Oxide manufacturing method

Abstract

The present invention relates to an exothermic process for producing metal oxides or metalloid oxides, wherein a metal precursor and / or a metalloid precursor is introduced into a flame formed by burning a gas mixture comprising oxygen and hydrogen, wherein at least a portion of the hydrogen and at least a portion of the oxygen are obtained from the electrolysis of water or an aqueous solution using electrical energy obtained at least in part from a renewable energy source, wherein water (HO) is introduced into the flame, and wherein the total molar ratio TRON of oxygen gas to nitrogen gas, TRON=n(O):n(N), of all streams introduced into the flame prior to ignition is TRON≧0.25 and ≦1.

Description

[Technical Field]

[0001] The present invention relates to an exothermic process for producing metal oxides or metalloid oxides that solves these problems, wherein a metal precursor and / or a metalloid precursor is introduced into a flame formed by burning a gas mixture comprising oxygen, hydrogen, and nitrogen, wherein at least a portion of the hydrogen and at least a portion of the oxygen are obtained from the electrolysis of water or an aqueous solution using electrical energy obtained at least in part from a renewable energy source, wherein water (HO) is introduced into the flame, and wherein the total molar ratio TRON of oxygen gas to nitrogen gas combined of all streams introduced into the flame before ignition, TRON=n(O):n(N), is TRON≧0.25 and ≦1. [Background technology]

[0002] Finely dispersed metal oxide and metalloid oxide powders, such as silica, alumina, and titania, are needed for a wide range of technological applications today. Well-established routes for their production are based on exothermic processes, i.e., processes involving flame hydrolysis and / or flame pyrolysis of precursors (see Ullmann's Encyclopedia of Industrial Chemistry (1982) Volume 21, page 464). The flames used in these processes are typically formed by combining and igniting a stream of a hydrogen-containing gas mixture and a gas mixture containing oxygen with a burner. Volatile metal or metalloid precursors are fed into the hydrogen or oxygen stream, or directly into the flame, and converted to finely dispersed metal oxide and / or metalloid oxide powders.

[0003] US Patent No. 6,248,495 discloses a method for producing metal oxides by introducing metal precursors into a flame, the flame used being formed by burning a gas mixture containing oxygen and hydrogen.

[0004] The oxygen used in the exothermic process can be derived from air or obtained by energy-consuming fractional distillation of air. In the first case (using air), a large amount of nitrogen is introduced into the system, thus significantly increasing the overall gas volume and therefore reducing the productivity of the plant.

[0005] Furthermore, due to dilution with nitrogen when using air as the oxygen source, the temperature of the flame (usually calculated as the adiabatic flame temperature) is limited to about 1600-2000° C. Therefore, given the fact that some products of exothermic processes require higher adiabatic flame temperatures, the use of oxygen-enriched mixtures instead is necessary in these cases (see, for example, WO2004054929).

[0006] However, temperature gradients within the flame may be more pronounced in processes using oxygen-enriched mixtures than when using unmodified air, and such temperature gradients may result in a less uniform product. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] U.S. Patent No. 6,248,495 [Patent Document 2] International Publication No. 2004054929 Brochure [Non-patent literature]

[0008] [Non-Patent Document 1] Ullmann's Encyclopedia of Industrial Chemistry(1982)Volume 21, page 464 Summary of the Invention [Problem to be solved by the invention]

[0009] In view of the above, the problem solved by the present invention is to provide a method for producing pyrogenic metal oxides of well-established, homogeneous quality, which provides higher productivity (i.e., higher metal or semi-metal oxide content per unit gas volume in the product mixture), while reducing overall CO2 emissions and minimizing fossil energy consumption.

[0010] Hydrogen and / or oxygen prepared by water electrolysis typically contain a significant amount of water. Drying these gases after electrolysis is an additional process step, increasing the overall process cost and CO₂ footprint. It has been found that the water present in the hydrogen and / or oxygen obtained by water electrolysis can be at least partially used directly in the production of fumed metal oxides according to the present invention, thus eliminating the need to introduce additional water. Particularly preferably, all of the water present in the oxygen and / or hydrogen obtained by water electrolysis is used in the exothermic process. Surprisingly, the process of the present invention not only provides finely dispersed metal oxide and semi-metal oxide powders of high quality, but also significantly reduces the overall CO₂ emissions for hydrogen and oxygen production and helps increase plant productivity.

