| 1. |
- Hosseinpourpia, Reza, 1983-, et al.
(author)
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Hydrophobic Formulations Based on Tall Oil Distillation Products for High-Density Fiberboards
- 2020
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In: Materials. - : MDPI. - 1996-1944. ; 13:18, s. 1-13
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Journal article (peer-reviewed)abstract
- This study investigates the effect of renewable formulations based on tall oil bio-refinery products on the water vapor sorption and interfiber strength of cellulosic fibers as well as on the properties of high-density fiberboard (HDF) panels. The results obtained for HDF prepared using renewable formulations were compared to the results for HDF obtained using conventional synthetic paraffin wax (hydrowax), which is the hydrophobic agent currently utilized by the industry. Four tall oil distillation products (TODPs) with different levels of fatty and rosin acids were used for preparing the hydrophobic formulations with furfuryl alcohol as an organic solvent. According to determinations with an automated vapor sorption apparatus, the formulations had a similar effect with hydrowax on the sorption behavior of natural fibers. Unlike to hydrowax treatment, the ultimate tensile strength of cellulosic paper-sheets treated with the formulations remained unchanged or significantly increased. At the standard addition load of 1% (wt/wt dry fibers) of the formulations, HDF panels showed comparable and only in one case, e.g., TODP3-based formulation, slightly higher thickness swelling (24 h) than those with hydrowax. The best performing formulation (TODP2-based) in terms of tensile strength of paper sheets did not significantly change the mechanical properties of HDF panels in both standard climate and high humid conditions. Promising results at the standard and humid climate conditions were obtained for HDF panels manufactured with higher TODP2-based formulation amounts (3-5%) and reduced melamine-urea-formaldehyde resin content (10-12% instead of 14%, wt dry resin/wt dry fibers).
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| 2. |
- Maslova, Marina, et al.
(author)
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Formation of titanium phosphate composites during phosphoric acid decomposition of natural sphene
- 2008
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In: Journal of Solid State Chemistry. - : Elsevier BV. - 0022-4596 .- 1095-726X. ; 181:12, s. 3357-3365
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Journal article (peer-reviewed)abstract
- Decomposition of mineral sphene, CaTiOSiO4, by H3PO4 is investigated in detail. During the dissolution process, simultaneous calcium leaching and formation of titanium phosphate (TiP) take place. The main product of decomposition is a solid titanium phosphate-silica composite. The XRD, solid-sate NMR, IR, TGA, SEM and BET data were used to identify and characterize the composite as a mixture of crystalline Ti(HPO4)2H2O and silica. When 80% phosphoric acid is used the decomposition degree is higher than 98% and calcium is completely transferred into the liquid phase. Formation of Ti(HPO4)2H2O proceeds via formation of meta-stable titanium phosphate phases, Ti(H2PO4)(PO4)2H2O and Ti(H2PO4)(PO4).The sorption affinities of TiP composites were examined in relation to caesium and strontium ions. A decrease of H3PO4 concentration leads to formation of composites with greater sorption properties. The maximum sorption capacity of TiP is observed when 60% H3PO4 is used in sphene decomposition.The work demonstrates a valuable option within the Ti(HPO4)2H2O-SiO2 composite synthesis scheme, to use phosphoric acid flows for isolation of CaHPO42H2O fertilizer.
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| 3. |
- Maslova, Marina, et al.
(author)
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Synthesis, characterization, and sorption properties of amorphous titanium phosphate and silica-modified titanium phosphates
- 2008
-
In: Inorganic Chemistry. - : American Chemical Society (ACS). - 0020-1669 .- 1520-510X. ; 47:23, s. 11351-11360
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Journal article (peer-reviewed)abstract
- Amorphous titanium hydroxyphosphate with formula Ti(OH)1.36(HPO4)1.322.3H2O and a new silica-modified titanium hydroxyphosphate with a general formula Ti(OH)2x(HPO4)2-xySiO2nH2O are synthesized and characterized using IR, TG, XRD, SEM, solid-state NMR, and BET techniques. It is concluded that SiO2 is evenly distributed within the titanium phosphate (TiP) agglomerates and that neither the separate silica phase nor the titanium silicates are formed during the synthesis of silica-modified titanium hydroxyphosphate. Correlations between the texture, ion-exchange properties of the amorphous titanium hydroxyphosphate, and the amount of SiO2 present within the TiP matrix are established. Sorption properties of silica-modified titanium hydroxyphosphate toward Cs+ and Sr2+ are studied in a series of samples with an increasing amount of silica, at different pH, and in NaCl solutions with a varying ionic strength. It is found that sorption of Cs+ does not depend practically on the amount of SiO2 present, whereas the Sr2+ uptake drastically decreases with an increase of silica amount. The effects of pH and of the electrolyte concentration on the sorption behavior of titanium phosphate are discussed in terms of ionic hydration shell and titanium phosphate structural specificity. The kinetics of sorption processes is also investigated, and the diffusion coefficients for cesium and strontium are obtained.
