Nanocrystalline Sn-Beta zeolites have been successfully prepared via an improved two-step postsynthesis strategy, which consists of creating vacant T sites with associated silanol groups by dealumination parent H-Beta and subsequent dry impregnation the resulting Si-Beta organometallic dimethyltin dichloride. Characterization results from UV–vis, XPS, Raman, 119Sn solid-state MAS NMR reveal that most Sn species incorporated into framework Beta zeolite through process exist as isolated...

SAPO-34 materials with comparable Brønsted acid site density but different crystal sizes were applied as methanol-to-olefin (MTO) catalysts to elucidate the effect of size on their deactivation behaviors. 13C HPDEC MAS NMR, FTIR, and UV/vis spectroscopy employed monitor formation nature organic deposits, densities accessible sites active hydrocarbon-pool species studied a function time-on-stream (TOS) by 1H NMR spectroscopy. The above-mentioned spectroscopic methods gave very complex picture...

Little is known on the early stages of methanol-to-olefin (MTO) conversion over H-SAPO-34, before steady-state with highly active polymethylbenzenium cations as most important intermediates reached. In this work, formation and evolution carbenium ions during MTO a H-SAPO-34 model catalyst were clarified via 1H MAS NMR 13C NMR. Several initial species (i.e., three-ring compounds, dienes, polymethylcyclopentenyl, polymethylcyclohexenyl cations) were, for first time, directly verified...

Mesoporous Zr-Beta exhibits a remarkable catalytic activity and regio-selectivity to β-amino alcohols in epoxide aminolysis. Intra-crystalline mesopores greatly promote the reaction through enhanced mass transfer suppress deactivation.

Abstract Nearly all atoms contributing to the local structure of Br⊘nsted acid sites in zeolites exhibit isotopes accessible for multinuclear solid-state nuclear magnetic resonance (NMR) investigations. Therefore, last 15 years, NMR spectroscopy has found numerous applications determination types hydroxyl proton zeolites, their concentration, accessibility, and mobility, characterization strength structure. It allows study role groups formation adsorbate complexes heterogeneously catalyzed...

[Reaction: see text]. A solid understanding of the mechanisms involved in heterogeneously catalyzed reactions is fundamental interest for modern chemistry. This information can help to refine theories catalysis and, a very practical way, researchers optimize existing industrial processes and develop new ones. To understand heterogeneous catalysis, we need observe identify reaction intermediates on working catalyst. Motivated by this goal, have monitored catalytic events systems using situ...

Recent progress reveals that, in the methanol-to-olefin (MTO) process on acidic zeolites, conversion of an equilibrium mixture methanol and DME is dominated by a "hydrocarbon pool" mechanism. However, initial C-C bond formation, that is, chemistry during kinetic "induction period" leading to reactive hydrocarbon pool, still remains unclear. With application stopped-flow protocol, present work, pure surface methoxy groups [SiO(CH(3))Al] were prepared various zeolite catalysts (H-Y, H-ZSM-5,...

The development of new solid catalysts for use in industrial chemistry has hitherto been based to a large extent upon the empirical testing wide range different materials. In only few exceptional cases success achieved understanding overall, usually very complex mechanism chemical reaction through elucidation individual intermediate aspects heterogeneously catalyzed reaction. With modern approach combinatorial catalysis it is now possible prepare and test much more rapidly materials within...

On weakly rehydrated dealuminated zeolites and amorphous silica–aluminas the presence of different types acidic centres can be ascertained by proton magic-angle spinning nuclear magnetic resonance (1H MAS NMR) measurements. A 1H NMR line at ca. 6.5 ppm is caused water adsorption on Lewis-acid sites. The shift Brønsted-acid sites (bridging OH groups) to lower field for hydrated samples interpreted quantitatively a fast exchange between molecules, bridging groups hydroxonium ions.

The in situ preparation and isolation of surface methoxy species on acidic zeolites are followed by further investigations their reactivity heterogeneously catalyzed reactions. For the first time, following solid-state NMR evidence for high has been obtained: (i) Surface react readily with ammonia at room temperature, which methylamines methylammonium cations formed. (ii) transformation to other alkoxy can be achieved reaction corresponding alkyl halides zeolites. (iii) hydrochloride, giving...

Ti-Beta zeolite prepared <italic>via</italic> a reproducible and scalable two-step post-synthesis strategy is robust catalyst for the epoxidation of unsaturated ketones with hydrogen peroxide.

Silicoaluminophosphates (SAPO) with different framework structures and amounts of Brønsted acid sites, that is, SAPO-34, SAPO-41, SAPO-11, SAPO-46, were synthesized studied as catalysts for the methanol-to-olefin (MTO) conversion. Besides well-known SAPO-34 catalyst, also SAPO-41 exhibits a good MTO performance methanol conversion 100% selectivity to light olefins about 70% at reaction temperature 723 K, which maintains up time-on-stream 10 h. The sites silicoaluminophosphate employed in...

Selective dehydration of glycerol, a byproduct from the biodiesel industry, on solid acids is an important reaction in production value-added chemical acrolein for economic-sustainable biorefinery. Most efforts have been made development strong Brønsted acid sites (BAS) to improve acrolein, because Lewis (LAS) generally promote generation acetol. However, exclusively tuning properties BAS or LAS did not well-promote glycerol as indicated this work. We provide new route efficient and...

Bifunctional Zn–Y/Beta catalyst was applied in the reaction mechanism study of ethanol to butadiene conversion clarify roles Zn and Y functional sites each individual step. According results several complementary methods, i.e., temperature-programmed desorption (TPD), surface (TPSR), situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), network consisting key steps, dehydrogenation, acetaldehyde aldol condensation, crotonaldehyde reduction, elucidated. An enolization...

Ga-modified nano H-ZSM-5 zeolites with different Ga contents were prepared and applied as methanol-to-aromatics (MTA) catalysts. The introduction can strongly increase the selectivity to aromatics but also decrease catalyst lifetime simultaneously. Upon cofeeding of n-butanol methanol, a significant prolongation from 18 ca. 50 h be achieved. According several spectroscopic results, e.g., TGA, GC–MS, in situ UV/vis, solid-state MAS NMR spectroscopy, addition during MTA conversion shows no...

We report a heterogeneous catalysis strategy to the sustainable hydration of epoxides by designing robust Lewis acid catalysts confined in zeolite cages as natural shape-selective nanoreactors. In case ethylene oxide hydration, Sn-H-SSZ-13 exhibits remarkable catalytic performance, with an conversion above 99% and monoethylene glycol selectivity 99%, at approaching stoichiometric water/ethylene ratios near-ambient reaction temperatures. It is revealed theoretical studies that partially...

A variety of Sn-containing Beta zeolites possessing framework or extraframework Sn sites were prepared by a two-step postsynthesis procedure. The nature these species was systematically investigated several approaches, including DRIFT, XPS, UV–vis, and solid-state 119Sn MAS NMR spectroscopy. subtle distinctions the Lewis acidic features between identified via acetone-2-13C, TMPO, NH3 adsorption, studied 13C, 31P, 1H spectroscopy, respectively. Two types acid (LAS) have been observed...

The formation of the initial carbon–carbon (C–C) bonds in methanol-to-hydrocarbon (MTH) conversion on acidic zeolite has been hotly debated for decades. Recently, surface-bound acetyl groups involving C–C during period MTH disclosed. Understanding exact bond-containing intermediates triggering and critical roadmap is essential further development this important reaction. Herein, acetaldehyde from hydrogenation species was identified to be responsible H-ZSM-5 zeolite. By combining kinetic...