Supported Ni Catalysts Research Articles

Coke formation pathway under various reaction conditions during the production of syngas in a dielectric barrier discharge plasma environment using CeO2 nanorods supported Ni catalysts

Plasma-assisted dry reforming of methane (DRM) was investigated using CeO2 nanorods (NR) supported Ni catalysts in a fixed-bed coaxial dielectric barrier discharge (DBD) reactor. This study individually examined the catalyst support, packing material, and 10 wt% Ni-CeO2 NR catalyst under pure thermal and plasma-assisted thermal DRM environments to explore the plasma-thermal synergy. Support and packing material displayed no discernible reactivity under thermal DRM within 450 °C; however, the catalyst exhibited reactivity beginning around 350 °C. Alternatively, plasma-assisted DRM experiments revealed a distinct reaction occurrence at significantly lower temperatures across all sample types. Introducing plasma demonstrated a significant enhancement in CH4 conversion compared to CO2 conversion. The 10 wt% Ni-CeO2 NR catalyst in plasma-assisted DRM testing showed increasing conversions of CH4 and CO2 with rising temperatures, peaking at 52.1 % and 46.1 %, respectively, at 450 °C. The catalyst’s improved performance in the plasma environment can be attributed to the enhanced metal-support interaction between NiO and the CeO2 NR support, a consequence of the rich surface oxygen vacancy concentration. However, this increase in conversion was accompanied by an escalation in carbon deposition. Considering contributions from the thermal DRM process, the optimal operating temperature was determined as 350 °C. Increasing plasma power at this temperature led to enhanced conversion. However, beyond a threshold of 23.8 W power, the reaction path altered, resulting in reduced syngas output. Increasing the CH4:CO2 feed gas flow ratio, while maintaining constant plasma power and temperature, elevated H2/CO generation. Moreover, increasing the total flow rate under identical conditions, with a constant feed gas flow ratio, reduced both conversions due to decreased chemical residence time. Consequently, under a constant feed gas ratio, a higher syngas yield is achievable with lower overall flow rates.

Intrinsic kinetics of benzyltoluene hydrogenation over a supported Ni catalyst for green hydrogen storage

Liquid organic hydrogen carrier technology is a promising alternative for hydrogen storage and transportation. Benzyltoluene (BT) is a high-performance hydrogen storage carrier, but the hydrogenation kinetic parameters that are important to guide reactor and catalyst design are not clear. Here, we systematically investigated the kinetics of BT hydrogenation over a supported Ni catalyst for its potential application in hydrogen storage. Our results suggest that BT hydrogenation reaction follows a two-step series reaction from BT to 12H-BT with 6H-BT as the intermediate. The reaction order is 0 and 1 with respect to BT and 6H-BT concentration, respectively, whereas that with respect to H2 pressure is approximately equal (1.0 and 1.1 for BT and 6H-BT hydrogenation, respectively). Calculated activation energy suggests that 6H-BT hydrogenation is the rate-determining step in the whole process. Moreover, both kinetic and DFT results indicate that the presence of BT would inhibit the further 6H-BT hydrogenation to 12H-BT. This study is expected to provide a new understanding of BT hydrogenation reactions and a useful guideline for reactor and catalyst design.

Highly effective chainlike Ni/CZ5-x catalysts for catalytic reduction of p-nitrophenol: Effect of Si/Al ratio of ZSM-5 support

