Catalyst orthophosphoric acid

Manufacture of 2-acetylthiophenes involves direct reaction of thiophene or alkylthiophene with acetic anhydride or acetyl chloride. Preferred systems use acetic anhydride and have involved iodine or orthophosphoric acid as catalysts. The former catalyst leads to simpler workup, but has the disadvantage of leading to a higher level of 3-isomer in the product. Processes claiming very low levels of 3-isomer operate with catalysts that are proprietary, though levels of less than 0.5% are not easily attained. 

The reaction of step 2 is carried out by heating the reagents with various acid catalysts, such as orthophosphoric acid or its acid salts, bringing the pH down to 2.3-3.2 [4]. The Igepon A type of surfactant is quite susceptible to hydrolysis, particularly on the alkaline side, as is characteristic for most esters of carboxylic acids. It is therefore used most advantageously at a fairly neutral pH, such as combination soap-syndet toilet bars. 

This survey focuses on recent developments in catalysts for phosphoric acid fuel cells (PAFC), proton-exchange membrane fuel cells (PEMFC), and the direct methanol fuel cell (DMFC). In PAFC, operating at 160-220°C, orthophosphoric acid is used as the electrolyte, the anode catalyst is Pt and the cathode can be a bimetallic system like Pt/Cr/Co. For this purpose, a bimetallic colloidal precursor of the composition Pt50Co30Cr20 (size 3.8 nm) was prepared by the co-reduction of the corresponding metal salts [184-186], From XRD analysis, the bimetallic particles were found alloyed in an ordered fct-structure. The elecbocatalytic performance in a standard half-cell was compared with an industrial standard catalyst (bimetallic crystallites of 5.7 nm size) manufactured by co-precipitation and subsequent annealing to 900°C. The advantage of the bimetallic colloid catalysts lies in its improved durability, which is essential for PAFC applicabons. After 22 h it was found that the potential had decayed by less than 10 mV [187],... 

Orthophosphoric acid and pyrophosphoric acid are preferred catalysts. Phosphorus pentoxide is catalytically active but no conclusive evidence has been described to show whether or not its activity depends on the presence of traces of water as promoter. Copper pyrophosphate and acid phosphates of cadmium are also good catalysts that the former probably owes its activity to partial conversion to acid or acidic salt under the polymerization conditions seems to be shown by the fact that there is an induction period. A composite prepared by calcining kiesel-guhr impregnated with orthophosphoric acid (the so-called solid phosphoric acid ) has found wide commercial use. 

For the preparation of the foam, a solution of 1 g technical sodium diisobutyl naphthalene sulfonate in 50 ml of 3% orthophosphoric acid is prepared. 20 ml of this solution are poured into a 11 beaker and air is stirred in with a fast running mixer until the cream-like dispersion has reached a volume of 300-400 ml.Then,20 ml of the prepared urea/formaldehyde resin are mixed in, whereby the resin must be evenly distributed. After 3-4 min the introduced resin gellifies into a molded article permeated with many water/air pores under the influence of the acidic catalyst. After 24 h,the crosslinking is completed. Drying for 12 h at 40 °C in a circulating air dryer yields a brittle thermoset foam.The foamed plastic obtained is hydrophobic and has a large internal surface. It can take up about 30 times its own weight of petroleum ether. 

These catalysts were modified by adding non-volatile inorganic acids and their salts, namely orthophosphoric acid, boric acid, barium sulfate, sodium silicate, barium nitrate, and hydrofluoric acid. The additives were added to the finished catalyst by direct impregnation from solution. The presence of the additives did not alter the specific surface or the geometric structure of the final preparations. 

Orthophosphoric acid and phosphates form complexes with many transition metal ions. The precipitation of insoluble phosphates from fairly concentrated acid solution (3-6 M HNO3) is characteristic of 4+ cations such as those of Ce, Th, Zr, U, and Pu. Phosphates of B, Al, Zr, and so on, are used industrially as catalysts for a variety of reactions. The phosphate ions, H2PO4, HPO4, and POJ are well known as ligands, of monodentate, chelating, or bridging types examples of the last two are... 

