Medium Acid Sites Research Articles

Catalytic Application of Cs‐Substituted Phosphotungstic Acid (CsxH3‐xPW12O40)‐Mesoporous Zirconium Phosphate (m‐ZrP) Nanocomposite Towards Synthesis of Structurally Diverse Tetrazole Moieties

AbstractThe rational design of a high surface area heterogeneous nanocomposite catalyst with well‐defined surface acidic sites and structural porosity is a promising approach with potential application in expeditious synthesis of biologically active molecules/scaffolds. In this work, mesoporous zirconium phosphate (m‐ZrP) was synthesized through a hydrothermal process and used as a porous matrix for dispersion of cesium‐exchanged phosphotungstic acid (CsxH3‐xPW12O40) nanoparticles to prepare CsxH3‐xPW12O40‐mZrP nanocomposite systems. Various characterization techniques, including XRD, UV–vis‐DRS, FTIR, FESEM, HRTEM, TGA‐DTA, BET, and TPD, were used to understand the structural, morphological, and surface properties of the composites. XRD analysis revealed the presence of m‐ZrP and cubic CsxH3‐xPW12O40 crystalline phases in the nanocomposite materials. A microscopic study indicated the existence of rod‐shaped morphology that was formed by the coalescence of a large number of spherical nanoparticles with diameters between 150 and 200 nm. The dispersion of CsxH3‐xPW12O40 over the m‐ZrP surface results in significant enhancement of medium and strong acidic sites, with the maximum number of acidic sites observed for the Cs0.5‐PTA‐mZrP composite (0.406 mmol g−1). The catalytic activity of the CsxH3‐xPW12O40‐mZrP nanocomposites was evaluated for rapid synthesis of tetrazole derivatives through [3 + 2] cycloaddition reactions of substituted nitrile and NaN3 under mild conditions. The detailed optimization study revealed that the use of Cs0.5‐PTA‐mZrP catalyst in DMF media afforded 90% yield of the tetrazole at 120 °C. Reaction kinetics study suggested that the optimal Cs0.5‐PTA‐mZrP catalyst exhibited the highest reaction rate of 2.06 × 10−3 mmol h−1m−2 towards tetrazole formation. Structurally diverse tetrazole derivatives in high yield and purity were synthesized under mild conditions using CsxH3‐xPW12O40‐mZrP nanocomposite as catalyst.

A Kinetic Model for Catalytic N-Butane Oxidative Dehydrogenation under Oxygen-Free Reaction Conditions in a Fluidized CREC Riser Simulator

This study considers the development of a kinetic model for the n-butane oxidative dehydrogenation (ODH) to C4-olefins using a VOx/MgO−γAl2O3 catalyst. The prepared catalyst contained 5 wt% V on an MgO modified γAl2O3 support. The developed catalyst exhibited both weak and medium acid sites, as revealed by NH3-temperature-programmed desorption. TPR/TPO analyses also indicated that 73% of the loaded VOx was reducible. Kinetic experiments were conducted in a fluidized CREC Riser Simulator at temperatures ranging from 475–550 °C and residence times of 5–20 s. An optimal C4-olefin selectivity of 86% was achieved at 500 °C and 10 s, with this selectivity then decreasing at higher temperatures and longer residence times. The kinetic model developed involved a Langmuir–Hinshelwood-type of kinetics that incorporated cracking, oxydehydrogenation, and complete oxidation reactions. Model parameters were determined by fitting experimental data with kinetic parameters established with narrow 95% confidence intervals and low cross-correlation.