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| 4. |
- Maslova, Marina V., et al.
(author)
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Extended study on the synthesis of amorphous titanium phosphates with tailored sorption properties
- 2012
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In: Journal of Non-Crystalline Solids. - : Elsevier BV. - 0022-3093 .- 1873-4812. ; 358:22, s. 2943-2950
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Journal article (peer-reviewed)abstract
- The influence of concentrations of both TiO2 and H2SO4 in the syntheses of amorphous titanium phosphates (TiP) is reported. IR, XRD, TGA, BET and NMR techniques were used to characterise the isolated TiP products. The concentration of sulphuric acid in the initial synthesis plays a major role in the structural diversity and sorption properties of the final ionites. In the primary solutions, Ti(IV) is in monomeric, polymeric and colloidal forms. Upon addition of H3PO4 the presence of monomeric titanium ensures formation of the Ti(HPO4)2 phase. The polymeric Ti(IV) is responsible for formation of the titanium hydroxo-phosphate phase, Ti(OH)2(HPO4), whilst the colloidal form of Ti(IV) appears to have a role in coagulation of a minor Ti(OH)4 phase in an amorphous TiP. It is found that TiP ion-exchange capacities gradually increase with an increase of both TiO2 and H2SO4 concentrations and reach a maximum value of 3.8 mg-eq g− 1 when TiO2 is 70–100 g L− 1 and H2SO4 is 480–560 g L− 1. Analyses of compositional, structural and sorption data allowed 3D correlation diagrams to be built that can facilitate fabrication of TiP with tailored sorption properties.
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| 5. |
- Naydenov, Valeri, et al.
(author)
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Chromium containing zeolite beta macrostructures
- 2002
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In: Impact of zeolites and other porous materials on the new technologies at the beginning of the new millennium. - Amsterdam : Elsevier. - 0444511741 ; , s. 1449-1455
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Conference paper (peer-reviewed)
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| 6. |
- Naydenov, Valeri, et al.
(author)
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Meso/macroporous AlPO-5 spherical macrostructures tailored by resin templating
- 2005
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In: Microporous and Mesoporous Materials. - : Elsevier BV. - 1387-1811 .- 1873-3093. ; 78:2-3, s. 181-188
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Journal article (peer-reviewed)abstract
- A multi-step procedure for the preparation of meso/macroporous AlPO-5 spherical macrostructures using cation exchange resin beads as macrotemplates is presented. Firstly, aluminum species were introduced into the resin beads by ion exchange resulting in a resin-aluminum composite. Thereafter, the resin-aluminum composite was mixed with TEAOH, H3PO4 and distilled water and hydrothermally treated at 150 °C to yield resin-AlPO-5 composite. Finally, the resin was removed by calcination leaving behind self-bonded AlPO-5 spheres. The product AlPO-5 macrostructures were thoroughly characterized by SEM, XRD, nitrogen adsorption measurements, 31P and 27Al solid state NMR spectroscopy. The influence of various components of the synthesis mixture on the crystallinity, phase purity and stability of the AlPO-5 spheres was systematically studied. Samples prepared for different treatment times using the initial synthesis composition that gives spheres of the highest quality were used to study the crystallization process within the resin.
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| 7. |
- Naydenov, Valeri, et al.
