Sulfur with mineral additives

Figure 6. Effects of water on sulfur with mineral additives...

For the more difficult operations, neat oils containing EP (extreme-pressure) additives have to be used. The EP cutting oils usually contain additives based on sulfur or chlorine, or combinations of them. The sulfur in EP oil can be present in two forms. In the inactive fluid, it is chemically combined with a fatty-oil additive, which is blended with mineral oil to produce sulfured fatty oil. The active version, on the other hand, contains sulfur in elemental form, dissolved in mineral oil the fluid is known as sulfured mineral oil. Chlorine is usually present only as chlorinated paraffin, which is blended sometimes singly with mineral oils and sometimes in combination with fatty oils and sulfured additives. 

It is recommended that the concentration of sulfuric acid in the initial solution be kept at 2-4 mol per liter for the extraction of tantalum, whereas for the extraction of niobium, the concentration of sulfuric acid must be increased to a minimum of 6 mol per liter [458,481]. In some cases, the presence, in the initial solution, of titanium in the form of fluorotitanic acid ensures the successful and selective extraction and purification of tantalum and niobium with no addition of any other mineral acid [482]. 

Sulfur concretes (SC) are basically simple materials, made by mixing sulfur plus certain additives with heated mineral aggregates. On cooling, SC sets to give a high-strength material with superb corrosion resistance. 

Eckart and co-workers have published a series of papers on laboratory studies of biodesulfurization of petroleum and petroleum fractions. The ability of various aerobic mixed cultures to desulfurize Romashkino crude oil (1.69 wt.% S) was addressed by Eckart et al. (21). After 5 days of incubation at 30°C in sulfur-free mineral medium with oil as sole source of carbon and sulfur, approximately 55% of the total sulfur was recovered in the aqueous phase from two of the most active cultures. In another study, gas oil (1.2 to 2 wt.% S), vacuum distillates (1.8 to 2 wt.% S) and fuel oil (up to 4 wt.% S) were used as sole carbon and sulfur sources for the oil-degrading microorganisms (36). The addition of an emulsifying agent was required to enhance desulfurization. Sulfur removals of up to 20% from the gas oil, 5% from the vacuum distillates, and 25% from the fuel oil were observed after 5 to 7 days of incubation. In a later study (37). approximately 30% of the sulfur was removed from fuel-D-oil by a mixed population of bacteria. The removal of benzothiophene, dibenzothiophene and naphthobenzothiophene was shown by high resolution MS analysis. Hydrocarbon degradation was observed in each of these studies. For example, in the latter study with fuel-D-oil, the decreases in the n-alkane and aromatic content were 59% and 14%, respectively. 

In the powder process, finely divided cadmium carbonate or cadmium oxide is subjected to intensive mechanical mixing with sulfur and mineralizers and then calcined in the absence of oxygen. The addition of zinc or selenium produces the same effects as in the precipitation process. The product is worked up in the same way as in the precipitation process. The main producer of cadmium pigments is Millenium (USA). 

The optimum in the copolymerisation process occurs at 50% monomer concentration with both additives. The behaviour of sulfuric acid in these reactions is representative of the most reactive of the mineral acids (12). A comparison of TMPTA with H SO (0.2 M) also indicates that similar trends in enhancement in radiation grafting to polyethylene film are observed with both additives (Table III). Again, when polypropylene film is used as backbone polymer (Table IV), acid and DVB show similar increases in grafting yield with styrene in methanol, however in this system, it is interesting to note that the concentration of monomer at the position of the Trommsdorff peak does not vary for neutral and acidified grafting solutions but changes from 30% to 35% when DVB is additive. 

These precursors are prepared by reaction of fuming nitric acid in excess acetic anhydride at low temperatures with 2-furancarboxaldehyde [98-01-1] (furfural) or its diacetate (16) followed by treatment of an intermediate 2-acetoxy-2,5-dihydrofuran [63848-92-0] with pyridine (17). This process has been improved by the use of concentrated nitric acid (18,19), as well as catalytic amounts of phosphoms pentoxide, trichloride, and oxychloride (20), and sulfuric acid (21). Orthophosphoric acid, -toluenesulfonic acid, arsenic acid, boric acid, and stibonic acid, among others are useful additives for the nitration of furfural with acetyl nitrate. Hydrolysis of 5-nitro-2-furancarboxyaldehyde diacetate [92-55-7] with aqueous mineral acids provides the aldehyde which is suitable for use without additional purification. 

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