Combined Steam and CO₂ Reforming of Methane over Ni-Based CeO₂-MgO Catalysts: Impacts of Preparation Mode and Pd Addition

The sol–gel template technique makes it possible to synthesize a stable and efficient nickel catalyst based on magnesium-modified cerium oxide Ce0.5Mg0.5O1.5 for the combined steam and CO2 reforming of methane. To stabilize dispersed forms of the active component in the matrix of the support, the catalysts were synthesized by changing the support precursor (cerium acetate and chloride), the active component composition (Ni, NiPd) and the method of introducing nanoparticles. The relationship was established between the physicochemical and catalytic characteristics of the samples. The use of cerium acetate as a support precursor provided smaller pore and crystallite sizes of the support, a stabilization of the dispersed forms of the active component, and excellent catalytic characteristics. The introduction of Pd into the Ni nanoparticles (Pd/Ni = 0.03) increased the resistance of the active component to sintering during the reaction, ensuring stable operation for 25 h of operation. The increased stability was due to a higher concentration of defective oxygen, a higher dispersion of bimetallic NiPd nanoparticles, and the Ni clusters strongly interacting with the NiO-MgO solid solution. An efficient and stable Ni0.194Pd0.006Ce0.4Mg0.4O1.4 catalyst for the conversion of CO2 into important chemicals was developed. With the optimal composition and synthesis conditions of the catalyst, the yield of the target products was more than 75%

Selective Hydrogenation of 2-Methyl-3-butyn-2-ol in Microcapillary Reactor on Supported Intermetallic PdZn Catalyst, Effect of Support Doping on Stability and Kinetic Parameters

The development of active, selective, and stable multicrystalline catalytic coatings on the inner surface of microcapillary reactors addresses environmental problems of fine organic synthesis, in particular by reducing the large quantities of reagents and byproducts. Thin-film nanosized bimetallic catalysts based on mesoporous pure titania and doped with zirconia, ceria, and zinc oxide, for use in microreactors, were developed, and the regularities of their formation were studied. The efficiency of PdZn/TixM1−xO2±y (M = Ce, Zr, Zn) in the hydrogenation of 2-methyl-3-butyn 2-ol was studied with an emphasis on the stability of the catalyst during the reaction. The catalytic parameters depend on the adsorption properties and activity of PdZn and Pd(0) active centers. Under reaction conditions, resistance to the decomposition of PdZn is a factor that affects the stability of the catalyst. The zinc-doped coating proved to be the most selective and stable in the reaction of selective hydrogenation of acetylenic alcohols in a microcapillary reactor. This coating retained a high selectivity of 98.2% during long-term testing up to 168 h. Modification of the morphology and electronic structure of the active component, by doping titania with Ce and Zr, is accompanied by a decrease in stability

Hydrogen Production through Autothermal Reforming of Ethanol: Enhancement of Ni Catalyst Performance via Promotion

Autothermal reforming of bioethanol (ATR of C2H5OH) over promoted Ni/Ce0.8La0.2O1.9 catalysts was studied to develop carbon-neutral technologies for hydrogen production. The regulation of the functional properties of the catalysts was attained by adjusting their nanostructure and reducibility by introducing various types and content of M promoters (M = Pt, Pd, Rh, Re; molar ratio M/Ni = 0.003–0.012). The composition–characteristics–activity correlation was determined using catalyst testing in ATR of C2H5OH, thermal analysis, N2 adsorption, X-ray diffraction, transmission electron microscopy, and EDX analysis. It was shown that the type and content of the promoter, as well as the preparation mode (combined or sequential impregnation methods), determine the redox properties of catalysts and influence the textural and structural characteristics of the samples. The reducibility of catalysts improves in the following sequence of promoters: Re < Rh < Pd < Pt, with an increase in their content, and when using the co-impregnation method. It was found that in ATR of C2H5OH over bimetallic Ni-M/Ce0.8La0.2O1.9 catalysts at 600 °C, the hydrogen yield increased in the following row of promoters: Pt < Rh < Pd < Re at 100% conversion of ethanol. The introduction of M leads to the formation of a NiM alloy under reaction conditions and affects the resistance of the catalyst to oxidation, sintering, and coking. It was found that for enhancing Ni catalyst performance in H2 production through ATR of C2H5OH, the most effective promotion is with Re: at 600 °C over the optimum 10Ni-0.4Re/Ce0.8La0.2O1.9 catalyst the highest hydrogen yield 65% was observed

Hydrogen Production through Bi-Reforming of Methane: Improving Ni Catalyst Performance via an Exsolution Approach

