Large Mesopore Volume Research Articles

Disproportionation and Transalkylation of Phenol and Dimethylphenol on Zeolite Catalysts

AbstractSubstantial amounts of phenolic compounds are present in medium‐low temperature coal tar (MLCT), of which dimethylphenol (DMP) is not as valuable to be utilized as the more abundant cresol due to its complex composition and difficulty in isolation. In this study, the disproportionation and transalkylation reactions of MLCT‐related model compound, i.e., 2,6‐DMP, in phenol over zeolite catalysts are investigated using a fixed‐bed reactor for sustainable new option to utilize MLCT‐derived phenolic mixtures. Reactivity is promoted at high temperatures and associated with zeolite acidity and pore structure. Since disproportionation and transalkylation reactions have certain spatial requirements, the micropores of MFI‐type zeolite may cause spatial barriers that make it difficult to carry out the reactions. MCM‐22, characterized by MWW‐type zeolite, maximized the conversion of 2,6‐DMP due to its strong Bronsted acidity and large mesopore volume. FAU‐type zeolite HY with a 3D large 12‐ring through‐channel shows relatively small spatial confinement and certain molecular sieving ability, which enables bimolecular reactions while allowing cresols to flow out of the pores efficiently to obtain the highest cresol selectivity. The addition of phenol significantly inhibits the spontaneous disproportionation of 2,6‐DMP to tricresol. Besides, o‐cresol dominate the cresol products, suggesting that the selectivity of o‐cresol is kinetically controlled.

A recyclable and durable magnetic cobalt nanoparticle-embedded mesoporous graphene nanohybrid for removal of pollutants from aqueous media

Cobalt nanoparticles (Co NPs) embedded in mesoporous graphene (MG) were prepared via a hydrothermal reaction followed by carbothermal reduction in an argon atmosphere. This cobalt nanoparticle-embedded mesoporous graphene (CoMG) was systematically investigated for structural, morphological, and magnetic properties before and after 10 successive cycles of adsorption and regeneration, using methylene blue (MB) dye as a model pollutant. The CoMG nanohybrid has a superior specific surface area of 807 m2 g−1, with a significant mesopore volume of 1.63 cm3 g−1 that allows fast and high pollutant removal efficiency of ∼84 % within 30 min as well as the maximum adsorption capacity of 178.6 mg g−1 with MB solution of 100 mg L−1, which is well described with pseudo-second-order adsorption kinetics. The consecutive adsorption−regeneration experiments revealed that the CoMG nanohybrid retained more than half of the initial dye removal efficiency even after being reused 10 times. After the tenth cycle, the regenerated CoMG maintained a high specific area of 688 m2 g−1 and a large mesopore volume of 1.51 cm3 g−1, indicating the long-lasting porous structure of the CoMG nanohybrid. The metallic cobalt phase and ferromagnetic nature of the Co NPs in the nanohybrid are retained because of the host MG, which prevents nanoparticle aggregation and serves as a protective environment for the embedded Co NPs in aqueous media during the adsorption−regeneration cycle tests of the adsorbent. The experimental results demonstrate that the CoMG nanohybrid has superior pollutant removal capacity and maintains more than half of the initial efficiency even after 10 cycles of use, making it a cost-efficient and energy-saving material for the removal of organic pollutants from aqueous media and in other environmental applications.

Continuous and controllable synthesis of MnO2 adsorbents for H2S removal at low temperature

H2S is an extremely noxious impurity generated from nature and chemical industrial processes. High performing H2S adsorbents are required for chemical industry and environmental engineering. Herein, α-, γ-, and δ-MnO2 adsorbents with high sulfur capacity were synthesized through a continuous-flow approach with a microreactor system, achieving much higher efficiency than hydrothermal methods. The relationship between crystal structure and synthesis conditions such as residence time, reaction temperature, concentration of K+ in solution and reactant ratio is discussed. According to the H2S breakthrough tests at 150 °C, continuously prepared α-, γ-, and δ-MnO2 exhibited sulfur capacities of 669.5, 193.8 and 607.6 mg S/g sorbent, respectively, which was at a high level among the reported adsorbents. Such enhanced performance is related to the large surface area and mesopore volume, high reducibility, and a large number of oxygen species with high reactivity and mobility. Manganese sulfide and elemental sulfur were formed after desulfurization, which indicated the reaction consisted of two steps: redox and sulfidation of the sorbents. This study provides an innovative design strategy for the construction of nanomaterials with high H2S adsorption performances.

