Selective Hydrogenation Of Acetylene Research Articles

Nonintrusive parameter adaptation of chemical process models with reinforcement learning

Model-based control is one of the most prevalent techniques for designing and controlling engineering systems. However, many of these systems are complex and characterized by changing dynamics. Hence, online system identification is required to achieve optimum adaptive control performance for such complex systems. This work proposes an algorithm for nonintrusive, online, nonlinear parameter estimation of physical models using deep reinforcement learning (RL). The problem of training a neural network for parameter estimation is formulated as a reinforcement learning problem. The RL-based parameter estimation policy is tested on a simulation of the selective hydrogenation of acetylene, which is a highly nonlinear system. The learned model estimation policy is able to correctly predict the states of the system with a prediction error of less than 1% in various conditions, such as in the presence of measurement noise and structural differences in models.

Advances in Selective Electrocatalytic Hydrogenation of Alkynes to Alkenes.

Selective electrochemical hydrogenation of alkynes to alkenes under ambient conditions is a promising alternative to the traditional energy-intensive and high-cost thermocatalytic hydrogenation. However, the systematic summary on the electrocatalysts and electrolyzers remains lacked. Herein, we demonstrate a comprehensive review about recent achievements in the electrocatalysts including noble metal and non-noble-metal materials. Several effective strategies of catalyst design were developed to improve alkyne conversion, and alkene selectivity, for example, accelerating the formation of active hydrogen species, enhancing alkyne adsorption and suppressing the side reactions. Furthermore, the advantages and disadvantages of various electrolyzers are systematically discussed. Accordingly, major challenges and future trends in this field are proposed.

Ni -chitosan/carbon nanotube: An efficient biopolymer -inorganic catalyst for selective hydrogenation of acetylene

This work developed an efficient Ni catalyst based on chitosan for selective hydrogenation of acetylene. The Ni catalyst was prepared by the reaction of the chitosan/carbon nanotube composite with NiSO4 solution. The synthesized Ni-chitosan/carbon nanotube catalyst was characterized by inductively coupled plasma, FTIR, SEM and XRD. The results of FTIR and XRD demonstrated that Ni2+ successfully coordinated with chitosan. The addition of chitosan greatly improved the catalytic performances of Ni-chitosan/carbon nanotube catalyst. Over the Ni-chitosan/carbon nanotube catalyst, both the acetylene conversion and the selectivity to ethylene all achieved 100% at 160 °C and 190 °C, respectively. The catalytic performances of 6 mg Ni-chitosan/carbon nanotube catalyst were even better than that of 400 mg Ni single atom catalyst in literature. Extending the crosslinking time of chitosan and increasing the amount of the crosslinking agent were beneficial to enhance the catalytic effect of Ni-chitosan/carbon nanotube catalyst.

Selective semi-hydrogenation of alkynes on palladium-selenium nanocrystals

The selective hydrogenation of alkyne plays a crucial role in chemical industry, yet great challenges still remain for suppressing the over-hydrogenation to alkane while maintaining high activity. Herein, we demonstrate that palladium–selenium intermetallic nanocrystals (Pd4.5Se NCs, Pd4Se NCs, Pd7Se2 NCs, and Pd7Se4 NCs) can enable the semi-hydrogenation of alkyne to alkene. In situ characterizations and theoretical simulations indicate that the geometric and electronic synergetic effects of Pd–Se NCs can facilitate the σ-π associative adsorption of CC bond in alkyne but suppress the over-hydrogenation of alkene. In particular, Pd4.5Se NCs exhibit high selectivity to the semi-hydrogenation of phenylacetylene (PA) to styrene (≥98.0 %) in the full conversion range, which has outperformed Pd NCs/C and commercial Lindlar catalyst. This work expands the mechanism understanding of Pd-based catalysts for selective hydrogenation, which may attract great interests of researchers in material science, chemistry, and catalysis.

Understanding the Role of Coordinatively Unsaturated Al3+ Sites on Nanoshaped Al2O3 for Creating Uniform Ni–Cu Alloys for Selective Hydrogenation of Acetylene

Understanding the Role of Coordinatively Unsaturated Al³⁺ Sites on Nanoshaped Al₂O₃ for Creating Uniform Ni–Cu Alloys for Selective Hydrogenation of Acetylene

Selective hydrogenation of highly concentrated acetylene streams over mechanochemically synthesized PdAg supported catalysts

The effect of multiple parameters on the selective hydrogenation of acetylene in equimolar acetylene–ethylene streams on supported PdAg catalysts was studied, and optimal conditions were found for high conversion, selectivity, and catalyst stability.

