Method and device for preparing electronic-grade trichlorosilane by deeply removing trace phosphorus and boron impurities

Abstract

The present application provides a method for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane, which includes: rectifying and separating the crude trichlorosilane to remove heavy-component impurities and light-component impurities in sequence to obtain a trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove; evaporating the trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove into trichlorosilane vapor and then introducing it into a fluidized bed for adsorbing phosphorus and boron impurities, and fully contacting and mixing it with a modified activated carbon adsorbent under fluidization conditions, so that the trace phosphorus and boron impurities in the trichlorosilane vapor are fully adsorbed by the modified activated carbon adsorbent and removed, thereby obtaining trichlorosilane with a low content of phosphorus and boron impurities. The modified activated carbon adsorbent is prepared by oxidative modification for expansion and reduction modification for loading highly active nitrogen-containing functional groups. The present application also provides a device for the above method. The present application can deeply remove the content of phosphorus and boron impurities in electronic-grade trichlorosilane and greatly reduce the energy consumption in the production of electronic-grade trichlorosilane.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of electronic-grade trichlorosilane, and relates to the technology for deeply removing trace phosphorus and boron impurities in trichlorosilane. Specifically, it is a method and device for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane. Background Art

[0002] Electronic-grade trichlorosilane has very wide applications, mainly used in industries such as electronics and photovoltaic. However, the purity requirement of electronic-grade trichlorosilane is very high (≮9N), and strict requirements are imposed on the impurity content. At present, multi-stage rectification technology is basically adopted to remove impurities in trichlorosilane. For example, compounds such as iron, copper, and manganese can be easily removed by rectification. However, boron and phosphorus impurities basically exist in the form of chlorides (referred to as phosphorus-boron impurities). The properties of these chlorides are similar to those of chlorosilanes, and their boiling points are very close to that of trichlorosilane. It is difficult to remove them. Therefore, it is necessary to increase the reflux ratio and reduce the take-off amount during multi-stage rectification to ensure the quality index, resulting in high energy consumption, low yield, and unstable product quality.

[0003] In order to remove trace phosphorus and boron impurities in trichlorosilane, it is necessary to combine other efficient phosphorus-boron removal technologies with rectification technology. The use of activated carbon adsorption technology is an important technology for removing trace phosphorus and boron impurities in trichlorosilane. It has good removal effect, and the raw material of activated carbon is widely sourced and inexpensive, with strong economic cost advantages. It is one of the important technologies for removing trace phosphorus and boron impurities in trichlorosilane at present. If the activated carbon adsorption technology can be combined with the rectification technology, it can not only improve the deep removal effect of phosphorus and boron impurities and produce electronic-grade trichlorosilane with low phosphorus and boron impurity content, but also effectively reduce energy consumption.

[0004] However, the specific surface area of conventional activated carbon is relatively small (generally not exceeding 1000m 2 / g); at the same time, when the adsorption technology is used to remove phosphorus and boron impurities, the separation is mainly achieved by the different properties such as polarity between trichlorosilane and phosphorus and boron impurities. That is, the polarity of trichlorosilane is very weak, while the polarity of phosphorus and boron impurities such as phosphorus trichloride or boron chloride is very strong, and they strongly tend to form addition chemical bonds and are easily adsorbed by strong polar adsorbents. However, the polarity of activated carbon is weak, and the adsorption affinity of conventional activated carbon adsorbents for phosphorus and boron impurities is weak. It is difficult to deeply remove trace phosphorus and boron impurities, which is the defect and technical bottleneck of the current activated carbon adsorption method.

[0005] In summary, the existing production technology of electronic-grade trichlorosilane basically adopts rectification technology. When removing phosphorus and boron impurities in trichlorosilane, since the phosphorus and boron impurities in trichlorosilane basically exist as chlorides with properties similar to those of trichlorosilane and close boiling points, a large reflux ratio is required for removal, the removal effect is poor, it is difficult to produce electronic-grade trichlorosilane products with low phosphorus and boron impurities, and the energy consumption is high.

[0006] The activated carbon used in the existing activated carbon adsorption technology has a small specific surface area, weak polarity and activity, small adsorption affinity and adsorption rate, and it is difficult to deeply remove trace phosphorus and boron impurities.

[0007] Therefore, in order to effectively combine the rectification technology with the activated carbon adsorption technology, it is of great significance to develop a trace phosphorus and boron impurity adsorption technology using modified activated carbon with a high specific surface area and high activity as an adsorbent. Summary of the Invention

[0008] In view of the above problems, the present application provides a method and device for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane, which can solve at least one of the problems existing in the background technology.

[0009] In order to achieve the above object, the present application provides the following technical solutions:

[0010] On the one hand, the present invention provides a method for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane, including:

[0011] S1. Rectifying and separating the crude trichlorosilane to remove heavy component impurities and light component impurities in turn, and obtaining a trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove;

[0012] S2. Evaporating the trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove into trichlorosilane vapor, and then introducing it into a fluidized bed adsorption device for phosphorus and boron impurities, and fully contacting and mixing with the modified activated carbon adsorbent under fluidization, so that the trace phosphorus and boron impurities in the trichlorosilane vapor are fully adsorbed by the modified activated carbon adsorbent and removed, and an electronic-grade trichlorosilane with a low content of phosphorus and boron impurities is obtained;

[0013] Among them, the modified activated carbon adsorbent is an adsorbent prepared by oxidation modification for expansion and reduction modification for loading high-activity nitrogen-containing functional groups, and is an activated carbon with a large specific surface area, loaded with nitrogen functional groups, and having strong polarity and activity.

[0014] Through this scheme, the present invention combines the rectification technology with the modified activated carbon adsorption technology to prepare electronic-grade trichlorosilane with a low phosphorus and boron content, can deeply remove the phosphorus and boron impurity content in the electronic-grade trichlorosilane, and because the modified activated carbon technology is used to deeply remove the phosphorus and boron impurities in the trichlorosilane, and the activated carbon used has a relatively large specific surface area and is loaded with nitrogen-containing element functional groups, and is a modified activated carbon with high activity, large adsorption affinity and fast adsorption rate, it can effectively reduce the reflux ratio of trichlorosilane rectification and greatly reduce the energy consumption in the production of electronic-grade trichlorosilane.

[0015] A preferred scheme is that the preparation method of the above adsorbent is:

[0016] Under a certain temperature and pressure environment, with a particle size of 0.1 mm and a specific surface area of 800 m2 The g-shaped activated carbon is mixed with an oxidant in a certain proportion and brought into full contact to undergo an oxidation reaction, adjusting the internal structure of the activated carbon to obtain oxidized activated carbon with a specific surface area of 1200 m 2 / g;

[0017] In an oxygen-free environment at a certain temperature and pressure, the oxidized activated carbon is mixed with a nitrogen-containing reducing agent in a certain proportion and undergoes a reduction reaction to load nitrogen-containing functional groups on the surface of the oxidized activated carbon, obtaining a modified activated carbon adsorbent;

[0018] Among them, when the oxidant is a solid, the oxidant is formulated into a solution, which can be a saturated solution or an unsaturated solution, that is, the content of the oxidant in the solution varies between zero and the saturation concentration, preferably a saturated or nearly saturated solution; the mass ratio (mass fraction) of the oxidant to the activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the oxidation temperature is as high as possible under the condition of ensuring that the oxidant solution does not vaporize (i.e., does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the oxidant; the pressure during oxidation can be normal pressure or positive pressure;

[0019] For example, when the oxidant is KMnO4, it is formulated into a saturated aqueous solution of KMnO4, the ratio of potassium permanganate to activated carbon is 1:1, the temperature is 80 °C, and the pressure is 1 atm.

[0020] When the oxidant is a liquid, the mass ratio (mass fraction) of the oxidant to the activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the oxidation temperature is as high as possible under the condition of ensuring that the oxidant solution does not vaporize (i.e., does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the oxidant; the pressure during oxidation can be normal pressure or positive pressure;

[0021] For example, when the oxidant is 60% concentrated nitric acid, the ratio of 60% concentrated nitric acid to activated carbon is 0.5:1, the temperature is 50 °C, and the pressure is 1.5 atm.

[0022] When the oxidant is a gas, the mass ratio (mass fraction) of the oxidant to the activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the oxidation temperature is as high as possible under the condition of ensuring that no violent oxidation reactions such as gasification or combustion occur between the oxidant and the activated carbon; the pressure during oxidation can be positive pressure;

[0023] For example, when the oxidant is O3, the ratio of O3 to activated carbon is 0.1:1, the temperature is 150 °C, and the pressure is 5 atm.

