Low Ni Loading Research Articles

Promotional effects of Nb2O5 on ceria doped Ni catalysts for selective hydrogenation of 1,3-butadiene to butenes: Combined experimental and DFT approach

Developing low cost, active and selective catalysts that would replace the more deployed noble metals is desirable for hydrogenation of 1,3-butadiene. Herein, we prepared Ni catalysts supported on niobium-cerium oxides and characterization was carried out with TGA, XRD, H2-TPR, H2-TPD, HR-TEM, XPS, FTIR, N2 adsorption–desorption, and EDS mapping. Density functional theory (DFT) computes the reaction energies controlling the 1,3-butadiene hydrogenation. H2-TPR revealed that the inclusion of niobium oxide in the catalysts confer stronger metal support interaction that promotes the surface and bulk reduction of cerium oxide and leads to the improvement in the formation of surface Ce3+ as confirmed from the XPS analysis. 1,3-butadiene conversion was tested between 100 °C-350 °C and the catalysts exhibit high conversion at lower Ni loading. We found that the niobium inclusion directed the selectivity towards near complete butene formation even at higher temperature. The onset of decline in activity was observed at temperatures above 250 °C with the simultaneous formation of propene and propane and the disappearance of butane. Guided by the reaction results and the temperature programmed oxidation analysis (TPO), we proposed the reaction mechanism leading to the deactivation, and this entails butane decomposition to propene and surface carbene, while propane is formed from propene, the surface carbene occasioned in the formation of harmful carbon as evident from TPO results. Carbonaceous species formed on the catalysts were minimized on the niobium containing catalysts.

Construction of multi-porous Ni-based monolithic catalyst by combining wood carbon and SBA-15 for strengthening CO2 methanation

Monolithic catalysts meet the needs of practical application compared with powder catalysts. In this work, we constructed a Ni-based monolithic catalyst (Ni/SAB-15/WWC) by in situ growth of rod-like mesoporous SBA-15 in the microchannels of wood carbon. The small Ni-based nanoparticles (∼5.3 nm) were uniformly dispersed into the mesoporous channels via a post-loading method. The monolithic Ni/SAB-15/WWC catalyst with a multilevel porous structure could provide a laminar gas flow on the surface of Ni active sites, increasing the low-temperature activity and high-temperature durability of CO2 methanation. The Ni/SAB-15/WWC with low Ni loading (∼2%) displayed superior CO2 methanation catalytic performance in terms of low-temperature activity and CH4 selectivity compared with the powder Ni/SAB-15 with high Ni loading (∼15 %). The combination of wood carbon and mesoporous materials is an innovative strategy for the design monolithic catalysts with low metal loading and excellent catalytic performance.

Hydrogenation of phenol by defective ZSM-5 supporting Ni catalyst to produce cyclohexanol

Cyclohexanol is an essential intermediate in the chemical industry, which can be produced from hydrogenation of phenol. In this work, a defective ZSM-5 zeolite supporting Ni catalyst (Ni/D-ZSM) is prepared by sequenced nitric acid treatment, impregnation, and reduction. In conversion of phenol, the highly dispersed Ni with strong interaction with the defective Si-OH delivers relative higher adsorption and spillover of active hydrogen, thus promoting the hydrogenation of phenol. Moreover, owing to the unique coordination environment of Ni in defective ZSM-5 zeolite with moderate acid properties, the desorption of intermediate cyclohexanol is promoted. The turnover frequency (TOF) calculated based on the yield of cyclohexanol and amount of metal reveals that, the Ni/D-ZSM sample by 48 h acid treatment (Ni/D-ZSM-48) delivers TOF values up to 17.73 × 10-3·s−1. The designed Ni/D-ZSM-48 catalyst with relative low Ni loading of ∼ 5 wt% delivers equivalent (slightly higher) production rates of cyclohexanol with the ever-reported noble-metal samples (Rh, Ru etc.) and significantly higher than the transition-metal based catalysts.

