Reforming Of Biomass Tar Research Articles

No.48 Ni 担持褐炭触媒のバイオマスタール超低温改質特性(バイオマス(2))

No.48 Ni 担持褐炭触媒のバイオマスタール超低温改質特性(バイオマス(2))

Catalyst property of Co–Fe alloy particles in the steam reforming of biomass tar and toluene

Performance of Co–Fe/Al2O3 catalysts with the optimum composition (Fe/Co=0.25) was much higher than corresponding monometallic Co and Fe catalysts in the steam reforming of tar from the pyrolysis of cedar wood in terms of the catalytic activity and the suppression of coke deposition. According to the catalyst characterization, the fcc and bcc Co–Fe alloys were formed by H2 reduction on the Co–Fe/Al2O3 catalyst. In the steam reforming of toluene, the addition of H2 to the reactant gas enhanced the activity of Co–Fe/Al2O3 remarkably. Without H2 addition, bcc Co–Fe alloy particles were oxidized and this is connected to the deactivation. With H2 addition, the bcc Co–Fe alloy with an appropriate composition is maintained in metallic state and it contribute to high activity in the steam reforming of toluene.

Development of Ni-Based Catalysts for Steam Reforming of Tar Derived from Biomass Pyrolysis

Nickel catalysts are effective for the steam reforming of tar derived from biomass pyrolysis, but the improvement is needed in terms of activity, stability, suppression of coke deposition and aggregation, and regeneration. Our recent development of Ni-based catalysts for the steam reforming of tar is reviewed including the modification with CeO 2 (or MnO), trace Pt, and MgO. The role of additives such as CeO 2 , MnO, Pt, and MgO is also discussed. The development of multi-functional Ni catalysts for steam reforming of biomass tar was presented, and it may provide useful information toward the design of novel catalysts for the conversion of biomass to synthesis gas.

Catalytic performance and characterization of Ni–Co catalysts for the steam reforming of biomass tar to synthesis gas

The performances of Ni–Co/Al2O3 catalysts with the optimum composition were much higher than the corresponding monometallic Ni and Co catalysts in terms of the catalytic activity, the resistance to coke formation and catalyst life in the steam reforming of biomass tar. This behavior can be related to the formation of the Ni–Co solid solution alloys indicated from the characterization with XRD, TPR, TEM, H2 adsorption and EXAFS.

Catalytic steam reforming of biomass tar over iron- or nickel-based catalyst supported on calcined scallop shell

Calcined scallop shell (CS) exhibits alkaline property with a porous structure, and could be applied for the adsorption and decomposition of biomass-derived tar. In this study, steam reforming of tar derived from pruned apple branch over CS was investigated in a fixed bed at 650°C. It was found that CS had good activity for the steam reforming of tar to produce synthesis gas (syngas), and was able to be recycled. To promote the gas production efficiency, iron or nickel was supported on the CS, and used for the reforming of tar. The effect of heating rate on the gas production rate was investigated, and it was found that reduced iron- or nickel-supported CS showed better activities under the condition of rapid heating. Iron- or nickel-based catalyst in its oxide state was also investigated for the reforming of tar. No catalytic activity was found at the beginning, but good activity appeared after approximately 30min of reaction when the metal oxide was reduced to its metallic form by the initially generated syngas (CO and H2) from the pyrolysis of biomass without the aid of catalyst. Iron and nickel in their metallic forms rather than their oxide ones were considered as active sites for the reforming of tar. Furthermore, the alkaline elements in the biomass, which could enhance the activity of the catalysts, were identified to be accumulated on the surface of the catalysts with the biomass-derived tar. As a result, a larger amount of syngas was produced when the regenerated catalysts were applied. Based on these experimental results, a possible catalytic process was proposed.

Catalytic reforming of tar during gasification. Part II. Char as a catalyst or as a catalyst support for tar reforming

Char, char-supported catalysts and ilmenite were investigated for the steam reforming of biomass tar derived from the pyrolysis of mallee wood in situ. Special attention was given to the reforming of aromatic ring systems in tar. The results indicated that the char-supported iron/nickel catalysts exhibited much higher activity for the reforming of tar than the char itself. Ilmenite and the char-supported iron catalyst contained similar active phase but showed different tar reforming activities. Kinetic compensation effects demonstrated that the reaction pathways on the char-supported catalysts were similar but were different from those on ilmenite. The proprieties of support could play important roles for the activities of the catalysts and the reaction pathways on the catalysts. Char would not only disperse the catalysts but also interact with the catalysts to enhance their activity for the steam reforming of tar.