[0024] When the reducing agent is solid, the reducing agent is formulated into a solution, which can be a saturated solution or an unsaturated solution, that is, the content of the reducing agent in the solution varies between zero and the saturation concentration, preferably a saturated or nearly saturated solution; the mass ratio (mass fraction) of the reducing agent to activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the reduction temperature is as high as possible under the condition of ensuring that the reducing agent solution does not vaporize (i.e., does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the reducing agent; the pressure of the reduction reaction can be atmospheric pressure or positive pressure.

[0025] For example, when the reducing agent is NH4HCO3, it is formulated into a saturated aqueous solution of NH4HCO3, the ratio of NH4HCO3 to activated carbon is 1:1, the temperature is 40 °C, and the pressure is 1 atm.

[0026] When the reducing agent is liquid, the mass ratio (mass fraction) of the reducing agent to activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the reduction temperature is as high as possible under the condition of ensuring that the reducing agent solution does not vaporize (i.e., does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the reducing agent; the pressure of the reduction reaction can be atmospheric pressure or positive pressure.

[0027] For example, when the reducing agent is saturated ammonia water, the ratio of ammonia water to activated carbon is 0.5:1, the temperature is 30 °C, and the pressure is 2 atm.

[0028] When the reducing agent is gas, the mass ratio (mass fraction) of the reducing agent to activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the reduction temperature is as high as possible under the condition of ensuring that no physical property changes occur between the reducing agent and activated carbon; the pressure of the reduction reaction is positive pressure.

[0029] For example, when the reducing agent is ammonia gas, the ratio of ammonia gas to activated carbon is 0.1:1, the temperature is 750 °C, and the pressure is 20 atm.

[0030] Among them, the nitrogen-containing functional group is elemental nitrogen (ammonia gas) or nitrogen-containing compound (such as NH3, etc.) that is combined with activated carbon atoms through chemical bonds (chemical loading) or van der Waals forces (physical loading), etc. The content of the functional group is between zero and the saturation loading amount, preferably saturated or close to the saturation loading amount.

[0031] The structural characteristics of the modified activated carbon are as follows: 1) It has an internal structure with a large specific surface area and well-developed internal pores through modification and expansion; 2) The surface is loaded with nitrogen-containing functional groups of nitrogen-containing simple substances or compounds through chemical or physical methods.

[0032] The above-mentioned oxidizing agent is any one or more of HNO3, O3, H2O2, HClO3, KMnO4, H2SO4; the reducing agent is any one or more of nitrogen gas, ammonia gas, ammonia water, ammonium bicarbonate.

[0033] Based on the above method, the present invention further provides an improvement. After the adsorbent adsorbs phosphorus and boron impurities, a desorbent is used to desorb the phosphorus and boron impurities in the adsorbent. The desorbent is a chemical desorbent or a physical desorbent; among them, the chemical desorbent is water or ethanol; the physical desorbent is nitrogen gas or carbon tetrachloride.

[0034] Based on the above method, the present invention further provides an improvement. A cleaning agent is used to clean the adsorbent after removing impurities. The cleaning agent is a physical dissolution cleaning agent or a chemical reaction cleaning agent; among them, the physical dissolution cleaning agent is water or ethanol, and the chemical reaction cleaning agent is an alkaline solution of a substance that can react with the desorbent and phosphorus and boron impurities but does not form precipitation.

[0035] On the other hand, the present invention provides a device for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane for the above method, including: a rectification separation system for removing heavy component impurities and light component impurities in the crude trichlorosilane to obtain a trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove; an activated carbon modification system for shaping conventional activated carbon and preparing a highly active modified activated carbon adsorbent; an adsorption system for using the modified activated carbon adsorbent to remove trace phosphorus and boron impurities from the trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove, including an evaporator and a fluidized bed adsorption device for phosphorus and boron impurities connected in sequence.

[0036] The adsorption system of the present invention is connected to the rectification separation system and the activated carbon modification system for using the modified activated carbon adsorbent to remove trace phosphorus and boron impurities from the trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove.

[0037] Among them, the evaporator is used to evaporate and gasify the trichlorosilane coming from the outlet of the de-lighting tower kettle. The inlet of the evaporator is connected to the outlet of the de-lighting tower kettle, and the outlet of the evaporator is connected to the inlet of the fluidized bed adsorption device for phosphorus and boron impurities.

[0038] Furthermore, the rectification separation system includes a heavy component removal column and a light component removal column connected in sequence. The bottom discharge port of the light component removal column is connected to the evaporator of the adsorption system.

[0039] The heavy component removal column is used to remove impurities with boiling points higher than that of trichlorosilane in the crude trichlorosilane. The feed inlet of the heavy component removal column is connected to the trichlorosilane raw material supply system. The top discharge port of the heavy component removal column is connected to the feed inlet of the light component removal column, and the bottom discharge port of the heavy component removal column is connected to the heavy component treatment system for treating the heavy component removal column.

[0040] The light component removal column is used to remove impurities with boiling points lower than that of trichlorosilane in the crude trichlorosilane. The feed inlet of the light component removal column is connected to the top discharge port of the heavy component removal column. The top discharge port of the light component removal column is connected to the light component treatment system for pre-treating the heavy component removal column, and the bottom discharge port of the light component removal column is connected to the evaporator of the adsorption system.

[0041] Furthermore, the fluidized bed device for adsorbing phosphorus and boron impurities in the present invention is provided with: a fluidized bed device air inlet arranged at the bottom of the fluidized bed device for adsorbing phosphorus and boron impurities, and the fluidized bed device air inlet is connected to the outlet of the evaporator; a fluidized bed device feed inlet arranged in the middle of the fluidized bed device for adsorbing phosphorus and boron impurities and opening upward, and the fluidized bed device feed inlet is used for adding a modified activated carbon adsorbent; a gas-solid separation device of the fluidized bed device for adsorbing phosphorus and boron impurities arranged at the upper part of the fluidized bed device for adsorbing phosphorus and boron impurities, wherein the air inlet of the gas-solid separation device of the fluidized bed device for adsorbing phosphorus and boron impurities is connected above the fluidized bed device for adsorbing phosphorus and boron impurities, the solid discharge port of the gas-solid separation device of the fluidized bed device for adsorbing phosphorus and boron impurities is connected to the middle of the fluidized bed device for adsorbing phosphorus and boron impurities, and the gas outlet of the gas-solid separation device of the fluidized bed device for adsorbing phosphorus and boron impurities faces upward; an adsorbent discharging device arranged in the middle of the fluidized bed device for adsorbing phosphorus and boron impurities and opening downward.

[0042] The fluidized bed device for adsorbing phosphorus and boron impurities is a fluidized bed type device, which can be a bubbling fluidized bed and a boiling fluidized bed, or other types of fluidized beds such as a pneumatic fluidized bed, or a composite fluidized bed combined with other types. A bubbling fluidized bed is preferred.

[0043] As an improvement of the above adsorption system, the adsorption system of the present invention further includes an adsorbent phosphorus and boron impurity desorption device, an adsorbent cleaning device, and an adsorbent drying device connected in sequence; wherein, the adsorbent phosphorus and boron impurity desorption device is provided with: an activated carbon phosphorus and boron impurity desorption device inlet for adsorbent connected to the adsorbent discharging device; an activated carbon phosphorus and boron impurity desorption device inlet for desorbent connected to the residual material outlet of the adsorbent cleaning device; an activated carbon phosphorus and boron impurity desorption device outlet for adsorbent connected to the adsorbent inlet of the adsorbent cleaning device; an activated carbon phosphorus and boron impurity desorption device outlet for residual material connected to the desorbed residual material treatment system; the adsorbent cleaning device is provided with: an adsorbent cleaning device inlet for adsorbent connected to the activated carbon phosphorus and boron impurity desorption device outlet for adsorbent; an adsorbent cleaning device inlet for cleaning agent connected to the cleaning agent supply system; an adsorbent cleaning device outlet for adsorbent connected to the adsorbent inlet of the adsorbent drying device; an adsorbent cleaning device outlet for residual material connected to the cleaning residual material treatment system. The adsorbent drying device is provided with: the adsorbent drying device inlet for adsorbent is connected to the adsorbent cleaning device outlet for adsorbent, and the adsorbent drying device outlet for adsorbent is connected to the feed inlet of the fluidized bed for adsorbing phosphorus and boron impurities and the activated carbon outlet of the activated carbon reduction and modification device.

[0044] The adsorbent phosphorus and boron impurity desorption device is used to remove substances such as adsorbed phosphorus and boron impurities in the deactivated adsorbent. The adsorbent cleaning device is used to wash and remove the desorbed residual material in the decontaminated adsorbent. The adsorbent drying device is used to remove the cleaning residual material in the washed adsorbent.

