Hydrogen, iron oxide reduced

The liquid-phase hydrogenation of -4-phenyl-3-buten-2-one (benzalace-tone) has been followed with gold supported on various forms of iron oxide, reduced at only 343 K the sequence of selectivities was... 

The iron carbide process is alow temperature, gas-based, fluidized-bed process. Sized iron oxide fines (0.1—1.0 mm) are preheated in cyclones or a rotary kiln to 500°C and reduced to iron carbide in a single-stage, fluidized-bed reactor system at about 590°C in a process gas consisting primarily of methane, hydrogen, and some carbon monoxide. Reduction time is up to 18 hours owing to the low reduction temperature and slow rate of carburization. The product has the consistency of sand, is very britde, and contains approximately 6% carbon, mostly in the form of Ee C. 

In atomization, a stream of molten metal is stmck with air or water jets. The particles formed are collected, sieved, and aimealed. This is the most common commercial method in use for all powders. Reduction of iron oxides or other compounds in soHd or gaseous media gives sponge iron or hydrogen-reduced mill scale. Decomposition of Hquid or gaseous metal carbonyls (qv) (iron or nickel) yields a fine powder (see Nickel and nickel alloys). Electrolytic deposition from molten salts or solutions either gives powder direcdy, or an adherent mass that has to be mechanically comminuted. 

In the Bnchamp process, nitro compounds are reduced to amines in the presence of iron and an acid. This is the oldest commercial process for preparing amines, but in more recent years it has been largely replaced by catalytic hydrogenation. Nevertheless, the Bnchamp reduction is still used in the dyestuff industry for the production of small volume amines and for the manufacture of iron oxide pigments aniline is produced as a by-product. The Bnchamp reduction is generally mn as a batch process however, it can also be mn as a continuous (48) or semicontinuous process (49). 

The largest consumer of coke is the iron and steel industry. In the United States, ca 600 kg of coke is used to produce a metric ton of steel. Japanese equipment and practice reduce the requirement to 400—450 kg. Coke is also used to gas from the char in one vessel. The reducing gas converts iron oxide to iron in the upper two stages of a second vessel. Steam is converted to hydrogen and reoxidizes the iron in two stages in the lower half of the vessel. 

Hydrogen production by SIP can be accomplished through direct and indirect employment of hydrocarbon feedstocks (e.g., NG). In the direct employment method, iron oxide directly reacts with methane or other hydrocarbons to produce the reduced form of iron oxide and methane oxidation products, according to the following generic reaction ... 

The subsequent reaction of the reduced iron oxide with steam regenerates the original oxidized form of iron oxide (i.e., magnetite) and yields pure hydrogen (mixed with unreacted steam) as follows ... 

After calcinations, the precipitated iron catalyst is composed of a mixture of iron oxide phases before activation. The exact nature of this phase is not critical for the discussion and will be referred to in general as an oxide phase. During activation the catalyst is subjected to a reducing environment that will lead to the formation of either metallic iron if pure hydrogen is used or some iron carbide if the reduction is done with either CO or syngas. During reduction with a gas... 

The active enzyme abstracts a hydrogen atom stereospecifically from the intervening methylene group of a PUFA in a rate-limiting step, with the iron being reduced to Fe(II). The enzyme-alkyl radical complex is then oxidized by molecular oxygen to an enzyme-peroxy radical complex under aerobic conditions, before the electron is transferred from the ferrous atom to the peroxy group. Protonation and dissociation from... 

H-Iron [Hydrogen iron] A process for making iron by reducing powdered iron oxides from ores or scrap, using hydrogen. A variation on the process will convert iron/titanium ores to a titanium concentrate and metallic iron. Developed by Hydrocarbon Research and United States Steel Corporation, and used in Pennsylvania and California. See also DR. 

TPR of supported bimetallic catalysts often reveals whether the two metals are in contact or not. The TPR pattern of the 1 1 FeRh/SiOi catalyst in Fig. 2.4 shows that the bimetallic combination reduces largely in the same temperature range as the rhodium catalyst does, indicating that rhodium catalyzes the reduction of the less noble iron. This forms evidence that rhodium and iron are well mixed in the fresh catalyst. The reduction mechanism is as follows. As soon as rhodium becomes metallic it causes hydrogen to dissociate atomic hydrogen migrates to iron oxide in contact with metallic rhodium and reduces the oxide instantaneously. 

This behavior, as well as complementary observations, can be explained on the basis of the reaction mechanism depicted in Scheme 5.3. The main catalytic cycle involves three successive forms of the enzyme in which the iron porphyrin prosthetic group undergoes changes in the iron oxidation state and the coordination sphere. E is a simple iron(III) complex. Upon reaction with hydrogen peroxide, it is converted into a cation radical oxo complex in which iron has a formal oxidation number of 5. This is then reduced by the reduced form of the cosubstrate, here an osmium(II) complex, to give an oxo complex in which iron has a formal oxidation number of 4. 

The biological classification schemes for bacteria and archaea are still being developed because of the rapid pace of new discoveries in genomics. The two most important phyla of marine bacteria are the cyanobacteria, which are photosynthetic, and the proteobacteria. The latter include some photosynthetic species, such as the purple photosynthetic bacteria and N2 fixers. Other members of this diverse phylum are the methanotrophs, nitrifiers, hydrogen, sulfur and iron oxidizers, sulfete and sulfur reducers, and various bioluminescent species. 

Some metals such as iron are reduced or oxidized by specific enzymes of microorganisms. Microbial metabolism generates products such as hydrogen, oxygen, H2O2, and reduced or oxidized iron that can be used for oxidation/reduction of metals. Reduction or oxidation of metals is usually accompanied by metal solubilization or precipitation. 

Fig. 4.1 outlines the Haber process to make ammonia. The reaction of nitrogen and hydrogen gases was first studied by Haber with Nemst and Bosch in the period 1904-1916. The two gases are adjusted to a 3 1 H2 N2 mixture and compressed to 2,000-10,000 psi (150-600 atm). The mixture is filtered to remove traces of oil, joined to recycled gases, and is fed to the reactor at 400-600°C. The reactor (Fig. 4.2) contains an iron oxide catalyst that reduces to a porous iron metal in the H2 N2 mixture. Ruthenium on... 

---