Lead oxide, compositions containing lead oxide and methods for making lead oxide

Abstract

Compositions are provided that include one or more of alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and Pb3O4, the compositions comprising particles that include subparticles, the subparticles having an average largest dimension of 10 to 300 nm. Methods of making such compositions are also described.

Description

[Technical Field]

[0001] Background of the Invention The present disclosure relates to lead oxide. [Background technology]

[0002] The present invention relates to lead oxides (e.g., alpha lead(II) oxide, beta lead(II) oxide, minium, and PbO). More particularly, but not exclusively, the present invention relates to methods of making such lead oxides, compositions comprising such lead oxides, battery plates made using such compositions, and batteries comprising such battery plates.

[0003] Lead oxide is used in the manufacture of lead-acid batteries. Such lead oxide may be obtained by recycling lead-acid batteries. Traditional recycling methods are energy intensive and typically involve smelting, which involves heating to high temperatures. WO 2008 / 056125 describes a low-energy method for recovering lead for use in lead-acid batteries, which includes forming lead citrate and then forming a composition containing lead and / or lead(II) oxide. The composition can then be used to make battery plates that can be used in lead-acid batteries. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to alleviate one or more of the problems set out above. Alternatively or additionally, the present invention aims to provide an improved method for making lead oxide. [Means for solving the problem]

[0005] Summary of the Invention According to a first aspect of the present invention, there is provided a method of making a composition comprising alpha lead(II) oxide, comprising the steps of: Converting organic lead salts to PbOPbCO3, and heating the PbOPbCO3 in a substantially inert atmosphere; A method is provided, comprising:

[0006] The inventors have discovered that alpha lead(II) oxide can be made by converting an organic lead salt, such as lead citrate, to lead(II) oxide, optionally converting the lead(II) oxide to PbOPbCO3, and then heating the PbOPbCO3. Throughout this specification, references to "lead oxide" will be taken to mean lead(II) oxide (PbO) unless the context indicates otherwise.

[0007] Alpha lead(II) oxide, often known as litharge, has a tetragonal crystal structure.

[0008] The organic lead salt may be anhydrous or partially or fully hydrated. The organic lead salt may include a lead carboxylate. The carboxylate may be aliphatic. The carboxylate may be linear or branched. The carboxylate may be saturated or unsaturated. The carboxylate may be an alkyl carboxylate. The carboxylate may contain at least 2 carbon atoms, optionally at least 3 carbon atoms, optionally at least 4 carbon atoms, optionally at least 5 carbon atoms, and optionally at least 6 carbon atoms. The carboxylate may contain up to 20 carbon atoms, optionally up to 18 carbon atoms, optionally up to 16 carbon atoms, optionally up to 14 carbon atoms, optionally up to 12 carbon atoms, optionally up to 10 carbon atoms, and optionally up to 8 carbon atoms. The carboxylate may contain 2 to 15 carbon atoms, optionally 2 to 12 carbon atoms, optionally 2 to 8 carbon atoms, and optionally 2 to 6 carbon atoms.

[0009] The organic lead salts may include lead salts of monocarboxylic acids, such as lead acetate. The monocarboxylic acids may optionally be saturated acids. The monocarboxylic acids may optionally be linear or branched acids. The organic lead salts may include lead salts of dicarboxylic acids, such as glutaric acid. The dicarboxylic acids may optionally be saturated acids. The dicarboxylic acids may optionally be linear or branched acids. The organic lead salts may include lead salts of tricarboxylic acids, such as citric acid. The tricarboxylic acids may optionally be saturated acids. The tricarboxylic acids may optionally be branched acids.

[0010] The organic lead salt is preferably lead citrate.

[0011] For convenience, the term "lead citrate" is used to refer to Pb(C6H6O7) and its hydrates, as well as other stoichiometries, such as 3Pb.2(C6H5O7) and their hydrates. In some embodiments of the present invention, the term "lead citrate" is used to refer to Pb(C6H6O7) and its hydrates, as well as the product of PbSO4 treated with aqueous citric acid and aqueous trisodium citrate. In further embodiments of the present invention, the term "lead citrate" is used to refer to Pb(C6H6O7) and its hydrates. In particular, "lead citrate" may refer to triplead disitrate [3Pb.2(C6H5O7)], often known as triplead citrate, and its hydrates.

[0012] The organic lead salt (e.g., lead citrate) is optionally provided in the form of elongated particles, optionally in the form of rod-like particles, and optionally as particles. The particles of the organic lead salt may have an average maximum dimension of at least 0.5 μm, optionally at least 1.0 μm, optionally at least 1.5 μm, and optionally at least 2.0 μm. The particles of the organic lead salt may optionally have an average maximum dimension of no more than 20 μm, optionally no more than 15 μm, and optionally no more than 10 μm. The inventors have discovered that the use of relatively large particles of the organic lead salt (particularly lead citrate) is advantageous for the formation of alpha lead(II) oxide. The particles of the organic lead salt may have an average aspect ratio of at least 1.5:1, optionally at least 2.0:1, and optionally at least 3.0:1. The particles of the organic lead salt may optionally have an average aspect ratio of 20:1 or less, optionally 15:1 or less, optionally 10:1 or less, optionally 7.5:1 or less, optionally 5:1 or less.

[0013] Converting the organic lead salt, optionally lead citrate, to PbOPbCO3 may include converting the organic lead salt to lead(II) oxide, converting the lead(II) oxide to lead carbonate, and converting the lead carbonate to PbOPbCO3. Converting the organic lead salt to lead(II) oxide may include heating the organic lead salt in the presence of an oxidizing agent, such as an oxidizing gas, for example, an oxygen-containing gas, e.g., a gas containing molecular oxygen or O2. Converting the lead(II) oxide to lead carbonate may include heating the lead(II) oxide in the presence of carbon dioxide. Heating the organic lead salt to form lead(II) oxide and converting the lead(II) oxide to lead carbonate may be performed sequentially and / or simultaneously. For example, heating the organic lead salt to form lead(II) oxide and converting the lead(II) oxide to lead carbonate may be performed by heating lead citrate in the presence of an oxidizing agent, such as an oxidizing gas (e.g., a gas containing molecular oxygen or O2) and carbon dioxide. Thus, converting an organic lead salt to lead carbonate may include heating the organic lead salt in the presence of an oxidizing gas and carbon dioxide. Without wishing to be bound by theory, it is understood that heating an organic lead salt in the presence of an oxidizing agent results in the formation of beta-lead(II) oxide. Those skilled in the art will recognize that beta-lead(II) oxide may not be the only product formed. Beta-lead(II) oxide reacts with carbon dioxide to form lead carbonate.

[0014] Converting lead carbonate to PbOPbCO3 may include heating the lead carbonate. Heating the lead carbonate optionally forms lead oxide (optionally alpha lead oxide). The lead oxide may react with lead carbonate to form PbOPbCO3. For the avoidance of doubt, converting lead carbonate to form lead oxide may be a reversible process. Lead carbonate may form lead oxide and carbon dioxide when heated. Lead oxide and carbon dioxide may react to form lead carbonate.

[0015] When the oxidant comprises a gas (e.g., a gas containing molecular oxygen, O), the oxidant may be provided as a gas stream. The method may include contacting lead citrate with the oxidant stream.

[0016] The carbon dioxide may be provided as a carbon dioxide stream. The method may comprise contacting lead(II) oxide with the carbon dioxide stream.

[0017] When the oxidizer includes molecular oxygen (e.g., when air is used as the oxidizer), and when forming the lead carbonate includes heating lead(II) oxide in the presence of carbon dioxide, the molar ratio of carbon dioxide to molecular oxygen can optionally be at least 10:1, optionally at least 12:1, optionally at least 15:1, optionally at least 18:1, optionally at least 20:1, optionally at least 25:1, optionally at least 30:1, optionally at least 40:1, and optionally at least 50:1. The inventors have discovered that a molar ratio of carbon dioxide to molecular oxygen of at least 25:1 can be beneficial because it results in a significantly greater amount of alpha lead oxide in the final composition than a molar ratio of 12:1. The inventors have also discovered that a molar ratio of carbon dioxide to molecular oxygen of at least 50:1 can be beneficial because it results in a significantly greater amount of alpha lead oxide in the composition than a molar ratio of 40:1. For the avoidance of doubt, where air is used to provide the molecular oxygen, the amount of molecular oxygen may be determined based on air containing 21% oxygen. The inventors have discovered that a relatively high ratio of carbon dioxide to molecular oxygen is effective to produce a high percentage of alpha lead oxide in the composition, particularly when an organic lead salt (e.g., lead citrate) is heated in a mixture of gases containing molecular oxygen (e.g., air) and carbon dioxide.

[0018] The molar ratio of carbon dioxide to molecular oxygen may optionally be 250:1 or less, optionally 200:1 or less, optionally 150:1 or less, optionally 100:1 or less.

[0019] PbOPbCO3 is heated in a substantially inert atmosphere (e.g., nitrogen) to form alpha lead(II) oxide. The PbOPbCO3 may be heated for a time long enough to form alpha lead(II) oxide. The PbOPbCO3 may be heated optionally for at least 5 minutes, optionally for at least 10 minutes, optionally for at least 20 minutes, or optionally for at least 30 minutes. The PbOPbCO3 may be heated for optionally 120 minutes or less, optionally for 90 minutes or less, optionally for 75 minutes or less, or optionally for 60 minutes or less. It has been found that PbOPbCO3 must be heated for a sufficient time to produce a relatively large amount of alpha lead(II) oxide.

[0020] PbOPbCO3 may be heated at a temperature high enough to promote the formation of alpha lead(II) oxide. PbOPbCO3 may be heated at a temperature of at least 250°C, optionally at least 275°C, optionally at least 300°C, and optionally at least 325°C. PbOPbCO3 may optionally be heated at no more than 450°C, optionally no more than 425°C, optionally no more than 400°C, and optionally no more than 375°C.

[0021] The PbOPbCO3 may be heated at a temperature between 300°C and 400°C, optionally between 325°C and 375°C, optionally for a period of 10 to 90 minutes, optionally for a period of 20 to 60 minutes, optionally for a period of about 30 minutes.

[0022] Those skilled in the art will appreciate that the methods of the present invention need not result solely in alpha lead oxide, and that the composition may include other components, such as one or more of beta lead oxide, lead metal, lead oxide carbonate, lead carbonate, minium, and carbon. However, the methods of the present invention may result in a composition comprising at least 20 wt% alpha lead oxide, optionally at least 30 wt% alpha lead oxide, optionally at least 40 wt% alpha lead oxide, optionally at least 50 wt% alpha lead oxide, optionally at least 60 wt% alpha lead oxide, optionally at least 70 wt% alpha lead oxide, optionally at least 80 wt% alpha lead oxide, optionally at least 90 wt% alpha lead oxide, optionally at least 95 wt%, and optionally at least 98 wt% alpha lead oxide. The alpha lead oxide content may be measured, for example, using acid dissolution or X-ray diffraction, as described below.

[0023] The composition samples were homogenized using a pestle and mortar. The homogenized samples were characterized using a Gen9 B3 (BB) Bruker D8 DAVINCI (Bruker D8 Advance, USA) in the 2θ range of 10° to 90° using Cu-Kα radiation (λ = 1.5406 Å) at 40 mA and 40 kV, with a step size of 0.0300° 2θ, a scan step of 96.00 seconds (2628 steps total), and 0.5 seconds per step. Diffraction data were background corrected and analyzed using "Highscore" data analysis software (Bruker-Pan Analytica) using library data for target substances to identify the substances present and their relative amounts. This information was used to calculate the relative proportions of alpha lead oxide and beta lead oxide in the composition. One limitation of using X-ray diffraction is that when one substance dominates (e.g., lead oxide), it can be difficult to identify and / or quantify diffraction peaks from other substances. X-ray diffraction can also be used to identify and / or quantify other oxides of lead, such as Pb2O3 and Pb3O4. However, it can be difficult to identify and / or quantify materials present in amounts below about 10 wt%.

