Temperature Iron Phosphating

The tertiary metal phosphates are of the general formula MPO where M is B, Al, Ga, Fe, Mn, etc. The metal—oxygen bonds of these materials have considerable covalent character. The anhydrous salts are continuous three-dimensional networks analogous to the various polymorphic forms of siHca. Of limited commercial interest are the alurninum, boron, and iron phosphates. Boron phosphate [13308-51 -5] BPO, is produced by heating the reaction product of boric acid and phosphoric acid or by a dding H BO to H PO at room temperature, foUowed by crystallization from a solution containing >48% P205- Boron phosphate has limited use as a catalyst support, in ceramics, and in refractories. 

Fig. 15.4 Effecl of heating on phosphate coatings for 16 h at various temperatures, showing loss of water of hydration. Curve A zinc phosphate, B iron phosphate and C iron manganese phosphate (courtesy y./.S./., 170, II (1952))...

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]. 

The reaction was performed over the iron phosphate catalyst by changing the feed rate of oxygen from zero to 350 mmol/h, while fixing the sum of feed rates of oxygen and nitrogen at 350 mmol/h. The feed rate of pyruvic acid was fixed at 10.5 mmol/h. The yields of citraconic anhydride obtained at a temperature of 230°C and a short contact time of 0.52 s (amount of catalyst used = 2 g) are plotted as a function of the feed rate of oxygen in Figure 3. 

Effects of reaction temperature on the reaction over iron phosphate catalyst... 

As may be seen in Figures 5 and 6, when iron phosphate is used as the catalyst, the selectivity is dependent largely on the reaction temperature. Therefore, the activation energy for the citraconic anhydride formation is considered to be much lower than that for the acetic acid formation. Indeed, the selectivity to acetic acid decreases steadily with a decrease in the temperature. However, the selectivity to citraconic anhydride shows a maximum at about 200 C. Possibly, the vaporization of pyruvic acid may become difficult at temperatures below 200°C. 

The quality observed with "Mannich" derivatives of polyvinylphenol is affected by the concentration, time of treatment, temperature, pH, and whether or not a final deionized water rinse is used. The results shown in Tables I-III below represent evaluations conducted for poly-[methy1(2-hydroxyethy1)amino]methyl-4-vinylphenol, as shown in Structure I. Post-treatments based on polyvinylphenols overcome deficiencies observed with previous chrome-free rinses, since these systems are reactive and a final water rinse actually improves performance as is illustrated in Table I where the new non-chrome system is evaluated on Bonderite 1000, an iron phosphate conversion coating, as a function of concentration with and without a final water rinse. It is also... 

POLYVINYLPHENOL POST-TREATMENT IRON PHOSPHATE TEMPERATURE - PH (TREATMENT TIME - 30 SECONDS)... 

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... 

Iron phosphate CBPCs may provide inexpensive means to recycle these waste streams. Iron mine tailings and red mud may be recycled in building components by fabricating ceramics from them at ambient temperature. Iron-rich swarfs may be recycled if a way is found to solidify these fines into pellets and feed them back into a blast furnace. Thus, iron phosphate CBPCs facilitate solidification of iron-rich waste streams and recycling. 

The product is bluish grey in appearance, permanent in air, but, when heated to a high temperature, it oxidises to phosphorus pentoxide and an iron phosphate, the former being evolved as fumes. Density 5-04. It is not magnetic.11... 

The products of such reactions depend upon the pressure, temperature, pH, phosphate, and cation concentrations, and may be difficult to predict or rationalize. For example, the equation (3) produces an acid phosphate and a phosphate hydroxide. Microporous aluminophosphates and related phases (see Section 5.1.2) are prepared in hydrothermal bombs using hydrated cations or molecular templates such as organic amines or ammonium cations to direct the porous framework. Many new structures with metal phosphate chains, layers, or three-dimensional networks have been prepared hydrothermally in recent years, for example, templated vanadium phosphates and iron phosphates. ... 

One laboratory did not observe any difference in the results obtained with and without addition of V2O5. However, the pyrohydrolysis method as used by this laboratory was suspected not to be sufficient for stripping off fluoride. It was suspected that V2O5 would not completely destroy the Christmas tree balls at 1250°C a complete fusion was assumed to be achieved at 1400-1500°C. However, at the temperature chosen the duration of the treatment and the amount of water used in the reaction became important the volume of water was found to be too small in this case (ca. 100 mL) 500 mL should be used instead. The 20 min chosen were found to be insufficient (60 min would be more suitable). Finally, it was said that iron phosphate would have been more appropriate that V2O5 under the condition chosen. The sets of results were consequently withdrawn. 

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 %. 

Effect of calcination temperature on the catalytic performance of iron phosphate... 