[0045] Among them, the adsorbent drying device can be an infrared drying device, a vacuum drying device or various other drying devices, and a vacuum drying device is preferred.

[0046] Furthermore, the above activated carbon modification system includes an activated carbon forming device, an activated carbon oxidation modification device, and an activated carbon reduction modification device connected in sequence; the activated carbon oxidation modification device and the activated carbon reduction modification device are kettle-type devices.

[0047] The activated carbon modification system is used to form conventional activated carbon and prepare highly active modified activated carbon.

[0048] Among them, the activated carbon forming device is used to prepare activated carbon into the external shape specifications required for fluidization in the fluidized bed for adsorbing phosphorus and boron impurities. The feed inlet of the activated carbon forming device is connected to the activated carbon supply system, and the discharge outlet of the activated carbon forming device is connected to the activated carbon oxidation modification device.

[0049] The activated carbon oxidation modification equipment is used to oxidize formed activated carbon to increase its specific surface area. The activated carbon inlet of the activated carbon oxidation modification equipment is connected to the discharge port of the activated carbon forming equipment. The oxidant inlet of the activated carbon oxidation modification equipment is connected to the oxidant supply system. The activated carbon outlet of the activated carbon oxidation modification equipment is connected to the activated carbon inlet of the activated carbon reduction modification equipment. The residual oxidant outlet of the activated carbon oxidation modification equipment is connected to the oxidant residue treatment system.

[0050] The outstanding technical effects of the present invention are as follows:

[0051] The present invention combines the rectification technology with the activated carbon adsorption technology using modified activated carbon with a greatly increased activity of activated carbon as the raw material to prepare electronic-grade trichlorosilane with low phosphorus and boron contents, which can deeply remove the phosphorus and boron impurity contents in the electronic-grade trichlorosilane. And because the activated carbon technology is used to deeply remove the phosphorus and boron impurities in the trichlorosilane, and the used activated carbon is modified activated carbon with a relatively large specific surface area, loaded with nitrogen-containing functional groups, high activity, large adsorption affinity, and fast adsorption rate, it can effectively reduce the reflux ratio of the trichlorosilane rectification and greatly reduce the energy consumption in the production of electronic-grade trichlorosilane. Description of the Drawings

[0052] Figure 1 It is a schematic diagram of the device used in the method adopted in Embodiment 1 of the present invention;

[0053] Figure 2 It is the device used in the method adopted in Comparative Example 1;

[0054] Figure 3 It is the device used in the method adopted in Comparative Example 2;

[0055] Reference Signs:

[0056] 1. Rectification separation system; 101. Heavy component removal tower; 101-1. Heavy component removal tower feed port; 101-2. Heavy component removal tower top discharge port; 101-3. Heavy component removal tower bottom discharge port;

[0057] 102. Light component removal tower; 102-1. Light component removal tower feed port; 102-2. Light component removal tower bottom discharge port; 102-3. Light component removal tower top discharge port;

[0058] 2. Adsorption system;

[0059] 201. Evaporator; 201-1. Evaporator feed port; 201-2. Evaporator discharge port; 202. Fluidized bed for adsorbing phosphorus and boron impurities; 202-1. Fluidized bed for adsorbing phosphorus and boron impurities gas inlet; 202-2. Fluidized bed for adsorbing phosphorus and boron impurities feed port; 202-3. Fluidized bed for adsorbing phosphorus and boron impurities gas-solid separation equipment gas outlet; 202-4. Fluidized bed for adsorbing phosphorus and boron impurities discharge equipment discharge port;

[0060] 203. Adsorbent desorption equipment for phosphorus and boron impurities; 203-1. Inlet for adsorbent of activated carbon desorption equipment for phosphorus and boron impurities; 203-2. Inlet for desorbent of activated carbon desorption equipment for phosphorus and boron impurities; 203-3. Outlet for adsorbent of activated carbon desorption equipment for phosphorus and boron impurities; 203-4. Outlet for residual material of activated carbon desorption equipment for phosphorus and boron impurities;

[0061] 204. Adsorbent cleaning equipment; 204-1. Inlet for adsorbent of adsorbent cleaning equipment; 204-2. Inlet for cleaning agent of adsorbent cleaning equipment; 204-3. Outlet for adsorbent of adsorbent cleaning equipment; 204-4. Outlet for residual material of adsorbent cleaning equipment;

[0062] 205. Adsorbent drying equipment; 205-1. Inlet for adsorbent of adsorbent drying equipment; 205-2. Outlet for adsorbent of adsorbent drying equipment;

[0063] 3. Activated carbon modification system;

[0064] 301. Activated carbon forming equipment; 301-1. Feed inlet of activated carbon forming equipment; 301-2. Discharge outlet of activated carbon forming equipment;

[0065] 302. Activated carbon oxidation modification equipment; 302-1. Inlet for activated carbon of activated carbon oxidation modification equipment; 302-2. Inlet for oxidant of activated carbon oxidation modification equipment; 302-3. Outlet for activated carbon of activated carbon oxidation modification equipment; 302-4. Outlet for residual oxidant of activated carbon oxidation modification equipment;

[0066] 303. Activated carbon reduction modification equipment; 303-1. Inlet for activated carbon of activated carbon reduction modification equipment; 303-2. Inlet for reducing agent of activated carbon reduction modification equipment; 303-3. Outlet for activated carbon of activated carbon reduction modification equipment; 303-4. Outlet for residual oxidant of activated carbon reduction modification equipment;

[0067] 1a. Crude trichlorosilane; 1b. Components at the top of the deweighting tower; 1c. Heavy components impurities; 1d. Trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove; 1e. Light components impurities;

[0068] 2a. Trichlorosilane vapor; 2b. Adsorbent raw material; 2c. Low phosphorus and boron electronic grade trichlorosilane; 2d. Deactivated adsorbent; 2e. Desorbent; 2f. Impurity-removing adsorbent; 2g. Desorption residual material; 2h. Cleaning agent; 2i. Cleaning residual material; 2j. Adsorbent after cleaning; 2k. Reactivated adsorbent;

[0069] 3a. Activated carbon raw material; 3b. Formed activated carbon; 3c. Oxidant; 3d. Oxidation-modified activated carbon; 3e. Oxidant residual material; 3f. Reducing agent; 3g. Modified activated carbon; 3h. Reducing agent residual material. Detailed implementation method

[0070] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0071] In view of the problems existing in the prior art, the present invention provides a method for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane, including:

[0072] S1. The crude trichlorosilane 1a is subjected to rectification separation to sequentially remove heavy component impurities 1c and light component impurities 1e, and a trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove is obtained;

[0073] S2. The trichlorosilane product 1d containing trace phosphorus and boron impurities that are difficult to remove is evaporated into trichlorosilane vapor 2a and then introduced into a fluidized bed for adsorbing phosphorus and boron impurities, and is brought into full contact and mixing with a modified activated carbon adsorbent 2b under fluidization, so that the trace phosphorus and boron impurities in the trichlorosilane vapor 2a are fully adsorbed by the modified activated carbon adsorbent and removed, and electronic-grade trichlorosilane 2c with a low content of phosphorus and boron impurities is obtained;

[0074] Among them, the modified activated carbon adsorbent is an activated carbon with a large specific surface area, loaded with nitrogen functional groups, strong polarity and activity, which is prepared by oxidative modification for expansion and reduction modification for loading highly active nitrogen-containing functional groups.

[0075] The preparation method of the modified activated carbon adsorbent is as follows:

[0076] Under a certain temperature and pressure environment, activated carbon with a particle size of 0.1 mm and a specific surface area of 800 m 2 / g is mixed with an oxidant and brought into full contact to undergo an oxidation reaction to adjust the internal structure of the activated carbon, and activated carbon with an oxidative modification with a specific surface area of 1200 m 2 / g is obtained;

[0077] Among them, when the oxidant is a solid, the oxidant is formulated into a solution, and the solution is a saturated solution or an unsaturated solution, that is, the content of the oxidant in the solution varies between zero and the saturation concentration, preferably a saturated or nearly saturated solution; the mass ratio (mass fraction) of the oxidant to the activated carbon is 0.1:1 - 1:1, and can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the oxidation temperature is as high as possible under the condition of ensuring that the oxidant solution does not vaporize (that is, does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the oxidant; the pressure during oxidation can be normal pressure or positive pressure.

[0078] For example, when the oxidant is KMnO4, a saturated aqueous solution of KMnO4 is prepared, and the ratio of potassium permanganate to activated carbon is 1:1, the temperature is 80 °C, and the pressure is 1 atm.

