Next Article in Journal
Catalytic Oxidation of Heavy Residual Oil by Pulsed Nuclear Magnetic Resonance
Previous Article in Journal
Nitrogen Removal from Agricultural Subsurface Drainage by Surface-Flow Wetlands: Variability
Previous Article in Special Issue
Catalytic Performance of Lanthanum Promoted Ni/ZrO2 for Carbon Dioxide Reforming of Methane
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Processes
Volume 9
Issue 1
10.3390/pr9010157
processes-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Role of Mixed Oxides in Hydrogen Production through the Dry Reforming of Methane over Nickel Catalysts Supported on Modified γ-Al2O3

by
Ahmed Sadeq Al-Fatesh
1,*,
Mayankkumar Lakshmanbhai Chaudhary
2,
Anis Hamza Fakeeha
1,3,
Ahmed Aidid Ibrahim
1,
Fahad Al-Mubaddel
1,3,
Samsudeen Olajide Kasim
1,
Yousef Abdulrahman Albaqmaa
1,
Abdulaziz A. Bagabas
4,
Rutu Patel
2 and
Rawesh Kumar
2
1
Chemical Engineering Department, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia
2
Sankalchand Patel University, Visnagar 384315, India
3
King Abdullah City for Atomic & Renewable Energy, Energy Research & Innovation Center (ERIC) in Riyadh, Riyadh 11451, Saudi Arabia
4
National Petrochemical Technology Center (NPTC), Materials Science Research Institute (MSRI), King Abdulaziz City for Science and Technology (KACST), P.O. Box 6086, Riyadh 11442, Saudi Arabia
*
Author to whom correspondence should be addressed.
Processes 2021, 9(1), 157; https://0-doi-org.brum.beds.ac.uk/10.3390/pr9010157
Submission received: 15 December 2020 / Revised: 6 January 2021 / Accepted: 8 January 2021 / Published: 15 January 2021
(This article belongs to the Special Issue Design of an After-Treatment Catalyst System for Combustion Applications)
Browse Figures
Versions Notes

Abstract

:
H2 production through dry reforming of methane (DRM) is a hot topic amidst growing environmental and atom-economy concerns. Loading Ni-based reducible mixed oxide systems onto a thermally stable support is a reliable approach for obtaining catalysts of good dispersion and high stability. Herein, NiO was dispersed over MOx-modified-γ-Al2O3 (M = Ti, Mo, Si, or W; x = 2 or 3) through incipient wetness impregnation followed by calcination. The obtained catalyst systems were characterized by infrared, ultraviolet–visible, and X-ray photoelectron spectroscopies, and H2 temperature-programmed reduction. The mentioned synthetic procedure afforded the proper nucleation of different NiO-containing mixed oxides and/or interacting-NiO species. With different modifiers, the interaction of NiO with the γ-Al2O3 support was found to change, the Ni2+ environment was reformed exclusively, and the tendency of NiO species to undergo reduction was modified greatly. Catalyst systems 5Ni3MAl (M = Si, W) comprised a variety of species, whereby NiO interacted with the modifier and the support (e.g., NiSiO3, NiAl2O4, and NiWO3). These two catalyst systems displayed equal efficiency, >70% H2 yield at 800 °C, and were thermally stable for up to 420 min on stream. 5Ni3SiAl catalyst regained nearly all its activity during regeneration for up to two cycles.

1. Introduction

Hydrogen (H2) is a green energy source. In fact, the energy content of this molecule is three times higher than that of gasoline [1]. H2 is a critical feedstock for the chemical industry in oil refining, fertilizer production, and fuel cell manufacture [2]. Notably, biomass pyrolysis and biomass gasification have always been environmentally questionable approaches to hydrogen production; moreover, the implementation of these methods renders H2 isolation and purification quite difficult, as the desired product associates with many side-products [3]. A more convenient approach is hydrogen production from compounds such as ethanol [4], glycerol [5], glucose [6], starch, and catechol [7], by steam or thermal reforming over a heterogeneous catalyst. Environmental concerns and the high demand for atom-economies have driven the development of hydrogen production methods, relying on clean sources, such as water splitting, thermal reforming of methane, stream reforming of methane, and CO2 (dry) reforming of methane (DRM) [8,9]. DRM in particular, has drawn great deal of attention globally because it fulfils the goal of hydrogen production while raising hope for the reduction of the atmospheric concentrations of carbon dioxide and methane, the two gases whose emissions are most responsible for global warming.
From a catalytic standpoint, metal oxide and mixed metal oxide systems have attracted the attention of the industry, due to their ease of formation, development of mixed oxide potential, tuneable surface topology, high temperature sustainability, and ease of handling in drastic industrial conditions [10]. Ni-based catalysts supported on thermally-stable neutral SiO2 [11], acidic Al2O3 [12], and reducible TiO2 [13,14] have been investigated thoroughly in recent years. Due to the need of acid-base bi-functional catalyst for DRM, TiO2 and Al2O3 supports were investigated more than SiO2. Reducibility characteristics of TiO2 controls the coke deposition. However, the coverage of Ni species by the TiOx and partial transformation of amorphous titania phase into the anatase phase limit its DRM application [15]. Nevertheless, the addition of 25% Al2O3 to TiO2 support was found to be beneficial [16]. Overall, the highly thermal stability, low cost, wide availability, and strong metal–support interaction favor alumina as the support for Ni dispersion [17]. Nickel form bulk NiO is sintered into large Ni particles during DRM, and these nanoparticles are encapsulated by carbon. Due to encapsulation and loss of catalytic active sites, the catalytic activity was affected badly [18]. Alumina supported Nickel catalyst system has mixed oxide NiAl2O4 phases, confirming strong metal–support interaction in the catalyst system. Reduced Ni derived from NiAl2O4 favors the formation of carbon filament by putting the Ni particle on tip. Therefore, it showed high resistant to sintering and coking without affecting the catalytic activity. Al2O3 nanosheet provides superior anchoring surface (100) for Ni nanoparticle and so Ni-based catalysts supported on nanosheet (S) were claimed to result in more than 85% CO2 and CH4 conversion with excellent H2 and CO selectivity [19]. However, Ni-based catalysts supported on nanofiber exhibited superior catalytic stability due to its abundant confined spaces and steady chemisorption behavior. Under other synthetic methodology, such as evaporation-induced self-assembly method [20] and microwave-assisted combustion [21] and atomic layer deposition [22] method have drawn attentions. As a sandwiched catalyst Al2O3/Ni/Al2O3 (prepared by atomic layer deposition) prevented Ni gathering over alumina by coating of porous Al2O3 thin-film over Ni/Al2O3. Moreover, Ni had double interaction with Al2O3 in this catalyst system and so it was claimed nearly 100% CO2 and CH4 conversion with absolute selectivity towards CO and H2.
Incorporation of Cu, Mo, Si, Sr, B, Ca, Mg, Ba, Ga, Gd, Zn, Ti, W, Mn, Co, Zr, Ce, La, and Yb, in the alumina supported Ni catalyst was examined in the search of high catalytic activity and coke resistance. The addition of Cu resulted in inferior performance due to sintering of Cu particles and presence of free NiO (weak metal support interaction) [23,24]. The inferior performance of Mo promoted Ni/Al2O3 catalyst was due to weak metal support interaction, the formation of MoNi4 phase and the lower basicity of catalyst [25]. Modification of Ni/Al2O3 with 11.9 wt% W modified Ni/Al2O3 showed 76% less carbon decomposition than unmodified samples [26]. It was supposed that Ni-W alloy formed during reduction and hindered the carbon deposition inside the lattice and further tungsten carbide formed and carried out carbon gasification. However, Ni-W alloy formation caused inferior catalytic activity because alloy might be less active for methane decomposition. Monolithic Ni-Al2O3-SiC catalyst was claimed higher CO2 conversion (>40%) and CH4 conversion (~30%) than Ni/Al2O3 catalyst due to stereo-structure and highly dispersed Ni species [27]. The addition of 0.75 wt% Sr addition improved the metal (Ni) support (Al2O3) interaction and boosts Lewis basicity. It favored CO2 absorption and dissociation which in turn decreased the coke deposition [28]. Modification of 0.6–5.6 wt% B2O3 led to size-reduction of Ni particles which induced 74–86% less coke formation during DRM without significantly affecting activity and selectivity [29]. Among the basic modifier: MgO, CaO and BaO; it was found that 3 wt% MgO addition improved the catalytic activity (>70% CH4 and CO2 conversion up to 300 min) due to formation of MgAl2O4 mixed oxide [30]. Promotional addition of Ga, Gd and Zn claimed high CH4 and CO2 conversions (close to 80% during 420 min time on stream) with H2/CO = 1.0 due to content of NiO interacted moderately and strongly with the support [24]. Co-addition to Ni/Al2O3 nano catalyst showed high Ni/Al ratio than Ni/Al2O3 which led to better Ni dispersion over the alumina surface (by reducing the ensemble size of Ni) [23]. It was claimed good catalytic activity (CO2 and CH4 conversion >80% at 750 °C) with H2/CO ratio was close to one and less coke deposition. Mn-addition caused partial blockage of large Ni particle which was assumed for rapid coke formation. Further addition of potassium caused stability in activity [31]. ZrO2 addition enhanced the dissociation of CO2 near the contact between ZrO2 and nickel where the deposited coke was gasified afterwards [32]. Optimum ceria addition caused formation of CeAlO3 mixed phase. Ceria added mobile lattice oxygen in the surface reaction mechanism of DRM which endorsed minimum coking [33,34]. The addition of lanthana enhanced Ni stability and alkalinity of catalyst [35]. Alkalinity caused profound carbon dioxide adsorption, activation and oxidation of carbon deposit. The addition of 1–2 wt% Yb in NiO-containing Al2O3 (prepared by sol-gel process) matrix controlled the size/mobility of Ni nanoparticles. Moreover, the high ease of reducibility and low carbon deposition led to high catalytic activity and catalyst stability (CH4 conversions 75–81.5% and CO2 conversions 83.5–89% for 22 h time on stream), and H2/CO close to unity (~0.95) [36]. The active elements in doped/promoted Al2O3-supported Ni catalyst systems are presented as the color blocks in periodic table in Figure 1.
In these systems, apart from the dispersed, stable NiO, other Ni-containing phases, like Ni2SiO4, NiAl2O4, MgAl2O4, CeAlO3, NiTiO3, and Ni2TiO4, have also been detected. The presence of NiWO4 [37] and NiMoO4 species [38] has also been reported in Ni-based catalysts supported on WCx or MoCx, respectively, for DRM. In this context, understanding the role played by different metal oxides or mixed metal oxides matrices in the production of hydrogen through DRM is imperative. Recently, we prepared a modified γ-Al2O3 support by incipient wetness impregnation followed by calcination; notably, the modifier was loaded as 3.0 wt% MOx (M = W, Mo, Si, or Ti; x = 2 or 3) [39]. The active Ni catalyst was then loaded onto the modified γ-Al2O3 support by incipient wetness impregnation, followed by calcination to reach 5.0 wt% NiO loading. The catalysts, thus obtained, are abbreviated as 5Ni3MAl (M = W, Mo, Si, or Ti). This synthetic strategy gave the chance of interaction of all types of oxides and, hence, the formation of mixed metal oxides. The study of this type of catalytic systems may provide information that would help understand the role of metal oxides and mixed metal oxides in DRM. Herein, we report the preparation of the 5Ni3MAl (M = W, Mo, Si, or Ti) catalyst systems, their characterization by infrared (IR), ultraviolet–visible (UV-Vis), X-ray photoelectron (XPS) spectroscopies, and by H2 temperature-programmed reduction (H2-TPR). We also report the results of tests run on these systems for H2 production. We attempted to identify the metal, metal oxides, and mixed metal oxides responsible for H2 production through DRM. Crucially, this information would be useful in the design of metal oxide matrix catalyst systems suitable for the industrial production of H2 through DRM.

