Sulfur economic advantages

Research is currently directed toward development of novel technologies that may present economic advantages with respect to the conventional acetone cyanohydrin lACHl route. Mitsubishi Gas Chemical Co. has developed and patented n modified acetone cyanohydrin-based route that docs not use sulfuric acid and therefore presents the opportunity lor reduced waste costs. A nuvel C-3 route based on the palladium-catalyzed carbonylaiion of methylatelylenc has been developed by Shell Oil Co. There have been significant improvements in catalysts and resulting yields for key transformations in many routes since the 19K(K... 

The synthesis of 1,8-diaminonaphthalene by electrolysis of a suspension of 1,8-dini-tronaphthalene in sulfuric acid containing a titanium salt gives a yield and purity similar to the synthesis by catalytic hydrogenation [160], Technical and economic comparisons show that for large productions (several hundred tons per year) the catalytic hydrogenation is advantageous, whereas for smaller productions (several tons per year) the flexibility of electrolysis has some economic advantages. 

The traditional acetone cyanohydrin (ACH) process is the most widely used in Europe and North America, while other processes are more often used in Asia. In the ACH process (Figure 2.63), acetone and hydrogen cyanide react to yield acetone cyanohydrin the latter is then reacted with an excess of concentrated sulfuric add to form methacrylamide sulfate. In a later stage, methacrylamide is treated with excess aqueous methanol the amide is hydrolyzed and esterified, with formation of a mixture of methyl methacrylate and methacrylic acid. The ACH process offers economical advantages, especially in Europe, where large plants are in use - most of them have been in operation for decades. The process also suffers from drawbacks that have been the driving forces for the development of alternative technologies. 

These reasons often occur, of course. Refineries produce many by-products whose value as chemical raw materials far exceeds their value as fuels, if there are chemical markets available. Proximity to chemical plants often affords such markets. Chemicals used by refineries may be producible from refinery by-products (e.g., sulfuric acid from hydrogen sulfide). Research may yield chemical extraction or chemical production processes which afford economic advantages. 

Provides an economic advantage by allowing the use of high sulfur fuel while providing low sulfur dioxide emissions... 

Materials of Construction. The reactors and the first of the two heat exchangers are lined with copper to prevent corrosion. Since the small amount of acid carried over is neutralized, the other parts of the reaclion system and the purification unit are constructed of steel. One of the economic advantages of the direct hydration process over the sulfuric acid process is the use of steel in a large part of the plant. 

The characteristics of the process wastewaters from the manufacture of plastic and synthetic materials are shown in Table 17. The plastic and synthetic materials industry is typically a continuous year-round operation. Because it is technically and economically advantageous, many hrms manufacture several different, but related chemical products at one location. For example, a typical complex makes ethylene, polyethylene, sulfuric acid, ethyl chloride, ammonia, nitric-acid and phosphoric acid. 

Conventional acid gas removal processes produce purified coal gas and a concentrated acid gas. The H2S and COS in this low-pressure acid gas stream convert easily and efficiently to high-value liquid elemental sulfur. Sulfur recovery processes are commercially well-proven technologies that the oil, chemical, and natural gas industries have used extensively for over 50 years. In fact, U.S. oil refineries have been required to operate their sulfur plants with over 99.8% sulfur recovery for many years. The conversion of H2S to sulfur in coal gasification processes has a number of technical and economic advantages over sulfur recovery from SOj in direct coal combustion processes. 

Any hydrogen cyanide contained in the gas is absorbed quantitatively and converted to ammonium thiocyanate. In order to avoid losses of sulfur caused by this reaction, the hydrogen cyanide may be removed from the gas before it enters the desulfurization plant, and converted to alkali ferrocyanide. This procedure is economically advantageous, since the ferro-cyanide can be used as makeup to replace the iron-blue" lost with the wet sulfur. 

The Thylox process offered some economic advantages over processes previously discussed in this chapter. The consumption of alkali due to thiosulfate formation was reduced markedly, and the sulfur was produced in a much more valuable form. Estimated operating requirements for a plant treating 5 million cu ft/day of refinery gas containing 1,000 grains hydrogen sulfide/100 cu ft were reported by Dunstan (1938), and are shown in Table 9-4. 

Sulfur Compounds. Various gas streams are treated by molecular sieves to remove sulfur contaminants. In the desulfurization of wellhead natural gas, the unit is designed to remove sulfur compounds selectively, but not carbon dioxide, which would occur in Hquid scmbbing processes. Molecular sieve treatment offers advantages over Hquid scmbbing processes in reduced equipment size because the acid gas load is smaller in production economics because there is no gas shrinkage (leaving CO2 in the residue gas) and in the fact that the gas is also fliUy dehydrated, alleviating the need for downstream dehydration. 

Application to solid polymer/additive formulations is restricted, for obvious reasons. SS-ETV-ICP-MS (cup-in-tube) has been used for the simultaneous determination of four elements (Co, Mn, P and Ti) with very different furnace characteristics in mg-size PET samples [413]. The results were compared to ICP-AES (after sample dissolution) and XRF. Table 8.66 shows the very good agreement between the various analytical approaches. The advantage of directly introducing the solid sample in an ETV device is also clearly shown by the fact that the detection limit is even better than that reported for ICP-HRMS. The technique also enables speciation of Sb in PET, and the determination of various sulfur species in aramide fibres. ETV offers some advantages over the well-established specific sulfur analysers very low sample consumption the possibility of using an aqueous standard for calibration and the flexibility to carry out the determination of other analytes. The method cannot be considered as very economic. 

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