Catalysts For Steam Reforming Of Ethanol Research Articles

Cu-promoted Ni-LaCeOx/SBA-15 catalysts for ethanol steam reforming

Hydrogen is a globally recognized high-energy, clean, and ecofriendly fuel that is currently produced by means of electrocatalysis, biomass conversion, coal gasification, and thermal decomposition of hydrocarbons, with the steam reforming showing high potential. The present work is focused on Cu-promoted SBA-15-supported Ni-LaCeOx catalysts for ethanol steam reforming (ESR). The catalysts were prepared by incipient wetness impregnation and characterized by XRF, N2 adsorption-desorption, IR spectroscopy, SAXS, XRD, H2-TPR, Raman, and STA methods. The support features caused by the distribution of LaCeOx NPs and Cu promoter in proper ratios affect the conditions of formation of active dispersed Ni species to determine the catalyst performance and its reducibility. At 800 оС, the NiСu-LaCeOx/SBA-15 (1:1) catalyst demonstrates a 100 % ethanol conversion and 55 % hydrogen yield. Thus, the role of the Cu-containing promoter comprises both a significant decrease of carbon deposits on the catalyst surface and redirecting of the intermediate interactions towards the formation of the desired gaseous products.

Effect of active sites distributions on temperature dependent–coke formation over Ni/CexZr1−xO2–Al2O3 catalysts for ethanol steam reforming: Coke precursor gasification

Understanding coke formation routes over Ni-based catalysts is essential in determining the catalytic performance in ethanol steam reforming. In this study, we focused on optimizing the active sites distribution via the metal-support interactions and understanding the coke precursor gasification in Ni/CexZr1-xO2–Al2O3 (CZA) catalysts for ethanol steam reforming. We found that the optimized active sites distribution could minimize coke formation by enabling efficient gasification of a coke precursor on Ni. In the 20Ni/40CZA catalyst, the crystalline CZ exhibited a strong interaction with Ni, maintaining a uniform distribution of highly dispersed Ni nanoparticles and creating abundant oxygen vacancies on CZ, even at 20 wt% of Ni loading. Consequently, the resistance to coking over 20Ni/40CZA was significantly enhanced due to the efficient delivery of active oxygen atoms from steam on the abundant oxygen vacancies to the coke precursor on the Ni surface, resulting in fast gasification of the coke precursor.

Insight into CeO2 and Ni collaboration in ethanol steam reforming: Enhanced activity and stability of CeO2 modified Ni/MgAl2O4

This work focused on optimizing the synergistic effect between CeO2 and Ni in CeO2 modified Ni/MgAl2O4. Six catalysts for ethanol steam reforming (ESR), including NiCeMgAl, CeO2/NiMgAl, Ni/CeMgAl, Ni-CeO2/MgAl2O4, Ni/CeO2/MgAl2O4 and CeO2/Ni/MgAl2O4, were synthesized by sol–gel and/or impregnation methods, which controlled the introduction order of Ce(NO3)3. Ni/CeMgAl showed a satisfactory stability with 90.6 % of ethanol conversion after 100 h test, 66.9 % of H2 concentration in product, and an excellent anti-coking ability with 0.72 mgc/(gcat·h). The optimal catalytic performance of Ni/CeMgAl benefits from the unique distribution of components, which provides adequate Ni0 active sites for C-C bonds scission, maintains a stable particle size of metallic Ni, and suppresses the side reactions and carbonization of intermediates on CeO2 sites. This work illuminates the important of coordinating the ability of Ni and CeO2 for ESR and presents a new insight into the design of low-cost and high-performance catalysts in practical applications.

Metal–support interactions over Ni/CeO2–ZrO2 catalysts for ethanol steam reforming and their effects on the coke gasification

In this study, we investigated the metal–support interactions over Ni/CeO2–ZrO2 (Ni/CZ) catalysts for ethanol steam reforming. Different Ni contents (5, 10, and 15 wt%) were loaded onto the CZ support using two catalyst preparation methods, namely one-pot, and successive impregnation methods. Using the one-pot method, the Ni species over the Ni/CZ catalysts strongly interacted with the CZ support, resulting in smaller Ni nanoparticles with abundant oxygen vacancies. In contrast, the successive impregnation method mainly generated an isolated Ni phase at a high Ni content, resulting in large Ni clusters with limited oxygen vacancies. The poor Ni dispersion over the Ni/CZ catalysts prepared by the successive impregnation method induced low ethanol conversions and hydrogen production rates. In addition, the large Ni clusters over the Ni/CZ catalysts prepared by the successive impregnation method achieved a fast-coking behavior, thereby increasing the coke amount. Further, coke gasification was demonstrated to dominate the Ni surface with the Ni/CZ catalysts prepared by the one-pot method because of the high Ni dispersion and abundant oxygen vacancies.

