Process for producing pyrolytic metal and metalloid oxides

Abstract

Method for producing pyrolytic metal and / or metalloid oxides with the aid of a burner (200) having a burner head (100) comprising an outlet end (104), a central section (110) having at least one central channel (112), and a jacket channel (116) positioned concentrically around the central section, and wherein the following method steps are included: providing at least one metal or metalloid precursor, at least one fuel gas and oxygen via the central section (110); providing at least one fuel gas via the jacket channel (116); providing a flame (190) by combusting the fuel gas at the outlet end (104), wherein the ratio R1 = VC / VJ is at most 6.0, wherein VC is the normalized gas outlet velocity of all gases from the central section (110), and VJ is the normalized outlet gas velocity of all gases from the jacket channel (116).

Description

Technical Field

[0001] This invention relates to a method for producing pyrolytic metal oxides and quasi-metal oxides using a burner. Background Technology

[0002] Pyrolysis, also known as flame hydrolysis or flame pyrolysis, is a well-known method for producing gaseous (pyrolytic) metal and near-metal oxides such as SiO2, Al2O3, and TiO2. This method involves the intense exothermic combustion of hydrogen fuel to produce water (H2 + 0.5O2). The process involves the hydrolysis of metal precursors, such as SiCl4 or AlCl3, using water obtained from the combustion of fuels like hydrogen (H2O) and flame hydrolysis. In the flame pyrolysis process, the organic precursors are pyrolyzed in a flame obtained by burning fuels such as hydrogen.

[0003] Generally, products with relatively high BET surface area, small particles, and narrow particle size distribution can be achieved through pyrolysis. Higher BET surface area is typically achieved by using more air to cool the flame. However, a disadvantage is that in this case, the plant productivity decreases because the same amount of metal oxide is distributed in a larger gas volume.

[0004] In typical pyrolysis processes, burner geometries such as those shown in Ind. Eng. Chem. Res. 2022, 61, 21, 7235–7244 are used to produce metal oxides or near-metal oxides. In this method, a metal or near-metal precursor, air, and H2 fuel are premixed and introduced to the outlet end of the burner head via a central reaction channel (pipe). Simultaneously, a small amount of fuel gas (hydrogen) is directed through another inlet into a jacketed channel located around the central reaction channel and ignited in the presence of auxiliary air around the burner head. Thus, the hydrogen fed through the jacket burns at the reactor opening and sustains the flame during pyrolysis, while the main fuel portion, main air, and metal precursor are fed into this flame via the central reaction channel.

[0005] The production of metal oxides with relatively high BET surface areas typically requires reducing the flame temperature. This is usually achieved through measures or combinations thereof: (a) using a hydrogen feedstock in a minimum amount relative to the reaction stoichiometry and / or (b) using additional air or steam to “dilute” and cool the flame. The method using a minimum amount of hydrogen feedstock is described, for example, in US 2014 / 0030525 A1. This method produces BET surface areas of 400 to 600 m². 2A method for producing / g of silica powder includes: igniting a gas mixture comprising an oxidizable and / or hydrolyzable silicon compound, hydrogen, and an oxygen-containing first gas in a burner, and burning the resulting flame into a reaction chamber, introducing an oxygen-containing second gas into the reaction chamber, and separating the resulting solid material from the gaseous material, wherein the quotient formed in the burner by the amount of hydrogen supplied and the amount of hydrogen required for stoichiometry is 0.70 to 1.30.

[0006] According to EP 0015315 A1, the use of additional air and a minimum amount of additional water vapor in flame hydrolysis processes is described as beneficial for higher BET surface area and particle size.

[0007] However, using a more diluted feed stream, such as additional air or additional steam, typically leads to an unavoidable reduction in production capacity and higher production costs. Therefore, it would be beneficial to reduce the flame temperature and obtain a fumed oxide with a higher BET surface area without adding a diluted feed stream. Summary of the Invention

[0008] The object of the present invention is to provide a method for producing metal and / or quasi-metal oxides with relatively high BET surface area under high throughput of a production apparatus, i.e., without diluting the flame with additional air, water vapor and other gases.

[0009] These requirements can be met by a method for producing pyrolytic metal oxides and / or quasi-metal oxides using a burner having a burner head, the burner head comprising...

[0010] - Export end,

[0011] - A central segment having at least one central channel, and

[0012] - A jacketed channel concentrically positioned around the central segment, and

[0013] This includes the following methods and steps:

[0014] - At least one metallic precursor and / or quasi-metallic precursor (collectively, "MP"), a first fuel gas, and an oxygen-containing gas are provided via the at least one central channel of the central segment;

[0015] - A second fuel gas is provided via the jacketed channel;

[0016] - A flame is provided by burning a first fuel gas and a second fuel gas at the outlet end, wherein the ratio R1 = V C / V J For a maximum of 6.0, and of which V CV is the normalized gas outlet velocity of all gases from the central section. J It is the standardized outlet gas velocity of all gases from the jacket channel.

[0017] The first fuel gas and the second fuel gas are collectively referred to as "fuel gas" or "multiple fuel gases". The first and second fuel gases can be the same or different gases. The fuel gas can be a mixture of fuel gases that (in addition) contain other gases besides the fuel gas components, such as inert gases, such as, but not limited to, nitrogen (N2) and / or carbon dioxide (CO2). The additional gas besides the fuel gas components can be an oxygen-containing gas. The oxygen-containing gas can be pure oxygen (O2), air, or oxygen-enriched (O2) air.

[0018] The burner head, as part of the burner, is typically at least partially mounted and positioned within the burner housing. The burner may further include a combustion chamber, also called a flame chamber, into which the flame extends at the outlet end of the burner head. The housing is typically connected to an outlet (line) or product line. Such a product line and / or burner housing may include a flame tube. Preferably, the flame tube forms the outlet portion of the flame chamber, which is part of the housing, and / or the first segment of the product line. According to an advantageous solution, the flame tube is connected to a (subsequent) cooling line, whereby the cooling line may also be a segment of the product line and / or form a cooling unit connectable to the product line.

