Absence Of Hydrogen Research Articles

Study of olivine supported copper sorbents performances in the desulfurization process in link with biomass gasification

In this study, a Cu/olivine system was prepared with different loading (3–10wt.%) by wet impregnation method and calcined at different temperatures in order to raise and to optimize its performances in the presence and in the absence of hydrogen in desulfurization process during gasification of biomass. The Cu/olivine catalysts are as well characterized by XRD and H2-TPR experiments. XRD patterns are found to show formation of copper and iron oxides and mixed Cu–Fe oxides after calcination process. H2-TPR results revealed that the materials calcined in the 900–1000 °C temperature range were more difficult to reduce than those calcined at lower temperatures because of their strong interactions between copper and olivine material. Desulfurization over 3% Cu/olivine sorbent calcined in the 900–1000°C temperature range has been considered to be the best materials offering the highest breakthrough times and the highest amounts of H2S removed in the presence or in the absence of hydrogen with low production of SO2. Regeneration/sulfidation cycles performed on 3% Cu/olivine sorbent calcined at 1000°C revealed that the material is not deactivated and exhibits the same performances after 10cycles.

PE/Clay Nanocomposite with Bimodal Molecular Weight Distribution Produced Via In-Situ Polymerization

A Ti-based Ziegler–Natta catalyst supported on the clay was used for producing the polyethylene/clay nanocomposites through in situ polymerization. This catalyst showed high activity in the ethylene polymerization. The two-step polymerization approach, i.e. in the presence and absence of hydrogen, was laid out to broaden the molecular weight distribution of the polyethylene/clay nanocomposite. The molecular weights and molecular weight distribution of the nanocomposites were characterized by the gel permeation chromatography. It was found that the molecular weight distribution was remarkably widened towards bimodal distribution by using the above mentioned approach. The thermal properties of the produced nanocomposites were studied by differential scanning calorimetry and thermal gravimetric analysis. The microstructure of the resulting bimodal polyethylene/clay nanocomposite was investigated by X-ray diffraction and transmission electron microscopy. The thermal gravimetric analysis indicated an improved thermal stability of the produced nanocomposites. In addition, the studies proved the nanocomposite formation with the exfoliated structure of the clay in the polyethylene matrix.

High-pressure fast-pyrolysis, fast-hydropyrolysis and catalytic hydrodeoxygenation of cellulose: production of liquid fuel from biomass

A lab-scale, high-pressure, continuous-flow fast-hydropyrolysis and vapor-phase catalytic hydrodeoxygenation (HDO) reactor has been successfully designed, built and tested with cellulose as a model biomass feedstock. We investigated the effects of pyrolysis temperature on high-pressure cellulose fast-pyrolysis, hydrogen on high-pressure cellulose fast-hydropyrolysis, reaction pressure (27 bar and 54 bar) on our reactor performance and candidate catalysts for downstream catalytic HDO of cellulose fast-hydropyrolysis vapors. In this work, a liquid chromatography-mass spectrometry (LC-MS) method has been developed and utilized for quantitative characterization of the liquid products. The major compounds in the liquid from cellulose fast-pyrolysis (27 bar, 520 °C) are levoglucosan and its isomers, formic acid, glycolaldehyde, and water, constituting 51 wt%, 11 wt%, 8 wt% and 24 wt% of liquid respectively. Our results show that high pressures of hydrogen do not have a significant effect on the fast-hydropyrolysis of cellulose at 480 °C but suppress the formation of reactive light oxygenate species like glycolaldehyde and formic acid at 580 °C. The formation of permanent gases (CO, CO2, CH4) and glycolaldehyde and formic acid increased with increasing pyrolysis temperature in the range of 480 °C–580 °C in high-pressure cellulose fast-pyrolysis, in the absence of hydrogen. Candidate HDO catalysts Al2O3, 2% Ru/Al2O3 and 2% Pt/Al2O3 resulted in extents of deoxygenation of 20%, 22% and 27%, respectively, but led to carbon loss to gas phase as CO and CH4. These catalysts provide useful insights for other candidate HDO catalysts for improving the extent of deoxygenation with higher carbon recovery in the liquid product.

