Mesoporous SBA-15 Catalysts Research Articles

Vanadium–phosphorous oxide supported on mesoporous SBA-15 catalysts for ammoxidation of toluene to benzonitrile

Reaction scheme of ammoxidation of toluene over VPO/SBA-15.

N-BOC protection of amines over mesoporous SBA-15 catalyst at room temperature

N-BOC protection of amines over mesoporous SBA-15 catalyst at room temperature

Development of Ni-Co supported on SBA-15 catalysts for non-thermal plasma assisted co-conversion of CO2 and CH4: Results and lessons learnt

This study presents an investigation of using Co doping strategy to improve the Ni on mesoporous SBA-15 catalyst for promoting catalytic dry reforming of methane (DRM) under non-thermal plasma (NTP) conditions. The work was conducted by following the conventional procedures including pre-/post-reaction characterisation of the relevant catalysts, comparative assessment of various scenarios under the NTP condition and longevity tests. However, we found that the performance enhancement of the NTP system was mainly due to the use of the catalytically inert SBA-15 packing, rather than the variation of metal species on it though the results suggest the possible surface reactions on the metal surfaces. Hence, under the NTP condition, the so-called DRM might be mistaken because (i) the production of H2 and CO was likely due to the electron-impact dissociation of CO2/CH4 in gas discharge and (ii) surface reactions on a DRM catalyst are rather insignificant. We then carefully analysed and reflected on the findings and proposed further research questions to be shared with the colleagues in the field of NTP catalysis.

Direct cascade hydrogenation of biorenewable levulinic acid to valeric acid biofuel additives over metal (M = Nb, Ti, and Zr) supported SBA-15 catalysts

Chemoselective hydrogenation of biomass platform molecules into value-added chemicals and fuels is essential for the exploitation of biomass, and SBA-15 based metal catalysts with hydrogenation centers and acid sites seem promising in this regard. Valeric acid (VA) is the most important platform molecule for valeric biofuels and value-added chemicals production. The main issue with using such bifunctional catalysts for biomass conversion is maintaining the catalyst's stability in the liquid phase under harsh conditions. In-addition, direct one-pot selective hydrogenation of levulinic acid (LA) into VA synthesis is challenging due to its complex reaction conditions involved. Herein, we design a bifunctional mesoporous catalysts (SBA-15 mesoporous material doped with various metals Nb, Ti, and Zr) investigated for this reaction under the vapour phase. Different instrumental approaches were used to examine the structure, phase composition, morphology, and surface elemental analyses of catalysts as-prepared. Among those catalysts, Zr-doped mesoporous SBA-15 catalyst showed the 91% conversion of LA and the 68% selectivity toward VA and promising stability in a 52 h time on-stream run. Metal dispersion inside the SBA-15 and their surface acidity (sufficient number of acid sites and surface-active metal oxide species) and higher surface area are beneficial for the selectivity of VA. This work offers a highly-efficient bifunctional catalyst for selective hydrogenation of biomass feedstocks.

Sulfated zirconia catalysts supported on mesoporous Mg-SBA-15 with different morphologies for highly efficient conversion of fructose to 5-hydroxymethylfurfural

In this work, the novel acid-base bi-functional mesoporous SBA-15 catalysts with four kinds of morphologies were synthesized by Mg incorporated and sulfated zirconia (SZ) grafted. The introduction of Mg to mesoporous SBA-15 materials significantly improves the strength of the base. And the supported SZ group exhibit effective Brønsted/Lewis acid strength. The physical and chemical properties of the prepared materials were systematically analyzed by the characterization tests of SEM, TEM, XRD, N 2 adsorption-desorption of, FT-IR, TGA, XPS, NH 3 /CO 2 -TPD and in-suit PY-IR. The obtained catalysts of SZ@Mg-SBA-15 could be applied to the fructose conversion into 5-hydroxymethylfurfural (5-HMF) with the co-solvent system of iPrOH/DMSO ( v / v = 9:1). 5-HMF was achieved under the optimal reaction condition with the highest yield of 98.6%. The result shows that the reaction of fructose dehydration into 5-HMF could be caused by the combination of Brønsted acid site and basic site. This work developed reaction system could avoid the large use of environmentally dangerous solvents, and provides a new economical and feasible method for the large-scale conversion of fructose biomass. • Mesoporous SZ@Mg-SBA-15 catalysts were successfully synthesized. • The acid-base bifunctional sites showed synergistic effects in catalytic activity. • The highest 5-HMF yields of 98.6% can be obtained from fructose. • The developed iPrOH/DMSO co-solvent has a minimal environmental impact. • The prepared catalyst can be reused without significant loss of activity.

