Selective CO oxidation on a Ru/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst in the surface ignition regime: 1. Fine purification of hydrogen-containing gases

Selective CO oxidation in a mixture simulating the methanol steam reforming product with an air admixture was studied over Ru/Al₂O₃ catalysts in a quasi-adiabatic reactor. On-line monitoring of the gas temperature in the catalyst bed and of the residual CO concentration at different reaction conditions made it possible to observe the ignition and quenching of the catalyst surface, including transitional regimes. A sharp decrease in the residual CO concentration takes place when the reaction passes to the ignition regime. The evolution of the temperature distribution in the catalyst bed in the ignition regime and the specific features of the steady-state and transitional regimes are considered, including the effect of the sample history. In selective CO oxidation and in H₂ oxidation in the absence of CO, the catalyst is deactivated slowly because of ruthenium oxidation. In both reactions, the deactivated catalyst can be reactivated by short-term treatment with hydrogen. A 0.1% Ru/Al₂O₃ catalyst is suggested. In the surface ignition regime, this catalyst can reduce the residual CO concentration from 0.8 vol % to 10–15 ppm at O₂/CO = 1 even in the presence of H₂O and CO₂ (up to ～20 vol %) at a volumetric flow rate of ～100 1 (g Cat)^?1 h^?1, which is one magnitude higher than the flow rates reported for this process in the literature.     

Photochemical Reduction of Low Concentrations of CO2 in a Porous Coordination Polymer with a Ruthenium(II)–CO Complex

Direct use of low pressures of CO₂ as a C1 source without concentration from gas mixtures is of great interest from an energy‐saving viewpoint. Porous heterogeneous catalysts containing both adsorption and catalytically active sites are promising candidates for such applications. Here, we report a porous coordination polymer (PCP)‐based catalyst, PCP‐Ru^II composite, bearing a Ru^II‐CO complex active for CO₂ reduction. The PCP‐Ru^II composite showed improved CO₂ adsorption behavior at ambient temperature. In the photochemical reduction of CO₂ the PCP‐Ru^II composite produced CO, HCOOH, and H₂. Catalytic activity was comparable with the corresponding homogeneous Ru^II catalyst and ranks among the highest of known PCP‐based catalysts. Furthermore, catalytic activity was maintained even under a 5 % CO₂/Ar gas mixture, revealing a synergistic effect between the adsorption and catalytically active sites within the PCP‐Ru^II composite.     

The industrial hydroformylation of olefins with a rhodium-based supported liquid phase catalyst (SLPC): III. The kinetics of propylene hydroformylation catalyzed by the rhodium-based supported liquid phase catalyst

Hydridocarbonyltris(triphenylphosphine)-rhodium(I), dissolved in triphenylphosphine and capillary condensed in the pores of α-Al₂O₃, was studied as a catalyst for hydroformylation of propylene. The activity and selectivity for n-butyraldehyde were measured in the range 90 – 110 °C. Even up to a degree of conversion of 25 mol.% propylene no deactivation was found at 110 °C. Varying the partial pressures of hydrogen, carbon monoxide and propylene gave the reaction orders. With respect to propylene the order is 1.57. The other reaction orders are smaller than 0.1. The stability of the catalyst depends mainly on the partial pressure of CO. At p_CO = 0.180 MPa the catalyst is stable. The activation energy is then 70.6 kJ mol⁻¹. The selectivity to n-butyraldehyde is increased by lowering p_CO. The lowest ratio of n-butyraldehyde to the isoproduct is 14.     

Selective oxidation of CO under conditions of catalyst surface ignition

The oxidation of CO in the presence of an excess of hydrogen and to 20% CO₂ and H₂O in the starting mixture was studied in flow reactors with high and low rates of heat removal. The ignition of the catalyst surface was observed in the reactor with a low rate of heat removal; catalyst surface ignition initially occurred at a “hot” spot (section) of the catalyst bed and gradually propagated along the bed. Experimental data on the relaxation dynamics of residual CO concentration and temperature in a catalyst bed under conditions of small heater temperature disturbances near and at the critical temperature of ignition and the effect of oxygen concentration in the starting mixture on this process are reported. It was found exprimentally that the ignition regime in the tested cases was more favorable for the selective oxidation of CO in an excess of hydrogen than the reaction in an isothermal reactor; this was likely due to the more favorable temperature distribution over the length of the catalyst bed.     

