Catalyst alkali carbonate

A halogen atom directly attached to a benzene ring is usually unreactive, unless it is activated by the nature and position of certain other substituent groups. It has been show n by Ullmann, however, that halogen atoms normally of low reactivity will condense with aromatic amines in the presence of an alkali carbonate (to absorb the hydrogen halide formed) and a trace of copper powder or oxide to act as a catalyst. This reaction, known as the Ullmant Condensation, is frequently used to prepare substituted diphenylamines it is exemplified... 

Pure decarbonylation typically employs noble metal catalysts. Carbon supported palladium, in particular, is highly elfective for furan and CO formation.Typically, alkali carbonates are added as promoters for the palladium catalyst.The decarbonylation reaction can be carried out at reflux conditions in pure furfural (165 °C), which achieves continuous removal of CO and furan from the reactor. However, a continuous flow system at 159-162 °C gave the highest activity of 36 kg furan per gram of palladium with potassium carbonate added as promoter. In oxidative decarbonylation, gaseous furfural and steam is passed over a catalyst at high temperatures (300 00 °C). Typical catalysts are zinc-iron chromite or zinc-manganese chromite catalyst and furfural can be obtained in yields of... 

Tanaka et al. reported that gasoline POX over Rh, Pt, and Pt-Rh is promoted by alkali (Li) and alkaline earth metals (Ba, Ca, K) supported on magnesium aluminate spinel. The catalysts were tested isothermally at 800°C at an air to fuel ratio of 5.1 and GHSV 50,000 h Li, Mg and MgLi promoters were added to Pt supported on MgAl204 spinel. All catalysts produced similar H2 and CO reformate concentrations of 23 and 25 vol%, respectively. There was a discernable difference in the carbon deposition. The unpromoted Pt catalyst showed carbon levels of 0.02 wt% carbon, where the alkali and alkaline earth promoted Pt catalysts had carbon levels of 0.01 wt%. 

Other reported syntheses include the Reimer-Tiemann reaction, in which carbon tetrachloride is condensed with phenol in the presence of potassium hydroxide. A mixture of the ortho- and para-isomers is obtained the para-isomer predominates. -Hydroxybenzoic acid can be synthesized from phenol, carbon monoxide, and an alkali carbonate (52). It can also be obtained by heating alkali salts of -cresol at high temperatures (260—270°C) over metallic oxides, eg, lead dioxide, manganese dioxide, iron oxide, or copper oxide, or with mixed alkali and a copper catalyst (53). Heating potassium salicylate at 240°C for 1—1.5 h results in a 70—80% yield of -hydroxybenzoic acid (54). When the dipotassium salt of salicylic acid is heated in an atmosphere of carbon dioxide, an almost complete conversion to -hydroxybenzoic acid results. They>-aminobenzoic acid can be converted to the diazo acid with nitrous acid followed by hydrolysis. Finally, the sulfo- and halogenobenzoic acids can be fused with alkali. 

Tantalic Acid and Tantalates. Tantalic acid [75397-94-3], Ta2Os H20, is the name of the white insoluble precipitate formed by hydrolysis of alkali hydroxide or alkali carbonate fusions containing tantalum, or by adding ammonia to an acidic solution containing tantalum ions. Tantalic acid is characterized by a high surface acidity, affording it potential use as a catalyst. 

Poisoning by water vapor is a reversible effect and can be overcome by redrying the catalyst. Alkali poisoning, on the other hand, is permanent and may involve the formation of a salt, such as a manganite or cobaltite in the surface layer. In such cases, the manganese or cobalt atom is more completely coordinated and the reactivity of the surface considerably lessened thereby. Carbon monoxide is therefore oxidized only stoichiometrically by poisoned Mn02. 

It is an old practice [46] to add to metallic catalysts a chemical compound which itself is inactive but which improves the activity/selectivity and/or stability of the metallic catalyst. This is also a common situation in FTS iron is used in the double-promoted form (AI2O3, alkali carbonate) Co supported, and promoted by alkalis and, for example, TT1O2, etc. The additives — promoters — have been shown to have the following functions [47] ... 

The effects of the starting amount of catalyst, alkali conccnlraiion, partial pressure of CO2 or lU, and temperature, on the formation rate of formate, were examined in a kinetic study. Takezaki et al. assumed a reaction path involving hydrogen carbonate and palJadium hydrugen intermediates. 

Abstract Rice straw was catalytically gasified over nickel catalysts supported on kieselguhr. This has been done by varying the content of alkali carbonate, lithium metal (3-20wt%) and various sodium compounds. In the case which alkali metal carbonates were separately added with nickel catalyst, conversion to gas was increased in the following order of Li< Cs< Kalkali metals were used to as co-catalyst by impregnation method, gas formation was increased in the following order Cs< tC a< Li. These results showed same aspects with TPR patterns. 

Elliott et al. reported that nickel catalyst showed an excellent activity on the gasification. Also, Lee et. al demonstrated that main reaction course to produce gas from rice straw was the formation of gas from oil step and alkali carbonate like Li2C03,Na2C03, K2CO3 activate the formation step. 