Promote the efficient co-combustion of toluene & CO in Pt/CeO2 catalyst: Orientally adjusting the oxidized SMSI to optimize acid site and oxygen vacancy

By effectively controlling the strong metal-support interaction (SMSI), the formation of acid sites and oxygen vacancies (Ov) on the Pt/CeO2 catalyst was optimized. The efficient co-combustion of toluene and CO on Pt/CeO2-450 was achieved. In the dual-pollutant system, when the conversion rate was 90 %, the corresponding conversion temperatures of toluene and CO were 165 °C and 173 °C, respectively. With the increase of SMSI, the catalytic activity of Pt/CeO2 showed a trend of first increase and then decrease. This was proportional to the content of weak acid sites, medium acid sites, and Ov generated on their surfaces. Compared with the combustion of a single pollutant, the result displays that toluene and CO had significant competitive adsorption on Pt/CeO2. The inhibition of toluene on CO also showed the same trend as the catalytic activity with the increase of SMSI. Under the double inhibition, Pt/CeO2 exhibited preferential selectivity for toluene combustion. However, the in situ DRIFTS results showed that this competitive adsorption phenomenon did not interfere with the combustion reaction path. The co-combustion of toluene and CO follows independent reaction paths. This work provides valuable insights and ideas for realizing the development of efficient and environmentally friendly catalysts through SMSI regulation.

One-pot catalytic conversion of sugars to methyl lactate over acid-base bifunctional Sn/MgO catalysts

Alkyl lactates represent such green added-value chemicals that commonly used as biodegradable green solvents, detergents, pharmaceutical intermediates et al. Catalytic conversion of carbohydrates to methyl lactate (MLA) is a representative way for high-value utilization of biomass and the key lies in the development of highly efficient catalysts. In methanol, strong acid or alkaline catalysts are usually used under high temperature and high pressure, suffering from problems such as low selectivity, high cost or contamination of environment. This study aims to develop an acid-base bifunctional heterogeneous catalyst for the one-pot conversion of sugars to MLA under mild conditions. Sn/Mg composite oxides was synthesized by a coprecipitation method and further modified by poly (vinyl imidazole) ([PVIM]) to tune the hydrophilicity. Effect of polymer and Sn amount, calcination temperature, reaction temperature, catalyst dosage, and substrate concentration were investigated. The acid-base properties were characterized by NH3-TPD, pyridine-FTIR and CO2-TPD analysis. It was found that the presence of medium acid sites and medium base sites played an important role to the cascade reactions of carbohydrates to MLA. An optimum MLA yield of 55.4% was achieved over 10[PVIM]-5Sn/MgO (0.05 g) with complete conversion of glucose (28 mM) at 140 ℃, 2 MPa N2 for 10 h. The reaction conditions are mild and no strong acid or strong base catalyst is required. Furthermore, a possible reaction mechanism was proposed that the introduction of [PVIM] effectively regulated the local microenvironment of active sites and the acid base synergism greatly promoted the retro-aldol condensation, dehydration and hydrogen transfer reactions during the conversion of glucose to MLA.

Sustainable methyl formate generation by dehydrogenation of green methanol over Cu_SiO2/MgO

Copper impregnated SiO2 and MgO catalysts were prepared, characterised, and tested for the synthesis of methyl formate (MF) from methanol by dehydrogenation. Compared to the Cu-impregnated pure oxides, MF formation was improved when SiO2/MgO mixtures were used as support. For further comparison, a silver impregnated mixed oxide catalyst, known for its dehydrogenation ability, and a typical methanol catalyst (Cu/ZnO/Al2O3) were tested. Both catalysts displayed non or poorer performance under tested reaction conditions. High catalytic activity was assigned, besides the Cu content, to the presence of both medium acidic and basic sites. At 240 °C and 1 bar, the highest MF yield of 34 % has been obtained with the mixture of oxides containing the highest MgO ratio of 35 mol%. By exposing the prepared catalyst to a methanol/water mixture (36 wt% water), methanol conversion drops to 5 %, but compared to the reference Cu/ZnO/Al2O3 catalyst, two times the selectivity towards MF was obtained. With respect to sustainable technology development, direct coupling of green methanol synthesis from CO2/H2 gas feed and MF production without water removal is not recommended, since the yield to MF is below 2 % in this case.