Iron carbonyl complex containing bis[2‐(diphenylphosphino)phenyl]ether enhancing efficiency in the palladium‐catalyzed Suzuki–Miyaura reaction

The reaction of [Fe₃(CO)₁₂] with bis[2‐(diphenylphosphino)phenyl]ether (DPEphos) in refluxing THF afforded a mononuclear complex, [Fe(CO)₄(η¹‐P‐DPEphos)] (1), as major product and a binuclear complex, [Fe₂(CO)₆(μ‐CO)(μ‐P,P‐DPEphos)] (2), as minor product respectively. The DPEphos ligand acts as a terminal P‐donor in complex 1 and a bridging P,P‐donor in complex 2. Complexes 1 and 2 were characterized by elemental analysis, fast atom bombardment mass spectrometry, FT‐IR, ¹H and ³¹P{¹H} NMR spectroscopy. The structure of complex 1 has been tentatively assigned by density functional theory calculations and its analogy with reported complexes. Combination of complex 1 and PdCl₂ furnished an active catalyst for the Suzuki–Miyaura cross‐coupling reactions of various aryl halides with arylboronic acids. Interestingly, under the same experimental condition, complex 1/PdCl₂ as catalyst showed superior activity over the DPEphos/PdCl₂ system. Copyright © 2012 John Wiley & Sons, Ltd.     

Laser isotope separation and the multiphoton decomposition of methanol using a pulsed HF or DF laser

The focussed beam from a single line [P₁(6)] pulsed HF laser has been used to decompose CH₃OH (for pressures between 0.169 and 14.95 kPa) and isotopic mixtures of methanol. The normalized yields (number of product molecules Pulse/P_METHANOL) of the non-condensable products H₂, CO and CH₄ increased linearly with pressure (for the range ≈ 1 - 7 kPa). For sufficiently low pressures, selective excitation of one component of an isotopic mixture gives an isotopically enriched product. For example, selective excitation of CH₃OH in equimolar of mixture CH₃OH/CH₃OD at a total pressure of 269 Pa gives hydrogen which is enriched 60-fold in H versus D. The degree of isotopic enrichment decreases with increasing mixture pressure. The efficiency of conversion of photon energy to reaction product has been observed to increase linearly with pressure. Decomposition studies have been performed in the presence of additives. These imply that the decomposition of methanol to H₂ involves mainly molecular rather than free radical steps.     

合成气一步法制备液化石油气单管实验研究

采用甲醇合成催化剂与脱水催化剂机械混合,制备了液化石油气(LPG)合成催化剂。以模拟生物质气为原料气,在固定床单管实验装置上,温度(220~330 ℃)、压力(1.2~5.1 MPa)和空速(500~3 000 h^-1)条件下考察催化剂的性能。结果表明,在325 ℃、2.1 MPa、1 500 h^-1条件下,CO转化率达到72.36%,LPG占烃类产物的71.21%。当设定温度为325 ℃、压力2.1 MPa时、空速≤2 500 h^-1时,系统可以稳定运行;空速达到3 000 h^-1时,反应器内部温度迅速升高无法控制,造成催化剂烧结失活。针对上述催化剂,采用NH₃-TPD、XRD、N₂吸附-脱附和TPO对催化剂进行了表征。结果表明,催化剂的积炭、强酸位酸性降低及比表面积的降低是导致催化剂活性降低的重要影响因素。     

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.

     

ZIF-8基复合材料高效、稳定电催化还原CO2

电催化CO₂还原反应(eCO₂RR)受到催化剂本征活性以及传质的限制，导致材料的催化活性低、反应起始电位高等问题。我们以类沸石锌盐咪唑骨架(ZIF-8)材料为研究对象，探究了不同粒径ZIF-8材料的eCO₂RR性能。优选粒径为50 nm的ZIF-8材料，进一步引入碳纳米管(CNT)作为其导电基底材料，通过原位生长，构建了复合材料ZIF-8-50@CNT的多级孔结构和疏水界面。eCO₂RR实验结果表明，CNT的引入提高了催化剂的导电性，优化后的复合材料有效地降低了反应的起始电位。在-1.1 V (相对可逆氢电极(RHE))电位下，CO部分电流密度为15.6 mA·cm^-2，ZIF-8-50@CNT催化剂的比表面活性提升了3.5倍(相比ZIF-8-50)，塔菲尔斜率降低到136 mV·dec^-1。并且产物CO的选择性和稳定性得到了提高，在宽电势窗口-0.9~-1.2 V (vs RHE)内，CO的法拉第效率(FE)保持在80%以上。在10 h稳定性测试中，催化剂活性保持稳定，整体增强了复合材料eCO₂RR的性能。     

