Influence of the Ni-Co/Al-Mg Catalyst Loading in the Continuous Aqueous Phase Reforming of the Bio-Oil Aqueous Fraction (original) (raw)
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Steam Reforming of Bio-oil Fractions: Effect of Composition and Stability
Energy & Fuels, 2011
The efficacy of steam reforming of the aqueous species in bio-oils produced from the fast pyrolysis of biomass is examined. A fractionating condenser system was used to collect a set of fractions of fast pyrolysis liquids with different chemical characteristics. The water-soluble components from the different fractions were steam-reformed using a nickel-based commercial catalyst in a fixed-bed reactor system. When reforming at 500°C, an overall positive effect in hydrogen yields was observed for the fractions with higher concentrations of lower molecular-weight oxygenates, such as acetic acid and acetol, while the heavier compounds, such as the carbohydrates, showed an opposite effect. In general, higher selectivity toward hydrogen correlated to a lower tendency toward carbon deposits. Overall, the bio-oil fraction corresponding to the light end performed the best with the highest activity toward hydrogen. A range of steam/carbon ratios was examined. Carbon accumulation in the reactor was clearly a main issue during steam reforming of all of the bio-oil fractions studied. Chemical changes caused by aging of aqueous bio-oil were found to have a detrimental effect on hydrogen production.
Fuel Processing Technology, 2013
A study was carried out on the effect of temperature (in the 500-800°C range) and space-time (between 0.10 and 0.45 g catalyst h(g bio-oil ) −1 ) on Ni/La 2 O 3 -αAl 2 O 3 catalyst deactivation by coke deposition in the steam reforming of bio-oil aqueous fraction. The experiments were conducted in a two-step system, provided with a thermal step at 200°C for the pyrolytic lignin retention and an on-line step of catalytic reforming in fluidized bed reactor. Full bio-oil conversion and a hydrogen yield of around 95% (constant for 5 h) were achieved at 700°C, S/C (steam/carbon) ratio of 12 and space-time of 0.45 g catalyst h(g bio-oil ) −1 . The results of catalyst deactivation were explained by mechanisms of coke formation and evolution, which are established based on kinetic results and coke analysis by temperature programmed combustion. At 700°C the coke is gasified and Ni does not undergo sintering. The results of hydrogen yield were compared with those obtained in the literature using different reaction technologies.
International Journal of Hydrogen Energy, 2014
Hydrogen production from renewable resources has received extensive attention recently for a sustainable and renewable future. In this study, hydrogen was produced from catalytic steam reforming of the aqueous fraction of crude bio-oil, which was obtained from pyrolysis of biomass. Five Ni-Al catalysts modified with Ca, Ce, Mg, Mn and Zn were investigated using a fixed-bed reactor. Optimized process conditions were obtained with a steam reforming temperature of 800 ˚C and a steam to carbon ratio of 3.54. The life time of the catalysts in terms of stability of hydrogen production and prohibition of coke formation on the surface of the catalyst were carried out with continuous feeding of raw materials for 4 hours. The results showed that the Ni-Mg-Al catalyst exhibited the highest stability of hydrogen production (56.46%) among the studied catalysts. In addition, the lifetime test of catalytic experiments showed that all the catalysts suffered deactivation at the beginning of the experiment (reduction of hydrogen production), except for the Ni-Mg-Al catalyst; it is suggested
Fuel, 2013
h i g h l i g h t s Bone oil was converted to environmentally friendly gas product rich in H 2 and CO. Catalytic steam reforming of bone oil was carried out using a dual catalytic system. The first reactor contained calcined granular dolomite as guard catalyst bed. The active Ni/c-Al 2 O 3 catalyst was used in granular or monolith-supported form. The product gas can be used as fuel for gas engines or as syngas after purification.
Catalytic steam reforming of bio-oil
International Journal of Hydrogen Energy, 2012
Hydrogen and synthesis gas can be produced in an environmentally friendly and sustainable way through steam reforming (SR) of bio-oil and this review presents the stateof-the-art of SR of bio-oil and model compounds hereof. The possible reactions, which can occur in the SR process and the influence of operating conditions will be presented along with the catalysts and processes investigated in the literature. Several catalytic systems with Ni, Ru, or Rh can achieve good performance with respect to initial conversion and yield of hydrogen, but the main problem is that the catalysts are not stable over longer periods of operation (>100 h) due to carbon deposition. Support materials consisting of a mixture of basic oxides and alumina have shown the potential for low carbon formation and promotion with K is beneficial with respect to both activity and carbon formation. Promising results have been obtained in both fluidized and fixed bed reactors, but the coke formation appears to be less significant in fluidized beds. The addition of O 2 to the system can decrease the coke formation and provide autothermal conditions at the expense of a lower H 2 and CO-yield. The SR of bio-oil is still in an early stage of development and far from industrial application mainly due the short lifetime of the catalysts, but there are also other aspects of the process which need clarification. Future investigations in SR of bio-oil could be to find a sulfur tolerant and stable catalyst, or to investigate if a prereformer concept, which should be less prone to deactivation by carbon, is suitable for the SR of bio-oil.