Sustainable mechanochemical synthesis of catalytically graphitized mesoporous carbons

So far it is difficult to achieve both a high graphitization degree and uniform mesopores in carbons, especially via a sustainable synthesis approach. This work shows that mesoporous graphitized carbons predominantly composed of amorphous and/or partially graphitic carbon nanotubes can be obtained by a simple mechanochemical synthesis using tannins as carbon precursors, iron salt as a graphitization catalyst and block copolymer as a soft template. The one-pot synthesis relied on the fast ball milling of a Pluronic-type template, tannins, and iron salt, followed by the direct thermal treatment at a certain temperature (e.g., 750 °C) leading to mesoporous carbons with a high degree of graphitization (up to 75%), high specific surface areas up to 360 m2/g, and large mesopore volumes up to 0.40 cm3/g. Moreover, the procedure can be extended for the synthesis of highly porous activated carbons with uniform mesoporosity by adding potassium oxalate to the milling system. The procedure afforded activated mesoporous carbons with substantially uniform mesopores of about 7.7 nm, a high specific surface area of 1100 m2/g, a large pore volume of 0.84 cm3/g, and enhanced CO2 adsorption capacity up to 4.0 mmol/g at ambient conditions. This synthetic approach offers advantages in terms of scalability, simplicity, and reduced environmental impact in comparison to traditional synthesis methods.

Soft-templating synthesis of hierarchical mordenite as high-performance catalyst for cyclic acetals production via acetylation of glycerol and benzaldehyde

Highly active hierarchical mordenite zeolite with micro/mesoporosity (TM-n) for selective synthesis of cyclic acetals via acetylation reaction is reported. The hierarchical zeolite is synthesized using soft-templating approach with variations in octadecyltrimethoxysilane (OTMS/Al2O3 ratio, n = 0.2, 0.3 and 0.4) in precursor hydrogels. The results reveal that OTMS not only creates secondary mesoporosity in zeolite framework (larger mesopore volume, external surface area, average pore diameter), but also influences the crystallization process, altering the crystal morphology, crystallinity and Si/Al ratios. Among TM-n zeolites prepared, TM-0.3 hierarchical mordenite has the optimum OTMS amount incorporated while further increasing the OTMS amount leads to the formation of ANA/GIS intergrowth. Thanks to the accessible hierarchical porosity, reduced acidity and morphological effects, the TM-0.3 hierarchical mordenite exhibits excellent catalytic performance (84.1% conversion, TOF = 0.087 s−1, 61.5% dioxolane selectivity) in acetylation of glycerol and benzaldehyde (160 °C, 20 min) better than pristine mordenite. The catalyst is reusable for five runs with minimal loss of activity (TOF = 0.087 → 0.084 s−1), making it a promising catalyst for chemical productions involving bulky molecules. In addition, comparative catalytic tests with classical homogeneous and heterogeneous catalysts, including H2SO4, HCl, CH3COOH, H–Y, H-LTL, Na-X, Na-A, were performed.