Hydrogen production through the bi-reforming of methane over exsolution-derived Ni catalysts has been studied. Nickel-based catalysts were prepared through the activation of (CeM)1−xNixOy (M = Al, La, Mg) solid solutions in a reducing gaseous medium. Their performance and resistance to coking under the reaction conditions were controlled by regulating their textural, structural, morphological, and redox properties through adjustments to the composition of the oxide matrix (M/Ce = 0–4; x = 0.2–0.8; y = 1.0–2.0). The role of the M-dopant type in the genesis and properties of the catalysts was established. The efficiency of the catalysts in the bi-reforming of methane increased in the following series of M: M-free 1−xNixOy catalysts. At 800 °C the optimum Ce0.6Mg0.2Ni0.2O1.6 catalyst provided a stable H2 yield of 90% at a high level of CO2 and CH4 conversions (>85%)

Hydrogen Production through Bi-Reforming of Methane: Improving Ni Catalyst Performance via an Exsolution Approach

Hydrogen production through the bi-reforming of methane over exsolution-derived Ni catalysts has been studied. Nickel-based catalysts were prepared through the activation of (CeM)1−xNixOy (M = Al, La, Mg) solid solutions in a reducing gaseous medium. Their performance and resistance to coking under the reaction conditions were controlled by regulating their textural, structural, morphological, and redox properties through adjustments to the composition of the oxide matrix (M/Ce = 0–4; x = 0.2–0.8; y = 1.0–2.0). The role of the M-dopant type in the genesis and properties of the catalysts was established. The efficiency of the catalysts in the bi-reforming of methane increased in the following series of M: M-free < La < Al < Mg, correlating with the structural behavior of the nickel active component and the anti-coking properties of the support matrix. The preferred M-type and M/Ce ratio determined the best performance of (CeM)1−xNixOy catalysts. At 800 °C the optimum Ce0.6Mg0.2Ni0.2O1.6 catalyst provided a stable H2 yield of 90% at a high level of CO2 and CH4 conversions (>85%)

Nanoscale control during synthesis of Me/La2O3, Me/CexGd1-xOy and Me/CexZr 1-xOy (Me = Ni, Pt, Pd, Rh) catalysts for autothermal reforming of methane

Supported catalysts Me/La2O3, Me/CexGd1−xOy and Me/CexZr1−xOy (Me = Ni, Pt, Pd, Rh) were developed for the autothermal reforming of methane (ATR of CH4). The influence of support composition (La2O3, CexGd1−xOy, x = 0.50–0.90 and CexZr1−xOy, x = 0.33–0.67), type and content of the active component (5–30 wt% Ni; 0.5–1.5 wt% Pt, Pd or Rh) on the nanostructure of catalysts and their performance in the ATR of CH4 was investigated. The properties and structure of the catalysts in the course of their preparation and operation in the reaction were systematically characterized by means of X-ray diffraction, BET N2 adsorption/desorption, H2 temperature-programmed reduction, transmission electron microscopy and X-ray photoelectron spectroscopy techniques. The state and particle size of Ni-containing species were regulated by the support composition and Ni content. In case of the La2O3 support, the strong interaction between NiO and La2O3 led to the formation of two binary oxides LaNiO3 and La2NiO4 in the fresh samples, the composition of which was regulated by the Ni content. In case of the CexGd1−xOy and CexZr1−xOy supports, in contrast to the La2O3 support, nickel oxide and ceria-based solid solution were formed in the fresh samples. The catalyst evolution under reaction condition was studied. The conversion of methane and product (H2, CO) yields considerably increased when Ce0.8Gd0.2Oy or Ce0.5Zr0.5Oy instead of La2O3 were used as catalyst supports: at 850 °C the yields of ∼35% H2 and ∼41% CO at CH4 conversion ∼76% were observed for the 10 wt%Ni/La2O3, while the yields of ∼49% H2 and ∼66% CO at CH4 conversion ∼97% were observed for the 10 wt% Ni/Ce0.5Zr0.5O2, which correlates with the increase of reducibility of Ni species as a result of weakening of the Ni–support interaction. The optimal value of metal content for the catalyst performance also depends on the support composition. The best ATR of CH4 performance is provided by 10 wt% Ni/Ce0.5Zr0.5O2 and 1 wt% Rh/Ce0.8Gd0.2O2 catalysts.The presented research has received funding from the European Union 7th Framework Programme (FP7/2007–2013) under grant agreement No. 262840.Peer Reviewe

Design of highly efficient catalyst for rational way of direct conversion of methane