[0019] Typical gas velocities at the burner head outlet are described in US 2007 / 025388 A1. A total outlet velocity of gas exiting the burner of 10 m / s or even 25 m / s or higher is described as advantageous. The gas exiting the burner head and forming the flame is further cooled to produce gaseous metal oxides or near-metal oxides. However, little is known about the effect of the gas velocity at the burner head on the gaseous oxide products. Even less is known from the prior art regarding the effect of the outlet gas velocity from the jacket channel.

[0020] In the context of this invention, the term "outlet end" refers to the outer portion of the burner head, that is, the respective outlet end of the corresponding gas passage of the burner head, where the gas leaves the corresponding passage of the burner head and forms a flame.

[0021] In the context of this invention, the term "channel" refers to any space suitable for supplying gas to the outlet end, such as, but not limited to, pipelines, conduits, and annular gaps.

[0022] In this invention, the term "jacketed channel" refers to a channel surrounding the central section, i.e., located around the central section, such that the jacketed channel and the central section form a concentric channel system, and can alternatively be described as, for example, a tube-in-tube system, wherein the central section is located inside (centrally) within the system. The jacketed channel is preferably the outermost portion of the concentric channel system of the burner head.

[0023] In a preferred embodiment, the central segment includes multiple concentric channels to form a concentric channel subsystem.

[0024] The central section includes at least one central channel for supplying MP, as well as a first fuel gas and an oxygen-containing gas, and optionally other gases.

[0025] According to a preferred embodiment of the invention, the central segment comprises at least one channel or at least two concentric channels having a circular or non-circular shape, such as, but not limited to, elliptical, approximately square, rectangular, and / or polygonal shapes. In another advantageous embodiment, at least one concentric channel of the jacket channel and / or the central segment is formed by a set of smaller conduits, which together form a group surrounding at least one additional channel. The concentric channel formed by the set of smaller conduits can be at least one of the channels of the jacket channel and / or the central segment. The smaller conduits forming the concentric channels can have a circular or non-circular shape, such as, but not limited to, elliptical, approximately square, rectangular, and / or polygonal shapes.

[0026] Preferably, the outlet end of each channel and / or the smaller conduit of such channel is located in or near a plane, advantageously near an average (outlet) plane of up to + / - 10 mm, more preferably up to + / - 5 mm.

[0027] In another preferred embodiment of the invention, the central section consists of a bundle of tubes, i.e., a group of parallel tubes close to each other, each having a circular, elliptical, approximately square, rectangular, and / or polygonal shape. The outlet end of each such tube is preferably located in or near a plane, advantageously near an average (outlet) plane up to + / - 10 mm, more preferably up to + / - 5 mm.

[0028] The jacketed channel is used to supply at least one (second) fuel gas and optionally other gases, which can help maintain continuous flame combustion and ensure smooth operation throughout the entire production process.

[0029] According to a preferred embodiment of the invention, a single jacketed channel in the burner head is provided in the form of a pipe having a circular, elliptical, approximately square, rectangular, and / or polygonal shape. This (external) jacketed channel can also be described as an annular channel or groove having a circular orifice at the outlet end. In the case of a circular form, the circular orifice has a ring shape.

[0030] In a preferred embodiment, the jacketed channel consists of a bundle of tubes, i.e., a group of (smaller) tubes. This group of (smaller) tubes can be positioned close to each other around a central section, each having a circular, elliptical, approximately square, rectangular, and / or polygonal shape. The outlet end of each such tube is preferably located in or near a plane, advantageously near an average (outlet) plane by up to + / - 10 mm, more preferably up to + / - 5 mm.

[0031] In this invention, the term "standardized gas velocity" refers to the corresponding value measured or calculated under standard conditions, i.e., 0°C and 1 atm pressure. A suitable unit for this value is, for example, Nm³. 3 / h, where the letter "N" stands for "normalized" value. For simplicity, such "normalized" values ​​are used to compare flow rates or feed rates under varying reaction conditions.

[0032] In this invention, the term "gas outlet velocity" refers to the average gas velocity of the respective gas (or multiple gases) from the corresponding section and / or at least one channel. Therefore, the velocity "V" C "V" refers to the standardized average velocity of all gases exiting from the center section of the burner head in this method. Similarly, the velocity "V" J "" refers to the standardized average velocity of all gases exiting the jacket passage of the burner head in this method.

[0033] Ratio R1 = V C / V J By V C Divide by V J To calculate:

[0034] - V C The total volume (in m³) of all feed gas leaving the central section per hour under standard conditions (= Nm³) 3 The calculation is based on the area (in m²) of the total cross-sectional area of ​​all channels in the central section at the outlet end of the burner head, divided by the area of ​​the cross-section.

[0035] - V J The total volume (in m³) of all feed gas leaving the jacket channel per hour under standard conditions (= Nm 3 The calculation is based on the area of ​​the cross-section of the jacket channel at the outlet end of the burner head (in m²).

[0036] The burner head itself is typically at least partially located and mounted within a housing that is part of the burner. The burner and / or burner head may include and / or be connected to additional elements, such as, but not limited to, feed lines, outlet lines, maintenance elements, control and sensor devices, and mounting elements. In a preferred embodiment of the invention, an inlet and / or passage (auxiliary passage) for supplying oxygen-containing gas is provided outside the jacket passage, preferably for supplying atmospheric air to the process flame. In an advantageous embodiment, the auxiliary passage is located between the jacket passage and the burner housing and / or at least a portion of its length is formed by the outer surface of the jacket passage and the inner surface of the burner housing. The auxiliary passage preferably concentrically surrounds the jacket passage.