[0079] When the oxidant is a liquid, the mass ratio (mass fraction) of the oxidant to the activated carbon is 0.1:1 - 1:1, and can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the oxidation temperature is as high as possible under the condition of ensuring that the oxidant solution does not vaporize (i.e., does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the oxidant; the pressure during oxidation can be atmospheric pressure or positive pressure.

[0080] For example, when the oxidant is 60% concentrated nitric acid, the ratio of 60% concentrated nitric acid to activated carbon is 0.5:1, the temperature is 50 °C, and the pressure is 1.5 atm.

[0081] When the oxidant is a gas, the mass ratio (mass fraction) of the oxidant to the activated carbon is 0.1:1 - 1:1, and can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the oxidation temperature is as high as possible under the condition of ensuring that no violent oxidation reactions such as gasification or combustion occur between the oxidant and the activated carbon; the pressure during oxidation can be positive pressure.

[0082] For example, when the oxidant is O3, the ratio of O3 to activated carbon is 0.1:1, the temperature is 150 °C, and the pressure is 5 atm.

[0083] In an oxygen-free environment at a certain temperature and pressure, a reaction occurs between the oxidized modified activated carbon and a nitrogen-containing reducing agent, so that nitrogen-containing functional groups are loaded on the surface of the oxidized modified activated carbon, and a modified activated carbon adsorbent is obtained;

[0084] Among them, when the reducing agent is a solid, the reducing agent is prepared into a solution, and the solution is a saturated solution or an unsaturated solution, that is, the content of the reducing agent in the solution varies between zero and the saturation concentration, and a saturated or nearly saturated solution is preferred; the mass ratio (mass fraction) of the reducing agent to the activated carbon is 0.1:1 - 1:1, and can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the reduction temperature is as high as possible under the condition of ensuring that the reducing agent solution does not vaporize (i.e., does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the reducing agent; the pressure of the reduction reaction can be atmospheric pressure or positive pressure.

[0085] For example, when the reducing agent is NH4HCO3, a saturated aqueous solution of NH4HCO3 is prepared, the ratio of NH4HCO3 to activated carbon is 1:1, the temperature is 40 °C, and the pressure is 1 atm.

[0086] When the reducing agent is a liquid, the mass ratio (mass fraction) of the reducing agent to the activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the reduction temperature is as high as possible under the condition of ensuring that the reducing agent solution does not vaporize (i.e., does not exceed the boiling point of the solution) or does not cause property changes such as decomposition of the reducing agent; the pressure of the reduction reaction can be atmospheric pressure or positive pressure.

[0087] For example, when the reducing agent is saturated ammonia water, the ratio of ammonia water to activated carbon is 0.5:1, the temperature is 30 °C, and the pressure is 2 atm.

[0088] When the reducing agent is a gas, the mass ratio (mass fraction) of the reducing agent to the activated carbon is 0.1:1 - 1:1, which can be 0.1:1, 0.2:1, 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, etc.; the reduction temperature is as high as possible under the condition of ensuring that no physical property changes occur between the reducing agent and the activated carbon; the pressure of the reduction reaction is positive pressure.

[0089] For example, when the reducing agent is ammonia gas, the ratio of ammonia gas to activated carbon is 0.1:1, the temperature is 750 °C, and the pressure is 20 atm.

[0090] In the embodiments of the present invention, the oxidizing agent used in the above steps is any one or more of HNO3, O3, H2O2, HClO3, KMnO4, H2SO4; the reducing agent is nitrogen, ammonia, ammonia water, ammonium bicarbonate.

[0091] In the embodiments of the present invention, after the adsorbent adsorbs phosphorus and boron impurities, a desorbent is used to desorb the phosphorus and boron impurities in the adsorbent, and the desorbent is a chemical desorbent or a physical desorbent; wherein the chemical desorbent is water or ethanol; the physical desorbent is nitrogen or carbon tetrachloride.

[0092] In the embodiments of the present invention, the adsorbent after impurity removal is washed with a cleaning agent, and the cleaning agent is a physical dissolution cleaning agent or a chemical reaction cleaning agent; wherein the physical dissolution cleaning agent is water or ethanol, and the chemical reaction cleaning agent is an alkaline solution of a substance that can react with the desorbent and phosphorus and boron impurities but does not form a precipitate.

[0093] In the embodiments of the present invention, after the washing of the adsorbent after impurity removal is completed, drying is carried out, and the drying can be drying by infrared heating, or various drying methods such as vacuum drying, and vacuum drying is preferred.

[0094] The present invention also provides an apparatus for the above method. The apparatus for preparing electronic-grade trichlorosilane by deeply removing trace phosphorus and boron impurities provided by the present invention includes: a rectification separation system 1 for removing heavy component impurities 1c and light component impurities 1e in the crude trichlorosilane to obtain a trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove; an activated carbon modification system 3 for shaping conventional activated carbon and preparing a highly active modified activated carbon adsorbent; and an adsorption system 2 for removing trace phosphorus and boron impurities from the trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove, including an evaporator 201 and a fluidized bed for adsorbing phosphorus and boron impurities device 202 connected in sequence.

[0095] Among them, the rectification separation system 1 includes a de-heavy tower 101 and a de-light tower 102 connected in sequence, and the bottom discharge port of the de-light tower 102 is connected to the evaporator 201 of the adsorption system 2.

[0096] In the embodiment of the present invention, the fluidized bed for adsorbing phosphorus and boron impurities device 202 is provided with: a fluidized bed for adsorbing phosphorus and boron impurities device air inlet 202-1 arranged at the bottom of the fluidized bed for adsorbing phosphorus and boron impurities device 202, and the fluidized bed for adsorbing phosphorus and boron impurities device air inlet 202-1 is connected to the outlet of the evaporator 201; a fluidized bed for adsorbing phosphorus and boron impurities device feed port 202-2 arranged in the middle of the fluidized bed for adsorbing phosphorus and boron impurities device 202 and opening upward, and the fluidized bed for adsorbing phosphorus and boron impurities device feed port 202-2 is used to add the modified activated carbon adsorbent; a fluidized bed for adsorbing phosphorus and boron impurities device gas-solid separation device 202-3 arranged at the upper part of the fluidized bed for adsorbing phosphorus and boron impurities device 202, wherein the air inlet of the fluidized bed for adsorbing phosphorus and boron impurities device gas-solid separation device 202-3 is connected above the fluidized bed for adsorbing phosphorus and boron impurities device 202, the solid discharge port of the fluidized bed for adsorbing phosphorus and boron impurities device gas-solid separation device 202-3 is connected to the middle of the fluidized bed for adsorbing phosphorus and boron impurities device 202, and the gas outlet of the fluidized bed for adsorbing phosphorus and boron impurities device gas-solid separation device 202-3 faces upward; and an adsorbent discharge device 202-4 arranged in the middle of the fluidized bed for adsorbing phosphorus and boron impurities device 202 and opening downward.

[0097] In the embodiment of the present invention, the adsorption system 2 further includes an adsorbent desorption phosphorus and boron impurity device 203, an adsorbent cleaning device 204, and an adsorbent drying device 205 that are connected in sequence; wherein, the adsorbent desorption phosphorus and boron impurity device 203 is provided with: an activated carbon desorption phosphorus and boron impurity device inlet for adsorbent 203-1 connected to the adsorbent discharging device 202-4; an activated carbon desorption phosphorus and boron impurity device inlet for desorbent 203-2 connected to the residual material outlet 204-4 of the adsorbent cleaning device; an activated carbon desorption phosphorus and boron impurity device outlet for adsorbent 203-3 connected to the adsorbent inlet 204-1 of the adsorbent cleaning device; an activated carbon desorption phosphorus and boron impurity device outlet for residual material 203-4 connected to the desorbed residual material treatment system; the adsorbent cleaning device 204 is provided with: an adsorbent cleaning device inlet for adsorbent 204-1 connected to the activated carbon desorption phosphorus and boron impurity device outlet for adsorbent 203-3; an adsorbent cleaning device inlet for cleaning agent 204-2 connected to the cleaning agent supply system; an adsorbent cleaning device outlet for adsorbent 204-3 connected to the adsorbent inlet 205-1 of the adsorbent drying device; an adsorbent cleaning device outlet for residual material 204-4 connected to the cleaning residual material treatment system; the adsorbent drying device 205 is provided with: the adsorbent drying device inlet for adsorbent 205-1 is connected to the adsorbent cleaning device outlet for adsorbent 204-3, and an adsorbent drying device outlet for adsorbent 205-2 connected to the fluidized bed adsorption phosphorus and boron impurity device inlet 202-2 and the activated carbon reduction and modification device outlet for activated carbon 303-3.

