Effect of the catalyst preparation method on the performance of Ni-supported catalysts for the synthesis of saturated amines from nitrile hydrogenation

The liquid-phase hydrogenation of butyronitrile to saturated amines was studied on silica- supported Ni catalysts prepared by either incipient-wetness impregnation (Ni/SiO2-I) or ammonia (Ni/SiO2-A) methods. A Ni/SiO2-Al2O3-I sample was also used. Ni/SiO2-I was a non-acidic catalyst containing large Ni^0 particles of low interaction with the support, while Ni/SiO2-A was an acidic catalyst due to the presence of Ni^2+ species in Ni phyllosilicates of low reducibility. Ni/SiO2-I formed essentially butylamine (80%), and dibutylamine as the only byproduct. In contrast, Ni/SiO2-A yielded a mixture of dibutylamine (49%) and tributylamine (45%), being the formation of butylamine almost completely suppressed. The selective formation of secondary and tertiary amines on Ni/SiO2-A was explained by considering that butylamine is not release to the liquid phase during the reaction because it is strongly adsorbed on surface acid sites contiguous to Ni^0 atoms, thereby favoring the butylimine/butylamine condensation to higher amines between adsorbed species.

Effect of preparation methods on the structure and catalytic performance of Fe–Zn/K catalysts for CO2 hydrogenation to light olefins

Potassium promoted iron–zinc catalysts prepared by co-precipitation method(C–Fe–Zn/K),solvothermal method(S–Fe–Zn/K)and hydrothermal method(H–Fe–Zn/K)could selectively convert CO_2to light olefins,respectively.The physicochemical properties of the obtained catalysts were determined by SEM,N_2physisorption,XRD,H_2-TPR,CO_2-TPD and XPS measurements.The results demonstrated that preparation methods had great influences on the morphology,phase structures,reduction and adsorption behavior,and hence the catalytic performance of the catalysts.The samples prepared by hydrothermal and co-precipitation method generated small uniform particles and led to lower specific surface area.In contrast,microspheres with larger specific surface area were formed by self-assembly of nanosheets using solvothermal method.ZnFe_2O_4was the only detectable phase in the fresh C–2Fe–1Zn/K,S–3Fe–1Zn/K and S–2Fe–1Zn/K samples.ZnFe_2O_4and ZnO co-existed with increasing Zncontent in S–1Fe–1Zn/K sample,while ZnO and Fe_2O_3could be observed over H–2Fe–1Zn/K sample.All the used samples contained Fe_3O_4,ZnO and Fe_5C_2.The peak intensity of ZnO was strong in the AR-H–2Fe–1Zn/K sample while it was the lowest in the AR-C–2Fe–1Zn/K sample after reaction.The formation of ZnFe_2O_4increased the interaction between iron and zinc for C–2Fe–1Zn/K and S–Fe–Zn/K samples,causing easier reduction of Fe_2O_3to Fe_3O_4.The surface basicity of the sample prepared by co-precipitation method was much more than that of the other two methods.During CO_2hydrogenation,all the catalysts showed good activity and olefin selectivity.The CO selectivity was increased with increasing Zncontent over S–Fe–Zn/K samples.H–2Fe–1Zn/K catalyst preferred to the production of C_5^+hydrocarbons.CO_2conversion of 54.76%and C_2~=–C_4~=contents of 57.38%were obtained on C–2Fe–1Zn/K sample,respectively.

PREPARATION OF ULTRAFINE PARTICLE IRON-CARBONIDE CATALYST AND CHARACTERIZATION OF ITS CATALYTICAL BEHAVIOR

Studies on ultrafine particle catalyst have attracted many researchers' attention by its large surface area,higher activity and selectivity.Based on the mechanism of α-Fe and Fe_xC_y as the catalytical active species this paper reports for the first time the preparation method of Fe_3C ultrafine parti- cle catalyst,from highly dispersed amorphous Fe powder and free carbon.The Fe powder and free car- bon,prepared by laser pyrolysis technique,was then treated by washing and heating at high tempera- ture protected with N_2.The catalyst prepared under different experimental conditions was characterazed by means of XRD,electronic diffraction and TEM.It shows that the crystlline grain size is in a range of 1-4nm and composed of Fe_3C and α-Fe.It has been found that the ultrafine particle iron-carbonide catalyst exhibited much higher activity and selectivity to light olefins.At the standard atmosphere and 380℃ reaction temperature,the conversion of CO reached a maximum of 80%.

