Method for producing higher silane and catalyst for producing higher silane

Abstract

Provided is a method for producing a higher silane having a high trisilane selectivity even when a lower silane is reacted with a catalyst for a long time.　The present invention includes a method for producing a higher silane, the method involving bringing a porous oxide and a lower silane into contact with each other and converting the lower silane into a higher silane having a higher number of silicon atoms than the lower silane, wherein the higher silane contains trisilane, the cumulative reaction time is 200 to 10,000 hours (exclusive of 200 hours), the temperature at the time of contact between the porous oxide and the lower silane is 100 to 400 °C, and the retention time represented by formula (1) is 80 to 150 seconds (exclusive of 150 seconds).　(1): Retention time [sec]=catalyst amount [L]×((pressure [MPaG]+0.101325) / 0.101325)×(273.15 / (temperature [°C]+273.15))×(3600 / gas supply amount [NL / h]) (In formula (1), the catalyst amount represents the amount of the porous oxide to be brought into contact with the lower silane, the pressure and the temperature represent a pressure and a temperature when the porous oxide and the lower silane are brought into contact with each other, and the gas supply amount represents the supply amount per unit time of the raw material gas containing the lower silane when the lower silane is brought into contact with the porous oxide.

Description

Method for producing higher silanes and catalyst for producing higher silanes

[0001] The present invention relates to a method for producing higher silanes and a catalyst for producing higher silanes.

[0002] With the development of the electronics industry, the demand for silicon-based thin films for semiconductor manufacturing, such as polycrystalline silicon thin films and amorphous silicon thin films, is rapidly increasing. ４ ), and disilane (Si ２ H ６ ) and trisilane (Si ３ H ８ Higher silanes (Si ｎ H ２ｎ＋２ ; n is an integer of 2 or more) have recently become increasingly important as raw materials for producing silicon-based thin films for semiconductor manufacturing.

[0003] In the production of silicon-based thin films used in semiconductors, etc., technology is being developed that will enable stable and efficient production of high-grade silanes on an industrial scale, as well as being economical.

[0004] For example, Patent Document 1 discloses a catalyst for producing higher silanes from lower silanes using a catalyst having specified pores, and an example of producing higher silanes by reacting the catalyst with the lower silane for 10 to 200 hours. Patent Document 2 discloses a method for producing oligosilanes from hydrosilanes using a continuous reactor equipped with a specified catalyst layer, and discloses a production example in which the catalyst layer is reacted with the hydrosilane for 1 to 10 hours.

[0005] International Publication No. 2015 / 060189 International Publication No. 2016 / 027743

[0006] Stable and efficient production of trisilane on an industrial scale requires continuous reaction while keeping the equipment as small as possible. However, the inventors' investigations have revealed a new problem: continuous reaction of a catalyst with a lower silane for a long period of time, exceeding the reaction times disclosed in Patent Documents 1 and 2, results in a low trisilane selectivity.

[0007] In view of the above circumstances, the present invention provides a method for producing higher silanes that has a high selectivity to trisilane even when reacting lower silanes with a catalyst for a long period of time.

[0008] The present inventors conducted extensive research to solve the above-mentioned problems. As a result, they found that the above-mentioned problems can be solved by having the following configuration, and have completed the present invention. That is, aspects of the present invention relate to the following [1] to

[10] , for example: [1] A method for producing higher silanes by contacting a porous oxide with a lower silane to convert it into a higher silane having a higher silicon number than the lower silane, wherein the higher silane contains trisilane, the cumulative reaction time is more than 200 hours and not more than 10,000 hours, the temperature during contact between the porous oxide and the lower silane is 100°C or higher and 400°C or lower, and the residence time represented by the following formula (1) is 80 seconds or higher and less than 150 seconds. Residence time [seconds] = catalyst amount [L] x ((pressure [MPaG] + 0.101325) / 0.101325) x (273.15 / (temperature [°C] + 273.15)) x (3600 / gas supply rate [NL / h]) ... (1) (In formula (1), the catalyst amount represents the amount of porous oxide to be contacted with the lower silane, the pressure and temperature represent the pressure and temperature, respectively, when the porous oxide and the lower silane are contacted, and the gas supply rate represents the amount of raw material gas containing the lower silane supplied per unit time when contacted with the porous oxide.) [2] The method for producing higher silanes according to [1], wherein the residence time is 80 seconds or more and less than 120 seconds. [3] The method for producing higher silanes according to [1] or [2], wherein, before contacting the porous oxide with the lower silane, the temperature of the lower silane is adjusted to 0°C or higher but 30°C or lower, and the pressure of the temperature-adjusted lower silane is increased to set the temperature of the lower silane to 40°C or higher but 200°C or lower. [4] The method for producing higher silanes according to any of [1] to [3], wherein the porous oxide has at least regularly arranged pores, is composed mainly of silicon oxide, and has an alkali metal and alkaline earth metal content of 0.00% by weight or higher but 2.00% by weight or lower. [5] The method for producing higher silanes according to [1] to [4], wherein the pore diameter of the porous oxide is 0.4 nm or higher but 0.6 nm or lower. [6] The method for producing higher silanes according to any of [1] to [5], wherein the porous oxide has a crystalline zeolite structure composed of an aluminosilicate or metallosilicate.[7] The porous oxide is an aluminosilicate, and SiO in the porous oxide. ２ / Al ２ O ３

[0013] A method for producing higher silanes according to any one of [1] to [6], wherein the molar ratio is from 10 to 3,000. [8] A method for producing higher silanes according to any one of [1] to [7], wherein the porous oxide is MFI zeolite. [9] A method for producing higher silanes according to any one of [1] to [8], further comprising separating and recovering trisilane from the higher silanes.

