Liquid-phase Hydrogenation Of Acetylene Research Articles

Kinetic Studies of Liquid Phase Hydrogenation of Acetylene for Ethylene Production Using a Selective Solvent over a Commercial Palladium/Alumina Catalyst

Kinetic Studies of Liquid Phase Hydrogenation of Acetylene for Ethylene Production Using a Selective Solvent over a Commercial Palladium/Alumina Catalyst

Experimental study and modeling of the liquid phase hydrogenation of acetylene

Selective hydrogenation of acetylene is an important process for both ethylene purification and ethylene production from acetylene in the industry. Herein, we proposed liquid phase acetylene hydrogenation for high feed concentrations of C2H2 (8 %) and CO (20 %), which is used to produce ethylene as a subsequent process of partial oxidation of natural gas. The experiments were carried out in a stirred tank reactor using N-methylpyrrolidone (NMP) as solvent and PdAg/SiO2 as catalyst. The liquid phase process obtained a much higher selectivity to ethylene (92 %) with only 8 % selectivity to green oil (GO) and C4, compared to 71 % ethylene selectivity in gas phase hydrogenation. Furthermore, in the liquid phase ethylene selectivity increased with increasing acetylene conversion, especially in the conversion range of 80–100 %. We developed a model incorporating reaction kinetics, mass transfer and reactor model to predict the acetylene conversion and ethylene selectivity in liquid phase hydrogenation. The calculation results indicated that hydrogenation in the liquid phase operated at a lower acetylene concentration and a higher H2/C2H2 ratio, especially under high acetylene conversions. This explains why the liquid phase hydrogenation of acetylene has a much higher selectivity to ethylene than the gas phase process.

The nature of modifying effect of gallium on Pd-Ga/Al2O3 catalyst for liquid-phase selective acetylene hydrogenation

The structural properties of Pd-Ga/γ-Al2O3 samples prepared from joint Pd(NO3)2 and Ga(NO3)3 solution and their catalytic properties in liquid-phase acetylene hydrogenation have been studied. Using temperature programmed reduction (TPR-H2), transmission electron microscopy (TEM), diffuse reflectance infrared Fourier transform spectroscopy of adsorbed CO (CO-DRIFTS) and X-ray photoelectron spectroscopy (XPS) it was found that an increase in the ethylene selectivity to ∼ 66–70% is explained by the modification of the electronic properties of palladium by gallium at a Ga:Pd molar ratio of 0.5 and by the formation of bimetallic Pd2Ga particles in the case of Ga:Pd = 2.

Gas-Phase and Liquid-Phase Hydrogenation of Acetylene in Lean and Enriched Mixtures over Supported Modified Palladium Catalysts

The results of studies on selective hydrogenation of acetylene to ethylene over bimetallic palladium-containing catalysts were summarized. Regular and specific features of the catalyst action in gas-phase hydrogenation of traces of acetylene in the acetylene-ethylene mixture produced by pyrolysis of petroleum feedstock, as well as in liquid-phase hydrogenation of mixtures enriched in acetylene and hydrogen were analyzed. The advantages of ethylene production by liquid-phase hydrogenation of acetylene were shown, and ways of increasing the selectivity to ethylene in this process were considered.

Liquid-phase acetylene hydrogenation over Ag-modified Pd/Sibunit catalysts: Effect of Pd to Ag molar ratio

A series of bimetallic Pd–Ag catalysts supported on the carbon material Sibunit was synthesized for selective liquid-phase acetylene hydrogenation. Using XRD and EXAFS it was shown that palladium and silver in the 0.5% Pd–Ag/Sibunit can form bimetallic PdxAg(1−x) nanoparticles with the composition depending on the Pd:Ag ratio. The active component of Pd–Ag(1:0.25)/Sibunit, Pd–Ag(1:1)/Sibunit and Pd–Ag(1:4)/Sibunit is represented by the particles of Pd0.74Ag0.26, Pd0.60Ag0.40 and Pd0.41Ag0.59 nanoalloys, respectively. An increase of the quantity of silver decreases the catalyst activity. The XPS study revealed that this phenomenon is caused by a decrease in the surface concentration of palladium (geometrical effect) and an increase in the degree of palladium electronic modification with silver (electronic effect). The latter exerts a beneficial effect on the reaction selectivity: as the Pd:Ag molar ratio is raised to 1:2, selectivity to ethylene increases to 81% (X > 97%), which exceeds 2.7-fold the selectivity of Pd/Sibunit.

