Temperature-programmed Desorption Of Ammonia Research Articles

Facile adjusting the concentration of siliceous seed to obtain different HZSM-5 zeolite catalysts for effective catalytic depolymerization reaction of lignin

To improve lignin depolymerization reaction performance of HZSM-5 zeolite catalyst, we reported the effective catalytic depolymerization of rice husk lignin (RHL) to lignin phenolic monomer (LP) products over the different Si/Al mole ratios of HZSM-5 zeolite catalyst. Firstly, five samples comprising different Si/Al mole ratio of HZSM-5 zeolite catalyst were prepared by the physical method. The X-ray powder diffraction (XRD), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), pyridine adsorption Fourier transform infrared spectroscopy (FT-IR), and temperature-programmed desorption of ammonia (NH3-TPD) were used to characterize various catalysts. Secondly, gas chromatography–mass spectrometry (GC-MS), 2D heteronuclear single quantum coherence (2D-HSQC), and gel permeation chromatography (GPC) were used to characterize various catalytic depolymerization products. The effect of different Si/Al molar ratios on the lignin conversion to LP products and the structural changes of residual lignin were analyzed. Finally, according to the results of LP products, we discovered that after the use of different Si/Al molar ratios of HZSM-5 zeolite catalysts, the content of acid in the different catalysts which increased with decreasing the Si/Al mole ratios. Among them, the A4P PM products (A4P: having a saturated or unsaturated aliphatic side chain in C4 position) increased from 0.58% (SA560, Si/Al: 560) to 1.83% (SA70, Si/Al: 70), the C6P PM products (C6P: having no side chain in C4 position of G, S, and H structure) increased from 1.53% (SA560, Si/Al: 560) to 3.41% (SA70, Si/Al: 70). Finally, the highest 6.05% PM products yield appeared in the SA70 (Si/Al: 70) catalytic system. It is worth noting that PM products produced by this HZSM-5 zeolite catalyst SA70 have great potential to be a promising renewable alternative to fossil resources.

A new method for synthesis of a HMFI/SiC composite

HMFI/SiC composites show considerable potential for applications in heterogeneous catalysis due to the combination of the high catalytic performance of HMFI zeolites and the high thermal conductivity, mechanical strength, high-temperature resistance, and good chemical stability of SiC. Herein, we report for the first time the fast synthesis of HMFI/SiC composites directly in proton form under microwave irradiation without the addition of seed crystals. The preferable conditions for producing HMFI/SiC directly in proton form are 3 h at 190–200 °C. The structure and properties of the synthesized HMFI/SiC were determined by X-ray diffraction, scanning electron microscopy, low-temperature adsorption-desorption of nitrogen and temperature-programmed desorption of ammonia.

Iron-Based Composite Oxide Catalysts Tuned by CTAB Exhibit Superior NH3–SCR Performance

Iron-based oxide catalysts for the NH3–SCR (selective catalytic reduction of NOx by NH3) reaction have gained attention due to their high catalytic activity and structural adjustability. In this work, iron–niobium, iron–titanate and iron–molybdenum composite oxides were synthesized by a co-precipitation method with or without the assistance of hexadecyl trimethyl ammonium bromide (CTAB). The catalysts synthesized with the assistance of CTAB (FeM0.3Ox-C, M = Nb, Ti, Mo) showed superior SCR performance in an operating temperature range from 150 °C to 400 °C compared to those without CTAB addition (FeM0.3Ox, M = Nb, Ti, Mo). To reveal such enhancement, the catalysts were characterized by N2-physisorption, XRD (Powder X-ray diffraction), NH3-TPD (temperature-programmed desorption of ammonia), DRIFTS (Diffuse Reflectance Infrared Fourier Transform Spectroscopy), XPS (X-ray Photoelectron Spectroscopy), and H2-TPR (H2-Total Physical Response). It was found that the crystalline phase of Fe2O3 formed was influenced by the presence of CTAB in the preparation process, which favored the formation of crystalline γ-Fe2O3. Owing to the changed structure, the redox-acid properties of FeM0.3Ox-C catalysts were modified, with higher exposure of acid sites and improved ability of NO oxidation to NO2 at low-temperature, both of which also contributed to the improvement of NOx conversion. In addition, the weakened redox ability of Fe prevented the over-oxidation of NH3, thus accounting for the greatly improved high-temperature activity as well as N2 selectivity.

