چكيده فارسي :
اين رساله شامل سه پژوهش است، كه از كاتاليست¬ هاي اسيدي جامد براي تهيه آلكيل لوولينات استفاده شده است. در پژوهش اول از مزوپور زيركونيم فسفات اصلاح شده به عنوان كاتاليزور ناهمگن براي توليد آلكيل لوولينات¬ها از زايلوز استفاده شد. در بين كاتالسست¬هاي سنتزي، MZP-Pr-SO3H در وا.كنش¬هاي انجام شده با بازده 84 در.صد تحت دماي 170 درجه¬سانتي¬گر.اد و مدت زمان 6 ساعت، عملكرد كاتاليستي مناسب¬تري از خود نشان داد. در پژوهش دوم اصلاح بستر KIT-5 با استفاده ا.ز مقادير مختلف نمك آلومينيوم KIT5(X=5,10,20) انجام شد و .پس از آن گروه پروپيل سولفونيك اسيد بر ر.وي كاتاليستي كه بهترين عملكرد را داشت، قرار گرفت. بعد از بهينه سازي پارامتر هايي از قبيل دما ، زمان، نوع، ميزا.ن كاتاليست و ميزان واكنش دهنده بازده قابل توجه 52 درصد در دماي 170 درجه¬سانتي گراد و مدت زمان 7 ساعت در واكنش توليد هگزيل¬لوولينات از زايلوز را بدست آمد. در پژوهش سوم بستر KIT-5 به وسيله نمك آلومينيوم به دو روش متفاوت، آلومينيوم¬دار شد و در واكنش تبديل نشاسته به تركيب پر كاربرد بوتيل لوولينات بررسي شد. پس از بهينه سازي واكنش در دماي موثر 230 درجه¬سانتي گراد و مدت زمان 10 ساعت به همراه 30 ميلي گرم كاتاليست، بازده واكنش 31 درصد گزارش شد. از اين كاتاليست.¬ها 4 مرتبه بدون تغيير بازده واكنش استفاده گرديد. ساختار اين كاتاليست-ها با تكنيك هاي XRD، FT-IR، BET، SEM، TEM و ICP-OES بررسي شد.
چكيده انگليسي :
In the first section of the thesis, we have focused on the synthesis and characterization of MZP. Alkyl levulinates (AL), which are important biomass derivatives, have the potential of conversion into different valuable compounds. This study addressed the production of alkyl levulinate from xylose by applying mesoporous zirconium phosphates (AL-MZP-Pr-SO3H, MZP-Pr-SO3H), which served as good heterogeneous catalysts. The characterization of these catalysts was done using FT-IR spectroscopy, low and wide-angle XRD, N2 adsorption–desorption, ICP, TEM, and SEM. Then the impact of a large number of parameters, like the temperature of reaction, the time of reaction, the catalyst amount, and xylose initial amount was probed. The findings revealed that the maximum n-butyl levulinate yield was 82 % at the temperature of 170 °C, after 6 h; meanwhile, the maximum ethyl levulinate yield was 49% at 150 °C, after 6 h. The catalysts can be easily separated from the reaction mixture and regenerated by a simple activation step, with the possibility of reusing at least four times without significant reduction in the catalytic activity.
In the second section of the thesis, we have focused on the synthesis and characterization of Al-KIT-5(20)-Pr-SO3H and direct covertion of xylose to n-hexyl levulinate. Levulinate esters are bio-based molecules with wide industrial applications as solvents, flavorings, fragrances, diesel blend components, and plasticizers. The current study deals with the synthesis and characterization of a series of acidic mesoporous alumino-silicates (KIT-5, Al-KIT-5x (X = 20,10,5), and a hybrid organic-inorganic Al-KIT-5(20)-Pr-SO3H) and their application in the preparation of n-hexyl levulinate from xylose. The prepared catalysts were thoroughly characterized using various techniques, including FT-IR, XRD, N2 adsorption-desorption, ICP, and SEM. The best catalytic performance was achieved in the presence of Al-KIT-5(20)-Pr-SO3H, which is found to be a bi-functionalized Lewis/Bronsted acid catalyst. The yield of n-hexyl levulinate reached a maximum of 52% at 170 ℃ in only 7 h. Al-KIT-5(20)-Pr-SO3H represents not only excellent reusability over four successive runs but also shows simple separation from the reaction mixture.
In the last section of the thesis, an easy and effective catalytic method for direct covertion of starch to butyl levulinate. Biomass is the only renewable organic fuel that has high energy content. Due to the significant amount of biomass resources, especially crop residues, the use of biomass as fuel has attracted much attention. The current study deals with the synthesis of butyl levulinate as a biomass-derived compound from starch using alumina-doped KIT-5 catalysts ((Al-KIT-5 (5) (wetness impregnation method), Al-KIT-5 (5) (in-situ method)). The effect of the catalyst preparation method on the reaction yield and other influential factors was thoroughly investigated. The textural properties of these catalysts were characterized by various analytical techniques such as SEM, TEM, ICP-OES, XRD, N2 adsorption-desorption isotherm, FT-IR, and Py-FT-IR. Under the optimized conditions (230℃, 10 h, 30 mg catalyst, and 70 mg starch), 31% yield and 74% conversion were obtained for butyl levulinate and starch, respectively. Finally, the catalysts were regenerated and reused for four successive runs without any variation in the product yield.
