CN110551893B

CN110551893B - Diluent and its preparing process

Info

Publication number: CN110551893B
Application number: CN201910869265.8A
Authority: CN
Inventors: 苏哲; 何辉; 王文涛; 谢书宝; 曹智; 袁洁琼; 罗方祥
Original assignee: China Institute of Atomic of Energy
Current assignee: China Institute of Atomic of Energy
Priority date: 2019-09-16
Filing date: 2019-09-16
Publication date: 2020-12-15
Anticipated expiration: 2039-09-16
Also published as: CN110551893A

Abstract

The invention provides a preparation method of a diluent, which is characterized in that under the action of a catalyst, triisobutene serving as a raw material is subjected to hydrogenation reaction to prepare the diluent; wherein, the hydrogenation reaction is carried out at the temperature of 60-200 ℃, the pressure of 0.1-4.0 MPa and the volume ratio of hydrogen to triisobutene of (200-600): 1; further, the catalyst adopts a supported metal catalyst; the hydrogenation reaction adopts a fixed bed reaction. The preparation method has the advantages of simple operation, low investment, low technical difficulty, high hydrogenation selectivity and the like; and the prepared diluent hydrogenated triisobutene has strong compatibility to TBP (tert-butyl-tert-butyl) so that the extraction capacity of the mixed solvent to uranium and plutonium is increased.

Description

Diluent and its preparing process

Technical Field

The invention relates to a diluent for spent fuel aftertreatment, in particular to a diluent and a preparation method thereof.

Background

The Purex process (Prefix process) is the most widely applied process in the current spent fuel post-treatment, and the process adopts a solvent extraction method to extract uranium and plutonium from a spent fuel dissolving solution. Among them, the most commonly used extraction system is a mixture of tributyl phosphate (TBP) and a diluent, wherein the diluent has the effects of reducing the density and viscosity of the solvent phase, improving the hydrodynamic properties of the system, adjusting the extraction capacity and selectivity of the TBP, and preventing the nuclear critical risk. Therefore, the choice of diluent has a significant impact on the extraction performance of the Purex process. At present, the diluent used in the spent fuel post-treatment process mainly comprises two types of normal alkane mixture and isoparaffin mixture; wherein the normal alkane mixture comprises n-dodecane, kerosene and the like, and the isoparaffin mixture comprises hydrogenated Triisobutene (TPH) and the like.

In practical application, the composition of the diluent is found to have an important influence on the performance of an extraction solvent system, wherein isoparaffin with a branched structure has better compatibility with TBP complex, the formed mixed solvent has larger extraction capacity of uranium and plutonium and stronger flow adaptability, and the performance of the mixed solvent is better than that of kerosene and other normal alkanes. However, the isoparaffin mixture has the disadvantages of complex components, great difficulty in synthesis and separation, technical secrecy, and difficulty in market purchase. At present, the isoparaffin mixture is mainly prepared by the processes of propylene oligomerization, fraction cutting, hydrogenation and the like, and the preparation method has the defects of poor catalyst selectivity, low yield, long flow, high process operation cost, great technical difficulty and the like. Based on the above, the invention develops an isomeric alkane mixture diluent and a preparation method thereof, triisobutene is taken as a raw material, the diluent is prepared through a one-step hydrogenation reaction, and the diluent is applied to spent fuel post-treatment.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the preparation method of the diluent, which is simple to operate, low in cost, small in technical difficulty and high in hydrogenation selectivity, and triisobutene is taken as a raw material and is prepared through hydrogenation reaction; the diluent prepared by the method has stronger compatibility with TBP, so that the mixed solvent formed by the diluent and the TBP has larger extraction capacity on uranium and plutonium.

According to the embodiment of the invention, the diluent is prepared by carrying out one-step hydrogenation reaction on triisobutene under the action of a catalyst; wherein the catalyst is a supported metal catalyst, the active component of the catalyst is at least one of Pt, Pd, Ni, Ag, Au, Ir and Fe, and the carrier is active carbon, ZSM series molecular sieve, SAPO series molecular sieve, mordenite, Y zeolite, beta zeolite, Al₂O₃、TiO₂Amorphous aluminum silicate; the hydrogenation reaction is carried out at the temperature of 60-200 ℃, the pressure of 0.1-4.0 MPa and the volume ratio of hydrogen to triisobutene of (200-600): 1.

