Low-temperature Nitrogen Physisorption Research Articles

SBA-15 Type Mesoporous Silica Modified with Vanadium as a Catalyst for Oxidative and Extractive Oxidative Desulfurization Processes.

One of the current challenges is the reduction of sulfur emitted into the atmosphere, usually in the form of sulfur oxides generated by fossil fuel combustion. To achieve this goal, the sulfur content should be reduced in fuel. In this context, vanadium-containing materials based on SBA-15 mesoporous silica supports and two different sources of vanadium were prepared, characterized, and applied as catalysts for oxidative desulfurization (CODS) and extractive oxidative desulfurization processes (ECODSs). The novelty of this work was the comparative study of vanadium-containing materials in two desulfurization systems. The properties of the catalysts, the concentration and state of vanadium species, and their role in the catalytic process were examined by low-temperature nitrogen physisorption, XRD, UV-Vis, XPS, and chemisorption of pyridine combined with FTIR spectroscopy. The catalytic performance of the material prepared using ammonium metavanadate was superior to that of the catalyst obtained using vanadium(IV) oxide sulfate, which was explained by a higher concentration of vanadium species on the surface of the support and their lower oxidation state in the former. Both types of catalysts showed high activity and stability in the ECODS process.

CO2 Hydrogenation to Methanol on CuO-ZnO/SiO2 and CuO-ZnO/CeO2-SiO2 Catalysts Synthesized with β-Cyclodextrin Template

A series of mixed copper (II)—zinc oxide catalysts supported on unmodified and ceria-modified silica supports were synthesized using β-cyclodextrin as a template. The novelty of this work lies in the use of cyclosextrins for the template synthesis of catalyst supports. The obtained samples were analyzed by XRD, SEM-EDX, low-temperature nitrogen physisorption, XPS, and EPR. The magnetic properties of the catalysts were also measured. The thermal decomposition of precursors was analyzed by TGA combined with mass-spectrometric analysis of the evolved gases. The effects of the support pore size, the nature of the active phase and its loading, as well as the sequence of component deposition on the catalyst performance in the CO2 conversion to methanol were studied. The catalysts with cerium added at the gelation stage demonstrated the best performance. The selectivity of these samples reaches values of more than 90% over a fairly ide temperature range, with the productivity reaching 480 g/kg cat·h at 300 °C.

The Occurrence Mechanism of Lacustrine Shale Oil in the Second Member of the Paleogene Kongdian Formation, Cangdong Sag, Bohai Bay Basin

The lacustrine shale in the second member of the Kongdian Formation (Ek2) is the most significant target of shale oil exploration in the Cangdong Sag, Bohai Bay Basin, China. To investigate the occurrence mechanisms and to reveal the influencing factors of shale oil mobility in Ek2, a series of analyses (X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), total organic carbon (TOC) analysis, Rock-Eval pyrolysis, low-temperature nitrogen physisorption (LNP), mercury intrusion porosimetry (MIP), and multiple isothermal stage (MIS) pyrolysis) were conducted on samples collected from well cores in the Cangdong Sag. The results show that the lithofacies can be categorized as laminated felsic shales, laminated and massive mixed shales, and laminated and massive carbonate shales. The shales were characterized by a high organic matter abundance and moderate thermal evolution with good to excellent hydrocarbon generation potential and contained a high abundance of Type I and II1 kerogens. Laminated felsic shales and laminated mixed shales, compared with other lithofacies, had clear advantages in the amount of free hydrocarbon that can be volatilized from the rock (S1), the oil saturation index (OSI) value, and the free oil and movable oil content. LNP, MIP, and MIS pyrolysis analyses show that the residual shale oil mainly occurred in pores with diameters smaller than 200 nm, and the pore diameter when residual oil occurred in some laminated shale samples could reach 50 μm. The lower limits of the pore diameter where free oil and movable oil occurred were 7 and 30 nm, respectively. The mobility of shale oil is controlled by the shale oil component, thermal maturity, TOC content, and pore volume. The results herein provide a basis for the evaluation of optimal shale oil intervals.

