Ato Zeolite Microwave Synthesis And N-decane Hydroisomerization Performance Studies

AlPO4-31 molecular sieve were synthesized by microwave irradiation using aluminum isopropoxide, orthophosphoric acid, and di-n-butylamine as sources of aluminum, phosphoric and template, respectively. And the crystallization conditions of AlPO4-31 were optimized. SAPO-31 molecular sieves with different silicon contents and MeAPO-31 (Me= Mg,Co) with different heteroatom contents were synthesized at the optimal conditions. The structure and acidity of the samples were characterized by X-ray diffraction, N2 physical adsorption, Scanning electron microscopy, 29Si MAS NMR, UV-Vis spectrum, ammonia temperature-programmed desorption, FT-IR of pyridine adsorbed. The catalytic performance of Pd/SAPO-31 bifunctional catalysts for hydroisomerization of n-decane was investigated. The results indicated that the AlPO4-31, SAPO-31 and MeAPO-31 molecular sieves with pure crystal phase and higher crystallinity assigned to ATO topology structure were obtained at 170 oC for 2 h by microwave irradiation. The BET surface area and micropore volume were increased because of the introduction of Si to the framework of AlPO4-31. With the increase of silicon content, the acid content and strength of SAPO-31 molecular sieves increased gradually.On the same gel composition conditions, the acidity of SAPO-31 molecular sieve synthesized by microwave heating was weaker than that synthesized by the conventio- nal hydrothermal synthesis, so SAPO-31 molecular sieve synthesized by microwave heating has higher catalytic activity at higher reaction temperatures.The 0.5%Pd/SAPO -31 bifunctional catalyst synthesized with SAPO-31 molecular sieve which was with suitable acidity (SiO2/Al2O3 = 1.0) showed high activity and isomerization selectivity in n-decane hydroisomerization reaction. Under the conditions of 360 oC, 2 MPa, WHSV is 2.5 h-1, H2 flow rate 120 ml/min, the conversion of n-decane was 89.75%, and Isomerization selectivity of n-decane was up to 87.51%.MgAPO-31 and CoAPO-31 molecular sieve synthesized by introducing a small amount of Mg and Co (MgO/Al2O3, CoO/Al2O3= 0.05, 0.1) into the AlPO4-31 framework will obtain more abundant acid sites. 0.5%Pd/MgAPO-31 bifunctional catalyst synthesized by using MgAPO-31 (MgO/Al2O3= 0.05) molecular sieve as acid carrier which were synthesized by using magnesium nitrate as source of magnesium have shown higher catalytic activity and isomerization selectivity in decane hydroisomerization, for acid sites and metal sites have a good synergy. At 330 oC, while the conversion of n-decane was 85.42%, isomerization selectivity in n-decane reached to 90.34%.