112 results about "Molecular oxygen" patented technology

Embodiments pertain to a laser arrangement configured for enhancement of an ionizaon process of molecular oxygen by causing a two-photon-based transion followed by a (e.g., disnct) third photon- based transion for ionizing the molecular oxygen. In some examples, the laser arrangement comprises at least one laser source configured to output towards at least one oxygen molecule laser light having mulple wavelengths (WL), as follows: outpu[ng at least one electromagnec (EM) radiaon within a first WL range adapted to cause two-photon-based excitaon of the molecular oxygen into a (e.g., disnct) excited state; and outpu[ng at least one addional EM radiaon that is within a second WL range adapted to cause ionizaon of the molecular oxygen from the (e.g., disnct) excited state.

The present invention provides a method and application for the simultaneous activation of molecular oxygen oxidation and flocculation to remove low-valent phosphorus using an aluminum-carbon-based composite material. The method comprises: placing aluminum powder, a divalent iron salt, and activated carbon pretreated by acid leaching under an inert atmosphere for ball milling to obtain an aluminum-carbon-based composite material; adding the aluminum-carbon-based composite material to wastewater containing low-valent phosphorus and reacting under aerobic conditions. After ball milling, the exposed active zero-valent aluminum can activate molecular oxygen, which synergistically produces strong oxidizing free radicals with the iron salt to oxidize low-valent phosphates into orthophosphates; at the same time, a large number of microscopic primary cells composed of zero-valent aluminum and activated carbon can form local alkalinity on the surface of the activated carbon to promote further dissolution of aluminum, generate flocs and precipitate to remove phosphates, thereby achieving simultaneous oxidation and flocculation removal of low-valent phosphates. The material source of the present invention is wide and low-cost, the material preparation method is simple, the process for removing low-valent phosphorus is efficient and simple, the investment cost is low, and it is easy to apply in engineering.

The application discloses a lanthanum-cobalt composite catalyst and a preparation method and application thereof. The lanthanum-cobalt composite catalyst is composed of La2O2SO4, Co4S3 and Co3O4. Co(NO3)2.6H2O, La(NO3)3.6H2O, urea and sodium dodecyl sulfate are dissolved in an isopropyl alcohol solution to form a reaction solution, a precursor is obtained through a solvothermal method, and the lanthanum-cobalt composite catalyst is prepared through calcination. The prepared catalyst is used for selectively oxidizing ethylbenzene into acetophenone under the condition that molecular oxygen is used as an oxidant and no solvent is used, and excellent catalytic performance is shown. The catalytic system meets the requirements of green chemical industry and sustainable development.

A process and apparatus for the production of maleic anhydride by reacting a mixed gas containing molecular oxygen and a hydrocarbon, usually n-butane, over a suitable catalyst, wherein the maleic anhydride is produced in a tubular catalytic reactor, wherein after recovery of the maleic anhydride product by absorption with an organic solvent and after appropriate treatment steps, the gaseous effluent from the reactor is recycled back to the inlet of the catalytic reactor by compression.

The application relates to the field of thermal catalysis, and discloses a method for preparing 1-cyclohexylbenzene hydrogen peroxide by solvent-free thermal catalytic selective oxidation of cyclohexylbenzene with molecular oxygen. The method uses a metal bromide as a catalyst, azobisisobutyronitrile or t-butyl hydroperoxide as an initiator, and pure oxygen as an oxidant, and can effectively selectively oxidize cyclohexylbenzene (CHB) into 1-cyclohexylbenzene hydrogen peroxide under normal pressure, solvent-free conditions and at a temperature above 90 DEG C. The catalytic system has the advantages of low cost, simple operation process, high catalytic oxidation efficiency and high selectivity of the target oxidation product.

The invention discloses a preparation method and photocatalytic application of a metal viologen derivative framework for catalyzing C-H bond activation oxidative coupling, and belongs to the technical field of photocatalytic materials. In the preparation method, Zn < 2 + > is selected as a metal node, a viologen derivative with an excellent oxygen activation function is selected as a ligand, and a metal viologen derivative framework Zn-bcbpy is obtained through coordination by a solvent evaporation method. The viologen derivative can effectively activate molecular oxygen to generate superoxide free radicals, and then selective activation of C-H bonds is achieved through a hydrogen atom transfer mechanism. Through optimization of reaction conditions, under irradiation of blue light, the reaction yield of the Zn-bcbpy catalytic substrate is 55%, the Zn-bcbpy catalytic substrate can be stably recycled for five times, and good photocatalytic response performance of the catalyst is proved through electrochemical and impedance experiments.