Impact of chelating agents on precursor formation and efficiency of Ni/MgO-Al2O3 catalysts in dry reforming of methane

Using cheap and non-toxic chelating agents during catalyst preparation is considered as an effective tool to control the particle size and to strengthen the metal-support interactions (MSI), while keeping the simplicity of the selected preparation method. The previous properties are useful to improve the catalyst activity, stability, and selectivity in dry reforming of methane (DRM). Therefore, we prepared a series of low Ni loading (2.5 wt%) catalysts supported over MgO-Al2O3 (Mg/Al = 1.3) mixed oxide using the classic wet impregnation method modified with chelating agents (citric acid (CA), tartaric acid (TA) and diethylenetriaminepentaacetic acid (DTPA)) and subsequently evaluated these in DRM. Intensive catalyst characterization (ICP, BET, XRD, XPS, STEM, H2-TPR and O2-TPO) suggested the presence of different structure-activity relationships. Particularly, using chelating agents during catalyst preparation controlled the final particle size range, which in turn played a pivotal role in shaping the strength of the metal support interactions (MSI). These impacts were crucial to improve the activity, stability and to control the formation of coke deposits. Moreover, special focus was put on the catalytic testing of the outperforming sample (Ni(TA)/Mg1.3AlOx) prepared using tartaric acid as chelating agent under severe regimes prone to catalyst deactivation to demonstrate the benefits of the proposed preparation technique.

Synergistic performance of a new bimetallic complex supported on magnetic nanoparticles for Sonogashira and C–N coupling reactions

This paper describes the synthesis of a novel Cu–Ni bimetallic system comprising of magnetic nanoparticles, as the core, and 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (4-ABPT), as a conjugated bridge, between nickel and copper species. With low Cu and Ni loading (0.06 mol% Ni, 0.08 mol% Cu), the resulting Fe3O4@SiO2@4-ABPT/Cu–Ni showed to be a highly efficient catalyst for the Sonogashira and C–N cross-coupling reactions. The developed catalyst was well characterized by FT-IR, XRD, EDX-mapping, FE-SEM, TEM, ICP, VSM, TGA/DTG/DTA, LSV, and XPS techniques. Fe3O4@SiO2@4-ABPT/Cu–Ni nanocatalyst was compatible with a wide range of amines and aryl halides in the Sonogashira and C–N cross-coupling reactions and offered desired coupling products in high to excellent yields under palladium- and solvent-free conditions. Based on the XPS results, the 4-ABPT ligand can adjust electron transfer between Ni and Cu in Fe3O4@SiO2@4-ABPT/Cu–Ni, promoting the formation and stabilization of Cu+ and Ni3+ species. Electronic interactions and the synergistic effect between these metals increased the selectivity and activity of Fe3O4@SiO2@4-ABPT/Cu–Ni catalyst in the Sonogashira and C–N cross-coupling reactions compared with its monometallic counterparts. Additionally, the magnetic properties of Fe3O4@SiO2@4-ABPT/Cu–Ni facilitated its separation from the reaction mixture, promoting its reuse for several times with no significant loss in its catalytic activity or performance.

Green diesel-like hydrocarbon production by H2-free catalytic deoxygenation of oleic acid via Ni/MgO-Al2O3 catalysts: Effect of the metal loading amount

To develop an efficient and feasible catalyst for converting inedible vegetable oil to green biodiesel via a one-step decarboxylation process, a series of Ni-based MgO-Al2O3 catalysts with different active Ni species were fabricated by adjusting the various Ni loading amounts (2.5–20%) and applied to the catalytic deoxygenation of OA to generate green biodiesel. Additionally, the structure-property relationship, deactivation mechanism and regeneration performance were also evaluated via various characterization technologies (XRD, BET, NH3-TPD, H2-TPR, XPS, SEM-EDX, HRTEM, TGA, Raman as well as GC/MS and UV-fluorescence spectra). The experimental results indicated that Ni introduction obviously enhanced the conversion ratio. Ni (10%)/MgO-Al2O3 catalysts exhibited excellent catalytic performance with the highest HCs (95.12%), olefin content (57.37%) and green biodiesel content (75.90%) due to mild Brønsted-rich acidity sites, lower reduction temperature, higher active metallic Ni species content, suitable oxygen vacancy content and favorable texture properties via the decarbonylation reaction pathway. Furthermore, lower Ni loading was beneficial to gasoline and bioaviation fuel generation due to higher Brønsted-rich acidity sites and total acid amount, which boosted C-C scission by cracking reaction, and higher Ni content facilitated biodiesel formation. Additionally, Ni (10%)/MgO-Al2O3 catalysts showed excellent reusability and regeneration due to Ni active species, but these advantages were slightly decreased (HCs: from 95.12% to 61.63%; biodiesel: from 75.90% to 57.52%) due to coke deposition and metal active species leaching and oxidation.

