Porosity Design of Shaped Zeolites for Improved Catalyst Lifetime in the Methanol-to-Hydrocarbons Reaction

Additional porosity, such as meso- and macropores, was introduced in zeolite extrudates with the intention intuit of improving the effective diffusivity of the catalysts. The samples were characterized in depth by nitrogen adsorption-desorption, mercury intrusion porosimetry, ammonia temperature programmed desorption and adsorption of pyridine followed by infrared spectroscopy. The results revealed no significant change in the acidity but an increase of the pore volume. According to significant improvement in the effective diffusivity, the samples were tested in the methanol-to-hydrocarbons reaction. The catalytic stability was greatly enhanced with an increase in the pore volume, demonstrating a relation between effective diffusivity and resistance to deactivation by coke formation. Further experiments also revealed a higher toluene adsorption capacity and a raise in the breakthrough time over the most porous samples due to better accessibility of toluene molecules into the active sites of the zeolite.

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Design of composite micro/mesoporous molecular sieve catalysts

Pure and Applied Chemistry ◽

10.1351/pac200476091647 ◽

2004 ◽

Vol 76 (9) ◽

pp. 1647-1657 ◽

Cited By ~ 62

Author(s):

I. I. Ivanova ◽

A. S. Kuznetsov ◽

V. V. Yuschenko ◽

E. E. Knyazeva

Keyword(s):

Mesoporous Materials ◽

Active Sites ◽

Nitrogen Adsorption ◽

Mesoporous Molecular Sieve ◽

Magic Angle Spinning ◽

Magic Angle ◽

X Ray Diffraction ◽

Temperature Programmed ◽

Angle Spinning ◽

Adsorption Desorption

Two series of composite micro/mesoporous materials with different contributions of micro- and mesoporosity were prepared by dealumination and recrystallization of mordenite zeolite. The materials were characterized by X-ray diffraction, infrared spectroscopy, 27Al magic angle spinning (MAS) NMR, nitrogen adsorption–desorption, and temperature-programmed desorption of ammonia (TPD NH3). Catalytic properties were studied in transalkylation of biphenyl with diisopropylbenzene. Both types of composite materials showed remarkably high activity, stability, and selectivity toward formation of di-isopropylbiphenyls with respect to both pure microporous and mesoporous materials. The effect is due to high zeolitic acidity combined with improved accessibility of active sites and transport of bulky molecules provided by mesopores.

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Bulk Versus Surface Modification of Alumina with Mn and Ce Based Oxides for CH4 Catalytic Combustion

Materials ◽

10.3390/ma12111771 ◽

2019 ◽

Vol 12 (11) ◽

pp. 1771 ◽

Cited By ~ 2

Author(s):

Stefan Neatu ◽

Mihaela M. Trandafir ◽

Adelina Stănoiu ◽

Ovidiu G. Florea ◽

Cristian E. Simion ◽

...

Keyword(s):

Photoelectron Spectroscopy ◽

Catalytic Combustion ◽

Mixed Oxides ◽

Sol Gel ◽

Nitrogen Adsorption ◽

X Ray Diffraction ◽

X Ray ◽

Temperature Programmed ◽

Catalytic Combustion Of Methane ◽

Adsorption Desorption

This study presents the synthesis and characterization of lanthanum-modified alumina supported cerium–manganese mixed oxides, which were prepared by three different methods (coprecipitation, impregnation and citrate-based sol-gel method) followed by calcination at 500 °C. The physicochemical properties of the synthesized materials were investigated by various characterization techniques, namely: nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and H2–temperature programmed reduction (TPR). This experimental study demonstrated that the role of the catalytic surface is much more important than the bulk one. Indeed, the incipient impregnation of CeO2–MnOx catalyst, supported on an optimized amount of 4 wt.% La2O3–Al2O3, provided the best results of the catalytic combustion of methane on our catalytic micro-convertors. This is mainly due to: (i) the highest pore size dimensions according to the Brunauer-Emmett-Teller (BET) investigations, (ii) the highest amount of Mn4+ or/and Ce4+ on the surface as revealed by XPS, (iii) the presence of a mixed phase (Ce2MnO6) as shown by X-ray diffraction; and (iv) a higher reducibility of Mn4+ or/and Ce4+ species as displayed by H2–TPR and therefore more reactive oxygen species.

