An innovative SiO2-pyrazole nanocomposite for Zn(II) and Cr(III) ions effective adsorption and anti-sulfate-reducing bacteria from the produced oilfield water

Novel SiO₂-pyrazole (SiO₂-PYZ) nanocomposite was introduced for the elimination of Zn(II) and Cr(III) from oil reservoir water. Characterization analysis of prepared SiO₂-PYZ nanocomposite was investigated using SEM, FTIR, TGA, XRD, TEM, and BET. Studying the effects and optimization of the parameters such as retention time, pH, initial Cr(III) and Zn(II) ions concentrations, adsorbent dosage, and temperature were examined. For kinetics investigation, the pseudo-second-order (PSO) model matches the adsorption process effectively under different operating conditions. After applying two other isotherm models (Langmuir and Freundlich), the experimental data was adequately equipped with Langmuir, R² = 1. The thermodynamic results pointed that the adsorption of Zn(II) and Cr(III) ions was spontaneous, endothermic, and physisorption reaction. At pH 12, the influence of more than one ion, such as Ca(II) and Na(I), was checked, and the results revealed that this conjugate substance was highly selective to Cr(III). After washing with water in multiple cycles, the adsorbed material was regenerated with 0.1 M HCl and subsequently reused without deterioration in its case cavities. Interestingly, SiO₂-PYZ was highly effective against sulfate-reducing bacteria (SRB) in the petroleum field.     

Effect of zeolite pore morphology on solvent-less alkylation of benzene with 1-hexene

In an attempt to convert the carcinogenic benzene which is almost restricted for its use in gasoline, alkylation reaction with olefin 1-hexene has been conducted on various zeolites. Four zeolites having different pore topology and pore size have been applied as solid acid catalysts for effective production of alkylate in a liquid phase, solvent-less low temperature reaction. The textural properties of all the four zeolites (ZSM-5, MOR, BEA, HY) have been characterized for crystal morphology by TEM, crystal structure by XRD and FTIR, BET for surface area, N₂ sorption for porosity and TPD for acidity. Among the zeolite, BEA possessed high surface area (600.61 m²/g) and enhanced meso pores volume (0.3956 cm³/g) as compared to other zeolite samples. The performance of BEA was also observed to be superior in the liquid phase alkylation of benzene with 1-hexene in a batch reactor under autogenous pressure without using any solvent. At the optimum reaction conditions, the benzene conversion was 86.6 wt% and 3-Phenylhexane, 2-Phenylhexane yield were about 47.9 wt% and 38.7 wt% respectively on this catalyst. The BEA also exhibited longer time-on-stream and reusability performance, thus offers an attractive route for converting benzene into valuable (3-Phenylhexane, 2-Phenylhexane) alkylate product useful for the manufacturing of fine chemicals, dyestuff, detergents and scents.     

Constructing Intrapenetrated Hierarchical Zeolites with Highly Complete Framework via Protozeolite Seeding

Creation of intrapenetrated mesopores with open highway from external surface into the interior of zeolite crystals are highly desirable that can significantly improve the molecular transport and active sites accessibility of microporous zeolites to afford enhanced catalytic properties. Here, different from traditional zeolite-seeded methods that generally produced isolated mesopores in zeolites, nanosized amorphous protozeolites with embryo structure of zeolites were used as seeds for the construction of single-crystalline hierarchical ZSM-5 zeolites with intrapenetrated mesopores (mesopore volume of 0.51 cm³ g⁻¹) and highly complete framework. In this strategy, in contrast to the conventional synthesis, only a small amount of organic structure directing agents and a low crystallization temperature were adopted to promise the protozeolites as the dominant growth directing sites to induce crystallization. The protozeolite nanoseeds provided abundant nucleation sites for surrounding precursors to be crystallized, followed by oriented coalescence of crystallites resulting in the formation of intrapenetrated mesopores. The as-prepared hierarchical ZSM-5 zeolites exhibited ultra-long lifetime of 443.9 hours and a high propylene selectivity of 47.92 % at a WHSV of 2 h⁻¹ in the methanol-to-propylene reaction. This work provides a facile protozeolite-seeded strategy for the synthesis of intrapenetrated hierarchical zeolites that are highly effective for catalytic applications.     

壳壁上具有介孔的Si/Al复合氧化物中空微球的制备

近年来,由于中空的球形材料具有良好的表面渗透性、低密度和高比表面积等性质而受到人们的普遍关注,在无机中空球的制备过程中,所采用的方法大多为模板法,合成的无机中空球主要以SiO2、金属氧化物(如TiO2和SnO2等)及金属(金、银、钯和镍等)为主,而有关二元复合氧化物中空球合成的研究报道较少,制备球壳上具有介孔的中空球已有报道,但是,其得到的介孔常常不均一,因此,将中空球形材料、复合氧化物和均一介孔有效地结合起来将是非常有意义一项工作。     

Effect of mesopores on solidification of sirolimus self-microemulsifying drug delivery system

The mesoporous silica materials had a high loading efficiency of sirolimus-SMEDDS. The length of the mesopores played a more important role than the pore diameter in drug dissolution and in vivo absorption.     

