Ni Bimetallic Catalysts Research Articles

The promotion mechanisms of Mo for the dry reforming of methane reaction over a Mo-doped Ni(2 1 1) bimetallic catalyst

With the escalating severity of climate change, the DRM reaction has gained attention as an effective pathway for utilizing CO2. Enhancing reaction activity and identifying the sources of carbon deposition during the DRM reaction on Ni-based catalysts pose crucial yet challenging questions. In this study, we investigate the effects of Mo doping on the reaction activity and carbon deposition of Ni catalysts using a combined DFT and microkinetic method. In terms of the models, Mo replaced one Ni atom in the surface and subsurface layers to represent Mo in the initial stages and in prolonged on the reaction, namely NiMoU(211) and NiMoL(211). Through the analysis of electronic structure, intermediate structures, and reaction barriers compared with Ni(211), the impact of Mo doping on the surface activity and carbon deposition of Ni(211) is studied. The results indicate that the strong Ni-Mo interaction enhances intermediate stability, leading to increased reaction activity. Mo doping promotes the increase in O concentration, but at low temperatures, reaction rates decrease sharply. Furthermore, Mo doping enhances the resistance to carbon deposition on Ni(211) surfaces and improves the ability to remove carbon deposits, especially in prolonged reaction models. These findings provide new mechanistic insights into the DRM reaction on Ni(211) surfaces, which were previously well-explained by experimental results, and are valuable for understanding quantum processes.

Efficient ozone decomposition by amorphous Mn–Ni bimetallic catalysts under an entire humidity environment

Mn–Ni bimetallic catalysts with different Mn/Ni molar ratios were synthesized by means of a facile hydrothermal reaction and applied for the removal of ozone. The physicochemical properties of prepared samples were systematically characterized, confirming that Ni was incorporated into MnOx lattice to form the amorphous Mn–Ni solid solution. Abundant grain boundaries in amorphous Mn–Ni solid solution facilitated the formation of a large number of oxygen vacancies. Synergistic effects of Mn and Ni improved low-temperature reducibility and lattice oxygen mobility on Mn1Ni1 (molar ratio of Mn2+: Ni2+ = 1:1). In situ diffuse reflectance infrared Fourier transform spectra (in-situ DRIFTS) analyses displayed that the introduction of Ni enhanced the hydrophobicity of Mn1Ni1 and avoided the enrichment of water molecules on the catalyst surface, but also promoted the conversion of adsorbed water into surface hydroxyl groups to participate in the ozone decomposition. The rapid desorption of intermediate peroxides (O22−) on Mn1Ni1 accelerated the ozone decomposition cycle. Mn1Ni1 exhibited excellent activity and stability for ozone decomposition, keeping 100 % removal of 45 ppm ozone after running for 25 h under high relative humidity of 80 %.

Mechanism and Selectivities of [Cu]/[M] (M=Pd, Ni) Synergistic Catalyzed Alkene Arylboration: A DFT Investigation

ABSTRACTThe transition metal–catalyzed boronation reactions are considered as one of the most effective methods for the synthesis of alkylboranes in terms of functional group compatibility and reactivity. Herein, the mechanism of synergistic catalysis of alkene arylboration by [Cu]/[M] (M=Pd, Ni) bimetallic catalysts, as well as the regioselectivity and stereoselectivity of the reactions, has been investigated by using DFT calculations. The results show that four processes are involved in the whole reaction: [Cu]‐catalyzed borylcuprization of alkene, [Pd] or [Ni]‐catalyzed oxidative addition of halogenated aryl groups, transmetalation, and reductive elimination. [Cu]/[Ni] bimetallic catalysts show the same catalytic activity as [Cu]/[Pd] catalysts and are good economic alternatives for the alkene arylboration. The cleavage of B–B bond of B2Pin2 is the rate‐determining step. The regioselectivity of the title reaction is determined by the mode of the alkene insertion into the Cu–B bond. The attacking of C atom with the more electron‐rich character in alkyne makes for the formation of the main product. The small energy barrier difference between the rotation of the Cu‐C σ bond from the syn‐9 to the anti‐9 controls the stereoselectivity. Our findings provide a thorough explanation of the experimental results and shed light on the further development of the alkene functionalization.

