Structure and Catalytic Performance of Mg‐SBA‐15‐Supported Nickel Catalysts for CO2 Reforming of Methane to Syngas

A series of Mg‐modified SBA‐15 mesoporous silicas with different MgO contents were successfully synthesized by a simple one‐pot synthesis method and further impregnated with Ni. The Mg‐modified SBA‐15 materials and supported Ni catalysts were characterized by N₂ physisorption (BET), X‐ray diffraction (XRD), temperature‐programmed desorption of CO₂ (CO₂‐TPD), temperature‐programmed H₂ reduction (H₂‐TPR), and temperature‐programmed hydrogenation (TPH) techniques and used for methane dry reforming with CO₂. CO₂‐TPD results proved that the addition of Mg increased the total amount of basic sites which was responsible for the enhanced catalytic activity over the Mg‐modified Ni catalyst. The excellent catalytic stability of Ni/8Mg‐SBA‐15 was ascribed to less coking and higher stability of the Ni particle size due to the introduction of Mg.     

Nano‐engineered nickel catalysts supported on 4‐channel α‐Al2O3 hollow fibers for dry reforming of methane

A nickel (Ni) nanoparticle catalyst, supported on 4‐channel α‐Al₂O₃ hollow fibers, was synthesized by atomic layer deposition (ALD). Highly dispersed Ni nanoparticles were successfully deposited on the outside surfaces and the inside porous structures of hollow fibers. The catalyst was employed to catalyze the dry reforming of methane (DRM) reaction and showed a methane reforming rate of 2040 Lh^?1gNi^?1 at 800°C. NiAl₂O₄ spinel was formed when Ni nanoparticles were deposited on alpha‐alumina substrates by ALD, which enhanced the Ni‐support interaction. Different cycles (two, five, and ten) of Al₂O₃ ALD films were applied on the Ni/hollow fiber catalysts to further improve the interaction between the Ni nanoparticles and the hollow fiber support. Both the catalyst activity and stability were improved with the deposition of Al₂O₃ ALD films. Among the Al₂O₃ ALD coated catalysts, the catalyst with five cycles of Al₂O₃ ALD showed the best performance. © 2018 American Institute of Chemical Engineers AIChE J, 64: 2625–2631, 2018     

Preparation of Highly Active Nickel Catalysts Supported on Mesoporous Nanocrystalline γ‐Al2O3 for Methane Autothermal Reforming

Autothermal reforming (ATR) of methane was carried out over nanocrystalline Al₂O₃‐supported Ni catalysts with various Ni loadings. Mesoporous nanocrystalline γ‐Al₂O₃ powder with high specific surface area was prepared by the sol‐gel method and employed as support for the nickel catalysts. The prepared samples were characterized by X‐ray diffraction, Brunauer‐Emmett‐Teller, temperature‐programmed reduction, temperature‐programmed hydrogenation, and scanning electron microscopy techniques. It is demonstrated that the methane conversion increased with increasing in Ni content and that the catalyst with 25 wt % Ni exhibited the highest activity and a stable catalytic performance in the ATR process, with a low degree of carbon formation. Furthermore, the effects of the reaction temperature, the calcination temperature, the steam/CH₄ and O₂/CH₄ ratios, and the gas hourly space velocity on the catalytic performance of the 25 % Ni/Al₂O₃ catalyst were investigated.     

Ni‐Al2O3/Ni‐foam catalyst with enhanced heat transfer for hydrogenation of CO2 to methane

