Selective Hydrogenation Of Acetylene Research Articles

Array Modified Molded Alumina Supported PdAg Catalyst for Selective Acetylene Hydrogenation: Intrinsic Kinetics Enhancement and Thermal Effect Optimization

Array Modified Molded Alumina Supported PdAg Catalyst for Selective Acetylene Hydrogenation: Intrinsic Kinetics Enhancement and Thermal Effect Optimization

C2H2 selective hydrogenation over the CuxMy or PdxNy intermetallic compounds: The influences of partner metal type and ratio on the catalytic performance

• The most suitable partner metal type and ratio of CuxMy and PdxNy to catalyze C2H2 selective hydrogenation was firstly examined. • Cu3Pd1 or Pd1Cu3 is the most suitable among all considered CuxMy and PdxNy due to the unique surface structure and electronic properties. • Cu3Pd1 or Pd1Cu3 presents the industrially practical activity and selectivity toward C2H4 formation and the thermal stability. • Cu3Pd1 or Pd1Cu3 provides sufficient hydrogen source and effectively inhibit green oil production. The Cu x M y and Pd x N y intermetallic compounds (IMCs) have exhibited better catalytic performance in hydrogenation reactions; however, for C 2 H 2 selective hydrogenation, the most suitable partner metal type and ratio among Cu x M y and Pd x N y still remain unclear. This study investigated C 2 H 2 selective hydrogenation on the Cu x M y (M = Zn, Pt, Ni, Pd, Au and Ag) and Pd x N y (N = Zn, Ga, In, Sn, Cu, Ag and Au) with different Cu/M and Pd/N ratios using density functional theory calculations, the results reveal that Cu 3 Pd 1 IMCs with the surface isolated single-atom Pd anchored into the IMCs bulk as active center may serve as a promising catalyst for C 2 H 2 selective hydrogenation due to industrially practical activity and selectivity for C 2 H 4 formation, thermal stability, sufficient hydrogen source and green oil suppression, which is better than the previously reported single-atom Pd catalysts. This work would provide a guideline to design and screen out promising intermetallic compounds to catalyze selective hydrogenation of alkynes.

A carbonized cobalt catalyst supported by acid-activated clay for the selective hydrogenation of acetylene

A carbonized cobalt catalyst supported by acid-activated clay for the selective hydrogenation of acetylene

Tuning electronic structure of palladium from wheat flour-derived N-doped mesoporous carbon for efficient selective hydrogenation of acetylene

Designing efficient and sustainable catalysts for semi-hydrogenation of acetylene is of critical importance, but challenging. A novel and easily scaled-up strategy is described in this work for a well-performing Pd-based catalyst (Pd@NMC) fabrication by using a cheap and widely available biomass, wheat flour, as support precursor.The optimized catalyst exhibits superior performance for purification of crude ethylene stream compared with the commercial counterparts, providing an outstanding selectivity of exceeding 81% irrespective of conversion level. Moreover, the Pd@NMC catalyst has remarkable long-term stability during a 200-hours test, which would enable promising industrial applications. Comprehensive characterizations and DFT calculation reveal that the selectivity of Pd@NMC catalysts are primarily governed by the N configuration of the N-doped carbon support, which are strongly sensitive to the catalyst thermal treatment temperatures. Graphitic nitrogen is shown to tailor the electronic properties of Pd sites to promote the desorption of ethylene intermediate from the catalyst, endowing the modified Pd surface with high catalytic selectivity. These results indicate that the quantitative regulation of catalytic performance by tuning the local environment and electronic properties of Pd sites is a promising method, providing a solid foundation for designing chemoselective and long-lived Pd-based hydrogenation catalysts.

Copper Single-Atom-Covered Pt Nanoparticles for Selective Hydrogenation of Phenylacetylene

