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https://ptsldigital.ukm.my/jspui/handle/123456789/486805
Title: | Steam reforming of renewable glycerol for hydrogen production over ni, Pd and Ce based catalysts |
Authors: | Ali Salem b. Ebshish (P46813) |
Supervisor: | ZahiraYaakob, Professor Ir. Dr. |
Keywords: | Steam reforming Hydrogen Catalytic reforming |
Issue Date: | 30-Apr-2014 |
Description: | Hidrogen merupakan alternatif penggantian terbaik untuk bahan api fosil, terutamanya jika berasal dari bahan boleh diperbaharui seperti gliserol. Gliserol banyak dihasilkan sebagai bahan sampingan dalam proses penghasilan bio-diesel. Satu kajian sistematik telah dijalankan bagi menentukan kebolehlaksanaan penukaran bermangkin gliserol kepada hidrogen melalui proses pembentukan semula wap ke atas mangkin Ni, Pd, dan Ce.Walaupun kebanyakkan kajian terdahulu tentang pembentukan semula wap gliserol tertumpu pada pengisitepuan dan pemendakan sebagai kaedah sintesis mangkin, sebahagian kajian ini tertumpu pada kaedah sol-gel yang boleh secara relatif memberikan mangkin dengan luas permukaan tinggi. Diperingkat pertama, analisis termodinamik digunakan berdasarkan peminimuman proses tenaga bebas Gibbs untuk mengkaji kesan keadaan operasi ke atas keseimbangan tindak balas pembentukan semula gliserol. Keadaan yang dikaji adalah suhu tindakbalas (100 °C to 800 °C), tekanan (1-20 atm), dan nisbah molar gliserol kepada air GWMR (1:1-1:12). Kajian ini menunjukkan pembentukan semula wap gliserol diutamakan pada suhu tinggi (> 600 °C), tekanan rendah (1atm), dan GWMR (1:12). Peringkat kedua kajian adalah penukaran bermangkin gliserol bagi pengeluaran hidrogen. Prestasi aktiviti bermangkin dari segi pengeluaran hidrogen telah dinilai ke atas Ni/Al2O3, Ce/Al2O3, dan Pd/Al2O3. Tumpuan utama bahagian ini adalah terhadap kajian tindak balas bermangkin ke atas mangkin Ni/Al2O3. Teknik pencirian seperti pembelauan sinar-x (XRD), Brunauer-Emmett-Teller luas permukaan BET, mikroskopi elektron penskanan (SEM), mikroskopi elektron penghantaran (TEM), analisis termogravimetrik (TGA), dan penyaherapan berprogram suhu (TPD) telah dijalankan. Untuk mangkin Ce dan Pd, kajian mendedahkan Pd/Al2O3 mempunyai aktiviti lebih baik daripada Ce/Al2O3 dengan penghasilan H2 diperolehi sebanyak masing-masing 56 % and 44.5 %. Bagi mangkin Ni/Al2O3, kesan beban logam, penggalak, teknik-teknik sintesis, medium sol-gel, dan suhu pengkalsinan telah dikaji. Berdasarkan penghasilan hidrogen, mangkin Ni/Al2O3 yang disediakan dengan kaedah sol-gel dan dengan kehadiran poli etilena glikol (PEG) didapati merupakan mangkin pembentukan semula terbaik dengan Mol H2 tertinggi dihasilkan sebanyak 4.45. Ini boleh dikaitkan dengan luas permukaan tinggi yang dimiliki oleh mangkin ini iaitu 438 m2/g. Mangkin ini dipilih untuk keadaan proses pengoptimuman yang dijalankan menggunakan kaedah tindak balas permukaan (RSM). Rekabentuk komposit berpusat (CCD) digunakan untuk merekabentuk pelan eksperimen di mana nilai tinggi dan rendah keadaan kendalian seperti suhu (400 °C to 600 °C), kadar aliran suapan (0.05 - 0.1 ml/min), berat mangkin (0.2-0.5 g), beban mangkin (5 - 20 %), dan GWMR (1:1-1:12) dipilih berdasarkan analisis termodinamik, kajian sebelumnya dan eksperimen awal yang telah dijalankan. Keputusan dianalisis secara statistik dan dipadankan kepada model polinomial kuadratik yang boleh meramalkan hasil H2 dan penukaran gliserol dengan cekap. Satu sistem bersepadu yang mampu meramalkan penukaran gliserol dan hasil H2 telah dibangunkan dengan mengaplikasikan model rangkaian neural buatan (ANN). Sistem dengan input ANN pelbagai lapisan telah dikaji dan dilatih untuk meramalkan tindak balas pembentukan semula. Lima pembolehubah tindak balas telah dipertimbangkan. Kepentingan sistem ini telah dibuktikan melalui kemampuan model ANN dalam meramalkan hasil H2 dan penukaran gliserol dengan berkesan sebanyak masing-masing 97.1 % dan 95 % masingmasing. Kesimpulannya, matlamat utama kajian untuk memaksimakan penghasilan