The Preparation And Research Of Aluminum Phosphate Molecular Sieves-Montmorillonite Compositeand Catalytic Material

MMT is a kind of natural minerals with the crystal structure of 2:1 layered silicates. Because of its good characters of swelling, cation exchange, water uptake, thixotropy, binding and absorption, it is widely used in Petroleum, metallurgy, water treatment and so on. MMT is a good load of solid acid catalyst substrate materials, therefore the researcher can prepare the catalyst which can be easily separated with easy activation of the organic catalyst using its expandability and cation exchange of interlayer. In this way, MMT absorbs cationic reagent to the layer and formats numerous layers of acid centers.MMT has many advantages above, but the thermal stability in high-temperature calcination in which the layer structure is easily collapsed and this weakness greatly inhibited the acid catalyst in the field of application and development.Aluminum phosphate (AlPO-n) is a series of microporous zeolite crystal structure of new molecular sieve materials, which is the first manual prepared by the non-silica zeolite framework structure. Aluminophosphate molecular sieve has a good thermal stability and hydrothermal stability. By changing the composition, the number of acid and acid can be modulated. It has a tunable pore size range, which is very beneficial for the selective adsorption of a specific size of the molecule and regular pore shape leads to the selective catalysis. With a detailed study, it will be more widely used in petrochemical and fine chemical industries as a catalyst, adsorbent. To improve the thermal stability and catalytic performance of solid acid catalyst, we succeed in the synthesis of aluminophosphates prepared material introduced into the layers of montmorillonite and prepare the MMT-Molecular Sieve Composite Materials using application of ion exchange, solvent-based and template methods. We effectively improve the MMT thermal stability of solid acid catalyst and the shape-selective catalysis by transforming the two-dimensional layered structure to the three-dimensional pore structure.Using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM) and other modern test methods, we systematically analyze and characterize the structure, microstructure and the cracking performance of MMT-aluminophosphates composites.In this paper, different hydrothermal environment (water system, alcohol system) is used to synthesize montmorillonite composites and systematically analyze the effect of different pillared agents, templates, raw materials and raw material ratio, pH value, soil/A1 ratio, dispersion way, feeding sequence, and the surfactant coating methods such as reaction time and temperature parameters for the final crystal structure, morphology and other characteristics.The results show that:in the X-ray diffraction spectra, there is an aluminum phosphate molecular sieve (AlPO4-5) and the montmorillonite standard XRD diffraction peaks while in the field emission scanning electron microscopy data, there is no appearance of hexagon columnar crystalline substance outside the montmorillonite layer. We can get the conclusion that aluminum phosphate molecular sieves in the synthesis process actually are embedded in the layer structure of montmorillonite.In the preparation process, the cationic surfactant is introduced into the interlayer of montmorillonite by ion exchange, which provides a wide space, to ensure raw material can enter the interlayer maximally, making synthesis reaction smoothly.The aluminum phosphate molecular sieve-MMT prepared was evaluated by the way of fixed-bed high pressure reactor for catalytic cracking catalysts (250℃, normal pressure,2h). The result is shown as follow:The FCC conversion of the VGO:81.86%The selective for fraction 1:40.48%The selective for fraction2:59.52%By the process of pillaring Si into MMT provided a larger reaction space, we synthesized MMT-P-Al compounds system. The MMT pillared by Silicon own the mesoporous-porous structure which played the important role in shape-selective catalysis in catalytic cracking as well as and the P-Al compounds can introduce more acidic sites.The MMT-P/A1 compounds prepared was evaluated by the way of fixed-bed high pressure reactor for catalytic cracking catalysts (250℃, normal pressure,2h). The result is shown as follow:The FCC conversion of the VGO:89.8%The selective for fraction1:53.77%The selective for fraction2:46.23%...