Promotional Effects of Rare-Earth Praseodymium (Pr) Modification over MCM-41 for Methyl Mercaptan Catalytic Decomposition

Praseodymium (Pr)-promoted MCM-41 catalyst was investigated for the catalytic decomposition of methyl mercaptan (CH3SH). Various characterization techniques, such as X-ray diffraction (XRD), N2 adsorption–desorption, temperature-programmed desorption of ammonia (NH3-TPD) and carbon dioxide (CO2-TPD), hydrogen temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectrometer (XPS), were carried out to analyze the physicochemical properties of material. XPS characterization results showed that praseodymium was presented on the modified catalyst in the form of praseodymium oxide species, which can react with coke deposit to prolong the catalytic stability until 120 h. Meanwhile, the strong acid sites were proved to be the main active center over the 10% Pr/MCM-41 catalyst by NH3-TPD results during the catalytic elimination of methyl mercaptan. The possible reaction mechanism was proposed by analyzing the product distribution results. The final products were mainly small-molecule products, such as methane (CH4) and hydrogen sulfide (H2S). Dimethyl sulfide (CH3SCH3) was a reaction intermediate during the reaction. Therefore, this work contributes to the understanding of the reaction process of catalytic decomposition methyl mercaptan and the design of anti-carbon deposition catalysts.

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Tungsten Oxide-Modified SSZ-13 Zeolite as an Efficient Catalyst for Ethylene-To-Propylene Reaction

Catalysts ◽

10.3390/catal11050553 ◽

2021 ◽

Vol 11 (5) ◽

pp. 553

Author(s):

Mansurbek Urol ugli Abdullaev ◽

Sungjune Lee ◽

Tae-Wan Kim ◽

Chul-Ung Kim

Keyword(s):

Tungsten Oxide ◽

Fixed Bed ◽

Acid Sites ◽

Fixed Bed Reactor ◽

Incipient Wetness Impregnation ◽

Impregnation Method ◽

Efficient Catalyst ◽

X Ray ◽

Propylene Selectivity ◽

Temperature Programmed

Among the zeolitic catalysts for the ethylene-to-propylene (ETP) reaction, the SSZ-13 zeolite shows the highest catalytic activity based on both its suitable pore architecture and tunable acidity. In this study, in order to improve the propylene selectivity further, the surface of the SSZ-13 zeolite was modified with various amounts of tungsten oxide ranging from 1 wt% to 15 wt% via a simple incipient wetness impregnation method. The prepared catalysts were characterized with several analysis techniques, specifically, powder X-ray diffraction (PXRD), Raman spectroscopy, temperature-programmed reduction of hydrogen (H2-TPR), temperature-programmed desorption of ammonia (NH3-TPD), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), and N2 sorption, and their catalytic activities were investigated in a fixed-bed reactor system. The tungsten oxide-modified SSZ-13 catalysts demonstrated significantly improved propylene selectivity and yield compared to the parent H-SSZ-13 catalyst. For the tungsten oxide loading, 10 wt% loading showed the highest propylene yield of 64.9 wt%, which was 6.5 wt% higher than the pristine H-SSZ-13 catalyst. This can be related to not only the milder and decreased strong acid sites but also the diffusion restriction of bulky byproducts, as supported by scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (STEM-EDS) observation.

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

Catalysts ◽

10.3390/catal8110541 ◽

2018 ◽

Vol 8 (11) ◽

pp. 541 ◽

Cited By ~ 3

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.

