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66-453: Rectisol is the trade name for an acid gas removal process that uses methanol as a solvent to separate acid gases such as hydrogen sulfide and carbon dioxide from valuable feed gas streams. By doing so, the feed gas is made more suitable for combustion and/or further processing. Rectisol is used most often to treat synthesis gas (primarily hydrogen and carbon monoxide ) produced by gasification of coal or heavy hydrocarbons , as

132-500: A WSA Process unit to recover sulfuric acid , while at the same time the carbon dioxide can be sequestered ( CCS ) or used for enhanced oil recovery . Rectisol, like Selexol and Purisol , is a physical solvent, unlike amine based acid gas removal solvents that rely on a chemical reaction with the acid gases. Methanol as a solvent is inexpensive compared to the proprietary Selexol and Purisol solvents. The Rectisol process requires more electrical energy for refrigeration to maintain

198-410: A salt and water. acid   +   base   ⟶   salt   +   water {\displaystyle {\text{acid}}\ +\ {\text{base}}\ \longrightarrow \ {\text{salt}}\ +\ {\text{water}}} In this traditional representation an acid–base neutralization reaction is formulated as a double-replacement reaction . For example,

264-460: A base in liquid sulfuric acid: HNO 3 base + 2 H 2 SO 4 ⟶ NO 2 + + H 3 O + + 2 HSO 4 − {\displaystyle {\underset {\text{base}}{{\ce {HNO3}}}}+{\ce {2 H2SO4 -> NO2+ + H3O+ + 2 HSO4-}}} The unique strength of this definition shows in describing

330-564: A commercial baking powder might use sodium acid pyrophosphate as one of the two acidic components instead of sodium aluminium sulfate. Another typical acid in such formulations is cream of tartar ( KC 4 H 5 O 6 ), a derivative of tartaric acid . The Brønsted–Lowry definition, formulated in 1923, independently by Johannes Nicolaus Brønsted in Denmark and Martin Lowry in England,

396-435: A compound that can receive this electron pair. For example, boron trifluoride , BF 3 is a typical Lewis acid. It can accept a pair of electrons as it has a vacancy in its octet . The fluoride ion has a full octet and can donate a pair of electrons. Thus BF 3 + F − ⟶ BF 4 − {\displaystyle {\ce {BF3 + F- -> BF4-}}}

462-460: A fast reaction time and an ability to remove high percentages of CO 2 , even at the low CO 2 concentrations. Typically, monoethanolamine (MEA) can capture 85% to 90% of the CO 2 from the flue gas of a coal-fired plant, which is one of the most effective solvent to capture CO 2 . Challenges of carbon capture using amine include: The partial pressure is the driving force to transfer CO 2 into

528-407: A higher pressure and does not have inefficiencies associated with multi-pressure stripper. Energy and costs are reduced since the reboiler duty cycle is slightly less than normal pressure stripper. An Internal Exchange stripper has a smaller ratio of water vapor to CO 2 in the overhead stream, and therefore less steam is required. The multi-pressure configuration with split feed reduces the flow into

594-470: A pair of electrons to the metal ion. The reaction [ Ag ( H 2 O ) 4 ] + + 2 NH 3 ⟶ [ Ag ( NH 3 ) 2 ] + + 4 H 2 O {\displaystyle {\ce {[Ag(H2O)4]+ + 2 NH3 -> [Ag(NH3)2]+ + 4 H2O}}} can be seen as an acid–base reaction in which

660-401: A stronger base (ammonia) replaces a weaker one (water). The Lewis and Brønsted–Lowry definitions are consistent with each other since the reaction H + + OH − ↽ − − ⇀ H 2 O {\displaystyle {\ce {H+ + OH- <=> H2O}}}

726-953: A sweetened gas stream (i.e., a gas free of hydrogen sulfide and carbon dioxide) as a product and an amine solution rich in the absorbed acid gases. The resultant "rich" amine is then routed into the regenerator (a stripper with a reboiler ) to produce regenerated or "lean" amine that is recycled for reuse in the absorber. The stripped overhead gas from the regenerator is concentrated H 2 S and CO 2 . Alternative stripper configurations include matrix, internal exchange, flashing feed, and multi-pressure with split feed. Many of these configurations offer more energy efficiency for specific solvents or operating conditions. Vacuum operation favors solvents with low heats of absorption while operation at normal pressure favors solvents with high heats of absorption. Solvents with high heats of absorption require less energy for stripping from temperature swing at fixed capacity. The matrix stripper recovers 40% of CO 2 at

