Dehydrogenation Of Ethanol Research Articles

A CuZn-BTC derived stable Cu/ZnO@SiO2 catalyst for ethanol dehydrogenation

Cu-based catalysts play pivotal role in many industrial processes, however, its application under high temperature is restricted due to the low Tammann temperature of Cu. Improving the stability and activity of Cu-based catalysts at high temperature is a challenge. In this work, a stable Cu/ZnO@SiO2 catalyst was prepared, in which silicon was introduced into CuZn-BTC precursor via a steam-assisted hydrolysis method before calcination and reduction. Characterizations found that Cu/ZnO@SiO2 catalyst prepared via above strategy possesses increased surface area, more exposed active sites and excellent stability for ethanol dehydrogenation than Cu/ZnO (prepared from CuZn-BTC without SiO2). It was confirmed that the space-time yield of acetaldehyde reached 9.0 g-acetaldehyde/g-cat/h, and Cu/ZnO@SiO2 could maintain its activity within 200 h at 350 °C due to the ZnO decorated Cu particles (Cu/ZnO) were encapsulated in the octahedral shaped SiO2 hollow.

Synthesis and characteristics of mesoporous carbon catalysts via sulfonation process from surfactant residue and their catalytic properties toward gas-phase ethanol dehydrogenation

BackgroundThe several mesoporous materials are captive for applying in the different catalytic application due to its unique characteristics, which directly affected to the different selectivity of catalytic activity. This research aims to consider the possibility of the synthesis, characteristics, and catalytic activity of the different mesoporous carbon materials (SBA-15-C, MCF-C, KIT-6-C, and TMS-C) derived from the corresponding mesoporous silica materials (SBA-15, MCF, KIT-6, and TMS). MethodsMesoporous silica-based materials such as SBA-15, TMS, MCF, and KIT-6 were straightly synthesized and transformed as silica-based materials to mesoporous carbon-based materials denoted as SBA-15/C, TMS/C, MCF/C, and KIT-6/C using the surfactant residue with sulfuric acid as sulfonation process in order to enhance the physicochemical properties. In addition, these carbon catalysts were compared up on characteristics and catalytic performance towards ethanol dehydrogenation to convert ethanol into acetaldehyde. Significant findingsIt revealed that these mesoporous silica-based materials were successfully converted to the promising mesoporous carbon-based materials having appropriate physicochemical properties including acid-base properties owing to the significant existence of the carbon source. The MCF/C exhibited remarkable catalytic activity than any other carbon materials on ethanol dehydrogenation. Moreover, MCF/C is also stable toward ethanol dehydrogenation along the extensive time of the operation with behavioral recyclability. Thus, MCF/C is captivating as a potential catalyst for ethanol dehydrogenation to acetaldehyde owing to the appropriate physicochemical characteristic of the well-defined mesoporous carbon catalyst

Thermal transformation of copper incorporated hydrotalcite-derived oxides and their catalytic activity for ethanol dehydrogenation

Thermal transformation of copper incorporated hydrotalcite-derived oxides is investigated in ethanol dehydrogenation. Among the copper supported catalyst c-10Cu/HT600 prepared by impregnation of thermally treated hydrotalcite at 600 °C with Cu(NO3)2 solution followed by a calcination provides a high catalytic activity, selectivity and stability. XRD, DR-UV, TGA, H2-TPR, CO2-TPD, TEM and XPS techniques reveal that the nature of the copper species depended on the thermal treatment process and support. Such treatment at high temperatures yields a homogeneous dispersion mixed metal oxide. After copper incorporation generated CuAl2O4 spinel structure linked to the copper oxide species can suppress copper agglomeration leading to the catalytic stability. Moreover, the c-10Cu/HT600 catalyst can provide a high activity and high selectivity to acetaldehyde even at low reaction temperatures (200 °C). However, the copper species may agglomerate to form relatively larger clusters upon increasing metal loading leading to the deactivation.

Appraisal of Ni Species Supported on Porous MgO during Ethanol Steam Reforming by XAS

AbstractOperando time‐resolved X‐ray absorption spectroscopy (XAS) was used to determine nickel species supported on porous MgO during the ethanol steam reforming reaction. The Principal Component Analysis (PCA) of the nickel K‐edge XAS spectra revealed Ni(OH)2, NiMgO, and metallic Ni during the activation and reaction of the catalysts. The Multivariate Curve Resolution‐Alternating Least Squares (MCR‐ALS) method for the time‐resolved XAS spectra data permitted to calculate the concentration of species during the activation and reaction steps and to determine the formation of NiMgO and nickel reduction degree. The samples prepared with surfactants, Ni10MgO‐F127 and Ni10MgO‐P123, showed less nickel reduction (less than 30 %) but were more active and stable than the reference Ni10MgO catalyst, which reduced 52 %. It happened due to the smaller particle size and a larger specific area of the porous supports. The samples synthesized without Pluronic deactivated, and ethanol dehydrogenation became predominant instead of the ethanol steam reforming.

