Hydrochloric acid catalysts used

Uses of hydrogen chloride—Hydrogen chloride is sometimes used in the preparation of an ester, for example ethyl benzoate, where it acts as both an acid catalyst and a dehydrating agent. Hydrochloric acid is used primarily to produce chlorides, for example ammonium chloride. It is extensively used in the manufacture of anilme dyes, and for cleaning iron before galvanising and tin-plating. 

Miscellaneous. Hydrochloric acid is used for the recovery of semiprecious metals from used catalysts, as a catalyst in synthesis, for catalyst regeneration (see Catalysts, regeneration), and for pH control (see Hydrogen-ION activity), regeneration of ion-exchange (qv) resins used in wastewater treatment, electric utiUties, and for neutralization of alkaline products or waste materials. In addition, hydrochloric acid is also utilized in many production processes for organic and inorganic chemicals. 

The typical acid catalysts used for novolak resins are sulfuric acid, sulfonic acid, oxaUc acid, or occasionally phosphoric acid. Hydrochloric acid, although once widely used, has been abandoned because of the possible formation of toxic chloromethyl ether by-products. The type of acid catalyst used and reaction conditions affect resin stmcture and properties. For example, oxaUc acid, used for resins chosen for electrical appHcations, decomposes into volatile by-products at elevated processing temperatures. OxaUc acid-cataly2ed novolaks contain small amounts (1—2% of the original formaldehyde) of ben2odioxanes formed by the cycli2ation and dehydration of the ben2yl alcohol hemiformal intermediates. 

Oxychlorination of G2 Chlorinated Hydrocarbons. Tetrachloroethylene and trichloroethylene can be produced by reaction of EDC with chlorine or HCl and oxygen in the presence of a catalyst. When hydrochloric acid is used, additional oxygen is requked. Product distribution is varied by controlling reactant ratios. This process is advantageous in that no by-product HCl is produced, and it can be integrated with other processes as a net HCl consumer. The reactions may be represented as follows ... 

The acidic catalysts used for these reactions include formic acid, HX (X = F, Cl, Br), oxalic acid, phosphoric acid, sulfuric acid, sulfamic acid, and p-toluenesulfonic acid.4 Oxalic acid is preferred since resins with low color can be obtained. Oxalic acid also decomposes at high temperatures (>180°C) to C02, CO, and water, which facilitates the removal of this catalyst thermally. Typically, 1-6 wt % catalyst is used. Hydrochloric acid results in corrosive materials and reportedly releases carcinogenic chloromethyl ether by-products during resin synthesis.2... 

C. Usually the polymerisation is carried out in the presence of Ziegler-Natta catalysts based on titanium tetrachloride and aluminium alkyl. The catalyst may be either prepared or formed in the reactor. Usually, the polymerisation is carried out in presence of a hydrocarbon solvent. The polymer is insoluble in the solvent. The reaction is terminated by addition of an alcohol and catalyst extracted with alcoholic hydrochloric acid. Catalyst removal is important for electrical insolution used. The Polymer chain obtained by this process is essentially linear. 

High surface area fumed silica (about 99.8% SiOz), Cab-O-Sil grade M5, was donated by Cabot Corp. (Tuscola, IL). It was reported, and verified by N, adsorption, to have a surface area of 200 m2/g. The silica was heated to about 120°C for at least 24 h under vacuum before use, which did not change the surface area. Distilled acetone and water were used as solvents for the coupling agents. Acetic acid and hydrochloric acid were used as catalysts for the non-aminofunctional silane coupling agents. 

Reactions of a,(3-unsaturated ketones with anilines are not very diverse and usually yield the appropriate quinolines [204, 205, 206, 207, 208, 209, 210, 211]. As catalysts in such reactions, hydrochloric acids are often used [204, 205, 206, 207]. In [208] besides hydrochloric acid, the use of arsenic acid and zinc chloride was proposed, which led to increase of the yields. In [209] it was reported that the catalyst used was 3-nitrobenzensulfonic acid (Scheme 3.74). 

Aniline can also be made by two other methods. In the first, nitrobenzene is reduced by reaction with scrap iron in the presence of a hydrochloric acid catalyst. The iron is oxidized to the ferrous state, and the coproduct aniline is separated. This route accounts for less than 5 percent of the current aniline production. The other process avoids nitrobenzene entirely and involves the vapor-phase ammonolysis of phenol, using an alumina catalyst. Aniline is formed with dipheny-lamine as a by-product. About 20 percent of the aniline is produced by this route. 

To produce oxygen, hydrogen peroxide has been used. After compression to 24 MPa in the low temperature section of the apparatus, hydrogen peroxide is decomposed to water and oxygen by a platinum catalyst. The resulting oxygen concentration was 0,5 mol [O2] /kg. The hydrochloric acid concentrations used for the two experiments were 0.05 and 0.2 mol/kg. Such acid concentrations are high for typical SCWO applications. 

