水介质下金属基催化剂催化糠醛加氢的研究进展

糠醛是连接生物原料和生物炼制工业的桥梁。糠醛在水介质中的还原性转化是制备各种精细化学品的重要途径, 经多相催化剂催化可以得到大量的下游产品, 如(四氢)糠醇、2-甲基(四氢)呋喃、内酯、乙酰丙酸盐、环戊酮、环戊醇等。催化剂的活性主要取决于金属及载体的性质, 以及温度、时间、溶剂和压力等反应条件。本文针对不同的非贵金属(Cu、Ni和Co)和贵金属(Pd、Ru、Pt和Au)基催化剂对糠醛加氢制备环戊酮和环戊醇的研究进展进行了综述, Ru、Pd、Au和Cu基催化剂较其他催化剂有更高的选择性, Cu-Ni双金属催化剂具有优异的催化活性和选择性, 但稳定性有待提高。对金属表面发生氢化反应的机理进行了探讨, 结果表明: 水介质和较弱的路易斯酸性位点在环重排的反应中起关键作用, 同时提出了糠醛在水介质中的加氢反应的未来研究方向。     

糠醛气相加氢制2-甲基呋喃新型配合物催化剂研究

制备了一种新型、无毒Cu-Zn-Ca/γ- Al₂O₃配合物催化剂。采用固定床反应器,进行糠醛常压气相催化加氢反应,考察反应温度、催化剂组成、空速和氢醛比等因素的影响。结果表明,在508 K、空速0.32 h^-1、还原温度保持（493～513） K、活化6 h和氢醛物质的量比为10∶1条件下,糠醛转化率达到98.90%,2-甲基呋喃选择性达92.30%,2-甲基呋喃收率达91.28%。作为一种新型的无Cr催化剂,无毒,无污染,可代替Cu-Cr催化剂用于糠醛加氢过程,高活性和高选择性地制取2-甲基呋喃。     

Aqueous-phase catalytic process for production of pentane from furfural over nickel-based catalysts

Supported nickel catalysts for aqueous-phase catalytic hydrogenation/dehydration of furfural were prepared using impregnation method with different supporting materials. Effects of supporting materials, nickel loading and reaction temperature on conversion rate of furfural as well as selectivity for desired product C₅ were systematically studied. Experiments showed that catalytic activity of Ni/SiO₂-Al₂O₃ was obviously higher than that of Ni/γ-Al₂O₃. The conversion of furfural over 14 wt.%Ni/SiO₂-Al₂O₃ catalyst was 62.99% under the temperature of 140 °C and the cold pressure of H₂ 3.0 MPa, while that was 19.19% over 14 wt.%Ni/γ-Al₂O₃ under the same conditions. Conversion rate of furfural increased with temperature, but selectivity for desired product decreased with temperature. Tentative reaction mechanisms of hydrogenation/dehydration were proposed. In order to investigate catalyst recyclability, a batch of Ni/SiO₂-Al₂O₃ was reused three times and analyzed by Thermogravimetry (TG). It was found that considerable amount of coke formed on Ni/SiO₂-Al₂O₃ surface and deteriorated its activity dramatically after second use.     

Kinetics and mechanism of hydrogenation of furfural on Cu/SiO2 catalysts

The hydrogenation/hydrodeoxygenation of furfural was studied on a Cu/SiO₂ catalyst at 230–290 °C. Detailed kinetics, density function (DFT) calculations, and spectroscopic studies were combined to investigate this reaction. A Langmuir–Hinshelwood model was found to fit the kinetic data well and provided the parameters of physical significance. The heat of adsorption (ΔH_ads) of furfural, derived from the fitting, was found to be significantly higher than those of furfuryl alcohol and 2-methyl furan. Activation energies for the conversion of furfural and furfuryl alcohol were both about 12 kcal/mol. DFT calculations and DRIFTS provided guidance about the nature of the surface species. Accordingly, the most likely species adsorbed on the Cu surface is suggested to be a top η¹(O)-aldehyde. DFT calculations of the reaction path show that the predicted energy barriers are of the same order as the experimental values and suggest that the hydrogenation of furfural can occur via either an alkoxide or ahydroxyalkyl intermediate.     