High efficiency Al modified mesoporous SBA-15 catalyst for biomass-derived γ-valerolactone decarboxylation to butene

A series of x wt%Al-SBA-15 catalysts prepared by modified wetness impregnation was investigated for γ-valerolactone (GVL) decarboxylation to butene. It was found that the impregnation of Al species not only remained the ordered mesoporous structure of parent SBA-15, but also created large amounts of Brønsted and Lewis acid sites on the surface of catalyst. The considerable amount of solid acid sites and the suitable Brønsted/Lewis acid ratio endowed 2.23 wt%Al-SBA-15 catalyst an excellent catalytic performance. Under the optimized conditions, the GVL conversion and butene yield can reach 99.8% and 96.6% at 320 °C, respectively. Mechanism studies indicated that the decarboxylation of γ-protonated PEA controlled speed of the whole reaction. Moreover, the catalytic activity of regenerated 2.23 wt%Al-SBA-15 catalyst was satisfactory after eight cycle tests, and the butene yield could still reach 92.2%. GVL conversion of 99.8% with excellent butene yield of 96.6% was obtained over the 2.23 wt%Al-SBA-15 catalyst prepared by simple modified wetness impregnation method at the corresponding react conditions. • High active 2.23 wt%Al-SBA-15 for GVL to butene was prepared by simple method. • Suitable amount of acid site and B/L ratio endowed catalyst excellent performance. • Butene yield maintained 92.2% after 8 cycle tests over 2.23 wt%Al-SBA-15 at 320 °C. • Decarboxylation of γ-protonated PEA was found to be the speed control steps.

Synthesis, characterization and catalytic performance in enantioselective reactions by mesoporous silica materials functionalized with chiral thiourea-amine ligand

Chiral heterogeneous catalysts have been synthesized by grafting of silyl derivatives of (1R, 2R)- or (1S, 2S)-1,2-diphenylethane-1,2-diamine on SBA-15 mesoporous support. The mesoporous material SBA-15 and so-prepared chiral heterogeneous catalysts were characterized by a combination of different techniques such as X-ray diffractometry (XRD), Fourier transform infrared (FT-IR), thermogravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and Brunauer–Emmett–Teller (BET) surface area. Results showed that (1R, 2R)- and (1S, 2S)-1,2-diphenylethane-1,2-diamine were successively immobilized on SBA-15 mesoporous support. Chiral heterogeneous catalysts and their homogenous counterparts were tested in enantioselective transfer hydrogenation of aromatic ketones and enantioselective Michael addition of acetylacetone to β-nitroolefin derivatives. The catalysts demonstrated notably high catalytic conversions (up to 99%) with moderate enantiomeric excess (up to 30% ee) for the heterogeneous enantioselective transfer hydrogenation. The catalytic performances for enantioselective Michael reaction showed excellent activities (up to 99%) with poor enantioselectivities. Particularly, the chiral heterogeneous catalysts could be readily recycled for Michael reaction and reused in three consecutive catalytic experiments with no loss of catalytic efficacies.

Enhanced performance and selectivity of CO2 methanation over phyllosilicate structure derived Ni-Mg/SBA-15 catalysts

Ni and Ni-Mg phyllosilicate mesoporous SBA-15 catalysts were successfully prepared via ammonia evaporation (AE) method as evidenced by XRD, H2-TPR, TEM, FTIR and EXAFS fitting results. The catalysts derived from phyllosilicate structure exhibit superior catalytic performance in CO2 methanation as compared to catalyst prepared via wetness impregnation (WI) method due to enhanced metal-support interaction and the presence of weakly basic sites provided by surface hydroxyl groups. Incorporation of Mg into phyllosilicate structure with optimum 5 wt% is also found to increase medium basic sites, which can promote monodentate formate formation as identified by DRIFTS analysis and improve CO2 methanation activity at lower temperatures. Additionally, the turnover frequency of CO2 conversion can be well correlated with the concentration of basic sites. The strong metal-support interaction derived from phyllosilicate structure along with confinement effect of SBA-15 can suppress metal sintering, resulting in good stability.

N-Aryl Pyrrole Synthesis from Biomass-Derived Furans and Arylamine over Lewis Acidic Hf-Doped Mesoporous SBA-15 Catalyst

A mild and convenient method was developed to synthesize N-aryl pyrroles from biobased furans and arylamines over a Lewis acidic Hf catalyst for the first time. To demonstrate the broad utility and...

