scholarly journals Chemical and Physical Properties of the Al1-xFexPO4 System Prepared by the Coprecipitation Method. II. Surface Acidity, Textural Properties and Catalytic Activity

2002 ◽  
Vol 20 (8) ◽  
pp. 741-755 ◽  
Author(s):  
F.Sh. Mohamed
Keyword(s):  
Catalytic Activity ◽  
Calcination Temperature ◽  
Pore Volume ◽  
Pore Radius ◽  
Surface Acidity ◽  
Total Pore Volume ◽  
Textural Properties ◽  
Coprecipitation Method ◽  
Temperature Variations ◽  
Kinetics Of

A coprecipitation method for the preparation of Al1-xFexPO4 catalysts with x (or Fe/P ratio) = 0.0, 0.2, 0.4, 0.6 and 0.8 was developed. The samples were calcined at temperatures within the range 200–800°C. The surface structure, cumulative acidity, textural properties, and the catalytic activity and selectivity of the prepared samples towards isopropanol and cyclohexane conversion were studied using different techniques. The results showed that the freshly calcined samples consisted of an amorphous phase, a quartz-type and a tridymite-type phase depending on the calcination temperature. The total surface acidity decreased with FePO4 content or calcination temperature. Variations in the Fe/P ratio and the calcination temperature led to changes in both the surface area and total pore volume of the Al1-xFexPO4 samples. Increases in the Fe/P ratio and increasing calcination temperature led to increases in the pore radius. The catalytic activity and selectivity were significantly affected as the structures of the Al1-xFexPO4 catalysts varied. The kinetics of the reaction were also studied.

scholarly journals Characterization and Catalytic Behaviour of Co3(PO4)2–AlPO4 Catalysts

1998 ◽  
Vol 16 (4) ◽  
pp. 285-293 ◽  
Author(s):  
M.R. Mostafa ◽  
F.Sh. Ahmed
Keyword(s):  
Pore Radius ◽  
Surface Acidity ◽  
Total Pore Volume ◽  
Textural Properties ◽  
Acid Sites ◽  
Adsorption Of Nitrogen ◽  
Amorphous Structures ◽  
Ft Ir ◽  
Catalytic Behaviour ◽  
The Mean

Co3(PO4)2, AlPO4 and the binary system Co3(PO4)2-AlPO4 with different compositions were prepared by the coprecipitation method. The structural properties of these samples were determined using XRD, DTA and FT-IR techniques. The textural properties were determined from the adsorption of nitrogen at 77 K. The surface acidity was measured by a calorimetric titration method. The samples were tested as catalysts in the dehydration of ethanol and isopropanol using a pulse microcatalytic technique. The data obtained from XRD and FT-IR indicate the amorphous structures of the prepared catalysts. An increase in Co3(PO4)2 content led to a decrease in the surface area and in the total pore volume and an increase in the mean pore radius. The surface acidity of the catalyst depends on the chemical composition; the surface acidity increased with an increase in the AlPO4 content. The dehydration temperature and the distribution of acid sites are important parameters in determining the selectivity and activity of the catalyst.

scholarly journals Surface and Catalytic Properties of NiO and Fe2O3 Solids

1997 ◽  
Vol 15 (8) ◽  
pp. 593-607 ◽  
Author(s):  
A. Abd. El-Aal ◽  
A.M. Ghozza ◽  
G.A. El-Shobaky
Keyword(s):  
Catalytic Activity ◽  
Calcination Temperature ◽  
Active Sites ◽  
Pore Radius ◽  
Total Pore Volume ◽  
Surface Characteristics ◽  
Oxidation Of Co ◽  
Catalytic Activities ◽  
Catalytically Active ◽  
The Mean

