Kinetic Behavior of Quaternary Ammonium Hydroxides in Mixed Methane and Carbon Dioxide Hydrates

This study evaluates the kinetic hydrate inhibition (KHI) performance of four quaternary ammonium hydroxides (QAH) on mixed CH4 + CO2 hydrate systems. The studied QAHs are; tetraethylammonium hydroxide (TEAOH), tetrabutylammonium hydroxide (TBAOH), tetramethylammonium hydroxide (TMAOH), and tetrapropylammonium hydroxide (TPrAOH). The test was performed in a high-pressure hydrate reactor at temperatures of 274.0 K and 277.0 K, and a concentration of 1 wt.% using the isochoric cooling method. The kinetics results suggest that all the QAHs potentially delayed mixed CH4 + CO2 hydrates formation due to their steric hindrance abilities. The presence of QAHs reduced hydrate formation risk than the conventional hydrate inhibitor, PVP, at higher subcooling conditions. The findings indicate that increasing QAHs alkyl chain lengths increase their kinetic hydrate inhibition efficacies due to better surface adsorption abilities. QAHs with longer chain lengths have lesser amounts of solute particles to prevent hydrate formation. The outcomes of this study contribute significantly to current efforts to control gas hydrate formation in offshore petroleum pipelines.

Facile Preparation of a Binderless Hierarchical Beta Zeolite in Shaped Form and with Improved Acidity for Catalysis

<div> <div> <div> <div> <p>The synthesis of a technical hierarchical nanosized zeolite catalysts without growth modifiers and binders remains a major challenge in catalysis. Herein, we report a new synthetic approach to directly produce hierarchical nanosized Beta zeolites in technical form, without any binders in the final material. The synthesis consists of two steps, where a Beta zeolite powder is first shaped using tetraethyl orthosilicate; the extrude is then recrystallized at high temperature in the presence of tetraethylammonium hydroxide solution. This transforms the SiO2 binders into zeolite framework. A variety of characterization methods were applied to unlock structure-properties relationships of the materials and demostrate their catalytic functionality. We believe that this work opens avenues for the advanced manufacturing of hierarchical zeolite materials in shaped form, and will find useful applications in catalysis and materials science. </p> </div> </div> </div> </div>

Facile Preparation of a Binderless Hierarchical Beta Zeolite in Shaped Form and with Improved Acidity for Catalysis

<div> <div> <div> <div> <p>The synthesis of a technical hierarchical nanosized zeolite catalysts without growth modifiers and binders remains a major challenge in catalysis. Herein, we report a new synthetic approach to directly produce hierarchical nanosized Beta zeolites in technical form, without any binders in the final material. The synthesis consists of two steps, where a Beta zeolite powder is first shaped using tetraethyl orthosilicate; the extrude is then recrystallized at high temperature in the presence of tetraethylammonium hydroxide solution. This transforms the SiO2 binders into zeolite framework. A variety of characterization methods were applied to unlock structure-properties relationships of the materials and demostrate their catalytic functionality. We believe that this work opens avenues for the advanced manufacturing of hierarchical zeolite materials in shaped form, and will find useful applications in catalysis and materials science. </p> </div> </div> </div> </div>

Influence of Aluminum Sources on Synthesis of SAPO-34 and NH3-SCR of NOx by as-Prepared Cu/SAPO-34 Catalysts

The full article will be published in the English version of the journal "Catalysis in Industry" No. 1, 2021.The synthesis of the microporous SAPO-34 molecular sieve goes from a combination of three templates: triethylamine, tetraethylammonium hydroxide, and morpholine under hydrothermal conditions. Two aluminum sources, namely aluminum hydroxide, and aluminum isopropoxide, were used exclusively to synthesize SAPO-34 zeolites. The effects of aluminum sources on the crystallization and physicochemical properties of SAPO-34 were studied thoroughly. The synthesized samples were characterized by using different characterization methods, including XRD, FE-SEM, N2 isotherm, EDS, and NH3-TPD. The results illustrate that the various sources of aluminum used for the synthesis of SAPO-34 materials extremely affect the crystallinity, morphology, and density of acid sites. Besides, the influence of aluminum sources on the performance of NH3-SCR technology was studied with Cu/SAPO-34 catalysts in a fixed-bed flow reactor. The two Cu/SAPO-34 catalysts promoted different NO and NH3 conversions between 200–600 °C though they share similar Cu content, which was loaded by the ion-exchange method in aqueous solution. In addition, the different Cu species in the two catalyst samples are surveyed by H2-TPR, while the EPR method is also used to assess the coordination of the copper element in the two catalysts.