The influence of nitrogen-containing functional groups and pore structure on the adsorption of per- and polyfluoroalkyl substances in ultrapure and real water

Activated carbon adsorption has been identified as an effective technique for per- and polyfluoroalkyl substances (PFAS) removal. However, the role of nitrogen-containing functional groups and pore size on PFAS elimination is uncertain. Therefore, this study prepared a series of AC with different nitrogen groups and pore structures by thermal treatment with urea under different temperatures (denoted as AC400, AC600 and AC800). Their PFAS adsorption performance in ultrapure and real water were investigated to identify the contribution of different nitrogen groups and pore structures. The adsorption experiment indicated that the modified AC800 with high proportion of pyridine nitrogen and medium pore volume achieved the best performance in ultrapure water due to the electrostatic interaction. However, in the real water contained dissolved organic matter (DOM), rather than AC800, AC600 with large mesopore volume exhibited the maximum adsorption capacity and kinetic due to its better inhabitation of pore blockage by DOM. It could be inferred that the electrostatic attraction force was more important in PFAS adsorption in ultrapure water, but in real water the mesopore volume was more critical due to the pore blockage by DOM. This study can provide guidance and implications for selection and development of future PFAS adsorption carbon-based material.

Pore size distribution and Al oxide content significantly regulated the effects of humic acid on perfluorooctanoic acid transport in natural soils

The ubiquity of dissolved organic matter (DOM) makes it encounter the released perfluorooctanoic acid (PFOA) in subsurface environment. However, the effect of DOM (e.g., humic acid, HA) on PFOA transport in soils and the critical influencing factors and mechanisms remain obscure. Column experiments were conducted to explore PFOA transport with the presence of different concentrations of HA in three types of soils and two types of Al oxide coated sand. Results revealed soil properties significantly regulate the effects of HA on PFOA transport, for which pore size distribution, minerals content (e.g., Al oxide) and pH were critical influencing soil–properties. For soil with large mesopore volume, pore blockage caused by HA controlled the effect of HA on PFOA transport. Large mesopore volume significantly alleviated pore blockage of HA, and led to insignificant effects of HA on PFOA transport. For soil exhibited minimum mesopore volume, Al oxide content and pH dominated the effect of HA on PFOA transport. Results from Al oxide coated sand (low mesopore volume) columns further proved that higher Al oxide content and lower pH caused more significant facilitating effect of HA on PFOA transport via site competition. Results highlighted the importance of considering pore size distribution and Al oxide content when assessing PFOA mobility capacity with co–transport with DOM in soils.

Nanocrystallite Zeolite BEA for Regioselective and Continuous Acetyl Functionalization of Anisole Using Acetic Anhydride: Catalyst Deactivation Studies.

Ultrasonic pretreatment of gel composition followed by hydrothermal synthesis produces the nanocrystallite zeolite beta (ZB) with crystal sizes of 10.3, 22.6, and 9.1 nm for ZB-1, ZB-2, and ZB-3, respectively. The effect of ultrasonic pretreatment and the (SiO2/Al2O3) ratio of gel composition on physical, textural properties, and also on the catalytic activity of ZB catalysts with increasing time on stream (TOS) was investigated. The specific surface area and mesopore volume for ZB-1, ZB-2, and ZB-3 are 438, 380, and 429 m2/g and 0.17, 0.05, and 0.14 cm3/g, respectively. The activity studies of ZB-1 and ZB-3 catalysts were confirmed that the anisole conversion initially increased with TOS until it attained the maximum value and then started decreasing further with TOS due to the deactivation of the catalyst caused by the strong interaction of the product with the acidic sites in the mesopore region. However, in the case of ZB-2, the anisole conversion (>45%) was sustained for a longer TOS due to its smaller particle size, low mesopore volume, and more acidic sites in the micropore volume that are inclusively made for retardation in the catlytic deactivation rate. The CHNS and TGA analysis of the spent catalysts confirm that ZB-1 and ZB-3 catalysts are susceptible for a significant coke formation attributed due to strong product retention in their large mesopore volume, which lead to the catalytic deactivation.