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Nanostructured Co3O4 Oxide for Low Temperature Ethanol Oxidation

Materials Science Forum ◽

10.4028/www.scientific.net/msf.798-799.205 ◽

2014 ◽

Vol 798-799 ◽

pp. 205-210

Author(s):

Jairo Alberto Gomez-Cuaspud ◽

Martin Schmal

Keyword(s):

Ethanol Oxidation ◽

Physicochemical Characterization ◽

Fluorescence Analysis ◽

Product Distribution ◽

X Ray Diffraction ◽

Ethanol Oxidation Reaction ◽

Reaction Conditions ◽

X Ray ◽

Temperature Programmed ◽

Combustion Technique

We investigated the synthesis of nanosized Co3O4 oxide by the polymerization-combustion technique, with different concentrations (3, 12 and 25% w/w) in the ethanol oxidation reaction. Characterization was done by X-ray fluorescence analysis, X-ray diffraction, temperature programmed reduction, scanning and transmission electronic microscopy and CO and H2 chemisorption. Principal results from physicochemical characterization show that the concentration of the metal oxide influence the product distribution and selectivity under isothermal conditions at 420 °C showed the formation of intermediate etoxi-species and preferential dehydrogenation reaction on stream of material. Specific concentrations result in high conversions and H2 selectivity under present reaction conditions.

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MCM-41 Supported Co-Based Bimetallic Catalysts for Aqueous Phase Transformation of Glucose to Biochemicals

Processes ◽

10.3390/pr8070843 ◽

2020 ◽

Vol 8 (7) ◽

pp. 843 ◽

Cited By ~ 1

Author(s):

Somayeh Taghavi ◽

Elena Ghedini ◽

Federica Menegazzo ◽

Michela Signoretto ◽

Delia Gazzoli ◽

...

Keyword(s):

Catalytic Activity ◽

Bimetallic Catalysts ◽

High Surface ◽

High Surface Area ◽

Mesoporous Structure ◽

Acid Sites ◽

Weak Acid ◽

Reaction Conditions ◽

Temperature Programmed ◽

Mcm 41

The transformation of glucose into valuable biochemicals was carried out on different MCM-41-supported metallic and bimetallic (Co, Co-Fe, Co-Mn, Co-Mo) catalysts and under different reaction conditions (150 °C, 3 h; 200 °C, 0.5 h; 250 °C, 0.5 h). All catalysts were characterized using N2 physisorption, Temperature Programmed Reduction (TPR), Raman, X-ray Diffraction (XRD) and Temperature Programmed Desorption (TPD) techniques. According to the N2-physisorption results, a high surface area and mesoporous structure of the support were appropriate for metal dispersion, reactant diffusion and the formation of bioproducts. Reaction conditions, bimetals synergetic effects and the amount and strength of catalyst acid sites were the key factors affecting the catalytic activity and biochemical selectivity. Sever reaction conditions including high temperature and high catalyst acidity led to the formation mainly of solid humins. The NH3-TPD results demonstrated the alteration of acidity in different bimetallic catalysts. The 10Fe10CoSiO2 catalyst (MCM-41 supported 10 wt.%Fe, 10 wt.%Co) possessing weak acid sites displayed the best catalytic activity with the highest carbon balance and desired product selectivity in mild reaction condition. Valuable biochemicals such as fructose, levulinic acid, ethanol and hydroxyacetone were formed over this catalyst.

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The Effect of Catalyst Calcination Temperature on Catalytic Decomposition of HFC-134a over γ-Al2O3

Catalysts ◽

10.3390/catal11091021 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1021

Author(s):

Mahshab Sheraz ◽

Ali Anus ◽

Van Cam Thi Le ◽

Caroline Mercy Andrew Swamidoss ◽

Seungdo Kim

Keyword(s):

