Sonochemical synthesis of zeolite NaP from clinoptilolite

Prandtl and Ohnesorge numbers dependent of ultrasonic horn energy in Newtonian liquid under batch and continuous flow

The level of knowledge on the non-thermal contribution of ultrasonic wave's energy to perform physico-chemical phenomena is one of the bottlenecks for the commercialization purposes. Under constant nominal power of transducer (Pn), the input electrical power (Pin) is less and sensitive to the medium's physical properties. This study attempts to assess the conversion of acoustic to thermal power experimentally and numerically using COMSOL Multiphysis@ for a 24 kHz horn-type sonicator through a medium without any sono-chemical effect. Single- and homogeneous two-phase Newtonian mixtures of sunflower oil and water (o/w) with a relatively wide range of density (914-998 kg/m3) and viscosity (0.5-63.5 mPa.s) were irradiated in a lab-scale vessel (1 L) under batch and continuous flow configuration. The direct influence of Pn (80-400 W) and o/w ratio (0-1) on temperature rise and subsequent thermo-physical properties of liquid and the indirect influence on Pin and thermal energy conversion (TEC) were investigated employing calorimetric method. A new engineering concept including a power factor correlation was proposed and validated for prediction of Pin as a function of liquid space velocity (ϑ), temperature, Prandtl (Pr) and Ohnesorge (Oh) dimensionless groups. The results showed that under constant temperature and Pn, increasing Pr and Oh increased Pin with a similar trend for both modes of operation. An increase in temperature directly led to a decrease in Pin with a power factor closed to "-1". The Pin in continuous flow was higher compared to batch configuration at similar temperature, liquid properties, and Pn. This effect was more significant with increasing ϑ. An increase in ϑ at constant Pn led to a decrease in the inlet/outlet temperature difference in continuous flow and an increase in Pin. Increasing Pn resulted in higher TEC for both configurations; however, TEC was relatively lower in continuous flow than batch configuration indicating more efficient sonication in continuous flow.

Effect of the nickel impregnation method on clay supports in the hydroconversion reaction of n-decane

Ni bifunctional catalysts supported on vermiculite, halloysite and bentonite previously modified by means of delamination or acid treatment were synthesized.

Facile synthesis of mesoporous ZSM-5 aided by sonication and its application for VOCs capture

Application of ultrasound power to the mother liquor is popular pretreatment for zeolite synthesis which offers a simple way of accelerating crystallization process and finetuning the properties of nanocrystalline zeolites. In this work, sonication-aided synthesis of mesoporous ZSM-5 at low temperature and ambient pressure was systematically studied, in an attempt to reach efficient and benign synthesis of zeolites with hierarchical pore structure, which has wide applications as catalysts and sorbents. The effects of sonication duration, power density, sonication temperature and seeding on the crystallization of ZSM-5 were investigated. The obtained samples were characterized by XRD, SEM, BET and VOCs capture. High quality mesoporous ZSM-5 can be obtained by a facile 5 d synthesis at 363 K, much faster than conventional hydrothermal synthesis. The reduced synthesis time was mainly attributed to the enhanced crystallization kinetics caused by the fragmentation of seeds and nuclei, while sonication radiation had little impact on the nucleation process. Compared with control sample, mesoporous ZSM-5 prepared by sonochemical method had higher surface area and mesoporosity which demonstrated improved adsorption performance for the capture of isopropanol.

Silica-rich Sodalite Synthesis: The Effect of Variations in Ultrasound Treatment and Hydrothermal Temperature

Silica-rich sodalite zeolite has been synthesized by ultrasound treatment and hydrothermal temperature variation. This study aimed to determine the effect of ultrasound treatment and hydrothermal temperature variations on the crystallinity, hydrophobicity, and structural properties of silica-rich sodalite zeolite. The synthesis was conducted by reacting a sodium aluminate and sodium silicate solution by varying Si/Al ratios of 20, 30, 40, 60, 80, and 90. The next step was to characterize the product. The product with the best crystallinity was used as a reference to determine the effect of ultrasound and hydrothermal temperature. The reaction gel was treated with and without ultrasound and hydrothermal using autoclave at 100, 150, and 200°C for 24 hours. The last step was the product characterization using XRD, FTIR, and GSA. The XRD showed similarity peaks at 2θ = 14.058°; 24.41°; 31.73°; 34.75°; 42.88°. The best crystallinity was silica-rich sodalite zeolite with a Si/Al ratio of 30. Meanwhile, silica-rich sodalite zeolite peaks were obtained at 2θ = 14.16°, 24.66°, 31.99°, 35.13°, and 43.39° by ultrasound treatment and hydrothermal temperature variation (100, 150, and 200°C). Ultrasound treatment revealed the presence of other peaks besides sodalite at 2θ = 19.05° and 27°, where these peaks were referred to as SAPO-56. In conclusion, the degree of crystallinity increased with increasing temperature, decreasing Si-OH/Si-O-Si showed increased hydrophobic properties. Increasing the hydrothermal temperature of 150 and 200°C with and without ultrasound treatment increased the surface area significantly to 114.137 m2/g and 160.717 m2/g, and the pore volume of sodalite with a Si/Al ratio of 30 to 0.318 cc/g and 0.274 cc/g.

