A self-catalytic metal silicon powder, a preparation method and application thereof

Abstract

The application belongs to the field of chemical raw materials, and particularly relates to a self-catalytic metal silicon powder and a preparation method and application thereof. The method comprises the following steps: 1) taking silicon raw materials to be smelted into a silicon melt; 2) adding a main catalyst and an auxiliary metal into the silicon melt to be mixed and smelted to obtain a mixed melt; and 3) after the mixed melt is rapidly cooled and solidified, the mixed melt is broken to obtain the self-catalytic metal silicon powder. Through the effective combination of silicon, a multi-element copper catalyst and a metal auxiliary agent, micron-level contact between raw materials and the catalyst in the Muller-Rochow reaction is changed into nanometer-level contact, so that the self-catalytic metal silicon powder has higher reaction activity, better M2 selectivity and silicon powder conversion rate, the use amount of the catalyst is reduced, the real-time adjustment frequency of the auxiliary agent in the reaction process is reduced, and the economic benefit of the production of organosilicon is improved.

Description

Technical Field

[0001] This invention belongs to the field of chemical raw materials, and particularly relates to a self-catalytic metallic silicon powder, its preparation method and application. Background Technology

[0002] The synthesis of organosilicon monomers is fundamental to the production of various organosilicon polymers. Currently, the main method for synthesizing organosilicon monomers is the Muller-Rochow process, the reaction mechanism of which is as follows: Figure 1 As shown, the key step in the Muller-Rochow process is the direct reaction of silicon with methyl chloride, typically carried out at high temperatures in the presence of catalysts and auxiliaries. The products exhibit diverse chemical structures and physical properties, suitable for various industrial needs, with the M2 monomer (Me2SiCl2) product being in the greatest demand. Therefore, this reaction must consider not only the highest achievable productivity—the maximum yield of silane per unit time and reactor volume—but also the high selectivity of the target product, dimethyldichlorosilane.

[0003] Over the decades, with continuous advancements in reactor design, catalyst improvements, and a deeper understanding of the reaction, the production efficiency and selectivity of dimethylsilicon in organosilicon synthesis have steadily increased. However, due to the accumulation and oxidation of impurities in silicon metal powder, as well as the decrease in activity of catalysts and silicon metal after being encapsulated by impurities, the reaction conversion rate (utilization rate) of silicon metal is low, and the activity in the later stages of the reaction is poor. In particular, with the consumption of high-quality silicon materials, the impurity composition of the silicon materials used in recent years has become increasingly complex and abundant, posing significant challenges to organosilicon production.

[0004] To improve the selectivity of the Rochow reaction for M2 and the conversion rate of metallic silicon, it is essential to address the reaction process itself. Over the decades, catalysts have evolved significantly, from copper, cuprous chloride, ternary copper, and composite catalysts. However, the reaction process remains a complex solid (silicon powder)-solid (catalyst)-gas (chloromethane) system. The continued reaction requires the catalyst to adhere to the silicon powder surface and collide with chloromethane gas molecules. This kinetic limitation is the fundamental bottleneck for improving the reactivity and selectivity of this system.

[0005] However, in traditional ternary systems, the contact, capture, adsorption, and reaction between the catalyst and silicon powder require a fluidized collision process, which is inefficient and not truly uniform. Therefore, the reaction activity can generally be promoted by increasing the specific surface area and reducing the particle size of silicon powder / catalyst. However, the fluidization process itself limits the powder to very fine particles to prevent them from being carried away by the airflow; at the same time, the production of ultrafine metallic silicon and catalysts requires additional power consumption, and ultrafine powders have high activity but are extremely difficult to store, transport, and handle.

[0006] Considering the complex solid-solid-gas system of silicon powder-catalyst-chloromethane currently used in industry, the key to overcoming its kinetic limitations is to simplify the reaction molecular process, transforming the ternary solid-solid-gas system into a binary solid-gas system, and obtaining autocatalytic silicon powder by compositing the catalyst and metallic silicon powder. The composite autocatalytic metallic silicon powder can continuously expose fresh copper-silicon active sites during the reaction. These sites are independent of collision probability, thus improving reaction activity and silicon powder conversion.

[0007] Therefore, simply mixing or blending silicon and copper catalysts cannot directly and effectively improve the efficiency of the Rochow reaction and the conversion rate of the target product M2 monomer in practical applications. Further composite construction of the microstructure is required to ensure the effectiveness of the Si-Cu system catalyst. Summary of the Invention

[0008] To address the problems of low catalytic activity, large additive requirements, and the need to improve silicon powder reaction rate and M2 monomer conversion rate in the existing Muller-Rochow process ternary catalytic reaction system, this invention provides a novel autocatalytic metallic silicon powder, as well as its preparation method and application.

[0009] The main objective of this invention is:

[0010] I. Constructing stable autocatalytic silicon powder with good reactivity;

[0011] II. Ensure that the self-catalytic silica powder has good contact catalytic ability;

[0012] Third, ensure that the autocatalytic silicon powder has a good silicon powder reaction rate and M2 monomer conversion rate in the Muller-Rochow process.

