by propylene ammoxidation reaction, which is one of the AN synthesis reactions. This composite oxide of antimony and uranium is difficult to dissolve even when a strong acid such as nitric acid or hydrochloric acid is used. For this reason, a catalyst supporting a composite oxide of uranium and antimony must be strictly stored and managed as a radioactive waste containing uranium without treatment.

  In Patent Document 1, waste containing uranium is heated while circulating and circulating chlorine trifluoride to produce uranium hexafluoride. After uranium hexafluoride is captured by sodium fluoride, trifluoride is collected. A method for decontaminating uranium waste is disclosed in which chlorine is cooled and liquefied and recovered, and a halogen-based by-product is reacted with an alkali to form a salt.

In Patent Document 2, a solid material contaminated with uranium oxide (uranium dioxide or triuranium octoxide) is converted into a supercritical carbon dioxide fluid containing a nitric acid-tributyl phosphate complex (HNO ₃ -TBP complex) as a reactant. Immerse it and keep it at 50 to 60 ° C. and 100 to 200 atmospheres for 1 to 2 hours to selectively convert the uranium oxide into supercritical carbon dioxide as uranium (VI) -TBP complex (UO ₂ .2NO ₃ .2TBP). A method of decontaminating solid materials contaminated with uranium oxide by dissolution is disclosed.

JP2008-116245 JP 2002-303694 A

  However, in the method of Patent Document 1, it is necessary to handle highly toxic and corrosive fluorides in order to produce uranium hexafluoride, and in the first place, it is clear about the recovery of uranium from a composite oxide of uranium and antimony. Not been.

  In the method of Patent Document 2, nitric acid-tributyl phosphate complex is used as a uranium oxide reactant. However, since the composite oxide of uranium and antimony is hardly soluble in nitric acid, this method is used for the composite oxide. It cannot be used for dissolution.

  Therefore, the present invention provides a method for facilitating the recovery of uranium from a catalyst supporting a composite oxide of uranium and antimony in a relatively easy form without using a highly toxic and corrosive fluoride. The purpose is to provide.

  In the present invention, a catalyst in which a composite oxide of uranium and antimony is supported on a porous carrier is chlorinated, and antimony is volatilized and separated from the composite oxide as antimony chloride, and the remaining uranium is converted into uranium oxide. To provide a method for facilitating the recovery of uranium.

  According to the present invention, antimony can be selectively removed from the composite oxide as antimony chloride by chlorination treatment of the catalyst containing the composite oxide of uranium and antimony. The remaining uranium oxide is, for example, triuranium octoxide, and can be dissolved in dilute nitric acid. As a result, uranium recovery from the catalyst can be performed relatively easily.

  According to one aspect of the present invention, there is provided a method for facilitating recovery of uranium from a catalyst in which a composite oxide of uranium and antimony is supported on a porous carrier, the step of installing the catalyst in a reaction furnace, and the reaction A step of heating the catalyst in the furnace to a predetermined temperature in an inert gas atmosphere, a step of replacing the inert gas in the reaction furnace with a chloride gas, and after a predetermined time has elapsed, the heating is stopped and the chloride gas is inactivated. Substituting with an active gas.

  According to this embodiment of the present invention, since the chloride gas is a gas, it can be easily diffused into the pores of the porous carrier, and uranium and antimony supported in the pores as well as the carrier surface. Antimony can be selectively volatilized as antimony chloride from these composite oxides. The remaining uranium oxide is, for example, triuranium octoxide, and can be dissolved in dilute nitric acid. As a result, uranium recovery from the catalyst can be performed relatively easily. Furthermore, since it is a gas treatment process using gas, its control is easier compared to a liquid treatment process using solution.

It is a figure which shows the outline | summary of the processing apparatus which is one Embodiment of this invention. It is a figure which shows the processing flow which is one Embodiment of this invention.

  Embodiments of the present invention will be described below. FIG. 1 is a diagram showing an overview of a processing apparatus according to an embodiment of the present invention. The processing apparatus 100 includes a heating furnace including the reaction furnace 10 and the heater 12, means (valves, pipes) 18, 26, and 28 for supplying gas from the gas cylinders 22 and 24 into the reaction furnace 10, and a controller 30.

  The reaction furnace 10 may be a tubular furnace made of, for example, quartz. The heater 12 can use an electric heater, an infrared heater, or the like to heat the inside of the reaction furnace to a set temperature up to about 1000 ° C. The controller 30 monitors the temperature in the reaction furnace 10 and the heater 12 with the controller 30 and controls on / off of the heater 12 according to the detected temperature.

  The gas cylinder 22 contains an inert gas such as argon or nitrogen. The gas cylinder 24 contains a chloride gas such as hydrogen chloride gas. The gas cylinders 22 and 24 are selectively connected to the pipe 18 leading to the reaction furnace 10 by opening and closing the valves 26 and 28. The valves 26 and 28 are, for example, electromagnetic valves, and are controlled by the controller 30 to open and close at a set predetermined time. The gas from the gas cylinders 22 and 24 is introduced into the furnace from the upper part of the reaction furnace 10. An exhaust pipe 20 is connected to the reaction furnace 10, and the gas in the reaction furnace is guided to a gas exhaust treatment apparatus (not shown) through the exhaust pipe 20.

  A sample dish 14 is installed in the reaction furnace 10 by a hanging hook 13. The hanger 13 and the sample pan 14 are made of a metal such as platinum that does not corrode even under high temperature gas. A catalyst 16 in which a composite oxide of uranium and antimony as a sample is supported on a porous carrier is placed on the sample dish 14.