The selective hydrogenation of alkynes to alkenes is very important for both industry and scientific investigation, and overhydrogenation of alkynes to alkanes is the biggest problem to be solved. Suppressing the catalytic hydrogenation of alkenes to alkanes and keeping the efficient conversion from alkynes to alkenes at the same time is a viable solution, but the slight difference in structure between alkynes and the corresponding alkenes causes great difficulty in realizing such a target. The Pt/C–Cu bimetallic catalysts are used to catalyze the selective hydrogenation of phenylacetylene (PA) to styrene (ST). High-resolution STEM and EXAFS results show that the prepared Pt/C–Cu catalysts are composed of copper single atoms and Pt nanoparticles. In particular, Pt/C–Cu is a catalyst in which copper single atoms cover the surface of Pt nanoparticles. The experimental results reveal that the selectivity of ST strongly depends on the coverage of Cu single atoms over Pt nanoparticles in Pt/C–Cu, so selective hydrogenation of PA is a structure-sensitive reaction. The selectivity of ST can reach 94.4% at a PA conversion of 100% in the selective hydrogenation of PA over Pt/C–0.5Cu, an optimized Pt–Cu bimetallic catalyst; after selective removal of PA in ST from 100 to 30 ppm over the same catalyst, the yield of ST reaches 99.97%. The chemisorption results of H2 and probe molecule ethene (C2H4) over the Pt–Cu/C catalysts reveal that Cu single atoms covering on the surface of Pt nanoparticles weaken the Pt–H and Pt–C2H4 interactions, so the catalytic hydrogenation of the carbon–carbon double bond over Pt/C–0.5Cu can be tremendously suppressed. The added Cu single atoms over Pt nanoparticles are not poisonous sites because they can also act as the active centers to activate hydrogen and the carbon–carbon double bond.

The influence of palladium on the hydrogenation of acetylene on Ag(111).

We have used reflection absorption infrared spectroscopy (RAIRS) and temperature programmed reaction (TPR) to study the selective hydrogenation of acetylene on both a clean Ag(111) surface and on a Pd/Ag(111) single-atom-alloy surface. The partial hydrogenation of acetylene to ethylene is an important catalytic process that is often carried out using PdAg alloys. It is challenging to study the reaction with ultrahigh vacuum techniques because H2 does not dissociate on Ag(111), and while H2 will dissociate at Pd sites, H-atom spillover from Pd to Ag sites does not generally occur. We bypassed the H2 dissociation step by exposing the surfaces to atomic hydrogen generated by the hot filament of an ion gauge. We find that hydrogen atoms react with acetylene to produce adsorbed ethylene at 85 K, the lowest temperature studied. This is revealed by the appearance of a RAIRS peak at 950 cm-1 due to the out-of-plane wagging mode of adsorbed ethylene when acetylene is exposed to a surface on which H atoms are pre-adsorbed. The formation of both ethylene and ethane are detected with TPR, but no acetylene coupling products, such as benzene, were found. From quantitative analysis of the TPR results, the percent conversion and selectivities to ethylene and ethane were determined. Low coverages of Pd enhance the conversion but do so mainly by increasing ethane formation.

Highly Selective Acetylene Semihydrogenation Catalyst with an Operation Window Exceeding 150 °C

The operating window (OW) is a primary performance criterion for the selective hydrogenation of acetylene in excess ethylene. Currently, most state-of-the-art catalyst systems have an OW of less th...

Homogeneous-like Alkyne Selective Hydrogenation Catalyzed by Cationic Nickel Confined in Zeolite

The selective hydrogenation of alkynes to their corresponding alkenes is an important type of organic transformation, which is currently accomplished by modified palladium catalysts. Herein, we rep...

Atomically Dispersed Pd Atoms on a Simple MgO Support with an Ultralow Loading for Selective Hydrogenation of Acetylene to Ethylene.

We report a simple and efficient Pd/MgO catalyst loaded with ppm level of Pd (7.8 ppm) for semi-hydrogenation of acetylene to ethylene. The catalyst showed excellent performance with high acetylene conversion (97%), high ethylene selectivity (89%) and good stability. Moreover, the atomically dispersed Pd atoms are inactive for ethylene hydrogenation. Isotopic and FTIR results suggest that H2 dissociates at isolated Pd atoms in a heterolytic manner forming O-H bond, which may account for the high selectivity.

Influence of Active Metal Precursors on the Structure and Catalytic Behavior of Pd/Al2O3 Catalysts for Selective Acetylene Hydrogenation

Influence of Active Metal Precursors on the Structure and Catalytic Behavior of Pd/Al2O3 Catalysts for Selective Acetylene Hydrogenation

From amorphous to ordered: Structural transformation of Pd nanoclusters in 1-pentyne hydrogenation reactions

Nanostructured palladium catalysts are used industrially for selective alkyne hydrogenation reactions. However, structural changes can lead to a loss of performance. In this study, we show the evolution of the atomic structure of monodispersed Pd nanoclusters undergoing a vapour-phase 1-pentyne hydrogenation reaction. A specific structural transformation, from amorphous to highly symmetrical structures, is observed at the atomic level with aberration-corrected scanning transmission electron microscopy (AC-STEM). This surprising behaviour which occurs concurrently with the alkyne hydrogenation reaction, is clearly size-dependent. The results provide new understanding of the long-term stability of commercial heterogeneous catalysts.

