Mesoporous TS-1 Research Articles

The promoting role of framework Ti(IV) in enhancing the hydrodeoxygenation performance of palmitic acid over a mesoporous TS-1 supported Ni catalyst

Developing a highly efficient Ni-based hydrodeoxygenation catalyst is crucial for the production of renewable biodiesel. Herein, a mesoporous TS-1 zeolite supported Ni catalyst (Ni/TS-1-M) exhibited exceptional hydrodeoxygenation (HDO) activity and achieved 100 % yield of deoxygenated hydrocarbons (97.3 % pentadecane vs 2.7 % hexadecane), outperforming other catalysts such as Ni on mesoporous ZSM-5 (Ni/ZSM-5-M), mesoporous Silicalite-1 (Ni/Silicalite-1-M) and TiO2 (Ni/TiO2). The Ti(IV) atoms in the form of TiO4 and TiO6 can transfer its electron to nearby metal Ni, leading to the increase in electron density of metal Ni, which enhanced the hydrogenation activity and facilitated the C–C bond cleavage of the hexadecanal to produce pentadecane. Furthermore, the framework Ti(IV) species accelerated the esterification process to generate palmityl palmitate, which was easily hydrogenolyzed to the main intermediate of hexadecanol under the synergistic effect of metal Ni and Ti(IV) on Ni/TS-1-M catalyst. The formed hexadecanol mainly underwent successive dehydrogenation/decarbonylation process to transform into pentadecane.

Mesoporous TS-1 zeolite-confined metal oxides photocathode for efficient reduction of carbon dioxide to methanol

Excessive CO2 emission has caused serious environmental problems, and converting CO2 to high value-added fuels is attractive for solving energy and environmental crisis. Herein, a novel mesoporous TS-1(mTS-1) zeolite-confined metal oxides nanoclusters Cu-Bi@mTS-1 was developed for efficient photoelectrochemical reduction reaction of CO2 (PEC CO2RR). The catalyst Cu-Bi@mTS-1 as a photocathode showed high activity, achieving a maximum methanol Faraday efficiency (FECH3OH) of 93.4 % at −0.7 V vs. RHE. The C2 product ethanol could be also detected at higher potentials during PEC CO2RR. In-situ FTIR results indicate the occurrence of key reaction intermediates *CO, *CHO, *OCCO and *COCHO during the conversion of CO2 to CH3OH and CH3CH2OH. It is believed that the hierarchically porous structure of mTS-1 is conducive to the enrichment of CO2 molecules to increase the reactant concentration, also can promote C-C coupling through photoelectric synergism. This work provides a favorable reference for the rational design of photocathodes by confinement effect of porous structure.

Kinetics of phenol hydroxylation reaction of open mesoporous TS-1 with high backbone titanium content

Abstract High skeletal titanium content, open mesoporous TS-1 titanosilica molecular sieves with more accessible active centres exhibit higher catalytic activity, target product selectivity and resistance to coking deactivation in green catalytic oxidation reactions using hydrogen peroxide as oxidant. In this paper, TS-1 titania-silica molecular sieves without anatase, with the highest theoretical skeletal titanium content (2.0 wt%) and open mesopores (mesopore volume 0.71 cm3/g) were synthesised based on the ageing dry gel limited domain conversion method invented in previous research work. The intrinsic kinetics of the catalytic reaction of phenol with hydrogen peroxide for direct hydroxylation of benzenes was investigated. The effects of stirring rate, phenol concentration, hydrogen peroxide concentration, catalyst dosage and reaction temperature on the initial conversion rate of phenol were investigated, and the experimental data were fitted with a power function equation to obtain the intrinsic kinetic equation of the catalyst ( r = 2.98 × 10 6 exp ( − 56.43 × 10 3 R T ) c 1.07 ( Phenol ) c 0.10 ( H 2 O 2 ) ) \left( {{\rm{r}} = 2.98 \times {{10}^6}\,\exp \,\left( { - {{56.43 \times {{10}^3}} \over {RT}}} \right){c^{1.07}}\left( {{\rm{Phenol}}} \right){c^{0.10}}\left( {{{\rm{H}}_2}{{\rm{O}}_2}} \right)} \right) . Under the condition of eliminating the effect of internal and external diffusion, the reaction was 1.07 and 0.10 for phenol and hydrogen peroxide, respectively, with a reaction activation energy of 56.43 kJ/mol. This study provides a theoretical basis for the reactor and process design of hydroxylation of phenol to benzenediol based on this new catalyst.