[0037] Surprisingly, it has now been found that adjusting the gas velocity exiting from the jacket channel of the burner head relative to the gas velocity exiting from the center section of the burner head results in a significant change in the obtained pyrolytic oxides. Specifically, results show that reducing the ratio of the outlet gas velocity from the center section to the outlet gas velocity from the jacket channel leads to a higher BET surface area without any reduction in plant productivity. Furthermore, it has a positive effect on the particle size of the obtained metal oxide and quasi-metal oxide particles.

[0038] The term "oxygen-containing gas" refers to O2, air, and / or O2-rich air. In the context of this invention, the term "MP" refers to the corresponding substance, namely a metal precursor and / or a quasi-metal precursor, and / or a mixture containing a metal precursor and / or a quasi-metal precursor, which is present at least at the outlet end of the burner head in a non-solid, preferably gaseous, form (e.g., gas, spray, steam, aerosol, etc.).

[0039] In a preferred embodiment of the method, the central channel of the central section serves as the sole channel within the central section for supplying MP, fuel gas, and oxygen. In this embodiment, the central channel of the central section may be connected upstream to a mixing chamber or any other mixing unit to mix the MP, fuel gas, oxygen, and optionally other gases before supplying them to the central section of the burner head.

[0040] In an alternative preferred embodiment of the invention, the central section has at least two central channels for separately supplying MP, fuel gas, and / or oxygen.

[0041] According to a further preferred embodiment of the method, the metal oxide or quasi-metal oxide is selected from oxides of the following substances: aluminum (Al), titanium (Ti), zirconium (Zr), yttrium (Y), lithium (Li), magnesium (Mg), lanthanum (La), cerium (Ce), iron (Fe), zinc (Zn), silicon (Si) and mixtures thereof, preferably alumina (Al2O3), titanium dioxide (TiO2) and / or silicon dioxide (SiO2) and mixtures thereof, most preferably silicon dioxide (SiO2).

[0042] According to a further preferred embodiment of the method, MP is selected from at least one of the following substances: aluminum chloride (AlCl3), aluminum oxychloride (AlOCl), titanium tetrachloride (TiCl4), titanium trichloride (TiCl3), titanium oxychloride (TiOCl2), tetraalkoxytitanates such as tetraethoxytitanate Ti(OC2H5)4, tetraalkoxysilicates such as tetraethoxysilicate Si(OC2H5)4, for example octamethylcyclotetrasiloxane, cyclic siloxanes (R3Si-[O-SiR2)). n -O-SiR3), acyclic siloxanes (R3Si-[O-SiR2) n -O-SiR3) such as silicone oil, silicon tetrachloride (SiCl4), trichlorosilane (HSiCl3), methyltrichlorosilane (CH3SiCl3), dichlorosilane (H2SiCl2) and / or monochlorosilane (H3SiCl).

[0043] According to a further preferred embodiment of the method, the first and second fuel gases are selected from the following substances: hydrogen (H2), hydrogen-containing gas mixtures, carbon monoxide (CO), organic compounds having at least one hydrogen atom, such as hydrocarbons or alcohols, and mixtures thereof. Hydrocarbons may have the general formula C2. n H 2n+2 The fuel gas is an alkane, wherein "n" is preferably 1 to 6, and most preferably "n" is a number from 1 to 4. The alcohol can be a primary alcohol, a secondary alcohol, and / or a tertiary alcohol. Most preferably, the fuel gas is hydrogen or a mixture of hydrogen-containing gases.

[0044] In another advantageous embodiment, the second fuel gas supplied via the jacketed channel is selected from hydrogen (H2) or a hydrogen-containing gas mixture. Preferably, the only substance supplied via the jacketed channel as the combustible component (fuel gas) is hydrogen. In one embodiment of the method, the second fuel gas supplied via the jacketed channel is a hydrogen-containing gas mixture containing nitrogen (N2), carbon dioxide (CO2), and / or other inert gases.

[0045] In an alternative embodiment of the method, the second fuel gas supplied via the jacket channel may be different from the first fuel gas supplied via the central section. Therefore, the second fuel gas supplied via the jacket channel may be hydrogen (H2), and the first fuel gas in at least one channel of the central section may be…

[0046] - A mixture of hydrogen-containing gases,

[0047] - Carbon monoxide (CO), and / or

[0048] - An organic compound having at least one hydrogen atom. Suitable examples of such organic compounds are given above.

[0049] Most preferably, both the first and second fuel gases are hydrogen or a mixture of hydrogen-containing gases.

[0050] According to another advantageous embodiment of the method, the central section includes a single channel for supplying MP, fuel gas, and oxygen-containing gas.

[0051] The oxygen (O2) used in the method of the present invention may be supplied to the method in the form of air or oxygen-enriched (O2) air, and are collectively referred to herein as oxygen-enriched gas.

[0052] Oxygen supplied to the flame via the central section is typically referred to as "primary" oxygen. Conversely, oxygen supplied to the flame via other routes, such as through additional channels, feed lines, or orifices in the combustion chamber, and thus compressed or drawn into the flame, is typically referred to as "auxiliary" oxygen. In the most typical case, oxygen (in the form of atmospheric air) is drawn into the flame from outside the burner via a channel located between the jacket passage and the combustion chamber shell.

[0053] Standardized outlet gas velocity (V) from the center section C The velocity is preferably at least 15 m / s. In a more preferred version of this embodiment, the normalized outlet gas velocity (V) from the center section... C The speed is at least 20 m / s, more preferably at least 25 m / s, and most preferably at least 29 m / s. A V greater than 100 m / s C It may be difficult to achieve and is impractical in actual production facilities.