Catalytic Activity ◽

Catalytic Pyrolysis ◽

Catalytic Decomposition ◽

Temperature Programmed Desorption ◽

X Ray Diffraction ◽

X Ray ◽

Hfc 134A ◽

Acidic Sites ◽

Temperature Programmed ◽

Decomposition Efficiency

This paper explores the thermal and catalytic pyrolysis of HFC-134a over γ-Al2O3 calcined at temperatures of 550 °C (A550), 650 °C (A650), 750 °C (A750), and 850 °C (A850). The physicochemical properties of catalysts were studied through thermogravimetric analysis (TGA), Brunauer–Emmett–Teller equation for nitrogen physisorption analysis (BET), X-ray diffraction (XRD), and temperature-programmed desorption of ammonia (NH3-TPD). The non-catalytic pyrolysis of HFC-134a showed less than 15% decomposition of HFC-134a. Catalysts increased the decomposition as A650 revealed the highest decomposition efficiency by decomposing more than 95% HFC-134a for 8 h followed by A750, A850, and A550. The larger surface area and pore volume paired with a low amount of strong acidic sites were considered as the main contributors to the comparatively longer catalytic activity of A650.

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Cellulose Conversion to 5 Hydroxymethyl Furfural (5-HMF) Using Al-Incorporated SBA-15 as Highly Efficient Catalyst

Journal of Chemistry ◽

10.1155/2019/5785621 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8 ◽

Cited By ~ 1

Author(s):

Son Tung Pham ◽

Manh B. Nguyen ◽

Giang H. Le ◽

Trang T. T. Pham ◽

Trang T. T. Quan ◽

...

Keyword(s):

Hydrothermal Process ◽

Strong Acid ◽

Acid Sites ◽

Efficient Catalyst ◽

Cellulose Conversion ◽

X Ray ◽

Hydroxymethyl Furfural ◽

Temperature Programmed ◽

Strong Acid Sites ◽

Adsorption Desorption

Al-incorporated SBA-15 samples (xAl/SBA-15) were successfully prepared by “atomic implantation” method. The samples were characterized by X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), N2 adsorption-desorption isotherms (BET), and temperature-programmed desorption (NH3-TPD). In this catalyst, metal oxide species were highly dispersed on the SBA-15 surface and existed as isolated atoms. It was shown that the Al incorporation lead to the formation of medium and strong acid sites. The catalytic activity and selectivity were tested in a mild hydrothermal process for degradation of cotton cellulose to 5-hydroxymethyl furfural (5-HMF). A cellulose conversion of 68.5% and 5-HMF selectivity of 62.1% after 2 h of reaction at 170°C were achieved. The very high 5-HMF yield (42.57%) obtained in this paper is much higher than that was reported in the literature.

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

Catalysts ◽

10.3390/catal10040386 ◽

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.

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Effect of the Ni/Al Ratio on the Performance of NiAl2O4 Spinel-Based Catalysts for Supercritical Methylcyclohexane Catalytic Cracking

Catalysts ◽

10.3390/catal11030323 ◽

2021 ◽

Vol 11 (3) ◽

pp. 323

Author(s):

Kyoung Ho Song ◽

Soon Kwan Jeong ◽

Byung Hun Jeong ◽

Kwan-Young Lee ◽

Hak Joo Kim

Keyword(s):

Spinel Structure ◽

Coke Formation ◽

Strong Acid ◽

Acid Sites ◽

The Other ◽

X Ray ◽

Temperature Programmed Oxidation ◽

Temperature Programmed ◽

Co Precipitation ◽

Strong Acid Sites

Supercritical methylcyclohexane cracking of NiAl2O4 spinel-based catalysts with varying Ni/Al deficiencies was investigated. Thus, catalysts with Ni content of 10–50 wt.% were prepared by typical co-precipitation methods. The calcined, reduced, and spent catalysts were characterized by X-ray diffraction, O2 temperature-programmed oxidation, NH3 temperature-programmed desorption, N2 physisorption, O2 chemisorption, scanning and transmission electron microscopy, and X-ray fluorescence. The performance and physicochemical properties of the reference stoichiometric Ni3Al7 catalyst differed significantly from those of the other catalysts. Indeed, the Ni-deficient Ni1Al9 catalyst led to the formation of large Ni particles (diameter: 20 nm) and abundant strong acid sites, without spinel structure formation, owing to the excess Al. These acted with sufficient environment and structure to form the coke precursor nickel carbide, resulting in a pressure drop within 17 min. On the other hand, the additional NiO linked to the NiAl2O4 spinel structure of the Al-deficient Ni5Al5 catalyst formed small crystals (10 nm), owing to the excess Ni, and displayed improved Ni dispersion. Thus, dehydrogenation proceeded effectively, thereby improving the resistance to coke formation. This catalytic behavior further demonstrated the remarkable activity and stability of this catalyst under mild conditions (450 °C and 4 Mpa).

