Special Issue "Reforming Catalysts"

A special issue of Catalysts (ISSN 2073-4344).

Deadline for manuscript submissions: closed (15 December 2016)

Special Issue Editor

Guest Editor
Dr. Simon Penner

Institute of Physical Chemistry, University of Innsbruck, Innsbruck, Austria
Website | E-Mail
Interests: high-resolution analytical electron microscopy in catalysis; structure-activity correlations in pure and complex oxide catalysts; interfacial engineering of the metal-oxide phase boundary; reactive activation of intermetallic compounds in catalysis; mechanism of methanol and methane steam reforming reactions; preparation and characterization of complex oxide, bi- and multimetallic thin film catalyst systems; operando and in situ structural and spectroscopic studies of catalysts

Special Issue Information

Dear Colleagues,

Steam reforming of hydrocarbons (mostly methane) or alcohols (mostly methanol and ethanol) is one of the most promising and effective routes to enhanced hydrogen production. The most crucial step of this reaction is the efficient water activation, which is a necessary prerequisite for both a high CO2 selectivity and an associated high hydrogen yield. The reactions have been studied on a variety of different catalytic surfaces encompassing oxides, supported metal-oxide systems or (supported) intermetallic compounds likewise. The controllable steering of product selectivity is thereby an obvious key criterion for technical usage. For methanol steam reforming, the key targets—apart from pronounced CO2 selectivity—are, thus, a maximum hydrogen yield and a low CO content in the reformate to realize the efficient on-board production of clean hydrogen in, e.g., automotive applications. Given the structural and chemical complexity and diversity of the materials used, the question about the common elementary reaction steps of the steam reforming reaction is imperative. For structurally complexer materials, such as the recently-put-forward oxide-supported Pd-based intermetallic phases, a bifunctional synergism is usually assumed, where the participating catalytic entities (or the in situ created interface) synergistically act in the catalytic reaction.

This particular Special Issue of Catalysts is, therefore, aimed at providing details and showing promising state-of-the-art research on latest developments in unraveling the mechanisms of the steam reforming reaction on a variety of different catalytic material classes, including oxides, metal-oxide systems and intermetallic compounds.

Dr. Simon Penner
Guest Editor

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Keywords

  • methanol steam reforming
  • hydrocarbon steam reforming
  • water activation
  • CO2 selectivity
  • intermetallic compounds
  • oxides
  • bifunctional synergism
  • metal-oxide interface
  • mechanism
  • hydrogen production

Published Papers (11 papers)

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Editorial

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Open AccessEditorial Reforming Catalysts
Catalysts 2017, 7(11), 334; doi:10.3390/catal7110334
Received: 3 November 2017 / Revised: 4 November 2017 / Accepted: 4 November 2017 / Published: 9 November 2017
PDF Full-text (161 KB) | HTML Full-text | XML Full-text
Abstract
Steam and dry reforming of hydrocarbons (e.g., methane, ethane or propane), alcohols (e.g., methanol, ethanol or glycerol) or bio-compounds is one of the most promising and effective routes to enhanced hydrogen production and for the production of synthesis gas likewise.[...] Full article
(This article belongs to the Special Issue Reforming Catalysts)