Insights by in-situ studies on the nature of highly-active hydrotalcite-based Ni-Fe catalysts for CO2 methanation

Designing CO2 methanation catalysts that meet industrial requirements is still challenging. We report Ni-Fe hydrotalcite-derived catalysts with a wide range of Ni and Mg loadings showing that an optimised composition with Ni0.4 gives a very high CO2 conversion rate of 0.37 mmol/gcat/s at 300 °C. This catalyst is studied by in-situ APXPS and NEXAFS spectroscopies and compared with the other synthesised samples to obtain new mechanistic insights on methanation catalysts active for low-temperature (300 °C) methanation, which is an industrial requirement. Under methanation conditions, in-situ investigations revealed the presence of metallic Ni sites and low nuclearity Ni-Fe species at xNiL (Ni loading) = 21.2 mol%. These sites are oxidised on the low Ni-loaded catalyst (xNiL= 9.2 mol%). The best CO2 conversion rate and CH4 selectivity are shown at intermediate xNiL (21.2 mol%), in the presence of Mg. These superior performances are related to the high metallic surface area, dispersion, and optimal density of basic sites. The TOFCO2(turnover frequency of CO2 conversion) increases exponentially with the fractional density of basic to metallic sites (XB) from 1.1 s-1 (xNiL= 29.2 mol%) to 9.1 s-1 (xNiL= 7.6 mol%). It follows the opposite trend of the CO2 conversion rate. In-situ DRIFTS data under methanation conditions evidence that the TOFCO2at high XB is related to the presence of a formate route which is not predominant at low XB (high xNiL). A synergistic interplay of basic and metallic sites is present. This contribution provides a rationale for designing industrially competitive CO2 methanation catalysts with high catalytic activity while maintaining low Ni loading.

Ni nanoparticles Entrapped by a Functional Dendrimer as a Highly Efficient and Recyclable Catalyst for Suzuki‐Miyaura Cross‐Coupling Reactions

AbstractNi nanoparticles (NiNPs) were prepared by thermal decomposition of nickel acetylacetonate in the presence of a third generation polypyridylphenylene dendrimer (G3) which acts both as a coordinating ligand due to presence of pyridine groups and as a stabilizing agent due to highly branched architecture. Transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), and X‐ray photoelectron spectroscopy (XPS) were used to extensively evaluate structure and morphology of the synthesized NiNPs@G3. The selected area electron diffraction (SAED) allowed us to conclude about fcc structure of NiNPs while STEM EDS analysis demonstrated a formation of core‐shell NiO@Ni NPs. Further, the catalyst was tested in selected Suzuki‐Miyaura cross‐coupling reactions at mild conditions and demonstrated a high efficiency at low Ni loading with negligible content of Ni0 on the NP surface. The functional hyperbranched dendrimer macromolecule provided an excellent stabilization for NiNPs@G3 while allowing an easy access for reactants to catalytic sites. The high activity of the catalyst in the recycling experiments was maintained by the absence of Ni leaching from the NiNPs@G3.

