Synthesis of Al-MCM-41 and FCC diesel hydrorefining study

摘要

Mesostructured aluminosilicates (MCM-41) with ordered 2-dimensional hexagonal structure were successfully synthesized via the alkali-treatment step and nanocrystal aluminosilicates assembly in the basic and hydrothermal synthesis conditions by sol-gel approach. Highly hydrothermally stable MCM-41 coupled with large surface area and pore volume is desirable. To find out the optimum conditions, An orthogonal experiment L_(16)(4~3) with three factors and four levels was adopted and the effects were also discussed. Various techniques including X-ray diffraction (XRD), N_2 adsorption-desorption, temperature program desorption and fourier transform infrared spectroscopy were used to monitor the physical-chemical properties of MCM-41. When the synthesis was operated under 80 ℃ lasting 1 h with C_(NaOH) 0.5 mol/L and molar ratio of CTAB to ZSM-5 0.15, the synthesized MCM-41 possessed high specific surface area 1,150 m~2/g, large pore volume 1.23 cm~3/g with appropriate acid distribution as well as highly hydrothermal stability. In addition, the results reveal that the as-synthesized samples have a uniform phase without MFI structure. Samples have a 5-membered ring in the framework and have a better hydrothermal stability than the conventional Al-MCM-41. Performance evaluation was carried out on a 20 mL fixed-bed hydrorefining unit with the Daqing FCC diesel as feedstock. The sulfur and nitrogen removal is 99.3% and 99.6%, respectively, while the cetane number was increased by 5.4.