A series of ZSM-5 supported Ni catalysts with different Si/Al ratios (Si/Al=25, 30, 50 and 70) wzmpregnation method for p-nitrophenol (4-NP) reduction were investigated. The Ni/CZ5-x catalysts with chainlike morphology exhibited higher catalytic activity as compared with cubic aggregating Ni/Z5–25, and the activity gradually increased with decreasing of the Si/Al ratios of catalysts in the order of Ni/CZ5–30 > Ni/CZ5–50 > Ni/CZ5–70. For Ni/CZ5-x catalysts with similar morphology, the Ni/CZ5–30 catalyst showed the optimal activity with TOF value of 4.7995 × 10−3 s−1 and reaction time of 7 min, which was comparable to those of precious metals and significantly superior to cheap metal catalysts have been reported in the identical reaction condition. The excellent performance was mainly attributed to the synergistic effect between the more Ni0 fraction promoting the 4-NP catalytic conversion and strong surface hydrophilicity and acidity effectively accelerating the BH4- adsorption and dissociation in the Ni/CZ5-x catalysts with appropriate Si/Al ratio. The larger Ni0 fraction derived from the better dispersion of Ni species with smaller diameter on the surface of chainlike crystal, benefitting from the elevated hydrophilicity in the aqueous environment with the decreasing Si/Al ratio. This work first provided the influence of Si/Al ratio of support on catalytic performance of 4-NP reduction reaction and a new designing approach of the catalyst with high metal dispersion and good surface hydrophilicity for other catalytic fields in the future.

Dry Reforming of Methane over Dual Metal Oxide Al2O3 + MOx (M = Ti, Zr, Si, Y) Supported Ni Catalyst: A Simple and Practical Approach

The complex catalyst synthesis procedure is always a hurdle in the industrialization of catalysts. Industry eagerly needs catalysts for the dry reforming of methane, which can be prepared through straightforward, cheap processes by semi-skilled workers. Herein, dual metal oxide support 10 wt% MOx (M = Ti, Si, Zr, Y) & 90 wt% Al2O3 is prepared by just mixing mechanically and thereafter, catalytic active 5 wt% Ni is dispersed over the support by impregnation method. Metal oxide pairs in ZrO2 + Al2O3, TiO2-Al2O3, SiO2 + Al2O3, and Y2O3 + Al2O3 supports are non-interacting, partially-interacting, significantly interacting (through Si–O–Al) and highly interacting (with maximum covalence character) respectively. Ni dispersed over SiO2 + Al2O3 or Y2O3 + Al2O3 supports are strongly interacted, whereas Ni/Y2O3 + Al2O3 catalyst has oxide enrichment over the surface for potential oxidation of carbon deposit. The interacting nature of metal oxide pair in support, stability of active sites and extent of oxide enrichment over the surface confirms the following order of coke deposition, Ni/Y2O3 + Al2O3 (8%) < Ni/SiO2 + Al2O3 (17%) < Ni/TiO2-Al2O3 (38.2%) < Ni/ZrO2 + Al2O3 (52.3%), as well as reverse order of catalytic activity, Ni/Y2O3 + Al2O3 (60%) > Ni/SiO2 + Al2O3 (55%) > Ni/TiO2-Al2O3 (50%) > Ni/ZrO2 + Al2O3 (47%).Graphical

Different supported Ni catalysts for dry reforming of methane: Effect of calcination temperature

Due to the increased environmental consciousness about reducing greenhouse gas emissions of CH4 and CO2, an intriguing study issue is the dry reformation of CH4 (DRM) over a catalyst made of Ni.). Herein in this work, 5.0 wt% NiO was loaded on various supports (S = TiO2-P25, Al2O3, MgO, and ZrO2) through the process of dry impregnation. At 600 °C or 800 °C, the catalysts were then calcined to investigate the impact of calcination temperature on the catalytic performance. The catalysts were characterized by N2 physisorption, Raman spectroscopy, thermalgravimetric analysis, XRD, and TEM. The best catalyst was obtained when the MgO-supported Ni catalyst was operated at 700 °C and was calcined at 600 °C. This catalyst gave average conversions of CH4 and CO2 of 70.04 % and 77.2 %, respectively. However, when the calcination temperature of the same catalyst was increased to 800 °C, the average conversions of CH4 and CO2 dropped to 37.9 % and 48.07 %, respectively. Thus, the calcination pretreatment strongly influenced the catalyst performance, where rising the calcination temperature lowered the activity. The Al2O3-supported sample had the highest surface area, metal-support interaction, and activity. It produced a large amount of carbon nanotubes, whereas the MgO-supported sample presented the least carbon formation, the lowest deactivation factor, and no morphology change due to the reaction in the TEM.