Au-Based Bimetallic Catalysts for Aerobic Oxidation of 5-Hydroxymethylfurfural to 2,5-Furandicarboxylic Acid under Base-Free Reaction Conditions.

The aerobic oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) plays a pivotal role in the synthesis of renewable, biodegradable plastics and sustainable chemicals. Although supported gold nanoclusters (NCs) exhibit significant potential in this process, they often suffer from low selectivity. To address this challenge, a series of gold-M (M means Ni, Fe, Cu, and Pd) bimetallic NCs catalysts were designed and synthesized to facilitate the selective oxidation of HMF to FDCA. Our findings indicate that the introduction of doped metals, particularly Ni and Pd, not only improves the reaction rates for HMF tandem oxidation but also promotes high yields of FDCA. Various characterizations techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy of CO adsorption (CO-DRIFTS), and temperature-programmed desorption of oxygen (O2-TPD), were employed to scrutinize the structural and electronic properties of the prepared catalysts. Notably, an electronic effect was observed across the Au-based bimetallic catalysts, facilitating the activation of reactant molecules and enhancing the catalytic performance. This study provides valuable insights into the alloy effects, aiding in the development of highly efficient Au-based bimetallic catalysts for biomass conversions.

Design of highly active meso-zeolite enveloping Pt–Ni bimetallic catalysts for degradation of toluene

Degrading volatile organic compounds at low temperatures and active sites aggregation are still challenging. In this study, a novel mesoporous zeolite silicalite-1 (S-1-meso) enveloped Pt–Ni bimetallic catalysts (noted as Pt1Ni1@S-1-meso) were synthesized via a facile in situ mesoporous template-free method. The Pt–Ni bimetallic nanoparticles were uniformly distributed and displayed a large specific surface area and enriched mesopores to facilitate the deep oxidation of toluene. The presence of the Pt–NiO interface both increased the dispersion of the catalyst and improved its catalytic performance, thereby reducing the consumption of Pt. The Mars-van Krevelen mechanism and density function theory (DFT) calculations revealed that the Pt–NiO interface effect changed the electronic structure of Pt and Ni species, reduced the activation potential for oxygen, formed reactive oxygen species, and facilitated the adsorption and activation of reactants in the direction favorable to the toluene oxidation. This study provides a guideline for minimizing the proportion of precious metals used in practical applications and a promising method for toluene elimination at low temperatures.

Catalytic Oxidation of Benzene over Atomic Active Site AgNi/BCN Catalysts at Room Temperature.

Benzene is the typical volatile organic compound (VOC) of indoor and outdoor air pollution, which harms human health and the environment. Due to the stability of their aromatic structure, the catalytic oxidation of benzene rings in an environment without an external energy input is difficult. In this study, the efficient degradation of benzene at room temperature was achieved by constructing Ag and Ni bimetallic active site catalysts (AgNi/BCN) supported on boron-carbon-nitrogen aerogel. The atomic-scale Ag and Ni are uniformly dispersed on the catalyst surface and form Ag/Ni-C/N bonds with C and N, which were conducive to the catalytic oxidation of benzene at room temperature. Further catalytic reaction mechanisms indicate that benzene reacted with ·OH to produce R·, which reacted with O2 to regenerate ·OH. Under the strong oxidation of ·OH, benzene was oxidized to form alcohols, carboxylic acids, and eventually CO2 and H2O. This study not only significantly reduces the energy consumption of VOC catalytic oxidation, but also improves the safety of VOC treatment, providing new ideas for the low energy consumption and green development of VOC treatment.

Structure and Electrocatalytical Properties of Electrodeposited M-Ir (M = Co, Ni) Bimetallic Alloy Catalysts with Low Ir Loading Obtained on Copper Foams for Hydrogen Evolution Reaction

Structure and Electrocatalytical Properties of Electrodeposited M-Ir (M = Co, Ni) Bimetallic Alloy Catalysts with Low Ir Loading Obtained on Copper Foams for Hydrogen Evolution Reaction

First-principles study on the design of nickel based bimetallic catalysts for xylose to xylitol conversion.