ZnO Particles Stabilized in Polymeric Matrix for Liquid-Phase Methanol Synthesis

ZnO supported on hypercrosslinked polystyrene was developed for liquid-phase methanol synthesis. The synthesized catalyst was characterized using the low-temperature nitrogen physisorption, TEM, XPS, XAS, and CO DRIFT methods. The analysis showed that the catalyst has a high specific surface area (720 m2/g) and is characterized by the micro-mesoporous structure typical of the polymer used. The active phase is represented by ZnO species with a hexagonal wurtzite structure. ZnO-HPS showed high activity, selectivity, and stability in liquid-phase methanol synthesis in comparison with the industrial catalyst. The activity of the proposed catalyst was found to be 1.64 times higher than that of the conventional Cu/ZnO/Al2O3.

Rice husk-derived activated carbon electrode in redox-active electrolyte – New approach for enhancing supercapacitor performance

Processing of renewable, abundant, and low-cost biomass into porous carbon materials for application in supercapacitor electrodes has been attracting interest in last years. In this study, activated carbons (ACs) were produced via carbonization of rice husk followed by the chemical activation with KOH. SEM, Raman spectroscopy, XPS, and low temperature nitrogen physisorption were used to characterize the morphology, defectiveness, surface composition and textural parameters of the synthesized ACs. Activation significantly increased the specific surface area of AC up to 2700 m2·g−1 forming a well-developed porous structure favorable for charge accumulation. The electrochemical performance of ACs was tested in the 1 M Na2SO4 and 1 M Na2SO4 + 0.03 M K3Fe[CN]6 electrolytes by cyclic voltammetry, galvanostatic charge – discharge measurements and impedance spectroscopy. The addition of redox-active K3Fe[CN]6 to the conventional 1 M Na2SO4 electrolyte noticeably (in 3.6 times) increased the specific capacitance of the AC-based electrode up to 400 F·g−1 at a current density of 0.5 A·g−1. The high capacitance retentions of 99.6 % in 1 M Na2SO4 and 97.7 % in 1 M Na2SO4 + 0.03 M K3Fe[CN]6 after 5000 charge–discharge cycles, developed microporosity and high electrochemical performance make the rice husk-derived AC a promising electrode material for energy storage applications. At a current density of 0.5 A·g−1 the symmetric AC2-based supercapacitor with the redox-active electrolyte delivered an energy density of 16.7 Wh·kg−1 at power density of 0.4 kW·kg−1.

Design and Catalytic Behaviour of Hosted in Activated Carbon Foam CoxZn1−xFe2O4 Ferrites

Carbon foams with different surface functionality and tailored texture characteristics were prepared from mixtures containing coal tar pitch and furfural in different proportions. The obtained materials were used as a host matrix for the preparation of zinc- and cobalt-mixed ferrite nanoparticles. The texture, morphology, phase composition, and the related redox and catalytic properties of the obtained composites were characterized by low-temperature nitrogen physisorption, XRD, SEM, HRTEM, FTIR, Mössbauer spectroscopy, TPR and catalytic decomposition of methanol to syngas. The impact of the carbon support on the formation of Co- and Zn-mixed ferrites was discussed in detail using KIT-6 silica-based modifications as reference samples. The catalytic behavior of the ferrites was considered in a complex relation to their composition, morphology, location in the porous matrix and metal ions distribution in the spinel sub-lattices. The higher amount of furfural in the carbon foam precursor promoted the formation of cobalt-rich, more accessible and highly active methanol decomposition to syngas spinel particles.

