Catalytic performances of Ni-based catalysts on supercritical water gasification of phenol solution and coal-gasification wastewater

Activity and stability of the supported Ni-based catalysts for the gasification performances of phenol solution and coal-gasification wastewater in supercritical water were studied in a continuous reactor at 480 °C, 25 MPa and oxygen ratio of 0.2 for 50 h operation. The influences of the supports (γ-Al₂O₃, active carbon (AC) and carbon nanotube (CNT)) on gas yields, gasification efficiencies for phenol solution were investigated, and the loading amount of Ni were optimized. Results showed that the catalytic activity and the stability of the catalysts followed the order of Ni/CNT > Ni/AC > Ni/γ-Al₂O₃. The activity of Ni/AC and Ni/γ-Al₂O₃ decreased after 30 h continuous operation, and there occurred significant leaching of Ni²⁺. For Ni/CNT catalyst, H₂ yield increased obviously when the loading amount of Ni lower than 15 wt%, while increased little at higher loading amount. Then, 15 wt% Ni/CNT with a thickness of 1.5 mm was coated on 316 L stainless steel (SS316L, an economic material usually used as the reactor material), which can act as a "catalytic tube wall" in reactor. The catalytic activity and corrosion resistance of Ni/CNT/SS316L for the gasification of real coal-gasification wastewater were studied. Results showed that Ni/CNT/SS316L gave a great positive effect on H₂ production. H₂ yield increased from 25.36 mmol/g (total organic carbon) without catalyst to 75.12 mmol/g (total organic carbon) with Ni/CNT/SS316L after operated for 20 h, respectively. However, obvious pealing of the coating was found after 50 h operation. Further study is necessary for the improvement of the coating preparation method.     

Enhancing hydrogen production by dry reforming process with strontium promoter

Hydrogen is an ideal energy carrier and can play a very important role in the energy system. The present study investigated the enhancement of hydrogen production from catalytic dry reforming process. Two catalysts namely Ni/γ-Al₂O₃ and Co/γ-Al₂O₃ promoted with different amounts of strontium were used to explore selectivity and yield of hydrogen production. Spent and fresh catalysts were characterized using techniques such as BET, XRD, H₂-TPR, CO₂-TPD, TGA and O₂-TPO. The catalyst activity and characterization results displayed stability improvement due to addition of Sr promoter. The least coke formations i.e. 3.8 wt% and 5.1 wt% were obtained using 0.75 wt% Sr doped in Ni/γ-Al₂O₃ and 0.5 wt% Sr doped in Co/γ-Al₂O₃ catalysts respectively. Time on stream tests of promoted catalysts for about six hours at 700 °C showed stable hydrogen selectivity. Moreover, the hydrogen selectivity was significantly improved by the addition of Sr in Ni and Co based catalysts. For instance the hydrogen selectivity increased from 45.9% to 47.8% for Ni/γ-Al₂O₃ and from 48% to 50.9% for Co/γ-Al₂O₃ catalyst by the addition of 0.75 wt% Sr in Ni/γ-Al₂O₃ and 0.5 wt% Sr in Co/γ-Al₂O₃ catalyst respectively.     

Catalytic steam reforming of biomass-derived acetic acid over modified Ni/γ-Al2O3 for sustainable hydrogen production

In order to obtain sustainable H₂, the catalytic steam reforming of acetic acid derived from biomass was performed by using the catalysts modified with basic promoters (Mg, La, Cu, and K). La and K increased the total basicity of Ni/γ-Al₂O₃ by 30.6% and 93.4%, respectively, which could induce ketonization, producing acetone. In contrast, Mg reduced the number of middle and strong basic sites by 17.2% and improved the number of weak basic sites by 5% for Ni/γ-Al₂O₃, which promoted the steam reforming of acetic acid (ca. 100% of H₂ and carbon selectivity at even 450 °C) without ketonization. Moreover, the amount of carbon deposited on Ni/Mg/γ-Al₂O₃ was 55.1% less than that deposited on Ni/γ-Al₂O₃. When Cu was employed, the conversion was ca. 60% with less than 70% of H₂ selectivity, at all temperatures considered herein.     