Transformation of cyclopentanone into cyclopentanethiol over a sulfided CoMo/Al2O3 catalyst

The transformation of cyclopentanone in the presence of H₂S/H₂ was investigated at atmospheric pressure over a sulfided CoMo/Al₂O₃ catalyst. The main reaction products were cyclopentanethiol and cyclopentene, the relative amounts of which depended on the reaction temperature and on the H₂S to cyclopentanone molar ratio. The best results were obtained at 220°C, with a 2.5 H₂S to cyclopentanone molar ratio: under these conditions, the cyclopentanethiol molar selectivity remained at about 90%, in a range of cyclopentanone conversion of 10–70%.     

以类水滑石为前躯体的铜镍基催化剂催化糠醛液相加氢

该文以类水滑石为前驱体经500℃焙烧得到铜镍基催化剂(Cu11.2Ni4.7-MgAlO)及相应的单组分铜基(Cu11.2-MgAlO)或镍基催化剂(Ni4.7-MgAlO),并采用X射线粉末衍射(XRD)、程序升温还原(H2-TPR)等技术对催化剂进行了表征.以糠醛液相加氢为探针反应,考察了3种催化剂的催化性能,并详细研究了催化剂还原活化温度、加氢反应温度、加氢压力、反应时间及催化剂用量等工艺条件对Cu11.2Ni4.7-MgAlO催化糠醛液相加氢反应的影响.结果表明,Cu11.2Ni4.7-MgAlO的催化性能均优于Cu11.2-MgAlO和Ni4.7-MgAlO;在最佳反应条件下,以Cu11.2Ni4.7-MgAlO为催化剂的糠醛转化率和糠醇选择性均可分别达到95.6%和93.1%,Cu11.2Ni4.7-MgAlO循环使用6次后,催化性能无明显下降,具有较好的稳定性.     

Selective hydrogenation of nitriles to imines over a multifunctional heterogeneous Pt catalyst

Imines and their derivatives are versatile synthetic intermediates for the industrial preparation of both bulk and fine chemicals and for pharmaceuticals, but preparing these compounds efficiently through direct hydrogenation of nitriles are hindered by overhydrogenation to secondary amines. Here we report a highly efficient multifunctional catalyst system for selective hydrogenation coupling of nitriles to secondary imines using a heterogeneous Pt catalyst that was deposited on a nickel‐based metal‐organic framework (MOF) containing DABCO. The catalyst showed excellent synergy in promoting the hydrogenation of a variety of nitriles, giving significantly improved activity and selectivity (up to >99% yield) even under atmospheric pressure of H₂. It is suggested that the Lewis base (DABCO) sites on the Ni‐MOF inhibit further hydrogenation of the imines. The influence of H₂ pressure, reactant concentration, stirring speed, and reaction temperature was investigated. The kinetics and mechanism of hydrogenation of benzonitrile (BN) by the Pt/Ni‐MOF catalyst has been studied. The reaction showed a first‐order dependence on both BN concentration and H₂ pressure. A kinetic model was proposed based on the mechanism of nitriles hydrogenation and compared with experimental observations. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3565–3576, 2014     

Oxidative Reforming of Bio-Ethanol Over CuNiZnAl Mixed Oxide Catalysts for Hydrogen Production