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The Different Morphology of Co3O4 Catalysts and Application in the Abatement of Carbon Monoxide

Journal of Nanoscience and Nanotechnology ◽

10.1166/jnn.2021.19527 ◽

2021 ◽

Vol 21 (12) ◽

pp. 6082-6087

Author(s):

Chih-Wei Tang ◽

Hsiang-Yu Shih ◽

Ruei-Ci Wu ◽

Chih-Chia Wang ◽

Chen-Bin Wang

Keyword(s):

Carbon Monoxide ◽

Catalytic Activity ◽

Co Oxidation ◽

Nitrogen Adsorption ◽

Catalytic Performance ◽

Precipitation Method ◽

X Ray Diffraction ◽

X Ray ◽

Temperature Programmed ◽

Adsorption Desorption

The increase of harmful carbon monoxide (CO) caused by incomplete combustion can affect human health even lead to suffocation. Therefore reducing the CO discharged by vehicles or factories is urgent to improve the air quality. The spinel cobalt (II, III) oxide (Co3O4) is an active catalyst for CO abatement. In this study, we tried to fabricate dispersing Co3O4 via the dispersion-precipitation method with acetic acid, formic acid, and oxalic acid as the chelating dispersants. Then, the asprepared samples were calcined at 300 ºC for 4 h to obtain active catalysts, and assigned as Co(A), Co(F) and Co(O) respectively, the amount of the dispersants used are labeled as I (0.12 mole), II (0.03 mole) and III (0.01 mole). For comparison, another CoAP sample was prepared via alkaliinduced precipitation and calcined at 300 ºC. All samples were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), scanning electron microscope (SEM), and nitrogen adsorption/desorption system, and the catalytic activity focused on the CO oxidation. The influence of chelating dispersant on the performance of abatement of CO was pursued in this study. Apparently, the results showed that the chelating dispersant can influence the catalytic activity of CO abatement. An optimized ratio of dispersant can improve the performance, while excess dispersant lessens the surface area and catalytic performance. The series of Co(O) samples can easily donate the active oxygen since the labile Co–O bonding and indicated the preferential performance than both Co(A) and Co(F) samples. The nanorod Co(O)-II showed preferential for CO oxidation, T50 and T90 approached 96 and 127 ºC, respectively. Also, the favorable durability of Co(O)-II sample maintains 95% conversion still for 50 h at 130 ºC and does not emerge deactivation.

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Non-oxidative dehydrogenation of isobutane over supported vanadium oxide: nature of the active sites and coke formation

Catalysis Science & Technology ◽

10.1039/d0cy01174f ◽

2020 ◽

Vol 10 (18) ◽

pp. 6139-6151 ◽

Cited By ~ 1

Author(s):

Alberto Rodriguez-Gomez ◽

Abhishek Dutta Chowdhury ◽

Mustafa Caglayan ◽

Jeremy A. Bau ◽

Edy Abou-Hamad ◽

...

Keyword(s):

Raman Spectroscopy ◽

Vanadium Oxide ◽

Oxidative Dehydrogenation ◽

Active Sites ◽

Coke Formation ◽

Temperature Programmed Reduction ◽

Structure Activity Relationships ◽

Structure Activity ◽

Temperature Programmed ◽

Oxidative Dehydrogenation Of Isobutane

We combine Raman spectroscopy, EPR, XPS, temperature programmed reduction, XRD, 51V MAS ssNMR, TEM and N2-physisorption to unravel structure–activity relationships during the non-oxidative dehydrogenation of isobutane over a V based catalyst.

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Sol–Gel Approach for Design of Pt/Al2O3-TiO2 System—Synthesis and Catalytic Tests

Ceramics ◽

10.3390/ceramics4040047 ◽

2021 ◽

Vol 4 (4) ◽

pp. 667-680

Author(s):

Marta Dobrosielska ◽

Michał Zieliński ◽

Miłosz Frydrych ◽

Mariusz Pietrowski ◽

Piotr Marciniak ◽

...

Keyword(s):

Sol Gel ◽

Nitrogen Adsorption ◽

Molar Ratio ◽

Hydrogen Chemisorption ◽

Titania Gel ◽

Fourier Transformation Infrared Spectroscopy ◽

Alumina Gel ◽

Hydrogenation Of Toluene ◽

Temperature Programmed ◽

Adsorption Desorption

Al2O3-TiO2 systems with Ti:Al 0.1, 0.5 and 1.0 molar ratio obtained by the sol–gel method have been used as a platinum support. As a precursor of alumina gel, aluminum isopropoxide has been chosen. Titanium tert-butoxylate was applied to obtain titania gel and hexachloroplatinic acid was applied as a source of platinum. The systems have been characterized by the following methods: thermogravimetric analysis (TGA), Fourier transformation infrared spectroscopy (FTIR), X-ray powder diffraction (XRPD), low-temperature nitrogen adsorption–desorption isotherms (BET, BJH), temperature-programmed reduction with hydrogen (TPR-H2) and hydrogen chemisorption. Reactions of toluene to methylcyclohexane and selective o-chloronitrobenzene (o-CNB) to o-chloroaniline (o-CAN) hydrogenation were used as the tests of systems’ catalytic activity. The application of Al2O3-TiO2 as a support has enabled the obtaining of platinum catalysts showing high activities for hydrogenation of toluene and selective hydrogenation of o-chloronitrobenzene to o-chloroaniline in the liquid phase. The highest activity in both reactions has been found for Pt/Al2O3-0.5TiO2 catalyst and the highest selectivity for Pt/Al2O3-. The activity of Pt/Al2O3-TiO2 catalysts was higher than that of alumina-supported ones.