Combustion heat of nitrogen-doped graphene nanoflakes studied by differential scanning calorimetry

Nitrogen-doped graphene nanoflakes (NGNFs) with variable N-doping level of 5.0–10.7 at.% were produced by chemical vapor deposition from different CH3CN/C6H6 mixtures. NGNFs were characterized by transmission electron microscopy, low-temperature nitrogen physisorption, X-ray photoelectron and Raman spectroscopies. Their combustion heats were measured by differential scanning calorimetry in the temperature range of 303–1273 K and showed a bell-shaped dependence on the nitrogen content with a maximum of 30.1 ± 1.0 kJ g−1 at a nitrogen level of 7.8 at.%. The contributions of the π–π stacking, resonance and surface/edge energies to the combustion heat were discussed. The approach for estimation of the combustion heat of NGNFs assuming the contributions from pyridinic, pyrrolic and graphitic nitrogen species was proposed for the first time.

Magnetic Composites Based on Cobalt Ferrite, Vermiculite, and Rice Husks: Synthesis and Properties

Magnetic sorbents show promise in technologies for they can be removed with a magnet after sewage waters are decontaminated. Sol–gel strategy was implemented to manufacture new cost-efficient composite sorbents based on cobalt ferrite, vermiculite, and alkaline rice husks hydrolyzate. An alkaline solution of the rice husks hydrolyzate was added with a suspension of Co[Fe2O4] nanoparticles, and then neutralized with vermiculite suspension in 12% hydrochloric acid. The thus-manufactured magnetic sorbents were characterized by X-ray powder diffraction, IR and positron annihilation spectroscopy. Their physical and chemical characteristics were determined by low-temperature nitrogen physisorption as well as by adsorption of Methylene Blue dye in solution. The morphology of composites was identified by means of scanning electron microscopy. The bulk and surface elemental compositions of samples were found by energy dispersive fluorescent analysis. The magnetic saturation and coercivity of the samples were measured in the range of 0 to 2500 Oe fields. Sorbent particles were easily separated from solutions with a magnet. The sorbents showed high adsorption capacity with respect to Methylene Blue dye. The effect of the sodium phenyl siliconate template on the magnetic properties of the composites was elucidated.

Nitrogen-doped mesoporous graphene nanoflakes for high performance ionic liquid supercapacitors

Mesoporous nitrogen-doped graphene nanoflakes (N-GNFs) with high nitrogen doping level of 5.0–10.7 at.% were produced by a facile template CVD synthesis using the mixture of acetonitrile and benzene as a precursor. The pore structure, morphology and physicochemical properties of N-GNFs were characterized by TEM, XPS, Raman spectroscopy, and low-temperature nitrogen physisorption. The electrochemical performance of N-GNFs was tested in electric double-layer capacitor (EDLC) with ionic liquid electrolyte (1.2 M N+Et4TFSI− solution in CH3CN) by cyclic voltammetry, galvanostatic charge-discharge measurements, and electrochemical impedance spectroscopy. With increasing the nitrogen content in N-GNFs their specific capacitance increased and achieved 167 F g−1 at a scan rate of 5 mV s−1. The maximum delivered energy density was 46.3 Wh kg−1, which corresponded to a power density of 0.74 kW kg−1. The high electrochemical performance of N-GNFs was attributed both to the pseudo-capacitance of active nitrogen sites and to the developed mesoporosity. Different tetraalkylammonium bis(trifluoromethylsulfonyl)imide ionic liquids were used to evaluate the cation size effect on the stability and performance of N-GNFs-based EDLCs. In contrast to N+Et4TFSI− and N+Bu4TFSI− electrolytes, the cycling performance of N-GNFs in N+Me4TFSI− was limited because of the electrode degradation resulted from the intercalation of N+Me4 ions between graphene layers and their exfoliation.

