Alkaline Integrity Method for R&D of Automotive Stop System Dryers

Kaolin was used for the kaolin selection and purification test. It was the original ore-purifying soil of China Kaolin Corporation. The process route is as follows: The three-stage cyclone of raw ore crushing pulp is selected and filtered to dry milling. Sample A is the ore of Yangdong Mine and Taoyuan Mine. The crystal structure of the mineral is mainly tubular. The B-form is the original ore of Yangxi Mine. The crystal structure of the mineral is dominated by flakes. Sample composition analysis results.

Experimental Materials and Equipment Kaolin samples: A and B samples. Instruments and equipment: Sealed reactor, stainless steel; Extrusion machine, stainless steel; Constant temperature tank, Shanghai Instrument Factory production; Muffle furnace, China Experimental Electric Furnace production; precision temperature controller, Shanghai Medical Instrument Factory production.

Sample preparation: Weigh 20 g of kaolin sample and a certain amount of NaAlO2 and water glass, mix thoroughly, add about 10 ml of water, mix evenly, and then use a extruding machine to form the squeezing bar. Then, the sample is dried at 100 hrs for 24 h and then put into the muffle. The furnace was calcined at 500 for 810 h. The baked sample was placed in a stainless steel sealed reactor and 200 ml of 20% NaOH was added. The reactor was sealed, placed in an oven, and subjected to pressure and crystallization at 120°C for about 10 hours. Take out the reactor, remove the excess lye, remove the crystallized sample, and then wash it to neutrality, and finally activate the sample at 100 for 4 hours to obtain a desiccant sample.

The process adopts the process route of natural kaolin molding-roasting into granules and crystallization in NaOH solution. Different from the traditional process, raw materials such as drying, grinding and sifting are avoided, and the raw material particles after roasting have considerable strength enough to meet the requirements of the handling process. After the crystallization is finished, the process of washing and drying the 4A molecular sieve particles is much simpler than the powder, but the crystallization conditions are different. The kaolin raw material that we use is a kind of porous amorphous material, which is a mixture of Al2O3 and SiO2 and has a relatively high activity. When it comes into contact with the NaOH solution, the latter invades the entire particle interior through its pores. First alkali dissolves Al2O3 and SiO2 in the inner wall of the hole, 14 Page 2

A silica-alumina gel forms. Between the gel and the solid phase, the solubility is balanced. When heating. The increase of the solubility of the solid phase increases the concentration of silicate, aluminate and aluminosilicate ions in the liquid phase, and strengthens the polycondensation between ions, and when it reaches a certain level, it begins to crystallize. Since the solubility of the 4A molecular sieve crystals is smaller than that of the gel phase, the balance is destroyed and the dissolution crystallization will proceed until all the raw materials are dissolved. Since the crystallization is performed inside the entire raw material particle, the crystallized 4A molecular sieve crystal grains are congested in a small space, forming a structure in which the crystal grains are embedded with each other. Therefore, the higher the crystallinity, the higher the particle strength, and reflect the degree of crystallinity and the magnitude of the strength from the water absorption.

Performance tests include static water adsorption rate tests, phase analysis (XRD), and crush strength tests. XRD phase analysis of the sample: The test spectrum shows that, in the case of unpressurized crystallization, although there is an additive in the sample, the crystal phase does not change much with respect to the kaolin raw material. On the other hand, the XRD pattern of the sample containing the additive and 20% alkali under pressured crystallization conditions shows that a new crystal phase (relative to the kaolin raw material) has been produced, and a characteristic peak that is different from other silicon aluminum compounds has emerged ( At d=47), coincides exactly with the characteristic peak of the 4A molecular sieve (d=47). The eight-strength line of the core is basically in line with, and it can be considered that the desiccant sample has already formed a 4A molecular sieve crystal phase, and its molecular formula is found to be: Na12Si12O48XH2O. A 75% alkali treated crystallization-containing additive agent sample, and its crystal phase ratio Kaolin raw materials have not changed, so it can be considered: in the formation of kaolin 4A molecular sieve crystallization process, the alkali concentration is a very important parameter, below a certain concentration, there is no crystallization conditions. In the sample without additive, although it was also subjected to pressure crystallization and 20% alkali treatment, the characteristic peak of the 4A molecular sieve did not appear in the phase diagram. However, the crystal phase of the kaolinite phase material in this phase diagram has been greatly changed, and its structure is all Na4Al3Si3O12. Both the experiment and the above analysis show that the 4A molecular sieve structure can only be formed under the condition that the additive is added and the pressure is homogenized at the same time.

Results and discussion Water absorption of blank samples: A (powdery), 12%; B (powdered), 163%; A (bar), 72%; B (bar), 9%. As can be seen, A Samples B and B have a certain degree of water adsorption capacity when they are powdery; however, their water absorption rate drops sharply after molding. Therefore, A and B samples as desiccants for automotive brake systems are far from the required requirements in terms of adsorption capacity and strength, and must be studied to improve their performance.