Non-promoted Catalyst Research Articles

Renewable Hydrogen Production from Butanol Steam Reforming over Nickel Catalysts Promoted by Lanthanides

Hydrogen is mainly produced by steam reforming of natural gas, a nonrenewable resource. Alternative and renewable routes for hydrogen production play an important role in reducing dependence on oil and minimizing the emission of greenhouse gases. In this work, butanol, a model compound of bio-oil, was employed for hydrogen production by steam reforming. The reaction was evaluated for 30 h in a tubular quartz reactor at 500 °C, atmospheric pressure, GHSV of 500,000 h−1, and an aqueous solution feed of 10% v/v butanol. For this reaction, catalysts with 20 wt.% NiO were prepared by wet impregnation using three supports: γ-alumina and alumina modified with 10 wt.% of cerium and lanthanum oxides. Both promoters increased the reduction degree of the catalysts and decreased catalyst acidity, which is closely related to coke formation and deactivation. Ni/La2O3–Al2O3 presented a higher nickel dispersion (14.6%) which, combined with other properties, led to a higher stability, higher mean hydrogen yield (71%), and lower coke formation per mass (56%). On the other hand, the nonpromoted catalyst suffered a significant deactivation associated with coke formation favored by its highest acidity (3.1 µmol m−²).

Catalysis by sulfides: Advanced IR/CO spectroscopy for the identification of the most active sites in hydrodesulfurization reactions

Sulfided CoMo supported on TiO2, Al2O3, or SiO2 was studied by CO adsorption followed by infrared spectroscopy (IR/CO). The inversion of adsorption isotherms obtained by IR spectroscopy (the 2D-IRIS method) was performed on promoted and nonpromoted catalysts to verify that ν(CO) vibration contributions from 2090 to 2000 cm−1 can be attributed to CO/CoMoS interactions, free of the contribution coming from the CO/nonpromoted S-edges of MoS2 nanoparticles. The second derivative of the spectra evidences the presence of three different promoted sites. Promotion of MoS2 by in situ chemical vapor deposition makes it possible to ascribe the different ν(CO/CoMoS) contributions to partially or totally promoted M-edges (2072–2074 cm−1, 2082–2085 cm−1) and partially promoted S-edges (2054–2057 cm−1). Then the IR/CO method highlights Co promotion on both edges (the S-edge and the M-edge) of MoS2 slabs. The hydrodesulfurization activity of these catalysts shows that the total concentration of promoted sites is an important but not unique factor, since the structures of the CoMoS sites modify their intrinsic activity. A parallel with the different CoMoS site amounts reveals that partially promoted M-edge sites of CoMo-supported catalysts are the most active for hydrodesulfurization. This makes IR/CO a direct way to account for the most active types of promoted sites of CoMo supported catalysts.

Surface-dependent activity of model CoMoS hydrotreating catalysts

The current environmental and industrial contexts require constant revision and improvement of hydrotreating processes for obtaining cleaner (bio)fuels through the development of supported transition metal sulfide (TMS) catalysts. The present work proposes a surface-science approach to describe the surface-dependent genesis of the cobalt-promoted active phase (CoMoS) supported on α-Al2O3 single crystals used as surrogates of the industrial γ-Al2O3 support. Co-Mo precursor solutions are deposited by aqueous-phase impregnation onto four α-Al2O3 single crystals of C(0001), A(112¯0), M(101¯0), and R(11¯02) orientations, which display specific OH sorption sites. The model catalysts are characterized in the oxide and sulfide states by XPS, AFM, and TEM revealing a surface dependent sulfidation and dispersion as a result of metal-support interactions of diverse nature. The surfaces can be ranked following metal-support interactions of increasing strength C(0001) < A(112¯0), M(101¯0) < R(11¯02) in good agreement with model non-promoted catalysts. However, AFM and TEM imaging also reveal that cobalt incorporation leads to an increase in the stacking of CoMoS particles with respect to non-promoted catalysts. The activity of the model catalysts in thiophene hydrodesulfurization cannot be simply related to the common features of the active phase (sulfidation, dispersion, promotion extent) but a volcano-shape curve is obtained when plotting the activity as a function of metal-support interactions. These results suggest that high activity is obtained on surfaces with intermediate metal-support interactions that lead to an optimal metal-sulfur bond energy in agreement with the Sabatier principle. Transposing these results to the traditional γ-Al2O3 support suggests an enhanced activity of the (100) facet, which can lead to the development of improved supports for hydrotreating catalysts.

