A preparation process and equipment for high-purity diborane

Abstract

The present invention belongs to the technical field of preparing diborane, and in particular, provides a process for preparing high-purity diborane. The process comprises the steps of using excess boron trifluoride and potassium borohydride as raw materials, reacting and preparing the diborane under low-temperature conditions, complexing the boron trifluoride in the diborane, distilling the crude diborane, reusing the boron trifluoride, and recovering the solvent. The present invention provides a safer, lower-cost, waste-liquid-free, and continuously waste-liquid-free preparation process for producing high-purity diborane, provided that the boron trifluoride used as the reaction raw material is in excess.

Description

Technical Field

[0001] The invention belongs to the technical field of preparing diborane, in particular to a preparation process and equipment for high-purity diborane. Background Art

[0002] Diborane is typically prepared by reacting boron trifluoride and potassium borohydride in a reactor at low temperatures. Since boron trifluoride is gaseous and potassium borohydride is solid during the reaction, to prevent boron trifluoride from mixing into the prepared diborane, an excess of potassium borohydride is typically used, as described in "CN111892020A - A Method and Apparatus for Synthesizing High-Purity Electronic-Grade Diborane," or the amount of boron trifluoride is precisely controlled by an instrument, as described in "CN113120862A - A Method for Continuously Producing High-Purity Diborane." The entire process typically employs a solvent-free dry process to avoid wastewater contamination caused by the use of solvents. However, potassium borohydride is an explosive and hazardous chemical, making safe handling difficult. Furthermore, potassium borohydride reacts readily in humid environments, making it difficult to store and reuse excess potassium borohydride even after removal from the reactor. Boron trifluoride is non-flammable and non-combustible, making it safer than potassium borohydride. Using an instrument to precisely control the amount of boron trifluoride significantly increases production costs and increases the workload of personnel. Summary of the Invention

[0003] To address the above-mentioned problems, the present invention aims to provide a safer, lower-cost, waste-liquid-free, and continuously productive process for producing high-purity diborane, provided that the reaction raw material, boron trifluoride, is in excess. The specific technical solution employed is a process for producing high-purity diborane, comprising at least the following steps:

[0004] Step 1: Place KBH4 into the reactor;

[0005] Step 2: Control the reaction temperature of the reactor at -80 to -30°C and the pressure at 0.5 to 2 MPa, introduce an excess of BF3 into the reactor and allow BF3 to condense on KBH4, and react for 4 to 8 hours to generate crude diborane;

[0006] Step 3: crude diborane and unreacted BF3 are introduced from the discharge port of the reactor to the bottom of a complexing tower. A solvent is provided in the complexing tower, wherein the solvent is ethylene glycol dimethyl ether or ethylene glycol. After entering the complexing tower, BF3 reacts with the solvent to form a complex, and gaseous diborane is drawn out from the top of the complexing tower.

[0007] Step 4: introducing the gas obtained in step 3 into a first distillation tower, separating and removing light component impurities in the gas in the first distillation tower, and then introducing the obtained diborane from the tower bottom outlet into a second distillation tower for distillation;

[0008] Step 5: The diborane obtained in step 4 is separated into heavy components in a second distillation tower to obtain 5N grade diborane;

[0009] Step 6: After the reaction in step 2 is completed and all the gaseous diborane in step 3 is drawn out from the top of the complexing tower and introduced into the first distillation tower, repeat step 1, then heat the liquid temperature in the complexing tower to 60°C, pass the generated gas into the reactor and repeat steps 2 to 5.

[0010] Moreover, the reactor in step 1 is a tubular reactor, and the KBH4 placed therein is solid.

[0011] Moreover, the mass ratio of the raw materials KBH4 and BF3 added to each batch of reaction in step 2 is not greater than 1:1.65.

[0012] Moreover, the diborane content in the crude diborane obtained in step 2 is greater than 98%.

[0013] And an apparatus for the preparation process of the high-purity diborane, comprising at least a reactor, a complexing tower, a first distillation tower and a second distillation tower, wherein the top of the complexing tower is connected to the reactor and the first distillation tower respectively through independent gas pipelines, and the bottom of the complexing tower is provided with a heating device; and a swirl plate, a wind pressure gauge and an O2 content online monitor are provided in the second distillation tower.