M supported on Al-defective Al2-δO3 (M = Fe, Co, Ni, Cu, Ag, Au) as catalysts for acetylene semi-hydrogenation: a theoretical perspective.

Semi-hydrogenation of acetylene is of great importance for both industry and academia. High prices and limited supplements of noble metals leave room for developing base metal catalysts. Experiments revealed the atomically dispersed Cu supported by Al2O3 with excellent long-term stability and high ethylene selectivity, but the physical nature has rarely been investigated theoretically. DFT calculations and microkinetic modeling revealed that the surface OH species could stabilize Cu1/Al2-δO3 and enhance its catalytic performance. The selectivity of ethylene formation decreases with increasing copper clusters (e.g., Cu1/Al2-δO3> Cu4/Al2-δO3> Cu8/Al2-δO3), meaning that the atomically dispersed copper may be a potential candidate for acetylene semi-hydrogenation. The structures of a series of single site catalysts M1/Al2-δO3 (M = Fe, Co, Ni, Ag, Au) are similar to that of Cu1/Al2-δO3, but their performances in catalyzing acetylene semi-hydrogenation are different. M1/Al2-δO3 (M = Ag, Au) shows higher selectivity than Cu1/Al2-δO3, while M1/Al2-δO3 (M = Fe, Co, Ni) demonstrates a higher turnover frequency (TOF) of ethylene than Cu1/Al2-δO3. Moreover, our results indicate that the Ni1-Cu1/Al2-δO3 alloy shows both high activity and ethylene selectivity. The present results show a compensation between the reactivity and the selectivity, suggesting that alloys of VIIIB metals with IB metals like Ni1-Cu1/Al2-δO3 may be efficient candidate catalysts in acetylene selective hydrogenation.

Selective hydrogenation of acetylene to ethylene by alkali-metal palladium complex hydrides.

A series of alkali-metal palladium complex hydrides have been shown to be catalytically active and selective for partial hydrogenation of acetylene to ethylene. The complex hydrides differ in composition, structure, and catalytic function as compared to the conventional Pd metal or alloy catalysts.

A highly active catalyst derived from CuO particles for selective hydrogenation of acetylene in large excess ethylene.

The removal of acetylene impurities is indispensable in the production of ethylene. An Ag-promoted Pd catalyst is industrially used to remove acetylene impurities by selective hydrogenation. It is highly desirable to replace Pd with non-precious metals. In the present investigation, CuO particles, which are most frequently used as the precursors for Cu-based catalysts, were prepared through the solution-based chemical precipitation method and used to prepare high-performance catalysts for selective hydrogenation of acetylene in large excess ethylene. The non-precious metal catalyst was prepared by treating CuO particles with acetylene-containing gas (0.5 vol% C2H2/Ar) at 120 °C and subsequent hydrogen reduction at 150 °C. The obtained catalyst was tested in selective hydrogenation of acetylene in a large excess of ethylene (0.72 vol% CH4 as the internal standard, 0.45 vol% C2H2, 88.83 vol% C2H4, 10.00 vol% H2). It exhibited significantly higher activity than the counterpart of Cu metals, achieving 100% conversion of acetylene without ethylene loss at 110 °C and atmospheric pressure. The characterization by means of XRD, XPS, TEM, H2-TPR, CO-FTIR, and EPR verified the formation of an interstitial copper carbide (CuxC), which was responsible for the enhanced hydrogenation activity.

Carbon-Confined Cu-Pd Alloy Nanoparticles as High-Performance Catalysts for Acetylene Selective Hydrogenation

Carbon-Confined Cu-Pd Alloy Nanoparticles as High-Performance Catalysts for Acetylene Selective Hydrogenation

Rational Design of PdAg Catalysts for Acetylene Selective Hydrogenation via Structural Descriptor-based Screening Strategy

Pd-based catalysts are widely used in selective hydrogenation reactions, where the surface structure has been found as a key factor to improve the yield of the target product. However, little study is involved in a prediction model for rationally engineering the surface structure of Pd-based catalysts with their catalytic properties. Here, using PdAg bimetal catalyzed acetylene selective hydrogenation as a probe reaction, we combined density functional theory calculations and microkinetic models and then revealed structure–performance relationships for PdAg bimetal based on structure descriptors, which qualitatively reflect the ligand effect and stress effect on the adsorption of reactants. The descriptor-based screening strategy allows us to rationally engineer the surface status (element composition and atomic arrangement) of PdAg bimetals and identify candidates with an optimized yield of ethylene product, namely, Pd1Ag3 alloy, which is further confirmed by available references and our catalysis experiments. This screening strategy based on structure descriptors may be generalized for rationally designing the surface structure of Pd-based catalysts for other hydrogenation reactions beyond acetylene selective hydrogenation.