Reductive Amination of 2-Propanol to Monoisopropylamine Over Ni/γ-Al2O3 Catalysts

Ni/γ-Al2O3 catalysts with different nickel loadings (4–27 wt%) were used for the synthesis of monoisopropylamine by the reductive amination of 2-propanol in the presence of hydrogen and ammonia. H2-chemisorption analysis indicated that the highly reduced nickel metal surface area could be correlated with the enhancement of the 2-propanol conversion. During the reaction, the catalyst was progressively deactivated in the absence of hydrogen but its initial activity was completely recovered by re-exposure to the feed containing hydrogen. The deactivation was due to the formation of surface nickel nitride and excess hydrogen hindered the phase transition of the nickel metal to the corresponding nitride, ultimately preventing deactivation.

Influence of temperature and H2 adsorption on the structure of silica-supported gold subnanometer clusters

The structure of selected gold subnanometer clusters (AuN, N=6–7) deposited onto a silicon oxide (silica) surface is studied as a function of temperature and background hydrogen pressure via first-principles calculations. It is predicted that, in the absence of hydrogen, heating above 400°C leads to the desorption of a water molecule, and correspondingly to a flip of the Au clusters from vertical to horizontal configurations to better adhere to the dehydroxylated silica surface. In the presence of hydrogen, instead, the gold clusters are predicted to dissociate hydrogen molecules and at high temperature to finally detach from the surface and start sintering. These results elucidate the importance of Au–H interactions for very small gold clusters, and their possible role on the structure and chemistry of these nano-catalytic systems.

Localization of plastic deformation in alloyed γ-iron single crystals electrolytically saturated with hydrogen

On chromonickel γ-iron single crystals with \(\left[ {\bar 111} \right]\) orientation and low packing-defect density, the plastic-flow localization during electrolytic saturation with hydrogen within a three-electrode electrochemical cell is investigated, with constant controllable cathode potential. On the plastic-flow curve for the extension of single crystals in the initial state (without hydrogen), beyond the transition from elasticity to developed plastic flow, linear strain hardening and then parabolic (Taylor) strain hardening may be observed. The plastic-flow curve for single crystals of austenitic steel saturated with hydrogen includes a small projection and a flow trough, stages of linear strain hardening and parabolic strain hardening, and a prefailure stage. Saturation of \(\left[ {\bar 111} \right]\) single crystals with hydrogen reduces the yield point, increases the plasticity to failure by a factor of 1.3, and suppresses necking in crystals oriented for multiple slip. By double-exposure speckle photography, the basic types of plastic flow location at different stages of strain hardening may be identified, in the presence and absence of hydrogen, and the corresponding parameters may be determined. Hydrogenation of chromonickel γ-iron single crystals intensifies the localization of deformation and leads to considerable changes in the characteristic distances between the plastic-shear bands and the localized-strain zones.

The influence of residual oxidizing impurities on the synthesis of graphene by atmospheric pressure chemical vapor deposition

The growth of graphene on copper by atmospheric pressure chemical vapor deposition in a system free of pumping equipment is investigated. The emphasis is put on the necessity of hydrogen presence during graphene synthesis and cooling. In the absence of hydrogen during the growth step or during cooling at slow rate, weak carbon coverage, consisting mostly of oxidized and amorphous carbon, is obtained on the copper catalyst. The oxidation originates from the inevitable occurrence of residual oxidizing impurities in the reactor’s atmosphere. Graphene with appreciable coverage can be grown within the vacuum-free furnace only upon admitting hydrogen during the growth step. After formation, graphene is preserved from the destructive effect of residual oxidizing contaminants if exposure at high temperature is minimized by fast cooling or if cooling down is performed under the protection of hydrogen. Under these conditions, micrometer-sized hexagon-shaped graphene domains of high structural quality are achieved.

