Method for producing hydrogen fluoride from its aqueous solutions

Abstract

Extraction of anhydrous hydrogen fluoride from its aqueous solution is provided. A method provides hydrogen fluoride from aqueous solutions, including the reduction of water component of the aqueous solution at an elevated temperature into carbon oxide, carbon dioxide and hydrogen. The condensation and distillation of the obtained hydrogen fluoride and water vapor are characterized by the fact that the mixture of hydrogen fluoride and water is reduced at a temperature of 800 K and above, the molar ratio of carbon to water in the reducing agent is from 0.5 to 4, and using a reducing agent of the general formula C.sub.nH.sub.mO.sub.k, where k≥0, m>0, and n>0, and the reducing agent may be saturated, unsaturated, aromatic hydrocarbons, oxygen-containing organic compounds, their isomers and their mixtures. The method makes it possible to extract hydrogen fluoride from its mixtures with water in any ratio and from azeotropic mixtures.

Claims

1. A method to produce hydrogen fluoride from an aqueous solution, the method comprising: reducing the aqueous solution having hydrogen fluoride and water with a reducing agent for reduction of the water to produce gaseous carbon monoxide, carbon dioxide and hydrogen elevated temperature of 800 K and above; producing hydrogen fluoride from the aqueous solution with the elevated temperature by distillation with unreacted water; condensing the obtained hydrogen fluoride; and collecting the condensed hydrogen fluoride and unreacted water vapor; wherein the molar ratio of carbon in the reducing agent to water is from 0.5 to 4, with the reducing agent having a general formula of C.sub.nH.sub.mO.sub.k, where k≥0, m>0 and n>0.

2. The method in claim 1, wherein the reducing agent is selected from the group consisting of a saturated or unsaturated hydrocarbon reducing agent, aromatic hydrocarbon reducing agent, oxygen-containing organic compound reducing agent, and mixtures thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention of some of the embodiments will be explained in greater detail below with reference to examples of possible embodiments. Same elements in the figures are indicated by the same index numbers. It should be understood that the drawings are diagrammatic and schematic representations of such example embodiments and, accordingly, are not limiting the scope of the present invention, nor are the drawings necessarily drawn to scale. The drawings show schematically:

(2) FIG. 1 includes a schematic diagram for a system capable of performing separation of hydrogen fluoride from its aqueous solutions.

DETAILED DESCRIPTION

(3) The patent relates to the technology of inorganic substances, namely the extraction of anhydrous hydrogen fluoride from its aqueous solution. Anhydrous hydrogen fluoride is widely used in industry. It is used to conduct various chemical processes, for example, in the synthesis of fluorinated coolants, in the production of uranium hexafluoride and more. The nature of the patent is that a method was developed to obtain hydrogen fluoride from aqueous solutions, including the reduction of water component of the aqueous solution at an elevated temperature into carbon oxide, carbon dioxide and hydrogen. The condensation and distillation of the obtained hydrogen fluoride and water vapor are characterized by the fact that the mixture of hydrogen fluoride and water is reduced at a temperature of 800 K and above, the molar ratio of carbon to water in the reducing agent is from 0.5 to 4, and using a reducing agent of the general formula C.sub.nH.sub.mO.sub.k, where k≥0, m>0, and n>0, and the reducing agent may be saturated, unsaturated, aromatic hydrocarbons, oxygen-containing organic compounds, their isomers and their mixtures. The method makes it possible to extract hydrogen fluoride from its mixtures with water in any ratio and from azeotropic mixtures.

(4) The nature of the patent is that a method was developed to obtain hydrogen fluoride from aqueous solutions, including the reduction of water component of the aqueous solution at an elevated temperature to carbon oxide, carbon dioxide and hydrogen, condensation of the obtained hydrogen fluoride and water vapor and their distillation, which is characterized by the fact that the mixture of hydrogen fluoride and water is reduced at a temperature of 800 K and above and with the molar ratio of carbon to water in the reducing agent from 0.5 to 4, and using a reducing agent of the general formula C.sub.nH.sub.mO.sub.k, where k≥0, m>0, and n>0, and the reducing agent can be saturated, unsaturated, aromatic hydrocarbons, oxygen-containing organic compounds, their isomers and their mixtures.

(5) The term “reducing agents” means saturated, unsaturated, aromatic hydrocarbons, oxygen-containing organic compounds, such as but not limited to methane, ethane, propane, butane, ethene, propene, ethyne, ethanol, acetone, etc., their isomers and mixtures in various ratios. The specified substances and their mixtures can be defined by the general empirical formula C.sub.nH.sub.mO.sub.k, where κ≥0, m>0, and n>0. Using reducing agents with the general empirical formula C.sub.nH.sub.mO.sub.k makes it possible to the use of liquid and/or gaseous compounds in the process, eliminate the introduction of additional purification stages for the raw materials or final product, and reduce the amount of waste generated.

(6) The method for extracting hydrogen fluoride from its aqueous solution, including azeotropic solutions, involves the interaction of water of the specified solution with a reducing agent, followed by condensation and recycling of unreacted aqueous solution, while water oxidizes the carbon-containing material:
yH.sub.2O.sub.gas+HF.sub.gas+xC.sub.nH.sub.mO.sub.k.fwdarw.zCO.sub.gas+wCO.sub.2gas+vH.sub.2gas+HF.sub.gas

(7) The water is almost fully reduced to hydrogen, while the hydrogen fluoride remains unaffected.

