Selective Hydrogenation Of Acetylene Research Articles

Trimetallic catalyst, prepared by ultrasonic -impregnation method for selective hydrogenation of acetylene: investigation of potassium addition to Fe-Pd/α-Al2O3 catalyst

Trimetallic catalyst, prepared by ultrasonic -impregnation method for selective hydrogenation of acetylene: investigation of potassium addition to Fe-Pd/α-Al2O3 catalyst

Understanding the role of butadiene in the selective hydrogenation of acetylene under adiabatic conditions

The influence of added 1,3-butadiene on the selective hydrogenation of acetylene over Pd-Ag/Al2O3 catalyst was studied under tail-end conditions in an adiabatic reactor. It was found that 1,3-butadiene was hydrogenated to 1-butene, cis-2-butene, trans-2-butene and butane. Importantly, no increase of C6+ products from coupling with acetylene or ethylene could be observed. Presented results contradict an earlier hypothesized role of 1,3-butadiene in the formation of higher hydrocarbons. It is argued that a precursor of butadiene, vinyl-like C4H5 surface species, is the key intermediate in the formation of higher hydrocarbons.

Flexible Borane–Nitrogen Frustrated Lewis Pair Organic Microsphere for Selective Alkyne Hydrogenation

Flexible Borane–Nitrogen Frustrated Lewis Pair Organic Microsphere for Selective Alkyne Hydrogenation

Enriching Pt3 ensemble with isolated 3-fold hollow site by crystal-phase engineering of Pt3Fe single-nanoparticle for acetylene hydrogenation

Tuning the crystal-phase of bimetallic particles enables a precise control of catalytically active sites but is experimentally challenged by the averaging ensemble effects that are caused by the particle communications occurred during the crystal-phase transformation. Here, H2-treatment at 773–973 K of Pt3Fe single-nanoparticle, confined by a permeable silica shell, achieved crystal-phase transformation from the disordered A1 phase to the chemically ordered L12 phase. Detailed microscopic and spectroscopic characterizations have identified that the disordered A1 particle possessed contiguously connected large Pt domains while the ordered L12 particle afforded regularly populated Pt3 ensembles surrounded by Fe single-atoms. The isolated 3-fold hollow Pt site in the three-atom ensemble efficiently boosted the adsorption of acetylene, yielding a much higher hydrogenation activity. The reaction rate of the L12 particle was twice of that for the A1 particle. Moreover, the charge transfer from the neighboring Fe single-atoms to the Pt atoms on the L12 particle expedited the desorption of ethylene, promoting the selectivity as well. Overall, both geometric and electronic interactions in the ordered crystal-phase synergistically facilitated the selective hydrogenation of acetylene to ethylene.

Cu Single-Atom Catalysts for High-Selectivity Electrocatalytic Acetylene Semihydrogenation.

The site isolation strategy has been employed in thermal catalytic acetylene semihydrogenation to inhibit overhydrogenation and C-C coupling. However, there is a dearth of analogous investigations in electrocatalytic systems. In this work, density functional theory (DFT) simulations demonstrate that isolated Cu metal sites have higher energy barriers on overhydrogenation and C-C coupling. Following this result, we develop Cu single-atom catalysts highly dispersed on nitrogen-doped carbon matrix, which exhibit high ethylene selectivity (>80% Faradaic efficiency for ethylene, <1% Faradaic efficiency for C4, and no ethane) at high concentrations of acetylene. The superior performance observed in the electrocatalytic selective hydrogenation of acetylene can be attributed to the weak adsorption of ethylene intermediates and highly energy barriers on C-C coupling at isolated sites, as confirmed by both DFT calculations and experimental results. This study provides a comprehensive understanding of the isolated sites inhibiting the side reactions of electrocatalytic acetylene semihydrogenation.