Research

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Open AccessArticle Promotion of Ca-Co Bifunctional Catalyst/Sorbent with Yttrium for Hydrogen Production in Modified Chemical Looping Steam Methane Reforming Process
Catalysts 2017, 7(9), 270; doi:10.3390/catal7090270
Received: 6 June 2017 / Revised: 4 August 2017 / Accepted: 17 August 2017 / Published: 13 September 2017
Cited by 2 | PDF Full-text (4972 KB) | HTML Full-text | XML Full-text
Abstract
In this study, the application of a calcium-based bifunctional catalyst/sorbent is investigated in modified chemical looping steam methane reforming (CLSMR) process for in situ CO2 sorption and H2 production. The yttrium promoted Ca-Co samples were synthesized and applied as bifunctional catalysts/sorbent.
[...] Read more.
In this study, the application of a calcium-based bifunctional catalyst/sorbent is investigated in modified chemical looping steam methane reforming (CLSMR) process for in situ CO2 sorption and H2 production. The yttrium promoted Ca-Co samples were synthesized and applied as bifunctional catalysts/sorbent. The influence of reduction temperature (500–750 °C), Ca/Co and Ca/Y ratios (1.5–∞ and 3–18, respectively) and catalyst life time are determined in CLSMR process. The physicochemical transformation of fresh, used and regenerated samples after 16 redox cycles are determined using X-ray powder diffraction (XRD), N2 adsorption–desorption, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) techniques. The effect of yttrium promoter on the structure of catalyst and regeneration step on the reversibility of bifunctional catalyst/sorbent was two important factors. The characterization results revealed that the presence of yttrium in the structure of Ca-9Co sample could improve the morphology and textural properties of catalyst/sorbents. The suitable reversibility of bifunctional catalyst/sorbents during the repeated cycles is confirmed by characterization of calcined samples. The Ca-9Co-4.5Y as optimal catalyst illustrated superior performance and stability. It showed about 95.8% methane conversion and 82.9% hydrogen yield at 700 °C and stable activity during 16 redox cycles. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle Improved H2 Production by Ethanol Steam Reforming over Sc2O3-Doped Co-ZnO Catalysts
Catalysts 2017, 7(8), 241; doi:10.3390/catal7080241
Received: 2 July 2017 / Revised: 15 August 2017 / Accepted: 16 August 2017 / Published: 18 August 2017
Cited by 1 | PDF Full-text (2518 KB) | HTML Full-text | XML Full-text
Abstract
H2 production by catalytically ethanol steam reforming (ESR) is an effective and prospective method for the application of fuel cells. However, the catalysts’ desirable activity and stability remains an unprecedented challenge. Herein, a type of Sc2O3-doped Co-ZnO catalyst
[...] Read more.
H2 production by catalytically ethanol steam reforming (ESR) is an effective and prospective method for the application of fuel cells. However, the catalysts’ desirable activity and stability remains an unprecedented challenge. Herein, a type of Sc2O3-doped Co-ZnO catalyst was developed by a co-precipitation method. The so-constructed Co2Zn1Sc0.3 catalyst exhibited a superb catalytic performance compared with Co-ZnO, giving a STY(H2) as high as 1.099 mol·h−1·g-cat−1 (data taken 100 h after the reaction started). In comparison, the pristine Co-ZnO catalyst only afforded a STY(H2) of 0.684 mol·h−1·g-cat−1 under identical reaction conditions. Characterization results revealed that the Sc2O3 dopant strengthened the electronic interaction between Co species and ZnO, which was in favour of elevating the reduction temperature of Co oxides and boosting the dispersion of the Con+ (n = 1 or 2). The introduction of Sc2O3 induced the formation of O2− and OH. All of these effects effectively inhibited the sintering of active Co species and markedly improved the activity and operating stability of the catalyst. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle Steam Reforming of Bio-Compounds with Auto-Reduced Nickel Catalyst
Catalysts 2017, 7(4), 114; doi:10.3390/catal7040114
Received: 15 February 2017 / Revised: 31 March 2017 / Accepted: 31 March 2017 / Published: 13 April 2017
Cited by 1 | PDF Full-text (5611 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
As an extension of chemical looping combustion, chemical looping steam reforming (CLSR) has been developed for H2 production. During CLSR, a steam reforming (SR) process occurs following the reduction of catalysts by the reforming feedstock itself (termed “auto-reduction”), as opposed to a separate,
[...] Read more.
As an extension of chemical looping combustion, chemical looping steam reforming (CLSR) has been developed for H2 production. During CLSR, a steam reforming (SR) process occurs following the reduction of catalysts by the reforming feedstock itself (termed “auto-reduction”), as opposed to a separate, dedicated reducing agent like H2. This paper studied SR performances of four common bio-compounds (ethanol, acetone, furfural, and glucose) with a nickel catalyst that had undergone auto-reduction. A packed bed reactor was used to carry out the experiment of auto-reduction and subsequent SR. The effects of temperature and steam to carbon ratio (S/C) on the carbon conversions of the bio-compounds to gases and yields of gaseous products were investigated. The carbon deposition on spent catalysts was characterized by CHN elemental analysis and Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX). The SR performance with the auto-reduced catalyst was close to that with the H2-reduced catalyst. In general, an increase in temperature or S/C would lead to an increase in H2 yields. The dependence of SR performance on temperature or S/C was specific to the type of bio-compounds. Accordingly, the main bottlenecks for SR of each bio-compound were summarized. A large amount of CH4 existed in the reforming product of ethanol. Severe carbon deposition was observed for SR of acetone at temperatures below 650 °C. A high thermal stability of furfural molecules or its derivatives restricted the SR of furfural. For SR of glucose, the main problem was the severe agglomeration of catalyst particles due to glucose coking. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle Production of Renewable Hydrogen from Glycerol Steam Reforming over Bimetallic Ni-(Cu,Co,Cr) Catalysts Supported on SBA-15 Silica
Catalysts 2017, 7(2), 55; doi:10.3390/catal7020055
Received: 11 December 2016 / Revised: 23 January 2017 / Accepted: 6 February 2017 / Published: 10 February 2017
Cited by 4 | PDF Full-text (4439 KB) | HTML Full-text | XML Full-text
Abstract
Glycerol steam reforming (GSR) is a promising alternative to obtain renewable hydrogen and help the economics of the biodiesel industry. Nickel-based catalysts are typically used in reforming reactions. However, the choice of the catalyst greatly influences the process, so the development of bimetallic
[...] Read more.
Glycerol steam reforming (GSR) is a promising alternative to obtain renewable hydrogen and help the economics of the biodiesel industry. Nickel-based catalysts are typically used in reforming reactions. However, the choice of the catalyst greatly influences the process, so the development of bimetallic catalysts is a research topic of relevant interest. In this work, the effect of adding Cu, Co, and Cr to the formulation of Ni/SBA-15 catalysts for hydrogen production by GSR has been studied, looking for an enhancement of its catalytic performance. Bimetallic Ni-M/SBA-15 (M: Co, Cu, Cr) samples were prepared by incipient wetness co-impregnation to reach 15 wt % of Ni and 4 wt % of the second metal. Catalysts were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), N2-physisorption, X-ray powder diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermogravimetric analyses (TGA), and tested in GSR at 600 °C and atmospheric pressure. The addition of Cu, Co, and Cr to the Ni/SBA-15 catalyst helped to form smaller crystallites of the Ni phase, this effect being more pronounced in the case of the Ni-Cr/SBA-15 sample. This catalyst also showed a reduction profile shifted towards higher temperatures, indicating stronger metal-support interaction. As a consequence, the Ni-Cr/SBA-15 catalyst exhibited the best performance in GSR in terms of glycerol conversion and hydrogen production. Additionally, Ni-Cr/SBA-15 achieved a drastic reduction in coke formation compared to the Ni/SBA-15 material. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle A Comparative Discussion of the Catalytic Activity and CO2-Selectivity of Cu-Zr and Pd-Zr (Intermetallic) Compounds in Methanol Steam Reforming
Catalysts 2017, 7(2), 53; doi:10.3390/catal7020053
Received: 10 January 2017 / Accepted: 7 February 2017 / Published: 9 February 2017
Cited by 4 | PDF Full-text (6052 KB) | HTML Full-text | XML Full-text
Abstract
The activation and catalytic performance of two representative Zr-containing intermetallic systems, namely Cu-Zr and Pd-Zr, have been comparatively studied operando using methanol steam reforming (MSR) as test reaction. Using an inverse surface science and bulk model catalyst approach, we monitored the transition of
[...] Read more.
The activation and catalytic performance of two representative Zr-containing intermetallic systems, namely Cu-Zr and Pd-Zr, have been comparatively studied operando using methanol steam reforming (MSR) as test reaction. Using an inverse surface science and bulk model catalyst approach, we monitored the transition of the initial metal/intermetallic compound structures into the eventual active and CO2-selective states upon contact to the methanol steam reforming mixture. For Cu-Zr, selected nominal stoichiometries ranging from Cu:Zr = 9:2 over 2:1 to 1:2 have been prepared by mixing the respective amounts of metallic Cu and Zr to yield different Cu-Zr bulk phases as initial catalyst structures. In addition, the methanol steam reforming performance of two Pd-Zr systems, that is, a bulk system with a nominal Pd:Zr = 2:1 stoichiometry and an inverse model system consisting of CVD-grown ZrOxHy layers on a polycrystalline Pd foil, has been comparatively assessed. While the CO2-selectivity and the overall catalytic performance of the Cu-Zr system is promising due to operando formation of a catalytically beneficial Cu-ZrO2 interface, the case for Pd-Zr is different. For both Pd-Zr systems, the low-temperature coking tendency, the high water-activation temperature and the CO2-selectivity spoiling inverse WGS reaction limit the use of the Pd-Zr systems for selective MSR applications, although alloying of Pd with Zr opens water activation channels to increase the CO2 selectivity. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle Response Surface Methodology and Aspen Plus Integration for the Simulation of the Catalytic Steam Reforming of Ethanol
Catalysts 2017, 7(1), 15; doi:10.3390/catal7010015
Received: 20 November 2016 / Revised: 27 December 2016 / Accepted: 27 December 2016 / Published: 14 January 2017