Sn species modified mesoporous zeolite TS-1 with oxygen vacancy for enzyme-free electrochemical H2O2 detecting.

Sn species modified zeolite TS-1 with a unique mesopore structure (Sn-TS-1) and rich oxygen vacancy defects has been designed via a sol-gel method and an ion-exchange process, which can be used as an enzyme-free electrochemical sensor for H2O2 detection. The resultant composite Sn-TS-1 has a high BET surface area of 191 cm2 g-1, fast electron transfer, rich oxygen vacancies, and abundant active sites, showing super performance in H2O2 reduction with a low detection limit (0.27 μM, S/N = 3). The current is linear with H2O2 concentration from 1 to 1000 and 1000 to 11 000 μM, and the corresponding sensitivities are 360.4 and 80.44 μA mM-1 cm-1, respectively. More importantly, this Sn-TS-1 sensor also shows excellent anti-interference ability and stability. This work provides a new idea for an enzyme-free sensor for H2O2 detection in biological environments, which has promising potential in point-of-care (POC) testing for H2O2.

Bimetallic Pt-Fe catalysts supported on mesoporous TS-1 microspheres for the liquid-phase selective hydrogenation of cinnamaldehyde

Mesoporous TS-1 microspheres (MTS-1-MS) were applied to load Pt-Fe bimetallic components with different Fe/Pt molar ratios for the liquid-phase selective hydrogenation of cinnamaldehyde (CAL) to produce cinnamyl alcohol (COL). Combining the XRD and XPS characterization results, Fe dopant co-existed as PtFe fcc alloy or FeOx species, which modified the electronic properties of Pt active sites through the electron transfer from Fe to Pt, therefore, the catalytic performance was improved remarkably with the Fe-doped Pt/MTS-1-MS catalyst. As a result, the PtFe0.25/MTS-1-MS-350 catalyst, which contains Fe amount with a Fe/Pt molar ratio of 0.25 and was calcined at 350 °C before reduction in hydrogen at 400 °C, furnished 95.7% CAL conversion and 89.2% COL selectivity with an initial activity (in terms of TOF value) reaching 19440 h−1, much better than its analogue Pt/MTS-1-MS-350, which only showed 56.6% CAL conversion and 74.4% COL selectivity under the same conditions. To the best of our knowledge, it is one of the most active Pt-Fe bimetallic catalysts up to now. Moreover, the PtFe0.25/MTS-1-MS-350 catalyst can also be cycled for at least 9 times without obvious loss in activity or COL selectivity. Furthermore, theoretical calculations based on several simplified surface models were conducted using the density-functional theory (DFT) to reveal the differences in electronic structures and geometric properties caused by Fe dopant and to explain the reason why CO hydrogenation was preferential on the PtFe0.25/MTS-1-MS-350 catalyst from the perspective of CAL adsorption and COL desorption on/from Pt-Fe surface.

Highly dispersed Ni2P clusters inlaid in micropore openings on mesoporous ZSM-5 zeolite and its catalytic performance in the phenylacetylene semi-hydrogenation

Preparation of Ni2P phase with cluster size and high stability is significant for enhancing its catalytic performance. Herein, Ni2P nanoclusters (<1nm) inlaid in micropore openings on mesoporous ZSM-5 zeolite (MZSM-5) was prepared through citric acid-assisted, two-step impregnation method under the reduction temperature of 400°C. The facilitation effect of the citric acid and support surface properties on the formation of Ni2P clusters was investigated. The formation of Ni(H2cit)+ complex promotes the dispersion of the Ni precursor on the zeolite surface. After calcination, the free Ni species interact stronger with the acidic hydroxyl groups on MZSM-5 than that with silanol on mesoporous TS-1(MTS-1), Silicalite-1 (MSilicalite-1) and SiO2, facilitating the formation of Ni2P nanoclusters on the MZSM-5 micropore openings after the calcined Ni catalyst was loaded with P species and followed by activation treatment. The obtained Ni2P clusters exhibit higher intrinsic activity (robs=1.50molkg−1s−1) than MTS-1, MSilicalite-1 and SiO2 supported Ni2P catalysts (0.80, 0.76, 0.40molkg−1s−1) in the semi-hydrogenation of phenylacetylene.