H2 melalui penukaran bermangkin gliserol telah berjaya dicapai.,Hydrogen is an excellent substitute for fossil fuels, especially if derived from renewable material, such as glycerol. A large amount of glycerol is produced as a byproduct in the biodiesel production process. Utilizing glycerol to produce hydrogen can also enhance the economics of biodiesel production. In this work, a systematic study has been performed to investigate the feasibility of the catalytic conversion of glycerol to hydrogen via steam reforming process using Ni, Pd, and Ce catalysts. Although early studies conducted on the steam reforming of glycerol have investigated impregnation and precipitation as catalyst synthesis methods, part of the current study was focused on sol-gel method, which can relatively provide catalysts with high surface area. In the first stage, the thermodynamic analysis was applied, on the basis of the minimization of Gibbs free energy process, to determine the effects of operating conditions on the glycerol reforming reaction equilibrium. The conditions examined were reaction temperature (100 °C to 800 °C), pressure (1 atm to 20 atm), and glycerol-water molar ratio (GWMR) at 1:1 to 1:12. This study showed that the steam reforming of glycerol is favored at high temperature (> 600 °C), low pressure (1atm), and GWMR (1:12). The second stage of this study involved the catalytic conversion of glycerol for hydrogen production. The performance of catalytic activity in terms of hydrogen yield was evaluated using Ni/Al2O3, Ce/Al2O3, and Pd/Al2O3. However, this portion primarily focused on the study of the catalytic reaction using Ni/Al2O3 catalysts. Characterization techniques such as X-ray diffraction, Brunauer-Emmett-Teller surface area, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and temperature-programmed desorption were performed. For Ce and Pd catalysts, Pd/Al2O3 had better activity than Ce/Al2O3 with 56 % and 44.5 % H2 yield respectively. For the Ni/Al2O3 catalysts, the effects of metal loading, promoters, synthesis techniques, sol-gel medium, and calcination temperatures were investigated. Based on hydrogen yield, Ni/Al2O3 catalyst prepared by sol-gel method in the presence of poly ethylene glycol was found to be the best reforming catalyst with the highest H2 mole yield of 4.45. This result could be attributed to the high surface area (438 m2/g) of the catalyst. This catalyst was chosen for optimization studies, which used response surface methodology (RSM). Central composite design (CCD) was employed to design the experimental plan. The operating conditions ranged are as follows: temperature, 400 °C to 600 °C; feed flow rate at 0.05 mL/min to 0.1mL/min; catalyst weight at 0.2 g to 0.5 g; catalyst loading at 5 % to 20 %; and GWMR, 1:1 to 1:12. These conditions were chosen based on the thermodynamic analysis, previous studies, and preliminary experiments. The results were statistically analyzed and fitted to quadratic polynomial models, which can efficiently predict H2 yield and glycerol conversion. Finally, an integrated system that can predict glycerol conversion and H2 yield was developed by applying artificial neural network (ANN) model. The system with multi-layer ANN input was examined and trained to predict the reforming responses. Five reaction variables were considered in this study. The significance of the system was demonstrated as the capability of the ANN model to predict the H2 yield and glycerol conversion with a significant efficiency of 97.1 % and 95.0 %, respectively. In conclusion, optimal H2 production by catalytic conversion of glycerol was successfully achieved.,PhD |
Pages: | 213 |
Call Number: | TP690.45.A445 2014 3 tesis |
Publisher: | UKM, Bangi |
Appears in Collections: | Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina |
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ukmvital_80198+SOURCE1+SOURCE1.0.PDF Restricted Access | 26.2 MB | Adobe PDF | View/Open |
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