Synthesis Of Pinene-based High-density Biofuel Using Acidic Mesoporous Molecular Sieves

Pinenes, as newable bioresources, have great potential and wide foregrounds onthe synthesis of high-density biofuels. In this thesis, a series of acidic mesoporousmolecular sieves were synthesized and used in the isomerization and dimerization ofpinene, along with a reaction mechanism analysis. The properties of the biofuels wereevaluated after hydrogenation treatment.The acidic mesoporous catalysts involved in this work is as follows: two kinds ofAl-MCM-41hydrothermally synthesized using two different templates, two kinds ofsupported catalysts HPW/MCM-41and SA/MCM-41synthesized using impregnationmethod. All the samples were characterized by various methods and evaluated by theisomerization and dimerization of pinene. The influence of structure and acidity of thesamples on their catalytic performances was studied.The content of framework aluminum in Al-MCM-41steadily increases whileSiO₂/Al₂O₃changes from200to20. However, when it reduces to10, the contents ofboth framework and non-framework aluminum decrease sharply. The reason is thatexcessive27Al line-boardening accounts for the appearance of “NMR invisible”aluminum species, which causes the reduction of aluminum detected. The sample withSiO₂/Al₂O₃of20has the most surface acid amount and the best catalytic performance.Lewis acid is more active to trigger the reaction than Br nsted ones. Pinenes areisomerized into various isomerized products very quickly, once the reaction istriggered. Then the hetero-and homo-dimerization of pinene and the isomerizedproducts take place and produce the dimers mixture. The isomerized and dimerizedproducts of α-pinene are the same as that of β-pinene, which proves that the dimerscome from the isomerized products mainly but not only pinene itself. With thisconsideration, turpentine oil consisting of pinene and its isomerized products can beused directly for the sythsis of pinene-based high-density biofuels.To further increase the surface acid amount of the catalyst, HPW/MCM-41andSA/MCM-41were synthesized. The impregnation of strong acids has no effect on theporous characters of the samples but directly affects the acidity. The modificatedMCM-41samples with80%HPW and50%SA have the highest acidity and catalyticactivity, respectively. Compared to Al-MCM-41, the increase of surface aciditycontributes to the improvement of the catalytic activity of the modificated MCM-41samples. Hydrogenated pinene dimers have the identical density and volumetric heatingvalue compared to JP-10but poor low-temperature performance. However, thehydrogenated products of pinene and turpentine have low viscosity and freezing pointthough moderate density. Therefore, these biofuels can be used as high-density fueldirectly or as addictives of mixed fuels.