A significant challenge for effective biomass utilization and upgrading is catalysis. This research paper focuses on the conversion of xylose into xylitol, a valuable chemical used in the pharmaceutical and food industries. The primary objective is to design more efficient and cost-effective catalysts for this conversion process. The study investigates the use of Ni-bimetallic catalysts by employing a first-principles technique. Catalyst models derived from subsets of Ni (111) surfaces with various transition metals (M = Ti, V, Cr, Fe, Co, and Cu) are examined. The catalyst surfaces are screened based on the rate-determining step (RDS) involved in the conversion of xylose to xylitol, with Ni (111) serving as a reference. Electronic structure calculations are used to analyze the activities of the investigated Ni-bimetallic catalysts relative to the RDS. The results show that certain bimetallic surfaces exhibit significantly lower kinetic barriers compared to the Ni (111) surface. The hydrogenation process when investigated using different transition state paths, reveals that hydrogenation commences at the carbon atom of the carbonyl group of xylose after the ring-opening step. Stability segregation tests demonstrate varying behaviors among the screened catalysts, with Ni (111)/Cr/Ni showing greater stability than Ni (111)/Co. This study sheds light on the theoretical design of catalysts for xylose conversion, providing insights for the development of more efficient and active catalysts for industrial applications. The research highlights the significance of theoretical methodologies in tailoring catalyst surfaces to optimize their performance in biomass upgrading.

Hydrodeoxygenation of anisole over SBA-15-supported Ni, Pd, and Pt mono- and bimetallic catalysts: effect of the metal's nature on catalytic activity and selectivity.

Monometallic Ni, Pd and Pt and bimetallic catalysts formed by combinations of the above metals supported on SBA-15 silica were synthesized, characterized and tested in the hydrodeoxygenation reaction of anisole. The objective of the work was to detect the effect of the nature of metals on the activity of the catalysts at different steps of anisole hydrodeoxygenation: hydrogenation of the aromatic ring of anisole and C-O bond cleavage in the intermediate cyclohexyl methyl ether. The support and the catalysts were characterized by N2 physisorption, X-ray diffraction, UV-vis diffuse reflectance spectroscopy, temperature-programmed reduction, scanning electron microscopy-energy dispersive X-ray spectroscopy, transmission electron microscopy and HAADF-STEM. The catalytic activity tests were carried out in a batch reactor at 280 °C and 7.3 MPa pressure. The activity results show that the NiPd/SBA-15 catalyst had the greatest ability for hydrogenation of the aromatic ring of anisole, while its NiPt/SBA-15 analog resulted in better activity for C-O bond hydrogenolysis. The bimetallic NiPt/SBA-15 catalyst showed the best catalytic performance in the HDO of anisole ascribed to the formation of a Ni-Pt alloy. On the other hand, the combination of Pd and Pt metals in the PdPt/SBA-15 catalyst resulted in the formation of bimetallic particles with Pd-rich and Pt-rich domains, showing high selectivity for the formation of the cyclohexyl methyl ether, which can be useful for the hydrogenation of aromatic rings in O-containing reactants with the formation of saturated O-containing products. According to the characterization results (HAADF-STEM), the different catalytic behavior of NiPd/SBA-15, NiPt/SBA-15, and PdPt/SBA-15 catalysts could be attributed to different characteristics of the bimetallic active phases in them.

