Alumina-supported Ni Catalysts Research Articles

Production of CO-rich hydrogen gas from glycerol dry reforming over La-promoted Ni/Al2O3 catalyst

Dry reforming of glycerol has been carried out over alumina-supported Ni catalyst promoted with lanthanum. The catalysts were characterized using EDX, liquid N2 adsorption, XRD technique as well as temperature-programmed reduction. Significantly, catalytic glycerol dry reforming under atmospheric pressure and at reaction temperature of 1023 K employing 3 wt%La–Ni/Al2O3 catalyst yielded H2, CO and CH4 as main gaseous products with H2:CO < 2.0. Post-reaction, XRD analysis of used catalysts showed carbon deposition during glycerol dry reforming. Consequently, BET surface area measurement for used catalysts yielded 10–21% area reduction. Temperature-programmed gasification studies with O2 as a gasification agent has revealed that La promotion managed to reduce carbon laydown (up to 20% improvement). In comparison, the unpromoted Ni/Al2O3 catalyst exhibited the highest carbon deposition (circa 33.0 wt%).

Effect of Interfacial NiAl&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Layer and Calcination Temperature over Anodic Alumina Supported Ni Catalysts during Steam Reforming of Methane

A metal-monolithic anodic alumina supported nickel catalyst with an interfacial NiAl2O4 layer was prepared to investigate its performance in the steam reforming of methane (SRM). Compared with commercial catalysts, this catalyst showed excellent SRM durability at 700°C. This is believed to result from the presence of the interfacial NiAl2O4 layer, which could anchor the top metallic Ni particles, and thus effectively suppress oxidation and sintering of Ni. The nickel reduced from the interfacial NiAl2O4 layer was found to be vital for SRM durability. By varying the preparation conditions of calcination temperature and impregnation sequence, a catalyst with an optimum interfacial NiAl2O4 layer was obtained. The catalyst morphologies in this study are also examined.

Unsupported versus alumina-supported Ni nanoparticles as catalysts for steam/ethanol conversion and CO2 methanation

Nickel nanoparticles (NPs, particle radius <8nm) were prepared via reduction method in aqueous solution and were structurally and morphologically characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). A DC-SQUID magnetometer was also used to determine the particle size. As a reference, a high loading (125% Ni wtNi/wtsupport) Ni/Al2O3, prepared through wet impregnation technique, was also studied. The results of the catalytic tests in ethanol conversion in the presence of steam on unsupported Ni NPs at 523K show already an ethanol conversion higher than 90% together with high yields in methane, CO and H2. These NPs actually behave as very active ethanol decomposition catalysts, in these conditions. Increasing the reaction temperature (673K) they convert into good steam reforming catalysts. On the other hand, the conventional alumina-supported Ni catalyst is poorly active in dehydrogenation to acetaldehyde below 673K, but behaves as a good steam reforming catalyst at this temperature. In CO2 methanation at 773K the best catalytic activity was obtained on 125% Ni/Al2O3, while Ni NPs result poorly active in catalysing this reaction. The characterization of the exhaust materials shows: (i) hexagonal Ni particles on both catalysts after ethanol conversion in the presence of steam, (ii) cubic nickel particles on both samples after methanation of CO2. Mechanistic implications of these results are discussed.

Simultaneous oxidative conversion and CO2 reforming of methane to syngas over Ni/vermiculite catalysts

Modified-vermiculite supported Ni catalysts were prepared and characterized by XRD, BET, TGA, TPR and TEM. The catalytic activity of these catalysts for simultaneous oxidative conversion and CO2 reforming of methane to syngas was evaluated. The results indicated that vermiculite has a great potential as a support of Ni component due to its excellent thermal stability. Among these catalysts, the expanded-vermiculite supported Ni catalyst exhibited the highest catalytic activity and stability. It was found that Ni oxides supported on vermiculite was reduced more easily and also Ni-based vermiculite catalysts suppressed coke depositing in the reaction, in comparison with alumina-supported Ni catalyst.

