scholarly journals Effect of Modification of Amorphous Silica with Ammonium Agents on the Physicochemical Properties and Hydrogenation Activity of Ir/SiO2 Catalysts

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 968
Author(s):  
Monika Kot ◽  
Robert Wojcieszak ◽  
Ewa Janiszewska ◽  
Mariusz Pietrowski ◽  
Michał Zieliński
Keyword(s):  
Pore Diameter ◽  
Textural Properties ◽  
Acid Sites ◽  
Average Pore ◽  
Amorphous Sio2 ◽  
Iridium Catalysts ◽  
Toluene Hydrogenation ◽  
Highly Active ◽  
Acidic Sites ◽  
Materials Used

The modification of commercial silica with solutions of NH4F or NH4Cl salts, followed by thermal treatment, enabled generation of the acidic sites in SiO2 and changed its textural properties. The use of ammonium salts solution also caused the generation of additional porosity. Using NH4F solution caused significant decrease in the specific surface area and the increase in the average pore diameter. The number and strength of resulting acid sites depend on the nature of anion in the applied ammonium salt and the concentration of salt solution. It has been found that the sample treated with NH4F presented higher total acidity (TPD–NH3) and the amount as well as the strength of acid sites increased with the concentration of the used modifier. As modified amorphous SiO2 materials used as a support for iridium (1 wt %, Ir(acac)3) nanoparticles permitted to obtain highly active catalysts for toluene hydrogenation under atmospheric pressure. The highest activity (expressed as the apparent rate and TOF) was obtained for iridium catalysts supported on silica modified by NH4F with the highest acidity. The modification of silica with NH4F favors the generation of centers able to adsorb toluene, which results in higher activity of this catalyst.

scholarly journals Hydrochloric Acid and/or Sodium Hydroxide-modified Zeolite Y for Catalytic Hydrotreating of α-Cellulose Bio-Oil

2020 ◽  
Author(s):  
Jason Mandela ◽  
Wega Trisunaryanti ◽  
Triyono Triyono ◽  
Mamoru Koketsu ◽  
Dyah Ayu Fatmawati
Keyword(s):  
Pore Diameter ◽  
Zeolite Y ◽  
Weight Ratio ◽  
Textural Properties ◽  
Catalytic Performance ◽  
Average Pore Diameter ◽  
Average Pore ◽  
Bio Oil ◽  
Liquid Products ◽  
Naoh Treatment

The zeolite Y had been successfully modified by HCl and/or NaOH treatment. The modification of zeolite Y was performed by leaching the protonated zeolite Y (HY) in HCl solution (0.1 and 0.5 M) at 70 °C for 3 h resulting in DY0.1 and DY0.5. Subsequently, HY, DY0.1, and DY0.5 zeolites were immersed in 0.1 M NaOH for 15 min at room temperature resulting in AHY, ADY0.1, and ADY0.5. All samples were analyzed for acidity, crystallinity, Si/Al ratio, morphology, and textural properties. The catalytic performance of all samples was investigated in hydrotreating of α-cellulose bio-oil with a catalyst/feed weight ratio of 1/30. The HCl and NaOH treatment led to the decrease of the zeolite Y crystallinity and the increase of the zeolite Y average pore diameter (i.e., the mesopore distribution). The ADY0.5 gave the highest mesopore distribution, which was 43.7%, with an average pore diameter of 4.59 nm. Moreover, both of the treatments were found to increase the Si/Al ratio that caused the decrease of zeolites Y acidity. All the zeolite Y samples gave better catalytic activity to produce liquid products after being treated by NaOH. The sample ADY0.5 managed to produce 6.12% of 1-isopropyl-2,4-dimethylbenzene that has good potential to be processed into fuel.

scholarly journals Soybean oil bleaching by Al-pillared montmorillonite

2002 ◽  
pp. 27-34 ◽  
Author(s):  
Erne Kis ◽  
Jonjana Ranogajec ◽  
Radmila Marinkovic-Neducin ◽  
Etelka Dimic ◽  
Tatjana Vulic
Keyword(s):  
Soybean Oil ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Diameter ◽  
Textural Properties ◽  
Oil Industry ◽  
Average Pore Diameter ◽  
Average Pore ◽  
Pillared Montmorillonite