Газофазное и жидкофазное гидрирование ацетилена в обедненных и обогащенных смесях на нанесенных модифицированных палладиевых катализаторах

В представленном обзоре обобщены результаты исследований, посвященных селективному гидрированию ацетилена в этилен на биметаллических палладиевых катализаторах. Проанализированы общие закономерности и особенности их действия в газофазном гидрировании следов ацетилена в ацетилен-этиленовой смеси, получаемой пиролизом нефтяного сырья, а также в процессе жидкофазного гидрирования смесей, обогащенных ацетиленом и водородом. Показаны преимущества получения этилена путем гидрирования ацетилена в жидкой фазе и рассмотрены способы повышения селективности этого процесса.

Liquid-Phase Hydrogenation of Acetylene to Ethylene in a Flow on Pd/Al2O3 and Pd-Ga/Al2O3 Catalysts in the Presence of CO

Catalytic properties of Pd/Al2O3 and Pd-Ga/Al2O3 in selective liquid-phase hydrogenation of acetylene in a flow under pressure and the effect exerted on them by introduction of CO into the feed were studied. The presence of CO in the reaction mixture ensures the reaction with the predominant formation of ethylene. Introduction of gallium into the catalyst formulation prevents the catalyst deactivation. Simultaneous action of these factors allows reaching high yield of the target product in combination with long operation life of the catalyst.

Study of the Influence Exerted by Zinc Additive on the Structure and Catalytic Properties of Pd/Al2O3 Catalysts for Liquid-Phase Hydrogenation of Acetylene

Effect of the phase composition of aluminum oxide [γ- and (δ + θ) phase] and introduction of zinc additives on the catalytic properties of 0.5% Pd/Al2O3 systems in the reaction of liquid-phase hydrogenation of acetylene into ethylene under an elevated pressure in a flow-through mode was studied. An increase in the activity of the Pd catalyst upon modification with zinc is only observed in the case of a system supported by the mixed phase of (δ + θ) aluminum oxide. XAFS spectroscopy was used to find that the increase in the activity and selectivity with respect to ethylene (in the presence of carbon monoxide) on the (0.5% Pd–0.62% Zn)/(δ + θ)-Al2O3 catalyst is correlated with the formation of the PdZn intermetallic compound.

Synthesis and characterization of Sibunit-supported Pd–Ga, Pd–Zn, and Pd–Ag catalysts for liquid-phase acetylene hydrogenation

Pd/Sibunit and Pd–M/Sibunit (M = Ga, Zn, or Ag) catalysts have been synthesized, and their catalytic properties in liquid-phase acetylene hydrogenation have been investigated. Doping of the palladium catalyst with a metal M leads to the formation of the Pd2Ga, PdZn, or Pd0.46Ag0.54 bimetallic compound. The bimetallic particles are much smaller (1.6–2.0 nm) than the monometallic palladium particles (4.0 nm). Doping with zinc raises the ethylene selectivity by 25% without affecting the activity of the catalyst. Specific features of the effect of each of the dopants on palladium are reported.

Effect of Preparation Conditions on Characteristics of Modified Palladium Catalysts of Liquid-Phase Acetylene Hydrogenation

Effect of Preparation Conditions on Characteristics of Modified Palladium Catalysts of Liquid-Phase Acetylene Hydrogenation

Pd/Ga2O3–Al2O3 catalysts for the selective liquid-phase hydrogenation of acetylene to ethylene

The structure of Ga2O3–Al2O3 supports and Pd/Ga2O3–Al2O3 catalysts and the performance of these catalysts in liquid-phase acetylene hydrogenation have been investigated. The deposition of Ga(NO3)3 onto Al2O3 by impregnation followed by calcination of the impregnated support at 600°C yields γ-Ga2O3–Al2O3 solid solutions containing up to 50 wt % Ga2O3. X-ray diffraction characterization of model palladium catalysts and their temperature-programmed reduction with hydrogen have demonstrated that, while palladium in Pd/Ga2O3 is in the form of a Pd2Ga alloy, in the Pd/γ-Ga2O3–Al2O3 catalyst there is no direct interaction between PdО and Ga2O3 particles and palladium is in the monometallic state. The introduction of 10–20 wt % gallium oxide into Al2O3 lowers the activity of the supported palladium catalyst relative to that of the initial Pd/Al2O3 but increases the ethylene yield by enhancing the ethylene formation selectivity.

Селективное жидкофазное гидрирование ацетилена в этилен в проточном режиме на нанесенных палладиевых катализаторах

Селективное жидкофазное гидрирование ацетилена в этилен в проточном режиме на нанесенных палладиевых катализаторах

Comparative EXAFS and TEM study of Pd/Sibunit and Pd-Ga/Sibunit catalysts for liquid-phase acetylene hydrogenation

The structural characteristics and catalytic properties of Pd/Sibunit and Pd-Ga/Sibunit catalysts for the liquid-phase hydrogenation of acetylene prepared via impregnation of joint alcoholic precursor solutions are studied. A surface film of gallium oxide covering the surfaces of bimetallic particles forms on a sample modified with gallium, leading to partial blocking of its active centers. This explains the lower activity and selectivity to ethylene of Pd-Ga/Sibunit catalyst, relative to Pd/Sibunit.