Highly coke-resistant Ni-La2O2CO3 catalyst with low Ni loading for dry reforming of methane with carbon dioxide

A series of xNi-La2O2CO3 catalysts with Ni loadings of 0.5–5 wt%, composed of Ni components supported on lanthanum oxycarbonate, were constructed via a simple wet impregnation method and systematically investigated for the reaction of dry reforming of methane with carbon dioxide to syngas (DRM). The xNi-La2O2CO3 catalyst with Ni loading lower than 1 wt% was primarily composed of well-defined Ni-La interfaces after reduction. However, xNi-La2O2CO3 with Ni loading of 2–5 wt% mainly possessed isolated Ni nanoparticles and Ni-La interfaces after reduction. The process of coke formation was proposed that carbon deposition was quickly occurring around the isolated active Ni sites, and then gradually evolved into carbon nanotubes encapsulating Ni nanoparticles, which were finally exsolved from the catalyst surface as the reaction proceeded. Interestingly, no coke formation was observed on the Ni-La interfaces after the DRM reaction even for 300 h. Therefore, the creation of catalytically active Ni-La interfaces indeed significantly improved the coke-resistant performance of the catalyst and was responsible for the much higher catalytic durability of 1Ni-La2O2CO3 than 5Ni-La2O2CO3. Moreover, the catalyst model and its activation of CH4 and CO2 in the DRM reaction were tentatively proposed based on the structure-performance relationship. The current study not only guides for potential industrial pathways for the DRM reactions but also provides a simple and effective method for the design of coke-resistant catalysts for other challenging reactions.

Elucidating the promoting role of Mo2C in methane activation using Ni-xMo2C/FAU to catalyze methane steam reforming

We report the synthesis and characterization, reaction kinetics, and deactivation mechanism of a series of catalysts with metallic nickel (Ni) and molybdenum carbide (Mo2C) particles supported on zeolite Y (Ni-Mo2C/FAU) in methane steam reforming (MSR) reaction at 850 °C. Despite a low Ni loading of 2.4 wt%, MSR on Ni-Mo2C/FAU exhibits high activity and stability, yet deactivation of Ni-FAU is significant. Further investigations elucidate that the catalyst deactivation is caused by Ni particle sintering via Ostwald ripening instead of coking, and steam induces hydroxylated Ni surface that accelerates sintering. Moreover, Mo2C boosts the activity and stability of Ni on zeolite Y by enhancing CH4 activation rather than activating H2O. The interplays among Mo2C and Ni particles dynamically balance the carbon formation and consumption rates, and inhibit Ni sintering. This study demonstrates that high MSR activity and stability can be achieved on transition metal carbide – Ni catalysts with systematically tuned compositional, structural, and interfacial factors.

Effects of modifier (Gd, Sc, La) addition on the stability of low Ni content catalyst for dry reforming of model biogas

Biogas consists of a larger part of methane and a smaller part of carbon dioxide. Reforming biogas is highly desirable due to the direct conversion of the two components, yet not possible due to the current state of catalyst development. For such dry reforming of methane-rich gases (CH4/CO2 = 2) we now present catalysts with low Ni loading (2.5 wt%) modified with Gd, Sc, or La. The best catalyst reaches 49% CH4 conversion and 95% CO2 conversion at 750 °C. The La-modification only shows limited influence on coking and protection against catalyst deactivation although this catalyst exposed highest basicity. On the other side, Sc- and especially Gd-modified catalysts exposed stronger metal-support interaction and thus enhanced stabilization of fine Ni particles during the reaction, which is critical to preserve high performance in CH4-rich DRM. This suppressed carbon deposition and the growth of structured carbon as evidenced by STEM images and TPO of spent catalysts. In this way, exceptionally high specific H2 productivity (94 l/(gcat·h)) compared to literature was obtained on Gd-modified catalyst, and, most noteworthy, after extending the time on stream from 8 to 100 h the amount of deposited coke increased only from 3 to 4 wt%.

Structural impact of carbon nanofibers/few-layer-graphene substrate decorated with Ni for CO2 methanation via inductive heating

The structure of catalyst containing Ni nanoparticles (NPs) supported over carbon nanofibers/few layer graphene (CNFs/FLG) was tailored via modification of chemical vapor deposition parameters in view of methanation of CO2 under induction heating mode (IH). High edges-to- graphitic plane ratio in the support achieved due to the specific herringbone morphology of CNFs allowed to get high CO2 conversion of 85 % at relatively low temperature (360 °C) at very low Ni loading of only 10 %. A design of catalyst included also the use of FLG known for high temperature conductivity and by occasion serving as a support to grow CNFs. The performances of certain catalysts are also tested under “standard” Joule heating in order to check the role of the magnetic and conductive carbon support. The morphology, chemical composition and SAR measurements of the catalysts and carbon supports themselves are addressed and their structure-catalytic performances are discussed.