Cu Single‐Atom Catalysts for High‐Selectivity Electrocatalytic Acetylene Semihydrogenation

AbstractThe site isolation strategy has been employed in thermal catalytic acetylene semihydrogenation to inhibit overhydrogenation and C−C coupling. However, there is a dearth of analogous investigations in electrocatalytic systems. In this work, density functional theory (DFT) simulations demonstrate that isolated Cu metal sites have higher energy barriers on overhydrogenation and C−C coupling. Following this result, we develop Cu single‐atom catalysts highly dispersed on nitrogen‐doped carbon matrix, which exhibit high ethylene selectivity (&gt;80 % Faradaic efficiency for ethylene, &lt;1 % Faradaic efficiency for C4, and no ethane) at high concentrations of acetylene. The superior performance observed in the electrocatalytic selective hydrogenation of acetylene can be attributed to the weak adsorption of ethylene intermediates and highly energy barriers on C−C coupling at isolated sites, as confirmed by both DFT calculations and experimental results. This study provides a comprehensive understanding of the isolated sites inhibiting the side reactions of electrocatalytic acetylene semihydrogenation.

Engineering of Ag@Pd/Al2O3 with varied Pd-shell thickness: Dynamic evolution of ligand and strain effects on acetylene selective hydrogenation

Bimetallic nanoparticles exhibit a synergistic effect that critically depends on their surface composition, but such promotion mechanisms become vague with varying surface compositions. Here, alumina supported Ag@Pd core–shell and PdAg alloy structure with controlled size and surface compositions were prepared to demonstrate synergetic mechanisms, particularly, ligand and strain effects on activity and ethylene selectivity for acetylene hydrogenation. The performance evaluation indicates that Ag@Pd catalysts with well-controlled Pd-shell thickness can effectively lower apparent activation energy and improve ethylene selectivity. Hydrogenation activity increases from 0.019 to 0.062 s−1 with decreasing Pd-shell thickness under mild conditions, which is 3–6 times higher than their alloyed and monometallic counterparts. Combined characterizations and density functional theory are conducted to reveal such shell-thickness-dependent performance. The ligand effect arising from Ag alloying in the interface of Ag@Pd2ML observes the strongest binding of acetylene, but it diminished sharply and the strain effect gets more prevailing with increasing shell thickness. The competition of ethylene desorption and deep-hydrogenation were also investigated to understand the selectivity governing factors, and the selectivity descriptor (0.5BE(C2H4) – BE(H)) was built to match the contribution of ligand and strain effect on the different surfaces of Pd-Ag bimetallic NPs. The exploration of synergetic mechanisms among bimetallic NPs with varied structure and surface compositions in this work can help us to deepen the understanding catalyst structure–activity relationship and provide a feasible way to optimize the overall catalytic performance.

Regulating metal-support interactions of Pd/MgAl2O4 for efficient selective hydrogenation of acetylene

Selective hydrogenation of a trace amount of acetylene to ethylene is a green and economical process to purify the ethylene stream in the olefin industry. Pd-based catalysts are widely explored for this process due to their excellent H2 and C2H2 activation abilities. However, the strong adsorption of C2H4 on metallic Pd sites often leads to the undesired over-hydrogenation product (i.e., ethane). Herein, we fabricated Pd/MgAl2O4 catalysts with tunable metal-support interactions by changing calcination temperatures to efficiently modify the electronic structure of Pd species. The Pd/MgAl2O4 with the optimized calcination temperature exhibits 96 % acetylene conversion and enhanced ethylene selectivity of 87 % due to weak adsorption of intermediates at 120 ℃, and shows excellent stability with negligible activity decay during a 50 h test. This work provides a strategy for designing catalysts with regulated metal-support interactions for selective hydrogenation processes.

