阅读说明：本技术 使用四聚丙烯原料制备稀释剂的方法 (Method for preparing diluent by using tetrapropylene raw material ) 是由 苏哲 何辉 曹智 袁洁琼 谢书宝 何喜红 王文涛 罗方祥 于 2019-09-16 设计创作，主要内容包括：本发明提供了一种使用四聚丙烯原料制备稀释剂的方法,属于核燃料循环技术领域,该方法为：四聚丙烯选择加氢生成氢化四聚丙烯；在氢化四聚丙烯中加入第二组分,混合得支链烷烃混合物稀释剂；其中,催化剂选自铑、镍、钌、Pd/C、Pt/C、Pd(OH)<Sub>2</Sub>、PtO<Sub>2</Sub>、Pt-Pd/Al<Sub>2</Sub>O<Sub>3</Sub>、Au-Pd/C、硼烷化合物中的一种；第二组分选自聚α-烯烃、超支化聚乙烯油、C<Sub>10</Sub>-C<Sub>13</Sub>馏分油、C<Sub>9</Sub>-C<Sub>14</Sub>的F-T合成油中的至少一种。本发明制备稀释剂的方法,具有操作简单、流程短、成本低、技术难度小等优点；其中,通过引入第二组分调控氢化产物的组成和性能,为高放废液处理等应用场景提供了新思路。(The invention provides a method for preparing a diluent by using a tetrapropylene raw material, belonging to the technical field of nuclear fuel circulation, and the method comprises the following steps: selectively hydrogenating tetrapropylene to generate hydrogenated tetrapropylene; adding a second component into hydrogenated tetrapropylene, and mixing to obtain a branched alkane mixture diluent; wherein the catalyst is selected from rhodium, nickel, ruthenium, Pd/C, Pt/C, Pd (OH) 2 、PtO 2 、Pt‑Pd/Al 2 O 3 One of Au-Pd/C and borane compound; the second component is selected from poly-alpha-olefin, hyperbranched polyethylene oil and C 10 ‑C 13 Fraction oil, C 9 ‑C 14 At least one of the F-T synthetic oils of (1). The method for preparing the diluent has the advantages of simple operation, short flow, low cost, small technical difficulty and the like; wherein, the composition and the performance of the hydrogenated product are regulated and controlled by introducing the second component, so that a new idea is provided for application scenes such as high-level radioactive liquid waste treatment and the like.)

1. A process for preparing a diluent using a tetrapropylene starting material, comprising the steps of:

the method comprises the following steps of (1) carrying out catalytic hydrogenation, wherein the catalytic hydrogenation is to selectively hydrogenate tetrapropylene under the action of a catalyst to generate a first component;

compounding, wherein the compounding is to add a second component into the first component and mix to obtain a diluent;

wherein the catalyst is selected from rhodium, nickel, ruthenium, Pd/C, Pt/C, Pd (OH)₂、PtO₂、Pt-Pd/Al₂O₃One of Au-Pd/C and borane compound;

the second component is selected from poly-alpha-olefin, hyperbranched polyethylene oil and C₁₀-C₁₃Fraction oil, C₉-C₁₄At least one of F-T synthetic oils.

2. The method of claim 1, wherein the second component is a polyalphaolefin and C₁₀-C₁₃And (3) distillate oil.

3. The process of claim 1, wherein the catalyst is Au-Pd/C.

4. The method according to claim 1, wherein the catalyst is used in an amount of 0.1 to 10 wt% based on the tetrapropylene.

5. The process of claim 1, wherein the reaction conditions for the catalytic hydrogenation are: the reaction temperature is 100-300 ℃, the reaction pressure is 0.1-4 MPa, and the reaction time is 12-72 h.

6. The method of claim 1, wherein the second component is added in an amount of no more than 60 wt% of the first component.

7. A diluent produced using the method of any one of claims 1 to 6.

Technical Field

The invention relates to a diluent for spent fuel aftertreatment, in particular to a method for preparing the diluent by using a tetrapropylene raw material.

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, part of national post-treatment plants use normal paraffin mixtures such as kerosene and the like as diluents, such as odorless kerosene adopted in the uk and normal paraffin mixtures adopted in russia; other plants use mixtures of branched alkanes as diluents, e.g. C from French, Belgium, India, etc₁₀-C₁₃Mixed branched alkanes as diluents. Compared with the prior art, the extraction system consisting of the branched alkane mixture and the TBP has the advantages of large plutonium extraction capacity, difficulty in forming three phases, strong flow adaptability and the like. However, the branched alkane mixture has the disadvantages of complex components, great difficulty in synthesis and separation, technical secrecy and difficulty in market purchase.

At present, a branched alkane mixture is mainly prepared by the processes of propylene oligomerization, fractionation, hydrogenation and the like, and the method has the defects of long process, poor catalyst selectivity, low yield, high investment, high process operation cost, high technical difficulty and the like. Therefore, how to develop a diluent with comprehensive performance reaching or being superior to that of the existing branched alkane mixture is one of the problems to be solved urgently in the field of spent fuel post-treatment in China.