The cleavage of tetrahydrofuran and its alkylated derivatives with halogen acids is an excellent method for the preparation of, A-dihalo-alkanes.The reaction of tetrahydrofuran with the less-reactive hydrogen chloride stops at the chlorohydrin stage, whereas the reaction in the presence of zinc chloride catalyst leads to the formation of the dichloride. The crude reaction mixture containing the intermediate chlorohydrin may be treated directly with phosphorus tribromide, yielding tetramethylene chlorobromide. The preparation of dibromides can be accomplished easily with hydrogen bromide or phosphorus and bromine and diiodides, by the action of potassium iodide and orthophosphoric acid. ... 

This survey focuses on recent catalyst developments in phosphoric acid fuel cells (PAFC), proton exchange membrane fuel cells (PEMFC), and the previously mentioned direct methanol fuel cell (DMFC). A PAFC operating at 160-220 °C uses orthophosphoric acid as the electrolyte the anode catalyst is Pt and the cathode can... 

Barothermal regeneration of the spent sample D2 with orthophosphoric acid vapors (Bpa) is found to enrich sufficiently the phosphorus content at the surface (Table 2). In so doing, the catalytic properties are improved as compared with D2 sample and the selectivity towards maleic anhydride reaches that of the fresh catalyst. 

Impregnated catalysts (IPV) were prepared by mixing of ammonium vanadate aqueous solution and orthophosphoric acid with aerosil suspension at the presence of oxalic acid followed by heating under stirring and ftuther calcination of the solids at 600 C for 2-3 h (fp=0.6). 

The polyethers made with phosphazenium catalysts are purified by conventional methods such as neutralisation with an acid in the presence of water (for example with orthophosphoric acid), anhydrisation and filtration in the presence of an adsorbent. 

Hydrogen ion (H ) and hydroxyl ion OH ) are common catalysts in aquatic systems. The effect of their catalysis is manifested by changes in reaction rate that occur with changes in pH. For example, one of the major constituents of household synthetic detergents is the salt of condensed phosphoric acid such as pyrophosphoric acid, H4P2O7, and tripo-lyphosphoric acid, H5P3OKJ, These compounds react with water in a reaction known as hydrolysis to form orthophosphoric acid thus ... 

Acid hydrolysis of nylon 6 wastes [21, 22] in the presence of superheated steam has been used to produce aminocaproic acid, which under acid conditions is converted to e-caprolactam, and several patents have been obtained by BASF [23, 24]. Acids used for the depolymerization of nylon 6 include inorganic or organic acids such as nitric acid, formic acid, benzoic acid, and hydrochloric acid [23, 25]. Orthophosphoric acid [24] and boric acid are typically used as catalysts at temperatures of 250-350°C. In a typical process, superheated steam is passed through the molten nylon 6 waste at 250-300°C in the presence of phosphoric acid. The resulting solution underwent a multistage chemical purification before concentration to 70% liquor, which was fractionally distilled in the presence of base to recover pure e-caprolactam. Boric acid (1%) may be used to depolymerize nylon 6 at 400°C under ambient pressure. A recovery of 93-95% e-caprolactam was obtained by passing superheated steam through molten nylon 6 at 250-350°C [23]. 

In an orthophosphoric acid-dihydrogen phosphate buffer (130), the rate of the acidic decomposition of chlorous acid appears to be independent of the concentration of added ferric ion, whereas in an acetate buffer (167), ferric ion was found to catalyze the decomposition of chlorous acid, Nakamori et al. (167) reported that ferric ion, cupric ion, cobalt(II) ion, and nickel (II) ion change the stoichiometry and catalyze the rate of decomposition of chlorous acid at pH 3.5 in an acetate buffer. Their conclusions, however, are subject to question, since they used the chloride salts of the metals as catalysts. In view of the known effects of chloride ion on the stoichiometry... 

Thiophene was found in tar, gas and industrial benzene obtained from coal in the nineteenth century. A large number of thiophene derivatives are described in the literature and their physical properties, nucleophilic substitution and biological activity are still of current interest [ ] As for polymers, thiophene was oxidized by such acidic materials as orthophosphoric acid or a synthetic silica-alumina catalyst to yield liquid oligomer which consisted of its trimer containing a small amount of its pentamer. A report on this was published as early as 1883 [2], However, modem studies on polythiophene, aiming at the preparation of electrically conductive polymers, started at the beginning of the 1980s [3-5]. 