2. Results

2.1. Catalytic Activity

Data reflecting the catalytic activity of the prepared catalysts, in terms of H2 yield over 420 min on stream at 700 °C are reported in Figure 2A. On the other hand, Figure 2B shows values for the H2 yield at different reaction temperatures. Among the investigated catalysts, 5Ni3SiAl and 5Ni3WAl exhibited the highest catalytic performance, and the activities and stabilities of these two species were found to be identical. The H2 yield recorded for both catalysts over 420 min on stream was about 62% at 700 °C. The H2 yield over 5Ni3MoAl catalyst was 47% after 20 min on stream, which decreased to 39% after 420 min on stream. The catalytic performance of 5Ni3TiAl was found to be the worst: ~30% H2 yield after 420 min on stream. Notably, the H2 yield in the presence of all catalyst systems increased as the reaction temperature increased. At 800 °C, the use of 5Ni3SiAl and 5Ni3WAl was associated with more than 70% H2 yield, whereas in the case of 5Ni3MoAl and 5Ni3TiAl, H2 yield was measured to be around 60%. Higher conversion trend at higher temperature indicated the endothermic nature of DRM reaction. For silicon- or tungsten-modified alumina-supported nickel catalyst system, the rise of H2 yield with temperature were similar. For titanium- and molybdenum-modified catalyst systems, the rise of H2 yield with temperature were similar up to 650 °C, and after this temperature, molybdenum-modified catalyst system showed better H2 yield.