Highly stable and active Ni-mesoporous alumina catalysts for dry reforming of methane

Nanostructured Ni-incorporated mesoporous alumina (MAl) materials with different Ni loading (7, 10 and 15 wt %) were prepared by a template assisted hydrothermal synthesis method and tested as catalysts for CO₂ reforming of methane under different conditions (nickel loading, gas hourly space velocity (GHSV), reaction temperature and time-on-stream (TOS)). The most active catalyst tested (Ni(10 wt%)-MAl) showed a very high stability over 200 h compared to a Ni(10 wt%)/γ-Al₂O₃ prepared using a co-precipitation method which had a significant loss in activity after only ∼4 h of testing. The high stability of the Ni-MAl materials prepared by the template assisted method was due to the Ni nanoparticles in these catalysts being highly stable towards migration/sintering under the reaction conditions used (800 °C, 52,000 mL h⁻¹ g⁻¹). The low susceptibility of the Ni nanoparticles in these catalysts to migration/sintering was most likely due to a strong Ni-support interaction and/or active metal particles being confined to the mesoporous channels of the support. The Ni-MAl catalysts also had significantly lower amounts of carbon deposited compared to the catalyst prepared using the co-precipitation method.     

Autothermal reforming of iso-octane and gasoline over Rh-based catalysts: Influence of CeO2/γ-Al2O3-based mixed oxides on hydrogen production

Autothermal reforming (ATR) of iso-octane in the presence of Rh-based catalysts (0.5 wt% of Rh) supported onto γ-Al₂O₃, CeO₂, and ZrO₂ were initially carried out at 700 °C with a S/C ratio of 2.0, an O/C ratio of 0.84, and a gas hourly space velocity (GHSV) of 20,000 h⁻¹. The activity of Rh/γ-Al₂O₃ was found to be higher than Rh/CeO₂ and Rh/ZrO₂, with H₂ and (H₂ + CO) yields of 1.98 and 2.48 mol/mol C, respectively, after 10 h. This Rh/γ-Al₂O₃ material, however, was potentially susceptible to carbon coking and produced 3.5 wt% of carbon deposits following the reforming reaction, as evidenced by C, H, N, and S elemental analysis. In contrast, Rh/CeO₂ catalyst exhibited lower activity but higher stability than Rh/γ-Al₂O₃, with nearly no carbon being formed within 10 h. To combine the superior activity originated from Rh/γ-Al₂O₃ with high stability from Rh/CeO₂, Rh/CeO₂/γ-Al₂O₃ catalysts with different CeO₂ contents were synthesized and examined for the ATR reactions of iso-octane. Compared to Rh/γ-Al₂O₃, the newly prepared Rh/CeO₂/γ-Al₂O₃ catalysts (0.5 wt% of Rh and 20 wt% of CeO₂) showed even enhanced activity during 10 h, and H₂ and (H₂ + CO) yields were calculated to be 2.08 and 2.62 mol/mol C, respectively. In addition, as observed with Rh/CeO₂, the catalyst was further found to be stable with less than 0.3 wt% of carbon deposition after 10 h. The Rh/γ-Al₂O₃ and Rh/CeO₂/γ-Al₂O₃ catalysts were eventually tested for ATR reactions using commercial gasoline that contained sulfur, aromatics, and other impurities. The Rh/γ-Al₂O₃ catalyst was significantly deactivated, showing decreased activity after 4 h, while the Rh/CeO₂/γ-Al₂O₃ catalyst proved to be excellent in terms of stability against coke formation as well as activity towards the desired reforming reaction, maintaining its ability for H₂ production for 100 h.     