Photocatalytic reduction of CO2 using Pt/C3N4 photocatalyts

C3N4 is an abundant carbon based, conjugated polymer with an attractive electronic band structure and increased physicochemical stability. As far as photocatalytic CO2 reduction is concerned, the adsorption of CO2 on the surface of C3N4 based photocatalyst is the first step of the reaction mechanism. In case of the combination of C3N4 with metal complexes such as those of Pt, C3N4 acts as a visible light harvesting system and catalyst whereas Pt complex provides the CO2 active sites. The complex method of the photocatalytic reduction of CO2 emissions in the presence of photocatalyst can be done using previously published methods The pristine C3N4 (g- C3N4 and p- C3N4) and platinum doped C3N4 photocatalysts with 3 wt% of Pt were prepared by two different ways and investigated for the photocatalytic reduction of CO2. The main detected reaction products were methane, hydrogen and carbon monoxide. The physico-chemical properties of photocatalysts were characterized in detail by low-temperature nitrogen physisorption, X-ray powder diffraction and diffuse reflectance UV–Vis spectroscopy. The highest yields of CH4, H2 and CO were achieved in presence of 3 wt% Pt/p-C3N4. The correlation between textural, optical and photoelectrochemical properties and the photocatalysts activity was a subject of this research.

Highly Effective Supported Ionic Liquid-Phase (SILP) Catalysts: Characterization and Application to the Hydrosilylation Reaction

Organosilicon compounds, because of their unique properties, are widely used in a variety of organic processes, and thus the constant improvement of current methods is still needed. We present slurry-phase hydrosilylation reactions using novel supported ionic liquid-phase (SILP) catalysts containing rhodium complexes immobilized in four phosphonium ionic liquids (ILs) on silica support. The obtained new SILP catalysts were analyzed by infrared technique, low-temperature nitrogen physisorption at 77 K, and scanning electronic microscopy with energy-dispersive X-ray spectroscopy to provide structural information on these materials. Moreover, the catalytic activity in hydrosilylation reactions was evaluated and compared with the catalytic activity of rhodium catalysts dissolved in the same ILs when using a biphasic reaction system (IL/catalyst as one phase and mixture of substrates as a second phase). The rhodium-based SILP catalysts proved to be much more efficient than when used in a biphasic system compos...

Adsorption of nicotine from aqueous solutions on montmorillonite and acid-modified montmorillonite

Montmorillonite (Mt) and acid modified montmorillonite (MtA) were tested as nicotine adsorbents. The samples were characterized using FT-IR spectroscopy and low temperature nitrogen physisorption. Nicotine adsorption was performed with respect to contact time, pH and initial nicotine concentration. The kinetics of adsorption obeyed the pseudo-second-order kinetics. The optimal pH values for nicotine adsorption were 6 and 9 for Mt and MtA, respectively. The isotherms related to adsorption on Mt at pH = 6 and 9 as well as for MtA at pH=6 were best fitted with Sips isotherm model, while adsorption onto MtA at pH=9 obeyed Langmuir isotherm model.

A Generalized Procedure for the Production of High-Grade, Porous Biogenic Silica

Biomasses are a sustainable, CO2 neutral source used in biorefining. Si-accumulating plants can be used for the production of biogenic silica in a biomass valorisation process. This study examines the production of high-grade porous silica from different plant parts like rice, oat and spelt husk, rice straw and horsetail using a generalized procedure for all. The silica materials were produced by a 2-step method. First, the biomasses were pretreated with water and then subjected to leaching with citric acid. As a second step, a sequential burning program was applied. The characterization of the untreated biomasses was carried out by X-ray fluorescence (XRF) analysis and thermal analysis (TG–DTA). The biogenic silica samples were subjected to XRF, carbon content analysis, low temperature nitrogen physisorption, scanning and transmission electron microscopy as well as X-ray diffraction. Independent of the initial composition of the plant part, the established method resulted in amorphous, biogenic silica with up to 99.7% purity, mesopores between 2 and 30 nm with pore volumes of up to 0.46 cm3 g−1 and specific surfaces of up to 303 m2 g−1. It was shown that the generalized method developed works not only for all the biomasses separately, but also if treated in the same batch. The produced biogenic silica can be considered as sustainable alternative to other silica products like precipitated silica, silica gel and fumed silica which are produced in highly energy consuming processes.

