Catalytic Hydrogenation Of Carbon Dioxide Research Articles

Catalytic Hydrogenation of Carbon Dioxide with a Highly Active Hydride on Ir(III)–Pincer Complex: Mechanism for CO2 Insertion and Nature of Metal–Hydride Bond

Abstract A reaction mechanism for the hydrogenation of CO2 to formate catalyzed by an Ir(III)–pincer trihydride complex has been investigated with density functional theory calculations. Two routes for the formation of formate were considered: (I) the insertion of CO2 into the Ir–H bond with the assistance of the metal center, and (II) the direct addition of hydride to CO2 via nucleophilic attack. Route II is energetically more favorable than route I. Molecular orbital and natural bond orbital analyses showed that this trihydride complex consists of two kinds of hydrides with distinct Ir–H bond properties, and the hydride in the plane vertical to the pyridine moiety is highly active. The whole catalytic cycle for CO2 hydrogenation to formate is exothermic by 30.3 kcal mol−1, and the rate-limiting step is the regeneration of the active complex, which involves a barrier of 15.6 kcal mol−1. The theoretical results are in good agreement with and give a reasonable explanation to the experimental observations. Moreover, the results imply that the type of a metal–hydride bond might determine which route the CO2 insertion takes, route I or route II.

Recent advances in catalytic hydrogenation of carbon dioxide

Owing to the increasing emissions of carbon dioxide (CO(2)), human life and the ecological environment have been affected by global warming and climate changes. To mitigate the concentration of CO(2) in the atmosphere various strategies have been implemented such as separation, storage, and utilization of CO(2). Although it has been explored for many years, hydrogenation reaction, an important representative among chemical conversions of CO(2), offers challenging opportunities for sustainable development in energy and the environment. Indeed, the hydrogenation of CO(2) not only reduces the increasing CO(2) buildup but also produces fuels and chemicals. In this critical review we discuss recent developments in this area, with emphases on catalytic reactivity, reactor innovation, and reaction mechanism. We also provide an overview regarding the challenges and opportunities for future research in the field (319 references).

A growing position of methanol and hydrogen as energy carriers in the global economy

The changes taking place in the pool of materials available for the production of energy carriers and for the global chemical industry have been characterized. The report was prepared with due consideration of the growing population of our planet and the development of our civilization. The hydrogen production methods have been described. Subsequently, the research findings have been provided on catalytic hydrogenation of carbon dioxide to methanol and hydrocarbons in the Fischer-Tropsch synthesis process.

Catalytic Hydrogenation of Carbon Dioxide Using Ir(III)−Pincer Complexes

Catalytic hydrogenation of carbon dioxide in aqueous potassium hydroxide was performed using a newly synthesized isopropyl-substituted PNP-pincer iridium trihydride complex as a catalyst. Potassium formate was obtained with turnover numbers up to 3,500,000 and a turnover frequency of 150,000 h(-1), both of which are the highest values reported to date.

Hybrid artificial neural network—First principle model formulation for the unsteady state simulation and analysis of a packed bed reactor for CO2 hydrogenation to methanol

Abstract Carbon dioxide emission is well recognized as the main source of global warming. The catalytic hydrogenation of carbon dioxide to methanol represents an effective method for preventing this side effect. The objective of this paper is to present a hybrid neural network model (NNM) for the simulation of a differential catalytic hydrogenation reactor of carbon dioxide to methanol. The hybrid model consists of two parts: a mechanistic model and a neural model. The mechanistic model employs heat transfer, mass transfer and pressure drop equations and calculates the effluent temperature of the reactor by taking outlet mole fractions from the output of a neural network model. The prepared hybrid model was used to simulate and identify an existing industrial methanol reactor. The bed of the reactor was assimilated to a pile of layers, each corresponding to a neural network (NN) model that can predict outlet composition of each layer as a function of time. The model was successfully tested with plant experimental data. The insights of this research indicate a very fast responding model in comparison to traditional models to demonstrate CO2 reduction as a function of time and reactor length. Variation of temperature and other compositions with time and bed height are also investigated in this article.

Catalytic hydrogenation of carbon dioxide over LaNi 5 activated during the reaction

The hydrogenation of carbon dioxide to methane can be catalyzed over an intermetallic compound of LaNi 5 at 250–350°C. The catalytic activity at 250°C increases during the reaction while X-ray diffraction (XRD) analyses show that the structure of the compound decomposes to La(OH) 3, LaCO 3OH, and metallic nickel. Formation of metallic nickel species during the reaction also takes place in a nickel–lanthanum oxides catalyst prepared by a coprecipitation method, however, the activity is not so high as the former catalyst. Surface analyses by X-ray photoelectron spectroscopy (XPS) suggest that new nickel species interacting with lanthanum cation, possibly Ni–O–La, are formed in LaNi 5 during the reaction, and the species are supposed to be rather active than metallic nickel.