AI-pillared montmorillonite was synthesized from raw clay, mined at Sipovo Srpska Republic. Its textural properties and bleaching capacity were compared with some commercial adsorbents and filtration aid materials commonly used in domestic oil industry. The bleaching capacity of AI-pillared montmorillonite is lower than that of commercial Super Celite L748 (Johns Manville, USA) or Perfit PF-3 (Termika dd., Zrenjanin Yugoslavia), but somewhat is higher than the bleaching capacity of pure montmorillonite. The results suggest that the bleaching capacity of the investigated samples is primarily determined by average pore diameter and not by specific surface area.

Synthesis of Si-Based Mesoporous Materials with Different Structural Regularity

2010 ◽  
Vol 132 ◽  
pp. 38-44
Author(s):  
Li Fang Chen ◽  
Jesus López ◽  
Jin An Wang ◽  
Luis E. Noreña-Franco ◽  
Guo Xian Yu ◽  
...  
Keyword(s):  
Mesoporous Materials ◽  
Pore Diameter ◽  
Acid Sites ◽  
29Si Mas Nmr ◽  
Lewis Acid Sites ◽  
Average Pore ◽  
Structural Regularity ◽  
Nmr Techniques ◽  
Mcm 41 ◽  
Uniform Pore Size

Two types of mesoporous Si-MCM-41 materials were synthesized via a cationic surfactant template method using different Si-precursors. The materials obtained were characterized by FTIR, XRD, BET, TEM and 29Si MAS-NMR techniques. When fumed silica was used as Si precursor, a Si-MCM-41-I solid with wormhole-like pore topologies was obtained. However, when tetraethylorthosilicate (TEOS) was used as Si precursor, a mesoporous Si-MCM-41-II solid with hexagonal arranges and a long-range ordered structure could be obtained. These two kinds of mesoporous materials had a uniform pore size distribution with an average pore diameter within 2.3-2.8 nm. Rather weak Lewis acid sites were formed on both the Si-MCM-41 samples prepared by the two methods.

Effect of La2O3 Derived from Thai Monazite Ore Chemical Processing on the Properties of SO4-1/ZrO2

2019 ◽  
Vol 821 ◽  
pp. 195-200
Author(s):  
Sasikarn Nuchdang ◽  
Dussadee Rattanaphra
Keyword(s):  
Pore Diameter ◽  
Solid Acid Catalyst ◽  
Acid Sites ◽  
Bet Surface Area ◽  
Solid Catalyst ◽  
Chemical Processing ◽  
Impregnation Method ◽  
Average Pore ◽  
Monazite Ore ◽  
Calcined Temperature

La2O3 derived from Thai monazite ore chemical processing was used as a precursor to prepare SO4-1-1%La2O3/ZrO2 solid acid catalyst. The SO4-1-1%La/ZrO2 catalyst was synthesized by co-precipitation with subsequent impregnation method. Various characterization techniques such as X-ray diffraction (XRD), nitrogen adsorption-desorption (BET) and Fourier transform infrared spectroscopy (FTIR) were used to study crystalline structural, textural and acid properties of the prepared catalysts. XRD results revealed that the presence of stable La2O3/ZrO2 tetragonal phase for SO4-1-1%La2O3/ZrO2 was observed at calcined temperature up to 600 °C. No diffraction peaks of La2O3 appeared in the profile of SO4-1-1%La2O3/ZrO2, indicated that the La2O3 was finely dispersed on the ZrO2 support. The doping of SO4-1-ZrO2 with La2O3 led to a significant decrease in its BET surface area, total pore volume and pore diameter. A relatively uniform pore size distribution of SO4-1-1%La2O3/ZrO2 catalyst with average pore diameter of 6 nm was found at the calcined temperature of 600 °C. Lewis acid sites existed in the synthesized SO4-1-1%La2O3/ZrO2 were lower than that counterpart. A loss of sulfate species was noted at high calcined temperature. The prepared SO4-1-1%La2O3/ZrO2 will be further used as a solid catalyst for transesterification of waste cooking oil to biodiesel, and the addition of La2O3 on the support could lead to enhance the catalytic activity and thermal stability.