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Radioisotopic study of 11C-labelling methanol decomposition on iron oxide modified mesoporous MCM-41 silica

Canadian Journal of Chemistry ◽

10.1139/v08-185 ◽

2009 ◽

Vol 87 (3) ◽

pp. 478-485 ◽

Cited By ~ 6

Author(s):

Eva Sarkadi-Pribóczki ◽

Tanya Tsoncheva ◽

Ljubomira Ivanova

Keyword(s):

Iron Oxide ◽

Surface Coverage ◽

Methanol Conversion ◽

Methanol Decomposition ◽

Reaction Pathways ◽

X Ray Diffraction ◽

Iron Species ◽

X Ray ◽

Temperature Programmed ◽

Mcm 41

Novel 11C-radiolabelling method was applied for the investigation of methanol conversion on iron oxide modified mesoporous MCM-41. Changes in the selectivity were observed varying the state of the loaded iron species or the degree of the surface coverage with 11C-radiolabelling methanol. Combining the Moessbauer spectroscopy, X-ray diffraction (XRD), N2-physisorption, and temperature-programmed reduction- thermogravimetric (TPR-TG) techniques with the high sensitive 11C-radioisotopic catalytic analysis, the contribution of the different reaction pathways of methanol conversion was discussed.

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Effect of Zn/ZSM-5 and FePO4Catalysts on Cellulose Pyrolysis

Journal of Chemistry ◽

10.1155/2015/749875 ◽

2015 ◽

Vol 2015 ◽

pp. 1-11 ◽

Cited By ~ 3

Author(s):

Haian Xia ◽

Xiaopei Yan ◽

Siquan Xu ◽

Li Yang ◽

Yuejie Ge ◽

...

Keyword(s):

Lewis Acid ◽

Value Added ◽

Product Distribution ◽

Acid Sites ◽

Gas Chromatography Mass Spectrometry ◽

Lewis Acid Sites ◽

Liquid Products ◽

Temperature Programmed ◽

Xrd Techniques ◽

Brønsted And Lewis Acid

A series of Zn/ZSM-5 catalysts with different Zn contents and FePO4were used to pyrolyze cellulose to produce value added chemicals. The nature of these catalysts was characterized by ammonia-temperature programmed desorption (NH3-TPD), IR spectroscopy of pyridine adsorption, and X-ray diffraction (XRD) techniques. Noncatalytic and catalytic pyrolytic behaviors of cellulose were studied by thermogravimetric (TG) technique. The pyrolytic liquid products, that is, the biooils, were analyzed by gas chromatography-mass spectrometry (GC-MS). The major components of the biooils are anhydrosugars such as levoglucosan (LGA), 1,6-anhydro-β-D-glucofuranose (AGF), levoglucosenone (LGO, 1,6-anhydro-3,4-dideoxy-β-D-pyranosen-2-one), and 1,4:3,6-dianhydro-α-D-glucopyranose (DGP), as well as furan derivatives, alcohols, and so forth. Zn/ZSM-5 samples with Brønsted and Lewis acid sites and the FePO4catalyst with Lewis acid sites were found to have a significant effect on the pyrolytic behaviors of cellulose and product distribution. These results show that Brønsted and Lewis acid sites modified remarkably components of the biooil, which could promote the production of furan compounds and LGO. On the basis of the findings, a model was proposed to describe the pyrolysis pathways of cellulose catalyzed by the solid acid catalysts.

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