[0013] To achieve the above objectives, the present invention adopts the following technical solution.

[0014] A method for preparing autocatalytic metallic silicon powder,

[0015] The method includes:

[0016] 1) Take silicon raw materials and melt them into silicon melt;

[0017] The silicon raw material is metallurgical silicon, which is obtained as silicon melt after reduction smelting and refining to remove impurities.

[0018] After metallurgical silicon refining is completed, the oxygen content and impurity content in the silicon melt are reduced to a low level. At this time, adding a catalyst metal under a protective atmosphere can achieve better precise control of its composition.

[0019] 2) Add the main catalyst and auxiliary metal to the silicon melt and mix and melt to obtain a mixed melt;

[0020] 3) Rapid cooling of the mixed melt to obtain self-catalytic silicon metal powder.

[0021] Preferably, the main catalyst in step 2) is metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide is 10-80 wt%.

[0022] Step 2) The auxiliary metal is zinc and / or tin and / or aluminum;

[0023] When the additive metal contains zinc, the amount of zinc added is 0.1 to 0.3 wt% of the silicon melt;

[0024] When the additive metal contains tin, the amount of tin added is 0.005 to 0.020 wt% of the silicon melt;

[0025] When the additive metal contains aluminum, the amount of aluminum added is 0.1 to 0.3 wt% of the silicon melt;

[0026] The zinc and / or tin and / or aluminum in the additive metals are added in the form of elemental metals and / or copper alloys.

[0027] As a preferred option

[0028] Step 2) The total amount of copper in the main catalyst and auxiliary metal is 0.5 to 5.0 wt% of the silicon melt.

[0029] As a preferred option

[0030] In step 2), the total amount of copper in the main catalyst and auxiliary metal is 0.5–2.0 wt% of the silicon melt.

[0031] In step 2), the mass percentage of cuprous oxide in the main catalyst is 20–40 wt%.

[0032] Preferably, the melting process in step 2) controls the melting temperature to be 1600–1800°C and the melting time to be 5–10 min.

[0033] As a preferred option

[0034] In step 2), when adding the main catalyst and auxiliary metal to the silicon melt, copper is added first for smelting. Then, depending on the composition of the auxiliary metal, aluminum is added first if it is present. Zinc and tin are then added for smelting, and finally cuprous oxide is added for mixed smelting.

[0035] As a preferred option

[0036] Step 3) describes a rapid cooling process with a cooling rate ≥ 50℃ / s;

[0037] Step 3) The powder preparation adopts solidification and crushing powder preparation and / or atomization powder preparation.

[0038] As a preferred option

[0039] Step 3) describes a powdering process in which the material is crushed to a mesh size of ≥80 mesh.

[0040] A self-catalytic metallic silicon powder.

[0041] An application of autocatalytic metallic silicon powder,

[0042] The autocatalytic silicon powder is used for the catalytic synthesis of Me2SiCl2.

[0043] This invention presents a novel catalytic system based on traditional Cu-Si catalytic silicon powder. Traditional autocatalytic silicon powder preparation processes typically do not involve the addition of auxiliary metals; usually, only an additional ternary copper catalyst is added to improve its reactivity, M2 selectivity, and reaction efficiency. However, these processes all involve removing elements such as aluminum and phosphorus as impurities through refining. Furthermore, additional exogenous ternary copper catalyst powder is required during production or use.

[0044] However, such exogenous additions require prolonged mixing in a fluidized bed reaction to ensure uniform mixing, which to some extent prolongs the reaction start-up time and causes lag in the later stages of the reaction. This invention, on the other hand, employs a mixing and melting method to fuse the required components together with the silicon matrix to form a unified whole, avoiding the effects of exogenous additions during production and reaction. The active sites exposed during the reaction process can continuously promote the reaction, thereby greatly improving the reactivity and conversion rate of the silicon powder.

[0045] In addition to the copper catalyst, this invention adds catalytic promoters such as zinc, tin, and aluminum. Because Cu is difficult to dissolve in silicon and the melting points of the two are significantly different, Cu easily segregates during solidification, forming copper-rich segregated microregions in the silicon matrix. Since the amount of copper added as a catalyst is low, copper segregation will cause most of the silicon to lose its autocatalytic activity. Therefore, the key to maintaining the catalytic activity of copper and a low addition amount is to ensure its uniform distribution in the silicon matrix. From an alloy design perspective, the addition of promoter metals can improve the stability of the Si-Cu system through multi-element eutectic and the formation of complex intermediate phases. Since Cu is similar to Zn, Sn, and Al, its addition can suppress copper segregation to some extent. Furthermore, Zn, Sn, and Al also promote the diffusion and activity of Cu ions during the reaction, contributing to its more efficient free radical exchange capacity.

