Contenido

El dióxido de carbono está presente, en forma gaseosa, en las atmósferas de varios planetas del sistema solar. Entre ellos, Venus, la Tierra y Marte. En los casos de Venus y Marte, sus atmósferas contienen más de un 95 % de CO. En el caso de la Tierra, esta concentración es mucho menor, de alrededor de un 0,042 % (unas 421 ppm).

La concentración de CO en la atmósfera terrestre ha variado a través de las edades. En el periodo devónico se produjo una elevada concentración de CO atmosférico sobre las 3000 ppm (muy por encima de las actuales 421 ppm) y se verificó[7]​ una extinción masiva hace 400 millones de años. Por otro lado, en el periodo jurásico (hace 150 millones de años), los niveles superaron las 1700 ppm. La alta presencia se ha relacionado con un intenso vulcanismo y una alta temperatura ambiente en esos periodos.[8]​[9]​.

Actualmente, el dióxido de carbono representa menos de un 1% del volumen de la atmósfera de la Tierra (lo que lo incluye dentro del concepto de gas traza). En el año 2018 tenía una concentración de 407,8 partes por millón en volumen.[10]​ Esta cifra es una media anual, pero la concentración atmosférica de CO muestra estacionalidad, es decir, fluctúa ligeramente a lo largo del año. Esto se debe a la variación que se produce en la masa vegetal presente en el hemisferio norte como consecuencia del cambio de las estaciones. Desde la segunda mitad de la primavera hasta el final del verano en el norte, las plantas están en su mayor desarrollo, lo que hace que consuman más CO y se reduzca la concentración de este en la atmósfera. Por el contrario, durante el otoño y el invierno del norte, las plantas entran en estado latente o mueren y se descomponen, lo que hace que consuman menos CO y aumente la concentración de este en la atmósfera. Las concentraciones varían también a nivel regional, con más fuerza cerca del suelo con variaciones mucho menores en lo alto. En las zonas urbanas las concentraciones son generalmente más altas[11]​ y en el interior de viviendas se pueden alcanzar concentraciones de 10 veces el nivel ambiental.

La combustión de combustibles fósiles y la deforestación han provocado un aumento de la concentración atmosférica de CO cercana al 43 % desde el comienzo de la era de la industrialización.[12]​ La mayor parte del dióxido de carbono de las actividades humanas es liberado por la quema de carbón y otros combustibles fósiles. Otras actividades humanas, como la deforestación, la quema de biomasa y la producción de cemento también producen CO. Los volcanes emiten entre 0,2 y 0,3 mil millones de toneladas de CO por año, en comparación con los cerca de 29 mil millones de toneladas por año de CO emitido por las actividades humanas.[13]​ Hasta el 40 % de los gases emitidos por algunos volcanes en erupción subaérea") es dióxido de carbono.[14]​.

Carbon dioxide and the greenhouse effect

Carbon dioxide is a greenhouse gas, which absorbs and emits infrared radiation at its two active infrared vibration frequencies. This process causes carbon dioxide to heat the surface and lower atmosphere and cool the upper atmosphere.

The most extreme case of this greenhouse effect is that which occurs in the atmosphere of the planet Venus "Venus (planet)"). In the atmosphere of this planet, which has a concentration of 96.5% carbon dioxide, the gaseous layers of this gas, combined with sulfuric acid, heat the atmosphere under a pressure of 94 Earth atmospheres, creating a surface temperature of hundreds of degrees Celsius.[15]​.

In the case of the planet Mars, its atmosphere contains more than 95.3% CO in gaseous form and due to its low temperatures it is present as a solid in its polar caps. Despite the high presence of CO in the atmosphere of Mars, this planet does not have a greenhouse effect since its tenuous atmosphere with low atmospheric pressure could perhaps prevent the hydrodynamic support of clouds of this gas.[16]​.

In the case of Earth, a large majority of climatologists agree that the increase in the atmospheric concentration of CO, and therefore in the greenhouse effect induced by CO, is the main reason for the increase in global average temperature since mid-century. Although the main greenhouse gas responsible for warming is carbon dioxide, methane, nitrous oxide (Nitrogen (I) oxide), ozone, and other long-lived greenhouse gases also contribute. CO is the most worrying, since it exerts a greater overall warming influence than all other gases combined, and because it has a long atmospheric life. According to the IPCC, more than half of the CO emitted takes a century to be eliminated from the atmosphere and about 20% of the CO emitted will remain in the atmosphere for millennia.[18]​.

Not only do increasing CO concentrations lead to increases in the planet's surface temperature, but increasing global temperatures also cause increased CO concentrations. This produces a positive feedback to changes induced by other processes, such as orbital cycles. Half a billion years ago the concentration of carbon dioxide was 20 times greater than today, decreased to 4-5 times during the Jurassic period and then slowly declined with a particularly rapid reduction occurring 49 million years ago.