Acetylene Semi-Hydrogenation on Intermetallic Ni–In Catalysts: Ni Ensemble and Acetylene Coverage Effects from a Theoretical Analysis

DFT-based reaction profiles and microkinetic simulations were used to describe the catalytic selective hydrogenation of acetylene on Ni, Ni3In, NiIn, and Ni2In3 model intermetallic surfaces. Among the NixIny intermetallic catalysts, NiIn showed the highest ethylene yield. Decreased formation of ethane was observed on NiIn and Ni2In3 accompanied by increased formation of oligomers compared to Ni and Ni3In. This emphasizes the significance of accounting for the oligomerization reactions when evaluating the selectivity of the catalysts. Inconsistent acetylene coverage was obtained when performing microkinetic simulations using free energy values calculated at low acetylene coverage, while a fully consistent coverage was obtained using high-coverage free energy values. Results from the high-coverage microkinetic model showed that the presence of In on the catalytic surface decreased the rate of acetylene consumption with a trade-off relation between activity and selectivity. Simulations in the absence of ethylene in the feed confirmed that ethylene hydrogenation and acetylene C–C coupling were the primary sources for ethane and oligomer formation, respectively. This study highlights the importance of considering oligomerization reactions, coverage effect, and feed composition when describing the activity and the selectivity of catalysts during the competitive hydrogenation of alkynes.

Pd(2‐pymo)2]n/Al2O3 as MOF Single Site Catalyst for the Selective Hydrogenation of Acetylene**

AbstractDespite the great potential of metal‐organic frameworks (MOFs) in catalysis, industrial applications are still scarce. This is mainly due to a lack of performance when changing from idealized lab conditions towards realistic conditions of the actual application. In this work, we demonstrate the applicability and outstanding catalytic performance of an alumina‐supported [Pd(2‐pymo)2]n MOF catalyst in the selective hydrogenation of acetylene to ethylene under industrial front‐end conditions. It shows a competitive performance to an industrial benchmark catalyst and even exceeds it in terms of ethane selectivity due to the combination of well‐defined isolated Pd active sites and synergies due to MOF‐support‐interactions. The high stability was proven for up to 60 h time‐on‐stream and supported by XPS and XRD structural analysis.

Selective Hydrogenation of Acetylene over Pd-Co/C Catalysts: The Modifying Effect of Cobalt

Novel bimetallic Pd-Co catalysts supported on the carbon material Sibunit were synthesized by an incipient wetness impregnation method and used for ethylene production by selective acetylene hydrogenation. It has been established that an increase in the Pd:Co molar ratio from 1:0 to 1:2 in 0.5%Pd-Co/C catalysts, treated in hydrogen at 500 °C, leads to an increase in the ethylene selectivity from 60 to 67% (T = 45 °C). The selectivity does not change with a further increase in the modifier concentration. The catalysts were investigated by TPR-H2, XRD, TEM HR, EDS, and XPS methods. It was shown that palladium and cobalt in the 0.5%Pd-Co/C samples form Pd(1−x)Cox phases of solid solutions with different compositions depending on the Pd:Co ratio. The cobalt concentration in the Pd-Co particles increases with an increase in the Pd:Co ratio up to 1:2 and then remains at a constant level. In addition, monometallic Co particles were present in the samples with the Pd:Co ratio higher then 1:2. The optimal combination of catalytic properties (the ethylene yield is 62–63%) is typical for catalysts with a Pd:Co molar ratio of 1:2–1:4. which is mainly due to the presence of bimetallic particles containing ~41–43% by at. of cobalt.

Highly Active Ruthenium Phosphide Catalyst for Selective Hydrogenation of Acetylene and Its Reaction Mechanism

Highly Active Ruthenium Phosphide Catalyst for Selective Hydrogenation of Acetylene and Its Reaction Mechanism

Single-Atom Alloy Pd1Ag10/CeO2–ZrO2 as a Promising Catalyst for Selective Alkyne Hydrogenation