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792-460: A variety of amine mixtures are being synthesized and tested to achieve a more desirable set of overall properties for use in CO 2 capture systems. One major focus is on lowering the energy required for solvent regeneration, which has a major impact on process costs. However, there are trade-offs to consider. For example, the energy required for regeneration is typically related to the driving forces for achieving high capture capacities. Thus, reducing

858-824: A water molecule is split into a hydrogen ion, which is donated to a pyridine molecule, and a hydroxide ion. In the Brønsted–Lowry model, the solvent does not necessarily have to be water, as is required by the Arrhenius Acid–Base model . For example, consider what happens when acetic acid , CH 3 COOH , dissolves in liquid ammonia . CH 3 COOH + NH 3 ↽ − − ⇀ NH 4 + + CH 3 COO − {\displaystyle {\ce {CH3COOH + NH3 <=> NH4+ + CH3COO-}}} An H ion

924-534: Is a hydrogen-containing compound whose hydrogen can be replaced by a metal. This redefinition was based on his extensive work on the chemical composition of organic acids , finishing the doctrinal shift from oxygen-based acids to hydrogen-based acids started by Davy. Liebig's definition, while completely empirical, remained in use for almost 50 years until the adoption of the Arrhenius definition. The first modern definition of acids and bases in molecular terms

990-1232: Is a strong acid. In liquid sulfur dioxide ( SO 2 ), thionyl compounds (supplying SO ) behave as acids, and sulfites (supplying SO 2− 3 ) behave as bases. The non-aqueous acid–base reactions in liquid ammonia are similar to the reactions in water: 2 NaNH 2 base + Zn ( NH 2 ) 2 amphiphilic amide ⟶ Na 2 [ Zn ( NH 2 ) 4 ] 2 NH 4 I acid   +   Zn ( NH 2 ) 2 ⟶ [ Zn ( NH 3 ) 4 ] I 2 {\displaystyle {\begin{aligned}{\underset {\text{base}}{{\ce {2 NaNH2}}}}+{\underset {{\text{amphiphilic}} \atop {\text{amide}}}{{\ce {Zn(NH2)2}}}}&\longrightarrow {\ce {Na2[Zn(NH2)4]}}\\[4pt]{\underset {\text{acid}}{{\ce {2 NH4I}}}}\ +\ {\ce {Zn(NH2)2}}&\longrightarrow {\ce {[Zn(NH3)4]I2}}\end{aligned}}} Nitric acid can be

1056-421: Is a typical Lewis acid, Lewis base reaction. All compounds of group 13 elements with a formula AX 3 can behave as Lewis acids. Similarly, compounds of group 15 elements with a formula DY 3 , such as amines , NR 3 , and phosphines , PR 3 , can behave as Lewis bases. Adducts between them have the formula X 3 A←DY 3 with a dative covalent bond , shown symbolically as ←, between

1122-422: Is an acid–base reaction in both theories. One of the limitations of the Arrhenius definition is its reliance on water solutions. Edward Curtis Franklin studied the acid–base reactions in liquid ammonia in 1905 and pointed out the similarities to the water-based Arrhenius theory. Albert F.O. Germann , working with liquid phosgene , COCl 2 , formulated the solvent-based theory in 1925, thereby generalizing

1188-455: Is an important parameter in the design and operation of an amine gas treating process. Depending on which one of the following four amines the unit was designed to use and what gases it was designed to remove, these are some typical amine concentrations, expressed as weight percent of pure amine in the aqueous solution: The choice of amine concentration in the circulating aqueous solution depends upon several factors and may be quite arbitrary. It

1254-441: Is based upon the idea of protonation of bases through the deprotonation of acids – that is, the ability of acids to "donate" hydrogen ions ( H ) – otherwise known as protons  – to bases, which "accept" them. An acid–base reaction is, thus, the removal of a hydrogen ion from the acid and its addition to the base. The removal of a hydrogen ion from an acid produces its conjugate base , which