[0098] In the embodiment of the present invention, the activated carbon modification system 3 includes an activated carbon forming device 301, an activated carbon oxidation modification device 302, and an activated carbon reduction modification device 303 that are connected in sequence; wherein the activated carbon oxidation modification device 302 and the activated carbon reduction modification device 303 are kettle-type devices.

[0099] Next, the technical solutions and effects of the present invention will be described in combination with specific examples and comparative examples.

[0100] Example 1

[0101] As Figure 1 , this example will be described in detail for the preparation of electronic-grade trichlorosilane by using the combined technology of rectification and modified adsorption.

[0102] Specifically as follows:

[0103] The crude trichlorosilane product 1a with a content of 99.9% is added into the deweighting tower 101 through the deweighting tower feed inlet 101-1, and heat and mass transfer between gas and liquid are carried out for separation. The components with a boiling point higher than that of trichlorosilane are gradually separated out and enter the bottom of the deweighting tower kettle. Adjust the reflux ratio R H= 22, the heavy components 1c including phosphorus impurities such as phosphorus trichloride are separated and removed from the crude trichlorosilane 1a, and the trichlorosilane product from which the heavy component impurities are removed is discharged from the top of the heavy component removal tower 101 in the form of the light components 1b of the heavy component removal tower.

[0104] The light components 1b of the heavy component removal tower mainly composed of trichlorosilane discharged from the top of the heavy component removal tower 101 enter the light component removal tower 102 through the light component removal tower feed port 102-1, and heat and mass transfer between gas and liquid occur and separation is carried out. The components with boiling points lower than that of trichlorosilane are gradually separated, exit and enter the top of the light component removal tower, and the reflux ratio R is adjusted L = 26, the light components 1e including boron impurities such as boron trichloride are separated and removed from the crude trichlorosilane 1b, and the trichlorosilane product 1d from which the impurities are removed is discharged from the bottom of the light component removal tower kettle in the form of the heavy components of the light component removal tower.

[0105] After rectification separation, the yield of the prepared trichlorosilane product 1d is 99.86%, the content of trichlorosilane in the product is 5.5N, and the content of phosphorus and boron impurities is 3 ppm.

[0106] The trichlorosilane product 1d containing trace phosphorus and boron impurities that are difficult to remove, discharged in the form of the heavy components 1d of the light component removal tower, enters the adsorption system 2 through the evaporator feed port 201-1 for in-depth treatment to further remove phosphorus and boron impurities. It is first heated into trichlorosilane vapor 2a by the evaporator 201, and then enters the fluidized bed phosphorus and boron impurity adsorption device 202 through the air inlet at the bottom of the fluidized bed phosphorus and boron impurity adsorption device 202, and is in full contact and mixing with the adsorbent 2b with a diameter of 1.0 mm added through the fluidized bed phosphorus and boron impurity adsorption device feed port 202-2 under fluidization. The adsorbent is continuously supplemented, and the supplementary amount of the adsorbent is 5% of the amount of the adsorbent used (normally, during the use of the adsorbent, due to reasons such as abrasion and material carrying, a certain amount of the adsorbent will be lost. After the adsorbent is lost, a certain amount of new adsorbent needs to be supplemented). The trace phosphorus and boron impurities in the trichlorosilane vapor 2a are fully adsorbed by the adsorbent and removed, so as to obtain electronic-grade trichlorosilane 2c with a low content of phosphorus and boron impurities, and after gas-solid separation through the gas-solid separation device outlet 202-3 of the fluidized bed phosphorus and boron impurity adsorption device, it is discharged, so as to obtain an electronic-grade trichlorosilane product with a low phosphorus and boron content. This product is sent to the storage electronic-grade trichlorosilane system for centralized treatment; the inactivated adsorbent 2d that has adsorbed a sufficient amount of phosphorus and boron impurities and lost its activity is discharged from the discharge device outlet 202-4 of the fluidized bed phosphorus and boron impurity adsorption device.

[0107] The deactivated adsorbent 2d discharged from the discharge port 202-4 of the discharging equipment of the fluidized bed adsorbent for phosphorus and boron impurities enters the activated carbon desorption equipment for phosphorus and boron impurities 203 and is fully mixed with the desorbent from the desorbent supply system. Among them, chemical desorption is adopted for desorption, and the desorbent is a 2% sodium hydroxide aqueous solution. The phosphorus and boron impurities react with the desorbent to form a mixed brine solution composed of sodium phosphate, sodium chloride, and sodium borate. The desorbent is used to remove substances such as phosphorus and boron impurities adsorbed in the deactivated adsorbent to obtain the desorbed adsorbent 2f, which is discharged from the activated carbon desorption equipment for phosphorus and boron impurities 203. The mixed brine solution formed by the reaction of the residual desorbent and phosphorus and boron impurities after use is discharged as desorption residue 2g, and the discharged desorption residue 2g is sent to the desorption residue treatment system for centralized treatment.

[0108] The desorbed adsorbent 2f discharged from the activated carbon desorption equipment for phosphorus and boron impurities 203 enters the adsorbent cleaning equipment 204 and is cleaned with the cleaning agent 2h. Among them, the cleaning agent is selected for physical cleaning, and the cleaning agent used is water. The residual desorption liquid in the desorbed adsorbent is washed away, so as to obtain the cleaned adsorbent 2j, which is discharged from the adsorbent cleaning equipment 204, and the cleaned cleaning residue liquid 2i is also discharged from the adsorbent cleaning equipment 204.

[0109] The cleaning residue liquid 2i discharged from the adsorbent cleaning equipment 204 is sent to the activated carbon desorption equipment for phosphorus and boron impurities 203 for reuse.

[0110] The cleaned adsorbent 2j discharged from the adsorbent cleaning equipment 204 enters the adsorbent drying equipment 205 for drying, and the residual substances in the cleaned adsorbent 2j are fully removed, so as to obtain the regenerated adsorbent 2k, which is recycled as a fresh adsorbent.

[0111] When the adsorbent is modified activated carbon and is insufficient due to damage during use, fresh modified activated carbon 3g is prepared and provided through the modified activated carbon preparation system 3. The modified activated carbon is mainly modified by oxidation to increase the specific surface area of the activated carbon and by reduction to increase the active components of nitrogen-containing functional groups on the surface of the activated carbon. The specific methods are as follows:

[0112] Activated carbon raw material 3a without nitrogen-containing elemental active functional groups with a particle size of 0.1 mm and a specific surface area of 800 m 2 / g is provided from the activated carbon supply system to the forming equipment 301 of the activated carbon modification system 3, and it is processed into formed activated carbon 3b with a particle size of 0.1 mm and a specific surface area of 800 m 2 / g without nitrogen-containing elemental active functional groups.

[0113] The shaped activated carbon 3b is added into the activated carbon oxidation modification device 302 and mixed with the oxidant 3c hydrogen peroxide and brought into full contact to undergo an oxidation reaction, adjusting the internal structure of the activated carbon. The mass ratio of the activated carbon to hydrogen peroxide is 1:0.2. The reaction temperature is controlled at 50°C, the pressure is 1 atm, and the reaction time is 2 h, thus turning into the oxidized modified activated carbon 3d with a specific surface area of 1200 m 2 / g, which is discharged from the activated carbon oxidation modification device 302. The residual oxidant liquid after the reaction is discharged from the activated carbon oxidation modification device 302 and sent to the centralized treatment system for residual oxidant for treatment.

[0114] The oxidized modified activated carbon 3d discharged from the activated carbon oxidation modification device 302 is added into the activated carbon reduction modification device 303 and reacts with the nitrogen-containing reducing agent 3f ammonia gas to load nitrogen-containing functional groups on the surface of the oxidized modified activated carbon 3d. The mass ratio of the oxidized modified activated carbon 3d to ammonia gas is 1:0.1. The reaction temperature is controlled at 750°C, the pressure is 20 atm, and the reaction time is 1.5 h, thus preparing the modified activated carbon 3g rich in nitrogen-containing functional group active components, which is discharged from the activated carbon reduction modification device 303. The residual reducing agent after the reaction is also discharged from the activated carbon reduction modification device 303 and sent to the centralized treatment system for residual oxidant for treatment.

[0115] The modified activated carbon 3g discharged from the activated carbon reduction modification device 303 is added into the fluidized bed adsorption device 202 for phosphorus and boron impurities as a fresh raw material for the adsorbent.

[0116] After rectification separation and adsorption by the modified activated carbon, the yield of the trichlorosilane product 1d obtained is 99.9%. The content of trichlorosilane in the product is 9N, and the content of phosphorus and boron impurities is 100 ppb.