[0046] The main reason for the above phenomenon is that aluminum, zinc and tin have solid solution limits in the Cu-Si system. Aluminum has a relatively large solid solution limit, and its maximum direct usage is typically about 4.2 wt% of copper. However, zinc and tin both have very small solid solution limits, only about 0.7 wt% of copper. The amount of aluminum, zinc, and tin added to the additive metals of this invention is obviously more than this. For example, the amount of aluminum is about 2.0 to 60.0 wt% of copper, and in a preferred range, the amount of aluminum is about 5.0 to 60.0 wt% of copper, which obviously exceeds the solid solution limit of aluminum. Similarly, the amount of zinc in this invention is also about 2.0 to 60.0 wt% of copper, and in a preferred range, the amount of zinc is about 5.0 to 60.0 wt% of copper, which completely exceeds the solid solution limit of zinc. Tin is relatively better; in this invention, the amount of tin is about 0.1 to 4.0 wt% of copper, and in a preferred range, the amount of tin is about 0.5 to 4.0 wt% of copper. However, it also obviously exceeds its solid solution limit, and zinc and tin compete with each other, making it easier for them to exceed their solid solution limits. This will lead to segregation. However, if the amount added is insufficient, it will not effectively promote the diffusion of Cu ions and activate their activity, resulting in a weak effect.

[0047] To address this, the present invention controls the order of addition of the additive metals and the cooling rate. Preferential addition of aluminum can, to some extent, increase the solid solution limits of zinc and tin in the system, thereby inhibiting their precipitation, especially significantly inhibiting zinc precipitation. Simultaneously, the present invention must provide a sufficient cooling rate to maintain the melt in a homogeneous supersaturated solid solution state, ensuring a uniform distribution of the active catalytic metals. This ensures that the three additive metal elements—aluminum, zinc, and tin—are uniformly distributed, avoiding segregation. Furthermore, the supersaturated solid solution significantly enhances the catalytic activity of silicon powder because the supersaturated solid solution is in a high-energy state, providing more active sites and improving catalytic activity. Additionally, supersaturated solid solutions typically have a more suitable band gap and delocalized valence band top, which also significantly improves contact catalysis.

[0048] It is evident that the present invention, through the addition and regulation of auxiliary metals to form a supersaturated solid solution, effectively enhances the reactivity, M2 selectivity, and reaction efficiency of silicon powder.

[0049] The beneficial effects of this invention are:

[0050] This invention effectively combines silicon, multi-element copper catalysts, and metal additives to transform the micron-level contact between the raw materials and catalyst in the Muller-Rochow reaction into a nano-level contact, thereby achieving higher reactivity, better M2 selectivity, and silicon powder conversion rate. At the same time, it reduces the amount of catalyst used and the frequency of real-time adjustment of additives during the reaction, thus improving the economic efficiency of organosilicon production. Attached Figure Description

[0051] Figure 1 A schematic diagram of the reaction mechanism of the Muller-Rochow process;

[0052] Figure 2 The microstructure of the catalytic metal silicon powder prepared in Example 1 is shown in the image.

[0053] Figure 3 The microstructure of the catalytic metal silicon powder prepared in Comparative Example 2 is shown in the diagram.

[0054] Figure 4 This is a microscopic elemental distribution diagram of the self-catalytic silicon metal powder prepared in Comparative Example 3. Detailed Implementation

[0055] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0056] In the description of this invention, it should be understood that the terms "thickness," "upper," "lower," "horizontal," "top," "bottom," "inner," "outer," "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified, and "several" means one or more.

[0057] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0058] Unless otherwise specified, all raw materials used in the embodiments of the present invention are commercially available or obtainable by those skilled in the art; unless otherwise specified, all methods used in the embodiments of the present invention are methods mastered by those skilled in the art.

[0059] Example 1

[0060] A method for preparing autocatalytic metallic silicon powder,

[0061] The method includes:

[0062] 1) Take high-purity metallurgical silicon as raw material, add carbon at a mass ratio of about 3wt%, heat to 1600℃ in a vacuum atmosphere for melting, hold for 30min for refining to obtain silicon melt. The oxygen content in the silicon melt is ≤60ppm, and the content of other unavoidable impurities is ≤180ppm.

[0063] 2) Maintain the melting temperature and add the main catalyst and auxiliary metal to the silicon melt in a vacuum atmosphere to mix and melt to obtain a mixed melt;

[0064] The main catalyst is composed of metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide is 20 wt%.

[0065] The additive metal is composed of copper-aluminum alloy, zinc metal and copper-tin alloy;

[0066] During the addition process, the total amount of copper added was controlled to be 1.0 wt% of the silicon melt, the amount of zinc added was 0.2 wt% of the silicon melt, the amount of tin added was 0.01 wt% of the silicon melt, and the amount of aluminum added was 0.2 wt% of the silicon melt.

[0067] When adding the main catalyst and auxiliary metal, first add copper and continue stirring and melting for 2 minutes. After adding copper, add copper-aluminum alloy and continue stirring and melting for 2 minutes. After adding copper-aluminum alloy, add zinc and copper-tin alloy and continue stirring and melting for 3 minutes. After adding zinc and copper-tin alloy, add cuprous oxide and continue stirring and melting for 3 minutes to obtain a mixed melt.

[0068] 3) After the mixed melt is rapidly cooled and solidified at a cooling rate of 50℃ / s, it is crushed by air jet mill and passed through an 80-mesh sieve to obtain autocatalytic silicon metal powder.