EXAFS study of Pd/Sibunit and Pd–Ga/Sibunit catalysts for liquid-phase hydrogenation of acetylene to ethylene

A series of catalysts Pd/Sibunit and Pd–Ga/Sibunit were prepared by impregnation with joint solutions of palladium and gallium nitrates in ethanol. The state of the active component and catalytic properties of the samples were studied in the liquid-phase hydrogenation of acetylene. The EXAFS method showed that the active component in the gallium-modified catalysts exists in the form of a non-stoichiometric Pd–Ga solid solution. The activity of the catalysts was found to be determined by the ratio Pd:Ga. It was shown that at the molar ratios Ga:Pd>0.5:1, the catalytic activity is reduced by blocking the surface of the bimetallic particles by gallium oxide.

The influence of a carbon support on the catalytic properties of Pd/Sibunit and Pd-Ga/Sibunit catalysts for liquid-phase acetylene hydrogenation

The Pd/Sibunit and Pd-Ga/Sibunit catalysts, which were supported on Sibunit with different textural characteristics, for liquid-phase acetylene hydrogenation were investigated. It was shown that the use of the support with a large surface area leads to an increase in catalytic activity and selectivity due to the increased dispersion of the active component. The promoting effect of gallium correlates with the probability of contact between the supported Pd and Ga components.

EXAFS study of model Pd/Ga2O3 catalysts for the liquid-phase hydrogenation of acetylene before and after the reaction

The catalytic characteristics of Pd/Ga2O3 samples in the liquid-phase hydrogenation of acetylene to ethylene are studied. The structure of the catalyst’s components before and after the reaction is examined by EXAFS spectroscopy. The activity of the original (after drying) samples results from the reduction of the original palladium oxide to a metallic state in the reaction medium. According to EXAFS, the catalysts reduced at 200°C contain small amounts of Pd-Ga alloy that was preserved in the reaction medium during the liquid-phase hydrogenation of acetylene and presumably increased the activity and selectivity of the samples.

Pd/Fiber glass and Pd/5% γ-Al2O3/Fiber glass catalysts by surface self-propagating thermal synthesis

The technique of Surface Self-propagating Thermal Synthesis (SSTS) was used to prepare Pd/γ-Al2O3/fiber glass (FG) catalysts for selective liquid-phase hydrogenation of acetylene in the presence of CO. The results of XRD SR analysis (in synchrotron radiation) in combination with the technique of arrested combustion shed new light on the dynamic of phase transformations in the systems under study and variation in the size of diffraction-active crystallites. The catalytic performance of synthesized catalysts was found to be close to that of similar conventionally prepared catalysts. The EXAFS and TEM data afforded to estimate the variation in relative amounts of Pd0 and PdO in synthesized catalysts. In the course of selective hydrogenation, PdO rapidly (<15 min) reduced to Pd0.

EXAFS study of Pd/Ga2O3 model catalysts of selective liquid-phase hydrogenation of acetylene to ethylene

Model catalysts Pd/Ga2O3 of selective liquid-phase hydrogenation of acetylene to ethylene were prepared by impregnation of β-Ga2O3 with a palladium nitrate solution with following drying and reduction in a hydrogen flow at 200°C. A part of the samples was then calcined in an argon flow at 200–500°C. The as-prepared samples were tested in the reaction of selective liquid-phase hydrogenation of acetylene. EXAFS was used to study structure of the catalyst components. Based on the EXAFS data it was found that Pd–Ga alloys present in the subsurface region of Pd particles. The presence of these alloys increases activity and selectivity of catalysts. The alloys are decomposed by calcination in inert atmosphere following decrease in catalytic activity.

Liquid-phase hydrogenation of acetylene on the Pd/sibunit catalyst in the presence of carbon monoxide

The liquid-phase catalytic hydrogenation of acetylene into ethylene in the presence of CO over palladium supported on the graphite-like material Sibunit has been investigated. Carbon monoxide is an effective modifier of the selective hydrogenation process, exerting its effect by competing with acetylene and ethylene for chemisorption sites on the palladium surface. Under the optimum conditions (T = 90°C; N-methylpyrrolidone solvent; feed consisting of 2 vol % C2H2, 90 vol % H2, and He balance), the introduction of 2 vol % CO ensures a high ethylene selectivity of 89.6 ± 1.5% at an acetylene conversion of 95.8 ± 1.3%, with the acetylene converted into hydrooligomers taken into account.