[0014] Compared with the prior art, the beneficial effects of the present technical solution are: 1. In the process of preparing diborane by reacting boron trifluoride and potassium borohydride, excess boron trifluoride is used to ensure that the explosive potassium borohydride is completely reacted to form potassium borofluoride with low risk, thereby reducing safety risks. At the same time, there is no problem of taking out the excess potassium borohydride from the reactor and storing it for reuse, thereby increasing economic benefits; 2. In order to remove the boron trifluoride mixed in the diborane, the mixed gas is passed into a complexing tower equipped with ethylene glycol dimethyl ether or ethylene glycol. After entering the complexing tower, the boron trifluoride is complexed with the solvent to form a complex, and the diborane and light component impurities are further purified by entering a distillation tower, thereby completely eliminating the boron trifluoride. Interference of boron fluoride; 3. In order to further realize the continuous production of diborane, the characteristic that boron trifluoride will separate from the solvent after heating the complex is utilized. After the reaction is completed and all diborane is drawn out from the top of the complexing tower and introduced into the first distillation tower, new reaction raw material potassium borohydride is added to the reactor, and then the liquid temperature in the complexing tower is heated to 60°C, the generated gas is introduced into the reactor and steps 2 to 5 are repeated. This not only realizes the recovery and utilization of boron trifluoride in the complexing tower, but also realizes the reuse of the solvent in the complexing tower. The continuous production of diborane can be efficiently realized without opening the complexing tower to replace the solvent, and at the same time minimizes the problem of waste liquid pollution caused by the use of solvents. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1Schematic diagram of the equipment connection used in the preparation process in the embodiment;

[0016] Explanation of the accompanying symbols: 1. Reactor, 2. Complexing tower, 3. Gas pipeline connecting the complexing tower and the first distillation tower, 4. Gas pipeline connecting the complexing tower and the reactor, 5. First distillation tower, 6. Second distillation tower, 7. Cyclone plate, 8. Wind pressure gauge and O2 content online monitor. DETAILED DESCRIPTION

[0017] The present invention will be described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the following embodiments.

[0018] A process for preparing high-purity diborane comprises at least the following steps:

[0019] Step 1: Place KBH4 into reactor 1;

[0020] Step 2: Control the reaction temperature of the reactor at -80 to -30°C and the pressure at 0.5 to 2 MPa, introduce an excess of BF3 into the reactor and allow BF3 to condense on KBH4, and react for 4 to 8 hours to generate crude diborane;

[0021] Step 3: crude diborane and unreacted BF3 are introduced from the discharge port of the reactor to the bottom of the complexing tower 2. A solvent is provided in the complexing tower, and the solvent is ethylene glycol dimethyl ether or ethylene glycol. After entering the complexing tower, BF3 is complexed with the solvent to form a complex, and gaseous diborane is drawn out from the top of the complexing tower;

[0022] Step 4: Introduce the gas obtained in step 3 into the first distillation tower 5. After separating and removing light component impurities in the gas using conventional methods in the first distillation tower, the obtained diborane is introduced into the second distillation tower from the tower bottom outlet for rectification;

[0023] Step 5: The diborane obtained in step 4 is separated into heavy components using conventional methods in a second distillation tower 6 to obtain 5N grade diborane. The obtained 5N grade diborane product can be cooled and liquefied before being collected centrally;

[0024] Step 6: After the reaction in step 2 is completed and all the gaseous diborane in step 3 is drawn out from the top of the complexing tower and introduced into the first distillation tower, step 1 is repeated, and the liquid temperature in the complexing tower is heated to 60°C. The generated gas is introduced into the reactor and steps 2 to 5 are repeated, thereby achieving continuous production of diborane without opening the complexing tower to replace the solvent.

[0025] Moreover, the mass ratio of the raw materials KBH4 and BF3 added to each batch of reaction in step 1 is not greater than 1:1.65.

[0026] Moreover, the reactor in step 1 is a tubular reactor, and the KBH4 placed therein is solid.

[0027] Moreover, the diborane content in the crude diborane obtained in step 2 is greater than 98%.

[0028] And an apparatus for the preparation process of said high-purity diborane, such as Figure 1 As shown in the figure, the arrows are the gas flow directions in the pipeline. The leftmost pipeline in the figure is the pipeline for introducing excess BF3, and the rightmost pipeline is for collecting the obtained 5N grade diborane product into the storage tank. It at least includes a reactor 1 with added KBH4 solid, a complexing tower 2 with added ethylene glycol dimethyl ether or ethylene glycol, a first distillation tower 5 and a second distillation tower 6. The top of the complexing tower is provided with two independent gas pipelines, each of which is provided with an independent valve, namely the gas pipeline 3 connecting the complexing tower and the first distillation tower and the gas pipeline 4 connecting the complexing tower and the reactor. The bottom of the complexing tower is provided with a heating device; a swirl plate 7, a wind pressure gauge and an O2 content online monitor 8 are provided in the second distillation tower to improve the effect of separating heavy components in the second distillation tower and monitor the gas conditions in and on the top of the second distillation tower. After the whole set of equipment works together, a 5N grade diborane product is finally obtained.