Activation-self-activation craft for one-step synthesis of GO-inbuilt mesopore-dominated N-doped hierarchical porous carbon in capacitive deionization capture of Ni(II)

Capacitive deionization (CDI) is considered a polar-promising technology to remove heavy-metal ions from wastewater. Herein, a green activation-self-activation strategy was exploited to build graphene (GO)-inbuilt mesopore-dominated N-doped hierarchical porous carbons (ENHPCs) using sodium lignosulfonate (SLS) as carbon sources/self-activators. Different from SLS self-activation and K2C2O4-SLS activation-self-activation, ENHPCLKG gained via GO-mediated K2C2O4-SLS activation-self-activation showed suitable mesopore-dominated micro-mesoporous structures with high surface area of 1795.5 m2/g, large mesoporous volume of 0.87 m3/g, 3.65 % N-doping and excellent conductivity. Its unique hierarchical porous structure and abundant active sites facilitated the ion rapid insertion and extraction. When utilized to capture low-concentration nickel (Ni2+) ions, ENHPCLKG delivered splendid salt removal capacity of 17.86 mg/g, rapid average salt removal rate of 0.99 mg/g/min and standout cycle stability. Meanwhile, ENHPCLKG was further extended to remove NaCl, MgCl2, CaCl2 and Ni-containing wastewater, showing superior CDI property. Moreover, the recycled ENHPCLKG (10th) taken to eliminate indomethacin (IDM) depicted a splendid adsorption capacity. This work proved the significant applicant potential of the novel and green ENHPCLKG for disposing of Ni2+ ions via CDI technology.

Ultrasonic-pretreated hydrothermal synthesis of less dense zeolite CHA from the transformation of zeolite T

Because of containing the same double 6-ring (D6R) building unit, the pure zeolite CHA with lower framework density (FDSi = 15.1 T/1000 Å3) has been transformed from zeolite T with higher framework density (FDSi = 16.1 T/1000 Å3) through ultrasonic-pretreated hydrothermal synthesis in MOH (KOH and NaOH) solution without adding organic template or seed crystals. Ultrasonic pretreatment facilitates the transformation rate and generates high-quality zeolite CHA. The ultrasound condition should be precisely controlled because that CHA phase is metastable, which is inclined to transform to other more stable phase. The ultrasonic conditions at 313 K and 333 K have been investigated in detail. In KOH solution, the ultrasonic treatment at 313 K can effectively restrain the generation of MER phase, however, it is hard to avoid the existence of MER phase when ultrasound temperature is 333 K. In NaOH solution, the samples with ultrasonic treatment of 313 K show the small particles size of about 1 μm, and the GIS framework topology starts to grow with the ultrasonic treatment of 333 K. The products prepared with the appropriate ultrasonic pretreatment represents smaller particles size, larger mesopore volume and higher CO2 adsorption capacity than the sample without the ultrasonic pretreatment. The structural evolution of interzeolite transformation has been explored by XRD, FT-IR and SEM observations. With the assistance of ultrasound, the parent zeolite T can quickly decompose into intermediate phase and then regenerate into CHA phase.

Green synthesis of shaped nano-ZSM-5 toward more efficient methanol-to-hydrocarbon conversion

Commonly, in the synthesis of zeolites, calcination is necessary prior to ion exchange to remove organic templates. Herein, shaped nano-ZSM-5 was successfully prepared with the assistance of template-free nano-aggregate seed without the calcination step before ion exchange. This synthesis method dramatically increased mesopores volume compared with the one calcined prior to ion exchange. Besides, employing nano-aggregate as seed gave the synthesized ZSM-5 a markedly smaller particle size and higher yield than the one prepared with conventional silicate-1 as seed, and simultaneously accelerated the crystallization process by providing more nuclei. A possible formation mechanism of the shaped nano-ZSM-5 zeolites was proposed. The shaped nano-ZSM-5 possessed the smallest crystal size, largest mesopore volume, most acid sites and strongest acid strength, which endowed it highest catalytic activity and longest lifetime in methanol to hydrocarbons reaction. This work could attract more attention on the application of nanoscale ZSM-5 catalyst to industry.