A Binuclear Iron–Thiolate Catalyst for Electrochemical Hydrogen Production in Aqueous Micellar Solution

The substituted iron–thiolate complex [Fe₂(μ‐bdt)(CO)₄{P(OMe)₃}₂] (bdt=benzenedithiolate) is an active catalyst for electrochemical hydrogen production in aqueous sodium dodecyl sulfate solution, with a high apparent rate constant of 4×10⁶ M ^?1 s^?1. The half‐peak potential for catalysis of proton reduction is less negative than ?0.6 V versus the standard hydrogen electrode at pH 3. Voltammetric data are consistent with the rate of electrode reaction controlled by diffusion. A mechanism that begins with the rapid protonation of the iron–thiolate catalyst is proposed. The Faradaic efficiency in diluted HCl solutions is close to 100 %, but the catalytic activity decayed after about twelve turnovers when electrolysis was carried out in the presence of acetic acid.     

Laser isotope separation and the multiphoton dissociation of formic acid using a pulsed HF laser

The focussed beam from a single line [P₂ (5)] of a pulsed HF laser has been used to stimulate the decomposition of formic acid. The yield (Y is the number of product molecules per pulse / formic acid pressure) of the non-condensable (77 K) products, hydrogen and CO, has been studied as a function of laser radiant energy (from 25-115 mJ) and pressure (from 0.4-2.7 kPa). The intensity dependence of Y suggests that each dissociating formic acid requires the equivalent of at least 6 HF P₂(5) photons (260 kJ/mole). For pressures above about 0.6 kPa, Y_H2 = (?0.6 ± 1.7) × 10¹² + (2.4 ± 1.0) × 10¹² P and Y_CO = (?0.5 ± 6.1) × 10¹³ × (8.7 ± 3.7) × 10¹³ P. The linear dependerrce of yields indicates that a collisionally assisted decomposition process is important at these pressures. The efficiency of the conversion of photon energy to reaction products at a pressure of 2.7 kPa is ? 7% for CO and ? 0.2% for hydrogen. Selective excitation of HCOOH in equimolar mixtures of HCOOH/HCOOD, at a total pressure of 0.6 kPa, has provided a physically separated product, hydrogen gas, which is isotopically enriched in H versus D 25 fold as compared to the formic acid mixture. The degree of enrichment decreases as the total pressure of the mixture is increased. A possible mechanism accounting for isotope enrichment and the collisionally assisted dissociation is outlined.     

Carbon monoxide hydrogenation in the mode of Ru/Al2O3 catalyst surface ignition

The specifics of CO hydrogenation over a 5%Ru/Al₂O₃ catalyst in a flow reactor at a pressure of 1.5 MPa has been considered. The feed gas mixture has been composed of (vol %) 30.5 CO, 2.3 CO₂, 65 H₂, and N₂ as the rest. The CO methanation reaction readily passes to the external-diffusion regime—catalyst surface ignition (CSI) mode—either by heating the catalyst in the reaction medium or by replacing H₂ with the reactant gas having a temperature above the critical ignition temperature. On passing to the CSI mode, the temperature at the entrance to the catalyst bed and the methane content at the reactor outlet abruptly increase, the yield of CO₂ produced via the water-gas shift reaction increases, and the CO content drops to zero. Under the CSI regime, temperature oscillations with a period of 3–5 min and an amplitude of ～3°C are observed, which are sustained during catalyst cooling until the extinction of the reaction. A comparison of the product compositions at the reactor outlet in the cases of the “thick” (20 mm) and “thin”(3 mm) catalyst bed has shown that the reverse water-gas shift, an endothermic reaction, occurs in lower, colder layers of the thick bed. As a result, the extinction of the reaction is faster in the thick than in the thin bed. Methanation of CO is accompanied by the Fischer-Tropsch reaction: a variety of carbon compounds are formed with their yield being decreased on passing to the CSI mode.     