Properties of Ni/Y2O3 and its catalytic performance in methane conversion to syngas

Ni/Y₂O₃, with Y₂O₃ support prepared by the conventional precipitation method, was prepared by an impregnation method. The physicochemical properties of Y₂O₃ and Ni/Y₂O₃ were characterized by BET, CO₂-TPD, NH₃-TPD, TPR, XRF and TGA, and compared with those of γ-Al₂O₃ and Ni/γ-Al₂O_3, respectively. The catalytic performance of Ni/Y₂O₃ in the reaction of partial oxidation of methane (POM) to syngas was evaluated and compared with that of Ni/γ-Al₂O₃ catalyst, too. The results showed that, Y₂O₃ was a basic support with few acidic sites while γ-Al₂O₃ was an acidic support. NiO particles supported on Y₂O₃ were more easily to be reduced than those supported on γ-Al₂O₃. In the partial oxidation of methane, Ni/Y₂O₃ catalyst showed high catalytic activity and exhibited better catalytic stability than Ni/γ-Al₂O₃. After POM reaction at 700 °C for 550 h, methane conversion decreased little and only 2.2 wt% carbon was deposited on Ni/Y₂O₃ catalyst. Ni/Y₂O₃ was stable in POM even after a series of reaction temperature variations within the temperature range of 400 ∼ 800 °C.     

Syngas production from methane dry reforming via optimization of tungsten trioxide-promoted mesoporous γ-alumina supported nickel catalyst

Syngas production via dry reforming of methane was conducted over 5 wt%Ni + xWO₃/γ-Al₂O₃ (x = 1, 3, 5, 7, or 9 wt%) catalysts at 700 °C and ambient pressure for 7.5 h in a tubular fixed-bed reactor. Textural, morphological, and catalytic properties were investigated in relation to the weight percent of tungsten trioxide loading. The physicochemical properties of the catalysts were evaluated using XRD, N₂-physisorption, TGA, H₂-TPR, CO₂-TPD, NH₃-TPD, SEM, EDX, and Raman techniques. N₂-physisorption analysis showed that tungsten trioxide promoter had a minor impact on the textural properties upon varying its weight percentage loading. With increasing tungsten trioxide loading, the total amount of reducible NiO-interacting species was increased over the catalyst surface. 5Ni+5WO₃/γ-Al₂O₃ catalyst showed stable 79% CH₄ conversions and 83% CO₂ conversion with the lowest carbon deposition due to the presence of stable metallic Ni species (derived from reducible NiAl₂O₄ and NiWOAl), the highly acidic sites, and moderate basic sites.     

Screening of supported transition metal catalysts for hydrogen production from glucose via catalytic supercritical water gasification

In total 17 heterogeneous catalysts, with combinations of 4 transition metals (Ni, Ru, Cu and Co) and various promoters (e.g., Na, K, Mg, or Ru) supported on different materials (γ-Al₂O₃, ZrO₂, and activated carbon (AC)), were investigated with respect to their catalytic activity and stability for H₂ production from glucose via supercritical water gasification (SCWG). The experiments were carried out at 600 °C and 24 MPa in a bench-scale continuous-flow tubular reactor. Ni (in metallic form) and Ru (in both metallic and oxidized forms) supported on γ-Al₂O₃ exhibited very high activity and H₂ selectivity among all of the catalysts investigated for a time-on-stream of 5-10 h. With Ni20/γ-Al₂O₃ (i.e., γ-Al₂O₃ with 20 wt% Ni), a H₂ yield of 38.4 mol/kg glucose was achieved, approximately 20 times higher than that obtained during the blank test without catalyst (1.8 mol/kg glucose). In contrast, Cu and Co catalysts were much less effective for glucose SCWG reactions. As for the effects of catalyst support materials on activity, the following order of sequence was observed: γ-Al₂O₃ > ZrO₂ > AC. In addition, Mg and Ru were found to be effective promoters for the Ni/γ-Al₂O₃ catalyst, suppressing coke and tar formation.     

