scholarly journals Rhodium catalysts build into the structure of a silicate support in the hydroformylation of alkenes

2013 ◽  
Vol 11 (4) ◽  
pp. 561-568 ◽  
Author(s):  
Thomas Borrmann ◽  
Andrew McFarlane ◽  
Uwe Ritter ◽  
James Johnston
Keyword(s):  
Surface Area ◽  
Heterogeneous Catalyst ◽  
Pore Volume ◽  
Calcium Silicate ◽  
Rhodium Catalysts ◽  
Product Phase ◽  
Silicate Structure ◽  
Acid Washing ◽  
Catalytic Material ◽  
Low Alcohol

AbstractRhodium is build into a nano-structured calcium silicate during the synthesis of the silicate. Thereby, it was desired to create a robust heterogeneous catalyst, which does not suffer from catalyst leaching like rhodium impregnated on a pre-formed silicate. While this was achieved, the silicate structure was adversely affected by the incorporation of rhodium — the surface area and pore volume of the material were found to be comparatively low. Alcohol and acid washing were tested to address this issue. The alcohol treatment proved detrimental as catalytic material was leached from the silicate. The acid washed rhodium containing calcium silicate was quite active in the hydroformylation of alkenes and did not suffer loss of catalyst into the product phase. Acid treated rhodium containing silicates were more active than their untreated counterparts but less selective due to access to the rhodium centers being opened.

scholarly journals The Internal Recycle Reactor Enhances Porous Calcium Silicate Hydrates to Recover Phosphorus from Aqueous Solutions

2017 ◽  
Vol 2017 ◽  
pp. 1-10 ◽  
Author(s):  
Wei Guan ◽  
Shichao Tian
Keyword(s):  
Surface Area ◽  
Pore Volume ◽  
Calcium Silicate ◽  
Ph Value ◽  
Optimal Operation ◽  
Phosphorus Recovery ◽  
Operation Conditions ◽  
Calcium Silicate Hydrates ◽  
Recycle Reactor ◽  
Adsorption Desorption

In this experiment, the porous calcium silicate hydrates (P-CSHs) were prepared via a hydrothermal method and then modified by polyethylene glycol (PEG). The modified P-CSHs combined with an internal recycle reactor could successfully recover the phosphorus from electroplating wastewater. The modified P-CSHs were characterized by X-ray diffraction (XRD), N2 adsorption-desorption isotherms, and Fourier transform infrared spectroscopy (FT-IR). After compared with different samples, the modified P-CSHs-PEG2000 sample had larger specific surface area of 87.48 m2/g and higher pore volume of 0.33 cm3/g, indicating a high capacity for phosphorus recovery. In the process of phosphorus recovery, the pH value of solution was increased to 9.5, which would enhance the recovery efficiency of phosphorus. The dissolution rate of Ca2+ from P-CSH-PEG2000 was fast, which was favorable for phosphorus precipitation and phosphorus recovery. The effects of initial concentration of phosphorus, P-CSHs-PEG2000 dosage, and stirring speed on phosphorus recovery were analyzed, so the optimal operation conditions for phosphorus recovery were obtained. The deposition was analyzed by XRD, N2 adsorption-desorption, and SEM techniques; it was indicated that the pore volume and surface area of the P-CSHs-PEG2000 were significantly reduced, and the deposition on the surface of P-CSHs-PEG2000 was hydroxyapatite.

scholarly journals The Synthesis and Characterisation of Nano-Structured Calcium Silicate

2021 ◽  
Author(s):  
◽  
Andrew James McFarlane
Keyword(s):  
Surface Tension ◽  
Surface Area ◽  
Pore Volume ◽  
Calcium Silicate ◽  
Continuous Process ◽  
Substantial Reduction ◽  
Geothermal Water ◽  
Atomic Scale ◽  
Open Framework ◽  
Macro Scale

