Light alkanes in shale gas are an attractive source of carbon for the production of alkenes and aromatics compared to petroleum-derived naphtha. Zinc-exchanged zeolite H-MFI (Zn/ H-MFI) is active and selective for light alkane dehydrogenation and dehydroaromatization. In this study, Zn/H-MFI with varying Zn/Al ratios was prepared via solid-state ion exchange (SSIE) of ZnCl 2 and characterized by various methods. As-prepared Zn/H-MFI with Zn/Al ≤ 0.52 contains isolated [ZnCl] + and [ZnCl-(HCl)] + species; Zn/H-MFI with higher Zn loadings also contains ZnAl 2 O 4 /ZnAl 2 O 4−x Cl 2x nanoclusters. Postsynthetic treatment in He and subsequently in 2.5% H 2 in He at 773 K removes Cl and adsorbed HCl, resulting in the formation of [ZnH] + cations. Studies of C 3 H 8 dehydrogenation and cracking suggest that in the absence of cofed H 2 , [ZnH] + cations are transformed to bridging Zn 2+ cations, which exhibit higher C 3 H 8 dehydrogenation activity and selectivity relative to [ZnH] + cations. The kinetics of dehydrogenation and cracking over Zn/H-MFI were investigated as a function of Zn loading, C 3 H 8 partial pressure, and temperature. The turnover frequency for propane dehydrogenation and cracking increases with Zn loading, which we propose is due to localization of Zn 2+ cations either at increasingly distant pairs of Al atoms or at the β-site in the MFI framework. The selectivity to dehydrogenation over cracking over Zn 2+ is independent of C 3 H 8 partial pressure and temperature, consistent with dehydrogenation and cracking pathways that proceed via a common surface intermediate and have similar enthalpies of activation. The product distribution is thus determined by the entropy of activation for each pathway, which is less negative in the case of C 3 H 8 dehydrogenation.

Catalysts for hydroformylation of ethene were prepared by grafting Rh into nests of �SiOZn−OH or �SiOCo−OH species prepared in dealuminated BEA zeolite. X-ray absorption spectra and infrared spectra of adsorbed CO were used to characterize the dispersion of Rh. The Rh dispersion was found to increase markedly with increasing M/Rh (M = Zn or Co) ratio; further increases in Rh dispersion occurred upon use for ethene hydroformylation catalysis. The turnover frequency for ethene hydroformylation measured for a fixed set of reaction conditions increased with the fraction of atomically dispersed Rh. The ethene hydroformylation activity is 15.5-fold higher for M = Co than for M = Zn, whereas the propanal selectivity is slightly greater for the latter catalyst. The activity of the Co-containing catalyst exceeds that of all previously reported Rhcontaining bimetallic catalysts. The rates of ethene hydroformylation and ethene hydrogenation exhibit positive reaction orders in ethene and hydrogen but negative orders in carbon monoxide. In situ IR spectroscopy and the kinetics of the catalytic reactions suggest that ethene hydroformylation is mainly catalyzed by atomically dispersed Rh that is influenced by Rh−M interactions, whereas ethene hydrogenation is mainly catalyzed by Rh nanoclusters. In situ IR spectroscopy also indicates that the ethene hydroformylation is rate limited by formation of propionyl groups and by their hydrogenation, a conclusion supported by the measured H/D kinetic isotope effect. This study presents a novel method for creating highly active Rh-containing bimetallic sites for ethene hydroformylation and provides new insights into the mechanism and kinetics of this process.

Because of their relatively low cost, ethane and propane derived from shale gas are the currently preferred feedstocks for the production of aromatics. Ga-exchanged H-MFI zeolite (Ga/H-MFI) exhibits high activity and selectivity for light alkane dehydroaromatization, a process that involves alkane dehydrogenation to form alkenes, followed by alkene oligomerization and cyclization, and further dehydrogenation of the resulting products. Recent work has shown (Phadke et al. Characterization of Isolated Ga3+ Cations in Ga/H-MFI Prepared by Vapor-Phase Exchange of H-MFI Zeolite with GaCl3. ACS Catal. 2018, 8, 6106–6126; Phadke et al. Mechanism and Kinetics of Propane Dehydrogenation and Cracking over Ga/H-MFI Prepared via Vapor-Phase Exchange of H-MFI with GaCl3. J. Am. Chem. Soc. 2019, 141, 1614–1627; Phadke et al. Mechanism and Kinetics of Light Alkane Dehydrogenation and Cracking over Isolated Ga Species in Ga/H-MFI. ACS Catal. 2021, 11, 2062–2075; Mansoor et al. ACS Catal. 2018, 8, 2146–6162) that Ga3+ ([GaH]2+ and [Ga(H)2]+) sites catalyze the initial dehydrogenation of alkanes; however, the role of Ga3+ sites in the subsequent alkene oligomerization step requires clarification. In this work, the kinetics of ethene oligomerization over Ga/H-MFI were investigated as a function of Ga loading, feed space time, temperature, and ethene partial pressure. The presence of Ga3+ sites gives rise to enhanced rates of ethene oligomerization and higher selectivities to butene and hexene relative to H-MFI. However, selective titration of Brønsted acid sites with NH3 reveals that, in the absence of Brønsted acid sites, [GaH]2+ and [Ga(H)2]+ cations do not contribute appreciably to the higher activity of Ga/H-MFI. Similarly, in situ Fourier-transform infrared spectroscopy shows that the reaction pathway for ethene oligomerization over Ga/H-MFI involves the same intermediates as that over H-MFI. The higher ethene oligomerization activity and selectivity to even-carbon-numbered alkenes of Ga/H-MFI stems from cooperative effects between Ga3+ sites and Brønsted acid protons.

Tubular grafts were fabricated from blends of polycaprolactone (PCL) and poly(glycolide -co-caprolactone) (PGC) polymers and coated with an extracellular matrix containing collagens, laminin, and proteoglycans, but not growth factors (HuBiogel™). Multifunctional scaffolds from polymer blends and membrane proteins provide the necessary biomechanics and biological functions for tissue regeneration. Two crosslinking agents, a natural crosslinker namely genipin (Gp) and a carbodiimide reagent namely 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), were used for further stabilizing the protein matrix and the effect of crosslinking was evaluated for structural, morphological, mechanical properties using SEM, DSC and DMA. SEM images and fiber diameter distribution showed fiber-size between 0.2 µm to 1 µm with the majority of fiber diameters being under 500 nm, indicating upper range of protein fiber-sizes (for example, collagen fibers in extracellular matrix are in 50 to 500 nm diameter range). HB coating did not affect the mechanical properties, but increased its hydrophilicity of the graft. Overall data showed that PCL/PGC blends with 3:1 mass ratio exhibited mechanical properties comparable to those of human native arteries (tensile strength of 1–2 MPa and Young’s modulus of <10 MPa). Additionally, the effect of crosslinking on coating stability was investigated to assure the retention of proteins on scaffold for effective cell-matrix interactions.