Effect of H2S on carbon-catalyzed methane decomposition and CO2 reforming reactions

The effect of H2S on catalytic processing of methane is of a great practical importance. In this work, the effect of small quantities (0.5–1.0 vol.%) of H2S present in the feedstock on the methane decomposition and CO2 reforming reactions over carbon and metal based catalysts was investigated. Activated carbon (FY5), an in-house prepared alumina-supported Ni catalyst (NiA) and the mixture of both (FY5 + NiA) were used as catalysts in this study. It was found that CH4 and CO2 conversions were noticeably increased when H2S was added to the reacting mixture, which points to (i) the tolerance of carbon catalyst to H2S and (ii) the catalytic effect of H2S on carbon-catalyzed decomposition and dry reforming of methane. In contrast, NiA catalyst and the mixture FY5 + NiA were deactivated in the presence of H2S in both reactions. The effect of the heating system (i.e., conventional electric resistance vs microwave heating) on the products yield of the dry reforming reaction in the presence of H2S is also discussed in this paper.

Acetic acid hydroconversion to ethanol over novel InNi/Al2O3 catalysts

Abstract Consecutive reduction of acetic acid (AA) to ethanol was studied looking for an advantageous catalyst for the processing of VFAs (volatile fatty acids) that can be produced by thermochemical or biological biomass degradation. A fixed bed flow-through reactor was applied with hydrogen stream at 21 bar total pressure in the temperature range of 220–380 °C. AA hydroconversion activity of the parent alumina supported Ni catalyst and the yield of selectively produced alcohol can be increased drastically by In2O3 addition. Efficient catalysts, containing finely dispersed metal particles were obtained by reduction with H2 at 450 °C. In the catalysts modified with In2O3 additive formation of indium metal and/or an intermetallic compound (InNi2) was observed resulting in a different catalytic behavior as for pure nickel particles supported on alumina. Appearance of metallic indium can direct the step by step catalytic reduction to ethanol formation inhibiting decarbonylation, decarboxylation, and additional dehydration. On comparing the commercial, conventionally used catalysts with the bimetallic alumina supported composite (InNi/Al2O3) the novel catalyst proved to be much more active and selective for producing ethanol.

Sunflower oil to green diesel over Raney-type Ni-catalyst

There are intensive efforts for reforming triglycerides to fuels. A non-pyrophoric Raney nickel type catalyst was investigated in the hydroconversion of sunflower oil. The catalyst was also tested in the transformation of octanoic acid as a model compound at 21bar in temperature range of 280–340°C. It was found that alumina supported Ni catalysts (one of them is non-pyrophoric Raney type Ni) selectively catalyze the hydrodecarbonylation and decarboxylation of fatty acids being corrosive intermediates of trigliceride deoxygenation process. Beside the main hydrodecarbonylation reaction Ni-containing catalysts are active in disadvantageous side reactions such as CO methanization and hydrogenolysis of paraffins producing methane byproduct in high concentration with extensive hydrogen consumption. Non-pyrophoric Raney nickel catalyst is more active than Ni/Al2O3 samples especially in the side reactions. To eliminate the active sites responsible for the side reactions the catalyst was modified with tin and lead. It turned out that poisoning either with Sn or Pb did not improve selectivity. Finally addition of In2O3 proved to be effective by directing the transformation to a different deoxygenating reaction pathway resulting in high alcohol yields.

Catalytic steam reforming of biomass-derived tar for hydrogen production with K2CO3/NiO/γ-Al2O3 catalyst

A major problem of using Ni-based catalysts is deactivation during catalytic cracking and reforming, lowering catalytic performance of the catalysts. Modification of catalyst with alkali-loading was expected to help reduce coke formation, which is a cause of the deactivation. This paper investigated the effects of alkali-loading to aluminasupported Ni catalyst on catalytic performance in steam reforming of biomass-derived tar. Rice husk and K2CO3 were employed as the biomass feedstock and the alkali, respectively. The catalysts were prepared by a wet impregnation method with γ-Al2O3 as a support. A drop-tube fixed bed reactor was used to produce tar from biomass in a pyrolysis zone incorporated with a steam reforming zone. The result indicated that K2CO3/NiO/γ-Al2O3 is more efficient for steam reforming of tar released from rice husk than NiO/γ-Al2O3 in terms of carbon conversion and particularly hydrogen production. Effects of reaction temperature and steam concentration were examined. The optimum temperature was found to be approximately 1,073 K. An increase in steam concentration contributed to more tar reduction. In addition, the K2CO3-promoted NiO/γ-Al2O3 was found to have superior stability due to lower catalyst deactivation.