Graphdiyne anchoring to construct highly dense palladium trimer active sites for the selective hydrogenation of acetylene

Graphdiyne anchoring to construct highly dense palladium trimer active sites for the selective hydrogenation of acetylene

The Role of Interstitial Solid Solutions in the Formation of Active Component in Supported Palladium Catalysts for Selective Hydrogenation of Acetylene to Ethylene

The effect of adsorption of the reaction medium components on selective hydrogenation of acetylene to ethylene under the action of supported palladium catalysts is considered. The role of interstitial solid solutions of carbon and hydrogen in palladium, which are formed upon contact of the catalyst with the reaction medium, in the mass-transfer processes between surface and subsurface layer of the active component is revealed. The ratio of activation barriers for ethylene desorption/adsorption processes, which determines the selectivity of acetylene hydrogenation, can change in dependence on the structure of palladium nanoparticles and its electronic state. Therewith, changes in the electronic state affect the energy of activated desorption of ethylene from palladium particles, and their structural features determine the energy of activated adsorption and the subsequent hydrogenation of ethylene to ethane.

Synergistic trimetallic Ni–Cu–Sn catalysts for efficient selective hydrogenation of phenylacetylene

Selective hydrogenation of phenylacetylene is the most effective way to remove a small amount of phenylacetylene from styrene, but it is still a challenge to develop catalysts with high activity and selectivity. Herein, a series of non-precious bimetallic Ni3M/SiO2 (M = Zn, Sn, Cd, Fe, Co, Cu, or Mo) and trimetallic Ni3Cu–Sn/SiO2 catalysts were prepared and applied to selective hydrogenation of phenylacetylene. A trade-off between activity and selectivity was observed on Ni3M/SiO2, where Ni3Cu/SiO2 showed the best hydrogenation activity because of the hydrogen spillover effect of the Ni–Cu alloy, while Ni3Sn/SiO2 exhibited the highest selectivity to styrene due to the active-site isolation effect of the Ni–Sn alloy. Impressively, trimetallic Ni3Cu–Sn/SiO2 offered superior catalytic performance (94 % styrene selectivity at >99 % phenylacetylene conversion) as compared to bimetallic catalysts, owing to the synergistic effect among Ni, Cu, and Sn. In the case of Cu and Sn co-doping, the hydrogen spillover on the Ni–Cu alloy was deeply suppressed by Sn, which enabled an effective modification of the geometric and electronic structures of Ni to favor styrene desorption. The hydrogenation activity of Ni3CuSn0.3/SiO2 can be readily enhanced by increasing the metal loading and further improved by elevating the reaction temperature and pressure, but meanwhile the high selectivity is little affected. This work demonstrates a multi-metal synergistic strategy to break the activity–selectivity trade-off of Ni-based bimetallic catalysts in the selective hydrogenation of alkynes.

Direct utilization of crude and waste H2 via CO-tolerant hydrogenation

Direct utilization of crude and waste H2 via CO-tolerant hydrogenation

Chain length effects of phenylene sulfide modifiers on selective acetylene partial hydrogenation over Pd catalysts

We recently reported that polymer chains with phenylene sulfide moieties can efficiently modify the Pd catalyst surface, enabling selective partial hydrogenation of acetylene under ethylene-rich conditions. In the present study, we synthesized oligomeric and polymeric phenylene sulfides with tailored molecular sizes to systematically investigate the catalytic effect of chain length of organic modifiers. The results showed that the increased chain length of the modifiers is beneficial for improving the acetylene partial hydrogenation selectivity by inhibiting adsorption and full hydrogenation of ethylene. This was attributed to the fact that modifiers with a greater number of sulfide groups per molecule can bind more efficiently to the Pd surface for entropic reasons (chelate effect) and thus better inhibit ethylene adsorption. In contrast, the adsorption of acetylene to Pd was nearly unaffected by the presence and size of the modifiers owing to its stronger binding ability and small kinetic diameter. Modifiers with larger chain lengths were also advantageous in improving long-term catalyst stability because of their higher thermochemical stability and greater ability to inhibit the formation of carbonaceous deposits. The present results showed that polymers can act as more efficient and long-lasting selectivity modifiers than commonly used small organic molecules.