  FIG. 2 is a diagram showing a processing flow according to an embodiment of the present invention. This processing flow is executed under the control of the controller 30 in FIG. In step S <b> 102, a catalyst in which a composite oxide of uranium and antimony is supported on a porous carrier is placed on a sample dish 14 in the reaction furnace 10. The catalyst may be in the form of solid or powder. In step S <b> 104, the valve 26 is opened and the inert gas in the gas cylinder 22 is supplied into the reaction furnace 10. Prior to the supply, the air in the reactor 10 is exhausted by an exhaust pump (not shown).

  After the atmosphere in the reaction furnace 10 is filled with an inert gas, the interior of the reaction furnace 10 is heated by the heater 12 in step S106. In step S108, it is determined whether the temperature in the reaction furnace 10 has reached a predetermined temperature. The predetermined temperature should just be about 700 degreeC or more high temperature, for example, is 700-800 degreeC. After the temperature in the reaction furnace 10 reaches a predetermined temperature, in step S110, the valve 26 is closed, the supply of the inert gas from the gas cylinder 22 is stopped, and the exhaust is performed. Thereafter, the valve 28 is opened to supply the chloride gas in the gas cylinder 24 into the reactor 10. Chlorine gas is supplied to the composite oxide as a sufficient amount (predetermined flow rate) equal to or greater than the reaction equivalent. Chlorine gas comes into solid-gas contact with the porous carrier and proceeds (diffuses) into the surface and pores of the carrier.

In step S112, it is determined whether a predetermined time has elapsed after the atmosphere in the reaction furnace 10 is replaced with the chloride gas. This predetermined time is determined as the time during which antimony reacts with the chloride gas and the antimony chloride is sufficiently generated and volatilized according to the amount of the complex oxide and the like. Note that antimony chloride (SbCl ₃ ) is generated by the following reaction formulas (1) and (2).
USb ₃ O ₁₀ + 9HCl → 3SbCl ₃ + (1/3) U ₃ O ₈ + (9/2) H ₂ O + (17/12) O ₂ (1)
USbO ₅ + 3HCl → SbCl ₃ + (1/3) U ₃ O ₈ + (3/2) H ₂ O + (5/12) O ₂ (2)

  Antimony chloride produced by the reaction is volatile and is exhausted by an exhaust pump (not shown). After a predetermined time, heating in the reactor 10 by the heater 12 is stopped in step S114.

In step S112, the valve 28 is closed to stop the supply of the chloride gas from the gas cylinder 24. Chlorine gas in the reaction furnace 10 is exhausted by an exhaust pump (not shown). At this time, the valve 26 is opened, an inert gas is supplied from the gas cylinder 22 into the reaction furnace 10, and the atmosphere in the reaction furnace 10 is replaced with the inert gas from the chloride gas. The temperature in the reaction furnace 10 is lowered to normal temperature in an inert gas atmosphere. In the catalyst on the sample pan 14, uranium remains as an oxide (uranium trioxide). In addition, triuranium octoxide (U ₃ O ₈ ) is produced by the above reaction formulas (1) and (2).

  Hereinafter, an embodiment will be described. The Example was implemented in the reaction apparatus illustrated by FIG. 1 using the processing flow of FIG. As a sample, a sample in which a composite oxide of uranium and antimony was supported on a porous bead-shaped carrier made of silicon dioxide (screened with a sieve having an opening of 0.125 mm and 0.212 mm) was used. The uranium, antimony, and silicon contents of this sample were 12, 12, and 21 (wt%), respectively.

A sample 40 mg was loaded on the sample pan 14 and placed in a tubular reactor 10 having a core tube having an inner diameter of 25 mm and a length of 400 mm made of quartz. While supplying argon gas to the reaction furnace 10 at 50 cm ³ / min, the temperature in the furnace was raised by the heater 12. After the inside of the furnace reached about 800 ° C., the gas was changed from argon gas to 1 vol% hydrogen chloride gas diluted with argon, and the treatment was performed at about 800 ° C. for about 6 hours. Thereafter, the heating in the heater 12 was stopped, and the gas in the furnace was replaced with argon gas again when the temperature dropped.

The treated sample was immersed in ³ mol / dm ³ of nitric acid cm ³ with stirring in an 80 ° C. water bath for 10 minutes, and the dissolution amount of uranium was examined. As a result, 97% dissolution was confirmed. On the other hand, when 40 mg of the sample not subjected to the treatment was immersed in the same manner, the dissolved amount of uranium was 1% or less. From the above, it was confirmed that uranium existing as a complex oxide with antimony can be made into a form that can be easily recovered (triuranium octoxide) by the method of the present invention.

  The above-described embodiment (example) is an example, and the present invention is not limited to this. Various modifications are possible without departing from the spirit of the present invention.

Claims (4)

  A catalyst in which a composite oxide of uranium and antimony is supported on a porous carrier is chlorinated, and antimony is volatilized and separated from the composite oxide as antimony chloride, and the remaining uranium is converted into uranium oxide. A method that facilitates recovery.   The method according to claim 1, wherein the chlorination treatment includes bringing hydrogen chloride gas having a reaction equivalent amount or more into solid-gas contact with the composite oxide at a temperature of 700 ° C. or more. A method for facilitating the recovery of uranium from a catalyst in which a composite oxide of uranium and antimony is supported on a porous carrier,
Installing the catalyst in a reactor;
Supplying an inert gas into the reaction furnace in which the catalyst is installed and heating to a predetermined temperature;
Replacing the inert gas in the reactor with chloride gas;
And after the elapse of a predetermined time from the replacement with the chloride gas, the heating is stopped and the chloride gas is replaced with the inert gas.   The method according to claim 3, wherein the inert gas is argon gas, the chloride gas includes hydrogen chloride gas, and the predetermined temperature is 700 ° C. or higher.

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