Steam Reforming Of Tar Research Articles

3-11 循環流動層における木質系バイオマスチャーならびにタールの水蒸気改質速度((3)ガス化3,Session 3 バイオマス等)

3-11 循環流動層における木質系バイオマスチャーならびにタールの水蒸気改質速度((3)ガス化3,Session 3 バイオマス等)

3-1-1 Steam reforming of biomass tar over Ni/MCM-41 catalyst at low temperatures

3-1-1 Steam reforming of biomass tar over Ni/MCM-41 catalyst at low temperatures

3-33.バイオマス迅速熱分解タールの水蒸気改質反応系における改質促進剤のin-situ生成((10)ガス化II,Session 3 バイオマス等)

3-33.バイオマス迅速熱分解タールの水蒸気改質反応系における改質促進剤のin-situ生成((10)ガス化II,Session 3 バイオマス等)

Characterization and performance analysis of an innovative Ni/Mayenite catalyst for the steam reforming of raw syngas

Biomass gasification is an effective way to produce syngas that must be conditioned to remove the main pollutants (tars) for its use in energy production systems. Catalytic steam reforming of tar and CH4 is thus necessary; Nickel catalysts are excellent candidates but still have deactivation problems related to carbon deposition and sulphur poisoning. Various studies demonstrated that Mayenite as binder for Nickel has free oxygen ions that protect the catalyst from coke formation and H2S poisoning. Similar studies are carried out only with tar representative compounds (e.g. toluene); here the catalyst was tested with real syngas from biomass gasification containing CH4, benzene and tars. Ni/Mayenite was synthesized with citrate sol-gel method, characterized (XRD, BET, SEM, XRF), tested for 50 h and again characterized in order to study its degradation. Heavier tars were 100% converted; lower tars were converted with high rate; CH4 showed a decrease in conversion after 2 h.

A High-Performance, Low-Tortuosity Wood-Carbon Monolith Reactor.

A highly efficient 3D wood-derived carbon monolith reactor with a low tortuosity is demonstrated for high-temperature reaction applications, using catalytic steam reforming of biomass tar as the model system. Outstanding catalytic activity is achieved as the reactant gases flow through this 3D natural wood-derived catalyst, where over 99% toluene conversion and good stability at 700 °C are observed.

Preparation and performance of Ni‐based catalysts supported on Ca12Al14O33 for steam reforming of tar in coke oven gas

The catalytic activities of the Ni‐based catalysts with Ca12Al14O33 as carrier for the steam reforming of tar from coke oven gas were studied. The carriers were prepared with three methods, high temperature roasting (HTR), coprecipitation (CP) and sol−gel (SG), respectively. Compared to the catalyst with CP, the catalyst with HTR showed stronger peaks of NiO as well as Ca12Al14O33, similar to the one with SG, and had obviously higher catalytic activity than those with CP and especially with Al2O3 as carrier, just slightly lower than that with SG. When the calcination temperature was 1350°C (HTR‐1350), the prepared catalyst showed the strongest peaks of Ca12Al14O33 and NiO and the highest surface area, resulting in the excellent performance for tar reforming. For Ni/Mg−Ca12Al14O33 catalyst with HTR‐1350, the catalytic activity and stability were improved as the reforming temperature and the steam/carbon ratio (S/C) rose, and especially at 850°C and the S/C ratio of 12:1, the hydrogen yield can reach 93.16%, with the carbon conversion reaching 97.14%. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 729–735, 2017

Fe-Ca interactions in Fe-based/CaO catalyst/sorbent for CO2 sorption and hydrogen production from toluene steam reforming