MgO/SiO2 prepared by wet-kneading as a catalyst for ethanol conversion to 1,3-butadiene: Prins condensation as the predominant mechanism

MgO/SiO2 catalysts prepared by wet-kneading with various compositions were applied to directly convert ethanol to 1,3-butadiene. The MgO/SiO2 molar ratio significantly affected the structural, textural, and surface properties of the catalysts, leading to different activities toward ethanol conversion. At low MgO loading (51 mol %), magnesium silicate is formed on the amorphous silica surface, resulting in a higher activity for ethanol dehydration to ethylene. Increasing the MgO loading, crystalline magnesium oxide is formed in addition to the magnesium silicate, producing strong basic sites capable of increasing the ethanol conversion to 1,3-butadiene. Interestingly, for the mixed oxides prepared herein, a linear correlation was found between the forward reaction rate for 1,3-butadiene formation as a function of the reaction rate for acetaldehyde and ethylene. This behavior suggests a predominance of the Prins condensation mechanism. Therefore, the paired arrangement and the strength of the acid-basic conjugate sites of these catalysts must be determinant for the dehydrogenation and dehydration of ethanol and the condensation of the respective intermediates acetaldehyde and ethylene to form 1,3-butadiene.

Photocatalyst: To Be Dispersed or To Be Immobilized? The Crucial Role of Electron Transport in Photocatalytic Fixed Bed Reaction.

Photocatalytic fixed bed reactors allow a straightforward separation from the process stream and simplify the installation and operation in practical application. However, it is widely believed that the restriction on mass transport and volume activation severely slows the reaction. Here, we demonstrate that photocatalytic fixed bed reactors can deliver a superior reaction rate to the slurry suspension by rationally modulating the electronic process and the most concerning issue of mass transport occurring on a decisecond time scale does not retard the reaction. Although the long-distance transport of photogenerated electrons in porous semiconductor films toward catalytic sites encounters boundary scattering, this electronic process can be far faster than semiconductor-cocatalyst interfacial electron transfer occurring on the decisecond-second time scale. Besides, the fixed bed reaction can be freely amplified without losing photon utilization. Under irradiation provided by a 320 W Hg lamp, we realize a reaction rate of 0.262 mol/h with 65.2% quantum yield for anaerobic dehydrogenation of ethanol.

Copper Supported on MgAlOx and ZnAlOx Porous Mixed-Oxides for Conversion of Bioethanol via Guerbet Coupling Reaction

The direct conversion of biomass-derived ethanol to high-valued-added chemicals has attracted widespread attention recently due to the great economic and environmental advantages. In the present study, the conversion of bioethanol through the Guerbet coupling process was studied in a fixed-bed reactor for MgAlOx and ZnAlOx mixed-oxides supported Cu catalysts. From the results, Cu adding into the system greatly enhance the dehydrogenation of ethanol and increase the H-transfer in the course of Guerbet coupling process. Simultaneously, the porous mixed-oxides provide the acid-base property of the catalysts for intermediate transformation. Notably, for Cu/MgAlOx, the main product of ethanol conversion is butanol, but for Cu/ZnAlOx, the primary product is ethyl acetate. Characterizations such as X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and CO2 temperature programmed desorption (TPD) were carried out to evaluate the structure and property of the catalysts. In combination with the catalytic performances with the characterization results, the synergistic catalytic effect between metal sites and acid-base sites were elaborated.

Comparative Study of Physicochemical Characteristics and Catalytic Activity of Copper Oxide over Synthetic Silicon Oxide and Silicon Oxide from Rice Husk in Non-Oxidative Dehydrogenation of Ethanol

The article presents the results of comparative research on the physicochemical characteristics and catalytic activity of copper oxide supported on synthetic SiO2 and SiO2 (RH) from rice husk. SiO2 (RH) is more hydrophobic compared to SiO2, which leads to the concentration of copper oxide on its surface in the form of a “crust”, which is very important in the synthesis of low-percentage catalysts. According to SEM, XRD, and TPR-H2, the use of SiO2 (RH) as a carrier leads to an increase in the dispersion of copper oxide particles, which is the active center of ethanol dehydrogenation.