Catalytic Performance and Mechanism of Meso–Microporous Material β-SBA-15-Supported FeZr Catalysts for CO2 Desorption in CO2-Loaded Aqueous Amine Solution

The huge energy consumption of rich amine solution regeneration severely restricts the large-scale application and promotion of the CO2 capture process by the amine method. In order to reduce the operating energy consumption during the CO2 capture process using amines, especially the energy consumption of absorbent regeneration, zeolite β/SBA-15 (BS) has been synthesized in this work using the hydrothermal method with zeolite beta (β) as the silicon source; β was used to prepare the novel Zr@BS and Fe–Zr@BS catalysts for amine regeneration. Experiments for CO2 stripping were performed at 370.15 K using amine solvent [monoethanolamine (MEA)] with an initial CO2 loading of 0.50 mol CO2/mol amine. Additionally, all the materials were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, N2 adsorption–desorption experiment, ammonia temperature-programmed desorption, and pyridine adsorption infrared spectroscopy. Also, the catalytic CO2 desorption performances of seven different catalysts (β, SBA-15, three BS catalysts, Zr@BS, and Fe–Zr@BS) were investigated and assessed from the aspects of the cyclic capacity, desorption rate, and energy consumption. Experimental results indicated that the Fe–Zr@BS catalysts exhibited superior catalytic behaviors than other catalysts studied in this work, improving the desorption factor of MEA solution by 212% and bringing down the energy heat by 33% compared with 5 M MEA solution without catalysts. Furthermore, the Fe–Zr@BS catalysts show good stability and easy regeneration and do not influence absorption performance of the amine solution. Moreover, the possible catalytic mechanism for amine regeneration was proposed, and the stability of the material in terms of the structure of the material and the regeneration heat duty were also studied.

The effect of Si/Al ratio of zeolite Y in NiW catalyst for second stage hydrocracking

The effect of Si/Al ratio of zeolite Y on the performance of NiW catalysts for second stage hydrocracking was studied. The zeolites were characterized by IR spectroscopy of adsorbed pyridine, low-temperature N2 adsorption, and temperature-programmed desorption of ammonia. The observed decrease of Brønsted and Lewis acid sites concentration relates to the increase of Si/Al ratio in zeolites. According to HRTEM and XPS, sulfide component of catalysts differs in morphology, NiWS phase content and tungsten sulfidation degree. The catalysts were tested in hydrocracking of model (squalane) and real feedstock (unconverted oil (UCO) from two-stage industrial hydrocracker) at different temperatures. The increase of Si/Al ratio in zeolites was found to result in the decrease of catalytic activity and the increase of selectivity to middle distillates. However, similar selectivity of 52 and 53% at the 50% of UCO conversion was observed for catalysts containing zeolites with Si/Al ratio 24 and 37 respectively. This can be attributed mainly to the differences in the textural properties of the zeolites. The catalyst based on amorphous silica-alumina (without zeolites) was found to have a higher selectivity to middle distillates and lower activity as compared to zeolite-based catalysts.

Zr-DBS with Sulfonic Group: A Green and Highly Efficient Catalyst for Alcoholysis of Furfuryl Alcohol to Ethyl Levulinate

The alcoholysis of furfuryl alcohol (FA) produce ethyl levulinate (EL) plays a crucial role in the field of biomass conversion. In this work, a novel Zr-base catalyst with sulfonic groups in its structure was prepared by the co-precipitation of sodium dodecyl benzene sulfonate and ZrOCl2 (Zr-DBS) under non-toxic conditions. It was found that Zr-DBS has an excellent catalytic performance for this reaction and an EL yield of 95.27% could be achieved. Besides, Zr-DBS could be easily separated from the reaction system and reused at least four times without a significantly decrease in activity. Meanwhile, Zr-DBS was characterized by Fourier transform infrared spectroscopy (FT-IR), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), N2 adsorption–desorption, inductively coupled plasma optical emission spectroscopy (ICP-OES) and Temperature-programmed desorption of ammonia (NH3-TPD). The main reason for the high catalytic activity of the Zr-DBS was that the synergetic effects of Lewis and Bronsted acid sites and appropriate textural properties.