After biomass gasification, tar can be removed by steam reforming and additional hydrogen production. This latter can be enhanced by CO2 sorption using the global process known as sorption enhanced hydrogen production (SEHP). Toluene was studied as tar model compound and its reforming was carried out at a compromise temperature (700°C) to permit simultaneous activation of iron based catalyst and CO2 sorption on CaO based sorbent.Fe-Ca interactions on Fe-based/CaO catalyst/sorbent performances occur during steam reforming of toluene. In order to determine the specific conditions for the formation of the different iron species, Fe-based/CaO bi-functional materials have been prepared following three different methods with various calcium and iron precursors. The characterizations (XRD, Mossbauer spectroscopy, TGA, TPR, SEM, and BET/BHJ) performed before and after steam reforming of toluene provide information about the evolution of the iron species and Fe-Ca interactions during catalytic tests. The results suggest that the activity of Fe/CaO materials depends not only on the presence of Fe2O3 but also on the stability of the interactions between iron and calcium under reaction conditions.The bi-functional material prepared from iron acetate and calcium acetate by mechanical mixing (FeAc/CaO (M)) has properties (large specific surface area, appropriate sorption capacity at 700°C, and the lowest deactivation) that play an important role for CO2 capture. Moreover, the presence of the α-Fe2O3 phase, precursor of the active phase in steam reforming of tar, reducible at 700°C, intervenes in the hydrogen production rate by enhancing the Water Gas Shift reaction. Finally, its higher availability of iron (Fe2O3) limit the selectivity towards undesirable products such as benzene.

Steam reforming of biomass tar over calcined egg shell supported catalysts for hydrogen production

Calcined egg shell (CES) shows porous structure and exhibits alkaline property, which is expected to be applied for the adsorption and decomposition of biomass-derived tar. In this research, steam reforming of tar derived from cedar wood over CES was firstly investigated in a fixed bed reactor and found that CES had high catalytic activity for steam reforming of tar to produce hydrogen-rich gas. Then, iron, nickel, cobalt and copper were loaded on CES, more syngas especially hydrogen gas was produced. Among them, copper loaded CES exhibited more enhanced catalytic activity. The optimum Cu loading amount on CES was found to be 1–2 wt%, which resulted in the most amount of syngas and exhibited excellent reusability.

Characterization and catalytic performance of hydrotalcite-derived Ni-Cu alloy nanoparticles catalysts for steam reforming of 1-methylnaphthalene

Supported Ni-Cu alloy nanoparticles prepared from Ni-Cu-Mg-Al hydrotalcite-like compounds (HTlcs) with Cu/Ni=0.25 have been shown to be an active catalyst for the steam reforming of tar derived from the biomass pyrolysis. In the present work, Ni-Cu alloy catalysts with wider compositions of Cu/Ni were characterized and their performances were evaluated in the steam reforming of 1-methylnaphthalene (1-MN), which has lower reactivity than the biomass tar, in order to make the effect of Cu/Ni much clearer. The characterizations with XRD, STEM-EDX, H2 chemisorption, and FIIR of CO adsorption suggest that the obtained Ni-Cu alloy nanoparticles had uniform composition in the range of Cu/Ni=0.1–1; the particle size was decreased with the increase of Cu/Ni ratio (ca. 5–7nm), and Cu tended to be enriched on the particle surface. The HTlcs-derived Ni-Cu alloy catalysts showed a volcano-type dependence of activity on the alloy composition; the highest reforming activity and lower yields of byproducts including benzene, naphthalene, and coke were obtained at Cu/Ni=0.25. The kinetic study indicates that 1-MN was strongly adsorbed on both the Ni and Ni-Cu catalysts; in contrast, the adsorption of steam was promoted by the alloying of Ni with Cu even in the presence of strongly adsorbed 1-MN. The property of stronger adsorption of steam can be connected to higher reforming activity and lower coke deposition through the dissociative adsorption of steam to supply more adsorbed oxygen species, which enhance the gasification of carbonaceous species.