Sugar-cane based biorefineries: The butadiene synthesis from ethanol employing ZnZr/SiO2 catalyst

1 ZnZr/SiO 2 is composed of Zn, Zr isolated species, ZrO 2 nanoparticles and SiO 2 . 2 Ethanol dehydrogenation occurs on pairs of Zn isolated species and neighbor O. 3 Both Zr species promote the generation of butadiene from acetaldehyde. 4 The ZrO 2 nanoparticles do not show Zn in their monoclinic lattice.

Ethanol dehydrogenation over (K)(Co)MoS2[sbnd]catalysts supported on activated carbon: Effect of active phase composition

The conversion of ethanol to synthesize various oxygenated hydrocarbons was studied over monometallic-, bimetallic-, and trimetallic-(K)(Co)MoS2-based catalysts supported on activated carbon. The catalysts were synthesized using the incipient wetness impregnation method and sulfidized with H2S. The catalysts were characterized by the following techniques: N2 adsorption-desorption, UV spectroscopy of pyridine-adsorption; scanning electron microscopy (SEM); SEM energy dispersive X-ray (EDX). SEM/EDX results revealed that the active metals formed a uniform phase. Synthesized catalysts were tested in a fixed-bed tubular reactor. It was established that the addition of K and Co significantly altered the physical-chemical properties, activity and selectivity of sulfide catalysts. The addition of K decreased the catalytic activity (i.e., over KMoS2/C and KCoMoS2/C) relative to the reference MoS2/C and CoMoS2/C samples. The incorporation of a promoter atom, Co, and an alkali metal, K, inhibited ethanol dehydration (into ethene) and intermolecular dehydration (into diethyl ether). K incorporation led to the formation of active sites for higher alcohol synthesis (HAS) and other oxygenates, namely (aldol-) condensation and coupling processes, and increased the ratio of liquids to hydrocarbons. Ethanol was transformed into ethyl acetate, ethyl acetoacetate, acetaldehyde, butonal-1, propanol-1, and short-chain hydrocarbons. The acidity of the catalysts did not have a direct influence on conversion. The obtained results led us to conclude that product yields are highly dependent on the active phase composition, with ethyl acetate being the most preferred product.

Uniformly Dispersed Cu Nanoparticles over Mesoporous Silica as a Highly Selective and Recyclable Ethanol Dehydrogenation Catalyst

Selective dehydrogenation of ethanol to acetaldehyde has been considered as an important pathway to produce acetaldehyde due to the atom economy and easy separation of acetaldehyde and hydrogen. Copper catalysts have attracted much attention due to the high activity of Cu species in O-H and C-H bonds oxidative cleavage, and low process cost; however, the size of the Cu nanoparticle is difficult to control since it is easily suffers from metal sintering at high temperatures. In this work, the Cu/KIT-6 catalyst exhibited an ultra-high metal dispersion of 62.3% prepared by an electrostatic adsorption method, due to the advantages of the confinement effect of mesoporous nanostructures and the protective effect of ammonia water on Cu nanoparticles. The existence of an oxidation atmosphere had a significant effect on the valence state of copper species and enhancing moderate acid sites. The catalyst treated by reduction and then oxidation possessed a moderate/weak acid site ratio of ~0.42 and a suitable proportion of Cu+/Cu0 ratio of ~0.53, which conceivably rendered its superior ethanol conversion of 96.8% and full acetaldehyde selectivity at 250 °C. The catalyst also maintained a high selectivity of >99% to acetaldehyde upon time-on-stream of 288 h.

“Reverse combustion” of carbon dioxide in water: The influence of reaction conditions