[0117] Example 2

[0118] The difference between this example and Example 1 is only that the oxidant, reducing agent, oxidation reaction conditions, and reduction reaction conditions used in the activated carbon modification process are different. The activated carbon modification process is as follows:

[0119] The activated carbon raw material 3a with a particle size of 0.1 mm, a specific surface area of 800 m 2 / g and no nitrogen-containing active functional groups is provided from the activated carbon supply system to the forming device 301 of the activated carbon modification system 3, and it is processed into the shaped activated carbon 3b with a particle size of 0.1 mm, a specific surface area of 800 m 2 / g and no nitrogen-containing active functional groups.

[0120] The formed activated carbon 3b is added into the activated carbon oxidation modification device 302 and mixed with the oxidant 3c saturated KMnO4 aqueous solution and brought into full contact to undergo an oxidation reaction. The mass ratio of the activated carbon to the saturated KMnO4 aqueous solution is = 1:1. The internal structure of the activated carbon is adjusted, the reaction temperature is controlled at 80 °C, the pressure is 1 atm, and the reaction time is 2 h, thus becoming the oxidized modified activated carbon 3d with 1200 m 2 / g and discharged from the activated carbon oxidation modification device 302. The residual oxidant liquid after the reaction is discharged from the activated carbon oxidation modification device 302 and sent to the oxidant residue centralized treatment system for treatment.

[0121] The oxidized modified activated carbon 3d discharged from the activated carbon oxidation modification device 302 is added into the activated carbon reduction modification device 303 and reacts with the nitrogen-containing reducing agent 3f saturated NH4HCO3 aqueous solution, and nitrogen-containing functional groups are loaded on the surface of the oxidized modified activated carbon 3d. The mass ratio of the oxidized modified activated carbon 3d to the NH4HCO3 aqueous solution is = 1:1. The reaction temperature is controlled at 40 °C, the pressure is 1 atm, and the reaction time is 1.5 h, thus preparing the modified activated carbon 3g rich in nitrogen-containing functional group active components and discharging it from the activated carbon reduction modification device 303. The residual reducing agent after the reaction is also discharged from the activated carbon reduction modification device 303 and sent to the oxidant residue centralized treatment system for treatment.

[0122] The modified activated carbon 3g discharged from the activated carbon reduction modification device 303 is added into the fluidized bed adsorption phosphorus and boron impurity device 202 and used as the fresh raw material of the adsorbent.

[0123] The yield of the trichlorosilane product 1d finally obtained in this example is 99.9%, the content of trichlorosilane in the product is 9N, and the content of phosphorus and boron impurities is 100 ppb.

[0124] Example 3

[0125] The difference between this example and Example 1 is only that the oxidant, reducing agent, oxidation reaction conditions, and reduction reaction conditions used in the activated carbon modification process are different. The activated carbon modification process is as follows:

[0126] The activated carbon raw material 3a with a particle size of 0.1 mm, a specific surface area of 800 m 2 / g and no nitrogen-containing active functional groups is provided from the activated carbon supply system to the forming device 301 of the activated carbon modification system 3 and processed into the formed activated carbon 3b with a particle size of 0.1 mm, a specific surface area of 800 m 2 / g and no nitrogen-containing active functional groups.

[0127] The formed activated carbon 3b is added into the activated carbon oxidation modification equipment 302 and mixed with the oxidant 3c saturated KMnO4 aqueous solution and comes into full contact to undergo an oxidation reaction. The mass ratio of the activated carbon to the 60% concentrated nitric acid solution is = 1:0.5. The internal structure of the activated carbon is adjusted. The reaction temperature is controlled at 50 °C, the pressure is 1.5 atm, and the reaction time is 2 h, thus turning it into the oxidized modified activated carbon 3d with a specific surface area of 1200 m 2 / g, which is discharged from the activated carbon oxidation modification equipment 302. The residual oxidant liquid after the reaction is discharged from the activated carbon oxidation modification equipment 302 and sent to the centralized treatment system for residual oxidant for treatment.

[0128] The oxidized modified activated carbon 3d discharged from the activated carbon oxidation modification equipment 302 is added into the activated carbon reduction modification equipment 303 and reacts with the nitrogen-containing reducing agent 3f ammonia water, and nitrogen-containing functional groups are loaded on the surface of the oxidized modified activated carbon 3d. The mass ratio of the oxidized modified activated carbon 3d to the ammonia water is = 1:0.5. The reaction temperature is controlled at 30 °C, the pressure is 2 atm, and the reaction time is 1.5 h, thus preparing the modified activated carbon 3g rich in nitrogen-containing functional group active components, which is discharged from the activated carbon reduction modification equipment 303. The residual reducing agent after the reaction is also discharged from the activated carbon reduction modification equipment 303 and sent to the centralized treatment system for residual oxidant for treatment.

[0129] The modified activated carbon 3g discharged from the activated carbon reduction modification equipment 303 is added into the fluidized bed adsorption phosphorus and boron impurity device 202 and used as the fresh raw material of the adsorbent.

[0130] The yield of the trichlorosilane product 1d finally obtained in this example is 99.9%, the content of trichlorosilane in the product is 9N, and the content of phosphorus and boron impurities is 100 ppb.

[0131] Example 4

[0132] The difference between this example and Example 1 is only that the oxidant, reducing agent, oxidation reaction conditions and reduction reaction conditions used in the activated carbon modification process are different. The activated carbon modification process is as follows:

[0133] The activated carbon raw material 3a with a particle size of 0.1 mm, a specific surface area of 800 m 2 / g and no nitrogen-containing active functional groups is provided from the activated carbon supply system to the forming equipment 301 of the activated carbon modification system 3, and it is processed into the formed activated carbon 3b with a particle size of 0.1 mm, a specific surface area of 800 m 2 / g and no nitrogen-containing active functional groups.

[0134] The formed activated carbon 3b is added into the activated carbon oxidation modification device 302 and mixed with the oxidant 3c O3 to make full contact, and an oxidation reaction occurs. The mass ratio of the activated carbon to O3 is 1:0.1 to adjust the internal structure of the activated carbon. The reaction temperature is controlled at 150 °C, the pressure is 5 atm, and the reaction time is 2 h, thus becoming the oxidized modified activated carbon 3d with 1200 m 2 / g and discharged from the activated carbon oxidation modification device 302. The residual oxidant liquid after the reaction is discharged from the activated carbon oxidation modification device 302 and sent to the centralized treatment system for residual oxidant for treatment.

[0135] The oxidized modified activated carbon 3d discharged from the activated carbon oxidation modification device 302 is added into the activated carbon reduction modification device 303 and reacts with the nitrogen-containing reducing agent 3f ammonia water, and nitrogen-containing functional groups are loaded on the surface of the oxidized modified activated carbon 3d. The mass ratio of the oxidized modified activated carbon 3d to the ammonia water is 1:0.5. The reaction temperature is controlled at 30 °C, the pressure is 2 atm, and the reaction time is 1.5 h, thus preparing the modified activated carbon 3g rich in nitrogen-containing functional group active components and discharging it from the activated carbon reduction modification device 303. The residual reducing agent after the reaction is also discharged from the activated carbon reduction modification device 303 and sent to the centralized treatment system for residual oxidant for treatment.

[0136] The modified activated carbon 3g discharged from the activated carbon reduction modification device 303 is added into the fluidized bed adsorption phosphorus and boron impurity device 202 and used as the fresh raw material of the adsorbent.

[0137] The yield of the trichlorosilane product 1d finally obtained in this example is 99.9%, the content of trichlorosilane in the product is 9N, and the content of phosphorus and boron impurities is 100 ppb.

[0138] Comparative Example 1

[0139] As Figure 2 , this comparative example uses the technology combining rectification and adsorption to prepare electronic-grade trichlorosilane and is described in detail. Among them, the adsorbent is conventional activated carbon, as follows.

[0140] The trichlorosilane crude product 1a with a content of 99.9% is added into the deweighting tower 101 through the deweighting tower feed port 101-1 and undergoes heat and mass transfer between gas and liquid and separation. The components with a boiling point higher than that of trichlorosilane are gradually separated out and enter the bottom of the deweighting tower kettle. The reflux ratio R H = 25, and the heavy components 1c including most of the phosphorus impurities such as phosphorus trichloride are removed from the trichlorosilane crude product 1a, and the trichlorosilane product from which the heavy component impurities are removed is discharged from the top of the deweighting tower 101 in the form of the deweighting tower light component 1b.