The invention relates to a method for producing acrylic acid, wherein: a product gas mixture containing acrylic acid, water vapor and secondary components is produced by means of a heterogeneously catalyzed gas-phase partial-oxidation of at least one C3 precursor of acrylic acid with molecular oxygen on catalysts in a solid aggregate state at an increased temperature; the product gas mixture is then conducted into a condensation column equipped with fittings which have a separating effect; the product gas mixture is allowed to rise within the condensation column and in the process fractionally condenses, wherein the product gas mixture is separated into: a sump liquid containing secondary products, which are heavier-boiling than acrylic acid, and secondary components, a raw acrylic acid, which contains water and secondary components in an overall depleted state, as the target product, an acidic water also containing acrylic acid and secondary components, and a residual gas mixture containing secondary components which are lower-boiling than water; the target product is conveyed out of the condensation column via a side draw, and the side draw is above the point where the product gas mixture is fed into the condensation column; and the fittings which have a separating effect consist of different stainless steels, and fittings which have a separating effect and consist of a first stainless steel comprising at least 18 wt.% nickel are used in first regions of the condensation column in which the product gas mixture has 5 to 70 wt.% water, 15 to 85 wt.% acrylic acid, at least 8 wt.% acetic acid and at least 2 wt.% formic acid.

The invention belongs to the technical field of organic synthetic chemistry, and discloses a preparation method of an aromatic ketone compound, which comprises the following steps: by taking an unsaturated carbonyl compound obtained by condensing aryl acetaldehyde / acid and aldehyde / ketone molecules as a precursor, carrying out a reaction on the unsaturated carbonyl compound in the presence of a free radical precursor and molecular oxygen under the conditions of illumination and / or heating to obtain the aromatic ketone compound. And carrying out free radical mediated decarbonylation functionalization reaction in an organic solvent to obtain the aromatic ketone compound. The functional group contained in the free radical precursor is introduced to the alpha position of the ketone compound. By improving reaction participants and a reaction mechanism, the aromatic ketone compounds with various structures can be efficiently and highly selectively constructed in one step, the functionalization of the alpha position of the aromatic ketone compounds is synchronously realized, and the preparation method which is simple and convenient to operate, high in atom economy, green and environment-friendly is provided for the aromatic ketone compounds; the obtained compound is especially applicable to the fields of drug synthesis and synthesis of other materials.

The present disclosure provides a process. In an embodiment, the process includes introducing an antifoulant into an ethylene feed of a reactor system. The reactor system includes the ethylene feed, a hyper-compressor, a preheater and a polymerization reactor. The ethylene feed is located upstream of the hyper-compressor. The antifoulant consists of an inhibitor, molecular oxygen, and optionally a solvent. As the ethylene feed is located upstream of the hyper-compressor, the process includes introducing the antifoulant into the ethylene feed upstream of the hyper-compressor. The process further includes adding a free radical initiator to the polymerization reactor. The process further includes polymerizing the ethylene in the polymerization reactor under high pressure free-radical polymerization conditions, and forming an ethylene-based polymer.

The invention belongs to the technical field of environmental functional material preparation, and discloses a method for preparing a Cu-coated Cu2O-coated C net by an ethanol-assisted combustion method and molecular oxygen activation application of the Cu-coated Cu2O-coated C net. The cleaned copper net is soaked in ethyl alcohol and then calcined, and the Cu-coated Cu2O-coated C net is obtained after repeated soaking and calcination. According to the optimized net, the local O2 enrichment concentration of the net in an aqueous solution is 2.3 times of the oxygen content in a normal aqueous solution, and the degradation rate constant of ofloxacin reaches 0.178 min <-1 >, which exceeds that of traditional photocatalysis and Fenton-like systems. In addition, the net exhibits gt; gt; gt; gt; gt; the degradation efficiency is 95%, and the method has the feasibility of pilot scale (the cost is 0.001 dollar per liter when 144 L of wastewater is treated), and provides a sustainable example for on-site water remediation. The preparation method disclosed by the invention is simple and easy to implement, relatively short in process and suitable for industrial production and use.

