Modified Mesoporous Γ-Alumina From Kano Kaolin in Heterogeneous Transesterification of Rice Bran Oil

Abstract

The environmental problems caused by the excessive usage of fossil fuel, prompted the need for an alternative source of energy. Renewable energy from biodiesel is one of the most promising substitutions of fossil fuel due its environmental-friendliness. In the present work NaOH-modified γ-alumina heterogeneous base catalysts were prepared using wet impregnation method, and characterized by Nitrogen Adsorption Analysis (BET), Fourier Transform Infra-Red (FTIR), X-Ray Powder Diffraction (XRD), basic back titration, and Temperature Programmed Desorption-CO2 (CO2-TPD). The catalysts were tested for the transesterification of rice bran oil with methanol, and the biodiesel product characterized by Fourier Transform Infra-Red-Attenuated Total Reflection (FTIR-ATR) and Nuclear Magnetic Resonance Spectroscopy (NMR) analyses. Catalyst synthesize with 50% NaOH was found to have the highest basic sites and when applied for the transesterification of rice bran oil it gave the highest yield of 81.2%. The high catalytic activity is attributed to the formation of NaAlO2 that is believed to contribute to the basicity of the catalyst.

Solid Base Assisted n-Pentanol Coupling over VIII Group Metals: Elucidation of the Guerbet Reaction Mechanism by DRIFTS

“…A similar decrease of alumina surface area, the pore volume from 0.4 to 0.19 cm 3 /g as well as an increase of pore diameter from 7.5 to 17.5 nm after alumina wet impregnation with an aqueous solution of NaOH was reported by different researchers. 39,42 FTIR and X-ray diffraction (XRD) investigations detected formation of NaAlO 2 that seems to be responsible for changes in the catalyst microtexture. Obviously, a decrease of Pt/Al 2 O 3 catalyst surface area loaded with 100% NaOH from 130 to 12 m 2 /g may be due to partial conversion of NaOH to NaAlO 2 as was confirmed by the FTIR study in the current paper (section 3.5).…”

“…Formation of sodium aluminate was observed by treatment of alumina with sodium hydroxide aqueous solution. 39 An increase of the amount of introduced NaOH to the level of equivalent masses of sodium hydroxide (NaOH/Al 2 O 3 = 1) leads to a further growth of the basic sites strength (PA 970, 990, and 1000 kJ/mol) and appearance of additional super strong basic centers with PA 945, 1000, and 1010 kJ/mol. This may indicate presence of NaOH particles on the surface of these samples having a very high basicity.…”

“…Probably sodium aluminate is formed due to NaOH interaction with isolated and bridged OH groups of alumina. Formation of sodium aluminate was observed by treatment of alumina with sodium hydroxide aqueous solution …”

“…Treatment of aluminum oxide with solid NaOH modifies the surface according to eq . , At the same time, very strong base sites are formed on the surface. Current DRIFT data are showing that formation of sodium aluminate can also occur in the absence of water upon mechanical mixing of Al 2 O 3 or Pt/Al 2 O 3 with NaOH.…”

“…The obtained data are in a good agreement with the literature data 39,42 showing that increase of the sodium hydroxide amount deposited on alumina surface increased not only the amount but also the strength of basic sites. 39 Super strong base sites were identified on the surface of NaOH/Al 2 O 3 (1.0 wt %) containing sodium hydroxide, while they are absent in a material with a low NaOH/Al 2 O 3 content (0.1 wt %) where NaOH was transformed into sodium aluminate. It can be assumed that when large amounts of NaOH are deposited, the hydroxide phase is preserved.…”