Novel porous CaO-MgO-promoting γ-Al2O3-catalyzed selective hydrogenation of oleic acid to green hydrocarbon fuels in biogasoline range with methanol as an internal hydrogen source

An efficient and highly selective CaO-MgO-promoting γ-Al2O3 decarboxylation catalyst was fabricated with different CaO to MgO ratios via a ball-milling method for regulating product distribution and production of gasoline-kerosene-diesel hydrocarbons via the catalytic copyrolysis of oleic acid (OA) and methanol under hydrogen-generating conditions. In addition, influencing factors, reaction mechanisms, possible reaction pathways and deactivation mechanisms were probed. The results showed that combining Ca, Mg and AlOx was vital for boosting oleic acid conversion, and synergy between metal and acid active sites via strong metal-support interactions enhanced deoxygenation-cracking activity. High-alkalinity CaO boosted C-C/CC bond cleavage, and MgO provided medium-strength Lewis acid sites; additionally, a large BET surface area and mesopore volume suppressed excessive hydrocracking reactions, improving biogasoline yield. Methanol addition provided active hydrogen atoms to enhance biogasoline selectivity at the expense of diesel and heavy oil production via olefinic cycles and aromatic cycle mechanisms and reduced coke deposition. The maximum hydrocarbon and biogasoline yields of 94.53% and 57.59% were achieved at OA/methanol= 5:1 and pyrolysis/catalytic temperature= 450/500 °C with1 g catalyst at a feedstock input rate of 0.1 ml/min.

Optimization of photocatalytic degradation of malachite green using nano-scaled V/CeO2-functionalized steel-slag-based catalyst by response surface design approach

The utilization of steel slag with high added value is an important means for sustainable development of the iron and steel industry and environment. A new nano-scaled V/CeO2-functionalized steel-slag-based catalyst (V/CeO2-SC) was prepared. The XPS results revealed that V was embedded in the CeO2 lattice with V4+ and V5+ forms. The regression equation analysis of variance told that the order of influencing factors on malachite green dye degradation rate is: catalyst dosage > V doping amount > malachite green dye concentration. The optimum values of the parameters were dye concentration 10 mg/L, catalyst dosage 0.1 g, and V doping amount 1wt%. Under the optimal condition, the predicted and actual response values of the degradation rate of malachite green dye were 100.00%. UV–Visible light absorption spectroscopy results demonstrated that after the photocatalytic degradation reaction, the absorption peak of the malachite green dye solution almost completely disappeared, indicating that the malachite green dye solution was almost completely degraded. The excellent degradation activity of the 1V/CeO2-SC specimen was attributed to the co-action of the high SBET, large mesoporous volume, and the coupled semiconductors formed by V-doped CeO2 and FeO in the catalyst carrier. A possible photocatalytic degradation mechanism of the V/CeO2-SC specimen was proposed.

Synthesis of high-density bio-jet fuel by one-pot Mannich-Michael reaction and subsequent hydrodeoxygenation over alkali-treated zeolite catalysts

Cycloalkanes jet fuel with high-density derived from biomass are the ideal alternative to fossil fuel. The one-pot Mannich-Michael reaction of cyclopentanone and formaldehyde followed by hydrodeoxygenation (HDO) is a prospective route for the synthesis of cyclic high-density jet fuel. The synergistic interaction of pyrrolidine with acetic acid exhibited high catalytic activity in the one-pot Mannich-Michael reaction under mild conditions (50 ℃, 6 h). Additionally, solvents with appropriate polarity promote proton transfer to form Mannich bases, which are subsequently decomposed to produce 2-methylenecyclopentanone as the substrate for Michael addition. Thus, a high yield of condensed products (92.3%) with 93.3% conversion of cyclopentanone was obtained via an enamine catalytic pathway. The alkali-treated Hβ25-1 combined with Pd/C effectively catalyze the HDO of condensate products. The alkali-treated Hβ25-1 with larger mesoporous volume and sufficient acid sites lead to a high yield of dicyclopentylmethane (73.6%). The density and heating value of the HDO liquid products were 0.906 g/cm3 and 40.5 MJ/L, respectively. This work provided a novel route for high-density jet-fuel from lignocellulosic platform compounds.