Titania and zirconia binary oxides as catalysts for total oxidation of ethyl acetate and methanol decomposition

Template assisted hydrothermal and homogeneous precipitation with urea techniques were used for the preparation of TiO2-ZrO2 binary oxides with wide range variation of their composition. Low temperature nitrogen physisorption, XRD, SEM, HRTEM, XPS, UV–vis, FTIR, FTIR of adsorbed pyridine and Raman spectroscopy were used for the characterization of the obtained samples. Their catalytic properties were tested in total oxidation of ethyl acetate as a representative VOCs and methanol decomposition as hydrogen carrier. It was established that the template assisted hydrothermal technique provoked preparation of materials with good crystallinity, high BET surface area and well developed mesoporous structure, while the homogeneous precipitation with urea method facilitated the formation of more highly dispersed in wide Zr/Ti region samples. The degree of incorporation of Zr4+ ions into titania lattice could be controlled by the samples composition and the preparation method used, which revealed good opportunity for effective and simple regulation of their catalytic properties.

Catalytic performance of the modified H-ZSM-5 zeolite in methanol transformation to hydrocarbons

In the current work, we present the study of the catalytic performance and characterization of the modified H-ZSM-5 zeolite for methanol to hydrocarbons process. The modification of zeolite was performed by both alkali and acid treatment. The changes in the zeolite structure were studied using low-temperature nitrogen physisorption, NH3 chemisorption, and X-Ray photoelectron spectroscopy. It was found that the zeolite modification with oxalic acid (0.01 M) resulted in the lower catalytic activity loss (48%) after 120 h on stream as compared to both initial and alkali treated H-ZSM-5. Further, the chosen zeolite sample was modified with Co, Fe, and Ni by wet impregnation with the corresponding metal nitrates. The Ni-containing catalyst showed the highest catalytic performance in time on stream. The decrease in the methanol transformation rate for the Ni-containing zeolite was found to be only 27%. The metal-containing catalysts showed the minimal coke formation as well as the minimal decrease in acidity and surface area as compared to the initial zeolite and the samples treated with both alkali and oxalic acid.

Copper and platinum doped titania for photocatalytic reduction of carbon dioxide

The parent TiO2, platinum and copper doped TiO2 photocatalysts with 0.5–2wt. % of Pt, 0.5–2wt. % Cu and 1wt. % Pt combined with 1wt. % Cu were prepared by the sol-gel method. All the prepared photocatalysts were tested for the CO2 photocatalytic reduction in a stirred batch reactor. The main reaction product was methane, however, hydrogen and carbon monoxide were also detected. The textural, (micro)structural, optical and electronic properties of photocatalysts were characterized in detail by low-temperature nitrogen physisorption, X-ray powder diffraction, EDX, HRTEM, X-ray fluorescence, X-ray photon spectroscopy, scanning electron microscope, transmission electron microscope and diffuse reflectance UV–vis spectroscopy. The photoelectrochemical characteristics of the photocatalysts were determined using photoelectric spectrometry. The highest yields of CH4, H2 and CO were achieved in the presence of 2wt. % Cu/TiO2, 0.5 wt. % Cu/TiO2 and pure, amorphous TiO2. Based on the conducted experiments it was suggested that both the amount of chemisorbed oxygen or/and hydroxyl species on the TiO2 surface and specific surface area of photocatalyst highly influence its photocatalytic activity.

The nanoscale pore characteristics of coking coals: Part 1 – Optimization of the experimental conditions and calculation methods of specific surface area and micropore volume

