Direct Hydrothermal Synthesis Method Research Articles

Direct synthesis of Cu-TiO<sub>2</sub>-SBA-16 photocatalysts and its application for the oxidative desulfurization of fuel oil model

In this study, the Cu-TiO2-SBA-16 photocatalytic materials were successfully prepared by direct hydrothermal synthesis method. The products were characterized by X-ray diffraction (XRD), Ultraviolet–Visible Diffuse Reflectance Spectroscopy (UV-Vis DRS), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), N2 adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS) methods. The analysis illustrated that Cu-TiO2 nanocrystals were successfully incorporated into the SBA-16 mesopores. The photocatalytic activity of these Cu-TiO2-SBA-16 mesoporous materials have been tested by the oxidative desulfurization reaction of dibenzothiophene (DBT) using H2O2 as an oxidant under UV light irradiation. The results showed that the Cu-TiO2-SBA-16 mesoporous materials prepared at the Cu/Ti mole ratios of 0.05 showed higher photocatalytic activity than the rest due to the decrease in band gap energy.

Direct Hydrothermal Synthesis and Characterization of Zr–Ce-Incorporated SBA-15 Catalysts for the Pyrolysis Reaction of Algal Biomass

In recent years, algae have emerged as a promising feedstock for biofuel production, due to their eco-friendly, sustainable, and renewable nature. Various methods, including chemical, biochemical, and thermochemical processes, are used to convert algal biomass into biofuels. Pyrolysis, a widely recognized thermochemical technique, involves high temperature and pressure to generate biochar and bio-oil from diverse algal sources. Various pyrolytic processes transform algal biomass into biochar and bio-oil, including low pyrolysis, fast pyrolysis, catalytic pyrolysis, microwave-assisted pyrolysis, and hydropyrolysis. These methods are utilized to convert a range of microalgae and cyanobacteria into biochar and bio-oil. In this publication, we will discuss catalytic pyrolysis using mesoporous materials, such as SBA-15. Mesoporous catalysts have earned significant attention for catalytic reactions, due to their high surface area, facilitating the better distribution of impregnated metal. Pyrolysis conducted in the presence of a mesoporous catalyst is viewed more as efficient, compared to reactions occurring within the smaller microporous cavities of traditional zeolites. SBA-15 supports with incorporated Zr and/or Ce were synthesized using the direct hydrothermal synthesis method. The catalyst was characterized using structural and morphological technical analysis and utilized for the pyrolysis reaction of the algal biomass.

Synthesis of Hydroxy Sodalite from Coal Fly Ash for Biodiesel Production from Waste-Derived Maggot Oil

Zeolites are aluminosilicate crystalline materials known for their unique characteristics, and have been prominent for nearly half a century due to their wide and important industrial applications. The production of zeolites, however, remains a challenge due to the high cost of commercial reagents conventionally used as feedstocks. In the current study, hydroxy sodalite (HS) zeolite samples were synthesised from coal fly ash feedstock by a direct hydrothermal synthesis method. The effects of hydrothermal crystallisation synthesis time on phase crystallinity, crystal size, and morphology of the formed HS were investigated. The prepared samples were characterised using XRD, SEM, EDS and FT-IR techniques. The XRD results of the samples prepared with varying synthesis times confirmed the formation of HS from low to high phase purity and crystallinity from 11 to over 98%. The SEM results reflected gradual variation in crystal morphology, of which highly crystalline HS samples were associated with hexagonal-cubic and cubic-platelet crystals. The FTIR, depicting zeolite characteristics of T–O and T–O–T stretching vibrations in the molecular framework, further confirmed the formation of HS zeolites for samples obtained above the 24-h synthesis time. These zeolite samples were then evaluated for their catalytic activities in the conversion of maggot oil to biodiesel. The application of the various hydroxy sodalite samples for the transesterification of maggot oil yielded up to 84.10% biodiesel (FAME) with physicochemical properties that were in compliance with the biodiesel specification standards. This study investigated the novel use of a coal fly ash-derived, heterogeneous HS catalyst in biodiesel production from maggot oil, and indicates its potential to enhance biodiesel yield and quality upon process optimisation tests.