Monolithic Ni‐Al₂O₃/Ni‐foam catalyst is developed by modified wet chemical etching of Ni‐foam, being highly active/selective and stable in strongly exothermic CO₂ methanation process. The as‐prepared catalysts are characterized by x‐ray diffraction scanning electron microscopy, inductively coupled plasma atomic emission spectrometry, and H₂‐temperature programmed reduction‐mass spectrometry. The results indicate that modified wet chemical etching method is working efficiently for one‐step creating and firmly embedding NiO‐Al₂O₃ composite catalyst layer (～2 μm) into the Ni‐foam struts. High CO₂ conversion of 90% and high CH₄ selectivity of >99.9% can be obtained and maintained for a feed of H₂/CO₂ (molar ratio of 4/1) at 320°C and 0.1 MPa with a gas hourly space velocity of 5000 h^?1, throughout entire 1200 h test over 10.2 mL such monolithic catalysts. Computational fluid dynamics calculation and experimental measurement consistently confirm a dramatic reduction of “hotspot” temperature due to enhanced heat transfer. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4323–4331, 2015     

TPD‐TG‐MS Investigations of the Catalytic Conversion of Glycerol over MOx‐Al2O3‐PO4 Catalysts

The catalytic performance of bifunctional catalysts, MO_x‐Al₂O₃‐PO₄, that contain acidic centers and different transition metal oxide components were evaluated in the gas‐phase dehydration of glycerol using the TPD‐TG‐MS technique and a continuous flow reactor experiment. The initial catalytic activity and selectivity to acrolein and acetol significantly depends on the acidity and the type of transition metal oxide. The higher the total acidity, the higher the acrolein selectivity in the order W > Mo > Cu > V~ Fe ~Cr > Ce. On the other hand, Mn‐, Cr‐, and Fe‐containing catalysts favor the formation of products of oxidative C‐C cleavage. TPD‐TG‐MS investigations of catalysts loaded with glycerol are useful tools for fast‐screening of initial activities of catalysts in the gas‐phase dehydration of glycerol.     

Promoted Fe2O3‐Al2O3‐CuO Chromium‐Free Catalysts for High‐Temperature Water‐Gas Shift Reaction

Promoted Fe₂O₃‐Al₂O₃‐CuO (FAC) chromium‐free catalysts were prepared for high‐temperature water‐gas shift reactions and characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller method (BET), temperature‐programmed reduction (TPR), and transmission electron microscopy (TEM) techniques. The catalytic results revealed that among the investigated promoted catalysts with Ce, La, Zn, Y, and Mn as promoters, the Mn‐promoted sample showed higher activity compared to the other promoted catalysts. Increasing the Mn content improved the surface area and catalytic activity. The FAC catalyst promoted with a high Mn content exhibited maximum activity and relatively high stability in high‐temperature water‐gas shift reaction.     

Oxidation of 4‐nitrophenol in water over Fe(III), Co(II), and Ni(II) impregnated MCM41 catalysts

BACKGROUND: Nitrophenols are toxic constituents of the effluents of petroleum, textile, dye, iron and steel, foundries, pharmaceutical and electrical manufacturing industries. Aromatic nitro compounds are particularly resistant to normal chemical or biological oxidation making them environmentally persistent. Advanced oxidation using appropriate catalysts mineralize these organics to harmless final products. In this work, MCM41‐based catalysts incorporating Fe(III)‐, Co(II)‐ and Ni(II)‐ cations were used for oxidizing 4‐nitrophenol in water under variable conditions of reaction time, pH, mole ratio of the reactant and the oxidant, catalyst load, feed concentration, and temperature. RESULTS: The catalysts prepared were characterized with X‐ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), cation exchange capacity (CEC) and atomic absorption spectrometry (AAS) measurements. In typical reaction conditions of temperature 353 K, time 300 min, catalyst load 2 g L^?1 and 10^?3 mol L^?1 4‐nitrophenol, the oxidation was 48.7, 52.2 and 55.2% with H₂O₂ and 42.5, 56.6 and 60.2% without H₂O₂ for Fe(III)‐, Co(II)‐ and Ni(II)‐MCM41, respectively. Pseudo‐first‐order kinetics with kinetic constant of 2.0 × 10^?3 to 5.5 × 10^?3 Lg^?1 min^?1 was proposed along with a possible mechanism. 4‐nitrocatechol, 4‐nitropyrogallol, 1,2,4‐trihydroxybenzene, hydroquinone, acrylic acid, malonic acid, and oxalic acid were identified in the oxidation products. CONCLUSION: Introduction of Fe(III)‐, Co(II)‐ and Ni(II)‐ into MCM‐41 by impregnation produced effective catalysts for wet oxidation of 4‐nitrophenol. The catalysts were able to oxidize 4‐NP even without the presence of an oxidizing agent. The results suggest that the transition metal loaded MCM41 brings about a more effective interaction between 4‐NP molecules and OH radicals. Copyright © 2008 Society of Chemical Industry     