Seed-Induced Zeolitic TS-1 Immobilized with Bioinspired-Au Nanoparticles for Propylene Epoxidation with O2 and H2

In this work, bio-inspired Au nanoparticles (NPs) were loaded through an ionic-liquid-enhanced-immobilization method onto TS-1 support, leading to efficient Au/TS-1 catalysts for gas-phase propylene epoxidation in the presence of O2 and H2. Specifically, the mesoporous TS-1 was synthesized by a hydrothermal method using nanosized TS-1 (size of ∼ 220 nm) as seeds, and the support was then etched with acid (HCl or HNO3). Both the pristine TS-1 and Au/TS-1 catalysts were fully characterized to understand the effects of preparation conditions on the catalytic performance in propylene epoxidation. Interestingly, it was found that the amount of Lewis acid sites in the seed-induced TS-1 was greater than that on the control sample formed without seed; more importantly, the size of the loaded Au NPs can be regulated by changing the amount of Lewis acid site. Furthermore, we have demonstrated that the post-treatment of TS-1 with appropriate acid sites could enhance the propylene conversion and propylene oxide (PO) selectivity.

The Synthesis of Mesoporous TS-1 and Its Performance for Oxidation of Diphenyl Sulfide and Dibenzyl Sulfide

TS-1 zeolite has outstanding performance in the catalytic reactions with hydrogen peroxide as catalytic promoter. However, the narrow pore size (&lt; 1.0 nm) of traditional TS-1 makes it difficult for bulky organic compounds to contact with the active sites in the pores, which seriously limits application of TS-1. Recently, the introduction of mesoporous structure into microporous TS-1 becomes a hot research topic. Meanwhile, the huge synthesis cost of TS-1 is another main reason hindering its industrial application. In this paper, mesoporous TS-1 was successfully synthesized using sodium silicate as silicon source and titanium trichloride as titanium source under the template conditions of tetrapropylammonium hydroxide (TPAOH) and cationic polymer. The mesoporous TS-1 was characterized by X-ray diffraction (XRD), N2 adsorption, scanning electric microscopy (SEM), transmitting electric microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and UV-Vis Spectrum spectra (UV-Vis). Results show that the synthesized TS-1 zeolites have good crystallinity and tetra-coordinated framework Ti atoms, and there are abundant mesoporous structures in the zeolite crystals. The results of oxidation experiments show that conversion of diphenyl sulfide and dibenzyl sulfide with mesoporous TS-1 are 97.3 % and 85.3 % respectively, while that conversion with microporous TS-1 are 75.7 % and 63.5 respectively.

Preparation of partial crystalline mesoporous zeolite TS-1 for epoxidation of unsaturated fatty acid ester

Abstract Amorphous Ti-MCM-41 with/without cetyltrimethylammonium template could be crystallized into TS-1 zeolite by way of solid state crystallization with steam assisted conversion (SAC) method. The crystallinity with changing textural property of the SAC crystallized product could be controlled by the composition of mesoporous material and SAC processing time. The partial crystallized zeolite (PCZ) material showed much better catalytic performance in epoxidation of unsaturated fatty acid ester than either Ti-MCM-41 or TS-1, which is attributed to synergistic effect of enhanced crystallinity and retention of mesopore in PCZ. The optimum reaction condition was to use TBHP oxidant in using ethylacetate and acetonitrile solvent superior to the H2O2 oxidant in protic solvent.

Direct low-temperature hydrothermal synthesis of uniform Pd nanoparticles encapsulated mesoporous TS-1 and its excellent catalytic capability

A simple and direct low-temperature hydrothermal synthesis approach (100 °C) has been developed to encapsulate Pd nanoparticles (ca. 2.3 nm) within nano-sized mesoporous TS-1 zeolite by utilizing dichloro(ethylenediamine)palladium (DEAP) and cetyltrimethylammonium bromide (CTAB) as palladium source and mesoporogen, respectively. It's demonstrated that the aging process of the mother liquid and low-temperature hydrothermal treatment can effectively inhibit the premature precipitation of metal precursor and thus the successful encapsulation of Pd nanoparticles into mesoporous TS-1 nanocrystals, so that the frequently occurring of Pd nanoparticle aggregation at high temperature was expectedly avoided. Consequently, the as-synthesized catalysts with highly thermal stability and mesoporous channels exhibit excellent catalytic activity and recyclability in the oxidation of CO with relatively low Pd content (0.53 wt% Pd) and catalytic wet air oxidation of phenol (66.2% of phenol conversion, 100 °C).

