Precisely tailoring the distance between adjacent metal sites to match adsorption configurations of key species for the targeted reaction pathway is a great challenge in heterogeneous catalysis. Here, we report a proof‐of‐concept study on the atomically sites‐tailored pathway in Pd‐catalyzed acetylene hydrogenation, i.e., increasing the distance of adjacent Pd atoms (dPd‐a‐Pd) for configuration matching in acetylene semi‐hydrogenation against coupling. dPd‐a‐Pd is identified as a structural descriptor for describing the competitiveness for reaction pathways, and the increased dPd‐a‐Pd prefers the semi‐hydrogenation pathway due to simultaneously promoted C2H4 desorption and the destabilized transition state of the C2H3* coupling. Spectroscopic, kinetics and electronic structure studies reveal that increasing dPd‐a‐Pd to 3.31 Å delivers superior selectivity and stability due to energy matching and appropriate hybridization of Pd 4d with In 2s and, especially, 2p orbitals.
Precisely tailoring the distance between adjacent metal sites to match adsorption configurations of key species for the targeted reaction pathway is a great challenge in heterogeneous catalysis. Here, we report a proof-of-concept study on the atomically sites-tailored pathway in Pd-catalyzed acetylene hydrogenation, i.e., increasing the distance of adjacent Pd atoms (d Pd-a-Pd ) for configuration matching in acetylene semi-hydrogenation against coupling. d Pd-a-Pd is identified as a structural descriptor for describing the competitiveness for reaction pathways, and the increased d Pd-a-Pd prefers the semi-hydrogenation pathway due to simultaneously promoted C 2 H 4 desorption and the destabilized transition state of the C 2 H 3 * coupling. Spectroscopic, kinetics and electronic structure studies reveal that increasing d Pd-a-Pd to 3.31 Å delivers superior selectivity and stability due to energy matching and appropriate hybridization of Pd 4d with In 2s and, especially, 2p orbitals.
Starbucks has a lot of loyal consumers from all over the world. There are some reasons that consumers tend to purchase at Starbucks. This study examines the influences of brand reputation on customer satisfaction in Starbucks, Malaysia. The study adopted a survey research design. The method of data collection in this study are internet sources and questionnaires. A total of 100 respondents participated in this survey. The data were analyzed with descriptive statistics and inferential statistics. From the findings of the study, we find out that the aspects of brand reputation influence and correlate to customer satisfaction in Starbucks, Malaysia. Besides, some recommendations for Starbucks' improvement can be obtained through the findings.
Polyethylene terephthalate (PET) hydrogenolysis can produce benzene, toluene, and xylene (BTX), where the selectivity control is challenging. We report a reaction pathway dictated by the Ru coordination environment by examining the binding geometries of adsorbates on differently coordinated Ru centers and their evolution during PET hydrogenolysis. A BTX yield of 77 % was obtained using a Ru/TiO2 with a Ru coordination number of ca. 5.0 where edge/corner sites are dominant, while more gas and saturated products were formed for Ru/TiO2 containing primarily terrace sites. Density functional theory and isotopic labelling revealed that under‐coordinated Ru edge sites favor “upright” adsorption of aromatic adsorbates while well‐coordinated Ru sites favor “flat‐lying” adsorption, where the former mitigates ring hydrogenation and opening. This study demonstrates that reaction pathways can be directed through controlled reactant/intermediate binding via tuning of the Ru coordination environment for efficient conversion of PET to BTX.
Semihydrogenations of alkynes and alkadienes to light
olefins catalyzed
by a heterogeneous catalyst are widely applied in the chemical industry,
but it remains challenging to design high-performance catalysts for
these processes. The well-developed synthesis methodologies, characterization
techniques for catalyst structures, and theoretical calculations in
recent decades render opportunities for understanding mechanisms and
elaborating the structures of active sites at the atomic level. This
Review summarizes recent advances in the mechanistic and atomic-level
insights into semihydrogenation catalysis for alkynes and alkadienes
to light olefins. The structure-sensitivity, information on active
sites, and reaction kinetics are initially discussed to demonstrate
the knowledge on the mechanistic and kinetics details of the hydrogenations
of alkynes and alkadienes. We then introduce the regulations for the
active sites, especially at the atomic level, based on three categories,
i.e., site-isolation, local environment regulation, and oxygen vacancy
and interfacial sites. Followed by the discussion on the conventional
thermocatalytic hydrogenations, the emerging photocatalytic and electrocatalytic
semihydrogenations of alkynes and alkadienes are further covered.
Finally, we provide a brief overview on the current status of this
field and a perspective for future study on the atomic-level design
and regulation of catalysts for controlling the selectivity to target
products.
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