Selective hydrogenation of furfural to tetrahydrofurfuryl alcohol in isopropanol over hydrotalcite-derived nickel-based catalyst

A series of hydrotalcite-derived nickel-based catalysts were synthesized by coprecipitation, drying, calcination and reduction, and used for the selective hydrogenation of furfural to tetrahydrofurfuryl alcohol. Ni1Zr1Al2-R, with specific surface area (SBET) of 145.6 m2, narrow pore size distribution of 7.1 nm, and small Ni0 particle size of 7.31 nm, showed 100 % furfural conversion and 94.5 % tetrahydrofurfuryl alcohol selectivity under mild conditions (140 °C, 2 h). It was found that furfural was first hydrogenated to furfuryl alcohol, which was further hydrogenated to tetrahydrofurfuryl alcohol. XRD and TEM showed that Ni0 (111) plane played an important role on the catalytic hydrogenation process. Al increased the specific surface area (SBET) and total acid sites of the catalyst, providing more possibilities for the catalyst to contact the substrate. The introduction of Zr improved the ratio of medium acid sites and decreased the size of metal nickel particles, improving the resistance to carbon deposition and allowing the structure and catalytic performance to remain stable after five recycles.

Al2O3-Stabilized Pt Nanozymes: Peroxidase Mimetics and Application in Glucose Detection.

As promising alternatives for natural enzymes, much attention has been paid to nanozymes. And our recent study showed that the medium acid sites on the support are the active sites for the adsorption and oxidation of the substrate. Thus, in this work, due to the abundance of medium acid sites, Al2O3 was chosen as the support to prepare Pt/Al2O3 nanozymes. Through the Pt/Al2O3 samples, we further proved that the distribution of the Pt clusters and the amount of the medium acid sites can significantly influence the peroxidase-like activity. Then the Pt/Al2O3 sample was used for the detection of glucose. And as low as 0.96 μM glucose could be detected with a linear range from 5-60 μM via our method. This work showed the great potential applications of the easily prepared Pt/Al2O3 samples in varieties of simple, robust, and easy-to-make analytical approaches in the future.

Promotional effect of Ti on catalytic performance of Cs/Ti-SiO2 for conversion of methyl propionate and formaldehyde to methyl methacrylate

Synthesis of methyl methacrylate (MMA) by aldol condensation of methyl propionate (MP) with formaldehyde (FA) has received researchers’ attention in recent years. Herein, a kind of acid-base bi-functional Cs/Ti-SiO2 was developed for the conversion of MP and FA to MMA. A series of Cs/Ti-SiO2 samples with different acid-base properties were prepared by changing the loading amount of Cs and Ti elements and characterized using XRD, BET, FT-IR, DR UV–vis, SEM, TEM, XPS, CO2/NH3-TPD, O2-TPO, py-IR, and TGA. The introduction of Ti species could significantly regulate the acidity and affect the surface structure of catalyst, facilitating the activation of reactants and aldol reaction effectively. The relationship between the acid-base properties and catalytic activity was correlated, which revealed the crucial role of weak and medium acid sites in this transformative process. The production of MMA was optimized by using response surface methodology (RSM) based on the Box-Behnken design (BBD) approach. As a result, 62.8 % yield of MMA with selectivity of 75.6 % could be achieved at optimal reaction conditions. The catalyst would suffer deactivation from carbon deposition, which could be easily regenerated by simple thermal treatment without any decrease in initial activity during 600 h time-on-stream. Kinetic studies unraveled the activation energy of aldol condensation was 112.2 kJ/mol.

Elucidating the nature role of acid etching on the CoMnOx catalyst with outstanding performance for the catalytic combustion of o-dichlorobenzene

