scholarly journals Renewable glycerol esterification over sulfonic-modified mesoporous silicas

2018 ◽  
Vol 83 (1) ◽  
pp. 39-50 ◽  
Author(s):  
Margarita Popova ◽  
Hristina Lazarova ◽  
Agnes Szegedi ◽  
Magdolna Mihályi ◽  
Мojca Rangus ◽  
...  
Keyword(s):  
Mesoporous Materials ◽  
Solid State Nmr ◽  
Value Added ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Gravimetric Analysis ◽  
Acidic Properties ◽  
X Ray ◽  
Post Synthesis ◽  
Glycerol Esterification

SO3H-functionalised mesoporous materials with different pore structures (SBA-15 and SBA-16) were prepared by the post-synthesis surface modification. The materials were thoroughly characterized by X-ray powder diffraction, nitrogen physisorption, temperature-gravimetric analysis, elemental analysis and solid state NMR spectroscopy. The acidic properties were investigated by the temperature-programed desorption of ammonia. The catalytic performance of SO3H-functionalised mesoporous materials was studied in glycerol esterification with acetic acid.The different amount of silanol groups in the initial SBA-15 and SBA-16 silicas predetermined the different amount of propylsulfonic groups which are formed in them and therefore significantly influenced the acidity and the catalytic performance in glycerol esterification. Much higher amount of Br?nsted acid sites was generated in SO3H modified SBA-15 catalyst, which exhibited higher activity to value-added triacetyl glycerol.

scholarly journals Enhanced Photocatalytic Activity of Cu2O Cabbage/RGO Nanocomposites under Visible Light Irradiation

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1712
Author(s):  
Appusamy Muthukrishnaraj ◽  
Salma Ahmed Al-Zahrani ◽  
Ahmed Al Otaibi ◽  
Semmedu Selvaraj Kalaivani ◽  
Ayyar Manikandan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Thermo Gravimetric Analysis ◽  
Visible Region ◽  
Catalytic Performance ◽  
Precipitation Method ◽  
Gravimetric Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dye Pollutants ◽  
Transmission Electron

Towards the utilization of Cu2O nanomaterial for the degradation of industrial dye pollutants such as methylene blue and methyl orange, the graphene-incorporated Cu2O nanocomposites (GCC) were developed via a precipitation method. Using Hummers method, the grapheme oxide (GO) was initially synthesized. The varying weight percentages (1–4 wt %) of GO was incorporated along with the precipitation of Cu2O catalyst. Various characterization techniques such as Fourier-transform infra-red (FT-IR), X-ray diffraction (XRD), UV–visible diffused reflectance (UV-DRS), Raman spectroscopy, thermo gravimetric analysis (TGA), energy-dispersive X-ray analysis (EDX), and electro chemical impedance (EIS) were followed for characterization. The cabbage-like morphology of the developed Cu2O and its composites were ascertained from field-emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HR-TEM). In addition, the growth mechanism was also proposed. The results infer that 2 wt % GO-incorporated Cu2O composites shows the highest value of degradation efficiency (97.9% and 96.1%) for MB and MO at 160 and 220 min, respectively. Further, its catalytic performance over visible region (red shift) was also enhanced to an appreciable extent, when compared with that of other samples.

scholarly journals Influence of Sulfur-Containing Sodium Salt Poisoned V2O5–WO3/TiO2 Catalysts on SO2–SO3 Conversion and NO Removal

Catalysts ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 541 ◽  
Author(s):  
Haiping Xiao ◽  
Chaozong Dou ◽  
Hao Shi ◽  
Jinlin Ge ◽  
Li Cai
Keyword(s):  
Photoelectron Spectroscopy ◽  
No Reduction ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Impregnation Method ◽  
So2 Oxidation ◽  
Sodium Salts ◽  
X Ray ◽  
Temperature Programmed ◽  
Physical Features

A series of poisoned catalysts with various forms and contents of sodium salts (Na2SO4 and Na2S2O7) were prepared using the wet impregnation method. The influence of sodium salts poisoned catalysts on SO2 oxidation and NO reduction was investigated. The chemical and physical features of the catalysts were characterized via NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FT-IR). The results showed that sodium salts poisoned catalysts led to a decrease in the denitration efficiency. The 3.6% Na2SO4 poisoned catalyst was the most severely deactivated with denitration efficiency of only 50.97% at 350 °C. The introduction of SO42− and S2O72− created new Brønsted acid sites, which facilitated the adsorption of NH3 and NO reduction. The sodium salts poisoned catalysts significantly increased the conversion of SO2–SO3. 3.6%Na2S2O7 poisoned catalyst had the strongest effect on SO2 oxidation and the catalyst achieved a maximum SO2–SO3-conversion of 1.44% at 410 °C. Characterization results showed sodium salts poisoned catalysts consumed the active ingredient and lowered the V4+/V5+ ratio, which suppressed catalytic performance. However, they increased the content of chemically adsorbed oxygen and the strength of V5+=O bonds, which promoted SO2 oxidation.

