Al Catalyst Research Articles

The promotion effects of Ni on the properties of Cr/Al catalysts for propane dehydrogenation reaction

The Cr/Al and Cr-Ni/Al catalysts were prepared and contrastively studied for propane dehydrogenation reaction. The results verify that the catalytic performances of Cr-Ni/Al catalysts are evidently higher than those of Cr/Al catalysts due to the impregnation of Ni species. Especially, the propane conversion of 2.5Cr-Ni/Al catalyst attains ∼43%; while it is only ∼24% for 2.5Cr/Al catalyst without Ni species. The promotion effects of Ni on the properties of Cr/Al catalysts for propane dehydrogenation reaction are elaborated upon several state-of-art physico-chemical characterizations including UV–vis, XPS, H2-TPR, NH3-TPD and so on. These characterizations fully confirm the existence of interaction between Ni and Cr species on the surfaces of Cr-Ni/Al catalysts. In addition, the introduction of Ni promotes the formation of oligomeric chromium species and affects the valence of surface Cr species on supports, which would have crucial influences on the improvement of catalytic activity for propane dehydrogenation reaction.

Ni-Mg Bimetallic Catalysts for Preparation of Multi-Walled Carbon Nanotubes from Polypropylene: Influence of the Ratio of Ni/Mg

This study designs Ni–Mg bimetallic catalysts for preparation of multi-walled carbon nanotubes (MWCNTs) from polypropylene (PP). The study further investigates the influence of Mg content on the catalytic activity of Ni catalyst. It is found that bimetallic Ni–Mg catalysts have higher reduction temperature, smaller Ni particle size and improved stability. Consequently, the addition of Mg not only enhances the yield of MWCNTs, but simultaneously improves the morphology and graphitization of MWCNTs. The activities of the bimetallic Ni–Mg catalysts are dependent on their composition. Among the different Ni–Mg bimetallic catalysts ration, Ni–Mg catalyst shows the highest activity when the ratio of Ni/Mg is 9/1. Moreover, the obtained MWCNTs presents smooth surface with highest graphitization degree. With our bimetallic Ni–Al catalyst, it is promising to achieve mass production of MWCNTs by using waste polymers as feedstock.

Ru nanoparticles supported on MIL-53(Cr, Al) as efficient catalysts for hydrogen generation from hydrolysis of ammonia borane

For the first time, ultrafine Ru nanoparticles are successfully deposited on MIL-53(Cr) and MIL-53(Al) by using a simple liquid impregnation strategy and then characterized the structure, size, composition and specific area of the catalysts with different Ru loading by XRD, TEM, EDX, ICP-AES, XPS and BET. Their catalytic activities had been examined in ammonia borane hydrolysis to generate hydrogen gas. The results show that the as-synthesized 2.65 wt% Ru@MIL-53(Cr) and 2.59 wt% Ru@MIL-53(Al) exhibit the highly catalytic activity, owing to the uniform distribution of Ru nanoparticles and bi-functional effects between Ru nanoparticles and the host of MIL-53. The turn over frequency (TOF) values of the Ru@MIL-53(Cr) and Ru@MIL-53(Al) catalysts are 260.8 and 266.9 mol H2 min−1 (mol Ru)−1 and the activation energies (Ea) are determined to be 28.9 and 33.7 kJ mol−1, respectively. Moreover, the two catalysts exhibit satisfying durable stability after five cycles for the hydrolytic dehydrogenation of ammonia borane.

Pyrolysis-Catalytic-Dry Reforming of Waste Plastics and Mixed Waste Plastics for Syngas Production

The CO2 dry reforming of various types of waste plastics (LDPE, HDPE, PS, PET, and PP) and a simulated mixture of the different waste plastics was investigated over a Ni–Co–Al catalyst using a two-stage reactor. The first stage pyrolyzed the plastics, and the second stage involved catalytic-dry reforming of the product pyrolysis gases with CO2. The introduction of CO2 without a catalyst markedly increased the dry reforming reaction and significantly improved the production of H2/CO synthesis gas (syngas). The introduction of the Ni–Co–Al catalyst further significantly improved the production of syngas. LDPE produced the highest yield of syngas at 154.7 mmolsyngas g–1plastic from the pyrolysis-catalytic-dry reforming process. The order of syngas production for the different plastics was LDPE < HDPE < PP < PS < PET. The syngas yield from the processing of the simulated waste plastic mixture was 148.6 7 mmolsyngas g–1plastic which reflected the high content of the linear polyalkene plastics (LDPE, HDPE, PP) ...