Evaluation of catalytic subcritical water gasification of food waste for hydrogen production: Effect of process conditions and different types of catalyst loading

Food waste is a kind of wet bio-waste which has been a challenge for the ecological environment and disposal. In this paper, hydrogen production from subcritical water gasification (SbWG) of food waste with and without catalyst loading was systematically investigated. The effects of reaction temperature (300–360 °C), residence time (30–90 min), food waste concentration (10–30 wt%) and catalysts (Ni/γ-Al₂O₃, Ni/ZrO₂, NaOH, KOH, and FeCl₃) were studied within a pressure range of 10.5–20 MPa. The optimal process condition for SbWG of food waste without catalysts loading was determined to be 360 °C and 90 min with 10 wt% food waste. The liquid products and hydrochar were characterized by TOC, TGA/DTG, and SEM. The TOC concentration of liquid products decreased vastly with increasing reaction temperature. The highest H₂ yield (1.88 mol/kg), H₂ mole fraction (35.01%), and H₂ selectivity (53.86%) were achieved at 360 °C for 90 min with 5 wt% loading of KOH. It can be concluded that the performance of the catalysts for improving hydrogen production in SbWG of food waste was in the following order: KOH > NaOH > Ni/γ-Al₂O₃ > Ni/ZrO₂ > FeCl₃. The catalytic SbWG can be a potential alternative for energy conversion of food waste and hydrogen production.     

Catalytic characteristics of innovative Ni/slag catalysts for syngas production and tar removal from biomass pyrolysis

In this study, innovative Ni-based catalysts supported by five typical slag carriers (magnesium slag (MS), steel slag (SS), blast furnace slag (BFS), pyrite cinder (PyC) and calcium silicate slag (CSS)) were prepared by wet impregnation. With the prepared catalysts and Ni/γ-Al₂O₃ catalyst, catalytic reforming of pyrolysis volatiles from pine sawdust for syngas production and tar removal was investigated. The catalysts were characterized by BET, XRD, SEM, TEM and Raman. The catalytic performances of the six catalysts were decreasing in the following order: Ni/MS > Ni/γ-Al₂O₃ > Ni/SS > Ni/BFS > Ni/CSS > Ni/PyC. Ni/MS catalyst exhibited excellent catalytic reactivity as well as thermal stability in terms of tar conversion (95.19%), gas yield (1.46 Nm³/kg) and CO₂ capture ability (CO₂ yield of 0.5%). Both amorphous carbon and graphite-type carbon were formed on the catalysts after catalytic reforming and the D/G ratio (the relative intensity ratio of the D-band to the G-band) was positively correlated to the catalytic activity.     

Effects of different Al2O3 support on HDPE gasification for enhanced hydrogen generation using Ni-based catalysts

This study examined the effects of Ni loading on different types of alumina (γ-Al₂O₃, mesoporous Al₂O₃, 13 nm-sized Al₂O₃, and <50 nm-sized Al₂O₃) for high-density polyethylene gasification for enhanced hydrogen generation. The catalytic activity of Ni loaded alumina was observed in the order of 13 nm-sized Al₂O₃> mesoporous Al₂O₃> (<50 nm-sized Al₂O₃) > γ-Al₂O₃ for the gas yield and γ-Al₂O₃> (<50 nm Al₂O₃) > mesoporous Al₂O₃ > 13 nm Al₂O₃ for the oil yield, respectively. In addition, the production of hydrogen from Ni loaded alumina showed an increasing trend in the order of (<50 nm-sized Al₂O₃) > γ-Al₂O₃> 13 nm-sized Al₂O₃.> mesoporous Al₂O₃. In contrast, CO showed the trend as Ni/mesoporous Al₂O₃> Ni/13 nm-sized Al₂O₃> Ni/γ-Al₂O₃> (Ni/<50 nm Al₂O₃). The highest level of hydrogen production from the Ni/<50 nm-sized Al₂O₃ catalyst might be because of its highest Ni dispersion and surface area. The use of Ni-loaded nm-sized alumina could be an excellent method for increased hydrogen production compared to other types of alumina available.     

