Byproducts precipitation

The overall effects of the double alkali process are identical to those of die limestonedime slurry processes—SO2 is ranoved from die gas, lime or limestone is consumed, and a calcium sulfite or sulfate byproduct is produced. The int mediate st s, however, are quite different and result in a complete sqiaration of the SO2 absorption and byproduct precipitation reactions. This approach permits the gas to be contacted with a clear solution of highly soluble salts, thereby minimizing scaling, plugging, and oosion problems in the absorboit circuit. The use of a clear reactive solution instead of a slurry also offns the potential for a... 

Metal acyl complexes have been prepared from sodium carbonyl-metallates.7 In the reaction of Na[Mn(CO)s] with acyl halides in dry THF, the acyl complex that is formed remains in solution and the sodium halide byproduct precipitates. The authors report that the reaction is driven mainly by the high nucleophilicity of the carbonylmetallate anion but also by the poor solubility of the sodium halide in THF, Eq. 5.4 ... 

A typical modem phosphorus fumace (12 m diameter) can produce some 4 toniKs per hour and is rated at 60-70 MW (i.e. 140000A at SOOV). Three electrodes, each weighing 60 tonnes, lead in the current. The amounts of raw material required to make 1 tonne of white phosphorus depend on their purity but are typically 8 tonnes of phosphate rock. 2 tonnes of silica, 1.5 tonnes of coke, and 0.4 tonnes of electrode carbon. The phos rfKmis vapour is driven off from the top of the fumace together with the CO and some H2 it is passed through a hot electrostatic precipitator to remove dust and then condensed by water sprays at about 70 (P4 melts at 44.T). The byproduct CO is used for supplementary heating. 

The aqueous fraction was acidified to pH 1 with 6N HC1, and the small amount of humic acids which precipitated was removed by filtration. The filtrate was extracted three times with 100-ml portions of ethyl acetate. The organic extracts were combined, dried over anhydrous sodium sulfate, and filtered. The solvent was removed by rotary evaporation and the residue contained the freed byproducts from the hydrolyzed esterified and insoluble-bound compounds. 

These thermolysis reactions normally produce polymeric products, free of the cyclic analogs, in essentially quantitative yield and in sufficient purity to give satisfactory elemental analysis upon removal of the sHyl ether byproduct under vacuum. Final purification is generally achieved by precipitation of the polymer into a non-solvent such as hexane. With the exception of poly(diethylphosphazene) (2), which is insoluble in all common solvents (see below), the new polymers are readily soluble in CH CU and CHCU. In addition, the phenyl substituted compounds (3-6) are soluble in THF andvanous aromatic solvents. None of the polymers are water-soluble however, Me2PN]n (1) is soluble in a 50 50 water/THF mixture. 

Salts with the homoleptic [Au(C=CR)4]- anion have been obtained in only one case (R = Ph), with [nBu4N]+ as the counterion. The synthesis from (Me3P)Au(C=CPh)3 and PhC=CLi followed by precipitation with nBu4N+Br from thf requires carefully controlled conditions. It is accompanied by reductive elimination of diphenyldiacetylene to give [nBu4N]+[Au(G=CPh)2] as the byproduct. The crystal structure of the colorless, diamagnetic mixed-anion salt 2[nBu4N]+[Au(C=CPh)2] [Au(C=CPh)4] has been determined. The anions are linear and square planar, respectively.120... 

Soluble polyethylene glycol (PEG) as polymer support was also successfully investigated. Precipitation after each reaction step in order to remove excesses of reagents and soluble byproducts seemed to work well. Another topic of great interest is direct glycosylation of solid support connected peptides in order to arrive finally at glycopeptides. (9-Glycosyl trichloroacetimidates also proved successful in this endeavor. 

The only thallium compound to be discussed here is the Tlf,Cl2[Si(CMe3)3]6 cluster 61. This remarkable compound was formed by the reaction of thallium) 111) chloride with NaSi(CMe3)3 [Eq. (28)] and precipitated in the form of black crystals in 21% yield, when a solution in toluene was stored at —25 °C for six months [92], Solutions of 61 in benzene decompose slowly at room temperature by the formation of ClSi(CMe3)3 and a black, not identified precipitate. The structure of 61 consists of two four-membered T13C1 heterocycles, which are connected by one Tl-Tl and two Tl-Cl bonds. A monomeric TI3CI heterocycle was isolated as a byproduct in which one thallium atom was bonded to two Si(CMe3)3 substituents. 

The initial reaction (1) consumes NaOH and produces both hydrogen gas and an aluminate byproduct. Upon reaching its saturation limit, the aluminate compound decomposes (2) into sodium hydroxide and a crystalline precipitate of aluminum hydroxide. This process is similar to the reactions inside an aluminum battery. 

In 2000, Benaglia and coworkers reported preparation of MeO-PEG supported quaternary ammonium salt (10) and examined the catalytic efficiency in a series of phase-transfer reactions (Fig. 5.3) [69]. The reactions occurred at lower temperatures and with shorter reaction times than with comparable insoluble 2% cross-linked polystyrene-supported quaternary ammonium salts, although yields varied with respect to classical solution phase quaternary ammonium salt catalyzed reactions. It was observed that yields dropped with a shorter linker, and that PEG alone was not responsible for the extent of phase-transfer catalysis. While the catalyst was recovered in good yield by precipitation, it contained an undetermined amount of sodium hydroxide, although the presence of this byproduct was found to have no effect on the recyclability of the catalyst... 

Calcium sulfate is formed as a byproduct in industrial processes such as flue gas desulfurization and the production of zinc, fluoride, organic acids and phosphoric acid, in amounts of many million tons per year. In this study the attention is focussed on calcium sulfate from the production of phosphoric acid for fertilizer applications. It is precipitated, from solution after digestion of phosphate ore by addition of sulfuric acid according to [1] ... 

These latter cationic tagged salen ligand catalysts have the added advantage of being easily isolated from the copolymer and recycled. It should be noted that the conventional method for isolation of purified copolymer is by the addition of acidified methanol (IM HCl in MeOH) to a dichloromethane solution of the polymer/catalyst mixture. This process results in the precipitation of the copolymer, with the catalyst and other byproducts remaining in solution. In order to obtain... 

Cadmium is obtained as a byproduct in zinc recovery processes. The metal volatdizes during roasting of zinc concentrates and collected as dust or fume in bag houses or electrostatic precipitators. The dusts are mixed with coal (or coke) and zinc chloride and calcined. The cadmium chloride formed volatihzes upon calcination and thus separates out from zinc. The chloride then is treated with sulfuric acid in the presence of an oxidizing agent. This converts lead, present as impurity in cadmium ore, to lead sulfate which precipitates out. Cadmium is finally separated from copper by the addition of zinc dust and... 

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