99/00253 Effect of periodic operation on hydrogenation of carbon dioxide

Catalytic hydrogenation of carbon dioxide over Ni/SiO2 catalyst in a fixed-bed reactor was studied by varying the reaction temperature, space velocity, and mole fraction of the feed. Space velocity under 300 cm3/min·g-cat had no effect on the conversion of CO2. Conversion of CO2 increased and approached to the equilibrium conversion as the reaction temperature increased. There was no optimum fled composition for maximum COE conversion. Keeping the average feed composition in periodic operation with stoichiometric ratio of methanation reaction(H2/CO2=4), effect of cycle splits and periods of feeding cycle were studied. In periodic operation, conversion of CO2 and selectivity of methane were lower than those of steady state runs. However, selectivity to CO increased by periodic operation. Cycle period resonance of CO2 conversion was observed.

Catalytic hydrogenation of carbon dioxide with the cationic bis(chelate)rhodium complex [Rh(P⌢O) 2][BPh 4]

In contrast to the mono(chelate)rhodium complex CIRh(P∼O)(P⌢O) ( 1) ( P⌢ O = η 2(O,P)- chelated Cy 2PCH 2 CH 2OCH 3 ligand; P∼O = η 1( P)-coordinated) the corresponding cationic bis(chelate) complex [Rh(P⌢O) 2] + (anion: BPh 4 −) ( 4) acts as an efficient catalyst for the hydrogenation of carbon dioxide to produce formic acid. Turnover numbers up to 1000 within 7 h are achieved in methanol solution at 55°C. Stoichiometric reactions related to the characterization of possible reactive intermediates are also presented.

The Effect of Rhodium Particle Size on Ethanol Synthesis by Catalytic Hydrogenation of Carbon Dioxide over Silica Supported Rhodium Catalysts.

Ethanol synthesis by CO 2 hydrogenation was carried out over Rh/SiO 2 catalyst. Several catalysts were prepared using acetate hydrate, nitrate and chloride precursors of rhodium, and the effects of the precursor on reaction behavior were investigated. The remarkable effect of Rh precursor on the ethanol selectivity as well as activity of reaction was observed. The highest ethanol selectivity was obtained over the 5 wt% Rh/SiO 2 catalyst prepared from rhodium acetate hydrate precursor. It has been suggested that the difference in Rh precursor changed the mean particle size of Rh/SiO 2 catalysts, resulting in the change in the ethanol selectivity.

Catalytic hydrogenation of carbon dioxide into C2+ alcohols with Ir-Mo/SiO2

Catalytic hydrogenation of carbon dioxide into C2+ alcohols with Ir-Mo/SiO2

Mechanism and kinetics of CO and hydrocarbon formation in the heterogeneous catalytic hydrogenation of carbon dioxide on transition metals

A mechanism is proposed for the combined formation of carbon monoxide, methane, and higher hydrocarbons (C2+) from carbon dioxide and hydrogen in the presence of several transition metals. A complete kinetic model was obtained for a quantitative description of all the experimental data.

96/01448 Catalytic hydrogenation of carbon dioxide to hydrocarbons

96/01448 Catalytic hydrogenation of carbon dioxide to hydrocarbons

Activation of Carbon Dioxide, VI. Ligand Effects in the Catalytic Hydrogenation of Carbon Dioxide to Formic Acid Using in situ Catalysts Formed from [{(cod)Rh(μ‐Cl)}2] and Monodentate and Bidentate Phosphorus Ligands

AbstractHighly active catalysts for the hydrogenation of CO2 to formic acid in DMSO/NEt3 are formed in situ from [{(cod)Rh(μ‐Cl)}2] and various monodentate or bidentate ligands with phosphorus as the donor atom. Formic acid concentrations up to 2.3 · 0.2 mol l–1 can be obtained in less than 6 hours at ambient temperature under a total initial pressure of 40 atm by using rhodium concentrations of 5 · 10–3 mol l–1. The changes in catalytic activities observed upon structural changes of monodentate ligands are discussed in terms of classical ligand parameters like basicity and steric demand of the PR3 group, while with bidentate ligands R2P(CH2)nPR2 the chain length n plays a dominant role for the activity of the catalyst. The effects cannot be explained by a direct impact of the ligand on catalytically active intermediates only, but influences on the formation of these species must also be taken into account.

Catalytic hydrogenation of carbon dioxide to hydrocarbons

Hydrogenation of carbon dioxide was studied by using rare earth alloy catalysts, hybrid catalysts and Fe-Cu catalysts in order to convert carbon dioxide to fuel. Methanation of carbon dioxide was carried out by using rare earth metal alloys at 200∼400°C under 1–5MPa. Methane was obtained in high yield (93%). Hydrocarbons (C 1 to C 5) were obtained in 16% yield by using hybrid catalyst composed of Cu-Zn-Cr and zeolite HY at 400°C via methanol. Higher hydrocarbons (C 1∼C 9) were also obtained in 45% yield by using Fe-Cu catalyst at 400°C under 5MPa.