Syngas Production by Dry Methane Reforming over Mg Doped NiO-ZrO&lt;sub&gt;2&lt;/sub&gt; Catalysts

In producing syngas, which offers environmental benefits, dry reforming of methane (DRM) could promote the installation of the future carbon tax. This reaction has been already extensively studied and nowadays, no stable catalysts are enough efficient to scale up the process to its industrialization. It has been suggested that basic sites can affect the performance of catalyst. It is known that magnesium promotes the performance of catalyst. In order to understand the effect of Mg for dry reforming of methane, NiO-MgO-ZrO2 catalysts were studied. The activity was carried out at 700 °C in a fixed-bed micro-reactor under CH4:CO2:Ar=1:1:8. It was shown that the introduction of Mg led to an unexpected decrease in the activity when compared to non-promoted catalyst. It was also shown that the surface area, pore-volume, pore diameter, and weak basicity decreased when the Mg was introduced into NiO-ZrO2 catalyst. All these properties can cause a decrease in the activity, selectivity, and stability of NiO-MgO-ZrO2 catalyst for DRM.

CO2 reforming of methane over Ni and/or Ru catalysts supported on mesoporous KIT-6: Effect of promotion with Ce

CO2 reforming of methane was studied over Ni and/or Ru supported on KIT-6 and KIT-6 promoted with Ce catalysts synthesized using the wet impregnation technique. The percent of nickel and ruthenium in all catalysts was fixed at 15 wt% and/or 1 wt% respectively. All catalysts were calcined at 550 °C and characterized by XRD, N2 adsorption/desorption, H2-TPR and CO2-TPD. All catalysts exhibited type IVa isotherms attributed to their mesoporous nature. Ce promotion resulted in a significant destruction of the porous structure which was demonstrated by the change in the shape of the isotherm as well as decreased surface areas and pore volumes. H2-TPR profiles showed reduction peaks corresponding to the reduction of agglomerated RuO2 species as well as different NiO species that are either free or in interaction with the support. It was noticed that the incorporation of Ce impaired the interactions between the active phase and the support. CO2-TPD profiles demonstrated that promoting the catalysts with Ce increased their basicity. Among the non-promoted catalysts, Ni-Ru/KIT-6 presented enhanced active phase dispersion, reducibility, and the highest basicity which resulted in an ameliorated catalytic performance. However, the promoted Ni-Ru/Ce-KIT-6 catalyst exhibited much higher activity and stability after 12 h on stream despite the formation of graphitic carbon resulting from the decomposition of methane.

Green Diesel Production over Nickel-Alumina Nanostructured Catalysts Promoted by Copper