<p>Nano-structured calcium silicate consists of randomly stacked nano-sized platelets that make up an open framework structure of macropores that resembles a house of cards. This structure affords the material the desirable physical properties of a large pore volume and a highly accessible surface area that exceed many other silicas and silicates. The material is possibly related to other disordered calcium silicate hydrates at an atomic level, although it is the macro-structure and the potential of performing chemistry upon its surface that is of great interest. Due to the novelty of nano-structured calcium silicate, little was known about it before this work. The focus of this study has therefore been placed upon characterising the material and determining the conditions that allow the pore volume and surface area to be maximised. The material is prepared through an initial precipitation from the reaction of a calcium salt with monomeric silica, followed subsequently by self-ordering on both an atomic-scale and on a macro-scale to develop the porous framework. The framework of the material has been found to collapse due to forces created from surface tension during the removal of water from the pores upon drying. The result of this collapse is a substantial reduction in both the surface area and pore volume of the material. Three different methods have been developed to maintain the structure with each modification producing a material that is suitable for different applications. A reinforcing process following the development of the open framework whereby additional silica is polymerised upon the structure strengthens the material so that the forces resulting from the removal pore water are unable to cause collapse of the framework. This material is therefore able to be repeatedly re-wet and dried without any detrimental effect to the pore volume or surface area of the material. The replacement of water within the pores with 2-ethoxyethanol, that has a low surface tension, and by modifying the material through treatment with acid have also been found to prevent collapse of the structure. Through the knowledge gained of the development of the nano-structured calcium silicate and of the reaction conditions required for the optimisation of the surface area and pore volume, a semi-continuous process has been devised that has allowed for production of the material on a larger scale. This work also contains details on the formation of nano-structured calcium silicate by using geothermal water from an electricity generation plant as the source of monomeric silica rather than using sodium silicate. Currently, the formation of a scale from supersaturated geothermal water is problematic for the industries that use the fluid and limits the use of the resource. The removal of monomeric silica from geothermal water as a result of producing nanostructured calcium silicate prevents the formation of the scale and therefore allows a greater proportion of the thermal energy in the fluid to be potentially utilised.</p>

scholarly journals Ru0·Run+/Al2O3 as a Versatile Catalyst in the Isomerization of Allyl Alcohol

2021 ◽  
Vol 9 ◽  
Author(s):  
Julián Enciso ◽  
Alfonso Ramírez ◽  
Carlos Ostos ◽  
Adriana Echavarría ◽  
Misael Córdoba ◽  
...  
Keyword(s):  
Surface Area ◽  
Heterogeneous Catalyst ◽  
Pore Volume ◽  
Allyl Alcohol ◽  
Active Species ◽  
X Ray Diffraction ◽  
X Ray ◽  
Isomerization Product ◽  
Redox Sites ◽  
Alcohol Conversion

This study focuses on examining the isomerization of allyl alcohol using ruthenium (Ru) supported on alumina as a heterogeneous catalyst. The synthesized Ru/Al solids were characterized by various characterization techniques. The content of Ru was estimated by the energy dispersive x-ray technique. The x-ray diffraction (XRD) confirmed the presence of phases in the support and active species in the catalysts. The surface area of the support after Ru impregnation and the pore volume were determined by nitrogen physisorption. The analysis of programmed temperature (TPR and TPO) shows different redox sites which is confirmed by XPS. The catalytic results suggest a dependence on the amount of available metallic Ru, as well as the importance of the continuous regeneration of the metal using H2 to achieve a good conversion of the allyl alcohol. For comparison purposes, the commercial Ru on alumina 5% (CAS 908142) was used. The results show up to 68% alcohol conversion and 27% yield of the isomerization product using Ru(1,5.4h)/Al catalyst in comparison with 86% conversion and 39% yield of the isomerization product using CAS 908142. In contrast, our catalysts always presented higher TOF values (149–160) in comparison with CAS 908142 (101).

scholarly journals Chemical Composition and Porosity Characteristics of Various Calcium Silicate-Based Endodontic Cements

2018 ◽  
Vol 2018 ◽  
pp. 1-6 ◽  
Author(s):  
Seok Woo Chang
Keyword(s):  
Chemical Composition ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Calcium Silicate ◽  
Pore Diameter ◽  
Clinical Performance ◽  
Powder Analysis ◽  
Adsorption Desorption