The effect of support on the performance of Pd1Ag10/Al2O3 and Pd1Ag10/CeO2–ZrO2 catalysts in the selective hydrogenation of diphenylacetylene (DPA) was studied. Characterization of the catalyst by DRIFTS-CO and HRTEM revealed the formation of a PdAg single-atom alloy (SAA) structure on the surface of PdAg nanoparticles, with Pd1 sites isolated by Ag atoms. It was found that the use of CeO2–ZrO2 as a carrier makes it possible to increase the activity of the Pd1Ag10 catalyst by a factor of three without loss of selectivity compared to the reference Pd1Ag10/Al2O3. According to the HRTEM data, this catalytic behavior can be explained by an increase in the dispersion of Pd1Ag10/CeO2–ZrO2 compared to its Pd1Ag10/Al2O3 counterpart. As evidenced by DRIFTS-CO data, the high selectivity of the Pd1Ag10/CeO2–ZrO2 sample presumably stems from the stability of the structure of isolated Pd1 sites on the surface of SAA Pd1Ag10/CeO2–ZrO2.

Effect of silicon carbide-based iron catalyst on reactor optimization for non-oxidative direct conversion of methane

The conversion of methane to olefins, aromatics, and hydrogen (MTOAH) can be used to stably obtain hydrocarbons when the effect of the catalytic surface is optimized from the reaction engineering perspective. In this study, Fe/SiC catalysts were packed into a quartz tube reactor. The catalytic surfaces of SiC and the impregnated Fe species decreased the apparent activation energies (Ea) of methane consumption in the blank reactor between 965 and 1020 °C. Consequently, the hydrocarbon yield increased by 2.4 times at 1020 °C. Based on the model reactions of ethane, ethylene, and acetylene mixed with hydrogen in the range of 500–1020 °C, an excess amount of Fe in the reactor favored the C–C coupling reaction over the selective hydrogenation of acetylene; consequently, coke formation was favored over the hydrogenation reaction. The gas-phase reactions and catalyst properties were optimized to increase hydrocarbon yields while reducing coke selectivity. The 0.2Fe catalyst-packed reactor (0.26 wt% Fe) resulted in a hydrocarbon yield of 7.1% and a coke selectivity of <2% when the ratio of the void space of the post-catalyst zone to the catalyst space was adjusted to be ≥2. Based on these findings, the facile approach of decoupling the reaction zone between the catalyst surface and the gas-phase reaction can provide insights into catalytic reactor design, thereby facilitating the scale-up from the laboratory to the commercial scale.

Carbon-confined Cu-Pd alloy nanoparticles as high-performance catalysts for acetylene selective hydrogenation

A catalyst with high selectivity for acetylene selective hydrogenation is highly desirable, yet ideal selectivity often comes at the price of activity loss. Here, a carbon confined Cu15Pd catalyst (Cu15Pd@C) was fabricated through an eco-friendly and efficient approach, which improves ethylene selectivity while at the same time, maintains high activity. Under optimized conditions, acetylene conversion of 100% and ethylene selectivity of 91% were simultaneously achieved. Comprehensive characterization and DFT reveal that the carbon layer not only promotes the formation of smaller nanoparticles, but effectively inhibits the production of green oil, which is associated to the confined spatial microenvironment by the carbon layer, posing steric hindrance to chain growth from acetylene coupling. A series of carbon confined Cu and Ag-based bimetal catalysts were fabricated through the same method, proving the facilitation of carbon layer on such selective hydrogenation universal, and also showed great potential of our method and catalysts in practical application.

Structure–Activity Relationship of Continuous Transformed Palladium Nanoclusters and Single Atoms for Selective Phenylacetylene Hydrogenation

Heterogeneous solid catalysts based on atomically dispersed Pd species are the most applicable catalysts in selective alkyne hydrogenation. However, the understanding of their structure–activity relationship remains ambiguous due to lack of structural analysis tools available and a unified synthetic system to obtain comparable Pd-based catalysts. Herein, we reported a convenient method to obtain Pd nanoclusters and Pd single atoms loaded on a nitrogen-doped carbon support (marked as Pd-NC@NC and Pd-SA@NC, respectively) in a uniform procedure and explored their structure–activity relationship in phenylacetylene hydrogenation. By the application of various kinds of characterization methods, we legibly illustrated the structures of Pd-NC@NC and Pd-SA@NC and found that Pd-NC@NC exhibited much higher mass activity than Pd-SA@NC (6.70 vs 0.33 mmol g–1 h–1) in phenylacetylene semi-hydrogenation. Theoretical calculations revealed that the different abilities of Pd nanoclusters and Pd1-N4 sites to adsorb reactants caused by steric hindrance were most likely to contribute to their different catalytic performances. This established structure–activity relationship provides guidelines for rationally designing metal catalysts for selective alkyne hydrogenation.