[0141] The light components 1b of the de - heavy tower mainly composed of trichlorosilane discharged from the top of the de - heavy tower 101 enter the de - light tower 102 through the de - light tower feed port 102 - 1, where heat and mass transfer occur between gas and liquid and separation is carried out. Components with a boiling point lower than that of trichlorosilane are gradually separated and enter the top of the de - light tower. The reflux ratio R L is adjusted to 30. The light components 1e including most of the boron impurities such as boron trichloride are removed from the crude trichlorosilane 1b, and the trichlorosilane product 1d with impurities removed is discharged from the bottom of the de - light tower as the heavy components of the de - light tower.

[0142] After rectification separation, the yield of the prepared trichlorosilane product 1d is 99.85%. The content of trichlorosilane in the product is 6N, and the content of phosphorus and boron impurities is 2 ppm.

[0143] The trichlorosilane product 1d containing trace phosphorus and boron impurities that are difficult to remove, discharged in the form of the heavy components 1d of the de - light tower, enters the adsorption system 2 through the evaporator feed port 201 - 1 for in - depth treatment to further remove phosphorus and boron impurities. It is first heated by the evaporator 201 into trichlorosilane vapor 2a, and then enters the fluidized bed phosphorus - boron impurity adsorption device 202 through the fluidized bed phosphorus - boron impurity adsorption device inlet 202 - 1 at the bottom of the fluidized bed phosphorus - boron impurity adsorption device, and is fully contacted and mixed with the ordinary activated carbon adsorbent 2b with a diameter of 0.1 mm and a specific surface area of 800 m 2 / g added through the fluidized bed phosphorus - boron impurity adsorption device feed port 202 - 2 under fluidization. The trace phosphorus and boron impurities in the trichlorosilane vapor 2a are fully adsorbed by the adsorbent and removed, so as to obtain electronic - grade trichlorosilane 2c with a low content of phosphorus and boron impurities, which is discharged after gas - solid separation through the gas - solid separation equipment outlet 202 - 3 of the fluidized bed phosphorus - boron impurity adsorption device, thus obtaining an electronic - grade trichlorosilane product with a low phosphorus and boron content. This product is sent to the electronic - grade trichlorosilane storage system for centralized treatment; the inactivated adsorbent 2d that has adsorbed sufficient phosphorus and boron impurities and lost its activity is discharged from the discharge port 202 - 4 of the discharging equipment of the fluidized bed phosphorus - boron impurity adsorption device.

[0144] The inactivated adsorbent 2d discharged from the discharge port 202 - 4 of the discharging equipment of the fluidized bed phosphorus - boron impurity adsorption device enters the activated carbon phosphorus - boron impurity desorption equipment 203 and is fully mixed with the desorbent coming from the desorbent supply system. Among them, chemical desorption is used for desorption, and the desorbent is a 2% sodium hydroxide aqueous solution. The phosphorus and boron impurities react with the desorbent to form a mixed brine solution composed of sodium phosphate, sodium chloride, and sodium borate. The desorbent is used to remove the adsorbed phosphorus and boron impurities and other substances in the inactivated adsorbent to obtain the desorbed adsorbent 2f, which is discharged from the activated carbon phosphorus - boron impurity desorption equipment 203. The mixed brine solution formed by the reaction of the remaining desorbent after use and the phosphorus and boron impurities is discharged as desorption residue 2g, and the discharged desorption residue 2g is sent to the desorption residue treatment system for centralized treatment.

[0145] The impurity-removed adsorbent 2f discharged from the activated carbon phosphorus and boron impurity desorption device 203 enters the adsorbent cleaning device 204 and is cleaned with the cleaning agent 2h. Among them, the cleaning agent uses a physical method for cleaning, and the cleaning agent used is water. The desorption residual liquid remaining in the impurity-removed adsorbent is washed away, so as to obtain the cleaned adsorbent 2j and discharge it from the adsorbent cleaning device 204. The cleaned cleaning residual liquid 2i is also discharged from the adsorbent cleaning device 204.

[0146] The cleaning residual liquid 2i discharged from the adsorbent cleaning device 204 is sent to the activated carbon phosphorus and boron impurity desorption device 203 for reuse.

[0147] The cleaned adsorbent 2j discharged from the adsorbent cleaning device 204 enters the adsorbent drying device 205 for drying, and the residual substances in the cleaned adsorbent 2j are fully removed, so as to obtain the regenerated adsorbent 2k, which is recycled as a fresh adsorbent.

[0148] When the adsorbent is damaged and insufficient during use, fresh activated carbon 3a is added to supplement it.

[0149] After rectification separation and activated carbon adsorption, the yield of the trichlorosilane product 1d prepared is 99.9%, the content of trichlorosilane in the product is 9N, and the content of phosphorus and boron impurities is 500 ppb.

[0150] Comparative Example 2

[0151] Such as Figure 3 , the trichlorosilane crude product 1a with a content of 99.9% is added into the deweighting tower 101 through the deweighting tower feed port 101-1 and undergoes heat and mass transfer between gas and liquid and is separated. The components with a boiling point higher than that of trichlorosilane are gradually separated out and enter the bottom of the deweighting tower kettle. Adjust the reflux ratio R H = 30, the heavy components 1c including phosphorus impurities such as phosphorus trichloride are separated from the trichlorosilane crude product 1a, and the trichlorosilane product after removing the heavy component impurities is discharged from the top of the deweighting tower 101 in the form of the deweighting tower light component 1b.

[0152] The deweighting tower light component 1b mainly composed of trichlorosilane discharged from the top of the deweighting tower 101 enters the de-lighting tower 102 through the de-lighting tower feed port 102-1 and undergoes heat and mass transfer between gas and liquid and is separated. The components with a boiling point lower than that of trichlorosilane are gradually separated out and enter the top of the de-lighting tower. Adjust the reflux ratio R L = 35, the light components 1e including boron impurities such as boron trichloride are separated from the trichlorosilane crude product 1b, and the trichlorosilane product 1d after removing the impurities is discharged from the bottom of the de-lighting tower kettle in the form of the de-lighting tower heavy component, and the electronic-grade trichlorosilane product is obtained.

[0153] The yield of the prepared electronic-grade trichlorosilane product is 99.8%, the content of trichlorosilane in the product is 9N, and the content of phosphorus and boron impurities is 1 ppm.

[0154] From the above Examples 1, Comparative Example 1, and Comparative Example 2, it can be seen that:

[0155] Compared with Comparative Example 2, through the technology of combining rectification and activated carbon adsorption with conventional activated carbon as the adsorbent used in Comparative Example 1, an electronic-grade trichlorosilane product with phosphorus and boron impurities of 500 ppb can be prepared. The content of phosphorus and boron impurities is greatly reduced, and the reflux ratios R H and R L are respectively reduced from 30 and 35 to 25 and 30. Since the content of the materials processed in the de-light tower, de-heavy tower, and evaporator is all materials with a trichlorosilane content of more than 99.9%, their evaporation enthalpies should be basically the same. Therefore, the energy consumed for one reflux in the de-heavy tower and de-light tower is basically the same, and the energy consumed by the material during the evaporation of trichlorosilane is calculated based on one evaporation treatment. Then, the energy consumed by the material during evaporation in the evaporator is equivalent to the energy consumed by one reflux during rectification. Without considering other energy consumptions, compared with the rectification technology, when using the technology of combining rectification and activated carbon adsorption to prepare electronic-grade trichlorosilane, its energy consumption is reduced by about 14%.

[0156] Compared with Comparative Example 1, through the technology of combining rectification and activated carbon adsorption with modified activated carbon as the adsorbent used in Example 1, an electronic-grade trichlorosilane product with phosphorus and boron impurities of 100 ppb can be prepared. Its content of phosphorus and boron impurities is lower, the removal degree is deeper, and the removal effect is better; and the reflux ratios R H and R L are respectively reduced from 30 and 35 to 22 and 26. Compared with Example 1, its energy consumption is reduced by about 24%.