[10] A catalyst for producing higher silanes, which contains a porous oxide and is contacted with a lower silane to convert the lower silane into a higher silane having a higher silicon number than the lower silane, the porous oxide having at least regularly arranged pores and consisting primarily of silicon oxide, and having an alkali metal and alkaline earth metal content of from 0.00% by weight to 2.00% by weight, and which satisfies the following production conditions A to C: A: The temperature at which the catalyst and the lower silane are contacted is 100°C or higher and 400°C or lower. B: The pressure at which the catalyst and the lower silane are contacted is 0.1 MPaG or higher and 1.0 MPaG or lower. C: The cumulative reaction time is more than 200 hours and 10,000 hours or less.

[0009] According to the present invention, it is possible to provide a method for producing higher silanes that has high selectivity to trisilane even when reacting lower silanes with a catalyst for a long period of time.

[0010] Furthermore, because trisilane can be produced with high selectivity, industrial production of trisilane can be carried out efficiently, and even if by-products such as disilane are not reused, unnecessary waste can be reduced, making it possible to produce trisilane economically.

[0011] FIG. 1 is a diagram showing a schematic diagram of the production flow of the present invention when monosilane is used as a raw material.

[0012] Preferred embodiments for carrying out the present invention will be described below. Note that the embodiment described below is an example of a typical embodiment of the present invention, and the scope of the present invention should not be construed as being narrow.

[0013] <Method for Producing Higher Silanes> One embodiment of the present invention is a method for producing higher silanes, comprising the step of contacting a porous oxide with a lower silane to convert the higher silane into a higher silane having a higher silicon number than the lower silane, wherein the higher silane comprises trisilane, the cumulative reaction time is more than 200 hours and not more than 10,000 hours, the temperature during contact of the porous oxide with the lower silane is 100°C or higher and 400°C or lower, and the residence time represented by the following formula (1) is 80 seconds or higher and less than 150 seconds.

[0014] Residence time [seconds]=catalyst amount [L]×((pressure [MPaG]+0.101325) / 0.101325)×(273.15 / (temperature [°C]+273.15))×(3600 / gas supply rate [NL / h]) (1) (In formula (1), the catalyst amount represents the amount of porous oxide to be contacted with the lower silane, the pressure and temperature represent the pressure and temperature, respectively, when the porous oxide is contacted with the lower silane, and the gas supply rate represents the amount of source gas containing the lower silane supplied per unit time when contacted with the porous oxide.)

[0015] [Porous Oxide] The porous oxide used in the method for producing higher silanes of the present invention is a catalyst that, when in contact with a lower silane, converts the lower silane into a higher silane having a higher silicon number than the lower silane.

[0016] The porous oxide used in the present invention is mainly composed of silicon oxide, and its content is preferably 60% by weight or more and 100% by weight or less. Components contained other than silicon oxide are not particularly limited as long as they are components generally contained in catalyst supports, and examples include aluminum oxide, titanium oxide, zirconium oxide, zinc oxide, magnesium oxide, iron oxide, boron oxide, and gallium oxide. These components may be contained in a state of being physically mixed with silicon oxide, or may be contained in a state of being chemically composited (composite oxide state).

[0017] The porous oxide of the present invention, which is primarily composed of silicon oxide, has uniform pores. Uniform pores refer to pores that are regularly arranged, and the diameter of these regularly arranged pores is preferably 0.4 nm or more and 0.6 nm or less. The pore size of the porous oxide can be determined by nitrogen adsorption. In the examples, the values ​​used are those listed in the International Zeolite Association's Atlas of Zeolite Framework Types, Sixth Revised Edition (Elsevier). When there are multiple diameters, if there is at least one diameter within the range of 0.4 nm or more and 0.6 nm or less, that diameter is listed.

[0018] The pores of the porous oxide primarily composed of silicon oxide are formed by repeated bonds of silicon-oxygen bonds and oxygen bonds of other elements (e.g., aluminum, titanium, zirconium, magnesium, zinc, etc.) that are optionally incorporated into the framework formed by the silicon-oxygen bonds. It is expected that the pore diameters will be the same if the bond configuration is the same. In the present invention, when the number of oxygen atoms is 8 to 12, i.e., when the oxygen atoms are 8 to 12-membered rings, the pore diameter will be approximately the target size. Therefore, it is preferable that the pores of the porous oxide are pores composed of 8 to 12-membered oxygen rings. When multiple types of rings are present in a single compound, it is preferable that the ring with the greatest number of oxygen atoms is an 8 to 12-membered oxygen ring.