THE PREPARATION CHEMISTRY OF V/MgO CATALYST FOR OXIDATIVE DEHYDROGENATION OF ETHYLBENZENE

The structures and catalytic performances of V_2O_5, Mg_3V_2O_8 and V/MgO catalysts have been correlated by means of XRD, FTIR, TPR and flow micro-reactor tests. The postulation about active site has been made. Based on it, better catalysts have been first prepared via grafting and modification with Sb which are better than that via impregnation.

Plasma methods for preparing green catalysts: Current status and perspective

Most current catalyst preparation methods cause pollution to air, water and land with the use of hazardous chemicals, lengthy operation time, high energy input and excessive water usage. The development of green catalyst preparation is necessary to prevent and eliminate waste from each step of the catalyst preparation. We summarize recent progress in the application of cold plasmas for green catalyst preparation. Cold plasma preparation can reduce the catalyst size, improve the dispersion and enhance catalyst-support interaction with the use of less or no hazardous chemicals. These improvements also lead to the enhancement of catalyst activity and stability. An alternative room temperature electron reduction with a non-hydrogen plasma as an electron source was developed for the reduction of noble metal ions in which no hazardous chemical reducing agent or hydrogen was needed. This creates many opportunities for the development of supported catalysts with heat sensitive substrates, including metal organic frameworks （MOFs）, covalent organic framework（COFs）, high surface area carbon, peptide, DNA, proteins and others. A novel floating metal catalyst on a water（or solution） surface has been established. Template removal using low temperature cold plasmas also leads to the formation of high surface area porous materials with characteristics that are normally only obtainable with high temperature calcination, but sintering can be avoided. Micro combustion has been developed for the removal of carbon template using cold plasma. This is promising for preparing many structured oxides in a simple way with no use of auxiliary chemicals. Many opportunities exist for the use of cold plasmas to make multi-metallic oxides. Some future development ideas are addressed.

Atomic layer deposition: Catalytic preparation and modification technique for the next generation

Atomic layer deposition(ALD)attracts great attention nowadays due to its ability for designing and modifying catalytic systems at the molecular level.There are several reported review papers published recently discussing this technique in catalysis.However,the mechanism on how the deposited materials improve the catalyst stability and tune the reaction selectivity is still unclear.Herein,catalytic systems created via ALD on stepwise preparation and/or modification under self-limiting reaction conditions are summarized.The effects of deposited materials in terms of electronic/geometry modification over the catalytic nanoparticles(NPs)are discussed.These effects explain the mechanism of the catalytic stability improvement and the selectivity modification.The unique properties of ALD for designing new catalytic systems are further investigated for building up photocatalytic reaction nanobowls,tandem catalyst and bi-active-component metallic catalytic systems.

Shape Selective Hydrogenation of Alkenes with Supported Pd@MOF-5 Catalyst in Supercritical Carbon Dioxide

The metal-organic framework MO-5 has been synthesized by solvothermal method. Obtained material consists of nano-sized particle of ca. 100 nm size. The material has been physico-chemical characterized regarding structural and textural properties by XRD, FTIR, nitrogen adsorption/desorption, thermal analysis and ESA experiments. Palladium supported MOF-5 catalyst has been prepared by adsorption inclusion method. The catalyst was activated by treatment with supercritical carbon dioxide （scCO2） followed by mild reduction with hydrogen solved in scCO2. The obtained catalyst is shown to be stable and active and shape selective in hydrogenation reactions of alkenes using supercritical carbon dioxide as reaction medium. The catalytic active Pd species are located inside the pores. Positive surface charging seems to prevent deposition of active species at the crystal surface of the MOF. The catalyst is long time stable and re-useably. These findings show the potential of porous MOFs for applications under supercritical conditons and resisted repeated pressuring to 120 bar at elevated temperature.