(author)
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Mesoporous Me-AlPO-5 spheres prepared using cation-exchange resins as templates
- 2004
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In: Recent advances in the science and technology of zeolites and related materials. Part A. - Amsterdam : Elsevier. - 0444518274 ; , s. 660-666
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Conference paper (peer-reviewed)abstract
- Mesoporous self-bonded transition metal-containing AIPO-5 spheres were prepared by a multi-step procedure using macroporous cation exchange resin beads as a template. Aluminum was firstly introduced into the resin by ion exchange using an aluminum chlorohydrate solution. After separation and drying, tf Al-resin composite was mixed with phosphoric acid, tetraethylammonium hydroxide distilled water and hydrothermally treated to yield AIPO-5-resiii composite. Thereafter, vanadium or chromium were ion exchanged into the AIPO-5-resiii composites utilizing the residual ion exchange capacity of the resistor. Finally, the resin was combusted leaving behind Me-AlPO-5 (where Me is V or Cr) spheres similar in shaping and size to the original resin beads. The appearance of the spheres and the nature of the metal species were dependent on the metal loading. The metal introduction affected mainly the mesopore structure of the Mesophare AlPO-5 spheres.
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| 8. |
- Naydenov, Valeri
(author)
-
Modified molecular sieve macrostructures
- 2002
-
Licentiate thesis (other academic/artistic)abstract
- The preparation of molecular sieve based catalysts in appropriate macroforms suitable for practical utilization is of great technological importance. This thesis is dedicated to the preparation of metal containing molecular sieve macrostructures (modified macrostructures). Modified molecular sieve macrostructures were prepared by the resin templating method. Firstly, molecular sieves were synthesized within the pore structure of macroporous anion exchange resin beads. After this step, a certain degree of ion exchange capacity is retained by the resin facilitating the secondary insertion of metal anions. Metal anionic species were ion exchanged into the resin-molecular sieve composites obtained in a following step. Finally, the resin was removed by calcination leaving behind self-bonded metal containing molecular sieve spheres with a shape and size similar to the original resin beads. V, W, Cr and Pd containing macrostructures were prepared by the method. Resin-silica composites, in which the structure of the silica was changed from amorphous to crystalline silicalite-1 were used for the preparation of the V and W spheres. The Cr and Pd containing spheres were prepared from resin-zeolite beta composites. The properties of the product spheres (metal content, crystallinity, morphology, nature of the metal species, etc.) were extensively characterized by atomic adsorption spectrometry, X-ray diffraction, scanning electron microscopy, energy dispersive, Raman and UV-vis spectroscopy, nitrogen adsorption and chemisorption measurements. The materials prepared are of interest for application mainly in the area of catalysis.
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| 9. |
- Naydenov, Valeri, et al.
(author)
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Palladium-containing zeolite beta macrostructures prepared by resin macrotemplating
- 2002
-
In: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 14:12, s. 4881-4885
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Journal article (peer-reviewed)abstract
- A multistep procedure for the preparation of palladium-containing zeolite beta spheres using anion-exchange resin beads as shape-directing macrotemplates is presented. In a first step, resin beads are hydrothermally treated with zeolite beta synthesis solutions, and as a result resin-zeolite beta composite particles are obtained. In a second step, anionic palladium precursor species are introduced into the composite using the residual ion-exchange capacity of the resin. Finally, the ion exchanger is removed by calcination, leaving self-bonded palladium-containing zeolite beta spheres. The spheres obtained by the procedure were characterized by AAS, XRD, SEM, EDS, UV-vis DRS spectroscopy, nitrogen adsorption measurements, and chemisorption. Materials with controlled macroshape, porosity, and palladium content were prepared by the method.
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| 10. |
- Naydenov, Valeri, et al.
(author)
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Self-bonded zeolite beta/MCM-41 composite spheres
- 2005
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In: Journal of porous materials. - : Springer Science and Business Media LLC. - 1380-2224 .- 1573-4854. ; 12:3, s. 193-199
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Journal article (peer-reviewed)abstract
- Self-bonded zeolite Beta/MCM-41 composite spheres were prepared using a two-step synthesis procedure. In the first step, mesoporous zeolite Beta spheres were obtained using anion exchange resin as macrotemplate. In the second step, the MCM-41 or Al-MCM-41 was grown both on sphere surfaces and in the pore structure of the pre-formed zeolite Beta spheres. Finally, the templating agents used in the synthesis of mesophase were removed by calcination leaving behind self-bonded Beta/MCM-41 composite spheres. Beta/MCM-41 composites were characterized by XRD, SEM and nitrogen adsorption measurements. Materials with controlled macroshape, composition and complex porosity were prepared by the approach.
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