The surface characteristics, viz., the specific surface area SBET, the total pore volume Vp and the mean pore radius r̄, of NiO and Fe2O3 were determined from N2 adsorption isotherms conducted at −196°C for the different adsorbents preheated in air at temperatures in the range 300–800°C. The catalytic activities exhibited in CO oxidation by O2 on the various solids were investigated at temperatures varying between 150°C and 400°C. The effect of heating the NiO and Fe2O3 solids in CO and O2 atmospheres at 175–275°C on their catalytic activities was also studied. The results showed that increasing the calcination temperature in the range 300–800°C resulted in a progressive decrease in the SBET value of NiO and Fe2O3. The computed values of the apparent activation energy for the sintering of the oxides were 71 and 92 kJ/mol, respectively. The sintering of NiO and Fe2O3 took place mainly via a particle adhesion mechanism. The catalytic activity of NiO decreased progressively on increasing its calcination temperature from 300°C to 800°C, due to a decrease in its SBET value and the progressive removal of excess O2 which was present as non-stoichiometric NiO. This treatment also decreased the catalytic activity of Fe2O3. The decrease was, however, more pronounced when the temperature increased from 300°C to 400°C which was a result of the crystallization of the ferric oxide into the α-Fe2O3 phase. An increase in the calcination temperature for both oxides from 300°C to 800°C did not modify the mechanism of oxidation of CO by O2 over the various solids but rather changed the concentration of catalytically active sites. Heating NiO and Fe2O3 in CO and O2 atmospheres at 175–275°C modified their catalytic activities, with Fe2O3 being influenced to a greater extent than NiO.

scholarly journals Surface and Catalytic Properties of γ-Irradiated Cr2O3/Al2O3 Solids

1997 ◽  
Vol 15 (6) ◽  
pp. 465-476 ◽  
Author(s):  
G.A. El-Shobaky ◽  
A.M. Ghozza ◽  
G.M. Mohamed
Keyword(s):  
Catalytic Activity ◽  
Co Oxidation ◽  
Surface Area ◽  
Pore Volume ◽  
Active Sites ◽  
Catalytic Properties ◽  
Total Pore Volume ◽  
Bet Surface Area ◽  
Two Samples ◽  
Γ Rays

Two samples of Cr2O3/Al2O3 were prepared by mixing a known mass of finely powdered Al(OH)3 with a calculated amount of CrO3 solid followed by drying at 120°C and calcination at 400°C. The amounts of chromium oxide employed were 5.66 and 20 mol% Cr2O3, respectively. The calcined solid specimens were then treated with different doses of γ-rays (20–160 Mrad). The surface and catalytic properties of the different irradiated solids were investigated using nitrogen adsorption at −196°C and the catalysis of CO oxidation by O2 at 300–400°C. The results revealed that γ-rays brought about a slight decrease in the BET surface area, SBET (15%), and in the total pore volume, Vp (20%), of the adsorbent containing 5.66 mol% Cr2O3. The same treatment increased the total pore volume, Vp (36%), and the mean pore radius, r̄ (43%), of the other adsorbent sample without changing its BET surface area. The catalytic activities of both catalyst samples were found to increase as a function of dose, reaching a maximum value at 80–160 Mrad and 40 Mrad for the solids containing 5.66 and 20 mol% Cr2O3, respectively. The maximum increase in the catalytic activity measured at 300°C was 59% and 100% for the first and second catalyst samples, respectively. The induced effect of γ-irradiation on the catalytic activity was an increase in the concentration of catalytically active sites taking part in chemisorption and in the catalysis of CO oxidation by O2 without changing their energetic nature. This was achieved by a progressive removal of surface hydroxy groups during the irradiation process.

scholarly journals Pembuatan Katalis Pd-Ce/γ –Al2O3 dan Uji Aktivitas terhadap Oksidasi Metana

1999 ◽  
Vol 2 (3) ◽  
pp. 104-111
Author(s):  
Ahmad Suseno ◽  
Triyono Triyono ◽  
Bambang Setiaji
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Pore Volume ◽  
Pore Radius ◽  
Flow Reactor ◽  
Chloride Salt ◽  
Oxidation Of Methane ◽  
Sorption Method ◽  
Determine Surface Area ◽  
Products Of Reaction