Coke-resistance enhancement of mesoporous γ-Al2O3 and MgO-supported Ni-based catalysts for sustainable hydrogen generation via steam reforming of acetic acid

Highly ordered mesoporous γ-Al₂O₃ particles and MgO materials were synthesized by evaporation induced self-assembly (EISA) and template-free hydrothermal co-precipitation routes, respectively. Ni, Ni–MgO, and Ni–La₂O₃-containing catalysts were prepared using a wet-impregnation method. The synthesized catalysts were characterized by N₂ adsorption–desorption, XRD, SEM-EDS, DRIFTS, XPS, TGA-DTA, and Raman spectroscopy analysis. The mesoporous γ-Al₂O₃ catalyst support exhibited a high surface area of 245 m²/g and average pore volume of 0.481 cm³/g. The DRIFTS results indicate the existence of large Lewis's acid regions in the pure γ-Al₂O₃ and metal-containing catalysts. Catalytic activity tests of pure materials and metal-containing catalysts were carried out at the reaction temperature of 750 °C and a feed molar ratio of AA/H₂O/Ar:1/2.5/2 over 3 h. Complete conversion of acetic acid and 81.75% hydrogen selectivity were obtained over the catalyst 5Ni@γ-Al₂O₃. The temperature and feed molar ratio had a noticeable impact on H₂ selectivity and acetic acid conversion. Increasing the water proportion in the feed composition from 2.5 to 10 considerably improved the catalytic activity by increasing hydrogen selectivity from 81.75% to 91%. Although the Ni-based γ-Al₂O₃-supported catalysts exhibited higher activity performance compared to the Ni-based MgO-supported catalysts, they were not as resistant to coke formation as were MgO-supported catalysts. The introduction of MgO and La₂O₃ into the Ni@γ-Al₂O₃ and Ni@MgO catalysts' structures played a significant role in lowering the carbon formation (from 37.15% to 17.6%–12.44% and 12.17%, respectively) and improving the thermal stability of the catalysts by decreasing the agglomeration of acidic sites and reinforcing the adsorption of CO₂ on the catalysts' surfaces. Therefore, coke deposition was reduced, and catalyst lifetime was improved.     

Hydrogen generation from Al-Water reaction promoted by M-B/γ-Al2O3 (M = Co,Ni) catalyst

Al-water reaction promoted by catalysts is a promising hydrogen generation technology. In this work, a high-activity M-B/γ-Al₂O₃ (M = Co, Ni) catalyst is prepared by wet chemical reduction method. It is found that M-B/γ-Al₂O₃ catalyst significantly promotes the Al-water reaction and decreases the induction time. When the molar ratio of γ-Al₂O₃ to Co-M in Co–B/γ-Al₂O₃ catalyst is 1:1, the induction time is only 0.43 h. The catalytic activity of M-B/γ-Al₂O₃ is proportional to its active area. SEM analyses show that M-B particles are dispersed on γ-Al₂O₃ surface, which reduces the agglomeration of M-B and increases the active surface of M-B/γ-Al₂O₃, leading to a high catalytic activity. A possible mechanism is proposed, which shows that the dissociation of water molecules on γ-Al₂O₃ surface and the microgalvanic interaction between M-B and Al can promote the hydration process of passive oxide film on Al particle surface, speeding up the Al-water reaction.     

Effect of nickel loading on hydrogen production and chemical oxygen demand (COD) destruction from glucose oxidation and gasification in supercritical water