scholarly journals Effect of Ce-modified Fe/ZSM-5 zeolite for selective catalytic reduction of NOx by ammonia

2020 ◽  
Vol 218 ◽  
pp. 03032
Author(s):  
Chenxi Li ◽  
Fanwei Meng ◽  
Qing Ye
Keyword(s):  
Selective Catalytic Reduction ◽  
Photoelectron Spectroscopy ◽  
Catalytic Reduction ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Impregnation Method ◽  
Adsorption Ability ◽  
In Situ Drifts ◽  
X Ray

A series of xCe-Fe/ZSM-5 (x = 0, 0.25, 0.5 wt%) samples were prepared by the impregnation method, and the catalytic activity was evaluated by the selective catalytic reduction of NOx with ammonia (NH3-SCR). The physicochemical properties of prepared samples were characterized by various techniques such as X-ray diffraction (XRD), Brunner-Emmet-Teller (BET) measurement, hydrogen temperatureprogrammed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), ammonia temperatureprogrammed desorption (NH3-TPD) and in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS). XRD and BET results demonstrated that Ce and Fe species were uniform dispersed on the surface of the ZSM-5 zeolite and the micropore structure of ZSM-5 was still maintained. H2-TPR analysis indicated that the doping of Ce created more isolated Ce4+ and Fe3+ on the surface of catalysts, and the abundant Ce4+ and Fe3+ could enhance the reduction ability of catalysts. XPS analysis suggested that the doping of Ce could generate more oxygen vacancies, thereby increasing the number of chemisorption oxygen. According to the in-situ DRIFTS and NH3-TPD results, Ce species provided more acidic sites, which is beneficial to the NH3 adsorption ability of ZSM-5 zeolite. Additionally, the abundant chemisorption oxygen, medium and strong Brønsted acid sites, excellent NH3 adsorption ability and outstanding reduction property are beneficial to the NH3-SCR reaction. Among all prepared samples, the 0.25Ce-Fe/ZSM-5 sample possessed the widest reaction temperature window and the best catalytic performance (NO conversion over 98% at 350-450 °C), which was associated with the abundant acid sites and remarkable adsorption ability of NH3, outstanding redox ability and abundant chemisorption oxygen after the doping of Ce.

scholarly journals The Synergistic Effect of Acidic Properties and Channel Systems of Zeolites on the Synthesis of Polyoxymethylene Dimethyl Ethers from Dimethoxymethane and Trioxymethylene

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1192
Author(s):  
Jianbing Wu ◽  
Sen Wang ◽  
Haitao Li ◽  
Yin Zhang ◽  
Ruiping Shi ◽  
...  
Keyword(s):  
Synergistic Effect ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Acidic Properties ◽  
Polyoxymethylene Dimethyl Ethers ◽  
Pore Mouth ◽  
Maximal Space ◽  
Essential Prerequisite ◽  
End Group ◽  
Channel Systems

A series of zeolites with different topology structures, including SAPO-34, SUZ-4, ZSM-5, USY, MOR, and beta, were used to synthesize polyoxymethylene dimethyl ethers (PODEn) from dimethoxymethane (DMM) and trioxymethylene (TOM). The influence of acidic properties and channel systems were studied by activity evaluation, characterization, and theoretical calculation. The results confirmed that pore mouth diameter larger than a TOM molecule was an essential prerequisite for the synthesis of PODEn over zeolites, and the synergistic effect between medium-strong Brønsted acid sites (Brønsted MAS) and the maximal space of zeolites available determined the catalytic performance of all studied zeolites. DMM and TOM were firstly decomposed into methoxymethoxy groups (MMZ) and monomer CH2O over Brønsted MAS. Subsequently, the steric constraint of the maximum included sphere, with an appropriate size in zeolite channels, can promote the combination of CH2O and MMZ to form transition species ZO(CH2O)nCH3, which reacted with the methyl-end group to form PODEn over Brønsted MAS. Moreover, the reaction temperature showed different effects on the product selectivity and distribution, which also mainly depends on the size of the maximum space available in zeolite channels.

scholarly journals Influence of Chemical Surface Characteristics of Ammonium-Modified Chilean Zeolite on Oak Catalytic Pyrolysis

