Solar hydrogen sulfide and carbon dioxide reforming to produce synthesis gas and carbon disulfide

Abstract

Process for the simultaneous production of synthesis gas and carbon disulfide (CS2), in which a gas mixture comprising hydrogen sulfide, carbon dioxide and methane is used as starting material and the gases are reacted under the influence of concentrated solar radiation in the absence of oxygen at a temperature of 1200 °C or more, whereby the following reaction takes place: 2 H2S + CO2 + 2 CH4 → 2 CO + 6 H2 + CS2.

Description

[0001] The present invention relates to solar hydrogen sulfide and carbon dioxide reforming for the production of synthesis gas and carbon disulfide.

[0002] Diminishing oil and gas resources are intensifying competition for the remaining fossil fuels. Therefore, in the future, deposits located at ever greater depths will have to be exploited using lower-quality fuels. However, some of these energy sources contain high levels of hydrogen sulfide (H2S) and carbon dioxide (CO2). This makes it increasingly difficult to comply with the Kyoto Protocol's climate protection agreements to reduce CO2 emissions. Furthermore, hydrogen sulfide is a highly toxic substance that should not be released into the environment but ideally processed into usable products. Hydrogen sulfide and carbon dioxide (CO2) also place extreme demands on the corrosion resistance of the materials used in the construction of transmission pipelines. At the same time, pipeline operators are placing ever higher demands on the strength of the steels used.When transporting oil or gas containing hydrogen sulfide, the hydrogen sulfide reacts with the water or steam contained in the oil or gas to form sulfurous acid, which has a corrosive effect on the pipeline wall. This corrosion process produces hydrogen, which can diffuse into the steel and cause cracks. This creates a need to find alternative processes that can further process H2S and CO2 in an environmentally friendly manner and simultaneously convert them into other high-quality products.

[0003] To make raw gas usable for a wide variety of technical applications, its contaminants must be removed. Carbon dioxide (CO2) and hydrogen sulfide (H2S) are typically separated first. Physical and chemical separation processes are used for this. Among the chemical processes, gas scrubbing with amines is one of the most well-known. In this process, the CO2 and H2S contaminants in the raw gas are absorbed by an aqueous amine solution. Commonly used amines are monoethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA). In addition to chemical gas scrubbing processes, there are also purely physical processes. The best-known processes include pressurized water scrubbing, the Rectisol process, and the Selexol process.

[0004] In conventional physical and chemical processes, hydrogen sulfide (H2S) and carbon dioxide (CO2) are not further utilized. CO2 is released into the environment after separation. Hydrogen sulfide is typically burned during the processing of natural gas from natural gas fields, particularly in North Africa and the Middle East, and released into the environment as sulfur dioxide—with corresponding environmental implications. In this case, no further use occurs.

[0005] US 2003 / 0182861 A1 discloses a process for conducting high-temperature thermal dissociation reactions requiring rapid heating and short residence times using solar energy. In particular, the disclosure describes a process for conducting high-temperature thermal reactions such as the dissociation of hydrocarbon-containing gases and hydrogen sulfide to produce hydrogen, as well as the dry reforming of hydrocarbon-containing gases with carbon dioxide.

[0006] US 4,552,741 A describes a process and apparatus for producing synthesis gas, for example, hydrogen, by catalytic conversion of hydrocarbons under the influence of heat. To reduce the fuel energy losses associated with such chemical processes, the reactors filled with a catalyst are heated at least partially by direct or indirect solar energy.

[0007] GB 1530314 A discloses fluid-wall reactors. Chemical reactions at elevated temperatures are carried out by exposing one or more reactants to radiation in a reaction zone defined by a radiation-permeable fluid wall. The fluid wall is located within a heat shield made of refractory material that reflects the radiation.

[0008] The object of the present invention is therefore to provide a process for reusing gases that arise, in particular, as waste products (waste gases) during the purification of crude oil and / or natural gas. These waste gases are hydrogen sulfide and carbon dioxide. In addition to natural gas and crude oil as sources, exhaust gases generated by power plants, such as coal-fired power plants, can also be used as starting materials for the present invention. This object is achieved by a process in which solar energy is used as an energy source, now from waste materials to obtain products such as synthesis gas and carbon disulfide.

[0009] In a first embodiment, the present invention relates to a process for the simultaneous production of synthesis gas and carbon sulfide (CS2), in which a gas mixture comprising hydrogen sulfide, carbon dioxide and methane is used as starting material and the gases are reacted with each other under the influence of concentrated solar radiation with exclusion of oxygen at a temperature of 1200 °C or more, whereby the following reaction takes place: 2 H2S + CO2 + 2 CH4 → 2 CO + 6 H2 + CS2.

[0010] Synthesis gas, or syngas, is a gas mixture used in a synthesis. The gas mixture consists primarily of the main components carbon monoxide (CO) and hydrogen (H2). The synthesis gas can be converted into a wide range of gaseous and liquid hydrocarbons through further processing, such as Fischer-Tropsch synthesis. The most important products produced by Fischer-Tropsch synthesis include raw materials for the chemical industry, as well as diesel, gasoline, and heating oil. Synthesis gas also represents the starting material for the production of ammonia, making syngas a high-value product in the chemical industry. Carbon disulfide is used as a starting material for the production of cellulose fibers and as a solvent for fats.