(Invited) Highly Selective Detection of Propanol and Ethanol Gas Sensing Characteristics of SnO2/NiO and SnO2/NiO/Au Hollowspheres Based Chemiresistive Sensors

IntroductionThe enormous market demands for gas sensors to detect and monitor volatile organic compounds (VOCs) and toxic gases in environmental protection, medical treatment and safety requirements of industry and daily life have motivated enormous awareness in the fabrication of high performance gas sensing materials. Generally, VOCs are considered as low boiling point carbon-comprising materials that can evaporate simply at room temperature and contribute in atmospheric photochemical reactions, such as photochemistry smog and ozone formation. Besides, controlling and detection of these VOCs, such as methanol, ethanol, propanol and acetone is significant because they are considered as widespread concerns for common pollutants in indoor/outdoor air quality and for testing alcohol levels of drivers [1]. In comparison to other VOCS, propanol is less toxic, nonetheless its usage for numerous daily applications, for example hand sanitizer, cosmetics, maybe imagined to be polluting the breathing air. Besides, Iso-propanol was presented to behave as an aesthetic and central nervous system sedative, leading in symptoms that can frighten the mental ability of the individual [2].Yet, the fabrication of the anticipated gas sensor with superior sensitivity, low detection limit, and exceptional long-term stability is still a significant research issue. In addition, the high operating temperatures and poor selectivity often limits the application and commercialization of semiconductor metal oxide (SMO) gas sensors. Thus, this work is directed to improve the selective, sensitivity, stability and reduce the operating temperatures of the metal oxides based sensors, by exploiting SnO2 hollowspheres loaded with various NiO nanoparticles contents and SnO2/NiO loaded with various Au nanoparticles contents synthesized using a simple hydrothermal method. Our findings showed improved stability upon loading SnO2 hollowspheres with various NiO contents. Amongst the various NiO contents, the 0.01 wt.% NiO loaded SnO2 demonstrated higher response and sensitivity towards propanol (C3H7OH) in dry air and in the presence of 40 and 60 % RH at an operating temperature of 150 °C. While the as-fabricated SnO2/NiO/Au (2.5 wt.%) based sensor exhibited a response that is more than 2 times higher in comparison to that of SnO2/NiO (0.01wt. %) and lower operating temperature 75 °C towards ethanol (C2H5OH) and C3H7OH. The long-term stability analyses established that both the fabricated SnO2/NiO (0.01 wt.%) and SnO2/NiO/Au (2.5 wt. %) sensors were very stable towards C3H7OH and C2H5OH after a month in the presence of 40% RH. These findings showed that the current sensors can be employed for detecting C3H7OH and C2H5OH in a vastly sensitive and selective way with insignificant interference from ambient humidity.MethodPorous hollowspheres were synthesized according to the following procedure reported in ref. [3]. While the NiO loaded SnO2 hollowspheres were fabricated using the as-prepared hollowspheres as templates. Gold (Au) loaded NiO/SnO2 hollowspheres were prepared using NiO/SnO2 hollowspheres as template. Detailed synthesis preparation can be found in ref. [4].Sensing preparations and testing of the sensors towards various reducing gases (e.g. CO, CH4, and NH3), volatile organic compounds (C2H5OH and C3H7OH), and an oxidizing gas (NO2) in a background of synthetic dry air were performed according to the procedure in ref [3,4].Results and ConclusionsTo investigate the operational temperature influence on the gas sensing characteristics, the sensing layers were analysed at various operating temperatures (75 to 225 °C). The variations in the gas sensing resistance (Ra) of the SnO2 loaded with various NiO contents and SnO2/NiO loaded with various Au contents as a function of operating temperature were presented. The Ra of the all sensing materials decreased with an increase in operating temperature, except that that of low Ni loading (see Fig. 1A). A decrease could be that when the operational temperature increases more electrons from valence band of the sensing layer will jump to conduction band and accordingly more electrons are available for carrying current, resulting in a decrease of Ra [4]. While the increase in Ra values for SnO2/NiO can be justified by the formation of nanoscale p/n junctions between the NiO and SnO2 phases.We further explored the stability of the SnO2/NiO (0.01 wt.%)-and SnO2/NiO (0.01 wt.%)/Au best performing based sensors in terms of repeatability and long-term stability measurements in dry air and in the presence of relative humidity (RH). The fresh sensor in day one and that tested after 30 days displayed a flawless repeatability of eight successive cycles towards 40 ppm C3H7OH (see Fig. 1B). Based on the findings, after 7 to 30 days, only minimal drift on the repeatability performance was witnessed, while the response increased by almost 8%, validating that our sensor is very stable. Same behavior was observed for the SnO2/NiO (0.01 wt.%)/Au(2.5 wt.%) based sensor [4]. Thus, these findings corroborated that the current sensors are very stable when either exposed to dry air or in real conditions after long exposure to C3H7OH and C2H5OH.