[0019] The content of alkali metals and alkaline earth metals contained in the porous oxide used in the present invention is 0.00% by weight or more and 2.00% by weight or less, preferably 0.00% by weight or more and preferably 1.00% by weight or less, and more preferably 0.5% by weight or less. The above values ​​are the contents of alkali metals and alkaline earth metals in terms of metals contained in the catalyst, and can be measured by methods such as ICP optical emission spectrometry, ICP mass spectrometry, and atomic absorption spectrometry.

[0020] For example, when silicon oxide contained in the porous oxide used in the present invention is produced using a material containing silicates such as alkali metal silicates or alkaline earth metal silicates as a raw material, the alkali metals and alkaline earth metals are contained in the raw material as ions, so the silicon oxide may contain alkali metals or alkaline earth metals. When this silicon oxide is treated with acid, the alkali metal ions or alkaline earth metal ions are removed and replaced with hydrogen ions to maintain electrical neutrality. These hydrogen ions function as a Bronsted acid, and by controlling their amount, not only the acidity distribution but also the acid strength can be controlled.

[0021] The porous oxide used in the present invention has uniform and regular pores as described above, but it is preferable that the porous oxide is crystalline and that the regularly arranged pores are formed due to its crystalline structure. In this case, although it is possible to form crystals using silicon oxide (silicon-oxygen bonds) alone, if aluminum or other metals are coexistent, the crystals may be formed by incorporating these metals. Known examples of such crystalline porous oxides containing primarily silicon oxide include aluminosilicates containing aluminum and silicon, and metallosilicates containing silicon and metals other than aluminum (e.g., titanium, zirconium, zinc, iron, boron, gallium, etc.). Among these crystalline silicon oxides, crystalline zeolites are preferably used because of their uniform pores.

[0022] The crystalline zeolite preferably used as the catalyst of the present invention generally has a composition represented by the following formula (2): (M １ , M ２ １／２ ) ｍ (Al ｍ Si ｎ O ２（ｍ＋ｎ） ) xH ２ O...(2) In the above formula (2), M １ Li ＋ , Na ＋ , K. ＋ represents an alkali metal ion such as M or a hydrogen ion; ２ is Ca ２＋, Mg ２＋ , Ba ２＋ and the like, wherein m and n are integers, satisfying n≧m, and x is an integer.

[0023] In the above zeolite, M １ and M ２ The cation of Al ｍ Si ｎ O ２（ｍ＋ｎ） The basic unit structure of zeolite is SiO ４ or AlO ４ These tetrahedrons are connected infinitely in three dimensions to form crystals. The zeolite may have a metallosilicate framework in which at least a portion of the aluminum element in formula (2) is replaced with another element such as zinc, iron, boron, gallium, or phosphorus. Zeolites having a framework in which at least a portion of the silicon element of the zeolite is replaced with another element may also be used.

[0024] Although natural zeolites are available as the above-mentioned zeolites (natural zeolites), highly regular synthetic zeolites are preferred from the viewpoint of use as catalysts. Synthetic zeolites are generally produced by using water glass, sodium silicate, colloidal silica, or the like as a silica source, mixing this with an alumina source and compounds serving as oxide sources of elements such as iron, boron, titanium, gallium, and phosphorus, and subjecting the mixture to hydrothermal synthesis in an alkaline aqueous solution. Zeolites produced by hydrothermal synthesis still contain alkali metals such as sodium and potassium, as shown in the above formula (2). Even if lower silanes are contacted in this state to convert them into higher silanes, the catalytic activity is low.

[0025] As described above, in the present invention, even in the zeolite represented by formula (2), all or at least a portion of the alkali metal ions and alkaline earth metal ions must be substituted with hydrogen ions by ion exchange or the like, so that the alkali metal and alkaline earth metal content is 0.00% by weight or more and 2.00% by weight or less. This is thought to result in the development of acid sites on the surface of the silicon oxide (typically the zeolite), thereby imparting catalytic activity.

[0026] The zeolite framework structures are compiled into a database by the International Zeolite Association and are represented by a structure code consisting of three capital letters. Examples of the zeolites include BEA zeolite, FER zeolite, LTA zeolite, MFI zeolite, MOR zeolite, MWW zeolite, LTL zeolite, FAU zeolite, ERI zeolite, CHA zeolite, and OFF zeolite.

[0027] Among the above-mentioned zeolites, BEA-type zeolite, FER-type zeolite, LTA-type zeolite, MFI-type zeolite, MOR-type zeolite, and MWW-type zeolite are preferred in terms of their favorable conversion reaction of monosilane to higher silanes, including trisilane, with MFI-type zeolite being more preferred. These zeolites are presumed to have an appropriate acid distribution and acid strength for the above-mentioned reaction.

[0028] Examples of the BEA type zeolite include β-type zeolite. Examples of the FER type zeolite include ferrierite. Examples of the LTA type zeolite include A-type zeolite. Examples of the MFI type zeolite include ZSM-5 and TS-1. Examples of the MOR type zeolite include mordenites. Examples of the MWW type zeolite include MCM-22. Examples of the LTL type zeolite include L-type zeolite. Examples of the FAU type zeolite include X-type zeolite, Y-type zeolite, and faujasite. Examples of the ERI type zeolite include erionite. Examples of the CHA type zeolite include chabazite. Examples of the OFF type zeolite include offretite. Among these zeolites, ZSM-5 and TS-1 are more preferred, with ZSM-5 being particularly preferred.