CONDITIONS FOR SUCCESSFUL HELIUM DETONATIONS IN ASTROPHYSICAL ENVIRONMENTS

Several models for type Ia-like supernovae events rely on the production of a self-sustained detonation powered by nuclear reactions. In the absence of hydrogen, the fuel that powers these detonations typically consists of either pure helium (He) or a mixture of carbon and oxygen (C/O). Studies that systematically determine the conditions required to initiate detonations in C/O material exist, but until now no analogous investigation of He matter has been conducted. We perform one-dimensional reactive hydrodynamical simulations at a variety of initial density and temperature combinations and find critical length scales for the initiation of He detonations that range between 1 - $10^{10}$ cm. A simple estimate of the length scales over which the total consumption of fuel will occur for steady-state detonations is provided by the Chapman-Jouguet (CJ) formalism. Our initiation lengths are consistently smaller than the corresponding CJ length scales by a factor of $\Sim 100$, providing opportunities for thermonuclear explosions in a wider range of low-mass white dwarfs (WDs) than previously thought possible. We find that virialized WDs with as little mass as 0.24 $M_\odot$ can be detonated, and that even less massive WDs can be detonated if a sizable fraction of their mass is raised to a higher adiabat. That the initiation length is exceeded by the CJ length implies that certain systems may not reach nuclear statistical equilibrium within the time it takes a detonation to traverse the object. In support of this hypothesis, we demonstrate that incomplete burning will occur in the majority of He WD detonations and that $^{40}$Ca, $^{44}$Ti, or $^{48}$Cr, rather than $^{56}$Ni, is the predominant burning product for many of these events. We anticipate that ...

The electroreduction of benzoic acid: voltammetric observation of adsorbed hydrogen at a platinum microelectrode in room temperature ionic liquids

The electrochemical reduction of benzoic acid in the presence and absence of hydrogen (H(2)) has been investigated using a 10 μm diameter platinum microelectrode in four different room temperature ionic liquids (RTILs), namely [C(4)mim][NTf(2)], [C(4)mpyrr][NTf(2)], [C(4)mim][OTf] and [C(4)mim][BF(4)], versus Ag/Ag(+). In all cases, reductive voltammetry is observed, and is suggested to occur via a CE mechanism in which dissociation of benzoic acid is followed by electron transfer to H(+) ultimately forming adsorbed hydrogen. Furthermore, the adsorbed H atoms, formed from the reduction of benzoic acid, could be used to achieve the rapid hydrogenolysis of the organic compound (bis(benzyloxycarbonyl)-l-lysine) on the timescale of the voltammetric technique under moderate conditions (25 °C).

Enhancement of the hydrogen storage capacity of Mg(AlH4)2by excess electrons: a DFT study

The enhancement of hydrogen storage in complexes of magnesium alanate ([Mg(AlH(4))(2)](n)(-) where n = 2, 3) and their anions was investigated using the B3LYP/6-311++G** method. Hydrogen atoms were chemically absorbed on [Mg(AlH(4))(2)](n)(-) (n = 2, 3) with binding energies of -83 to -91.23 kcal mol(-1). It was determined that a maximum of two hydrogen atoms can be absorbed on [Mg(AlH(4))(2)](n)(-) (n = 2, 3) complexes at 10.51 and 10.21 wt%, respectively. Natural bond order analysis revealed that, in the absence of hydrogen, the excess electron population lies predominantly along the sigma bonds between Mg(2+) atoms, while, upon absorption of the hydrogen atoms, the excess electron population lies on the absorbed hydrogen atoms. The vertical detachment energy showed that the excess electron is strongly bound to [Mg(AlH(4))(2)](n)(-) (n = 2, 3) complexes with energies of 78 to 153 kcal mol(-1). It can be seen from the stabilization energy values that the stability of hydrogen-absorbed complexes with excess electrons was significantly enhanced.

Cyanate ester resins – 'old newcomers' among high performance composite materials

resistant thermosetting polymer materials, cyanate ester resins offer numerous advantages over the widely used commodity resins. Due to the high aromatic content of the monomer and the cured polymer, they possess higher glass transition temperatures (Tg) than epoxy resins (up to 400°C), while the triazine ring formed during addition polymerization is responsible for high thermal stability, high char yield and low smoke generation. Balanced dipoles in the cured state and absence of hydrogen bonding functionality provide further important advantages as low dielectric properties and low moisture absorption. This latter is one of the most significant advantages, as high water uptake would plasticize the resins, lower the Tg value and thus limit the hot/wet service temperature of it. As for the mechanical properties, the relatively low crosslink density and high free volume is responsible for appropriate toughness. These properties can be further fine-tuned through backbone structure (using different linking groups between the aromatic rings of the monomer) or by blending them with other polymers as epoxy resins, phenolic resins, bismaleimides, benzoxazines. Further advantage of the cyanate ester resins is that they can be processed using the same composite preparation methods (resin transfer moulding (RTM), vacuum-assisted resin transfer moulding (VARTM), moulding, filament winding, prepregging) as epoxy resins. But in comparison to epoxy resins, they offer greater dimensional stability due to reduced outgassing during the addition type polymerization reaction. Despite the listed advantages and the fact that they were commercialized already in 1976, cyanate esters are still considered as relative newcomers in the composite industry. The reason behind is not only their relatively high cost (approximately twice as high performance epoxy resins), but also lack of formulation knowledge (moisture sensitivity of the uncured resin, toughness). Moisture sensitivity of the cyanate ester curing process is a known issue: the hydrolysis of the cyanate function leads to formation of carbamates, decomposing to amine and CO2 over 190°C, resulting in voids in the composite structure, decrease in mechanical properties, lower crosslink density and Tg. The use of rapidly developing process analytical technologies during composite preparation (e.g. in-line fibre-optic-coupled Raman spectrometric monitoring of the curing reaction and moisture uptake with possible feedback to process parameters itself) may offer a key to overcome these problems and facilitate the headway of cyanate esters in high-tech composite applications.