(Invited) Highly Selective Detection of Propanol and Ethanol Gas Sensing Characteristics of SnO2/NiO and SnO2/NiO/Au Hollowspheres Based Chemiresistive Sensors

IntroductionThe enormous market demands for gas sensors to detect and monitor volatile organic compounds (VOCs) and toxic gases in environmental protection, medical treatment and safety requirements of industry and daily life have motivated enormous awareness in the fabrication of high performance gas sensing materials. Generally, VOCs are considered as low boiling point carbon-comprising materials that can evaporate simply at room temperature and contribute in atmospheric photochemical reactions, such as photochemistry smog and ozone formation. Besides, controlling and detection of these VOCs, such as methanol, ethanol, propanol and acetone is significant because they are considered as widespread concerns for common pollutants in indoor/outdoor air quality and for testing alcohol levels of drivers [1]. In comparison to other VOCS, propanol is less toxic, nonetheless its usage for numerous daily applications, for example hand sanitizer, cosmetics, may be imagined to be polluting the breathing air. Besides, Iso-propanol was presented to behave as an aesthetic and central nervous system sedative, leading in symptoms that can frighten the mental ability of the individual [2].Yet, the fabrication of the anticipated gas sensor with superior sensitivity, low detection limit, and exceptional long-term stability is still a significant research issue. In addition, the high operating temperatures and poor selectivity often limits the application and commercialization of semiconductor metal oxide (SMO) gas sensors. Thus, this work is directed to improve the selective, sensitivity, stability and to reduce the operating temperatures of the metal oxides based sensors, by exploiting SnO2 hollowspheres loaded with various NiO nanoparticles contents and SnO2/NiO loaded with various Au nanoparticles contents synthesized using a simple hydrothermal method. Our findings showed improved stability upon loading SnO2 hollowspheres with various NiO contents. Amongst the various NiO contents, the 0.01 wt.% NiO loaded SnO2 demonstrated higher response and sensitivity towards propanol (C3H7OH) in dry air and in the presence of 40 and 60 % RH at an operating temperature of 150 °C. While the as-fabricated SnO2/NiO/Au (2.5 wt.%) based sensor exhibited a response that is more than 2 times higher in comparison to that of SnO2/NiO (0.01wt. %) and lower operating temperature 75 °C towards ethanol (C2H5OH) and C3H7OH. The long-term stability analyses established that both the fabricated SnO2/NiO (0.01 wt.%) and SnO2/NiO/Au (2.5 wt. %) sensors were very stable towards C3H7OH and C2H5OH after a month in the presence of 40% RH. These findings showed that the current sensors can be employed for detecting C3H7OH and C2H5OH in a vastly sensitive and selective way with insignificant interference from ambient humidity.MethodPorous hollowspheres were synthesized according to the following procedure reported in ref. [3]. While the NiO loaded SnO2 hollowspheres were fabricated using the as-prepared hollowspheres as templates. Gold (Au) loaded NiO/SnO2 hollowspheres were prepared using NiO/SnO2 hollowspheres as template as reported elsewhere.The gas sensing properties of the Au-loaded SnO2/NiO were measured using the KSGAS6S gas testing system (KENOSISTEC, Italy). Sensing preparations and testing were performed according to the procedure in ref [3, 4].Results and ConclusionsTo investigate the operational temperature influence on the gas sensing characteristics, the sensing layers were analysed at various operating temperatures (75 to 225 °C). The variations in the gas sensing resistance (Ra) of SnO2/NiO loaded with various NiO contents and SnO2/NiO loaded with various Au contents as a function of operating temperature. The Ra of the all sensing materials decreased with an increase in operating temperature, except that that of low Ni loading. A decrease could be when the operational temperature increases more electrons from valence band of the sensing layer will jump to conduction band and accordingly more electrons are available for carrying current, resulting in a decrease of Ra and this is accordance with the previous studies. While the increase in Ra values for SnO2/NiO can be justified by the formation of nanoscale p/n junctions between the NiO and SnO2 phases.We further explored the stability of the SnO2/NiO (0.01 wt.%)-and SnO2/NiO (0.01 wt.%)/Au best performing based sensors in terms of repeatability and long-term stability measurements in dry air and in the presence of relative humidity (RH). The results exhibited the repeatability behavior of the SnO2/NiO (0.01 wt.%)-based sensor for eight successive cycles at 40 ppm C3H7OH for a month in the presence of 40% RH. The fresh sensor in day one and that tested after 30 days displayed a flawless repeatability of eight successive cycles towards 40 ppm C3H7OH. After 7 to 30 days, only minimal drift on the repeatability performance was witnessed, while the response increased by 8%, validating that our sensor is very stable. Same behavior was observed for the SnO2/NiO (0.01 wt.%)/Au(2.5 wt.%) based sensor. Thus, these findings corroborate that the current sensors are very stable when either exposed to dry air or in real conditions after long exposure to C3H7OH and C2H5OH.