Study on Steam Reforming of Tar in Hot Coke Oven Gas for Hydrogen Production

Thermodynamic analysis and experiments of the steam reforming process of 1-methylnaphthalene as the tar model compound from coke oven gas (COG) were performed in this paper. In the thermodynamic analysis, as the temperature and steam/carbon (S/C) ratio rose, the hydrogen yield first increased and then flattened out yet with the compound completely converted and almost no coke deposition formed. In the experiments using a Ni/Mg catalyst with Ca12Al14O33 as a carrier, with the increases of the temperature and S/C ratio and the decrease of the methane-equivalent gas hourly space velocity (GC1HSV), the reforming result for hydrogen production became better gradually. After the temperature and S/C ratio increased to 800 °C and 12:1, respectively, and the GC1HSV decreased to 145 h–1, the hydrogen yield and carbon conversion could reach over 90% and 97%, respectively, even very close to the thermodynamic values. Additionally, the catalytic stability and resistance to coke formation of the used catalyst also impr...

Nickel-substituted bariumhexaaluminates as novel catalysts in steam reforming of tars

This work investigates the performance of Ba–Ni-hexaaluminate, BaNixAl12−xO19, as a new catalyst in the steam-reforming of tars. Substituted hexaaluminates are synthesized and characterized. Steam reforming tests are carried out with both a model-substance (1-methylnaphthalene) and a slip-stream from a circulating fluidized bed gasifier. The water–gas-shift activity is studied in a lab-scale set-up. Barium–nickel substituted hexaaluminates show a high catalytic activity for tar cracking, and also shows activity for water–gas-shift.

Kinetic modeling of a combined tar removal and methanation reactor for biogenous synthesis gas at medium temperature conditions

Combined tar steam reforming and methanation at relative low temperatures are an interesting gas cleaning option for decentralized, small-scale allothermal gasification plants. In the course of the work, a thermodynamic model for the tar removal reactor is developed, applying mass and energy balances, reaction kinetics and equilibrium equations. To describe the chemical reactions accurately, kinetic data, for the gas reactions and the steam reforming of tar, considered as two lumps (heterocyclic and polycyclic aromatics), is implemented into the model. The kinetic coefficients are obtained by regressing experimental data considering literature values. Since catalyst deactivation is a major obstacle especially at low temperature conditions, catalyst deactivation is implemented into the model by using the specific-catalyst-consumption, an empirically determined parameter, avoiding the data requirements of a kinetic model. The performance of the reactor model is evaluated and compared to experimental data, showing good agreement with the measured values.

Reforming of tar contained in a raw fuel gas from biomass gasification using nickel-mayenite catalyst

Catalytic steam reforming of tar is a very efficient process to clean the gas produced by biomass gasification. Ni catalysts remain an affordable solution for this problem, even if this catalytic material suffers degradation due to carbon deposition and sulphur poisoning. In this study, the properties of a new catalyst Ni/Mayenite (Mayenite as binder), prepared by impregnation method and tested with a real gas obtained from a bench scale fluidized bed steam gasification of biomass, were investigated. Experiments were carried out in a microreactor fed by a slipstream coming from the bench scale gasifier to evaluate gas cleaning and upgrading options. Preliminary tests were carried out at three different temperatures, 700, 750 and 800 °C. In all the tests, the catalysts showed high activities reaching to a conversion rate of 90% in the case at highest temperature (800 °C). The conversion efficiency remained stable around this value during a 3 h test. A decrease in the performance was observed at 700 and 750 °C, even if the conversion remained stable around a lower value. An increase of H2 (>50%) and a decrease of CH4 were observed at all the temperatures, due to the occurrence of steam reforming reaction. A long duration test (12 h) was carried out at 800 °C and demonstrated that, at this temperature, the conversion was stable for a longer period.

Promoting effect of trace Pd on hydrotalcite-derived Ni/Mg/Al catalyst in oxidative steam reforming of biomass tar