[0029] When the porous oxide used in the present invention is a crystalline oxide containing an aluminosilicate or metallosilicate, it is preferable that some or all of the alkali metal ions or alkaline earth metal ions that compensate for the negative charge of the framework in the aluminosilicate or metallosilicate in the porous oxide are substituted with hydrogen ions. The amount of hydrogen ions contained in the aluminosilicate or metallosilicate can be calculated by subtracting the total amount of alkali metal ions and alkaline earth metal ions contained in the aluminosilicate or metallosilicate from the total amount of ions necessary to compensate for the negative charge of the aluminosilicate or metallosilicate framework and maintain electrical neutrality. Because hydrogen ions function as an acid as described above, the calculated amount of hydrogen ions is the amount of acid contained in the porous oxide.

[0030] In addition to the above-mentioned ion exchange method, a crystalline oxide (typically a zeolite) containing an aluminosilicate or metallosilicate substituted with hydrogen ions can also be obtained by using finely powdered silica, colloidal silica, tetraethoxysilane (TEOS), or the like as a silica source, mixing this with an alumina source such as metallic aluminum, aluminum sulfate, aluminum nitrate, or sodium aluminate, or a compound that serves as an oxide source of an element such as iron, boron, titanium, phosphorus, or gallium, and adding an organic structure-directing agent such as a quaternary ammonium salt and water to carry out hydrothermal synthesis.

[0031] When aluminum is contained in the silicon oxide contained in the porous oxide of the present invention, typically when aluminosilicate is contained, SiO ２ / Al ２ O ３ The molar ratio can be any value, but is usually 5 or more, preferably 10 or more, more preferably 20 or more, and is usually 5,000 or less, preferably 3,000 or less, more preferably 2,000 or less. ２ / Al ２ O ３ By having the molar ratio within the above range, the acid strength tends to be suitable for the reaction to produce higher silanes such as trisilane. ２ / Al ２ O ３ The molar ratio can be determined, for example, by X-ray fluorescence analysis.

[0032] As described above, the amount of hydrogen ions can be calculated by subtracting the total amount of alkali metal ions and alkaline earth metal ions contained in the aluminosilicate or metallosilicate from the total amount of ions necessary to compensate for the negative charge of the framework and maintain electrical neutrality, but a specific example of the calculation method will be described here. ２ / Al ２ O ３Consider an example where ZSM-5 zeolite with a molar ratio of 1500 contains 0.01 wt% Na. The amount of Al contained in 1 g of ZSM-5 zeolite is 83.8 micromoles, which is the total amount of ions required to compensate for the negative charge of the framework and maintain electrical neutrality. Meanwhile, the amount of Na contained in 1 g of ZSM-5 zeolite is 4.3 micromoles. As a result, the amount of hydrogen ions contained in 1 g of ZSM-5 zeolite is calculated to be 79.5 micromoles.

[0033] The specific surface area of ​​the porous oxide used in the present invention as measured by the BET method (Source: Science and Applications of Adsorption, Yoshio Ono and Isao Suzuki, edited by Kodansha Scientific) is preferably 100 m ２ / g or more, more preferably 200m ２ / g or more, preferably 1,000m ２ / g or less, more preferably 800m ２ / g or less.

[0034] In order to further improve the performance and characteristics of the catalyst, a suitable transition metal element having catalytic function, such as platinum, palladium, ruthenium, rhodium, copper, silver, molybdenum, nickel, iron, or cobalt, may be introduced into the porous oxide used as the catalyst of the present invention as needed by an ion exchange method, an impregnation method, or the like.

[0035] When it is necessary to mold the porous oxide, it can be molded by various methods according to known methods or methods equivalent to known methods. For example, a suitable binder such as alumina, silica, silica alumina, zirconia, magnesia, titania, or a clay mineral may be mixed with the porous oxide, and the resulting mixture may be molded by a method such as extrusion molding. Alternatively, the porous oxide may be molded without using a binder, for example, by compression molding. By molding in this manner, it is possible to obtain an appropriate size and shape, which can be adapted to the reaction type and process used to produce higher silanes in the present invention.

[0036] [Lower silanes, higher silanes] Examples of lower silanes used as raw materials in the production method of the present invention include monosilane. Examples of higher silanes having a higher silicon number than the lower silanes obtained by the production method of the present invention include silanes (Si ｎ H ２ｎ＋２ ; n is an integer of 2 or more).

[0037] In the production method of the present invention, the lower silane used as the raw material may be used as is without dilution, or may be used as a mixed gas diluted with another diluent gas. When diluting, the diluent gas is not particularly limited as long as it is a gas inert to the lower silane, such as nitrogen, hydrogen, argon, or helium. The concentration of the lower silane in the raw material gas is usually 1 vol% or more, preferably 10 vol% or more, and more preferably 20 vol% or more, and usually 95 vol% or less, preferably 90 vol% or less, and more preferably 80 vol% or less. However, a higher concentration is preferable because it allows for a more compact production apparatus. Furthermore, taking into consideration the need to compact the production apparatus, the concentration of the lower silane in the raw material gas is preferably 50 vol% or more, and preferably 100 vol% or less. In non-catalytic systems, a method of making hydrogen coexist in the raw material gas is sometimes used to suppress the deposition of solid silicon. However, in the present invention, there is little need to make hydrogen coexist in the raw material gas, and productivity can be improved compared to non-catalytic production methods, such as by reducing the size of the production equipment and reducing production costs.