The synthesis of value-added organic products from the hydrothermal conversion of CO2 and H2O has been demonstrated, revealing the impact that reaction conditions have on the product distribution and yield. CO2 has the potential to become a valuable feedstock for the chemicals sector, in part displacing fossil resources and improving the economics of carbon capture. Herein the conversion of CO2 with H2O, in the absence of gas-phase H2, to methanol and other products is shown to occur under sub-critical water conditions in the presence of iron as a reductant and catalyst: this process can be considered as a form of “reverse combustion”. The influence of reaction temperature between 200–350°C and CO2:O2 mole ratio from 9 to 119 (in addition to pure 100% CO2) have been investigated in the presence of Fe powder. The influence of reaction time has also been investigated, employing Fe3O4 as a catalyst. Product analysis is conducted by GC-MS and MS for liquid- and gas-phase products respectively, while SEM and XRD are employed to analyse morphological changes in the catalyst and TPO investigates any coke deposited during reaction. Methanol is the major product formed at all conditions investigated, with a maximum concentration of 8 mmol L−1 after 12 h of reaction, or after 4 h in the presence of oxygen. Acetone and ethanol are also formed, although in smaller quantities than methanol, with larger-chained species also present. An inverse relationship is observed between acetone and ethanol concentrations. Based on the analysis of the reaction data it is hypothesized that ethanol and acetone may be competitively produced in one reaction pathway, while methanol is produced in an independent, parallel, pathway. The observation of acetaldehyde in the gas-phase at all studied conditions suggests that acetone may be produced from the dehydrogenation of ethanol via an acetaldehyde intermediate; catalyzed by zero-valent iron sites. Morphological characterization indicates that the catalysts are stable under the reaction conditions. These studies facilitate the development of improved catalysts and processes for the hydrothermal conversion of CO2, allowing further development of this promising sustainable process.

Influence of hydrotalcite/rosasite precursors over Cu/Zn/Al mixed oxides on ethanol dehydrogenation

Cu/Zn/Al mixed oxides catalysts were obtained from their corresponding layered precursors synthesized by coprecipitation of components varying M(II)/M(III) molar ratios of 2, 3, and 4 while maintaining Cu2+/Zn2+ molar ratio at 1.0. Crystalline phases concentration in the precursors was determined by Rietveld refinement analysis. Hydrotalcite (HTLc) phase concentration decreased from 79 to 32 wt % as M(II)/M(III) molar ratio increased from 2 to 4, respectively. A constant value of M(II)/M(III) molar ratio of 1.3–1.4 was determined for HTLc formation independently of the M(II)/M(III) molar ratio used for the synthesis. The excess of M(II), Cu and Zn components, segregate as Rosasite phase. Therefore, mixed oxides with different surface properties were obtained depending on the precursor crystalline phase component. Precursor with mainly HTLc phase generates mostly a homogenous Cu/Zn/Al mixed oxide where Al atoms hinder Cu reduction. On that sample no Cu0 was detected by XPS, then, hydrogen consumption during its reduction process was related to the presence of anionic vacancies, where H2 can be heterolytically dissociated and stored in its hydric form, generating highly active hydro/dehydrogenation sites, with highest Lewis acidity. When the mixed oxides come from a precursor with mainly Rosasite phase, mixed oxides decompose into Cu0, ZnO, and Al2O3 during reduction, where metallic Cu0 acts as dehydrogenating sites during ethanol dehydrogenation to acetaldehyde. In fact, higher Cu surface concentration favors the dehydrogenation route, increasing the yield towards acetaldehyde, whereas a high Al surface concentration enhances the dehydration path increasing diethyl ether yield.

Production of hydrogen from gas-phase ethanol dehydrogenation over iron-grafted mesoporous Pt/TiO2 photocatalysts

We report the photocatalytic activity of iron-grafted mesoporous Pt/TiO2 catalysts, combining the properties of heterojunction photocatalysts with mesoporosity, for the gas-phase production of hydrogen from water-ethanol mixtures. GC–MS analysis reveals a preferential ethanol dehydrogenation reaction pathway, resulting in the formation of acetaldehyde with high selectivity versus carbon dioxide, for all of the catalysts investigated. Multi-technique characterization reveals that, in all the iron-grafted samples, Fe is located predominantly on the surfaces of the catalysts as Fe2O3 rather than doping the anatase structure, while the mesoporosity of the starting TiO2 is preserved. Among the different materials, the activity for photocatalytic ethanol dehydrogenation is optimum in the catalyst with the lowest iron content. According to XPS and time-resolved fluorescence measurements, this can be accounted for by higher Fe surface dispersion and consequent efficient formation of a surface heterojunction between Fe2O3 and TiO2 that favours charge separation.