Catalytic hydrogenation of carbon dioxide into C 2+ alcohols with Ir-Mo/SiO 2

The hydrogenation of CO 2 was investigated with SiO 2-supported Ir-Mo bimetallic catalysts. The C 2 + alcohols (ethanol, 1-propanol and 1-butanol) were found to be formed by the synergistic action of Ir and Mo. The CO 2 conversion was dependent upon metal impregnation procedures and Mo/Ir molar ratios, but the selectivity to C 2 + alcohols was almost constant regardless of these factors. Iridium-Mo/SiO 2 catalysts exhibited the highest CO 2 conversion and yield of C 2 + alcohols at a Mo/Ir ratio of about 0.3. The results obtained in this work are similar to those in the CO hydrogenation with Ir-Mo/SiO 2 catalysts. As a result, it is suggested that the active species of Ir-Mo/SiO 2 catalysts might be the same both in the CO 2 hydrogenation and in the CO hydrogenation.

ロジウム系触媒を用いた二酸化炭素の接触水素化によるエタノールの合成　（第１報）　シリカ担持ロジウム系触媒を用いた二酸化炭素の接触水素化によるエタノールの合成に対する添加物の効果

シリカ担持ロジウム(Rh/SiO2)系触媒を用い,二酸化炭素(CO2)の接触水素化によるエタノール(EtOH)の合成を検討した.Rh単味触媒ではEtOHは生成せず,主生成物はメタン(CH4)であった.反応の活性や生成物の選択性に及ぼす触媒添加物の効果を約30種類の酸化物系添加物や金属系添加物を用いて検討した.添加物によりCO2転化活性が著しく増大したり,生成物選択率がCH4から一酸化炭素(CO),メタノール(MeOH),EtOHへと大きく変化する事が明らかとなった.リチウム(Li)塩はCO2転化率の向上とEtOH選択率の向上に著しい効果があり,Rh/SiO2触媒を用いたCO2からのEtOH合成に最も好ましい添加物であることが明らかになった.Rh-Li/SiO2触媒を用い,EtOH合成に与える反応条件の影響について検討した.その結果, 5MPa,240℃, 100ml/min, H2/CO2=3の反応条件下でCO2転化率7.0%,EtOH選択率15.5%を得ることができた.EtOH合成の反応機構を高温高圧 in situ FT-IR 法で検討した.その結果,反応はCO中間体経由で進行することが示唆された.LiはRhの電子状態を変化させる役割をもつものと考えられる.

Novel preparation of metal-supported catalysts by colloidal microparticles in a water-in-oil microemulsion; catalytic hydrogenation of carbon dioxide

A novel catalyst preparation method of employing microemulsions, and the carbon dioxide hydrogenation activities of silica- or zirconia-supported catalysts loaded with colloidal rhodium microparticles in water-in-oil microemulsions are reported; the catalysts thus prepared exhibit much higher activity than those prepared by classical methods.

接触水素化反応による二酸化炭素のメタノール変換技術の評価

The recent status of catalytic hydrogenation of carbon dioxide to methanol was investigated. Although catalytic hydrogenation of CO2 requires H2 and energy, it shows much higher reaction rate than other CO2 conversion technologies. Especially, conversion to methanol is a promising technology because of its excellent characteristics as a fuel. Thermodynamically, lower temperatures and lower pressures are favorable for methanol synthesis from CO2 and higher temperatures are favorable for the reverse water gas shift reaction. Thus, a catalyst which is highly active below 473 K promises low-energy conversion to methanol. CO2 hydrogenation technology is classi-fied into a gas-phase synthesis and a liquid-phase synthesis from its reaction method. In the gas-phase synthesis, Cu/ZnO-based catalysts show space time yields comparable to those in the conventional methanol production process from syngas. The liquid-phase synthesis employing a homogeneous catalyst is expected to operate at lower temperatures than the gas-phase synthesis. In order to achieve efficient CO2 conversion to methanol, it is necessary to develop an active catalyst system at lower temperatures.

Carbonate Rock A Resource for Energy

Abstract Carbonate rock is considered one of the major sources of carbon dioxide, capable of catalytic conversion to methane, synthetic natural gas (SNG), and other organic products. A brief account of various research reports available in the literature on the catalytic hydrogenation of carbon dioxide is included. Finally, carbon dioxide or, more specifically, carbonate rock is advanced as a potential source of products that might serve either as feedstocks for petrochemical industries or for production of energy.