Hydrogen (H₂) is expected to become an important fuel for the future to be used as an energy carrier in automobiles and electric power plants. A promising route for H₂ production involves catalytic reforming of a suitable primary fuel such as methanol or ethanol. Since ethanol is a renewable raw material and can be cheaply produced by the fermentation of biomass, the ethanol reforming for H₂ production is beneficial to the environment. In the present study, the steam reforming of ethanol in the presence of added O₂, which in the present study is referred to as oxidative steam reforming of ethanol (OSRE), was performed for the first time over a series of CuNiZnAl mixed oxide catalysts derived from layered double hydroxide (LDH) precursors. The effects of Cu/Ni ratio, temperature, O₂/ethanol ratio, contact time, CO co-feed and substitution of Cu/Ni by Co were investigated systematically in order to understand the influence of these parameters on the catalytic performance. An ethanol conversion close to 100% was noticed at 300 °C over all the catalysts. The Cu-rich catalysts favor the dehydrogenation of ethanol to acetaldehyde. The addition of Ni was found to favor the C–C bond rupture, producing CO, CO₂ and CH₄. Depending upon the reaction condition, a H₂ yield between 2.5 and 3.5 moles per mole of ethanol converted was obtained. A CoNi-based catalyst exhibited better catalytic performance with lower selectivity of undesirable byproducts, namely CH₃CHO, CH₄ and CO.     

High selective production of tetrahydrofurfuryl alcohol: Catalytic hydrogenation of furfural and furfuryl alcohol

Tetrahydrofurfuryl alcohol could be obtained by catalytic hydrogenation of either furfural or furfuryl alcohol using Pd-, Ru-, Rh- and Ni-supported catalysts as well as their mixtures with a Cu-supported catalyst. In the case of furfural hydrogenation, the best results (97 % yield, 100 % conversion, 98 % selectivity) were obtained in the presence of Ni and Cu. However, this catalytic mixture could not be recycled. In the case of furfuryl alcohol hydrogenation, Ni-supported catalysts were the most active. Nickel-onsilica-alumina catalyst containing 59 % of metal lead to the best results (98–99 % yield, selectivity and conversion >99 %). Moreover, it could be recycled. Hydrogenation of furfuryl alcohol in the presence of this catalyst was the best procedure for the production of tetrahydrofurfuryl alcohol.     

Dual‐bed catalyst system for the direct synthesis of high density aviation fuel with cyclopentanone from lignocellulose

In this article, we demonstrated an integrated process for the direct production of tri(cyclopentane) with cyclopentanone which can be obtained from lignocellulose. The reaction was carried out in a dual‐bed continuous flow reactor. In the first bed, cyclopentanone was selectively converted to 2,5‐dicyclopentylcyclopentanol over the Pd‐MgAl‐HT (hydrotalcite) catalyst. Under solvent‐free and mild conditions (443 K, 0.1 MPa H₂), high carbon yield (81.2%) of 2,5‐dicyclopentylcyclopentanol was achieved. Subsequently, the 2,5‐dicyclopentylcyclopentanol was further hydrodeoxygenated to tri(cyclopentane) in the second bed. Among the investigated catalysts, the Ni‐Hβ‐DP prepared by deposition‐precipitation (DP) method exhibited the highest activity for the hydrodeoxygenation step. By using Pd‐MgAl‐HT as the first bed catalyst and Ni‐Hβ‐DP as the second bed catalyst, tri(cyclopentane) was directly produced at high carbon yield (80.0%) with cyclopentanone as feedstock. This polycycloalkane has high density (0.91 kg/L) and can be used as additive to improve the density and volumetric heating value of bio‐jet fuel. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2754–2761, 2016     

Determining the Best Composition of a Ni–Fe/Al2O3 Catalyst used for the CO2 Hydrogenation Reaction by Applying Response Surface Methodology