Enhancing chlorine and water resistance and suppressing by-product generation are crucial issues in the catalytic degradation of CVOCs. In this paper, surface acid modified (sulfurized and phosphorized) CoMnOx rhombic dodecahedra catalysts were synthesized for the deep destruction of o-Dichloroethane (o-DCB), considering its better reducibility, abundant acid sites, excellent mass transfer and higher specific surface area. The strong interaction between Co and Mn in the acid-modified CoMnOx stimulated the efficient production of active Co3+, Mn4+ and oxygen species, which considerably promoted C-H bond and C-Cl bond cleavage. Acid etching also creates a rich surface defect structure that promotes the exposure of more reactive sites and facilitates the adsorption of reactant molecules. Furthermore, we found that the acid sites of the prepared CoMnOx-TAA materials effectively inhibited by-product formation and were highly selective for HCl. TPSR analysis gave the distribution of the reaction products and further confirmed that the final products were CO2 and HCl. More importantly, CoMnOx-TAA exhibited excellent water and chloride resistance. Moreover, EPR characterization confirmed a significant increase in the number of oxygen vacancies on the catalyst surface after acid modification of CoMnOx. TPD indicated that the modified catalyst possessed abundant weak and medium acid sites. The formation pathway and reaction mechanism of oxidative decomposition were also studied by in-situ FTIR and DFT calculations. This work provides promising candidates and new insights into the industrial catalytic degradation of o-DCB.

Catalytic ozonation of p-xylene over Mn/Ce oxide nanorods treated by vacuum deoxidation

Xylene with high photochemical activity is commonly used as a raw material and organic solvent. The treatment of waste gases containing xylene is a necessary measure to ensure the air quality. Mn/Ce oxide nanorods were prepared using SBA-15 as a template and subjected to vacuum deoxidation for catalytic ozonation of p-xylene. Hydrothermal demolding conduced to detach the nanorods to improve the surface area and porosity, providing massive active sites for catalytic ozonation. The results indicated that numerous Mn-O-Ce solid solution structures formed in Mn/Ce composite oxides, especially Mn0.5Ce0.5Ox, to enhance weak- and medium-acid sites and oxygen vacancies (OVs) on the catalysts. Vacuum deoxidation effectively and facilely raised OVs for the catalysts. Vacuum-deoxidated Mn0.5Ce0.5Ox with the most Mn-O-Ce structures achieved the highest removal rate of p-xylene and CO2 selectivity since the most OVs and weak- and medium-acid sites appeared in it compared with the other catalysts. The mechanism of catalytic ozonation may be that p-xylene adsorbed on the acid site of vacuum-deoxidized Mn0.5Ce0.5Ox is attacked by the reactive oxygen species (ROS) generated by the dissociation of O3 on OVs. The degraded p-xylene and its intermediate are finally oxidized by ROS to CO2 and H2O.

Influence of pseudoboehmite properties on characteristics of CoMo/ASA-Al2O3 catalysts for selective hydrotreating of FCC gasoline

The influence of alumina precursor (pseudoboehmites) in CoMo/ASA + Al2O3 catalysts on catalytic activity in FCC gasoline hydrotreating has been studied. Pseudoboehmites prepared by alcoholate, precipitate and hydrothermal technologies were used. Parent powders, supports and catalysts were characterized by low-temperature N2 adsorption, TPD of ammonia, STEM, HRTEM, UV–vis spectroscopy. Catalysts were tested in hydrotreating of the model FCC gasoline feedstock. It is shown that the choice of pseudoboehmite has significant effect on textural, acid and mechanical properties of supports and catalysts, as well as dispersity of the active phase. The type of pseudoboehmite affects the amount of tetrahedral cobalt in catalysts that changes surface activity per 1 g of the catalyst. The linear dependence between the ratio of the medium and weak acid sites and catalyst selectivity was found. It is established that isomerizing activity is higher than the hydrogenating one, when medium/weak acid sites ratio in the catalyst is lower than 1.85.

Effect of Strontium Modification in Mg-Al Mixed Oxide Catalysts on Product Distribution toward Catalytic Reaction of Ethanol.