Mesoporous Sn(IV) doping MCM-41 supported Pd nanoparticles for enhanced selective catalytic oxidation of 1,2-propanediol to pyruvic acid

The conversion of biomass derivative 1,2-propanediol (PDO) to value-added chemicals by selective catalytic oxidation is of great research interest. Herein, we provide an alternative and effective strategy for selectively catalyzing the PDO oxidation to pyruvic acid using Sn(IV) doping MCM-41 (SnM) supported Pd nanoparticles (2%Pd/SnM) as catalyst, in which the SnM with the Si/Sn ratios ranging from 6 to 50 are prepared by direct hydrothermal synthesis (DHS) method and the Pd nanoparticles are in situ reduced on the SnM surfaces. When the Si/Sn ratios are above 12, decreasing the Si/Sn ratio favors the incorporation of more Sn(IV) species into the framework, the formation of smaller Pd nanoparticles with higher distribution and the increment of basicity, contributing to the significant enhancement in the selective oxidation of PDO to pyruvic acid, but if the ratio is further reduced to 6, larger Pd nanoparticles are formed in the 2%Pd/SnM6 with less ordered mesostructure due to excess Sn(IV) resulting in the formation of SnO2 crystallites, displaying much lower catalytic activity than the 2%Pd/SnM12. The Sn(IV) species incorporated into MCM-41 can be used as effective promoter for enhancing the selective oxidation of PDO to pyruvic acid over the Pd/SnM catalyst.

Microwave synthesis of zeolites from waste glass cullet using indirect fusion and direct hydrothermal methods: A comparative study

The present work studied the conversion of waste glass (WG) cullet into zeolite using microwave (MW) radiation technique. The temperature and power of radiation were monitored through constant temperature (MWCT) and constant power (MWCP) modes. Indirect fusion synthesis (IFS) and direct hydrothermal synthesis (DHS) conversion methods were studied and the zeolites synthesized by these methods were compared in terms of their characteristics using various techniques including XRD, EDX, SEM, FTIR, TGA, and cation exchange capacity (CEC). IFS was an efficacious synthesis technique and produced zeolites with a much higher crystal growth efficiency compared with those synthesized by DHS method. The IFS method was better than the DHS method as it eliminated the inhibitive effect of soluble aluminates on Si release. The IFS zeolites also provided lower Si/Al ratio and consequently higher cation exchange and water holding capacities compared to DHS zeolites, as validated by EDX, TGA, and CEC results. In addition, high pressure and high-temperature environment deteriorated the zeolite structure and diminished the crystal growth performance. The application of cooling air jet (CAJ) through MWCP mode provided efficient monitoring of temperature overshoot and excessive pressure generation by cooling the excessive generated hot spot zones. Therefore, the CAJ application improved the crystal growth in IFS method as higher radiation powers were applied.

Synthesis of SiGeAl-ITQ-13 and SiAl(B)-ITQ-13 and their catalytic performance in the conversion of methanol to hydrocarbons

Al-ITQ-13 molecular sieves, viz., SiGeAl-ITQ-13 and SiAl(B)-ITQ-13, were prepared by the direct hydrothermal synthesis and post-synthesis methods and characterized by XRD, 27Al MAS NMR, NH3-TPD, Py-FTIR and SEM; their catalytic performance in the conversion of methanol to hydrocarbons (MTH) was investigated. The results indicated that two Al-ITQ-13 samples have high crystallinity with a slice-like morphology. In comparison with ZSM-5, Al-ITQ-13 as a catalyst in MTH exhibits higher selectivity to propene, higher propene/ethene (P/E) ratio and longer catalytic lifetime. Moreover, as the amount of strong acid sites on SiAl(B)-ITQ-13 is decreased by post-synthesis, SiAl(B)-ITQ-13 exhibits better catalytic performance in MTH, in comparison with SiGeAl-ITQ-13 obtained by direct hydrothermal synthesis.