[0011] Furthermore, the presence of water in the feed gas, for example in the oxygen stream, is believed to improve the thermal conductivity of the feed gas and therefore improve the thermal balance of the feed gas and product gas mixture, thereby reducing the overall temperature and temperature gradient within the flame, thus allowing for lower adiabatic flame temperatures and access to more uniform products. [Means for solving the problem]

[0012] The present invention The above problem is solved by a method for producing a metal oxide and / or a metalloid oxide, comprising the steps of: (X) introducing a metal precursor and / or a metalloid precursor into the flame, (a) the flame used in step (X) is formed by burning a gas mixture containing oxygen, hydrogen, and nitrogen; at least a portion of the hydrogen and at least a portion of the oxygen are obtained from the electrolysis of water or an aqueous solution using electrical energy obtained at least in part from a renewable energy source, (b) Water (H2O) is introduced into the flame; (c) introducing a total molar ratio TRON of oxygen gas to nitrogen gas, TRON=n(O2):n(N2), of all streams introduced into the flame prior to ignition, such that TRON≧0.25 and ≦1.

[0013] The formation of a flame by burning a gas mixture containing oxygen, hydrogen, and nitrogen and introducing a metal precursor and / or metalloid precursor therein, according to the present invention, can be achieved by any means known to those skilled in the art. Comprehensive descriptions of such exothermic processes particularly suited to the purposes of the present invention are described in the art; see, for example, Ullmann's Encyclopedia of Industrial Chemistry (1982), Volume 21, page 464. In the context of the present invention, it is important to point out that in addition to gas streams introduced into the flame before ignition, some exothermic processes also apply a second type of gas stream—a gas stream introduced into the flame after ignition. The stream introduced into the flame before ignition enters the flame in its most upstream region and therefore participates in and / or interacts with the combustion reaction in a very comprehensive manner throughout the entire length of the flame. On the other hand, the stream introduced into the flame after ignition does not pass through the most upstream region of the flame and therefore does not participate in and / or interact with the combustion reaction as comprehensively as the stream added before ignition. The post-ignition flow is typically added to stabilize the flame and prevent deposits within the reactor. DETAILED DESCRIPTION OF THE INVENTION

[0014] In a preferred embodiment of the present invention, the renewable energy source is selected from the group consisting of solar energy, wind energy, geothermal energy, hydroelectric power from flowing water, tidal energy, energy obtained from the combustion of biomass, waste or biofuels, and combinations of these energy sources.

[0015] According to the present invention, at least a portion of the hydrogen and at least a portion of the oxygen used to form the flame are obtained from the electrolysis of water or an aqueous solution using electrical energy obtained at least in part from a renewable energy source. A wide range of methods for the production of hydrogen and / or oxygen from the electrolysis of water or an aqueous solution are available in the art, all of which can be used in the context of the present invention.

[0016] In a preferred embodiment of the invention, the oxygen used to form the flame, obtained from the electrolysis of water or an aqueous solution, contains at least 0.1% water by weight.

[0017] In a particularly preferred embodiment of the invention, the oxygen used to form the flame, obtained from the electrolysis of water or an aqueous solution, contains at least 0.5% by weight water, preferably at least 1% by weight.

[0018] In a preferred embodiment of the invention, the total molar ratio of oxygen gas to nitrogen gas, TRON=n(O2):n(N2), of all streams introduced into the flame combined prior to ignition is at least 0.26, more preferably at least 0.270, and most preferably at least 0.275, and is 1 or less, preferably 0.8 or less, and more preferably 0.6 or less. The inventive range of TRON is important to the invention because if the TRON value is too high (i.e., an O2-rich mixture, not enough N2), safety risks in process control increase (pure O2 compared to air) and process costs increase significantly (due to the need for more pure O2).

[0019] In a preferred embodiment of the present invention, the metal oxide or semi-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), and silicon (Si).

[0020] In a preferred embodiment of the present invention, the metal oxide or semi-metal oxide is selected from oxides of aluminum (Al), titanium (Ti), and silicon (Si).

[0021] According to the present invention, a metal or metalloid precursor is a compound containing one or more metals or metalloids which, when exposed to a flame formed by burning a gas mixture containing oxygen and hydrogen, is chemically converted to a mixture of one or more solid (25°C and atmospheric pressure) oxides of the metals or metalloids and compounds that are gaseous or volatile at 25°C and atmospheric pressure.

[0022] In a preferred embodiment of the present invention, the metal or semi-metal precursor is selected from aluminum chloride, aluminum oxychloride, titanium tetrachloride, titanium trichloride, titanium oxychloride, tetraalkoxytitanates, tetraalkoxysilicates, cyclic or acyclic siloxanes, silicon tetrachloride, trichlorosilane, methyltrichlorosilane, dichlorosilane, monochlorosilane or mixtures thereof.

[0023] In a preferred embodiment of the invention, the total molar ratio of water to metal and / or metalloid precursors introduced into the flame, TRWM=n(HO):n(combined metal and / or metalloid precursors), is TRWM≧0.005.

[0024] In a particularly preferred embodiment of the invention, the total molar ratio of water to metal and / or metalloid precursors introduced into the flame TRWM=n(HO):n(metal and / or metalloid precursors) is TRWM≧0.01.