A series of nickel–alumina catalysts promoted by copper containing 1, 2, and 5 wt. % Cu and 59, 58, and 55 wt. % Ni, respectively, (symbols: 59Ni1CuAl, 58Ni2CuAl, 55Ni5CuAl) and a non-promoted catalyst containing 60 wt. % Ni (symbol: 60NiAl) were prepared following a one-step co-precipitation method. They were characterized using various techniques (N2 sorption isotherms, XRD, SEM-EDX, XPS, H2-TPR, NH3-TPD) and evaluated in the selective deoxygenation of sunflower oil using a semi-batch reactor (310 °C, 40 bar of hydrogen, 96 mL/min hydrogen flow rate, and 100 mL/1 g reactant to catalyst ratio). The severe control of the co-precipitation procedure and the direct reduction (without previous calcination) of precursor samples resulted in mesoporous nano-structured catalysts (most of the pores in the range 3–5 nm) exhibiting a high surface area (192–285 m2 g−1). The promoting action of copper is demonstrated for the first time for catalysts with a very small Cu/Ni weight ratio (0.02–0.09). The effect is more pronounced in the catalyst with the medium copper content (58Ni2CuAl) where a 17.2% increase of green diesel content in the liquid products has been achieved with respect to the non-promoted catalyst. The copper promoting action was attributed to the increase in the nickel dispersion as well as to the formation of a Ni-Cu alloy being very rich in nickel. A portion of the Ni-Cu alloy nanoparticles is covered by Ni0 and Cu0 nanoparticles in the 59Ni1CuAl and 55Ni5CuAl catalysts, respectively. The maximum promoting action observed in the 58Ni2CuAl catalyst was attributed to the finding that, in this catalyst, there is no considerable masking of the Ni-Cu alloy by Ni0 or Cu0. The relatively low performance of the 55Ni5CuAl catalyst with respect to the other promoted catalysts was attributed, in addition to the partial coverage of Ni-Cu alloy by Cu0, to the remarkably low weak/moderate acidity and relatively high strong acidity exhibited by this catalyst. The former favors selective deoxygenation whereas the latter favors coke formation. Copper addition does not affect the selective-deoxygenation reactions network, which proceeds predominantly via the dehydration-decarbonylation route over all the catalysts studied.

Methanation of CO2 over zeolite–promoted Ni/Al2O3 nanocatalyst under atmospheric pressure

Zeolite was added at different weight percentages as a promoter to 10% Ni/Al2O3 and tested under atmospheric pressure for CO2 methanation for the first time. The influence of operational conditions and stability of the catalysts were investigated. The highest CO2 conversion of 99% and CH4 selectivity of 56% were achieved with 2% zeolite added catalyst at 350 °C reaction temperature. The textural and morphological characteristics of the non-promoted and zeolite promoted catalysts were established with Scanning electron microscopy, Fourier transform infrared spectrophotometer, BET analyser and X-Ray diffractometer. The addition of 2% zeolite increased the specific surface area of the catalyst while sustaining similar Ni metal surface area to the non-promoted one. However, at higher zeolite content, the CH4 selectivity reduced considerably due to the reduced Ni dispersion and specific surface area. The calcination temperature of 400 °C, H2/CO2 ratio of 4, GHSV of 72,000 SmL(gcat h)−1 resulted in the highest CH4 selectivity. The 2% zeolite added catalyst demonstrated superior resistance to deactivation in comparison to the non-promoted catalyst showing potential as a low-cost catalyst for further optimization studies.

Direct conversion of CO2 into methanol over promoted indium oxide-based catalysts

Supported indium oxide catalysts are investigated for the CO2 hydrogenation to methanol at a total pressure of 40 bar (528–573 K) using a laboratory flow reactor. Surface reducibility, optical spectral characteristics, and catalytic rates and selectivity were correlated to catalyst composition. Promoted catalysts, especially Yttrium or Lanthanum-promoted indium oxide, require higher temperatures (H2-TPR) for surface reduction and display higher CO2 desorption temperatures (CO2-TPD). The promoted samples also have ˜20% higher methanol selectivity compared to the non-promoted catalyst, while having similar methanol formation rates (0.330–0.420 gMeOH gcat.−1 h−1 at 573 K). From 528 K to 558 K, methanol selectivity was over 80%, over all the promoted catalysts, and nearly 100% selectivity was observed at the low temperature range (˜528 K) investigated. The reaction kinetics of Y-promoted catalyst and the results of CO co-feeding experiments suggest that formate pathway is the likely reaction mechanism for methanol formation.

