scholarly journals Coke-Resistant Rh and Ni Catalysts Supported on γ-Al2O3 and CeO2 for Biogas Oxidative Steam Reforming

2020 ◽  
Vol 2 (1) ◽  
pp. 10
Author(s):  
Simona Renda ◽  
Antonio Ricca ◽  
Vincenzo Palma
Keyword(s):  
Steam Reforming ◽  
Fossil Fuels ◽  
Supported Catalysts ◽  
Coke Formation ◽  
Coke Deposition ◽  
Ni Catalysts ◽  
Ceo2 Sample ◽  
Active Metal ◽  
Metal Sintering ◽  
Selection Of

The depletion of fossil fuels and the growing concerns related to the environmental impact of their processing has progressively switched the interest towards the utilization of biomass-derived materials for a large variety of processes. Among them, biogas, which is a CH4-rich gas deriving from anaerobic digestion of biomass, has acquired a lot of interest as a feedstock for reforming processes. The main issue in employing biogas is related to the carbon deposition and active metal sintering, which are both responsible for the deactivation of the catalyst. In this work, bimetallic and monometallic Rh- and Ni-based formulations were supported on alumina and ceria with the aim of evaluating their activity and stability in biogas oxidative steam reforming. The Rh addition to the monometallic Ni/γ-Al2O3 formulation enhances its catalytic performances; nevertheless, this induces a higher coke deposition, thus suggesting a preferential coke formation on Rh sites. The initial activity of the CeO2-supported catalysts was found to be lower than the Al2O3-supported catalysts, but the 5%Ni/CeO2 sample showed a very good stability during the test and, despite the lower activity, 0.5%Rh-5%Ni/CeO2 did not show coke deposition. The results suggest that the promotion of Ni/CeO2 catalysts with other active metals could lead to the selection of a highly stable and performing formulation for biogas oxidative steam reforming.

scholarly journals Effect of Mg Contents on Catalytic Activity and Coke Formation of Mesoporous Ni/Mg-Aluminate Spinel Catalyst for Steam Methane Reforming

Catalysts ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 828 ◽  
Author(s):  
Hyunjoung Kim ◽  
Young-Hee Lee ◽  
Hongjin Lee ◽  
Jeong-Cheol Seo ◽  
Kyubock Lee
Keyword(s):  
Catalytic Activity ◽  
Coke Formation ◽  
Coke Deposition ◽  
Methane Reforming ◽  
Reaction Conditions ◽  
Ni Catalysts ◽  
Steam Methane Reforming ◽  
Steam Methane ◽  
Spinel Catalysts ◽  
Mg Content

Ni catalysts are most suitable for a steam methane reforming (SMR) reaction considering the activity and the cost, although coke formation remains the main problem. Here, Ni-based spinel catalysts with various Mg contents were developed through the synthesis of mesoporous Mg-aluminate supports by evaporation-induced self-assembly followed by Ni loading via incipient wetness impregnation. The mesoporous Ni/Mg-aluminate spinel catalysts showed high coke resistance under accelerated reaction conditions (0.0014 gcoke/gcat·h for Ni/Mg30, 0.0050 gcoke/gcat·h for a commercial catalyst). The coke resistance of the developed catalyst showed a clear trend: the higher the Mg content, the lower the coke deposition. The Ni catalysts with the lower Mg content showed a higher surface area and smaller Ni particle size, which originated from the difference of the sintering resistance and the exsolution of Ni particles. Despite these advantageous attributes of Ni catalysts, the coke resistance was higher for the catalysts with the higher Mg content while the catalytic activity was dependent on the reaction conditions. This reveals that the enhanced basicity of the catalyst could be the major parameter for the reduction of coke deposition in the SMR reaction.

scholarly journals Steam Reforming of Model Bio-Oil Aqueous Fraction Using Ni-(Cu, Co, Cr)/SBA-15 Catalysts

2019 ◽  
Vol 20 (3) ◽  
pp. 512 ◽  
Author(s):  
José A. Calles ◽  
Alicia Carrero ◽  
Arturo J. Vizcaíno ◽  
Lourdes García-Moreno ◽  
Pedro J. Megía
Keyword(s):  
Steam Reforming ◽  
Fossil Fuels ◽  
Carbon Number ◽  
Fixed Bed ◽  
Fixed Bed Reactor ◽  
Coke Deposition ◽  
Aqueous Fraction ◽  
Promising Alternative ◽  
Bio Oil ◽  
Carbon Filaments