As is seen in Figure 3, use of a low temperature of 240°C is beneficial to the selectivity to glyoxylic acid. The iron phosphate catalyst shows a relatively high oxidation activity even at a low temperature of 240°C. This suggests that the redox cycles on the surface takes place rapidly. However, the rate of re-oxidation of reduced bulk iron phosphate should be very slow at a low temperture of 240°C. It is therefore necessary to avoid the reduction of bulk in order to keep the activity. It is also noted that the deactivated catalyst was fully regenerated by heat-treatment at about 450°C in stream of air. 

The performance exhibited hy these catalysts was surprisingly good (above all in terms of selectivity to MAA), remarkably better them that reported in literature for heteropolycompoeinds wiihout vanadium (1,2,4,9). The reference add showed a slightly lower activity, but above all a lower selectivity to MAA. The best selectivities obtained were similar to those reported for iron phosphate-based catalyst (13) this system, however, operates at higher temperatures (400C). 

Soils contaminated with Pb may also be remediated by iron-based nanoparticles. Iron phosphate (vivianite) nanoparticles stabilized with CMC have been reported to reduce the toxicity-characteristic leaching procedure (TCLP) and physiologically based extraction test (PBET) bioaccessibility in calcareous, neutral, and acidic soils (84). While phosphate addition has been known since at least 1993 to immobilize Pb(II) in soils, phosphate addition can cause its own problems in that it easily leaches into surface and groundwaters, where it causes problems related to excessive nutrient input. CMC-vivianite nanoparticles release 50% less phosphate into the environment than more traditional phosphate soil amendments, partly because of the insolubility of vivianite. Unlike the PdNPs/S mixture, the Pb-sequestering reactions take place at ambient temperatures. At acidic pH values, the reaction sequence is as shown in Equations (20.5a) and (20.5b). 

There is some disagreement about how polyphosphates function as corrosion inhibitors. Generally accepted theory is that, in an aerated system, they cause formation of a protective surface film which contains both iron oxide and phosphorus, perhaps an iron phosphate. Polyphosphates will not work in a system that is devoid of oxygen, nor in a stagnant system. Polyphosphate corrosion inhibition required flow, to replace the iron-phosphate film as fast as it is removed or depleted. Polyphosphates are unstable and subject to problems in high temperature circuits, or where pH fluctuation occurs. Ecological considerations also are involved, because of possible pollution contributions of residual... 

Iron is readily attacked by orthophosphoric acid over a wide range of temperature and concentration. This attack involves the initial formation of sparingly soluble dihydrogen phosphate (12.32). As the pH rises in the vicinity of the metal snrface, insoluble monohydrogen phosphate is precipitated (12.33), and eventually tribasic iron phosphate may also form (12.34). 

Iron phosphate coatings are amorphous coatings and very thin (0.1-lgm ). The working solution contains primary sodium or ammonium phosphates, together with other ingredients which may include an oxidizing accelerator, and surfactants to combine degreasing with the chemical treatment. The pretreatments operate between pH 3 and 5.5 at temperatures... 

In [22], A1 Sakka et al., proposed a thermal model for cylindrical electric double-layer capacitors (EDLC), by performing specific techniques on the layer level. In [23] a methodology is proposed for simulation of the internal temperature of a cylindrical lithium iron phosphate battery cell. 

In the previous section, a thermal model has been proposed and a methodology has been illustrated for extraction of the model parameters. In this section, the experimental results are compared and analyzed with simulation results. Below a number of comparisons are illustrated at different working temperatures (40 °C, 25 °C, 10 °C, 0 °C). The comparison results are based, for the experimental results, on the 10 7t current rate at 80% SoC, and on the model as demonstrated in Figure 11.5 for the simulation results. The battery (lithium iron phosphate-based) has already been described. 

All lithium-ion (Li-ion) batteries require a BMS. This is due to the fact that all Li-ion batteries will fail if overcharged, completely discharged or operated outside their safe temperature window. Each Li-ion cell type has its own safe operating area, which makes it necessary to program the BMS accordingly. Figure 15.1 shows the safe operating area typical for a C/lithium iron phosphate cell. 

One of the issues we wanted to explore was the relative influence of tribological conditions and temperature on the reactions occurring between ZnDTP and the steel surface. It appears that while polyphosphates can be formed by purely thermal treatment at elevated temperatures, tribological conditions lead to the formation of simple iron phosphates and tough, short-chain polyphosphates (2.38). 

The tribological stress leads to the formation of poly(thio)phosphate tribofilms at all temperatures investigated, while in the non-contact areas only very thin thermal films were formed at 30 °C and 80°C. The contact pressure presumably leads to local frictional heating, which accelerates a chemical reaction of the adsorbed additives (see Fig. 13). Also, a purely tribochemical effect is likely at 30 °C, iron phosphate was found in the reaction layer, which is an indication that nascent iron, released because of wear, reacts with the phosphoryl groups and forms a component of the tribofilm. 

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