Copyright (c) 2015 Eurasian Chemico-Technological JournalEffects of composition and preparation method of MnNaW/SiO2 and LaSr/CaO catalysts on their physical-chemical properties and performance in oxidative coupling of methane (OCM) have been studied. For MnNaW/SiO2 catalysts the synthesis method and type of SiO2 have a significant effect on the texture, while the Na/W ratio determines the phase composition. The variation of preparation method and temperature of catalyst calcination allows regulation of the metal surface concentration and mode of metal distribution across the SiO2 support. For LaSr/CaO catalysts the synthesis method determines the specific surface area, surface and phase composition. Correlations between catalyst performance, preparation method and state of the catalyst were established. The rational preparation procedure and perspective composition of OCM catalyst have been developed. The 20La/CaO catalysts prepared by citrate sol-gel method were shown to provide ~20% C2 yield and ~40% methane conversion at 800 ºC.The presented research was initiated by European Union 7th Framework Programme (FP7/2007–2013) under grant agreement No. 262840 and has received funding from Russian Federal Agency of Scientific Organizations (V45-1-10).Peer Reviewe

Hydrogen production by autothermal reforming of methane: Effect of promoters (Pt, Pd, Re, Mo, Sn) on the performance of Ni/La2O3 catalysts

We developed bimetallic catalysts Ni–Me/La2O3 (Me = Pt, Pd, Re, Mo, Sn) for hydrogen production by autothermal reforming of methane (ATR of CH4). The preparation procedure was based on the reduction of an appropriate LaNi1 − xMexO3 (x = 0.01–0.05) perovskite precursor obtained by the citrate sol–gel method. We investigated the effects of promoter type and molar ratio Me/Ni (Me = Pt, Pd, Re, Mo, Sn; Me/Ni = 0.01–0.05) on the structural, reducing and catalytic properties of Ni–Me/La2O3 samples in the ATR of CH4 and systematically studied the genesis of catalysts by means of X-ray diffraction, thermogravimetric and differential thermal analysis, Ar adsorption, H2 temperature-programmed reduction, high-resolution transmission electron microscopy with energy-dispersive X-ray analysis, and X-ray photoelectron spectroscopy techniques. The genesis of the active phase is shown to be strongly affected by the promoter type. The Pt, Re, Mo or Sn promoters in contrast to Pd impede the destruction of LaNiO3 structure and formation of Ni0 phase. The catalytic performance of Ni–Me/La2O3 samples in the ATR of CH4 can be regulated by the type and content of the promoter. At low reaction temperatures (700–800 °C) and at the molar ratio Me/Ni = 0.01 the conversion of methane and product (H2, CO) yields increases in the following order of promoters: Pt < Sn < Mo < Re < Pd, which correlates with the increase of reducibility of Ni species as a result of promoter addition. At 850 °C the LaNi0.99Pd0.01O3 catalyst provided the yields of ∼41% H2 and ∼57% CO at CH4 conversion ∼100% during a stability test that lasted 24 h.The presented research has received funding from the European Union 7th Framework Programme (FP7/2007–2013) under Grant Agreement No. 262840 (Project DEMCAMER).Peer Reviewe

Hydrogen production by autothermal reforming of methane over NiPd catalysts: Effect of support composition and preparation mode

NiPd/Ce0.5Zr0.5O2/Al2O3 and NiPd/La2O3/Ce0.5Zr0.5O2/Al2O3 catalysts were prepared by incipient wetness co-impregnation method or sequential impregnation method for autothermal reforming of methane (ATR of CH4). The influence of the preparation mode, Ce0.5Zr0.5O2 and La2O3 additives on the physicochemical properties of NiPd supported catalysts and the effect on their activity to produce hydrogen by ATR of CH4 were investigated. Characterization of fresh and spent Ni-based catalysts by X-ray fluorescence spectroscopy, N2 adsorption, X-ray diffraction, H2 temperature-programmed reduction, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were performed. It was demonstrated that support composition determines NiO dispersion as well as reducibility of Ni species through different strength of Ni-support interaction. The preparation method modifies the phase composition and catalyst ability for reduction. The catalyst evolution under reaction conditions was studied. The NiO (∼15 nm) and NiPd alloy (∼18 nm) phases were observed in the spent catalysts. It was found that the Nio/NiO ratio can be regulated by support composition and preparation mode of catalysts. It is demonstrated that studied catalysts provide high methane conversion of 90–100%, CO yield of 55–85% and H2 yield of 55–75% in ATR of CH4 at 750–950 °C. The optimal composition and preparation method of catalyst were selected. The best ATR of CH4 performance is provided by 10 Ni0.5Pd/10Ce0.5Zr0.5O2/Al2O3 catalyst prepared by Pd/Ni sequential impregnation method that can be associated with peculiarity of NiPd particles structure and the optimal ratio between NiO species with different ability for reduction.The presented research has received funding from the European Union 7th Framework Programme (FP7/2007–2013) under grant agreement No. 262840.Peer Reviewe