The intermediates formed upon the interaction of methane with Cu-modified ZSM-5 zeolites (Cu/H-ZSM-5) have been analyzed solid-state NMR spectroscopy and DFT methods. Methane activation by Cu/H-ZSM-5 gives rise to three distinct surface methoxy-like species (−O–CH3) detected 13C MAS specific chemical shifts in range 53–63 ppm. calculations on representative cluster models different sites potentially present used assign these signals (i) methanol adsorbed two neighboring Cu (Cu–(HOCH3)–Cu,...

Cu‐modified zeolites provide methane conversion to methanol with high selectivity under mild conditions. The activity of different possible Cu‐sites for transformation is still discussion. Herein, ZSM‐5 zeolite has been loaded Cu2+ cations (1.4 wt% Cu) as characterized by UV–vis DRS, EPR, EXAFS, and 1H MAS NMR. It inferred that cations, attached the cation‐exchange Al–O––Si sites framework, can exist in form either isolated or paired sites. on these verified observation methoxy species...

Plastic waste is a major environmental issue; converting it directly into valuable chemicals by using catalysts promising alternative to plastic recycling. Here, we report the selective catalytic cracking of polypropylene (PP), typical commodity plastic, high-value light olefins (C2–C5), below pyrolytic temperature (290 °C) and without external hydrogen supply, zeolite catalysts. Among H+-form zeolites with different structures, HMFI showed highest yields hydrocarbons which (C2–C5) were...

The analysis of n-but-1-ene transformation on Zn-modified zeolite H-BEA, containing zinc exclusively in the form either Zn2+ cations (Zn2+/H-BEA sample) or small clusters ZnO (ZnO/H-BEA sample), has been performed with 13C solid-state nuclear magnetic resonance (NMR) at 296–673 K. number intermediates, including π-complex n-but-2-ene, methylallylzinc, and delocalized carbanionic species formed by interaction oligomeric polyenes Zn sites, have identified for both samples. Methyl-substituted...

Cu-modified zeolites have enormous potential as the catalysts facilitating conversion of methane to methanol. It becomes important investigate active sites and reaction mechanisms involved. In this paper, several spectroscopic methods such UV-vis diffuse reflectance spectroscopy (UV-vis DRS), pulse electron paramagnetic resonance (EPR), Fourier transform infrared spectroscopy, solid-state (13C MAS) NMR been employed characterize state Cu intermediates formed during catalyst activation...

The stoichiometric conversion of methane to methanol by Cu-exchanged zeolites can be brought highest yields the presence extraframework Al and high CH4 chemical potentials. Combining theory experiments, differences in reactivity monometallic Cu-oxo bimetallic Cu-Al-oxo nanoclusters stabilized zeolite mordenite (MOR) are investigated. Cu-L3 edge X-ray absorption near-edge structure (XANES), infrared (IR), ultraviolet-visible (UV-vis) spectroscopies, combination with oxidation activity tests,...

With regard to possible involvement of zeolite Brønsted acid sites (BAS) in the activation methane molecules for transformation methanol, effect different Cu(II) species loaded on kinetic parameters reaction H/D hydrogen exchange alkane with BAS Cu-modified ZSM-5 zeolites has been investigated 1H MAS NMR situ at 533–563 K. It is found that acceleration by 1 order magnitude occurs containing Cu2+ cations (Z2Cu(II) sites) or [Cu3(μ-O)3]2+ oxo-clusters (Z2[Cu3(μ-O)3] compared pure H-form...

Rational plastic recycling is critical for addressing the environmental challenges associated with waste. Among various methods, chemical recycling, particularly via homogeneous catalysis, holds promise converting waste into valuable products. Post-consumer polymer wastes could present a challenge catalytic upcycling due to structural inhomogeneity and functionalization of polyolefin chains. The impact substrate aging on performance catalyst can be viewed as an "inverse problem"...

Selective dimerization of ethene to 2-butene on Zn2+-containing ZSM-5 zeolite (Zn2+/ZSM-5) at 296–523 K has been discovered. The intermediate but-3-en-1-ylzinc species is identified with 13C CP/MAS NMR and Fourier transform infrared spectroscopy. density functional theory study two alternative pathways reveals that the formed involvement saturated bridged dimeric Zn–(CH2)4–O species. It also shown conversion increases increase in quantity Brønsted acid sites Zn2+/ZSM-5 zeolite; however,...