The esterification was carried out in a glass batch reactor at atmospheric pressure. Isoamyl alcohol (0.058 mol) and acetic acid (0.058 mol) were dissolved in toluene (0.114 mol). Then, the TPA-PVA-PEG catalyst (0.100 g) was added and the resulting mixture was heated to reflux. The reaction was followed by gas chromatography, using a thermal conductivity detector. Also, hydrochloric acid was used as catalyst for comparative purpose. 

Furthermore, some cross-linking reactions were studied. The gum is easily cross-linked in the solid state with formaldehyde, when hydrochloric acid is used as catalyst. The acid causes some hydrolysis of the glycosidic linkages. The products obtained are completely insoluble in water. It is believed that, especially between primary hydroxyl groups of different molecules, methylene bridges are formed. Cross-linking with urea-formaldehyde condensation products was useful in preparing water-resistant films. 

Copper(l) chloride is essentially covalent and its structure is similar to that of diamond l.e. each copper atom is surrounded tetrahedrally by four chlorine atoms and vice versa. In the vapour phase, dimeric and trimeric species are present Copper(l) chloride is used in conjunction with ammonium chloride as a catalyst in the dimerization of ethyne to but-1 -ene-3-yne (vinyl acetylene), which is used in the production of synthetic rubber. In the laboratory a nuxture of cop-per(I) chloride and hydrochloric acid is used for converting benzene diazonlum chloride to chlorobenzene - the Sandmeyer reactioit... 

The variables affecting the product distribution are aniline concentration, hydrochloric acid concentration, and temperature. The higher the excess of aniline, the higher is the diamine concentration. Higher hydrochloric acid concentration and lower initial temperature favor the formation of 4,4 -MDA. Attempts were made over the years to replace the aqueous hydrochloric acid catalyst with slower reacting solid acidic clay catalysts, but the obtained product distribution was different, and therefore this approach was never used. 

The issue of reaction conditions was addressed above in a previous chapter (DADP) but to summarize it, TATP forms at lower molar ratios of catalyst to acetone and with lower concentrations of catalyst [8]. The formation of chlorinated TATP (3-(chloromethyl)-3,6,6,9,9-pentamethyl-l,2,4,5,7,8-hexoxonane and 3,6-bis(chloromethyl)-3,6,9,9-tetramethyl-l,2,4,5,7,8-hexoxonane) was recently published by Matyas et al. when hydrochloric acid is used as a catalyst in very large excess. Other hydrohalic acids do not provide similar halogenated cyclic peroxides by this method TATP forms as a product of the following reaction [72]. 

By 1890, formaldehyde could be obtained commercially as a 40% aqueous solution. Research in the famous laboratory of Emil Fischer (1852-1919, Nobel 1902) was instituted by W. Kleeberg on the reactions of phenol and formaldehyde. When hydrochloric acid was used as the catalyst a resinous product was obtained. Heating of this substance produced a solid which was insoluble in most solvents [32]. 

Deacon, Henry (1822-76) A British chemistandindusiriallstwho foundedamajorchemical factory in Widnes, Lancashire. He filedapatentfor an improved process for the manufacture ofsulphuric acid in 1853. He later filed many more patents which included alkallmanufacture. In 1870, he invented an improved method for the manufactme of chlorine and hydrochloric acid that used copper chloride as a catalyst The Deacon process is named after him. 

A catalyst consisting of cuprous chloride in hydrochloric acid is used and reaction is carried out in the liquid phase. In a typical process, hydrogen cyanide and a large excess of acetylene, slightly above atmospheric pressure. 

For this reaction, charcoal is a catalyst if this is omitted and hydrogen peroxide is used as the oxidant, a red aquopentammino-cobalt(lll) chloride, [Co(NH3)jH20]Cl3, is formed and treatment of this with concentrated hydrochloric acid gives the red chloro-p0itatnmino-coba. t(lll) chloride, [Co(NH3)5Cl]Cl2. In these latter two compounds, one ammonia ligand is replaced by one water molecule or one chloride ion it is a peculiarity of cobalt that these replacements are so easy and the pure products so readily isolated. In the examples quoted, the complex cobalt(III) state is easily obtained by oxidation of cobalt(II) in presence of ammonia, since... 

Nitriles react with ammonia, or primary or secondary amines in the presence of an acid catalyst to give amidines (Scheme 26) (75, 77, 81). The catalysts used are hydrochloric acid and aluminium chloride. The amidines are anthelmintics for animals such as sheep, goats, cattle, horses, and Swine. 

HF is used as a source of fluorine for production of all the various fluorocarbon products. HF reacts in the presence of a suitable catalyst and under the appropriate temperature and pressure conditions with various organic chemicals to yield a family of products. A by-product stream of hydrochloric acid may be co-produced. 

---