Adjustment of the ZSM-5 zeolite support towards the efficient hydrogen production by ethanol steam reforming on cobalt catalysts

The world is on track for replacing fossil fuels with alternative energy carriers. In the face of the ongoing global energy transformation, the focus is on hydrogen. Its production in the ethanol steam reforming (ESR) process with the use of a substrate from bio-sources deserves special attention. The ESR process requires a catalyst, which should be selective and resistant to the deactivation processes. We have taken a challenge to develop the cobalt catalyst based on the ZSM-5 zeolite support. We synthesized a series of catalysts based on zeolite with increasing Si/Al ratios (32, 750, ∞ that is Al-free zeolite) and different zeolite morphology. The substantial difference in their performance we discussed based on the multifaceted physicochemical characterization and unique operando UV–Vis and FT-IR spectroscopy studies in the ESR conditions. We have checked the effect of potassium introduction to the Co|ZSM-5 catalyst. The increase in ethanol conversion and decrease in selectivity to undesired C2H4 product with the decrease of the Al content, and further competitive activity and stability of the Al-free catalyst we discussed in terms of the zeolite acidity and its impact on the cobalt phase oxidation state. The advantage of nanometric zeolite over the micrometric one, we attributed to much better dispersion of cobalt active phase over its surface. Thus, the adjustment of zeolite support properties allows us to get the extraordinary ESR catalyst. Our results overthrow the existing paradigm of low activity and stability of zeolite-based ESR catalysts, opening the way to the development of competitive catalysts that give real hope for implementation.

Ethanol steam reforming over attapulgite-based MCM-41 supported Ni-Ce-Zr catalyst for hydrogen production

Ethanol steam reforming (ESR) was considered as a promising technology that could realize high-efficiency hydrogen production from biomass resources. In this work, it utilized attapulgite (ATP) as silicon source to synthesize ATP-based MCM-41 (AM) and then manufactured AM-supported Ni/Ce/Zr catalysts (named as NixCeyZr/AM-T) by sol–gel assisted impregnation method. Meanwhile, the effects of Ce/Zr additives and calcination temperature on the structure of as-prepared catalysts were also studied. Various characterizations illustrated that the AM promoted the uniform distribution of metal oxides due to its adequate surface area and physical confinement effect that originated from ordered hexagonal mesoporous (OHM) structure. Additionally, the characterization results demonstrated that appropriate Ce-Zr simultaneous addition (2.5 wt%) and calcination temperature optimized the electronic interaction among Ni/Ce/Zr components. Amongst, the Ni2.5Ce2.5Zr/AM-600 catalyst presented the highest concentration of metallic Ni, OV and strong basic sites, attributed to the synergistic effect between physical confinement effect and optimal electronic interaction among Ni/Ce/Zr components. Therefore, the Ni2.5Ce2.5Zr/AM-600 exhibited the highest conversion of ethanol to gas product (95.0%), H2 yield (64.6%) and outstanding stability in ESR process. Furthermore, XRD, HRTEM and TG analyses confirmed that Ni2.5Ce2.5Zr/AM-600 also presented superior resistance to sintering, oxidation and carbon deposit. This paper provided a new opportunity to prepare efficient and low-cost AM-supported Ni/Ce/Zr catalysts for ESR.

Effect of Sr Substitution on the Novel La1-xSrxCo0.5Ni0.5O3-δ Perovskite-Type Catalysts for Hydrogen Production in Ethanol Steam Reforming