2.2. Result

SEM images and EDX patterns of 5Ni3MAl (M = W, Si, Mo, Ti) are shown in Figures S1 and S2, respectively. EDX patterns showed the presence of all claimed elements in the catalyst systems (Figure S2). In all IR spectra, the sharp peak at 1644 cm−1 and the broad intense peak at 3450 cm−1 could be due to the bending and stretching vibrations, respectively, of adsorbed water molecules or surface hydroxyl groups [40]. The IR peaks in the 600–750 cm−1 wavenumber range could be attributed to the vibrations of AlO6 octahedral units (Al-O bonds in an octahedral environment), whereas those in the 750–850 cm−1 range could be attributed to AlO4 tetrahedral units (Al-O bonds in a tetrahedral environment) [41]. The three peaks in the 1640−1350 cm−1 wavenumber range might be assigned to the bending vibration of the water molecules coordinated to different unsaturated surface sites. Furthermore, the peak at 1635 cm−1 could be due to the vibration of physically adsorbed water molecules, whereas the peak at 1380 cm−1 could be due to the bending vibration of water molecules coordinating tetrahedral aluminum [40]. The IR spectrum of γ-Al2O3 was characterized by the presence of three peaks at 1635 cm−1, 1517 cm−1, and 1382 cm−1 [42]. IR peaks in the 400–470 cm−1 wavenumber range could be due to the vibration of the Ni-O bond [43] in free NiO or to the said bond in mixed oxides such as NiSiO4, NiAl2O4, NiTiO3, NiWO4, and NiMoO4. The IR spectrum of the titanium-modified catalyst sample, 5Ni3TiAl, (Figure 3A,B and Figure S3A,B), comprised an absorption peak at 433 cm−1, which could be due to the Ni-O vibration of free NiO species in a cubic lattice, and peaks at 455 cm−1 and 547 cm−1, which may be due to the Ni-O bond vibration of NiTiO3 [44,45]. After NiO loading, the peak due to TiO2 in the low-frequency region of the spectrum (below 500 cm−1) was replaced by peaks due to Ni-O vibrations, which was an indication of the extent of interaction of NiO species with the modifier over the support.
The IR spectrum of the molybdenum-containing catalyst, 5Ni3MoAl, (Figure 3C,D and Figure S3A,B), comprised a band at 424 cm−1 due to Ni-O bond vibration, which appeared at lower wavenumber values than that attributed to free NiO (433 cm−1) in the spectrum of the titanium-modified catalyst. No other prominent peaks due to Ni-O vibrations were noticed in the spectrum of the molybdenum-containing catalyst, indicating the deformation of cubic NiO species and the formation of species, whereby NiO interacted with the support, the modifier, or both [46,47]. After NiO loading, the peak due to MoOx in the low-frequency region was completely replaced by the vibrational peak of Ni-O, indicating the extent of the interaction of NiO species with the modifier over the support.
In the IR spectrum of 5Ni3SiAl (Figure 3E,F and Figure S3A,B), Ni-O vibrational peaks at 430 cm−1, due to free NiO, and 403 cm−1, due to strongly interacting-NiO (as a result of the weakening of the Ni-O bond), were noticed, alongside a peak at 453 cm−1, due to the Si-O-Si bending vibration [48], and one at 481 cm−1, due to the asymmetric vibration of Si-O [49]. However, the S-O asymmetric vibration peak was not noticed in the spectrum of SiO2-Al2O3, indicating that this vibration was related to an interaction of NiO with silica species or to the presence of amorphous nickel silicate species. This finding is in agreement with our previous claim of an interaction of NiO species, as deduced from H2-TPR data, and the absence of nickel silicate phases, as deduced from X-ray diffraction data. The IR peak and its shoulder appearing in the 549–560 cm−1 wavenumber range could be attributed to the presence of Al-O-Ni bonding interactions in NiAl2O4 [50].
In both 5Ni3SiAl and 5Ni3WAl, following NiO loading, the infrared spectra of the modified catalysts became populated with intense peaks, indicating the presence and dispersion of a wide variety of species, whereby NiO interacted with catalyst components on the catalyst surface. In the IR spectrum of 5NiWAl (Figure 3G,H) the low-intensity absorption bands below 500 cm−1 could be attributed to the stretching vibrations of NiO6 polyhedral in NiWO4 species [51].
The infrared spectra of the catalyst samples showed a clear shift of Ni–O peak from 433 cm−1 (for 5Ni3TiAl) to 424 cm−1 (for 5Ni3MoAl) and 403 cm−1 (for 5Ni3SiAl). That reflects the presence of “free NiO” species in 5Ni3TiAl; NiO species interacted with the modifier in 5Ni3MoAl and NiO species strongly interacted with the support/modifier in 5Ni3SiAl. 5Ni3WAl catalyst samples had a wide interaction NiO species as it showed stretching vibration of NiO6 polyhedral.
UV–Vis spectroscopy is the most suitable characterization technique to understand the electronic environment of Ni2+ or d8-configuration systems. The UV–Vis absorption spectra of all catalyst samples are reported in Figure 4. The peak observed at 250–350 nm is associated with the charge transfer transition from O2− to Ni2+ in an octahedral coordination environment (O2− → Ni2+) in the NiO lattice [29]. The peak centered at around 410 nm is associated with the d-d transition from the 3A2g(F) state to the 3T1g(P) state of Ni2+ in an octahedral environment, whereas the doublet peak with maxima at 593 nm and 634 nm were attributed to the d-d transition from the 3T1(F) state to the 3T1(P) state of Ni2+ in a tetrahedral environment [52]. Among all four catalysts, only the silicon- and tungsten-containing catalysts (5Ni3SiAl and 5Ni3WAl) included Ni2+ ions in both tetrahedral and octahedral environments. The NiAl2O4 phase is known to comprise Ni2+ ions in both tetrahedral and octahedral coordination environments. Therefore, 5Ni3SiAl and 5Ni3WAl may contain NiAl2O4 phases. In the case of the other catalysts, the mentioned bands either displayed low intensity or had shifted toward higher wavelengths, indicating a weak interaction between the modifier and Ni2+ and the support. In the case of the titanium-containing catalyst (5Ni3TiAl), no peaks attributable to Ni2+ ions in tetrahedral environments were observed, indicating the absence of an NiAl2O4 phase. By contrast, the UV–Vis spectrum of 5Ni3TiAl displayed a peak at 740 nm attributable to Ni2+ in an octahedral coordination environment, as segregated or crystallized NiO which was as near as bulk NiO [53], indicating that octahedral coordinated Ni2+ was present in segregated form in 5Ni3TiAl. An additional hump in the 260–330 nm wavelength range for 5Ni3TiAl could be assigned to a charge transfer from O2− to octahedral/tetrahedral Ti4+ (O2− → Ti4+) in a possible NiTiO3 phase [44]. The hump in the 280–330 nm wavelength range observed in the UV–Vis spectrum of 5NiMoAl could be attributed to a charge transfer from O2− to octahedral/tetrahedral Mo6+ (O2− → Mo6+) in a possible NiMoO4 phase/Al2(MoO4)3 phase [54].
In order to clarify further the interaction of Ti and Mo with the support and with catalytic active sites (NiO), Al (2p, 2s) XPS analysis was conducted on 5Ni3TiAl and 5Ni3MoAl (Figure 5A). The Al (2p) XPS spectrum of 5Ni3TiAl was characterized by peaks at 74.30 eV and at 119.17 eV. These peaks were quite similar to those observed in the Al (2p) XPS spectrum of pure γ-Al2O3 [55]. This evidence indicated that the γ-Al2O3 support doesn’t interact with TiO2 and NiO. However, in the presence of molybdenum as a modifier, a substantial shift to lower energy values (to 71.5 eV and 116.34 eV) was observed for the mentioned peaks in the Al (2p) spectra. This shift was indicative of changes in the electronic environment around Al ions, resulting from an increase in negative charge in the vicinity of Al3+ due to an excess of oxygen atoms around it. It may indicate an oxide enrichment resulting from the formation of Al2(MoO4)3 [56]. However, the absence of peak shifts to higher energy in the case of the Al (2p) and Al (2s) XPS spectra of 5Ni3MoAl indicates a poor interaction between NiO and the γ-Al2O3 support (i.e., the formation of a NiAl2O4 phase was not observed) [57,58]. Notably, Mo (3d) XPS analysis was also carried out on 5Ni3MoAl (Figure 5B). The Mo (3d) XPS spectrum of this catalyst showed a doublet peak with maxima at 234.75 eV and 235.8 eV, which is attributable to the interaction of NiO with MoOx species [59,60], and a peak at 233.52 eV, which is attributable to a strong interaction between MoO3 and γ-Al2O3 or the formation of Al2(MoO4)3 [61]. Overall, 5Ni3TiAl can be said to comprise negligibly interacting species, whereas 5Ni3MoAl may include species whereby NiO interacted with MoOx, and MoO3 interacted with γ-Al2O3, although little interaction appeared to exist between NiO and the γ-Al2O3 support [62].
Till now, catalysts 5Ni3SiAl and 5Ni3WAl were thus found to be enriched with NiO species interacting with the support and the modifier. The tendency of these species to undergo reduction needs, however, to be determined because only reduced nickel species (i.e., metallic nickel) can initiate CH4 decomposition for hydrogen production through DRM [63,64]. In order to determine their reducibility, H2-TPR experiments were carried out for 5Ni3SiAl and 5Ni3WAl catalysts (Figure 6). The deconvoluted peak profiles are shown in Figure S4. These reduction peaks can be categorized into four regions; region I 200–400 °C, region II 400–700 °C, region III 700–900 °C, and region IV 900–1000 °C [65]. The H2-TPR profile of 5Ni3SiAl was characterized by a low prominent reduction peak in region I and largely overlapped peaks in regions II and III. The less prominent peak in region I was due to reduction of free NiO species. Region II showed reduction peak for NiO interacting with the modifier or NiSiO3, whereas region III showed reduction peaks for NiO interacting with the support or NiAl2O4 [55,59]. Formation of NiAl2O4 was explained by Scheffer et al. [66]. Nickel ions diffused into the A12O3 support, where it was coordinated tetrahedrally and octahedrally to form NiAl2O4. UV of 5Ni3SiAl sample also detected Ni+2 in tetrahedral and octahedral coordination. On the other hand, the H2-TPR profile of 5Ni3WAl catalyst was characterized by absence of region I peak (for free NiO) and an additional peak in region IV [67]. The absence of free NiO species suggested that some interaction was occurred between NiO and WO3 or Al2O3 species. Scheffer et al. discussed that from NiAl2O4 species some of aluminium ions may be replaced and form new NiO species (or NiWOAl) and the reduction peak of this new NiO species would be at higher temperature beside reduction peak of NiAl2O4 species. Thus, additional peak in region IV can be claimed to reduction peaks of NiWOAl species. Further, the reduction peaks in regions II and III were largely overlapped in which region III was more prominent. Region II showed reduction peaks for NiWO4 species, whereas region III showed reduction peaks for NiAl2O4 [56,60]. Overall, it can be said that 5Ni3SiAl catalyst system had NiSiO3 and NiAl2O4 species, whereas 5Ni3WAl catalyst system had NiWO4 and NiAl2O4 species majorly.