Disclosure of Invention

In order to solve at least one aspect of the technical problems, the invention provides a method for preparing a branched alkane mixture diluent suitable for a Purex process by taking tetrapropylene as a raw material through catalytic hydrogenation and compounding.

According to one aspect of the present invention, there is provided a process for preparing a diluent using a tetrapropylene starting material, comprising the steps of: the method comprises the following steps of (1) carrying out catalytic hydrogenation, wherein the catalytic hydrogenation is to selectively hydrogenate tetrapropylene under the action of a catalyst to generate a first component; compounding, wherein the compounding is to add a second component into the first component and mix to obtain a diluent; wherein the catalyst is selected from rhodium, nickel, ruthenium, Pd/C, Pt/C, Pd (OH)₂、PtO₂、Pt-Pd/Al₂O₃One of Au-Pd/C and borane compound; the second component is selected from poly-alpha-olefin, hyperbranched polyethylene oil and C₁₀-C₁₃Fraction oil, C₉-C₁₄At least one of F-T synthetic oils.

Preferably, the second component is a polyalphaolefin and C₁₀-C₁₃And (3) distillate oil.

Preferably, the catalyst is Pd/C, the loading amount of Pd is 0.5-5 wt%, and the loading amount of Pd is more preferably 1-3 wt%.

Further preferably, the catalyst is Au-Pd/C.

Preferably, the catalyst is used in an amount of 0.1 to 10 wt% based on the tetrapropylene.

Preferably, the reaction conditions for catalytic hydrogenation are: the reaction temperature is 100-300 ℃, the reaction pressure is 0.1-4 MPa, and the reaction time is 12-72 h.

Preferably, the second component is added in an amount of no more than 60 wt% of the first component.

The catalyst used in the catalytic hydrogenation step is a metal or supported metal catalyst, has the characteristics of good hydrogenation selectivity, high branching rate of the hydrogenation product and the like, and has an obvious promotion effect on the conversion rate of the raw materials and the configuration selection of the hydrogenation product. Meanwhile, the second component is introduced in the compounding step, so that the performance of the hydrogenated product as a diluent can be further optimized. Therefore, the method for preparing the diluent has the advantages of simple operation, short flow, low cost, small technical difficulty and the like.

According to another aspect of the present invention, there is also provided 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 method for preparing the diluent takes the tetrapropylene as the raw material, prepares the isoparaffin mixture (namely hydrogenated product) with controllable structure and performance by utilizing the relatively cheap and easily-obtained hydrogenation catalyst, and further optimizes the performance of the hydrogenated product as the diluent by introducing the second component, thereby greatly reducing the technical difficulty of the production of the existing diluent and having the advantages of short flow, low cost and the like;

(2) the introduction of the second component can regulate and control the physical and chemical properties of the hydrogenated product in a larger range, and the mode provides a new idea for application scenes such as high-level radioactive liquid waste treatment and the like.

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.

A method for preparing a diluent using a tetrapropylene starting material according to an embodiment of the present invention comprises the steps of:

carrying out catalytic hydrogenation, namely selectively hydrogenating tetrapropylene under the action of a catalyst to generate a first component;

compounding, namely adding a second component into the first component, and mixing to obtain a diluent;

wherein the catalyst is selected from rhodium, nickel, ruthenium, Pd/C, Pt/C, Pd (OH)₂、PtO₂、 Pt-Pd/Al₂O₃One of Au-Pd/C and borane compound; the second component is selected from poly-alpha-olefin, hyperbranched polyethylene oil and C₁₀-C₁₃Fraction oil, C₉-C₁₄At least one of F-T synthetic oils.

Specifically, the preparation method of the diluent may be performed according to the following steps:

(1) catalytic hydrogenation: adding raw material tetrapropylene into a reaction kettle, adding a certain amount of catalyst, vacuumizing, filling nitrogen, repeatedly vacuumizing for more than three times, vacuumizing for the last time, introducing hydrogen, and reacting for a period of time under certain pressure and temperature conditions to prepare a first component, namely hydrogenated tetrapropylene;

(2) compounding: transferring the hydrogenated tetrapropylene prepared in the step (1) into a stirring kettle, adding the second component, and mixing and stirring to obtain a final product;

in the step (1), the hydrogenation catalyst may be a metal catalyst, such as platinum, palladium, rhodium, ruthenium, iridium, nickel, etc.; because the noble metal catalyst is scarce in resources and expensive, a supported noble metal catalyst such as Pd/C, Pt/C, Pt/Al is usually used₂O₃、Rh/SiO₂Etc., and supported bimetallic catalysts, e.g. Pt-Pd/Al₂O₃Au-Pd/C, etc.; alternatively, it may be a metal catalyst in other forms such as Pd (OH)₂、PtO₂Etc.; in addition, the hydrogenation catalyst may also be of the non-metallic type, such as borane compounds. It is to be understood that the selection of hydrogenation catalysts includes, but is not limited to, those listed above.