Fe-Ni bimetallic supported on mordenite catalyst for selective oxidation of veratryl alcohol in a continuous reactor

Veratryl alcohol (VA) is preferentially oxidized to veratraldehyde (VADE) using a heterogeneous catalyst, which is more favoured in industries. Commercial mordenite (Ca,Na2,K2) Al2Si10O24·7H2O) was desilicated with NaOH and loaded with nickel and iron bimetal by the wet impregnation method. The synthesised Mordenite-Fe(5 %)/Ni(5–20 %) bimetallic catalyst, possessing active Bronsted acid sites, was employed to selectively oxidize the veratryl alcohol reaction. FT-IR, XRD, BET, HR-SEM, HR-TEM, and TPD were employed to determine the catalyst's textural attributes, morphology, chemical properties, and stability. Selective oxidation was performed over the catalysts using TBHP as an oxidant in a continuous reactor. To examine the most active catalyst among the four and to maximise the conversion and yield, the reaction conditions are optimised for various reaction parameters The reaction conditions were optimized by attaining 100 % conversion at temperature (90° C) for time (2 hr) and a maximum conversion of 97 % and a selectivity of 99 % at 10 bar pressure, WHSV (1.0 h−1) with acetonitrile solvent. The result of the study display that Fe (5 %) and Ni(15 %) impregnated on mordenite exhibits excellent catalytic stability with conversion (100 %) and selectivity (99 %) among the other catalysts. During regeneration, the conversion rate declined from 99.5 to 92.4.7 % and selectivity declined from 100 % to 96.2 % at the end of the seventh cycle. The high selectivity and stability of MOR-Fe(5 %)/Ni(15 %) imply that they might function properly as appropriate catalysts for the oxidation of aromatic alcohols. The advantages of the current synthesis are its cost-efficiency and eco-friendliness.

A comparative study on the influence of potential 4th period promoters in Ni-bimetallic catalysts for CO2 methanation

Because of their simplicity, bimetallic nickel catalysts are a rational step to further develop improved CO2-methanation catalysts suitable for specific applications and feed gas situations. In this study, hydrotalcite-based catalysts incorporating a second metal from the 4th period (chromium, manganese, iron, cobalt, copper, zinc and gallium) were synthesized, characterized (ICP-OES, XRD, BET, XPS) and performance tested under comparable conditions. The study aims at the clarification of inconsistencies regarding these additives found in the literature by ensuring comparability as good as possible. To achieve this goal the catalysts were tested using the same reactor, were prepared by the same type of synthesis possessing the same atomic ratio of Ni to the potential promoter element. In catalytic tests, performed at atmospheric pressure and at 20 bar, all catalysts were active in respect to CO2 hydrogenation. While Cu, Zn, and Ga acted as inhibitors, reducing the activity approximately by half, Fe and Mn proved to be very active promotors. The catalyst without promotor shows 80 % yield at 400 °C whereas the iron containing catalyst reaches this value already at 320 °C, but undergoes a irreversible loss at high temperatures (20 % loss after being exposed to 480 °C). In contrast, the manganese containing catalyst possesses a significantly improved activity without showing such a deactivation process, indicating a high level of stability.

Efficient depolymerization of alkali lignin to monophenols using one-step synthesized Cu–Ni bimetallic catalysts inlaid in homologous biochar

The efficient depolymerization of lignin for the production of high-value chemicals is essential for the development of a sustainable and competitive biorefinery. In this study, we report the preparation of homologous biochar-supported inlaid Cu–Ni catalysts (CuxNiy/BC) using a one-step method, and their application for lignin depolymerization in mild water without the need for external hydrogen, additives, or co-catalysts. The Cu1Ni3/BC (0.05 g catalyst, 8 h, 280 °C, and 18 mL water) showed exceptional catalytic activity, with a monophenol yield of 94.35 ± 2.92 mg/g, bio-oil yield of 68.98 ± 1.42%, and a lignin conversion rate of 92.36 ± 1.99%, which outperformed both the biochar support and monometallic catalysts. The outstanding catalytic performance of Cu1Ni3/BC was attributed to its strong metal-support interaction, alloy sites, and well-dispersed nanoparticles. Reusability experiments demonstrated that the Cu1Ni3/BC exhibited relatively good stability for up to four reuses, with only a 2.32% reduction in catalytic activity per cycle. Mechanism investigation revealed that the Cu1Ni3/BC, with its abundant mesoporous structure and enhanced acid sites, displayed excellent deoxygenation ability, enabling effective cleavage of C–O/C–C bonds and the production of G-type phenols. This approach provides new insights into the large-scale utilization of lignin for the production of high-value chemicals.

