Synthesis of Al-MCM-41 and FCC diesel hydrorefining study
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 L16(43) with three factors and four levels was adopted and the effects were also discussed. Various techniques including X-ray diffraction (XRD), N2 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 °C lasting 1 h with CNaOH 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 m2/g, large pore volume 1.23 cm3/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.