Selective oxidation of propane to acrylic acid over mixed metal oxide catalysts

The effects of metal atomic ratio, water content, oxygen content, and calcination temperature on the catalytic performances of MoVTeNbO mixed oxide catalyst system for the selective oxidation of propane to acrylic acid have been investigated and discussed. Among the catalysts studied, it was found that the MoVTeNbO catalyst calcined at a temperature of 600 ℃ showed the best performance in terms of propane conversion and selectivity for acrylic acid under an atmosphere of nitrogen. An effective MoVTeNbO oxide catalyst for propane selective oxidation to acrylic acid was obtained with a combination of a preferred metal atomic ratio （Mo1V0.31Te0.23Nb0.12）. The optimum reaction condition for the selective oxidation of propane was the molar ratio of C3H8 ：O2 ： H2O ： N2 = 4.4： 12.8 ： 15.3 ： 36.9. Under such conditions, the conversion of propane and the maximum yield of acrylic acid reached about 50% and 21%, respectively.

Effect of preparation conditions on selective oxidation of propane to acrylic acid

The effects of chemical composition and preparation conditions,especially calcination atmosphere and water content on the catalytic performances of MoVTeNbO mixed oxide catalyst system for the selective oxidation of propane to acrylic acid were investigated.Among the catalysts studied,Mo_(1.0)V_(0.3)Te_(0.23)Nb_(0.12)O_(x) catalyst calcined in inert atmosphere at 600℃shows the best performance in terms of propane conversion and selectivity to acrylic acid.The results reveal that proper chemical composition, calcination atmosphere and water content affect greatly the catalysts in many ways including structure,chemical composition,which are related to their catalytic performances;and 51.0%propane conversion and 30.5%one-pass yield to acrylic acid can be achieved at the same time.

Magnetic and Relativistic Effects in Uranium Catalysts and the Movement of Charged Particles under the Effect of Electric and Magnetic Fields

We first received and examined X-ray spectroscopy of uranium catalyst. We studied magnetic and relativistic effects in uranium catalysts, and the movement of charged particles under the effect of a uniform electric field and uniform magnetic field. We proposed the mechanism of the motion of charged particles under the influence of a uniform electric field and a uniform magnetic field.

Property and Activity of Molybdates Dispersed on Silica Obtained from Various Synthetic Procedures

The synthesis and characterization of several dispersed molybdena catalysts on silica support (MoO3-SiO2) prepared from a variety of precursors (Mo(VI)-acetylacetonate, oxo-peroxo Mo-species, hydrated ammonium heptamolybdate) and preparation methods (deposition of the Mo-phase on finite SiO2 support by aqueous and methanol impregnations, by adsorption, by oxo-peroxo route-like, and by one-step synthesis of MoO3-SiO2 system with molecular precursors) are presented. The molybdena concentration on silica was comprised in a large interval (1.5 - 14 wt%) depending on the preparation method which governed the Mo-loading on silica. Convenient comparisons among samples at similar Mo-concentration have been made discussing the morphologic-structural (XRD, XPS, UV-vis-DRS, and N2-adsorption) and physicochemical (TG-DTG, TPR, and n-butylamine-TPD) sample properties. Polymeric octahedral polymolybdate aggregates predominated in the samples prepared by aqueous and methanol impregnations, which were at high Mo-concentration. On the contrary, isolated Mo(VI) species in distorted Td symmetry predominated in the sample prepared by adsorption which was at very low Mo-concentration. The sample acidity was composed of a weak acidy site population, associated with the silica support, and a strong acid site population associated with the Mo-dispersed phase. Oxidation tests of formaldehyde, an oxygen-containing VOC (Volatile Organic Compound), were performed to determine the prevalent redox or acidic function of the Mo-species at the surface of the catalysts.