Interzeolitic Transformation of Clinoptilolite into GIS and LTA Zeolite

A natural clinoptilolite zeolite was transformed into other zeolites of greater industrial interest, such as zeolites with GIS and LTA structures. The synthesis conditions were studied, and the interzeolitic transformation was characterized by X-ray diffraction (XRD), X-ray fluorescence (FRX), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). From the results, it was possible to observe that the GIS and LTA zeolites were successfully synthesized. Furthermore, the results revealed that a synthesis time of 4 days was enough to obtain the GIS structure, and 4 h was sufficient to obtain LTA. The interzeolitic transformation can be explained by the RBU (Ring Building Unit) approach using C4 units from the HEU topology. The use of clinoptilolite in the synthesis of other zeolites is an innovative, economically viable, and environmentally sustainable process that exploits a material that exists in large quantities and is still little explored by industry.

Optimized Preparation of Nanosized Hollow SSZ-13 Molecular Sieves with Ultrasonic Assistance

Because of its unique eight-membered ring pore structure and the arrangement of cations in its structure, the SSZ-13 molecular sieve has a higher affinity for CO2 than other gases, meaning it has attracted more attention than other porous materials for CO2 adsorption. However, the expensive template and long preparation time limits the industrial production of SSZ-13. In this work, a hollow structure was successfully introduced into the nanosized SSZ-13 molecular sieve with ultrasonic treatment. The effects of the amount of seed added and the ultrasonic time on the structure were investigated. When the amount of seed added was 0.5 wt.% and the ultrasonic time was 60 min, the sample showed a hollow cubic crystal with a diameter of about 50 nm. The specific surface area reached 791.50 m2/g, and the mesoporous ratio was 66.3%. The samples were tested for CO2 adsorption performance at 298 K. It was found that the hollow sample prepared in this work has higher CO2 adsorption capacity compared with the SSZ-13 zeolite prepared with conventional methods. When the adsorption pressure was 0.27 bar, the adsorption amount reached 2.53 mmol/g. The hollow SSZ-13 molecular sieve reached a CO2 adsorption capacity of 4.24 mmol/g at 1 bar.

Synthesis of zeolite SSZ-13 from coal gangue via ultrasonic pretreatment combined with hydrothermal growth method

SSZ-13 zeolite has been widely used in catalysis and adsorption because of good hydrothermal stability and pore structure. However, long crystallization time is the main challenge limiting its industry application. As increased emissions and ineffective treatment, coal gangue not only occupies land, but also pollutes the waterbody and farmland. Using coal gangue as raw material to synthetize zeolite has been considered as an environmentally friendly and effective alternative to solve the issues of accumulation and pollution, which also improves the added value of coal gangue. The ultrasonic assistance has been proven to be one of the potential pretreatment methods to promote the dissolution of crystalline silicon aluminum and reduce the crystallization time of molecular sieve. In this work, SSZ-13 was synthesized by coal gangue via ultrasonic pretreatment combined with hydrothermal growth method. The ultrasonic frequency and power were 20 kHz and 120 W, respectively. The synthesized samples were characterized by XRD, SEM, EDS, BET. The results showed that the crystallization time was shorten to 18 h, which was about 12 h lower than the same conditions of conventional chemicals synthesis. Furthermore, the specific surface area of the synthesized sample was more than 620 m²/g, which also indicated over 95% NO_x conversion across a broad range from 180 to 400 °C and over 94% NO_x conversion at 200-400 °C after hydrothermal treatment 6 h. This study provides a reference for the environmentally friendly utilization of coal gangue and the low-cost rapid synthesis and application of SSZ-13.

A time- and cost-effective synthesis of CHA zeolite with small size using ultrasonic-assisted method

In this paper, the ultrasonic-assisted method has been used to the rapid hydrothermal synthesis of CHA zeolite in the absence of expensive organic template. The influence of different sonicated time on the crystallinity and micromorphology of CHA-type crystals has been studied in detail. The bath-type ultrasound processor produces acoustic waves at the frequency of 20 kHz and the power of ultrasound wave is 150 W. The synthesized products have been characterized by XRD, SEM, EDX, TG and N₂ adsorption analyses. Due to the acceleration on homogeneous nucleation caused by acoustic cavitation cracks during the ultrasonic vibrative process, the crystallization time can be shorten from 48 h to 10 h and the crystal size can be reduced from about 20 μm to 5 μm. The SEM observations of samples with different ultrasonic treatment time distinctly revealed the morphology evolution of the walnut-like CHA zeolites. From EDX, TG and N₂ adsorption comparisons, it is clear that untreated sample and ultrasonic sample both have similar element distribution, thermal stability, and pore size distribution. The research work in this paper has demonstrated the ultrasonic treatment can significantly improve crystallinity degree, reduce crystallization time and crystal size of CHA zeolite.