The hydrogenation catalyst selected according to the embodiment of the invention has the characteristics of low price and easy obtaining, and more importantly, compared with oligomerization and hydrogenation reaction of propylene, the preparation method directly adopts tetrapropylene as a raw material to prepare hydrogenated tetrapropylene under the improved catalytic hydrogenation process condition, and the advantages of the preparation method are reflected in two aspects: firstly, tetrapropylene is directly used as a raw material (traditionally, the tetrapropylene is obtained by propylene oligomerization, and the controllability of propylene polymerization products is poor) to carry out hydrogenation reaction, so that saturated hydrogenation products are prepared, the selectivity of a catalyst is improved, and the yield of the hydrogenation products is increased; secondly, in the molecular structure of the prepared hydrogenated tetrapropylene, the branched chain configuration accounts for the main distribution, and the branched chain alkane mixture structure which is finally expected to be obtained has very favorable influence.

The second component in the step (2) is selected from poly alpha-olefin, hyperbranched polyethylene oil and C₁₀-C₁₃Fraction oil, C₉-C₁₄At least one of F-T synthetic oils.

Wherein the synthetic oil of poly alpha-olefin (PAO for short) is prepared from C₄(butene-1), C₆(hexene-1) and C₈(octene-1) and the like by polymerization and hydrogenation; the molecular chains of the PAO have certain branched structures, and the unique structure ensures that the PAO has the advantages of good low-temperature fluidity, low volatility, no toxicity, strong thermal stability and the like, can be used as high-end lubricating oil base oil, and can also be used as a solvent. The poly-alpha-olefin according to the embodiment of the present invention is selected from the group consisting of poly-alpha-olefin having a low molecular weight and a high degree of molecular chain branching, for example, PAO-2, PAO-2.5, PAO-4, PAO-5, or a product having a lower viscosity and a lower molecular weight, but is not limited to these. The introduction of poly-alpha-olefin can improve the physical and chemical indexes of hydrogenated tetrapropylene such as flash point, and is favorable for promoting the interaction between the diluent and the extracting agent due to the unique molecular topological structure, thereby improving the extraction capacity of the extraction system.

The hyperbranched polyethylene oil is prepared by modifying the preparation method of the low-viscosity hydrogenated polyethylene disclosed in the Chinese patent invention 201310248390X and the embodiment 1, wherein the modification is that (1) the polymerization reaction time of the ethylene polymerization stage is shortened from 18h to 4-6 h; (2) subjecting the hydrogenated polyethylene product to distillation and collecting only the fraction between 170 ℃ and 250 ℃ for use in the application of the second component of the post-treatment diluent.

The Fischer-Tropsch (F-T) synthesis technology refers toSynthesis gas (CO and H)₂) The reaction for producing hydrocarbons by a chain growth mode under the action of a catalyst is an important way for synthesizing clean fuels and chemical products by a non-petroleum route, and the raw materials are mainly derived from the conversion of coal, natural gas and biomass. The product of coal indirect liquefaction is F-T synthetic oil, which can be divided into naphtha fraction, diesel fraction, heavy oil fraction, and wax according to distillation range division. The F-T synthetic oil according to the embodiment of the invention selects C according to the carbon number₉-C₁₄A range of F-T synthetic oils.

The introduction of the second component can regulate and control the composition and the performance of the hydrogenated tetrapropylene prepared in the step (1) in a larger range, so that the finally prepared diluent product has a better effect on the extraction of uranium and plutonium: such as increasing the flash point of the diluent (higher safety in use), accelerating the phase separation of the extraction system, increasing the extraction capacity of the target extract, etc.

Furthermore, in the step (1), the catalyst is used in an amount of 0.1 to 10 wt% based on the weight of the tetrapropylene serving as the raw material. 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 catalyst according to the embodiment of the present invention is preferably used in an amount of 0.1 to 10% by mass based on the mass of the reactant tetrapropylene, that is, the amount of the catalyst is 0.1 to 10 wt% (mass percentage) based on the raw tetrapropylene.

The reaction conditions for catalytic hydrogenation were set as follows: the reaction temperature is 100-300 ℃, the reaction pressure is 0.1-4 MPa, and the reaction time is 12-72 h.

In the step (2), the adding amount of the second component is not more than 60 wt% (mass percentage) of the first component; the first component, namely the hydrogenated tetrapropylene, has higher saturation, the second component is mostly unsaturated alkane, and the first component and the second component are mixed according to a certain proportion, so that the finally obtained branched alkane mixture is adjustable in a certain range, and the service performance of the diluent is fully optimized. In addition, when the second component is a mixed composition of the above substances, the proportion of the components can be arbitrarily regulated and controlled according to the actual application scene.

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