3. Discussion

The chief route of H2 production via DRM comprises the dissociation of CH4 over the surface of Ni (or supported Ni) to produce carbon deposits and H2, followed by the oxidation of the carbon deposits by CO2 to produce CO (CH4 + CO2 → CO + H2). Nevertheless, the reverse water gas shift (RWGS) reaction due to a spill over effect of molecular hydrogen, produced over the surface of Ni, (CO2 + H2 → CO + H2O) and the gasification of the carbon deposits by hydrogen gas (C + 2H2 → CH4) [68] are not reaction routes that can be ignored. In fact, these parallel reactions can affect H2 yield. Notably, not all parallel reactions, taking place over the catalyst surface, are detrimental to the mean yield of H2. For instance, the presence of water at the catalyst surface (possibly due to RWGS) may contribute to the gasification of carbon deposits, leading to the production of molecular hydrogen and carbon monoxide (C + 2H2O → CO + H2), and thus increasing H2 yield.
The dispersion and stability of “Ni-related species” over a support determine the H2 yield of a DRM reaction, taking place over the surface of a catalyst. The 5Ni3TiAl catalyst was characterized by infrared-active Ni-O vibration frequencies close to those of free NiO; in fact, NiO interacted with the modifier to produce the characteristic peaks of NiTiO3. UV–Vis absorption evidence also confirmed the presence of Ni2+ ions in an octahedral environment, in the form of segregated, crystallized, or bulk NiO, and the presence of Ti4+ in both tetrahedral and octahedral environments in NiTiO3. Overall, 5Ni3TiAl comprised free NiO and NiTiO3. XPS Al (2p) evidence on 5Ni3TiAl also confirmed the intact nature of TiO2 and NiO over the Al2O3 support. The inferior catalytic performance of 5Ni3TiAl with respect to those of the other systems could be due to the free NiO species present in it. Use of 5Ni3TiAl as DRM catalyst was observed to be associated with a 30% H2 yield at 700 °C and more than 60% at 800 °C. The IR spectrum of 5Ni3MoAl did not include any peaks attributable to the vibration of the Ni-O bond of free NiO. The UV–Vis spectrum of 5Ni3MoAl was indicative of the presence of Mo6+ in octahedral/tetrahedral environments, as environment of Mo6+ in NiMoO4. XPS Mo (3d) evidence on 5Ni3MoAl indicated the presence of a species, whereby NiO interacted with MoOx, which was the dominant one, with a smaller prevalence of a species whereby NiO interacted with the support (γ-Al2O3). The absence of free NiO in 5Ni3MoAl caused a larger fraction of Ni-interacted species with the modifier (as NiMoO4) at the surface than that at 5Ni3TiAl. An increased fraction of species whereby Ni interacted with MoOx (i.e., NiMoO4) caused the catalyst to increase in stability and resulted in >45% H2 yield of the DRM reaction at 700 °C. At high reaction temperature, about 800 °C, an endothermic feature of DRM reaction promoted enhanced CH4 decomposition at “Ni-interacted species surfaces” as NiMoO4 and NiTiO3 [69]. Therefore, NiMoO4 and NiTiO3 species (in 5Ni3MoAl and 5Ni3TiAl catalyst systems, respectively) displayed high catalytic efficiency and thermal stability at high temperatures, with an over 60% H2 yield of the DRM reaction at 800 °C.
The IR spectra of 5Ni3SiAl and 5Ni3WAl were characterized by vibrational frequencies due to a variety species, whereby NiO interacted with the modifier or the support. 5Ni3SiAl comprised species, whereby NiO interacted with the modifier to form NiSiO3 and with the support to produce NiAl2O4, much like 5Ni3WAl comprised species, whereby NiO interacted with the modifier to form NiWO4 and with the support to form NiAl2O4. UV–Vis absorbance data confirmed the presence of Ni2+ in tetrahedral and octahedral environments in NiAl2O4 in both catalysts. H2-TPR evidence validated the ability of these “interacting-Ni species” in both 5Ni3SiAl and 5Ni3WAl catalyst systems to undergo reduction. As both catalysts comprised a variety of stable interacting-NiO species, they displayed equally high catalytic efficiency. Use of both catalysts in the DRM reaction resulted in >60% H2 yield at 700 °C and >70% H2 yield at 800 °C over 420 min on stream. Evidence suggested that the NiSiO3, NiWO4, and NiAl2O4 mixed oxides present in 5Ni3SiAl and 5Ni3WAl were more thermally stable than the NiTiO3 and NiMoO4 mixed oxides present in 5Ni3TiAl and 5Ni3MoAl, respectively. The catalyst system, composed of 12.5 wt% Ni and 12.5 wt% Co and supported on La2O3, showed 31% and 60% H2 yield for the catalyst calcined at 700 °C and 900 °C, respectively [70]. The 5 wt% MgO-promoted Ni-Co/Al2O3-ZrO2 nanocatalyst showed about 20% H2 yield at 650 °C and 40% hydrogen yield at 750 °C [71]. Ni catalysts supported on Gd-doped ceria (prepared by conventional impregnation method) showed 64% H2 yield [72]. The Sr-promoted Al2O3 supported Nickel catalyst showed 70% H2 yield [73]. In our catalyst system, only 3 wt% promoter of either W or Si in Al2O3-supported nickel catalyst resulted into more than 60% H2 yield at 700 °C and more than 70% H2 yield at 800 °C. In the regeneration study with 5Ni3SiAl catalyst, the H2 yields after the first and second recycling were 58 and 59%, respectively at at 700 °C. It can be inferred that the catalyst regained nearly all its performance after the removal of carbon deposits by using oxygen (Figure 7).

4. Materials and Methods

4.1. Catalyst Preparation

The 5Ni3MAl (M = Si, Ti, Mo, or W) catalyst systems were prepared by incipient wetness impregnation, followed by calcination. The detailed procedure for catalyst preparation is described as follows. The required amounts of well-grounded γ-Al2O3 and metal oxides precursors ((NH4)6Mo7O24·4H2O (Sigma-Aldrich, St. Louis, MO, USA) or (NH4)10H2(W2O7)6 (Aldrich)) were mixed together and then crushed mechanically by mortar and pestle. Droplets of deionized H2O was added to form a paste. The mechanical mixing was carried out until the dried compact mixture was accomplished. Wetting and drying processes of the solid mixture were done three times. The dried mixture was calcined in a programmable muffle furnace at 600 °C at the rate 3 °C/min for three hours. γ-Alumina with titania (3.0 wt% TiO2/γ-Al2O3) and silica (2.0 wt% SiO2/γ-Al2O3) in the form of pellets, were gifts from the Inorganic Chemistry Laboratory, Oxford University, Oxford, UK. Same as the above discussed procedure, the essential amount of Ni (NO3)2.6H2O along, with doped γ-Al2O3 support were grounded, were made in paste form, and then were dried and calcined. The calcined 5 wt% NiO /3 wt% MOx-γ-Al2O3(M = Ti, Mo, W, Si) catalysts were abbreviated as 5Ni3MAl (M = Ti, Mo, W, Si).

4.2. Catalyst Characterization

Catalysts were characterized by SEM, EDXS, IR, UV–Vis, and X-ray Photoelectron spectroscopy techniques and H2-TPR. The morphology of the catalyst samples was investigated by using a field emission scanning electron microscope (FE-SEM, model: JEOL JSM-7100 F, St. Lucia, Queensland, Australia), furnished with energy dispersive X-ray spectroscopy (EDXS) for surface elemental analysis. The Fourier transform infrared (FTIR) measurements were carried out by using IR Prestige-21 SHMADZU, spectrophotometer, Kyoto, Japan. The spectra were documented in the range 400–4000 cm−1 with 4 cm−1 energy resolution, using KBr pellet. Ultraviolet-visible measurement was carried out by using V-570 JASCO, Eston, PA, USA) spectrophotometer. The spectra were registered in the range of 200–800 nm wavelength with resolution of 1 nm at a scanning speed of 200 nm/min. The XPS was carried out using Thermo Scientific X-ray Photoelectron Spectrometer, Manchester, UK. Monochromatic Al Kα (1486.6 eV) radiation source operating at a power of 72 W with a pass energy of 50 eV for high resolution area scans and 200 eV for inspection scans was used. For charge adjustment, a one-point scale with the C1s peak moved to 285.0 eV was used. Temperature-programmed reduction (TPR) was carried out with the Micromeritics AutoChem II, Atlanta, GA, USA. 0.07 g of the sample (in sample holder) was degassed using argon at 150 ℃ for 60 min and then cooled to 25 ℃. Further, it was heated to 800 ℃ at the rate of 10 ℃/minute under 10% H2 in argon flow. The flow rate of 10% H2 in argon was set at 40 mL/minute. At the reactor outlet, thermal conductivity detector (TCD) monitors the gas mixture and peaks corresponding to the consumption of H2 as a function of temperature were obtained.