Hydrogen obtained from biomass derivatives is considered a promising alternative to fossil fuels. The aim of this work is to test the viability of Ni-M/SBA-15 (M: Co, Cu, Cr) catalysts for the hydrogen production from bio-oil aqueous fraction reforming. Tests were performed in a fixed-bed reactor at 600 °C and atmospheric pressure. Firstly, the steam reforming (SR) of acetic acid, hydroxyacetone, furfural and phenol, as representative constituents of the bio-oil aqueous fraction, was carried out. Lower reactivity with increasing carbon number and decreasing steam-to-carbon ratio was observed. Coking rate during SR is a consequence of carbon number and aromaticity of the reactant, as well as the steam-to-carbon ratio. However, deactivation also depends on the graphitization degree of carbon filaments, higher in the case of coke formed from phenol. Then, the performance of the Ni-M/SBA-15 catalysts was studied in the reforming of a bio-oil aqueous fraction surrogate containing the four model compounds. Ni-Co/SBA-15 and Ni-Cr/SBA-15 samples were the most active because Co also catalyze the steam reforming reactions and Cr promotes the formation of very small Ni crystallites accounting for high conversion and the low coke deposition (~8 times lower than Ni/SBA-15) in the form of poorly condensed carbon filaments.

Mechanism of Catalytic Coke Formation and Some Means to Limit it in Refinery Processes

2008 ◽  
Vol 595-598 ◽  
pp. 681-688 ◽  
Author(s):  
François Ropital ◽  
Frédéric Bonnet
Keyword(s):  
Coke Formation ◽  
Mass Gain ◽  
Coke Deposition ◽  
X Ray Diffraction ◽  
Adsorption Sites ◽  
Carbon Filaments ◽  
Mechanisms Of Formation ◽  
Purity Iron ◽  
High Purity Iron ◽  
Selection Of

The formation of carbon filaments which occurs at carbon activities ac > 1 in a range of temperatures 450-700°C is a major problem in many chemical, petrochemical and refinery processes where hydrocarbons or other strongly carburizing atmospheres are involved. An excessive carbon deposition causes deterioration of the furnace alloys, such as an important migration of carbon into the alloys. In order to better control and limit this deterioration, this work has been performed to on one side get a more accurate understanding of the mechanisms of formation of catalytic coke and on the other side to find remedies as the injection of selected additives in the feed. Thermogravimetric analyses (TGA) were performed on iron samples in simulated conditions of isobutane dehydrogenation. X ray diffraction (XRD) and scanning electron microscopy examinations were used to identify the different steps during the formation of the catalytic coke. The selection of appropriate remedies to reduce the catalytic coke deposition, requires accurate understanding on both mechanisms of the catalytic particles formation and of the growth of the graphite filaments. We have studied the first steps of the catalytic coke formation on high purity iron that has been previously reduced or oxidised. The comparison of the catalytic coke deposition kinetics indicates that the mass gain is much faster on a pre oxidised state than on a reduced one. In refinery and petrochemical processes, several methods can be selected in order to limit the deposition phenomena of catalytic coke: selection of an appropriate metallurgy, protection of the surfaces by application of coatings, injection of additives with the feed. Steric inhibitors (that block the adsorption sites and slow down the germination and diffusion steps) such as sulfur additives are currently industrially used but special care has to be taken in order to prevent consequential secondary effects such as, for catalytic refinery process, the deactivation of catalysts. Based on TGA experiments, the accurate amount of inhibitor to be injected has been selected regarding the oxidising state of the iron surface.

Catalytic Performances of Bi-Metallic Ni-Co Catalysts in Acetic Acid Steam Reforming Reaction: Effect of Mg Incorporation

2019 ◽  
Vol 17 (6) ◽  
Author(s):  
Sahika Ozel Sahin ◽  
Huseyin Arbag ◽  
Nuray Oktar ◽  
Kirali Murtezaoglu
Keyword(s):  
Acetic Acid ◽  
Reaction Temperature ◽  
Steam Reforming ◽  
Sol Gel ◽  
Mesoporous Alumina ◽  
Coke Deposition ◽  
Ni Catalysts ◽  
Alumina Support ◽  
Co Catalysts ◽  
Catalytic Performances