[0054] In the method of the present invention, it may be advantageous to normalize the outlet gas velocity (V) from the jacket channel. J The velocity is adjusted to at least 4 m / s. In a preferred version of this embodiment, the normalized outlet gas velocity (V) from the jacket channel is... J The speed is at least 6 m / s, more preferably at least 8 m / s, and most preferably at least 10 m / s. A V greater than 100 m / s JIt may be difficult to achieve and is impractical in actual production facilities.

[0055] In a preferred embodiment of the invention, the ratio R1 = V C / V J More preferably, the ratio R1 is in the range of 0.5 to 6.0, even more preferably in the range of 1.0 to 5.0, even more preferably in the range of 1.2 to 4.5, and even more preferably in the range of 1.5 to 4.0. These narrow ranges of R1 enable the production of pyrolytic metal oxides and / or quasi-metal oxides with particularly high BET surface areas and small particle sizes.

[0056] According to a further preferred embodiment of the method, the produced pyrolytic metal oxide or quasi-metal oxide has a 10 m 2 / g to 600 m 2 / g, preferably 50 to 400 m 2 / g BET surface area.

[0057] According to a further preferred embodiment of the method, the produced pyrolytic metal oxide or quasi-metal oxide has a number-average particle size d of up to 200 nm, preferably 20-200 nm, more preferably 50-180 nm, and even more preferably 100-170 nm. 50 .

[0058] According to a further preferred embodiment of the method, the produced pyrolytic metal oxide or quasi-metal oxide having a molecular weight of at most 0.35, preferably 0.25-0.35, is defined as (d 90 -d 10 ) / d 50 The particle size distribution span. d 10 d 50 and d 90 The value can be determined by static light scattering (SLS).

[0059] According to a further preferred embodiment of the method, with Nm 3 The total normalized feed rate of all gases introduced into the burner head, measured in Nm³ / h, is compared with the total normalized feed rate of all gases introduced into the burner head, measured in Nm³ / h. 3 The ratio (R2) of the feed rate of the metal precursor per hour is at least 5, more preferably between 5 and 20. The standardized feed rate of all gases is defined as the total amount of gas (e.g., but not limited to gaseous metal and / or near-metal precursors, O2, H2, CO, C) supplied to the burner head per hour. n H 2n+2 The volumetric flow rate (in m³) of N2 and / or N2 under standard conditions (0°C, 1 atm). 3 count).

[0060] In the method of the present invention, the fuel gas supplied via the jacket channel is preferably hydrogen or a hydrogen-containing gas. Additionally, nitrogen can advantageously also be supplied via the jacket channel. In this embodiment, it may be advantageous to supply nitrogen in Nm³. 3 The standardized feed rate of nitrogen (N2) into the jacket channel, measured in Nm³ / h, is compared with the standard feed rate of nitrogen (N2) into the jacket channel. 3 The ratio (R3) of the standardized feed rate of hydrogen (H2) to the jacket channel, measured in h, is in the range of 0.10 to 1.0, preferably 0.15 to 0.6, and more preferably 0.2 to 0.5. Surprisingly, it has been observed that the addition of inert nitrogen (particularly at the ratio specified above) to the hydrogen fuel gas leaving the jacket channel results in smoother continuous operation of the production unit, more uniform flame formation, and improved flame stability over long operating times.

[0061] In a preferred embodiment of the method of the present invention, using Nm 3 The standardized feed rate of fuel gas passing through the central section, measured in Nm³ / h, and the... 3 The ratio (R4) of the total standardized feed rate of fuel gas through the jacketed channel, measured in units of / h, is between 2 and 20, more preferably between 3 and 16, and even more preferably between 4 and 10. Therefore, providing a relatively small portion of the fuel gas through the jacketed channel and the remainder through the central section has proven to be the most efficient process mode to ensure economical and smooth operation.

[0062] The pyrolytic metal oxides or quasi-metal oxides obtained according to one of the embodiments or versions of the methods mentioned herein can be used as components of paints or coatings, organosilicon, pharmaceutical or cosmetic preparations, adhesives or sealants, toner compositions, for modifying the rheological properties of liquid systems, as anti-settling agents, for improving the flowability of powders, for improving the mechanical or optical properties of organosilicon compositions, and as components of lithium-ion batteries.

[0063] The following figures are intended to illustrate the methods and suitable apparatus (e.g., burners, burner heads) of the invention in more detail. These figures represent only some exemplary suitable forms of burners used, and should not be construed as limiting the scope of the invention itself in any way. Attached Figure Description

[0064] Therefore, as shown below:

[0065] Figure 1 : As two cross-sectional views (I, II), the first burner and the burner head, one (I) is parallel to and includes the longitudinal axis, and the other (II) is perpendicular to the longitudinal axis;

[0066] Figure 2The second burner and burner head are shown in two cross-sectional views (I, II), one (I) is parallel to and includes the longitudinal axis, and the other (II) is perpendicular to the longitudinal axis;

[0067] Figure 3 The third burner head is shown as a cross-sectional view parallel to and including the longitudinal axis.

[0068] Figure 4 Cross-sectional views perpendicular to the longitudinal axis of three other types of burner heads (I, II, III); and

[0069] Figure 5 : A graph showing the BET surface area and average particle size of fumed silica samples obtained by adjusting various R1 ratios.

[0070] Burner 200 in Figure 1 Partial view I schematically shows a burner head 100 with longitudinal axis A, several feed lines 150, 152, 154, a housing 160, and a product line 170. Reference numeral 190 indicates a flame, shown schematically as a dashed line, having a flame center axis parallel to or the same as longitudinal axis A. Figure 1 The overall flow direction of the burner head 100 shown in (I) is indicated by arrow B. The burner head 100 includes an inlet end 102, an outlet end 104, and several (gas) channels 112, 116, each channel having an outlet opening 140, 144 at the outlet end 104. No additional equipment required for operating the burner and the method is shown in the figures, such as, but not limited to, additional processing units, pumps, compressors, tanks, sensors, actuators, ignition devices, power supplies, etc. Additional processing units, such as, but not limited to, cooling units, deacidification units, and separation units for metal oxides and / or quasi-metal oxides produced by the method of the present invention, are also present in the flow direction B and connected to the product line 170; these are also not shown in the figures.