[0024] Acid dissolution may be used to determine the relative amounts of various components in a composition. Two grams of the composition was contacted with 50 mL of 5% aqueous acetic acid in a 250 mL Erlenmeyer flask, and the suspension was stirred at 500 rpm for 5 minutes using a magnetic stirrer. All of the lead oxide dissolved in the acetic acid, leaving one or more of metallic lead, carbon, red lead, and Pb2O3 undissolved. Whether undissolved material floats depends in part on particle size, the density of the material, and the particle charge. Denser materials tend to settle; however, very small particles tend to remain in suspension. Thus, small particles of inherently dense materials may float. However, generally, carbon and metallic lead (which may be carbon-coated) settle to the bottom of the flask, while red lead and Pb2O3 remain in suspension.

[0025] The suspension or solution was decanted from any solid material that had settled to the bottom of the flask, if any.

[0026] If the settled contents showed a black coloration, this indicated the presence of carbon. The settled contents were washed with water and dried, and the weight of the settled contents was determined. The settled contents were then washed with water to facilitate separation of carbon and metallic lead due to their density differences. The settled contents were washed to facilitate separation until the heavier solids no longer showed a black coloration, indicating that the heavier solids were metallic lead. The metallic lead was then dried. The weight of the metallic lead could then be determined. The weight of the carbon could also be determined. The percentage of metallic lead and carbon in the composition could also be determined.

[0027] If the suspension in the flask appeared reddish-orange, this indicated the presence of minium. The suspension was filtered, and the residue was washed with Milli-Q high-purity water and dried. The weight of the residue could then be used to determine the weight of minium, and thus the percentage of minium in the composition.

[0028] If the suspension in the flask appeared brown, this indicated the presence of Pb2O3. The wt% of Pb2O3 was determined by reference to the X-ray diffraction data as described above.

[0029] As described above, alpha and beta lead oxides are dissolved in acid to form lead acetate. The solvent can be removed to obtain lead acetate, which can be used to calculate the total amount of alpha and beta lead oxides in the sample. X-ray diffraction data was used to determine the relative amounts of alpha and beta lead oxides in the original sample before acid dissolution, and the relative amounts of alpha and beta lead oxides determined by X-ray diffraction were used to calculate the amount of alpha and beta lead oxides in the composition.

[0030] The process of the first aspect of the invention may be carried out in a rotary furnace.

[0031] As described above, the method of the first aspect of the present invention can be used to make a composition comprising alpha lead oxide. According to a second aspect of the present invention, there is provided a composition comprising alpha lead oxide, the composition being producible or produced by the method of the first aspect of the present invention. The composition may include the parameters described above in relation to the method of the first aspect of the present invention. The composition may, for example, comprise at least 80 wt% alpha lead oxide, optionally at least 85 wt% alpha lead oxide, optionally at least 90 wt% alpha lead oxide, optionally at least 95 wt% alpha lead oxide, optionally at least 98 wt% alpha lead oxide, or optionally consist essentially of alpha lead oxide. The composition may also include metallic lead.

[0032] The composition may include particles. The composition may include rod-shaped particles. The composition may include amorphous particles (i.e., particles without a clearly defined shape). The composition may include particles having openings and / or channels therein. Such particles may have a structure having a network of openings and / or channels therein. The particles may include subparticles. The subparticles are smaller than the particles. At least some of the subparticles may optionally be in the form of protrusions. The particles may optionally have an average maximum dimension of 0.2 μm to 20 μm. The subparticles may optionally have an average maximum dimension of at least 10 nm, optionally at least 15 nm, optionally at least 20 nm, optionally at least 25 nm, optionally at least 30 nm, optionally at least 40 nm, or optionally at least 50 nm. The subparticles may have an average maximum dimension of 300 nm or less, optionally 250 nm or less, optionally 200 nm or less, optionally 150 nm or less, or optionally 100 nm or less. The subparticles may have an average largest dimension of 10 to 300 nm, optionally 15 nm to 200 nm, optionally 20 nm to 150 nm. The subparticles may be spherical or subspherical. The subparticles may or may not have the same chemical composition as the rest of the particle.

[0033] The present inventors have discovered that compositions comprising lead-based materials that may be useful in the battery industry have advantageous properties (particularly a relatively high surface area) when the compositions comprise relatively large particles on which are formed relatively small sub-particles that may be in the form of protrusions.

[0034] Particle and subparticle dimensions may be measured using any suitable method, such as scanning electron microscopy.

[0035] Optionally, at least 20% by number of the particles of the composition are rod-shaped particles. Optionally, at least 40%, optionally at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90%, optionally at least 95% by number of the particles of the composition are rod-shaped.

[0036] Optionally, of the rod-shaped particles, optionally at least 50% by number have a maximum dimension between 0.2 μm and 20 μm, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90% by number have a maximum dimension between 0.2 μm and 20 μm.

[0037] As described above, the composition optionally includes rod-shaped particles. The rod-shaped particles may have an average aspect ratio of at least 1.5:1, optionally at least 2.0:1, and optionally at least 3.0:1. The rod-shaped particles may have an average aspect ratio of no more than 20:1, optionally no more than 15:1, optionally no more than 10:1, optionally no more than 7.5:1, and optionally no more than 5:1.

[0038] Optionally, of the rod-shaped particles, optionally at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90% by number have an aspect ratio of at least 1.5:1, optionally at least 2.0:1, optionally at least 3.0:1. Optionally, at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90% by number have an aspect ratio of 20:1 or less, optionally 15:1 or less, optionally 10:1 or less, optionally 7.5:1 or less, optionally 5:1 or less.

[0039] The composition may include particles having a core portion rich in lead metal and poor in lead oxide, and an outer portion rich in lead oxide. The inventors have discovered that some particles have a core portion rich in lead metal and poor in lead oxide, and an outer portion rich in lead oxide. This arrangement may be preferable because the outer portion effectively protects the core portion from oxidation when the composition is exposed to air. Without wishing to be bound by theory, it is expected that batteries made from such compositions may have improved cycle life because the outer portion protects the core portion from sulfation.

[0040] The core portion may comprise at least 95 wt% lead metal, optionally at least 96 wt% lead metal, optionally at least 98 wt% lead metal. The core portion may be substantially free of lead oxide.

[0041] The outer portion may include one or more of alpha lead oxide, beta lead oxide, red lead, and Pb2O3.

[0042] The core portion may be spherical or sub-spherical.

[0043] The volume of the core portion is optionally greater than the volume of the outer portion, optionally at least 2 times, optionally at least 3 times, optionally at least 5 times, optionally at least 10 times, optionally at least 15 times, optionally at least 20 times, optionally at least 30 times, optionally at least 40 times, optionally at least 50 times, optionally at least 100 times the volume of the outer portion.

[0044] The core portion may have an average largest dimension of at least 1 μm, optionally at least 2 μm, optionally at least 5 μm, optionally at least 10 μm. The core portion may optionally have an average largest dimension of no more than 100 μm, optionally no more than 80 μm, optionally no more than 60 μm, optionally no more than 50 μm, optionally no more than 40 μm, optionally no more than 30 μm.

[0045] The composition optionally has a BET surface area (optionally determined using nitrogen, optionally at 77 K) of at least 1.0 m 2 / g, optionally at least 1.5m 2 / g, optionally at least 1.8m 2 / g, optionally at least 2.0m 2 / g, optionally at least 2.5m 2 / g, optionally at least 3.0m 2 The BET surface area (optionally determined using nitrogen, optionally at 77 K) is optionally greater than 10 m 2 / g or less, optional 8m 2 / g or less, optional 6m 2 / g or less, optional 5m 2 / g or less.

[0046] The data obtained to determine the BET surface area can also be used to determine the pore volume. In this regard, the pore volume as determined by BJH analysis (optionally using nitrogen, optionally at 77 K) is optionally at least 0.0050 cm 3 g -1 , optionally at least 0.0060 cm 3 g -1 , optionally at least 0.0070 cm 3 g -1 The pore volume determined by BJH analysis is optionally 0.025 cm 3 g -1 Below, optional 0.020cm 3 g -1 Below, optional 0.015cm 3 g -1 Below, optional 0.010cm 3 g -1 or less, optionally at least 0.0080 cm 3 g -1 Below, optional 0.0070cm 3 g -1 The following is the result.

[0047] The pore diameter of the composition, as determined by adsorption measurements, may optionally be at least 150 Å, optionally at least 175 Å, optionally at least 200 Å, optionally at least 225 Å, optionally at least 250 Å, optionally at least 275 Å, or optionally at least 300 Å. The pore diameter, as determined by adsorption measurements, may optionally be no greater than 400 Å, optionally no greater than 375 Å, optionally no greater than 350 Å, optionally no greater than 325 Å, optionally no greater than 300 Å, optionally no greater than 275 Å, optionally no greater than 250 Å, optionally no greater than 225 Å, or optionally no greater than 200 Å.

[0048] The acid absorption of the composition may optionally be at least 200 mg of acid per gram of sample, optionally at least 220 mg of acid per gram of sample, or optionally at least 240 mg of acid per gram of sample. The acid absorption may optionally be no more than 1000 mg of acid per gram of sample, optionally no more than 800 mg of acid per gram of sample, optionally no more than 600 mg of acid per gram of sample, optionally no more than 500 mg of acid per gram of sample, optionally no more than 400 mg of acid per gram of sample, optionally no more than 350 mg of acid per gram of sample, optionally no more than 300 mg of acid per gram of sample, or optionally no more than 280 mg of acid per gram of sample. Acid absorption may be determined using sulfuric acid, e.g., 16 wt% sulfuric acid. For the avoidance of doubt, the terms "acid absorption" and "acid adsorption" are generally used interchangeably in the art.

[0049] According to a third aspect of the present invention, there is also provided a method of making a composition comprising beta lead(II) oxide, the method comprising heating an organic lead salt in a gas stream comprising an oxidizer.

[0050] The present inventors have unexpectedly discovered that the production of beta-lead(II) oxide can be better controlled by contacting an organic lead salt (e.g., lead citrate) with a gas stream containing an oxidizing agent.

[0051] Beta lead oxide, often known as Massicot, has an orthorhombic crystal structure that can be easily identified using X-ray diffraction.

[0052] The oxidizer-containing gas typically includes an inert diluent. For example, the gas may include air containing an oxidizer in the form of molecular oxygen gas and an inert diluent in the form of nitrogen gas. The presence of an inert diluent has been found to favor the formation of beta lead oxide. While air includes an inert diluent in the form of nitrogen gas, the inventors have found that further reducing the concentration of the oxidizer can be beneficial. Thus, the method may include mixing an oxidizer-containing precursor gas with a diluent gas to prepare an oxidizer-containing gas. The precursor gas may include, for example, air. The diluent gas may be an inert diluent, such as nitrogen. The molar ratio of the diluent gas to the precursor gas (particularly when the precursor gas is air) may be at least 1:10, optionally at least 1:5, optionally at least 1:2.5, optionally at least 1:2, or optionally at least 1:1.5. The molar ratio of diluent gas to precursor gas may optionally be 5:1 or less, optionally 4:1 or less, optionally 3:1 or less, and optionally 2:1 or less. The molar ratio of diluent gas to precursor gas may be 1:10 to 5:1, optionally 1:5 to 3:1, and optionally 1:2 to 2:1. The use of a diluent gas to dilute the oxidizer reduces the concentration of the oxidizer, thereby reducing the temperature rise associated with the exothermic reaction of the oxidizer with lead citrate. At higher temperatures, the formation of metallic lead is promoted. At lower temperatures, the formation of beta-lead oxide is favored.

[0053] When the oxidant is in the form of a gaseous oxidant such as molecular oxygen, the gas optionally comprises no more than 20 wt% oxidant, optionally no more than 18 wt% oxidant, optionally no more than 16 wt% oxidant, optionally no more than 14 wt% oxidant, optionally no more than 12 wt% oxidant, optionally no more than 10 wt% oxidant.

[0054] When the oxidant is in the form of a gaseous oxidant such as molecular oxygen, the gas optionally comprises at least 1 wt% oxidant, optionally at least 2 wt% oxidant, optionally at least 3 wt% oxidant, optionally at least 5 wt% oxidant, optionally at least 7.5 wt% oxidant, optionally at least 10 wt% oxidant.