CO methanation on ordered mesoporous Ni–Cr–Al catalysts: Effects of the catalyst structure and Cr promoter on the catalytic properties

CO methanation is the main route in industry to produce synthetic natural gas (SNG), and the conventional Ni-based catalysts for this reaction often deactivate severely because of sintering of the Ni particles and coke formation on them. To overcome these technical barriers, we designed and synthesized a group of ternary Ni–Cr–Al metal oxide composites with ordered mesoporous structure and various Cr and Ni contents via a one-pot evaporation-induced self-assembly strategy and tested them for CO methanation to produce SNG. The support and the catalysts before and after the catalytic reaction were thoroughly characterized. It was found that, after reduction at 700°C, metallic Ni particles were generated and anchored in the ordered mesoporous alumina channels while the Cr species started to surround the metallic Ni particles. The long-range ordered mesoporous structure could be maintained well when the total loading of nickel and chromium oxides was below 22wt.%. In general, the optimized ordered mesoporous Ni–Cr–Al catalysts show much better anti-coking and anti-sintering properties and much higher catalytic activity and stability than the conventional Ni catalysts. The improved catalytic performance is attributed to the reduced Ni particle size, the confinement effect of the mesoporous materials, and the promoting effect of Cr, which can significantly reduce the Ni particle size and increase the H2 uptake. These findings shed light on the design of ordered mesoporous alumina-supported materials with high loading of active metal oxides for many high-temperature reactions.

Yttrium-modified alumina as support for trimetallic PtSnIn catalysts with improved catalytic performance in propane dehydrogenation

The yttrium(Y)-modified γ-Al2O3 was used as support for trimetallic PtSnIn catalysts (PtSnIn/xY–Al) and applied in propane dehydrogenation reaction. The PtSnIn/xY–Al catalysts were characterized by several state-of-art techniques such as XRD, BET, NH3-TPD, TEM, H2-TPR, and XPS measurements. The results show that the catalytic performances of PtSnIn/xY–Al catalysts for propane dehydrogenation reaction are clearly improved. The NH3-TPD curves demonstrate that Y-modified γ-Al2O3 could greatly weaken the acidity of the support. The PtSnIn/0.6Y–Al catalyst has the smallest Pt particle size of 16nm and homogenized particle distribution. XPS and H2-TPR techniques verify that the loading of Y influences the state of metals and its interactions with support. In this study, the initial propane conversion and propylene selectivity attain above 50% and 97% for PtSnIn/0.6Y–Al catalyst, respectively. However, with excessive Y loading, the agglomerations of Pt particles and more metallic (Sn0) are found, which leads to the loss of catalytic activity.

Catalytic reversible alkene-nitrile interconversion through controllable transfer hydrocyanation.

Nitriles and alkenes are important synthetic intermediates with complementary reactivity that play a central role in the preparation of materials, pharmaceuticals, cosmetics, and agrochemicals. Here, we report a nickel-catalyzed transfer hydrocyanation reaction between a wide range (60 examples) of alkyl nitriles and alkenes. This strategy not only overcomes the toxicity challenge posed by the use of HCN in traditional approaches, but also encompasses distinct chemical advances, including retro-hydrocyanation and anti-Markovnikov regioselectivity. In a broader context, this work highlights an approach to the reversible hydrofunctionalization of alkenes through thermodynamically controlled transfer reactions to circumvent the use of volatile and hazardous reagents in the laboratory.