Development of Highly Efficient Hydroisodeparaffinization Catalysts Based on Micro-Mesoporous SAPO-31: New Approaches in the Synthesis of SAPO-31 and the Preparation of Bifunctional Catalysts

A method is proposed for the synthesis of micro-mesoporous SAPO-31 with a high external surface area and large mesopore volume using tetraethoxysilane as a source of silicon. The synthesis of SAPO-31 is based on the principles underlying the Stöber process approach, which allows control of the pore diameter and volume and, hence, the external surface area of the product material. The use of the proposed methods for depositing the hydro-dehydrogenating component on the synthesized micro-mesoporous SAPO-31 made it possible to obtain highly efficient bifunctional hydroisodeparaffinization catalysts with the platinum or palladium content not higher than 0.2 wt.%. As a result, the process temperature can be decreased by 50–60 °C in comparison with the known analogs. Therewith, for example, in the test reaction of n-decane hydroisodeparaffinization at a temperature of 300 °C and feed rate of 1.5 h−1, the conversion above 90%, and the 97–98% yield of liquid products, the 95% selectivity to isomeric products were achieved.

Highly improved pH-Responsive anticancer drug delivery and T2-Weighted MRI imaging by magnetic MOF CuBTC-based nano/microcomposite.

Cu-BTC framework has received a considerable attention in recent years as a drug carrier candidate for cancer treatment due to its unique structural properties and promising biocompatibility. However, its intrinsic deficiency for medical imaging potentially limits its bioapplications; To address this subject, a magnetic nano/microscale MOF has been successfully fabricated by introducing Fe3O4 nanoparticles as an imaging agent into the porous isoreticular MOF [Cu3(BTC)2] as a drug carrier. The synthesized magnetic MOFs exhibits a high loading capacity (40.5%) toward the model anticancer DOX with an excellent pH-responsive drug release. The proposed nanocomposite not only possesses large surface area, high magnetic response, large mesopore volume, high transverse relaxivity (r 2) and good stability but also exhibits superior biocompatibility, specific tumor cellular uptake, and significant cancer cell viability inhibitory effect without any targeting agent. It is expected that the synthesized magnetic nano/microcomposite may be used for clinical purposes and can also serve as a platform for photoactive antibacterial therapy ae well as pH/GSH/photo-triple-responsive nanocarrier.

Ultrasound-assisted H2O2 directional-modification of powdered activated carbon for the enhanced adsorption of secondary effluent organic matter from printing and dyeing processes

The physicochemical properties of powdered activated carbon (PAC) are important factors affecting its adsorption performance, which is also related to the characteristics of target organic pollutants. In this study, the key indicators affecting the adsorption performance of PAC were identified, and the physicochemical properties of PACs were modified by hydrogen peroxide and/or ultrasound in a targeted manner to improve the adsorption performance. The results indicated the adsorption properties of printing and dyeing secondary effluent organic matter (EfOM) in terms of CODcr and UV absorbance at 254 nm (UV254) positively correlated with mesoporous volume, average pore size and acid group content of PAC. After modification, the mesoporous volume and average pore size of PAC increased, and the number of acidic groups increased, thus enhancing the adsorption efficiency. EfOM removal characteristics showed that PAC preferentially adsorbed unsaturated bonds or aromatic compounds, tryptophan-like proteins, soluble microbial metabolites and low molecular weight fractions below 1 kDa. In addition, the relative contents of specific surface area, pore volume and oxygen-containing functional groups (O-CO, C-OH, CO/O-C-O) of PAC decreased after adsorption, indicating that EfOM adsorption was a physical and chemical process, including pore filling, hydrophobic interaction and chemical bond force interaction. In general, PACs with larger mesoporous volume, average pore size and abundant acid groups possessed good adsorption performance towards EfOM.