[0055] When the oxidant is in the form of a gaseous oxidant such as molecular oxygen, the gas optionally comprises 1-20 wt% oxidant, optionally 1-18 wt% oxidant, optionally 3-16 wt% oxidant, optionally 5-14 wt% oxidant.

[0056] While exposed to the gas flow, the organic lead salt may be heated to a temperature of at least 250° C., optionally at least 275° C., optionally at least 300° C., optionally at least 325° C. The lead carbonate may optionally be heated to a temperature of no more than 450° C., optionally no more than 425° C., optionally no more than 400° C., optionally no more than 375° C.

[0057] While exposed to the gas flow, the organic lead salt may optionally be heated for 240 minutes or less, optionally for 180 minutes or less, optionally for 150 minutes or less, optionally for 120 minutes or less, optionally for 90 minutes or less, optionally for 75 minutes or less, or optionally for 60 minutes or less. While exposed to the gas flow, the organic lead salt may optionally be heated for at least 30 minutes, optionally for at least 60 minutes, or optionally for at least 90 minutes. Those skilled in the art will appreciate that the heating time may depend on both the amount of organic lead salt and the volume of the reaction chamber / furnace. In this regard, a larger amount of organic lead salt is associated with a longer heating time.

[0058] While exposed to the gas flow, the organic lead salt may be heated to a temperature of 275°C to 375°C for a period of 60 to 180 minutes, optionally for a period of 90 to 150 minutes.

[0059] The inventors have discovered that it is possible to tailor the composition by modifying the method used to make the composition. For example, the inventors have discovered that by heating an organic lead salt (particularly lead citrate) at a temperature of 325-375°C in the presence of a gas stream containing a relatively low concentration of oxidizer (e.g., 6-10 wt%, which may be achieved by mixing, for example, 1 / 2 or 1 volume of air with 1 volume of nitrogen), a composition containing a high percentage of beta-lead oxide (e.g., at least 80 wt%, optionally at least 85 wt%, optionally at least 90 wt% beta-lead oxide) can be obtained. Heating to higher temperatures (e.g., 400°C) and / or using a higher percentage of oxidizer (e.g., 13 wt%, which may be achieved by mixing, for example, 2 volumes of air with 1 volume of nitrogen) may also result in a relatively high percentage of beta lead oxide (optionally at least 70 wt%, optionally at least 75 wt%, optionally at least 80 wt%, optionally at least 85 wt% beta lead oxide), but with a higher percentage of lead metal (optionally at least 5 wt%, optionally at least 6 wt%, optionally at least 7 wt%, optionally at least 8 wt%). This is important because the presence of lead metal in the composition is useful in preparing lead-acid battery products. Heating to lower temperatures (e.g., 300-325°C) and / or using a higher percentage of oxidizer (e.g., 13 wt%, which may be achieved by mixing, for example, 2 volumes of air with 1 volume of nitrogen) may also result in a relatively high percentage of beta lead oxide (optionally at least 70 wt%, optionally at least 75 wt%, optionally at least 80 wt%, optionally at least 85 wt% beta lead oxide), but with a lower percentage of lead metal (optionally 5 wt% or less, optionally 3 wt% or less, optionally 1 wt% or less), and a percentage of alpha lead oxide (e.g., at least 1 wt%, optionally at least 3 wt%, optionally at least 5 wt%).

[0060] Those skilled in the art will appreciate that the methods of the present invention need not result solely in beta-lead oxide, and that components other than beta-lead oxide may be present in the composition, such as one or more of alpha lead oxide, lead metal, minium, and carbon. However, the methods of the present invention may result in a composition comprising at least 60 wt% beta-lead oxide, optionally at least 70 wt% beta-lead oxide, optionally at least 80 wt% beta-lead oxide, and optionally at least 90 wt% beta-lead oxide. The beta-lead oxide content may be measured, for example, using acid dissolution or by X-ray diffraction.

[0061] The organic lead salt may be as defined above in relation to the method of the first aspect of the invention.

[0062] The process of the third aspect of the invention may be carried out in a rotary furnace.

[0063] As noted above, the method of the third aspect of the invention is used to produce a composition comprising beta-lead oxide. Thus, according to a fourth aspect of the invention, there is provided a composition comprising beta-lead oxide, the composition being producible or produced by the method of the third aspect of the invention. The composition may, for example, comprise at least 85 wt%, optionally at least 90 wt%, of beta-lead oxide. The composition of the fourth aspect of the invention may include any of the features described above in relation to the method of the third aspect of the invention. The composition may comprise metallic lead.

[0064] The composition of the fourth aspect of the invention may include the features described above in relation to the composition of the second aspect of the invention. For example, the composition of the fourth aspect of the invention may include particles that optionally include subparticles. The subparticles may be protrusions.

[0065] According to a fifth aspect of the present invention, there is provided a method of making a composition comprising minium, comprising the steps of: Converting organic lead salts to PbOPbCO3, and Converting PbOPbCO3 into red lead A method is provided, comprising:

[0066] Minium is well known to those skilled in the art. It has the general formula Pb3O4 and is also known as lead tetroxide, minium, and lead(II, IV) oxide.

[0067] Converting the organic lead salt, optionally lead citrate, to PbOPbCO3 may optionally include converting the organic lead salt, optionally lead citrate, to lead(II) oxide and optionally converting the lead(II) oxide to lead carbonate. The lead carbonate may be heated to form alpha lead oxide. The alpha lead oxide may react with lead carbonate to form PbOPbCO3. Converting the organic lead salt to the lead(II) oxide may include heating the organic lead salt in the presence of an oxidizing agent, e.g., an oxidizing gas such as an oxygen-containing gas, e.g., a gas containing molecular oxygen (O2). Converting the lead(II) oxide to lead carbonate may include heating the lead(II) oxide in the presence of carbon dioxide. Heating the organic lead salt to form lead(II) oxide and converting the lead(II) oxide to lead carbonate may occur sequentially and / or simultaneously. For example, heating an organic lead salt to form lead(II) oxide and converting the lead(II) oxide to lead carbonate may be performed by heating the organic lead salt in the presence of an oxidizing agent, such as an oxidizing gas (e.g., a gas containing molecular oxygen, O2) and carbon dioxide. Thus, converting an organic lead salt to lead carbonate may include heating the organic lead salt in the presence of an oxidizing gas and carbon dioxide. Without wishing to be bound by theory, it is understood that heating an organic lead salt in the presence of an oxidizing agent results in the formation of beta-lead(II) oxide. One skilled in the art will appreciate that beta-lead(II) oxide may not be the only product formed. Beta-lead(II) oxide reacts with carbon dioxide to form lead carbonate.

[0068] When the oxidant comprises a gas (e.g., a gas comprising molecular oxygen), the oxidant may be provided as a gas stream. The method may include contacting the organic lead salt with the oxidant stream.

[0069] The carbon dioxide may be provided as a carbon dioxide stream. The method may comprise contacting lead(II) oxide with the carbon dioxide stream.

[0070] When the oxidizing agent includes molecular oxygen (e.g., when air is used as the oxidizing agent) and forming lead carbonate includes heating lead(II) oxide in the presence of carbon dioxide, the molar ratio of carbon dioxide to molecular oxygen may optionally be at least 10:1, optionally at least 12:1, optionally at least 15:1, optionally at least 18:1, optionally at least 20:1, or optionally at least 25:1. For the avoidance of doubt, when air is used to provide the molecular oxygen, the amount of molecular oxygen may be determined based on air containing 21% oxygen. The inventors have discovered that a relatively high ratio of carbon dioxide to molecular oxygen is effective in producing a high percentage of alpha lead oxide, particularly when lead citrate is heated in a gas mixture containing molecular oxygen (e.g., air) and carbon dioxide.

[0071] The molar ratio of carbon dioxide to molecular oxygen may optionally be 250:1 or less, optionally 200:1 or less, optionally 150:1 or less, optionally 100:1 or less.

[0072] Converting PbOPbCO3 to minium may optionally include converting PbOPbCO3 to alpha lead oxide and converting the alpha lead oxide to minium. Converting PbOPbCO3 to alpha lead oxide may include heating PbOPbCO3 in the presence of a gas, optionally a gas stream containing an oxidizing agent such as O2. The oxidizing agent does not react with PbOPbCO3, but the gas stream removes carbon dioxide that would otherwise react with the alpha lead oxide. Converting alpha lead oxide to minium may include heating alpha lead oxide in the presence of an oxidizing agent, optionally an oxidizing gas such as a gas containing molecular oxygen (O2), such as air.

[0073] Converting PbOPbCO3 to minium may include heating PbOPbCO3 at a temperature sufficiently high to promote the formation of minium. PbOPbCO3 may be heated to a temperature of at least 325° C., optionally at least 350° C., optionally at least 375° C., optionally at least 400° C., optionally at least 425° C. Applicants have found that the formation of minium is promoted by heating to a relatively high temperature.

[0074] The PbOPbCO3 may optionally be heated at a temperature of 500°C or less, optionally 475°C or less, optionally 450°C or less, optionally 425°C or less.

[0075] The PbOPbCO3 may be heated for a time sufficiently long to promote the formation of minium lead. For example, the PbOPbCO3 may be heated for at least 30 minutes, optionally at least 45 minutes, and optionally at least 60 minutes. Applicants have discovered that the formation of minium lead is relatively slow and requires extended heating, the duration of which is somewhat dependent on temperature.

[0076] The PbOPbCO3 may be heated at a temperature of 350°C to 400°C, optionally 375°C to 425°C, optionally for a period of 30 to 90 minutes, optionally for a period of 60 to 90 minutes.

[0077] The method may be carried out in a rotary furnace.

[0078] The organic lead salt may be as defined above in relation to the method of the first aspect of the invention.

[0079] Those skilled in the art will appreciate that the methods of the present invention need not result solely in minium lead, and that components other than minium lead may be present. For example, one or more of alpha lead oxide, beta lead oxide, lead metal, and Pb2O3 may be present. However, the methods of the present invention may result in compositions comprising at least 50 wt% minium lead, optionally at least 60 wt% minium lead, optionally at least 70 wt% minium lead, optionally at least 80 wt% minium lead, optionally at least 90 wt% minium lead, optionally at least 95 wt% minium lead, and optionally at least 98 wt% minium lead. The minium lead content may be measured, for example, using acid dissolution or X-ray diffraction, as described above.

[0080] As noted above, the method of the fifth aspect of the invention may be used to produce a composition comprising minium lead. According to a sixth aspect of the invention, there is provided a composition comprising minium lead, the composition being producible or produced by a method according to the fifth aspect of the invention. The composition may therefore comprise any of the features described above in relation to the method of the fifth aspect of the invention. The composition may, for example, comprise at least 85 wt%, optionally at least 90 wt%, of minium lead.

[0081] The composition of the sixth aspect of the invention may include the features described above in relation to the composition of the second aspect of the invention. For example, the composition of the sixth aspect of the invention may include particles that optionally include subparticles. The subparticles may be, for example, protrusions.

[0082] According to a seventh aspect of the present invention, there is provided a method of making a composition comprising Pb2O3, comprising the steps of: Converting organic lead salts to PbOPbCO3, and Converting PbOPbCO3 to Pb2O3 A method is provided, comprising:

[0083] Pb2O3 (or lead sesquioxide) is well known to those skilled in the art.

[0084] Converting the organic lead salt to PbOPbCO3 may include the features described above in relation to the method of forming minium according to the fifth aspect of the invention.

[0085] Converting PbOPbCO3 to Pb2O3 may optionally include converting PbOPbCO3 to alpha lead oxide and converting the alpha lead oxide to Pb2O3. Converting PbOPbCO3 to alpha lead oxide may include heating PbOPbCO3 in the presence of a gas stream, optionally a gas containing an oxidizing agent such as O2. The oxidizing agent does not react with PbOPbCO3, but the gas stream removes carbon dioxide that would otherwise react with the alpha lead oxide. Converting alpha lead oxide to Pb2O3 may include heating alpha lead oxide in the presence of an oxidizing agent, optionally an oxidizing gas such as a gas containing molecular oxygen (O2), such as air. The general method for converting PbOPbCO3 to Pb2O3 is similar to the method for converting PbOPbCO3 to minium, except that lower temperatures are used to obtain Pb2O3 than those used to obtain minium.