Acetaldehyde production by ethanol dehydrogenation over Cu-ZnAl2O4: Effect of catalyst synthetic strategies on performances

CuO-ZnAl2O4 based catalysts (Cu 7.4 wt%) were tested for selective dehydrogenation of ethanol to acetaldehyde. Different preparation procedures were adopted: wet and incipient-wetness impregnation using commercial ZnAl2O4 as catalyst support, chitosan complexation, hard template, solid state and carbon-assisted solid state syntheses (SSC) starting from mixed Cu/Zn/Al precursors. Moreover, support role was investigated by synthesizing unsupported Cu and CuO nanoparticles. Catalysts show high ethanol conversion and high selectivity to acetaldehyde, whereas unsupported Cu and CuO nanoparticles appear to be poorly active in the whole temperature range. Novel Cu-SSC catalyst allows 68.8% yield in acetaldehyde at 623 K in steady state conditions even though a very high selectivity was obtained at 573 K (99.5%). Investigated catalysts can be efficiently pre-reduced directly in the reactant mixture, and they deactivate slowly at the timescale of 8 h on stream, when kept at 573 K. Apparent activation energies are in the range 100–350 kJ/mol, in excellent agreement with literature data.

A New Paradigm in Pincer Iridium Chemistry: PCN Complexes for (De)Hydrogenation Catalysis and Beyond.

The discovery and development of organometallic catalysts is of paramount importance in modern organic synthesis, among which the ligand scaffolds play a crucial role in controlling the activity and selectivity. Over the past several decades, d8 transition-metal complexes of pincer ligands have been developed extensively thanks to their easy structural modification, versatile reactivities, and high stability. One paradigm is the bis(phosphine)-based pincer iridium complexes PCP-Ir, which are highly active for alkane dehydrogenation, partly due to their high thermostability. However, except for alkane dehydrogenation and related transformations, few applications of pincer iridium catalysis have been seen in organic synthesis. This mainly arises from the low functional-group compatibility and poor substrate scope and the limited catalytic chemistry that invariably involves Ir(I/III) redox processes initiated by oxidative addition of substrates to 14-electron (PCP)Ir fragments (the proposed catalytically active intermediates). In this Account, we describe our endeavor on the development of a new family of PCN-Ir complexes with initial intention on creating more efficient alkane dehydrogenation catalysts. The replacement of a soft, σ-donor phosphine arm in the PCP ligands by a harder, π-acceptor N-heteroarene (pyridine or oxazoline) not only provides an additional platform to modify the structural properties but also offers new modes of bond activation and novel reactivities and catalysis. One uniqueness of the PCN-Ir system lies in the formation, via ortho-C(sp2)-H cyclometalation of the pyridine unit in the PCNPy ligand, of the neutral monohydride (PCC)IrIIIHL (L = neutral ligand), which catalyzes positional and stereoselective 1-alkene-to-(E)-2-alkene isomerization. Moreover, the PCN-Ir catalysts effect ethanol dehydrogenation without decarbonylation, allowing for transfer hydrogenation of unactivated alkenes and trans-selective semihydrogenation of internal alkynes with user-friendly ethanol as the H-donor. Another feature originates from the ability of the pentacoordinate hydrido chloride complex (PCN)IrIIIHCl to undergo reversible solvent-coordination-induced-ionization (SCII), furnishing a cationic monohydride [(PCN)IrIIIH(Sol)]+Cl- bearing an uncoordinated Cl anion that effects selective hydrometalation of internal alkynes over the corresponding (Z)-alkenes; the resulting (PCN)IrIII(vinyl)Cl complex undergoes amine-assisted formal alcoholysis involving the protonation of the Cl anion by the activated IrIII-bound EtOH, again via the SCII pathway. Together these elementary reactions lay the foundation for cis-selective semihydrogenation of alkynes with EtOH. Further, the design of the oxazoline-containing chiral complexes (PCNOxa)IrIIIHCl enables asymmetric transfer hydrogenation of alkenes/ketones with ethanol. The efficient catalytic α-alkylation of unactivated esters/amides with alcohols is another case showing the benefit that the PCN-Ir catalyst can offer. These examples illustrate the profound impact of the pincer ligands on the reactivities and catalysis. We hope this Account will provide an in-depth view into the fundamentals of pincer iridium chemistry and ultimately broaden its applications in organic synthesis.

Zeolite-encapsulated Cu nanoparticles with enhanced performance for ethanol dehydrogenation

The selective dehydrogenation of ethanol to acetaldehyde is one of the pivotal reactions for biomass valorization, wherein the well-defined and robust Cu-based solid catalysts are highly desired for potential practical application. Herein, ultra-small Cu metal nanoclusters (∼1.8 nm), encapsulated inside Silicate-1 (S-1), have been successfully fabricated by an in-situ approach. The as-synthesized Cu@S-1 catalyst shows a near quantitative ethanol conversion, a good acetaldehyde selectivity up to ∼90 %, and more importantly an excellent stability with no apparent deactivation even after a TOS of 110 h in the continuous dehydrogenation of ethanol to acetaldehyde at 523 K. Comprehensive and thorough characterization studies reveal that the spatial constraint environment of the zeolite could not only efficiently restrict the movements of Cu entities, which thus prevents the metal sintering during catalysis, but also induce a predominant amount of well-retained Cu+ species (up to ∼70 %) that play an essential role for the enhanced performance.