La1-xSrxCo0.5Ni0.5O3-δ perovskites with different substitution of La by Sr have been firstly synthesized and applied as catalysts for ethanol steam reforming (ESR). The effect of partial Sr substitution on the performance and stability of La1-xSrxCo0.5Ni0.5O3-δ for ESR was investigated. The synthesized samples were characterized by XRD, SEM, BET, and EDS techniques. The results show that with the increase of substitution of La by Sr, the pore size and surface area of La1-xSrxCo0.5Ni0.5O3-δ perovskite increase. The doping of Sr causes changes in the specific surface area, pore volume, and pore size of the catalyst, which in turn causes changes in its catalytic activity. Meanwhile, La0.1Sr0.9Co0.5Ni0.5O3-δ with a highest SBET presents the highest ethanol conversion rate among all the samples. The modifications of catalyst characteristics caused by the Sr substitution in La1-xSrxCo0.5Ni0.5O3-δ directly affect its catalytic performance in the ESR. What is more, the influences of operating parameters on the catalytic activity of La0.1Sr0.9Co0.5Ni0.5O3-δ were studied in detail, and the optimum conditions were determined and applied for stability experiments. When the temperature is lower than 500°C, the selectivity of gas products is most likely affected by the dehydrogenation of ethanol and the decomposition of acetaldehyde. Meanwhile, the improving hydrogen selectivity and reducing the formation of by-products can be achieved by increasing the reaction temperature. The best catalytic performance for hydrogen production was achieved with La0.1Sr0.9Co0.5Ni0.5O3-δ which presented the highest ethanol conversion (98.7%) under the optimal reaction conditions. La0.1Sr0.9Co0.5Ni0.5O3-δ perovskites with higher strontium degree of substitution exhibited an excellent activity and stability of the catalysts derived.

Magnesium promoted hydrocalumite derived nickel catalysts for ethanol steam reforming

Hydrocalumite derived nickel (Ni) catalysts with different loading of magnesium (Mg) (7.5/10/15 wt%, as promoters) were for the first time prepared and tested for ethanol steam reforming (ESR) in this work. The catalytic performances of different Mg promoted catalysts were mainly evaluated in the temperature range between 550 and 700 °C as determined by thermodynamic simulation. Experimental results showed that the optimal reaction temperature was 650 °C in terms of the hydrogen yields for these ESR catalysts, especially for 15Ni7.5Mg/HCa which presented a remarkable catalytic performance. Its hydrogen yields reached 90% while ethanol was almost fully converted at 650 °C. Based on the characterization results, it's believed that 15Ni7.5Mg/HCa with a certain amount of Mg loading can get the smallest Ni0 crystallite sizes, better H2 reducibility and suitable basicities on strong basic sites. The catalytic performances of ESR catalysts were mainly related to the Ni0 crystallite size, reducibility and basicity for the prepared hydrocalumites derived Ni catalysts, and 15Ni7.5Mg/HCa could be considered as one of the best catalysts for ESR.

A mini review on recent progress of steam reforming of ethanol.

H2 is one of the promising renewable energy sources, but its production and transportation remain challenging. Distributed H2 production using liquid H2 carriers is one of the ideal ways of H2 utilization. Among common H2 carriers, ethanol is promising as it has high H2 content and can be derived from renewable bio-energy sources such as sucrose, starch compounds, and cellulosic biomass. To generate H2 from ethanol, steam reforming of ethanol (SRE) is the most common way, while appropriate catalysts, usually supported metal catalysts, are indispensable. However, the SRE process is quite complicated and always accompanied by various undesirable by-products, causing low H2 yield. Moreover, the catalysts for SRE are easy to deactivate due to sintering and carbon deposition under high reaction temperatures. In recent years, lots of efforts have been made to reveal SRE mechanisms and synthesize catalysts with high H2 yield and excellent stability. Both active metals and supports play an important role in the reaction. This mini-review summarizes the recent progress of SRE catalysts from the view of the impacts of active metals and supports and draws an outlook for future research directions.

Cooperative role of cobalt and gallium under the ethanol steam reforming on Co/CeGaOx

The performance of gallium promoted cobalt-ceria catalysts for ethanol steam reforming (ESR) was studied using H2O/C2H5OH = 6/1 mol/mol at 500 °C. The catalysts were synthetized via cerium-gallium co-precipitation and wetness impregnation of cobalt. A detailed characterization by N2-physisorption, XRD, H2-TPR and TEM allowed the normalization of contact time and rationalization of the role of each catalysts component for ESR. The gallium promoted catalyst, Co/Ce90Ga10Ox, was more efficient for the ethanol conversion to H2 and CO2, and the production of oxygenated by-products (such as, acetaldehyde and acetone) than Co/CeO2. The catalytic performance is explained assuming that: (i) bare ceria is able to dehydrogenate ethanol to ethylene; (ii) Ce–O–Ga interface catalyzes ethanol reforming; (iii) both Ce–O–Co and Ce–O–Ga interfaces takes part in acetone production; and (iv) cobalt sites further allow C–C scission. It is suggested that a cooperative role between Co and Ce–O–Ga sites enhance the H2 and CO2 yields under ESR conditions.