Abstract In this study, mesoporous alumina supported bi-metallic Ni-Co catalysts were synthesized and catalytic performances were investigated in hydrogen production through steam reforming of acetic acid reaction. Mesoporous alumina support was synthesized using a sol-gel method and metals were co-impregnated into the structure of the catalyst. The physicochemical properties of the synthesized materials were characterized by XRD, N2 adsorption-desorption, SEM and TG-DT analysis. The activity test results showed that the bi-metallic 4Ni-1Co@SGA catalyst showed high and stable activity in steam reforming of acetic acid, giving a high H2 selectivity at 750 °C. Bi-metallic Ni-Co catalysts showed higher performance than monometallic Co catalyst, yielding less methane production and coke deposition. Co incorporation decreased activity of Ni catalysts at high reaction temperature of 750 °C in terms of AcOH conversion; however, improved the activity of Ni catalysts at low reaction temperature of 550 °C in terms of AcOH conversion and H2 Selectivity. Mg incorporation enhanced the coke resistance of the catalyst and further, among the bi- and tri-metallic catalysts, the lowest coke deposition was obtained over Mg incorporated 4Ni-1Co@SGA catalyst at 750 °C.

scholarly journals Nanowire-Based Materials as Coke-Resistant Catalyst Supports for Dry Methane Reforming

Catalysts ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 175
Author(s):  
Apolo Nambo ◽  
Veerendra Atla ◽  
Sivakumar Vasireddy ◽  
Vivekanand Kumar ◽  
Jacek B. Jasinski ◽  
...  
Keyword(s):  
Supported Catalysts ◽  
Coke Formation ◽  
Packed Bed ◽  
High Ratio ◽  
Titania Nanoparticles ◽  
Coke Deposition ◽  
Methane Reforming ◽  
Co2 Conversion ◽  
Spent Catalyst ◽  
Long Time

In this paper, nanowire-supported catalysts loaded with nickel are shown to be coke resistant compared to nanoparticle-supported catalysts. Specifically, Ni-loaded titania-based nanowire catalysts were tested with the dry methane reforming process in a laboratory-scale continuous packed-bed atmospheric reactor. The CO2 conversion rate stayed above 90% for over 30 h on stream under coke-promoting conditions, such as high flow rates, low temperatures, and a high ratio of CH4 to CO2. The coke (CxHy, x>>y) on the spent catalyst surface for both nanowire- and nanoparticle-supported catalysts was characterized by TGA, temperature-programmed reduction (TPR), and electron microscopy (SEM/TEM/EDS), and it was revealed that the types of carbon species present and their distribution over the morphology-enhanced materials played a major role in the deactivation. The CO2 conversion activity of Ni supported on titania nanoparticles was reduced from ~80% to less than 72% in 30 h due to the formation of a graphitic coke formation. On the other hand, Ni particles supported on nanowires exhibited cube-octahedral morphologies, with a high density of non- (111) surface sites responsible for the increased activity and reduced graphitic coke deposition, giving a sustained and stable catalytic activity during a long time-on-stream experiment.

scholarly journals Support Effects on the Activity of Ni Catalysts for the Propane Steam Reforming Reaction

Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1948
Author(s):  
Aliki Kokka ◽  
Athanasia Petala ◽  
Paraskevi Panagiotopoulou
Keyword(s):  
Steam Reforming ◽  
Supported Catalysts ◽  
Catalytic Performance ◽  
Dissociative Adsorption ◽  
Ni Catalysts ◽  
Long Term Stability ◽  
Parallel Increase ◽  
Order Of Magnitude

The catalytic performance of supported Ni catalysts for the propane steam reforming reaction was investigated with respect to the nature of the support. It was found that Ni is much more active when supported on ZrO2 or YSZ compared to TiO2, whereas Al2O3- and CeO2-supported catalysts exhibit intermediate performance. The turnover frequency (TOF) of C3H8 conversion increases by more than one order of magnitude in the order Ni/TiO2 < Ni/CeO2 < Ni/Al2O3 < Ni/YSZ < Ni/ZrO2, accompanied by a parallel increase of the selectivity toward the intermediate methane produced. In situ FTIR experiments indicate that CHx species produced via the dissociative adsorption of propane are the key reaction intermediates, with their hydrogenation to CH4 and/or conversion to formates and, eventually, to CO, being favored over the most active Ni/ZrO2 catalyst. Long term stability test showed that Ni/ZrO2 exhibits excellent stability for more than 30 h on stream and thus, it can be considered as a suitable catalyst for the production of H2 via propane steam reforming.

scholarly journals Hydrogen Production from Steam Reforming of Acetic Acid as a Model Compound of the Aqueous Fraction of Microalgae HTL Using Co-M/SBA-15 (M: Cu, Ag, Ce, Cr) Catalysts