scholarly journals The Role of Cations in Resorcinol–Formaldehyde Gel Textural Characteristics

Gels ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 60
Author(s):  
Stewart J. Taylor ◽  
Liu Yang ◽  
Ashleigh J. Fletcher
Keyword(s):  
Pore Size ◽  
Pore Diameter ◽  
Textural Properties ◽  
Average Pore ◽  
Salting Out ◽  
Resorcinol Formaldehyde ◽  
Catalyst Composition ◽  
Solids Content ◽  
Insight Into

The production of resorcinol–formaldehyde xerogels has yielded insight into the gelation processes underpinning their structures. In this work, the role of the cation species from the catalyst is probed by studying the simultaneous addition of sodium carbonate and calcium carbonate to a resorcinol–formaldehyde mixture. Twenty-eight xerogels were prepared by varying the solids content, catalyst concentration, and catalyst composition, and each was analysed for its textural properties, including the surface area and average pore diameter. The results indicate that the role of the cation is linked to the stabilisation of the clusters formed within the system, and that the Group II catalyst causes the salting out of the oligomers, resulting in fewer, larger clusters, hence, an increase in pore size and a broadening of the pore size distribution. The results provide insight into how these systems can be further controlled to create tailored porous materials for a range of applications.

Fuels Desulphurisation by Adsorbtion on Fe / Bentonite

2017 ◽  
Vol 68 (3) ◽  
pp. 483-486
Author(s):  
Constantin Sorin Ion ◽  
Mihaela Bombos ◽  
Gabriel Vasilievici ◽  
Dorin Bombos
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Pore Diameter ◽  
Adsorption Process ◽  
Continuous System ◽  
Gas Oil ◽  
Average Pore ◽  
Atmospheric Distillation

Desulfurisation of atmospheric distillation gasoline and gas oil was performed by adsorption process on Fe/ bentonite. The adsorbent was characterized by determining the adsorption isotherms, specific surface area, pore volume and average pore diameter. Adsorption experiments of atmospheric distillation gasoline and gas oil were performed in continuous system at 280�320oC, 5 atm and volume hourly space velocities of 1�2 h-1. The efficiency of adsorption on Fe / bentonite was better at desulphurisation of gasoline versus gas oil.

scholarly journals Insight into Active Centers and Anti-Coke Behavior of Niobium-Containing SBA-15 for Glycerol Dehydration

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 488
Author(s):  
Katarzyna Stawicka ◽  
Maciej Trejda ◽  
Maria Ziolek
Keyword(s):  
Coke Formation ◽  
Catalytic Performance ◽  
Acid Sites ◽  
Silica Matrix ◽  
High Concentration ◽  
Active Centers ◽  
Acidic Sites ◽  
Glycerol Dehydration ◽  
Adsorption Desorption ◽  
Insight Into

Niobium containing SBA-15 was prepared by two methods: impregnation with different amounts of ammonium niobate(V) oxalate (Nb-15/SBA-15 and Nb-25/SBA-15 containing 15 wt.% and 25 wt.% of Nb, respectively) and mixing of mesoporous silica with Nb2O5 followed by heating at 500 °C (Nb2O5/SBA-15). The use of these two procedures allowed obtaining materials with different textural/surface properties determined by N2 adsorption/desorption isotherms, XRD, UV-Vis, pyridine, and NO adsorption combined with FTIR spectroscopy. Nb2O5/SBA-15 contained exclusively crystalline Nb2O5 on the SBA-15 surface, whereas the materials prepared by impregnation had both metal oxide and niobium incorporated into the silica matrix. The niobium species localized in silica framework generated Brønsted (BAS) and Lewis (LAS) acid sites. The inclusion of niobium into SBA-15 skeleton was crucial for the achievement of high catalytic performance. The strongest BAS were on Nb-25/SBA-15, whereas the highest concentration of BAS and LAS was on Nb-15/SBA-15 surface. Nb2O5/SBA-15 material possessed only weak LAS and BAS. The presence of the strongest BAS (Nb-25/SBA-15) resulted in the highest dehydration activity, whereas a high concentration of BAS was unfavorable. Silylation of niobium catalysts prepared by impregnation reduced the number of acidic sites and significantly increased acrolein yield and selectivity (from ca. 43% selectivity for Nb-25/SBA-15 to ca. 61% for silylated sample). This was accompanied by a considerable decrease in coke formation (from 47% selectivity for Nb-25/SBA-15 to 27% for silylated material).