Effects of Ce addition on Pt/γ - Al2O3 catalysts preparation and their catalytic activity on oxidation of methane have been investigated. In this study, the catalysts were prepared by impregnating chloride salt solution of palladium and sulphate salt of cerium on γ-AI2O3 support. Characterization of catalysts was conducted by gas sorption method to determine surface area, pore radius and pore volume. The test of catalytic activity on oxidation of methane was carried out in a flow reactor system at a temperature range from 350°C to 600°C. Products of reaction were analysed by non-dispersive IR spectroscopy. It was observed that the surface area, pore radius and pore volume decrease with the addition of cerium. The results of oxidation process showed that Pd-Ce/γ-Al2O3 catalyst can be used for oxidation of methane up to 90.62% conversion

scholarly journals The Effect of Calcium Doping on the Surface and Catalytic Properties of Cobaltic Oxide Catalysts

2003 ◽  
Vol 21 (3) ◽  
pp. 229-243 ◽  
Author(s):  
Nasr-Allah M. Deraz
Keyword(s):  
Activation Energy ◽  
Calcination Temperature ◽  
Calcium Oxide ◽  
Total Pore Volume ◽  
Textural Properties ◽  
Peroxide Decomposition ◽  
Cobaltic Oxide ◽  
Adsorption Of Nitrogen ◽  
Activation Energy Of Sintering ◽  
Calcium Doping

The effects of calcium oxide doping (0.75, 1.5 and 3 mol% CaO) and calcination temperature (400, 500, 600 and 700°C) on different surface properties of Co3O4 were investigated. The structural properties of pure and doped oxide samples were determined by XRD methods, the textural properties were investigated via the adsorption of nitrogen at −196°C while the hydrogen peroxide decomposition activity of the investigated solids was determined by oxygen gasometric measurement of the reaction kinetics at 20–40°C. The dissolution of calcium ions in the Co3O4 lattice at temperatures in the range 400–600°C was accompanied by a marked decrease in the mean hydraulic radii (rh) and an increase in the surface area (SBET) and total pore volume (Vp) of the prepared oxide samples. In contrast, doping at 700°C brought about a decrease in the SBET and Vp values of the investigated solids. The catalytic activity for H2O2 decomposition on cobaltic oxide calcined at 400–700°C was found to decrease considerably on doping with CaO. The activation energy for sintering (ΔEs) of the pure and doped solids was determined from the variation in their SBET values as a function of the calcination temperature of these solids. Calcium oxide treatment resulted in a 50% increase in the activation energy of sintering of cobaltic oxide solid calcined at 400–600°C. This increase reflects the role of CaO doping in hindering the sintering of cobaltic oxide.

CuO/CeO2 and CuO/PrO2-CeO2 Catalysts for Preferential Oxidation of CO

2013 ◽  
Vol 773 ◽  
pp. 601-605 ◽  
Author(s):  
Zhi Jun Zhao ◽  
Ruo Yu Wang ◽  
Qian Long Zhao ◽  
En Peng Wang ◽  
Hai Quan Su ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Hydrothermal Method ◽  
Surface Area ◽  
Pore Volume ◽  
Crucial Role ◽  
Textural Properties ◽  
Bet Surface Area ◽  
Oxidation Of Co ◽  
Preferential Oxidation Of Co ◽  
Adsorption Desorption

The CuO/CeO2and CuO/PrO2-CeO2catalysts were prepared by the hydrothermal method, and characterized via XRD, SEM and N2adsorption-desorption techniques. The study shows that the BET surface area and pore volume of the CuO/PrO2-CeO2catalysts increase with the increase of praseodymium content. The CuO/CeO2catalyst presents higher catalytic activity in compare with the CuO/PrO2-CeO2catalysts although the addition of praseodymium promotes textural properties of the CuO/CeO2catalysts, and it proves that the interaction of CuO and CeO2has a crucial role in CO-PROX.

scholarly journals On the Gas Storage Properties of 3D Porous Carbons Derived from Hyper-Crosslinked Polymers

Polymers ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 588 ◽  
Author(s):  
Giorgio Gatti ◽  
Mina Errahali ◽  
Lorenzo Tei ◽  
Maurizio Cossi ◽  
Leonardo Marchese
Keyword(s):  
Thermal Treatment ◽  
Surface Area ◽  
Pore Volume ◽  
Chemical Activation ◽  
Chemical Characterization ◽  
Total Pore Volume ◽  
Textural Properties ◽  
Gas Storage ◽  
Bet Surface Area ◽  
Porous Carbons