CO rich syngas production from catalytic CO2 gasification-reforming of biomass components on Ni/CeO2

The advancement of biomass utilization technology is vital for addressing global climate change and the depletion of fossil resources. CO rich syngas production from the CO2 gasification-reforming of biomass components (cellulose, xylan, lignin, and starch) was investigated by a two-stage fixed bed reactor. The four biomass components were heated from room temperature to 600 °C in a CO2 atmosphere, among which lignin exhibited the highest residue fraction (51.6 wt.%) and the lowest gas yield (5.7 mmol gbiomass−1), whereas cellulose demonstrated the highest gas yield from CO2 gasification-reforming (14.6 mmol gbiomass−1). Nanorod CeO2 supported Ni catalysts were used to enhance volatile (tar) CO2 reforming reactions, and the gas yield increased by 104.3 % for cellulose, 103.3 % for xylan, 149.3 % for lignin, and 128.3 % for starch compared with noncatalytic CO2 gasification-reforming. Furthermore, the structure of fresh and used catalysts were characterized by X-ray diffraction (XRD), N2 adsorption/desorption isotherm, scanning electron microscope (SEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), H2-temperature programmed reduction (H2-TPR), and thermogravimetry (TGA). For the CO2 gasification-reforming of cellulose, the optimum CO yield of 27.6 mmol gbiomass−1 was achieved at a gasification/reforming temperature of 600/700 °C and a biomass/catalyst ratio of 6.25 using 2 %Ni/CeO2 catalyst. The stability tests of catalysts showed an approximately linear decrease in CO yield with the increase of the number of cycles, and catalyst deactivation resulted from Ni sintering and coke deposition.

Role of promoters over yttria‐zirconia supported Ni catalyst for dry reforming of methane

AbstractDry reforming of methane (DRM) bears great hope for the catalytic community as well as environmentalists for its potential to convert two greenhouse gases, CH4 and CO2, together into synthetic feedstock “syngas”. The stable tetragonal zirconium yttrium oxide phase over the “Yttria‐zirconia supported Ni” catalyst (Ni/YZr) brings &gt;70% CH4 conversion against 50% CH4 conversion over zirconia supported Ni catalyst) in 7 h time‐on‐stream (TOS). The use of the second metal oxide (MOx; M = Ho, Ga, Gd, Ba, Cs) in a small amount (4 wt%) over Ni/YZ catalyst is found to promote the catalytic activity further. Herein, we have prepared such metal‐promoted yttria‐zirconia supported Ni catalyst, employed them for DRM and characterized them with surface area porosity, X‐ray diffraction, spectroscopic techniques, temperature programmed techniques and transmission electron microscopy. A fine correlation of characterization results with catalytic activity brings out various useful information that would be useful for establishing yttria‐zirconia supported Ni catalyst for DRM. Ni stabilized over cubic zirconium holmium oxide phase in 5Ni4Ho/YZr catalyst, cubic zirconium gadolinium oxide phase in 5Ni4Gd/YZr catalyst and cubic zirconium barium oxide phase in 5Ni4Ba/YZr catalyst perform excellent toward DRM. Catalytically, 5Ni4Ho/YZr catalyst achieves CH4 conversion as high as ~85% whereas 5Ni4Ba/YZr and 5Ni4Gd/YZr show CH4 conversions of about ~80%. Even in 30 h TOS study, 5Ni4Ho/YZr catalyst showed &gt;81% CH4 conversion with retaining highest H2/CO (0.97).

Ni-Based SBA-15 Catalysts Modified with CeMnOx for CO2 Valorization via Dry Reforming of Methane: Effect of Composition on Modulating Activity and H2/CO Ratio.