Gasification and partial oxidation of 0.25 molar glucose solution was conducted over different metallic nickel (Ni) loadings (7.5, 11, and 18 wt%) on different catalyst supports (θ-Al₂O₃ and γ-Al₂O₃) in supercritical water. Experiments were carried out at three different temperatures (T) of 400, 450, and 500 °C at constant pressure of 28 MPa and a 30 min reaction time (t). For comparison, some experiments were conducted using high loading commercial catalyst (65 wt% Ni on Silica–alumina). Hydrogen peroxide (H₂O₂) was used as a source of oxygen in the partial oxidation experiments. Oxygen to carbon molar ratios (MR) of 0.5–0.9 were examined to increase the hydrogen production via carbon monoxide (CO) production. Results showed that in the absence of the catalyst, the optimum molar ratio was 0.8 i.e. 80% of the amount of oxygen required for complete oxidation of glucose. At a molar ratio of 0.8, the hydrogen yield was 0.3 mol/mol, as compared to 0.2 mol/mol glucose at molar ratio of 0.5 and 0.9. This optimized oxygen dose was adopted as a base line for catalysts evaluation. The main gaseous products were carbon dioxide (CO₂), carbon monoxide (CO), hydrogen (H₂), and methane (CH₄). Results also showed that the presence of Ni increased the total gas yield increased in the 7.5–18 wt Ni/Al₂O₃ catalyst. An increase in MR from 0.55 to 0.8 increased the of carbon dioxide and hydrogen yields from 1.8 to 3.8 mol/mol glucose and from 0.9 to 1.1 mol/mol. The carbon monoxide and methane yields remain constant at 2 and 0.5 mol/mol glucose, respectively. The introduction of hydrogen peroxide (H₂O₂) prior to the feed injection inhibited the catalyst activity and did not increase the hydrogen yield whereas the introduction of H₂O₂ after 15 min of reaction time increased the hydrogen yield from 0.62 mol/mol to 1.5 mol/mol. This study showed that approximately the same hydrogen yield can be obtained from the synthesized low nickel alumina loading (18 wt%) catalyst as with the 65 wt% nickel on silica–alumina loading commercial catalyst. The highest H₂ yield of 1.5 mol/mol glucose was obtained with commercial Ni/silica–alumina with a BET surface area of 190 m²/g compared to 1.2 mol/mol with the synthesized Ni/θ alumina with a BET surface area of 46 m²/g.     

Hydrogen production from catalytic supercritical water reforming of glycerol with cobalt-based catalysts

Glycerol reforming under catalytic supercritical water at temperatures in the range of 723–848 K using Co catalyst deposited on various supports including ZrO₂, yttria-stabilized zirconia (YSZ), La₂O₃, γ-Al₂O₃, and α-Al₂O₃ was investigated. An increase in operating temperature promoted the continued increase in glycerol conversion; however, carbon formation causing system operation failure was observed for γ-Al₂O₃ and α-Al₂O₃ at high operating temperatures (i.e. 748–798 K). Co supported on YSZ provided the most efficient performance for hydrogen production. 10 wt.% Co loading on YSZ support was an optimum amount to enhance the reaction. The increase in glycerol conversion and reduction of the amount of liquid products were observed for lower weight hourly space velocity (WHSV), higher operating temperature or higher cobalt loading. On Co/YSZ catalyst, glycerol conversion of 0.94 and hydrogen yield of 3.72 was obtained with WHSV of 6.45 h⁻¹at 773 K.     

Enhancement of the quality of syngas from catalytic steam gasification of biomass by the addition of methane/model biogas

In this study, methane and model biogas were added during the catalytic steam gasification of pine to regulate the syngas composition and improve the quality of syngas. The effects of Ni/γ-Al₂O₃ catalyst, steam and methane/model biogas on H₂/CO ratio, syngas yield, carbon conversion rate and tar yield were explored. The results indicated that the addition of methane/model biogas during biomass steam gasification could increase the H₂/CO ratio to about 2. Methane/model biogas, steam and Ni/γ-Al₂O₃ catalyst significantly affected the quality of syngas. High H₂ content syngas with H₂/CO ratio of about 2, biomass carbon conversion >85% and low tar yield was achieved under the optimum condition: S/C = 1.5, α = 0.2 and using Ni/γ-Al₂O₃ catalyst. According to ANOVA, methane and catalyst were the key influencing factors of the H₂/CO ratio and syngas yield, and the tar yield mainly depended on the Ni/γ-Al₂O₃ catalyst. Biogas, as a more environmentally friendly material than methane, can also regulate the composition of syngas co-feeding with biomass.     

Novel highly efficient alumina-supported cobalt nitride catalyst for preferential CO oxidation at high temperatures

Novel alumina-supported cobalt nitride catalysts with Co loading ranging from 1 to 10 wt% prepared by NH₃-temperature-programmed reaction were investigated as potential catalysts for preferential CO oxidation (PROX) in excess H₂ at high temperatures. The formation of the Co₄N phase was confirmed by a combination of XRD and XPS, and the Co 2p binding energies of Co₄N reported previously were corrected to 798.2 ± 0.2 and 782.5 ± 0.2 eV. We observed that the catalytic activities of these nitrided Co/γ-Al₂O₃ catalysts were greatly related to their Co loadings. The nitrided 3 wt% Co/γ-Al₂O₃ catalyst showed the best PROX performance in temperature range of 200-220 °C, which was quite different from Co oxide precursor but was similar to Pt-group metals.     