Quantitative Studies of the Key Aspects in Selective Acetylene Hydrogenation on Pd(111) by Microkinetic Modeling with Coverage Effects and Molecular Dynamics

Selective acetylene hydrogenation as a vital industrial reaction has been studied for decades. However, some key issues remain elusive. Herein, a detailed microkinetic model using density functiona...

Selective hydrogenation of ethyne with highly-dispersed sub-2 nm Pd nanoparticles in a hemicellulosic gel-based microreaction chamber

Ethyne is often an unwanted impurity in ethene streams used in plastics industry. Supported Pd catalysts offer high ethyne conversion, but poor ethene selectivity due to over-hydrogenation which leads to the formation of carbonaceous deposits. In this paper, acrylamide was grafted by free radical polymerization onto bagasse pith hemicellulose (to form HEMI-g-AAMs), which was then used as a porous bio-based carrier of Pd nanoparticles. The obtained Pd/HEMI-g-AAMs catalyst showed an ethyne conversion and ethene selectivity of 100% and 94.70%, respectively, at 100 °C and a space velocity of 70,000 h−1. The nitrogen-rich bio-based support regulated the physicochemical properties and catalytic activity of the supported Pd nanoparticles. Results guide the development of new and improved Pd-based catalysts for the partial catalytic hydrogenation of ethyne to ethene.

Adsorption Behavior and Electron Structure Engineering of Pd-IL Catalysts for Selective Hydrogenation of Acetylene

Developing the catalytic activity and selectivity of palladium (Pd) catalysts for acetylene hydrogenation is key importance in the chemical industry and remains a challenge to this day. Here, the catalytic performance of Pd catalysts are influenced by the Pd electronic structure, in turn, controlled by different heteroatom doped support. Different catalysts are prepared by ionic liquids (ILs) with different precursors, and catalytic activity of selective hydrogenation of acetylene was investigated. The Pd/NC catalyst exhibits extraordinary conversion, selectivity and stable for the hydrogenation of acetylene (94.6% acetylene conversion with 91.3% selectivity to ethylene). This remarkable catalytic performance of Pd/NC is mainly linked to nitrogen-doped (N-doped) changes the electronic structure of Pd nanoparticles, ensures the rapid desorption of ethylene and prevents the formation of unnecessary ethane by over hydrogenation (demonstrated by XPS and DFT). Our strategy of controlling the electronic structure of Pd can be widely used in the reactions that change the micro electrochemical properties of active metals. The selective hydrogenation of acetylene to ethylene over Pd/NC with excellent conversion and selectivity is investigated. The doping of nitrogen leads to the unique electronic structure of Pd on the Pd/NC catalyst, which influences the adsorption of ethylene and acetylene, thus promoting its catalytic activity.

The Effect of Addition Method of Impregnation Solution on Properties and Performance of Pd-Ag/Al2O3 Catalyst in Tail-End Acetylene Selective Hydrogenation

The impregnation of alumina support with PdCl2 solution was investigated in batch and semi-batch operation modes using a recycle packed-bed reactor. UV-visible analysis was used to evaluate the kinetics of Pd adsorption on alumina support. Transient palladium adsorption data showed that Pd adsorption was very rapid completing within few minutes. Bi-metallic Pd-Ag/Al2O3 catalysts were synthesized by sequential impregnation method. CO-chemisorption, CO-TPD and FE-SEM tests were used to characterize the synthesized bi-metallic samples. Catalytic performance of the samples was evaluated for tail-end acetylene selective hydrogenation process in a fixed-bed reactor. Moreover, the deactivation of the catalysts was evaluated mathematically by integral method of analysis, considering reaction kinetics as power laws in terms of nth orders in H2 and C2H2 partial pressures. It was observed that by batch-wise addition of Pd precursor solution, a sample was obtained with lowest amount of Pd dimmers that had highest ethylene selectivity and lowest hydrogenation reaction rate.

Front Cover: Ruthenium‐Catalyzed E‐Selective Partial Hydrogenation of Alkynes under Transfer‐Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source (5/2021)

Front Cover: Ruthenium‐Catalyzed <i>E</i>‐Selective Partial Hydrogenation of Alkynes under Transfer‐Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source (5/2021)

High‐Performance Catalysts Derived from Cupric Subcarbonate for Selective Hydrogenation of Acetylene in an Ethylene Stream

