Iron:phosphate ratio

Citraconic anhydride (Methyl maleic anhydride) was found to be produced from pyruvic acid by an oxidative decarboxy-condensation. The best catalyst is iron phosphate with a P/Fe atomic ratio of 1.2. The presence of oxygen is required to promote the reaction. The main side-reaction is formation of acetic acid and CO2 by oxidative C-C bond fission. The best results are obtained at a temperature of 200°C. The yield of citraconic anhydride reaches 71 mol% at a pyruvic acid conversion of 98%. 

Pyruvic acid is the simplest homologue of the a-keto acid, whose established procedures for synthesis are the dehydrative decarboxylation of tartaric acid and the hydrolysis of acetyl cyanide. On the other hand, vapor-phase contact oxidation of alkyl lactates to corresponding alkyl pyruvates using V2C - and MoOa-baseds mixed oxide catalysts has also been known [1-4]. Recently we found that pyruvic acid is obtained directly from a vapor-phase oxidative-dehydrogenation of lactic acid over iron phosphate catalysts with a P/Fe atomic ratio of 1.2 at a temperature around 230°C [5]. 

An iron phosphate catalyst with a P/Fe atomic ratio of 1.2 used in this study was prepared according to the procedures described in the previous studies [6-8]. On the other hand, a V-P oxide catalyst with a P/V atomic ratio of 1.06 and pumice supported 12-molybdophosphoric acid (H3PM012O40) and its cesium salt (CS2HPM012O40) catalysts were the same as used in a previous study [9]. Pumice supported W03-based mixed oxide catalysts were the same as used in a previous study [10]. 

Typically, mammalian ferritins can store up to 4500 atoms of iron in a water-soluble, nontoxic, bioavailable form as a hydrated ferric oxide mineral core with variable amounts of phosphate. The iron cores of mammalian ferritins are ferrihydrite-like (5Fe203 -9H20) with varying degrees of crystallinity, whereas those from bacterioferritins are amorphous due to their high phosphate content. The Fe/phosphate ratio in bacterioferritins can range from 1 1 to 1 2, while the corresponding ratio in mammalian ferritins is approximately 1 0.1. 

The vapor-phase oxidation of lactic acid with air was executed using an iron phosphate catalyst with a P/Fe atomic ratio of 1.2. It was found that lactic acid is selectively converted to form pyruvic acid by oxidative dehydrogenation. The one-pass yield reached 50 mol% however, acetaldehyde, acetic acid, and CO2 was still formed, and the pyruvic acid produced decomposes over time to give acetic acid and C02. ... 

Oxidation has also been tried over iron phosphates with a P/Fe atomic ratios of 1.2, including FeP04, Fc2P207 and Fe3(P207)2, at 230 °C. The catalysts containing both Fe and Fe performed better than those with just one oxidation state present. The best results were 62% selectivity at 60% conversion. 

LDH LEU LIBD LAW LET LILW LIP LLNL LLW LMA LMFBR LOI LREE L/S LTA LWR Layered double hydroxide Low enriched uranium Laser-induced breakdown detection Low-activity waste Linear energy transfer Low- and intermediate-level nuclear waste Lead-iron phosphate Lawrence Livermore National Laboratory Low-level nuclear waste Law of mass action Liquid-metal-cooled fast-breeder reactor Loss on ignition Light rare earth elements (La-Sm) Liquid-to-solid ratio (leachates) Low-temperature ashing Light water reactor... 

Isolated phosvitin usually has two to three atoms of iron, with Fe/phosphate ratio about 1 50. Considerably larger amounts of Ca2+ and Mg2+ are bound [(Ca2+ + Mg2+)/phosphate =0.7]. It appears to have no known enzymatic or regulatory role. 

Another group of As-bearing minerals contains arsenic in the 5+ valence state as arsenate commonly substituting for the phosphate group. An unidentified As-bearing iron phosphate, usually associated with banded iron oxyhydroxide as veins or masses, has a P/As atomic ratio on the order of 4 (Belkin et al., 1997). Jarosite... 

Tables lO.l to 10.5 may be useful as an orientation and a source of specific information for sections in this chapter. Table 10.1 lists the inorganic nutrients in various foods. One of the more striking aspects of these data is the fact that potassium concentrations in plant foods are much higher than those of sodium. Another point, raised under calcium and phosphate, is that green leafy vegetables (broccoli) and dairy products (cottage cheese) are high in calcium, whereas meats have relatively low levels of this nutrient. The calcium/phosphate ratios of various fcKids are also discussed in this section. These ratios can be easily calculated from the data in the table. Food iron data from tw o sources are listed. Milk and milk products, which contain high levels of many nutrients, are very low in iron.