Response surface methodology (RSM) with central composite design (CCD) was applied to determine the composition of an alumina-supported nickel-iron (Ni–Fe) catalyst that provided the highest CH₄ yield for the CO₂ hydrogenation reaction. This involved synthesis of alumina-supported Ni–Fe catalysts of compositions that were specified by CCD. The catalysts were then tested for the CO₂ hydrogenation reaction, and a model equation was developed that related the catalyst composition to the CH₄ yield. The model equation was validated by analysis of variance, and it was found to adequately represent the experimental data. The model equation predicted that the alumina-supported Ni–Fe catalyst containing 32.8% Ni and 7.7% Fe would provide the highest CH₄ yield. A catalyst with this specific composition and the same metal deposition method and two other catalysts of the same composition but different metal deposition metal were also synthesized, characterized, and tested for the CO₂ hydrogenation reaction. The three catalysts did show activities similar to those predicted by the model equation. Furthermore, characterization and reaction studies revealed that the three catalysts were similar, suggesting that the metal deposition methods do not have any effect on the catalytic activity.     

Pt-Promoted Cu/SBA-15 Catalysts with Excellent Performance for Chemoselective Hydrogenation of Dimethyl Oxalate to Ethylene Glycol

Cu/SBA-15 catalysts containing a small amount of Pt (Cu–Pt/SBA-15) were prepared by sequential adsorption–reduction method and examined for chemoselective hydrogenation of dimethyl oxalate (DMO) to ethylene glycol (EG). The Cu–Pt/SBA-15 catalyst with an optimal Cu/Pt atomic ratio of 10 showed a DMO conversion close to 100 % with a 98 % selectivity to EG at a temperature as low as 463 K. The results showed that the best Cu–Pt/SBA-15 enhanced the space time yield of EG by about 1.47 times compared with Cu/SBA-15. The introduction of Pt with stronger ability for H₂ adsorption and activation substantially enhanced the reducibility of the Cu²⁺ species and further promoted the chemisorption capacity of H₂. After reduction, a portion of Cu was alloyed with Pt, which was beneficial for the generation and stabilization of a balanced Cu⁺/Cu⁰ ratio during the hydrogenation process.     

Comparative Study on CO2 Hydrogenation to Higher Hydrocarbons over Fe-Based Bimetallic Catalysts

This paper reports on notable promotion of C₂ ⁺ hydrocarbons formation from CO₂ hydrogenation induced by combining Fe and a small amount of selected transition metals. Al₂O₃-supported bimetallic Fe–M (M = Co, Ni, Cu, Pd) catalysts as well as the corresponding monometallic catalysts were prepared, and examined for CO₂ hydrogenation at 573 K and 1.1 MPa. Among the monometallic catalysts, C₂ ⁺ hydrocarbons were obtained only with Fe catalyst, while Co and Ni catalysts yielded higher CH₄ selectively than other catalysts. The combination of Fe and Cu or Pd led to significant bimetallic promotion of C₂ ⁺ hydrocarbons formation from CO₂ hydrogenation, in addition to Fe–Co formulation discovered in our previous work. CO₂ conversion on Ni catalyst nearly reached equilibrium for CO₂ methanation which makes this catalyst suitable for making synthetic natural gas. Fe–Ni bimetallic catalyst was also capable of catalyzing CO₂ hydrogenation to C₂ ⁺ hydrocarbons, but with much lower Ni/(Ni+Fe) atomic ratio compared to other bimetallic catalysts. The addition of a small amount of K to these bimetallic catalysts further enhanced CO₂ hydrogenation activity to C₂ ⁺ hydrocarbons. K-promoted Fe–Co and Fe–Cu catalysts showed better performance for synthesizing C₂ ⁺ hydrocarbons than Fe/K/Al₂O₃ catalyst which has been known as a promising catalyst so far.     

The difference in the active sites for CO2 and CO hydrogenations on Cu/ZnO-based methanol synthesis catalysts

The effect of Zn in copper catalysts on the activities for both CO₂ and CO hydrogenations has been examined using a physical mixture of Cu/SiO₂+ZnO/SiO₂ and a Zn-containing Cu/SiO₂ catalyst or (Zn)Cu/SiO₂. Reduction of the physical mixture with H₂ at 573–723 K results in an increase in the yield of methanol produced by the CO₂ hydrogenation, while no such a promotion was observed for the CO hydrogenation, indicating that the active site is different for the CO₂ and CO hydrogenations. However, the methanol yield by CO hydrogenation is significantly increased by the oxidation treatment of the (Zn)Cu/SiO₂ catalyst. Thus it is concluded that the Cu–Zn site is active for the CO₂ hydrogenation as previously reported, while the Cu–O–Zn site is active for the CO hydrogenation.     

