Catalytic Cracking Of Supercritical N-dodecane Over Nano-HZSM-5Zeolite Coatings

Hydrocarbon fuels, not only provides propellant power via combusion for the aircraft, but also works as an ideal coolant for the thermal management system to offer enough heat sink by both physical and chemical processes. Thereofre, it was meaningful to study the catalytic cracking of the hydrocarbons fuels in view of further improving the heat sink of the fuels.In this work, series of zeolite coatings were perpared by washcoating method, and used as tube reactors for catalytic cracking of supercritical n-dodecane (4MPa,550℃). By investigating the acidity properities and pore structure of this kind of zeolite, we studied the reason why does this zeolite shows high activity and stability in the catalytic reaction. In order to further improve the catalytic ability of nano-zeolite, we applied several method to modified the rude zeolite, as a result, the acidity properties and pore structure of the zeolites were changed, and the catalytic performance of the zeolites were improved as well.Wall-coated HZSM-5with micro-and nanoscale crystal sizes were prepared and coated to the inner surface of SS304stainless-steel tubes using washcoating methods. It was found that nanoscale HZSM-5zeolite slurry has different rheological properties, washcoat loadings, and adhesions with microscale HZSM-5. Catalytic activities of the prepared micro-and nanoscale HZSM-5zeolite coatings were studied using catalytic cracking of supercritical-phase n-dodecane, indicating that catalytic cracking activity and stability were remarkably improved more than1time by nanoscale HZSM-5coatings compared to microscale HZSM-5coatings. Acid and pore structure characterization showed that the better performance of nanoscale HZSM-5coating may be attributed to the shorter diffusion length of the micropore, the higher diffusion rate of supercritical n-dodecane in the intracrystal mesopore, and the special acid nature of nanoscale HZSM-5coatings.A series of Ag modified nanoscale zeolites were prepared with different Ag content. Then, we investigated the acidity properities and pore structure of the zeolites before and after modification, as well as the catalytic cracking of n-dodecane over the zeolite coatings. We found that the increase of the amount of the zeolite acidity was the main reason that of the enhancement of the n-dodecane conversion in the reation, and the proper content in the zeolite acidity composition was necessary for the well performance of the zeolite catalyst in the catalytic reation.A series of nanoscale zeolites modified with different methods, including alkali treatment, hydrothermal treatment and ammonium silicofluoride treatment, were also prepared. We investigated their acidity properities and pore structure, as well as the degree of the Si and Al element removing from the zeolites after modifiction. In the catalytic cracking of n-decane over the zeolite coatings, we found that the removal of the two element in the zeolite led to the change of the acidity and pore structure of the zeolite after modified, as a result the catalytic performance of the zeolite coatings were affected.