Effective hierarchization of TS-1 and its catalytic performance in propene epoxidation

Abstract Hierarchical TS-1 zeolites have been synthesized by dry-gel conversion method employing conventional block copolymers F127 as scaffold. The proportion of the F127 added to the synthesis gel has a significant influence on the textural properties of the hierarchical TS-1 zeolites. Thus, by controlling the addition proportion of F127, the mesoporous pore volume and external surface area can be tailored. The functional mechanism of F127 was studied and proposed. The catalytic activity of this mesoporous TS-1 (denoted as MTS-1) was evaluated in propene epoxidation with H2 and O2. Well developed mesoporosity together with the Ti4+ atoms in tetrahedral coordination contributed to high catalytic stability than TS-1. After 120 h reaction at 200 °C, no significant decrement of catalytic activity can be observed. Moreover, the intrinsic reason for the enhanced stability is elucidated. The increased external surface and the better mass transfer ability results in the diminished coke formation and absence of heavier aromatic coke.

Mesoporous Titanium-Silicalite Zeolite Containing Organic Templates as a Bifunctional Catalyst for Cycloaddition of CO2 and Epoxides.

Mesoporous TS-1 (MTS-1) containing organic templates tetrapropylammonium hydroxide (TPAOH) and polydiallyldimethylammonium chloride is synthesized and treated with different concentrations of hydrochloric acid aqueous solution. The as-synthesized MTS-1 are characterized using X-ray diffraction, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy, transmission electron microscopy, UV-vis, 13C cross-polarization/magic angle spinning (CP/MAS) NMR, thermogravimetry analysis, CO2-temperature-programmed desorption (TPD), N2 adsorption-desorption, X-ray fluorescence, and elemental analysis. The results of 13C CP/MAS NMR show that the structures of organic templates are retained after acid washing treatment. Not required to be removed by calcination, the organic templates embedded in MTS-1 can take the role of basic sites and activate carbon dioxide (CO2), which is confirmed by FT-IR. Moreover, the amount of acid sites and basic sites in the samples before and after acid treatment is characterized by modified Hammett indicator method and CO2-TPD, respectively. The results show that both the acidity and the basicity in the material are improved after acid washing. Thus, the sample after acid treatment contains two active sites: basic sites stemming from organic species and acid sites coming from framework Ti, which is beneficial to be used as a bifunctional catalyst in the cycloaddition reaction of CO2 and epoxides. It is highly active in the cycloaddition reaction, in which the conversion of epichlorohydrin (ECH) could reach 97.8% and the selectivity of cyclic carbonate is 98.0% under 1.6 MPa at 393 K for 6 h when acetonitrile is used as a solvent. Moreover, the kinetics of the cycloaddition reaction are studied using ECH as a substrate by varying the reaction parameters. More importantly, the organic-inorganic hybrid catalyst is reusable and stable against leaching of organic species in the cycloaddition reaction.

Acidic Mesoporous Zeolite ZSM-5 Supported Cu Catalyst with Good Catalytic Performance in the Hydroxysulfurization of Styrenes with Disulfides.

Development of highly active heterogeneous catalysts is an effective strategy for modern organic synthesis chemistry. In this work, acidic mesoporous zeolite ZSM-5 (HZSM-5-M), acidic-free mesoporous zeolite TS-1 (TS-1-M), and basic ETS-10 zeolite supported metal Cu catalysts were prepared to investigate their catalytic performances in the hydroxysulfurization of styrenes with diaryl disulfides. The effect of pore size and acidities of the supports, as well as the Cu species electronic properties of the catalysts on reaction activity were investigated. The results show that Cu+ and Cu2+ binded on HZSM-5-M show the highest activity and product selectivity for the desired β-hydroxysulfides compounds.

Simultaneously Enhanced Stability and Selectivity for Propene Epoxidation with H2 and O2 on Au Catalysts Supported on Nano-Crystalline Mesoporous TS-1

It is a challenging task to design efficient Au/Ti-containing catalysts for propene epoxidation with H2 and O2 that simultaneously achieve high catalytic stability and selectivity to propylene oxide (PO). This contribution first describes the synthesis of a nanocrystalline mesoporous titanium silicalite-1 (MTS-1) by dry-gel conversion that employs cheap triblock copolymers as template. Compared with TS-1, MTS-1 has a shortened reactant/product diffusion length as a result of smaller crystal size (<100 nm) and the presence of mesopores (ca. 3 nm). Surprisingly, this designed catalyst shows simultaneously improved PO selectivity over 95% as well as stability over 40 h, much better than the traditional Au/TS-1 catalyst. Moreover, the intrinsic reason for the enhanced performance is elucidated. The better mass transfer ability together with higher hydrophobicity of Au/MTS-1 results in lower coke weight and absence of refractory aromatic coke. In this way, the side reactions and deactivation caused by blocking...