[0025] In a particularly preferred embodiment of the invention, the total molar ratio of water to metal and / or metalloid precursors introduced into the flame, TRWM=n(HO):n (combined metal and / or metalloid precursors), is TRWM≧0.005, and the total molar ratio TRON of oxygen gas to combined nitrogen gas, TRON=n(O):n(N), of all streams introduced into the flame before ignition is TRON≧0.26 and ≦1.

[0026] In the context of the present invention, standard conditions are defined as a temperature of 273.15 K = 0°C and a pressure of 100000 Pa = 1,000 bar.

[0027] The adiabatic flame temperature is calculated using commercially available software tools using the initial temperatures, reaction enthalpies and heat capacities of all components present in the flame zone.

[0028] Throughout this specification, the terms "gamma" or "gamma ratio" and "lambda" or "lambda ratio" are defined as follows:

[0029] "Gamma" or "Gamma Ratio" = H2 supplied / H2 stoichiometrically required "Lambda" or "Lambda ratio" = O2 supplied / O2 stoichiometrically required [Example]

[0030] Comparative Example 1: 2.7 kg / h of SiCl4 in vapor form, 1.0 m 3 / h hydrogen, 0.2m 3 / h nitrogen and 2.4m 3 A mixture of 0.5 m / h of air was premixed in the burner as known from the prior art. These gases, called core gases, mainly contribute to the product properties and are listed in Table 1. A 0.5 m flame was used as the mantle flame. 3 The burner flame was stabilized by hydrogen at 6m / h. 3 / h of secondary air shielded the flame from the combustion chamber. The reaction mixture was ignited and passed through the burner opening into the combustion chamber and further combusted in a cooled flame tube. The particle-gas mixture was further cooled, and the resulting fumed silica powder was separated from the gas and deoxidized. The adiabatic flame temperature calculated from the core gas and particle properties is shown in Table 2.

[0031] Comparative Example 2: 2.7 kg / h of SiCl4 in vapor form, 1.0 m 3 / h hydrogen, 0.2m 3 / h nitrogen and 1.4m 3 / h air, 0.2m 3 A mixture of 10 ... 3 The burner flame was stabilized by hydrogen at 6m / h. 3 / h of secondary air shielded the flame from the combustion chamber. The reaction mixture was ignited and passed through the burner opening into the combustion chamber and further combusted in a cooled flame tube. The particle-gas mixture was further cooled, and the resulting fumed silica powder was separated from the gas and deoxidized. The adiabatic flame temperature calculated from the core gas and particle properties is shown in Table 2.

[0032] Example 2: 2.7 kg / h of SiCl4 in steam form, 1.0 m obtained from water electrolysis 3 / h hydrogen, 0.2m 3 / h nitrogen, 1.4m 3 / h of air and 0.2m3 obtained from water electrolysis containing steam equivalent to 0.003 kg / h of evaporated water. 3 A mixture of 0.5 m / h oxygen was premixed in the burner as known from the prior art. These gases, called core gases, mainly contribute to the product properties and are listed in Table 1. A 0.5 m flame was used as the mantle flame. 3 The burner flame was stabilized by hydrogen at 6m / h. 3 / h of secondary air shielded the flame from the combustion chamber. The reaction mixture was ignited and passed through the burner opening into the combustion chamber and further combusted in a cooled flame tube. The particle-gas mixture was further cooled, and the resulting fumed silica powder was separated from the gas and deoxidized. The adiabatic flame temperature calculated from the core gas and particle properties is shown in Table 2.

[0033] Example 3: 2.7 kg / h of SiCl4 in steam form, 1.0 m obtained from water electrolysis 3 / h hydrogen, 0.2m 3 / h nitrogen, 1.0m 3 / h of air and 0.3m3 obtained from water electrolysis containing steam equivalent to 0.003 kg / h of evaporated water. 3 A mixture of 0.5 m / h oxygen was premixed in the burner as known from the prior art. These gases, called core gases, mainly contribute to the product properties and are listed in Table 1. A 0.5 m flame was used as the mantle flame. 3 The burner flame was stabilized by hydrogen at 6m / h. 3 / h of secondary air shielded the flame from the combustion chamber. The reaction mixture was ignited and passed through the burner opening into the combustion chamber and further combusted in a cooled flame tube. The particle-gas mixture was further cooled, and the resulting fumed silica powder was separated from the gas and deoxidized. The adiabatic flame temperature calculated from the core gas and particle properties is shown in Table 2.