Further, the carrier is one of mordenite, Y zeolite, beta zeolite, SAPO-11, ZSM-22 and ZSM-23.

Wherein, the catalyst is prepared by adopting an impregnation method.

Furthermore, the dosage of the catalyst is 0.1-10 wt% (mass percent) of the raw material triisobutene.

Further, the hydrogenation reaction adopts a gas-liquid-solid three-phase fixed bed reaction.

Also provided according to an embodiment of the present invention is a diluent prepared using the above preparation method.

Compared with the prior art, the invention has at least one of the following beneficial effects:

(1) the preparation method of the diluent takes triisobutene as a raw material, and prepares the C with controllable structure and performance by using a relatively cheap and easily-obtained hydrogenation catalyst₁₂The preparation method of the isoparaffin mixture greatly reduces the technical difficulty of the existing diluent production, and has the advantages of short flow, low cost, high hydrogenation selectivity and the like;

(2) the diluent prepared by the invention has stronger compatibility to TBP, can effectively improve the extraction efficiency and extraction capacity of the mixed solvent to uranium and plutonium, and has good performance when being used in a spent fuel post-treatment process.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention are described below clearly and completely. It should be apparent that the described embodiment is one embodiment of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the described embodiments of the invention without any inventive step, are within the scope of protection of the invention.

Unless defined otherwise, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention belongs.

Dilution according to embodiments of the inventionThe preparation method of the agent comprises the steps of carrying out one-step hydrogenation reaction on triisobutene under the action of a catalyst to prepare a diluent; wherein the catalyst is a supported metal catalyst, the active component of the catalyst is at least one of Pt, Pd, Ni, Ag, Au, Ir and Fe, and the carrier is active carbon, ZSM series molecular sieve, SAPO series molecular sieve, mordenite, Y zeolite, beta zeolite, Al₂O₃、TiO₂Amorphous aluminum silicate; the hydrogenation reaction is carried out at the temperature of 60-200 ℃, the pressure of 0.1-4.0 MPa, the volume ratio of hydrogen to triisobutene of (200-600): 1 and the volume space velocity of 3-15 h^-1Under the conditions of (1).

The catalyst used in the hydrogenation reaction is a supported metal catalyst, compared with a metal catalyst, the metal dosage is greatly reduced, the cost is favorably reduced, and meanwhile, the metal is supported on a carrier with a certain specific surface area and pores, the contact action area of reactants and the catalyst is favorably increased, and the reaction efficiency is improved.

The active component of the common supported metal catalyst can be one or more selected from Pt, Pd, Ni, Ag, Au, Ir and Fe, and the carrier can be selected from active carbon, ZSM series molecular sieve, SAPO series molecular sieve, mordenite, Y zeolite, beta zeolite and Al₂O₃、TiO₂Any one of amorphous aluminum silicate; wherein, the carrier can be one of SAPO-11, ZSM-22 and ZSM-23.

Further, in the catalyst composition, the content of the active component may be controlled to be 0.5 to 5 wt% (mass percentage) of the whole supported metal catalyst; it is, of course, 1 to 3 wt% (mass percentage).

The dosage of the catalyst is 0.1-10 wt% of the raw material triisobutene. It is generally accepted that a catalyst is a substance that is capable of changing the rate of reaction (i.e., the rate at which the reaction approaches equilibrium) without itself undergoing a quantitative change or a chemical change before or after the reaction; the amount of catalyst used during the reaction often has a significant effect on its activity. For example, different amounts of catalyst may be used to catalyze different reactant conversions (or product yields) at the same reaction time, i.e., the amount of catalyst has an effect on the reaction rate, and the catalyst is usually used in an optimal amount at a given reactant condition. The amount of the catalyst used according to the embodiment of the present invention is 0.1 to 10% by mass of the triisobutene as a reactant, that is, the amount of the catalyst is 0.1 to 10% by mass of the triisobutene as a raw material.

And as for the preparation method of the catalyst, commonly used methods include a mechanical mixing method, an impregnation method, a coprecipitation method, a sol-gel method, an ion exchange method, and the like. In the embodiment, an impregnation method is adopted, that is, soluble salts of corresponding active component elements are impregnated on different carriers, adsorbed and saturated, and then the active component elements are prepared through the steps of drying, roasting, gas reduction and the like. The catalyst is prepared by adopting an impregnation method, and has the advantages of simple operation, high metal dispersion degree and the like.