[0038] The lower silane used in the present invention may contain impurities as long as they are inert to the reaction. However, impurities such as oxygen, carbon dioxide, carbon monoxide, nitrogen-containing compounds such as amines and nitriles, oxygen-containing compounds such as water, alcohols, aldehydes and ketones, olefins such as ethylene and acetylene, and phosphines may inhibit catalytic activity, so it is preferable to reduce their presence as much as possible.

[0039] [Contacting Porous Oxide with Lower Silane] In the production method of the present invention, the contacting of the porous oxide with the lower silane is carried out, for example, in a reactor containing the porous oxide as a catalyst, as exemplified in FIG.

[0040] (Temperature) The temperature at which the porous oxide is brought into contact with the lower silane is usually 100° C. or higher, preferably 120° C. or higher, more preferably 140° C. or higher, and usually 400° C. or lower, preferably 350° C. or lower, more preferably 300° C. or lower, and even more preferably 250° C. or lower. Within this temperature range, the temperature will not be too low to result in an insufficient conversion rate of the raw material lower silane, nor will the reaction temperature be too high to cause significant solid silicon precipitation, resulting in adhesion or deposition of solid silicon on the inner walls of the reactor or piping, making stable operation difficult.

[0041] (Residence Time) The residence time is a concept corresponding to the time during which a lower silane contacts a porous oxide, and in the example of FIG. 1 , it indicates the contact time between the porous oxide serving as the catalyst in the reactor and the monosilane raw material introduced into the reactor after temperature adjustment and pressure adjustment of any lower silane described below.

[0042] The residence time is calculated by the following formula (1): Residence time [sec] = Amount of catalyst [L] × ((Pressure [MPaG] + 0.101325) / 0.101325) × (273.15 / (Temperature [°C] + 273.15)) × (3600 / Gas supply rate [NL / h]) (1)

[0043] In formula (1), the catalyst amount indicates the amount of porous oxide to be contacted with the lower silane. In formula (1), the pressure and temperature indicate the pressure and temperature in the reactor when the porous oxide and the lower silane are contacted, respectively, and can be measured using the respective sensors installed in the reactor. In formula (1), the gas supply rate indicates the amount of raw material gas containing the lower silane supplied per unit time to the reactor when contacting the porous oxide, and is measured using a flow meter at the inlet of the reactor. If it is difficult to install a flow meter at the inlet of the reactor, the gas supply rate may be measured using a flow meter installed upstream or downstream of the inlet of the reactor. If the gas supply rate measured using the flow meter is not a value under standard conditions, the gas supply rate may be calculated based on the measurement conditions and converted to the standard conditions. In formula (1), L indicates liters, and NL indicates normal liters.

[0044] The residence time is usually 80 seconds or more, preferably 90 seconds or more, more preferably 100 seconds or more, and usually less than 150 seconds, preferably 140 seconds or less, more preferably 130 seconds or less. If the residence time is within this range, it is possible to increase the selectivity of trisilane and also to reduce the selectivity of disilane and the like, thereby reducing unnecessary waste and increasing the production efficiency of trisilane (production amount per unit time).

[0045] (Pressure) The pressure when contacting the porous oxide with the lower silane is not particularly limited as long as it satisfies the above-mentioned range of reaction temperature and residence time, but is usually 0.1 MPaG or more, preferably 0.2 MPaG or more, more preferably 0.42 MPaG or more, and usually 1.0 MPaG or less, preferably 0.8 MPaG or less, more preferably 0.6 MPaG or less. Within the above-mentioned lower limit range, the size of the reactor and associated equipment can be reduced, and within the above-mentioned upper limit range, the generation of the solid silicon due to high pressure can be suppressed.

[0046] (Cumulative Reaction Time) The cumulative reaction time is the time required from the time lower silanes are introduced into a higher silane production apparatus, including a reactor used to contact the porous oxide with the lower silanes, until the lower silanes are circulated within the production apparatus and continuously contacted with the porous oxide within the reactor under conditions within the above-mentioned residence time range, temperature range, and preferably pressure range, and the resulting higher silanes, including trisilane, are separated in a separator; in other words, the operating time of the production apparatus under the above-mentioned conditions. The production apparatus may also include a raw material heater, compressor, and raw material preheater for adjusting the temperature and pressure of the lower silanes, as described below. For example, in the production flow shown in Figure 1, monosilane is optionally diluted with a diluent gas and introduced into a production apparatus, and then optionally passes through a raw material heater, compressor, and raw material preheater. The monosilane is then brought into contact with a porous oxide in a reactor, unreacted monosilane is recovered in a separator, and the unreacted monosilane, or a mixed gas mixed with optionally added monosilane or diluent gas, is again brought into contact with the porous oxide in the reactor, and this cycle is continuously repeated until the final reaction product, higher silanes including trisilane, are separated.