[0069] The microstructure and elemental distribution of the autocatalytic silicon metal powder obtained in this example were characterized. The characterization results are as follows: Figure 2 As shown, the silicon powder of this invention did not exhibit segregation even with excessive addition of aluminum, zinc, and tin. The distribution of each element was highly uniform.

[0070] Furthermore, the performance of the self-catalytic silicon powder prepared in this example was verified and characterized. It was directly used as a catalyst (i.e., a reaction catalyst) in a conventional Muller-Rochow process. Before the reaction, the reaction system was first purged with nitrogen, then switched to MeCl gas. The MeCl gas, after preheating, reacted with the catalyst. The product flowed out from the bottom of the reactor, was condensed in a condenser, and collected with toluene solution to obtain the test liquid. The tail gas was post-treated with alkaline solution. After the test liquid was brought to a final volume, it was quantitatively analyzed by gas chromatography. The product was characterized and calculated, and the selectivity of the M2 monomer (Me2SiCl2) and the silicon conversion rate were calculated. These results were compared with those of a traditional silicon-ternary copper catalytic system (using equal amounts of catalyst, composed of silicon, ternary copper, and zinc powder, with a mass ratio of Si:Cu / Cu). 2 A comparison was made between O / CuO:Zn = 20:9.95:0.05.

[0071] The characterization results are shown in the table below.

[0072]

[0073] The characterization results clearly show that the self-catalytic silicon powder of this invention has excellent catalytic effect, far surpassing existing silicon-ternary copper catalytic systems in both M2 selectivity and silicon conversion rate. In particular, the silicon conversion rate is improved by more than 50%. This is mainly because in the traditional silicon-ternary copper catalytic system, the catalytic reaction is achieved through the contact between the feed gas and the silicon and ternary copper catalyst, resulting in micron-level contact with limited contact probability and area, and relatively low directional conversion rate. However, with the self-catalytic silicon powder of this invention, the contact between the feed gas and the catalyst is at the nanometer level, significantly increasing both contact probability and area. Simultaneously, the addition of the auxiliary metal greatly enhances the catalytic effect, efficiency, and selectivity of product M2. Under the combined effect of these two factors, the actual silicon conversion rate also experiences an explosive increase. Furthermore, the effective combination of Si and ternary copper enhances the synergistic catalytic effect, further improving the selectivity of M2.

[0074] Example 2

[0075] Based on Example 1, only step 2) was changed by using different total amounts of copper (by changing only the amount of copper and cuprous oxide used as the main catalyst) and the resulting autocatalytic silicon metal powder was subjected to the same performance characterization. The characterization results are shown in the table below.

[0076] Si:Cu mass ratio M2 Selectivity Silicon conversion rate Si:Cu mass ratio M2 selectivity Silicon conversion rate 1：0.003 89.9％ 46.3％ 1：0.020 94.7％ 51.3％ 1：0.005 94.2％ 50.2％ 1：0.050 94.9％ 49.6％ 1：0.015 95.2％ 50.8％ 1：0.065 95.0％ 43.1％

[0077] The above comparison reveals that when the amount of Cu is insufficient, the actual M2 selectivity is insufficient. However, as the amount of copper gradually increases, the M2 selectivity increases and remains relatively stable in the experiment. But as the amount of copper increases, the silicon conversion rate shows a trend of first increasing and then decreasing. This is because when the amount of copper is too large, the actual support structure stability gradually decreases and the ability to adsorb raw gas is also weakened, thus resulting in the above situation. It can be seen that the mass ratio of Si to Cu should be controlled within an appropriate range to maintain the optimal catalytic effect.

[0078] Based on Example 1, only step 2) was changed by using different amounts of aluminum (the silicon-aluminum alloy was replaced with equal amounts of metallic copper and metallic aluminum, and only the amount of metallic aluminum was adjusted) and the resulting autocatalytic silicon metal powder was subjected to the same performance characterization. The characterization results are shown in the table below.

[0079] Si:Al mass ratio M2 selectivity Silicon conversion rate Si:Cu mass ratio M2 Selectivity Silicon conversion rate 1：0.0005 83.9 32.7％ 1：0.0025 94.5％ 51.6％ 1：0.0010 90.1 43.9％ 1：0.0030 93.2％ 49.2％ 1：0.0015 95.0％ 50.6％ 1：0.0045 91.2％ 39.1％

[0080] The above comparison reveals that sufficient Al is required to produce a promoting effect. However, insufficient aluminum content cannot effectively improve reaction selectivity and efficiency, while excessive aluminum content will inevitably lead to severe segregation, resulting in a direct decrease in reaction efficiency and conversion rate.