[0011] The reforming process underlying this invention is a new process that enables the conversion of hydrogen sulfide (H2S) and carbon dioxide (CO2) into synthesis gas and carbon disulfide. Hydrogen sulfide is harmful to the environment, and carbon dioxide is harmful to the climate. At the same time, both substances represent a valuable raw material base. Therefore, it makes sense to convert these substances into valuable materials, provided there is demand and production is economical. This is made possible by the process according to the invention, so that it can contribute to a sustainable solution for further processing the environmentally harmful substances hydrogen sulfide and carbon dioxide. The major advantage of the process according to the invention is that it leads to the production of high-quality products during the processing.This produces both synthesis gas, which can be converted into other intermediates and products, and carbon disulfide (CS2). High-temperature process heat is required for this production process because the reaction is highly endothermic. According to the invention, the process heat is provided by concentrated solar radiation. This provides a process that prevents the emission of pollutants while simultaneously enabling added value through the production of high-quality chemical products.

[0012] The starting material used is preferably a gas mixture consisting essentially of hydrogen sulfide, carbon dioxide, and methane. Within the context of the present invention, "essentially" means that the gas mixture consists of at least 90 vol.% of the gases mentioned, in particular at least 95 vol.%, particularly preferably at least 98 vol.%, in particular at least 99 vol.% or 99.5 vol.%. Minor impurities do not interfere with the process, so the desired products are still obtained.

[0013] Hydrogen sulfide and carbon dioxide, in particular, can be obtained from natural gas. Crude oil is also freed of these gases in a first step, so that natural gas, crude oil, and / or exhaust gases from power plants are preferably available as the basis for the gas mixture.

[0014] The process takes place at a reaction temperature of at least 1,200 °C. At this temperature, the following reaction takes place 2 H2S + CO2 + 2 CH4 → 2 CO + 6 H2 + CS2 At this temperature, the synthesis gas, i.e., the mixture of hydrogen (H2) and carbon monoxide (CO), escapes from the reaction mixture in gaseous form. Carbon disulfide (CS2) is then present as a liquid. Cooling may be necessary after the actual reaction to separate the liquid carbon disulfide from the hydrogen and carbon monoxide.

[0015] The reaction preferably takes place in a temperature range of 1,200 °C to 1,700 °C, preferably at a temperature in the range of 1,300 °C to 1,600 °C, in particular of 1,400 °C to 1,500 °C.

[0016] Lower temperatures result in very low yields, making the process uneconomical. Preferably, the temperature does not exceed 1,700°C. Higher temperatures place extremely high loads on the equipment in which the reaction takes place, necessitating the use of special reactors. This increases the costs of the process according to the invention, which is not economically desirable. Temperatures in the range of 1,400°C to 1,500°C are particularly preferred. These temperatures enable a good yield of synthesis gas and carbon disulfide without excessive loads on the reactors or other equipment in which the process according to the invention takes place.

[0017] According to the invention, the reaction takes place in the absence of oxygen. This also enables an improved reaction yield, so that in particular the desired products are obtained. This can be achieved, for example, by carrying out the reaction under vacuum. It is also possible according to the invention to carry out the reaction under an inert gas atmosphere. Suitable inert gases are, for example, helium, argon or other noble gases. With regard to the economic efficiency of the process, working under vacuum and the use of noble gas as the inert gas are particularly preferred. Nitrogen is less preferred since at the prevailing temperatures it leads to the formation of NO x which could be harmful to the further course of the reaction.

[0018] Preferably, the gases used in the gas mixture are dried before the reaction. If hydrogen sulfide comes into contact with water, sulfurous acid is formed. This is corrosive. Reactors in which the process can take place typically contain metal, which can be attacked by the sulfurous acid that may be formed. To prevent this, the gases used in the gas mixture are first dried. This can be done using conventional methods.

[0019] To increase the yield, the reaction of the gas mixture is preferably carried out in the presence of a catalyst.

[0020] The starting materials for the proposed reforming process are hydrogen sulfide (H2S), carbon dioxide (CO2), and methane (CH4). The high-temperature heat required for the endothermic process is provided by concentrated solar radiation. Reforming leads to the production of synthesis gas, particularly at temperatures above 1200°C. The major advantage of the process is that the formation of carbon disulfide (CS2) and synthesis gas occurs in parallel.

[0021] The solar process of hydrogen sulfide (H2S) and carbon dioxide (CO2) reforming is particularly suitable for natural gas purification. Natural gas from natural gas fields typically contains these substances in significant concentrations. These can be processed in a climate-friendly manner using solar reforming with methane (CH4). Furthermore, synthesis gas (H2 / CO) and carbon disulfide (CS2) are produced. The resulting synthesis gas can be converted into other products (e.g., gasoline, diesel, etc.) in Fischer-Tropsch plants. The byproduct carbon disulfide is used in the production of cellulose fibers or can be used as a solvent for fats.

[0022] The process is relevant for the chemical industry, especially the petrochemical industry, and for companies active in natural gas and oil production.

Claims

[1] Process for the simultaneous production of synthesis gas and carbon disulfide (CS2), in which a gas mixture containing hydrogen sulfide, carbon dioxide and methane is used as starting material and the gases are reacted under the influence of concentrated solar radiation in the absence of oxygen at a temperature of 1200 °C or more, whereby the following reaction takes place: 2 H2S + CO2 + 2 CH4 → 2 CO + 6 H2 + CS2. [2] Method according to claim 1, characterized by that natural gas, crude oil and / or exhaust gases from power plants, in particular coal-fired power plants, are used as a gas mixture. [3] Method according to claim 1 or 2, characterized by that the gas mixture essentially comprises and consists in particular of hydrogen sulphide, carbon dioxide and methane. [4] Method according to one of claims 1 to 3, characterized bythat the reaction takes place in a temperature range of 1200 °C to 1700 °C, preferably at a temperature in the range of 1300 °C to 1600 °C or of 1400 °C to 1500 °C.