Synthesis of high‐molecular weight poly(trimethylene terephthalate) catalyzed by MoO3 supported Al2O3‐TiO2 catalysts

Poly(trimethylene terephthalate) (PTT) is an excellent fiber materials. Although it was synthesized as early as 1940s, obtaining high‐molecular weight PTT suitable for spinning is not easy due to no evident breakthrough in the catalysts for PTT synthesis. Patents and literatures disclosed a lot of the catalysts of preparing PTT, but which are more or less disadvantageous. Based on acid catalytic mechanism of PTT preparation, a series of solid acid as x% MoO₃/(50% Al₂O₃ ? 50% TiO₂) (briefly written as xM/(A ? T), x = 0, 10, 15, 20 by weight) were prepared by sol–gel coprecipitation and wetting impregnation methods, and first used for PTT synthesis in this work. When 50% Al₂O₃ ? 50% TiO₂ (briefly written as A ? T) was supported by MoO₃ using wetting impregnation technique of (NH₄)₆Mo₇O₂₄.4H₂O aqueous solution, a lot of Brφnsted acid and Lewis acid sites were formed on xM/(A ? T) catalyst surfaces, which was confirmed by the characteristics of their NH₃‐TPD (temperature programmed desorption). All the prepared catalysts were highly active ones toward synthesis of PTT. PTT with high‐intrinsic viscosity (IV) was obtained in the presence of trace amount of the catalysts. IV ranging of the PTT synthesized from 0.66 to 0.95 dL g^?1 corresponds to weight average molecular weight from 49,197 to 73,004. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Cr‐Doped La‐Ni‐O Catalysts Derived from Perovskite Precursors for CH4‐CO2 Reforming under Microwave Irradiation

The nickel catalysts derived from Cr‐doped LaNiO₃ perovskite‐like precursors were characterized by X‐ray diffraction, high‐resolution transmission electron microscopy, temperature‐programmed oxidation, temperature‐programmed reduction, and X‐ray photoelectron spectroscopy. Their catalytic performance in CO₂ reforming of methane under microwave irradiation was investigated. It was found that the structure and morphology of the oxide composites in this research were influenced by the ratio of Ni and Cr, and the mismatch of La³⁺, Ni³⁺, and Cr³⁺ may cause phase segregation. The catalytic performance of the Ni catalysts is dependent on the oxygen mobility of the perovskite oxide matrix, the content of the reduced Ni⁰, and the content of the remaining perovskite structure. The mobile oxygen in the perovskite matrix in the catalyst may enhance the conversion of CO₂ during the reaction.     

Katalysatorcharakterisierung mit O2‐TPD,N2‐ und Kr‐Gassorption sowie REM am Beispiel der Epoxidierung von 1,3‐Butadien

The temperature‐programmed O₂ desorption (O₂‐TPD), the N₂‐ and Kr‐ sorption as well as the scanning‐electron microscope (SEM) are important analysis methods in catalysis chemistry. By the example of a corundum and of a calcium hexaaluminate substrate the methods are used and the potential regarding to the surface properties and the activity of the assigned catalysts thereby pointed. Which of the two catalyst systems for the Ag‐catalyzed epoxidation of 1,3‐butadiene to 3,4‐epoxy‐1‐butene is more favorable is tested in a tubular reactor.     