Syngas for Fischer-Tropsch synthesis by methane tri-reforming using nickel supported on MgAl2O4 promoted with Zr, Ce and Ce-Zr

Nickel catalysts supported on magnesium aluminate promoted with ZrO2, CeZrO2 and CeO2 were evaluated under methane tri-reforming reaction. MgAl2O4 synthesis was assisted by P123® surfactant, assuring high porosity. The catalysts were tested at 650 °C and 750 °C. Zr and CeZr promoted catalysts showed less coke deposition and increased conversions, mainly at 750 °C, while the non-promoted catalyst featured lowest reactants conversion due to an unstable performance caused by filamentous coke deposition. The H2/CO ratio produced at 750 °C was at around 2, suitable to FT synthesis. In situ XPD analysis suggested nickel remained active as Ni0 throughout the reaction, even in the oxidant environment, containing water and oxygen, and high-temperature exposure. Considering that nickel oxidation during the process is one of the concerns related to the catalyst deactivation during tri-reforming of methane, along with carbon deposition, these catalysts are promising to active and stable syngas production.

Increase of Ceria Redox Ability by Lanthanum Addition on Ni Based Catalysts for Hydrogen Production

The effects of lanthanum addition in Ni/CeO2 catalysts were investigated. The influence of synthetic procedures, namely, impregnation or coprecipitation of lanthanum and cerium oxide, were evaluated. Materials were analyzed by BET, AAS, DRIFT-MS, TPR, OSC, XRD, and SEM-EDX. Samples were tested in ethanol steam reforming (ESR). Both lanthanum-promoted samples exhibited a higher stability in time than nonpromoted catalyst. Nonetheless, catalytic behavior is strongly affected by the preparation method. TPR, OSC, and XRD analyses showed that the coprecipitation method allowed the best interaction between ceria and lanthana, leading to an increased redox ability and best catalytic performances as a result. A catalyst with a support prepared via the coprecipitation method showed ethanol conversion of 90% and hydrogen selectivity higher than 70% even after 60 h of reaction.

Effects of cerium and lanthanum on Ni-based catalysts for CO2 reforming of toluene

The dry reforming of toluene (DRT) has been studied on Cerium and Lanthanum-promoted Ni–Al catalysts derived from hydrotalcites precursors in the temperature range 300–800 °C. X-ray powder diffraction (XRD) and thermogravimetric and differential thermal analyses (TGA-DSC) of as-prepared samples confirmed the formation of the hydrotalcite structure. Temperature programmed reduction (TPR) and desorption (CO2-TPD) indicated that Ni phase reducibility and basicity of the catalysts were influenced by the presence of the promoters. Ce-promoted catalyst was reducible at lower temperatures and had higher total basicity than the La-promoted and non-promoted catalysts. Furthermore textural property of solid was modified after cerium incorporation. These factors played a key role in the enhancement of the catalytic activity and suppression of carbon deposition. Post-reaction characterization of the catalysts by Temperature Programmed Oxidation (TPO) and TGA-DSC evidenced a better resistance towards carbon deposition for the Ce and La promoted catalysts. The promoted and non-promoted catalysts showed similar toluene conversion but promoted catalysts presented lower carbon deposition after test.Benefit effect of Cerium promotion catalyst was related by its characteristic which greatly influenced the activity. Lanthanum promoted exhibited a similar textural and physico-chemical characteristic than non-promoted catalyst but showed a higher performance than this latter. Promotion-activity relationship of the La containing catalyst was related by the presence of La2O3 on Ni based catalyst which could influence the transport and the adsorption of the CO2 onto the active sites surface.

Ethylene Dimerization and Oligomerization to 1-Butene and Higher Olefins with Chromium-Promoted Cobalt on Carbon Catalyst

Industrial dimerization of ethylene to 1-butene is achieved with catalysts bearing ligand structures and activated by a co-catalyst. Here, we report that a Cr-promoted cobalt oxide on carbon catalyst was able to produce 1-butene with 53.5–82.4% total selectivity at ethylene conversions between 8.9 and 31.5% without the use of a co-catalyst. The Cr-promoted catalyst showed enhanced activity and stability compared to the nonpromoted catalyst. The characterization results revealed that the incorporation of Cr into the cobalt oxide on carbon catalyst was able to decrease the cobalt oxide particle size. Charge transfer from Cr to Co was also observed in the Cr-promoted catalyst compared to monometallic Co and Cr on carbon. The kinetic model built to rationalize the experimental observations predicted a 50% increase in active site dispersion in the Cr-promoted catalyst, which explained the 1.6× apparent reaction rate increase compared to the nonpromoted catalyst.