Catalytic deoxygenation of C18 fatty acids over HAlMCM-41 molecular sieve

The large demand for energy combined with ecological, economic, and social reasons encouraged the studies for alternative sources of fuel. The deoxygenation process of oils and fatty acids has emerged as a promising resource in obtaining fuels. This paper studied the deoxygenation process of oleic and stearic acids carried out in a distillation system, under the temperature of 450 °C over MCM-41, AlMCM-41-41, and HAlMCM-41 molecular sieves, which were synthesized by direct hydrothermal synthesis method and characterized by X-ray diffraction (XRD) spectroscopy in the infrared site (FTIR), adsorption and desorption of N2, and scanning electron microscopy (SEM). The products were analyzed by gas chromatography (GC) and acid-base titration. The results showed that stearic acid deoxygenates more than the oleic acid, and that the performance of HAlMCM-41 was superior to AlMCM-41, indicating that the total acidity positively influenced the process. Furthermore, from the stearic acid deoxygenation, it obtained mainly heptadecanes (C17:0) structures, while the oleic acid produces heptadecenes (C17:1).

Functioned carbon nanotube templated hierarchical Silicate-1 synthesis: On the existence of super-micropore

In present study, the functioned carbon nanotube was used as secondary template for hierarchical Silicate-1 synthesis. Special attentions were paid to the existence of super-micropore (1–2 nm) and additional hysteresis loop between 0.1 and 0.2 in nitrogen adsorption isotherms of the synthesized samples. The main findings of present study are: (1) Silicate-1 with additional mesoporosity can be synthesized with functioned carbon nanotube as secondary template through impregnation or direct hydrothermal synthesis method. The functional group in carbon nanotube doesn't influence the crystallization process with impregnation method but have large influence in direct hydrothermal synthesis method; (2) With typical subsequently impregnation method, no hysteresis loop between 0.1 and 0.2 was found in the nitrogen adsorption isotherms of samples. And the single wall carbon nanotube penetrated the zeolite crystal as a bundle other than separate nanotube with size range in 1–2 nm, (3) In zeolite samples synthesized with direct hydrothermal method, additional hysteresis loop was found in several samples. However, SEM and crystallization process analysis indicated that the hysteresis loop was more likely due to the large crystal size other than the existence of any real pores.

Facile Styrene Epoxidation with H2O2 over Novel Niobium Containing Cage Type Mesoporous Silicate, Nb-KIT-5

Niobium has been incorporated into cage-like ordered mesoporous KIT-5, a cubic close-packed (Fm3m) structured silica, for the first time by a direct hydrothermal synthesis method. Small-angle X-ray scattering spectra and nitrogen physisorption results confirm the formation of the KIT-5 structure. The incorporation of Nb and its coordination were confirmed by techniques such as elemental analysis, diffuse reflectance UV–Vis, Raman, HR-SEM and NH3-TPD. When tested as epoxidation catalyst for styrene with H2O2, Nb-KIT-5 mainly yielded (1,2-dimethoxyethyl) benzene with methanol as solvent. It also showed better catalytic activity compared to other mesostructured catalysts such as Nb-KIT-6 and Nb-SBA-15.

Excellent antimicrobial properties of silver-loaded mesoporous silica SBA-15.