AbstractA high‐performance base metal catalyst for acetylene selective hydrogenation was prepared from cupric subcarbonate (Cu2(OH)2CO3) by thermal treatment with an acetylene‐containing gas followed by hydrogen reduction. The characterization results revealed that the copper catalyst was composed of interstitial copper carbide (CuxC) and metal Cu, which were embedded in porous carbon matrix. The CuxC crystallites, which showed outstanding hydrogenation activity, were derived from the hydrogen reduction of copper (II) acetylide (CuC2) which was generated from the reaction between acetylene and Cu2(OH)2CO3. The Cu particles and porous carbon were generated from the unavoidable thermal decomposition of CuC2. The prepared Cu‐derived catalyst completely removed the acetylene impurity in an ethylene stream with a very low over‐hydrogenation selectivity at 110 °C and atmospheric pressure. No obvious deactivation was observed in a 180‐h test run. In the Cu‐derived catalyst, CuxC served as the catalytic site for H2 dissociation, Cu mainly functioned as the site for selective hydrogenation of acetylene, whereas the porous carbon matrix posed a steric hindrance effect on the chain growth of linear hydrocarbons so as to suppress the undesired oligomerization.

Ruthenium‐Catalyzed E‐Selective Partial Hydrogenation of Alkynes under Transfer‐Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source

AbstractE‐alkenes were synthesized with up to 100 % E/Z selectivity via ruthenium‐catalyzed partial hydrogenation of different aliphatic and aromatic alkynes under transfer‐hydrogenation conditions. Paraformaldehyde as a safe, cheap and easily available solid hydrogen carrier was used for the first time as hydrogen source in the presence of water for transfer‐hydrogenation of alkynes. Optimization reactions showed the best results for the commercially available binuclear [Ru(p‐cymene)Cl2]2 complex as pre‐catalyst in combination with 2,2‐bis(diphenylphosphino)‐1,1‐binaphthyl (BINAP) as ligand (1 : 1 ratio per Ru monomer to ligand). Mechanistic investigations showed that the origin of E‐selectivity in this reaction is the fast Z to E isomerization of the formed alkenes. Mild reaction conditions plus the use of cheap, easily available and safe materials as well as simple setup and inexpensive catalyst turn this protocol into a feasible and promising stereo complementary procedure to the well‐known Z‐selective Lindlar reduction in late‐stage syntheses. This procedure can also be used for the production of deuterated alkenes simply using d2‐paraformaldehyde and D2O mixtures.

Copper-Based Catalysts for Selective Hydrogenation of Acetylene Derived from Cu(OH)2.

Replacing precious metals with cheap metals in catalysts is a topic of interest in both industry and academia but challenging. Here, a selective hydrogenation catalyst was prepared by thermal treatment of Cu(OH)2 nanowires with acetylene-containing gas at 120 °C followed by hydrogen reduction at 150 °C. The characterization by means of transmission electron microscopy observation, X-ray diffraction, and X-ray photoelectron spectroscopy revealed that two crystallites were present in the resultant catalyst. One of the crystal phases was metal Cu, whereas the other crystal phase was ascribed to an interstitial copper carbide (CuxC) phase. The reduction of freshly prepared copper (II) acetylide (CuC2) at 150 °C also afforded the formation of Cu and CuxC crystallites, indicating that CuC2 was the precursor or an intermediate in the formation of CuxC. The prepared catalysts consisting of Cu and CuxC exhibited a considerably high hydrogenation activity at low temperatures in the selective hydrogenation of acetylene in the ethylene stream. In the presence of a large excess of ethylene, acetylene was completely converted at 110 °C and atmospheric pressure with an ethane selectivity of <15%, and the conversion and selectivity were constant in a 260 h run.

N8 stabilized single-atom Pd for highly selective hydrogenation of acetylene

Single-atom catalysts show a promising future in many reactions even though great challenges still remain such as facile synthesis and long stability. In this work, a single-atom Pd catalyst attached to a designed N8 Lewis base species (Pd1-N8/CNT) is synthesized with cyclic voltammetry (CV) method. The catalyst demonstrates long stability and enhanced C2H4 selectivity in selective hydrogenation of acetylene at 40 °C. CV is carried out in a three-electrode setup with PdO/CNT as the working electrode in NaN3 solution. HAADF-STEM confirms single-atom Pd sites are successfully isolated. XPS measurements and Bader charge calculations indicate N8 is effectively synthesized on CNT substrate after CV treatment while single-atom Pd is stabilized by attaching to the end N of N8. Acetylene-temperature programed desorption (C2H2-TPD) and density functional theory (DFT) calculations suggest C2H2 favors the π bonding on single Pd atom, while H2 dissociates on the N atom (next to Pd) instead of conventionally on Pd. The synergistic effect favors C2H4 formation but prevents full hydrogenation of acetylene to C2H6. This work opens up a new perspective to design and synthesize more selective catalysts with isolated single-atom sites.