Molybdenum is a refractory metal. It is related to the progress of many high-tech fields, but also to the sustainable development of many economic sectors, such as the steel industry, petrochemical industry and so on. In recent years, the application of molybdenum is increasing rapidly, and it is becoming more and more prominent as an important non-renewable resource. Molybdenum oxide is the most important compound of molybdenum. If a total of 160,000 tons of molybdenum were consumed in the world in 2005, and the average molybdenum content was 52%, that is, about 310,000 tons of molybdenum concentrate was consumed. In this way, at least 98% of the molybdenum concentrate, that is, about 300,000 tons of molybdenum concentrate, should be converted to molybdenum oxide before application.
In application, molybdenum oxide is a terminal product, is also a kind of intermediate product, molybdenum oxide is environmentally friendly goods, in the use of various molybdenum oxide process need not worry about its short-term and long-term harm to the ecological environment. Industrial molybdenum oxide is the most widely used product of molybdenum oxide series. Traditional industrial molybdenum oxide, whether bottled or canned, usually contains 57% molybdenum. The industrial molybdenum oxide produced by most manufacturers in China contains less than 57% molybdenum. Molybdenum oxide containing Mo57% still contains a large number of impurities such as copper, lead, phosphorus, calcium, arsenic and silicon, molybdenum oxide phase in industrial molybdenum oxide, there are MoO3, MoO2, Mo3O8 and Mo8O11 low molybdenum oxides, as well as copper, iron and calcium molybdate.
With the progress of science and technology, the function of experimental testing equipment is deepening. The physical and chemical properties of molybdenum oxide produced by traditional methods are difficult to meet the requirements of molybdenum industry development. In addition, scientists have a new understanding of the properties, structure and other aspects of molybdenum oxide. In particular, some prospective studies have found that many molybdenum oxides show some new properties.
Molybdenum oxide is known as molybdenum trioxide (MoO3). It is an important intermediate product in the process of molybdenum purification. Specific production process: Molybdenum concentrate is treated by chemical ammonia leaching process, producing ammonium molybdate first and then secondary ammonium molybdate. Calcination of ammonium paramolybdate produces molybdenum trioxide (99.95% purity). Molybdenum oxide can be used as additive to make steel directly or as raw material to make molybdenum metal powder.
classification
1. Highly soluble molybdenum oxide
In 2001, the research team at Endako, a primary molybdenum mine in Canada, developed what is called HighsolubemolyOxide. Its appearance was immediately favored by many manufacturers of molybdenum chemicals. It is reported that in 2002, most of the high-quality molybdenum concentrate produced by the mine was processed into highly soluble molybdenum oxide. In 2003, nearly 5000t molybdenum was produced and processed into this product, which was used to process various molybdenum chemicals, such as molybdate, molybdenum catalyst, molybdenum lubricant, etc., which consumed more than 50% of the total output of molybdenum.
2. Industrial molybdenum oxide
The traditional industrial molybdenum oxide production method is to oxidize and roast molybdenum concentrate by rotary kiln or multi-bore furnace. GunterBauer produces industrial molybdenum oxide from high pressure molybdenum oxide concentrate. Reaction kettle in the process of discharging by filtering will be part of the filtrate back to high pressure reaction kettle, this part of the circulating fluid to the kettle in molybdenite slurry to provide large amounts of heat energy, which can ensure the kettle in the required quantity of heat, plus reaction is exothermic reaction, oxygen pressure reaches 2 mpa in kettle, for most of molybdenite oxidation molybdenum trioxide. The process flow is shown in figure.
3. Molybdenum oxide pressing block
Molybdenum oxide briquetting (MolybdenumOxidebriquettes) is all kinds of molybdenum alloy steel, such as the low alloy steel, cast iron, cast steel, alloy steel and stainless steel alloy additives, can be widely applied. KennecotHoldingsCo of kennicott copper company in the United States has made a detailed study of the production method of molybdenum oxide block, with a total of five formulations. Using chemically pure molybdenum trioxide as raw material, the fineness of the material is as follows: 5-10 μm10%, 10-16 μm50%, 25-50 μm80%, 35-70 μm70%.