Insight into MgO promoter with low concentration for the carbon-deposition resistance of Ni-based catalysts in the CO2 reforming of CH4

The CO2 reforming of CH4 is studied over MgO-promoted Ni catalysts, which were supported on alumina prepared from hydrotalcite. This presents an improved stability compared with non-promoted catalysts. The introduction of the MgO promoter was achieved through the ‘‘memory effect’’ of the Ni-Al hydrotalcite structure, and ICP-MS confirmed that only 0.42 wt.% of Mg2+ ions were added into the Ni-Mg/Al catalyst. Although no differences in the Ni particle size and basicity strength were observed, the Ni-Mg/Al catalyst showed a higher catalytic stability than the Ni/Al catalyst. A series of surface reaction experiments were used and showed that the addition of a MgO promoter with low concentration can promote CO2 dissociation to form active surface oxygen arising from the formation of the Ni-MgO interface sites. Therefore, the carbon-resistance promotion by nature was suggested to contribute to an oxidative environment around Ni particles, which would increase the conversion of carbon residues from CH4 cracking to yield CO on the Ni metal surface.

Cobalt molybdenum nitrides co-promoted by chromium and potassium as catalysts for ammonia synthesis

Chromium and potassium compounds were added to the ammonia synthesis catalyst based on cobalt molybdenum nitrides. A better developed porous structure was obtained together with the increase of the catalytic activity. In comparison to the non-promoted catalyst, the total surface area and the catalytic activity increased more than 50%. The behavior of the system is discussed in light of the double-layer model of the catalyst surface.

Effect of promoter on selective hydrogenation of furfural over Cu-Cr/TiO2 catalyst

The selective hydrogenation of furfural has been investigated over the titania-supported monometallic (Cu) and bimetallic (Cu–Cr) catalysts. The catalytic performances were assessed over 4 h of run length under atmospheric pressure at the hydrogen-to-hydrocarbon ratio of 10.6 and 453 K. The results represented that the level of furfural conversion over the non-promoted catalyst was very low (below 10%) while the promoted one showed considerable furfural conversion during this period (higher than 70%). However, both catalysts exhibited high durability and selectivity towards furfuryl alcohol.

Sensitivity of supported MoS2-based catalysts to carbon monoxide for selective HDS of FCC gasoline: Effect of nickel or cobalt as promoter

The impact of CO, a by-product of biomass transformation, on the transformation of a model FCC gasoline composed of 2-methylthiophene (2MT) and 2,3-dimethylbut-2-ene (23DMB2N) molecules, over MoS2 based catalyst supported over alumina was investigated. More specifically, the effect of the presence and the type of the promoter (Ni or Co) was studied. A gain in activity in HDS of 2MT and hydrogenation of olefins has been confirmed in the presence of the catalysts promoted by cobalt or nickel. However, surpringly, depending on the promoter (Ni or Co), the effect of the presence of CO is really different. In fact, while the carbon monoxide has a significant negative impact on the CoMoS/Al2O3 catalyst for the transformation of model molecules, no effect is observed for other catalysts. These differences could be attributed to a lower adsorption energy of CO on the non-promoted catalyst and promoted by nickel relative to the catalyst promoted by cobalt as calculated.