[0157] Finally, it should be noted that:

[0158] The above examples are only used to illustrate the technical solutions of the present invention, not to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane, characterized in that, Including: S1. Rectify and separate the crude trichlorosilane (1a) to successively remove heavy component impurities (1c) and light component impurities (1e), obtaining a trichlorosilane product containing trace amounts of phosphorus and boron impurities that are difficult to remove. S2. Evaporate the trichlorosilane product (1d) containing trace amounts of phosphorus and boron impurities that are difficult to remove into trichlorosilane vapor (2a), then introduce it into a fluidized bed for adsorbing phosphorus and boron impurities, and fully contact and mix it with a modified activated carbon adsorbent (2b) under fluidization conditions, so that the trace amounts of phosphorus and boron impurities in the trichlorosilane vapor (2a) are fully adsorbed by the modified activated carbon adsorbent and removed, obtaining electronic-grade trichlorosilane (2c) with a low content of phosphorus and boron impurities. Among them, the modified activated carbon adsorbent is an activated carbon with a large specific surface area, loaded with nitrogen functional groups, having strong polarity and activity, which is prepared by oxidative modification for expansion and reduction modification for loading highly active nitrogen-containing functional groups. The preparation method of the adsorbent is as follows: Under a certain temperature and pressure environment, activated carbon particles with a particle size of 0.1 mm and a specific surface area of 800 m 2 / g are mixed with an oxidant in a certain proportion and brought into full contact to undergo an oxidation reaction, adjusting the internal structure of the activated carbon to obtain oxidized modified activated carbon with a specific surface area of 1200 m 2 / g; Under an anaerobic environment at a certain temperature and pressure, mix the oxidized activated carbon with a nitrogen-containing reducing agent in a certain proportion and carry out a reduction reaction, so that nitrogen-containing functional groups are loaded on the surface of the oxidized activated carbon, obtaining the modified activated carbon adsorbent. Among them, when the oxidant is a solid, the oxidant is formulated into a solution, which is a saturated solution or an unsaturated solution. The mass ratio of the oxidant to the activated carbon is 0.1:1 - 1:

1. The oxidation temperature is the temperature that ensures that the oxidant solution does not vaporize or the oxidant does not decompose. The pressure during oxidation is normal pressure or positive pressure. When the oxidant is a liquid, the mass ratio of the oxidant to the activated carbon is 0.1:1 - 1:

1. The oxidation temperature is the temperature that ensures that the oxidant solution does not vaporize or the oxidant does not decompose. The pressure during oxidation is normal pressure or positive pressure. When the oxidant is a gas, the mass ratio of the oxidant to the activated carbon is 0.1:1 - 1:

1. The oxidation temperature is the temperature that ensures that the oxidant and the activated carbon do not vaporize or burn. The pressure during oxidation is positive pressure. When the reducing agent is a solid, the reducing agent is formulated into a solution, which is a saturated solution or an unsaturated solution. The mass ratio of the reducing agent to the activated carbon is 0.1:1 - 1:

1. The reduction temperature is the temperature that ensures that the reducing agent solution does not vaporize or the reducing agent does not decompose. The pressure of the reduction reaction is normal pressure or positive pressure. When the reducing agent is a liquid, the mass ratio of the reducing agent to the activated carbon is 0.1:1 - 1:

1. The reduction temperature is the temperature that ensures that the reducing agent solution does not vaporize or the reducing agent does not decompose. The pressure of the reduction reaction is normal pressure or positive pressure. When the reducing agent is a gas, the mass ratio of the reducing agent to the activated carbon is 0.1:1 - 1:

1. The reduction temperature is the temperature that ensures that the reducing agent and the activated carbon do not undergo physical property changes. The pressure of the reduction reaction is positive pressure. Among them, the nitrogen-containing functional group is elemental nitrogen or a nitrogen-containing compound that is combined with activated carbon atoms through chemical bonds or van der Waals forces, and the content of the functional group is between zero and the saturated loading amount.

2. The method according to claim 1, characterized in that, The oxidant is any one or more of HNO3, O3, H2O2, HClO3, KMnO4, H2SO4. The reducing agent is any one or more of nitrogen, ammonia, ammonia water, ammonium bicarbonate.

3. The method according to claim 1 or 2, characterized in that, After the adsorbent adsorbs phosphorus and boron impurities, a desorbent is used to desorb the phosphorus and boron impurities in the adsorbent. The desorbent is a chemical desorbent or a physical desorbent; Among them, the chemical desorbent is water or ethanol; the physical desorbent is nitrogen or carbon tetrachloride.

4. The method according to claim 3, wherein The adsorbent after impurity removal is cleaned with a cleaning agent. The cleaning agent is a physical dissolution cleaning agent or a chemical reaction cleaning agent; Among them, the physical dissolution cleaning agent is water or ethanol, and the chemical reaction cleaning agent is an alkaline solution of a substance that can react with the desorbent and phosphorus and boron impurities but does not form precipitation.

5. An apparatus for deeply removing trace phosphorus and boron impurities to prepare electronic-grade trichlorosilane, which is used in the method according to any one of claims 1 to 4, and is characterized in that Including: A rectification separation system (1) for removing heavy component impurities (1c) and light component impurities (1e) from the crude trichlorosilane to obtain a trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove, An activated carbon modification system (3) for shaping conventional activated carbon and preparing a highly active modified activated carbon adsorbent; An adsorption system (2) for removing trace phosphorus and boron impurities from the trichlorosilane product containing trace phosphorus and boron impurities that are difficult to remove by using the modified activated carbon adsorbent, including: An evaporator (201) and a fluidized bed for adsorbing phosphorus and boron impurities (202) connected in sequence; The adsorption system (2) further includes an adsorbent desorbing phosphorus and boron impurity device (203), an adsorbent cleaning device (204), and an adsorbent drying device (205) connected in sequence; Among them, on the adsorbent desorbing phosphorus and boron impurity device (203), there are provided: an inlet for the adsorbent of the activated carbon desorbing phosphorus and boron impurity device (203-1) connected to the adsorbent discharging device (202-4); an inlet for the desorbent of the activated carbon desorbing phosphorus and boron impurity device (203-2) connected to the residual material outlet (204-4) of the adsorbent cleaning device; an outlet for the adsorbent of the activated carbon desorbing phosphorus and boron impurity device (203-3) connected to the inlet for the adsorbent of the adsorbent cleaning device (204-1); a residual material outlet (203-4) of the activated carbon desorbing phosphorus and boron impurity device connected to the desorbed residual material treatment system; The adsorbent cleaning device (204) is provided with: an inlet for the adsorbent of the adsorbent cleaning device (204-1) connected to the outlet for the adsorbent of the activated carbon desorbing phosphorus and boron impurity device (203-3); an inlet for the cleaning agent of the adsorbent cleaning device (204-2) connected to the cleaning agent supply system; an outlet for the adsorbent of the adsorbent cleaning device (204-3) connected to the inlet for the adsorbent of the adsorbent drying device (205-1); a residual material outlet (204-4) of the adsorbent cleaning device connected to the cleaning residual material treatment system; The adsorbent drying device (205) is provided with: an inlet for the adsorbent of the adsorbent drying device (205-1) connected to the outlet for the adsorbent of the adsorbent cleaning device (204-3), and an outlet for the adsorbent of the adsorbent drying device (205-2) connected to the inlet for the material of the fluidized bed for adsorbing phosphorus and boron impurities (202-2) and the outlet for the activated carbon of the activated carbon reduction and modification device (303-3).

6. The device according to claim 5, characterized in that The fluidized bed for adsorbing phosphorus and boron impurities (202) is provided with: An inlet for gas of the fluidized bed for adsorbing phosphorus and boron impurities (202-1) arranged at the bottom of the fluidized bed for adsorbing phosphorus and boron impurities (202), and the inlet for gas of the fluidized bed for adsorbing phosphorus and boron impurities (202-1) is connected to the outlet of the evaporator (201); A fluidized bed phosphorus and boron impurity adsorption device feed inlet (202-2) that is arranged in the middle of the fluidized bed phosphorus and boron impurity adsorption device (202) and has an upward opening. The fluidized bed phosphorus and boron impurity adsorption device feed inlet (202-2) is used to add a modified activated carbon adsorbent. A gas-solid separation device (202-3) of the fluidized bed phosphorus and boron impurity adsorption device that is arranged in the upper part of the fluidized bed phosphorus and boron impurity adsorption device (202). The inlet of the gas-solid separation of the fluidized bed phosphorus and boron impurity adsorption device is connected to the upper part of the fluidized bed phosphorus and boron impurity adsorption device (202). The solid discharge port of the gas-solid separation device (202-3) of the fluidized bed phosphorus and boron impurity adsorption device is connected to the middle of the fluidized bed phosphorus and boron impurity adsorption device (202). The gas outlet of the gas-solid separation device (202-3) of the fluidized bed phosphorus and boron impurity adsorption device is upward. An adsorbent discharging device that is arranged in the middle of the fluidized bed phosphorus and boron impurity adsorption device (202) and has a downward opening.

7. The device according to claim 5, characterized in that, The activated carbon modification system (3) includes: an activated carbon forming device (301), an activated carbon oxidation modification device (302), and an activated carbon reduction modification device (303) that are connected in sequence. Among them, the activated carbon oxidation modification device (302) and the activated carbon reduction modification device (303) are kettle-type devices.

8. The device according to claim 5, characterized in that, The rectification separation system (1) includes: a heavy component removal tower (101) and a light component removal tower (102) that are connected in sequence. The bottom discharge port of the light component removal tower (102) is connected to the evaporator (201) of the adsorption system (2).

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