1320-782: Is demonstrated in the image below: Here, one molecule of water acts as an acid, donating an H and forming the conjugate base, OH , and a second molecule of water acts as a base, accepting the H ion and forming the conjugate acid, H 3 O . As an example of water acting as an acid, consider an aqueous solution of pyridine , C 5 H 5 N . C 5 H 5 N + H 2 O ↽ − − ⇀ [ C 5 H 5 NH ] + + OH − {\displaystyle {\ce {C5H5N + H2O <=> [C5H5NH]+ + OH-}}} In this example,

1386-432: Is important to think of the acid–base reaction models as theories that complement each other. For example, the current Lewis model has the broadest definition of what an acid and base are, with the Brønsted–Lowry theory being a subset of what acids and bases are, and the Arrhenius theory being the most restrictive. The concept of an acid–base reaction was first proposed in 1754 by Guillaume-François Rouelle , who introduced

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1452-436: Is mostly H 2 S, much of which often comes from a sulfur-removing process called hydrodesulfurization . This H 2 S-rich stripped gas stream is then usually routed into a Claus process to convert it into elemental sulfur . In fact, the vast majority of the 64,000,000 metric tons of sulfur produced worldwide in 2005 was byproduct sulfur from refineries and other hydrocarbon processing plants. Another sulfur-removing process

1518-437: Is not to be confused with baking soda , which is sodium bicarbonate ( NaHCO 3 ). Baking powder is a mixture of baking soda (sodium bicarbonate) and acidic salts. The bubbles are created because, when the baking powder is combined with water, the sodium bicarbonate and acid salts react to produce gaseous carbon dioxide . Whether commercially or domestically prepared, the principles behind baking powder formulations remain

1584-525: Is removed from acetic acid, forming its conjugate base, the acetate ion, CH 3 COO . The addition of an H ion to an ammonia molecule of the solvent creates its conjugate acid, the ammonium ion, NH + 4 . The Brønsted–Lowry model calls hydrogen-containing substances (like HCl ) acids. Thus, some substances, which many chemists considered to be acids, such as SO 3 or BCl 3 , are excluded from this classification due to lack of hydrogen. Gilbert N. Lewis wrote in 1938, "To restrict

1650-482: Is the WSA Process which recovers sulfur in any form as concentrated sulfuric acid . In some plants, more than one amine absorber unit may share a common regenerator unit. The current emphasis on removing CO 2 from the flue gases emitted by fossil fuel power plants has led to much interest in using amines for removing CO 2 (see also: carbon capture and storage and conventional coal-fired power plant ). In

1716-399: Is the acid with a hydrogen ion removed. The reception of a proton by a base produces its conjugate acid , which is the base with a hydrogen ion added. Unlike the previous definitions, the Brønsted–Lowry definition does not refer to the formation of salt and solvent, but instead to the formation of conjugate acids and conjugate bases , produced by the transfer of a proton from the acid to

1782-400: Is usually made simply on the basis of experience. The factors involved include whether the amine unit is treating raw natural gas or petroleum refinery by-product gases that contain relatively low concentrations of both H 2 S and CO 2 or whether the unit is treating gases with a high percentage of CO 2 such as the offgas from the steam reforming process used in ammonia production or

1848-826: The HCl produces the chloride ion, Cl , the conjugate base of the acid. The addition of H to the H 2 O (acting as a base) forms the hydronium ion, H 3 O , the conjugate acid of the base. Water is amphoteric  – that is, it can act as both an acid and a base. The Brønsted–Lowry model explains this, showing the dissociation of water into low concentrations of hydronium and hydroxide ions: H 2 O + H 2 O ↽ − − ⇀ H 3 O + + OH − {\displaystyle {\ce {H2O + H2O <=> H3O+ + OH-}}} This equation

1914-403: The flue gases from power plants . Both H 2 S and CO 2 are acid gases and hence corrosive to carbon steel . However, in an amine treating unit, CO 2 is the stronger acid of the two. H 2 S forms a film of iron sulfide on the surface of the steel that acts to protect the steel. When treating gases with a high percentage of CO 2 , corrosion inhibitors are often used and that permits