AimsTo synthesize silver‐loaded mesoporous silica SBA‐15 (Ag/SBA‐15) materials and examine their antimicrobial action and antimicrobial mechanism.Methods and ResultsAg/SBA‐15 materials were prepared by means of incipient wetness impregnation, impregnation and direct hydrothermal synthesis methods. The antimicrobial activity of Ag/SBA‐15 was investigated using Escherichia coli as an indicator bacterium, and the antimicrobial mechanism was explored. The properties and Ag+ release behaviour of Ag/SBA‐15 materials were compared. Experimental results showed that Ag/SBA‐15 materials resulted in 7·5 log inactivation of E. coli for only 60 min, which exhibited very high antimicrobial activities at room temperature without using any light or electrical power input. The cell wall and cell membrane were destroyed in the antimicrobial process, leading to leakage of intracellular components. The formation of extracellular reactive oxygen species (ROS) involved in the bactericidal process was confirmed. Production of intracellular ROS was also discovered.Conclusions Ag/SBA‐15 exhibited high antimicrobial activity against E. coli. This antimicrobial effect was a synergistic action between extracellular ROS and the toxicity of Ag+, which induced intracellular ROS production and subsequent cell death.Significance and Impact of the StudyThis study revealed for the first time the antimicrobial activities and mechanisms of Ag/SBA‐15 materials prepared with different methods.

ChemInform Abstract: SnTUD‐1: A Solid Acid Catalyst for Three Component Coupling Reactions at Room Temperature.

A novel wormhole structured mesoporous material containing tin, SnTUD-1, was prepared by a direct hydrothermal synthesis method using triethanolamine (TEA) as an organic inexpensive mesoporous structure directing agent. XRD and N2 sorption studies of SnTUD-1 confirmed the amorphous mesoporous nature of SnTUD-1, which possessed a large surface area of 555 m2 g−1 and a pore diameter of 7.4 nm. HR-TEM further ascertained the disordered pores in their morphology and the presence of nano-domains of SnO2 species. The nature of the Sn4+ ion co-ordination with the silica matrix was evaluated by using different techniques including diffuse reflectance UV-Vis, FTIR, 29Si MAS NMR and XPS. SnTUD-1 had an interesting Lewis acidity as measured by FTIR of pyridine adsorption which provided excellent activities in one-pot three-component Mannich-type reactions of ketones with aldehydes and amines at room temperature.

Evaluation of Iron-Containing Aluminophosphate Molecular Sieve Catalysts Prepared by Different Methods for Phenol Hydroxylation

Three iron-containing AlPO4-5 molecular sieve catalysts (i.e. FeAlPO-5-Iono, FeAlPO-5-Hydro and FeAlPO-5-Imp) were prepared by ionothermal synthesis, direct hydrothermal synthesis and impregnation method, and characterized by various techniques. N2 adsorption/desorption measurements, together with the results of SEM and TEM, showed that FeAlPO-5-Iono was a new type of aluminophosphate molecular sieve with hierarchical micro- and meso-porous structure, whereas both FeAlPO-5-Hydro and FeAlPO-5-Imp were typical microporous materials. DR UV–Vis analysis suggested that the order of the amounts of isolated Fe3+ species in these three samples was as follows: FeAlPO-5-Hydro > FeAlPO-5-Iono > FeAlPO-5-Imp. However, the order of their catalytic performances towards phenol hydroxylation was in opposition to that of the amounts of isolated Fe3+ species. Detailed analysis revealed that it was textural properties of these catalysts that determined phenol conversion and dihydroxylbenzene selectivity. The catalyst-recycling tests suggested that extra-framework iron clusters were readily leached into the reaction system and had great influence on the hydroxylation of phenol. Due to the sole presence of isolated Fe3+ species and enhanced mass transport of reactants and products to/from these active sites, FeAlPO-5-Hydro was found to have the best reusability among these catalysts. .

Preparation of monodispersed NiO particles in SBA-15, and its enhanced selectivity for reverse water gas shift reaction

The preparation of monodispersed NiO particles in SBA-15 using the direct hydrothermal synthesis method with various combinations of metallic salt precursors and acids was investigated in detail. With NiO/SBA-15 containing less than 1wt% NiO, the NiO particles were monodispersed in the SBA-15 framework using the HCl+Ni(NO3)2 combination, whereas when the NiO amount exceeded 2wt%, the NiO particles aggregated. However, with NiO/SBA-15 containing less than 25wt% NiO, the NiO particles were monodispersed in the SBA-15 framework using the HCl+NiSO4 combination, whereas when the NiO amount exceeded 30wt%, the NiO particles aggregated. In addition, the reverse water gas shift (RWGS) reaction was studied using NiO/SBA-15 obtained by different combinations. Regardless of the combination and temperature, the CO selectivity was 100% using monodispersed NiO particles. In the presence of aggregated NiO particles, the CO selectivity was 100% only at high temperature; by contrast, the CO selectivity was less than 100% at low temperature. To achieve high CO2 conversion and 100% CO selectivity, the HCl+Ni(NO3)2 combination was not desired due to small metal loading, whereas the HCl+NiSO4 combination was necessary owing to large metal loading. Moreover, NiO/SBA-15 had relatively high thermal stability.