β-Si4Al2O2N6 supported Ni catalyst for enhanced ethanol steam reforming: Tuning metal-support interaction by high-temperature solution of Si3N4 with Al2O3

Developing a high-performance Ni-based catalyst for ethanol steam reforming (ESR) reaction is desirable for sustainable hydrogen production. In this work, β-Si4Al2O2N6, the high-temperature solid solution of Si3N4 and Al2O3, was utilized as support to fabricate Ni catalyst (Ni/Si4Al2O2N6) for ESR reaction to enhance hydrogen-production efficiency. The catalytic experiments demonstrated that Ni/Si4Al2O2N6 catalyst exhibited higher C–C bond cleavage capacity, hydrogen-production efficiency, catalytic durability and better anti-coke performance as compared with Ni/Si3N4 and Ni/Al2O3 catalysts. H2-TPR, XPS and NH3-TPD studies revealed that the stronger metal-support interaction (MSI) in Ni/Si4Al2O2N6 catalysts induced more distinct charge transfer from Ni species to Si4Al2O2N6 support, fabricating Ni active sites with higher oxidation state and achieving higher catalytic activity and durability for ESR reaction.

Promoting the Selectivity of Pt/m-ZrO2 Ethanol Steam Reforming Catalysts with K and Rb Dopants.

The ethanol steam reforming reaction (ESR) was investigated on unpromoted and potassium- and rubidium-promoted monoclinic zirconia-supported platinum (Pt/m-ZrO2) catalysts. Evidence from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterization indicates that ethanol dissociates to ethoxy species, which undergo oxidative dehydrogenation to acetate followed by acetate decomposition. The acetate decomposition pathway depends on catalyst composition. The decarboxylation pathway tends to produce higher overall hydrogen selectivity and is the most favored route at high alkali loading (2.55 wt.% K and higher or 4.25 wt.% Rb and higher). On the other hand, decarbonylation is a significant route for the undoped catalyst or when a low alkali loading (e.g., 0.85% K or 0.93% Rb) is used, thus lowering the overall H2 selectivity of the process. Results of in situ DRIFTS and the temperature-programmed reaction of ESR show that alkali doping promotes forward acetate decomposition while exposed metallic sites tend to facilitate decarbonylation. In previous work, 1.8 wt.% Na was found to hinder decarbonylation completely. Due to the fact that 1.8 wt.% Na is atomically equivalent to 3.1 wt.% K and 6.7 wt.% Rb, the results show that less K (2.55% K) or Rb (4.25% Rb) is needed to suppress decarbonylation; that is, more basic cations are more efficient promoters for improving the overall hydrogen selectivity of the ESR process.

Nickel catalysts promoted with lanthanum for ethanol steam reforming: Influence of support and treatment on activity

The effect of support nature on the catalytic performance of Ni-based catalysts for ethanol steam reforming (ESR) was investigated. Nickel catalysts supported on lanthanum-modified Al2O3, TiO2, Al2O3-TiO2 and Al-pillared bentonite (denoted as Clay) were prepared by impregnation, characterized by X-ray diffraction (XRD), N2 adsoption-desorption, IR spectroscopy of acetonitrile adsorption and thermogravimetric analysis (TGA), and evaluated at 500 °C under atmospheric pressure. Both Ni/La-Al2O3 and Ni/La-TiO2-Al2O3 exhibited the best stability, whereas Ni/La-TiO2 and Ni/La-Clay deactivated quickly but with similar or higher H2 production. Catalyst deactivation was caused by carbon deposition, which formation was related to strong Brønsted sites. Efficiency of lanthanum as inhibitor of carbon deposition depended on the support nature.Oxidative regeneration allowed recovering initial activity of all used catalysts and even improving the performance of the latter two catalysts. This unexpected improvement can be due to change of nickel centres nature, caused by local overheating during the deposited carbon combustion.

