Basic catalysts magnesium oxide

In the vapor phase, acetone vapor is passed over a catalyst bed of magnesium aluminate (206), 2iac oxide—bismuth oxide (207), calcium oxide (208), lithium or 2iac-doped mixed magnesia—alumina (209), calcium on alumina (210), or basic mixed-metal oxide catalysts (211—214). Temperatures ranging... 

For binder preparation, dilute hydrochloric or acetic acids are preferred, because these faciUtate formation of stable silanol condensation products. When more complete condensation or gelation is preferred, a wider range of catalysts, including moderately basic ones, is employed. These materials, which are often called hardeners or accelerators, include aqueous ammonia, ammonium carbonate, triethanolamine, calcium hydroxide, magnesium oxide, dicyclohexylamine, alcohoHc ammonium acetate, and tributyltin oxide (11,12). 

It was previously reported that magnesium oxide with a moderate basicity formed reactive surface carbonate species, which reacted with carbon deposited on foe support by foe methane decjomposition [6]. Upon addition of Mg to foe Ni/HY catalyst, reactive carbonate was formed on magnesium oxide and carbon dioxide could be activated more easily on the Mg-promoted Ni/HY catal t. Reactive carbonate species played an important role in inhibiting foe carbon deposition on the catalyst surface. 

Figure 7 compares in function of time the activities of catalyst B and platinum supported on magnesium oxide MgO, a well-known basic industrial catalyst. 

Acrylonitrile was first produced in Germany and the United States on an industrial scale in the early 1940s. These processes were based on the catalytic dehydration of ethylene cyanohydrin. Ethylene cyanohydrin was produced from ethylene oxide and aqueous hydrocyanic acid at 60°C in the presence of a basic catalyst. The intermediate was then dehydrated in the liquid phase at 200°C in the presence of magnesium carbonate and alkaline or alkaline earth salts of fonnic acid. A second commercial route to acrylonitrile was the catalytic addition of hydrogen cyanide to acetylene. The last commercial plants using these process technologies were shut down in 1970 (Langvardt, 1985 Brazdil, 1991). 

Tretyakov and Filimonov (219) describe a coordinative interaction between benzonitrile and aprotic sites on magnesium oxide, and Zecchina et al. (256) came to the same conclusion for the adsorption of propionitrile, benzonitrile, and acrylonitrile on a chromia-silica catalyst. Chapman and Hair (257) observed an additional chemical transformation of benzonitrile on alumina-containing surfaces, which they describe as an oxidation. Knozinger and Krietenbrink (255) have shown that acetonitrile is hydrolyzed on alumina by basic OH- ions, even at temperatures below 100°C. This reaction may be described as shown in Scheme 2. The surface acetamide (V) is subsequently transformed into a surface acetate at higher temperatures. Additional reactions on alumina are a dissociative adsorption and polymerizations (255) analogous to those observed for hydrogen cyanide by Low and Ramamurthy (258), and a dissociative adsorption. Thus, acetonitrile must certainly be refused as a probe molecule and specific poison. 

It has previously been reported that hydrotalcite catalyzes the aldol condensation of acetone (25). Polyoxometalates are known to dehydrate alcohols due to their acidic nature (IS ). In order to compare the relative basicity of polyoxometalate-pillared hydrotalcites to that of hydrotalcite itself, a variety of hydrotalcites were screened for 2-propanol conversion (Table II). This reaction is known to give propylene when the catalyst contains acidic sites (such as alumina) and acetone when the catalyst contains basic sites (such as magnesium oxide). 

Red mercuric oxide is less reactive [387], Less often, oxidations are carried out with silver oxide [370, mercurous tri-fluoroacetate [405], mercuric trifluoroacetate [406], lead tetraacetate [445], manganese dioxide [370], and nickel peroxide [955]. The most common solvents are pentane, petroleum ether, benzene, toluene, ether, and ben-zonitrile. Basic catalysts such as alcoholic potassium hydroxide are sometimes used. Anhydrous calcium oxide, sodium sulfate, and magnesium sulfate are frequently added to remove the water of reaction. The reaction temperatures range from room temperature to the reflux temperature of the solvents. 

The use of aqueous solutions with basic oxide supports such as magnesium oxide presents some difficulties because of the partial solubility of these oxides in water. To overcome this problem, highly dispersed Ru/MgO catalysts were prepared using ruthenium chloride dissolved in either anhydrous acetone or acetonitrile for the impregnation. ... 