Hydrodeoxygenation upgrading of bio-oil on Ni-based catalysts with low Ni loading

Ni/γ-Al2O3, Ni/AlSBA-15 and Ni/HZSM-5 catalyst with small amount of active metal of 1 wt% Ni loading were prepared. The performance for hydrodeoxygenation upgrading of a model bio-oil was evaluated under different reaction conditions. It was found that Ni/γ-Al2O3 displays the highest anisole conversion 60% at WHSV = 81.6 h−1 and nearly 100% at WHSV = 20.4 h−1 as compared with Ni/AlSBA-15 and Ni/HZSM-5. Toluene, a premium aromatic product, could form and the maximum toluene selectivity 20% could be obtained at WHSV = 20.4 h−1 at 3 bars over Ni/HZSM-5. 10% n-hexane selectivity could be obtained over Ni/HZSM-5 at WHSV = 20.4 h−1 at 3 bars. 70% arene selectivity could be obtained at WHSV = 81.6 h−1 at 3 bars over Ni/HZSM-5.

Ethanol steam reforming on Ni/CaO catalysts for coproduction of hydrogen and carbon nanotubes

Catalytic steam reforming of ethanol is considered as a promising technology for producing H2 in the modern world. In this study, using a fixed-bed reactor, steam reforming of ethanol was performed for production of carbon nanotubes (CNTs) and H2 simultaneously at 600°C on Ni/CaO catalysts. Commercial CaO and a synthetic CaO prepared using sol-gel were scrutinized for ethanol's catalytic steam reforming. Analysis results of N2 isothermal adsorption indicate that the CaO synthesized by sol-gel has more pore volume and surface area in comparison with the commercial CaO. When Ni was loaded, the Ni/CaO catalyst shows an encouraging catalytic property for H2 production, and an increase in Ni loading could improve H2 production. The Ni/CaO catalyst with sol-gel CaO support has presented a higher hydrogen production and better catalytic stability than the catalysts with the commercial CaO support at low Ni loading. The highest hydrogen yield is 76.8% at Ni loading content of 10% for the Ni/sol-gel CaO catalyst with WHSV of 3.32/h and S/C ratio of 3. The carbon formed after steam reforming primarily consists of filamentous carbons and amorphous carbons, and CNTs are the predominant type of carbon deposition. The deposited extent of carbon on the used Ni/CaO catalyst lessen upon more Ni loading, and the elongated CNTs are desired to be formed at the surface of the Ni/sol-gel CaO catalyst. Thus, an efficient process and improved economic value is associated with prompt hydrogen production and CNTs from ethanol steam reforming.