The Ru−Ni bimetallic catalyst activated by high-voltage atmospheric cold plasma (HVACP) and application in the isomerization of grape seed oil

Grape seed oil, as a high-linoleic acid type, can be used for the production of conjugated linoleic acid, which cannot be synthesized by the human body, through isomerization under the action of catalysts. Improving the activity of the catalyst is an effective way to obtain conjugated linoleic acid-rich edible oils. In this study, the Ru−Ni bimetallic catalyst was activated by high-voltage atmospheric cold plasma (HVACP) catalyst modification. The results showed that the specific surface area, pore size distribution, and average particle size of the Ru−Ni bimetallic catalyst were enhanced when the treatment condition was 180 s, the power at both ends of the plate was 150 W, and the gas composition was 5% H2/95% He. The catalyst characterization showed that the dispersion of the HVACP-treated Ru−Ni bimetallic catalyst was enhanced, which elevated the catalytic performance of the catalyst. Linoleic acid in grape seed oil was isomerized by the HVACP-treated Ru−Ni bimetallic catalyst, and grape seed oil rich in conjugated linoleic acid was obtained. The conjugated linoleic acid content, trans oleic acid content, peroxide value, and p-anisidine value were 42.52%, 0.63%, 5.01 mmol kg−1, and 12.41, respectively. Quantum chemical analysis further predicted the reaction sites and clarified the rationality of the isomerization reaction. This method provided a scientific basis for producing high-quality functional oils.

High-Temperature Rotating Disk Electrode Study of Platinum Bimetallic Catalysts in Phosphoric Acid

Understanding the H3PO4 effect on the catalyst’s activity under a relevant condition is important for high-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) catalyst research. Here, we report a high-temperature rotating disk electrode (HT-RDE) study of oxygen reduction reaction (ORR) in H3PO4. With the regular electrochemical protocol, we found that H3PO4 reduction could occur during cyclic voltammetry study and form a reductive species─phosphorus acid (H3PO3). To obtain reliable ORR measurement, we optimized the protocol to avoid the H3PO3 generation. The ORR activity of carbon-supported PtM (M = Fe, Co, Ni, Ru, Pd, and Ir) bimetallic alloy catalysts measured with this HT-RDE method showed higher ORR activity than Pt. To understand the alloying effect, we combine experiments in diluted solutions to distinguish the alloying effect on Pt–O binding and Pt–H3PO4 binding. The results indicate that H3PO4 mainly reduces available sites for ORR, with little effect on neighboring site’s Pt–O binding via Pt–H3PO4 interaction, which is also supported by the density functional theory calculation of the Pt–O binding energy with/without H2PO4. Further study in a phosphoric acid-doped quaternary ammonium-biphosphate ion pair coordinated polyphenylene (PA-QAPOH) membrane electrode assembly (MEA) shows that the active alloy catalyst has better performance in both the HT-RDE and MEA. Also, the MEA gives higher ORR activity than the HT-RDE because of the higher pressure and less phosphoric acid content of the MEA. Yet, the gap between the HT-RDE and MEA is significantly smaller than that between the room temperature (RT)-RDE and MEA, suggesting the importance of temperature and H3PO4 concentration in understanding ORR in HT-PEMFCs.

Production of 2-methyl furan, a promising 2nd generation biofuel, by the vapor phase hydrodeoxygenation of biomass-derived furfural over TiO2 supported Cu[sbnd]Ni bimetallic catalysts