The invention provides a water electrolysis method with an expanded operating range and a related device. The water electrolysis process comprises: recovering a mixture of electrolyte and molecular oxygen from an anode chamber and separating it in a molecular oxygen separator to obtain a molecular oxygen stream and an electrolyte stream containing molecular oxygen; recovering a mixture of electrolyte and molecular hydrogen from the cathode chamber and separating it in a molecular hydrogen separator to obtain a molecular hydrogen stream and an electrolyte stream containing molecular hydrogen; the molecular oxygen containing electrolyte stream and the molecular hydrogen containing electrolyte stream are recycled. Rinsing the molecular hydrogen in the electrolyte fed to the or each cathode chamber upon detection of conditions susceptible to causing the ratio of molecular oxygen to molecular hydrogen in the cathode chamber to be greater than an OTH safety threshold or / and the ratio of molecular hydrogen to molecular oxygen in the anode chamber to be greater than an HTO safety threshold, and / or flushing molecular oxygen in the electrolyte fed to the or each anode chamber.

The present invention provides a catalyst for preparing perfluoro-2,3-epoxy-2-methylpentane from hexafluoropropylene dimer, belonging to the technical field of perfluoro-2,3-epoxy-2-methylpentane synthesis. A fluorocarbon cyclic ether compound is added as a reaction medium to a polymerization vessel with an agitator, the reaction vessel is started and stirred, and then the hexafluoropropylene dimer and an oxidation catalyst are added. The polymerization vessel is heated to perform a molecular oxygen oxidation reaction to obtain perfluoro-2,3-epoxy-2-methylpentane. This method effectively improves the efficiency of the molecular oxygen oxidation reaction and the molar yield of perfluoro-2,3-epoxy-2-methylpentane. Both the reaction medium and the oxidation catalyst can be recycled, generating less three wastes, and being environmentally friendly.

The present invention provides a g-C3N4-based nanocomposite material for removing tetracycline, and its preparation method and application. The composite material is prepared by the following method: a sulfur source, a copper source and g-C3N4 are reacted in a solvent at 60-70°C for 1-6h, and then a g-C3N4-based precursor is separated; after drying, the precursor is calcined at a constant temperature of 350-500°C under an air atmosphere to obtain the product. The material of the present invention can utilize green molecular oxygen as an oxidant, and has excellent catalytic performance and adsorption efficiency, high selectivity and stability through the combination of advanced oxidation process and adsorption. Using the composite material, wastewater can be directly used to remove tetracycline without dilution treatment. The present invention is simple to prepare, convenient and fast, and is synthesized using relatively cheap and easily available raw materials. The cost is low, the reproducibility of the sample is relatively good, and it is suitable for large-scale production. It has certain development potential and application prospects in the field of water environment treatment.

The present invention belongs to the field of chemical and chemical engineering technology, specifically a method for the continuous cleavage of alcohols into amides using a manganese oxide compound as a catalyst and molecular oxygen or air as an oxidant. The reaction is carried out at 130-150°C for 12 hours in the presence or absence of a solvent to oxidize the alcohols into amides. The catalyst can be recycled and reused at least nine times while maintaining excellent activity and selectivity. The catalyst is simple to prepare, inexpensive, highly selective, and environmentally friendly.

This invention discloses a flow-through photoelectric synergistic catalytic filtration system for efficiently activating molecular oxygen to remove novel pollutants from wastewater. It possesses multiple advantages, including efficient activation of molecular oxygen, photo-electric synergistic enhancement, and enhanced mass transfer through a flow system, thus facilitating the efficient removal of novel pollutants. The flow-through photoelectric synergistic catalytic filtration system comprises a shell, anode and cathode electrodes, and a separator. The shell contains, in sequence, an anode, a non-woven fabric separator, a cathode, and a sealing ring. The anode is a bismuth oxybromine / carbon nitride / smarium-vanadate photoelectrode, and the cathode is a cobalt-iron two-atom confined carbon nanotube electrode. Its broad-spectrum responsive materials and novel catalyst design significantly improve anti-interference capabilities, adapting to complex water quality and low-concentration pollution scenarios. Novel pollutant wastewater can be efficiently removed in this flow-through photoelectric synergistic catalytic filtration system after being irradiated and electrolyzed in a circulating flow mode. The removal rate of ibuprofen can reach 96% within 2 hours. This invention features a simple design, is easy to operate, has low cost and low energy consumption, and solves the problems of low removal efficiency and high energy consumption in ordinary treatment systems. At the same time, it combines the full spectrum utilization of solar energy and a low catalyst dosage design to further reduce operating costs, demonstrating comprehensive advantages of high efficiency, stability, economy and environmental protection.