Glyoxylic acid was found to be produced by a vapor-phase oxidative dehydrogenation of glycolic acid over iron phosphate catalysts with a P/Fe atomic ratio of 1.2. The best results were obtained with iron phosphates freshly calcined at 400 to 450°C. Reduced iron phosphates showed a markedly lower activity. The optimum reaction temperature was about 240°C. The selectivity to glyoxylic acid was 74 mol% up to the glycolic acid conversion of about 70% the highest yield of glyoxylic acid was 56.5 mol% at the conversion of 80 %. 

Ferritin consists of a shell of protein subunits surrounding a core of ferric hydroxyphosphate. For some time the inorganic component of ferritin was thought to be attached to the surface of the protein (65). However, the demonstration that ferritin and apoferritin have the same electrophoretic mobilities and are precipitated equally well with horse ferritin antibody (66) together with electron microscopic evidence (67) clearly showed that the iron is concentrated in the middle of the apoferritin protein shell. The iron micelle has a diameter of 70—75 A whilst the protein shell has a diameter of the order of 120 A (67—70, 62). Somewhat lower values are found in dried preparations (71, 72). The micelle contains ferric iron, predominantly as (FeO.OH) but also with some 1—1.5% phosphate (4,50) and it seems that the iron phosphorus ratio is constant for ferritins of different iron content (52). The composition (FeO.OH) g. (FeO.OPOgHg) has been suggested (73, 74). The percentage of iron in the micelle on this basis is 57%. 

However, a certain fraction of the active material reacts with the surface phosphate groups of the support to inactive iron phosphate and molybdenum phosphate. The amount of metal phosphate depends on the specific surface area of the support and the surface concentration of phosphate groups. Both are influenced by the pH of precipitation of the support and by the Al/P ratio in the initial Al3+ and P04 solution. Although the formation of metal phosphate decreases the capacity of the absorbent towards the removal of H2S, the strong interaction with the support ensures a high thermal stability. 

Tricalcium phosphate, Ca2(P0 2> is formed under high temperatures and is unstable toward reaction with moisture below 100°C. The high temperature mineral whidockite [64418-26-4] although often described as P-tricalcium phosphate, is not pure. Whidockite contains small amounts of iron and magnesium. Commercial tricalcium phosphate prepared by the reaction of phosphoric acid and a hydrated lime slurry consists of amorphous or poody crystalline basic calcium phosphates close to the hydroxyapatite composition and has a Ca/P ratio of approximately 3 2. Because this mole ratio can vary widely (1.3—2.0), free lime, calcium hydroxide, and dicalcium phosphate may be present in variable proportion. The highly insoluble basic calcium phosphates precipitate as fine particles, mosdy less than a few micrometers in diameter. The surface area of precipitated hydroxyapatite is approximately... 

The relation between free phosphoric acid content and total phosphate content in a processing bath, whether based on iron, manganese or zinc, is very important this relation is generally referred to as the acid ratio. An excess of free acid will retard the dissociation of the primary and secondary phosphates and hinder the deposition of the tertiary phosphate coating sometimes excessive loss of metal takes place and the coating is loose and powdery. When the free acid content is too low, dissociation of phosphates (equations 15.2, 15.3 and 15.4) takes place in the solution as well as at the metal/solution interface and leads to precipitation of insoluble phosphates as sludge. The free acid content is usually determined by titrating with sodium... 

Mention has been made of the necessity for controlling the acid ratio of phosphating baths, particularly those of iron, manganese and zinc operating... 

How far the formulation of a phosphating bath influences The Ratio is not entirely clear. Nitrite alone or in combination with chlorate has been the most widely used accelerator system for many years but more recently nitrite-free chlorate/organic systems have been increasingly favoured. Low zinc systems in which the bath is starved of zinc to promote a high iron content in the coating, originally introduced in Japan, have become widespread. 

However, ferritins isolated from the bacterium Pseudomonos aeruginosa (Mann et ah, 1986) and from the chiton Acanthopleura hirtosa (St. Pierre et ah, 1990) have iron cores of limited crystallinity, despite having P Fe ratios of around 1 40, perhaps suggesting that core crystallinity is influenced by the rate of iron deposition as well as by the composition of the medium. The way in which phosphate may influence core development is discussed below. 

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