The Presence of Carbon Dioxide

In the presence of lime water, carbon dioxide forms calcium carbonate. This is insoluble in water, so it precipitates out of solution. To test this, breathe through a straw into a solution of lime water, like blowing bubbles. This works according to the following formula  

When all the lime has reacted, the product is calcium carbonate, which can be concentrated by evaporating the water. 

Colloidal stability is a temporary phenomenon associated with insoluble substances of a particularly small size, often with nanometer dimensions. The stability comes from the small size and the interaction between the electrical charges of the colloid and the solvent. This interaction gives the tiny colloid some temporary stability that mimics solubility (see Chapters 8 and 19). 

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If produced gas contains water vapour it may have to be dried (dehydrated). Water condensation in the process facilities can lead to hydrate formation and may cause corrosion (pipelines are particularly vulnerable) in the presence of carbon dioxide and hydrogen sulphide. Hydrates are formed by physical bonding between water and the lighter components in natural gas. They can plug pipes and process equipment. Charts such as the one below are available to predict when hydrate formation may become a problem. 

The essential protective film on the 2inc surface is that of basic 2inc carbonate, which forms in air in the presence of carbon dioxide and moisture (Fig. 1). If wet conditions predominate the normally formed 2inc oxide and 2inc hydroxide, called white mst, do not transform into a dense protective layer of adhesive basic 2inc carbonate. Rather the continuous growth of porous loosely adherent white mst consumes the 2inc then the steel msts. 

A vacuum-retort process (Pidgeon process) was used during World War II for the production of magnesium and calcium. SiHcon, in the form of ferrosihcon, was used as the reducing agent instead of carbon to avoid the problem of cooling magnesium vapor in the presence of carbon dioxide ... 

Henkel Rearrangement of Benzoic Acid and Phthalic Anhydride. Henkel technology is based on the conversion of benzenecarboxyhc acids to their potassium salts. The salts are rearranged in the presence of carbon dioxide and a catalyst such as cadmium or zinc oxide to form dipotassium terephthalate, which is converted to terephthahc acid (59—61). Henkel technology is obsolete and is no longer practiced, but it was once commercialized by Teijin Hercules Chemical Co. and Kawasaki Kasei Chemicals Ltd. Both processes foUowed a route starting with oxidation of napthalene to phthahc anhydride. In the Teijin process, the phthaHc anhydride was converted sequentially to monopotassium and then dipotassium o-phthalate by aqueous recycle of monopotassium and dipotassium terephthalate (62). The dipotassium o-phthalate was recovered and isomerized in carbon dioxide at a pressure of 1000—5000 kPa ( 10 50 atm) and at 350—450°C. The product dipotassium terephthalate was dissolved in water and recycled as noted above. Production of monopotassium o-phthalate released terephthahc acid, which was filtered, dried, and stored (63,64). 

Final Purification. Oxygen containing compounds (CO, CO2, H2O) poison the ammonia synthesis catalyst and must be effectively removed or converted to inert species before entering the synthesis loop. Additionally, the presence of carbon dioxide in the synthesis gas can lead to the formation of ammonium carbamate, which can cause fouHng and stress-corrosion cracking in the compressor. Most plants use methanation to convert carbon oxides to methane. Cryogenic processes that are suitable for purification of synthesis gas have also been developed. 

Roasting. Copper and lead sulfides are direcdy smelted but not zinc sulfide. However, theoretical calculations are encouraging (20) and, if an efficient means of condensing zinc rapidly from 1600 K in the presence of carbon dioxide, sulfur dioxide, and steam can be devised, the process may be feasible. The reaction of zinc vapor to yield zinc oxide or zinc sulfide presents the main difficulty. 

Figure 4-469 shows the effect on corrosion rates of 1020 steel in different water systems with dissolved hydrogen sulfide. The difference in corrosion rates is due to different corrosion products formed in different solutions. In solution I, kansite forms. Kansite is widely protective as the pyrrhotite coats the surface giving slightly more protection until a very protective pyrite scale is formed. In solution II, only kansite scale forms, resulting in continued increase in the corrosion rate. Finally, in solution 111, pyrite scale is formed as in solution I however, continued corrosion may be due to the presence of carbon dioxide. 

Terephthalic acid is an important monomer for producing polyesters. The main route for obtaining the acid is the catalyzed oxidation of paraxylene. It can also be produced from benzoic acid by a disproportionation reaction of potassium benzoate in the presence of carbon dioxide. Benzene is the coproduct ... 

Oxygen is not the only noncondensable gas found in boiler circuits, Problems occur due to the presence of carbon dioxide (C02). Carbon dioxide is steam-volatile and reacts with condensing steam to produce carbonic acid, which attacks steel condensate return lines. 

In the case of carbanion and radical intermediates the solvent is less important but the products are partially determined by the resistance of the medium to proton or hydrogen atom abstraction respectively. The increased stability of these intermediates compared with carbonium ions allows the reaction mechanism to be more readily modified by the addition of trapping agents. For example, carbanions are trapped in high yields by the presence of carbon dioxide in the electrolysis medium (Wawzonek and Wearring, 1959 Wawzonek et al., 1955). 

The electrochemical results suggested to explore the possibility of creating a C-C bond between the electrogenerated a-carbanion fi and carbon nucleophiles. Results of practical importance have hitherto been obtained upon electroreduction of 2-bromoisobutyramides in acetonitrile at Hg or Pt cathodes, in the presence of carbon dioxide and an alkylating agent. The enolate-amide fi undergoes quantitative carboxy-alkylation, to yield ester amides of 2,2-dimethylmalonic acid (ref. 16). 