4.3. Catalytic Reaction

The reaction was performed at atmospheric pressure in a tubular, stainless steel, fixed-bed micro-reactor (ID = 9 mm) (supplied by PID Eng and Tech, Madrid, Spain). 0.10 g catalyst was reduced under 20 mL/min flow of H2 at 800 °C for 60 min. Now, nitrogen gas was passed through the reactor for 20 min to eliminate adsorbed H2 at 700 °C. Afterwards, dry reforming of methane was carried out by passing CH4, CO2, and N2 gas mixture feed at flow rates of 30, 30, and 10 mL/min respectively through the catalyst bed. The temperature, pressure and reaction variables were monitored through the reactor panel. GC-2014 (SHIMADZU, Kyoto, Japan) gas chromatograph equipped with Porapak Q and Molecular Sieve 5A columns and thermal conductivity detector was joined in series/bypass connections to have a whole examination of the reaction products and the feed. For regeneration process, fresh 5Ni-3SiO2 + Al2O3 catalyst is packed in the reactor. The sample was activated with H2 flow of 20 mL/min for an hour and then followed by a reaction for 820 min at 700 °C. The spent catalyst is then treated with 10 mL/min O2 for 30 min to remove the deposited carbon. Subsequently, the recycled catalyst was activated with H2 to take care of any oxidized Ni metal during the recycling and thereafter, reaction was performed. Again, the recycling operation was repeated and the reaction carried out the third time.

5. Conclusions

The titanium-modified catalyst (5Ni3TiAl) had free NiO and NiTiO3 species. Free NiO species were completely unsuitable for H2 production through DRM. The presence of the free NiO fraction caused 5Ni3TiAl to display about 30% H2 yield at 700 °C. The molybdenum-modified catalyst (5Ni3MoAl) had no free NiO species, but had NiO interacting with MoO3 species or NiMoO4 species, which displayed a moderate catalytic performance of about 45% H2 yield at 700 °C. Notably, at a higher reaction temperature (800 °C), the endothermic feature of the DRM reaction enhanced CH4 decomposition, and both catalysts displayed a higher but equal efficiency of about 60% H2 yield. On the other hand, the silicon-modified catalyst (5Ni3SiAl) and tungsten-modified catalyst (5Ni3WAl) were comprised of a variety of thermally stable species, whereby NiO interacted with the modifier and the support. The 5Ni3SiAl catalyst system had NiSiO3 and NiAl2O4 species, whereas the 5Ni3WAl catalyst system had NiWO4 and NiAl2O4 species. The sets of mixed oxides present in 5Ni3SiAl and 5Ni3WAl were responsible for displaying higher thermal stability and catalytic performance than 5Ni3TiAl and 5Ni3MoAl. In fact, the 5Ni3SiAl and 5Ni3WAl catalyst systems displayed equally high catalytic efficiency of about 60% H2 yield at 700 °C and about 70% H2 yield at 800 °C, over 420 min on stream. The 5Ni3SiAl catalyst regained nearly all its activity after the removal of carbon deposits by using oxygen.

Supplementary Materials

The following are available online at https://0-www-mdpi-com.brum.beds.ac.uk/2227-9717/9/1/157/s1, Figure S1: SEM image of different catalyst system; Figure S2: EDX spectra of different catalyst system, Figure S3: Infrared spectroscopy of different catalyst system, Figure S4: Deconvoluted H2 temperature-programmed surface reduction profiles of (A) 5Ni3SiAl catalyst, and (B) 5Ni3WAl catalyst.

Author Contributions

A.S.A.-F., A.A.I., and S.O.K. synthesized the catalysts, carried out all the experiments and characterization tests, and wrote the manuscript. R.P., F.A.-M., and R.K. prepared the catalyst and contributed to proofreading of the manuscript. F.A.-M., M.L.C., Y.A.A., and A.A.B., writing—review and editing; A.H.F. contributed to the analysis of the data and proofread the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

The work is supported by the Deanship of Scientific Research programs of King Saud University via project No. RGP-119.

Data Availability Statement

Data is contained within the article.

Acknowledgments

The authors would like to express their sincere appreciation to the Deanship of Scientific Research at King Saud University for funding this research project (#RGP-119).

Conflicts of Interest

The authors declare no competing interests.