Improving the catalytic behavior of Ni/Al2O3 by indium in reduction of carboxylic acid to alcohol

Octanoic acid (OA) was used as reactant with medium chain length to model the aliphatic carboxylic acids which can be produced by catalytic, thermochemical or biological degradation of biomass. A flow through reactor was applied at 21 bar total pressure (in general 20 bar hydrogen and 1 bar octanoic acid partial pressures) and 240–360 °C. Fatty acid conversion activity of alumina supported Ni catalysts and the yield of selectively produced alcohol can be increased drastically by In2O3 doping. Appearance of metallic indium can effectively direct the step by step catalytic reduction to alcohol formation over partly reduced Ni catalysts instead of chain shortening hydrodecarbonylation. On comparing a commercial, conventionally used Adkins catalyst (consisting of 72 wt.% CuCr2O4 and 28 wt.% CuO) and novel bimetallic alumina supported composite (InNi/Al2O3) producing alcohol with high selectivity, the chromium-free, environmental benign hydrogenation catalyst seems to be much more active.

Trace Ru-doped anodic alumina-supported Ni catalysts for steam reforming of kerosene: Activity performance and electrical-heating possibility

A plate-type Ru-doped anodic alumina-supported Ni catalyst was synthesized to investigate its activity and electrical-heating possibility in steam reforming of kerosene (SRK). The catalyst showed a favorable SRK durability, which was associated with a synergistic effect between Ru and Ni, referring to the formation of Ru–Ni alloy. Under an electrical-heating pattern, the SRK system could reach stability within ca. 15 min, and no deactivation was observed during the 10 h test. Therefore, this plate-type catalyst is very promising, because it is a multipurpose reforming catalyst for SRK as well as SRM and has a swift startup.

Oxidative CO 2 reforming of CH 4 over Ni/α-Al 2O 3 catalyst

Oxidative carbon dioxide reforming of methane to synthesis gas over alumina-supported Ni catalysts was investigated at atmospheric pressure. The reforming reactions were carried out using a CO 2 to CH 4 feed ratio of one and reaction temperatures in the range 600–800 °C. The activity and stability of the catalyst, carbon deposition, and synthesis gas (H 2/CO) ratio were determined. Catalyst deactivation was primarily due to coke formation. energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and thermo-gravimetric/differential analyzer (TG/DTA) techniques were used to confirm carbon deposition. It was observed that increasing the oxygen feed concentration and/or reaction temperatures, enhanced methane conversion and reduced coke formation. When 20% O 2 feed was used at 800 °C, catalyst stability test revealed a 99.7% CH 4 conversion, 1.0% CH 4 conversion drop and 1% carbon formation.

Preparation and Characterization of Carbon-Covered Alumina Supported Ni Catalyst and Its Catalytic Performance for Hydrogenation

Preparation and Characterization of Carbon-Covered Alumina Supported Ni Catalyst and Its Catalytic Performance for Hydrogenation

Steam reforming reactions over a metal-monolithic anodic alumina-supported Ni catalyst with trace amounts of noble metal

A trace amount of noble metal (Ru or Pt <0.1 wt%) was doped onto an anodic alumina-supported Ni catalyst, to investigate its performance in the steam reforming of methane (SRM), especially during DSS (daily startup and shutdown) operation. Although the steam purge treatment at high temperatures seriously deactivated the Ni catalyst because of the oxidation of metallic nickel with steam into Ni 2+, trace Ru assisted the regeneration of active metallic nickel by hydrogen-spillover. And, the Ni sintering was largely alleviated by the addition of Ru, and it was probably due to the formation of Ru–Ni alloy. In comparison with the Ru-doped Ni catalyst, the Pt-doped Ni catalyst showed a more favorable tolerance to steam oxidation, even at 900 °C. In a stationary SRM test of 3000 h and a DSS SRM test of 500 times where the town gas 13A was used as hydrogen source, no obvious deterioration was detected over the Pt-doped Ni catalyst. Especially, when electrically heating the plate-type Pt-doped Ni catalyst to 700 °C, the SRM reaction system could reach a stable state within ca. 10 min, which offered a strong possibility to shorten the startup time from the 1–2 h of conventional reformer to just few minutes. In addition, the noble metal-doped Ni catalyst also showed favorable activity and durability when being applied to other steam reforming systems, such as kerosene and ethanol.