ZIF-8基复合材料高效、稳定电催化还原CO2

电催化CO₂还原反应(eCO₂RR)受到催化剂本征活性以及传质的限制,导致材料的催化活性低、反应起始电位高等问题。我们以类沸石锌盐咪唑骨架(ZIF-8)材料为研究对象,探究了不同粒径ZIF-8材料的eCO₂RR性能。优选粒径为50 nm的ZIF-8材料,进一步引入碳纳米管(CNT)作为其导电基底材料,通过原位生长,构建了复合材料ZIF-8-50@CNT的多级孔结构和疏水界面。eCO₂RR实验结果表明,CNT的引入提高了催化剂的导电性,优化后的复合材料有效地降低了反应的起始电位。在-1.1 V(相对可逆氢电极(RHE))电位下,CO部分电流密度为15.6 mA·cm^-2,ZIF-8-50@CNT催化剂的比表面活性提升了3.5倍(相比ZIF-8-50),塔菲尔斜率降低到136 mV·dec^-1。并且产物CO的选择性和稳定性得到了提高,在宽电势窗口-0.9～-1.2 V(vs RHE)内,CO的法拉第效率(FE)保持在80%以上。在10 h稳定性测试中,催化剂活...     

Hydroesterification of ethylene oxide catalyzed by 1-butyl-3-methylimidazolium cobalt tetracarbonyl ionic liquid

In this paper, functional ionic liquid 1-butyl-3-methylimidazolium cobalt tetracarbonyl [Bmim][Co(CO)₄] is prepared in a metathesis reaction between [Bmim]Cl and KCo(CO)₄. The structure of [Bmim]⁺ is illustrated by ¹H NMR, while [Co(CO)₄]⁻ is confirmed by IR(ν_CO) spectrum. Methyl 3-hydroxypropionate(3-HPM), an intermediate to 1,3-propanediol (1,3-PDO), can be prepared in high yield by hydroesterification of ethylene oxide in the presence of a [Bmim][Co(CO)₄] catalyst. Under a pressure of 3.7 MPa and at a temperature of 75 °C, the yield of 3-HPM can reach 90.8% in 10 h. Even after the catalyst is recycled three times, a yield of more than 80% can be obtained. A possible reaction mechanism has also been proposed.     

New process of low-temperature methanol synthesis from CO/CO2/H2 based on dual-catalysis

A new process of low-temperature methanol synthesis from CO/CO₂/H₂ based on dual-catalysis has been developed. Some alcohols, especially 2-alcohol, were found to have high catalytic promoting effect on the synthesis of methanol from CO hydrogenation. At 443 K and 5 MPa, the synthesis of methanol could process high effectively, resulting from the synergic catalysis of Cu/ZnO solid catalyst and 2-alcohol solvent catalyst. The primary results showed that when 2-butanol was used as reaction solvent, the one-pass average yield and the selectivity of methanol, in 40 h continuous reaction at temperature as low as 443 K and 5 MPa, were high up to 46.51% and 98.94% respectively. The catalytic activity was stable and the reaction temperature was 80 K or so lower than that in current industry synthesis process. This new process hopefully will become a practical method for methanol synthesis at low temperature.     

Highly efficient heterogeneous acylations of aromatic compounds with acid anhydrides and carboxylic acids by montmorillonite-enwrapped titanium as a solid acid catalyst

Montmorillonite-enwrapped titanium hydroxide species (Ti⁴⁺-mont) acted as a highly efficient heterogeneous acid catalyst for the acylation of aromatic compounds with acid anhydrides or carboxylic acids. The catalytic activity of the Ti⁴⁺-mont was higher than those of other acid catalysts such as zeolites, SO ₄ ²⁻ /ZrO₂ and p-toluenesulfonic acid. For example, the reaction of anisole with dodecanoic acid in the presence of the Ti⁴⁺-mont catalyst gave 1-(4-methoxyphenyl)-1-dodecanone in 97% yield. Furthermore, the Ti⁴⁺-mont catalyst was easily separated from the reaction mixture and was recyclable.     

Selective oxidation of CO in the presence of hydrogen on CuO/CeO<Subscript>2</Subscript> catalysts modified with Fe and Ni oxides

The selective oxidation of CO in the presence of hydrogen on CuO/CeO₂ systems containing Fe and Ni oxides as promoters was studied. The catalysts containing 1–5 wt % CuO and 1–2.5 wt % Fe₂O₃ supported on CeO₂ and the CuO/CeO₂ systems containing 1–2.5 wt % NiO were synthesized, and their catalytic activity as a function of temperature was determined. It was found that the additives of Fe and Ni oxides increased the activity of the CuO/CeO₂ catalysts with a low concentration of CuO. In this case, the conversion of CO at 150°C approached 100%. At the same time, these additives had no effect on the activity of the CuO/CeO₂ systems at a CuO concentration of 5 wt % or higher, which exhibited an initially high activity in the above temperature region. The forms of CO adsorption and the amounts of active sites for CO adsorption and oxidation were studied using temperature-programmed desorption. It was found that the introduction of Fe and Ni additives in a certain preparation procedure facilitated the formation of an additional amount of active centers associated with CuO. Data on the temperature-programmed reduction of samples (the amount of absorbed hydrogen and the maximum temperature of hydrogen absorption) suggested the interaction of all catalyst components, and the magnitude of this interaction depended on the sample preparation procedure. With the use of Mössbauer spectroscopy, it was found that the procedure of iron oxide introduction into the CuO/CeO₂ system was responsible for the electron-ion interactions of catalyst components and the reaction mixture.     