Catalysts ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 465
Author(s):  
Serguei Alejandro-Martín ◽  
Adán Montecinos Acaricia ◽  
Cristian Cerda-Barrera ◽  
Hatier Díaz Pérez
Keyword(s):  
Catalytic Pyrolysis ◽  
Value Added ◽  
Surface Characteristics ◽  
Acid Sites ◽  
Bronsted Acid ◽  
X Ray ◽  
Chemical Surface ◽  
Brönsted Acid ◽  
Bio Oil ◽  
Modified Zeolites

The influence of chemical surface characteristics of Chilean natural and modified zeolites on Chilean Oak catalytic pyrolysis was investigated in this study. Chilean zeolite samples were characterised by nitrogen absorption at 77 K, X-ray powder diffraction (XRD), and X-ray fluorescence (XRF). The nature and strength of zeolite acid sites were studied by diffuse reflectance infrared Fourier transform (DRIFT), using pyridine as a probe molecule. Experimental pyrolysis was conducted in a quartz cylindrical reactor and bio-oils were obtained by condensation of vapours in a closed container. Chemical species in bio-oil samples were identified by a gas chromatography/mass spectrophotometry (GC/MS) analytical procedure. Results indicate that after the ionic exchange treatment, an increase of the Brønsted acid site density and strength was observed in ammonium-modified zeolites. Brønsted acids sites were associated with an increment of the composition of ketones, aldehydes, and hydrocarbons and to a decrease in the composition of the following families (esters; ethers; and acids) in obtained bio-oil samples. The Brønsted acid sites on ammonium-modified zeolite samples are responsible for the upgraded bio-oil and value-added chemicals, obtained in this research. Bio-oil chemical composition was modified when the pyrolysis-derived compounds were upgraded over a 2NHZ zeolite sample, leading to a lower quantity of oxygenated compounds and a higher composition of value-added chemicals.

scholarly journals Mesoporous Beta Zeolite Catalysts for Benzylation of Naphthalene: Effect of Pore Structure and Acidity

Catalysts ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 504 ◽  
Author(s):  
Wenming Hao ◽  
Weimin Zhang ◽  
Zaibin Guo ◽  
Jinghong Ma ◽  
Ruifeng Li
Keyword(s):  
Catalytic Performance ◽  
Acid Sites ◽  
Zeolite Catalysts ◽  
Beta Zeolite ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acid Type ◽  
Beta Zeolites ◽  
Acidic Sites ◽  
Xrd Patterns

To improve the catalytic performance of zeolite catalysts in reactions involving bulky molecules, a series of mesoporous Beta zeolite were prepared using organic functionalized fumed silica as the silicon source, which were thoroughly characterized in terms of porosity and acidity. The peaks in X-ray diffraction (XRD) patterns showed broadening, and the external surface area and mesoporosity increased progressively when the content of organic functionalization increased. An infrared (IR) spectroscopy study of adsorbed probe molecules, including pyridine (Py-IR), 2,6-ditertbutylpyridine (DTBPy-IR) and pivalonitrile (Pn-IR), showed that the improvement of mesoporosity increased the accessibility of acidic sites. In the catalytic benzylation of naphthalene with benzyl chloride (BC) over the mesoporous Beta zeolite catalysts, the conversion of BC was significantly increased when the accessibility of Brönsted acid sites improved. The increase of mesoporosity not only improved the diffusion ability of the reactants and products, but also increased the accessibility of acid sites, which greatly enhanced the activity of the mesoporous Beta zeolite catalysts. It is highlighted that the interdependence of mesoporosity, acid type, acid concentration, and strength of the mesoporous Beta zeolites on the catalytic performance in the benzylation of naphthalene with BC was comprehensively studied.

scholarly journals Catalytic Behavior of Alkali Treated H-MOR in Selective Synthesis of Ethylenediamine via Condensation Amination of Monoethanolamine

Catalysts ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 386
Author(s):  
Feng-Wei Zhao ◽  
Qian Zhang ◽  
Feng Hui ◽  
Jun Yuan ◽  
Su-Ning Mei ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Active Sites ◽  
Alkali Treatment ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Selective Synthesis ◽  
Catalytic Behavior ◽  
X Ray ◽  
Bulk Catalyst ◽  
Temperature Programmed

Catalytic behavior of alkali treated mordenite (H-MOR) in selective synthesis of ethylenediamine (EDA) via condensation amination of monoethanolamine (MEA) was investigated. Changes in the structural and acidic properties of alkali treated H-MOR were systematically investigated by N2 adsorption/desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), temperature programmed ammonia desorption (NH3-TPD), pyridine adsorption was followed by infrared spectroscopy (Py-IR), and X-ray fluorescence (XRF) analyses. The results show that alkali treatment produces more opening mesopores on the H-MOR crystal surfaces and leads to an increase in the number of B acid sites and the strength of the acid sites. The mesopores effectively enhance the rate of diffusion in the bulk catalyst. Moreover, the B acid sites are active sites in selective synthesis of EDA. Due to improvements in the diffusion conditions and reactivities, alkali treated H-MOR shows an excellent catalytic performance under mild reaction conditions. The conversion of MEA was 52.8% and selectivity to EDA increased to 93.6%, which is the highest selectivity achieved so far. Furthermore, possible mechanism for the formation of EDA is discussed.

