Conversion Of Bioethanol Research Articles

On-board reforming of biodiesel and bioethanol for high temperature PEM fuel cells: Comparison of autothermal reforming and steam reforming

In the 21st century biofuels will play an important role as alternative fuels in the transportation sector. In this paper different reforming options (steam reforming (SR) and autothermal reforming (ATR)) for the on-board conversion of bioethanol and biodiesel into a hydrogen-rich gas suitable for high temperature PEM (HTPEM) fuel cells are investigated using the simulation tool Aspen Plus. Special emphasis is placed on thermal heat integration. Methyl-oleate (C19H36O2) is chosen as reference substance for biodiesel. Bioethanol is represented by ethanol (C2H5OH). For the steam reforming concept with heat integration a maximum fuel processing efficiency of 75.6% (76.3%) is obtained for biodiesel (bioethanol) at S/C=3. For the autothermal reforming concept with heat integration a maximum fuel processing efficiency of 74.1% (75.1%) is obtained for biodiesel (bioethanol) at S/C=2 and λ=0.36 (0.35). Taking into account the better dynamic behaviour and lower system complexity of the reforming concept based on ATR, autothermal reforming in combination with a water gas shift reactor is considered as the preferred option for on-board reforming of biodiesel and bioethanol. Based on the simulation results optimum operating conditions for a novel 5kW biofuel processor are derived.

Catalytic Conversion of Bio-ethanol to Ethylene over La-Modified HZSM-5 Catalysts in a Bioreactor

Ethylene production from petroleum or natural gas is an energy intensive process. Bio-ethanol catalytic dehydration to ethylene is an attractive alternative for oil based ethylene. Catalytic dehydration conversion of bio-ethanol to ethylene using HZSM-5 modified by 3 wt% rare earth metal (lanthanum) was carried out in a laboratory bioreactor. The physicochemical properties of the catalyst were characterized. The stability test showed that ethanol conversion and selectivity over this catalyst could be maintained above 98% for more than 950 h. The regenerated catalyst also displayed high reactivity and stability of up to 830 h can be obtained. The effects of temperature, liquid hourly space velocity, particle size of catalyst, and bio-ethanol partial pressure on products formation rate were investigated. The external and internal diffusion resistances were eliminated and the kinetic control range was identified. An apparent kinetics model was used to describe the dehydration reaction of ethanol over 3 wt% La-HZSM-5 catalyst, and the kinetic parameters were determined.

High effective dehydration of bio-ethanol into ethylene over nanoscale HZSM-5 zeolite catalysts

Nanoscale and microscale HZSM-5 zeolite catalysts were prepared and characterized by using SEM, XRD, IR, TPD and modified Hammett indicator method. Their performances in the dehydration of bio-ethanol into ethylene were compared in a fixed-bed reactor at 240 °C under atmospheric pressure. The results show that nanoscale HZSM-5 zeolite catalyst exhibits better stability than microscale HZSM-5 zeolite catalyst. When the 95(v) % bio-ethanol is used as the reactant, over nanoscale HZSM-5 catalyst, the conversion of bio-ethanol and the selectivity for ethylene almost keep constant during 630 h reaction, while over microscale HZSM-5 zeolite catalyst, the conversion of bio-ethanol decreases after 60 h reaction; in the case of the 45(v) % bio-ethanol employed as the feedstock, over nanoscale HZSM-5 catalyst, the conversion of bio-ethanol and the selectivity for ethylene almost keep constant during 320 h reaction, while over microscale HZSM-5 zeolite catalyst, both the conversion of bio-ethanol and the selectivity for ethylene decrease almost at the beginning of the reaction.

Synthesis of Light Olefins from Bioethanol over Ni-MFI Catalysts

The effects of Ni addition on the catalytic activity of MFI zeolite catalysts were examined with the ethanol conversion reaction under high space velocity conditions, using pure ethanol, ethanol diluted with water, and bioethanol produced from corn, and the effects of impurities on deactivation were evaluated. Addition of Ni to MFI zeolite strongly suppressed the formation of aromatic compounds, and greatly improved the selectivities for C3 and C4 olefins from pure ethanol, but decreased the selectivities for C3 and C4 olefins, and slightly reduced the suppression effect of the Ni site for aromatic formation from bioethanol. The yields of C3 and C4 olefins decreased with time-on-stream despite the presence of the Ni sites. XPS analysis of the catalysts after reaction at 673 K showed presence of oxidized carbon species, indicating the deposit of the impurity from the bioethanol. In addition, the electronic state of Ni after the reaction of bioethanol was also different to that after the reaction of reagent ethanol. XPS analysis showed the formation of Ni2O3 species or nickel sulfate during the reaction of bioethanol, which caused catalyst deactivation. In the reaction at 773 K, a large amount of filament carbon was deposited on the catalyst surface. These factors caused significant decreases in the formation of C3 and C4 olefins in the conversion of bioethanol.