Selective Hydrogenation of Acetylene over Palladium Catalysts Based on Aluminosilicate Nanotubes

Selective Hydrogenation of Acetylene over Palladium Catalysts Based on Aluminosilicate Nanotubes

Selective hydrogenation of acetylene to ethylene: Performance of a Pt monolayer over an α-WC(0001) surface for binding and hydroconversion of acetylene

Ethylene (C2H4) is a useful hydrocarbon in polymerization reactions and as a probe system to understand hydrogenation reactions of complex unsaturated hydrocarbons and olefins. However, C2H4 streams usually contain small amounts of acetylene (C2H2), which deactivates the catalyst used for ethylene hydroconversions. This issue is overcome by hydrogenating C2H2 selectively into C2H4, avoiding further ethylene hydrogenation reactions. For this process, expensive palladium-based catalysts have shown good performance. Here, based on the results of density functional calculations, we propose the use of cheap and easily available tungsten carbide (WC) as a support of Pt, being an alternative material to Pt-group metals. Clean α-WC(0001)-C and α-WC(0001)-W were compared with Pt-supported on them, i.e. Pt/α-WC(0001)-C and Pt/α-WC(0001)-W. The theoretical results indicate that among the evaluated systems, the Pt/α-WC(0001)-W surface has a remarkable capacity to achieve selective hydrogenation of C2H2 into C2H4, with a reaction energy of -0.44 eV, avoiding further hydrogenation into ethyl (C2H5, +0.29 eV) and ethane (C2H6, +0.33 eV). In Pt/α-WC(0001)-W, the surface poisoning is avoided since ethylidyne (CCH3), a species responsible of catalyst deactivation is not formed. In contrast, the selective acetylene hydrogenation is not feasible on Pt/α-WC(0001)-C, α-WC(0001)-C, and α-WC(0001)-W; these surfaces are all poisoned due to the formation and deposition of CCH3 and C2H2 on them. The atomic charges indicate that the electron density flux from the Pt/α-WC(0001)-W surface to the C2H2 and C2H4 molecules is higher as compared to bare α-WC(0001)-W, since the Pt monolayer modulates electron density migration, as verified by a Projected Density of States (PDOS) analysis. The C2H4 desorption rate from Pt/α-WC(0001)-W is reasonable in the temperature range from 340 to 640 K, providing a theoretical basis for further practical catalysis. The results of this work show that Pt/α-WC(0001)-W is a good candidate for acetylene selective hydrogenation, opening a new window for further experimental and/or theoretical works.

Amino acid (histidine) modified Pd/SiO2 catalyst with high activity for selective hydrogenation of acetylene

Suppressing the excessive hydrogenation capacity of palladium has great significance for selective hydrogenation of acetylene. Herein, an amino acid (histidine or His in abbreviation) modified Pd/SiO2 catalyst (Pd-His/SiO2) for selective hydrogenation of acetylene was prepared by incipient wetness impregnation, followed by hydrogen reduction at 240 °C. The intense interaction between Pd and histidine greatly affects the structure and properties of Pd-His/SiO2. The Pd nanoparticles are highly dispersed on the support with an average diameter of 1.0 nm and positively charged. The use of histidine weakens the adsorption of acetylene and ethylene on the metal. Especially, the adsorption of di-σ-bonded ethylene is significantly impaired on the catalyst, which is beneficial to improve the ethylene selectivity. The conversion of acetylene is up to 100.0 % at 160 °C on Pd-His/SiO2 while the ethylene selectivity reaches 81.5 %. A 50-hour test at 160 °C confirms the good stability of Pd-His/SiO2.

Semi-Hydrogenation of Acetylene to Ethylene Catalyzed by Bimetallic CuNi/ZSM-12 Catalysts

The purpose of this work is to develop a low-cost and high-performance catalyst for the selective catalytic hydrogenation of acetylene to ethylene. Non-precious metals Cu and Ni were selected as active ingredients for this study. Using ZSM-12 as a carrier, Cu-Ni bimetallic catalysts of CuNix/ZSM-12 (x = 5, 7, 9, 11) with different Ni/Cu ratios were prepared by incipient wetness impregnation method. The total Cu and Ni loading were 2 wt%. Under the optimal reaction conditions, the acetylene conversion was 100%, and the ethylene selectivity was 82.48%. The CuNi7/ZSM-12 prepared in this work exhibits good performance in the semi-hydrogenation of acetylene to ethylene with low cost and has potential for industrial application.