[0081] Similarly, based on the aforementioned comparative experiments with aluminum, comparative experiments with zinc and tin were also conducted. When the zinc content decreased to 0.05 wt% of the silicon melt, it produced almost no improvement effect. However, when the zinc content increased to 0.36 wt% of the silicon melt, segregation began to occur and gradually intensified. When the zinc content reached 0.50 wt% of the silicon melt, it produced negative optimization, meaning that compared to the performance without zinc, there was a decrease in selectivity and reactivity. The optimal zinc content was 0.1–0.3 wt% of the silicon melt. Likewise, when the tin content was only about 0.003 wt% of the silicon melt, it produced almost no promoting optimization effect. However, when the tin content reached 0.022 wt% of the silicon melt, an explosive decrease in selectivity and conversion rate occurred, with the conversion rate plummeting to about 39.7%. The effective tin content was only 0.005–0.020 wt% of the silicon melt. This indicates that the system of this invention has the highest sensitivity to tin, and the tin content should be controlled most strictly.

[0082] Example 3

[0083] A method for preparing autocatalytic metallic silicon powder,

[0084] The method includes:

[0085] 1) Take high-purity metallurgical silicon as raw material, add carbon at a mass ratio of about 3wt%, heat to 1600℃ in a vacuum atmosphere for melting, hold for 30min for refining to obtain silicon melt. The oxygen content in the silicon melt is ≤60ppm, and the content of other unavoidable impurities is ≤180ppm.

[0086] 2) Maintain the melting temperature and add the main catalyst and auxiliary metal to the silicon melt in a vacuum atmosphere to mix and melt to obtain a mixed melt;

[0087] The main catalyst is composed of metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide is 5-90 wt%.

[0088] The additive metal is composed of copper-aluminum alloy, zinc metal and copper-tin alloy;

[0089] During the addition process, the total amount of copper added was controlled to be 1.0 wt% of the silicon melt, the amount of zinc added was 0.2 wt% of the silicon melt, the amount of tin added was 0.01 wt% of the silicon melt, and the amount of aluminum added was 0.2 wt% of the silicon melt.

[0090] When adding the main catalyst and auxiliary metal, first add copper and continue stirring and melting for 2 minutes. After adding copper, add copper-aluminum alloy and continue stirring and melting for 2 minutes. After adding copper-aluminum alloy, add zinc and copper-tin alloy and continue stirring and melting for 3 minutes. After adding zinc and copper-tin alloy, add cuprous oxide and continue stirring and melting for 3 minutes to obtain a mixed melt.

[0091] 3) After the mixed melt is rapidly cooled and solidified at a cooling rate of 50℃ / s, it is crushed by air jet mill and passed through an 80-mesh sieve to obtain autocatalytic silicon metal powder.

[0092] The self-catalytic silicon powder prepared in this example was used for performance verification and characterization. It was directly used as a catalyst (i.e., a reaction catalyst) in the traditional Muller-Rochow process. Before the reaction, the reaction system was first purged with N, and then MeCl gas was switched. After preheating, MeCl reacted with the catalyst. The product after the reaction flowed out from the bottom of the reactor, was condensed in a condenser, and collected with toluene solution to obtain the test liquid. The tail gas was post-treated with alkaline solution. After the test liquid was brought to a certain volume, it was quantitatively analyzed by gas chromatography. The product was characterized and calculated. The selectivity of M2 monomer (Me2SiCl2) and silicon conversion rate were calculated respectively, and compared with the traditional silicon-ternary copper catalytic system (using equal amounts of catalyst, the catalyst is composed of silicon, ternary copper and zinc powder, and the mass ratio of silicon, ternary copper and zinc powder Si:Cu / Cu2O / CuO:Zn=20:9.95:0.05).

[0093] The results of the cross-sectional characterization of the controlled cuprous oxide content in the main catalyst are shown in the table below.

[0094]

[0095]

[0096] The results show that as the proportion of cuprous oxide increases, the selectivity of M2 exhibits a definite trend of first increasing and then decreasing. The selectivity improvement is particularly significant in the early stages, but decreases with further increases, while the silicon conversion rate generally maintains an upward trend. This is directly due to the fact that excessive cuprous oxide affects its crystal structure. As a catalyst, crystal facet engineering has a significant impact on its catalytic performance, and excessive cuprous oxide alters the crystal facet structure, affecting both adsorption and catalytic activity. Furthermore, increasing the amount of cuprous oxide may lead to a large aggregation of cuprous oxide crystals. This aggregation may affect the recombination of photogenerated electron pairs, thus affecting the formation of electron-hole pairs. During catalysis, electron-hole pairs need to move to the crystal surface and contact the reactants to react. If cuprous oxide crystals aggregate, it increases the difficulty for electron-hole pairs to contact the reactants, potentially leading to more electron-hole pairs recombinating before contacting the reactants, thus affecting catalytic efficiency. However, regarding silicon conversion efficiency, excess cuprous oxide promotes silicon conversion by providing more comprehensive active sites. In the Cu-Si system, cuprous oxide may contribute by forming specific interfacial active sites, such as Cu-SiO₂. x Interfaces and other methods can be used to promote silicon conversion, but the controllability of the conversion direction is reduced.

[0097] Therefore, for the system of this invention, the content of cuprous oxide in the main catalyst should be controlled between 10 and 80 wt%, and the optimal effect can be achieved, especially between 20 and 70 wt%.