Thermal and hydrothermal stability of a metal monolithic anodic alumina support for steam reforming of methane

In this work, a plate-type Al/Fe–Cr alloy/Al clad material was prepared into a metal-monolithic anodic alumina support (Al 2O 3/Fe–Cr alloy/Al 2O 3) to investigate its thermal and hydrothermal stability and potential use in the steam reforming of methane (SRM). re-heating of the base material at 500 °C for 3 h or longer significantly enhanced the thermal resistance temperature of the support, which was associated with the formation of the diffusion layer between the alumina layer and the alloy layer. Pore widening treatment (PWT) in 4.0 wt.% oxalic acid solution at 20 °C for 4–8 h provided an excellent anodic support that was strong enough to endure a 1000 °C calcination without the alumina layer shelling off. The appearance of an increased number of smaller fragments and cracks on the support surface was considered to be one of the main reasons for the promotion effect of PWT. During a thermal shock test of the heating–cooling cycles from ambient temperature to 800 °C for 5000 times, no alumina layer was found to shell off from the alloy interlayer, which highlighted the good adhesion between the alumina layer and the alloy layer in the anodic alumina support. Although an obvious decrease of surface area was observed when calcining the support in air or steam at 700 °C, the anodic alumina-supported Ni catalyst showed favorable catalytic durability and hydrothermal stability in the stationary SRM test for 3000 h and the DSS-like (daily start-up and shut-down) test for 500 times in a typical hydrothermal environment (700 °C, Steam/Carbon = 3, 157,000 mL/(h g)). Especially, under an electrical-heating pattern, the SRM reaction system could reach stability within ca. 10 min, offering a strong possibility for shortening the start-up time of conventional SRM reformers from 1 to 2 h to a few minutes.

High-Throughput Screening for the Promoters of Alumina Supported Ni Catalysts in Autothermal Reforming of Methane

The conversion of natural gas(methane) to syngas (reforming reaction) is regarded as alternative routes for production of great value compounds, such as synthetic liquid fuels and oxygenated compounds. The aim of this work is to investigate the highest activity catalyst among 30 catalyst candidates which consists of Ni-M [M (promoter) = Co, Fe, Ce] on γ-Al2O3, by combinatorial method for autothermal reforming. The catalyst candidates with different M/Ni molar ratio were prepared by the impregnation method. The consistent results were found between 32 channel reactors and single fixed bed reactor. It was found that the best catalyst is 5.54 wt%Ni-13.3wt% Ce/γ-Al2O3.

Synthesis of hydrogen and carbon monoxide from methane and carbon dioxide over Ni-Al2O3 catalyst

The mixed gas of CH 4 (50%) and CO 2 (50%) was fed into the porous compacts of alumina-supported Ni (30 vol%) catalyst heated at 673-973 K. Hydrogen was produced by the reaction of the mixed gas (CH 4 + CO 2 →2CO + 2H 2 ). A part of produced CO decomposed to CO 2 and C (2CO→CO 2 + C) below 873 K. As a parallel reaction, the decomposition of CH 4 occurred in the wide temperature range from 673-973 K. The carbon deposition suppressed the flow of the outlet gas.

Alumina-supported Ni catalysts modified with silver for the steam reforming of methane: Effect of Ag on the control of coke formation

Abstract The effect of Ag loading (0.1–0.6 wt.%) on the physicochemical properties and catalytic behavior of Al2O3-supported Ni catalysts on steam reforming of methane was studied. The surface properties of catalysts were evaluated by applying FTIR of adsorbed CO. Additional information was obtained by SBET, XRD, TPR, XANES, XPS and TEM characterizations. Ag caused a strong modification at the surface properties of the samples related to the CO adsorption and the stability to graphitic carbon deposition. The FTIR spectra of adsorbed CO on Ni/Al2O3 catalyst showed bands in two regions: (i) high frequency region (HF) with bands at 2075 cm−1 (HF1) and 2037 cm−1 (HF2), and (ii) low frequency region (LF) with bands at 1946 cm−1 (LF1) and 1902 cm−1 (LF2). The spectra of TPD-CO revealed that the HF2 species were favored with increasing the Ag loading, while the LF species were strongly suppressed. The kinetics parameters E a app versus ln A showed a compensation effect. The catalysts with Ag loading ≥0.3 wt.% submitted to stability tests showed high resistance to coke deposition. The high stability of the Ni catalysts promoted with Ag was attributed to changes in the superficial structure of Ni sites as result of the combination of different effects: (i) the decrease of Ni ensemble by geometric effect of Ag, (ii) changes of Ni sites involved in the nucleation of the graphite structure and (iii) equilibration of different steps of reaction rate decreasing the C* formation rate.