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Single-Pot Synthesis of Biodiesel using Efficient Sulfonated-Derived Tea Waste-Heterogeneous Catalyst

Materials ◽

10.3390/ma12142293 ◽

2019 ◽

Vol 12 (14) ◽

pp. 2293 ◽

Cited By ~ 3

Author(s):

Umer Rashid ◽

Junaid Ahmad ◽

Mohd Lokman Ibrahim ◽

Jan Nisar ◽

Muhammad Asif Hanif ◽

...

Keyword(s):

Fatty Acid ◽

Nitrogen Adsorption ◽

Biodiesel Production ◽

Catalyst Loading ◽

Reaction Conditions ◽

Tea Waste ◽

Before And After ◽

Optimum Reaction ◽

Temperature Programmed ◽

Adsorption Desorption

The main purpose of this manuscript is to report the new usage of tea waste (TW) as a catalyst for efficient conversion of palm fatty acid distillate (PFAD) to biodiesel. In this work, we investigate the potential of tea waste char as a catalyst for biodiesel production before and after sulfonation. The activated sulfonated tea waste char catalyst was characterized using Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray diffractometry (XRD), elemental composition (CHNS), nitrogen adsorption-desorption using Brunauer-Emmett-Teller (BET) and ammonia-temperature-programmed desorption (NH3-TPD). The activated tea waste char catalyst shows higher acid density of 31 μmol g−1 as compared to tea waste char of 16 μmol g−1 and higher surface area of 122 m2/g. The optimum fatty acid conversion conditions were found that 4 wt % of catalyst loading with 9:1 of methanol:PFAD for 90 min of reaction time at 65 °C gives 97% free fatty acid (FFA) conversion. In conclusion, the sulfonated tea waste (STW) catalyst showed an impressive catalytic activity towards the esterification of PFAD at optimum reaction conditions with significant recyclability in five successive cycles without any reactivation step.

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Three-Dimensional Mesoporous Ni-CeO2 Catalysts with Ni Embedded in the Pore Walls for CO2 Methanation

Catalysts ◽

10.3390/catal10050523 ◽

2020 ◽

Vol 10 (5) ◽

pp. 523 ◽

Cited By ~ 3

Author(s):

Luhui Wang ◽

Junang Hu ◽

Hui Liu ◽

Qinhong Wei ◽

Dandan Gong ◽

...

Keyword(s):

Three Dimensional ◽

Nitrogen Adsorption ◽

Combustion Method ◽

Catalytic Performance ◽

Oxide Interface ◽

Solution Combustion ◽

Co2 Methanation ◽

Transmission Electron ◽

Temperature Programmed ◽

Adsorption Desorption

Mesoporous Ni-based catalysts with Ni confined in nanochannels are widely used in CO2 methanation. However, when Ni loadings are high, the nanochannels are easily blocked by nickel particles, which reduces the catalytic performance. In this work, three-dimensional mesoporous Ni-CeO2-CSC catalysts with high Ni loadings (20−80 wt %) were prepared using a colloidal solution combustion method, and characterized by nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and H2 temperature programmed reduction (H2-TPR). Among the catalysts with different Ni loadings, the 50% Ni-CeO2-CSC with 50 wt % Ni loading exhibited the best catalytic performance in CO2 methanation. Furthermore, the 50% Ni-CeO2-CSC catalyst was stable for 50 h at 300° and 350 °C in CO2 methanation. The characterization results illustrate that the 50% Ni-CeO2-CSC catalyst has Ni particles smaller than 5 nm embedded in the pore walls, and the Ni particles interact with CeO2. On the contrary, the 50% Ni-CeO2-CP catalyst, prepared using the traditional coprecipitation method, is less active and selective for CO2 methanation due to the larger size of the Ni and CeO2 particles. The special three-dimensional mesoporous embedded structure in the 50% Ni-CeO2-CSC can provide more metal–oxide interface and stabilize small Ni particles in pore walls, which makes the catalyst more active and stable in CO2 methanation.