The current evaluation system of the properties of coking coals is not sufficient since the so-called “abnormal coal” appears out control in some cases. In this study, in order to obtain reliable nanoscale pore structural parameters (specific surface area and micropore volume) to supplement and perfect the current evaluation system, a middle rank coking coal was investigated using low-temperature nitrogen physisorption technique to optimize the experimental conditions and calculation methods. the experimental conditions were listed as follows: sample evacuation times 4, 8, and 16 h; target temperatures 125, 150, 175 and 200 °C; sample weights 2000, 3500, and 5000 mg; sample particle size ranges -plot, and Dubinin-Radushkevich (DR) methods only within the adsorption isotherm branch were adopted. The optimal experimental conditions were found to be as follows: 8 h sample evacuation time, 150 °C target temperature, 5000 mg sample weight, and -plot, and DR methods, BET method is more accurate to calculate total specific surface area compared with t -plot method; t -plot method can distinguish between micropore and external specific surface areas; besides, t -plot method based on Magee’s equation is more applicable to the coking coal sample than that based on de Boer’s equation. DR method is more sensitive to evaluate micropore volume than t -plot method. In order to obtain reliable and comprehensive pore parameters, these three methods should be combined with each other.

Template-assisted hydrothermally obtained titania-ceria composites and their application as catalysts in ethyl acetate oxidation and methanol decomposition with a potential for sustainable environment protection

High surface area mesoporous ceria-titania binary materials with high Lewis acidity and improved reduction properties were synthesized using template assisted hydrothermal technique. The obtained materials were characterized by low temperature nitrogen physisorption, XRD, SEM, TEM, Raman, UV–vis, XPS, FTIR, FTIR of adsorbed pyridine and thermo-programmed reduction with hydrogen. Their catalytic activity was tested in total oxidation of ethyl acetate and methanol decomposition to CO and hydrogen with a potential application in VOCs elimination and alternative fuels, respectively. The structural changes in the binary materials, which could be tuned by the variation in the Ce/Ti ratio and the temperature of hydrothermal treatment, provoked significant changes in their textural, surface and redox properties, which is in close relation to the catalytic activity and selectivity in various catalytic processes. The intimate contact between the individual oxides results in the formation of different catalytic active sites and their role in the studied catalytic reactions was discussed in details.

Stearic acid hydrodeoxygenation over Pd nanoparticles embedded in mesoporous hypercrosslinked polystyrene

Abstract Stearic acid hydrodeoxygenation into n-heptadecane on the catalyst containing Pd nanoparticles incorporated in the hypercrosslinked polystyrene matrix was studied. The used catalysts were characterized using TEM, CO chemisorption, low-temperature nitrogen physisorption and XPS. A clear hydrogen pressure dependent induction period was noticed. Kinetic regularities were studied for the indicated reaction in the presence of polymer based catalysts. A mathematical model for decarboxylation was suggested which was able to adequately describe experimental data at different temperatures, hydrogen pressures and initial concentrations of stearic acid. Kinetic constants were calculated and their statistical analysis was performed.

Catalytic hydrodeoxygenation of fatty acids for biodiesel production

This paper is devoted to the production of second generation biodiesel via catalytic hydrodeoxygenation of fatty acids. Pd/C catalysts with different metal loading were used. The palladium catalysts were characterized using low-temperature nitrogen physisorption and X-ray photoelectron spectroscopy. It was revealed that the most active and selective catalyst was 1%-Pd/C which allowed reaching up 97.5% of selectivity (regarding to n-heptadecane) at 100% conversion of substrate. Moreover, the chosen catalyst is more preferable according to lower metal content that leads the decrease of the process cost. The analysis of the catalysts showed that 1%-Pd/C had the highest specific surface area compared with 5%-Pd/C. Copyright © 2016 BCREC GROUP. All rights reserved Received: 31 st July 2015; Revised: 9 th December 2015; Accepted: 30 th December 2015 How to Cite : Stepacheva, A.A., Sapunov, V.N., Sulman, E.M., Nikoshvili, L.Z., Sulman, M.G., Sidorov, A.I., Demidenko, G.N., Matveeva, V.G. (2016). Catalytic Hydrodeoxygenation of Fatty Acids for Biodiesel Production. Bulletin of Chemical Reaction Engineering & Catalysis , 11 (2): 125-132 (doi:10.9767/bcrec.11.2.538.125-132) Permalink/DOI : http://dx.doi.org/10.9767/bcrec.11.2.538.125-132 Article Metrics: (click on the button below to see citations in Scopus)