[0086] The PbOPbCO3 may be heated in the presence of an oxidizing agent at a sufficiently high temperature to promote the formation of Pb2O3. The PbOPbCO3 may be heated to a temperature of at least 275°C, optionally at least 300°C, optionally at least 325°C, and optionally at least 350°C. However, because temperatures that are too high promote the formation of minium, the lead carbonate may preferably be heated to a temperature of no more than 400°C, optionally no more than 375°C, optionally no more than 350°C, and optionally no more than 325°C.

[0087] The PbOPbCO3 may be heated for at least 30 minutes, optionally at least 45 minutes, optionally at least 60 minutes, and optionally at least 90 minutes. The PbOPbCO3 may be heated for up to 300 minutes, optionally up to 240 minutes, optionally up to 180 minutes, optionally up to 150 minutes, optionally up to 120 minutes, and optionally up to 90 minutes. Applicants have discovered that the formation of Pb2O3 is relatively slow, especially at the lower temperatures preferred to inhibit the formation of red lead.

[0088] The PbOPbCO3 may be heated at a temperature between 275°C and 350°C, optionally between 275°C and 325°C, optionally for a period of 30 to 180 minutes, optionally for a period of 60 to 120 minutes.

[0089] The method may be carried out in a rotary furnace.

[0090] The organic lead salt may be as defined in relation to the process of the first aspect of the invention.

[0091] Those skilled in the art will appreciate that the methods of the present invention need not result solely in PbO, and that components other than PbO may be present. For example, one or more of alpha lead oxide, beta lead oxide, lead metal, and minium may be present. In particular, alpha lead oxide and / or minium may be present. However, the methods of the present invention may result in compositions comprising at least 40 wt% PbO, optionally at least 50 wt%, and optionally at least 60 wt% PbO. The PbO content may be measured, for example, using acid dissolution and by X-ray diffraction, as described above.

[0092] As noted above, the method of the seventh aspect of the invention may be used to produce a composition comprising Pb2O3. According to an eighth aspect of the invention, there is provided a composition comprising Pb2O3, the composition being producible or produced by a method according to the seventh aspect of the invention. The composition may include the features described above in relation to the method of the sixth aspect of the invention. The composition may, for example, comprise at least 40 wt%, optionally at least 60 wt%, of Pb2O3.

[0093] The composition of the eighth aspect of the invention may include the features described above in relation to the composition of the second aspect of the invention. For example, the composition of the eighth aspect of the invention may include particles that optionally include subparticles. The subparticles may be, for example, protrusions.

[0094] According to a ninth aspect of the present invention, there is provided a method for producing a composition containing a desired one or more of alpha lead oxide, beta lead oxide, Pb2O3, minium and lead metal, comprising the steps of: determining whether any one or more of alpha lead oxide, beta lead oxide, Pb2O3, minium lead, and lead metal are desired in the composition; selecting one or more reaction parameters from a list consisting of one or more heating temperatures, one or more heating durations, and one or more gas compositions based on said determination; heating the organic lead salt according to one or more selected reaction parameters, thereby forming said composition containing a desired one or more of alpha lead oxide, beta lead oxide, Pb2O3, minium lead, and lead metal. A method is provided, comprising:

[0095] The present inventors have discovered that it is possible to control the components in a lead-containing composition primarily by controlling the gas composition in which the organic lead salt is heated.

[0096] The method may include determining that alpha lead oxide is desired, and selecting one or more reaction parameters includes selecting a first gas composition including carbon dioxide and an oxidizer, preferably including molecular oxygen. Selecting the one or more reaction parameters optionally includes selecting a second gas composition, the second gas composition including an inert gas. The method may include heating the organic lead salt in the presence of the first gas composition. The method may include continuing heating in the presence of the second gas composition. The method of the ninth aspect of the present invention may include the features of the method of producing alpha lead oxide described according to the first aspect of the present invention.

[0097] The method may include determining that beta lead oxide is desired, and selecting one or more reaction parameters includes selecting a gas composition including an oxidizer, preferably including molecular oxygen, and optionally including air. The gas composition may include an oxidizer and an inert diluent. The method may include mixing a gas including the oxidizer with the inert diluent. The method may include heating an organic lead salt in the presence of the gas composition, optionally in a stream of the gas composition. The method of the ninth aspect of the present invention may include features of the method for producing beta lead oxide described according to the third aspect of the present invention.

[0098] The method may include determining that minium lead is desired, and selecting one or more reaction parameters includes selecting a first gas composition including carbon dioxide and an oxidizer, preferably including molecular oxygen. Selecting the one or more reaction parameters may optionally include selecting a second gas composition, the second gas composition including an oxidizer such as O2, and optionally excluding carbon dioxide. Selecting the one or more reaction parameters may include selecting a temperature at which the second gas composition contacts the reagent. The temperature is optionally at least 350°C, optionally at least 375°C. The method may include heating the organic lead salt in the presence of the first gas composition. The method may optionally include subsequent heating at the selected temperature in the presence of the second gas composition. The method of the ninth aspect of the present invention may include the features of the method of producing minium lead described according to the fifth aspect of the present invention.

[0099] The method may include determining that PbO is desired, and selecting one or more reaction parameters includes selecting a first gas composition including carbon dioxide and an oxidant, preferably including molecular oxygen. Selecting the one or more reaction parameters optionally includes selecting a second gas composition, the second gas composition including an oxidant, optionally including O, and optionally excluding carbon dioxide. Selecting the one or more reaction parameters may include selecting a temperature at which the second gas composition contacts the reagent. The temperature is optionally at least 275°C and optionally not more than 375°C. The method may include heating an organic lead salt in the presence of the first gas composition. The method may optionally include subsequent heating at a selected temperature in the presence of the second gas composition. The method of the ninth aspect of the present invention may include the features of the method for producing PbO described according to the seventh aspect of the present invention.

[0100] The method may include determining that more than one of alpha lead oxide, beta lead oxide, Pb2O3, minium, and lead metal is desired.

[0101] The method may include determining that a desired amount of a desired component is desired. For example, the method may include determining that beta lead oxide is desired and that at least 5 wt% lead metal is desired. Selecting the one or more parameters may include selecting a gas composition including an oxidizer, preferably including molecular oxygen, and optionally including air. Selecting the one or more parameters may include selecting a temperature of at least 350°C. The gas composition may include an oxidizer and an inert diluent. The method may include mixing a gas including the oxidizer with the inert diluent. The method may include heating an organic lead salt at a selected temperature in the presence of the gas composition.

[0102] Those skilled in the art will understand that the chemical composition of the synthesized composition need not be identical to the intended chemical composition, and that given the nature of chemical synthesis, the synthesized chemical composition may differ to some extent from that intended.

[0103] The organic lead salt may be as defined in relation to the process of the first aspect of the invention.

[0104] According to a tenth aspect of the present invention there is provided a composition comprising one or more of alpha lead oxide, beta lead oxide, metallic lead, Pb2O3 and Pb3O4, the composition comprising particles including sub-particles, the sub-particles optionally having an average largest dimension of 10 to 300 nm, the sub-particles optionally being in the form of protrusions.

[0105] The present inventors have discovered that compositions comprising lead-based materials that may be useful in the battery industry have advantageous properties (particularly a relatively high surface area) when the compositions comprise relatively large particles that optionally contain relatively small subparticles in the form of protrusions. As described above in connection with the second aspect of the present invention, subparticles are smaller than particles. Those skilled in the art will understand that not all subparticles need be in the form of protrusions. Thus, particles may include subparticles that are not in the form of protrusions. Thus, at least some of the subparticles may be in the form of protrusions.

[0106] The particles may be of any shape. For example, the composition optionally includes rod-shaped particles having the protrusions thereon. The rod-shaped particles optionally have an average maximum dimension of 0.2 μm to 20 μm. For example, the composition may include spherical or subspherical particles.

[0107] Particle and subparticle dimensions may be measured using any suitable method, such as scanning electron microscopy.

[0108] The average largest dimension of the subparticles may be calculated using at least 30% by number of the subparticles, optionally at least 40% by number of the subparticles, optionally at least 50% by number of the subparticles, optionally at least 60% by number of the subparticles, optionally at least 70% by number of the subparticles, optionally at least 80% by number of the subparticles.

[0109] When determining the average maximum dimension of the subparticles, the maximum dimension of the subparticles may be determined using at least 30% by number of the particles, optionally using at least 40% by number of the particles, optionally using at least 50% by number of the particles, optionally using at least 60% by number of the particles, optionally using at least 70% by number of the particles, optionally using at least 80% by number of the particles, optionally using at least 90% by number of the particles.

[0110] When determining the average maximum dimension of the subparticles, the maximum dimension of the subparticles may be determined using at least 50% by weight of the composition, optionally using at least 60% by weight of the composition, optionally using at least 70% by weight of the composition, optionally using at least 80% by weight of the composition, and optionally using at least 90% by weight of the composition.

[0111] Optionally, at least 20% by number of the particles of the composition are rod-shaped particles. Optionally, at least 40%, optionally at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90%, optionally at least 95% by number of the particles of the composition are rod-shaped.

[0112] Optionally, of the rod-shaped particles, optionally at least 50% by number have a maximum dimension between 0.2 μm and 20 μm, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90% by number have a maximum dimension between 0.2 μm and 20 μm.

[0113] As described above, the composition optionally includes rod-shaped particles. The rod-shaped particles may have an average aspect ratio of at least 1.5:1, optionally at least 2.0:1, and optionally at least 3.0:1. The rod-shaped particles may optionally have an average aspect ratio of no more than 20:1, optionally no more than 15:1, optionally no more than 10:1, optionally no more than 7.5:1, and optionally no more than 5:1.

[0114] Optionally, of the rod-shaped particles, optionally at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90% by number have an aspect ratio of at least 1.5:1, optionally at least 2.0:1, optionally at least 3.0:1. Optionally, at least 50%, optionally at least 60%, optionally at least 70%, optionally at least 80%, optionally at least 90% by number have an aspect ratio of 20:1 or less, optionally 15:1 or less, optionally 10:1 or less, optionally 7.5:1 or less, optionally 5:1 or less.

[0115] The BET surface area of ​​the composition, optionally determined at 77 K, optionally using nitrogen, is optionally at least 1.0 m 2 / g, optionally at least 1.5m2 / g, optionally at least 2.0m 2 / g, optionally at least 2.5m 2 / g, optionally at least 3.0m 2 The BET surface area, optionally determined at 77 K, optionally using nitrogen, is optionally 10 m 2 / g or less, optional 8m 2 / g or less, optional 6m 2 / g or less, optional 5m 2 / g or less.

[0116] The subparticles may have an average maximum dimension of at least 10 nm, optionally at least 15 nm, optionally at least 20 nm, optionally at least 25 nm, optionally at least 30 nm, optionally at least 40 nm, and optionally at least 50 nm. The subparticles may optionally have an average maximum dimension of 300 nm or less, optionally 250 nm or less, optionally 200 nm or less, optionally 150 nm or less, and optionally 100 nm or less. The subparticles may have an average maximum dimension of 10 to 300 nm, optionally 15 nm to 200 nm, optionally 20 nm to 150 nm, and optionally 50 to 150 nm. The subparticles may be spherical or subspherical.

[0117] The pore volume of the composition, optionally determined by BJH analysis, optionally from BET data obtained using nitrogen, optionally at 77 K, is optionally at least 0.0050 cm 3 g -1 , optionally at least 0.0060 cm 3 g -1 , optionally at least 0.0070 cm 3 g -1 The pore volume is optionally 0.025 cm 3 g -1 Below, optional 0.020cm 3 g -1 Below, optional 0.015cm 3 g -1 Below, optional 0.010cm 3 g -1Below, optional 0.0080cm 3 g -1 Below, optional 0.0070cm 3 g -1 The following is the result.

