1,721,003 research outputs found
Development of a High Temperature CO2 Sorbent Based on Hydrotalcite for a H2-Rich Syngas Production
Full text linkTo adapt hydrotalcite-based sorbents (also known as layered double hydroxides—LDHs) to high-temperature CO2 sorption compatible with tar steam reforming, the addition of CaO was investigated, maintaining the LHDs porosity and accessibility but mostly assuring the CO2 sorption stability during sorption/desorption cycles. In co-precipitation synthesis, the investigated parameters are (i) various interlayer anions with different sizes and valences (carbonate, oxalate, and stearate); (ii) various pH values; (iii) different Mg/Ca molar ratios. The characterization of these modified LDHs by TGA, XRD, N2 adsorption, SEM, sorption capacity, and sorption/desorption stability (cyclic TGA) allowed understanding the effect of the various synthesis parameters and highlighted the effect of oxalate use as the interlayer anion. After calcination of sorbent with Mg/Ca/Al ratio = 1/2/1, typical LDH sand roses were formed both with carbonate and oxalate anions: this former exhibited the highest sorption capacity and accessibility of CaO sites at 600 °C, higher than pure CaO. However, the best stability during cycles was obtained with the sorbent from oxalate and Mg/Ca/Al ratio = 1.5/1.5/1 at pH 10 for which comparable sorption results are reached. For these two samples, the observed macro-porosity was associated with the highest specific surface area and pore volume. Graphic Abstract: [Figure not available: see fulltext.]
Iron based catalyst for hydrocarbons catalytic reforming: A metal-support interaction study to interpret reactivity data
No full textEffect of Ni precursor salts on Ni-mayenite catalysts for steam methane reforming and on Ni-CaO-mayenite materials for sorption enhanced steam methane reforming
No full textIn view of climate change containment, sorption enhanced steam methane reforming (SESMR) appears as an interesting production route for H 2 with the additional advantage of CO 2 capture application performed by high-temperature solid sorbents. CaO is largely employed as CO 2 sorbent because of its low-cost mineralized forms (limestone and dolomite), of its high sorption capacity in the high temperature range compatible with steam methane reforming (SMR). Many recent studies have proposed purposely synthesized Ni-based reforming catalysts, used with high-temperature CO 2 solid sorbents, or combined sorbent-catalyst materials (CSCM). For this last purpose, we studied the effect of Ni salt precursor (Ni nitrate hexahydrate or Ni acetate tetrahydrate) on properties and reactivity of Ni-mayenite catalysts or Ni-CaO-mayenite CSCM, synthesized by an already validated sequence of wet mixing (for sorbents synthesis) and wet impregnation (for catalysts and CSCM synthesis) methods. Although Ni acetate tetrahydrate was often reported as the best choice to improve textural properties, our study identified Ni nitrate hexahydrate as a definitely more suitable precursor than Ni acetate tetrahydrate in the purpose of developing efficient materials for SESMR. The dissimilar behaviors observed in reforming reactivity are related and explained by the differences in textural properties, Ni species dispersion, and reducibility
Iron and Nickel Doped Alkaline-Earth Catalysts for Biomass Gasification with Simultaneous Tar Reformation and CO2 Capture
No full textThe tar reforming catalytic activity of iron and nickel based catalysts supported on alkaline- earth oxides CaO, MgO and calcined dolomite [a (CaMg)O solid solution] has been investigated in a fixed bed reactor operating at temperatures ranging from 650 to 850 °C; toluene and 1-methyl naphthalene were used as model compounds for tar generated during biomass gasification. The CO2 absorption capacities of Fe/(CaMg)O and Ni/(CaMg)O were also investigated at the lower temperature condition (650 °C) at which the sorption process is thermodynamically favoured. It was found that iron and nickel may be optimised in the substrate particles to enhance both the catalytic activity and the carbon deposition resistance during catalytic tests, at the same time reducing critical limitations on CO2 capture capacity
Bi-functional catalyst/sorbent for a h2-rich gas from biomass gasification
No full textThe aim of this work is to identify the effect of the CaO phase as a CO2 sorbent and mayenite (Ca12 Al14 O33) as a stabilizing phase in a bi-functional material for CO2 capture in biomass syngas conditioning and cleaning at high temperature. The effect of different CaO weight contents is studied (0, 56, 85, 100 wt%) in sorbents synthesized by the wet mixing method. These high temperature solid sorbents are upgraded to bi-functional compounds by the addition of 3 or 6 wt% of nickel chosen as the metal active phase. N2 adsorption, X-ray diffraction, scanning electronic microscopy, temperature-programmed reduction analyses and CO2 sorption study were performed to characterize structural, textural, reducibility and sorption properties of bi-functional materials. Finally, sorption-enhanced reforming of toluene (chosen as tar model), of methane then of methane and toluene with bi-functional compounds were performed to study the best material to improve H2 content in a syngas, provided by steam biomass gasification. If the catalytic activity on the sorption enhanced reforming of methane exhibits a fast fall-down after 10–15 min of experimental test, the reforming of toluene reaches a constant conversion of 99.9% by using bi-functional materials
Experimental study on sorption enhanced steam methane reforming by Ni-CaO-mayenite combined materials
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Experimental multicycle sorption enhanced steam methane reforming by Ni-CaO-mayenite materials
No full textNi-CaO Combined Sorbent-Catalyst Materials usage for Sorption Enhanced Steam Methane Reforming
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