Local carbon dioxide concentrations can reach high values ​​near strong sources, especially those that are isolated by surrounding terrain. At the Bossoleto hot springs near Rapolano Terme in Tuscany, Italy, situated in a bowl-shaped depression approximately 100 m in diameter, CO concentrations rise by more than 75% at night, enough to kill insects and small animals. After dawn the gas disperses by convection during the day.[22]​ High emissions of CO into the air—produced by the disturbance of the deep lake water, saturated with CO—are believed to have caused 37 deaths in Lake Monoun (Cameroon) in 1984 and 1,700 victims in Lake Nyos (Cameroon) in 1986.[23]​.

It has different industrial uses. Worldwide, its main use is in oil wells to improve the amount of crude oil extracted, mainly in the United States of America.[24]​.

It is also used as an extinguishing agent, eliminating the oxygen found in that space, and preventing combustion from occurring.

In the food industry, it is used in carbonated drinks to give them effervescence.

It can also be used as a harmless or low-polluting acid. Acidity can help curdle dairy products more quickly and therefore cheaper, without adding any flavor, and in industry it can be used to neutralize alkaline residues without adding another more polluting acid such as sulfuric acid.

In agriculture, it can be used as fertilizer. Although plants cannot absorb it through the roots, it can be added to lower the pH, prevent lime deposits and make some nutrients in the soil more available.

It is used in greenhouses and indoor crops to increase the CO in the environment through combustion (propane or natural gas) or injection of pure liquid CO and achieve an increase in the harvest.[25]​.

Also in refrigeration it is used as a kind of refrigerant liquid in refrigeration machines or frozen as dry ice. This same compound is used to create artificial fog and the appearance of water boiling in special effects in movies and shows.

Another use that is increasing is as an extracting agent when it is found in supercritical conditions, given its little or no presence of residues in the extracts. This use is currently limited to obtaining alkaloids such as caffeine and certain pigments, but a small review by scientific journals can give a vision of the enormous potential that this extraction agent presents, since it allows extractions to be carried out in anoxide media, which allows obtaining products with high antioxidant potential. The critical temperature and pressure of carbon dioxide can be modified by the addition of other substances known as doping fluids, which is useful for certain applications, such as its use in thermodynamic cycles for electricity generation.[26]​ The combination of CO with such fluids is called a supercritical carbon dioxide mixture.[27]​.

It is also used as an active material to generate coherent light (CO laser).

Along with water, it is the most used solvent in processes with supercritical fluids.

Carbon dioxide is an unwanted by-product in many large-scale chemical processes, such as the selective oxidation of hydrocarbons to oxygenates. Carbon dioxide is the thermodynamically favored product in each oxidation reaction. Therefore, the challenge in the development of these processes is to find a suitable catalyst and process conditions that allow the production of the thermodynamically less favored target product and minimize the production of carbon dioxide.[28]​[29]​[30][31]​.

The Perseverance astromobile carried to Mars "Mars (planet)") a module called MOXIE – Mars Oxygen ISRU Experiment (ISRU Mars Oxygen Experiment), an in situ resource utilization device whose purpose is to produce oxygen from the atmosphere of Mars, which is composed of carbon dioxide.[33]​ This technology based on electrolysis could be considered in the future to sustain human life or make rocket fuel for missions of return.[34]​ MOXIE managed to produce oxygen from Martian atmospheric CO on a small scale.[35]​ The net reaction is shown below:.

Carbon dioxide can be qualitatively detected in the gas form by the reaction with barite water (Ba(OH)) with which it reacts forming barium carbonate, a white precipitate insoluble in excess reagent but soluble in acid solutions. The quantification of carbon dioxide is done by indirect acid-base methods and by instrumental methods using infrared.

Carbon dioxide was one of the first gases to be described as a substance distinct from breathing air. In the 19th century, the Flemish chemist Jan Baptist van Helmont observed that when coal was burned in a closed container, the resulting mass of the ash was much less than that of the original coal. His interpretation was that the charcoal was transformed into an invisible substance that he called a "gas" or "wild spirit" (spiritus sylvestre).

The properties of carbon dioxide were studied further in 1750 by Scottish physician Joseph Black, who found that limestone (calcium carbonate) when heated or treated with acids produced a colorless gas that he called "fixed air." He observed that fixed air was denser than atmospheric air and that it did not support the flame of combustion or animal life. Black also found that bubbling through an aqueous solution of lime (calcium hydroxide) precipitated calcium carbonate. This phenomenon was later used to illustrate that carbon dioxide is produced organically by animal respiration and microbial fermentation. In 1772, English chemist Joseph Priestley published a paper titled Impregnation of Water with Fixed Air in which he described a process of dripping sulfuric acid (or oil of vitriol, as Priestley knew it) onto chalk to produce carbon dioxide, forcing the gas to dissolve; By shaking a bowl of water in contact with the gas, he obtained carbonated water. This was the invention of carbonated water.