The initial step in the preparation of a coprecipitated catalyst is the reaction between a solution of two or more metal salts and a base, generally a hydroxide, alkali carbonate or bicarbonate. The resulting precipitate may contain not only the insoluble hydroxides and/or carbonates but also a mixed metal compound if the solubility equilibria are favorable. Even if the formation of a mixed metal compound is not favorable, some of the support material is usually trapped in the active metal precipitate. This dilutes the precipitate and inhibits the formation of large crystals of the active metal compound. Smaller crystals are easier to reduce and give more finely divided metal particles. ... 

HYDEOCARBON STEAM REFORMING CATALYSTS - ALKALI INDUCED RESISTANCE TO CARBON FORMATION... 

The acylal (4) can also be used to carry out reactions with nascent dimethylketene formed in situ. It is stable to t-butanol at the reflux temperature but with potassium carbonate present to ciitaly/,c cleavage it reacts smoothly to form /-butyl isobutyrate It reacts with an amine without other catalyst at room temperature to give an isohutyramide. In the presence of an alkali carbonate or the salt of a carboxylic acid, it converti an acid Into Its anhydride, probably via a mixed anhydride. With... 

Subsequent graphite gasification research by White and his group (3,4) found potassium carbonate to be an excellent catalyst at an optimum proportion of 20 percent (by weight) of the carbonaceous fuel feed. White and Weiss (3J noted that alkali carbonates also catalyzed the water-gas shift reaction when steam was injected during gasification ... 

More recent research has recognized alkali carbonates as efficient catalysts in the pyrolysis and gasification of urban refuse, coal, and biomass. 

The literature indicates that gasification rates may be significantly accelerated by employing such catalysts as alkali carbonates and metallic oxides. 

Another characteristic of DMC that is important is hydrolysis. Dimethylcarbonate can react with water to produce methanol and CO2. Conditions that favor this reaction are elevated temperature, excess free water, and alkali metal carbonates. Under normal circumstances, in gasoline without any free water, the reaction does not proceed at all. With a small amount of free water and adequate time and temperature, some of the DMC will enter aqueous phase and hydrolyze. In a completely aqueous system with an alkali carbonate catalyst present and elevated temperature, DMC hydrolyzes slowly. For example, DMC in water held at 70°C (158°F) for Iweek with ample K2CO3 present was hydrolyzed to methanol and CO2 with a conversion of 50%. 

MCFCs have a liquid alkali carbonate mixture and nickel catalysts. 

Aromatic hydroxycarboxylic acids, especially salicylic acid, have a wide range of applications, for example, as valuable raw materials and intermediates in the production of pharmaceutical chemicals. Originally, salicylic acid was synthesized by the Kolbe-Schmitt reaction [57], which consists of two steps (1) the synthesis and purification of alkali metal phenoxides and (2) carboxylation (Scheme 4.4). Another possible synthetic method is via the attack of a trichloromethyl cation (generated by a copper catalyst from carbon tetrachloride) on the phenoxide anion, followed by hydrolysis of the C—Cl bonds with concentrated sodium hydroxide, because it is fairly difficult to replace an aromatic hydrogen with carboxyl functionality [58]. 

Sulfur-free catalyst is generally obtained by treating nickel nitrate with alkali carbonate, hydroxide, or hydrogen carbonate. The alkali salts formed during the precipitation must be removed so far as possible from the product. The nickel hydroxide or basic carbonate is then reduced, without prior conversion into the oxide. Nickel oxide is usually prepared by decomposition of nickel acetate or nitrate. 

Condensing agents are basic catalysts such as alkali carbonates, hydrogen carbonates, hydroxides, or alkoxides, or primary aliphatic amines or calcium hydroxide zinc chloride may also be used with aromatic aldehydes. Ethylene-diamine was introduced by Lerner972 for use in the synthesis of unsaturated nitriles in the aromatic series and he gave a large number of examples in which yields were around 95%. 

To address the recoverability of the alkali carbonate catalyst from the ash, both ambient and warm water washes were used. In the ambient temperature wash, 1 gram of ash was stirred 1 hr in 100 ml H20. Between 80-100% (87% average for 24 samples) of the initial potassium used in the gasification run could be dissolved in the aqueous solution. The range of potassium solubility reflects some of the difficulties previously referred to. No attempt was made to recrystallize potassium compounds from the ambient temperature washes. 

In the presence of the methanation catalyst the K2C03 coal ratio was optimized at about 20-25 wt %. This amount of the alkali carbonate has produced the maximum total gas and methane production under experimental conditions. A deviation from this quantity of potassium... 

In contrast to hydrogenation and oxidation reactions, much less is known about the ability of materials to effect the catalysis of hydrogasification reactions. Alkali carbonates, 1-10 wt % catalyze the hydrogasification of coals and cokes at 800°-900°C (6). The suggested mechanism is that adsorption of the alkalies by carbon prevents graphitization of the surface. Zinc and tin halides are effective hydrogasification catalysts. There is, however, little kinetic information on any of the catalyzed hydrogasification reactions. 

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