1980-2170: The Arrhenius definition to cover aprotic solvents. Germann pointed out that in many solutions, there are ions in equilibrium with the neutral solvent molecules: For example, water and ammonia undergo such dissociation into hydronium and hydroxide , and ammonium and amide , respectively: 2 H 2 O ↽ − − ⇀ H 3 O + + OH − 2 NH 3 ↽ − − ⇀ NH 4 + + NH 2 − {\displaystyle {\begin{aligned}{\ce {2 H2O}}&{\ce {\, <=> H3O+ + OH-}}\\[4pt]{\ce {2 NH3}}&{\ce {\, <=> NH4+ + NH2-}}\end{aligned}}} Some aprotic systems also undergo such dissociation, such as dinitrogen tetroxide into nitrosonium and nitrate , antimony trichloride into dichloroantimonium and tetrachloroantimonate, and phosgene into chlorocarboxonium and chloride : N 2 O 4 ↽ − − ⇀ NO + + NO 3 − 2 SbCl 3 ↽ − − ⇀ SbCl 2 + + SbCl 4 − COCl 2 ↽ − − ⇀ COCl + + Cl − {\displaystyle {\begin{aligned}{\ce {N2O4}}&{\ce {\, <=> NO+ + NO3-}}\\[4pt]{\ce {2 SbCl3}}&{\ce {\, <=> SbCl2+ + SbCl4-}}\\[4pt]{\ce {COCl2}}&{\ce {\, <=> COCl+ + Cl-}}\end{aligned}}} A solute that causes an increase in

2046-524: The Arrhenius model. The calculation of pH under the Arrhenius model depended on alkalis (bases) dissolving in water ( aqueous solution ). The Brønsted–Lowry model expanded what could be pH tested using insoluble and soluble solutions (gas, liquid, solid). The general formula for acid–base reactions according to the Brønsted–Lowry definition is: HA + B ⟶ BH + + A − {\displaystyle {\ce {HA + B -> BH+ + A-}}} where HA represents

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2112-440: The acid gases from the feed gas at relatively high pressure, usually 400 to 1000 psia (2.76 to 6.89 MPa). The rich solvent containing the acid gases is then let down in pressure to release and recover the acid gases. The Rectisol process can operate selectively to recover hydrogen sulfide and carbon dioxide as separate streams, so that the hydrogen sulfide can be sent to either a Claus unit for conversion to elemental sulfur or

2178-1007: The acid, B represents the base, BH represents the conjugate acid of B, and A represents the conjugate base of HA. For example, a Brønsted–Lowry model for the dissociation of hydrochloric acid (HCl) in aqueous solution would be the following: HCl acid   +   H 2 O base ↽ − − ⇀ H 3 O + conjugate  acid    + Cl − conjugate base {\displaystyle {\underset {\text{acid}}{{\ce {HCl_{\,}}}}}\ +\ {\underset {\text{base}}{{\ce {H2O}}}}\quad {\ce {<=>}}\quad {\underset {{\text{conjugate }} \atop {\text{acid }}}{{\ce {H3O+}}}}\ +{\underset {{\text{conjugate}} \atop {\text{base}}}{{\ce {Cl_{\,}-}}}}} The removal of H from

2244-426: The alkanolamines DEA, MEA, and MDEA. These amines are also used in many oil refineries to remove sour gases from liquid hydrocarbons such as liquified petroleum gas (LPG). Gases containing H 2 S or both H 2 S and CO 2 are commonly referred to as sour gases or acid gases in the hydrocarbon processing industries. The chemistry involved in the amine treating of such gases varies somewhat with

2310-593: The amine concentration, the reader is referred to Kohl and Nielsen's book. MEA and DEA are primary and secondary amines. They are very reactive and can effectively remove a high volume of gas due to a high reaction rate. However, due to stoichiometry , the loading capacity is limited to 0.5 mol CO 2 per mole of amine. MEA and DEA also require a large amount of energy to strip the CO 2 during regeneration, which can be up to 70% of total operating costs. They are also more corrosive and chemically unstable compared to other amines. In oil refineries, that stripped gas