[0118] The pore diameter of the composition, as determined by adsorption measurements, may optionally be at least 150 Å, optionally at least 175 Å, optionally at least 200 Å, optionally at least 225 Å, optionally at least 250 Å, optionally at least 275 Å, or optionally at least 300 Å. The pore diameter, as determined by adsorption measurements, may optionally be no greater than 400 Å, optionally no greater than 375 Å, optionally no greater than 350 Å, optionally no greater than 325 Å, optionally no greater than 300 Å, optionally no greater than 275 Å, optionally no greater than 250 Å, optionally no greater than 225 Å, or optionally no greater than 200 Å.

[0119] The acid absorption of the composition may optionally be at least 200 mg of acid per gram of sample, optionally at least 220 mg of acid per gram of sample, or optionally at least 240 mg of acid per gram of sample. The acid absorption may optionally be no more than 1000 mg of acid per gram of sample, optionally no more than 800 mg of acid per gram of sample, optionally no more than 600 mg of acid per gram of sample, optionally no more than 500 mg of acid per gram of sample, optionally no more than 400 mg of acid per gram of sample, optionally no more than 350 mg of acid per gram of sample, optionally no more than 300 mg of acid per gram of sample, or optionally no more than 280 mg of acid per gram of sample. Acid absorption may be determined using sulfuric acid, for example, 16 wt% sulfuric acid.

[0120] The average maximum dimension of the subparticles may optionally be no more than three times the average minimum dimension of the subparticles. For example, the average "length" of the subparticles may be no more than three times the average "width" of the protrusions. The average maximum dimension of the subparticles may optionally be no more than 2.5 times, optionally no more than 2.0 times, or optionally no more than 1.5 times the average minimum dimension of the subparticles.

[0121] Throughout this disclosure, when the subparticles are protrusions, the protrusions may optionally be approximately spherical or partially spherical (eg, hemispherical).

[0122] The composition may include particles having a core portion rich in lead metal and poor in oxide, and an oxide-rich outer portion. The wt% of lead metal in the core portion is optionally greater than the wt% of lead metal in the outer portion. The wt% of oxide in the core portion is optionally lower than the wt% of oxide in the outer portion. The inventors have discovered that some particles have a core rich in lead metal and low in lead oxide, and an outer portion rich in lead oxide. This arrangement is preferred because the outer portion effectively protects the core portion from oxidation when the composition is exposed to air. In connection with the composition of the outer portion, reference to "lead oxide" includes all oxides of lead, including alpha lead oxide, beta lead oxide, red lead, and Pb2O3.

[0123] The core portion may comprise at least 95 wt% lead metal, optionally at least 96 wt% lead metal, optionally at least 98 wt% lead metal. The core portion may be substantially free of oxides of lead.

[0124] The outer portion may include one or more of alpha lead oxide, beta lead oxide, red lead, and Pb2O3.

[0125] The core portion may be spherical or sub-spherical.

[0126] The core portion may have an average largest dimension of at least 1 μm, optionally at least 2 μm, optionally at least 5 μm, optionally at least 10 μm. The core portion may optionally have an average largest dimension of no more than 100 μm, optionally no more than 80 μm, optionally no more than 60 μm, optionally no more than 50 μm, optionally no more than 40 μm, optionally no more than 30 μm.

[0127] The volume of the core portion is optionally greater than the volume of the outer portion, optionally at least 2 times, optionally at least 3 times, optionally at least 5 times, optionally at least 10 times, optionally at least 15 times, optionally at least 20 times, optionally at least 30 times, optionally at least 40 times, optionally at least 50 times, optionally at least 100 times the volume of the outer portion.

[0128] Those skilled in the art will appreciate that the composition may contain components other than alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and red lead. For example, the composition may contain other oxides of lead (e.g., Pb 12 O 19 ) and carbon. These other components are expected to form a minor proportion of the composition, such as 5 wt% or less of the composition, optionally 3 wt% or less, optionally 2 wt% or less, optionally 1 wt% or less, optionally 0.5 wt% or less, optionally 0.1 wt% or less of the composition. Thus, optionally at least 95 wt%, optionally at least 97 wt%, optionally at least 98 wt%, optionally at least 99 wt%, optionally at least 99.5 wt%, optionally at least 99.9 wt% of the composition comprises one or more of alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and red lead.

[0129] The composition may include metallic lead. The composition may include alpha lead oxide. The composition may include beta lead oxide. The composition may include Pb2O3. The composition may include Pb3O4.

[0130] The composition may include more than one of alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and Pb3O4. For example, the composition may include metallic lead and one or both of alpha lead oxide and beta lead oxide. The composition may include alpha lead oxide and beta lead oxide.

[0131] The composition may, for example, include at least 1 wt% metallic lead, optionally at least 2 wt%, optionally at least 3 wt%, optionally at least 5 wt%, optionally at least 8 wt%, optionally at least 10 wt%, optionally at least 15 wt%, and optionally at least 20 wt% metallic lead. The composition may, for example, include up to 40 wt% metallic lead, optionally up to 35 wt%, optionally up to 30 wt%, optionally up to 25 wt%, and optionally up to 20 wt% metallic lead. Including an amount of metallic lead in the composition may be advantageous, particularly when the composition also includes alpha lead oxide and / or beta lead oxide.

[0132] The composition may consist essentially of one or more of alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and red lead.

[0133] The composition may comprise at least 98.0 wt% alpha lead oxide, optionally at least 98.5 wt%, optionally at least 99.0 wt%, optionally at least 99.5 wt% alpha lead oxide. The composition may comprise up to 99.9 wt% alpha lead oxide, optionally up to 99.8 wt% alpha lead oxide, optionally up to 99.7 wt% alpha lead oxide, optionally up to 99.6 wt% alpha lead oxide, optionally up to 99.5 wt% alpha lead oxide.

[0134] The composition may optionally comprise at least 40 wt% alpha lead oxide, optionally at least 50 wt% alpha lead oxide, optionally at least 55 wt% alpha lead oxide, optionally at least 60 wt% alpha lead oxide, optionally at least 65 wt% alpha lead oxide, optionally at least 70 wt% alpha lead oxide, optionally at least 75 wt% alpha lead oxide.

[0135] The composition may optionally comprise up to 95 wt% alpha lead oxide, optionally up to 90 wt% alpha lead oxide, optionally up to 85 wt% alpha lead oxide, optionally up to 80 wt% alpha lead oxide, optionally up to 75 wt% alpha lead oxide, optionally up to 70 wt% alpha lead oxide. Applicant has discovered that it can be beneficial for the composition to comprise a reasonably large amount of alpha lead oxide, optionally in the presence of metallic lead.

[0136] The composition may optionally comprise at least 40 wt% beta lead oxide, optionally at least 50 wt% beta lead oxide, optionally at least 55 wt% beta lead oxide, optionally at least 60 wt% beta lead oxide, optionally at least 65 wt% beta lead oxide, optionally at least 70 wt% beta lead oxide, optionally at least 75 wt% beta lead oxide.

[0137] The composition may optionally comprise 95 wt% or less beta lead oxide, optionally 90 wt% or less beta lead oxide, optionally 85 wt% or less beta lead oxide, optionally 80 wt% or less beta lead oxide, optionally 75 wt% or less beta lead oxide, optionally 70 wt% or less beta lead oxide. Applicant has discovered that it can be beneficial for the composition to comprise a reasonably large amount of beta lead oxide, optionally in the presence of metallic lead.

[0138] The composition may optionally comprise at least 40 wt% total beta lead oxide and alpha lead oxide, optionally at least 50 wt% total beta lead oxide and alpha lead oxide, optionally at least 55 wt% total beta lead oxide and alpha lead oxide, optionally at least 60 wt% total beta lead oxide and alpha lead oxide, optionally at least 65 wt% total beta lead oxide and alpha lead oxide, optionally at least 70 wt% total beta lead oxide and alpha lead oxide, optionally at least 75 wt% total beta lead oxide and alpha lead oxide.

[0139] The composition may optionally comprise up to 95 wt% combined beta lead oxide and alpha lead oxide, optionally up to 90 wt% combined beta lead oxide and alpha lead oxide, optionally up to 85 wt% combined beta lead oxide and alpha lead oxide, optionally up to 80 wt% combined beta lead oxide and alpha lead oxide, optionally up to 75 wt% combined beta lead oxide and alpha lead oxide, optionally up to 70 wt% combined beta lead oxide and alpha lead oxide. Applicant has discovered that it can be beneficial for the composition to comprise reasonably large amounts of beta and alpha lead oxide, optionally in the presence of metallic lead.

[0140] The composition may comprise 50-80 wt% alpha lead oxide and 10-20 wt% metallic lead. The composition may comprise 60-80 wt% alpha lead oxide, optionally 70-80 wt% alpha lead oxide, optionally 75-80 wt% alpha lead oxide. The composition may comprise 10-15 wt% metallic lead or 15-20 wt% metallic lead.

[0141] The composition may comprise 50-80 wt% beta lead oxide and 10-20 wt% metallic lead. The composition may comprise 60-80 wt% beta lead oxide, optionally 70-80 wt% beta lead oxide, optionally 75-80 wt% beta lead oxide. The composition may comprise 10-15 wt% metallic lead or 15-20 wt% metallic lead.

[0142] The composition may comprise at least 98.0 wt% beta lead oxide, optionally at least 98.5 wt%, optionally at least 99.0 wt%, optionally at least 99.5 wt% beta lead oxide. The composition may comprise no more than 99.9 wt% beta lead oxide, optionally no more than 99.8 wt% beta lead oxide, optionally no more than 99.7 wt% beta lead oxide, optionally no more than 99.6 wt% beta lead oxide, optionally no more than 99.5 wt% beta lead oxide.

[0143] The composition may comprise at least 98.0 wt% Pb3O4, optionally at least 98.5 wt%, optionally at least 99.0 wt%, optionally at least 99.5 wt% Pb3O4. The composition may comprise up to 99.9 wt% Pb3O4, optionally up to 99.8 wt% Pb3O4, optionally up to 99.7 wt% Pb3O4, optionally up to 99.6 wt% Pb3O4, optionally up to 99.5 wt% Pb3O4.

[0144] The composition may comprise at least 40 wt% Pb2O3, optionally at least 50 wt% Pb2O3, optionally at least 60 wt% Pb2O3, optionally at least 70 wt% Pb2O3, optionally at least 80 wt% Pb2O3, optionally at least 90 wt% Pb2O3, optionally at least 95 wt% Pb2O3, optionally at least 98 wt% Pb2O3.

[0145] The composition of the tenth aspect of the invention may be made using the methods of the first, third, fifth, seventh and ninth aspects of the invention, and therefore may comprise one or more features of those aspects of the invention. In contrast, the methods of the first, third, fifth, seventh and ninth aspects of the invention may comprise one or more features of the composition of the tenth aspect of the invention. Furthermore, the composition of the tenth aspect of the invention may comprise one or more features of the second, fourth, sixth and eighth aspects of the invention. In contrast, the compositions of the second, fourth, sixth and eighth aspects of the invention may comprise one or more features of the composition of the tenth aspect of the invention.

[0146] According to an eleventh aspect of the present invention, there is provided a composition comprising one or more of alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and Pb3O4, the composition comprising particles having a core portion rich in lead metal and poor in oxide, and an outer portion rich in oxide. The oxide-rich outer portion may be poor in lead metal. The inventors have discovered that some particles have a core rich in lead metal and low in lead oxide, and an outer portion rich in lead oxide. This arrangement is preferred because the outer portion effectively protects the core portion from oxidation when the composition is exposed to air. Without wishing to be bound by theory, it is expected that batteries made from such compositions may have improved cycle life because the outer portion protects the core portion from sulfation.

[0147] The core portion may comprise at least 95 wt% lead metal, optionally at least 96 wt% lead metal, optionally at least 98 wt% lead metal. The core portion may be substantially free of lead oxide.

[0148] The outer portion may include one or more of alpha lead oxide, beta lead oxide, red lead, and Pb2O3.

[0149] The core portion may be spherical or sub-spherical.

[0150] The core portion may optionally have an average maximum dimension of at least 1 μm, optionally at least 2 μm, optionally at least 5 μm, optionally at least 10 μm. The core portion may optionally have an average maximum dimension of no more than 100 μm, optionally no more than 80 μm, optionally no more than 60 μm, optionally no more than 50 μm, optionally no more than 40 μm, optionally no more than 30 μm.