Chemical composition and porosity characteristics of calcium silicate-based endodontic cements are important determinants of their clinical performance. Therefore, the aim of this study was to investigate the chemical composition and porosity characteristics of various calcium silicate-based endodontic cements: MTA-angelus, Bioaggregate, Biodentine, Micromega MTA, Ortho MTA, and ProRoot MTA. The specific surface area, pore volume, and pore diameter were measured by the porosimetry analysis of N2 adsorption/desorption isotherms. Chemical composition and powder analysis by scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) were also carried out on these endodontic cements. Biodentine and MTA-angelus showed the smallest pore volume and pore diameter, respectively. Specific surface area was the largest in MTA-angelus. SEM and EDS analysis showed that Bioaggregate and Biodentine contained homogenous, round and small particles, which did not contain bismuth oxide.

scholarly journals The Synthesis and Characterisation of Nano-Structured Calcium Silicate

2021 ◽  
Author(s):  
◽  
Andrew James McFarlane
Keyword(s):  
Surface Tension ◽  
Surface Area ◽  
Pore Volume ◽  
Calcium Silicate ◽  
Continuous Process ◽  
Substantial Reduction ◽  
Geothermal Water ◽  
Atomic Scale ◽  
Open Framework ◽  
Macro Scale

<p>Nano-structured calcium silicate consists of randomly stacked nano-sized platelets that make up an open framework structure of macropores that resembles a house of cards. This structure affords the material the desirable physical properties of a large pore volume and a highly accessible surface area that exceed many other silicas and silicates. The material is possibly related to other disordered calcium silicate hydrates at an atomic level, although it is the macro-structure and the potential of performing chemistry upon its surface that is of great interest. Due to the novelty of nano-structured calcium silicate, little was known about it before this work. The focus of this study has therefore been placed upon characterising the material and determining the conditions that allow the pore volume and surface area to be maximised. The material is prepared through an initial precipitation from the reaction of a calcium salt with monomeric silica, followed subsequently by self-ordering on both an atomic-scale and on a macro-scale to develop the porous framework. The framework of the material has been found to collapse due to forces created from surface tension during the removal of water from the pores upon drying. The result of this collapse is a substantial reduction in both the surface area and pore volume of the material. Three different methods have been developed to maintain the structure with each modification producing a material that is suitable for different applications. A reinforcing process following the development of the open framework whereby additional silica is polymerised upon the structure strengthens the material so that the forces resulting from the removal pore water are unable to cause collapse of the framework. This material is therefore able to be repeatedly re-wet and dried without any detrimental effect to the pore volume or surface area of the material. The replacement of water within the pores with 2-ethoxyethanol, that has a low surface tension, and by modifying the material through treatment with acid have also been found to prevent collapse of the structure. Through the knowledge gained of the development of the nano-structured calcium silicate and of the reaction conditions required for the optimisation of the surface area and pore volume, a semi-continuous process has been devised that has allowed for production of the material on a larger scale. This work also contains details on the formation of nano-structured calcium silicate by using geothermal water from an electricity generation plant as the source of monomeric silica rather than using sodium silicate. Currently, the formation of a scale from supersaturated geothermal water is problematic for the industries that use the fluid and limits the use of the resource. The removal of monomeric silica from geothermal water as a result of producing nanostructured calcium silicate prevents the formation of the scale and therefore allows a greater proportion of the thermal energy in the fluid to be potentially utilised.</p>

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 Nanometer Pore Structure Characterization of Taiyuan Formation Shale in the Lin-Xing Area Based on Nitrogen Adsorption Experiments

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 298
Author(s):  
Chenlong Ding ◽  
Jinxian He ◽  
Hongchen Wu ◽  
Xiaoli Zhang
Keyword(s):  
Specific Surface ◽  
Pore Structure ◽  
Surface Area ◽  
Specific Surface Area ◽  
Shale Gas ◽  
Pore Volume ◽  
Ordos Basin ◽  
Total Pore Volume ◽  
Nitrogen Adsorption ◽  
Taiyuan Formation