Cover Feature: Enhanced Stability of Atomically Dispersed Pd Catalysts via Ionic Liquid Layer Deposition for Selective Acetylene Hydrogenation to Ethylene in Excess Ethylene (ChemCatChem 6/2023)

Cover Feature: Enhanced Stability of Atomically Dispersed Pd Catalysts via Ionic Liquid Layer Deposition for Selective Acetylene Hydrogenation to Ethylene in Excess Ethylene (ChemCatChem 6/2023)

Frontispiece: Advances in Selective Electrocatalytic Hydrogenation of Alkynes to Alkenes

Graphical Abstract Selective electrocatalytic alkyne hydrogenation (EAH) is a promising alternative to traditional thermocatalytic hydrogenation for the purification of crude gaseous alkenes and the synthesis of fine chemicals. In this review, combining with the understandings on EAH mechanisms, the key development of EAH electrocatalysts and electrolyzers was systematically discussed. More information can be found in the Review article by J. Zhang and co-workers. (DOI: 10.1002/chem.202202979)

Controllable Deposition of Bi onto Pd for Selective Hydrogenation of Acetylene.

The rational regulation of catalyst active sites at atomic scale is a key approach to unveil the relationship between structure and catalytic performance. Herein, we reported a strategy for the controllable deposition of Bi on Pd nanocubes (Pd NCs) in the priority order from corners to edges and then to facets (Pd NCs@Bi). The spherical aberration-corrected scanning transmission electron microscopy (ac-STEM) results indicated that Bi2O3 with an amorphous structure covers the specific sites of Pd NCs. When only the corners and edges of the Pd NCs were covered, the supported Pd NCs@Bi catalyst exhibited an optimal trade-off between high conversion and selectivity in the hydrogenation of acetylene to ethylene under ethylene-rich conditions (99.7% C2H2 conversion and 94.3% C2H4 selectivity at 170 °C) with remarkable long-term stability. According to the H2-TPR and C2H4-TPD measurements, the moderate hydrogen dissociation and the weak ethylene adsorption are responsible for this excellent catalytic performance. Following these results, the selectively Bi-deposited Pd nanoparticle catalysts showed incredible acetylene hydrogenation performance, which provides a feasible perspective to design and develop highly selective hydrogenation catalysts for industrial applications.

Enhanced Stability of Atomically Dispersed Pd Catalysts via Ionic Liquid Layer Deposition for Selective Acetylene Hydrogenation to Ethylene in Excess Ethylene

AbstractA series of TiO2‐supported Pd catalysts with different amounts of ionic liquid (IL) were synthesized for the selective hydrogenation of acetylene to ethylene in excess ethylene. CO Fourier transform infrared spectroscopy (FTIR), high‐angle annular dark‐field‐scanning transmission electron microscopy (HAADF‐STEM), and X‐ray photoelectron spectroscopy (XPS) suggested that the Pd species in the catalysts synthesized via the strong electrostatic adsorption (SEA) method exist predominantly as isolated atoms on TiO2 independent of the presence of the IL. Using a combination of FTIR and XPS, it was found that IL deposition on Pd catalysts induces a change in the electronic structure of atomically dispersed Pd atoms. The IL‐modified catalysts exhibited improved stability in acetylene hydrogenation compared to IL‐free catalysts owing to their higher coke resistance. Thus, this study provides a novel synthetic strategy based on IL deposition for improving the coke resistance and stability of atomically dispersed catalysts.