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A combination of carbon nanotubes (CNTs) and diethylamine (DEA) was used as a multitemplate in sonochemical synthesis of silicoaluminophosphate (SAPO)-34 hierarchical catalyst. The results show that such use of CNTs as mesopore template in sonochemical synthesis generates catalysts with hierarchical structure and remarkably different external surface area and particle morphology; on addition of CNTs, nanoparticles with spherical hierarchical are formed, having much larger external surface area compared with the common, cubic shape of SAPO-34 particles. Comparing the performance of the improved hierarchical nanocatalyst obtained using the CNT template with the base catalyst (without use of CNTs) in the methanol to light olefins (MTO) process, it was observed that the improved catalyst remained active for a longer time. Also, a larger amount of light olefins could be produced using this nanocatalyst compared with the base catalyst. Additionally, the effect of crystallization time and amount of DEA as a micropore template on the physicochemical features and performance of SAPO-34 crystals in the MTO process was evaluated. Very low amounts of DEA and short crystallization time resulted in very low crystallinity of the synthesized SAPO-34. However, large amount or long time resulted in synthesis of agglomerated, large SAPO-34 catalysts. Neither of these is desirable, and intermediate values were found to be favorable for catalyst synthesis. [ABSTRACT FROM AUTHOR]

DFT calculations have been performed at the B3LYP/6-31++g** level to investigate the effect of the cluster size of ZSM-5 on the hydrogen atom of the Brönsted acid site via NQR and NMR parameters in methanol adsorption. ZSM-5 clusters have been modeled as 1T, 2T, 5T and 8T. T represents a general tetrahedral unit. Chemical shifts, δ, of H atom in the Brönsted acid site as well as quadrupole coupling constant, C, and asymmetry parameter, η, of H atom in the Brönsted acid site have been calculated. Spectrometric parameters showed that these parameters are influenced by the size and the shell of surrounding central T. Results indicate that inclusion of the next shell of T atoms (silicon atoms) around bridged hydroxyl group in the bare cluster models raises C and H δ from 1T to 5T, 2T to 8T, while no significant changes are observed in the same electronic environment. The calculated the natural charge distribution of hydrogen atom in the Brönsted acid site analyzed by the NBO method for comparison of the cluster models. [ABSTRACT FROM AUTHOR]

Silver ions can be reduced by 24 kHz ultrasonic waves in ion-exchanged Ag+–Y zeolite. In this research, silver ions were introduced into the nano-porous (1.2 nm) zeolite lattice by ion-exchange route. After the reduction process, silver nanoparticles were placed in the cavities, with a size of about 1 nm and also on the external surfaces of the zeolite, with sizes about less than 10 nm. Fast and simple lab-scale reduction of silver ions in the zeolite is important for researchers who work on catalytic properties of metallic silver–zeolite. Several reduction methods have been reported but reduction by ultrasonic waves is a new, simple, and size-controllable method with a high practical value which does not need any complicated facilities. In a sonochemical process, a huge density of energy is provided by the collapse of bubbles which formed by ultrasonic waves. The released energy causes the formation of reducing radicals that consequently reduce the silver ions. It is concluded that the higher silver content may result in the formation of larger silver crystals on the external surface of zeolite crystals. Also, the addition of 1-propanol and 2-propanol to the aqueous reaction medium does not cause better reduction. In addition, increasing the irradiation time and ultrasonic power does not affect the silver crystal growth significantly but the extent of silver ion reduction increases when the power of ultrasonic waves increases. All samples were irradiated under the same ultrasonic conditions. The samples were analyzed by XRD, EDS, SEM, and TEM. [ABSTRACT FROM AUTHOR]

In this work, molecular dynamics (MD) simulation is used to study the adsorption of the anticancer drug, doxorubicin (DOX), on the wall or surface of pristine and functionalized carbon nanotubes (FCNTs) in an aqueous solution. Initially, the CNTs were functionalized by tryptophan (Trp) and folic acid (FA), and then the DOX molecules were added to the system. The simulation results showed that the drug molecules can intensely interact with the FCNTs at physiological pH. Furthermore, it was found that as a result of functionalization, the solubility of FCNTs in an aqueous solution increases significantly. The effect of pH variation on drug release from both pristine and FCNTs was also investigated. The obtained results indicated that in acidic environments due to protonation of functional groups (Trp) and as a result of repulsive interaction between the DOX molecule and functional groups, the release of DOX molecules from FCNT's surface is facilitated. The drug release is also strongly dependent on the pH and protonated state of DOX and FCNT. [ABSTRACT FROM AUTHOR]