Effect of adamantane-containing additives on the isomerization of n-heptane in the ionic liquid trimethylammonium hydrochloride-aluminum chloride

We study the effect of adamantane-containing additives on the process of isomerization of n-heptane in the ionic liquid trimethylammonium hydrochloride-aluminum chloride (1 : 2 mol). It is shown that introducing 1-cyanomethyl-3-cyanoadamantane (5.0 wt %) into the reaction mixture slows conversion and lowers the yield of iso-products by a factor of more than 1.5, while adding adamantylpolyimide (0.5–5.0 wt %) substantially accelerates the isomerization of n-heptane and increases the yield of iso-products. In addition, this reaction proceeds under mild conditions at 40°C in the absence of hydrogen and precious metals.

Fate of Mycobacterium tuberculosis in peroxidase-loaded resting murine macrophages.

Myeloperoxidase (MPO), in the presence of hydrogen peroxide and a halide represent an efficient microbicidal mechanism of phagocytic cells. MPO is abundant in neutrophils which also respond to infection by producing large amounts of reactive oxygen species (ROS). MPO, ROS and halide constitute a very toxic antimicrobial system (called the Klebanoff system or KS). Resting mature macrophages do not contain granular MPO and thus are unable to kill pathogenic mycobacteria and some other microorganisms by this system. Under the hypothesis that transforming macrophages into peroxidase-positive (PO(+)) cells, these cells would be able to kill Mycobacterium tuberculosis, in this study, mature macrophages were loaded with exogenous peroxidase and were tested for their capacity to kill the Mycobacterium in the presence or in the absence of hydrogen peroxide. It was found that PO-loaded macrophages eagerly ingest M. tuberculosis, but do not show a significant mycobactericidal activity on this microorganism despite that it is highly susceptible to the Klebanoff system in vitro. Failure of PO-loaded macrophages to kill M. tuberculosis may obey either to an inappropriate location of the exogenous PO in these cells or more likely, to the presence of efficient detoxifying mechanisms in the bacteria. On the contrary, MPO-loaded or unloaded macrophages efficiently killed Listeria monocytogenes. The lack of granular MPO in mature macrophages, and the predilection of mycobacteria to infect these cells are two situations that favor the development of tuberculosis and related diseases, such as leprosy and Buruli ulcer.

Citrate adsorption on Pt{h k l} electrodes and its role in the formation of shaped Pt nanoparticles

The adsorption of citrate anions on Pt{hkl} single crystal electrodes and Pt nanoparticles was investigated using cyclic voltammetry (CV). Citrate is found to behave as a simple, specifically adsorbing anion, stronger in its surface interaction with platinum than either (bi-) sulphate or OH but displaying no tendency to decompose at 293K into molecular fragments such as chemisorbed carbon monoxide. No preference for a particular adsorption site was exhibited by citrate either, as would be expected from its reported ability to control the shape of growing Pt nanoparticles. Rather, citrate is readily removed from platinum surfaces either by exposure to aqueous sodium hydroxide (it acts as a non-specifically adsorbing anion at high pH) or potential excursions to potentials <0.15V vs. Pd/H. Hydrogen reduction of a platinum precursor (K2PtCl4) at 293K both in the presence and absence of citrate anions leads to almost identical nanoparticle structures being formed as measured by CV. It is concluded that at 293K in the presence of hydrogen, citrate anions play little part in controlling nanoparticle shape. In contrast, heating the platinum precursor at 373K using citrate as both reducing agent and stabilizer facilitated formation of Pt nanoparticles containing a slightly greater proportion of Pt{111} terrace sites and a relative diminution in the surface density of Pt{100} terraces. It proved impossible to clean these Pt nanoparticles via potential cycling/hydrogen evolution indicating that a much more tenaciously held intermediate is formed during the reduction process in the absence of hydrogen and it is speculated that it is this intermediate that facilitates shape selectivity during platinum nanoparticle synthesis in accordance with previous studies investigating gold nanoparticle formation using citrate.