Alkylation of isobutane with butenes under microcatalytic conditions in pulse mode

Alkylation of isobutane with butenes is one of few important petrochemical processes that is still implemented using liquid acids. New highly active solid alkylation catalysts are investigated for century. The development of new rapid methods for testing catalysts will contribute to progress in this area. Therefore, the aim of the work was to test the possibility of conducting a bimolecular reaction of alkylation of isobutane with butenes in a microreactor in a pulsed mode of feeding. A zeolite-containing alkylation catalyst was synthesized and characterized by X-ray diffraction analysis, temperature-programmed desorption of ammonia and low-temperature nitrogen adsorption. Catalytic studies were performed in a microreactor built into the gas chromatograph scheme, which provided online analysis of the reaction products. The isobutane /butenes mixture was fed into the helium carrier gas stream via a loop. Testing was performed at 80, 100, 135 and 1850C. It was found that a significant amount of products is not desorbed by the carrier gas and is retained by the catalyst at reaction temperatures, while an increase in desorption temperature to 3800C promotes removing the products from the catalyst surface. The highest yield of products was 27% at 800C. With increasing the reaction temperature, the yield drops to 15%. It was shown that the developed method of testing of alkylation catalysts is promising for further use in the search for efficient solid-phase alkylation catalysts.

ИССЛЕДОВАНИЕ НЕОКИСЛИТЕЛЬНОЙ КОНВЕРСИИ МЕТАНА НА ГРАНУЛИРОВАННЫХ Mo/ZSM-5 КАТАЛИЗАТОРАХ

The relevance of the investigation is caused by the need for rational use of natural hydrocarbon gases, containing methane as the main component. Currently, plenty of these gases are burned in flares at oil production sites, that does great damage to the environment in the oil-producing regions of our country. The most promising process that allows obtaining valuable chemical products is the non-oxidative methane conversion into aromatic hydrocarbons over zeolite catalysts modified with transition metal ions. The Mo/ZSM-5 catalysts have high activity in this process. These catalysts are obtained both by impregnation and solid-phase synthesis. Development of the method of preparation of Mo/ZSM-5 catalysts using binder is of great importance for the industrial technology of processing gaseous hydrocarbons. The aim of the work is to study the effect of concentration and method of introducing a binder on physicochemical and catalytic properties of the Mo/ZSM-5 catalyst in non-oxidative methane conversion. Methods of investigation: IR spectroscopy, low-temperature adsorption of nitrogen, temperature-programmed desorption of ammonia (TPD-NH3), gas chromatography. Results. The Mo-containing catalyst based on ZSM-5 zeolite and nanosized molybdenum powder was prepared via solid-phase synthesis. The authors have studied the effect of a binder on physicochemical properties and activity of the Mo/ZSM-5 catalyst in non-oxidative conversion of methane into aromatic hydrocarbons. It was ascertained that the addition of a binder to the Mo/ZSM-5 catalyst results in a change in its texture and acid characteristics. It is shown that the activity of the Mo-containing zeolite during the non-oxidative conversion of methane into aromatic hydrocarbons is determined by the concentration of the binder in the catalyst and does not depend on the method of its introduction.

Synthesis of a novel bifunctional mesoporous Ti-SBA-15-SO3H catalyst and studies on their enhanced performance and kinetic modeling of lactic acid esterification reaction with n-butanol

Abstract In the present study, the mesoporous Ti-SBA-15-SO3H catalyst is synthesized by using the sol-gel method. Further, these materials have been characterized by different advanced analytical techniques such as Low angle X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Thermogravimetry/Differential thermal analysis (TG/DTA), N2 adsorption/desorption studies, Fourier transform infrared spectroscopy (FT-IR), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), Temperature-programmed desorption of ammonia (NH3-TPD) and Lactic acid esterification catalytic activity studies. The Ti-SBA-15-SO3H catalyst is found to have a surface area of 457 m2/g, a pore volume of 0.12 cm3/g, a pore diameter of 3.16 nm, and a high acid density of 1.72 mmol/g. The optimum reaction conditions for lactic acid esterification with n-butanol are found to be a 1: 4 M ratio, 3 wt-% catalysts, 115 °C temperature, and 120 min reaction time to obtain 72% conversion. Further, the reusability tests reveal that the spent catalyst can be used for five successive runs without the loss of considerable activity. The pseudo-homogeneous model was able to describe the kinetics of this esterification with negligible error. The activation energy and equilibrium rate constant for Ti-SBA-15-SO3H is found to be Ea = 0.063 KJ/mol and K = 5.019 lit/mol min, respectively, to catalyze the esterification of lactic acid with n-butanol. A plausible mechanism for the catalytic activity is proposed.