Direct synthesis of amides from amines using mesoporous Mn-SBA-12 and Mn-SBA-16 catalysts

Abstract Manganese incorporated SBA-12 and SBA-16 catalyze the tandem reaction of aliphatic primary amine, aerial oxygen and ammonia solution at moderate conditions producing amide in yields as high as 50 mol%. The Mn-SBA-12 and Mn-SBA-16 catalysts with Si/Mn output molar ratio in the range 230 to 748 were prepared by the direct hydrothermal synthesis method and characterized. Weak acidity and Mn in + 3 oxidation state are the key factors enable the synthesis of product amide in high yields.

Synthesis of mesoporous ceria without template

The synthesis of mesoporous ceria (CeO2) without a template was studied in detail using NaOH and NH4OH solution. We first synthesized nanosized mesoporous CeO2 without a template by the direct hydrothermal synthesis method with NaOH. By using NaOH, mesoporous CeO2 could be obtained without a template through the oxidation of Ce3+ ions, the hydrolysis of Ce4+ ions, polymerization and precipitation. Under appropriate synthesis conditions, the obtained mesoporous CeO2 had a high surface area, a narrow pore size distribution and an ordered structure with uniform mesopores. The surface area of the mesoporous CeO2 increased with increasing synthesis temperature. The NaOH concentration induced different behavior on the mesoporous CeO2 surface with and without a template. The mesoporous CeO2 had nanoarrays with uniform mesopores (intercrystalline voids). However, when NH4OH solution was used, the CeO2 had nanoarrays with a hierarchical pore network. The mesoporous CeO2 obtained without template had relatively high thermal stability that increased with increasing synthesis temperature.

SnTUD-1: a solid acid catalyst for three component coupling reactions at room temperature

A novel wormhole structured mesoporous material containing tin, SnTUD-1, was prepared by a direct hydrothermal synthesis method using triethanolamine (TEA) as an organic inexpensive mesoporous structure directing agent. XRD and N2 sorption studies of SnTUD-1 confirmed the amorphous mesoporous nature of SnTUD-1, which possessed a large surface area of 555 m2 g−1 and a pore diameter of 7.4 nm. HR-TEM further ascertained the disordered pores in their morphology and the presence of nano-domains of SnO2 species. The nature of the Sn4+ ion co-ordination with the silica matrix was evaluated by using different techniques including diffuse reflectance UV-Vis, FTIR, 29Si MAS NMR and XPS. SnTUD-1 had an interesting Lewis acidity as measured by FTIR of pyridine adsorption which provided excellent activities in one-pot three-component Mannich-type reactions of ketones with aldehydes and amines at room temperature.

Room-temperature catalytic oxidation of benzo(a)pyrene by Ce-SBA-15 supported active CeSiO4 phase