[0098] Comparative Example 1

[0099] A method for preparing autocatalytic metallic silicon powder,

[0100] The method includes:

[0101] 1) Take high-purity metallurgical silicon as raw material, add carbon at a mass ratio of about 3wt%, heat to 1600℃ in a vacuum atmosphere for melting, hold for 30min for refining to obtain silicon melt. The oxygen content in the silicon melt is ≤60ppm, and the content of other unavoidable impurities is ≤180ppm.

[0102] 2) Maintain the melting temperature and add the main catalyst and auxiliary metal to the silicon melt in a vacuum atmosphere to mix and melt to obtain a mixed melt;

[0103] The main catalyst is composed of metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide is 20 wt%.

[0104] The additive metal is composed of copper-aluminum alloy, zinc metal and copper-tin alloy;

[0105] During the addition process, the total amount of copper added was controlled to be 1.0 wt% of the silicon melt, the amount of zinc added was 0.2 wt% of the silicon melt, the amount of tin added was 0.01 wt% of the silicon melt, and the amount of aluminum added was 0.2 wt% of the silicon melt.

[0106] When adding the main catalyst and auxiliary metal, first add copper and stir continuously for 3 minutes. After adding copper, add copper-aluminum alloy and stir continuously for 3 minutes. After adding copper-aluminum alloy, add zinc and copper-tin alloy and stir continuously for 5 minutes. After adding zinc and copper-tin alloy, add cuprous oxide and stir continuously for 5 minutes to obtain a mixed melt.

[0107] 3) After the mixed melt is rapidly cooled and solidified at a cooling rate of 50℃ / s, it is crushed by air jet mill and passed through an 80-mesh sieve to obtain autocatalytic silicon metal powder.

[0108] The self-catalytic silicon powder prepared in this example was used for performance verification and characterization. It was directly used as a catalyst (i.e., a reaction catalyst) in the traditional Muller-Rochow process. Before the reaction, the reaction system was first purged with N, and then MeCl gas was switched. After preheating, MeCl reacted with the catalyst. The product after the reaction flowed out from the bottom of the reactor, was condensed in a condenser, and collected with toluene solution to obtain the test liquid. The tail gas was post-treated with alkaline solution. After the test liquid was brought to a certain volume, it was quantitatively analyzed by gas chromatography. The product was characterized and calculated. The selectivity of M2 monomer (Me2SiCl2) and silicon conversion rate were calculated respectively, and compared with the traditional silicon-ternary copper catalytic system (using equal amounts of catalyst, the catalyst is composed of silicon, ternary copper and zinc powder, and the mass ratio of silicon, ternary copper and zinc powder Si:Cu / Cu2O / CuO:Zn=20:9.95:0.05).

[0109]

[0110] The characterization results show a significant decrease in the M2 selectivity and silicon conversion rate of the autocatalytic silicon powder prepared in this example. This is mainly because the actual melting points of the components in the auxiliary metal catalyst are relatively low, making them prone to burn-off during prolonged mixing and melting processes, thus leading to a significant decline in their performance enhancement. Therefore, for the technical solution of this invention, using a sufficiently high melting temperature, such as 1600–1800°C, and performing mixing and melting for a shorter time can ensure a relatively superior melting effect.

[0111] Comparative Example 2

[0112] A method for preparing autocatalytic metallic silicon powder,

[0113] The method includes:

[0114] 1) Take high-purity metallurgical silicon as raw material, add carbon at a mass ratio of about 3wt%, heat to 1600℃ in a vacuum atmosphere for melting, hold for 30min for refining to obtain silicon melt. The oxygen content in the silicon melt is ≤60ppm, and the content of other unavoidable impurities is ≤180ppm.

[0115] 2) Maintain the melting temperature and add the main catalyst and auxiliary metal to the silicon melt in a vacuum atmosphere to mix and melt to obtain a mixed melt;

[0116] The main catalyst is composed of metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide is 20 wt%.

[0117] The additive metal is composed of copper-aluminum alloy, zinc metal and copper-tin alloy;

[0118] During the addition process, the total amount of copper added was controlled to be 1.0 wt% of the silicon melt, the amount of zinc added was 0.2 wt% of the silicon melt, the amount of tin added was 0.01 wt% of the silicon melt, and the amount of aluminum added was 0.2 wt% of the silicon melt.

[0119] When adding the main catalyst and auxiliary metal, first add copper and continue stirring and melting for 2 minutes. After adding copper, add copper-aluminum alloy and continue stirring and melting for 2 minutes. After adding copper-aluminum alloy, add zinc and copper-tin alloy and continue stirring and melting for 3 minutes. After adding zinc and copper-tin alloy, add cuprous oxide and continue stirring and melting for 3 minutes to obtain a mixed melt.

[0120] 3) After the mixed melt is rapidly cooled and solidified at a cooling rate of 30℃ / s, it is crushed by air jet mill and passed through an 80-mesh sieve to obtain autocatalytic silicon metal powder.

