Effect of the order of Ni and Ce addition in SBA-15 on the activity in dry reforming of methane

Dry reforming of methane has been carried out on SBA-15 catalysts containing 5 wt% Ni and 6 wt% Ce. The effect of the order of Ni and Ce impregnation on the catalytic activity has been studied. Both metals were added using the “two-solvent” method that favors metal dispersion inside the pores. Characterizations by XRD (low and high angles), N₂ sorption, SEM and TEM of the materials after metal addition and calcination indicate good preservation of the porosities and high NiO and CeO₂ dispersion inside the porous channels. Reduction was carried out before the catalytic tests and followed by TPR measurements. The most active reduced catalyst was the Ni–Ce/SBA-15 sample prepared by impregnating cerium first, then nickel. All catalysts were highly active and selective towards H₂ and CO at atmospheric pressure. Full CH₄ conversion was obtained below 650 °C. The higher performances compared to those reported in the literature for mesoporous silica with supported Ni and Ce catalysts are discussed.     

Influence of gas hourly space velocity on the activity of monolithic catalysts for the simultaneous removal of soot and NOx

Cordierite-supported structured catalysts were prepared with several alumina-based suspensions containing K, Cs or Ba as alkali promoter, and Co, or Cu as active metals. The prepared catalysts were tested in a lab installation with a gas hourly space velocity (GHSV) from 1300 h⁻¹ to the one representative of the exhaust gases of a diesel engine, i.e. GHSV = 36,690 h⁻¹. Significant differences in the behavior of the catalysts are observed when increasing the GHSV, pointing to different predominant factors taking place in each case depending on the active metal and the alkali promoter used.     

Study of the acidity of H3PW12O40 supported on activated carbon by microcalorimetry and methanol dehydration reaction

H₃PW₁₂O₄₀/activated carbon catalysts have been studied by microcalorimetry and by the dehydration of methanol to dimethyl ether. It has been shown that the acidity of the polyacid is greatly reduced upon grafting on activated carbon. The decrease is so high that, at low polyanion loadings, the catalysts are relatively inactive in the dehydration of methanol to dimethyl ether.     

Hydrogenation of CO2 into hydrocarbons over bifunctional system Cu–ZnO/Al2O3 + HZSM-5: Effect of proximity between the acidic and methanol synthesis sites

A one-step CO₂ hydrogenation reaction into hydrocarbons (HC) using a bifunctional system constituted by a methanol synthesis catalyst [Cu–ZnO–Al₂O₃ (CZA)] and a zeolite (HZSM-5) has been studied. The influence of the catalyst bed configuration on activity, selectivity, and HC yield has been evaluated. The results obtained at T_R = 623 K, P_R = 3.0 MPa and WHSV = 6000 h⁻¹ show that CO₂ hydrogenation and hydrocarbon selectivity were strongly influenced by the proximity between oxide and zeolite, whatever the disposition of the two catalytic active sites. Indeed, the highest conversion and the best yield of hydrocarbons (mainly C₂) were obtained with the M1 bifunctional catalysts in which the oxide–zeolite proximity is the lowest. This is ascribed to the hydrogen spillover phenomenon, which does not promote the carbon chain growth.     

Copper,cobalt and manganese: Modified hydrotalcite materials as catalysts for the selective catalytic reduction of NO with ammonia. The influence of manganese concentration

Hydrotalcites containing Cu, Co and Mn with varying manganese contents were prepared by co-precipitation. Manganese was also introduced into the catalysts via adsorption of an Mn–EDTA complex from an aqueous solution. The obtained samples were characterized by room- and high-temperature XRD, low-temperature nitrogen sorption, and FT–IR. Calcination of the catalysts at 500 °C resulted in the formation of mixed oxides with specific surface areas of 166–187 m²/g. The calcined samples were tested as catalysts for selective catalytic reduction of NO_x with ammonia. It was found that the Mn content strongly influences the product selectivity in SCR–NH₃. Mn–EDTA modified samples exhibited higher selectivity towards N₂ than Mn hydrotalcites obtained by the co-precipitation method. A hydrotalcite sample containing 5.4 wt% of manganese showed the highest catalytic activity and the lowest selectivity to N₂ at the same time.     