Enhancement of Ni Catalyst Using CeO2–Al2O3 Support Prepared with Magnetic Inducement for ESR

The effect of magnetic inducement in support preparation was studied to reduce coke and improve the activity of Ni catalysts for ethanol steam reforming (ESR) at 550–650 °C. Magnetic inducement was introduced to prepare 5 mol % CeO2 in Al2O3 support in order to control the composition and the distribution of Ce in Al2O3. The results show that using CeO2–Al2O3 support with magnetic inducement affects both hydrogen production and coke reduction, where Ni/CeO2–Al2O3 support prepared under magnetic inducement with N–N pole arrangement (Ni/CeO2–Al2O3 (N–N)) exhibited the highest hydrogen production and the lowest coke formation among the catalysts used in this work. Compared with Ni/CeO2–Al2O3 (no magnet), Ni/CeO2–Al2O3 (N–N) catalysts yield 14.0% higher H2 production and 31.7% less coke production. The modified catalyst preparation process used in this study could create catalysts for hydrogen production from ESR which are high in performance and stability but low in preparation cost.

A multifunctional core–shell nanoreactor with unique features of sintering resistance for high-performance ethanol steam reforming reaction

Ethanol steam reforming (ESR) has drawn great attention for sustainable H2 production. Design active and sinter resistant nanocatalysts are critical issues for ESR reaction. Herein, a core–shell structured Pt-Cu@Ni-SiO2 nanocomposite for ESR reaction has been synthesized via a one-pot facile encapsulation strategy, which is featured by highly active and sintering resistance for ESR reaction. Structural and morphological characterizations revealed that each Pt-Cu@Ni-SiO2 nanocomposite contained a 3 nm Pt-Cu core and multiple Ni nanoparticles with diameters of around 3 nm anchored on the SiO2 shell. The Pt-Cu@Ni-SiO2 nanoreactor exhibited higher ethanol conversion (99.99%) and H2 selectivity (70.32%) and an excellent stability with no loss of activity after 50 h of reaction at 450 °C. The advantages were originated from the ultra-small size of metal nanoparticles and the unique core–shell structure provides a great opportunity to give full play to the catalytic activity of active sites thus guaranteed excellent catalytic activity. Compared with the supported Pt-Cu@Ni-SiO2 catalyst, the Pt-Cu@Ni-SiO2 nanoreactor exhibit good stability and sintering resistance due to the encapsulation of the metal nanoparticles and the enhanced metal-support interaction. Thus, it is supposed that this type of catalyst opens a new strategy for the design of the ESR catalyst.

Ni-exsolved PrBaMn2-xNixO6-δ–based catalysts for high performance of ethanol steam reforming

PrBaMn2O6-δ (PBMO) and PrBaMn2-xNixO6-δ (PBMNO) with exsolved Ni nanoparticles (1.25 wt.%, Ni-PBMNO) are prepared for the development of high-performance catalysts for ethanol steam reforming (ESR). The activity of Ni-PBMNO increases with temperature and is higher than that of PBMO. At 600 °C, Ni-PBMNO demonstrates an ethanol conversion above 90%, an H2–CO yield about 80%, and a negligible amount of CH4. Both Ni-PBMNO and PBMO remain unchanged structurally in dry and wet N2. The former adsorbs more H2O than the latter by forming hydroxyl groups in the lattice because of its higher concentration of oxygen vacancy caused by Ni exsolution, rendering a coking resistance one to two orders higher than conventional catalysts. In the ESR atmosphere, the PBMNO substrate decomposes increasingly without lowering ESR activity. The co-existence of CO2 and H2O is necessary for the decomposition that formed BaCO3 and MnO.

Insight into the mechanism of ethanol steam reforming on TM/Mo6S8 clusters catalysts: A theoretical investigation

Density functional theory (DFT) calculations were carried out to investigate the reaction mechanism of ethanol steam reforming (ESR) reaction on TM/Mo6S8 (TM = Rh, Ir) clusters. We investigated the reaction mechanism of TM/Mo6S8 catalyzed ESR by studying the cleavage of C–H, C–C, and O–H bonds and the formation of hydrogen, and explored the catalytic activity of TM/Mo6S8 in order to find superior catalyst. Our results indicate that ESR is first decomposed by ethanol and then subjected to water-gas shift (WGS) reaction to produce H2 and CO2. In addition, we found that the formation of CH4 and CO is favored as the products of ethanol decomposition, the O–H bond cleavage of OH* is considered as the key step in ESR. According to our calculations, we found that Ir/Mo6S8 was more favorable for catalyzing ethanol decomposition and Rh/Mo6S8 was beneficial for catalyzing WGS. However, for the whole reaction, Rh/Mo6S8 exhibits better catalytic performance than Ir/Mo6S8 because of low energy barrier of rate-determining step. A comparison of microkinetic modeling, the metals d-band and projected density of state (DOS) show that Rh/Mo6S8 is superior catalyst. This approach provides theoretical insight into the reaction mechanism for suppressing the carbon formation on TM/Mo6S8 (TM = Rh, Ir) and is expected to have a significant implication on general methods of the ESR catalyst design in order to have better activity and stability.