References

  1. Mazloomi, K.; Gomes, C. Hydrogen as an energy carrier: Prospects and challenges. Renew. Sustain. Energy Rev. 2012, 16, 3024–3033. [Google Scholar] [CrossRef]
  2. Balat, M. Potential importance of hydrogen as a future solution to environmental and transportation problems. Int. J. Hydrog. Energy 2008, 33, 4013–4029. [Google Scholar] [CrossRef]
  3. Ni, M.; Leung, D.Y.C.; Leung, M.K.H.; Sumathy, K. An overview of hydrogen production from biomass. Fuel Process. Technol. 2006, 87, 461–472. [Google Scholar] [CrossRef]
  4. Wu, G.; Zhang, C.; Li, S.; Huang, Z.; Yan, S.; Wang, S.; Ma, X.; Gong, J. Sorption enhanced steam reforming of ethanol on Ni-CaO-Al2O3 multifunctional catalysts derived from hydrotalcite-like compounds. Energy Environ. Sci. 2012, 5, 8942–8949. [Google Scholar] [CrossRef]
  5. Clough, P.T.; Boot-Handford, M.E.; Zheng, L.; Zhang, Z.; Fennell, P.S. Hydrogen production by sorption enhanced steam reforming (SESR) of biomass in a fluidised-bed reactor using combined multifunctional particles. Materials 2018, 11, 859. [Google Scholar] [CrossRef] [Green Version]
  6. Yu, D.; Aihara, M.; Antal, M.J. Hydrogen production by steam reforming glucose in supercritical water. Energy Fuels 1993, 7, 574–577. [Google Scholar] [CrossRef]
  7. Schmieder, H.; Abeln, J.; Boukis, N.; Dinjus, E.; Kruse, A.; Kluth, M.; Petrich, G.; Sadri, E.; Schacht, M. Hydrothermal gasification of biomass and organic wastes. J. Supercrit. Fluids 2000, 17, 145–153. [Google Scholar] [CrossRef]
  8. Osman, A.I.; Meudal, J.; Laffir, F.; Thompson, J.; Rooney, D. Enhanced catalytic activity of Ni on H-Al2O3 and ZSM-5 on addition of ceria zirconia for the partial oxidation of methane. Appl. Catal. B Environ. 2017, 212, 68–79. [Google Scholar] [CrossRef] [Green Version]
  9. Gutta, N.; Velisoju, V.K.; Tardio, J.; Patel, J.; Satyanarayana, L.; Sarma, A.V.S.; Akula, V. CH4 Cracking over the Cu-Ni/Al-MCM-41 catalyst for the simultaneous production of H2 and highly ordered graphitic carbon nanofibers. Energy Fuels 2019, 33, 12656–12665. [Google Scholar] [CrossRef]
  10. Kumar, R.; Ponnada, S.; Enjamuri, N.; Pandey, J.K.; Chowdhury, B. Synthesis, characterization and correlation with the catalytic activity of efficient mesoporous niobia and mesoporous niobia-zirconia mixed oxide catalyst system. Catal. Commun. 2016, 77, 42–46. [Google Scholar] [CrossRef]
  11. Tomiyama, S.; Takahashi, R.; Sato, S.; Sodesawa, T.; Yoshida, S. Preparation of Ni/SiO2 catalyst with high thermal stability for CO2-reforming of CH4. Appl. Catal. A Gen. 2003, 241, 349–361. [Google Scholar] [CrossRef]
  12. Al-Fatesh, A.S.A.; Ibrahim, A.A.; Fakeeha, A.H.; Abasaeed, A.E.; Siddiqui, M.R.H. Oxidative CO2 reforming of CH4 over Ni/α-Al2O3 catalyst. J. Ind. Eng. Chem. 2011, 17, 479–483. [Google Scholar] [CrossRef]
  13. Kim, D.H.; Kim, S.Y.; Han, S.W.; Cho, Y.K.; Jeong, M.G.; Park, E.J.; Kim, Y.D. The catalytic stability of TiO2-shell/Ni-core catalysts for CO2 reforming of CH4. Appl. Catal. A Gen. 2015, 495, 184–191. [Google Scholar] [CrossRef]
  14. Seo, H.O.; Sim, J.K.; Kim, K.D.; Kim, Y.D.; Lim, D.C.; Kim, S.H. Carbon dioxide reforming of methane to synthesis gas over a TiO2-Ni inverse catalyst. Appl. Catal. A Gen. 2013, 451, 43–49. [Google Scholar] [CrossRef]
  15. Shah, M.; Mondal, P.; Nayak, A.K.; Bordoloi, A. Advanced titania composites for efficient CO2 reforming with methane: Statistical method vs. experiment. J. CO2 Util. 2020, 39, 101160. [Google Scholar] [CrossRef]
  16. Shah, M.; Bordoloi, A.; Nayak, A.K.; Mondal, P. Effect of Ti/Al ratio on the performance of Ni/TiO2-Al2O3 catalyst for methane reforming with CO2. Fuel Process. Technol. 2019, 192, 21–35. [Google Scholar] [CrossRef]
  17. Xu, Y.; Du, X.H.; Li, J.; Wang, P.; Zhu, J.; Ge, F.J.; Zhou, J.; Song, M.; Zhu, W.Y. A comparison of Al2O3 and SiO2 supported Ni-based catalysts in their performance for the dry reforming of methane. Ranliao Huaxue Xuebao/J. Fuel Chem. Technol. 2019, 47, 199–208. [Google Scholar] [CrossRef]
  18. Zhou, L.; Li, L.; Wei, N.; Li, J.; Basset, J.-M. Effect of NiAl2O4 formation on Ni/Al2O3 stability during dry reforming of methane. ChemCatChem 2015, 7, 2508–2516. [Google Scholar] [CrossRef] [Green Version]
  19. Shen, D.; Huo, M.; Li, L.; Lyu, S.; Wang, J.; Wang, X.; Zhang, Y.; Li, J. Effects of alumina morphology on dry reforming of methane over Ni/Al2O3 catalysts. Catal. Sci. Technol. 2020, 10, 510–516. [Google Scholar] [CrossRef]
  20. Fang, X.; Peng, C.; Peng, H.; Liu, W.; Xu, X.; Wang, X.; Li, C.; Zhou, W. Methane dry reforming over coke-resistant mesoporous Ni-Al2O3 catalysts prepared by evaporation-induced self-assembly method. ChemCatChem 2015, 7, 3753–3762. [Google Scholar] [CrossRef]
  21. Medeiros, R.L.B.A.; Figueredo, G.P.; Macedo, H.P.; Oliveira, Â.A.S.; Rabelo-Neto, R.C.; Melo, D.M.A.; Braga, R.M.; Melo, M.A.F. One-pot microwave-assisted combustion synthesis of Ni-Al2O3 nanocatalysts for hydrogen production via dry reforming of methane. Fuel 2020, 119511. [Google Scholar] [CrossRef]
  22. Zhao, Y.; Kang, Y.; Li, H.; Li, H. CO2 conversion to synthesis gas: Via DRM on the durable Al2O3/Ni/Al2O3 sandwich catalyst with high activity and stability. Green Chem. 2018, 20, 2781–2787. [Google Scholar] [CrossRef]
  23. Rahemi, N.; Haghighi, M.; Babaluo, A.A.; Jafari, M.F.; Khorram, S. Non-thermal plasma assisted synthesis and physicochemical characterizations of Co and Cu doped Ni/Al2O3 nanocatalysts used for dry reforming of methane. Int. J. Hydrog. Energy 2013, 38, 16048–16061. [Google Scholar] [CrossRef]
  24. Fakeeha, A.H.; Bagabas, A.A.; Lanre, M.S.; Osman, A.I.; Kasim, S.O.; Ibrahim, A.A.; Arasheed, R.; Alkhalifa, A.; Elnour, A.Y.; Abasaeed, A.E.; et al. Catalytic performance of metal oxides promoted nickel catalysts supported on mesoporous γ-Alumina in dry reforming of methane. Processes 2020, 8, 522. [Google Scholar] [CrossRef]
  25. Yao, L.; Galvez, M.E.; Hu, C.; da Costa, P. Mo-promoted Ni/Al2O3 catalyst for dry reforming of methane. Int. J. Hydrog. Energy 2017, 42, 23500–23507. [Google Scholar] [CrossRef]
  26. Vroulias, D.; Gkoulemani, N.; Papadopoulou, C.; Matralis, H. W–modified Ni/Al2O3 catalysts for the dry reforming of methane: Effect of W loading. Catal. Today 2020, 355, 704–715. [Google Scholar] [CrossRef]
  27. Wei, Q.; Yang, G.; Yoneyama, Y.; Vitidsant, T.; Tsubaki, N. Designing a novel Ni-Al2O3-SiC catalyst with a stereo structure for the combined methane conversion process to effectively produce syngas. Catal. Today 2016, 265, 36–44. [Google Scholar] [CrossRef]
  28. Al-Fatesh, A.S.; Naeem, M.A.; Fakeeha, A.H.; Abasaeed, A.E. CO2 reforming of methane to produce syngas over γ-Al2O3-supported Ni–Sr catalysts. Bull. Chem. Soc. Jpn. 2013, 86, 742–748. [Google Scholar] [CrossRef]
  29. Fouskas, A.; Kollia, M.; Kambolis, A.; Papadopoulou, C.; Matralis, H. Boron-modified Ni/Al2O3 catalysts for reduced carbon deposition during dry reforming of methane. Appl. Catal. A Gen. 2014, 474, 125–134. [Google Scholar] [CrossRef]
  30. Alipour, Z.; Rezaei, M.; Meshkani, F. Effects of support modifiers on the catalytic performance of Ni/Al2O3 catalyst in CO2 reforming of methane. Fuel 2014, 129, 197–203. [Google Scholar] [CrossRef]