[0047] However, if the temperature and pressure in the reactor are outside the above temperature range, and preferably outside the above pressure range, the time required to return them to the above temperature range, and preferably within the above pressure range, is not included in the cumulative reaction time. Furthermore, if the contact between the porous oxide and the lower silane in the reactor is stopped, the time required to restart the contact is not included in the cumulative reaction time. If hydrogen gas or the like is passed through the reactor to perform a catalytic activation treatment of the porous oxide in order to remove lower silanes and higher silanes from the porous oxide in the reactor, the cumulative reaction time is reset to 0 hours.

[0048] The cumulative reaction time is usually more than 200 hours, preferably 500 hours or more, more preferably 1000 hours or more, and usually 10000 hours or less, preferably 8000 hours or less, more preferably 6000 hours or less. If the cumulative reaction time is within this range, higher silanes can be obtained with high selectivity to trisilane for a long period of time.

[0049] [Adjusting the temperature and pressure of the lower silane] In the production method of the present invention, it is preferable to adjust the temperature of the lower silane to 0°C or higher and 30°C or lower before contacting the porous oxide with the lower silane, and then increase the pressure of the lower silane after the temperature adjustment to set the temperature of the lower silane to 40°C or higher and 200°C or lower.

[0050] The device used to adjust the temperature of the lower silane to 0°C or higher and 30°C or lower (hereinafter, this temperature adjustment will also be referred to as "temperature adjustment 1") is not particularly limited, and can be, for example, a raw material heater such as a double-pipe heat exchanger. The temperature adjusted in temperature adjustment 1 is usually 0°C or higher, preferably 5°C or higher, and more preferably 10°C or higher, and usually 30°C or lower, preferably 28°C or lower, and more preferably 25°C or lower. The temperature adjusted in temperature adjustment 1 can be measured, for example, with a thermometer provided on the outlet side of the raw material heater. By adjusting the lower silane to the above temperature range in temperature adjustment 1, it is possible to prevent problems such as equipment freezing in the compressor used to increase the pressure of the lower silane next due to the temperature dropping below 0°C.

[0051] Next, the pressure of the lower silane whose temperature has been adjusted in the above-mentioned temperature adjustment 1 is increased (hereinafter, this pressure increase will also be simply referred to as "pressure adjustment"). The device used for pressure adjustment is not particularly limited, but for example, a compressor such as a diaphragm compressor can be used. The pressure of the lower silane to be adjusted by pressure adjustment is usually 0.1 MPaG or more, preferably 0.2 MPaG or more, more preferably 0.42 MPaG or more, and usually 1.0 MPaG or less, preferably 0.8 MPaG or less, more preferably 0.7 MPaG or less. The pressure adjusted by pressure adjustment can be measured, for example, with a pressure gauge installed on the outlet side of the compressor. By adjusting the pressure of the lower silane within the above range by pressure adjustment, the supply of raw materials to the reactor becomes smooth, and the contact conditions between the porous oxide and the lower silane in the reactor become easier to control.

[0052] Thereafter, the temperature of the lower silane whose pressure has been adjusted by the above pressure adjustment is adjusted to 40°C or higher and 200°C or lower (hereinafter, this temperature adjustment is also referred to as "temperature adjustment 2"). The method for adjusting the temperature in temperature adjustment 2 is not particularly limited, but for example, heating to the target temperature can be performed using a heat exchanger. The temperature of the lower silane adjusted in temperature adjustment 2 is usually 40°C or higher, preferably 80°C or higher, and more preferably 100°C or higher, and usually 200°C or lower, preferably 180°C or lower, and more preferably 150°C or lower. Adjusting the lower silane to the above temperature range in temperature adjustment 2 makes it easier to adjust the temperature of the lower silane introduced into the reactor.

[0053] [Production Method] The production method of the present invention is usually preferably carried out by a continuous flow method using a fixed bed, fluidized bed, moving bed or the like.

[0054] In the case of a fixed bed, specifically, it is preferred to continuously pass a lower silane or a mixed gas containing an optional diluent gas through a tubular reactor packed with a porous oxide appropriately shaped as described above. Only one reactor may be used, or when multiple reactors are used, they may be connected in series or in parallel, or a combination of these may be used.

[0055] When the conversion rate of lower silanes decreases due to the passage of production time, etc., the conversion rate of lower silanes can be improved by subjecting the porous oxide to catalytic activation treatment. The catalytic activation treatment can be performed by removing the porous oxide from the reactor, or by leaving the porous oxide in the reactor. However, since this simplifies the number of steps, it is preferable to perform the catalytic activation treatment while leaving the porous oxide in the reactor. The method of catalytic activation treatment is not particularly limited, but it is preferable to stop the flow of lower silanes or a mixture of lower silanes and a diluent gas such as hydrogen gas from a state in which lower silanes or a mixture of lower silanes and a diluent gas such as hydrogen gas are flowing, and then flow a gas containing hydrogen gas. The gas flowed during the catalytic activation treatment is preferably 100% hydrogen gas, but if necessary, it may be diluted with an inert gas such as nitrogen or argon. The temperature during the catalyst activation treatment is not particularly limited, but is preferably 20°C or higher, more preferably 50°C or higher, even more preferably 100°C or higher, and preferably 600°C or lower, more preferably 400°C or lower, and even more preferably 300°C or lower. The pressure during the catalyst activation treatment may be reduced pressure, normal pressure, or increased pressure, but is preferably 0.01 PaG or higher and 1.0 MPaG or lower. This catalyst activation treatment restores the catalytic activity of the porous oxide, resulting in an extension of the catalyst life.