[0151] Those skilled in the art will appreciate that the composition may contain components other than alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and red lead. For example, the composition may contain other oxides of lead (e.g., Pb 12 O 19) and carbon. These other components are expected to form a minor proportion of the composition, such as 5 wt% or less, optionally 3 wt% or less, optionally 2 wt% or less, optionally 1 wt% or less, optionally 0.5 wt% or less, optionally 0.1 wt% or less of the composition. Thus, optionally at least 95 wt%, optionally at least 97 wt%, optionally at least 98 wt%, optionally at least 99 wt%, optionally at least 99.5 wt%, optionally at least 99.9 wt% of the composition comprises one or more of alpha lead oxide, beta lead oxide, metallic lead, Pb2O3, and red lead.

[0152] The composition of the eleventh aspect of the invention may be made using the methods of the first, third, fifth, seventh and ninth aspects of the invention. The composition of the eleventh aspect of the invention may include the features described above in relation to the compositions of the second, fourth, sixth, eighth and tenth aspects of the invention.

[0153] In some embodiments, the compositions of the second, fourth, sixth, eighth, tenth, and / or eleventh aspects of the invention are processed into battery plates, for example, using methods known to those skilled in the art.

[0154] According to a twelfth aspect of the present invention, there is provided a method for forming a lead-acid battery plate, comprising combining the composition of the second, fourth, sixth, eighth, tenth, and / or eleventh aspects of the present invention with one or more battery paste additives and an acid to form a paste. The acid is typically sulfuric acid, which converts the lead oxide in the composition to PbSO4. Suitable battery paste additives include those listed above, including metal compounds, insoluble carbon, barium sulfate, and fibers. The paste may then be applied to a grid, typically a lead alloy grid, and cured to form the plate. The method for forming a lead-acid battery plate may be suitable for thin-plate pure lead (TPPL) batteries.

[0155] According to a thirteenth aspect of the present invention, there is provided a battery plate producible or produced by the method of the eleventh aspect of the present invention. The lead acid battery plate may be suitable for thin plate pure lead (TPPL) batteries.

[0156] The battery plates may then be assembled into a lead acid battery.The battery plates may be assembled into a lead acid battery using known methods.

[0157] Thus, according to a fourteenth aspect of the present invention, there is provided a lead acid battery comprising one or more battery plates according to the twelfth aspect of the present invention. The battery may be a thin plate pure lead (TPPL) battery.

[0158] The lead-acid battery of the fourteenth aspect of the present invention may include a battery casing in which one or more of the battery plates of the thirteenth aspect of the present invention are located. The casing may contain a battery acid, such as sulfuric acid. When the battery is assembled, the lead acid, e.g., PbSO4 (and basic lead sulfate) in the battery plates is converted to PbO2 in the positive plate and to metallic lead in the negative plate by applying an electric current during the cell formation stage.

[0159] It will of course be understood that features described in relation to one aspect of the invention may be incorporated in other aspects of the invention, for example a method of the invention may incorporate any of the features described with reference to an apparatus of the invention, and vice versa.

[0160] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying schematic drawings, in which: [Brief explanation of the drawings]

[0161] [Figure 1] 1 shows a schematic diagram of an example of a method for making alpha lead oxide according to a first embodiment of the present invention. [Figure 2A] 1 shows a low magnification scanning electron microscope image of an example of a composition comprising alpha lead oxide according to the second and tenth aspects of the present invention. [Figure 2B]1 shows a high magnification scanning electron microscope image of an example of a composition comprising alpha lead oxide according to the second and tenth aspects of the present invention. [Figure 3] 1 shows a schematic diagram of an example of a method for making a composition comprising beta-lead oxide according to a further embodiment of the present invention. [Figure 4A] 1 shows a low magnification scanning electron microscope image of an exemplary composition comprising beta lead oxide according to the fourth and tenth aspects of the present invention. [Figure 4B] 1 shows a high magnification scanning electron microscope image of an example of a composition comprising beta lead oxide according to the fourth and tenth aspects of the present invention. [Figure 5] 1 shows a schematic diagram of an example of a method for making red lead according to a further embodiment of the present invention; [Figure 6A] 1 shows a low-magnification scanning electron microscope image of an example of a composition containing red lead according to the sixth and tenth aspects of the present invention. [Figure 6B] 1 shows a high-magnification scanning electron microscope image of an example of a composition containing red lead according to the sixth and tenth aspects of the present invention. [Figure 7] FIG. 1 shows a schematic diagram of an example of a method for making Pb2O3 according to a further embodiment of the present invention. [Figure 8A] 10 shows a low-magnification scanning electron microscope image of an example of a composition including Pb2O3 according to the eighth and tenth aspects of the present invention. [Figure 8B] 1 shows a high-magnification scanning electron microscope image of an example of a composition containing Pb2O3 according to the eighth and tenth aspects of the present invention. [Figure 9] 1 shows a schematic diagram of an example of a method for making a composition containing desired ingredients according to a further embodiment of the present invention. [Figure 10] 10 shows a schematic diagram of an example method for making a battery plate according to yet another embodiment of the present invention. [Figure 11] 1 is a simplified perspective view of a battery according to an embodiment of the present invention. [Figure 12A] 1 shows a low magnification scanning electron microscope image of an example of a particle core derived from a composition comprising alpha lead oxide according to the second and tenth aspects of the present invention. [Figure 12B]1 shows a low magnification scanning electron microscope image of an example of a particle core derived from a composition comprising alpha lead oxide according to the second and tenth aspects of the present invention. [Figure 13] 1 shows metallic lead content in powder samples of lead oxide according to the present invention compared to conventional lead oxide when exposed to air over time. [Figure 14A] 10A and 10B show low and high magnification scanning electron microscope images, respectively, of an example of particles of a composition comprising lead oxide according to a tenth embodiment of the present invention. [Figure 14B] 10A and 10B show low and high magnification scanning electron microscope images, respectively, of an example of particles of a composition comprising lead oxide according to a tenth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0162] Detailed Description Method for forming a composition containing alpha lead oxide A composition containing alpha lead oxide was synthesized as follows: 30 g of lead citrate (Pb(CHO)3HO) was placed in a 4-liter rotary furnace. The lead citrate was prepared as disclosed in WO 2008 / 056125. Scanning electron microscopy showed that the lead citrate was elongated, with particle lengths of approximately 10-40 μm and particle widths of approximately 2-4 μm. X-ray diffraction was used to confirm that the lead citrate was indeed lead citrate. A mixture of air (18 L / h) and carbon dioxide (18-25 L / h) was passed through the lead citrate for a first known period of 1 hour 45 minutes to 2 hours while the lead citrate was heated to 350°C and then at 350°C. After this first period, a stream of nitrogen (12 L / h) was passed through the contents of the rotary furnace for a second known period of 3-30 minutes. The furnace was then cooled to room temperature, and nitrogen was passed through it (12 liters / hour). The furnace was rotated at a speed of 20 rpm throughout. The resulting composition was then analyzed using X-ray diffraction and acid dissolution techniques to determine the presence and relative amounts of various components within the composition, such as alpha lead oxide, beta lead oxide, minium, and lead metal, as described above in connection with the method of the first aspect of the present invention.

[0163] Table 1 below shows how the composition varies with process conditions. Residence time 1 refers to the time the lead citrate is heated and exposed to air and carbon dioxide. Residence time 2 refers to the time the contents of the rotary kiln are heated in the presence of nitrogen. In comparative examples CEx1-CEx4, a mixture of air and carbon dioxide is always passed through the rotary kiln.

[0164] [Table 1]

[0165] No carbon or red lead was found in any of the compositions of Examples 1 to 8. 2 wt% carbon was found in the composition of Example 9.

[0166] Examples 1-9 show that alpha lead oxide can be made by heating lead citrate in the presence of air and carbon dioxide, and then heating the reaction product in the presence of nitrogen.

[0167] Without wishing to be bound by theory, it is understood that the following reaction occurs: Pb3(C6H5O7)23H2O (s) +9O 2(g) →3βPbO (s) +12CO 2(g) +8H2O (g) ---------(1) βPbO (s) +CO 2(g) →PbCO 3(s) ---------(2) PbCO 3(s) ⇔αPbO (s) +CO 2(g) ----------(3) 2αPbO (s) +PbCO 3(s) →2PbOPbCO 3(s) ---------(4) 2PbOPbCO 3(s) +N 2(g) → 3αPbO (s) +CO 2(g)+N 2(g) ---------(5) Referring to FIG. 1, without wishing to be bound by theory, a method 100 of forming alpha lead oxide from lead citrate is expected to include converting lead citrate to 2PbOPbCO3 101, and converting 2PbOPbCO3 to alpha lead oxide 102. It is expected that oxygen in the air reacts with the lead citrate to form lead oxide (presumably beta lead oxide), which then reacts with carbon dioxide to form lead carbonate. Heating the lead carbonate forms alpha lead oxide, which reacts with lead carbonate to form 2PbOPbCO3. Heating 2PbOPbCO3 in an inert gas (nitrogen in this case) forms alpha lead oxide.

[0168] It appears that providing excess carbon dioxide is beneficial to promote the formation of lead carbonate. It is also beneficial to heat the PbOPbCO3 in an inert gas for a sufficiently long time to facilitate the formation of alpha lead oxide. Using a carbon dioxide flow of 250 liters / hour, the relatively low amount of oxygen and the relatively high amount of carbon dioxide are expected to result in carbon formation.

[0169] Examples 1-9 in Table 1 demonstrate that compositions containing a high percentage of alpha lead oxide can be produced. Furthermore, Examples 1-9 and 3-9 in particular demonstrate that the relative amounts of alpha and beta lead oxide can be controlled by controlling the relative amounts of air and carbon dioxide.

[0170] Scanning electron microscope images of the composition of Example 9 are shown in Figures 2A and 2B. The composition contains larger, elongated particles 150, 151, and 152 visible in Figure 2A. These particles have a shape and size similar to the lead citrate particles used to make the alpha lead oxide. The particles have an average length of more than 5 μm and an average width of about 1-2 μm. The surfaces of the particles appear roughened, and smaller subparticles are visible on the surfaces of the particles. Small subparticles 160, 161, and 162 are visible, with an average largest dimension of about 50-200 nm.

[0171] Method for forming a composition containing beta-lead oxide A composition containing beta-lead oxide was synthesized as follows: 30 g of lead citrate (Pb(CHO)3HO) was placed in a 4-liter rotary kiln. The lead citrate was prepared as disclosed in WO 2008 / 056125. Scanning electron microscopy showed that the lead citrate was elongated, with particle lengths of approximately 10-40 microns and particle widths of approximately 2-4 μm. X-ray diffraction was used to confirm that the lead citrate was in fact lead citrate. A mixture of air (6-100 L / h) and nitrogen (12 L / h) was passed through the lead citrate for 2 hours while it was heated to 350°C and then again while it was heated at 350°C. The rotary kiln was then cooled to room temperature, and the same mixture of nitrogen and air was passed through the rotary kiln. The rotary kiln was rotated at 20 rpm throughout. The resulting compositions were then analyzed using X-ray diffraction and acid dissolution techniques to determine the presence and relative amounts of various components within the compositions, such as the aforementioned alpha lead oxide, beta lead oxide, minium and lead metal.

[0172] Table 2 below shows how the composition varies with process conditions.

[0173] [Table 2]

[0174] In Example 19, there was no gas flow during the cool-down phase, i.e., after 2 hours of exposure to a mixture of air and nitrogen at 350°C. In Examples 20 and 21, nitrogen was omitted from the gas mixture, and like Example 19, there was no gas flow during the cool-down phase, i.e., after 2 hours of exposure to air at 350°C. In Example 22, nitrogen was omitted from the gas mixture, but in contrast to Examples 19-21, there was a nitrogen flow of 12 liters / hour during the cool-down phase.

[0175] Examples 10-22 demonstrate that controlled production of beta-lead oxide can be achieved by heating lead citrate in a stream of air. Referring to Figure 3, without wishing to be bound by theory, it is believed that a method 200 of forming beta-lead oxide from lead citrate involves heating 201 lead citrate in the presence of an oxidizing agent, in this case oxygen from air.