[0071] According to the partial view I shown Figure 1 In one example, burner 200 includes a main section 110 in the radial direction, having a single central channel 112 concentrically surrounded by a jacketed channel 116. The jacketed channel 116 is the final channel of the burner head 100 in the radial direction. A plane 148 oriented perpendicular to the longitudinal axis A defines the origin of the flame in the combustion chamber 162 in the flow direction B. Figure 1In the illustrated embodiment, the outlet openings 140 and 144 of the channels 112 and 116 of the burner head 100 are located in this plane 148. Pyrolysis occurs within the combustion chamber 162 located within the housing 160 of the burner 200. The burner head 100 is at least partially mounted within the burner 200 and / or housing 160, the mounting arrangements of which are not shown in detail here. Furthermore, the flame tube may be part of the product line 170, for example as a first section and / or as a connection portion to the flame chamber 162 of the housing 160 (not shown). Alternatively, the flame tube may be an integrated portion of the flame chamber 162 and / or housing 160 (not shown). Such a flame tube may have a conical shape in the axial direction.

[0072] The term "flame axis" is defined by the main or central axis of the gas released from the burner head and / or the pyrolysis flame. The terms "flame axis" and "central axis" are used synonymously herein. Although a single flame axis is mentioned, it should be understood that the dynamic gas release or flame defines a corridor containing multiple axes rather than a single axis in a mathematical sense. Therefore, the central axis refers to the position and orientation of the axis with the highest statistical probability. Furthermore, this axis is alternatively or additionally defined by the symmetry of the outlet opening of the burner head and / or the flame-forming gas. Similarly, "center" should refer to something radially adjacent to or overlapping the central axis and / or adjacent to or overlapping the flame axis. The terms "combustion chamber" and "flame chamber" are used synonymously herein.

[0073] The term "plane" refers to a surface area, projected plane, and / or direct surface in a technical rather than mathematical sense. It is used for illustrative and explanatory purposes. Thus, a "plane" can have a finite height or depth, and may be formed, for example, a narrow corridor.

[0074] The burner 200 includes an auxiliary passage 118 disposed radially outside the jacket passage 116, serving as a concentric gas passage surrounding passages 112 and 116. Passage 118 opens to the atmosphere via flange 158, and during this process, auxiliary air is drawn into (auxiliary) passage 118 as auxiliary oxygen-containing gas and subsequently into combustion chamber 162. The auxiliary passage 118 may be defined as a passage of the burner 200 or as a transitional space between the burner head 100 and the burner housing 160. According to an alternative embodiment (not shown), the auxiliary passage 118 for providing auxiliary air may be part of the burner head 100, serving as a concentric passage surrounding the jacket passage 116.

[0075] Figure 1Partial view II shows the concentric orientation of channels 112 and 116 of burner head 100, auxiliary channel 118 of burner 200, and housing 160. The DD line indicates the orientation of the cross section, which is oriented in the same, similarly, and / or parallel to plane 148 (partial view I).

[0076] In this method, a mixture of raw material MP and primary air is supplied via feed line 150 to a first central channel 112 oriented parallel to the longitudinal axis A. Additionally, (first) fuel gas is guided to the central channel 112 via feed line 152. An auxiliary oxygen-containing gas, such as atmospheric air, is drawn into an auxiliary channel 118 and released into the flame chamber 162 once the flame is ignited.

[0077] The second fuel gas is guided and released into the combustion chamber 162 via the jacket passage 116. The auxiliary fuel gas can be hydrogen or a fuel gas mixture containing hydrogen (H2) and an additional gas. The additional gas can be, for example, nitrogen (N2) or an N2-containing gas. The additional gas has a dilution effect and can also be supplied to the jacket passage 116 by the third feed line 154. The gas exiting the outlet opening 144 forms a jacket flame upon ignition.

[0078] Burner 200 in Figure 2 The diagram is schematically shown in partial view I, which includes a burner head 100 with longitudinal axis A, several feed lines 150, 152, 154, a housing 160, and a product line 170. According to... Figure 2 The burner head 100 includes three channels 112, 114, and 116, each having an outlet opening 140, 142, or 144 at an outlet end 104. The burner 200 is typically connected to and can be controlled by a control unit 120, with data connections indicated by dashed data lines 122. The product line 170 is an outlet line leading to another processing unit (not shown).

[0079] According to the partial views I and II shown Figure 2 For example, burner 200 includes a radially oriented central section 110 having two central channels 112, 114 concentrically surrounded by a jacketed channel 116. The first central channel 112 is concentrically surrounded by the second central channel 114. The jacketed channel 116 is the final channel of the burner head 100 in the radial direction. Longitudinally, burner 200 includes three main sections 130, 132, and 134. The main axial sections are as follows: feed section 130, guide section 132, and release section 134. A plane 148 oriented perpendicular to the longitudinal axis A defines the end point of guide section 132 and the beginning point of release section 134 and / or flame chamber 162 in the flow direction B. Figure 2In the illustrated embodiment, the outlet openings 140, 142, and 144 of the channels 112, 114, and 116 of the burner head 100 are located in this plane 148. The release section 134 includes a combustion chamber 162, also referred to as a "flame chamber," in which hydrolysis and / or pyrolysis of MP occurs. The feed section 130 is defined as a section including at least partially inserted feed lines 150, 152, and 154, each feed line connected to at least one of the internal channels 112, 114, and 116 of the burner head 100.