Methanol Dehydration to Dimethyl Ether over Modified γ-Al2O3 with Acid, Base and Zeolite (NaA and NaX)

The effect of acids, bases, zeolite NaA and zeolite NaX impregnation to g-Al2O3 on the catalyst characteristics and activity against methanol dehydration reaction were investigated. The catalyst characteristics include N2 physisorption, X-ray diffraction (XRD), and temperature-programmed desorption of ammonia (NH3-TPD) in addition to catalytic dehydration of methanol performed in a micro fixed-bed reactor at 270°C and 1 atm. The results of XRD characterization showed no changes related to the modification of alumina over acids, bases, and zeolite NaA and zeolite NaX. Therefore, the modification did not have any effect on the crystalline structure of alumina. The textural and surface acidity of g-Al2O3 changed post addition of acids, bases, zeolite NaA and zeolite NaX. NH3-TPD analysis results demonstrated that synthesized g-Al2O3 has three types of acid sites: weak, medium, and strong; however, the weak acid sites were not observed on alumina catalysts modified phosphate, KOH, zeolite NaA, and zeolite NaX. Furthermore, the concentration of strong acid sites increased in the catalyst containing KOH. The catalytic test results showed that the untreated g-Al2O3 catalyst gave prominent activity in dehydration of methanol compared to the treated catalyst following the number and strength of acid sites.

Titanium silicalite-1 supported bimetallic catalysts for selective hydrogenolysis of 5-hydroxymethylfurfural to biofuel 2, 5-dimethylfuran

Production of biofuels from biomass resources has received wide attention because of the current energy crisis. Recently, significant interest has been directed towards the selective hydrogenolysis of 5-hydroxymethylfurfural (HMF) to produce biofuel 2, 5-dimethylfuran (DMF). In this study, non-noble Ni–Cu catalysts with various Ni/Cu ratios, supported on titanium silicalite-1 (TS-1), were prepared through a solid-phase grinding method and used to catalyze the hydrogenolysis of HMF to DMF under a hydrogen atmosphere. The structure and surface morphology of the catalysts were characterized by X-ray diffraction, Fourier-transform infrared, thermogravimetry, X-ray photoelectron spectroscopy, temperature-programmed desorption of ammonia, scanning electron microscopy, and N2 adsorption-desorption techniques. Under the optimized reaction conditions, the conversion of HMF and the selectivity for DMF over a 40%Ni–5%Cu/TS-1 catalyst could reach 100.0% and 97.3%, respectively. Importantly, because the strong interaction of the Ni–Cu alloy structure prevents further reaction of the furan ring, almost no by-products are produced. The metal sites of Ni and Cu and the acid sites of TS-1 combine to provide a synergistic effect, which is beneficial to the hydrogenolysis of HMF. In addition, reusability experiments showed that the catalyst maintained good activity and stability.

Hydrocracking of Polyethylene to Jet Fuel Range Hydrocarbons over Bifunctional Catalysts Containing Pt- and Al-Modified MCM-48