Ir/Pt-HZSM5 for n-pentane isomerization: Effect of iridium loading on the properties and catalytic activity

The effects of iridium loading on the properties of Ir/Pt-HZSM5 and n-pentane isomerization were studied. XRD, IR, and NMR results indicated that increasing iridium loading did not much change the properties of catalysts, but eliminated the perturbed silanol groups at 3700 and 3520cm−1, whereas IR and ESR spectroscopy confirmed that increasing iridium loading continuously decreased the permanent Lewis and Brønsted acid sites and inhibited the formation of protonic acid sites induced by hydrogen. At low iridium loading (0–0.3wt%), cracking process proceed through dimerization-cracking step, whereas high iridium loading (0.5–2.0wt%) reduces the contribution of dimerization-cracking step and promotes the contribution of hydrogenolysis. The excessive amount of iridium loading, with the presence of a low amount of active protonic acid sites and hydrogen gas, accelerated the hydrogenolysis process. The activity of Ir/Pt-HZSM5 was marginal in the absence of hydrogen, showing the dependence of activity on promotive effect of hydrogen.

CO oxidation and preferential oxidation of CO in the presence of hydrogen over SBA-15-templated CuO-Co3O4 catalysts

Copper–cobalt mesostructured spinel replicas of SBA-15 were synthesized through a hard template pathway. The catalysts, with Cu/(Co+Cu) atomic ratio in the range 0–17%, were characterized as to their structure, morphology, texture and redox features by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy, N2 physisorption, and temperature-programmed reduction with hydrogen. The catalysts were tested in a fixed-bed reactor for CO oxidation both in the absence of hydrogen (1.5mol% CO, 1.5mol% O2, balance He, 40–140°C) and in a hydrogen-rich atmosphere (1.5mol% CO, 1.5mol% O2, 46mol% H2, balance He, 40–200°C). In the absence of hydrogen, catalytic activity for CO oxidation was similar for all the samples for temperatures up to ca. 100°C, at which 50% CO conversion was observed. Above such temperature the copper-containing catalysts appeared more active than the pure Co3O4. All the catalysts were active for the preferential oxidation of CO in hydrogen-rich atmosphere, with 50% CO conversion occurring in the 123–138°C range. Both CO and oxygen conversions were enhanced by the presence of copper, which however also favoured the occurrence of parasite hydrogen combustion. Methanation was observed (to a limited extent, at temperatures ≥160–180°C) only on the Cu-containing catalysts. The performance of the present catalysts was compared with literature results for CO oxidation and preferential CO oxidation on cobalt and copper–cobalt oxides prepared by different methods. The hard-templated catalysts seem superior to traditionally prepared ones in the case of CO oxidation in the absence of hydrogen, whereas no clear-cut conclusion can be drawn in the case of preferential CO oxidation.

Low power hydrogen sensors using electrodeposited PdNi–Si Schottky diodes

The use of electrodeposited PdNi-Si Schottky barriers as low power Hydrogen sensors is investigated. The Palladium content of the film causes the Hydrogen molecules to dissociate and be absorbed by the film, changing the metal work function and Schottky barrier current. In this work we show that electrodeposited Pd(Ni)-Si Schottky barriers exhibit very low reverse bias currents compared to evaporated Schottky diodes. The Schottky diodes were fabricated on 0.5-1.5 ohmcm 100 n-type Si by electrodeposition of PdNi followed by evaporation of Aluminium contact pads. Electrical measurements at different Hydrogen pressures were performed on back to back Schottky diodes in a vacuum chamber using pure Nitrogen and a 5% Hydrogen-Nitrogen mixture. Very low currents of 1nA were measured in the absence of Hydrogen. Large increases in the currents, upto a factor of 100, were observed upon exposure to different Hydrogen partial pressures. A back to back configuration forms a device that draws extremely low power when idle. The low idle current, simplicity of the fabrication process and ability to easily integrate with conventional electronics proves the suitability of electrodeposited PdNi-Si Schottky barriers as low power Hydrogen sensors.