scholarly journals Photocatalytic activity of Pr-modified TiO2 for the degradation of bisphenol A

2021 ◽  
Vol 3 (2) ◽  
Author(s):  
Denise S. Cordeiro ◽  
Fernando L. Cassio ◽  
Larissa Ciccotti ◽  
Thiago L. R. Hewer ◽  
Paola Corio ◽  
...  
Keyword(s):  
Photocatalytic Activity ◽  
Bisphenol A ◽  
Pore Diameter ◽  
Sol Gel ◽  
Bandgap Energy ◽  
Photocatalytic Efficiency ◽  
Average Pore ◽  
X Ray ◽  
Vis Spectroscopy ◽  
Adsorption Desorption

AbstractPraseodymium doped TiO2 nanoparticles were successfully prepared by the sol–gel method and characterized by X-ray powder diffraction, N2 adsorption–desorption isotherm, and UV–vis spectroscopy. The effects of the dopant on the crystallite size, specific surface area, average pore diameter, pore volume, and bandgap energy were investigated. The photocatalytic activity of the catalysts was evaluated by bisphenol A degradation and mineralization, which is a representative endocrine disruptor. Furthermore, under visible light irradiation the Pr-modified TiO2 photocatalysts exhibited higher photocatalytic efficiency than unmodified TiO2. When praseodymium was loaded (1.0–5.0%) onto the surface of TiO2, the rates of degradation and mineralization were increased 3–5 times.

Diffusion of Heavy Oil in SiO2 Model Catalyst and FCC Catalyst

2012 ◽  
Vol 550-553 ◽  
pp. 158-163 ◽  
Author(s):  
Zi Yuan Liu ◽  
Sheng Li Chen ◽  
Peng Dong ◽  
Xiu Jun Ge
Keyword(s):  
Diffusion Coefficient ◽  
Pore Size ◽  
Effective Diffusion Coefficient ◽  
Pore Diameter ◽  
Effective Diffusion ◽  
Model Catalyst ◽  
Average Pore ◽  
Diffusion Factor ◽  
Fcc Catalyst ◽  
Fcc Catalysts

Through the measured effective diffusion coefficients of Dagang vacuum residue supercritical fluid extraction and fractionation (SFEF) fractions in FCC catalysts and SiO2model catalysts, the relation between pore size of catalyst and effective diffusion coefficient was researched and the restricted diffusion factor was calculated. The restricted diffusion factor in FCC catalysts is less than 1 and it is 1~2 times larger in catalyst with polystyrene (PS) template than in conventional FCC catalyst without template, indicating that the diffusion of SFEF fractions in the two FCC catalysts is restricted by the pore. When the average molecular diameter is less than 1.8 nm, the diffusion of SFEF fractions in SiO2model catalyst which average pore diameter larger than 5.6 nm is unrestricted. The diffusion is restricted in the catalyst pores of less than 8 nm for SFEF fractions which diameter more than 1.8 nm. The tortuosity factor of SiO2model catalyst is obtained to be 2.87, within the range of empirical value. The effective diffusion coefficient of the SFEF fractions in SiO2model catalyst is two orders of magnitude larger than that in FCC catalyst with the same average pore diameter. This indicate that besides the ratio of molecular diameter to the pore diameter λ, the effective diffusion coefficient is also closely related to the pore structure of catalyst. Because SiO2model catalyst has uniform pore size, the diffusion coefficient can be precisely correlated with pore size of catalyst, so it is a good model material for catalyst internal diffusion investigation.

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.

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