Atmospheric synthesis

Hydrocyanic acid - [CYANIDES] (Vol 7) -atmospheric synthesis [IMINES, CYCLIC] (Vol 14)... 

In this work, the triflic acid modified Y-zeolite catalyst has been investigated for the atmospheric synthesis of MTBE and ETBE. In particular, the apparent activation energy for MTBE was determined, and this value is compared with those reported in the literature [1,6]. In addition, for both syntheses, the product selectivities are reported as functions of the contact time at the temperature where the catalyst activity is the highest. The catalyst stability for the MTBE synthesis was also examined. 

MacFarlane D.R. New inorganic glasses for optical wavegnides. Ceram. Inti. 1996 22 535-541 MaUhot A.M., Elyamani A., Riman R.E. Reactive atmosphere synthesis of sol-gel heavy metal fluoride glasses. J. Mater. Res. 1992 7 1534-1540... 

The steady state concentrations of HCN would have depended on the pH and temperature of the early oceans and the input rate of HCN from atmospheric synthesis. Assuming favorable production rates, Miyakawa et al (30) estimated steady state concentrations of HCN of 2 x 10 M at pH 8 and 0°C in the primitive oceans. At 100° C and pH 8 the steady state concentration was estimated as 7 x 10 M. HCN hydrolyzes to formamide which then hydrolyzes to formic acid and ammonia. It has been estimated that oligomerization and hydrolysis compete at approximately 10 M concentrations of HCN at pH 9 (31), although it has been shown that adenine is still produced from solutions as dilute as 10 M (32). If the concentration of HCN were as low as estimated, it is possible that HCN tetramer formation may have occurred on the primitive Earth in eutectic solutions of HCN-H2O, which may have existed in the polar regions of an Earth of the present average temperature. High yields of the HCN tetramer have been reported by cooling dilute cyanide solutions to temperatures between -10° C and -30° C for a few months (31). Production of adenine by HCN polymerization is accelerated by the presence of formaldehyde and other aldehydes, which could have also been available in the prebiotic environment (29). 

Wang, P., Huang, B., Wei, J., Qin, X., Yao, S. and Zhang, Q. (2007) Preparation of Cu nanopartides on carbon nanotubes by solution infusion method and caldning in ambient atmosphere. Synthesis and diaraclerization of copper nanopartides. Material Letters, 61, 5255 7. 

Interest in AIN, GaN, InN and their alloys for device applications as blue light-emitting diodes and blue lasers has recently opened up new areas of high-pressure synthesis. Near atmospheric pressure, GaN and InN are nnstable with respect to decomposition to the elements far below the temperatures where they might melt. Thus, large boules of these materials typically used to make semiconductor devices caimot be grown from the... 

The intramolecular oxidative earbonylation has wide synthetie applieation. The 7-lactone 247 is prepared by intramolecular oxycarbonylation of the alke-nediol 244 with a stoichiometric amount of Pd(OAc)2 under atmospheric pres-sure[223]. The intermediate 245 is formed by oxypalladation, and subsequent CO insertion gives the acylpalladium 246. The oxycarbonylation of alkenols and alkanediols can be carried out with a catalytic amount of PdCl2 and a stoichiometric amount of CuCb, and has been applied to the synthesis of frenolicin(224] and frendicin B (249) from 248[225]. The carbonylation of the 4-penten-l,3-diol 250, catalyzed by PdCl2 and CuCl2, afforded in the c -3-hydroxytetrahydrofuran-2-aeetie acid lactone 251[226J. The cyclic acetal 253 is prepared from the dienone 252 in the presence of trimethyl orthoformate as an accepter of water formed by the oxidative reaction[227]. 

The benzoic acid derivative 457 is formed by the carbonylation of iodoben-zene in aqueous DMF (1 1) without using a phosphine ligand at room temperature and 1 atm[311]. As optimum conditions for the technical synthesis of the anthranilic acid derivative 458, it has been found that A-acetyl protection, which has a chelating effect, is important[312]. Phase-transfer catalysis is combined with the Pd-catalyzed carbonylation of halides[3l3]. Carbonylation of 1,1-dibromoalkenes in the presence of a phase-transfer catalyst gives the gem-inal dicarboxylic acid 459. Use of a polar solvent is important[314]. Interestingly, addition of trimethylsilyl chloride (2 equiv.) increased yield of the lactone 460 remarkabiy[3l5]. Formate esters as a CO source and NaOR are used for the carbonylation of aryl iodides under a nitrogen atmosphere without using CO[316]. Chlorobenzene coordinated by Cr(CO)j is carbonylated with ethyl formate[3l7]. 