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n-Heptane isomerization activities of Pt catalyst supported on micro/mesoporous composites

BMC Chemistry ◽

10.1186/s13065-021-00787-6 ◽

2021 ◽

Vol 15 (1) ◽

Author(s):

Z. Ghaderi ◽

M. H. Peyrovi ◽

N. Parsafard

Keyword(s):

Nitrogen Adsorption ◽

Pt Catalyst ◽

Isomerization Reaction ◽

X Ray Diffraction ◽

Hy Zeolite ◽

Composite Catalysts ◽

Isomerization Selectivity ◽

Catalytic Stability ◽

Adsorption Desorption ◽

Heptane Conversion

AbstractPt loaded on a series of MCM-48 silica and composites with HZSM-5 zeolite, HY zeolite, or TiO2 has been prepared and studied for n-heptane isomerization reaction at 200–350 °C. The structural characterization, acid distribution, and morphology of these catalysts were characterized by X-ray diffraction, Fourier transform infrared, UV–Vis diffuse reflectance, scanning electron microscope, temperature-programmed desorption of NH3, and nitrogen adsorption–desorption methods. The results show that these catalysts have a good selectivity to multi branched isomers, while producing low aromatic compounds. Also, these new composite catalysts prove the catalytic stability during the time of reaction. The most desirable results, and significantly higher n-heptane conversion and isomerization selectivity were achieved with Pt/MCM48-HZSM5 catalyst.

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Hydrogen Production from Ethylene Glycol Aqueous Phase Reforming over Ni–Al Layered Hydrotalcite-Derived Catalysts

Catalysts ◽

10.3390/catal10010054 ◽

2020 ◽

Vol 10 (1) ◽

pp. 54

Author(s):

Jianguang Zhang ◽

Ningge Xu

Keyword(s):

Ethylene Glycol ◽

Aqueous Phase ◽

Nitrogen Adsorption ◽

Nitrogen Atmosphere ◽

Hydrogen Yield ◽

X Ray Diffraction ◽

Aqueous Phase Reforming ◽

Metal Composition ◽

Temperature Programmed ◽

Adsorption Desorption

By introducing Mg, Cu, Zn, Sn, and Mn into the synthesis processes of Ni and Al based hydrotalcite, Ni–Al layered hydrotalcite-derived catalysts with different metal compositions were prepared. In this paper, the effect of metal composition on the structure of Ni–Al layered hydrotalcite-derived catalysts is investigated, and then catalytic activities of prepared catalysts with different metal compositions on ethylene glycol aqueous-phase reforming are analyzed. The physicochemical properties of the Ni–Al layered hydrotalcite-derived catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and nitrogen adsorption–desorption technology. The obtained hydrotalcite-derived catalysts were applied to the process of ethylene glycol aqueous-phase reforming (APR). The XRD results confirmed that the precursors of hydrotalcite-derived catalysts with metal compositions of Ni/Mg/Al, Ni/Cu/Al, Ni/Zn/Al, and Ni/Sn/Al had hydrotalcite crystalloid morphology. During the process of ethylene glycol aqueous phase reforming, all the catalysts showed high conversion of ethylene glycol (>90%), and the optimum hydrogen yield (73.5%) was obtained when using the catalyst with metal composition of Ni/Mg/Al at 225 °C under 2.6 MPa in nitrogen atmosphere for 2.5 h.

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The Effect of MgO Precoating on the Perfomance of Ni/MgO-Al2O3 Catalysts for Carbon Dioxide Reforming of Methane

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.997.272 ◽

2014 ◽

Vol 997 ◽

pp. 272-278 ◽

Cited By ~ 1

Author(s):

Li Qiong Huang ◽

Zheng Hui Zhang ◽

Zhang Long Guo

Keyword(s):

Carbon Dioxide ◽

Surface Area ◽

Active Sites ◽

Impregnation Method ◽

X Ray Diffraction ◽

Carbon Dioxide Reforming ◽

Temperature Programmed ◽

Ni Species ◽

Adsorption Desorption ◽

Nickel Species

Ni catalysts supported on γ?-Al2O3 supports modified by different MgO precoating weight were prepared by impregnation method. The surface area, pore diameter and Ni crystallite size were investigated by N2 adsorption/desorption (BET) and X-ray diffraction (XRD) methods. The reducing temperature and quantity information of reducible nickel species were obtained by H2-TPR experiments. The CO2 adsorption/desorption abilities of catalysts were investigated and the activity of catalysts were also measured. The coke resistance performance of catalysts for carbon dioxide reforming of methane (CDRM) was studied by CO2 temperature programmed surface reaction (CO2-TPSR). H2-TPR results revealed that there were three kinds of Ni species on the supports. Appropriate modification amount of MgO could increase the surface nickel active sites which could be easily reduced and prevented the formation of NiAl2O4 spinel species. CO2-TPD indicated that the addition of MgO increased the amount of CO2 adsorption at lower temperatures. N2 adsorption/desorption results disclosed that the excessive modification of MgO would decrease the surface area and pore size of the samples. The reforming reaction results showed that the activity was elevated from 58.62% to 65.95% over the Ni/MgO-Al2O3 when the Mg/Al ratio was 0.05 (wt.) and there was less coke evidenced by the CO2-TPSR results comparing to the Ni/γ?-Al2O3 catalyst.

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