This work investigates the vapor phase hydrodeoxygenation (HDO) of FFR to 2-MeF over a series of TiO2-supported mono and bimetallic Cu-Ni catalysts with a fixed Cu content (10 wt%) and varying Ni content (0–20 wt%). The catalysts were synthesized through a simple wet impregnation method, and their properties were studied in depth through an array of analytical techniques such as X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), Scanning Electron Microscopy (SEM), N2-physisorption, Raman spectroscopy, and NH3-temperature programmed desorption (TPD). The catalyst characterizations revealed that the addition of Ni in progressively larger amounts resulted in greater dispersion of Cu species and an increase in the surface area & porosity of the bimetallic catalysts, arising from the strong interactions between NiO and CuO species. Detailed studies were carried out to evaluate the effect of various process parameters such as Ni content, temperature, and contact time on the selectivity of 2-MeF. Ni content of the bimetallic catalysts and temperature played a significant role in product distribution than the contact time. The bimetallic catalyst with the composition 10%Cu-10%Ni was observed to be the optimum, providing a FFR conversion of 100%, and a 2-MeF selectivity of 84.5% at 200 °C, H2/FFR molar ratio = 15, and WHSV = 0.87 gFFR h−1 gcatalayst−1 after 6 h time-on-stream (TOS). During the long-term catalytic activity evaluation, the catalyst exhibited a stable 100% FFR conversion and ∼ 85% selectivity towards 2-MeF over a period of 12 h. Even after a period of 15 h, conversion and selectivity values remained >90% and 70%, respectively.

Methane Reforming Processes: Advances on Mono- and Bimetallic Ni-Based Catalysts Supported on Mg-Al Mixed Oxides

Ni-based catalysts supported on Mg-Al mixed oxides (Mg(Al)O) have been intensively investigated as catalysts for CH4 reforming processes (i.e., steam reforming (SMR) and dry reforming (DRM)), which are pivotal actors in the expanding H2 economy. In this review, we provide for the first time an in-depth analysis of homo- and bimetallic Ni-based catalysts supported on Mg(Al)O supports reported to date in the literature and used for SMR and DRM processes. Particular attention is devoted to the role of the synthesis protocols on the structural and morphological properties of the final catalytic materials, which are directly related to their catalytic performance. It turns out that the addition of a small amount of a second metal to Ni (bimetallic catalysts), in some cases, is the most practicable way to improve the catalyst durability. In addition, besides more conventional approaches (i.e., impregnation and co-precipitation), other innovative synthesis methods (e.g., sol-gel, atomic layer deposition, redox reactions) and pretreatments (e.g., plasma-based treatments) have shown relevant improvements in identifying and controlling the interaction among the constituents most useful to improve the overall H2 productivity.

Coke-resistance over Rh–Ni bimetallic catalyst for low temperature dry reforming of methane

Methane and carbon dioxide can be converted into syngas using the prospective dry reforming of methane technology. Carbon deposition is a major cause of catalyst deactivation in this reaction, especially at low temperature. The superior stability of bimetallic catalysts has made their development more and more appealing. Herein, a series of bimetallic RhNi supported on MgAl2O4 catalysts were synthesized and used for low temperature biogas dry reforming. The results demonstrate that the bimetallic RhNi catalyst can convert CH4 and CO2 by up to 43% and 52% over at low reaction temperature (600 °C). Moreover, the reaction rate of CH4 and CO2 of RhNi–MgAl2O4 remains stable during the 20 h long time stability test, most importantly, there was no obviously carbon deposition observed over the spent catalyst. The enhanced coking resistance should be attributed to the addition of a little amount of noble metal Rh can efficiently suppress dissociation of CHX∗ species into carbon, and the high surface areas of MgAl2O4 support can also promote the adsorption and activation of carbon dioxide to generate more O∗ species. Balancing the rate of methane dissociation and carbon dioxide activation to inhibit the development of carbon deposition is a good strategy, which provides a guidance for design other high performance dry reforming of methane catalysts.