Ethanol reforming and partial oxidation with Cu/Nb2O5 catalyst

Ethanol reforming and partial oxidation were studied on Cu/Nb₂O₅ and Ni/Al₂O₃ catalysts. Compared to the Ni/Al₂O₃ catalyst, the Cu/Nb₂O₅ catalyst presents conversion as high as Ni/Al₂O₃ catalyst, however, for the same level of formation of hydrogen it occurs at much lower temperature on the Cu/Nb₂O₅ catalyst, 200 °C lower than for the Ni/Al₂O₃ catalyst, with remarkable little formation of CO, which can be attributed to the strong interaction between copper and niobia. Temperature-programmed desorption (TPD-ethanol) and surface reactions (TPSR) of partial oxidation of ethanol showed formation of ethylene, acetaldehyde, ethane and mainly H₂ and CO₂ besides little methane. DRIFTS results are in accordance with TPD analysis and the formation of acetate species at room temperature suggests reactivity of the surface and its oxidative dehydrogenation capacity. The adsorption of ethanol gives rise to ethoxide species, which form acetate and acetaldehyde that can be oxidized to CO₂ via carbonate. A comparison with reported results for Cu/Al₂O₃ this catalyst is promising, yielding high level of H₂ with little CO production during reforming and partial oxidation reaction. The maximum H₂ formation for the partial oxidation of ethanol was 41% at ratio (O₂/Et) 0.8, increasing to 50% at ratio 1.5. The H₂/CO is around 10 for the partial oxidation and 7 for steam reforming, which is excellent, compared to the Ni/Al₂O₃ catalyst with a factor 4–8 lower.     

Hydrogenation of m‐dinitrobenzene to m‐phenylenediamine over La2O3‐promoted Ni/SiO2 catalysts

BACKGROUND: Liquid‐phase catalytic hydrogenation of m‐dinitrobenzene is an environmentally friendly routine for m‐phenylenediamine production. The key to increasing product yield is to develop catalysts with high catalytic performance. In this work, La₂O₃‐modified Ni/SiO₂ catalysts were prepared and applied to the hydrogenation of m‐dinitrobenzene to m‐phenylenediamine. The effect of La₂O₃ loading on the properties of Ni/SiO₂ was investigated. The reaction kinetic study was performed in ethanol over Ni/3%La₂O₃–SiO₂ catalyst, in order to clarify the reaction mechanism of m‐dinitrobenzene hydrogenation. RESULTS: It was found that the activity of the silica supported nickel catalysts is obviously influenced by La₂O₃ loading. Ni/3%La₂O₃–SiO₂ catalyst exhibits high activity owing to its well dispersed nickel species, with conversion of m‐dinitrobenzene and yield of m‐phenylenediamine up to 97.1% and 94%, respectively. The results also show that Ni/3%La₂O₃–SiO₂ catalyst can be reused at least six times without significant loss of activity. CONCLUSION: La₂O₃ shows strong promotion of the effect of Ni/SiO₂ catalyst for liquid‐phase hydrogenation of m‐dinitrobenzene. La₂O₃ loading can affect the properties of Ni/SiO₂ catalyst. Based on the study of m‐dinitrobenzene hydrogenation kinetics over Ni/3%La₂O₃–SiO₂ catalyst, a possible reaction mechanism is proposed. Copyright © 2009 Society of Chemical Industry     

Study on Cu–Mn–Si catalysts for synthesis of cyclohexanone and 2-methylfuran through the coupling process