Supercritical fluids in mesopores—new insight using NMR

Supercritical fluids are an essential constitute of modern chemical industry. However, their optimal use in processes involving porous solids is rather limited due to our poor knowledge about their transport properties under confinements. By using the non-invasive pulsed field gradient NMR method, we directly assessed molecular diffusivities of n-pentane in mesopores at sub- and supercritical temperatures. The obtained results ultimately point out that criticality in pores occurs at lower temperatures than in the bulk liquid surrounding the porous solid. The data on molecular diffusivities and pore density may be self-consistently quantified using simple gas-kinetic arguments.     

增强LPG催化裂化催化剂ZSM-5稳定性的新方法：脱铝和负载硅

以碳纳米管为模板合成的带有介孔和微孔的ZSM-5分子筛具有不同的复合结构。用三氯乙酸(TCA)可选择性地将中孔的铝脱除。基于TCA分子大小,它可能只扩散到中孔中,因而使得微孔部分不脱铝。从分子筛结构中脱除铝原子导致催化剂中出现中空的空间。若将硅原子填充到空位中,那么介孔部分的结构会变得与硅酸盐类似,不具有催化性能。本文使用含硅的溶液来填充空位,将硅原子直接取代中孔结构中的铝原子。通过此特殊方法改变微孔和介孔的几何形状和性质,从而使改性HZSM-5上的积碳量从14%降低至3%。     

Silica filled poly(4-methyl-2-pentyne) nanocomposite membranes: Similarities and differences with poly(1-trimethylsilyl-1-propyne)–silica systems

The performance of poly(4-methyl-2-pentyne) (PMP)/silica nanocomposites was studied for membranes with a filler content between 10 and 40 wt%. An increase in permeability and a constant vapor selectivity were measured with increasing filler content. The constant selectivity was in contrast to earlier published results for silica filled poly(1-trimethylsilyl-1-propyne) (PTSMP) membranes. Therefore, a comparison between both materials was made. Free volume sizes and interstitial mesopore sizes were determined by use of positron annihilation lifetime spectroscopy (PALS) and image analysis was performed on transmission electron microscopy (TEM) pictures of both materials. Although both materials possessed interstitial mesopores, a difference in membrane structure was noticed, explaining the difference in membrane performance.     

A review on the green synthesis of hierarchically porous zeolite

Conventional bottom-up and top-down methods for synthesizing hierarchical zeolite have led to complicated economic and environmental issues due to the requirement of expensive and hazardous organic molecules, the large amount of acid/base solution, high energy, and expensive starting materials. Besides, the bottom-up method through the hydrothermal crystallization evokes safety issues due to the high autogenous pressure. Accordingly, considerable efforts have been made to develop green route synthesis of hierarchical zeolite by eliminating the use of a solvent (solvent-free), utilizing sustainable starting materials and green secondary template (mesoporogen), as well as eliminating the use of mesoporogen (mesoporogen-free). Other routes, including recycling of mother liquor, steam-assisted conversion, gel-like-solid phase method, and silanization, are also elaborated, as they are reported to promote a green and facile approach for the synthesis of hierarchical zeolites. In this review, we provide recent progress on the development of the green synthesis of hierarchically porous zeolite.     

The effect of hydrothermal treatment on column performance for monolithic silica capillary columns

Monolithic silica capillary columns with i.d. 100 μm and monolithic silica rods were prepared with tetramethoxysilane (TMOS) or a mixture of TMOS and metyltrimethoxysilane (MTMS) using different hydrothermal treatments at T=80 °C or 120 °C. Nitrogen physisorption was applied for the pore characterization of the rods and inverse size exclusion chromatography (ISEC) for that of the capillary columns. Using nitrogen physisorption, it was shown change of pore size and surface area corresponds to that of hydrothermal treatment and silica precursor. The results from ISEC agreed well with those from nitrogen physisorption regarding the pore size distribution (PSD). In addition, the retention factors for hexylbenzene with the ODS-modified capillary columns in methanol/water=80/20 at T=30 °C could also support the results from nitrogen physisorption. Furthermore, column efficiency for the columns was evaluated with alkylbenzenes and three kinds of peptides, leucine-enkephalin, angiotensin II, and insulin. Column efficiency for alkylbenzenes was similar independently of the hydrothermal treatment at T=120 °C. Even for TMOS columns, there was no significant difference in column efficiency for the peptides despite the difference in hydrothermal treatment. In contrast, for hybrid columns, it was possible to confirm the effect on hydrothermal treatment at T=120 °C resulting in a different column efficiency, especially for insulin. This difference supports the results from both nitrogen physisorption and ISEC, showing the presence of more small pores of ca. 3-6 nm for a hybrid silica without hydrothermal treatment at T=120 °C. Consequently, the results suggest that hydrothermal treatment for a hybrid column with higher temperature or longer time is necessary, compared to that for a TMOS column, to provide higher column efficiency with increase in molecular size of solute.