A low-density polyethylene was hydrocracked to liquid hydrocarbons in autoclave reactors over catalysts containing Pt- and Al-modified MCM-48. Two kinds of Al-modified MCM-48 were synthesized for the reaction: Al-MCM-48 was synthesized using a sol–gel method by mixing Al(iso-OC3H7)3 with Si(OC2H5)4 and surfactant in a basic aqueous solution before hydrothermal synthesis, and Al/MCM-48 was synthesized using a post-modification method by grafting Al3+ ions on the surface of calcined Al/MCM-48. X-ray diffraction (XRD) patterns indicated that both Al-MCM-48 and Al/MCM-48 had a cubic mesoporous structure. The Brunauer–Emmett–Teller (BET) surface areas of Al-MCM-48 and Al/MCM-48 were larger than 1000 m2/g. 27Al Magic Angle Spinning-NMR (MAS NMR) indicated that Al3+ in Al-MCM-48 was located inside the framework of mesoporous silica, but Al3+ in Al/MCM-48 was located outside the framework of mesoporous silica. The results of ammonia temperature-programmed desorption (NH3-TPD) showed that the acidic strength of various samples was in the order of H-Y > Al/MCM-48 > Al-MCM-48 > MCM-48. After 4 MPa H2 was charged in the autoclave at room temperature, 1 wt % Pt/Al/MCM-48 catalyst showed a high yield of C9−C15 jet fuel range hydrocarbons of 85.9% in the hydrocracking of polyethylene at 573 K for 4 h. Compared with the reaction results of Pt/Al/MCM-48, the yield of light hydrocarbons (C1−C8) increased over Pt/H-Y, and the yield of heavy hydrocarbons (C16−C21) increased over Pt/Al-MCM-48 in the hydrocracking of polyethylene. The yield of C9−C15 jet fuel range hydrocarbons over the used catalyst did not decrease compared to the fresh catalyst in the hydrocracking of polyethylene to jet fuel range hydrocarbons over Pt/Al/MCM-48.

A basic comprehensive study on synergetic effects among the metal oxides in CeO2-WO3/TiO2 NH3-SCR catalyst

• The impregnated CeW/Ti-I exhibits over 80% NO x conversion at 200–550 °C for NH 3 -SCR. • Substitution of Ce 4+ /Ti 4+ by W 6+ at the interface depends on dispersion of metal oxides. • Formation of solid solutions produces more lattice defects and M O M’ bridges. • Ce 3+ and oxygen vacancies facilitate the low-temperature activity via fast SCR route. • Unsaturated cations and Ce(Ti) O W bonds serve as Lewis and Brønsted acid sites. Two Ce-W-Ti mixed oxide catalysts were prepared by wet impregnation (CeW/Ti-I) and mechanical mixing (Ce/W/Ti-M) methods. CeW/Ti-I catalyst exhibits over 80% NO x conversion and nearly 100% N 2 selectivity at 200–550 °C. The superior catalytic performance is associated with the high dispersion of active CeO 2 and acidic WO 3 on TiO 2 and the synergistic effects among different components. The X-ray Diffraction, Raman spectroscopy, Nitrogen physisorption, X-ray photoelectron spectroscopy, H 2 temperature-programmed reduction, temperature-programmed desorption of ammonia and infrared spectroscopy were performed. It is found that the formation of solid solutions, as well as the high specific surface area, would increase the amounts of Ce 3+ , oxygen vacancies and acid sites in the catalyst. These broaden the operating temperature window of NH 3 -SCR reaction and enhance the N 2 selectivity by facilitating “fast SCR” reaction at low temperatures and inhibiting the unselective oxidation of NH 3 at high temperatures.

Bimetallic AgPd/UiO-66 Hybrid Catalysts for Propylene Glycol Oxidation into Lactic Acid.

Different methods (the wetness impregnation of Ag and Pd precursors dissolved in water or acetonitrile solution, and the double solvent impregnation technique) were employed to immobilize Ag–Pd nanoparticles (NPs) into the pores of the microporous zirconium-based metal-organic framework known as UiO-66. The obtained materials were characterized by using nitrogen adsorption-desorption at −196 °C, powder X-ray diffraction, UV-Vis diffusion reflectance spectroscopy, and transition electron microscopy measurements. Special attention was paid to the acid and redox properties of the obtained materials, which were studied by using temperature-programmed desorption of ammonia (TPD-NH3) and temperature-programmed reduction (TPR-H2) methods. The use of a drying procedure prior to reduction was found to result in metallic NPs which, most likely, formed on the external surface and were larger than corresponding voids of the metal-organic framework. The formation of Ag–Pd alloy or monometallic Ag and Pd depended on the nature of both metal precursors and the impregnation solvent used. Catalytic activity of the AgPd/UiO-66 materials in propylene glycol oxidation was found to be a result of synergistic interaction between the components in AgPd alloyed NPs immobilized in the pore space and on the external surface of UiO-66. The key factor for consistent transformation of propylene glycol into lactic acid was the proximity between redox and acid-base species.