Promoting effects of trace noble metals (Pd, Pt, Au, Ru, Rh and Ir) on the activity and stability of the Ni catalyst prepared from the hydrotalcite-like compounds containing Ni, Mg, and Al were investigated in steam reforming and oxidative steam reforming of tar derived from pyrolysis of biomass. The optimum loading of Pd was 0.05wt% (0.05PdNi catalyst; molar ratio of Pd/Ni=0.0023), and this catalyst showed higher performance than the other noble-metal-added catalysts with the same noble metal/Ni molar ratio. Characterization results indicated that the addition of 0.05wt% Pd enhanced the reducibility of Ni species and the dispersion of Ni metal particles simultaneously, which can be attributed to the highest catalytic performance. The monometallic Ni catalyst (0PdNi) totally lost the catalytic activity due to the oxidation of catalytically active Ni metal particles by oxygen after two hour stability test in oxidative steam reforming. In contrast, the oxidation of Ni metal particles did not occur on 0.05PdNi catalyst, and the 0.05PdNi catalyst showed stable catalytic performance during the two hour stability test, which can be due to the formation of highly dispersed Pd atoms on the surface of Ni metal particles on the 0.05PdNi catalyst as suggested by Pd K-edge EXAFS analysis.

Steam Reforming of Biomass Tar Using Iron-based Catalysts

Gasification of biomass is an important process for utilization of production of chemicals and fuels. During the gasification, biomass is converted with oxygen,air or steam into a gas mixture such as CO, CO2, H2, H20 etc. Besides the gases, a number of low, volatile hydrocarbons (mostly CH4) are obtained, together with tars. The tar represents a complex mixture of components, usually polyaromatic that are difficult to deal with in the downstream processes that accompany gasification as well as in utilization technologies. The gasification technology for biomass conversion is still in the development stage and cannot be considered as proven technology for small and medium scale applications. The main technical barrier remains the efficient removal of tar from the produced gases in gasification systems. The purpose of this work is to identify an appropriate catalyst that can be used as an active in-bed material for removal of biomass tar to increase the efficiency processing. Novel nano char-supported iron catalysts were prepared, tested for the steam reforming of biomass tar and their performances were compared with ilmenite catalyst. The activity of char-supported iron catalysts toward steam tar reforming process was investigated under different operational conditions. The experimental data show that catalysts have activity in steam tar reforming process. At low temperature, the tar was mainly converted into coke using iron carbon catalyst , whereas, at high temperature, the tar was primarily reformed into gas using ilmenite. The specific reactivity of the char-supported iron catalyst changed significantly after the steam reforming at different temperatures because of the changes in the properties of the char and the iron-containing species in the catalyst.

Development of a CFD model for the simulation of tar and methane steam reforming through a ceramic catalytic filter

This work concerns the issue of the generation of a clean, hydrogen rich syngas by means of biomass gasification for different downstream applications, such as fuel cell feeding. For a direct use of the syngas it is necessary to remove the major pollutants, first of all tar and particulate matter. Furthermore the production of a syngas with high content of hydrogen requires the reforming of methane. Ceramic catalytic filters have been proposed and tested to perform the removal of particulate and the steam reforming of tar and methane.The development of a CFD model is illustrated and discussed in this paper for the simulation of the ceramic catalytic filter behaviour inside the freeboard of a gasifier and the evaluation of its performance in the steam reforming of tar and methane. The kinetics of the chemical reactions inserted in the model were taken from literature. The model was validated by comparing the simulation outputs with experimental results of tests on a bench scale gasifier containing a ceramic catalytic filter.The model was then used to study the main parameters that have an influence on the performance of the catalytic filters. In particular the variables were temperature (750–850 °C) and filtration velocity (70–110 m/h). A stronger temperature dependency on the conversion of some hydrocarbons has been observed; in particular by increasing the temperature of 100 °C the conversion of CH4 and C7H8 rises of approximately 2 times, while the conversion of C6H6 and C10H8 rises of approximately 4 times.The best conditions for the conversion of tar and methane appear to be highest temperature (850 °C) and lowest filtration velocity (70 m/h). In this case the conversion obtained for methane and tar are about 33% for CH4, 41% for C6H6, 75% for C7H8 and 85% for C10H8.