Continuous Hydrogenation of Toluene over Sr‐ and PEG800‐Modified Ni/γ‐Al2O3 Catalysts

A series of γ‐Al₂O₃‐supported nickel‐based catalysts were evaluated in continuous hydrogenation of toluene. Sr‐ and poly(ethylene glycol) 800 (PEG800)‐modified Ni/γ‐Al₂O₃ catalysts provided the best activity with high conversion of toluene and selectivity for methylcyclohexane which was ascribed to the addition of Sr and PEG800 during the preparation process, resulting in smaller and highly dispersed Ni species on the surface and in the pores of γ‐Al₂O₃. Furthermore, the formation of SrCO₃ and NiAl₂O₄ is believed to be advantageous for the dispersion and stabilization of the active Ni species, accounting for its good stability.     

Catalytic Oxidative Dehydrogenation of n‐Butane on Gallium Nitride‐Containing Titanosilicate Catalyst

GaN‐containing titanosilicate catalysts were used for the first time for the oxidative dehydrogenation (ODH) of n‐butane at a relatively low reaction temperature (460 °C). Commercially available GaN powder with a wurtzite crystal structure showed superior reactivity and stability for the ODH of n‐butane. The catalytic property of GaN catalyst for ODH strongly depends on the GaN particle size. The effects of the GaN weight percentage and GaN particle size on the catalytic performance are investigated in a fixed bed reactor. Based on the physicochemical properties of the catalyst characterized via TEM, DLS, N₂ adsorption‐desorption, XRF, O₂‐TPD, XRD, XPS, and in‐situ FTIR, the textural and structural properties of catalyst were obtained. The catalytic results reveal that the presence of GaN increases the activity of the catalysts, indicating that GaN can be used as a new active phase for the ODH of n‐butane. XRD, XPS, O₂‐TPD, DLS, TEM, and in‐situ FTIR results show that activated O species exist on the surface of the GaN catalyst and enhance the catalytic performance with a decreasing GaN particle size, suggesting that smaller GaN particles possess a remarkable capability to activate O species in O₂ and C‐H bonds in light alkanes.     

Effects of Ga doping on Pt/CeO2‐Al2O3 catalysts for propane dehydrogenation

This paper describes catalytic consequencesThis paper describes catalytic consequences of Pt/CeO₂‐Al₂O₃ catalysts promoted with Ga species for propane dehydrogenation. A series of PtGa/CeO₂‐Al₂O₃ catalysts were prepared by a sequential impregnation method. The as‐prepared catalysts were characterized employing N₂ adsorption‐desorption, X‐ray diffrtaction, temperature programmed reduction, O₂ volumetric chemisorption, H₂‐O₂ titration, and transmission electron microscopy. We have shown that Ga³⁺ cations are incorporated into the cubic fluorite structure of CeO₂, enhancing both lattice oxygen storage capacity and surface oxygen mobility. The enhanced reducibility of CeO₂ is indicative of higher capability to eliminate the coke deposition and thus is beneficial to the improvement of catalytic stability. Density functional theory calculations confirm that the addition of Ga is prone to improve propylene desorption and greatly suppress deep dehydrogenation and the following coke formation. The catalytic performance shows a strong dependence on the content of Ga addition. The optimal loading content of Ga is 3 wt %, which results in the maximal propylene selectivity together with the best catalytic stability against coke accumulation. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4365–4376, 2016     

Polymerization of 4‐(4′‐N‐1,8‐naphthalimidophenyl)‐1,2,4‐triazolidine‐3,5‐dione with diisocyanates