The preparation of porous carbons by post-synthesis treatment of hypercrosslinked polymers is described, with a careful physico-chemical characterization, to obtain new materials for gas storage and separation. Different procedures, based on chemical and thermal activations, are considered; they include thermal treatment at 380 °C, and chemical activation with KOH followed by thermal treatment at 750 or 800 °C; the resulting materials are carefully characterized in their structural and textural properties. The thermal treatment at temperature below decomposition (380 °C) maintains the polymer structure, removing the side-products of the polymerization entrapped in the pores and improving the textural properties. On the other hand, the carbonization leads to a different material, enhancing both surface area and total pore volume—the textural properties of the final porous carbons are affected by the activation procedure and by the starting polymer. Different chemical activation methods and temperatures lead to different carbons with BET surface area ranging between 2318 and 2975 m2/g and pore volume up to 1.30 cc/g. The wise choice of the carbonization treatment allows the final textural properties to be finely tuned by increasing either the narrow pore fraction or the micro- and mesoporous volume. High pressure gas adsorption measurements of methane, hydrogen, and carbon dioxide of the most promising material are investigated, and the storage capacity for methane is measured and discussed.

scholarly journals Effect of Sulfation on Zirconia-Pillared Montmorillonite to the Catalytic Activity in Microwave-Assisted Citronellal Conversion

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Is Fatimah ◽  
Dwiarso Rubiyanto ◽  
Thorikul Huda
Keyword(s):  
Catalytic Activity ◽  
Surface Acidity ◽  
Total Pore Volume ◽  
High Catalytic Activity ◽  
X Ray Diffraction ◽  
Adsorption Method ◽  
X Ray ◽  
Pillared Montmorillonite ◽  
Microwave Assisted ◽  
Tandem Cyclization

Preparation of sulfated zirconia-pillared montmorillonite was carried out in two steps; zirconia pillarization and sulfation to zirconia-pillared montmorillonite. The prepared materials were characterized by using X-ray diffraction (XRD), measurement of the specific surface area, total pore volume and pore size distribution by the N2adsorption method, scanning electron microscopy-energy dispersive X-ray (SEM-EDX), and surface acidity determination by using pyridine adsorption-FTIR analysis. The activity of the materials as catalysts was evaluated for a microwave-assisted conversion of citronellal. The results showed that the prepared materials had a physicochemical character that promoted high catalytic activity to convert citronellal. From varied Zr content and study of the effect of sulfation on the activity, it was found that Zr content and sulfation increase the surface acidity of the material as shown by the higher total conversion and tendency to produce menthol as a product of the tandem cyclization-hydrogenation mechanism.

scholarly journals Biochar from Slow Catalytic Pyrolysis of Spirulina platensis Residue: Effects of Temperature and Silica-Alumina Catalyst on Yield and Characteristics

2020 ◽  
Vol 14 (2) ◽  
pp. 137
Author(s):  
Siti Jamilatun ◽  
Ilham Mufandi ◽  
Arief Budiman ◽  
Suhendra Suhendra
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Pore Volume ◽  
Spirulina Platensis ◽  
Catalytic Pyrolysis ◽  
Pore Radius ◽  
Fixed Bed ◽  
Total Pore Volume ◽  
Alumina Catalyst ◽  
Silica Alumina