[0034] Example 4: 2.7 kg / h of SiCl4 in steam form, 1.0 m obtained from water electrolysis 3 / h hydrogen, 0.2m 3 / h nitrogen, 1.0m 3 / h of air, and 0.3m3 obtained from water electrolysis containing steam and an additional 0.2 kg / h of evaporated water. 3 A mixture of 0.5 m / h oxygen was premixed in the burner as known from the prior art. These gases, called core gases, mainly contribute to the product properties and are listed in Table 1. A 0.5 m flame was used as the mantle flame. 3 The burner flame was stabilized by hydrogen at 6m / h. 3 / h of secondary air shielded the flame from the combustion chamber. The reaction mixture was ignited and passed through the burner opening into the combustion chamber and further combusted in a cooled flame tube. The particle-gas mixture was further cooled, and the resulting fumed silica powder was separated from the gas and deoxidized. The adiabatic flame temperature calculated from the core gas and particle properties is shown in Table 2.

[0035] [Table 1]

[0036] [Table 2]

[0037] The examples demonstrate that both electrolytically produced H and O can be used in the same exothermic process, reducing the overall CO emissions of the entire process (including H and O production). At the same time, plant productivity can be increased by using less N ballast gas (Examples 2 and 3) and water present in the feedstock (Example 4). Furthermore, as evidenced by Example 2 compared to Comparative Example 2, the use of undried oxygen from electrolysis can result in a product with a higher specific surface area, further eliminating the need for water removal.

[0038] Without wishing to be bound by any theory, it is believed that the small amount of water present in the feedstock (Examples 2, 3) improves the thermal conductivity of the process product gas mixture, making the temperature more uniform within the flame, while a larger amount of water (Example 4) is shown to significantly reduce the flame temperature, thus delivering a product with the desired BET and lower process gas volume (= higher productivity of the plant).

Claims

1. A method for producing a metal oxide and / or a semi-metal oxide, comprising step (X): (X) introducing a metal precursor and / or a metalloid precursor into the flame, (a) the flame used in step (X) is formed by burning a gas mixture comprising oxygen, hydrogen, and nitrogen; at least a portion of said hydrogen and at least a portion of said oxygen are obtained from the electrolysis of water or an aqueous solution using electrical energy obtained at least in part from a renewable energy source; (b) Water (H ２ O) is introduced into the flame, (c) the total molar ratio of oxygen gas to nitrogen gas, TRON, of all streams introduced into the flame prior to ignition, TRON = n(O ２ ): n(N ２ ) is TRON≧0.25 and ≦1.

2. 2. The method of claim 1, wherein the oxygen obtained from the electrolysis of water or an aqueous solution contains at least 0.1% by weight.

3. 3. The method according to any one of claims 1 to 2, wherein the oxygen obtained from the electrolysis of water or an aqueous solution comprises at least 0.5% by weight, preferably at least 1% by weight.

4. The total molar ratio of water to metal and / or metalloid precursors introduced into the flame, TRWM=n(H ２ 4. The method of any one of claims 1 to 3, wherein O):n (combined metal precursors and / or metalloid precursors) has a TRWM > 0.

005.

5. The total molar ratio of water to metal and / or metalloid precursors introduced into the flame, TRWM=n(H ２ 5. The method of claim 1, wherein the metal precursor and / or metalloid precursor has a TRWM≧0.

01.

6. 6. The method according to any one of claims 1 to 5, wherein the renewable energy source is selected from the group consisting of solar energy, wind energy, geothermal energy, hydroelectric power from flowing water, tidal energy, energy obtained from the combustion of biomass, waste or biofuels, and combinations of these energy sources.

7. 7. The method of any one of claims 1 to 6, wherein the metal oxide or semi-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), and silicon (Si).

8. The method according to any one of claims 1 to 7, wherein the metal oxide or semi-metal oxide is selected from oxides of aluminum (Al), titanium (Ti), and silicon (Si).

9. 9. The method according to any one of claims 1 to 8, wherein the metal or semi-metal precursor is selected from aluminum chloride, aluminum oxychloride, titanium tetrachloride, titanium trichloride, titanium oxychloride, tetraalkoxy titanates, tetraalkoxy silicates, cyclic or acyclic siloxanes, silicon tetrachloride, trichlorosilane, methyltrichlorosilane, dichlorosilane, monochlorosilane, or mixtures thereof.

10. The total molar ratio of oxygen gas to nitrogen gas of all streams introduced into the flame before ignition is TRON = n(O ２ ): n(N ２ 10. The method of any one of claims 1 to 9, wherein ≈(x,y) is at least 0.26, more preferably at least 0.270, most preferably at least 0.275 and is ≈1, preferably ≈0.8, more preferably ≈0.

6.

11. - the total molar ratio of water to metal and / or metalloid precursors introduced into the flame TRWM=n(H ２ O): n (combined metal precursors and / or metalloid precursors) has a TRWM≧0.005; - the total molar ratio TRON of oxygen gas to nitrogen gas combined of all streams introduced into the flame before ignition, TRON = n(O ２ ): n(N ２ ) is TRON≧0.25 and ≦1; The method according to any one of claims 1 to 10.