[0080] Similar to Figure 1 In the embodiment shown, the burner 200 includes an auxiliary passage 118 located between the jacket passage 116 and the housing 160. The auxiliary passage 118 is radially outside the jacket passage 116. At least one feed line 156, for example, connected to at least one flange element 158, leads into the auxiliary passage 118. According to an alternative embodiment not shown in the figures, the burner may not include such an auxiliary passage, and auxiliary air or (auxiliary) oxygen-containing gas may be supplied directly to the flame chamber 162 via at least one feed line.

[0081] Figure 2 Partial view II shows the concentric orientation of the channels 112, 114, 116, 18 of the burner 200 and the housing 160. The DD line markings indicate the orientation of the cross-section, which is oriented in the same, similarly, and / or parallel to the plane 148.

[0082] The guide section 132 is downstream of the feed section 130 in the flow direction, and is thus defined by the feeding of any raw material (reactant) in at least one of the internal channels 112, 114, 116 of the burner head 100, and, if applicable, by the auxiliary channel 118 for air supply to the burner 200. In other words, in the guide section 132, the (main) feed line is no longer connected, and a final gas flow in the flow direction B is formed within the burner head 100. The channel 118 opens to the atmosphere via flange 158 and draws in auxiliary O2 via orifice and flange 158.

[0083] Release section 134 is located at the opposite end of guide section 132 (relative to section 130). The end of guide section 132 is substantially defined and restricted in the flow direction B by the outlet openings 140, 142, 144 of channels 112, 114, 116 located within plane 148. Plane 148 in the flow direction B represents the inner combustion chamber 162 in which flame 190 extends and the inlet end of release section 134.

[0084] In this method, the raw material MP can be supplied through the feed line 150 to the first central channel 112, which is oriented parallel to the longitudinal axis A. Figure 2In the method performed in the burner 200 shown, the feedstock MP can form part of a mixture containing (primarily) oxygen O2. A first fuel gas is directed via feed line 152 into a second inner channel 114 surrounding the first central channel 112. Finally, an auxiliary oxygen-containing gas, such as atmospheric air, is drawn into an auxiliary channel 118 and released into the flame chamber 162 once the flame is ignited.

[0085] The auxiliary fuel gas guided into the combustion chamber 162 via the jacket passage 116 can be a mixture of hydrogen (H2) and an additional gas, such as nitrogen (N2), or an auxiliary fuel gas containing N2. The additional gas has a dilution effect and can also be supplied to the jacket passage 116 via the third feed line 154. The gas exiting the outlet opening 144 forms a jacket flame upon ignition.

[0086] exist Figure 3 In the embodiment shown, the burner 200 is substantially similar to Figure 1 and 2 The burner structure shown is such that missing components and reference numerals can be found from, for example... Figure 2 The flame 190 is obtained from the burner head 100. However, the burner head 100 provides flame formation by means of a conical section 136. The conical section 136 is part of the guide section 132. In addition, the conical section 136 includes an optional (short) annular section 138 at the outlet end (plane 148). The conical section 136 has the advantageous effect of forming a stable and uniform pyrolysis flame.

[0087] Unlike Figure 1 and 2 ,according to Figure 3 The burner head 100 includes a central section 110 with three concentric inner channels 112, 114.1, and 114.2 adjacent to the jacket channel 116. One central channel provides MP, the second provides oxygen-containing gas, and the third central channel provides the first fuel gas. Furthermore, a mixing chamber 180 is connected to a feed line 154 leading to the jacket channel 116, in which hydrogen (H2) and nitrogen, used as auxiliary fuel gases, are premixed.

[0088] exist Figure 4The concept of a concentric channel formed by a set of smaller pipes 115, 117 is shown in three different embodiments, each in a partial view I-III. The term "smaller" refers to the diameter of these "pipes" compared to the channel formed by the corresponding set of pipes. The smaller pipes 115, 117 have a circular cross-sectional area. In partial views I-III, only some of the smaller pipes in the set that constitute a channel are drawn. As indicated by the respective dashed lines, the entire channel is constructed and / or filled by this set of smaller pipes. However, the smaller pipes in the set of pipes may be in direct contact with each other or be spaced apart from each other in the circumferential direction (not shown). Alternatively, the set of (smaller) smaller pipes may have a non-circular shape (not shown).

[0089] In partial view I, it is shown that the jacketed channel 116 is constructed from a set of small pipes 117. In partial view II, it is shown that the radially outer central channel 114 is constructed from a set of small pipes 115. Finally, in partial view III, it is shown that the jacketed channel 116 and one of the three central channels 112, 113, and 114 can be constructed from a set of small pipes 115, and this concept of a set of smaller pipes 115 is shown for the radially outer central channel 114 and the jacketed channel 116.

[0090] Discussed with experimental results Figure 5 , where similar Figure 1 The burner. Furthermore, the features and details of the method and apparatus are discussed in conjunction with the experiments, and can be similarly or analogously compared to... Figures 2 to 4 The combination of implementation schemes.

[0091] It will be apparent to those skilled in the art that the burner 200 and / or burner head 100 may have any orientation different from that shown in the accompanying drawings, and any details provided herein require similar understanding in conjunction with different orientations of the burner or burner head. Furthermore, the burner 200 and / or burner head 100 need not have the simplified elongated form shown in the accompanying drawings, but rather have any available internal and external curved and / or angled geometry.

[0092] Generally speaking, any tips, advantages, and details provided regarding burners and burner heads, especially those related to... Figures 1 to 3 The discussion, together with the previous one, should apply in the same way, or if necessary, similarly to this method, and vice versa: the implementation scheme and details of the method can be related to the following. Figures 1 to 3 The discussion describes the details together with the application.