The reactivity theories and characterization studies for metal-containing zeolites are often focused on probing the metal sites. We present a detailed computational study of Zn-modified BEA zeolite towards C-H bond activation methane molecule as model system that highlights importance representing active site whole reactive ensemble integrating extra-framework ZnEF2+ cations, framework oxygens (OF2-), confined space pores. demonstrate our relationship between Lewis acidity, defined by probe...

The influence of the model and method choice on DFT predicted 13C NMR chemical shifts zeolite surface methoxide species has been systematically analyzed. Twelve shift calculation protocols full periodic hybrid periodic-cluster calculations with varied structural relaxation procedures are examined. primary assessment accuracy computational carried out for Si-O(CH3)-Al in ZSM-5 well-defined experimental parameters (chemical shift, δ(13C) value) as a reference. Different configurations these...

Sulfated zirconium oxide (SZO) catalyzes the hydrogenolysis of isotactic polypropylene (iPP, Mn = 13.3 kDa, Đ 2.4, 94 %) or high-density polyethylene (HDPE, 2.5 3.6) to branched alkane products. We propose that this reactivity is driven by pyrosulfate sites SZO, which open under mild reaction conditions transiently form adsorbed SO3 and sulfate groups. This a very strong Lewis acid binds 15N-pyridine tri-ethylphosphineoxide (TEPO) (Eads > –39 kcal mol-1), reacts with Ph3CH Ph3C+, mediates...

Sulfated zirconium oxide (SZO) catalyzes the hydrogenolysis of isotactic polypropylene (iPP, Mn = 13.3 kDa, Đ 2.4, 94 %) or high-density polyethylene (HDPE, 2.5 3.6) to branched alkane products. We propose that this reactivity is driven by pyrosulfate sites SZO, which open under mild reaction conditions transiently form adsorbed SO3 and sulfate groups. This a very strong Lewis acid binds 15N-pyridine tri-ethylphosphineoxide (TEPO) (Eads > –39 kcal mol-1), reacts with Ph3CH Ph3C+, mediates...

Organic electrochemistry is currently experiencing an era of renaissance, which closely related to the possibility carrying out organic transformations under mild conditions, with high selectivity, yields, and without use toxic solvents. Combination alternative approaches, such as photo-chemistry was found have great potential due induced synergy effects. In this work, we propose for first time utilization plasmon triggering enhanced regio-controlled chemical transformation performed in...

Some of our recent developments and applications algorithmic graph theory for extracting the physical chemical properties materials from molecular dynamics simulations are presented.

Sulfated zirconium oxide (SZO) catalyzes the hydrogenolysis of isotactic polypropylene (iPP, Mn = 13.3 kDa, Đ 2.4, <mmmm> 94 %) or high‐density polyethylene (HDPE, 2.5 3.6) to branched alkanes. We propose that this reactivity is driven by pyrosulfate sites SZO, which open under mild reaction conditions transiently form adsorbed SO3 and sulfate. This a very strong Lewis acid binds 15N‐pyridine triethylphosphineoxide (TEPO) (DEads > –39 kcal mol‐1), reacts with Ph3CH Ph3C+, mediates...

Sulfated zirconium oxide (SZO) catalyzes the hydrogenolysis of isotactic polypropylene (iPP, Mn = 13.3 kDa, Đ 2.4, <mmmm> 94 %) or high‐density polyethylene (HDPE, 2.5 3.6) to branched alkanes. We propose that this reactivity is driven by pyrosulfate sites SZO, which open under mild reaction conditions transiently form adsorbed SO3 and sulfate. This a very strong Lewis acid binds 15N‐pyridine triethylphosphineoxide (TEPO) (DEads > –39 kcal mol‐1), reacts with Ph3CH Ph3C+, mediates...

13C MAS NMR spectroscopy is a powerful technique to study the mechanisms of hydrocarbon transformations on heterogeneous catalysts. It can reliably identify surface intermediates and adsorbed products based analysis their chemical shifts, δ(13C). However, unambiguous assignment detected signals always challenge due uncertainty nature formed mechanism species interaction with active sites. The way solve this problem application DFT calculations predict shifts for expected intermediate...