[0176] Examples 10-16 show that using a high air flow rate promotes the formation of beta lead oxide and lead metal, as well as some alpha lead oxide. As the amount of air decreases, the amount of beta lead oxide increases and the amount of lead metal decreases. Examples 10-16 show that by controlling the relative amounts of air and nitrogen, the amount of lead metal in the composition can be controlled.

[0177] Examples 13, 17, and 18 show that the amount of lead metal increases as the temperature at which lead citrate is exposed to air and nitrogen increases from 300° C. to 400° C. Furthermore, scanning electron microscope images show that the composition produced by heating to 300° C. contains small subparticles approximately 50 μm in size, while the composition produced by heating to 400° C. contains larger subparticles several hundred microns in size.

[0178] Without wishing to be bound by theory, the expected reaction mechanism is as follows: Pb3(C6H5O7)23H2O (s) +9O 2(g) →3βPbO (s) +12CO 2(g) +8H2O (g) ---------(6) Scanning electron microscope images of the composition of Example 13 are shown in Figures 4A and 4B. The composition contains larger, elongated particles 250, 251, and 252 visible in Figure 4A. These particles have a shape and size similar to the lead citrate particles used to make the alpha lead oxide. The particles have an average length of more than 5 μm and an average width of about 1-2 μm. The surfaces of the particles appear roughened, and smaller subparticles are visible on the surfaces of the particles. Small subparticles 260, 261, and 262 are visible, with an average largest dimension of about 50-200 nm.

[0179] Method for forming a composition containing red lead A composition containing red lead was synthesized as follows: 30 g of lead citrate (Pb3(C6H5O7)2·3H2O) was placed in a 4-liter rotary kiln. The lead citrate was prepared as disclosed in WO 2008 / 056125. Scanning electron microscopy indicates that the lead citrate is elongated, with particle lengths of approximately 10–40 μm and particle widths of approximately 2–4 μm. X-ray diffraction was used to confirm that the lead citrate was indeed lead citrate. A mixture of air (18 L / h) and carbon dioxide (200 L / h) was passed through the lead citrate for 2 hours while it was heated to 350°C and then at 350°C. After this first period, a stream of air (200 L / h) was passed through the contents of the rotary kiln for a known second period of 30 or 60 minutes. The kiln was then cooled to room temperature and air was passed through it (200 liters / hour). The kiln was rotated at a speed of 20 rpm throughout. The resulting composition was then analyzed using X-ray diffraction and acid dissolution techniques to determine the presence and relative amounts of various components within the composition, such as the aforementioned alpha lead oxide, beta lead oxide, minium, and lead metal.

[0180] Table 3 below shows how the composition varies with process conditions. Residence time 2 is the period of heating in the air stream. Residence temperature is the temperature to which the product is heated in the air stream.

[0181] [Table 3]

[0182] Examples 23-27 demonstrate that compositions containing high percentages of minium and red lead can be produced by heating lead citrate in a stream of air and carbon dioxide and then heating the reaction product in a stream of air. Using higher temperatures when heating in air promotes the formation of minium. Referring to Figure 5, without wishing to be bound by theory, a method 300 for forming minium from lead citrate is believed to include converting lead citrate to PbOPbCO3 301 and converting PbOPbCO3 to minium 302.

[0183] Without wishing to be bound by theory, it is believed that the following reaction occurs: Pb3(C6H5O7)23H2O (s) +9O 2(g) →3βPbO (s) +12CO 2(g) +8H2O (g) ---------(1) βPbO (s) +CO 2(g) →PbCO 3(s) ---------(2) PbCO 3(s) ⇔αPbO (s) +CO 2(g) ----------(3) 2αPbO (s) +PbCO 3(s) →2PbOPbCO 3(s) ---------(4) 2PbOPbCO 3(s) → 3αPbO (s) +CO 2(g) ---------(7) 3αPbO (s) +1 / 2O 2(g) →PbO 4(s) ---------(8) 2PbOPbCO 3(s) +O 2(g) →PbO 4(s) +CO 2(g) ---------(11) Converting lead citrate to PbOPbCO3 301 involves heating the lead citrate to form beta lead oxide, which reacts with carbon dioxide to form lead carbonate. The lead carbonate decomposes upon heating to form alpha lead oxide, which reacts with lead carbonate to form PbOPbCO3. Heating the PbOPbCO3 in a stream of air forms alpha lead oxide, which reacts with oxygen to form minium.

[0184] Scanning electron microscope images of the composition of Example 27 are shown in Figures 6A and 6B. The composition contains larger, elongated particles 350, 351, and 352 visible in Figure 6A. These particles have a shape and size similar to the lead citrate particles used to make the alpha lead oxide. The particles have an average length of more than 5 μm and an average width of about 1-2 μm. The surfaces of the particles appear roughened, and smaller subparticles are visible on the surfaces of the particles. Small subparticles 360, 361, and 362 are visible, with an average largest dimension of about 50-100 nm.

[0185] Method for forming a composition comprising Pb2O3 A composition containing Pb2O3 was synthesized as follows: 30 g of lead citrate (Pb3(C6H5O7)2·3H2O) was placed in a 4-liter rotary kiln. The lead citrate was prepared as disclosed in WO2008 / 056125. Scanning electron microscopy indicates that the lead citrate is elongated, with particle lengths of approximately 10–40 μm and particle widths of approximately 2–4 μm. X-ray diffraction was used to confirm that the lead citrate was indeed lead citrate. A mixture of air (18 L / h) and carbon dioxide (200 L / h) was passed through the lead citrate for 2 hours while it was heated to 350°C and then at 350°C. After this first period, a stream of air (30–200 L / h) was passed through the contents of the rotary kiln for a known second period of 30–120 minutes at a temperature of either 300°C or 350°C. The kiln was then cooled to room temperature and air was passed through it (200 liters / hour). The kiln was rotated at a speed of 20 rpm throughout. The resulting composition was then analyzed using X-ray diffraction and acid dissolution techniques to determine the presence and relative amounts of various components within the composition, such as alpha lead oxide, beta lead oxide, red lead, and lead metal, as described above.

[0186] Table 4 shows how the composition changes with processing conditions.

[0187] [Table 4]

[0188] The temperatures referenced in Table 4 are the temperatures at which the contents of the rotary kiln are exposed to air. The periods referenced in Table 4 are the periods at which the contents of the rotary kiln are exposed to air.

[0189] Examples 28-36 show that compositions with a high percentage of Pb2O3 can be made by heating lead citrate in a stream of air and carbon dioxide, and then heating the reaction product in a stream of air, preferably at a relatively low temperature (300°C seems preferable in this case). Using higher temperatures when heating in air promotes the formation of minium, while using lower temperatures when heating in air promotes the formation of Pb2O3.

[0190] 7, without wishing to be bound by theory, it is believed that a method 400 of forming minium from lead citrate includes converting lead citrate to PbOPbCO3 401, and converting PbOPbCO3 to Pb2O3 402. Converting lead citrate to PbOPbCO3 401 includes heating the lead citrate to form beta lead oxide, which reacts with carbon dioxide to form lead carbonate. The lead carbonate decomposes upon heating to form alpha lead oxide, which reacts with lead carbonate to form PbOPbCO3. Heating PbOPbCO3 in a stream of air forms alpha lead oxide, which reacts with oxygen to form Pb2O3.

[0191] Without wishing to be bound by theory, it is believed that the following reaction occurs: Pb3(C6H5O7)23H2O (s) +9O 2(g) →3βPbO (s) +12CO 2(g) +8H2O (g) ---------(1) βPbO (s) +CO 2(g) →PbCO 3(s) ---------(2) PbCO 3(s) ⇔αPbO (s) +CO 2(g) ----------(3) 2αPbO (s) +PbCO 3(s) →2PbOPbCO 3(s) ---------(4) 2PbOPbCO 3(s) → 3αPbO (s) +CO 2(g) ---------(9) 2αPbO (s) +O 2(g) →PbO 3(s) ---------(10) PbOPbCO 3(s) +1 / 2O 2(g) →PbO 3(s) +CO 2(g) ---------(11) Scanning electron microscope images of the composition of Example 36 are shown in Figures 8A and 8B. The composition contains larger, elongated particles 450, 451, and 452 visible in Figure 6A. These particles have a shape and size similar to the lead citrate particles used to make the alpha lead oxide. The particles have an average length of more than 5 μm and an average width of about 1-2 μm. The surfaces of the particles appear roughened, and smaller subparticles are visible on the surfaces of the particles. Small subparticles 460, 461, and 462 are visible, with an average largest dimension of about 50-100 nm.

[0192] Compositions containing alpha lead oxide, beta lead oxide, red lead, and Pb2O3 according to the present invention were investigated to determine their BET surface area, pore volume, and pore diameter using a sample size of approximately 0.55-0.60 g, a bath temperature of 77 K, and N2 as the analytical adsorbent.

[0193] [Table 5]

[0194] The structures of beta-lead oxide according to the fourth, tenth, and eleventh embodiments of the present invention were investigated. A sticky carbon tape was relatively uniformly coated with beta-lead oxide according to the present invention and conventional ball-milled lead oxide. Powdered lead oxide was then pressed to firmly embed the powder into the tape. A drop of 1 wt% acetic acid solution was added to slowly dissolve the PbO. After 30 seconds, excess solution was removed with dry paper. This process of wetting with acetic acid and removing excess solution was repeated four times. The remaining material was then rinsed four times with a drop of distilled water.

[0195] Figures 12A and 12B show the particles remaining after exposing the particles to acetic acid. The remaining particles are essentially spherical or subspherical (essentially resembling a sphere) and approximately 15-30 μm in diameter. Each remaining particle is essentially the core of the original particle. Considering that a 1 wt% acetic acid solution dissolves only PbO but not Pb, the core is essentially made of lead metal. The outer region containing lead oxide has been dissolved by the acetic acid. This evidences a lead oxide structure, comprising a lead metal core covered by an outer region of lead oxide. Such a structure is beneficial because the lead oxide protects the inner lead metal from oxidation when the composition is exposed to a potentially oxidizing environment (e.g., air).

[0196] One of the key properties measured by battery manufacturers to determine lead oxide performance is acid absorption. The acid absorption properties of the material described above in connection with Figures 12A and 12B were investigated and compared with conventional ball mill and Barton pot lead oxides. A 22 g (20 ml) solution of 16 wt% sulfuric acid was prepared and cooled to room temperature. 10 g of lead oxide was then added while stirring at 350 rpm in an insulated container. The suspension was allowed to react for 20 minutes before analysis. H2SO4 absorption was determined by titrating the unreacted H2SO4 with NaOH and correlated with the temperature increase of the suspension during the reaction. The mass percentage of reacted lead oxide was also determined.

[0197] [Table 6]

[0198] The data in Table 6 show that the acid absorption properties of the alpha and beta lead oxides of the present invention are superior to those of conventional Barton pot and ball milled lead oxides. Furthermore, the mass percentage of lead oxide reacted is much greater for the alpha and beta lead oxides of the present invention than for conventional lead oxides.

[0199] The surface area and pore volume were measured for the materials discussed in Table 6 and are shown in Table 7.

[0200] [Table 7]

[0201] The stability of metallic lead in the materials described above in connection with Figures 12A and 12B was investigated. The metallic lead content of the lead oxide (x) according to the present invention was compared with that of the known Barton pot (o) and ball mill (+) lead oxides. The metallic lead content was determined by reaction with acid or alkali. Figure 13 shows how the metallic lead content changes over time. It is clear from Figure 13 that the lead oxide of the present invention has a much lower rate of metallic lead loss than conventional lead oxides.

[0202] Scanning electron microscope images of an example of a composition according to the tenth embodiment of the present invention are shown in Figures 14A and 14B. Figure 14A is a low-magnification image showing aggregated particles AG, which have a network of channels and pores within them. Particles AG have an ill-defined amorphous shape. As shown in Figure 14B, the particles contain multiple subparticles, two of which are labeled SP1 and SP2. The average largest dimension of the subparticles is approximately 50-100 nm.

