Formaldehyde platinum catalyst

The formylation of P-H bonds in mono and multiprimary phosphines, which result in the formation of hydroxymethyl phosphines, is among the facile useful reactions in organophosphorus chemistry. As shown in Scheme 9, formaldehyde in the presence of platinum catalysts transforms P-H bonds into hydroxymethyl (P-CHjOH) functionahties (Scheme 9) [52]. 

Childers CL, Huang H, Korzeniewski C. 1999. Formaldehyde yields from methanol electrochemical oxidation on carbon-supported platinum catalysts. Langmuir 15 786-789. 

In principle, the same methods used for the preparation of platinum catalysts may be applied for palladium catalysts. When palladium chloride is used as a starting material, it is usually dissolved into an aqueous solution as chloropalladic acid by adding hydrochloric acid prior to reduction or formation of precipitates. Unsupported and supported palladium catalysts have been prepared by reduction of palladium salts with alkaline formaldehyde,139 168 sodium formate,169 hydrazine,150 hydrogen,170,171 sodium borohydride,146,172 or sodium hydride-t-AmOH,173 or by reduction of palladium hydroxide174,175 or palladium oxide176 with hydrogen. 

For selective oxidations in the carbohydrate field, Heyns and coworkers have investigated the use of platinum catalysts in different forms. For reactions in which further oxidation of the desired product is probable (as, for example, in the oxidation of ketose and pentose derivatives ), a milder catalyst of 5 to 10% platinum on activated carbon is recommended. Care must be taken in the preparation of the catalyst otherwise, it is difficult to obtain catalysts of reproducible activity. The platinum is deposited on the carbon by hydrogenation or by reduction with formaldehyde or hydrazine sulfate. The catalyst prepared through formaldehyde... 

Limonene is a compound found in orange oil and lemon oil. When limonene is treated with excess hydrogen and a platinum catalyst, the product of the reaction is l-isopropyl-4-methylcyclohexane. When limonene is treated with ozone and then with dimethyl sulfide (M62S), the products of the reaction are formaldehyde (HCHO) and the following compound. Write a structural formula for limonene. 

In the electrochemical oxidation of methanol, carbon dioxide gas is the chief reaction product. The yields of other potential products of the oxidation reaction, such as formaldehyde, formic acid, and the like, are a few percent at most. Arico et al. (1998) concluded from a chromatographic analysis of the reaction products that the chief product of electrochemical oxidation of ethanol (with a yield of about 98%) is CO2, just as for methanol. This conclusion is inconsistent with the results obtained by other workers. Wang et al. (1995) studied the reaction products of ethanol and propanol oxidation by differential electrochemical mass spectrometry. They found that during the reaction, only 20 to 40% of the theoretical yield of CO2 is produced, whereas acetaldehyde is formed to 60 to 80% (even traces of acetic acid are formed). Rousseau et al. (2006) used a high-performance liquid chromatograph for analysis of the products of ethanol oxidation. According to their data, about 50% aldehyde, 30% acetic acid, and only about 20% CO2 are formed at a temperature of 90°C at a platinum catalyst. With Pt-Sn or Pt-Sn-Ru catalysts, somewhat different numbers were obtained 15% aldehyde, 75% acid, and 10% CO2. It follows from these data that the composition of the reaction products depends heavily on the catalyst used for the... 

A widely used industrial process for the production of salicylaldehyde is the Saligenin process that produces hydroxybenzyl alcohols (o- and p-isomers) from the base-catalyzed reaction of formaldehyde with phenol, followed by oxidation using a palladium or platinum catalyst to produce the hydroxybenzaldehyde (Eq 1 44) 129,130.131... 

By heating methanol in a reservoir over a water bath, Tollens was able to regulate the air-methanol A apor ratio, Avhich Avas found to have a direct effect on the formaldehyde yield. This and minor refinements were later applied to Loew s procedure v -hich replaced the platinum catalyst by copper gauze. LoeAv dreAA a rapid current of dry air through cold methanol (at about 18°C) and passed the resultant mixture through a... 

Method A. Cool a solution of the nitrate-free dichloride, prepared from or equivalent to 5 0 g. of palladium or platinum, in 50 ml. of water and 5 ml. of concentrated hydrochloric acid in a freezing mixture, and treat it with 50 ml. of formahn (40 per cent, formaldehyde) and 11 g. of the carrier (charcoal or asbestos). Stir the mixture mechanically and add a solution of 50 g. of potassium hydroxide in 50 ml. of water, keeping the temperature below 5°. When the addition is complete, raise the temperature to 60° for 15 minutes. Wash the catalyst thoroughly by decantation with water and finally with dilute acetic acid, collect on a suction filter, and wash with hot water until free from chloride or alkali. Dry at 100° and store in a desiccator. 

Oxidation catalysts are either metals that chemisorb oxygen readily, such as platinum or silver, or transition metal oxides that are able to give and take oxygen by reason of their having several possible oxidation states. Ethylene oxide is formed with silver, ammonia is oxidized with platinum, and silver or copper in the form of metal screens catalyze the oxidation of methanol to formaldehyde. Cobalt catalysis is used in the following oxidations butane to acetic acid and to butyl-hydroperoxide, cyclohexane to cyclohexylperoxide, acetaldehyde to acetic acid and toluene to benzoic acid. PdCh-CuCb is used for many liquid-phase oxidations and V9O5 combinations for many vapor-phase oxidations. 