[0121] The self-catalytic silicon powder prepared in this example was used for performance verification and characterization. It was directly used as a catalyst (i.e., a reaction catalyst) in the traditional Muller-Rochow process. Before the reaction, the reaction system was first purged with N, and then MeCl gas was switched. After preheating, MeCl reacted with the catalyst. The product after the reaction flowed out from the bottom of the reactor, was condensed in a condenser, and collected with toluene solution to obtain the test liquid. The tail gas was post-treated with alkaline solution. After the test liquid was brought to a certain volume, it was quantitatively analyzed by gas chromatography. The product was characterized and calculated. The selectivity of M2 monomer (Me2SiCl2) and silicon conversion rate were calculated respectively, and compared with the traditional silicon-ternary copper catalytic system (using equal amounts of catalyst, the catalyst is composed of silicon, ternary copper and zinc powder, and the mass ratio of silicon, ternary copper and zinc powder Si:Cu / Cu2O / CuO:Zn=20:9.95:0.05).

[0122]

[0123] The results of this example show that, compared to Example 1, a lower cooling rate was used, but a significant difference in performance was achieved. Figure 3 As shown in the image, microscopic elemental distribution characterization clearly reveals significant segregation and enrichment of elements such as tin and zinc. This indicates that lower cooling rates cannot effectively and quickly achieve element fixation, while slow cooling leads to compositional segregation and a decline in overall performance. Furthermore, this phenomenon intensifies with decreasing cooling rates. However, higher cooling rates do not cause significant effects.

[0124] Example 4

[0125] A method for preparing autocatalytic metallic silicon powder,

[0126] The method includes:

[0127] 1) Take high-purity metallurgical silicon as raw material, add carbon at a mass ratio of about 3wt%, heat to 1600℃ in a vacuum atmosphere for melting, hold for 30min for refining to obtain silicon melt. The oxygen content in the silicon melt is ≤60ppm, and the content of other unavoidable impurities is ≤180ppm.

[0128] 2) Maintain the melting temperature and add the main catalyst and auxiliary metal to the silicon melt in a vacuum atmosphere to mix and melt to obtain a mixed melt;

[0129] The main catalyst is composed of metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide is 20 wt%.

[0130] The additive metal is composed of copper-aluminum alloy, zinc metal and copper-tin alloy;

[0131] During the addition process, the total amount of copper added was controlled to be 1.0 wt% of the silicon melt, the amount of zinc added was 0.2 wt% of the silicon melt, the amount of tin added was 0.01 wt% of the silicon melt, and the amount of aluminum added was 0.2 wt% of the silicon melt.

[0132] When adding the main catalyst and auxiliary metal, first add copper and continue stirring and melting for 2 minutes. After adding copper, add copper-aluminum alloy and continue stirring and melting for 2 minutes. After adding copper-aluminum alloy, add zinc and copper-tin alloy and continue stirring and melting for 3 minutes. After adding zinc and copper-tin alloy, add cuprous oxide and continue stirring and melting for 3 minutes to obtain a mixed melt.

[0133] 3) Autocatalytic silicon metal powder was obtained by atomization and powdering under an argon atmosphere and sieved through an 80-mesh sieve.

[0134] The self-catalytic silicon powder prepared in this example was used for performance verification and characterization. It was directly used as a catalyst (i.e., a reaction catalyst) in the traditional Muller-Rochow process. Before the reaction, the reaction system was first purged with N, and then MeCl gas was switched. After preheating, MeCl reacted with the catalyst. The product after the reaction flowed out from the bottom of the reactor, was condensed in a condenser, and collected with toluene solution to obtain the test liquid. The tail gas was post-treated with alkaline solution. After the test liquid was brought to a certain volume, it was quantitatively analyzed by gas chromatography. The product was characterized and calculated. The selectivity of M2 monomer (Me2SiCl2) and silicon conversion rate were calculated respectively, and compared with the traditional silicon-ternary copper catalytic system (using equal amounts of catalyst, the catalyst is composed of silicon, ternary copper and zinc powder, and the mass ratio of silicon, ternary copper and zinc powder Si:Cu / Cu2O / CuO:Zn=20:9.95:0.05).

[0135]

[0136] The results above show that the atomization process does not significantly affect the product performance. This is because the cooling rate of atomization typically exceeds 1000℃ / s, exhibiting an extremely high cooling capacity. This confirms the above viewpoint that, for the technical solution of this invention, the cooling rate needs to be above a certain threshold. However, the atmosphere required for atomization is also crucial. For example, the oxygen content must be below 200ppm, i.e., a low-oxygen or even virtually oxygen-free environment must be created. Furthermore, due to the special nature of the metal components of the additives in this invention, using conventional nitrogen as a protective gas will significantly impact the results, leading to severe nitriding of the product powder. For instance, replacing the argon atmosphere with nitrogen and performing the same atomization process results in a decrease of approximately 13.8% in the M2 selectivity of the product, while the silicon conversion rate decreases to approximately 48.0%. Therefore, the choice of atmosphere for atomization is particularly critical.

[0137] Comparative Example 3

[0138] A method for preparing autocatalytic metallic silicon powder,

[0139] The method includes:

[0140] 1) Take high-purity metallurgical silicon as raw material, add carbon at a mass ratio of about 3wt%, heat to 1600℃ in a vacuum atmosphere for melting, hold for 30min for refining to obtain silicon melt. The oxygen content in the silicon melt is ≤60ppm, and the content of other unavoidable impurities is ≤180ppm.