[0056] [Separation and Recovery] The reaction product discharged from the reactor may be separated and recovered into unreacted lower silanes and the resulting higher silanes, including trisilane, by known methods such as cooling or distillation, or trisilane may be separated and recovered from the higher silanes, including trisilane. By separating and recovering in this manner, trisilane can be obtained efficiently. Furthermore, after separation into unreacted lower silanes and the resulting higher silanes, the lower silanes, which serve as raw materials for the higher silanes, can be recovered and recycled, and reused to produce higher silanes, including trisilane.

[0057] <Catalyst for Producing Higher Silanes> One embodiment of the present invention is a catalyst for producing higher silanes, which contains a porous oxide and is brought into contact with a lower silane to convert the lower silane into a higher silane having a higher silicon number than the lower silane, wherein the porous oxide has at least regularly arranged pores and is composed mainly of silicon oxide, and the alkali metal and alkaline earth metal content is 0.00% by weight or more and 2.00% by weight or less, and the catalyst for producing higher silanes satisfies the following production conditions A to C: A: The temperature at which the catalyst and the lower silane are contacted is 100°C or more and 400°C or less; B: The pressure at which the catalyst and the lower silane are contacted is 0.1 MPaG or more and 1.0 MPaG or less; and C: The cumulative reaction time is more than 200 hours and 10,000 hours or less.

[0058] The meanings of the terms used in the present invention are the same as those in the above section <Method for producing higher silanes>.

[0059] The temperature at which the catalyst of the present invention is brought into contact with the lower silane is usually 100° C. or higher, preferably 120° C. or higher, more preferably 140° C. or higher, and usually 400° C. or lower, preferably 350° C. or lower, more preferably 300° C. or lower, and even more preferably 250° C. or lower. Within this temperature range, the temperature will not be too low to result in an insufficient conversion rate of the raw material lower silane, nor will the reaction temperature be too high to cause significant precipitation of the solid silicon, resulting in adhesion or deposition of solid silicon on the inner walls and piping of the reactor, making stable operation difficult.

[0060] The pressure at which the catalyst of the present invention is contacted with the lower silane is usually 0.1 MPaG or more, preferably 0.2 MPaG or more, more preferably 0.42 MPaG or more, and usually 1.0 MPaG or less, preferably 0.8 MPaG or less, more preferably 0.6 MPaG or less. Within the above lower limit range, the size of the reactor and associated equipment can be reduced, and within the upper limit range, the production of solid silicon due to high pressure can be suppressed.

[0061] The present invention will be explained in more detail below based on examples, but the present invention is not limited to these examples and can be practiced with appropriate modifications within the scope of the present invention.

[0062] The concentrations of monosilane, disilane, and trisilane were analyzed by gas chromatography. The gas chromatography measurement was carried out as follows.

[0063] Analyte: monosilane Analytical equipment: gas chromatograph GC-8A (Shimadzu Corporation) Column: Porapak-QS (Waters), length 1 meter, diameter 3 mm Analyte retention time: monosilane = 7.5 minutes Carrier gas: helium (40 ml / min) Column temperature: 70°C, held for 5 minutes, then heated to 180°C at 16°C / min Injection port temperature: 200°C TCD detector temperature: 200°C TCD detector current: milliamperes

[0064] Analyte: disilane, trisilane Analytical equipment: Gas chromatograph GC-2030 (Shimadzu Corporation) Column: TC-BOND Q (GL Sciences), length 30 meters, diameter 0.32 mm Analyte retention time: disilane = 5.1 minutes, trisilane = 9.5 minutes Carrier gas: helium (3.4 mL / min) Column temperature: 70°C Injection port temperature: 150°C BID detector temperature: 180°C BID detector: discharge gas

[0065] Quantitative determination of raw materials and products: From the results of the gas chromatographic measurements described above, the contents (mol%) of monosilane (MS), disilane (DS), and trisilane (TS) contained in the reacted gas were determined. From the MS supply amount (mol / min) per hour and the contents of each of the above components, the amount of DS produced per hour (moles / min in terms of Si atoms), the amount of TS produced per hour (moles / min in terms of Si atoms), and the amount of unreacted MS remaining (moles / min in terms of Si atoms) were determined after the reaction. Note that in all cases, no higher silanes than tetrasilane were detected.

[0066] From these values, the MS conversion rate (mol%), DS selectivity (mol%), and TS selectivity (mol%) were calculated as follows: MS conversion rate (mol%) = (amount of DS produced (mol) x 2 + amount of TS produced (mol) x 3) / MS supply amount (mol) DS selectivity (mol%) = amount of DS produced (mol) x 2 / (amount of DS produced (mol) x 2 + amount of TS produced (mol) x 3) TS selectivity (mol%) = amount of TS produced (mol) x 3 / (amount of DS produced (mol) x 2 + amount of TS produced (mol) x 3)

[0067] The experimental apparatus and production flow used in this invention are shown in Figure 1. The reactor was filled with a catalyst and heated to a predetermined temperature in an electric furnace. The flow rate of the raw material gas was controlled by a mass flow meter.