A series of cerium-incorporated SBA-15 mesoporous materials were prepared through direct hydrothermal synthesis method, which was characterized by PXRD, N2 physisorption and TEM measurements. The low-angle PXRD and N2 physisorption results show the cerium successfully incorporated into the framework of SBA-15. The large angle PXRD results indicate that Ce-SBA-15 mesoporous materials supported CeSiO4 phase was in situ synthesized by adjusting pH to 6 with anhydrous triethylamine, and then calcined in air at 550°C. The room-temperature adsorption behaviors of SBA-15 and Ce-SBA-15 materials for benzo(a)pyrene in cyclohexane solutions were investigated. Interestingly, Ce-SBA-15 materials reveal good catalytic performance for room-temperature oxidation benzo(a)pyrene to corresponding quinone through a radical oxidation mechanism, attributable to in situ forming active CeSiO4 phase which was supported in Ce-SBA-15 material. The benzo(a)pyrene transfer to quinone by CeSiO4 phase leads to higher adsorption capacity owing to higher affinity of quinone with mesoporous channels, as a result, some Ce-SBA-15 materials exhibit higher adsorption capacity for benzo(a)pyrene than SBA-15 material. The radical oxidation mechanism was demonstrated by EPR and the interception effect of a radical scavenger, TEMPO. The quinone-type molecule was identified by photoluminescence, ESI-MS, IR and NMR.

Direct hydrothermal synthesis of nanosized mesoporous ramsdellite manganese oxide with high surface area

We first synthesized nanosized mesoporous R-MnO2 using different block copolymers and PEG by direct hydrothermal synthesis method. The block copolymers seemed to play the important role. At appropriate synthesis conditions, the mesoporous R-MnO2 with high surface area, narrow pore size distributions and ordered structure with uniform mesopores could be obtained. The mesoporous R-MnO2 had nanoarrays with uniform mesopores (intercrystalline voids). Because the residual copolymer in the product could be easily removed by washing after synthesis, the calcination procedure of the final mesoporous R-MnO2 obtained was not necessary, suggesting that this method is economical and environmental. This direct hydrothermal synthesis method can potentially develop a new method for preparing other metal oxide. We think that the mesoporous R-MnO2 formed through a mechanism that combines PEO moieties in block polymers self-assembly with complication of Mn species. The mesoporous R-MnO2 had high thermal stability.

Selective oxidation of cyclic olefins over framework Ti-substituted, three-dimensional, mesoporous Ti-SBA-12 and Ti-SBA-16 molecular sieves

Framework Ti-substituted, three-dimensional, mesoporous titanosilicates, Ti-SBA-12 and Ti-SBA-16, were prepared by direct hydrothermal synthesis method. These catalysts showed catalytic activity higher than the hitherto known titanosilicates for the oxidation of cyclic olefins (cyclohexene and cyclooctene) with tert.-butyl hydroperoxide. An epoxide selectivity of 100% and olefin conversion greater than 92% were obtained. Cubic Ti-SBA-16 with interconnected cage-like mesopore structure was more active than hexagonal Ti-SBA-12. X-ray diffraction and diffuse reflectance UV–vis, Fourier transform infrared, Raman and electron paramagnetic resonance spectroscopies provided evidence for the substitution of Ti4+ (for Si4+) in the framework locations. The catalytic activity correlated with the concentration of framework-substituted, tetrahedral Ti4+ ions. Easy accessibility of the active sites and the three-dimensional mesoporous structure are the possible causes for the superior activity of these titanosilicate catalysts.

A Comparative Characterization of the HPA‐MCM‐48 Type Catalysts Produced by the Direct Hydrothermal and Room Temperature Synthesis Methods

MCM‐48 type support materials synthesized by the direct hydrothermal synthesis (HTS) and room temperature synthesis (RTS) methods were incorporated with tungstophosphoric acid (TPA) in the range of 10–40 wt% by using a wet impregnation technique in methanol solutions. Resulting HPA‐MCM‐48 catalysts were characterized by the XRD, Nitrogen Physisorption, SEM, TEM, EDS, and FT‐IR methods in order to determine the effects of different initial synthesis conditions on the catalyst properties. RTS samples were found to have better crystalline structures, higher BET surface areas, and higher BJH pore volumes than HTS samples. They also had slightly higher TPA incorporation, except for the 40 wt% samples, as evidenced by the EDS results. Keggin ion structure was preserved, for both methods, even at the highest acid loading of 40 wt%. It was concluded that the simpler and more economical RTS method was more successful than the HTS method for heteropoly acid incorporation into MCM‐48 type materials.