Selective hydrogenation of acetylene over Pd on glass fiber catalysts

Key properties of silicate glasses are highlighted including the capability of stabilizing disperse Pd nanoparticles in the bulk of glass fibers (GF), high solubility of acetylene and hydrogen, as well as their high mobility. These properties provide the high activity and selectivity of Pd/GF catalysts to hydrogenation of acetylene in excess ethylene over a wide range of acetylene conversions up to its complete one. For a wide variety of mono-, bimetallic systems including catalysts with single palladium atoms, TOF was established to depend only slightly on the palladium dispersion and support nature, i.e. the reaction can be considered structure-insensitive. Nevertheless, a TOF decrease was observed in the systems with single atoms; that was accounted for by declining of the hydrogen dissociation rate or its slower spillover. Isotope-kinetic data were used for determining quantitatively undesirable contributions to the process selectivity caused by both hydrogenation of acetylene and gas-phase ethylene to ethane. High selectivities of alloyed bimetallic systems comprising isolated palladium atoms at approaching to the complete conversion of acetylene were caused by the low rate of hydrogenation of weakly adsorbed ethylene to ethane while for Pd/GF catalysts by the complete exclusion of the hydrogenation of ethylene from gas-phase.

Interaction of Ethylene with Irn (n = 1–10): From Bare Clusters to γ-Al2O3-Supported Nanoparticles

Comprehending the bond nature of ethylene-metal clusters at the atomic level is important for the design of nanocatalysts and their applications in the fields of fine chemistry and petroleum refining. The growth of Irn (n = 1–10) on γ–Al2O3(110) and ethylene adsorption on bare and γ–Al2O3(110)-supported Irn (n = 1–10) clusters were investigated using the density functional theory (DFT) approach. The mode stability of ethylene adsorption on the bare Irn clusters followed the order π > di-σ > B-T, with the exception of Ir8 where the π structure was less stable than the di-σ configuration. On supported Irn (n = 4–7 and 10) the stability sequence was π > di-σ > di-σ′ (at interface), while on supported Irn (n = 2, 3, 8, and 9) the sequence changed to di-σ > π > di-σ′ (at interface). Two-thirds of ethylene adsorption on the supported Irn clusters were weaker than its adsorption on the bare Irn clusters. The pre-adsorbed ethylene at the interface was found to facilitate the nucleation from the even-sized supported Irn to odd-sized Irn clusters, but hindered the nucleation from the odd-sized Irn to even-sized Irn clusters.

Ethylene oxide removal by sorption on aluminium oxide

The dynamics of ethylene oxide sorption and desorption on Al2O3 sorbent were investigated. The investigations of ethylene oxide sorption on Al2O3 show that significant sorption appeared above 125?C. The removal of sorbed ethylene oxide from Al2O3 was achieved by continuous increasing of the temperature up to 450?C in air stream. The analysis of desorbed products show that 90% of adsorbed ethylene oxide is converted to CO2 and the rest consists of the three derivatives of ethylene oxide. The exact composition of desorbed organic products will be determined in further investigation. The desorption temperature profiles point out the presence of two exothermic picks, as was confirmed by detection of CO2 and derivates of ethylene oxide at these temperatures. Investigation of textural characteristics and thermal stability of Al2O3 sorbent show that there are no changes of any characteristics of Al2O3 in sorption/desorption operating temperatures regimes. Only at 700?C the specific surface area of Al2O3 decreases of about 10%. This indicates that the investigated Al2O3 is convenient material for removal of ethylene oxide by sorption.