Cited by 3 | PDF Full-text (3947 KB) | HTML Full-text | XML Full-text
Abstract
The steam reforming of ethanol (SRE) on a bimetallic RhPt/CeO2 catalyst was evaluated by the integration of Response Surface Methodology (RSM) and Aspen Plus (version 9.0, Aspen Tech, Burlington, MA, USA, 2016). First, the effect of the Rh–Pt weight ratio (1:0, 3:1,
[...] Read more.
The steam reforming of ethanol (SRE) on a bimetallic RhPt/CeO2 catalyst was evaluated by the integration of Response Surface Methodology (RSM) and Aspen Plus (version 9.0, Aspen Tech, Burlington, MA, USA, 2016). First, the effect of the Rh–Pt weight ratio (1:0, 3:1, 1:1, 1:3, and 0:1) on the performance of SRE on RhPt/CeO2 was assessed between 400 to 700 °C with a stoichiometric steam/ethanol molar ratio of 3. RSM enabled modeling of the system and identification of a maximum of 4.2 mol H2/mol EtOH (700 °C) with the Rh0.4Pt0.4/CeO2 catalyst. The mathematical models were integrated into Aspen Plus through Excel in order to simulate a process involving SRE, H2 purification, and electricity production in a fuel cell (FC). An energy sensitivity analysis of the process was performed in Aspen Plus, and the information obtained was used to generate new response surfaces. The response surfaces demonstrated that an increase in H2 production requires more energy consumption in the steam reforming of ethanol. However, increasing H2 production rebounds in more energy production in the fuel cell, which increases the overall efficiency of the system. The minimum H2 yield needed to make the system energetically sustainable was identified as 1.2 mol H2/mol EtOH. According to the results of the integration of RSM models into Aspen Plus, the system using Rh0.4Pt0.4/CeO2 can produce a maximum net energy of 742 kJ/mol H2, of which 40% could be converted into electricity in the FC (297 kJ/mol H2 produced). The remaining energy can be recovered as heat. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle Hydrogen Generation from Catalytic Steam Reforming of Acetic Acid by Ni/Attapulgite Catalysts
Catalysts 2016, 6(11), 172; doi:10.3390/catal6110172
Received: 26 September 2016 / Revised: 24 October 2016 / Accepted: 31 October 2016 / Published: 4 November 2016
Cited by 6 | PDF Full-text (3363 KB) | HTML Full-text | XML Full-text
Abstract
In this research, catalytic steam reforming of acetic acid derived from the aqueous portion of bio-oil for hydrogen production was investigated using different Ni/ATC (Attapulgite Clay) catalysts prepared by precipitation, impregnation and mechanical blending methods. The fresh and reduced catalysts were characterized by
[...] Read more.
In this research, catalytic steam reforming of acetic acid derived from the aqueous portion of bio-oil for hydrogen production was investigated using different Ni/ATC (Attapulgite Clay) catalysts prepared by precipitation, impregnation and mechanical blending methods. The fresh and reduced catalysts were characterized by XRD, N2 adsorption–desorption, TEM and temperature program reduction (H2-TPR). The comprehensive results demonstrated that the interaction between active metallic Ni and ATC carrier was significantly improved in Ni/ATC catalyst prepared by precipitation method, from which the mean of Ni particle size was the smallest (~13 nm), resulting in the highest metal dispersion (7.5%). The catalytic performance of the catalysts was evaluated by the process of steam reforming of acetic acid in a fixed-bed reactor under atmospheric pressure at two different temperatures: 550 °C and 650 °C. The test results showed the Ni/ATC prepared by way of precipitation method (PM-Ni/ATC) achieved the highest H2 yield of ~82% and a little lower acetic acid conversion efficiency of ~85% than that of Ni/ATC prepared by way of impregnation method (IM-Ni/ATC) (~95%). In addition, the deactivation catalysts after reaction for 4 h were analyzed by XRD, TGA-DTG and TEM, which demonstrated the catalyst deactivation was not caused by the amount of carbon deposition, but owed to the significant agglomeration and sintering of Ni particles in the carrier. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessArticle Anodized Aluminum Oxide Supported NiO-CeO2 Catalyst for Dry Reforming of Propane
Catalysts 2016, 6(10), 154; doi:10.3390/catal6100154
Received: 29 July 2016 / Revised: 15 September 2016 / Accepted: 26 September 2016 / Published: 29 September 2016
Cited by 3 | PDF Full-text (11169 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Nano-porous anodic aluminum oxide (AAO) supported Ni-Ce mixed metal oxide catalysts were prepared and tested for dry reforming of propane to produce synthesis gas. The presence of Ce efficiently suppressed the nickel particle sintering and improved the reducibility of nickel oxide supported on
[...] Read more.
Nano-porous anodic aluminum oxide (AAO) supported Ni-Ce mixed metal oxide catalysts were prepared and tested for dry reforming of propane to produce synthesis gas. The presence of Ce efficiently suppressed the nickel particle sintering and improved the reducibility of nickel oxide supported on the AAO. The prepared NiO-CeO2/AAO catalyst was highly efficient for the dry reforming of propane (DRP) with CO2 over a temperature range of 480–580 °C. The catalyst achieved the best reforming performance of 90%–97%, and a H2/CO ratio close to 1.37 at 580 °C. The AAO supported NiO-CeO2 catalyst can be a promising catalytic system for DRP. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Review