The aim of this research was to examine the effect of strontium content in the MgAlO catalyst for the catalytic ethanol reaction on the product distribution. The structure of the catalysts and the actual amount of strontium on the catalysts were verified using XRD and ICP techniques, respectively. The acid and basic strength characteristics of catalysts were examined using NH3-TPD and CO2-TPD techniques, respectively. The strontium content was found to influence the textural properties and the acidic and basic characteristics of the catalysts, leading to differences in product selectivity and ethanol conversion. The MgAlO catalyst with 1.9 wt % strontium provided the maximum ethylene and butanol selectivity, probably due to the presence of appropriate medium acidic and strong basic sites. All catalysts can efficiently produce ethylene by a dehydration reaction and acetaldehyde by a dehydrogenation reaction. Acetaldehyde selectivity was dominant with increased strontium loading.

Toward maximizing the selectivity of diesel-like hydrocarbons from oleic acid hydrodeoxygenation using Ni/Co-Al2O3 embedded mesoporous silica nanocomposite catalysts: An experimental and DFT approach

The development of an effective hydrodeoxygenation (HDO) catalyst is crucial for controlling product selectivity and catalyst stability. In this study, we synthesized monometallic (Ni and Co), as well as a bimetallic, NiCo embedded mesoporous composite catalysts using a simple one-step method involving meso-macroporous silica, boehmite, nickel acetate, and cobalt acetate. The synthesized range of catalysts (5, 10, 15 wt% Ni, 10 wt% Co, 10 wt% NiCo) were thoroughly characterized by various techniques. The characterization results showed that the present method leads to the growth of nano-catalyst on porous silica surface (M−Al2O3/SiO2, M = Ni, Co, NiCo). These composites exhibited strong metal-support interaction, improved surface and texture properties and significant amount of weak to medium acid sites. The M−Al2O3/SiO2 composite catalysts demonstrated improved catalytic performance in the HDO of oleic acid. At temperature of 375 °C, the conversion trend of catalysts followed the order; 10NiCo-Al2O3/SiO2 (89%) > 10Ni-Al2O3/SiO2 (87%) > 10Co-Al2O3/SiO2 (85%) > 10Ni/SiO2 (81%). Moreover, the yield of C15-C18 hydrocarbons was substantially enhanced at moderate temperature compared to unmodified silica support. Time-on-stream experiments further confirmed the relative stability of the composite catalysts over a period of 20 h. Furthermore, density functional theory (DFT) ab initio calculations were performed where the adsorption of oleic acid on icosahedral monometallic M13 (M = Co or Ni) and bimetallic Ni2Co2 nanocluster deposited on γ-Al2O3 (110) support was investigated. The adsorption strength for the most stable conformations followed the order: Ni13/amorphous SiO2 >Ni2Co2/Al2O3 >Co13/Al2O3 >Ni13/Al2O3. Bader charge transfer analysis indicated higher charge transfer at the interfaces of γ-Al2O3Al2O3(110) supported catalysts compared to Ni13/amorphous SiO2 surface.

Catalytic co-liquefaction of microalgae + corn straw over K3PO4+γ-Al2O3 supported Fe and Ni mono- / bimetallic in-situ composite catalysts for the production of liquid biofuel

In the present study, an array of K3PO4 + γ-Al2O3 supported Fe and Ni in-situ composite catalysts including K3PO4-Fe/γ-Al2O3, K3PO4-Ni/γ-Al2O3, K3PO4-Fe-Ni/γ-Al2O3 were prepared and characterized by Nitrogen-physisorption, XRD, XPS, NH3-TPD, H2-TPR, SEM, and TEM analysis. The effects of catalyst type, catalysts loading, feedstock loading and the ratio between corn straw and spirulina on the products yield and distribution from co-hydrothermal liquefaction of spirulina and corn straw were investigated. The greater specific surface area, larger amount of medium acid sites, the key roles of K and Fe-Ni bimetallic system and enhanced interaction between Fe, Ni and γ-Al2O3 support of K3PO4-Fe-Ni/γ-Al2O3 are mainly responsible for the greatest amount of water-insoluble (35.73 wt%) and water-soluble (2.18 wt%) biocrude. Besides, the optimal reaction condition (5 wt% catalysts loading, 10 wt% feedstock loading and spirulina: corn straw = 1:1 w/w) was confirmed. The presence of catalysts especially for K3PO4-Fe-Ni/γ-Al2O3 significantly increased the energy recovery of biocrude. Meanwhile, K3PO4-Fe-Ni/γ-Al2O3 noticeably increased the fraction of lighter molecule in biocrude up to 57.18 wt%. The esters, phenols and N-heterocyclic compounds were found to be dominated in biocrude from all co-HTL cases, and the enhanced selectivity to esters with catalysts were observed. Finally, the prospective reaction pathway and mechanism of the catalytic co-HTL of spirulina and corn straw was proposed and discussed detailly and comprehensively.