A series of Cu–Mn–Si catalysts for synthesis of cyclohexanone (CHN) and 2-methylfuran (2-MF) through the coupling of cyclohexanol (CHL) dehydrogenation and furfural (FFA) hydrogenation were prepared by co-precipitation method. The catalysts were characterized by using N₂ physisorption, X-ray diffraction (XRD), H₂ temperature programmed reduction (H₂-TPR), N₂O-chemisorption and ammonia temperature-programmed desorption (NH₃-TPD) methods. The results show that metal–silica/or metal–metal interactions are presented in the catalysts, and the contents of copper, manganese and silicon affect the BET surface area, acidity and copper dispersion. The results of the catalytic tests indicate that manganese increases the activity of CHL dehydrogenation and FFA hydrogenation as well as the selectivity of 2-MF. A Cu–Mn–Si catalyst including appropriate copper, manganese and silicon is found to be most active, selective and stable under reaction conditions.     

Catalytic Steam Reforming of Fast Pyrolysis Bio‐Oil in Fixed Bed and Fluidized Bed Reactors

Catalytic steam reforming of bio‐oil is an economically‐feasible route which produces renewable hydrogen. The Ni/MgO‐La₂O₃‐Al₂O₃ catalyst was prepared with Ni as active agent, Al₂O₃ as support, and MgO and La₂O₃ as promoters. The experiments were conducted in fixed bed and fluidized bed reactors, respectively. Temperature, steam‐to‐carbon mole ratio (S/C), and liquid hourly space velocity (LHSV) were investigated with hydrogen yield as index. For the fluidized bed reactor, maximum hydrogen yield was obtained under temperatures 700–800 °C, S/C 15–20, LHSV 0.5–1.0 h^–1, and the maximum H₂ yield was 75.88 %. The carbon deposition content obtained from the fluidized bed was lower than that from the fixed bed. The maximum H₂ yield obtained in the fluidized bed was 7 % higher than that of the fixed bed. The carbon deposition contents obtained from the fluidized bed was lower than that of the fixed bed at the same reaction temperature.     

糠醛选择性催化加氢的研究进展

糠醛是种可再生的生物质能源,可从农副产品中萃取得到。糠醛加氢可合成很多高附加值的产物,如糠醇、四氢糠醇、2-甲基呋喃、呋喃、2-甲基四氢呋喃、环戊酮、环戊醇和1,4丁二醇等。糠醛氢化反应除了碳碳双键、呋喃环氢化外,还有其他衍生副反应(脱羰、开环反应、缩合反应、C O键氢化等)。糠醛催化加氢催化剂主要为金属催化剂以及非晶态合金催化剂,单金属催化剂用于反应时的选择性和活性较低,通常采用添加助剂或是另一种金属以提高催化剂的活性和选择性,目前糠醛选择性催化加氢的研究主要集中在催化剂载体和双金属催化剂的研制上。主要阐述糠醛选择性催化加氢催化剂研究进展,指出在研制低成本、高选择性、稳定性、绿色环保的催化剂同时,催化剂的工业化应用研究有待进一步完善,最终以实现糠醛高效高选择性加氢工业应用为目的。     

Carbon dioxide hydrogenation over nickel-, ruthenium-, and copper-based catalysts: Review of kinetics and mechanism

This study critically reviews the mechanism of CO₂ hydrogenation over Ni, Ru, and Cu, and the effect of catalyst properties and operating conditions on reaction kinetics. Most studies have reported the presence of CO and formate species on Ni-, Ru-, and Cu-based catalysts, where subsequent conversion of these species depends on the type of catalyst and the physicochemical properties of the catalyst support. Methane is the major product that forms during CO₂ hydrogenation over Ni and Ru catalysts, while methanol and CO are mainly produced on Cu catalysts. A different approach for catalyst formulations and/or process development is required where long chain hydrocarbons are desired.