2376-505: The atoms A (acceptor) and D (donor). Compounds of group 16 with a formula DX 2 may also act as Lewis bases; in this way, a compound like an ether , R 2 O , or a thioether , R 2 S , can act as a Lewis base. The Lewis definition is not limited to these examples. For instance, carbon monoxide acts as a Lewis base when it forms an adduct with boron trifluoride, of formula F 3 B←CO . Adducts involving metal ions are referred to as co-ordination compounds; each ligand donates

2442-447: The base. In this approach, acids and bases are fundamentally different in behavior from salts, which are seen as electrolytes, subject to the theories of Debye , Onsager , and others. An acid and a base react not to produce a salt and a solvent, but to form a new acid and a new base. The concept of neutralization is thus absent. Brønsted–Lowry acid–base behavior is formally independent of any solvent, making it more all-encompassing than

2508-410: The bottom section, which also reduces the equivalent work. Flashing feed requires less heat input because it uses the latent heat of water vapor to help strip some of the CO 2 in the rich stream entering the stripper at the bottom of the column. The multi-pressure configuration is more attractive for solvents with a higher heats of absorption. The amine concentration in the absorbent aqueous solution

2574-456: The concentration of the solvent ions. Under this definition, pure H 2 SO 4 and HCl dissolved in toluene are not acidic, and molten NaOH and solutions of calcium amide in liquid ammonia are not alkaline. This led to the development of the Brønsted–Lowry theory and subsequent Lewis theory to account for these non-aqueous exceptions. The reaction of an acid with a base is called a neutralization reaction. The products of this reaction are

2640-413: The concentration of the solvonium ions and a decrease in the concentration of solvate ions is defined as an acid . A solute that causes an increase in the concentration of the solvate ions and a decrease in the concentration of the solvonium ions is defined as a base . Thus, in liquid ammonia, KNH 2 (supplying NH − 2 ) is a strong base, and NH 4 NO 3 (supplying NH + 4 )

2706-415: The final products that are desired from the gas. It is very suitable to complex schemes where a combination of products are needed, such as for example hydrogen, carbon monoxide, ammonia and methanol synthesis gases and fuel gas side streams. Amine gas treating Processes within oil refineries or chemical processing plants that remove Hydrogen Sulfide are referred to as "sweetening" processes because

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2772-475: The gas phase. At the outlet of the amine scrubber, the sweetened gas is thus depleted in H 2 S and CO 2 . A typical amine gas treating process (the Girbotol process , as shown in the flow diagram below) includes an absorber unit and a regenerator unit as well as accessory equipment. In the absorber, the downflowing amine solution absorbs H 2 S and CO 2 from the upflowing sour gas to produce

2838-424: The group of acids to those substances that contain hydrogen interferes as seriously with the systematic understanding of chemistry as would the restriction of the term oxidizing agent to substances containing oxygen ." Furthermore, KOH and KNH 2 are not considered Brønsted bases, but rather salts containing the bases OH 2 and NH 2 . The hydrogen requirement of Arrhenius and Brønsted–Lowry

2904-519: The lack of oxygen in hydrogen sulfide ( H 2 S ), hydrogen telluride ( H 2 Te ), and the hydrohalic acids . However, Davy failed to develop a new theory, concluding that "acidity does not depend upon any particular elementary substance, but upon peculiar arrangement of various substances". One notable modification of oxygen theory was provided by Jöns Jacob Berzelius , who stated that acids are oxides of nonmetals while bases are oxides of metals. In 1838, Justus von Liebig proposed that an acid

2970-448: The liquid phase. Under low pressure, this transfer is hard to achieve without increasing the reboilers' heat duty, which will result in higher costs. Primary and secondary amines, for example, MEA and DEA, will react with CO 2 and form degradation products. O 2 from the inlet gas will cause degradation as well. The degraded amine is no longer able to capture CO 2 , which decreases the overall carbon capture efficiency. Currently,

3036-463: The low temperatures required but it also requires less steam energy for regeneration. Although capital costs for methanol solvent (Rectisol) units are higher than proprietary solvent units, methanol as a cold, physical solvent can remove greater percentages of acid gas components providing a higher purity cleaned gas. The Rectisol process is very flexible and can be configured to address the separation of synthesis gas into various components, depending on