Conversion of cassava rhizome into efficient carbonaceous adsorbents for removal of dye in water

The development of sustainable adsorbent materials for removing pollutants from water is of great interest for environmental remediation and human safety. This work presents the beneficial use of cassava rhizome (CR) to produce economical and efficient carbonaceous adsorbents for dye removal. CR derived activated carbons (AC) and magnetic AC were fabricated by one-pot hydrothermal carbonization in the presence of ZnCl2 and ZnCl2/FeCl3 respectively, followed by pyrolysis at 800 °C. Porosity tuning and degree of magnetization of as-prepared carbons were achieved by varying the amount of ZnCl2 and FeCl3 as an activating agent and source of magnetic particles respectively. The result indicated that the optimal condition to obtain ACs with a high SBET (1405 m2/g) and the largest mesopore volume (0.54 cm3/g) was using the weight ratio of ZnCl2 to CR of 3 (3AC). While, the magnetic mesoporous carbon with the highest SBET (554 m2/g) was yielded when addition of FeCl3 into the reaction mixture with a FeCl3 to ZnCl2 weight ratio of 1(3AC-1M). 3AC and 3AC-1M were tested as adsorbents to investigate the adsorption efficiency of methylene blue (MB) in water. The adsorption behavior of MB on 3AC and 3AC-1M were monolayer adsorption based on the Langmuir isotherm model with R2 of 0.9993 and 0.9953, respectively. 3AC showed the MB adsorption capacity of 274 mg/g which is comparable to that of commercial ACs. 3AC-1M that adsorbs MB with the maximum capacity of 102 mg/g, was separated from aqueous solution easily using an external magnet. This study demonstrates that the carbon precursors from biomass waste as CR can be conveniently converted into efficient carbonaceous adsorbents and functionalized for example by adding magnetic properties into the carbon structure to enable manipulations in industrial operations.

Aromatic compounds‐mediated synthesis of anatase‐free hierarchical TS‐1 zeolite: Exploring design strategies via machine learning and enhanced catalytic performance

AbstractSimultaneous achievement of constructing mesopores and eliminating anatase is a long‐term pursuit for enhancing the catalytic performance of TS‐1. Here, we developed an aromatic compounds‐mediated synthesis method to prepare anatase‐free and hierarchical TS‐1 for olefin epoxidation. A series of hierarchical TS‐1 zeolites were prepared by introducing aromatic compounds containing different functional groups via the crystallization process. The formation of intercrystalline mesopores and insertion of titanium into framework were facilitated at different extent. The synergistic coordination of carboxyl and hydroxyl in aromatic compounds with Ti(OH)4 realizes the uniform distribution of titanium species and eliminates the generation of anatase. Noteworthily, eight machine learning models were trained to reveal the mechanism of additive functional groups and preparation conditions on anatase formation and microstructure optimization. The prediction accuracy of most models can reach more than 80%. Benefiting from the larger mesopore volumes (0.37 cm3·g−1) and higher content of framework Ti species, TS‐DHBDC‐48h samples exhibit a higher catalytic performance than other zeolites, giving 1‐hexene conversion of 49.3% and 1,2‐epoxyhenane selectivity of 99.9%. The paper provides a facile aromatic compounds‐mediated synthesis strategy and promotes the application of machine learning toward the design and optimization of new zeolites.

Synthesis of Hierarchical ZSM‐11 Nanorods Aggregates and Catalytic Properties in Cyclohexene Hydration to Cyclohexanol

AbstractA series of hierarchical ZSM‐11 nanorods aggregates were prepared by a hydrothermal crystallization method with the addition of cetyltrimethylammonium bromide (CTAB). The physical and chemical properties of the samples were characterized and the catalytic properties in the direct hydration of cyclohexene to cyclohexanol were also investigated. The characterization results showed that adding CTAB effectively increased the crystallinity of the zeolite, and the external specific surface areas and pore volume of the zeolite increased dramatically. With the increase of CTAB addition, more and more mesopores were formed which could be clearly seen from TEM micrograph. The ratio of Brønsted/Lewis acid decreased first and then increased with the increase of CTAB addition, with the lowest point appeared at the ratio of CTAB/SiO2 of 0.015. The zeolite synthesized at the CTAB/SiO2 ratio of 0.015 exhibited the highest reaction rate with the cyclohexene conversion as high as 14.23 %. The excellent performance of the hierarchical ZSM‐11 nanorods aggregates can be attributed to the lowest Brønsted/Lewis acid ratio and large mesoporous volume.