TY  - MANSCPT
AU  - Nor Shahirah Mohd Nasir
TI  - Syngas production from catalytic glycerol pyrolysis over rare earths promoted Ni/alumina catalysts
SN  - THE0007915(Local)
PY  - 2017///
CY  - Kuantan, Pahang
PB  - UMP
KW  - Faculty of Chemical and Natural Resources Engineering
KW  - Dissertations
KW  - Universities and Colleges
KW  - Theses
N1  - Faculty of Chemical and Natural Resources Engineering; Thesis (Doctor of Philosophy in Chemical Engineering) -- Universiti Malaysia Pahang – 2017; Bibliography : p. 188-215
N2  - Glycerol is a polyol compound commonly produced as a by-product from the oleo-chemical and biodiesel plants. One of the most attractive ways to increase the value of the glycerol economy is by converting glycerol into syngas. The catalytic glycerol pyrolysis process only requires glycerol as sole reactant to reduce feedstock costing and clean gaseous product emission with minimum CO2. The main objective of the current research is to investigate the kinetics of syngas production from catalytic glycerol pyrolysis over the unpromoted 20wt%Ni/77wt%α-Al2O3 catalyst and also promoted by 3 wt% of light rare earth elements, viz. La, Ce, Pr and Sm. The catalysts were synthesized via wet impregnation method and its physicochemical properties were subsequently characterized. Reaction studies were performed in a 10 mm-ID stainless steel fixed bed reactor with reaction temperatures of 973, 1023 and 1073 K, respectively, employing weight-hourly-space-velocity (WHSV) of 4.5 × 104 ml g-1 h-1 under atmospheric condition. The calcination temperature for the fresh as-prepared catalysts was set at 1073 K as it was found that the nitrate group from the metal-salt has fully decomposed at temperature greater than 600 K. The rare earth metal promoted-Ni/α-Al2O3 catalysts exhibited 5.0-30.0% increment in BET specific surface area compared to the unpromoted-Ni/α-Al2O3 catalyst, in agreement with the FESEM images. The unpromoted- and promoted-Ni/α-Al2O3 catalysts possessed average crystal size in range of 39-44 nm. The NH3- and CO2-TPD analyses proved that all the catalysts have net acidity because the acid-basic ratios > 1.0. The reaction investigation was carried out under intrinsic condition. The yield of gaseous products in the descending rank was H2, CO, CO2 and CH4. No other gaseous products were detected. Moreover, based on glycerol conversion and products yield, the order of catalytic activity were La-Ni/α-Al2O3 > Ce-Ni/α-Al2O3 > Pr-Ni/α-Al2O3 > Sm-Ni/α-Al2O3 > Ni/α-Al2O3 (descending ranking). The H2:CO ratio was always less than 2.0. The best reaction conditions in order to achieve maximum glycerol conversion and products yield were temperature of 1073 K and glycerol partial pressure of 22.5 kPa. Subsequently, from the kinetics modelling via power law and Langmuir-Hinshelwood (LH) model, the unpromoted-Ni/α-Al2O3 catalyst showed the highest activation energy (70.64 kJ mol-1) compared to promoted-Ni/α-Al2O3 catalysts (8-46 kJ mol-1), demonstrating the beneficial effect of promoter in reducing the activation energy barrier. The model showed excellent fits to the data based on high R2 values (>0.9). Based on the mechanistic modelling, it can be deduced that the rate determining step of the glycerol pyrolysis was via a single site associative adsorption with molecular surface reaction as the rate-determining step. In addition, from the 72 h longevity study, the stability ranking in descending order was La-Ni/α-Al2O3 > Ce-Ni/α-Al2O3 > Pr-Ni/α-Al2O3 > Sm-Ni/α-Al2O3 > Ni/α-Al2O3, consistent with the 3 h reaction studies. The presence of elongated whisker-type carbonaceous species was detected from the used catalysts
ER  -