Single crystal metal-organic framework constructed by vertically self-pillared nanosheets and its derivative for oriented lithium plating

This vertically self‐pillared(VSP)structure extends the application range of traditional porous materials with facile mass/ion transport and enhanced reaction kinetics.Here,we prepare a single crystal metal‐organic framework(MOF),employing the ZIF‐67 structure as a proof of concept,which is constructed by vertically self‐pillared nanosheets(VSP‐MOF).We further converted VSP‐MOF into VSP‐cobalt sulfide(VSP‐CoS2)through a sulfidation process.Catalysis plays an important role in almost all battery technologies;for metallic batteries,lithium anodes exhibit a high theoretical specific capacity,low density,and low redox potential.However,during the half‐cell reaction(Li++e=Li),uncontrolled dendritic Li penetrates the separator and solid electrolyte interphase layer.When employed as a composite scaffold for lithium metal deposition,there are many advantage to using this framework:1)the VSP‐CoS2 substrate provides a high specific surface area to dissipate the ion flux and mass transfer and acts as a pre‐catalyst,2)the catalytic Co center favors the charge transfer process and preferentially binds the Li+with the enhanced electrical fields,and 3)the VSP structure guides the metallic propagation along the nanosheet 2D orientation without the protrusive dendrites.All these features enable the VSP structure in metallic batteries with encouraging performances.

Production of Synthesis Gases from Ethanol Steam Reforming Process

In this study, the production of synthesis gases has been purposed under between 250oC - 700oC and 1 - 2 bars pressures. The research was conducted over a commercial BASF catalyst and a laboratory prepared catalyst. The catalyst has a content of different substances including basically NiO/Al2O3 and some additionals (Ca, Mg, Cr, Si). The experimental measurements were carried out within a recently developed experimental equipment which can be operated up to 1200o and 1 to 3 bars pressures. The study was conducted over a commercial BASF catalyst and a laboratory prepared catalyst under different ethanol/water ratios, temperatures, and catalyst loads. Under the condition when ethanol/water ratios were decreased from 1/2 to 1/10, it was observed that hydrogen ratios increased in exit gas composition of the reactor. With increments in catalyst loads from 1 to 5 grammes, hydrogen ratios in exit gas composition gradually increased. Reaction of ethanol-steam reforming started nearly at 300oC, and when temperature increments continued further up to 700oC, hydrogen yields in exit gas compositions of the reactor increased significantly to a range of 70% - 80%. In the case of using commercial BASF catalyst, hydrogen ratios in exit gas composition were found slightly higher than laboratory prepared catalyst. According to our observations, life time of laboratory prepared catalyst was found higher than the commercial BASF catalyst. In this study which kinetic measurements were applied, some kinetic parameters of ethanol-steam reaction were calculated. The mean activation energy of ethanol consumptions at 573oK - 973oK was found as 26.87 kJ/mol, approximately. All kinetic measurements were analyzed with a first order reaction rate model. In this study, some diffusion limitations existed, however, overall reaction was chemically controlled.

Realization approach of Pd-only three-way catalysts with high catalytic performance and thermal stability

Pd-only three-way catalyst （TWC）, Pd supported on washcoating （the mixture of alumina and Ce-Zr solid solution）/cordierite, was prepared and its catalytic performance and the operation window （2-value） at 450 ℃ were evaluated with the simulated automotive exhaust feed gas. Surfactants such as Tween-80 and Span-20 were added in the process of preparing the catalyst in order to improve the thermal stability and catalytic performance of Pd-only TWC. The fresh and aged catalysts at 1000 ℃ for 4 h were characterized by low-temperature N2 adsorption, XRD, XPS, and H2-TPR techniques. The results show that the presence of surfactants in the synthesis slurry could influence the physicochemical properties of the final Pd-only TWC. The FTS catalyst prepared with the mixed surfactant of Tween-80 and Span-20 exhibited excellent three-way catalytic performance. After being aged at 1000℃ for 4 h, the catalytic performances of Pd-only TWCs slightly decreased, but the FTS catalyst still demonstrated higher catalytic performance and better thermal stability compared with the Pd-only catalysts prepared with single surfactant or without any surfactant. And the FTS catalyst has a wider 2 value （operation window） than other catalysts, even after being aged at 1000℃.