Although the hydrogenation catalyst is a common catalyst type, the catalyst has good promotion effect when applied to the hydrogenation of the triisobutene in the invention: on one hand, triisobutene is adopted as a raw material, compared with propylene, oligomerization reaction (the product configuration is uncontrollable) occurs, a complex intermediate reaction process is omitted, and the raw material is C₁₂The unsaturated hydrocarbon mixture is directly subjected to hydrogenation saturation, so that the reaction efficiency is improved and the reaction flow is simplified; meanwhile, on the premise of ensuring higher conversion rate of raw materials, the catalyst shows better selectivity, which is shown in that the proportion of branched chain configuration in a hydrogenated product is increased; however, since the branched alkane mixture has better extraction performance than normal alkane, the improvement of the isomerization degree of the product is the result expected by the invention.

The technical scheme and the effect of the invention are described by combining the specific embodiments as follows:

example 1:

(1) preparation of the catalyst:

50g of the support SAPO-11 was added to 100mL of H₂PdCl₄Stirring the solution at 50 ℃ for 24h, filtering the solid product, drying the solid product at 70 ℃ overnight, and then roasting the solid product at 480 ℃ for 6h to obtain the Pd/SAPO-11 catalyst。

(2) Triisobutene hydrogenation reaction:

a small fixed bed reaction device is adopted, the reaction temperature is 190 ℃, the reaction pressure is 2MPa, the volume ratio of hydrogen to triisobutene is 350:1, and the volume space velocity is 5h^-1Hydrogenation reaction is carried out under the condition. Then, a sample was taken and the conversion of triisobutene was measured by a fluorescent indicator adsorption method, and the reaction was stopped when the conversion was more than 99.5%. After the reaction is finished, filtering the reaction liquid obtained by the reaction by using a silica gel short column (the diameter of the silica gel is 30mm, and the height of the silica gel is 10cm), washing by using 30mL of normal hexane, combining the filtrates, and concentrating to obtain hydrogenated triisobutene; the physicochemical property parameters of the hydrogenated product were determined as: bromine number of 0.29g/100g and density of 0.71g/cm³(20 ℃ C.), a dynamic viscosity of 1.3cP (20 ℃ C.), and a flash point of 60 ℃.

(3) Extraction experiment:

taking 100g of the hydrogenated product prepared above and tributyl phosphate (TBP) to form a 30% TBP-diluent mixed solvent, and carrying out an extraction experiment; the extraction results are: 30% TBP-Diluent with 1mol/L HNO₃The phase separation time was 42s and the extraction capacity for Pu (IV) was 76 g/L.

Example 2:

(1) preparation of the catalyst:

50g of the support mordenite was added to 100mL of H₂PdCl₄And 25mL H₂PtCl₆The mixed solution was stirred at 50 ℃ for 24h, the solid product was filtered and dried at 70 ℃ overnight, and then calcined at 500 ℃ for 6h to give the Pd-Pt/mordenite catalyst.

(2) Triisobutene hydrogenation reaction:

a small fixed bed reaction device is adopted, the reaction temperature is 200 ℃, the reaction pressure is 2MPa, the volume ratio of hydrogen to triisobutene is 300:1, and the volume airspeed is 10h^-1Hydrogenation reaction is carried out under the condition. Then, a sample was taken and the conversion of triisobutene was measured by a fluorescent indicator adsorption method, and the reaction was stopped when the conversion was more than 99.5%. After the reaction, the reaction solution obtained by the above reaction was filtered through a short column of silica gel (silica gel having a diameter of 30mm and a height of 10cm), and then washed with 30mL of n-hexane, and the filtrates were combined,Concentrating to obtain hydrogenated triisobutene; the physicochemical property parameters of the hydrogenated product were determined as: bromine number of 0.50g/100g and density of 0.74g/cm³(20 ℃ C.), a kinematic viscosity of 1.5cP (20 ℃ C.), and a flash point of 55 ℃.

(3) Extraction experiment:

taking 100g of the hydrogenated product prepared above and tributyl phosphate (TBP) to form a 30% TBP-diluent mixed solvent, and carrying out an extraction experiment; the extraction results are: 30% of TBP-novice agent and 1mol/L of HNO₃The phase separation time was 37s and the extraction capacity for Pu (IV) was 74 g/L.