The application discloses a kind of ferrocarbonate / biochar composite electrofenton cathode material and its preparation method and application, the composite electrofenton cathode material (Fe3C / BC) is formed by iron-based metal organic framework material and straw mixed calcination, iron-based metal organic framework material accounts for 5% to 20% of straw mass, wherein metal iron mainly exists in the form of Fe3C.The Fe3C / BC electrofenton cathode material of the application only needs one-step hydrothermal and simple mixing grinding calcination to be prepared, the cathode material prepared can not only improve the dispersity and stability of electrofenton active site, while BC good conductivity and molecular oxygen activation capacity, can accelerate the electron transfer in system, promote the generation of active substance, thereby significantly improve the degradation effect of neonicotinoid pesticide pollutants.The electrofenton cathode material prepared by the application has excellent water matrix interference resistance and relatively wide pH and pollutant concentration application range, thus has great application value.

This invention provides a method for synthesizing dimethyl 2,5-furandicarboxylate by oxidative esterification of 2,5-furandiethanol using a cobalt-zinc-based carbon material, belonging to the field of catalytic synthesis technology. This method uses 2,5-furandiethanol as a raw material, molecular oxygen as an oxidant, and a cobalt-zinc-based carbon material as a heterogeneous catalyst to prepare dimethyl 2,5-furandicarboxylate via a one-step oxidative esterification reaction in methanol solvent using high-performance liquid phase. The cobalt-zinc-based material is prepared by mixing a certain amount of cobalt salt, zinc salt, and organic nitrogen-containing compound ligand to obtain a precursor, which is then calcined at 500-1100℃ under an inert atmosphere for 0.5-24 h. The oxidative esterification method provided by this invention is mild and efficient, and the catalyst is inexpensive and readily available, making this method highly practical and applicable.

This invention is directed to a method of oxygenating hydrocarbons with molecular oxygen, O2, as oxidant under electrochemical reducing conditions, using polyoxometalate compounds containing copper such as Q10[Cu4(H2O)2(B-α-PW9O34)2] or Q13{[Cu(H2O)]3[(A-α-PW9O34)2(NO3)−]} or solvates thereof as catalysts, wherein Q are each independently selected from alkali metal cations, alkaline earth metal cations, transition metal cations, NH4+, H+ or any combination thereof.

The invention relates to a method for activating molecular oxygen via the prior aggregation of alkene bonds in the liquid phase without any additives or solvents, which allows for the transformation of alkenes into oxiranes with high yield, using air as the only reagent, and occasionally ozone and free radical scavengers to prevent possible degradation.

The invention relates to the technical field of chemical industry, in particular to a method for preparing styrene by oxidative dehydrogenation of ethylbenzene, which comprises the following steps: under the condition of low temperature of 150-300 DEG C, ethylbenzene is contacted with an oxygen storage catalyst in an oxidation state, the catalyst catalyzes ethylbenzene dehydrogenation to generate styrene and hydrogen, and then the hydrogen is selectively oxidized into water by self lattice oxygen, directional movement of reaction balance is realized; the catalyst consuming lattice oxygen is regenerated through oxygen-containing gas flow to recover the oxidation state and is recycled. The oxygen storage catalyst is a composite metal oxide or carbide-oxide composite material with a specific structure, and has the functions of ethylbenzene activation, lattice oxygen storage and release and molecular oxygen activation. The invention also provides two reactor implementation schemes of fixed bed switching and fluidized bed circulation. The problems that traditional high-temperature dehydrogenation is high in energy consumption and limited in selectivity and existing oxidative dehydrogenation uses pure oxygen to cause safety and excessive oxidation are solved, and low-temperature, efficient and safe styrene production is achieved.

Aerobic microbial processes comprise culturing microbes comprising a (per)chlorate respiration pathway in a bioreactor in a bioprocess employing microbial respiration of chloroxyanions as a source of oxygen for the bioprocess, in the absence of external addition of molecular oxygen.