Rhombohedral Pd–Sb Nanoplates with Pd‐Terminated Surface: An Efficient Bifunctional Fuel‐Cell Catalyst

Developing high-performance electrocatalysts for both ethanol oxidation reaction (EOR) and oxygen reduction reaction (ORR) is essential for the commercialization of direct ethanol fuel cells (DEFCs), but it is still formidable challenging. Herein, for the first time we have successfully prepared a novel Pd-Sb hexagonal nanoplate for boosting both cathodic and anodic fuel cell reactions. Detailed structural characterizations reveal that the nanoplates have ordered rhombohedral phase of Pd8 Sb3 (denoted as Pd8 Sb3 HPs) with Pd-terminated surface. Significantly, the unique Pd8 Sb3 HPs can exhibit much enhanced activity towards the oxidation of various alcohols in alkaline media. In particular, Pd8 Sb3 HPs/C displays superior specific and mass activities of 29.3mA cm-2 and 4.5 A mgPd -1 towards EOR, which are 7.0 and 11.3 times higher than those of commercial Pd/C, and 9.8 and 3.8 times higher than those of commercial Pt/C, respectively, representing one of the best EOR catalysts reported to date. In-situ electrochemical ATR-SEIRAS measurements reveal that Pd8 Sb3 HPs/C can effectively promote the C2 pathway of EOR, which is the key to the improved activity. As further disclosed by the density functional theory calculations, the higher EOR intrinsic catalytic activity of Pd8 Sb3 HPs can be ascribed to the reduced energy barrier of ethanol dehydrogenation. In addition, Pd8 Sb3 HPs/C can also show superior performance to both commercial Pd/C and Pt/C in cathodic ORR. This work advances the controllable synthesis of Pd-Sb nanostructure, which give huge impetus to the design of high-efficiency bifunctional electrocatalysts for energy conversion and beyond. This article is protected by copyright. All rights reserved.

Catalytic dehydrogenation of ethanol over zinc-containing zeolites

Catalytic dehydrogenation of ethanol produces acetaldehyde, an important precursor for several value-added chemicals such as acetic acid and acetate esters. In this paper, we demonstrate that Zn-containing MFI zeolites are highly active and selective catalysts for this process. Furthermore, we show that their activity and selectivity depend on the chemical composition and preparation of the catalysts. The best catalyst comprises 5 wt% Zn on Silicalite-1 zeolite and results in 65.2% conversion and 94.5% selectivity towards acetaldehyde at 400 ℃. We relate the high selectivity to the absence of Brønsted acidic silanol groups, which suppresses the dehydration of ethanol into ethylene. Furthermore, while pure HZSM-5 and NaZSM-5 zeolites result in dehydration products, such as ethylene and diethyl ether, Zn on NaZSM-5 zeolite also results in acetaldehyde, which confirms that Zn is the active site. Finally, we compare different preparation procedures to show that several Zn-species may be active for the catalytic reaction.

Green reduction route via ethanol dehydrogenation and decomposition for Pd-promoted Co3O4/SBA-15 catalysts in reverse water gas shift reaction: An operando time-resolved X-ray absorption spectroscopy investigation

An alternative reduction route of Pd-promoted Co3O4 supported on SBA-15 under ethanol dehydrogenation and decomposition (ED) was studied by an operando time-resolved X-ray absorption spectroscopy (TR-XAS) to understand the insight nature of materials. The catalysts, xPd-10Co/SBA-15, were prepared by co-impregnation method where the Pd content, x = 0.2, 0.5 or 1.0 wt% and Co content = 10.0 wt%. The precursors were transformed to PdO and Co3O4 after calcination and to metallic form after reduction. The reducibility of Co3O4 to metallic Co in 1Pd-10Co/SBA-15 was 98.0%, whereas the metallic form was not produced in the absence of Pd. This catalyst also provided the highest H2 yield of 80% from ED at 500 °C. The ED-reduced 1Pd-10Co/SBA-15 was tested in reverse water gas shift reaction (RWGS) and characterized by the operando TR-XAS. The CO selectivity from CO2 was 97.8%, slightly higher than conventional H2-reduced 1Pd-10Co/SBA-15.