Accessibility enhancement of TS-1-based catalysts for improving the epoxidation of plant oil-derived substrates

TS-1-based catalysts with different textural features, namely layered TS-1, pillared TS-1, and Ti-pillared TS-1 as well as mesoporous TS-1, were investigated in the liquid-phase epoxidation of methyl oleate as a model compound for plant oil-derived substrates with hydrogen peroxide at 50 °C.

A kinetic study of vapor-phase cyclohexene epoxidation by H2O2 over mesoporous TS-1

A kinetic analysis of gas-phase cyclohexene epoxidation by H2O2 over mesoporous TS-1 was performed. The production of cyclohexene oxide was very stable with high selectivity. Based on the kinetic analysis, the gas-phase mechanism is proposed to be similar to that of the liquid-phase reaction: an Eley–Rideal type mechanism, in which the reaction between a Ti–OOH intermediate and the physisorbed alkene is the rate-determining step. When the partial pressure of water or H2O2 was varied, a compensation effect was observed. Based on the kinetic model, the compensation effect is attributed to variations in the surface coverage of intermediates, specifically the competitive adsorption of water and H2O2 at the Ti active sites. A meaningful activation energy can only be obtained at high surface coverages of H2O2 and was determined to be 40±2kJ/mol.

Highly efficient nano-sized TS-1 with micro-/mesoporosity from desilication and recrystallization for the epoxidation of biodiesel with H2O2

The epoxidation of the unsaturated fatty acid methyl esters (FAME) in biodiesel with H2O2was investigated at 323 K in the liquid phase over microporous nano-sized TS-1 as well as micro-/mesoporous nano-sized TS-1.

An Ultra-low-cost Route to Mesostructured TS-1 Zeolite for Efficient Catalytic Conversion of Bulk Molecules

Developing a low-cost route to synthesize mesoporous TS-1 (MTS-1) is of great importance because of its practical application in industry. Herein, we first synthesized a copolymer containing quaternary ammonium groups by a mesoporous template comprising inexpensive starting materials. Subsequently, waterglass (sodium metasilicate), TiCl3, and copolymer were dispersed in the preformed seeds emulsion, resulting in a gel for synthesizing MTS-1. The counterpart material (CTS-1) was also synthesized by the same procedure except for the absence of the copolymer. Compared with CTS-1, the MTS-1 exhibits good crystallinity and well-defined tetrahedral coordinated Ti species (TiIV) in the framework as well as excellent catalytic activity in the oxidation of bulky molecules, such as dibenzothiophene and benzyl phenyl sulfide. This feature may be attributed to the fact that the quaternary ammonium groups on copolymer facilitates the formation of the MFI structure and energetically incorporates the Ti species into the framework.

Epoxidation of Soybean Oil under Acid-Free Condition

Industrially the epoxidation of soybean oil utilize peracids as oxidizing agents together with strong mineral acids as catalyst. To avoid the corrosive waste and undesirable epoxy-ring opening as well as polymerization under acidic conditions, new green catalytic processes in acid-free system have been paid great attentions in recent years. In this paper, MoO3/Al2O3 simply prepared by impregnation method and mesoporous TS-1 prepared by one-pot hydrothermal method were evaluated as catalysts for the epoxidation of soybean oil with tert-butyl hydroperoxide. Orthogonal experiment design was used to optimize the reaction conditions for MoO3/Al2O3 and the optimized conditions are as reaction temperature of 80°C, reaction time of 4h, the ratio of double bond to TBHP of 1:1.4, and the ratio of Ti to double bond of 1%. Higher than 55.8% of selectivity would be obtained. The synthesized meso-TS-1 displayed worse performance than expected result, only 27.6% of epoxy selectivity at conversion of 38.7%.

Superior Catalytic Performance of Mesoporous Zeolite TS‐1 for the Oxidation of Bulky Organic Sulfides

Rich man, pore man: A facile and universal route to mesoporous zeolite TS-1 (MTS-1) is reported. Compared with mesoporous-free TS-1, the MTS-1 zeolite shows extraordinarily catalytic activity and highly controllable chemoselectivity for the oxidation of sulfides into sulfoxides or sulfones. Based on the catalytic data, the Tihydroperoxo (η2) group is proposed to be the active site for the oxidation of sulfides into sulfoxides and sulfones.