Dry reforming of methane with ratio CH4/CO2 = 1 is studied using supported Ni catalysts on SBA-15 modified by CeMnOx mixed oxides with different Ce/Mn ratios (0.25, 1 and 9). The obtained samples are characterized by wide-angle XRD, SAXS, N2 sorption, TPR-H2, TEM, UV-vis and Raman spectroscopies. The SBA-15 modification with CeMnOx decreases the sizes of NiO nanoparticles and enhances the NiO-support interaction. When Ce/Mn = 9, the NiO forms small particles on the surface of large CeO2 particles and/or interacts with CeO2, forming mixed phases. The best catalytic performance (at 650 °C, CH4 and CO2 conversions are 51 and 69%, respectively) is achieved over the Ni/CeMnOx/SBA-15 (9:1) catalyst. The peculiar CeMnOx composition (Ce/Mn = 9) also improves the catalyst stability: In a 24 h stability test, the CH4 conversion decreases by 18 rel.% as compared to a 30 rel.% decrease for unmodified catalyst. The enhanced catalytic stability of Ni/CeMnOx/SBA-15 (9:1) is attributed to the high concentration of reactive peroxo (O-) and superoxo (O2-) species that significantly lower the amount of coke in comparison with Ni-SBA-15 unmodified catalyst (weight loss of 2.7% vs. 42.2%). Ni-SBA-15 modified with equimolar Ce/Mn ratio or Mn excess is less performing. Ni/CeMnOx/SBA-15 (1:4) with the highest content of manganese shows the minimum conversions of reagents in the entire temperature range (X(CO2) = 4-36%, X(CH4) = 8-58%). This finding is possibly attributed to the presence of manganese oxide, which decorates the Ni particles due to its redistribution at the preparation stage.

Ni catalyst on ZSM-22 nanofibers bundles with good catalytic performance in the hydroisomerization of n-dodecane

Developing non-noble catalyst with high performance is significant in the hydroisomerization of long-chain n-alkane to iso-alkanes. In this study, nanofiber-bundled ZSM-22 without any additives was successfully synthesized and used to prepare Ni catalyst (Ni/NB-HZSM-22, Ni loading 1.0 wt%) for hydroisomerization of n-dodecane (n-C12). The obtained Ni/NB-HZSM-22 catalyst exhibited much higher intrinsic catalytic activity (TOF = 0.077 s−1) than a conventional needle-shaped ZSM-22 supported Ni catalyst (Ni/C-HZSM-22, 0.026 s−1), especially higher isomerization selectivity (TOFiso, 0.071 s−1) than the Ni/C-HZSM-22 catalyst (0.021 s−1). Additionally, the Ni/NB-HZSM-22 catalyst had lower cracking/iso-dodecanes (iso-C12, 0.08) and di-branched/mono-branched (0) ratios than the Ni/C-HZSM-22 catalyst (0.25 and 0.07) after extrapolation of the n-C12 conversion to zero. This is mainly attributed to the nanofiber–bundled NB-HZSM-22 with well-crystallized structures and suitable acidity, leading to good synergistic catalysis between metal and acidic function for the Ni/NB-HZSM-22 catalyst. Although the Ni catalyst on the parent NB-ZSM-22 was less active, it had a similar optimal iso-C12 yield compared to the Ni/NB-HZSM-22 catalyst. In addition, the Ni/NB-HZSM-22 catalyst showed a maximum iso-C12 yield of 74.8%, which was much better than the Ni/C-HZSM-22 catalyst (58.7%), and showed comparable performance to a Pt catalyst on the NB-HZSM-22 (76.7%). These results suggested that the Ni catalyst on the NB-HZSM-22 was a promising candidate for the hydroisomerization catalyst.

The Role of Strontium as an Economic Promoter Over WO3 + ZrO2 Supported Ni Catalyst for H2 Production Through Dry Reforming of Methane

The Role of Strontium as an Economic Promoter Over WO3 + ZrO2 Supported Ni Catalyst for H2 Production Through Dry Reforming of Methane

Supported Ni Catalysts: Simple Vapor Deposition Preparation Method and Improved Catalytic Performance for Oxidative Dehydrogenation of Ethane.

Developing new methods of catalyst preparation is one of the most important tasks in the field of catalysis. A simple one-tube vapor deposition (VD) is provided in this paper for preparing the supported Ni catalyst. Ni(acac)2 was used as the Ni precursor. This preparation method was successfully applied to three types of catalytic supports, that is, Al2O3 and zeolites 5A and Hβ. Varying Ni contents of less than 8 wt % can be obtained by employing different conditions. The Ni content, depending on different deposition conditions, was preliminarily explored. The catalytic performance for oxidative dehydrogenation of ethane (ODHE) was tested for the prepared Ni catalysts by the VD method. Several cases of catalytic tests showed that for the same Ni content, the VD-prepared Ni catalyst presented better performance for ODHE than the one prepared by a traditional impregnation method. Besides the improvement in catalytic performance, several advantages of our VD preparation method for catalysis are discussed.