The effect of FER zeolite acid sites in methanol-to-dimethyl-ether catalytic dehydration

In this paper, the effect of acidity of zeolites with FER framework was studied in the methanol dehydration to dimethyl ether reaction, by comparing catalysts with different Si/Al ratios(namely 8, 30 and60). The aim of this work was to investigate how the acid sites concentration, strength, distribution and typology(Br?nsted and Lewis) affect methanol conversion, DME selectivity and coke formation. It was found that the aluminium content affects slightly acid sites strength whilst a relevant effect on acid sites concentration and distribution(Br?nsted/Lewis) was observed as 24% of Lewis sites were found on Alrichest samples, whilst less than 10% of Lewis acid sites were observed on FER at higher Si/Al ratio. All the investigated catalyst samples showed a selectivity toward DME always greater than 0.9 and samples with the lowest Si/Al ratio exhibit the best performances in terms of methanol conversion, approaching the theoretical equilibrium value(around 0.85) at temperatures below 200 °C. Turnover-frequency analysis suggests that this result seems to be related not only to the higher amount of acid sites but also that the presence of Lewis acid sites may play a significant role in converting methanol. On the other hand, the presence of Lewis acid sites, combined with a high acidity, promote the formation of by-products(mainly methane) and coke deposition during the reaction. As final evidence, all the investigated catalysts exhibit very high resistance to deactivation by coke deposition, over 60 h continuous test, and a GC–MS analysis of the coke deposited on the catalyst surface reveals tetra-methyl benzene as main component.     

(Liquid + liquid) phase equilibria of 1-alkyl-3-methylimidazolium methylsulfate with alcohols,or ethers,or ketones

Solubilities of binary mixtures that contain a room-temperature ionic liquid and an organic solvent – namely, 1,3-dimethylimidazolium methylsulfate, [mmim][CH₃SO₄], or 1-butyl-3-methylimidazolium methylsulfate, [bmim][CH₃SO₄] with an alcohol (hexan-1-ol, or octan-1-ol, or nonan-1-ol, or decan-1-ol), or an ether (dipropyl ether, or dibutyl ether, or methyl-1,1-dimethylethyl ether, or methyl-1,1-dimethylpropyl ether), or a ketone (pentan-2-one, or pentan-3-one, or hexan-2-one, or heptan-4-one, or cyclopentanone) – have been measured by a visual method from T = 270 K to the boiling temperature of the solvent. The (liquid + liquid) equilibria curves were predicted by the COSMO-RS method. For [bmim][CH₃SO₄], the COSMO-RS predictions correspond better with experimental results than do the predictions for [mmim][CH₃SO₄].Complete miscibility has been observed in the systems of [mmim][CH₃SO₄] with water and with alcohols ranging from methanol to octan-1-ol and that of [bmim][CH₃SO₄] with water and with alcohols ranging from methanol to decan-1-ol at the temperature T = 310 K.     

Green process of fuel production under porous γ-Al2O3 catalyst: Study of activation and deactivation kinetic for MTD process

One of the methods of industrial dimethyl ether production is the catalytic dehydration of methanol. In this research work, methanol dehydration reactor has been modeled using continuous model and its results have been compared with experimental works and Voronoi pore network model. A 1D heterogeneous dispersed plug flow model was utilized to model an adiabatic fixed-bed reactor for the catalytic dehydration of methanol to dimethyl ether. The mass and heat transfer equations are numerically solved for the reactor. The concentration of the reactant and products and also the temperature varies along the reactor, therefore the effectiveness factor would also change in the reactor. We used the the effectiveness factor that was simulated according to the diffusion and reaction in the catalyst pellet as a Voronoi pore network model. Sensitivity analysis was performed to determine the influence of T, P and weight hourly space velocity on performance of the chemical reactor. Acceptable agreement was reached between the measured and the model data. The results showed that the maximum reaction conversion was obtained about 90 % at WHSV = 10 h^?1 and T = 560 K, while the inlet temperature (T_inlet) had a greater effect on methanol conversion. In addition, the effect of water in the feed on methanol conversion was quantitatively studied. Also, the deactivation kinetics of γ-Al₂O₃ heterogeneous-acidic catalyst in methanol to dimethyl ether dehydration process was studied using integral analysis method. Based on independent deactivation kinetics, a second order was found that accurately fitted the experimental conversion time data. The main reaction activation energies and catalyst deactivation energies were 143.1 and ?102.1 kJ/mol, respectively.     

CO2 reforming of CH4 over highly active and stable yRhNix/NaY catalysts

Ni_7.5/NaY catalysts were prepared using two different methods, the incipient wetness impregnation method and the “two-solvent” method. These catalysts were characterised by N₂ sorption, XRD, TEM and TPR. Their activity and stability in the dry reforming of methane were tested at atmospheric pressure under an equimolar mixture of methane and carbon dioxide. Three different Ni species, very small, spherical, and layers of nickel silicate were observed by TEM. The preparation by the two-solvent method led to a better dispersion of the active phase as well as to better activity and stability. These catalysts were promoted with small amounts (0.1 wt%) of rhodium. Rhodium facilitates the reducibility and greatly enhances catalytic activity. A complete conversion (100%) for CH₄ and CO₂ over the Rh promoted catalyst is achieved at 584 °C and 559 °C respectively, while for the non-promoted Ni7.5/NaY catalyst, only a 60% conversion rate for CH₄ and CO₂ is reached at the same temperatures.     