  31. Seok, S.H.; Sun, H.C.; Park, E.D.; Sung, H.H.; Jae, S.L. Mn-promoted Ni/Al2O3 catalysts for stable carbon dioxide reforming of methane. J. Catal. 2002, 209, 6–15. [Google Scholar] [CrossRef]
  32. Therdthianwong, S.; Siangchin, C.; Therdthianwong, A. Improvement of coke resistance of Ni/Al2O3 catalyst in CH4/CO2 reforming by ZrO2 addition. Fuel Process. Technol. 2008, 89, 160–168. [Google Scholar] [CrossRef]
  33. Laosiripojana, N.; Sutthisripok, W.; Assabumrungrat, S. Synthesis gas production from dry reforming of methane over CeO2 doped Ni/Al2O3: Influence of the doping ceria on the resistance toward carbon formation. Chem. Eng. J. 2005, 112, 13–22. [Google Scholar] [CrossRef]
  34. Chein, R.Y.; Fung, W.Y. Syngas production via dry reforming of methane over CeO2 modified Ni/Al2O3 catalysts. Int. J. Hydrog. Energy 2019, 44, 14303–14315. [Google Scholar] [CrossRef]
  35. Li, K.; Pei, C.; Li, X.; Chen, S.; Zhang, X.; Liu, R.; Gong, J. Dry reforming of methane over La2O2CO3-modified Ni/Al2O3 catalysts with moderate metal support interaction. Appl. Catal. B Environ. 2020, 264, 118448. [Google Scholar] [CrossRef]
  36. Amin, M.H.; Mantri, K.; Newnham, J.; Tardio, J.; Bhargava, S.K. Highly stable ytterbium promoted Ni/γ-Al2O3 catalysts for carbon dioxide reforming of methane. Appl. Catal. B Environ. 2012, 119–120, 217–226. [Google Scholar] [CrossRef]
  37. Zhang, Y.; Zhang, S.; Zhang, X.; Qiu, J.; Yu, L.; Shi, C. Ni modified WC x catalysts for methane dry reforming. In Advances in CO2 Capture, Sequestration, and Conversion; American Chemical Society: Washington, DC, USA, 2015; pp. 171–189. [Google Scholar]
  38. Shi, C.; Zhang, S.; Li, X.; Zhang, A.; Shi, M.; Zhu, Y.; Qiu, J.; Au, C. Synergism in NiMoOx precursors essential for CH4/CO2 dry reforming. Catal. Today 2014, 233, 46–52. [Google Scholar] [CrossRef]
  39. Al-Fatesh, A.S.; Kumar, R.; Kasim, S.O.; Ibrahim, A.A.; Fakeeha, A.H.; Abasaeed, A.E.; Alrasheed, R.; Bagabas, A.; Chaudhary, M.L.; Frusteri, F.; et al. The effect of modifier identity on the performance of Ni-based catalyst supported on γ-Al2O3 in dry reforming of methane. Catal. Today 2020, 348, 236–242. [Google Scholar] [CrossRef]
  40. Vlaev, L.; Damyanov, D.; Mohamed, M.M. Infrared spectroscopy study of the nature and reactivity of a hydrate coverage on the surface of γ-Al2O3. Colloids Surf. 1989, 36, 427–437. [Google Scholar] [CrossRef]
  41. Du, X.; Wang, Y.; Su, X.; Li, J. Influences of pH value on the microstructure and phase transformation of aluminum hydroxide. Powder Technol. 2009, 192, 40–46. [Google Scholar] [CrossRef]
  42. Dyer, C.; Hendra, P.J.; Forsling, W.; Ranheimer, M. Surface hydration of aqueous γ-Al2O3 studied by Fourier transform Raman and infrared spectroscopy-I. Initial results. Spectrochim. Acta Part A Mol. Spectrosc. 1993, 49, 691–705. [Google Scholar] [CrossRef]
  43. El-Kemary, M.; Nagy, N.; El-Mehasseb, I. Nickel oxide nanoparticles: Synthesis and spectral studies of interactions with glucose. Mater. Sci. Semicond. Process. 2013, 16, 1747–1752. [Google Scholar] [CrossRef]
  44. Zhou, G.; Soo Kang, Y. Synthesis and characterization of the nickel titanate NiTiO3 Nanoparticles in CTAB Micelle. J. Dispers. Sci. Technol. 2006, 27, 727–730. [Google Scholar] [CrossRef]
  45. Vijayalakshmi, R.; Rajendran, V. Effect of reaction temperature on size and optical properties of NiTiO3 nanoparticles. E-J. Chem. 2012, 9, 282–288. [Google Scholar] [CrossRef] [Green Version]
  46. Umapathy, V.; Neeraja, P.; Manikandan, A.; Ramu, P. Synthesis of NiMoO4 nanoparticles by sol–gel method and their structural, morphological, optical, magnetic and photocatlytic properties. Trans. Nonferrous Met. Soc. China 2017, 27, 1785–1793. [Google Scholar] [CrossRef]
  47. De Moura, A.P.; De Oliveira, L.H.; Rosa, I.L.V.; Xavier, C.S.; Lisboa-Filho, P.N.; Li, M.S.; La Porta, F.A.; Longo, E.; Varela, J.A. Structural, optical, and magnetic properties of NiMoOnanorods prepared by microwave sintering. Sci. World J. 2015, 2015. [Google Scholar] [CrossRef] [Green Version]
  48. Okuno, M.; Zotov, N.; Schmücker, M.; Schneider, H. Structure of SiO2-Al2O3 glasses: Combined X-ray diffraction, IR and Raman studies. J. Non-Cryst. Solids 2005, 351, 1032–1038. [Google Scholar] [CrossRef]
  49. Sadjadi, M.S.; Mozaffari, M.; Enhessari, M.; Zare, K. Effects of NiTiO3 nanoparticles supported by mesoporous MCM-41 on photoreduction of methylene blue under UV and visible light irradiation. Superlattices Microstruct. 2010, 47, 685–694. [Google Scholar] [CrossRef]
  50. Salleh, N.F.M.; Jalil, A.A.; Triwahyono, S.; Efendi, J.; Mukti, R.R.; Hameed, B.H. New insight into electrochemical-induced synthesis of NiAl2O4/Al2O3: Synergistic effect of surface hydroxyl groups and magnetism for enhanced adsorptivity of Pd (II). Appl. Surf. Sci. 2015, 349, 485–495. [Google Scholar] [CrossRef]
  51. Mancheva, M.N.; Iordanova, R.S.; Klissurski, D.G.; Tyuliev, G.T.; Kunev, B.N. Direct mechanochemical synthesis of nanocrystalline NiWO4. J. Phys. Chem. C 2007, 111, 1101–1104. [Google Scholar] [CrossRef]
  52. Torres-Mancera, P.; Ramírez, J.; Cuevas, R.; Gutiérrez-Alejandre, A.; Murrieta, F.; Luna, R. Hydrodesulfurization of 4,6-DMDBT on NiMo and CoMo catalysts supported on B2O3-Al2O3. Catal. Today 2005, 107–108, 551–558. [Google Scholar] [CrossRef]
  53. Carraro, P.; Elías, V.; García Blanco, A.; Sapag, K.; Moreno, S.; Oliva, M.; Eimer, G. Synthesis and multi-technique characterization of nickel loaded MCM-41 as potential hydrogen-storage materials. Microporous Mesoporous Mater. 2014, 191, 103–111. [Google Scholar] [CrossRef]
  54. Forzatti, P.; Mari, C.M.; Villa, P. Defect structure and transport properties of Cr2(MoO4)3 and Al2(MoO4)3. Mater. Res. Bull. 1987, 22, 1593–1602. [Google Scholar] [CrossRef]
  55. Strohmeier, B.R. Gamma-Alumina (γ-Al2O3) by XPS. Surf. Sci. Spectra 1994, 3, 135–140. [Google Scholar] [CrossRef]
  56. Reddy, B.M.; Chowdhury, B.; Smirniotis, P.G. XPS study of the dispersion of MoO3 on TiO2-ZrO2, TiO2-SiO2, TiO2-Al2O3, SiO2-ZrO2, and SiO2-TiO2-ZrO2 mixed oxides. Appl. Catal. A Gen. 2001, 211, 19–30. [Google Scholar] [CrossRef]
  57. Shok, J.; Raju, G.; Reddy, P.S.; Subrahmanyam, M.; Venugopal, A. Catalytic decomposition of CH4 over NiO-Al2O3-SiO2 catalysts: Influence of catalyst preparation conditions on the production of H2. Int. J. Hydrog. Energy 2008. [Google Scholar] [CrossRef]
  58. Kim, K.; Yang, S.; Baek, J.I.; Kim, J.W.; Ryu, J.; Ryu, C.K.; Ahn, D.G.; Shin, K. Distribution of NiO/Al2O3/NiAl2O4 in the fabrication of spray-dry oxygen carrier particles for chemical-looping combustion. In Advanced Materials Research; Trans Tech Publications: Bach, Switzerland, 2011; Volume 311. [Google Scholar] [CrossRef]
  59. Bianchi, C.L.; Cattania, M.G.; Villa, P. XPS characterization of Ni and Mo oxides before and after ‘in situ’ treatments. Appl. Surf. Sci. 1993, 70–71, 211–216. [Google Scholar] [CrossRef]
  60. Anwar, M.; Hogarth, C.A.; Bulpett, R. Effect of substrate temperature and film thickness on the surface structure of some thin amorphous films of MoO3 studied by X-ray photoelectron spectroscopy (ESCA). J. Mater. Sci. 1989, 24, 3087–3090. [Google Scholar] [CrossRef]