Nanoceria-promoted low Pd–Ni catalyst for the synthesis of secondary amines from aliphatic alcohols and ammonia

Pd–Ni catalysts supported over nanoceria with very low Ni and Pd loading (<0.5 wt%) showed high activity and selectivity for the direct amination of 1-octanol with ammonia towards dioctylamine with 80% yield.

Supporting Nickel To Replace Platinum on Zeolite Nanosponges for Catalytic Hydroisomerization of n-Dodecane

Hydroisomerization of linear paraffins to branched isomers is an important petrochemical process, which commonly uses a microporous zeolite catalyst supported with Pt metal nanoparticles. Although attempts were made in the past to find an alternative to costly Pt, replacement with low-cost metals was not successful for conventional bulk zeolites, due to the low metal dispersion resulting in poor catalytic performance. Here, we demonstrate that Ni can replace Pt when it is supported on zeolites with uniform mesopores. Ni-supported MFI-, *MRE-, and TON-type zeolites possessing mesopores showed the same or even better catalytic performance in comparison to that of Pt-supported conventional MFI, *MRE, and TON zeolites, respectively. The Ni-supported zeolites exhibited even better branched isomer yields, despite low Ni loading. This result is ascribed to the confinement or sandwiching effect of Ni nanoparticles by the mesopore walls in the zeolites, which stabilizes the highly dispersed Ni nanoparticles.

Direct Conversion of Methane to Methanol on Ni-Ceria Surfaces: Metal-Support Interactions and Water-Enabled Catalytic Conversion by Site Blocking.

The transformation of methane into methanol or higher alcohols at moderate temperature and pressure conditions is of great environmental interest and remains a challenge despite many efforts. Extended surfaces of metallic nickel are inactive for a direct CH4 → CH3OH conversion. This experimental and computational study provides clear evidence that low Ni loadings on a CeO2(111) support can perform a direct catalytic cycle for the generation of methanol at low temperature using oxygen and water as reactants, with a higher selectivity than ever reported for ceria-based catalysts. On the basis of ambient pressure X-ray photoemission spectroscopy and density functional theory calculations, we demonstrate that water plays a crucial role in blocking catalyst sites where methyl species could fully decompose, an essential factor for diminishing the production of CO and CO2, and in generating sites on which methoxy species and ultimately methanol can form. In addition to water-site blocking, one needs the effects of metal-support interactions to bind and activate methane and water. These findings should be considered when designing metal/oxide catalysts for converting methane to value-added chemicals and fuels.

Promotion effect of additive Fe on Al2O3 supported Ni catalyst for CO2 methanation

In this paper, the effect of additive Fe on Ni/Al2O3 catalyst for CO2 methanation was studied. A series of bimetallic Ni–Fe catalysts with different Ni/Fe ratios were prepared by impregnation method. For comparison, monometallic Fe‐based and Ni‐based catalysts were also prepared by the same method. The characterization results showed that adding Fe to Ni catalyst on the premise of a low Ni loading(≦12 wt.%) enhanced CO2 methanation performance. However, when the Ni loading reached 12 wt.%, the catalytic activity decreased with the increase of Fe content, but still higher than the corresponding Ni‐based catalyst without Fe. Among them, the 12Ni3Fe catalyst exhibited the highest CO2 conversion of 84.3 % and nearly 100% CH4 selectivity at 50000 ml g‐1 h‐1 and 420 °C. The enhancement effect of adding Fe on CO2 methanation was attributed to the dual effect of suitable electronic environment and increased reducibility generated by Fe species.