3102-483: The methanol solvent is well able to remove trace contaminants such as ammonia , mercury , and hydrogen cyanide usually found in these gases. As an acid gas and large component of valuable feed gas streams, CO 2 is separated during the methanol solvent regeneration. In the Rectisol process (licensed by both Linde AG and Air Liquide ), cold methanol at approximately –40 °F (–40 °C) dissolves (absorbs)

3168-405: The odor of the processed products is improved by the absence of "sour" hydrogen sulfide. An alternative to the use of amines involves membrane technology . However, membrane separation is less attractive due to the relatively high capital and operating costs as well as other technical factors. Many different amines are used in gas treating: The most commonly used amines in industrial plants are

3234-436: The other hand, solvent system theory has been criticized as being too general to be useful. Also, it has been thought that there is something intrinsically acidic about hydrogen compounds, a property not shared by non-hydrogenic solvonium salts. This acid–base theory was a revival of the oxygen theory of acids and bases proposed by German chemist Hermann Lux in 1939, further improved by Håkon Flood c.  1947 and

3300-431: The particular amine being used. For one of the more common amines, monoethanolamine (MEA) denoted as RNH 2 , the acid-base reaction involving the protonation of the amine electron pair to form a positively charged ammonium group (RNH 3 ) can be expressed as: The resulting dissociated and ionized species being more soluble in solution are trapped, or scrubbed, by the amine solution and so easily removed from

3366-483: The reaction mechanisms and their application in solving related problems; these are called the acid–base theories, for example, Brønsted–Lowry acid–base theory . Their importance becomes apparent in analyzing acid–base reactions for gaseous or liquid species, or when acid or base character may be somewhat less apparent. The first of these concepts was provided by the French chemist Antoine Lavoisier , around 1776. It

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3432-491: The reaction of hydrochloric acid (HCl) with sodium hydroxide (NaOH) solutions produces a solution of sodium chloride (NaCl) and some additional water molecules. HCl ( aq ) + NaOH ( aq ) ⟶ NaCl ( aq ) + H 2 O {\displaystyle {\ce {HCl_{(aq)}{}+ NaOH_{(aq)}-> NaCl_{(aq)}{}+ H2O}}} The modifier ( aq ) in this equation

3498-737: The reaction produces carbon dioxide by the following stoichiometry : 14 NaHCO 3 + 5 Ca ( H 2 PO 4 ) 2 ⟶ 14 CO 2 + Ca 5 ( PO 4 ) 3 OH + 7 Na 2 HPO 4 + 13 H 2 O {\displaystyle {\ce {14 NaHCO3 + 5 Ca(H2PO4)2 -> 14 CO2 + Ca5(PO4)3OH + 7 Na2HPO4 + 13 H2O}}} A typical formulation (by weight) could call for 30% sodium bicarbonate, 5–12% monocalcium phosphate , and 21–26% sodium aluminium sulfate . Alternately,

3564-560: The reactions in aprotic solvents; for example, in liquid N 2 O 4 : AgNO 3 base + NOCl   acid ⟶ N 2 O 4 solvent + AgCl   salt {\displaystyle {\underset {\text{base}}{{\ce {AgNO3}}}}+{\underset {\text{acid}}{{\ce {NOCl_{\ }}}}}\longrightarrow {\underset {\text{solvent}}{{\ce {N2O4}}}}+{\underset {\text{salt}}{{\ce {AgCl_{\ }}}}}} Because

3630-456: The regeneration energy can lower the driving force and thereby increase the amount of solvent and size of absorber needed to capture a given amount of CO 2 , thus, increasing the capital cost. Acid-base reaction In chemistry , an acid–base reaction is a chemical reaction that occurs between an acid and a base . It can be used to determine pH via titration . Several theoretical frameworks provide alternative conceptions of

3696-490: The same. The acid–base reaction can be generically represented as shown: NaHCO 3 + H + ⟶ Na + + CO 2 + H 2 O {\displaystyle {\ce {NaHCO3 + H+ -> Na+ + CO2 + H2O}}} The real reactions are more complicated because the acids are complicated. For example, starting with sodium bicarbonate and monocalcium phosphate ( Ca(H 2 PO 4 ) 2 ),