R. L. Banks takes up the subject of olefin metathesis previously discussed by J. J. Rooney and A. Stewart in Volume 1 and gives an authorative review of the very substantial literature which has appeared in the last four years. Naturally his account covers both heterogeneous and homogeneous catalysis and he summarizes as well the industrial applications which have been made to date of metathesis reactions. S. Malinowski and J. Kijeriski review the specialist field of very highly basic catalysts largely developed by the work of the Polish school. In their chapter they discuss the evidence for the nature of catalysts such as alkali-treated magnesium and other oxides and the kind of reactions that take place thereon. J. M. Winterbottom in a chapter with emphasis on the literature since 1973 concentrates mainly on the dehydration of alcohols as the fundamental studies on dehydration far exceed those on hydration, which features mainly in the patent literature. His chapter dis-... 

As described in Sections 2.3.1.2 and 2.2.3, Choudary et al. recently revealed nanocrystalline magnesium oxide (NAP-MgO) as a recyclable heterogeneous catalyst [40, 45]. These authors extended the use of this new type of heterogeneous catalyst for the asymmetric Michael reaction of different acyclic enones with nitromethane and 2-nitropropane [69a]. In a Michael reaction of chalcone with nitromethane in THF solvent at -20°C, NAP-MgO/(lR,2R)-(-)-diaminocyclohexane (DAC) was found to be an excellent catalyst system (96% ee, 95% yield) (Scheme 2.32). This Michael reaction proceeds via the dual activation of both substrates (nucleophiles and electrophiles) by NAP-MgO. The Lewis basic site (O /O ) of the NAP-MgO activates the nitroalkanes, while the Lewis acid moiety (Mg /Mg )... 

Kantam et al. investigated the selective oxidation of various alcohols into their corresponding aldehydes and ketones by ruthenium species stabilized on the nanocrystalline magnesium oxide (NAP-MgO) by the incorporation of choline hydroxide, a basic ionic liquid, in excellent yields [45]. Their procedure was simple, efficient, and environmentally benign, and the catalyst could be used for four cycles with almost consistent activity (Scheme 14.42). 

Solid catalysts active in MPVO reactions have surface basicity or Lewis acidity. They include, amongst others, alumina, zirconia, magnesium oxide, and magnesium phosphates. More recent developments include the chemical anchoring of catalytically active co-ordination complexes, and the application of hydrotalcites, mesoporous materials (MCM-41), and zeolites. Anchoring of co-ordination compounds might open the route to true heterogeneous enantioselective MPVO reactions. As a result of their inherent shape-selectivity zeolites uniquely afford remarkable stereoselectivity in MPVO reactions. 

DIHYDROXY-2-BUTYNE (110-65-6 54141-09-2) C4H5O2 Combustible solid. May react violently with strong acids, bases, alkali metals and alkali earth hydroxides halides basic catalysts, including magnesium oxide, calcium oxide (quicklime), alkaline earth oxides, etc. On small fires, use dry chemical powder (such as Purple-K-Powder), alcohol-resistant foam, or COj extinguishers. 

Cobalt catalysts are obtained by reducing the basic carbonate, hydroxide, or oxide in a stream of hydrogen. Howk prepared a cobalt-kieselguhr catalyst.176 Cobalt-barium oxide-aluminum oxide,177 cobalt-thorium oxide-kieselguhr,178 and cobalt-thorium oxide-magnesium oxide-kieselguhr179 may be mentioned as further examples. 

Aramendia, MA Borau. V Jimenez, C Marinas, A Marinas. JM Ruiz, JR Urbano, FJ. Magnesium-containing mixed oxides as basic catalysts base characterization by carbon dioxide TPD-MS and test reactions. Journal of Molecular Catalysis A Chemical, 2004 218,81-90. 

Among all the pyridine derivatives, 2-amino-3,5-dicyano-6-sulfanyl pyridines are even more interesting because of their potential therapeutic applications. In synthetic chemistry, the cyclocondensation of aldehydes, malononitrile, and thiols is the most straightforward pathway. In general, this transformation can be realized under basic conditions. The bases reported included EtsN, DABCO, piperidine, morpholine, thiomorpholine, pyrrolidine, N,N-DIPEA, pyridine, 2,4,6-collidine, DMAP, aniline, iV-methylaniline, A,A-dimethylaniline and N,N-diethylaniline. Reactions under neutral conditions have been explored as well. In these cases, Cul nanoparticles [75], ZnCl2 [76], and nanocrystalline magnesium oxide [77] have been applied as the catalysts. 

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