Carbon dioxide was first liquefied (at elevated pressures) in 1823 by Humphry Davy and Michael Faraday. The first description of solid carbon dioxide was given by Charles Thilorier"), who in 1834 opened a pressure vessel of liquid carbon dioxide, only to discover that the cooling produced by the rapid evaporation of the liquid produced "snow" of solid carbon dioxide (carbon dioxide).

Contenido

El dióxido de carbono está presente, en forma gaseosa, en las atmósferas de varios planetas del sistema solar. Entre ellos, Venus, la Tierra y Marte. En los casos de Venus y Marte, sus atmósferas contienen más de un 95 % de CO. En el caso de la Tierra, esta concentración es mucho menor, de alrededor de un 0,042 % (unas 421 ppm).

La concentración de CO en la atmósfera terrestre ha variado a través de las edades. En el periodo devónico se produjo una elevada concentración de CO atmosférico sobre las 3000 ppm (muy por encima de las actuales 421 ppm) y se verificó[7]​ una extinción masiva hace 400 millones de años. Por otro lado, en el periodo jurásico (hace 150 millones de años), los niveles superaron las 1700 ppm. La alta presencia se ha relacionado con un intenso vulcanismo y una alta temperatura ambiente en esos periodos.[8]​[9]​.

Actualmente, el dióxido de carbono representa menos de un 1% del volumen de la atmósfera de la Tierra (lo que lo incluye dentro del concepto de gas traza). En el año 2018 tenía una concentración de 407,8 partes por millón en volumen.[10]​ Esta cifra es una media anual, pero la concentración atmosférica de CO muestra estacionalidad, es decir, fluctúa ligeramente a lo largo del año. Esto se debe a la variación que se produce en la masa vegetal presente en el hemisferio norte como consecuencia del cambio de las estaciones. Desde la segunda mitad de la primavera hasta el final del verano en el norte, las plantas están en su mayor desarrollo, lo que hace que consuman más CO y se reduzca la concentración de este en la atmósfera. Por el contrario, durante el otoño y el invierno del norte, las plantas entran en estado latente o mueren y se descomponen, lo que hace que consuman menos CO y aumente la concentración de este en la atmósfera. Las concentraciones varían también a nivel regional, con más fuerza cerca del suelo con variaciones mucho menores en lo alto. En las zonas urbanas las concentraciones son generalmente más altas[11]​ y en el interior de viviendas se pueden alcanzar concentraciones de 10 veces el nivel ambiental.

La combustión de combustibles fósiles y la deforestación han provocado un aumento de la concentración atmosférica de CO cercana al 43 % desde el comienzo de la era de la industrialización.[12]​ La mayor parte del dióxido de carbono de las actividades humanas es liberado por la quema de carbón y otros combustibles fósiles. Otras actividades humanas, como la deforestación, la quema de biomasa y la producción de cemento también producen CO. Los volcanes emiten entre 0,2 y 0,3 mil millones de toneladas de CO por año, en comparación con los cerca de 29 mil millones de toneladas por año de CO emitido por las actividades humanas.[13]​ Hasta el 40 % de los gases emitidos por algunos volcanes en erupción subaérea") es dióxido de carbono.[14]​.

Carbon dioxide and the greenhouse effect

Carbon dioxide is a greenhouse gas, which absorbs and emits infrared radiation at its two active infrared vibration frequencies. This process causes carbon dioxide to heat the surface and lower atmosphere and cool the upper atmosphere.

The most extreme case of this greenhouse effect is that which occurs in the atmosphere of the planet Venus "Venus (planet)"). In the atmosphere of this planet, which has a concentration of 96.5% carbon dioxide, the gaseous layers of this gas, combined with sulfuric acid, heat the atmosphere under a pressure of 94 Earth atmospheres, creating a surface temperature of hundreds of degrees Celsius.[15]​.

In the case of the planet Mars, its atmosphere contains more than 95.3% CO in gaseous form and due to its low temperatures it is present as a solid in its polar caps. Despite the high presence of CO in the atmosphere of Mars, this planet does not have a greenhouse effect since its tenuous atmosphere with low atmospheric pressure could perhaps prevent the hydrodynamic support of clouds of this gas.[16]​.