Various organotin reagents react with acyl and aroyl halides under mild conditions without decarbonylation to give carbonyl compounds[390,39l]. Alkyl- or alkenyltin reagents react with acyl and aroyl chlorides to give ketones[548.733,734]. One example is the preparation of the a,/3-dnsaturated 7-keto esters 860 and 861, carried out under a CO atmosphere[735]. The reaction has been applied intramolecularly to the synthesis of the macrocyclic keto... 

Donor substituents on the vinyl group further enhance reactivity towards electrophilic dienophiles. Equations 8.6 and 8.7 illustrate the use of such functionalized vinylpyrroles in indole synthesis[2,3]. In both of these examples, the use of acetyleneic dienophiles leads to fully aromatic products. Evidently this must occur as the result of oxidation by atmospheric oxygen. With vinylpyrrole 8.6A, adducts were also isolated from dienophiles such as methyl acrylate, dimethyl maleate, dimethyl fumarate, acrolein, acrylonitrile, maleic anhydride, W-methylmaleimide and naphthoquinone. These tetrahydroindole adducts could be aromatized with DDQ, although the overall yields were modest[3]. 

Ma.nufa.cture. In general, manufacture is carried out in batch reactors at close to atmospheric pressure. A moderate excess of finely divided potassium hydroxide is suspended in a solvent such as 1,2-dimethoxyethane. The carbonyl compound is added, followed by acetylene. The reaction is rapid and exothermic. At temperatures below 5°C the product is almost exclusively the alcohol. At 25—30°C the glycol predominates. Such synthesis also... 

Metal organic decomposition (MOD) is a synthesis technique in which metal-containing organic chemicals react with water in a nonaqueous solvent to produce a metal hydroxide or hydrous oxide, or in special cases, an anhydrous metal oxide (7). MOD techniques can also be used to prepare nonoxide powders (8,9). Powders may require calcination to obtain the desired phase. A major advantage of the MOD method is the control over purity and stoichiometry that can be achieved. Two limitations are atmosphere control (if required) and expense of the chemicals. However, the cost of metal organic chemicals is decreasing with greater use of MOD techniques. 

Material System. There are two basic techniques for the industrial synthesis of Si3N powder, although other methods are available (36). The older and most widely used method is the nitridation of siHcon. SiHcon is heated in a nitrogen [7727-37-9] atmosphere at temperatures of 1100—1450°C in... 

The hydrogen can be used for organic hydrogenation, catalytic reductions, and ammonia synthesis. It can also be burned with chlorine to produce high quaHty HCl and used to provide a reducing atmosphere in some appHcations. In many cases, however, it is used as a fuel. 

Goal Upgrading via Fischer-Tropsch. The synthesis of methane by the catalytic reduction of carbon monoxide and hydrogen over nickel and cobalt catalysts at atmospheric pressure was reported in 1902 (11). 

G-9 Aromatic Petroleum Resins. Feedstocks typically used for aromatic petroleum resin synthesis boil in the approximate range of 100—300°C at atmospheric pressure, with most boiling in the 130—200°C range. The C-9 designation actually includes styrene (C-8) through C-10 hydrocarbons (eg, methylindene). Many of the polymerizable monomers identified in Table 1 for coumarone—indene type cmdes from coal tar are also present in aromatic fractions from cracked petroleum distillates. Therefore, the technology developed for the polymerization of coal-tar cmdes is also appHcable to petroleum-derived aromatic feedstocks. In addition to availabiHty, aromatic petroleum resins offer several advantages over coumarone—indene resins. These include improved color and odor, as weU as uv and thermal stabiHty (46). 

Fig. 1. General process operations for hydrothermal synthesis. Feedstocks may be oxides, hydroxides or salts, gels, organic materials, or acids or bases. The atmosphere within the reactor may be oxidising or reducing. To convert MPa to psi, multiply by 145.

The GdAlgB O QiCe ", Tb " is synthesized by a soHd-state firing of the rare-earth coprecipitated oxide plus boric acid and MgCO at 900° C in a slightly reducing atmosphere. As in the case of the lanthanum phosphate phosphor, a flux is usually used. The synthesis of this phosphor is further comphcated, however, by the fact that it is a ternary system and secondary phases such as gadolinium borate form and must then react to give the final phosphor. 

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