A route to nitrile that bypasses cyanide

Organic Chemistry The toxicity of hydrogen cyanide (HCN) is well known. Nonetheless, numerous useful nitrile compounds contain CN groups, and the reaction of HCN with C=C double bonds is often used. Fang et al. now report an alternative to shuttle a CN group from one molecule to another that relies on Ni and Al catalysts (see the Perspective by Schmalz). This transfer procedure circumvents the need for HCN and can be applied to complex substrates using a simple sacrificial nitrile donor. It can also be run “in reverse” to derive an olefin of interest from a nitrile precursor. Science , this issue p. [832][1]; see also p. [817][2] [1]: /lookup/doi/10.1126/science.aae0427 [2]: /lookup/doi/10.1126/science.aaf2215

An aromatic/aliphatic polyester prepared via ring-opening polymerisation and its remarkably selective and cyclable depolymerisation to monomer

The ring-opening polymerisation of 2,3-dihydro-5H-1,4-benzodioxepin-5-one gives polyester homopolymers and copolymers that contain both aromatic and aliphatic linkages. The polymers can be easily depolymerised by Al catalysts.

Promoting effect of Ce on a Cu–Co–Al catalyst for the hydrogenolysis of glycerol to 1,2-propanediol

In this work, the Ce-promoted Cu–Co–Al catalyst exhibited high catalytic performance and stability (100 h) for the hydrogenolysis of glycerol to 1,2-propanediol.

Effect of Mo/Ce ratio in Mo–Ce–Al catalysts on the hydrogen production by steam reforming of glycerol

Alumina-supported molybdena–ceria catalysts were prepared by a sol–gel method and characterized by X-ray diffraction, N2 sorptometry, UV-vis-NIR diffuse reflectance spectroscopy, SEM and TEM.

Effect of silica and alumina promoters on co-precipitated Fe–Cu–K based catalysts for the enhancement of CO2 utilization during Fischer–Tropsch synthesis

Silica and alumina were used as structural promoters to increase the catalytic activity of a co-precipitated Fe–Cu–K catalyst for the CO2 and CO hydrogenation during Fischer–Tropsch (FT) synthesis. The doubly-promoted Fe–Cu–K–Si–Al catalyst achieved higher CO and CO2 conversions than the Fe–Cu–K catalyst and singly-promoted Fe–Cu–K–Al and Fe–Cu–K–Si catalysts. The CO and CO2 conversions of the syngas with 54% H2/10% CO/29% CO2/7% N2 over the doubly-promoted catalyst were 88.3% and 25.2%, respectively, compared to 81.8% and 18.5% for the Fe–Cu–K catalyst. In this case, the C5+ selectivity of the doubly-promoted catalyst was 71.9%, which was slightly lower than 75.5% for the Fe–Cu–K catalyst. The CO2 was converted to hydrocarbons using the doubly-promoted catalyst when the CO2/(CO+CO2) ratio was higher than 0.35 for H2-balanced syngas at H2/(2CO+3CO2)=1.0, and 0.5 for H2-deficient syngas at H2/(2CO+3CO2)=0.5. The increase of hydrogen content in the syngas increased the methane selectivity at the expense of decrease in the liquid hydrocarbon selectivity.

Low-temperature CO oxidation over unsupported nanoporous gold catalysts with active or inert oxide residues

Nanoporous gold (NPG) catalysts with different types of oxide residues are fabricated by a simple electrochemical dealloying method with the aim of exploring the origin of high catalytic activity on unsupported gold catalyst systems. By leaching out the reactive components from AuCu and AuAl alloys, unsupported NPG with so-called active CuO and inert Al2O3 residues were generated, characterized by an open interconnected network architecture with a narrow ligament size distribution. The NPG catalyst with inert Al2O3 residues shows a CO reaction rate and turnover frequency similar to those on NPG with active CuO residues under the same measurement conditions. In comparison, NPG(Cu) with active CuO residues exhibits better catalytic durability for CO oxidation than NPG(Al) catalyst, possibly because of its stabilization for nanoporous architecture. Experimental observations suggest that the so-called active or inert oxide residues in the as-made NPG catalysts have almost no effect on the intrinsic catalytic activity of gold, whereas metallic gold plays the catalytic role in this unsupported NPG system.

