[Background and Overview][1][2]
Molybdic acid usually refers to orthomolybdic acid, also known as paramolybdic acid and metamolybdic acid. Molecular formula H2MoO4, white or light yellow hexagonal crystal. Relative density 3.12, it loses one molecule of water when heated to 70℃. The molecular formula of water is H2MoO4·H2O, yellow monoclinic crystal, relative density 3.11 (15/4℃). Both are slightly soluble in cold water and dilute acid, and easily soluble in hot water, ammonia and sodium hydroxide solution. Add nitric acid to the hot ammonium molybdate solution until pH=3-4, and precipitate out. Very pure molybdic acid can be obtained by hydrolysis of molybdenum oxychloride. Molybdic acid and its salts are used to prepare metal molybdenum, catalysts, chemical reagents, medicines, electroplating colorants, oil paints, mordants, etc.
Phosphomolybdic acid, chemical formula is H4MoO7P, CAS is 12026-57-2, molecular weight is 242.96100. Phosphomolybdic acid, also known as dodecamolybdic acid, or PMA for short, is a yellow-green inorganic compound and a heteropoly acid. Phosphomolybdic acid is soluble in water and polar organic solvents (such as ethanol). Phosphomolybdic acid hydrate is a yellow solid containing 28 water molecules. Phosphomolybdic acid is a highly efficient oxidant and has rapid multi-electron reversible oxidation-reduction properties under mild conditions. Therefore, it has become an important catalyst and is widely used in organic synthesis, oxidation processes of organic matter, corrosion inhibitors, and non-carbon fuels. in battery. In addition, it also has the characteristics of photochemical reaction, which can absorb the energy in light and convert it into chemical energy. At present, there are no reports at home and abroad about carbon fuel cells that introduce phosphomolybdic acid as the medium, and the use of phosphomolybdic acid as the medium for carbon indirect electro-oxidation can react under light conditions without the need for additional heating devices.
[Application][3][4]
Phosphomolybdic acid is an important catalyst and is widely used in organic synthesis, oxidation processes of organic matter, corrosion inhibitors, and non-carbon fuel cells. In addition, it also has the characteristics of photochemical reaction, which can absorb the energy in light and convert it into chemical energy. Application examples are as follows:
Preparation of cyclohexene catalyzed by phosphomolybdic acid: The preparation of cyclohexene is one of the classic experiments of basic organic chemistry in universities. Concentrated sulfuric acid is generally used to catalyze the dehydration of cyclohexanol to prepare cyclohexene. In order to establish a green synthesis method of cyclohexene, solid heteropolyacid-phosphomolybdic acid was used to catalyze the dehydration reaction of cyclohexanol. Add a certain amount of cyclohexanol and 3 mol% phosphomolybdic acid catalyst into a round-bottomed flask equipped with a spiny fractionating column and a straight condenser, place the reactant in an oil bath and heat it to 165-175 °C to evaporate cyclohexene. and water mixture. After the reaction is terminated, the catalyst can continue to efficiently catalyze the dehydration of cyclohexanol to cyclohexene without any treatment. The phosphomolybdic acid catalyst can be recycled more than three times without deactivation. This method has the advantages of high catalytic efficiency, recyclable catalyst, and synthetic Green and other characteristics.
In addition, because phosphomolybdic acid is easily soluble in water and difficult to recover, it is difficult to reuse the catalyst. Therefore, in practical applications, it is often loaded on some carriers. At present, inorganic carriers such as activated carbon and SiO2 are widely used. Since the interaction between these carriers and phosphomolybdic acid is weak, phosphomolybdic acid is easily dissolved and lost during use. Certain polymers can produce a relatively strong interaction with phosphomolybdic acid and can be used as carriers, which is gradually becoming a research hotspot. However, how to make phosphoaluminate acid evenly dispersed in the polymer matrix and how to increase the Its specific surface area promotes better performance of its photocatalytic performance, which is the main problem faced by polymer-loaded phosphomolybdic acid. Some studies have provided a preparation process that can not only stabilize the existence of phosphomolybdenum acid in the carrier, but also increase the specific surface area and disperse it evenly after being loaded. Polyacrylic acid and polyvinyl alcohol are selected as the polymer matrix, and phosphorus molybdenum is added. The acid is prepared into a homogeneous spinning solution, and electrospinning technology is used to prepare phosphomolybdic acid/polyacrylic acid/polyvinyl alcohol composite fibers to overcome the above-mentioned shortcomings in the prior art. The following Dow Corning emulsion technology solution is adopted: the preparation process of phosphomolybdic acid/polyacrylic acid/polyvinyl alcohol composite fiber, including the following steps:
1) Dissolve a certain amount of polyacrylic acid in absolute ethanol and stir at room temperature for 30 minutes to obtain a clear solution;
2) Dissolve a certain amount of polyvinyl alcohol in formic acid and stir at room temperature for 30 minutes to obtain a clear solution;
3) Mix the same volume of the above two solutions, add a certain amount of phosphomolybdic acid, and stir at 50°C for 1 hour to obtain a clear spinning solution;
4) Use a syringe with a needle to extract 1ml of spinning solution, place it on a micro-injection pump, adjust the spinning voltage, flow rate, and receiving distance coating additives for electrostatic spinning to obtain aluminophosphate/polyacrylic acid /polyvinyl alcohol composite fiber.
[References]
[1] Wang Yin. Preparation, modification and photocatalytic performance of silver molybdate/lead molybdate composite materials. Huazhong Agricultural University 2017-06-01
[2] Yin Jinling, Liu Jia, Wen Qing, et al. Phosphomolybdic acid as carbon indirect electrooxidation medium for low-temperature carbon fuel cells [J]. Acta Physica Sinica, 2017, 33(2): 370-376.
[3] Lan Jirong, Hu Xiaoyun, Chen Yu, et al. Research on green organic synthesis——Preparation of cyclohexene by phosphomolybdic acid catalysis[J]. Research & Exploration in Laboratory, 2015, 34( 10).
[4] Zhang Zhiming; Li Tingting; Liu Ce. Preparation process of phosphomolybdic acid/polyacrylic acid/polyvinyl alcohol composite fiber. CN201310422034.5 ��Application date 2013-09-07