In the case of Earth, a large majority of climatologists agree that the increase in the atmospheric concentration of CO, and therefore in the greenhouse effect induced by CO, is the main reason for the increase in global average temperature since mid-century. Although the main greenhouse gas responsible for warming is carbon dioxide, methane, nitrous oxide (Nitrogen (I) oxide), ozone, and other long-lived greenhouse gases also contribute. CO is the most worrying, since it exerts a greater overall warming influence than all other gases combined, and because it has a long atmospheric life. According to the IPCC, more than half of the CO emitted takes a century to be eliminated from the atmosphere and about 20% of the CO emitted will remain in the atmosphere for millennia.[18]​.

Not only do increasing CO concentrations lead to increases in the planet's surface temperature, but increasing global temperatures also cause increased CO concentrations. This produces a positive feedback to changes induced by other processes, such as orbital cycles. Half a billion years ago the concentration of carbon dioxide was 20 times greater than today, decreased to 4-5 times during the Jurassic period and then slowly declined with a particularly rapid reduction occurring 49 million years ago.

Local carbon dioxide concentrations can reach high values ​​near strong sources, especially those that are isolated by surrounding terrain. At the Bossoleto hot springs near Rapolano Terme in Tuscany, Italy, situated in a bowl-shaped depression approximately 100 m in diameter, CO concentrations rise by more than 75% at night, enough to kill insects and small animals. After dawn the gas disperses by convection during the day.[22]​ High emissions of CO into the air—produced by the disturbance of the deep lake water, saturated with CO—are believed to have caused 37 deaths in Lake Monoun (Cameroon) in 1984 and 1,700 victims in Lake Nyos (Cameroon) in 1986.[23]​.

It has different industrial uses. Worldwide, its main use is in oil wells to improve the amount of crude oil extracted, mainly in the United States of America.[24]​.

It is also used as an extinguishing agent, eliminating the oxygen found in that space, and preventing combustion from occurring.

In the food industry, it is used in carbonated drinks to give them effervescence.

It can also be used as a harmless or low-polluting acid. Acidity can help curdle dairy products more quickly and therefore cheaper, without adding any flavor, and in industry it can be used to neutralize alkaline residues without adding another more polluting acid such as sulfuric acid.

In agriculture, it can be used as fertilizer. Although plants cannot absorb it through the roots, it can be added to lower the pH, prevent lime deposits and make some nutrients in the soil more available.

It is used in greenhouses and indoor crops to increase the CO in the environment through combustion (propane or natural gas) or injection of pure liquid CO and achieve an increase in the harvest.[25]​.

Also in refrigeration it is used as a kind of refrigerant liquid in refrigeration machines or frozen as dry ice. This same compound is used to create artificial fog and the appearance of water boiling in special effects in movies and shows.

Another use that is increasing is as an extracting agent when it is found in supercritical conditions, given its little or no presence of residues in the extracts. This use is currently limited to obtaining alkaloids such as caffeine and certain pigments, but a small review by scientific journals can give a vision of the enormous potential that this extraction agent presents, since it allows extractions to be carried out in anoxide media, which allows obtaining products with high antioxidant potential. The critical temperature and pressure of carbon dioxide can be modified by the addition of other substances known as doping fluids, which is useful for certain applications, such as its use in thermodynamic cycles for electricity generation.[26]​ The combination of CO with such fluids is called a supercritical carbon dioxide mixture.[27]​.

It is also used as an active material to generate coherent light (CO laser).

Along with water, it is the most used solvent in processes with supercritical fluids.

Carbon dioxide is an unwanted by-product in many large-scale chemical processes, such as the selective oxidation of hydrocarbons to oxygenates. Carbon dioxide is the thermodynamically favored product in each oxidation reaction. Therefore, the challenge in the development of these processes is to find a suitable catalyst and process conditions that allow the production of the thermodynamically less favored target product and minimize the production of carbon dioxide.[28]​[29]​[30][31]​.

The Perseverance astromobile carried to Mars "Mars (planet)") a module called MOXIE – Mars Oxygen ISRU Experiment (ISRU Mars Oxygen Experiment), an in situ resource utilization device whose purpose is to produce oxygen from the atmosphere of Mars, which is composed of carbon dioxide.[33]​ This technology based on electrolysis could be considered in the future to sustain human life or make rocket fuel for missions of return.[34]​ MOXIE managed to produce oxygen from Martian atmospheric CO on a small scale.[35]​ The net reaction is shown below:.

Carbon dioxide can be qualitatively detected in the gas form by the reaction with barite water (Ba(OH)) with which it reacts forming barium carbonate, a white precipitate insoluble in excess reagent but soluble in acid solutions. The quantification of carbon dioxide is done by indirect acid-base methods and by instrumental methods using infrared.