Methanol is a major bulk chemical, and its global annual production exceeds 37 million tons. It is mainly used for the production of formaldehyde and methyl 6butyl ether (MTBE). Especially, formaldehyde is dominantly used for producing resins. At present, methanol and its decomposed derivatives can be oxidized to CO2 and H2O by the proper selection of supported noble metal catalysts such as palladium, platinum, and gold. 

Although a wide variety of metals were claimed as active catalysts for formaldehyde hydrophosphination, platinum salts were preferred. Similarly, Group 10 metal salts were used to catalyze acrylonitrile hydrophosphination. Russian workers showed that Ni(II) or Co(II) salts in the presence of ammonia or amines would also catalyze the addition of phosphine to formaldehyde [6]. More recently, academic and industrial interest in these reactions was sparked by a series of papers by Pringle, who investigated late metal phosphine complexes as hydrophosphination catalysts. These and related studies are arranged below by substrate. 

Harrison, K.N., Hoye, P.A.T., Orpen, A.G., Pringle, P.G., and Smith, M.B., Water soluble, zero-valent, platinum-, palladium,- and nickel-P(CH2OH)3 complexes catalysts for the addition of phosphine to formaldehyde, /. Chem. Soc., Chem. Commun., 1096, 1989. 

In principle, molecular sieve carbons (MSC) can be achieved by the pyrolysis of thermosetting polymers such as polyvinylidene chloride, polyfurfuryl alcohol, cellulose, cellulose triacetate, polyacrylonitrile and phenol formaldehyde (Koresh 1980). An example is given by Trimm and Cooper (1970,1973) for the preparation of MSC (mixed with metallic compounds) for catalyst systems. A mixture of furfuryl alcohol, platinum oxide and formaldehyde was heated to 40°C and additional formaldehyde was added to ensure the... 

Treatment of aldehydes or ketones with ammonia, primary or secondary amines in reducing media is called reductive alkylation (of ammonia or amines) or reductive amination (of aldehydes or ketones). Reducing agents are most frequently hydrogen in the presence of catalysts such as platinum, nickel or Raney nickel [955], complex borohydrides [705, 954, 955], formaldehyde or formic acid [522]. 

The resulting 2,6-xylidide a-pipecolinic acid (2.2.5) is methylated to mepivacaine using formaldehyde with simultaneous reduction by hydrogen in the presence of platinum on carbon catalyst [15]. 

The industrial preparation of formaldehyde has occurred since the late 1800s and involves the catalytic oxidation of methanol 2CH,OH,. + 0 ,. —> 2CH 0,.. The oxidation takes place at temperatures between 400°C and 700°C in the presence of metal catalysts. Metals include silver, copper, molybdenum, platinum, and alloys of these metals. Formaldehyde is commonly used as an aqueous solution called formalin. Commercial formalin solutions vary between 37% and 50% formaldehyde. When formalin is prepared, it must be heated and a methanol must be added to prevent polymerization the final formalin solution contains between 5% and 15% alcohol. 

The activity of the platinum-carbon catalyst is of prime concern in obtaining maximum yields of product in a minimum of time. It was found by Mehltretter and his associates14 that a modification of Trenner s procedure02 consistently produced an effective catalyst. In the modified method, platinum from an aqueous solution of chloroplatinic acid was deposited on acid-washed Darco G-60 brand of activated carbon by means of formaldehyde and sodium carbonate. To maintain high activ-... 

Platinum is not only suitable for accelerating reduction processes, but is also an excellent catalyst when oxidation is effected by air or oxygen. Formaldehyde was first prepared by passing the vapour of methyl alcohol and air over a heated platinum spiral.15... 

Metal wires and screens are used as fixed-bed catalysts in which reactants are passed through the openings in the gauze, the size of which is defined by the mesh and wire diameter (see Fig. 10A). Gauzes composed of an alloy of platinum and rhodium catalyze the air oxidation of ammonia to nitric oxide, which is subsequently converted to nitric acid, and the production of hydrogen cyanide from ammonia, air, and methane. Formaldehyde production by... 

For many catalysts, the major component is the active material. Examples of such unsupported catalysts are the aluminosilicates and zeolites used for cracking petroleum fractions. One of the most widely used unsupported metal catalysts is the precious metal gauze as used, for example, in the oxidation of ammonia to nitric oxide in nitric acid plants. A very fast rate is needed to obtain the necessary selectivity to nitric oxide, so a low metal surface area and a short contact time are used. These gauze s are woven from fine wires (0.075 mm in diameter) of platinum alloy, usually platinum-rhodium. Several layers of these gauze s, which may be up to 3 m in diameter, are used. The methanol oxidation to formaldehyde is another process in which an unsupported metal catalyst is used, but here metallic silver is used in the form of a bed of granules. 

A.F. Hofmann, in 1868, prepd formaldehyde by passing a mixture of methanol vapors and air over a heated platinum spiral, serving as a catalyst. The following reaction takes place CH3OH+ / 02 (air) - CH20+H20. The present method of preparation is essentially the same as used by Hofmann, except that cheaper catalysts than platinum are used, such as Ag and Cu in multilayer gauzes or screens, vanadium and molybdenum oxides, iron oxides or other metal oxides. Limited amounts of formaldehyde are also prepd by the oxidation of natural gas and the lower petroleum hydrocarbons... 

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