Steam Reforming of the Bio-Oil Aqueous Fraction in a Fluidized Bed Reactor with in Situ CO 2 Capture
Industrial & Engineering Chemistry Research, 2013
The effect of CO 2 capture in hydrogen production by steam reforming of the bio-oil aqueous fraction was studied. The reforming and cracking activity of the adsorbent (dolomite) and the relationship between these reactions and those corresponding to the catalyst (reforming and water gas shift (WGS)) were considered. The experiments were conducted in a two-step system with the first step at 300°C for pyrolytic lignin retention. The remaining volatiles were reformed in a subsequent fluidized bed reactor on a Ni/La 2 O 3 −α-Al 2 O 3 catalyst. A suitable balance was stricken between the reforming and WGS reactions, on the one side, and the cracking and coke formation reactions, on the other side, at 600°C for catalyst/ dolomite mass ratios ≥0.17. At this temperature and space-time of 0.45 g catalyst h (g bio-oil) −1 , bio-oil was fully converted and the H 2 yield was around 99% throughout the CO 2 capture step. Catalyst deactivation was very low because the cracking hydrocarbon products (coke precursors) were reformed.
Chemical Engineering Journal, 2018
Kinetics of the steam reforming (SR) of bio-oil over a Ni/La 2 O 3-αAl 2 O 3 catalyst is investigated in a two-step reaction system, which consists of a first thermal unit for pyrolytic lignin separation, followed by on-line reforming in a fluidized bed reactor where the catalyst is located. The kinetic data were obtained under the following operating conditions: 550-700°C; steam-to-carbon ratio in the feed (S/C), 1.5-6.0; space-time, of up to 0.38 g catalyst h/g BO ; time on stream, up to 5 h. Experiments in the absence of catalyst were also carried out with a view to quantifying the contribution of thermal routes of bio-oil decomposition. A kinetic scheme with six reaction steps is assumed for the process, and contribution of thermal and catalytic routes are considered in the kinetic equations. The reaction steps are: i) SR of bio-oil (C 3.9 H 6.1 O 3.0); ii) water-gas-shift (WGS) reaction; iii) bio-oil decomposition (thermal/catalytic) into (CO + CH 4 + H 2); iv) bio-oil decomposition (thermal/catalytic) into (CO 2 + hydrocarbons + H 2); v) methane SR and vi) hydrocarbons SR. The kinetic model also considers the catalyst deactivation by means of a deactivation equation, which is dependent on the partial pressure of bio-oil oxygenates. The complete kinetic model proposed is suitable for predicting the evolution with time on stream of the concentration of products (H 2 , CO 2 , CO, CH 4 , hydrocarbons), un-reacted bio-oil and water in the reaction medium for the whole range of operating conditions studied.
Steam reforming of bio-oil: Effect of bio-oil composition and stability
2008
Hydrogen can be obtained from biomass pyrolysis liquids by catalytic steam reforming. Catalyst deactivation by coking and the formation of carbon deposits are the major known limitations although the specific causes are unidentified. It is proposed that these limitations could be reduced by selectively reforming specific fractions of the bio-oil. The hydrophobic fraction mainly composed of heavy oligomers can be
Fuel, 2018
The hydrogen production by steam reforming (SR) of raw bio-oil (obtained by fast pyrolysis of pine sawdust) has been studied in a continuous two-step process, which consists of a thermal treatment at 500°C, followed by SR in a fluidized bed reactor with Ni/La 2 O 3-αAl 2 O 3 catalyst. The effect of SR temperature on bio-oil conversion, product yields and catalyst deactivation was evaluated in the 550-700°C range. The bio-oil conversion and H 2 yield were significantly enhanced by increasing temperature. A H 2 yield of around 88% and low catalyst deactivation were achieved at temperatures above 650°C, for a S/C (steam/carbon) ratio of 6 and space-time of 0.10 g catalyst h/g bio-oil. The influence temperature has on product yields and catalyst deactivation was explained by the different nature of the coke deposited. The temperature-programmed oxidation (TPO) curves of coke combustion allow identifying two fractions: i) Coke I, which is the main responsible for deactivation (by encapsulating the Ni sites), whose formation depends on the concentration of bio-oil oxygenates; ii) Coke II, which has filamentous nature and CO and CH 4 as main precursors. The effect of temperature on the formation of both types of coke depends on the space-time. Thus, for low values (0.04 g catalyst h/g bio-oil) there is significant formation of both types of coke, with their content increasing with temperature. For higher values (0.38 g catalyst h/ g bio-oil), the increase in reaction temperature promotes the removal of coke I, and therefore this is the prevailing fraction at 550°C and is negligible at 700°C. This fact is of special relevance for attenuating the Ni/La 2 O 3-αAl 2 O 3 catalyst deactivation.