SBA-15 Mesoporous Silica as Catalytic Support for Hydrodesulfurization Catalysts—Review

SBA-15 is an interesting mesoporous silica material having highly ordered nanopores and a large surface area, which is widely employed as catalyst supports, absorbents, drug delivery materials, etc. Since it has a lack of functionality, heteroatoms and organic functional groups have been incorporated by direct or post-synthesis methods in order to modify their functionality. The aim of this article is to review the state-of-the-art related to the use of SBA-15-based mesoporous systems as supports for hydrodesulfurization (HDS) catalysts.The authors acknowledge the financial support of the DGAPA-UNAM PAPIIT IN107311-3 project, CONACYT Ciencia Básica 2012 and CIC-UMSNH 2012-2013

SBA-15 Mesoporous Silica as Catalytic Support for Hydrodesulfurization Catalysts—Review

SBA-15 is an interesting mesoporous silica material having highly ordered nanopores and a large surface area, which is widely employed as catalyst supports, absorbents, drug delivery materials, etc. Since it has a lack of functionality, heteroatoms and organic functional groups have been incorporated by direct or post-synthesis methods in order to modify their functionality. The aim of this article is to review the state-of-the-art related to the use of SBA-15-based mesoporous systems as supports for hydrodesulfurization (HDS) catalysts

SBA-16 Cage-Like Porous Material Modified with APTES as an Adsorbent for Pb2+ Ions Removal from Aqueous Solution

© 2020 by the authors.Tridimensional cubic mesoporous silica, SBA-16, functionalized with aminopropyl groups, were employed as adsorbents for Pb2+ ion removal from aqueous solution. The adsorption capacity was investigated for the effect of pH, contact time, temperature, and concentration of 3-aminopropyltriethoxysilane (APTES) employed for adsorbent functionalization. The textural properties and morphology of the adsorbents were evaluated by N2 physisorption, small-angle X-ray diffraction (XRD), diffuse reflectance spectroscopy (UV-vis), and transmission electron microscopy (TEM). The functionalization of the SBA-16 was evaluated by elemental analysis (N), thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). Batch adsorption studies show that the total Pb2+ ions removal was archived on adsorbent having an optimized amount of aminopropyl groups (2N-SBA-16). The maximum of Pb2+ ions removal occurred at optimized adsorption conditions: pH = 5–6, contact time 40 min, and at a low initial lead concentration in solution (200 mg L−1). Under the same adsorption conditions, the amino-functionalized SBA-16 with cubic 3D unit cell structure exhibited higher adsorption capability than its SBA-15 counterpart with uniform mesoporous channels.Financial support by FOFI UAQ-2018 is gratefully acknowledged. V. Palos-Barba and A. Moreno-Martell thank the CONACyT for the scholarships

Efficient Removal of Hg(II) from Water under Mildly Acidic Conditions with Hierarchical SiO₂ Monoliths Functionalized with –SH Groups

In this work, novel adsorbents based on 3D hierarchical silica monoliths functionalized with thiol groups were used for the removal of Hg(II) ions from an acidic aqueous solution (pH 3.5). Silica monoliths were synthesized by using two different pluronic triblock polymers (P123 and F127) to study the effect of porous structure on their sorption capacity. Before and after functionalization by grafting with 3-mercaptopropyltrimethoxysilane (MPTMS), the monoliths were characterized by several techniques, and their Hg(II) removal potential was evaluated in batch experiments at 28 °C and pH 3.5, using different initial concentrations of Hg(II) ions in water (200–500 mg L−1). The thiol groups of the monoliths calcined at 550 °C showed thermal stability up to 300 °C (from TG/DTG). The functionalized monolith synthesized with P123 polymer and polyethylene glycol showed favorable hierarchical macro-mesopores for Hg(II) adsorption. M(P123)–SH exhibited 97% removal of Hg(II) at concentration 200 mg L−1. Its maximum adsorption capacity (12.2 mmol g−1) was two times higher than that of M(F127)–SH, demonstrating that the 3D hierarchical macro-mesoporosity allowing accessibility of Hg(II) to thiol groups favors the physical and chemical adsorption of Hg(II) under slightly acidic conditions