Renewable hydrogen production via steam reforming of simulated bio-oil over Ni-based catalysts

The production of hydrogen via steam reforming (SR) of simulated bio-oil (glycerol, syringol, n-butanol, m-xylene, m-cresol, and furfural) was investigated over Ni/CeO₂-Al₂O₃ and Me-Ni/CeO₂-Al₂O₃ (Me = Rh, Ru) catalysts. Monometallic (Ni) and bimetallic (Rh-Ni and Ru-Ni) catalysts were prepared by the wetness impregnation technique of the CeO₂-Al₂O₃ support previously synthesized by the surfactant-assisted co-precipitation method. The as-prepared powders were systematically characterized by N₂-physisorption, XRD, H₂-TPR, and TEM measurements to analyze their structure, morphology, and reducibility properties. Experiments were performed in a continuous fixed-bed reactor at atmospheric pressure, temperature of 800 °C, steam to carbon (S/C) ratio of 5, and WHSV of 21.15 h⁻¹. Then, the temperature was decreased to 700 °C and increased afterwards to 800 °C. After the experiments TPO and TEM analysis were performed on the spent catalysts to check any evidence of catalyst deactivation. The results showed that the incorporation of noble metal (Ru or Rh) promoter positively affected the activity of the Ni/CeO₂-Al₂O₃ catalysts by enhancing the reducibility of Ni²⁺ species. Ni-based catalyst deactivated under the studied conditions, whereas Ru- and mainly Rh-promoted systems showed increased resistance to carbon deposition by favouring the gasification of adsorbed carbon species. Between all tested catalysts, the Rh-Ni/CeO₂-Al₂O₃ provided the highest H₂ yield and coking-resistance in SR of simulated bio-oil.     

Rh- and Rh–Ni–MgO-based structured catalysts for on-board syngas production via gasoline processing

Rh/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl and Rh/Ni–MgO/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl FeCrAlloy wire mesh supported catalysts were prepared via multistep procedure. They were characterized by XRD, SEM and TEM techniques. A comparative study of autothermal reforming (ATR) of isooctane and simulated gasoline (blends of isooctane, ortho-xylene and naphthalene) over Rh/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl and Rh/Ni–MgO/Ce_0.75Zr_0.25O_2-δ-ƞ-Al₂O₃/FeCrAl was performed. Both catalysts showed excellent performance in ATR of isooctane at molar ratios of O₂:C = 0.51 and H₂O:C = 2.59, T = 750°С and GHSV = 10000 h⁻¹. In the ATR of isooctane – o-xylene blend in presence of Rh–Ni-containing catalyst carbon formation was observed. Rh-containing catalyst demonstrated rather good activity and stability even in the case of isooctane – o-xylene – naphthalene blend.     

Catalytic reforming of glycerol in supercritical water with nickel-based catalysts

The catalytic performance of nickel catalysts supported on La₂O₃, α-Al₂O₃, γ-Al₂O₃, ZrO₂, and YSZ for supercritical water reforming of glycerol was investigated. Experiments were conducted in a tubular reactor made of Inconel-625 with the temperature range of 723–848 K under a pressure of 25 MPa. Carbon formation causing operation failure was observed for α-Al₂O₃, γ-Al₂O₃ and ZrO₂ at temperatures higher than 748, 798 and 823 K, respectively. Ni/La₂O₃ exhibited the highest H₂ yield where almost complete conversion was obtained at 798 K. Moderate space velocities (WHSV = 6.45 h⁻¹) and glycerol feed concentration (5wt.%) favor high hydrogen selectivity and yield. Methanation is favored at a low WHSV or high glycerol feed concentration, resulting in a lower H₂ yield. Increasing Ni loading on the Ni/La₂O₃ catalyst strongly promoted the reforming, water–gas shift, and methanation reactions, which contributed significantly to the product species distribution.