4.α -molybdenum trioxide
α -MOO3 is an excellent smoke suppressor. Compared with iron compounds (ferrocene, ferric oxide), copper compounds (copper oxide), metal hydroxide (aluminum hydroxide and magnesium hydroxide), zinc borate and other smoke suppressor agents, α -Moo3 and ammonium octabolybdate have the best smoke suppressor effect. PVC combustion and smoke emission is mainly related to aromatic compounds such as benzene produced in the pyrolysis process. The higher the content of these compounds is, the greater the smoke emission from combustion. α -MOO3 can promote the crosslinking reaction between molecules in the early stage of PVC pyrolysis to generate carbonates. α -Moo3 is usually prepared by evaporative crystallization of molybdate.
Chemically pure molybdenum trioxide
Chemically pure molybdenum trioxide (CGMo) contains MoO3>99.95%, particle size ≥5μm, bulk density >0.8g/cm3. Molybdenum trioxide used as a catalyst has a finer particle size. The improved POX-MOSX method (high pressure oxidation solvent extraction method) was used to prepare the content of MoO3>99.95%, S0.0001%, P0.0001%, K0.0008%, Al<0.0001%, CA 0.0005%, CO 0.0001%, Mg0.0005%, PB 0.0001%, Sn0 .0001%, Ti0.0001%, Fe0.0001%, Cu0.0005%, Zn0.0001%, V0.0001% and ZR 0.0001% chemically pure molybdenum trioxide, its raw material is low grade molybdenum intermediate product containing Mo15% ~ 17%, molybdenum recovery is 98.5%. Molybdenum trioxide is also used to produce organic molybdenum compounds.
6. Nano-sized molybdenum trioxide
1) Nanometer molybdenum trioxide band
NanotrimolyOxideBelt, the section of the belt is about 30 ~ 300nm, 5 ~ 50mm thick, 2 ~ 4μm long. The electron microscope image is shown below.
The preparation method of the nanomaterials is to put polished silicon wafer in the far infrared heating furnace, and then place molybdenum foil of 15mm×15mm×0.2mm on the silicon wafer. The furnace is heated to 850℃ for 20min, and the molybdenum foil is oxidized into molybdenum trioxide. X-ray diffraction analysis showed that the molybdenum trioxide was rhombic crystal system with lattice constants a=0.398nm and B =0.13nm. Then the nano-molybdenum trioxide was carried into the discharge test. Aluminum rod with cross section of 1mm2 was used as anode and molybdenum trioxide strip as cathode. The voltage ranged from 0 v to 1100V. The spacing between anode and cathode was 45μm, 50μm, 60μm and 80μm, respectively.
2) Nano-sized molybdenum trioxide
Nano-sized molybdenum trioxide with diameter of 30nm and length of 80 ~ 100nm can be produced by sublimation-quench method. The raw materials are 24 ~ 260μm molybdenum oxide. Nanometer molybdenum trioxide is the catalyst for fluorination reaction, and alcohol oxidation is the catalyst for aldehydes. Recently, CyprusAmax nanosized Molybdenum trioxide was reduced by hydrogen to produce molybdenum powder with a specific surface of 2.5m2/g.
7. Molybdenum dioxide
Molybdenum dioxide is a brownish purple crystal, monoclinic, containing Mo74.99%, density 6.44g/cm3. As early as 1982, someone tried to react molybdenite and molybdenum trioxide vapor in rotary kiln to produce molybdenum dioxide, but the reaction was difficult to control and the product was not pure. Nowadays, the method of preparing molybdenum dioxide is still reducing ammonium dimolybdate or chemically pure molybdenum trioxide by hydrogen or reducing the mixture of ammonium dimolybdate and molybdenum trioxide by hydrogen. There is also hydrogen reduction of ammonium paramolybdate, reduction in a rotary furnace, can also be ammonium diamolybdate added in a boat in a multi-tube furnace.