In-situ constructed ultrathin hydrotalcite derivative supported PtIn catalyst for isobutane direct dehydrogenation

The stable and ultrathin hydrotalcite nanosheets with thickness of ca. 1.0 nm have been built on the surface of Al2O3 by sharing Al element and using layer growth inhibitor formamide. Based on the topological transformation characteristics of hydrotalcite and the structural memory effect of calcined product, the supported PtIn bimetallic catalyst was achieved by stepwise incipient wetness impregnation method followed by calcination and reduction, and evaluated in isobutane direct dehydrogenation (IDH) to isobutene. The derived ultrathin bimetallic catalyst possesses excellent IDH activity under extreme conditions, in which the isobutane conversion and isobutene selectivity can remain above 63% and 92% respectively, and the turnover frequency is as high as 13.45 s−1. The excellent activity can be attributed to the formation of ultrathin hydrotalcite precursor, which can greatly enhance the specific surface area, interaction among metal components, surface acidity of weak- and medium-acid sites and surface In3+/In0 ratio, and further effectively inhibit carbon deposition and improve dispersion and stability of active Pt species in the corresponding derivative.

Enhancing catalytic performance of red mud for palmitic acid hydrodeoxygenation by acid pretreatment-induced structural modification

Red mud (RM) is a metal oxide-enriched solid waste material that was subjected to various acid treatments to assess their effect on catalytic performance for hydrodeoxygenation (HDO). Acid pretreatment induces structural changes in RM, which enhances its stability and catalytic performance for HDO. Among the different acid treatments, acetic acid-treated RM catalyst (Ni/RM-HAC) exhibited superior catalytic performance and stability, yielding 81% cetane selectivity and maintaining efficient conversion for up to 400 h. The acetic acid treatment increased the Fe2O3 content in the catalyst, removed inert components such as Na2O and CaO that block pore channels, and greatly improved specific surface area and pore size. Moreover, the acetic acid treatment increased medium acid sites and oxygen vacancy in the catalyst, enhancing its catalytic performance. The increase of Fe3+ makes the catalyst have better stability. These results are expected to aid in the development of efficient, sustainable, and cost-effective catalysts for the production of the second-generation biodiesel.

Enhanced catalytic performance of hierarchical Zn/ZSM-5 with balanced acidities synthesized utilizing ZIF-14 as porogen and Zn source in methanol to aromatics

A series of Zn loaded ZSM-5 (Zn/ZSM-5) zeolites were prepared utilizing either Zn(NO3)2 or Zn-based MOFs (ZIF-61, ZIF-8 and ZIF-14) as Zn sources to explore their effects on the catalysts’ physiochemical properties through characterizations and simulations. Results revealed that hierarchical structures containing meso- to macro- pores of 10∼80 nm aside from the intrinsic micropores were constructed profiting from the use of Zn-based MOFs. On the other side, lager proportions of medium acid and Lewis acid sites were generated by more Zn(OH)+, whose content was proven to be inextricably linked to the binding energy between Zn and ligand as well as local charge valence state of Zn. Benefitting from hierarchical structures and balanced acidities, Zn/Z5(ZIF-14) employing ZIF-14 as Zn source demonstrated higher aromatic selectivity and longer catalyst lifetime (50.9% and 26 h) than the microporous counterpart synthesized from zinc nitrate hexahydrate (42.1% and 20 h) in methanol to aromatics (MTA) reaction.