4‐(4′‐Aminophenyl)‐1,2,4‐triazolidine‐3,5‐dione ( 1 ) was reacted with 1,8‐naphthalic anhydride ( 2 ) in a mixture of acetic acid and pyridine (3 : 2) under refluxing temperature and gave 4‐(4′‐N‐1,8‐naphthalimidophenyl)‐1,2,4‐triazolidine‐3,5‐dione ( NIPTD ) ( 3 ) in high yield and purity. The compound NIPTD was reacted with excess n‐propylisocyanate in N,N‐dimethylacetamide solution and gave 1‐(n‐propylamidocarbonyl)‐4‐[4′‐(1,8‐naphthalimidophenyl)]‐1,2,4‐triazolidine‐3,5‐dione ( 4 ) and 1,2‐bis(n‐propylamidocarbonyl)‐4‐[4′‐(1,8‐naphthalimidophenyl)]‐1,2,4‐ triazolidine‐3,5‐dione ( 5 ) as model compounds. Solution polycondensation reactions of monomer 3 with hexamethylene diisocyanate ( HMDI ), isophorone diisocyanate ( IPDI ), and tolylene‐2,4‐diisocyanate ( TDI ) were performed under microwave irradiation and conventional solution polymerization techniques in different solvents and in the presence of different catalysts, which led to the formation of novel aliphatic‐aromatic polyureas. The polycondensation proceeded rapidly, compared with conventional solution polycondensation, and was almost completed within 8 min. These novel polyureas have inherent viscosities in a range of 0.06–0.20 dL g^?1 in conc. H₂SO₄ or DMF at 25°C. Some structural characterization and physical properties of these novel polymers are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2861–2869, 2003     

Catalytic activity of Pt‐Re‐Pb/Al2O3 naphtha reforming catalysts

BACKGROUND: The main purpose of the naphtha reforming process is to obtain high octane naphtha, aromatic compounds and hydrogen. The catalysts are bifunctional in nature, having both acid and metal sites. The metal function is supplied by metal particles (Pt with other promoters like Re, Ge, Sn, etc.) deposited on the support. The influence of the addition of Pb to Pt‐Re/Al₂O₃ naphtha reforming catalysts was studied in this work. The catalysts were prepared by co‐impregnation and they were characterized by means of temperature programmed reduction, thermal programmed desorption of pyridine and several test reactions such as cyclohexane dehydrogenation, cyclopentane hydrogenolysis and n‐heptane reforming. RESULTS: It was found that Pb interacts strongly with the (Pt‐Re) active phase producing decay in the metal function activity. Hydrogenolysis is more affected than dehydrogenation. Part of the Pb is deposited over the support decreasing the acidity and the strength of the most acidic sites. CONCLUSION: The n‐heptane reforming reaction shows that Pb modifies the stability and selectivity of the Pt‐Re catalysts. Small Pb additions increase the stability and greatly improve the selectivity to C₇ isomers and aromatics while they decrease the formation of low value products such as methane and gases. Copyright © 2011 Society of Chemical Industry     

Structure and catalytic consequence of Mg‐modified VOx/Al2O3 catalysts for propane dehydrogenation

Supported VO_x catalysts are promising nonoxidative propane dehydrogenation (PDH) materials for their commercially attractive activity and propylene selectivity. However, they frequently suffer from rapid deactivation caused by coke deposition. This article describes the promoting role of magnesium on the stability of VO_x/Al₂O₃ catalysts for PDH. A series of VO_x/Al₂O₃ and Mg‐modified VO_x/Al₂O₃ catalysts were synthesized by an incipient wetness impregnation method. The catalysts were carefully characterized by Raman spectra, UV‐Vis spectra, STEM, TGA and in situ DRIFTS. We showed that the stability of a 12V/Al₂O₃ catalyst was significantly improved on addition of small amounts of MgO. Experimental evidences indicate that V₂O₅ nanoparticles emerge in the 12V/Al₂O₃ samples, and appropriate Mg addition helps dispersing the V₂O₅ nanoparticles into 2D VO_x species thus decreasing coke formation and improving stability in nonoxidative dehydrogenation of propane. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Isomérisation du n‐hexane sur des catalyseurs Ni‐WOx/Al2O3‐SiO2

Isomerization of n‐hexane into bi‐ and tri‐branched products was studied at atmospheric pressure on Ni‐WO_x/Al₂O₃‐SiO₂ catalysts. Two groups of catalysts (A and B) were prepared by using the sol‐gel method. The objective of the present study is the selection of the catalyst having the best isomer (bi‐ and tri‐branched) yield under optimum operating conditions (reaction temperature, reduction temperature, flow duration, etc.). The results show that the introduction of tungsten (group B) modifies siginificantly the catalyst activity and that the optimum nickel amount in these catalysts is 15 wt. %. When a steady flow is achieved (100 min), the catalyst containing 15 % nickel and 10 % tungsten exhibits the highest and largest selectivity at a reaction temperature of 250°C and a reduction temperature of 430°C.     