Development of an Adsorbing System Made of DMS-1 Mesh Modified by Amino Groups to Remove Pb(II) Ions from Water

Water pollution by heavy metals represents several health risks. Conventional technologies employed to eliminate lead ions from residual or drinking water are expensive, therefore an efficient and low-cost technique is required and adsorption processes are a good alternative. In this work, the goal was to determine the adsorption capacity of a Disordered Mesoporous Silica 1 material (DMS-1) functionalized with amino groups, for Pb(II) ions removal. DMS-1 was prepared by sol-gel method and the incorporation of amino groups was performed by ex-situ method. As the source of amine groups, (3-Aminopropyl) triethoxysilane (APTES) was used and three different xNH2/DMS-1 molar ratios (0.2, 0.3, 0.4) were evaluated. In order to evaluate the incorporation of the amino group into the mesopore channels, thermal and structural analysis were made through Thermogravimetric Analysis (TGA), nitrogen adsorption–desorption at 77 K by Specific Brunauer–Emmett–Teller (SBET) method, Fourier Transfer Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS). The higher Pb(II) ions removal was achieved with the 0.3 molar proportion of xNH2/DMS-1 reaching 99.44% efficiency. This result suggests that the functionalized material can be used as an efficient adsorbent for Pb(II) ions from aqueous solution.The authors acknowledge financial support of FOFI-UAQ2018. The authors V. Palos-Barba and C. Lugo-Nabor acknowledge the CONACYT for the scholarships.Peer reviewe

Catalytic performance of CoMoW Sulfide catalysts supported on hierarchically structured porous silicas for HDS reactions

In this work, monolithic silica materials with hierarchical porosity were synthesized by the sol-gel method combined with a dual hard-soft templating route. Silica materials were used for the synthesis of hydrodesulfurization CoMoW-S catalysts by the immersion technique using transition metal salts as precursors, followed by oxidation and sulfidation in H2S/H2 mixture. Styrene-HEMA copolymer hard template presented homogeneous well-defined spherical shape with an average diameter of about 800 nm. Samples prepared over the hard template presented similar morphology. The surface areas of all supports prepared resulted in around 800 m2.g−1 and decreased to 220 m2.g−1 on average after the sulfidation process. Small-angle X-ray diffraction confirmed the presence of the 2D hexagonal or Im3m array of mesopores in all samples. The CoMoW oxide state catalysts presented low intensity peaks assigned to the b-CoMo(W)O4 phase and minor peaks related to MoO3 and polyoxides with the general formula MoxW1-xO3. The high conversion was obtained for catalysts supported on hierarchically structured porous silicas, even greater than that of the commercial catalyst used as reference (>30–50%). XPS results revealed that the degree of sulfidation and CoMoWS active species resulted higher in the CoMoW-HOPSCM catalyst compared to the CoMoW-MoNoSBA-15 sample, which in turn coincides with the catalytic activity results

Physical and structural characterization of bis-acryl composite resin

Abstract During the preparation of fixed prosthesis (including individual bridges and crowns) it is important to select the materials that have the best features and properties to predict a successful clinical treatment. The objective of this study was to determine if the chemical and structural characteristics could cause to increase the fracture resistance, we used four bis-acryl resins Luxatemp, Protemp, Structur and Telio. Three-points bending by Flexural test were performed in ten bars and they were carried out to compare with Anova test. In addition, the bis-acryl resins were analyzed by scanning electron microscopy, to analyze microstructure and morphology and the molecular structure were performed by Infrared Spectroscopy through Attenuated Total Reflectance. A higher flexural strength was found in Luxatemp and Structur with, no significant differences between this study groups. Regarding Protemp and Telio, these study groups showed a lower flexural strength when were compared with Luxatemp and Structur. These results corroborate SEM and ATR analysis because Luxatemp sample showed a regular size particle on the surface and chemically presents a long cross-linkage polymer chain. The presence of CO3, SiO2 and N–H groups as a fillers particle interacting with OH groups cause a higher flexural strength compared with another groups