(8) To achieve this result, a mixture of hydrogen fluoride and water is brought into contact with a reducing agent at a temperature above 800 K. Heating is carried out by any known method, including but not limited to heating the walls of the reactor from the outside, feeding an additional reducing agent and oxidant to the reactor and their subsequent combustion, or using a plasma generator. In these conditions, water converts to hydrogen, carbon monoxide and carbon dioxide, and the degree of water conversion is 45-100%. The resulting hydrogen fluoride and unreacted water condense in condensers, and residual gases (carbon monoxide, carbon dioxide, and hydrogen) are fed to neutralization and then disposed. The condensed mixture of hydrogen fluoride and water with a hydrogen fluoride content greater than in the initial mixture is rectified [Corrosion and Protection of Chemical Equipment. Reference. Vol. 1, sub. edited by A. M. Sukhotin. L.: Chemistry, 1969, p. 206], producing primarily AHF as a distillate.

(9) This method extracts hydrogen fluoride from its mixtures with water in any ratio, including azeotropic mixtures, which are typically difficult to accomplish.

(10) The separation of hydrogen fluoride from its aqueous solutions was carried out using an installation, the diagram of which is shown in the FIG. 1, where

(11) A—reactor where water is reduced,

(12) B—condenser,

(13) C—distillation column.

(14) Stream 1—reacting agent into reactor A.

(15) Stream 2—mixture of hydrogen fluoride and water into reactor A.

(16) Stream 3—distillate from distillation column B.

(17) Stream 4—distillation residue from distillation column B.

(18) Stream 5—reaction products from reactor A.

(19) Stream 6—non-condensable reaction products, separated in condenser B.

(20) Stream 7—condensed mixture of hydrogen fluoride and water.

Method Embodiment

(21) A reducing agent was fed (Stream 1) into reactor A, in which the target temperature was maintained. The reducing agent composition and reactor temperature are reflected in the Table. A pre-evaporated mixture of hydrogen fluoride and water was also fed to reactor A (Stream 2). In the reactor, the reducing agent reduced the water to form carbon monoxide, carbon dioxide, and hydrogen. The hydrogen fluoride did not react. Reaction products (Stream 5) were sent to condenser B, where they were cooled. The condenser was maintained at a temperature of 190-195 K. Residual water vapor and hydrogen fluoride condensed inside the condenser. Hydrogen, carbon monoxide, and carbon dioxide exited the condenser and were sent for sanitization and dispersion (Stream 6). Condensed hydrogen fluoride and water (Stream 7) were sent to the distillation column B, which was filled with an irregular fluoroplastic packing. In the column, the hydrogen fluoride was separated as a distillate (Stream 3) and hydrofluoric acid at a concentration of 40 wt % as distillation residue.

(22) Experiment Conditions and Results are Listed in the Table A.

(23) The data shows that the problem addressed by the authors of the method was solved, namely the creation of a method to extract hydrogen fluoride from aqueous mixtures, including difficult-to-separate azeotropic solutions, to produce anhydrous hydrogen fluoride and/or concentrated hydrofluoric acid using a greater assortment of substances as reducing agents, while also solving the aforementioned problems, namely: achieving a reduction in the temperature at the reduction stage, preventing the use of bulk compounds, reducing the amount of waste generated, and reducing the number of process steps.

(24) TABLE-US-00001 TABLE A Concen- Consumption Reactor Consumption Concen- Reducing Consumption Conver- Unreacted tration of Hydrofluoric A of Mixture tration Agent of Mixture sion Reducing Distillate of H.sub.2O in Acid of 40 Re- Temper- HF and H.sub.2O, of HF Consumption, HF and H.sub.2O, of H.sub.2O in Agent in Consumption, Distillate wt % Concen- ducing ature, kg/h in Stream kg/h kg/h Reactor Stream 5, kg/h in Stream tration, kg/h Agent K (Stream 2) 2, wt % (Stream 1) (Stream 7) A, % kg/h (Stream 3) 3, wt % (Stream 4) C.sub.4H4 800 0.225 45.1 0.110 0.168 46.4 0.059 0.057 99.8 0.1102 C.sub.4H4 900 0.160 46.7 0.076 0.102 67.5 0.025 0.057 99.5 0.0457 C.sub.4H4 1000 0.165 41.2 0.086 0.085 82.5 0.015 0.057 99.6 0.0280 C.sub.3H.sub.3 900 0.155 32.1 0.257 0.057 93.5 0.177 0.046 99.4 0.0110 C.sub.3H.sub.3 1000 0.170 36.0 0.266 0.067 94.9 0.182 0.058 99.9 0.0091 C.sub.2H.sub.5OH 900 0.160 46.7 0.218 0.111 57.6 0.092 0.051 99.4 0.0598 C.sub.2H.sub.5OH 1000 0.165 41.2 0.248 0.087 80.5 0.048 0.057 98.2 0.0299 C.sub.2H.sub.2 1600 0.150 32.1 0.158 0.054 94.1 0.009 0.044 99.7 0.0097 C.sub.2H.sub.2 1600 0.236 41.2 0.200 0.106 93.4 0.013 0.092 99.4 0.0144