Coprecipitated Ni‐Co Bimetallic Nanocatalysts for Methane Dry Reforming

Methane dry reforming was studied over nanostructure bimetallic Ni‐Co‐MgO catalysts. The catalysts were prepared by coprecipitation with different Ni‐Co contents and characterized by XRD, BET, N₂ adsorption/desorption, temperature‐programmed reduction (TPR), SEM, and temperature‐programmed oxidation (TPO) techniques. XRD results let conclude that all samples contained MgO crystallite phases. With a higher Ni content the intensity of the diffraction peaks became stronger, indicating growth of the crystallite size of the prepared solid solutions. BET analysis demonstrated that a higher Ni‐Co content decreased the surface area. The optimal catalyst could be determined which had the highest activity and a good stability in dry reforming reaction.     

Light FCC gasoline olefin oligomerization over a magnetic NiSo4/γ‐Al2o3 catalyst in a magnetically stabilized bed

Magnetic NiSO₄/γ‐Al₂O₃ catalysts were prepared by impregnating NiSO₄ solutions onto the γ‐Al₂O₃ support containing a magnetic material of Fe₃O₄. Characterization by XRD, NH₃‐TPD, and thermal analysis showed that the magnetic NiSO₄/γ‐Al₂O₃ catalyst with a nickel content of 7.0% by weight had a monolayer dispersion of NiSO₄ and the largest number of moderate strength acid sites, and a high specific saturation magnetization. The magnetic catalyst was evaluated for light FCC gasoline olefin oligomerization in both fixed‐bed and magnetically stabilized bed (MSB) reactors. Comparing with that in the fixed‐bed reactor, the optimal reaction temperature in the MSB lowered to 443 K, and its space velocity ranged broadly from 2.0 to 6.0 h^?1. The sulfur‐free diesel distillate produced by operation of the MSB for 100 h had higher cetane number and good low‐temperature flow property, which illuminates a promising application of the MSB to manufacture clean diesel fuels with high productivity and flexibility. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Enhanced oxygen mobility and reactivity for ethanol steam reforming

This article describes a strategy for increasing oxygen storage capacity (OSC) of ethanol steam reforming (ESR) catalysts. Sintering and carbon deposition are major defects of nickel‐based catalysts for ESR; tuning oxygen mobility (OM) of CeO₂‐based supports can overcome these drawbacks and promote H₂ production. We have successfully increased OSC and OM by adding Mg into the lattice of Ni/CeO₂ to promote H₂ production in ESR. The insertion of Mg into the CeO₂ lattice efficiently promotes the reduction of Ce⁴⁺ according to X‐ray powder diffraction (XRD) and temperature‐programmed reduction (TPR) analysis. Mg‐modified Ni/CeO₂ catalysts have larger OSC and smaller nickel crystallite size compared with bare Ni/CeO₂. The optimal Mg addition is 7 mol % (Ni/7MgCe) with the best OM. We also present evidence indicating that Mg addition significantly promotes ethanol conversion and H₂ production in ESR, and that Ni/7MgCe yields the best performance due to the high OM of the support. These Mg‐modified catalysts also produce less carbon deposition compared with Ni/CeO₂, and the amount of deposited carbon decreases with increasing Mg addition. Ni/7MgCe has the best resistance to carbon deposition owing to the excellent OM. © 2011 American Institute of Chemical Engineers AIChE J, 2012