[0068] [Example 1] ZSM-5 (SiO ２ / Al ２ O ３ A catalyst pretreatment was carried out by filling a 284 mm inner diameter reactor tube with 132 L of a catalyst (molar ratio = 1500, Na content [wt%] = 0.01, alkali metals and alkaline earth metals other than Na below the detection limit, pore diameters = 0.51 nm, 0.53 nm, 0.55 nm, 0.56 nm (0.4 nm to 0.6 nm), shape: 3 mm pellets, binder type: alumina) and heating it at 200 °C under a nitrogen flow. A mixed gas of monosilane gas and hydrogen gas (monosilane concentration: 80 vol%) was introduced into the reactor and circulated within the production equipment at 120 °C and 0.5 MPaG for 2028 hours to produce higher silanes. The gas supply rate was appropriately controlled with a control valve from the start of the reaction, and the gas supply rate was changed as shown in the table below. The reaction product at the point where the cumulative reaction time reached 647 hours was introduced online into a gas chromatograph GC-8A (manufactured by Shimadzu Corporation), and the contents of monosilane, disilane, and trisilane were determined. Furthermore, no solid silicon deposition was observed visually on the wall surface of the reaction tube. From these values, the results of MS conversion, DS selectivity, TS selectivity, etc., and the respective conditions are shown in Table 1 below. The reactor temperature in Table 1 indicates the temperature at the time the reaction product was obtained.

[0069]

[0070] [Example 2, Comparative Examples 1 and 2, Reference Examples 1 and 2] The contents of monosilane, disilane, and trisilane were determined, and the MS conversion, DS selectivity, and TS selectivity were calculated in the same manner as in Example 1, except that the conditions were changed to those shown in Table 1. The results are shown in Table 1. No solid silicon deposition was visually observed on the wall surface of the reaction tube.

Claims

1. A method for producing higher silanes by contacting a porous oxide with a lower silane to convert it into a higher silane having a higher silicon number than the lower silane, wherein the higher silane comprises trisilane, the cumulative reaction time is more than 200 hours and not more than 10,000 hours, the temperature during contact between the porous oxide and the lower silane is 100°C or higher and 400°C or lower, and the residence time represented by the following formula (1) is 80 seconds or higher and less than 150 seconds. Residence time [seconds]=catalyst amount [L]×((pressure [MPaG]+0.101325) / 0.101325)×(273.15 / (temperature [°C]+273.15))×(3600 / gas supply rate [NL / h]) (1) (In formula (1), the catalyst amount represents the amount of porous oxide to be contacted with the lower silane, the pressure and temperature represent the pressure and temperature, respectively, when the porous oxide is contacted with the lower silane, and the gas supply rate represents the amount of source gas containing the lower silane supplied per unit time when contacted with the porous oxide.) 2. The method for producing higher silanes according to claim 1, wherein the residence time is 80 seconds or more and less than 120 seconds.

3. The method for producing higher silanes according to claim 1, wherein the temperature of the lower silane is adjusted to 0°C or higher but 30°C or lower before contacting the porous oxide with the lower silane, and the pressure of the lower silane after temperature adjustment is increased to set the temperature of the lower silane to 40°C or higher but 200°C or lower.

4. A method for producing higher silanes as set forth in claim 1, wherein the porous oxide has at least regularly arranged pores, is composed primarily of silicon oxide, and has an alkali metal and alkaline earth metal content of 0.00% by weight or more and 2.00% by weight or less.

5. The method for producing higher silanes according to claim 4, wherein the pore diameter of the porous oxide is 0.4 nm or more and 0.6 nm or less.

6. The method for producing higher silanes according to claim 1, wherein the porous oxide has a crystalline zeolite structure made of aluminosilicate or metallosilicate.

7. The porous oxide is an aluminosilicate, and SiO ２ / Al ２ O ３ 2. The method for producing higher silanes according to claim 1, wherein the molar ratio is 10 or more and 3,000 or less.

8. The method for producing higher silanes according to claim 1, wherein the porous oxide is MFI-type zeolite.

9. The method for producing higher silanes according to claim 1, further comprising separating and recovering trisilane from the higher silanes.

10. A catalyst for producing higher silanes, which contains a porous oxide and is brought into contact with a lower silane to convert the lower silane into a higher silane having a higher silicon number than the lower silane, wherein the porous oxide has at least regularly arranged pores and is composed mainly of silicon oxide, and the alkali metal and alkaline earth metal content is 0.00% by weight or more and 2.00% by weight or less, and the production conditions of the catalyst for producing higher silanes are met as follows: A. A: The temperature at which the catalyst and the lower silane are contacted is 100°C or higher and 400°C or lower. B: The pressure at which the catalyst and the lower silane are contacted is 0.1 MPaG or higher and 1.0 MPaG or lower. C: The cumulative reaction time is more than 200 hours and 10,000 hours or less.

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