Influence of the Reaction Temperature on the Nature of the Active and Deactivating Species During Methanol-to-Olefins Conversion over H-SAPO-34.

The selectivity toward lower olefins during the methanol-to-olefins conversion over H-SAPO-34 at reaction temperatures between 573 and 773 K has been studied with a combination of operando UV-vis diffuse reflectance spectroscopy and online gas chromatography. It was found that the selectivity toward propylene increases in the temperature range of 573-623 K, while it decreases in the temperature range of 623-773 K. The high degree of incorporation of olefins, mainly propylene, into the hydrocarbon pool affects the product selectivity at lower reaction temperatures. The nature and dynamics of the active and deactivating hydrocarbon species with increasing reaction temperature were revealed by a non-negative matrix factorization of the time-resolved operando UV-vis diffuse reflectance spectra. The active hydrocarbon pool species consist of mainly highly methylated benzene carbocations at temperatures between 573 and 598 K, of both highly methylated benzene carbocations and methylated naphthalene carbocations at 623 K, and of only methylated naphthalene carbocations at temperatures between 673 and 773 K. The operando spectroscopy results suggest that the nature of the active species also influences the olefin selectivity. In fact, monoenylic and highly methylated benzene carbocations are more selective to the formation of propylene, whereas the formation of the group of low methylated benzene carbocations and methylated naphthalene carbocations at higher reaction temperatures (i.e., 673 and 773 K) favors the formation of ethylene. At reaction temperatures between 573 and 623 K, catalyst deactivation is caused by the gradual filling of the micropores with methylated naphthalene carbocations, while between 623 and 773 K the formation of neutral poly aromatics and phenanthrene/anthracene carbocations are mainly responsible for catalyst deactivation, their respective contribution increasing with increasing reaction temperature. Methanol pulse experiments at different temperatures demonstrate the dynamics between methylated benzene and methylated naphthalene carbocations. It was found that methylated naphthalene carbocations species are deactivating and block the micropores at low reaction temperatures, while acting as the active species at higher reaction temperatures, although they give rise to the formation of extended hydrocarbon deposits.

Nano Cu metal doped on TiO2-SiO2 nanoparticle catalysts in photocatalytic degradation of direct blue dye.

The photo-assisted deposition (PAD) and impregnation (Img) synthesis of nano-sized Cu metal on TiO2-SiO2 are reported. The prepared catalysts were characterized by different techniques such as XRD, EXAFS, TEM and nitrogen adsorption analysis. Photocatalytic reactivity using Cu-TiO2-SiO2 catalysts under visible-light condition on the oxidation of direct blue dye with O2 reaction was evaluated. The results have shown notable photocatalytic activity of PAD-Cu/TiO2-SiO2 which was 1.6 and 10 times higher than that of Img-Cu/TiO2-SiO2 and TiO2-SiO2, respectively.

An eco-friendly N-sulfonylation of amines using stable and reusable Zn-Al-hydrotalcite solid base catalyst under ultrasound irradiation.

Synthetic nanosized Zn-Al-hydrotalcite (Zn-Al-HT) with 20 nm crystallite size and 61 m(2)/g BET-surface area is found to be a mild and efficient catalyst for N-sulfonylation of amines in quantitative yields under ultrasound irradiation. Exclusive synthesis of sulfonamides, using Zn-Al-HT, under ultrasound irradiation, was realized by compatible basic sites of catalyst used. The products were isolated after simple work-up in high yields and purity.