Co-pyrolysis induced strong metal-support interaction in N-doped carbon supported Ni catalyst for the hydrogenolysis of lignin

Designing highly active and stable catalysts for the selective cleavage of the C-O bond of lignin is important to convert it into high-valued aromatic compounds. Herein, a facile synthetic strategy was developed using melamine as a soft template to prepare a highly active catalyst consisting of highly dispersed Ni nanoparticles on defective N-doped carbon support. The results indicated that the decomposition of melamine during the pyrolysis process induced the nitrogen atoms into aromatic carbon. The introduction of N-doped carbon support acted as anchor points for the Ni nanoparticles, strengthening the metal-support interaction. Approximately 100 conversion of the representative lignin model compounds, including 2-phenylethyl phenyl ether, were converted into their aromatic monomers under mild conditions. The as-prepared catalyst was stable and reusable after five cycles with no apparent signs of deactivation. Moreover, the theoretical calculation revealed that N-doped carbon supported Ni-based catalyst possessed a lower activation energy of C-O bond than only carbon supported Ni-based catalyst for the C-O bond cleavage in hydrogenolysis of lignin and its model compounds.

Bioapatite derived from animal bones as support for environmentally concerned catalysts: WGS with suppressed methanation activity

The potential of natural apatite derived from pork bones to be used as a support of Ni catalysts for the Water-Gas Shift (WGS) reaction was investigated. Samples of bone char were chemically treated with either K2CO3 or H2SO4 and subsequently heated in inert or oxidizing atmosphere at various temperatures. Catalysts were characterized by ICP-AES, N2 physisorption, XRD, FTIR, TG-DTG, H2-TPR, XPS, H2 chemisorption and NH3-TPD, and tested in the WGS reaction, using both ideal and realistic (mixture of H2O, CO2 and H2) feed streams. Nickel was partly exchanged with Ca2+ ions in the support. Regarding the effect of the atmosphere, an inert atmosphere had a negative effect due to the collapse of the porous structure. On the contrary, the combination of an oxidizing atmosphere and treatment with K2CO3 allowed a superior WGS performance under real reformer conditions, with a substantial decrease in the methane formation (six-fold decrease, compared to the non-activated reference catalyst). The catalytic activity could be related to the apatitic phase growing geometry, which can be tailored by the activation method.

Surface-silanised and alkoxylated micro-mesoporous Ni/hierarchical nanozeolites for oleic acid hydrodeoxygenation

In this work, we report a novel and green method for the synthesis of hierarchical nanozeolites for the hydrodeoxygenation of oleic acid to diesel-range hydrocarbons. Hierarchical nanozeolites based on HZSM-5 and HBEA with appropriate mesopores (8–20 nm) were synthesised through the surface silanisation of zeolitic seeds. In this method, organosilane (hexadecyltrimethoxysilane) was used as a growth inhibitor while biomass-derived alcohols (1-decanol and isobutanol) were used to improve the miscibility and dispersion of the organosilane. 1H MAS NMR analysis confirmed the silanisation and alkoxylation of the zeolitic seeds. The physicochemical properties of the catalysts were analysed by XRD, N2 porosimetry, NH3-TPD, pyridine-DRIFTS, XPS and TEM, and the catalytic performance of bifunctional 10 wt.% Ni/h-HZSM-5 and Ni/h-HBEA were then evaluated in the HDO of a bulky feedstock, oleic acid. The hierarchical zeolites supported Ni catalysts achieved more than 86% conversion of oleic acid. Compared with their microporous nanozeolite counterparts, Ni/h-HBEA and Ni/h-HZSM-5 exhibited comparable or higher Brønsted/Lewis acid ratios, leading to high selectivity towards C18 alkanes (65% and 71%, respectively); they also demonstrated similar catalytic yields. More importantly, while their microporous analogues lost much of their activity after the first cycle, Ni/h-HZSM-5, in particular, displayed excellent stability, even after four cycles. Thus, our approach appears to be a promising way of preparing catalyst supports for efficient hydrotreatment of bulky substrates.