Synergistic Action of Montmorillonite with an Intumescent Formulation: The Impact of the Nature and the Strength of Acidic Sites on the Flame-Retardant Properties of Polypropylene Composites

A raw montmorillonite (Mt) was submitted to different acidic activation times in order to investigate the influence of the strength and the nature (Brønsted and Lewis) of acidic sites on the synergistic action with an intumescent formulation (IF) composed of ammonium polyphosphate (APP) and pentaerythritol (PER) when incorporated into a polypropylene (PP) matrix. The acidity of the Mt samples was quantified by ammonia temperature-programmed desorption (TPD-NH3) and Fourier transform infrared spectroscopy (FTIR) with pyridine adsorption. The mineral clays were also characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), nitrogen adsorption analysis and particle size distribution. Thermogravimetric analysis (TGA), limit oxygen index (LOI) and UL-94 were performed to evaluate the flame-retardant properties and the thermal stability. The TGA results show that the final residue increased 2 to 3 fold in comparison to the values predicted theoretically. The flammability properties achieved a maximum for the system containing an excess of moderate-strength Brønsted sites relative to the Lewis ones, reaching 38% in the LOI test. This result suggests that the presence of these Brønsted acidic sites is important, as they take part in the esterification reaction between APP and PER which gives rise to the char formation. The FTIR-Pyr adsorption and flammability results indicate that both the nature and strength of the acidic sites influence the flame-retardant properties.

Synthesis, Structure and Properties of an Extra‐Large‐Pore Aluminosilicate Zeolite NUD‐6

Pure silica zeolites possessing uniform micropores, large surface area and high thermal and chemical stability have been widely studied and used in the fields of fine chemicals and oil industry. The incorporation of aluminium into the framework of silica zeolites changes their properties, making them more industrially useful as adsorbents and catalysts. Herein, we report the synthesis and characterization of an extra-large-pore aluminosilicate zeolite NUD-6 with a 16-membered-ring pore channel. Aluminium was directly incorporated into the zeolite NUD-6 framework, as confirmed by 27 Al MAS NMR studies and ammonia temperature-programmed desorption probes. Al-NUD-6 was not stable when heated at 550 °C to remove the organic templates. However, the organic templates in Al-NUD-6 could be removed by oxidation in nitric acid at room temperature. The obtained Al-NUD-6H retained the crystalline structure and possessed both micropores and mesopores despite the occurrence of severe structural distortions due to the presence of the corner-sharing Q3 Si2 O7 units. The incorporation of aluminium resulted in both medium and strong acid sites in Al-NUD-6H, and could facilitate its use in adsorption and catalysis.

Investigation of ZSM-12 nanocrystals evolution derived from aluminosilicate nanobeads for sustainable production of ethyl levulinate from levulinic acid esterification with ethanol

Abstract The evolution of hierarchical ZSM-12 nanosized crystals as a function of crystallization time has been demonstrated using amorphous aluminosilicate (AS) nanobeads as simultaneous silica and alumina sources and cyclic diquaternary ammonium as a structure-directing agent (SDA) in a one-pot hydrothermal synthesis. The physicochemical properties of the derived ZSM-12 products were characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS) elemental analysis, N2 physisorption, temperature-programmed desorption of ammonia (NH3-TPD), and pyridine adsorption. It is clearly demonstrated that crystallinity, textural properties, and acidity of the zeolite products are enhanced as a function of crystallization time. The structure of nanocrystalline ZSM-12 is well-developed after 120 h of crystallization and the corresponding zeolite product exhibits the promising catalytic performance for sustainable production of ethyl levulinate (EL) from levulinic acid (LA) esterification with ethanol. This contribution illustrates an alternative way to synthesize hierarchical zeolite nanocrystals with MTW framework via the use of homogeneously dispersed aluminosilicate nanobeads as the starting materials and opens up the perspectives for the sustainable application of zeolites nanosized crystals in a bulky-molecule reaction of bio-based chemical synthesis.