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Open AccessReview Development of Ni-Based Catalysts Derived from Hydrotalcite-Like Compounds Precursors for Synthesis Gas Production via Methane or Ethanol Reforming
Catalysts 2017, 7(2), 70; doi:10.3390/catal7020070
Received: 13 December 2016 / Revised: 6 February 2017 / Accepted: 16 February 2017 / Published: 20 February 2017
Cited by 6 | PDF Full-text (1083 KB) | HTML Full-text | XML Full-text
Abstract
As a favorably clean fuel, syngas (synthesis gas) production has been the focus of concern in past decades. Substantial literatures reported the syngas production by various catalytic reforming reactions particularly in methane or ethanol reforming. Among the developed catalysts in these reforming processes,
[...] Read more.
As a favorably clean fuel, syngas (synthesis gas) production has been the focus of concern in past decades. Substantial literatures reported the syngas production by various catalytic reforming reactions particularly in methane or ethanol reforming. Among the developed catalysts in these reforming processes, Ni-based catalysts from hydrotalcite-like compounds (HTLcs) precursors have drawn considerable attention for their preferable structural traits. This review covers the recent literature reporting syngas production with Ni-based catalysts from HTLc precursors via methane or ethanol reforming. The discussion was initiated with catalyst preparation (including conventional and novel means), followed by subsequent thermal treatment processes, then composition design and the addition of promoters in these catalysts. As Ni-based catalysts have thermodynamic potential to deactivate because of carbon deposition or metal sintering, measures for dealing with these problems were finally summarized. To obtain optimal catalytic performances and resultantly better syngas production, based on analyzing the achievements of the references, some perspectives were finally proposed. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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Open AccessReview A Short Review on the Catalytic Activity of Hydrotalcite-Derived Materials for Dry Reforming of Methane
Catalysts 2017, 7(1), 32; doi:10.3390/catal7010032
Received: 29 October 2016 / Revised: 24 December 2016 / Accepted: 12 January 2017 / Published: 18 January 2017
Cited by 6 | PDF Full-text (2017 KB) | HTML Full-text | XML Full-text
Abstract
Nickel-containing hydrotalcite-derived materials have been recently proposed as promising materials for methane dry reforming (DRM). Based on a literature review and on the experience of the authors, this review focuses on presenting past and recent achievements on increasing activity and stability of hydrotalcite-based
[...] Read more.
Nickel-containing hydrotalcite-derived materials have been recently proposed as promising materials for methane dry reforming (DRM). Based on a literature review and on the experience of the authors, this review focuses on presenting past and recent achievements on increasing activity and stability of hydrotalcite-based materials for DRM. The use of different NiMgAl and NiAl hydrotalcite (HT) precursors, various methods for nickel introduction into HT structure, calcination conditions and promoters are discussed. HT-derived materials containing nickel generally exhibit high activity in DRM; however, the problem of preventing catalyst deactivation by coking, especially below 700 °C, is still an open question. The proposed solutions in the literature include: catalyst regeneration either in oxygen atmosphere or via hydrogasification; or application of various promoters, such as Zr, Ce or La, which was proven to enhance catalytic stability. Full article
(This article belongs to the Special Issue Reforming Catalysts)
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