Renewable hydrogen from glycerol steam reforming using Co–Ni–MgO based SBA-15 nanocatalysts

Steam reforming of glycerol was carried out using Si-based mesoporous SBA-15 catalysts. Different mesoporous catalysts- Co-SBA-15, Ni-SBA-15, Co–MgO-SBA-15, Ni–MgO-SBA-15, and Co–Ni-SBA-15 were prepared using a one-pot hydrothermal method. An incipient wetness impregnation method was used only for the bimetallic Co–Ni-SBA-15 catalyst (catalyst designated as Co–Ni-SBA-15-IMPG) to compare its activity to that prepared by the one-pot method. The catalysts were characterized using XRD, TPR, TEM, TGA-DSC, ICP-OES and N2 adsorption-desorption analytical techniques. A high surface area in the range of 540–750 m2/g was observed depending on the catalyst composition. The glycerol steam reforming (GSR) activity of the catalysts was studied in the reaction temperature range of 450 °C–700 °C for hydrogen production. Results from the GSR studies for continuous 40 h showed that both Co–Ni-SBA-15-IMPG (impregnation) and Co–Ni-SBA-15 (one-pot) were resistant to deactivation, and both yielded 100% glycerol conversion for the entire 40 h. 10%Co–5%Ni-SBA-15 and 10%Co–5%Ni-SBA-15-IMPG produced (70–78) % and (60–78) % H2 selectivity, respectively. Addition of MgO to Co-SBA-15 and Ni-SBA-15 increased the activity and stability of the catalysts. The catalyst stability performance followed the trend 10%Co–5%Ni > 10%Co–5%MgO >10%Co–5%Ni-IMPG. > 15%Co > 10%Ni–5%MgO >15%Ni-SBA-15. Thermal analyses of the spent catalyst showed a substantial amount of coke deposition which could be the major factor responsible for catalysts deactivation. Bimetallic catalysts prepared by one-pot method (10%Co–5%Ni-SBA-15) and incipient wetness impregnation (10%Co–5%Ni-SBA-15-IMPG) exhibited remarkable GSR activity compared to their monometallic counterparts. The GSR activity was observed in the order: 10%Co–5%Ni-IMPG ≥ 10%Co–5%Ni > 10%Co–5%MgO >15%Co > 15%Ni > 10%Ni–5%MgO.

5-Hydroxymethylfurfural production from hexose sugars using adjustable acid- and base-functionalized mesoporous SBA-15 catalysts in aqueous media

The conversion of glucose and fructose to 5-hydroxymethylfurfural (HMF) was investigated using a series of functionalized SBA-15 catalysts in a glass tube reactor. The synthesized SBA-15 as a support was grafted with various organosilanes in order to acquire the acid-modified SBA-15 (SBA-A), acid- and hydrophobicity-modified SBA-15 (SBA-AC), and base-modified SBA-15 (SBA-N) catalysts. Effects of the reaction temperature and time, reactant concentration, and catalyst loading level on the catalyst performances in this reaction, in terms of the hexose conversion level, product yield, and selectivity, were evaluated. The prepared catalysts were extensively characterized by X-ray diffractometry, nitrogen adsorption–desorption, Fourier transform infrared spectrometry, CHN/S elemental analysis, solid-state nuclear magnetic resonance spectroscopy, contact angle measurement, and acid–base titration. The hexose-to-HMF reaction was greatly enhanced by increasing the reaction temperature, whereas the other factors had only a minor effect. In the case of the glucose-to-HMF production, the SBA-N catalyst exhibited reasonably high levels of glucose conversion and HMF yield, but its catalytic activity was pretty low for the fructose-to-HMF reaction. Herein, fructose was identified as an intermediate substance for further dehydration to HMF. The different catalyst types provided different functions, where isomerization required a basic property, whereas dehydration was optimal over an acidic one. Suppression of the levulinic acid formation was obtained via an increased hydrophobicity of the SBA-AC catalyst.

A comparison study between V-SBA-15 and V-KIT-6 catalysts for selective oxidation of diphenylmethane

Vanadium incorporated mesoporous SBA-15 and KIT-6 catalysts were prepared by a direct hydrothermal method under mild acidic reaction conditions.