A non-precious metal catalyst for oxygen reduction prepared by heat-treating a mechanical mixture of carbon black,melamine and cobalt chloride

A non-precious metal catalyst CoMe]C for the oxygen reduction reaction is prepared by heat-treating a mechanical mixture of carbon black, melamine and cobalt chloride at 600 under nitrogen atmosphere for 2 h. The catalytic activity of CoMe/C is characterized by the electrochemical linear sweep voltammetry technique. The onset reduction potential of the catalyst is 0.55 V （vs. SCE） at a scanning rate of 5 mV/s in 0.5 mol/L H2SO4 solution. The formation of the ORR activity sites of CoMe/C is facilitated by metallic β- cobalt.

Morphology-dependent nanocatalysis on metal oxides

The design and fabrication of solid nanomaterials are the key issues in heterogeneous catalysis to achieve desired performance. Traditionally, the main theme is to reduce the size of the catalyst particles as small as possible for maximizing the number of active sites. In recent years, the rapid advancement in materials science has enabled us to fabricate catalyst particles with tuna- ble morphology. Consequently, both size modulation and morphology control of the catalyst particles can be achieved inde- pendently or synergistically to optimize their catalytic properties. In particular, morphology control of solid catalyst particles at the nanometer level can selectively expose the reactive crystal facets, and thus drastically promote their catalytic performance. In this review, we summarize our recent work on the morphology impact of Co304, CeO2 and Fe203 nanomaterials in catalytic reactions, together with related literature on morphology-dependent nanocatalysis of metal oxides, to demonstrate the importance of tuning the shape of oxide-nanocatalysts for prompting their activity, selectivity and stability, which is a rapidly growing topic in heterogeneous catalysis. The fundamental understanding of the active sites in morphology-tunable oxides that are enclosed by reactive crystal facets is expected to direct the development of highly efficient nanocatalysts.

Multi-walled Carbon Nanotubes as a Ligand in Nickel ?-Diimine Based Ethylene Polymerization

Two novel heterogeneous nickel a-diimine based polymerization catalysts, containing MWCNT as the main ligand, were synthesized by novel in situ catalyst preparation technique. The in situ synthesis was performed by covalent attachment of the acenaphthenic ligand core to amine functionalized MWCNT ligand arms through diimine bonding and further nickel dibromide chelation. The prepared catalysts were fully characterized and their structures and supporting efficiencies were determined. Single or double introduction of the MWCNTs through their ends or sidewall（s） in the catalytic system, as a ligand, influenced the catalytic performance, microstructure and morphology of obtained polyethylenes. MWCNT sidewall bonding to para-aryl position of the tetramethylphenyl moiety performed as more electron-donating ligand than MWCNT ends linked to the imine bond and protected the catalytic system to retain its activity. This character resulted in the maintenance of the resulting polymer topology at elevated temperatures so that the catalytic activity and the obtained polymer melting points remained around 110 g PE·mmol^-1 Ni·h^-1 and 123 ℃ in all polymerization temperatures respectively. In polymerization trials, molecular weight fall against temperature was not as sharp as what had been observed in sequentially prepared catalysts insofar as the molecular weight of resultant polymer at 60 ℃ reached to 310000 g·mol^-1 which was close to the highest value had been reported at 30 ℃ for sequentially prepared catalysts. TEM observations showed the presence of the stopped-growth polymer chains due to geometrical constrains or ligand debonding for both catalytic systems.