The use of biochar varies on its ability as an adsorbent which adsorbs liquid or gas molecules. Biochar from Spirulina platensis residue (SPR) as an energy source, as its richness in nutrients, can be used as fertilizer and maintain water resources in plantations. Biochar can be used as an intermediary for the synthesis of nanotubes, activated carbon, carbon black, and carbon fiber. One of the essential things to be considered in the application of activated carbon from SPR is char’s characteristics. This study aimed to obtain data on the biochar and components from the pyrolysis of Spirulina platensis residue. The study was conducted in a fixed-bed reactor with electric heaters with a variety of temperatures (300-700 ⁰C) and the amount of silica-alumina catalyst (0-20%). The biochar weight was obtained by weighing the char formed at the end of the pyrolysis. The char characteristics were obtained by the surface area, total pore volume, and pore size analysis. Based on the study results, the relationship between temperature and the amount of catalyst on the characteristics of biochar was studied. The higher the pyrolysis temperature, the less biochar. Also, the use of catalysts can reduce the amount of biochar. The higher the temperature, the higher the surface area and the total pore volume while the pore radius was reduced. The optimum condition for maximum biochar yield in non-catalytic pyrolysis at a temperature of 300 ⁰C was 49.86 wt.%. The surface area, the total pore volume, and the pore radius at 700 ⁰C catalytic pyrolysis with 5% silica-alumina was obtained as 36.91 m2/g, 0.052 cm3/g, and 2.68 nm, respectively.Keywords: biochar; pore radius; silica-alumina; surface area; total pore volumeA B S T R A KPenggunaan biochar bervariasi pada kemampuannya sebagai adsorben dalam menjerap molekul cairan atau gas. Biochar dari residu Spirulina platensis merupakan sumber energi, karena kaya akan unsur hara, dapat digunakan sebagai pupuk dan pemeliharaan sumber daya air di perkebunan. Biochar dapat juga digunakan sebagai perantara untuk sintesis nanotube, karbon aktif, carbon black, dan serat karbon. Salah satu hal penting yang harus diperhatikan dalam aplikasi karbon aktif dari SPR adalah karakteristik arang. Penelitian ini bertujuan untuk mendapatkan data biochar dan komponen dari pirolisis residu Spirulina platensis. Penelitian dilakukan di reaktor fixed-bed dengan pemanas listrik dengan variasi suhu (300-700 ⁰C) dan jumlah katalis silika-alumina (0-20%). Berat biochar diperoleh dengan cara menimbang arang yang terbentuk pada akhir pirolisis. Sedangkan karakteristik arang diperoleh dari analisis luas permukaan, volume pori total, dan ukuran pori. Berdasarkan hasil studi hubungan antara suhu dan jumlah katalis terhadap karakteristik biochar yang telah diteliti, semakin tinggi suhu pirolisis maka biochar semakin sedikit. Selain itu, penggunaan katalis dapat mengurangi jumlah biochar. Sebaliknya, semakin tinggi suhu semakin besar luas permukaan, dan volume pori total serta radius pori-pori semakin berkurang. Kondisi optimum untuk biochar maksimum pada pirolisis non katalitik pada suhu  300 ⁰C adalah 49,86 wt.%. Luas permukaan, total volume pori, dan radius pori pada suhu 700 ⁰C untuk pirolisis katalitik silika-alumina 5% diperoleh masing-masing sebesar 36,91 m2/g, 0,052 cm3/g, dan 2,68 nm.Kata kunci: biochar; luas permukaan; radius pori; silika-alumina; total volume pori  

scholarly journals Effect of Calcination Temperature on the Synthesis of ZrO2-Pillared Saponite to Catalytic Activity in Menthol Esterification

2018 ◽  
Vol 16 (1) ◽  
pp. 8 ◽  
Author(s):  
Is Fatimah ◽  
Dwiarso Rubiyanto ◽  
Nanda Candra Kartika
Keyword(s):  
Catalytic Activity ◽  
Surface Area ◽  
Calcination Temperature ◽  
Surface Acidity ◽  
Physicochemical Characteristics ◽  
Sem Analysis ◽  
X Ray Diffraction ◽  
X Ray ◽  
Calcination Temperatures ◽  
Solid Acidity

The influence of calcination temperature on the synthesis of zirconia-pillared saponite (PILS) and on its catalytic activity in menthol esterification has been studied. Zirconia pillarization was conducted using zirconium tetraisopropoxide as a precursor and with calcination temperatures of 450, 600 and 700 °C. Evaluation of physicochemical characteristics at these varied temperatures was carried out by X-Ray Diffraction (XRD), surface area analysis, Scanning Electron Eicroscope (SEM) analysis, Differential Thermal Analysis (DTA) and total acidity. The obtained results indicate that the structure and surface acidity of saponite were strongly influenced by calcination temperature. The solid acidity and surface parameters such as specific surface area, pore volume, and pore radius play an important role in the total conversion and selectivity in menthol esterification.

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