The invention belongs to the field of hydrogen production from waste water of oil and gas fields, and relates to a water quality treatment method and system before purification-free electrolytic hydrogen production from gas field produced water, the gas field produced water firstly enters a coalescence degreaser to carry out double coalescence of wetting and collision on oil components in the gas field produced water, so that oil drops of the oil components are coarsely granulated and adsorbed, and the oil content in water is reduced; then, the gas field produced water enters an ozone catalysis device, and an ozone catalyst in the ozone catalysis device promotes ozone to adsorb organic macromolecules and oxidizes and modifies the organic macromolecules at the same time, so that the organic macromolecules are oxidized and decomposed into small molecules, and the COD content in the water is reduced; and finally, the gas field produced water flows into a two-stage filtering device to remove suspended solids and dissolved solids in the water. Finally, the obtained water quality can meet the application requirements of the purification-free hydrogen production technology, and the purpose of purification-free electrolytic hydrogen production of the produced water is achieved.

The invention discloses a calculation method and system for a multiphase ceramic oxygen diffusion coefficient. The method comprises the following steps: respectively establishing a basic crystal structure and an oxygen particle model of ceramic; constructing a multiphase ceramic oxygen diffusion model by adopting an amorphization-recrystallization strategy; the mean square displacement parameters of oxygen particles (including oxygen atoms, oxygen molecules and oxygen ions) in the multiphase ceramic at each temperature and at each moment are calculated through LAMMPS software. According to molecular dynamics, an Einstein relation and an Arrhenius diffusion equation, the change rule of the oxygen diffusion coefficient in the multiphase ceramic along with the temperature is systematically obtained, so that the accurate evaluation of the oxygen diffusion behavior of the multiphase ceramic is realized. The final prediction result is accurate and reliable, and scientific basis and theoretical guidance are provided for multiphase ceramic oxygen diffusion behavior research.

The application discloses an atomic transition metal modified nitrogen-carbon catalyst and a preparation method and application thereof, and relates to the technical field of environmental functional materials.The atomic transition metal modified nitrogen-carbon catalyst is composed of edge-sharp wrinkle nanosheets, and the wrinkle nanosheets comprise an N3C carrier and transition metals uniformly distributed on the N3C carrier in the form of single atoms and atomic clusters.The atomic transition metal modified nitrogen-carbon catalyst is obtained by modifying transition metal atoms on the basis of nitrogen-carbon, constructing a metal active center, increasing the light-heat absorption capacity of the material, and not damaging the inherent morphology of the catalyst, so that the atomic transition metal modified nitrogen-carbon catalyst has high light-heat conversion capacity, can activate active oxygen species by activating molecular oxygen, and can realize efficient light-heat catalytic inactivation of pathogenic microorganisms by combining the physical and chemical synergistic effects of the sharp edges of the material.

The application discloses a high-performance epoxy resin adhesive based on boron trifluoride monoethylamine and a preparation and use method thereof. By adding specific triarylsulfonium hexafluorophosphate in the boron trifluoride monoethylamine epoxy resin system, a protonic acid is generated to act on the epoxy group to generate an activated monomer. The activated monomer and the boron trifluoride monoethylamine synergistically act to effectively avoid the generation of low-molecular oxygen-containing cyclic by-products in the boron trifluoride monoethylamine epoxy resin system, solve the problem of poor mechanical properties of the existing epoxy resin adhesive based on boron trifluoride monoethylamine, and significantly shorten the preliminary curing time of the adhesive due to the action of light, effectively avoid the slippage of the adhesive, and realize the pre-bonding. By adding nano metal, the cohesive energy in the system is reduced, and the adhesion of the epoxy resin adhesive to the metal surface is enhanced. In addition, by optimizing and screening the formula, the proportion of triarylsulfonium hexafluorophosphate and boron trifluoride monoethylamine in a specific range is regulated, the generation of low-molecular cyclic epoxy by-products in the system is maximally inhibited, the complete curing of the epoxy resin adhesive is realized, the epoxy resin adhesive reaches the best mechanical properties, and the problems of poor mechanical properties of the existing epoxy resin adhesive based on boron trifluoride monoethylamine and the like are solved.