SYNTHESIS OF THE ZSM-5 ZEOLITE WITH MIXTURES BINARY OF TETRAETHYLAMMONIUM HYDROXIDE AND AMINES AS ORGANIC STRUCTURE DIRECTING AGENTS

Among the microporous materials used in heterogeneous catalysis, zeolites have become promising due to the relevant physicochemical and catalytic properties. Noteworthy is the zeolite ZSM-5 used as a catalyst in reactions in the areas of petrochemical and fine chemistry, such as cracking, isomerization, alkylation and aromatization reactions of olefins. In view of this, the objective of this work was to synthesize the ZSM-5 zeolite, through binary mixtures of tetraethylammonium hydroxide (TEAOH) and different amines (n-butylamine, isobutylamine and diisobutylamine) acting as organic structure directing agents (SDA's). X-ray diffractometry indicated that only the reaction system containing TEAOH and n-butylamine provided the achievement of highly crystalline ZSM-5 and without competing phases. The nitrogen adsorption-desorption isotherms indicated that a material with a high surface area (329 m2·g-1) and pore volume (0.26 cm3·g-1) was obtained. Thus, it was possible to identify a new synthesis route in obtaining the ZSM-5 zeolite.

Catalytic conversion of glucose in fructose utilizing high-silica zeolite Sn-ZSM-12

Tin incorporation in high-silica ZSM-12 zeolite was evaluated using different concentrations of tin and different structure-directing agents (SDA), in order to be used in the glucose isomerization reaction in fructose. The tetraethylammonium hydroxide SDA successfully formed the structure of the high silica zeolite ZSM-12; however, in this system, the addition of Sn prevented the formation of the ZSM-12 zeolite. Therefore, tetraethylammonium bromide was used as SDA, but the syntheses of high-silica ZSM-12 zeolite without and with tin incorporation were not effective. Then methyltriethylammonium chloride was used as SDA, and the high-silica ZSM-12 structure was formed only with the incorporation of tin. The samples with ZSM-12 structure and different concentrations of tin were evaluated in reaction of glucose conversion to fructose. It was found that the sample with the lowest tin content ( Sn / Si = 0 . 005 ) achieved the highest glucose conversion and the highest fructose yield.

Copper-Iron Bimetal Ion-Exchanged SAPO-34 for NH3-SCR of NOx

SAPO-34 was prepared with a mixture of three templates containing triethylamine, tetraethylammonium hydroxide, and morpholine, which leads to unique properties for support and production cost reduction. Meanwhile, Cu/SAPO-34, Fe/SAPO-34, and Cu-Fe/SAPO-34 were prepared through the ion-exchanged method in aqueous solution and used for selective catalytic reduction (SCR) of NOx with NH3. The physical structure and original crystal of SAPO-34 are maintained in the catalysts. Cu-Fe/SAPO-34 catalysts exhibit high NOx conversion in a broad temperature window, even in the presence of H2O. The physicochemical properties of synthesized samples were further characterized by various methods, including XRD, FE-SEM, EDS, N2 adsorption-desorption isotherms, UV-Vis-DRS spectroscopy, NH3-TPD, H2-TPR, and EPR. The best catalyst, 3Cu-1Fe/SAPO-34 exhibited high NOx conversion (> 90%) in a wide temperature window of 250–600 °C, even in the presence of H2O. In comparison with mono-metallic samples, the 3Cu-1Fe/SAPO-34 catalyst had more isolated Cu2+ ions and additional oligomeric Fe3+ active sites, which mainly contributed to the higher capacity of NH3 and NOx adsorption by the enhancement of the number of acid sites as well as its greater reducibility. Therefore, this synergistic effect between iron and copper in the 3Cu-1Fe/SAPO-34 catalyst prompted higher catalytic performance in more extensive temperature as well as hydrothermal stability after iron incorporation.