Tungsten Oxide

Theoretically, many of the carriers found at present can be used as the carriers of tungstophosphoric acid, but most of them use oxidants as the carriers of oxidants or are easy to decompose when alkali is azeotropic. At present, SiO 2 , HZSM-5 molecular sieve, Y-type molecular sieve, HP, HMS molecular sieve, worm like molecular sieve, activated carbon, silica gel and so on are the main carriers of phosphotungstic acid catalyst. At present, the main preparation methods of phosphotungstic acid include impregnation method, adsorption method and sol gel method. 1. Impregnation method The impregnation method is to dissolve tungstophosphoric acid in water, then impregnate the carrier with this solution and stir it. After a certain period of time, take it out for drying, and then obtain the supported tungstophosphoric acid catalyst. Or the active component is directly loaded on the carrier by physical mixing, hydrothermal dispersion, CO impregnation or ion exchange. However, there are some p...

Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. In China, there are three main methods for preparation of the blue tungsten oxide: APT closed calcination method, APT mild hydric reduction method and intrinsic reduction method. And the APT closed calcination method is the most used method. APT closed calcination method always keeps the furnace system with positive pressure in the heating process, preventing the air from entering the furnace. By this way, ammonia from APT pyrolysis splits into hydrogen and nitrogen. And in the weak reductive atmosphere, the blue tungsten oxide is produced. The entire process is confined in a rotary calciner. The usage and control of rotary calciner need cautious operation, as it is the main carrier of APT closed calcination process. Rotary hearth furnace is a rotary calciner with high automation, of which the ring-shaped bottom can be rotated. Generally it is divided into two sections to con...

Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. Compared with yellow tungsten oxide, blue tungsten oxide with its high activity, large surface area, easy doping, original crystalline shape is seen as an upgraded version of the Yellow tungsten oxide. Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. In China, there are three main methods for preparation of the blue tungsten oxide: APT closed calcination method, APT mild hydric reduction method and intrinsic reduction method. And the APT mild hydric reduction method is the most used method. The whole preparation process reacts in a multi-tube furnace of which the heating zone is divided into three parts. In the furnace tube, the heated APT•5H2O installed on the heat resistant boat is decomposed. Feeding a small amount of hydrogen into the furnace tube can keep the reducing atmosphere. Decomposed gas product and waste ...

Blue tungsten oxide is one of the most important raw materials for the manufacture of tungsten powder. Compared with yellow tungsten oxide, blue tungsten oxide with its high activity, large surface area, easy doping, original crystalline shape is seen as an upgraded version of the Yellow tungsten oxide and used. There are three main methods for preparation of the blue tungsten oxide: APT closed calcination method, APT mild hydric reduction method and intrinsic reduction method. And the APT closed calcination method is the most used method. In APT closed calcinations, ammonia escaping by thermal decomposition or a small amount of introduced ammonia gas is used as reducing agent. Characteristics of this method: thermal decomposition temperature fluctuates between 550℃-700℃, high yield and stable quality. Phase composition of blue tungsten oxide is 70% W 20 O 58  and 30%WO 3 . APT closed calcination method always keeps the furnace system with positive pressure in the heating pro...

CO, the product of incomplete combustion of carbon fuels and cracking reactions occur at high temperatures, oxidation reaction ect. has become one of the major sources of air pollution, which greatly threats human life and health and environmental protection. The body of CO maximum allowable limit is 10 -4 , while in Europe the provisions of the environment CO must not exceed 10 -5 . So, the detection and controlling of CO is becoming urgent, tungsten trioxide based gas sensor is considered to be the most promising sensor for detecting NO x , O 2  and NH 3  and other poison gases, due to its simple structure, low cost, high sensitivity and gas sensing.  This paper presents preparation method of   tungsten trioxide nanowire CO gas sensor which shows as follow: 1. Dissolve the weighed analytically pure sodium tungstate dihydrate (Na 2 WO 4 .2H 2 O) in an appropriate amount of deionized water, and taken out ice water bath, magnet...