Highly stable and selective Ru/NiFe_2O_4 catalysts for transfer hydrogenation of biomass-derived furfural to 2-methylfuran

Spinel ferrites NiFe_2O_4 supported Ru catalysts have been prepared via a simple sol–gel route and applied for converting biomass-derived furfural to 2-methylfuran. The as-prepared catalysts were characterized by thermogravimetric analysis(TG), N_2 adsorption–desorption, X-ray diffraction(XRD), scanning electronic microscopy(SEM), and X-ray photoelectron spectroscopy(XPS). Results showed that the catalysts had well-dispersed Ru active sites and large surface area for calcination temperature ranging from 300 to 500 ℃. The conversion of biomass-derived furfural into 2-methylfuran was conducted over Ru/NiFe_2O_4 through catalytic transfer hydrogenation in liquid-phase with 2-propanol as the hydrogen source. A significantly enhanced activity and increased 2-methylfuran yield have been achieved in this study. Under mild conditions(180 ℃ and 2.1 MPa N_2), the conversion of furfural exceeds 97% and 2-methylfuran yield was up to 83% over the catalyst containing 8 wt% Ru. After five repeated uses, the catalytic activity and the corresponding product yield remained almost unchanged. The excellent catalytic activity and recycling performance provide a broad prospects for various practical applications.     

Transformation of South African coal fly ash into ZSM-5 zeolite and its application as an MTO catalyst

This study presents a way of using South African coal fly ash by extracting metals such as Al and Fe with concentrated sulphuric acid, and then using the solid residue as a feedstock for the synthesis of ZSM-5 zeolite. The percentage of aluminium and iron oxides decreased from 28.0 ± 0.2% and 5.0 ± 0.1% in coal fly ash to 24.6 ± 0.1% and 1.6 ± 0.01% in the acid treated coal fly ash respectively. The fly ash-based zeolite ZSM-5 sample synthesised from the solid residue after extraction of Al and Fe, contained 62% of ZSM-5 zeolite pure phase with a number of Brønsted acid site density of 0.61 mmol per g_zeolite.By properly treating the as-prepared coal fly ash-based ZSM-5 zeolite, an active and selective methanol-to-olefins acid catalyst could be designed, leading to full methanol conversion during 15 h on stream. The optimised catalyst exhibited a cumulative methanol conversion capacity of 71 g(MeOH_converted)/g(catalyst) and a light olefin productivity of 21 g(C₂₌–C₄₌)/g(catalyst).     

Investigation of steam reforming of acetic acid to hydrogen over Ni–Co metal catalyst

Catalytic generation of hydrogen by steam reforming of acetic acid over a series of Ni–Co catalysts have been studied. The catalyst with the molar ratio of 0.25:1 between Ni and Co was superior to other catalysts. The effects of reaction temperature, liquid hourly space velocity (LHSV) and molar ratios of steam-to-carbon (S/C) were studied in detail over this catalyst. At T = 673 K, LHSV = 5.1 h⁻¹, S/C = 7.5:1, the catalyst exhibited the best performances. Acetic acid was converted completely to hydrogen, while H₂ selectivity reached up to 96.3% and CO₂ selectivity up to 98.1% was obtained, respectively. Ni–Co catalyst showed rather stable performances for the 70 h time-on-stream without any deactivation.     

Performance of silver nanocubes based on electrochemical surface area for catalyzing oxygen reduction reaction

Ag nanocubes that are 45 nm in size are synthesized and successfully used as catalysts in oxygen electroreduction. Electrochemical surface areas (ESAs) are considered to determine the effect on HO₂⁻ production, which is found to be in the following order: nanocubes < nanoparticles. Comparative data generated using Tafel analyses in 0.1 M NaOH electrolyte without and with methanol show that unchanged slopes on the prepared cubic catalysts can indicate high resistance of Ag nanocubes for methanol oxidation during oxygen reduction reaction. Among these Ag catalysts, nanocubes exhibit 9.29 × 10^− 2 mA cm^− 2 (at − 0.15 V vs. Ag/AgCl), the better activity in the oxygen reduction reaction.     

Smart synthesis of silver nanoparticles supported in porous polybenzoxazine nanocomposites via a main-chain type benzoxazine resin

Novel silver nanoparticles immobilized on macroporous polybenzoxazine nanocomposites were prepared as catalysts for catalytic reduction reaction.     

