Selective Hydrogenation Of Propyne Research Articles

Isomerization and Selective Hydrogenation of Propyne: Screening of Metal-Organic Frameworks Modified by Atomic Layer Deposition.

Various metal oxide clusters upward of 8 atoms (Cu, Cd, Co, Fe, Ga, Mn, Mo, Ni, Sn, W, Zn, In, and Al) were incorporated into the pores of the metal-organic framework (MOF) NU-1000 via atomic layer deposition (ALD) and tested via high-throughput screening for catalytic isomerization and selective hydrogenation of propyne. Cu and Co were found to be the most active for propyne hydrogenation to propylene, and synergistic bimetallic combinations of Co and Zn, along with standalone Zn and Cd, were established as the most active for conversion to the isomerized product, propadiene. The combination of Co and Zn in NU-1000 diminished the propensity for full hydrogenation to propane as well as coking compared to its individual components. This study highlights the potential for high-throughput screening to survey monometallic and bimetallic cluster combinations that best affect the efficient transformation of small molecules, while discerning mechanistic differences in isomerization and hydrogenation by different metals.

The Role of Adsorbed and Subsurface Carbon Species for the Selective Alkyne Hydrogenation Over a Pd-Black Catalyst: An Operando Study of Bulk and Surface

The selective hydrogenation of propyne over a Pd-black model catalyst was investigated under operando conditions at 1 bar making use of advanced X-ray diffraction (bulk sensitive) and photo-electron spectroscopy (surface sensitive) techniques. It was found that the population of subsurface species controls the selective catalytic semi-hydrogenation of propyne to propylene due to the formation of surface and near-surface PdCx that inhibits the participation of more reactive bulk hydrogen in the hydrogenation reaction. However, increasing the partial pressure of hydrogen reduces the population of PdCx with the concomitant formation of a β-PdHx phase up to the surface, which is accompanied by a lattice expansion, allowing the participation of more active bulk hydrogen which is responsible for the unselective total alkyne hydrogenation. Therefore, controlling the surface and subsurface catalyst chemistry is crucial to control the selective alkyne semi-hydrogenation.

Selective hydrogenation of propyne on a solid Pd/Al2O3 catalyst modified with ionic liquid layer (SCILL)

The successful application of solid catalyst with ionic liquid layer (SCILL) concept in the selective hydrogenation of propyne is presented in this work. A Pd-based SCILL catalyst was prepared by spray impregnation of commercial available Pd/Al2O3 egg-shell catalyst and characterized by nitrogen sorption. Catalytic testing showed that even small amounts of ionic liquid were sufficient to suppress the consecutive reaction of propane formation, while propene selectivity was increased up to 97%. C6 oligomer formation, which is known to induce deactivation of the catalyst, could be prevented by excess hydrogen in the feed.

Palladium modified porous polymeric membranes and their performance in selective hydrogenation of propyne

The accessible pore system of polymeric ultrafiltration membranes was modified by titanium dioxide and treated further with palladium acetate to yield catalytically active, porous nanofiltration membranes. This procedure is in general applicable for any polymeric ultrafiltration membrane. To overcome the drawback of low thermal stability of common polymeric membranes, new ultrafiltration membranes were developed, based on a polyamideimide containing up to 40 wt.% of an inorganic filler admixed to the membrane casting solution. A similar treatment yielded catalytically active polymer membranes stable up to 200°C. The membranes were characterised by several methods and their performance was tested in a membrane reactor at 30°C. The hydrogenation of propene and the selective hydrogenation of propyne were examined as test reactions. For most effective membranes, 100% conversion of propene at a maximum yield of 98% of propane was obtained at the permeate side. In the selective hydrogenation of 5% propyne in propene, a selectivity of 99% for propene at 100% conversion of propyne was achieved at a permeate flux of 0.08 m 3/m 2 h bar at 0.9 bar pressure difference.

The Selective Hydrogenation of Propyne over a Copper/Silica Catalyst Prepared from a Monolayer Film of Copper 2,2′-Bipyridine Dimer on Cab–O–Sil

The hydrogenation of propyne to propene is a reaction of commercial interest to the polyolefins industry. A copper catalyst for this reaction is desirable as the diolefins and alkynes will be saturated to monoolefins only. However, one serious side reaction is the oligomerization of C{sub 3} adsorbed species to nonvolatiles called {open_quotes}green oil{close_quotes} by the industry. Zippert and White showed that Cu/silica catalysts which were prepared from Cu(acac){sub 2}/Cab-O-Sil catalyze the desired reaction with high selectivities to propene (60-90%); however, these catalysts were much less active than the low-dispersion Cu/silica catalysts made by aqueous impregnation. These low-dispersion catalysts (ca., 10-20%) suffered from low selectivities to propene (20%) with the oligomer as the major product. These data suggested that the yield of propene was influenced by the type of Cu precursor. Here, the authors report studies on the activity of Cu/SiO{sub 2} catalysts obtained from monolayer film dispersion of copper-2,2{prime}-bipyridine complexes over the silica surface. 25 refs., 5 figs.

ChemInform Abstract: Selective Hydrogenation of Propyne over an Ion‐Exchanged Copper on Silica Catalyst.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Selective hydrogenation of propyne over supported copper catalysts: influence of support

The selective hydrogenation of propyne over copper powder and various supported copper catalysts has been examined in a dynamic flow system. Increased hydrogenation activities were found for supported copper catalysts, where for example, the turnover frequency over an ion-exchanged Cu/SiO2 catalyst was 3.5·10-2 s-1 at 140°C as compared to 1.1·10-3 s-1 over unsupported copper powder. The increased selectivity to propene with increasing temperature was found to be a general property of all copper catalysts. However, the exact pattern of activity and selectivity was found to depend upon the particular supported copper system. Deactivation was found to depend on the acidity of the support and the dispersion of copper. Overall, the most active and selective catalysts that deactivate least were copper on silica prepared by the ion-exchange technique and copper on magnesia.

Selective hydrogenation of propyne over an ion-exchanged copper on silica catalyst

The selective hydrogenation of propyne over a Cu/SiO 2 catalyst in a dynamic flow system has been investigated. It was found that only propene and, depending on the reaction conditions, different amounts of oligomeric material, referred to as green oil or foulant, were formed. However, the selectivity to propene increased significantly at higher temperatures and it was possible to convert all the propyne selectively to propene, leaving a great potential for further development and industrial applications. Deactivation of the catalyst was found to be only a minor problem as 100% conversion and a selectivity of > 99.5% was obtained during a long-term test with an industrial raw propene feed (2 mol-%propyne/propadiene), even after one month on line. It is interesting to note that even at high propene concentrations and high temperatures no propane was detected. The conversion of propyne increased with temperature and reached 100% above 160°C. Between 90 and 150°C the selectivity was constant at about 20%, irrespective of hydrogen and propyne concentrations, the degree of conversion, the total flow-rate or the temperature. The addition of propene to the initial mixture decreased the conversion slightly but increased the selectivity markedly. It was possible to obtain 100% conversion of propyne to propene with nearly 100% selectivity at higher temperatures. The kinetic data observed showed a reaction order of zero for propyne at 100°C and a slightly positive reaction order (0.15) at 130°C. The reaction order was one for hydrogen irrespective of temperature. Propene decreased the activity slightly, corresponding to a reaction order of -0.16. The activation energy (68.6kJ/mol±5kJ/mol) was similar for the formation of propene and green oil between 90 and 150°C.