The application provides a method for improving the stability of water-soluble active substances. The method comprises mixing a solution containing water-soluble active substances, ethanol, ammonia, cetyltrimethylammonium bromide, tetraethyl orthosilicate and a reducing agent, performing hydrophobic treatment after reaction, and then dispersing in an oil phase for storage. The water-soluble active substances are wrapped in mesoporous silica by a specific process, the surface and mesoporous channels of the silica are modified by hydrophobic treatment, and then the silica is dispersed in an oil phase, so that the water-soluble active substances can avoid contact with external stimulating factors such as water molecules, oxygen and metal ions, thereby effectively improving the stability of the water-soluble active substances in long-term storage and further widening the application range of the water-soluble active substances.

The application discloses a PHI / zinc oxide heterojunction photocatalyst and a low-temperature synthesis method and application thereof. The structure of the photocatalyst is that PHI nanosheets grow well on the surface of ZnO and are tightly wrapped with ZnO, forming a sheet-shaped core layer structure, the thickness of the PHI nanosheet is 3-5 nm, and the ZnO is a wurtzite crystal structure. The low-temperature synthesis method comprises the following steps: mixing and heating a PHI precursor and a molten salt to obtain PHI, placing the PHI and a zinc oxide precursor in an aqueous solution, adding an alkali to adjust the pH, and then reacting to obtain the photocatalyst PHI / ZnO. The photocatalyst can be used for activating molecular oxygen to oxidize the C-H bond at the benzyl position of CM to prepare cumene hydroperoxide, and can also be used for a cascade oxidation reaction to form imine and sulfoxide series compounds. The application shows the advantages of the high-activity carbon nitride-based photocatalyst in the field of organic conversion, and provides an important platform for realizing the essence safety, green and efficient oxidation reaction by the peroxide strategy.

The invention discloses a method for characterizing water distribution uniformity of a porous material in water and application, and belongs to the technical field of porous material performance characterization. The method comprises the following steps: 1) constructing a porous material simulation system, inserting water molecules, and starting an NVT ensemble to carry out pre-balancing and finished product simulation; 2) calculating a coordination number function N1 (r) of oxygen atoms of water molecules based on the finished product simulation trajectory, and obtaining a first water molecule density rho1 (r) within a radius r range by combining the sphere volume; (3) subtracting N1 (r) and the sphere volume from the total water molecule number and the total volume of the system respectively, and calculating the second water molecule density rho2 (r) outside the range of r; and 4) calculating the density ratio R (r) = rho1 (r) / rho2 (r), and judging the uniformity according to the mean value of the R (r) within the range from 0.3 nm to half of the minimum side length of the box. The method realizes quantitative evaluation of water distribution uniformity, has the advantages of convenient operation, high quantification precision, wide applicability and reliable data, can be applied to performance evaluation of porous materials such as UiO-67 and graphene, and provides theoretical support for material design optimization in the fields of drying, atmospheric water collection and the like.

This invention relates to the field of bioremediation technology for environmental pollutants, specifically to a method for degrading side-chain-less polycyclic aromatic hydrocarbons (PAHs) using the dual-oxygenation function of polycopper oxidases. This invention is the first to discover and demonstrate that polycopper oxidases, without the need for exogenous mediators, possess the ability to catalyze the dual-oxygenation reaction of side-chain-less PAHs, directly adding two oxygen atoms from molecular oxygen to the aromatic ring of PAHs to generate the corresponding dihydroxylated intermediate. Under further catalysis by polycopper oxidase, this intermediate selectively undergoes ring-opening cleavage at specific carbon-carbon bonds in the aromatic ring via a free radical mechanism, ultimately generating low-toxicity, readily bioavailable monobenzene ring or straight-chain ester compounds. The method provided by this invention is mild, environmentally friendly, and achieves thorough degradation, offering a highly efficient and green new technology for the bioremediation of PAH-contaminated soil, water bodies, and industrial waste.

A process for manufacturing a coated glass article, said process comprising the following steps in order: (a) providing a glass substrate having a surface, (b) forming a gaseous mixture comprising a source of tin, a source of fluorine, molecular oxygen and water, (c) delivering the gaseous mixture to the surface of the glass substrate, and (d) depositing a coating based on fluorine-doped tin oxide on the surface of the substrate using chemical vapour deposition (CVD), and (e) exposing the substrate to an environment that is under a vacuum and is at a temperature of from 450°C to 750°C for at least 5 minutes.