[0203] An example of a method according to an embodiment of the ninth aspect of the present invention is described with reference to FIG. 9. The method, generally designated by reference numeral 500, is a method for producing a composition containing a desired one or more of alpha lead oxide, beta lead oxide, Pb2O3, minium, and lead metal. Method 500 includes determining 501 whether any one or more of alpha lead oxide, beta lead oxide, Pb2O3, minium, and lead metal are desired in the composition. In this particular example, determining 501 that a composition containing minium is desired. Based on the determination, method 500 includes selecting 502 one or more reaction parameters from a list including one or more heating temperatures, one or more heating durations, and one or more gas compositions. As indicated above, to produce a composition containing minium, lead citrate is heated in a mixture of air and carbon dioxide, and the resulting composition is then heated in a stream of air at a temperature of 400° C. Accordingly, in this context, selecting 502 a first gas composition containing carbon dioxide and air in which the lead citrate will be heated. Further, a second gas composition including air is selected for subsequent heating at 400° C. Next, lead citrate is heated in a mixture of air and carbon dioxide at 350° C. for 2 hours, and the resulting composition is then heated in air at 400° C. for 1 hour to form a composition including minium lead.

[0204] An example of a method for making a battery plate according to yet another embodiment of the present invention will now be described with reference to FIG. 10. The method for forming a lead-acid battery plate is generally designated by reference numeral 600. Method 600 includes forming a paste 601 with a composition according to the second, fourth, sixth, and / or eighth aspects of the present invention together with one or more battery plate additives and an acid. The acid is typically sulfuric acid, which converts the lead oxide in the composition to PbSO4. Suitable battery plate additives include those listed above, including metal compounds, insoluble carbon, barium sulfate, and fibers, such as lignin-based fibers. The paste may then be applied 602 to a grid, typically a lead alloy grid, and cured 603 to form a lead-acid battery plate.

[0205] Figure 11 is a simplified exploded perspective view of a battery according to an embodiment of the present invention. The battery is generally designated by reference numeral 1000 and includes a plurality of battery plates, only one of which, 1001, is labeled. Battery plate 1001 is a battery plate fabricated as described above in connection with the method of Figure 10. Battery plate 1001 is located in a plastic casing 1003. Sulfuric acid is provided within casing 1003 and is in contact with battery plate 1001.

[0206] Many of the methods described above involve an oxidation process, which in some cases is followed by a pyrolysis process. Oxidation processes are generally exothermic, while pyrolysis processes are generally endothermic. The net energy required for the process is the difference between the heat absorbed in the endothermic process and the heat generated in the exothermic process, so the energy required for the process may be relatively low or even neutral, although in some cases net energy is available from the process.

[0207] Although the present invention has been described and illustrated with reference to particular embodiments, those skilled in the art will appreciate that the present invention is susceptible to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0208] In some of the above examples, nitrogen is used as the inert gas. Those skilled in the art will appreciate that other inert gases, such as any of the noble gases, may be used.

[0209] The above example shows how air is used to provide molecular oxygen as an oxidant. Those skilled in the art will appreciate that oxidants other than molecular oxygen may be used. Furthermore, the molecular oxygen need not be provided in air.

[0210] The inventors have demonstrated that compositions according to the present invention have been made using the methods described herein. Those skilled in the art will appreciate that other methods may be used to arrive at compositions according to the present invention.

[0211] The above example demonstrates the use of lead citrate as a starting material. Those skilled in the art will appreciate that other organic lead salts may be used. In particular, those skilled in the art will appreciate that other lead carboxylates may be used.

[0212] The above example uses lead citrate having the size and shape of particulate matter. Those skilled in the art will appreciate that lead citrate having different shapes and sizes may be used.

[0213] The above exemplified method uses a rotary furnace. Those skilled in the art will appreciate that other furnaces or reaction vessels may be used.

[0214] Where the foregoing description refers to integers or elements that have known, obvious, or foreseeable equivalents, such equivalents are incorporated herein as if individually set forth. Reference should be made to the claims to determine the true scope of the invention, and the claims should be construed to encompass such equivalents. The reader will also understand that any integers or features of the invention described as preferred, advantageous, convenient, or the like are optional and do not limit the scope of the independent claims. Furthermore, it should be understood that while such optional integers or features may be beneficial in some embodiments of the invention, they may be undesirable and therefore may not be present in other embodiments.

Claims

1. Alpha lead oxide, beta lead oxide, metallic lead, Pb ２ O ３ and Pb ３ O ４ 1. A composition comprising one or more of: a particle comprising subparticles in the form of protrusions, said subparticles having an average largest dimension of from 10 to 300 nm.

2. 10. The composition of claim 1, comprising one or more of alpha beta oxide and beta lead oxide.

3. 3. The composition of claim 1 or claim 2, comprising metallic lead.

4. 4. The composition of claim 3 comprising at least 5 wt% metallic lead.

5. 5. The composition of claim 3 or claim 4, comprising up to 40 wt% metallic lead.

6. 10. A composition according to any preceding claim, comprising rod-shaped particles.

7. 7. The composition of claim 6, wherein the rod-shaped particles have a maximum dimension of from 0.2 μm to 20 μm.

8. 8. The composition of claim 6 or claim 7, wherein at least 50% by number of the particles of the composition are rod-shaped.

9. 9. A composition according to any one of claims 6 to 8, wherein at least 50% by number of said rod-shaped particles have a maximum dimension of between 0.2 μm and 20 μm.

10. 10. The composition of any of claims 6 to 9, wherein at least 50% by number of said rod-shaped particles have an aspect ratio of at least 1.5:1, and optionally an aspect ratio of 20:1 or less.

11. 10. The composition of any preceding claim, wherein the subparticles have an average largest dimension of at least 20 nm.

12. 10. The composition of any preceding claim, wherein the subparticles have an average largest dimension of 200 nm or less.

13. 10. A composition according to any preceding claim, wherein the subparticles have an average largest dimension of from 50 to 150 nm.

14. At least 95 wt% of said composition is alpha lead oxide, beta lead oxide, metallic lead, Pb ２ O ３ 10. The composition of any preceding claim, comprising one or more of: and red lead.

15. At least 98 wt% of said composition is alpha lead oxide, beta lead oxide, metallic lead, Pb ２ O ３ and red lead.

16. The composition has a BET surface area, as determined using nitrogen, of at least 1.0 m ２ 10. The composition of any preceding claim, wherein:

17. The BET surface area of ​​the composition is at least 2.5 m ２ The composition of claim 16, wherein the hydroxyl group is 0.15 to 0.25g.

18. 10. A composition according to any preceding claim, comprising particles comprising a core portion rich in lead metal and poor in oxide, and an outer portion rich in oxide, said core portion optionally being spherical or sub-spherical.

19. 1. A method of making a composition comprising alpha lead(II) oxide, comprising: Organic lead salts, optionally lead citrate, PbOPbCO ３ and PbOPbCO ３ heating the A method comprising:

20. Organic lead salts, optionally lead citrate, PbOPbCO ３ converting said organic lead salt, optionally lead citrate, to lead(II) oxide, and converting said lead(II) oxide to PbOPbCO ３ 20. The method of claim 19, comprising converting

21. Converting an organic lead salt such as lead citrate to lead(II) oxide comprises heating said organic lead salt, and optionally lead citrate, in the presence of an oxidizing agent to convert said lead(II) oxide to PbOPbCO ３ by heating said lead(II) oxide in the presence of carbon dioxide to form lead carbonate, and converting lead carbonate to PbOPbCO ３ 21. The method of claim 20, comprising converting

22. 22. The method of claim 21, wherein the oxidant comprises molecular oxygen and the molar ratio of carbon dioxide to molecular oxygen is at least 15:

1.

23. A composition comprising alpha lead oxide producible or produced by the method of any of claims 19 to 22.

24. A method of making a composition comprising beta lead oxide, comprising heating an organic lead salt, optionally lead citrate, in a gas stream comprising an oxidizer.

25. 25. The method of claim 24, comprising mixing the oxidizer-containing precursor gas with a diluent gas to provide the oxidizer-containing gas.

26. 26. The method of claim 25, wherein the molar ratio of the diluent gas to the precursor gas is at least 1:10 and not more than 3:

1.

27. 27. The method of any of claims 24 to 26, wherein the oxidant is in the form of a gaseous oxidant, and the gas comprising the oxidant comprises at least 5 wt% oxidant and no more than 14 wt% oxidant.

28. A composition comprising beta lead oxide producible or produced by the method of any of claims 24-27.

29. 1. A method of making a composition comprising red lead, comprising: Organic lead salts, optionally lead citrate, PbOPbCO ３ and PbOPbCO ３ to convert it into red lead A method comprising:

30. Organic lead salts, optionally lead citrate, PbOPbCO ３ converting the organic lead salt, optionally lead citrate, to lead(II) oxide, converting the lead(II) oxide to lead carbonate, and converting the lead carbonate to PbOPbCO ３ 30. The method of claim 29, comprising converting

31. 31. The method of claim 30, wherein converting the organic lead salt, optionally lead citrate, to lead (II) oxide comprises heating the organic lead salt, optionally lead citrate, in the presence of an oxidizing agent, and converting the lead (II) oxide to lead carbonate comprises heating the lead (II) oxide in the presence of carbon dioxide.

32. PbOPbCO ３ The conversion of PbOPbCO ３ to alpha lead oxide, and converting the alpha lead oxide to minium.

33. PbOPbCO ３ is converted to alpha lead oxide by heating PbOPbCO in the presence of a gas stream containing an oxidizing agent at a temperature of at least 350°C, optionally at least 375°C. ３ 33. The method of claim 32, comprising heating

34. A composition comprising red lead producible or produced by the method of any of claims 29 to 33.

35. Pb ２ O ３ 1. A method of making a composition comprising: Organic lead salts, optionally lead citrate, PbOPbCO ３ and PbOPbCO ３ Pb ２ O ３ Converting to A method comprising:

36. Organic lead salts, optionally lead citrate, PbOPbCO ３ by converting said organic lead salt, optionally lead citrate, to lead(II) oxide, optionally converting said lead(II) oxide to lead carbonate, and converting lead carbonate to PbOPbCO ３ 36. The method of claim 35, comprising converting

37. 37. The method of claim 36, wherein converting an organic lead salt, optionally lead citrate, to lead (II) oxide comprises heating the organic lead salt, optionally lead citrate, in the presence of an oxidizing agent, and converting the lead (II) oxide to lead carbonate comprises heating the lead (II) oxide in the presence of carbon dioxide.

38. PbOPbCO ３ Pb ２ O ３ PbOPbCO ３ and converting alpha lead oxide to Pb ２ O ３ 37. The method of claim 35 or claim 36, comprising converting

39. PbOPbCO ３ is converted to alpha lead oxide by heating in the presence of a gas stream containing an oxidizing agent at a temperature of 350° C. or less, optionally 325° C. or less, to PbOPbCO ３ 39. The method of claim 38, comprising heating

40. Pb that can be produced or is produced by the method according to any one of claims 35 to 39. ２ O ３ A composition comprising:

41. Alpha lead oxide, beta lead oxide, Pb ２ O ３ 1. A method for producing a composition containing a desired one or more of: red lead; red lead; and lead metal, comprising: Alpha lead oxide, beta lead oxide, Pb ２ O ３ determining whether any one or more of: red lead, red lead, and lead metal are desired in the composition; selecting one or more reaction parameters from a list consisting of one or more heating temperatures, one or more heating durations, and one or more gas compositions based on said determination; and heating an organic lead salt, optionally lead citrate, according to one or more selected reaction parameters, thereby producing alpha lead oxide, beta lead oxide, Pb ２ O ３ forming said composition containing a desired one or more of: red lead; A method comprising:

42. 42. The method of any one of claims 20 to 22, 24 to 27, 29 to 33, 35 to 39 and 41, wherein the particles of organic lead salt, optionally lead citrate, are rod-shaped and have an average largest dimension of at least 0.5 μm and no more than 20 μm.

43. 41. A method of forming a lead acid battery plate comprising forming a paste of the composition of any of claims 1-18, 23, 28, 34 and 40 with one or more battery plate additives and an acid.

44. 44. A lead acid battery plate producible or produced by the method of claim 43.

45. 45. A lead acid battery comprising one or more battery plates according to claim 44.

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