Triethanolamine-modified mesoporous SBA-15: Facile one-pot synthesis and its catalytic application for cycloaddition of CO2 with epoxides under mild conditions

Abstract A series of triethanolamine-modified mesoporous SBA-15 catalysts were synthesized by a facile one-pot process, and used as the catalyst for the synthesis of cyclic carbonates through the cycloaddition of CO2 with epoxides. The properties of catalysts were characterized by nitrogen adsorption–desorption, elemental analysis (EA), Fourier transform infrared (FT-IR) spectra, Magic angle spinning nuclear magnetic resonance (MAS NMR), X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscopy (TEM), and the results suggested that triethanolamine (TEA) had been successfully immobilized on SBA-15. It was highly active in the cycloaddition reaction, in which the maximum yield of PC could achieve 93.47% under the conditions as follow: catalyst amount of 0.20 g, reaction temperature of 110 °C, reaction pressure of 2.0 MPa and reaction time of 4 h. Notably, the catalyst can be easily recovered by filtration, and it can be retained most of its catalytic stability and activity after five recycling times. On the basis of the experimental results, the interactions between the catalysts and the substrates were studied by DFT calculations, and the possible mechanism for the reaction was proposed.

Caesium Salt of Tungstophosphoric Acid Supported on Mesoporous SBA-15 Catalyst for Selective Esterification of Lauric Acid with Glycerol to Monolaurin

$$\hbox {Cs}_{2.5}\hbox {H}_{0.5}\hbox {PW}_{12}\hbox {O}_{40}$$ supported on SBA-15 catalysts were prepared via two-sequential-step post-impregnation method with different ratios of cesium salt. The synthesized catalysts were then characterized using nitrogen adsorption–desorption, FTIR, EDX, SEM, BET and TGA analyses in order to determine the physicochemical properties of the catalysts. The activity of the catalysts in the esterification of glycerol to monolaurin was investigated under various reaction parameters including catalyst loadings, reaction temperatures and glycerol-to-lauric acid molar ratio. The highest lauric acid conversion (71.8%) with 44.9% of monolaurin yield was obtained using 20 wt%Cs-HPW/SBA-15 catalyst in 4 h at 170 $${^{\circ }}\hbox {C}$$ using 4:1 of glycerol-to-lauric acid molar ratio and 2.5 wt% of catalyst loading. This catalyst was stable and reusable for up to three cycles in the esterification reaction without significant loss in catalytic activity.

Vanadium oxide supported on mesoporous SBA-15 modified with Al and Ga as a highly active catalyst in the ODS of DBT

Vanadium oxides supported on mesoporous SBA-15 catalysts with different vanadium loadings were studied in the oxidative desulfurization (ODS) of dibenzothiophene as a model sulfur compound. The catalytic activity was improved when SBA-15 framework was modified by adding Al and Ga. Structural and textural characterization of the catalysts were performed by means of XRD, N2 adsorption, UV–Vis–DRS, XPS, NMR, TEM, Raman, TPR and Py-FTIR. UV–Vis–DRS and Raman demonstrated that highly dispersed vanadium VO4−3 species are responsible for the high activity in the sulfur removal. The Ga modified support with an intermediate V/Si ratio of 1/30 was the most active catalyst for ODS of DBT, using hydrogen peroxide as oxidant and acetonitrile as solvent. 100% of DBT elimination was attained at a short time in mild conditions. Gallium and aluminum incorporation into the support modified successfully the nature of the SBA-15 surface by generating Bronsted and Lewis acidity. The interaction between the acid sites with the active vanadium sites improved the activity of the catalysts. The high dispersion depended on the vanadium loading and on the nature of the support. The more acidic support allowed better dispersion of the vanadium species due to stronger interaction metal-support. The reusability of the catalysts indicates that vanadium oxide supported on mesoporous SBA-15 modified with Ga and Al are potential catalysts for the ODS of dibenzothiophene.

A new recyclable functionalized mesoporous SBA-15 catalyst grafted with chiral Fe(iii) sites for the enantioselective aminolysis of racemic epoxides under solvent free conditions

A mesoporous SBA-15 supported chiral Fe(iii)-catalyst was prepared and used for the synthesis of chiral β-amino alcohols with very good yields and enantioselectivities (ee upto 98%) under neat conditions at RT.

Preparation of Ru Nanocatalysts Supported on SBA-15 and Their Excellent Catalytic Activity Towards Decolorization of Various Dyes.