  61. Nefedov, V.I.; Firsov, M.N.; Shaplygin, I.S. Electronic structures of MRhO2, MRh2O4, RhMO4 and Rh2MO6 on the basis of X-ray spectroscopy and ESCA data. J. Electron Spectrosc. Relat. Phenom. 1982, 26, 65–78. [Google Scholar] [CrossRef]
  62. Zingg, D.S.; Makovsky, L.E.; Tischer, R.E.; Brown, F.R.; Hercules, D.M. A surface spectroscopic study of molybdenum-alumina catalysts using x-ray photoelectron, ion-scattering, and Raman spectroscopies. J. Phys. Chem. 1980, 84, 2898–2906. [Google Scholar] [CrossRef]
  63. Schouten, F.C.; Kaleveld, E.W.; Bootsma, G.A. AES-LEED-ellipsometry study of the kinetics of the interaction of methane with Ni(110). Surf. Sci. 1977, 63, 460–474. [Google Scholar] [CrossRef]
  64. Chen, Y.; Hu, C.; Gong, M.; Zhu, X.; Chen, Y.; Tian, A. Chemisorption of methane over Ni/Al2O3 catalysts. J. Mol. Catal. A Chem. 2000, 152, 237–244. [Google Scholar] [CrossRef]
  65. Guo, C.; Wu, Y.; Qin, H.; Zhang, J. CO methanation over ZrO2/Al2O3 supported Ni catalysts: A comprehensive study. Fuel Process. Technol. 2014, 124, 61–69. [Google Scholar] [CrossRef]
  66. Scheffer, B.; Molhoek, P.; Moulijn, J.A. Temperature-programmed reduction of NiO-WO3/A12O3 Hydrodesulphurization Catalysts. Appl. Catal. 1989, 46, 11–30. [Google Scholar] [CrossRef]
  67. Southmayd, D.W.; Contescu, C.; Schwarz, J.A. Temperature-programmed reduction and oxidation of nickel supported on WO3-Al2O3 composite oxides. J. Chem. Soc. Faraday Trans. 1993, 89, 2075–2083. [Google Scholar] [CrossRef]
  68. Chung, U.C. Effect of H2 on formation behavior of carbon nanotubes. Bull. Korean Chem. Soc. 2004, 25, 1521–1524. [Google Scholar] [CrossRef] [Green Version]
  69. Al-Fatesh, A.S.; Kumar, R.; Fakeeha, A.H.; Kasim, S.O.; Khatri, J.; Ibrahim, A.A.; Arasheed, R.; Alabdulsalam, M.; Lanre, M.S.; Osman, A.I.; et al. Promotional effect of magnesium oxide for a stable nickel-based catalyst in dry reforming of methane. Sci. Rep. 2020, 10, 1–10. [Google Scholar] [CrossRef]
  70. Fakeeha, A.H.; Khan, W.U.; Al-fatesh, A.S.; Ibrahim, A.A.; Abasaeed, A.E. Production of hydrogen from methane over lanthanum supported bimetallic catalysts. Int. J. Hydrog. Energy 2016, 41, 8193–8198. [Google Scholar] [CrossRef]
  71. Sajjadi, S.M.; Haghighi, M.; Rahmani, F. Dry reforming of greenhouse gases CH4/CO2 over MgO-promoted Ni-Co/Al2O3-ZrO2 nanocatalyst: Effect of MgO addition via sol-gel method on catalytic properties and hydrogen yield. J. Sol-Gel Sci. Technol. 2014, 70, 111–124. [Google Scholar] [CrossRef]
  72. Gurav, H.R.; Dama, S.; Samuel, V.; Chilukuri, S. Influence of preparation method on activity and stability of Ni catalysts supported on Gd doped ceria in dry reforming of methane. J. CO2 Util. 2017, 20, 357–367. [Google Scholar] [CrossRef]
  73. Ibrahim, A.A.; Fakeeha, A.H.; Al-Fatesh, A.S. Enhancing hydrogen production by dry reforming process with strontium promoter. Int. J. Hydrog. Energy 2014, 39, 1680–1687. [Google Scholar] [CrossRef]
Processes 09 00157 g001 550
Figure 1. Active elements in a doped/promoted Al2O3-supported Ni catalyst system for dry reforming of methane.
Figure 1. Active elements in a doped/promoted Al2O3-supported Ni catalyst system for dry reforming of methane.
Processes 09 00157 g001
Processes 09 00157 g002 550
Figure 2. (A) H2 yield over different catalyst systems up to 420 min TOS at 700 °C; (B) H2 yield over different catalyst systems in the 500–800 °C reaction temperature range.
Figure 2. (A) H2 yield over different catalyst systems up to 420 min TOS at 700 °C; (B) H2 yield over different catalyst systems in the 500–800 °C reaction temperature range.
Processes 09 00157 g002
Processes 09 00157 g003 550
Figure 3. (A–H) Infrared spectra of different catalyst systems. In (D), Ni-Oa indicates NiO species that interacted with the support. In (F) Ni-Ob indicates NiO species that strongly interacted with the support. In (H) inset indicates stretching vibration peaks of NiO6 polyhedra in NiWO4 species.
Figure 3. (A–H) Infrared spectra of different catalyst systems. In (D), Ni-Oa indicates NiO species that interacted with the support. In (F) Ni-Ob indicates NiO species that strongly interacted with the support. In (H) inset indicates stretching vibration peaks of NiO6 polyhedra in NiWO4 species.
Processes 09 00157 g003
Processes 09 00157 g004 550
Figure 4. Ultraviolet–visible spectra of different catalyst systems. Peak at 410 nm is associated with d–d transition 3A2g(F) → 3T1g(P) in Ni2+ in an octahedral environment. Peaks at 593 and 634 nm are associated with the d–d transition 3T1(F) → 3T1(P) in Ni2+ in a tetrahedral environment.
Figure 4. Ultraviolet–visible spectra of different catalyst systems. Peak at 410 nm is associated with d–d transition 3A2g(F) → 3T1g(P) in Ni2+ in an octahedral environment. Peaks at 593 and 634 nm are associated with the d–d transition 3T1(F) → 3T1(P) in Ni2+ in a tetrahedral environment.
Processes 09 00157 g004
Processes 09 00157 g005 550
Figure 5. (A) Al (2p, 2s) X-ray photoelectron spectra of catalysts 5Ni3TiAl and 5Ni3MoAl and (B) Mo (3d) X-ray photoelectron spectrum of 5Ni3MoAl.
Figure 5. (A) Al (2p, 2s) X-ray photoelectron spectra of catalysts 5Ni3TiAl and 5Ni3MoAl and (B) Mo (3d) X-ray photoelectron spectrum of 5Ni3MoAl.
Processes 09 00157 g005
Processes 09 00157 g006 550
Figure 6. H2 temperature-programmed surface reduction profiles of (A) Al2O3, 3SiAl, and 5Ni3SiAl catalysts, and (B) Al2O3, 3WAl, and 5Ni3WAl catalysts.
Figure 6. H2 temperature-programmed surface reduction profiles of (A) Al2O3, 3SiAl, and 5Ni3SiAl catalysts, and (B) Al2O3, 3WAl, and 5Ni3WAl catalysts.
Processes 09 00157 g006
Processes 09 00157 g007 550
Figure 7. H2 yield over fresh 5Ni3SiAl catalyst, H2 yield after first cycle (R1), and H2 yield after second cycle (R2).
Figure 7. H2 yield over fresh 5Ni3SiAl catalyst, H2 yield after first cycle (R1), and H2 yield after second cycle (R2).
Processes 09 00157 g007
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Al-Fatesh, A.S.; Chaudhary, M.L.; Fakeeha, A.H.; Ibrahim, A.A.; Al-Mubaddel, F.; Kasim, S.O.; Albaqmaa, Y.A.; Bagabas, A.A.; Patel, R.; Kumar, R. Role of Mixed Oxides in Hydrogen Production through the Dry Reforming of Methane over Nickel Catalysts Supported on Modified γ-Al2O3. Processes 2021, 9, 157. https://0-doi-org.brum.beds.ac.uk/10.3390/pr9010157

AMA Style

Al-Fatesh AS, Chaudhary ML, Fakeeha AH, Ibrahim AA, Al-Mubaddel F, Kasim SO, Albaqmaa YA, Bagabas AA, Patel R, Kumar R. Role of Mixed Oxides in Hydrogen Production through the Dry Reforming of Methane over Nickel Catalysts Supported on Modified γ-Al2O3. Processes. 2021; 9(1):157. https://0-doi-org.brum.beds.ac.uk/10.3390/pr9010157

Chicago/Turabian Style

Al-Fatesh, Ahmed Sadeq, Mayankkumar Lakshmanbhai Chaudhary, Anis Hamza Fakeeha, Ahmed Aidid Ibrahim, Fahad Al-Mubaddel, Samsudeen Olajide Kasim, Yousef Abdulrahman Albaqmaa, Abdulaziz A. Bagabas, Rutu Patel, and Rawesh Kumar. 2021. "Role of Mixed Oxides in Hydrogen Production through the Dry Reforming of Methane over Nickel Catalysts Supported on Modified γ-Al2O3" Processes 9, no. 1: 157. https://0-doi-org.brum.beds.ac.uk/10.3390/pr9010157

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop