Selective Hydrogenation Of Acetylene Research Articles

Design of Pd-Zn Bimetal MOF Nanosheets and MOF-Derived Pd3.9Zn6.1/CNS Catalyst for Selective Hydrogenation of Acetylene under Simulated Front-End Conditions.

Novel zinc–palladium–porphyrin bimetal metal–organic framework (MOF) nanosheets were directly synthesized by coordination chelation between Zn(II) and Pd(II) tetra(4-carboxyphenyl)porphin (TCPP(Pd)) using a solvothermal method. Furthermore, a serial of carbon nanosheets supported Pd–Zn intermetallics (Pd–Zn-ins/CNS) with different Pd: Zn atomic ratios were obtained by one-step carbonization under different temperature using the prepared Zn-TCPP(Pd) MOF nanosheets as precursor. In the carbonization process, Pd–Zn-ins went through the transformation from PdZn (650 °C) to Pd3.9Zn6.1 (~950 °C) then to Pd3.9Zn6.1/Pd (1000 °C) with the temperature increasing. The synthesized Pd–Zn-ins/CNS were further employed as catalysts for selective hydrogenation of acetylene. Pd3.9Zn6.1 showed the best catalytic performance compared with other Pd–Zn intermetallic forms.

Effective Inhibition of Ethane Generation on Fe5C2 Nanoparticles Doped with ppm Level of Pd for Selective Hydrogenation of Acetylene

Overhydrogenation to ethane is most undesired in selective hydrogenation of acetylene. Monometallic Pd supported on common oxide supports such as alumina and silica suffers from susceptibility of ethane formation, and the ethylene selectivity is usually unsatisfactory. Herein, Fe5C2 was carefully synthesized and employed as a new kind support doped with a (5–600) ppm level of Pd for selective hydrogenation of acetylene. The catalyst with appropriate Pd loadings exhibited more efficient ethane suppression and much higher ethylene selectivity than the traditional α-Al2O3 supported Pd catalyst, with full acetylene conversion under 240 °C, and maintained good stability after a 200 h tolerance test. Characterization and DFT calculation results reveal that the excellent ethylene selectivity is mainly derived from the special interaction between Pd atoms and the Fe5C2 support. Hydrogenation of ethylene to ethane needs to cross extremely high activation energy barriers on the catalyst surface, and ethylene desorption more easily occurs on it. Doping the appropriate amount of Pd atoms on the Fe5C2 surface can increase the obstacle for polymerization and will cause the unsaturated C2 species to be more inclined to be hydrogenated into C2H4. This synergy effect also acts as a guide in alkane suppression for selective hydrogenation of other alkynes.

Highly Active Isolated Single-Atom Pd Catalyst Supported on Layered MgO for Semihydrogenation of Acetylene

Selective hydrogenation of acetylene to ethylene is an important industrial reaction. In this work, we report a highly efficient Pd/MgO catalyst loaded with ultralow (0.05 wt %) levels of palladium for the selective hydrogenation of acetylene to ethylene. Palladium single-atom catalysts exhibited an excellent catalytic performance for semihydrogenation of acetylene with the highest ethylene selectivity of about 82% at 200 °C due to facile desorption of ethylene against the overhydrogenation to unwanted ethane. This work provides a very simple route to prepare a highly active, selective, and low-cost Pd catalyst for the semihydrogenation of acetylene.

Boosting the activity of PdAg2/Al2O3 supported catalysts towards the selective acetylene hydrogenation by means of CO-induced segregation: A combined NAP XPS and mass-spectrometry study

Selective hydrogenation (or semi-hydrogenation) of acetylene into ethylene is an important industrial process. The aim of the present work is thus to learn regularities governing the CO-induced segregation and elaborate practical procedures for tuning the surface structure of Pd-Ag nanoparticles to improve their catalytic performance towards the selective hydrogenation of acetylene to ethylene. Utilizing NAP XPS the CO adsorption-induced Pd atoms segregation in supported PdAg2/Al2O3 catalysts already at room temperature has been shown. The surface enrichment with Pd further increases if the treatment temperature is increased up to 250 °C. This specific configuration with a redistributed Pd/Ag surface atomic ratio is appreciably stable and self-sustained even at the absence of CO at moderately elevated temperatures. Nevertheless, a reductive treatment in hydrogen at 450 °C reverts the nanoparticle surface structure to the pristine state. Catalytic properties of this peculiar CO-induced configuration of PdAg2/Al2O3 towards the selective acetylene hydrogenation was investigated using a combination of NAP XPS and MS techniques. The PdAg2/Al2O3 catalyst with the surface enriched with Pd due to the CO-induced segregation manifests improved activity with 100 % selectivity under the conditions used. The results obtained clearly demonstrate that CO adsorption-induced segregation is a powerful tool that can be used to optimize the surface composition and catalytic performance of bimetallic nanoparticles.

Reaction Kinetics of an Industrial Front‐End Acetylene Hydrogenation Catalyst Using the Advanced TEMKIN Reactor

AbstractThe front‐end process integration of the selective acetylene hydrogenation provides several advantages over the tail‐end option. But extensive knowledge of the process and reaction kinetics are required. This work combines the ideal conditions of the advanced TEMKIN reactor in a laboratory plant for gradient‐free kinetic analysis of eggshell catalyst under industrially relevant front‐end conditions. With this system an industrial state of the art Pd‐Ag/Al2O3 eggshell catalyst is investigated and the temperature dependent data under various feed compositions including information on the formation of C4‐species are reported.

Ligand-coordination effects on the selective hydrogenation of acetylene in single-site Pd-ligand supported catalysts

The selective hydrogenation of acetylene to ethylene is a critical step in the synthesis of polyethylenes. Achieving high conversion to ethylene without over-hydrogenation to ethane is a challenge that requires control of the transition metal site, which we achieve through a ligand-coordinated supported catalyst (LCSC) strategy. Using Pd catalysts coordinated to 1,10-phenanthroline-5,6-dione (PDO) ligands on CeO2 supports, we have discovered that the reaction selectivity depends strongly on the ligand:metal ratio with higher selectivity when more ligand is present in the catalyst. Catalyst structure was examined by extended X-ray absorption fine structure spectroscopy, transmission electron microscopy, and CO adsorption, which indicate single-atom character of the Pd. The ligand:metal ratio is determined by X-ray photoelectron spectroscopy measurements and correlated with hydrogenation reactions under steady-state flow conditions to examine trends in hydrogenation activity and selectivity. Those trends can be better understood by density functional theory calculations that indicate hydrogen binding on the ligand to guide reaction selectivity toward the desired ethylene hydrogenation product. These results demonstrate the importance of considering the dynamic character of LCSCs and inform the design of future single-site heterogeneous catalysts.

Pd single-atom catalysts derived from strong metal-support interaction for selective hydrogenation of acetylene

Pd single-atom catalysts derived from strong metal-support interaction for selective hydrogenation of acetylene

Bidentate ligand modification strategy on supported Ni nanoparticles for photocatalytic selective hydrogenation of alkynes

The design of selective and stable non-precious metal catalysts for hydrogenation of alkyne is highly desirable. In this study, L-lysine modification strategy is applied to support Ni nanoparticles, which greatly improves the stability and photocatalytic performance in the hydrogenation of phenylacetylene to styrene. The robust stability is attributed to that both amino and carboxyl groups of L-lysine can function simultaneously as the anchor, much stronger than a single group, to strongly interact with metallic Ni via N and O coordination. The high selectivity to styrene is due to that L-lysine modification results in a larger adsorption energy difference between styrene and phenylacetylene on the surface of Ni, therefore phenylacetylene is preferentially adsorbed on Ni surface. This protocol shows that the modulation of interaction between ligands and Ni is favorable to design stable, active and selective catalysts for hydrogenation of alkynes.

A Magnetically Separable Pd Single-Atom Catalyst for Efficient Selective Hydrogenation of Phenylacetylene.

Selective hydrogenation of alkynes to alkenes plays a crucial role in the synthesis of fine chemicals. However, how to achieve high selectivity and effective separation of the catalyst and substrate while obtaining high activity is the key for this reaction. In this work, a Pd single-atom catalyst is anchored to the shell of magnetic core-shell particles that consist of a Ni-nanoparticles core and a graphene sheets shell (Ni@G) for semi-hydrogenation of phenylacetylene, delivering 93% selectivity to styrene at full conversion with a robust turnover frequency of 7074 h-1 under mild reaction conditions (303 K, 2bar H2 ). Moreover, the catalyst can be recovered promptly from the liquid phase due to its magnetic separability, which makes it present good stability for enduring five cycles. Experimental and theoretical investigations reveal that H2 and substrates are activated by atomically dispersed Pd atoms and Ni@G hybrid support, respectively. The hydrogenation reaction occurs on the surface of Ni@G via hydrogen spillover from the metal to the support. Such a strategy opens an avenue for designing highly active, selective, and magnetically recyclable catalysts for selective hydrogenation in liquid reaction systems.

Controlled One‐pot Synthesis of PdAg Nanoparticles and Their Application in the Semi‐hydrogenation of Acetylene in Ethylene‐rich Mixtures

AbstractIn the present paper, we report the synthesis of highly functionalized nanomaterials carefully nanoengineered to catalyze the semi‐hydrogenation of acetylene in ethylene‐rich mixtures. Surface functionalization and structure modification of a series of bimetallic PdAg nanoparticles was performed using HHDMA as stabilizer and alloying the active palladium phase with silver. Bimetallic PdAg NPs with adjustable Pd/Ag ratio were prepared in water through a novel one‐pot methodology using hydrogen gas as a benign reducing agent and cyanide as additive. UV‐Vis studies indicated the formation of the bimetallic nanostructures through a sequential displacement‐galvanic reduction process mediated by cyanide. The series of colloidal NPs were deposited onto alumina and successfully applied as catalysts in the selective hydrogenation of acetylene in ethylene rich mixtures. Geometric and electronic promotion of Ag over Pd based catalysts was evidenced by the increase of the ethylene selectivity with the Ag content. The reactivity of these materials demonstrated the applicability of HHDMA stabilized NPs in a gas phase reaction of industrial interest and the success of combining several strategies for the enhancement of the alkene selectivity.

Nano gold coupled black titania composites with enhanced surface plasma properties for efficient photocatalytic alkyne reduction

A nanocomposite design is proven for achieving efficient, selective, and robust alkyne semi-hydrogenation through photocatalytic process, which avoids the use of additional heat sources and traditional toxic Pb additives. The gold nanoparticles (Au NPs) coupled crystalline-core@amorphous-shell structured and wide-spectrum-responsive black titania (BT) with enhanced surface plasma properties holds the key to attaining high activity and selectivity. The hot electron injection from conductive BT to the surface of plasmonic Au NPs stimulated by solar light activates the alkynes and directly participates in the selective conversion to overcome the energy barriers. The engineered Au/BT gives a record turnover frequency of 1012 h−1 and excellent stability for phenylacetylene semi-hydrogenation under solar light irradiation and shows broad scope toward selective hydrogenation of alkynes containing various substituent groups of –CH3, –OH, and –Cl. The kinetic isotope effects and in situ infrared spectroscopy analysis for structure-activity relationship and reaction mechanism of phenylacetylene reduction were also demonstrated.

Alloyed PdCu Nanoparticles within Siliceous Zeolite Crystals for Catalytic Semihydrogenation.

Selective hydrogenation of acetylene to ethylene is an industrially important process to purify the raw ethylene stream for producing high-grade polyethylene. The supported Pd catalyst exhibits superior activity for acetylene hydrogenation but suffers from poor ethylene selectivity because of the easy overhydrogenation to produce ethane. Here, we report that the PdCu alloy nanoparticles within siliceous zeolite crystals effectively tuned Pd-catalyzed overhydrogenation into semihydrogenation. This catalyst displayed an ethylene selectivity of 92.9% with a full conversion of acetylene. Mechanism studies reveal that the zeolite fixation stabilized the alloyed structure, where the electron-enriched Pd surface benefits the rapid ethylene desorption to hinder the deep hydrogenation. This work provides an efficient strategy for a rational design of bimetallic metal catalysts for selective hydrogenations.

Numerical Simulation of Heat and Mass Transfer in an Open-Cell Foam Catalyst on Example of the Acetylene Hydrogenation Reaction

In the present work, based on numerical simulation, a comparative analysis of the flow of a chemically reacting gas flow through a catalyst is performed using the example of selective hydrogenation of acetylene in a wide range of flow temperatures variation. Catalyst models are based on open-cell foam material. A comparison is also made with calculations and experimental data for a granular catalyst. The porosity and cell diameter were chosen as variable parameters for the porous catalyst. The results of numerical studies were obtained in the form of component concentration fields of the gas mixture, vector fields of gas movement, values of conversion, and selectivity of the reaction under study. The parameters of the porous material of the catalyst are determined for the maximum efficiency of the process under study.

Polyphenylene sulfide as an efficient solid-phase ligand for improved selective alkyne hydrogenation

Liquid phase catalytic selective hydrogenation of alkynes to alkenes is a widely used reaction in the industry. Pairing nanocatalysts with soluble ligands or developing advanced catalytic nanostructures are two general protocols to realize preferable hydrogenation performance. However, both protocols are not cost-effective, and it is still challenging to achieve high selectivity and high activity with conventional hydrogenation nanocatalysts. In this work, commercial available, low-cost, and reactant-inert polyphenylene sulfide (PPS) is used as a new solid-phase ligand for palladium nanocatalysts in selective alkyne hydrogenation. Hydrogenation experiments have been carried out on different terminal and internal alkyne substrates, to investigate the universal effects of PPS on hydrogenation. As a result, over-hydrogenation and/or isomerization could be effectively suppressed upon the addition of solid PPS powders. The beneficial effects can be easily tuned by varying the PPS dosage. Importantly, both solid supported nanocatalysts and PPS can be simply separated via sedimentation and washing for subsequent experiments. A recycling experiment with PPS/Pd@CaCO3 has demonstrated the good cyclability (ten times of usage without much changes in effectiveness) of the catalyst system. X-ray photoelectron spectroscopy results indicate that the weak binding of PPS as a solid-phase ligand to nanocatalysts may contribute to the improved selective hydrogenation performance.

Synthesis of Pd–Ag/Al2O3 catalyst by colloidal oxide method for acetylene selective hydrogenation: a study on the sintering of PdO nanoparticles

Synthesis of Pd–Ag/Al2O3 catalyst by colloidal oxide method for acetylene selective hydrogenation: a study on the sintering of PdO nanoparticles

Room temperature Z-selective hydrogenation of alkynes by hemilabile and non-innocent (NNN)Co(ii) catalysts

Room temperature chemo- and stereoselective hydrogenation of alkynes is described using a well-defined and phosphine-free hemilabile cobalt catalyst.

An efficient NiCu@C/Al2O3 catalyst for selective hydrogenation of acetylene.

The development of non-noble metal catalysts for selective hydrogenation still remains a challenge. Herein, NiCu@carbon core-shell nanoparticles supported on Al2O3 (NiCu@C/Al2O3) were prepared, which showed enhanced catalytic performance of acetylene-selective hydrogenation in comparison with NiCu/Al2O3 without carbon encapsulation. In detail, NiCu@C/Al2O3 displayed high ethylene selectivity (>86%) even at an acetylene conversion of 100% and excellent stability (>90 h). Thus, NiCu@C/Al2O3 exhibited great potential as an alternative to Pd-based catalysts for acetylene-selective hydrogenation.

Reduction Degree of Pd at the Interface Dominates Selective Hydrogenation of Acetylene to Ethylene: A Systematic Kinetic Study on Elementary Steps, Kinetically Relevant(S) and Active Species

Reduction Degree of Pd at the Interface Dominates Selective Hydrogenation of Acetylene to Ethylene: A Systematic Kinetic Study on Elementary Steps, Kinetically Relevant(S) and Active Species

Controlling the speciation and selectivity of Si3N4 supported palladium nanostructures for catalysed acetylene selective hydrogenation

A convexity model is used to predict the catalytic performance of Pd catalysts in acetylene semi-hydrogenation. The surface Pdδ− species determines the catalytic activity and selectivity, and the Pd–Nx (Pdδ+) species regulates the catalyst stability.

Highly Selective and Stable Isolated Non-Noble Metal Atom Catalysts for Selective Hydrogenation of Acetylene

Highly Selective and Stable Isolated Non-Noble Metal Atom Catalysts for Selective Hydrogenation of Acetylene