Catalytic decomposition of ammonia in simulated coal-derived gas

Alumina-supported Ni and/or Ru catalysts were prepared and their ability to decompose ammonia in simulated coal-derived gas fuel from 250 to 900 °C using a conventional fixed-bed flow reactor at atmospheric and high pressure (0.9 MPa) was tested. The surface properties of the catalysts were investigated using BET, CO chemisorption, XRD, and TPD after NH 3 adsorption. Supported Ni catalyst promoted NH 3 decomposition to N 2 above 700 °C with and without oxygen addition in the fuel. Supported Ni catalyst had the potential to decompose NH 3 to N 2 from 400 to 550 °C with the addition of a small amount of oxygen in the fuel, while the addition of Ru significantly reduced the potential. Ni selectively promotes NH 3 oxidation to N 2 at low temperature, while Ru selectively promotes H 2 oxidation to H 2 O .

Comparison of reducibility and stability of alumina-supported Ni catalysts prepared by impregnation and co-precipitation

Three Ni–Al 2O 3 catalysts, with nickel loadings of 10–13 wt.%, were prepared by co-precipitation (Ni–Al co-precip), impregnation on an in-house sol–gel derived alumina (Ni/sol–gel Al 2O 3), and impregnation on a commercial γ-Al 2O 3 (Ni/γ-Al 2O 3). The catalysts were characterized by N 2 physisorption, H 2 chemisorption, TPR, XRD, SEM and TEM. The Ni species, Ni particle size, and Ni reducibility depended on the preparation method. The Ni–Al co-precip and Ni/sol–gel Al 2O 3 catalysts contained NiAl 2O 4 species after calcination, while the Ni/γ-Al 2O 3 catalyst contained NiO and NiAl 2O 4 species after calcination. Although the Ni/γ-Al 2O 3 catalyst was the easiest to reduce, according to TPR, this catalyst had the lowest hydrogen uptake over a 100 h temperature-staged reduction experiment. The Ni–Al co-precip and Ni/sol–gel Al 2O 3 catalysts had Ni dispersions of over 7% with reduction at 550 °C for 31 h, and maximum dispersions of ∼10%, after reduction at 650 °C for 7 h. After reduction at 550 °C, the Ni particles were not evident by TEM examination. The results suggest that the formation of a surface NiAl 2O 4 spinel phase during preparation is beneficial for a high Ni dispersion in the reduced catalyst.

Reforming of methane and coalbed methane over nanocomposite Ni/ZrO 2 catalyst

Nanocomposite Ni/ZrO 2-AN catalyst consisting of comparably sized Ni metal and ZrO 2 nanoparticles is studied in comparison with zirconia- and alumina-supported Ni catalysts (Ni/ZrO 2-CP and commercial Ni/Al 2O 3-C) for steam reforming of methane (SRM) and for combined steam and CO 2 reforming of methane (CSCRM). The reactions are performed under atmospheric pressure with stoichiometric amounts of H 2O and CH 4 or (H 2O + CO 2) and CH 4 at 1073 K. Under a wide range of methane space velocity (gas hourly space velocity of methane GHS V C H 4 = 12,000–96,000 ml/(h g cat.), the nanocomposite Ni/ZrO 2-AN catalyst always shows higher activity and stability for both SRM and CSCRM reactions. The two supported Ni catalysts (Ni/ZrO 2-CP and Ni/Al 2O 3-C) exhibit fairly stable catalysis under low GHS V C H 4 but they are easily deactivated under high GHS V C H 4 and become completely inactive when they are reacted for ca.100 h at GHS V C H 4 = 48,000 ml/(h g cat.). The CSCRM reaction is carried out with different H 2O/CO 2 ratios in the reaction feed while keeping the molar ratio (H 2O + CO 2)/CH 4 = 1.0, the results prove that the nanocomposite Ni/ZrO 2-AN catalyst can be highly promising in enabling a catalytic technology for the production of syngas with flexible H 2/CO ratios (ca. H 2/CO = 1.0–3.0) to meet the requirements of various downstream chemical syntheses.