Example 3:

(1) preparation of the catalyst:

50g of supported ZSM-22 was added to 100mL of H₂PdCl₄And 25mL H₂PtCl₆The mixed solution was stirred at 50 ℃ for 24 hours, the solid product was filtered and dried at 70 ℃ overnight, and then calcined at 500 ℃ for 6 hours to obtain a Pd-Pt/ZSM-22 catalyst.

(2) Triisobutene hydrogenation reaction:

a small fixed bed reaction device is adopted, the reaction temperature is 200 ℃, the reaction pressure is 2MPa, the volume ratio of hydrogen to triisobutene is 300:1, and the volume airspeed is 10h^-1Hydrogenation reaction is carried out under the condition. Then, a sample was taken and the conversion of triisobutene was measured by a fluorescent indicator adsorption method, and the reaction was stopped when the conversion was more than 99.5%. After the reaction is finished, filtering the reaction solution obtained by the reaction by using a silica gel short column (the diameter of the silica gel is 30mm, and the height of the silica gel is 10cm), washing by using 30mL of n-hexane, combining the filtrates, and concentrating to obtain hydrogenated triisobutene; the physicochemical property parameters of the hydrogenated product were determined as: bromine number of 0.31g/100g and density of 0.71g/cm³(20 ℃ C.), a kinematic viscosity of 1.2cP (20 ℃ C.), and a flash point of 59 ℃.

(3) Extraction test

Taking 100g of the hydrogenated product prepared above and tributyl phosphate (TBP) to form a 30% TBP-diluent mixed solvent, and carrying out an extraction experiment; the extraction results are: 30% TBP-Diluent with 1mol/L HNO₃The phase separation time was 48s and the extraction capacity for Pu (IV) was 87 g/L.

Example 4

The diluents prepared in examples 1 to 3 were subjected to extraction experiments under the same conditions as those of comparative example 1, and the extraction results are shown in table 1.

Of these, comparative example 1 is a case where a commercially available hydrogenated kerosene was used as a diluent.

TABLE 1 comparison of the results of the extraction experiments with the diluent of the present invention with those of the prior art

Source of diluent	Phase separation time(s)	Extraction Capacity (g/L)
			Example 1	42	76
Example 2	37	74
			Example 3	48	87
Comparative example 1	56	56

As shown in Table 1, the diluent prepared by the preparation method of the embodiment of the invention has obviously better effect than the commercial hydrogenated kerosene diluent product when being used for extraction experiments. Wherein, comparing examples 2 and 3, under the condition of only changing the kind of catalyst, the extraction performance of the hydrogenation product prepared in example 3 is different, and the diluent prepared in example 3 has a larger extraction capacity for extracting Pu (IV), which indicates that the proportion of branched alkane in the hydrogenation product is higher by using Pd-Pt/ZSM-22 catalyst to catalyze the hydrogenation reaction, thus being beneficial to obtaining better effect of the extraction experiment. Of course, other reaction conditions of the hydrogenation reaction are also the main factors of influence.

It should also be noted that, in the case of the embodiments of the present invention, features of the embodiments and examples may be combined with each other to obtain a new embodiment without conflict.

The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and the scope of the present invention is subject to the claims.

Claims

1. A preparation method of a diluent is characterized in that under the action of a catalyst, triisobutene is subjected to one-step hydrogenation reaction to prepare the diluent; the diluent is used as a component of an extraction system in a spent fuel post-treatment process; the diluent produced comprises a mixture of isoparaffins;

wherein the catalyst is a supported metal catalyst, the active component of the catalyst is at least one of Pt, Pd, Ni, Ag, Au, Ir and Fe, and the carrier is active carbon, ZSM series molecular sieve, SAPO series molecular sieve, mordenite, Y zeolite, beta zeolite, Al₂O₃、TiO₂Amorphous aluminum silicate;

the hydrogenation reaction is carried out at the temperature of 60-200 ℃, the pressure of 0.1-4.0 MPa and the volume ratio of hydrogen to triisobutene of (200-600) to 1;

the dosage of the catalyst is 0.1-10 wt% of triisobutene.

2. The preparation method according to claim 1, wherein the carrier is one of mordenite, Y zeolite, beta zeolite, SAPO-11, ZSM-22 and ZSM-23.

3. The preparation method according to claim 1, wherein the catalyst is prepared by an impregnation method.

4. The production method according to claim 1, wherein the hydrogenation reaction employs a gas-liquid-solid three-phase fixed bed reaction.

5. A diluent prepared by the method of any one of claims 1 to 4.