Ordos Basin is an important continental shale gas exploration site in China. The micropore structure of the shale reservoir is of great importance for shale gas evaluation. The Taiyuan Formation of the lower Permian is the main exploration interval for this area. To examine the nanometer pore structures in the Taiyuan Formation shale reservoirs in the Lin-Xing area, Northern Shaanxi, the microscopic pore structure characteristics were analyzed via nitrogen adsorption experiments. The pore structure parameters, such as specific surface area, pore volume, and aperture distribution, of shale were calculated; the significance of the pore structure for shale gas storage was analyzed; and the main controlling factors of pore development were assessed. The results indicated the surface area and hole volume of the shale sample to be 0.141–2.188 m2/g and 0.001398–0.008718 cm3/g, respectively. According to the IUPAC (International Union of Pure and Applied Chemistry) classification, mesopores and macropores were dominant in the pore structure, with the presence of a certain number of micropores. The adsorption curves were similar to the standard IV (a)-type isotherm line, and the hysteresis loop type was mainly similar to H3 and H4 types, indicating that most pores are dominated by open type pores, such as parallel plate-shaped pores and wedge-shaped slit pores. The micropores and mesopores provide the vast majority of the specific surface area, functioning as the main area for the adsorption of gas in the shale. The mesopores and macropores provide the vast majority of the pore volume, functioning as the main storage areas for the gas in the shale. Total organic carbon had no notable linear correlation with the total pore volume and the specific surface area. Vitrinite reflectance (Ro) had no notable correlation with the specific surface area, but did have a low “U” curve correlation with the total pore volume. There was no relationship between the quartz content and specific surface area and total pore volume. In addition, there was no notable correlation between the clay mineral content and total specific surface area and total pore volume.

scholarly journals Titanium Carbide Nanocrystals Synthesized from a Metatitanic Acid-Sucrose Precursor via a Carbothermal Reduction

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Hyunho Shin ◽  
Jun-Ho Eun
Keyword(s):  
Process Control ◽  
Titanium Carbide ◽  
Specific Surface ◽  
Surface Area ◽  
Pore Volume ◽  
Carbothermal Reduction ◽  
Crystal Size ◽  
Reduction Process ◽  
Specific Pore Volume ◽  
Metatitanic Acid

A TiC powder is synthesized from a micron-sized mesoporous metatitanic acid-sucrose precursor (precursor M) by a carbothermal reduction process. Control specimens are also prepared using a nanosized TiO2-sucrose precursor (precursor T) with a higher cost. When synthesized at 1500°C for 2 h in flowing Ar, the characteristics of the synthesized TiC from precursor M are similar to those of the counterpart from precursor T in terms of the crystal size (58.5 versus 57.4 nm), oxygen content (0.22 wt% versus 0.25 wt%), and representative sizes of mesopores: approximately 2.5 and 19.7–25.0 nm in both specimens. The most salient differences of the two specimens are found in the TiC from precursor M demonstrating (i) a higher crystallinity based on the distinctive doublet peaks in the high-two-theta XRD regime and (ii) a lower specific surface area (79.4 versus 94.8 m2/g) with a smaller specific pore volume (0.1 versus 0.2 cm3/g) than the counterpart from precursor T.

The relationship between geotechnical index properties and the pore-size distribution of compacted clayey silts

2015 ◽  
Vol 22 (6) ◽  
Author(s):  
Nazile Ural
Keyword(s):  
Specific Surface ◽  
Pore Size Distribution ◽  
Pore Size ◽  
Size Distribution ◽  
Surface Area ◽  
Specific Surface Area ◽  
Pore Volume ◽  
Correlation Coefficients ◽  
Liquid Limit ◽  
Index Properties

AbstractIn this study, the relationships between geotechnical index properties and the pore-size distribution of compacted natural silt and artificial soil mixtures, namely, silt with two different clays and three different clay percentages (10%, 20%, and 40%), were examined and compared. Atterberg’s limit tests, standard compaction tests, mercury intrusion porosimetry, X-ray diffraction, scanning electron microscopy (SEM) analysis, and Brunauer-Emmett-Teller specific surface analysis were conducted. The results show that the liquid limit, the cumulative pore volume, and specific surface area of artificially mixed soils increase with an increase in the percentage of clay. The cumulative pore volume and specific surface area with geotechnical index properties were compared. High correlation coefficients were observed between the specific areas and both the liquid limit and the plasticity index, as well as between the cumulative pore volume and both the clay percentage and the

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