Dimethyl Ether to Olefins on Hybrid Intergrowth Structure Zeolites

A series of catalysts based on hybrid intergrowth structure zeolites MFI-MEL, MFI-MTW, and MFI-MCM-41 are studied in the reaction of olefins synthesis from dimethyl ether at atmospheric pressure and a temperature of 340 °C. The total acidity of hybrid zeolite-based catalysts is shown to correlate with their activity. However, the use of zeolite with the structure MFI-MCM-41, which is characterized by a high content of medium acid sites, additionally catalyzes the methanol dehydration reaction, resulting in a decrease in the observed DME conversion. The obtained product distributions are brought into correlation with the texture of catalysts. It is shown that the use of hybrid zeolites does not change the mechanism of reaction, but the structural features of zeolites influence the priority of the competing MTO reactions: high ethylene yield is observed for catalysts with high micropore volume. The topology of the hybrid zeolite has been shown to influence the hydrogen transfer reaction rate, but not to change the isomerizing activity of the catalyst.

High performance of the morphologically controlled synthesis carrier of TiO2 for NH3 selective catalytic reduction of NO

TiO2 supported Ni and Ce with different morphologies (particle-like TiO2 (PT), flower-like TiO2 (FT), spherical-like TiO2 (ST), rod-like TiO2 (RT)) were prepared. Ni-Ce/flower-like TiO2 (NCFT) catalyst exhibits the best performance (NO conversion and N2 selectivity both approach to 100% approximately) in 250–450 °C and SO2 resistance (∼80%). The sequence of activities is NCFT > NCST > NCPT > NCRT. The FT carrier provides the largest specific surface area (145.9 m2 g−1), facilitating the dispersion of the active components. In addition, NCFT is abundant in Ni3+ and Ce3+ as well as Oα species, which support excellent redox properties. More weak acid and medium acid sites provided more adsorption sites for NH3-SCR reaction. This is also the main reason that NCFT catalyst has excellent denitrification activity. In-situ infrared results show that the reaction of NCFT catalyst is mainly through E-R mechanism, and NH3 (L) and -NH2 species formed on the catalyst surface were the main ammonia adsorption species and reaction species. Unfortunately, NCFT has not ideal sulfur resistance and stability due to its unique structure, which needs to be further improved.

Oxidative ethanol dry reforming for production of syngas over Co-based catalyst: Effect of reaction temperature

Till date, oxidative ethanol steam reforming use Ni-based catalysts to produce syngas. However, Ni catalysts suffer from easy deactivation due to the coke formation at low temperatures. Therefore, oxidative ethanol dry reforming is a promising method and was investigated over 10 %Co/Al2O3 catalyst due to their high activity and stability to produce high-quality syngas. More importantly, the syngas can be upgraded to produce liquid biofuels and chemicals. The catalyst was evaluated in a quartz fixed-bed reactor under atmospheric pressure at PCO2 =PO2= 5 kPa, PC2H5OH = 15 kPa, with reaction temperature ranging between 773 and 973 K. The γ-Al2O3 support and 10 %Co/Al2O3 catalyst had BET surface areas of 175.2 m2 g−1 and 143.1 m2 g−1, respectively. Co3O4 and spinel CoAl2O4 phases were detected through X-ray diffraction measurements on the 10 %Co/Al2O3 catalyst surface. H2-TPR measurements indicate that the 10 %Co/Al2O3 catalyst was completely reduced at a temperature beyond 1000 K. NH3-TPD measurements indicated the presence of the weak, medium, and strong acid sites on the γ-Al2O3 support and 10 %Co/Al2O3 catalyst. Due to increased reaction temperature from 773 to 973 K, C2H5OH and CO2 conversions improved from 22.5 % to 93.6 % and 16.9–52.8 %, respectively. Additionally, the optimal yield of H2 and CO obtained at 68.1 % and 58.3 %, respectively. Temperature-programmed oxidation experiments indicated that the amount of carbon deposition was the lowest (28,92 %) at 973 K and increased by 41.48 % at 773 K.