Pressure acidizing

Aldehydes are important products at all pressures, but at low pressures, acids are not. Carbon monoxide is an important low pressure product and declines with increasing pressure as acids increase. This is evidence for competition between reaction sequence 18—20 and reaction 21. Increasing pressure favors retention of the parent carbon skeleton, in concordance with the reversibiUty of reaction 2. Propylene becomes an insignificant product as the pressure is increased and the temperature is lowered. Both acetone and isopropyl alcohol initially increase as pressure is raised, but acetone passes through a maximum. This increase in the alcohoLcarbonyl ratio is similar to the response of the methanoLformaldehyde ratio when pressure is increased in methane oxidation. 

An extensive pesticide properties database was compiled, which includes six physical properties, ie, solubiUty, half-life, soil sorption, vapor pressure, acid pR and base pR for about 240 compounds (4). Because not all of the properties have been measured for all pesticides, some values had to be estimated. By early 1995, the Agricultural Research Service (ARS) had developed a computerized pesticide property database containing 17 physical properties for 330 pesticide compounds. The primary user of these data has been the USDA s Natural Resources Conservation Service (formerly the Soil Conservation Service) for leaching models to advise farmers on any combination of soil and pesticide properties that could potentially lead to substantial groundwater contamination. 

Pressure-acid leaching was used to extract cobalt from Blackbird mine ores before its closing in 1974. The result was a very fine cobalt powder which was subjected to a seeding process to produce cobalt granules. Leaching methods are also used in the refinement of lateritic ores. 

Oxidative pressure acid leaching is also applied to copper-nickel mattes. Nickel recoveries of >99% are obtained when leaching is carried out at 135-160 °C at oxygen partial pressures of 140-350 kPa,... 

Kyle, J. H. Pressure acid leaching of Australian nickel/cobalt laterites. Publ. Australas. Inst. Min. and Metall. 1996, 6/ 96, 245-250. 

Sole, K. C. Solvent extraction of copper from high concentration pressure acid leach liquors. International Solvent Extraction Conference, Cape Town, South Africa, Mar. 17-21, 2002, 1033-1038. 

AEA Technology Modified reverse assembly (high-pressure wash, new rocket shearing). Electrochemical oxidation using silver ions in nitric acid (SILVER II ). Treated with SILVER II process. High-pressure acid wash thermal treatment to 5X.b Shredded and treated with SILVER II process. 

The equation above suggests that one approach would be lo use a pore liquid that has a low surface tension. In fact, with a pore liquid that has a sufficiently small surface tension, ambient pressure acid catalyzed aerogels with comparable pore volume and with bulk density to those prepared with supercritical drying (see Big. 1) have been produced. 

The air or 0 supply [1] generally comes from tanks under slight pressure. Acidic impurities and water vapour are removed in [2],... 

Although biochemical reactions resemble ordinary chemical reactions, they differ in some important ways. Chemical reactions are frequently carried out in nonaqueous solvents, using elevated temperatures and pressures, acids or bases, or... 

When the low pressure acid gas stream reaches the permeate tube at the center of the element, the acid gas "permeate" is removed. 

FEP resists most chemicals and solvents, even at elevated temperatures and pressures. Acid and bases are not absorbed at 200°C (392°F) and exposures of 1 year. Organic solvents are absorbed only a little, typically 1% or less, even at elevated temperatures and long exposure times. The absorption does not affect the resin and its properties and is completely reversible. The only chemicals reacting with FEP resins are fluorine, molten alkali metal, and molten sodium hydroxide.48... 

The commercial importance of this metal was first recognized in 1950s when its high strength/density ratios were found attractive in aerospace applications. The corrosion resistance in a variety of conditions led to its use in wet chlorine gas coolers for chlor-alkali cells, chlorine and chlorine dioxide bleaching equipment in pulp/paper mills, and reactor interiors for pressure acid leaching of metallic ores. The metal and its alloys were used in seawater power plant condensers, with over 400 million feet installed in application.65,66 The most commonly used alloys and their composition are given in Table 4.48. 

PAL II [Pressure Acid Leach] A process for extracting nickel from laterite ores. Operated in Australia. 

Enzyme-catalyzed reactions may be carried out to the degree desired at temperatures lower than those used in the acid-catalyzed reactions this is important, because the need for the expensive reactors normally used in the high-temperature, high-pressure, acid-catalysis systems is obviated. 

Alami, I., W. Monnery, and W. Svrcek. 2005. Model predicts equilibrium water content of high-pressure acid gases. Oil Gas J. (July 11). 

In a well designed acid gas injection scheme, hydrates should not be a problem in normal operation. However, during start up, hydrates often occur in both pipelines and wells. This is because there is residual water left over from hydrotesting of the pipeline. Wells may have water in them from injection testing. When the high pressure acid gas comes in contact with the residual water, it will quickly freeze. 

PEP resists most chemicals and solvents, even at elevated temperatures and pressures. Acid and bases are not absorbed at 200°C (392°F) and exposures of 1 year. 

Mermet, J.M. Focused-microwave-assisted reactions atmospheric-pressure acid digestion, on-line pretreatment and acid digestion, volatile species production, and extraction. In Kingston, H.M., Haswell, S.J. (eds.) Microwave-Enhanced Chemistry. Fundamentals, Sample Preparation, and Applications. ACS, Washington, DC (1997)... 

Ravey, M., Farberman, B., Hendel, I., Epstein, S., Shemer, R. A vessel for low-pressure acid dissolution of mineral and inorganic samples. Anal. Chem. 67, 2296-2298 (1995)... 

Internal Standard Addition. An example of the use of an internal standard for phase quantification is the recent work by Madsen et in their study of the reaction mechanism of pressure acid leaching (PAL) of nickel laterite ores. This was an in situ study in which nickel laterites were reacted with sulfuric acid at elevated temperature and hydrothermal pressure to prevent the boiling of the acid. The purpose of pressure acid leaching is to dissolve any nickel-bearing phases into the acid and subsequently treat this with solvent extraction for the recovery of the nickel. There has been much ex situ work done to the reaction mechanisms of this system, but these studies have relied on the cooling of the system prior to any analytical work. 

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