Copper is resistant to oxidation, but over the course of time the metal acquires a coating of green corrosion called patina. The green compound is a mixed salt of Cu , hydroxide, sulfate, and carbonate that is formed by air oxidation in the presence of carbon dioxide and small amounts of sulfur dioxide ... 

The microalgae are cultured in bioreactors under solar or artiflcial light in the presence of carbon dioxide and salts. The bioreactors may be closed systems made of polyethylene sleeves rather than open pools. Optimal conditions for pigment production are low to medium light intensity and medium temperatures (20 to 30°C). Pigment extraction is achieved by cell breakage, extraction into water or buffered solution, and centrifugation to separate out the filtrate. The filtrate may then be partly purified and sterilized by microfiltration and spray dried or lyophilized. 

Powdered aluminium combusts - or even detonates, if it is heated in the presence of carbon dioxide. Ignition takes place at ambient temperature when anaqueous aluminium chloride is present. The same is true for the aluminium chlorideVcarbon monoxide mixture. 

From the beginning of the 1970s unhl the mid 1980s, several examples of the telomerization of dienes with water [76, 77] or methanol [78, 79] to isomeric mixtures of dienols or dienol ethers catalyzed by palladium-phosphine complexes in the presence of carbon dioxide have been reported. Neither the yield nor the selectivity were very high. However, when allene was employed as a diene , 3-methyl-2-meth-ylene-3-buten-l-ol was obtained with fairly good selectivity (up to 98%) (Eq. 6.43) [78]. 

Selocide is reported (4) to be a 30% solution of a mixture of potassium hydroxide, ammonium hydroxide, sulfur, and selenium in the proportions corresponding to the empirical formula (KNH4S)6Se. The commercial material contains 48 grams of selenium per liter, or approximately 6.4 ounces per gallon. The reactions that occur when a concentrated solution of Selocide is diluted with water to prepare a spray mixture, in the presence of carbon dioxide and oxygen of the air, may be represented as follows ... 

The TRM runs of N02 adsorption in the presence of C02 on the ternary Pt—Ba/Al203 catalyst at 350°C (Figure 6.8a) showed that, like in the absence of C02, (see Figure 6.3), the NO adsorption occurred via N02 disproportionation with evolution of NO. Also in the presence of carbon dioxide, the NO storage is accompanied by N02 decomposition on Pt sites, with evolution of NO and 02. 

Using on-line mass spectroscopy [65] carbon dioxide and formic acid were demonstrated as soluble products of methanol oxidation. The former gives the most intense MS signal according to the fact that it is the main product. There are two main problems to detect formic acid as such. In the presence of carbon dioxide most of the m/e signals of HCOOH overlap with signals of the major product. Besides this, in the presence of methanol, formic acid reacts to form the methyl ester ... 

Formation of 2,7-octadienyl alcohol (32) by the reaction of water has attracted much attention as a novel practical synthetic method for n-octanol, which is of considerable industrial importance. However, the reaction of water under usual conditions of the butadiene telomerization is very sluggish. Atkins, Walker, and Manyik found that the presence of a considerable amount of carbon dioxide showed a very favorable effect on the telomerization of water (40). Reaction of water (2.0 moles) with butadiene (1.0 moles) using Pd(acac)2 and PPh3 as the catalyst was carried out in the presence of carbon dioxide (0.5 mole) at 80-90°C. tert-Butyl alcohol, acetone, and acetonitrile were used as solvents. The products that were obtained are shown in Eq. (21) and Table I. 

The reaction is conducted in the melt, in the presence of carbon dioxide under pressure, catalyzed by zinc or cadmium compounds. Invented by B. Raecke at Henkel, Germany. Improved variations of this process, known as Henkel I and Henkel II, were operated by several other companies, but by 1975 had been abandoned in favor of various other methods of oxidizing /j-xylcne. 

Nickel(O) triphenylphosphine can be used to couple aryl halides and alkenes to synthesize substituted olefins [149], 1,2-bis[(di-2-propylphosphino)benzene]nick-el(0) can be used to couple aryl halides [150], and l,2-bis[(diphenylphos-phino)ethane]nickel(0) can be used to prepare benzoic acid from bromobenzene in the presence of carbon dioxide [151]. 

This enzyme [EC 2.7.1.40] catalyzes the reaction of ADP with phosphoenolypyruvate to produce ATP and pyruvate. Other nucleotides that can be used as substrates include UDP, GDP, CDP, IDP, and dADP. The enzyme will also phosphorylate hydroxylamine and fluoride in the presence of carbon dioxide. See Nucleoside 5 -Tri-phosphate Regeneration... 

Many commercial processes have been developed for manufacturing basic lead carbonate. These include Thomson-Stewart process, Carter process, and Dutch process. The method of preparation involves treating lead with acetic acid vapors in the presence of carbon dioxide at 60°C. In the Thomson-Stewart process, finely divided lead monoxide or lead metal is mixed with water to give aqueous slurry, which is then mixed with acetic acid in the presence of air and carbon dioxide. All these processes are slow, taking weeks to obtain products of desired composition. 

Bromopropylamine was reported to form tetrahydro-l,3-oxazin-2-one in moderate yield when treated with the carboxylating reagent (O2 /C02) formed by the electrochemical reduction of oxygen in acetonitrile in the presence of carbon dioxide <1997JOC6754>. 

Oxazolidinediones can be obtained from electrochemical reduction of a-halo amides in the presence of carbon dioxide. Originally, the 2,4-oxazolidine-... 

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