Post-Synthesis Conversion of Borosilicate Zeolite Beta to an Aluminosilicate with Isolated Acid Sites: A Quantitative Distance Analysis by Solid-State NMR

2016 ◽  
Vol 120 (18) ◽  
pp. 9811-9820 ◽  
Author(s):  
Hubert Koller ◽  
Soumya Senapati ◽  
Jinjun Ren ◽  
Tobias Uesbeck ◽  
Vassilios Siozios ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Acid Sites ◽  
Zeolite Beta ◽  
Distance Analysis ◽  
Post Synthesis

Characterization and Acidic Properties of AlMCM-41 Prepared by Conventional and Post-Synthesis Alumination

2015 ◽  
Vol 68 (1) ◽  
pp. 99 ◽  
Author(s):  
Maria J. F. Costa ◽  
Thiago Chellappa ◽  
Antonio S. Araujo ◽  
Viviane M. Fonseca ◽  
Valter J. Fernandes ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Synthesis Method ◽  
Textural Properties ◽  
Acid Sites ◽  
Isomorphous Substitution ◽  
Trivalent Cation ◽  
Isothermal Adsorption ◽  
X Ray ◽  
Model Free ◽  
Post Synthesis

The catalysts analysed in the current work are variations of MCM-41. The properties of these highly ordered mesoporous aluminosilicates were adjusted by an isomorphous substitution of Si by a trivalent cation, in this case Al3+, generating catalysts of the AlMCM-41 type. The materials were synthesized with a silicon/aluminium ratio of 40, through two methods of impregnation of the metal: conventional and post-synthesis alumination. With the aim of determining the density of the acid sites of the Al40MCM-41 prepared by post-synthesis and conventional alumination, studies of the adsorption of n-butylamine probe molecule were carried out. Further, the studied material was characterized by thermogravimetry measurements, providing the profile of decomposition of the samples, which allowed calculation of the densities of the acid sites. The model-free kinetic algorithms were applied in order to determinate conversion and apparent activation energy. Comparison of energy-dispersive X-ray fluorescence and X-ray photoelectron spectroscopy measurements indicated that the post-synthesis method was more favourable based on the metal positioning, ‘anchored’ in the surface of the catalyst. The textural properties of the calcined Al40MCM-41 prepared by post-synthesis and conventional alumination were characterized by X-ray diffraction, N2 isothermal adsorption measurements (Brunauer–Emmett–Teller and Barrett–Joyner–Halenda), transmission electron microscopy, and X-ray photoelectron spectroscopy.

scholarly journals Oxidative Condensation of Furfural with Ethanol Using Pd-Based Catalysts: Influence of the Support

Catalysts ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1309
Author(s):  
Juan Antonio Cecilia ◽  
Carmen Pilar Jiménez-Gómez ◽  
Virginia Torres-Bujalance ◽  
Cristina García-Sancho ◽  
Ramón Moreno-Tost ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Value Added ◽  
Textural Properties ◽  
Catalytic Performance ◽  
Oxidative Condensation ◽  
X Ray ◽  
Basic Sites ◽  
Carbonaceous Deposits ◽  
Β Zeolite ◽  
Adsorption Desorption

PdO nanoparticles were deposited on several supports (β-zeolite, Al2O3, Fe2O3, MgO, and SiO2), which displayed different crystallinity, textural properties, and amount of acid and basic sites. These catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms at −196 °C, NH3 and CO2 thermoprogrammed desorption analyses (NH3- and CO2-TPD, and X-ray photoelectron spectroscopy (XPS). Pd-based catalysts were tested in the oxidative condensation of furfural with ethanol to obtain value-added chemicals. The catalytic results revealed high conversion values, although the presence of a high proportion of carbonaceous deposits, mainly in the case of the PdO supported on β-zeolite and Al2O3, is also noteworthy. The presence of basic sites led to a beneficial effect on the catalytic behavior, since the formation of carbonaceous deposits was minimized. Thus, the 2Pd-MgO (2 wt.% Pd) catalyst reached the highest yield of furan-2-acrolein (70%) after 3 h of reaction at 170 °C. This better catalytic performance can be explained by the high basicity of MgO, used as support, together with the large amount of available PdO, as inferred from XPS.

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