Catalysts ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1013 ◽  
Author(s):  
Pedro J. Megía ◽  
Alicia Carrero ◽  
José A. Calles ◽  
Arturo J. Vizcaíno
Keyword(s):  
Acetic Acid ◽  
Hydrogen Production ◽  
Steam Reforming ◽  
Fossil Fuels ◽  
Model Compound ◽  
Complex Mixture ◽  
Coke Deposition ◽  
Aqueous Fraction ◽  
Thermochemical Processing ◽  
Renewable Hydrogen

Hydrogen production derived from thermochemical processing of biomass is becoming an interesting alternative to conventional routes using fossil fuels. In this sense, steam reforming of the aqueous fraction of microalgae hydrothermal liquefaction (HTL) is a promising option for renewable hydrogen production. Since the HTL aqueous fraction is a complex mixture, acetic acid has been chosen as model compound. This work studies the modification of Co/SBA-15 catalyst incorporating a second metal leading to Co-M/SBA-15 (M: Cu, Ag, Ce and Cr). All catalysts were characterized by N2 physisorption, ICP-AES, XRD, TEM, H2-TPR, H2-TPD and Raman spectroscopy. The characterization results evidenced that Cu and Ag incorporation decreased the cobalt oxides reduction temperatures, while Cr addition led to smaller Co0 crystallites better dispersed on the support. Catalytic tests done at 600 °C, showed that Co-Cr/SBA-15 sample gave hydrogen selectivity values above 70 mol % with a significant reduction in coke deposition.

scholarly journals Enhancement of Ni Catalyst Using CeO2–Al2O3 Support Prepared with Magnetic Inducement for ESR

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1357
Author(s):  
Pumiwat Vacharapong ◽  
Sirintra Arayawate ◽  
Sasimas Katanyutanon ◽  
Pisanu Toochinda ◽  
Luckhana Lawtrakul ◽  
...  
Keyword(s):  
Hydrogen Production ◽  
Steam Reforming ◽  
Coke Formation ◽  
Coke Production ◽  
H2 Production ◽  
Catalyst Preparation ◽  
Ni Catalyst ◽  
Ni Catalysts ◽  
Al2o3 Support ◽  
Ethanol Steam

The effect of magnetic inducement in support preparation was studied to reduce coke and improve the activity of Ni catalysts for ethanol steam reforming (ESR) at 550–650 °C. Magnetic inducement was introduced to prepare 5 mol % CeO2 in Al2O3 support in order to control the composition and the distribution of Ce in Al2O3. The results show that using CeO2–Al2O3 support with magnetic inducement affects both hydrogen production and coke reduction, where Ni/CeO2–Al2O3 support prepared under magnetic inducement with N–N pole arrangement (Ni/CeO2–Al2O3 (N–N)) exhibited the highest hydrogen production and the lowest coke formation among the catalysts used in this work. Compared with Ni/CeO2–Al2O3 (no magnet), Ni/CeO2–Al2O3 (N–N) catalysts yield 14.0% higher H2 production and 31.7% less coke production. The modified catalyst preparation process used in this study could create catalysts for hydrogen production from ESR which are high in performance and stability but low in preparation cost.

scholarly journals High Active and Selective Ni/Ceo2-Al2O3 and Pd-Ni/Ceo2-Al2O3 Catalysts for Oxy-Steam Reforming of Methanol

2018 ◽  
Author(s):  
Pawel Mierczynski ◽  
Agnieszka Mierczynska ◽  
Radoslaw Ciesielski ◽  
Magdalena Mosinska ◽  
Waldemar Maniukiewicz ◽  
...  
Keyword(s):  
Nickel Catalyst ◽  
Steam Reforming ◽  
Supported Catalysts ◽  
Binary Oxide ◽  
Impregnation Method ◽  
Ni Catalysts ◽  
Catalytic Systems ◽  
Steam Reforming Of Methanol ◽  
Bimetallic Palladium ◽  
Excellent Stability

Herein, we report about the monometallic Ni and bimetallic Pd-Ni catalysts supported on CeO2-Al2O3 binary oxide, which were investigated in oxy-steam reforming of methanol (OSRM). Monometallic and bimetallic supported catalysts were prepared by wet aqueous impregnation and subsequent impregnation method, respectively. The physicochemical properties of the catalytic systems were investigated using various methods such as: BET, XRD, TPR-H2, TPD-NH3, XPS and SEM-EDS techniques. It has been proven that the addition of palladium to the nickel catalyst facilitates its reduction. The activity tests performed for all catalysts confirmed the promotion effect of palladium on catalytic activity of nickel catalyst and selectivity towards hydrogen production. Both nickel and bimetallic palladium-nickel supported catalysts showed excellent stability during the reaction. Such catalytic systems are valuable for the advance of the field of fuel cell technology.

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