Acid-Base Properties of Cobalt Ferrite Surface Examined by Different Physicoсhemical Methods

The acid-base properties of cobalt ferrite synthesized by the mechanochemical method with different ratios of the main components Fe2O3 : Co3O4 have been investigated using the temperature-programmed desorption of ammonia, IR spectroscopy using adsorbed pyridine with ammonia, and the Hammett indicator method. A comparison of the results for the total content of Lewis and Bronsted acid sites by three methods has shown that all three samples were quite similar, with a probability of 0.5%. The introduction of cobalt oxide into the composition of cobalt ferrite leads to an increase in the concentration of Bronsted and Lewis centers with a simultaneous increase in the number of strong basic centers determined by the temperature-programmed desorption of ammonia. The indicator method is the most informative method for a quantitative study of the acid-base properties of the cobalt ferrite surface, since it allows one to assess the concentration and strength of Lewis and Bronsted acid sites and basic sites.

Divanadium substituted keggin [PV2W10O40] on non-reducible supports-Al2O3 and SiO2: synthesis, characterization, and catalytic properties for oxidative dehydrogenation of propane

Molecular metal oxide cluster, K5[α-1,2-PV2W10O40] (PV2W10), was found to have intrinsic catalytic activity for the oxidative dehydrogenation of propane with high selectivity (> 80%) to propylene at low propane conversion (0.3%). Synthesis of dispersed PV2W10 in non-reducible supports, γ-Al2O3 and SiO2, was done by incipient wetness impregnation. The supported catalysts were characterized by IR, Raman spectroscopy, nitrogen adsorption, x-ray powder diffraction (PXRD), elemental analysis, hydrogen temperature-programmed reduction (H2–TPR), and ammonia temperature-programmed desorption (NH3–TPD). Catalytic testing of the supported PV2W10 at equimolar cluster concentration revealed that when supported in γ-Al2O3 it is more active (sevenfold increase in propane conversion) but in SiO2 it is more selective to propylene (94%). The observed performance was due to both an increase in reducibility and higher concentration of strong acid sites for PV2W10 supported in γ-Al2O3 versus SiO2. Lastly, PV2W10 was shown to remain intact under reaction conditions indicating its thermal and oxidative stability.

Adsorptive desulfurization of model diesel fuel over mono-functionalized nickel/γ-alumina and bi-functionalized nickel/cerium/γ-alumina adsorbents

In this study, the S–M direct interaction and π-complexation mechanisms for selective adsorption of 4,6-dimethyldibenzothiophene (4,6-DMDBT) onto the prepared mono-functionalized nickel/γ-alumina (Ni/γ–Al2O3) and bi-functionalized nickel/cerium/commercial γ-alumina (Ce–Ni/γ–Al2O3) were investigated. To characterize the prepared adsorbents, X-ray fluorescence spectroscopy, energy-dispersive X-ray, X-ray diffraction, N2 adsorption–desorption, and temperature-programmed desorption of ammonia (NH3-TPD) were used. The influence of nickel–cerium contents, 4,6-DMDBT and competitive aromatic concentrations on the adsorptive desulfurization performance were also studied. The equilibrium and kinetic data were well described by Langmuir and pseudo-second-order models, respectively. The maximum adsorption capacity of γ-Al2O3, Ni/γ–Al2O3 and Ce–Ni/γ–Al2O3 was found to be 1.253, 15.970 and 17.970 mg/g, respectively. Diffusion studies showed that both π–Ni and S–Ce were the major adsorption mechanisms in the first fast adsorption stage, and the external mass transfer limited the adsorption rate. In the second stage, the adsorption rate was controlled by intra-particle diffusion (R2 = 0.976 for Ni/γ–Al2O3 and R2 = 0.981 for Ce–Ni/γ–Al2O3) confirming that acid–base interaction (S–H) was formed. The results showed that selective binding formation of sulfur compounds on adsorbent active sites was proceeded via π-interaction (π–Ni), direct sulfur–cerium interaction (S–Ce), and acid–base interaction (S–H). The multifunctional Ce–Ni/γ–Al2O3 exhibited a higher adsorptive selectivity for 4,6-DMDBT compared to Ni/γ–Al2O3 in diesel fuel in the presence of aromatic content. The regeneration results showed that the prepared adsorbents can be reused easily for three cycles.