Steam reforming of biomass tar for hydrogen production over NiO/ceramic foam catalyst

In this study, the catalytic steam reforming of biomass tar for hydrogen production was carried out in a fixed-bed reactor with NiO/ceramic foam catalyst. The ceramic foam used as catalyst carrier was a three-dimensional porous material with high porosity and high specific heat capacity. The effects of reaction temperature, steam to carbon ratio (S/C) and equivalence ratio (ER) on gas quality parameters were investigated. And the fresh, coked and regenerated NiO/ceramic foam catalysts were characterized by SEM and XRD analyses. It was found that, when the temperatures varied from 500 to 900 °C and S/C ratio from 0 to 4, H2 yields were in the range of 28.29–105.28 g H2/kg tar. With increasing ERs, the concentrations of H2 decreased from 63.13 to 18.96%. SEM and XRD analyses showed that the catalyst was in situ activated by reducing nickel oxide to the active nickel metal during a reducing atmosphere in steam reforming process.

Hydrogen production by steam reforming of biomass tar over biomass char supported molybdenum carbide catalyst

Catalytic steam reforming of tar derived from Japanese cedar pyrolysis was investigated over a prepared biomass char supported molybdenum carbide (Mo2C/BC) catalyst in a fixed-bed reactor. Mo2C/BC was prepared by in-situ solid state reaction, and characterized by XRD and SEM to study the effects of carburization temperature and Mo loading amount on Mo2C formation. The results show that Mo2C/BC catalyst was successfully prepared at a relatively low carburization temperature of 800 °C and the initial Mo loading amount for the preparation of this catalyst should be lower than 30 wt.%. The Mo2C/BC showed a good catalytic activity for the steam reforming of tar derived from biomass. In the case of Mo2C/BC with a Mo loading of 20 wt.%, the highest H2 yield was obtained, which is about 5 times higher than that of non-catalytic test. Mo2C/BC could be a promising catalyst in steam gasification of biomass to remove tar and produce H2-rich gas.

The Effects of Ca(OH)<sub>2</sub> on the Steam Gasification Process of Acid-Washed and Raw Lignite

The effect of Ca (OH)2 prepared by the wet-mixing method on acid-washed and raw lignite steam gasification process at 800°C were analyzed in a spout-fluid bed reactor. The addition of Ca (OH)2 on acid-washed lignite obviously increased the coal conversion, gas yield and reduced the tar yield, and the Ca (OH)2 addition on raw lignite significantly reduced the tar yield but just slightly increased the coal conversion and gas yield. As a catalyst, Ca (OH)2 can promote the tar steam reforming in the gasification process. Based on GC-MS data, it can be deduced that Ca (OH)2 has different catalytic activity on the steam reforming of tar with different molecular structures. Aliphatic hydrocarbons, Class 2 and Class 5 tars were clearly catalytic reformed, while the concentration of Class 4 tars increased. The CO concentration decreased and the CO2 and H2 concentration increased with the addition of Ca (OH)2 on both acid-washed and raw lignites, which was mainly caused by the catalytic effect of Ca (OH)2 on WGS reaction. The effect of Ca (OH)2 addition on acid-washed lignite was more significant than on raw lignite, and no adsorption of CO2 was detected in the process by using active carbon as a model compound.

Catalytic steam reforming of tar derived from steam gasification of sunflower stalk over ethylene glycol assisting prepared Ni/MCM-41

Ethylene glycol (EG) assisted impregnation of nickel catalyst on MCM-41 (Ni/MCM-41-EG) was performed and applied for steam reforming of tar derived from biomass. The catalyst was characterized by SEM–EDX, BET, XRD, and TPR. It is found that smaller nickel particles were well dispersed on MCM-41 and better catalytic activity was shown for the Ni/MCM-41-EG when compared with the catalyst of Ni/MCM-41 prepared by using the conventional impregnation method. H2 yield increased approximately 8% when using 20wt.% Ni/MCM-41-EG instead of 20wt.% Ni/MCM-41 for the steam reforming of tar derived from sunflower stalk. The catalyst reusability was also tested up to five cycles, and no obvious activity reduction was observed. It indicates that EG assisted impregnation method is a good way to prepare metal loaded porous catalyst with high catalytic activity, high loading amount and long-term stability for the tar reforming.