[0141] 2) Maintain the melting temperature and add the main catalyst and auxiliary metal to the silicon melt in a vacuum atmosphere to mix and melt to obtain a mixed melt;

[0142] The main catalyst is composed of metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide is 20 wt%.

[0143] The additive metal is composed of copper-aluminum alloy, zinc metal and copper-tin alloy;

[0144] During the addition process, the total amount of copper added was controlled to be 1.0 wt% of the silicon melt, the amount of zinc added was 0.2 wt% of the silicon melt, the amount of tin added was 0.01 wt% of the silicon melt, and the amount of aluminum added was 0.2 wt% of the silicon melt.

[0145] The main catalyst and auxiliary metal were added simultaneously and continuously stirred and smelted for 10 minutes to obtain a mixed melt.

[0146] 3) After the mixed melt is rapidly cooled and solidified at a cooling rate of 50℃ / s, it is crushed by air jet mill and passed through an 80-mesh sieve to obtain autocatalytic silicon metal powder.

[0147] The self-catalytic silicon powder prepared in this example was used for performance verification and characterization. It was directly used as a catalyst (i.e., a reaction catalyst) in the traditional Muller-Rochow process. Before the reaction, the reaction system was first purged with N, and then MeCl gas was switched. After preheating, MeCl reacted with the catalyst. The product after the reaction flowed out from the bottom of the reactor, was condensed in a condenser, and collected with toluene solution to obtain the test liquid. The tail gas was post-treated with alkaline solution. After the test liquid was brought to a certain volume, it was quantitatively analyzed by gas chromatography. The product was characterized and calculated. The selectivity of M2 monomer (Me2SiCl2) and silicon conversion rate were calculated respectively, and compared with the traditional silicon-ternary copper catalytic system (using equal amounts of catalyst, the catalyst is composed of silicon, ternary copper and zinc powder, and the mass ratio of silicon, ternary copper and zinc powder Si:Cu / Cu2O / CuO:Zn=20:9.95:0.05).

[0148]

[0149] Similarly, the product in this example was characterized by its microscopic elemental distribution. The characterization results are as follows: Figure 4 As shown in the results of this example, the co-addition of the main catalyst and auxiliary metals during the mixed smelting process prevented copper and aluminum from achieving initial distribution and blending. This altered the overall smelting environment, making it difficult to create conditions that inhibit the precipitation of components such as zinc and tin. Consequently, the uniformity of zinc and tin distribution decreased significantly, resulting in substantial segregation and diffusion, and ultimately a significant decline in the performance of the final product. Furthermore, the microscopic elemental distribution characterization also confirmed this finding.

Claims

1. A method for preparing autocatalytic metallic silicon powder, characterized in that, The method includes: 1) Take silicon raw materials and melt them into silicon melt; 2) Add the main catalyst and auxiliary metal to the silicon melt and mix and melt to obtain a mixed melt; 3) Rapid cooling of the mixed melt to obtain autocatalytic silicon metal powder; Step 2) The main catalyst is metallic copper and cuprous oxide, wherein the mass percentage of cuprous oxide in the main catalyst is 10–80 wt%. Step 2) The auxiliary metal is zinc and / or tin and / or aluminum; When the additive metal contains zinc, the amount of zinc added is 0.1–0.3 wt% of the silicon melt. When the additive metal contains tin, the amount of tin added is 0.005–0.020 wt% of the silicon melt. When the additive metal contains aluminum, the amount of aluminum added is 0.1–0.3 wt% of the silicon melt. The zinc and / or tin and / or aluminum in the additive metals are added in the form of elemental metals and / or copper alloys; Step 2) The total amount of copper in the main catalyst and auxiliary metal is 0.5–5.0 wt% of the silicon melt. Step 2) The mixing and smelting process is controlled with a smelting temperature of 1600-1800 ℃ and a smelting time of 5-10 min; Step 2) When adding the main catalyst and auxiliary metal to the silicon melt, first add metallic copper for smelting, then add aluminum first according to the composition of the auxiliary metal, then add zinc and tin for smelting, and finally add cuprous oxide for mixed smelting. Step 3) The rapid cooling process is controlled with a cooling rate ≥ 50 ℃ / s; Step 3) The powder preparation adopts solidification and crushing powder preparation and / or atomization powder preparation; The atomization powdering is carried out in an argon atmosphere.

2. The method for preparing autocatalytic metallic silicon powder according to claim 1, characterized in that, Step 2) The total amount of copper in the main catalyst and auxiliary metal is 0.5–2.0 wt% of the silicon melt. In step 2), the mass percentage of cuprous oxide in the main catalyst is 20–40 wt%.

3. The method for preparing autocatalytic metallic silicon powder according to claim 1, characterized in that, Step 3) The powdering process involves crushing the material to a mesh size of ≥80 mesh.

4. A self-catalytic metallic silicon powder prepared by any one of claims 1 to 3.

5. An application of the self-catalytic metallic silicon powder as described in claim 4, characterized in that, The autocatalytic silicon powder is used for the catalytic synthesis of Me2SiCl2.

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