Ethanol steam reforming with a Ni–BaZr0.1Ce0.7 Y0.1Yb0.1O3–δ catalyst

BaZr0.1Ce0.7 Y0.1Yb0.1O3–δ supported Ni catalyst is prepared by sol-gel and precipitation methods and evaluated as a catalyst for ethanol steam reforming. This catalyst demonstrates 100% conversion of ethanol into various amounts of H2, CO, CO2, CH4 depending on reforming temperature in the range between 500 and 750 °C. The yield of H2–CO reaches around 85% at temperatures below 600 °C and decreases to the level of 80% at 650 and 750 °C, and the amount of CH4 in the reformate is below 10% at all these temperatures. Decreasing H2O/ethanol ratio from 5 to 3 does obviously change the yield of H2–CO, and increasing temperature promotes H2 and CO2 and depresses CO formation. The BaZr0.1Ce0.7Y0.1Yb0.1O3–δ in Ni–BaZr0.1Ce0.7Y0.1Yb0.1O3–δ decomposes into BaCO3 and CeO2 based oxide in ethanol steam reforming atmosphere at all the temperatures, and this decomposition starts since 5 h of the reforming at 750 °C. Carbon deposition is observed in Ni–BaZr0.1Ce0.7 Y0.1Yb0.1O3–δ during 24 h reforming tests at 500 and 600 °C, but it is much more resistant to coking than catalysts with precious metals and Ni supported on other types of oxides.

Ni-based catalysts obtained from perovskites oxides for ethanol steam reforming

Perovskites as host structures of cations were used in order to generate in situ active and stable catalysts for ethanol steam reforming. For this purpose, La1-xMgxAl1-yNiyO3 (x = 0.1; y= 0, 0.1, 0.2, 0.3) perovskites were synthetized by the citrate method. Ni segregation is evident for a substitution level higher than 0.2. The segregation of Ni as NiO generated species interacts with different metal-support after the reduction step. The y= 0.1 catalyst presents the highest H2 yield value about 85% during reaction time, with low mean values of CH4 and CO selectivities of 3.4% and 11%, respectively and a low carbon formation. The better performance of y= 0.1 catalyst could be attributed to the minor proportion of segregated phases, thus a controlled expulsion of Ni is successfully reached.

Cobalt nanoparticles mechanically deposited on α‐Al2O3: a competitive catalyst for the production of hydrogen through ethanol steam reforming

AbstractBACKGROUNDCobalt (Co)‐containing materials are promising catalysts for Ethanol Steam Reforming (ESR) allowing renewable hydrogen production. Usually, complex catalysts are used where Co, produced by impregnation or coprecipitation, is supported on oxide or carbon‐based materials. Here Co nanoparticles (CoNPs) mechanically mixed with α‐Al2O3 are prepared and tested for ESR.RESULTSCoNPs mechanically mixed with α‐Al2O3 are very active catalysts in ESR at 773 K, even when retaining amorphous structure for Co. After annealing at 773 K, CoNPs crystallize into a cubic structure. These materials are even more active in ESR at 773 K with hydrogen yields ≈70% and nearly stable performances after 8 h on‐stream. Hydrogen yield is limited by the formation of some CH4, probably as a result of acetaldehyde formation and successive decomposition. Two kinds of Co particles are found in the used but still active catalysts: the former ones interacting with alumina and embedded in graphitic carbon, that are probably the most active components, whereas the latter are ‘isolated’ and partly aggregated CoNPs embedded in carbon nanotubes, which are probably less active in ESR.CONCLUSIONSMechanical mixing of CoNPs with α‐Al2O3 produced active and stable catalysts for ESR. The ‘chemical’ interaction of CoNPs with the support may not be an important factor for ESR catalysts. © 2018 Society of Chemical Industry