By using solid-state NMR, the hydrothermal stabilities (under 100% steam at 1073 K) of HZSM-5 zeolites modified by lanthanum and phosphorus have been studied. They are excellent zeolite catalysts for residual oil selective eatalytic cracking processes. It was indicated that the introduction of phosphorus to the zeolite via impregnation with orthophosphoric acid led to dealumination as well as formation of different A1 species, which were well distinguished by Al 3Q MAS NMR and P MAS NMR spectra. " ... 

Cardanyl acrylate, a derivate of cardanol, has been used for the preparation of a number of resins by condensing cardanyl acrylate with furfural and selective organic compdounds in the presence of acid as catalyst [284]). Cardanol has also been reacted with acetic anhydride and orthophosphoric acid to become acetylated cardanol and phosphorylated cardanol respectively [285]. 

After being separated from the solution as a high boiler, the acetamide is dehydrated into acetonitrile at a high temperature by using a catalyst of orthophosphoric acid-impregnated alumina. The acetonitrile is recycled to the reactors. In the hydrolysis step, the aqueous MEK-azine solution is partially decomposed into an aqueous solution of MEK and hydrazine. 

The alkylation of benzene by propan-l-ol and AICI3 in hexane or cyclohexane has been studied over the temperature range -40 to -f-100°C by n.m.r. spectroscopy. Structures of the several products of alkylation of mesitylene with 3,5-di-t-butyl-4-hydroxybenzyl alcohol and of resorcinol and its methyl ethers with a-butylbenzyl alcohol plus orthophosphoric acid have been elucidated. Allylation of guaiacol by allyl alcohol and an acid catalyst is... 

Among the other depolymerization methods of amide polymers, it is noteworthy to mention (i) application of microwaves for the PAG depolymerization (for the time being, on a laboratory scale) [42]. For instance, under the action of microwaves (200 W) for 12-23 min, aminocapronic acid was obtained in a 90% yield, together with some oligomers and cyclic compounds orthophosphoric acid was used as catalyst, (ii) pyrolysis with or without the use of catalysts [43,44], (iii) radiation method [45]. 

So-called 100% acid is a mixture comprising 88% orthophosphoric acid, 6% pyrophosphporic acid and 6% water. The optimum catalyst for the alkylation reaction contains 102%> phosphoric acid and therefore contains an even higher concentration of pyrophosphoric acid. 

Three MoP/AljOj catalysts having constant molybdenum and phosphorus contents (10 wt% MoOj and 4.5 wtX PjO,) were prepared by either consecutive (P->Mo or Mo->P) or simultaneous (Mo+P) impregnation of alumina extrudates (1/20 inch length) with aqueous solutions of ammonium heptamolybdate and/or orthophosphoric acid. The alumina has a specific surface area of 269 m /g and a pore volume of 0.69 cc/g. The impregnating solutions were adjusted to pH = 1.5-2.0 by adding nitric acid before contacting with the support. The samples were dried at 373 K for 2 h and then calcined in two steps at 623 k for 2 h and at 773 K for 3 h. 

Most nonmetallic elements (except nitrogen, oxygen, chlorine, and bromine) are oxidized to their highest state as acids. Heated with concentrated acid, sometimes ia the presence of a catalyst, sulfur, phosphoms, arsenic, and iodine form sulfuric, orthophosphoric, orthoarsenic, and iodic acid, respectively. SiHcon and carbon react to produce their dioxides. 

Farage and Janjic (1982-1 and 2) observed oscillations in the concentrations of bromide and redox potentials during the uncatalyzed oxidation of 1,4-cyclohexane-dione by bromate in sulfuric, nitric (1982-1), perchloric and orthophosphoric (1982-2) acid solutions. The system does not require a catalyst such as the redox couple Ce(IV)/Ce(III) or Mn(III)/Mn(II) of the B-Z reaction. Experimenting with this system Farage and Janjic (1982-3) observed that temperature, stirring and oxygen affect the frequency or amplitude of oscillations. 

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