In this paper, we report a simple aqueous solution based chemical method for preparation Ru nanocatalysts supported on mesoporous silica SBA-15 (Ru@SBA-15) catalysts. Synthesized catalysts were characterized by powder X-ray diffraction (XRD), Optical emission spectroscopy (ICP-OES), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscope (HRTEM) and N2 adsorption-desorption surface area and pore size analyzer, and particle size analyzer. Catalytic activity of the synthesized catalysts towards decolorization of various dyes, such as 4-nitrophenol, Methyl Orange, Congo Red, Rhodamine B, Methylene Blue and mixture of dyes was investigated in presence of excess NaBH4. Catalysis reactions were monitored by employing UV-vis spectroscopy. Catalysis reactions followed pseudo-first order rate equation. The catalyst with 2.5 wt% Ru nanoparticle exhibited excellent catalytic activity and convenient recycling. The high catalytic activity and simple preparation methodology make 2.5Ru@SBA-15 an attractive catalyst for decolorization of organic dyes.

Preparation of manganese oxide immobilized on SBA-15 by atomic layer deposition as an efficient and reusable catalyst for selective oxidation of benzyl alcohol in the liquid phase

Manganese oxide supported on mesoporous silica SBA-15 catalyst (Mn-SBA-15) was tested with Mn contents in the range of 0.8–23 wt%. Samples were prepared by the controlled grafting process of atomic layer deposition (ALD). Other sample was prepared for comparisons by the wet impregnation method. These samples were characterized by the techniques of ICP, XRD, SEM, Raman, FT-IR spectroscopy, diffuse reflectance UV–Vis, TGA-DSC, and N2 absorption–desorption surface area measurement. Results indicated that anchored manganese oxide particles have been successfully synthesized over the surface of SBA-15. These samples contained Red-Ox ion pairs of Mn2+ and Mn3+ highly dispersed on the mesoporous silica surface. The impregnated sample exhibited lower surface area and contained Red-Ox ion pairs of Mn3+ and Mn4+ more aggregated particles on the SBA-15 surface.Results determined Mn-SBA-15 as an efficient and selective catalyst for oxidation of benzyl alcohol with tert-butylhydroperoxide in liquid phase. In accordance with expectations, there was a negligible amount of leaching of immobilized manganese oxide from the support during the reaction, because of strong surface interaction between manganese oxide and hydroxyls groups. The influences of reaction temperature, reaction time, solvent, TBHP/benzyl alcohol molar ratio, amount of catalyst and reusability were investigated. Under optimized conditions (0.2 g catalyst, TBHP/benzyl alcohol molar ratio 1, solvent acetonitrile; T = 90 °C; reaction time 8 h), results achieved 70% conversion of benzyl alcohol and 100% selectivity to benzaldehyde.

Preparation of Cu nanoparticle loaded SBA-15 and their excellent catalytic activity in reduction of variety of dyes

In this paper, we report a simple aqueous solution based chemical method for preparation of Cu nanoparticle loaded mesoporous silica SBA-15 (Cu@SBA-15) catalysts. Synthesized catalysts were characterized by powder X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscope (HRTEM), N2 adsorption–desorption surface area and pore size analyzer, and particle size analyzer. Catalytic activity of Cu nanoparticle loaded SBA-15 towards reduction of various dyes, such as 4-nitrophenol, Methyl Orange, Congo Red, Rhodamine B, Methylene Blue and mixture of dyes were investigated in the presence of excess NaBH4. Catalysis reactions were monitored by employing UV–vis spectroscopy. Catalysis reactions followed pseudo-first order rate equation. These catalysts exhibited excellent catalytic activity and convenient recycling. The high catalytic activity, cost effectiveness and simple preparation methodology make 12.5Cu@SBA-15 an attractive catalyst for decolorization of organic dyes.

New non-metallic mesoporous SBA-15 catalyst with high selectivity for the gas-phase oxidation of cyclohexylamine to cyclohexanone oxime

Non-metallic mesoporous SBA-15 is firstly used for the gas-phase selective oxidation of cyclohexylamine to cyclohexanone oxime with air and exhibits the best performance among the investigated silica catalysts. The experimental results show that the catalytic activity is strongly dependent on the pore diameter of SBA-15. By combining catalytic performance experiments with the monitoring of catalyst transformations using themogravimetric analyses, N2-physisorption, and solid-state 29Si MAS NMR spectra, we show that the surface silanols play important roles to form a catalytically active carbon species, which is believed to be favorable to the activation of molecular oxygen. The carbon species formed are also studied by IR-spectroscopy, coke analysis by a catalyst dissolution/extraction protocol and elemental analyses.