Evaluation of different oxygen carriers for biomass tar reforming (II): Carbon deposition in experiments with methane and other gases

This work is a continuation of a previous paper by the authors [1] which analyzed the suitability of the Chemical Looping technology in biomass tar reforming. Four different oxygen carriers were tested with toluene as tar model compound: 60% NiO/MgAl2O4 (Ni60), 40% NiO/NiAl2O4 (Ni40), 40% Mn3O4/Mg–ZrO2 (Mn40) and FeTiO3 (Fe) and their tendency to carbon deposition was analyzed in the temperature range 873–1073K. In the present paper, the reactivity of these carriers to other compounds in the gasification gas is studied, also with special emphasis on the tendency to carbon deposition. Experiments were carried out in a TGA apparatus and a fixed bed reactor. Ni-based carriers showed a tendency to form carbon in the reaction with CH4, especially Ni60. The addition of water in H2O/CH4 molar ratios of 0.4–2.3 could decrease the carbon deposited, but not in the case of Ni60. Mn-based sample reacted with CH4 almost completely and with low tendency to carbon deposition, while the Fe-based sample showed low reactivity. Ni40 showed more reactivity to CO than Mn40, although in both cases carbon was deposited, especially at 873K. When H2 was present, it reacted rapidly with both carriers, decreasing the amount of carbon deposited. The presence of CO2 could also decrease the carbon deposited on Ni40 at 1073K. According to both these and the previous results [1], it can be concluded that Mn40 is the most adequate for minimization of carbon deposition in Chemical Looping Reforming (CLR).

Promoting effect of the alloy formation over Ni-Fe/Al2O3 catalysts for the steam reforming of biomass tar to synthesis gas

ABSTRACTThe addition of Fe addition with suitable amount to Ni /Al2O3 catalyst showed higher catalytic performance than corresponding monometallic Ni and Fe catalysts in the steam reforming of tar from the pyrolysis of cedar wood. Characterization of the catalysts indicates the formation of the Ni-Fe alloys and the surface segregation of Fe atoms on the alloys, and it was also suggested that the structure was almost maintained during the reaction. The surface Fe atoms accept oxygen atom from steam and subsequently supply oxygen species to adsorbed carbonaceous species on neighboring surface Ni atoms, which is connected to the promotion of the steam reforming reaction of tar and the suppression of the coke formation.

Evaluation of different oxygen carriers for biomass tar reforming (I): Carbon deposition in experiments with toluene

In this work, an innovative method for gas conditioning in biomass gasification is analyzed. The objective is to remove tar by selectively reforming the unwanted hydrocarbons in the product gas with a chemical looping reformer (CLR), while minimizing the carbon formation during the process. Toluene, in a concentration of 600–2000ppmv, was chosen as a tar model compound. Experiments were performed in a TGA apparatus and a fixed bed reactor. Four oxygen carriers (60% NiO/MgAl2O4 (Ni60), 40% NiO/NiAl2O4 (Ni40), 40% Mn3O4/Mg–ZrO2 (Mn40) and FeTiO3 (Fe)) were tested under alternating reducing/oxidizing cycles. Several variables affecting the reducing cycle were analyzed: temperature, time for the reduction step and H2O/C7H8 molar ratio. Ni40 and Mn40 presented interesting characteristics for CLR of biomass tar. Both showed stable reactivity to C7H8 after a few cycles. Ni40 showed a high tendency to carbon deposition compared to Mn40, specially at high temperatures. Carbon deposition could be controlled by decreasing the temperature and the time for the reduction step. The addition of water also reduced the amount of carbon deposited, which was completely avoided working with a H2O/C7H8 molar ratio of 26.4.

Plasma enhanced catalytic reforming of biomass tar model compound to syngas

Direct thermal decomposition, plasma-assisted decomposition, catalytic steam reforming and plasma enhanced catalytic steam reforming of biomass tar using toluene as a model compound were comparatively studied. Plasma enhanced catalytic steam reforming showed the best performance. The introduction of a plasma to the catalytic reforming reaction accelerated the decomposition of toluene, while the co-existing Ni/SiO2 reforming catalyst, on the other hand, guided the reaction towards formation of CO and H2, realizing the highest toluene conversion, and the highest CO and H2 formation rates simultaneously.

Development of new nickel based catalyst for biomass tar steam reforming producing H 2-rich syngas

Mayenite (Ca 12Al 14O 33 or 12CaO.7Al 2O 3) was previously developed and applied as Ni support for biomass tar steam reforming in the absence and presence of H 2S by our group because of its high oxygen restoring property in the structure [C. Li et al., Appl. Catal., B. 2008]. In this study, catalyst Ni/mayenite (mayenite as support) was prepared by impregnation method with nickel nitrate hexahydrate. Experiments were tested in a fixed-bed reactor, toluene as a tar model compound. The influence of the catalyst preparation and operating parameters (reaction temperature, steam to carbon ratio and space time) on catalyst activity and products selectivity were studied, and a long-time evaluation (more than 76 h) also exhibited excellent resistance to coking. These results were compared to these obtained by commercial-like catalysts: Ni/CaO x /MgO 1− x and our previous NiO/mayenite, showing that Ni/mayenite exhibited excellent property for biomass tar reforming, with higher H 2 yield than that of Ni/CaO x /MgO 1− x , and higher CO selectivity than that of NiO/mayenite. For kinetic model, the first order reaction used for toluene with activation energy of 80.24 kJ.mol − 1 was coincident with literature data.