Hydrogenolysis of glycerol to propanediols on Cu–Ca–Al hydrotalcites derived catalysts

A series of Cu–Ca–Al hydrotalcite derived catalysts were prepared by the co-precipitation method. Their catalytic activities were evaluated in the hydrogenolysis of glycerol. The catalysts were characterized by XRD, SEM, TEM, ICP, NH3-TPD, CO2-TPD and H2-TPR. It was observed that the incorporation of calcium and aluminum in the Cu–Ca–Al catalyst improved the conversion of glycerol and promoted the generation of 1,3-PDO. This is due to the appropriate acidity and basicity of the catalyst, which is confirmed by NH3-TPD and CO2-TPD. The conversion of glycerol over the catalyst with a Cu–Ca–Al mole ratio of 1:3:5 was up to 73.2 % with 42.6 % selectivity to 1,2-PDO and 9.1 % selectivity to 1,3-PDO. Effects of the reaction time, reaction temperature and initial hydrogen pressure on the conversion and selectivity were systematically investigated.

Synthesis, characterization and catalytic performance of ordered mesoporous Sn–Al catalysts

A series of ordered mesoporous Sn–Al catalysts with high specific surface area, large pore volume and uniform pore size were successfully synthesized via facile one-pot evaporation induced self-assembly method. Different characterization techniques, such as XRD, N2 adsorption–desorption, ICP, NH3-TPD, TEM and UV-vis spectra were employed to investigate their physical chemical properties, and these catalysts were applied in the Baeyer–Villiger oxidation of cyclohexanone by molecular oxygen. The characteristic results showed that Sn–Al catalysts exhibited wormhole-like mesostructured and narrow pore-size distribution. The acidity of Sn–Al catalysts can be promoted by homogeneous incorporation of Sn species into the framework of Al2O3, which is beneficial to their catalytic performances in the Baeyer–Villiger oxidation of cyclohexanone by molecular oxygen. The Sn–Al catalyst when adding 7 % the weight percent of Sn in the catalyst shows higher yield of e-caprolactone than other catalysts, and it exhibited excellent catalytic stability even after repeated reaction for five times.

Dehydrogenation of propane to propylene over CrOy-CeO2-K2O/γ-Al2O3 catalysts: Effect of cerium content

A series of CrOy(17.5wt.%)-CeO2(X wt.%)-K2O(2wt.%)/γ-Al2O3 catalysts (denoted as 17.5Cr-XCe-2K/Al) were prepared by a spray drying method and a subsequent incipient wetness impregnation method with a variation of cerium content (X, wt.%), and they were applied to the dehydrogenation of propane to propylene. It was revealed that the oxidation state of cerium species was closely related to the oxygen capacity (the amount of lattice oxygen) of the catalyst. The oxygen capacity served as a crucial factor in determining the catalytic performance in the reaction. Initial yield for propylene increased with increasing oxygen capacity of 17.5Cr-XCe-2K/Al catalysts.

Metal–organic framework MIL-53(Al)-supported copper catalyst for CO catalytic oxidation reaction

Metal–organic framework (MOF) material MIL-53(Al) (MIL: Materials of Institut Lavoisier) with high thermal stability has been prepared by solvothermal method, serving as a support material of copper catalyst for CO oxidation. A comparison between the catalytic performance of the MIL-53(Al) and the Al2O3 support material was carried out to understand the catalytic behavior of the catalysts. The catalysts were characterized by thermogravimetric-differential scanning calorimeter (TG-DSC), N2 adsorption–desorption, X-ray diffraction (XRD), and transmission electron microscopy (TEM). The TG and N2 adsorption–desorption analyses showed that MIL-53(Al) had excellent stability and high surface areas. The highly dispersed CuO nanoparticles, which resulted from the three dimension porous structure of MIL-53(Al), give rise to a superior catalytic activity for CO oxidation. Indeed, the heterogeneous catalytic composite materials Cu/MIL-53(Al) catalyst exhibited much higher activity than the Cu/Al2O3 catalyst in CO oxidation test, with 100% conversion at 220°C. The catalytic activity and structure of Cu/MIL-53(Al) catalyst were stable during the reaction.