3762-491: The solvent system definition depends on the solute as well as on the solvent itself, a particular solute can be either an acid or a base depending on the choice of the solvent: HClO 4 is a strong acid in water, a weak acid in acetic acid, and a weak base in fluorosulfonic acid; this characteristic of the theory has been seen as both a strength and a weakness, because some substances (such as SO 3 and NH 3 ) have been seen to be acidic or basic on their own right. On

3828-487: The sometimes high content of hydrogen sulfide is necessary to prevent corrosion of metallic parts after burning the bio gas. Amines are used to remove CO 2 in various areas ranging from natural gas production to the food and beverage industry, and have been since 1930. There are multiple classifications of amines, each of which has different characteristics relevant to CO 2 capture. For example, monoethanolamine (MEA) reacts strongly with acid gases like CO 2 and has

3894-430: The specific case of the industrial synthesis of ammonia , for the steam reforming process of hydrocarbons to produce gaseous hydrogen , amine treating is one of the commonly used processes for removing excess carbon dioxide in the final purification of the gaseous hydrogen. In the biogas production it is sometimes necessary to remove carbon dioxide from the biogas to make it comparable with natural gas. The removal of

3960-428: The symbol H is interpreted as a shorthand for H 3 O , because it is now known that a bare proton does not exist as a free species in aqueous solution. This is the species which is measured by pH indicators to measure the acidity or basicity of a solution. The Arrhenius definitions of acidity and alkalinity are restricted to aqueous solutions and are not valid for most non-aqueous solutions, and refer to

4026-467: The use of higher concentrations of amine in the circulating solution. Another factor involved in choosing an amine concentration is the relative solubility of H 2 S and CO 2 in the selected amine. The choice of the type of amine will affect the required circulation rate of amine solution, the energy consumption for the regeneration and the ability to selectively remove either H 2 S alone or CO 2 alone if desired. For more information about selecting

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4092-501: The word " base " into chemistry to mean a substance which reacts with an acid to give it solid form (as a salt). Bases are mostly bitter in nature. The first scientific concept of acids and bases was provided by Lavoisier in around 1776. Since Lavoisier's knowledge of strong acids was mainly restricted to oxoacids , such as HNO 3 ( nitric acid ) and H 2 SO 4 ( sulfuric acid ), which tend to contain central atoms in high oxidation states surrounded by oxygen, and since he

4158-522: Was devised by Svante Arrhenius . A hydrogen theory of acids, it followed from his 1884 work with Friedrich Wilhelm Ostwald in establishing the presence of ions in aqueous solution and led to Arrhenius receiving the Nobel Prize in Chemistry in 1903. As defined by Arrhenius: This causes the protonation of water, or the creation of the hydronium ( H 3 O ) ion. Thus, in modern times,

4224-454: Was implied by Arrhenius, rather than included explicitly. It indicates that the substances are dissolved in water. Though all three substances, HCl, NaOH and NaCl are capable of existing as pure compounds, in aqueous solutions they are fully dissociated into the aquated ions H , Cl , Na and OH . Baking powder is used to cause the dough for breads and cakes to "rise" by creating millions of tiny carbon dioxide bubbles. Baking powder

4290-465: Was not aware of the true composition of the hydrohalic acids ( HF , HCl , HBr , and HI ), he defined acids in terms of their containing oxygen , which in fact he named from Greek words meaning "acid-former" (from Greek ὀξύς (oxys)  'acid, sharp' and γεινομαι (geinomai)  'engender'). The Lavoisier definition held for over 30 years, until the 1810 article and subsequent lectures by Sir Humphry Davy in which he proved

4356-479: Was removed by the Lewis definition of acid–base reactions, devised by Gilbert N. Lewis in 1923, in the same year as Brønsted–Lowry, but it was not elaborated by him until 1938. Instead of defining acid–base reactions in terms of protons or other bonded substances, the Lewis definition defines a base (referred to as a Lewis base ) to be a compound that can donate an electron pair , and an acid (a Lewis acid ) to be

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