[0093] The effects of the invention are demonstrated below through a series of experiments, wherein the experiments were conducted using [the method described in the original text]. Figure 1 The burner. Detailed Implementation

[0094] experiment

[0095] Three test series (ACs) with different feed rates (Table 1) and different burner head geometries (Table 2) have been implemented:

[0096] exist Figure 1 The burner 200, schematically shown in the diagram, has a burner head 100, as previously discussed... Figure 1 The SiCl4 vapor, premixed with hydrogen, air, and nitrogen (added in addition to the N2 contained in the air), is introduced into the burner head via a single central channel. The central section 110 includes only a single central channel 112 communicating with feed lines 150 and 152. A mixture of hydrogen (H2) and nitrogen (N2) is supplied via a jacketed channel 116 concentrically positioned around the single central channel 112. Once ignited, the gas mixture exiting the jacketed channel 116 forms a jacketed flame, indicated by dashed line 190. The specific amounts of all feed gases are shown in Table 1. The introduced feed gases are mixed and ignited at the outlet of burner head 100, causing the flame to spread along flame axis A into combustion chamber 162 of burner 200. The resulting mixture of particles and exhaust gas is discharged via line 170 and further cooled downstream of burner 200. Subsequently, the formed fumed silica powder is separated from the gas and deacidified using steam at 600°C in a conventional deacidification unit. The properties of the obtained fumed silica samples are given in Table 2 below. This figure does not show subsequent processing downstream of product line 170.

[0097] Table 1: Feed rates and ratios used for test series A, B, and C

[0098]

[0099] STC = Silicon tetrachloride (SiCl4)

[0100] All gas velocities were measured using flow meters positioned along the respective feed lines of the gas or gas mixture. In all experiments and throughout the application text, the feed rate was normalized to Nm³. 3 The values ​​are given in units of / h and correspond to the gas throughput (volume / time) at standard temperature (0°C; 273.15 K) and pressure (1 atm; 101,325 kPa).

[0101] In each test series A, B, and C, burner heads with varying overall diameters of the center section as given in Table 2 were used for testing. The center section was constructed as a central channel, i.e., a central pipe, the outer diameter of which is given in Table 2. The outer diameters of the respective jacketed channels are also given in Table 2, where the jacketed channels are also constructed as a pipe surrounding the central channel. The wall thickness between the central channel and the jacketed channels was ~0.5 mm.

[0102] Considering the respective cross-sections of the outlet openings of the corresponding channels or sections, the final normalized gas outlet velocity at the outlet end of the burner head is calculated from the flow rates measured by flow meters at the respective gas sources and / or respective feed lines.

[0103] These test series were conducted at a constant flow rate while varying the cross-section of the outlet opening (in most cases, the jacket channel). Therefore, at a constant mass flow rate through the jacket channel, V can be significantly reduced by slightly increasing the outer diameter (and thus the cross-section) of the jacket channel. J .

[0104] Table 2: Calculation of burner geometry and R1 ratio

[0105]

[0106] Table 3 shows the dependence of the varying R1 ratio on the BET surface area of ​​the resulting silica in the test series AC.

[0107] The results (Table 3, also shown) Figure 5 The diagram illustrates that, in all three series, the ratio R1 = V C / V J Reducing the ratio to 5-7 and lower results in a significant increase in the BET surface area of ​​the produced fumed silica. Ratio R1 = Vc / V J The lower the value (below 5-7), the higher the BET. Importantly, these significant increases in BET surface area are achieved by simply adjusting the two outlet gas velocities without any reduction in plant throughput. In contrast, in conventional flame hydrolysis, the increase in BET surface area is typically achieved by diluting the flame gas with air, thus reducing plant productivity.

[0108] In fact, a certain increase in the BET surface area of ​​the resulting silica was also observed in the region where R1 > 10-15. However, such a high R1 value means that the outlet gas velocity from the jacket channel is very slow. Operating the production unit at such a slow outlet gas velocity from the jacket channel would be unfavorable and risky due to the possibility of flame backflow (back into the jacket channel). Therefore, a R1 ratio below ~6 was determined to be an advantageous limit to avoid the disadvantages at low gas velocities as described above.

[0109] The minimum R1 achieved in the proposed laboratory-scale experiments was 1.56, which was limited by the excessively narrow gap between the walls of the jacket channel and the central conduit, which is necessary to achieve a faster outlet gas velocity from the jacket channel and therefore a lower R1 value.

[0110] However, lower R1 values, such as R1 < 1.0, are achievable and well-suited for use in relatively large units for producing gas-phase oxides. Even in large-scale units, R1 values ​​< 0.5 are considered impractical due to the extremely high outlet gas velocities from the jacket channel.

[0111] Table 3: BET of the obtained products

[0112]

[0113] Table 4 shows the particle size distribution of the samples after test series A.

[0114] Surprisingly, adjusting the R1 ratio resulted in some changes in the particle size distribution of the resulting silica (Table 4). Figure 5 Therefore, in the range of 1.5-4.0, Vc / V J Obtain the smallest size (d) within the range 10 d 50 d 90 The number of particles is 0, while the maximum number of particles is obtained when R1 ~ 6.0 (Table 4). Figure 5 ).

[0115] Table 4: Particle size distribution of samples after test series A:

[0116]

[0117] These results in Tables 3 and 4 also partially show... Figure 5 middle. Figure 5 The graph shows m 2 Using the BET surface area in grams as the x-axis, the particle size distribution d of the sample after the test series is... 50 As the second x-axis (right). Therefore, as demonstrated in the example of SiCl4 flame hydrolysis to produce gas-phase SiO2, adjusting the normalized exit gas velocity from the jacket channel of the burner head relative to the normalized exit gas velocity from the central section of the burner head surprisingly leads to significant changes in the properties of the resulting pyrolytic metal oxides and quasi-metal oxides.