Catalytic pyrolysis of fatty acids and oils into liquid biofuels and chemicals over supported Ni catalysts on biomass-derived carbon

Herein, biomass-derived activated carbon (bio-AC) was synthesized using rice husk as a biotemplate and natural carbon source. After immobilization of Ni, the supported Ni/bio-AC showed excellent catalytic activity in the pyrolysis of fatty acids to paraffin-based biodiesel in H2-free and solvent-free conditions, corresponding to the conversion of 99.6% and a total alkane yield of 95.1%, including 88.9% heptadecane. Based on comprehensive characterizations, the calculated turnover frequency of Ni/bio-AC was 3.9 times that of conventional Ni/AC. Significantly enhanced olefin selectivity was further obtained by N-doping of Ni/bio-AC, which was attributed to the inhibition of -COO* dissociation by the Ni-N sites. The possible catalytic reaction pathways from stearic acid to heptadecane via aliphatic alcohol as a reaction intermediate were investigated. Besides, efficient conversions of saturated and unsaturated plant oils were also achieved over Ni/bio-NAC catalysts in Py-GC/MS through pulsed catalytic pyrolysis manner, showing a promising prospect for sustainable biofuels and chemical production.

The rate determining steps and rate equation for the oxidative dry reforming of methane over supported Ni catalyst

Dry reforming of methane (DRM) and its modification with O2 co-feed, the ODRM reaction, have been gaining importance. However, a general rate equation applicable for the ODRM reaction with varying O2 co-feed has not been reported. This general rate equation should be applicable for the DRM and ODRM reactions depending on the amount of O2 co-feed. Microkinetic models simulate catalytic reactions without making any a priori assumptions for the RDS and are helpful in developing rate equations. Unfortunately, microkinetic modelling for ODRM over supported monometallic Ni has not been carried out. Here, we perform microkinetic modelling using an existing reforming reaction mechanism for ODRM over an alumina-supported Ni catalyst. Validation is achieved by comparing experimental and microkinetic outlet flow rates at different feed rates of O2 and applying R2 analysis and F-tests. Once the model is validated, we identify the RDS through a hierarchical strategy using microkinetic results and sensitivity analysis for varying amounts of O2 co-feed. The results reveal that CH4 activation is the RDS. CH4 activation can occur through direct dehydrogenation on an empty site or oxidative dehydrogenation aided by adsorbed O, depending on the amount of O2 co-feed. Once the RDSs are identified, we derive a general rate equation that effectively simulates the DRM reaction with different amounts of O2 co-feed. We further examine the effect of the amounts of O2 co-feed and ascertain the presence of maximum hydrogen production for certain amounts of O2 co-feed.

Effect of desilication process on natural zeolite as Ni catalyst support on hydrodeoxygenation of palm fatty acid distillate (PFAD) into green diesel

Natural zeolite (NZ) from desilication and activation was prepared to support the Ni catalyst. The catalyst was utilized for the hydrodeoxygenation (HDO) of the palm fatty acid distillate (PFAD) into green diesel. Desilication using sodium hydroxide (NaOH) solution increases the porosity, surface area, and acidity of the natural zeolite, thus increasing the catalytic activity. This study aims to determine the effect of the NaOH concentration utilized in the desilication process on the characteristics of support and catalytic activity of the Ni/NZ catalyst. Additionally, pure Ni and Ni/NZ without desilication were also investigated for comparison. NZ underwent desilication by varying the concentration of NaOH (0.5, 1, and 2 N). Desilicated zeolite was then activated using a 1 M ammonium acetate solution and impregnated with Ni metals. The desilication NZ increases the acidity and surface area at a low NaOH concentration, while the zeolite structure (clinoptilolite) is still intact. Therefore, the catalytic activity of the catalyst was also increased compared to Ni and Ni/NZ catalysts without desilication. Conversely, a higher concentration of NaOH decreases the Si/Al ratio, acidity, and surface area of support. As a result, the catalytic activity of the catalyst decreases, as evidenced by the reduced liquid product in the hydrodeoxygenation of PFAD. The Ni/NZ0.5 catalyst revealed optimal catalytic activity with a liquid fraction and green diesel selectivity of 83.64% and 92.74%, respectively.