Ni–Al bimetallic catalysts for preparation of multiwalled carbon nanotubes from polypropylene: Influence of the ratio of Ni/Al

This study designed a novel Ni–Al bimetallic catalyst for preparation of multiwalled carbon nanotubes (MWCNTs) from polypropylene (PP). The study further investigated the influence of Al content on the catalytic activity of Ni catalyst. A series of bimetallic Ni–Al catalysts were prepared and then characterized by X-ray diffraction, N2-adsorption–desorption isotherms, transmission electron microcopy and temperature programmed reduction analysis. It was found that bimetallic Ni–Al catalysts had higher surface area, higher reduction temperature, smaller Ni particle size and improved stability. Consequently, the addition of Al not only dramatically enhanced the yield of MWCNTs, but simultaneously improved the morphology and graphitization of MWCNTs. The activities of the bimetallic Ni–Al catalysts were dependent on their composition. Among the different Ni–Albimetallic catalysts, Ni–Al catalyst showed the highest activity when the ratio of Ni/Al was 9/1. Moreover, the obtained MWCNTs presented smooth surface with highest graphitization degree. The improvement of catalytic activity and stability obtained for bimetallic Ni–Al catalysts was attributed to an appropriate interaction and synergy between Ni species and amorphous Al2O3. The combined results indicate that the addition of Al to Ni catalyst with an appropriate amount of Al can give rise to a bimetallic catalyst with excellent properties for synthesis of MWCNTs from PP. With our bimetallic Ni–Al catalyst, it is promising to achieve mass production of MWCNTs by using waste polymers as feedstock.

The Role of Ni Species Distribution on the Effect of Ce as a Promoter in C2-ODH Reaction

The aim of work was to analyse and discuss the effect of cerium on the catalytic behaviour of different types of nickel species in the oxidative dehydrogenation of ethane. Ni–Al and Ni–Ce–Al catalysts were prepared from cerium nitrate and nickel nitrate or nickel acetate as a precursor. As-prepared materials were characterized by using of XRD, DR UV–Vis spectroscopy and H2-TPR. It was found that the addition of cerium affects both the reducibility of nickel species and the population of nickel species. Firstly, the addition of cerium led to the significant decrease of the reduction peak at 755–785 °C to about 40 °C due to the Ni–Ce interaction at both Ni–Ce–Al–NO3 and Ni–Ce–Al–ac catalysts. Secondly, the addition of cerium affected the relative population of nickel species in tetrahedral and octahedral coordination, which population originated from used nickel precursor. The presence of cerium in Ni–Ce–Al–NO3 catalysts led to the decrease in the relative population of Ni(T d ) species, while the crystal size of NiO in Ni–Ce–Al–ac catalysts decreased with increasing Ce/Ni ratio. The highest ethylene productivity was achieved on catalysts with Ce/Ni molar ratio 0.13. Catalysts exhibited an ethylene productivity up to 1.0 gC2=·g cat −1 ·h−1 with a selectivity of 82 % (Ni–Ce–Al–NO3) and 1.3 gC2=·g cat −1 ·h−1 with a selectivity of 75 % (Ni–Ce–Al–ac).

Non-thermal plasma assisted NOx storage and reduction over a cobalt-containing Pd catalyst using H2 and/or CO as reductants

A catalyst of the type Pd/Co/Ba/Al was examined for lean NOx trap (LNT) applications, and compared with Pd/Ba/Al and Pt/Ba/Al reference catalysts for NOx storage and reduction using H2 and/or CO as reducing agents. The activity of Pt/Ba/Al was greatly depressed when using CO as reductant at low temperatures owing to the strong poisoning effect of CO on Pt. The Pd/Co/Ba/Al catalyst exhibited higher activity for NO oxidation to NO2 and better NOx storage capacity than Pt/Ba/Al and Pd/Ba/Al catalysts, also showed higher NOx reduction activity with CO compared to the other two catalysts. However, it shows relatively low NOx removal efficiency below 250°C, especially using CO as reductants, indicating that regeneration of stored NOx is the rate limiting step. By employing non-thermal plasma in the rich phase to assist reduction of the stored NOx, the Pd/Co/Ba/Al sample exhibited excellent NOx removal efficiency under plasma assisted lean/rich cycling conditions, affording NOx conversions close to 99% over a broad temperature window of 150–350°C, even when using CO as the reducing agent.