Assessing the Aflatoxin B₁ Adsorption Capacity between Biosorbents Using an In Vitro Multicompartmental Model Simulating the Dynamic Conditions in the Gastrointestinal Tract of Poultry

Experiments were carried out to evaluate the effectiveness of three different biosorbents (banana peel, Pyracantha leaves, and Aloe powder) in removing aflatoxin B₁ (AFB₁). A noncommercial mycotoxin binder (zeolite) was used as a reference material. A laboratory model that simulated the in vivo conditions of the poultry gastrointestinal tract was utilized to prove the removal efficiency of the biosorbents when added to AFB₁-contaminated diet (100 µg/kg). The concentration of AFB₁ was determined using antibody-based immunoaffinity column and spectrofluorometry methodologies. Z potential (ζ), point of zero charge (pHpzc), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), Fourier transform infrared spectroscopy with attenuated total reflection (FTIR-ATR), and UV-Vis diffuse reflectance spectroscopy (DRS) techniques were used to further characterize the biosorbents. The addition of the biosorbents (1.5%, w/w) to the diet significantly reduced the bioavailability of AFB₁ in the intestinal section. The highest aflatoxin adsorption values were 69% and 70% using Aloe powder and zeolite, respectively. A moderate biosorption uptake of 46% was achieved using Pyracantha leaves. The biomaterial with the lowest removal capacity was banana peel (28%). In conclusion, Aloe powder could be used as an alternative to conventional systems for AFB₁ removal.

Small-Pore Zeolites: Synthesis and Catalysis

In the past decade or so, small-pore zeolites have received greater attention than large- and medium-pore molecular sieves that have historically dominated the literature. This is primarily due to the commercialization of two major catalytic processes, NOx exhaust removal and methanol conversion to light olefins, that take advantage of the properties of these materials with smaller apertures. Small-pore zeolites possess pores that are constructed of eight tetrahedral atoms (Si⁴⁺ and Al³⁺), each time linked by a shared oxygen These eight-member ring pores (8MR) provide small molecules access to the intracrystalline void space, e.g., to NOx during car exhaust cleaning (NOx removal) or to methanol en route to its conversion into light olefins, while restricting larger molecule entrance and departure that is critical to overall catalyst performance. In total, there are forty-four structurally different small-pore zeolites. Forty-one of these zeolites can be synthesized, and the first synthetic zeolite (KFI, 1948) was in fact a small-pore material. Although the field of 8MR zeolite chemistry has expanded in many directions, the progress in synthesis is framework-specific, leaving insights and generalizations difficult to realize. This review first focuses on the relevant synthesis details of all 8MR zeolites and provides some generalized findings and related insights. Next, catalytic applications where 8MR zeolites either have been commercialized or have dominated investigations are presented, with the aim of providing structure-activity relationships. The review ends with a summary that discusses (i) both synthetic and catalytic progress, (ii) a list of opportunities in the 8MR zeolite field, and (iii) a brief future outlook.

Controllable synthesis of (NH4)Fe2(PO4)2(OH)·2H2O using two-step route: Ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment

(NH₄)Fe₂(PO₄)₂(OH)·2H₂O samples with different morphology are successfully synthesized via two-step synthesis route - ultrasonic-intensified impinging stream pre-treatment followed by hydrothermal treatment (UIHT) method. The effects of the adoption of ultrasonic-intensified impinging stream pre-treatment, reagent concentration (C), pH value of solution and hydrothermal reaction time (T) on the physical and chemical properties of the synthesised (NH₄)Fe₂(PO₄)₂(OH)·2H₂O composites and FePO₄ particles were systematically investigated. Nano-seeds were firstly synthesized using the ultrasonic-intensified T-mixer and these nano-seeds were then transferred into a hydrothermal reactor, heated at 170 °C for 4 h. The obtained samples were characterized by utilising XRD, BET, TG-DTA, SEM, TEM, Mastersizer 3000 and FTIR, respectively. The experimental results have indicated that the particle size and morphology of the obtained samples are remarkably affected by the use of ultrasonic-intensified impinging stream pre-treatment, hydrothermal reaction time, reagent concentration, and pH value of solution. When such (NH₄)Fe₂(PO₄)₂(OH)·2H₂O precursor samples were transformed to FePO₄ products after sintering at 650 °C for 10 h, the SEM images have clearly shown that both the precursor and the final product still retain their monodispersed spherical microstructures with similar particle size of about 3 μm when the samples are synthesised at the optimised condition.