Synthesis of dimethyl ether from CO and H<Subscript>2</Subscript>

Thermodynamic conditions for synthesizing dimethyl ether from synthesis gas are determined. The optimum conditions of the process are as follow: T ∼ 300°C at p = 3 MPa for two catalysts loaded into the reactor: methanol synthesis catalyst (Katalco-58) and catalyst of methanol dehydration to dimethyl ether (γ-Al₂O₃). The changes that occur with the catalysts during this process are demonstrated by electron scanning microscopy.     

Surface modified Pt/C as a methanol tolerant oxygen reduction catalyst for direct methanol fuel cells

A new procedure has been successfully developed by which PtN_x/C is synthesized to enhance methanol tolerance while maintaining a high catalytic activity for the oxygen-reduction reaction (ORR). The nitrogen-modified Pt surface, which is prepared using a chelating agent followed by heat treatment, exhibits considerable selectivity toward the ORR in the presence of methanol. The high methanol tolerance could be attributed to the suppression of methanol adsorption resulting from the modification of the Pt surface with nitrogen. A direct methanol fuel-cell (DMFC) test showed that a power density of up to 120 m W cm⁻² was generated when PtN_x/C was used as the cathode catalyst (1 mg cm⁻²) in 6 M methanol and oxygen at 70 °C.     

Identification of dissolved organic species in non-drinking tap water by solid-phase extraction and gas chromatography–mass spectrometry

A method is presented for qualitative identification of dissolved volatile organic compounds (VOCs) in non-drinking tap water samples based on applications of both solid-phase extraction (SPE) and gas chromatography–mass spectrometric (GC–MS) techniques. Water samples were collected and passed over a micro-column packed with acid treated active silica gel phase (pH = 2.6) for adsorption of dissolved organic species under this pH-condition. Silica-bound-organics were then divided into equal portions followed by suspension into organic solvents of different polarities such as methanol, ethanol, butan-1-ol, ethyl acetate, diethyl ether and chloroform. These suspensions were then automatically shaken for 1 h at room temperature. The organic extracts were subjected to GC–MS analysis under temperature programming conditions. The mass spectrum of each eluted chromatographic peak was library searched or manually interpreted to identify the correct name and structure. Blank solvent and silica samples were also subjected to the same GC–MS analysis for comparison.     

Enhanced stability and activity of PtRu nanotubes for methanol electrooxidation

PtRu 1D nanostructures on titanium are prepared and analysed as electrocatalysts for methanol electrooxidation. The morphology and composition of the 1D nanostructure are characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The electrocatalytic properties of such catalysts for methanol oxidation are investigated by cyclic voltammetry (CV) and chronoamperometry (CA) in 1.0 M CH₃OH + 0.5 M H₂SO₄ aqueous solution. The results show that Pt₄₆Ru₅₄ nanotubes yields to a five-fold improvement of the mass specific activity and to a three-fold improvement of the long-term poisoning rate as compared to PtRu black of similar composition.     

Selective pyrolysis of Organosolv lignin over zeolites with product analysis by TG-FTIR

Organosolv lignin has been selected to investigate the thermal behavior of lignin over zeolites by using a thermogravimetric analyzer coupled with a Fourier-transform infrared spectrometer (TG-FTIR). The chemical structure of this lignin has been determined by ¹H NMR to obtain the distribution of main functional groups such as methoxyl groups and free aliphatic and phenolic hydroxyl groups. All three zeolite catalysts tested, HZSM-5, H-β, and USY, exerted significant influences on the dehydration reaction in the initial stage, the deoxygenation reaction of oxygenated compounds such as methanol and phenols, and the char-forming process during lignin pyrolysis in the range 30–800 °C. The dehydration reaction was enhanced in the order USY > HZSM-5 > H-β, while char formation was suppressed in the reverse order. The presence of HZSM-5 and H-β catalyzed the conversion of both oxygenated compounds and chars into the low-molecular-weight gases CO, CO₂, and methane. The addition of USY clearly aided decomposition of the oxygenated compounds, but had little effect on the char degradation.     

Facile catalytic dehydration of fructose to 5-hydroxymethylfurfural by Niobium pentachloride

Different metal chlorides in ionic liquids were examined as catalysts for fructose dehydration to 5-hydroxymethylfurfural (5-HMF). Niobium pentachloride (NbCl₅) exhibited the highest 5-HMF yield. Reaction of 1.0 mmol fructose in 10.0 mmol 1-butyl-3-methylimidozolium chloride ([bmim]Cl) with 0.20 mmol NbCl₅ afforded 79% of 5-HMF at 80 °C after 30 min. No degradation products were formed under these conditions. FTIR analysis indicates the moderate Lewis acidity of NbCl₅, which was found suitable for the selective formation of 5-HMF. Other catalysts with higher Lewis acidities promoted 5-HMF side product formation which ultimately resulted in lower yields.