Ni based catalysts promoted with cerium used in the steam reforming of toluene for hydrogen production

NixMg6−xAl1.8Ce0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800 °C and characterized by different physico-chemical methods. The catalysts are then reduced before their use in the steam reforming of toluene. The XRD and TG/DTA confirmed the formation of the hydrotalcite structure for the non-calcined samples. The N2 adsorption/desorption results revealed that all catalysts correspond to mesoporous materials. The study by temperature programmed reduction (H2-TPR) showed that the reducibility of the catalysts is influenced by the nickel content. The CO2-TPD results showed that the catalyst with high magnesium content present the highest basicity. The Ni2Mg4Al1.8Ce0.2 shows the best toluene conversion among all the catalysts and it was then compared to a non-promoted catalyst. The spent catalysts were characterized by TPO, TG/DTA and XRD and they didn't reveal any coke formation.

Low temperature hybrid plasma-catalytic methanation over Ni-Ce-Zr hydrotalcite-derived catalysts

The activity of Ceria and Zirconia-promoted Ni-containing hydrotalcite-derived catalysts was assayed in a hybrid plasma-catalytic process for the hydrogenation of carbon dioxide into methane at low temperatures and in the presence of a cold dielectric barrier discharge (DBD) plasma. High methane yields, around 80%, were measured under hybrid plasma-catalytic conditions, even at very low temperatures (110°C, adiabatic conditions). In the absence of plasma, acceptably high CO2 conversions and methane yields were only observed at temperatures higher than 330°C. The presence of completely reduced Ni-crystallites of intermediate size, more readily available on the non-promoted catalysts was found to enhance the methanation reaction. Ce and Zr addition did not result in a noticeable improvement of the catalytic activity.

Development and Application of Highly Efficient Catalyst for Oligomerization of Butane-Butylene Fraction for the Production of High-Octane Component of Motor Gasoline

Main steps of the development of the technology for synthesis of a catalyst based on high-silica zeolite ZSM-5 for oligomerization of butane-butylene fraction (BBF) are reported. Application of a new procedure for the zeolite surface modification makes it possible to improve the selectivity and yield of the target product (against the known analogues), to synthesize more branched (and, hence, with a higher octane numbers) oligomers at lower pressures. Introduction of a metal-promoter, Ga, provides 0,9 % higher yield of the target gasoline fraction as compared to that over the non-promoted catalyst. Comparative pilot testing of the samples of industrial (BAC-70U) and developed (Ga-ZSM-5/Al2O3) catalysts for BBF oligomerization at 300 °C, feed flow rate 1,5 mL BBF/(mL cat·h) showed that the yield of the target fraction is 7 % higher over the modified ZSM-5 than over BAC-70U. Throughout the testing (191 h), a higher quality of the oligomerizate produced over Ga-ZSM-5/Al 2 O 3 was observed: MON was 2 points higher and concentration of gums twice as little. The results obtained during studies and testing were used for the development and industrial implementation of the technology for the production of the zeolite-containing catalyst COB-1 for oligomerization. A 2,5 t batch of the industrial catalyst was produced by September 2016 at the facilities of the Redkino Catalyst Company. The next important step in the implementation of the Gazpromneft strategy for innovative development in oil refining is to achieve a test run of the new catalyst using the industrial combined setup for the production of MTBE and oligomerizate at the Gazpromneft-Moscow Refinery. The use of COB-1 at the Refinery will be an important step to improve efficiency of the process for synthesis of high-margin products – components of the commercial motor gasoline.

Transient Mechanistic Studies of Methane Steam Reforming over Ceria‐Promoted Rh/Al2O3 Catalysts

AbstractTransient‐pulse experiments in temporal‐analysis‐of‐product (TAP) and conventional mode were performed to determine elementary reaction steps involved in the methane steam reforming reaction over Rh/Al2O3 and Rh/12 CeO2–Al2O3. TAP pulse experiments demonstrated that both catalysts dissociate methane at 773 K leading to hydrogen, carbon, and CHx adspecies. Conventional transient pulse experiments with alternating methane/argon and water pulses with a delay between them of 86, 73, and 5 s, respectively, showed that the reactivity of adspecies over the promoted and nonpromoted catalysts decrease with time. Ceria catalyzes the oxidation of carbon species by water.