Iron-promoted zirconia-alumina supported Ni catalyst for highly efficient and cost-effective hydrogen production via dry reforming of methane

Developing cost-effective and high-performance catalyst systems for dry reforming of methane (DRM) is crucial for producing hydrogen (H2) sustainably. Herein, we investigate using iron (Fe) as a promoter and major alumina support in Ni-based catalysts to improve their DRM performance. The addition of iron as a promotor was found to add reducible iron species along with reducible NiO species, enhance the basicity and induce the deposition of oxidizable carbon. By incorporating 1 wt.% Fe into a 5Ni/10ZrAl catalyst, a higher CO2 interaction and formation of reducible "NiO-species having strong interaction with support" was observed, which led to an ∼80% H2 yield in 420 min of Time on Stream (TOS). Further increasing the Fe content to 2wt% led to the formation of additional reducible iron oxide species and a noticeable rise in H2 yield up to 84%. Despite the severe weight loss on Fe-promoted catalysts, high H2 yield was maintained due to the proper balance between the rate of CH4 decomposition and the rate of carbon deposit diffusion. Finally, incorporating 3 wt.% Fe into the 5Ni/10ZrAl catalyst resulted in the highest CO2 interaction, wide presence of reducible NiO-species, minimum graphitic deposit and an 87% H2 yield. Our findings suggest that iron-promoted zirconia-alumina-supported Ni catalysts can be a cheap and excellent catalytic system for H2 production via DRM.

Methane conversion to H2 and carbon nanofibers over supported Ni catalysts: A sustainable process through utilization of deactivated catalysts

AbstractThe renewable resource such as rice husk has been utilized to synthesize Hβ zeolite as a support for Ni catalysts for the production of clean hydrogen and carbon nanofibers (CNFs) by CH4 cracking at 550°C without any CO or CO2 formation. Hydrogen production rates and area of surface Ni are in good correlation, implying the optimum Ni loading of 25 wt % that demonstrated better hydrogen yields and CNFs. The electrochemical properties of the deactivated catalysts indicated that they were near semiconducting in nature, showing future prospects as carbon electrode materials. The physicochemical characteristics of the fresh, reduced, and used catalysts were rationalized by BET surface area, p‐X‐ray diffraction, temperature programmed reduction using H2, SEM, TEM, H2‐pulse chemisorption, and Raman spectroscopic analyses in conjunction with hydrogen rates.

Investigation on deactivation progress of biochar supported Ni catalyst during biomass catalytic cracking process

Herein, the biochar-supported Ni catalysts was synthesized by carbothermal reduction and its catalytic activity for biomass-derived heavy components was investigated in a pyrolysis-catalysis two stage reactor at the catalytic cracking temperature of 700 °C. The change in catalytic activity of biochar-supported Ni catalyst was divided into three stages according to conversion efficiency of heavy components: rapid reduction stage (from 95.30% to 85.58%), stabilization stage (from 84.65% to 82.98%), and slow reduction stage of activity (from 81.21% to 76.98%), corresponding to rapid decreasing stage (from 88.95% to 63.53%), stable stage (from 62.1% to 57.55%), and slow increasing stage (57.66% to 60.17%) of the mass retention percentage of catalyst. The characterizations of catalyst after different cycles showed that the initial deactivation mainly caused by the sintering of Ni active sites. With the severe sintering of Ni nanoparticles, coke deposition became the main reason of later catalyst deactivation. Particularly, the carbon elimination reaction promoted by highly dispersed Ni particle was observed which contributed to enrich the mesoporous structure and retarded the deactivation of the catalyst. The research marks a further understanding of the interaction and deactivation mechanisms between biochar support and Ni active sites during catalytic cracking of biomass-derived heavy components.