[0029] The method for using the equipment in the preparation process is as follows: when performing steps 2 and 3, the valve of gas pipeline 3 is opened and the valve of gas pipeline 4 is closed, so that the gas obtained in step 3 is introduced into the first distillation tower; after the reaction of step 2 is completed and all the gaseous diborane in step 3 is drawn out from the top of the complexing tower and introduced into the first distillation tower, the valve of gas pipeline 3 is closed and the valve of gas pipeline 4 is closed and opened, so that the boron trifluoride separated from the solvent after heating the complex enters the reactor for continuous production of the next batch of diborane.

[0030] The reaction principle of this preparation process is:

[0031] The preparation of diborane is divided into three parts: the first part is synthesis, the second part is complexation, and the third part is distillation.

[0032] Diborane synthesis uses KBH4 and BF3 as raw materials to react in a reactor at low temperature to produce diborane and potassium borofluoride.

[0033] The reaction equation is as follows: 4BF3+3KBH4→2B2H6↑+3KBF4

[0034] The mass of KBH4 added to each batch of reaction raw materials is 20 kg, and the mass of BF3 added is not less than 33 kg. The reaction temperature of the reactor is controlled at -30 to -80°C, the pressure of the reactor is controlled at 0.5 to 2 MPa, and the reaction time is controlled at 4 to 8 hours. After the reaction is complete, the diborane content in the generated crude diborane exceeds 98%, and the unreacted BF3 is mixed with the diborane and discharged from the reactor into a complexing tower. The solvent in the complexing tower will complex with BF3 to achieve separation of diborane and the solvent can be recovered after heating the complex and the unreacted BF3 can be reused. The diborane enters a distillation tower for distillation.

[0035] The distillation tower is divided into two stages. The first stage distillation tower removes H2, N2, O2, CO, CO2, CH4 and other light component impurities in diborane. The diborane is transferred from the first stage distillation tower to the second stage distillation tower, and the second stage distillation tower removes B4H 10 、B5H9、B6H 10 The heavy component impurities are discharged from the top of the secondary distillation tower after passing the distillation and collected in the finished product storage tank; the distillation tower temperature is controlled at -20~-80℃, and the distillation tower pressure is controlled at 0.1~2MPa.

Claims

1. A process for preparing high-purity diborane, characterized in that: At least the following steps are included: Step 1: Place KBH4 into the reactor; Step 2: Control the reaction temperature of the reactor at -80 to -30°C and the pressure at 0.5 to 2 MPa, introduce an excess of BF3 into the reactor and allow BF3 to condense on KBH4, and react for 4 to 8 hours to generate crude diborane; the mass ratio of the raw materials KBH4 and BF3 added in each batch of reaction shall not be greater than 1:1.65; Step 3: crude diborane and unreacted BF3 are introduced from the discharge port of the reactor to the bottom of a complexing tower. A solvent is provided in the complexing tower, wherein the solvent is ethylene glycol dimethyl ether or ethylene glycol. After entering the complexing tower, BF3 reacts with the solvent to form a complex, and gaseous diborane is drawn out from the top of the complexing tower. Step 4: introducing the gas obtained in step 3 into a first distillation tower, separating and removing light component impurities in the gas in the first distillation tower, and then introducing the obtained diborane from the tower bottom outlet into a second distillation tower for distillation; Step 5: The diborane obtained in step 4 is separated into heavy components in a second distillation tower to obtain 5N grade diborane; Step 6: After the reaction in step 2 is completed and all the gaseous diborane in step 3 is drawn out from the top of the complexing tower and introduced into the first distillation tower, step 1 is repeated, and the liquid temperature in the complexing tower is heated to 60°C. The generated gas is introduced into the reactor and steps 2 to 5 are repeated, thereby achieving continuous production of diborane without opening the complexing tower to replace the solvent.

2. The process for preparing high-purity diborane according to claim 1, wherein: The reactor in step 1 is a tubular reactor, and the KBH4 placed therein is solid.

3. The process for preparing high-purity diborane according to claim 1, wherein: The diborane content in the crude diborane product obtained in step 2 is greater than 98%.

4. An apparatus for the preparation process of high-purity diborane according to claim 1, characterized in that: It includes at least a reactor, a complexing tower, a first distillation tower and a second distillation tower. The top of the complexing tower is connected to the reactor and the first distillation tower respectively through independent gas pipelines. The bottom of the complexing tower is provided with a heating device; the second distillation tower is provided with a swirl plate, a wind pressure gauge and an O2 content online monitor.

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