Kinetics of hydroformylation of camphene using rhodium-phosphite catalyst

Kinetics of hydroformylation of camphene was investigated in the presence of [Rh(CO)₂(acac)]/P(OPh)₃ catalyst in a temperature range of 363–383 K. The influence of parameters such as stirring speed, camphene, catalyst, ligand concentrations, and partial pressures of H₂ and CO on the activity and selectivity of the catalyst has been studied. The rate showed a first-order dependence with respect to catalyst and camphene concentrations. The effect of partial pressure of hydrogen showed fractional order dependence. The plots of rate versus excess ligand, that is, (P(OPh)₃) concentration and rate versus CO partial pressure passed through maxima and showed typical substrate/ligand inhibited kinetics. An empirical rate equation has been proposed and found to be in good agreement with the observed rate data. The kinetic parameters and activation energy were also evaluated.     

Catalytic properties of CoMo/Al2O3 sulfide catalysts in the hydrorefining of straight-run diesel fraction mixed with rapeseed oil

CoMo/Al₂O₃ sulfide catalysts varying in preparation method and Co/Mo ratio have been tested in the hydrorefining of a mixture of straight-run diesel fraction and rapeseed oil in a flow reactor at a temperature of 340–360°C, a hydrogen pressure of 4.0–7.0 MPa, and a liquid hourly space velocity of 1–2 h^?1. A comparison between catalysts prepared using citric acid (CoMo/Al₂O₃-1.5) and both citric and orthophosphoric acids (CoMoP/Al₂O₃-1.5) as promoters, with Co/Mo = 0.3 and 0.5, has demonstrated that the most active catalyst in hydrodesulfurization and hydrodenitrogenation is the phosphorus-containing Co/Mo ≈ 0.5 sample. The addition of rapeseed oil to straight-run diesel fraction lowers the hydrodesulfurization and hydrodenitrogenation activities of the CoMo sulfide catalysts, irrespective of the method by which they were prepared. The fatty acid triglyceride conversion selectivity of these catalysts depends on the Co/Mo ratio and on reaction conditions: decreasing the Co/Mo ratio from 0.46 to 0.26, lowering the reaction temperature, and raising the hydrogen pressure and hydrogen-to-feedstock ratio increase the C¹⁸/C¹⁷ hydrocarbon ratio in the hydrogenated product. The addition of rapeseed oil improves the quality of the product; however, for attaining the preset residual sulfur level in this case, the process needs to be conducted at a higher temperature than the hydrorefining of straight-run diesel fraction containing no admixture.     

An amide-based second coordination sphere promotes the dimer pathway of Mn-catalyzed CO2-to-CO reduction at low overpotential

The [fac-Mn(bpy)(CO)₃Br] complex is capable of catalyzing the electrochemical reduction of CO₂ to CO with high selectivity, moderate activity and large overpotential. Several attempts have been made to lower the overpotential and to enhance the catalytic activity of this complex by manipulating the second-coordination sphere of manganese and using relatively stronger acids to promote the protonation-first pathway. We report herein that the complex [fac-Mn(bpy-CONHMe)(CO)₃(MeCN)]⁺ ([1-MeCN]⁺; bpy-CONHMe = N-methyl-(2,2′-bipyridine)-6-carboxamide) as a pre-catalyst could catalyze the electrochemical reduction of CO₂ to CO with low overpotential and high activity and selectivity. Combined experimental and computational studies reveal that the amide NH group not only decreases the overpotential of the Mn catalyst by promoting the dimer and protonation-first pathways in the presence of H₂O but also enhances the CO₂ electroreduction activity by facilitating C–OH bond cleavage, making [1-MeCN]⁺ an efficient CO₂ reduction pre-catalyst at low overpotential.

The amide NH group decreases the overpotential of Mn-based CO₂ reduction catalysts by promoting the dimer and protonation-first pathways in the presence of H₂O and enhances the CO₂ electroreduction activity by facilitating C–OH bond cleavage.