[0118] Specifically, it can be demonstrated that reducing the ratio R1 of the outlet gas velocity from the central section to the outlet gas velocity from the jacket channel to below 6.0, preferably below 5.0 or even lower, results in a higher BET surface area without any reduction in plant productivity. Further reducing R1 to the range of 1.5-4.0 also helps to produce gas-phase oxide particles with the smallest particle size.

Claims

1. A method for producing pyrolytic metal oxides and / or quasi-metal oxides using a burner (200), said burner (200) having a burner head (100), said burner head (100) comprising - Export end (104), - A central segment (110) having at least one central channel (112), and - A jacketed channel (116) concentrically positioned around the central segment, and This includes the following methods and steps: - At least one metal precursor and / or quasi-metallic precursor (MP), a first fuel gas and an oxygen-containing gas are provided via the at least one central channel (112) of the central segment (110); - A second fuel gas is provided via the jacketed channel (116); - A flame (190) is provided by burning the first fuel gas and the second fuel gas at the outlet end (104), characterized in that Ratio R1 = V C / V J For a maximum of 6.0, of which V C V is the normalized gas outlet velocity of all gases from the central section (110). J It is the standardized outlet gas velocity of all gases from the jacket channel (116).

2. The method according to claim 1, wherein the first fuel gas and / or the second fuel gas is selected from hydrogen (H2), hydrogen-containing gas mixtures, carbon monoxide (CO), organic compounds having at least one hydrogen atom, such as hydrocarbons or alcohols, and mixtures thereof.

3. The method according to claim 1 or 2, wherein the second fuel gas provided via the jacket channel (116) is selected from hydrogen (H2) or a hydrogen-containing gas mixture.

4. The method according to claim 3, wherein the second fuel gas supplied via the jacket channel (116) is a hydrogen-containing gas mixture containing nitrogen (N2), carbon dioxide (CO2) and / or other inert gases.

5. The method according to any one of the preceding claims, wherein the second fuel gas supplied via the jacket channel (116) is different from the first fuel gas supplied via the central section.

6. The method according to any one of the preceding claims, wherein the central section (110) includes a single central channel (112) for supplying MP, a first fuel gas and an oxygen-containing gas.

7. The method according to any one of the preceding claims, wherein the central segment (110) comprises at least two central channels (112, 114) for separate supply. - Metallic precursors and / or quasi-metallic precursors, - First fuel gas, and / or - Oxygen-containing gas.

8. The method according to any one of the preceding claims, wherein the metal oxide or the quasi-metal oxide is selected from oxides of aluminum (Al), titanium (Ti), zirconium (Zr), yttrium (Y), lithium (Li), magnesium (Mg), lanthanum (La), cerium (Ce), iron (Fe), zinc (Zn), silicon (Si) and mixtures thereof, preferably alumina (Al2O3), titanium dioxide (TiO2) and / or silicon dioxide (SiO2) and mixtures thereof, most preferably silicon dioxide (SiO2).

9. The method according to any one of the preceding claims, wherein the MP is selected from at least one of the following substances: aluminum chloride (AlCl3), aluminum oxychloride (AlOCl), titanium tetrachloride (TiCl4), titanium trichloride (TiCl3), titanium oxychloride (TiOCl2), tetraalkoxytitanates such as tetraethoxytitanate Ti(OC2H5)4, tetraalkoxysilicates such as tetraethoxysilicate Si(OC2H5)4, cyclic siloxanes ([O-SiR2)). n Examples include octamethylcyclotetrasiloxane (D4) and acyclic siloxanes (R3Si-[O-SiR2)). n -O-SiR3) such as silicone oil, silicon tetrachloride (SiCl4), trichlorosilane (HSiCl3), methyltrichlorosilane (CH3SiCl3), dichlorosilane (H2SiCl2) and / or monochlorosilane (H3SiCl).

10. The method according to any one of the preceding claims, wherein the normalized outlet gas velocity (V) from said central section (110) C The speed is at least 15 m / s, more preferably at least 20 m / s, more preferably at least 25 m / s, and more preferably at least 29 m / s.

11. The method according to any one of the preceding claims, wherein the normalized outlet gas velocity (V) from the jacket channel (116) J The speed is at least 4 m / s, more preferably at least 6 m / s, more preferably at least 8 m / s, and more preferably at least 10 m / s.

12. The method according to any one of the preceding claims, wherein V C / V J The ratio (R1) is in the range of 0.5 to 6.0, more preferably 1.0 to 5.0, more preferably 1.2 to 4.5, and more preferably 1.5 to 4.

0.

13. The method according to any one of the preceding claims, wherein Nm 3 The total normalized feed rate of all gases introduced into the burner head, measured in Nm³, is given by the following formula: / h. 3 The ratio (R2) of the standardized feed rate of the metal precursor, measured in units of / h, is at least 5, more preferably between 5 and 20.

14. The method according to any one of claims 4 to 13, wherein Nm 3 The normalized feed rate of nitrogen (N2) to the jacket channel (116) in Nm³ / h is equal to the normalized feed rate in Nm³ / h. 3 The ratio (R3) of the standardized feed rate of hydrogen (H2) to the jacket channel (116) in terms of / h is in the range of 0.10 to 1.0, preferably 0.15 to 0.6, and more preferably 0.2 to 0.

5.

15. The method according to any one of the preceding claims, wherein Nm 3 The standardized feed rate of fuel gas passing through the central section (110) in Nm³ / h and the feed rate in Nm³ / h are respectively used to measure the fuel gas flow rate through the central section (110). 3 The ratio (R4) of the total standardized feed rate of fuel gas passing through the jacket channel (116) in terms of / h is between 2 and 20, more preferably between 3 and 16, and even more preferably between 4 and 10.

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