Co-Ni supported yttrium oxide material as a catalyst for ammonia decomposition to COx-free hydrogen

The preparation of CO2-free hydrogen by decomposing ammonia using non-precious metal catalysts has received widespread attention. Co-based catalysts have good catalytic activity and low synthesis costs. Therefore, we prepared a series of Y2O3-loaded Co and Co–Ni bimetallic catalysts by the co-precipitation method. The structure-activity relationship of the catalysts during NH3 decomposition was investigated by X-ray diffraction, N2 adsorption-desorption, transmission electron microscopy, and Temperature-programmed reduction by hydrogen. The ammonia decomposition performance of the bimetallic Co–Ni was examined to elucidate the effect of the relative amount of the active metal of the catalyst on the catalytic activity and compared it with the monometallic Co/Y2O3. Among the tested catalysts, 20Co–10Ni/Y2O3 showed the best catalytic performance as well as good stability. The ammonia decomposition rate of the 20Co–10Ni/Y2O3 catalyst was 85.02% at 550 °C and GHSV of 9000 mL h−1·gcat−1, which was 28.5% higher than that of the 20Co/Y2O3 catalyst. The high activity of 20Co–10Ni/Y2O3 catalyst was attributed to the uniform loading of Co and Ni, high specific surface area, and a large number of mesopores. At the same time, Co and Ni exhibited synergistic effects to produce suitable adsorption energy of nitrogen atoms, which further enhanced the catalytic activity of the catalyst.

Sorption enhanced aqueous phase reforming of biodiesel byproduct glycerol for hydrogen production over Cu-Ni bimetallic catalysts supported on gelatinous MgO

Hydrogen production from sorption enhanced aqueous phase reforming (APR) of biodiesel byproduct glycerol was studied by Ni-based monometallic and bimetallic catalysts supported on gelatinous MgO supports. Compared with Ni-based monometallic catalyst, the H2 selectivity and glycerol conversion of the Cu–Ni bimetallic catalyst were found to be increased more than 3% and 30%, respectively. Meanwhile, higher reaction temperature was found to have higher H2 yield with lower H2 selectivity. The H2 yield using the catalyst with gelatinous MgO support was 1.25 times higher than that of calcined support. Through in-situ CO2 capture, the addition of CaO to the Cu–Ni bimetallic catalyst increased more than 58.3% and 14.4% of the H2 yield and selectivity, respectively. An analysis about liquid product component indicate that the presence of CaO promote the further cleavage of the C–C bond, which further increased the conversion of glycerol. Furthermore, it was found that the presence of CaO could also improve the stability of the catalyst through the control experiments.

PtMx/SBA-15 (M = Co, Cu, Ni and Zn) bimetallic catalysts for crotonaldehyde selective hydrogenation

Herein, a series of the Pt-based bimetallic catalysts (PtMx/SBA-15) are gained by using ultrasonic incipient wetness impregnation method (M = Co, Cu, Ni or Zn). The experimental results show that the catalytic performance (including catalytic activity (turnover frequency-TOF), selectivity to crotyl alcohol) of PtCox/SBA-15 for catalyzing crotonaldehyde selective hydrogenation is the best among PtMx/SBA-15. Additionally, the ratio of Pt/Co in the PtCox/SBA-15 catalysts is changed to successfully synthesize PtCo/SBA-15, PtCo2/SBA-15, PtCo5/SBA-15. It demonstrates that the selectivity of the PtCox/SBA-15 catalysts for crotonaldehyde selective hydrogenation to crotyl alcohol is significantly improved with the increase of the Co content. The PtCo5/SBA-15 catalyst provides 83.8% conversion of crotonaldehyde, 94.3% selectivity to crotyl alcohol and TOF of 910.5 h−1 under mild reaction conditions (3.0 MPa H2, 80 °C and 2.0 h). And PtCo5/SBA-15 has much better catalytic performance (higher catalytic activity and selectivity to crotyl alcohol) than PtCu5/SBA-15, PtNi5/SBA-15 and PtZn5/SBA-15. The reasons are as follows: (1) PtCo alloy forms, which is conducive to crotonaldehyde adsorption and activation; (2) there is an appropriate synergy effect between Pt and Co, greatly improving the capacity of the catalyst activating hydrogen under mild conditions; (3) the electron transfers from Co to Pt, resulting in the increase of Pt electron density and decrease of Co electron density, then the Co sites are advantageous to CO group adsorption and activation and Pt sites for H2 adsorbing and activating; (4) with the increase of the Co proportion in PtCox/SBA-15, the synergy effect between Pt and Co in PtCo alloy strengthens and thus increases the selectivity of CO group hydrogenation.