WO3 monolayer loaded on ZrO2: Property–activity relationship in n-butane isomerization evidenced by hydrogen adsorption and IR studies

The property–activity relationship of WO3 supported on ZrO2 (WZ) was evaluated in n-butane isomerization for a series of catalysts with WO3 loading ranging from 5 to 20wt% on ZrO2. The catalysts were prepared by incipient-wetness impregnation of Zr(OH)4 with an aqueous solution of (NH4)6[H2W12O40·nH2O], followed by drying and calcination at 1093K. The introduction of WO3 continuously increased the tetragonal phase of ZrO2, WO3 surface density and coverage. The specific surface area and total pore volume passed through a maximum of WO3 loading at 13wt%; this loading corresponds to 5.9WO3/nm2 and is near the theoretical monolayer-dispersed limit of WO3 on ZrO2. The IR results indicate that the presence of WO3 eroded the absorbance bands at 3738 and 3650cm−1 corresponding to bibridged and tribridged hydroxyl groups up to near the monolayer-dispersed limit of WO3. A new broad and weak band appeared, centered at 2930cm−1, indicating the presence of bulk crystalline WO3 for WO3 coverage exceeding the theoretical monolayer-dispersion limit. In addition to the band at 2930cm−1, two WO stretching bands were observed at about 1021 and 1014cm−1 for all WZ catalysts, confirming the existence of WO connected to coordinative unsaturated (cus) Zr4+ through O and to the other W through O, respectively. Pyridine adsorbed IR and NH3-TPD revealed that the presence of WO3 modified the nature and concentration of acidic sites. The highest acidity was observed with 13wt% loading WO3. The decrease in the intensity of peaks due to increasing WO3 loading was much higher on Lewis acid sites than on Brønsted acid sites. Hydrogen adsorption isotherms and the IR results for hydrogen adsorption on preadsorbed pyridine were used to evaluate the formation of active protonic acid sites from molecular hydrogen. The catalyst with 13wt% WO3 loading showed the maximum hydrogen uptake capacity and formation of protonic acid sites. These results show a direct correlation with the activity of WZ in n-butane isomerization at 573K in which 13wt% WO3 loading on ZrO2 yielded the highest amount of isobutane. It is suggested that the presence of strong Lewis acid sites on monolayer-dispersed WO3 facilitates the formation of protonic acid sites from hydrogen in the gas phase which act as active sites in n-butane isomerization. The presence of permanent Brønsted acid sites could not be directly associated with activity. In fact, no isomerization activity was observed in the absence of hydrogen.

Copolymerization of ethylene with α‐olefins over supported titanium–magnesium catalysts. II. Comonomer as a chain transfer agent

AbstractThe data on the effect of comonomer (propylene and 1‐hexene) on molecular weight (Mw), molecular weight distribution (MWD), and content of terminal double bonds were obtained for ethylene/α‐olefin copolymers produced over a supported titanium–magnesium catalyst (TMC) upon polymerization in the absence of hydrogen. The experimental data on the effect of comonomer concentration on Mw of polymers were used to calculate the ratios between the effective rate constants of chain transfer with monomer and the propagation rate constant. It was shown that the effective rate constant of chain transfer with monomers increases in the row of monomers: ethylene &lt; 1‐hexene &lt; propylene. Meanwhile, the data on the effect of copolymers on content of terminal double bonds of various types demonstrate that different reactions of chain transfer with comonomer may simultaneously occur during copolymerization. It results in simultaneous formation of terminal vinylidene and trans‐vinylene bonds. Therefore, the calculated rate constants of chain transfer with comonomer are complex values, which include the rate constants of chain transfer with comonomer occurring via different mechanisms. The data on MWD, short chain branching (SCB) and terminal double bonds content of different types were obtained by molecular weight fractionation of copolymers followed by the analysis of narrow fractions. The analysis of the data on MWDs of SCB and terminal double bonds shows that active sites of the TMC are considerably heterogeneous with respect to the rates of different chain transfer reactions with monomers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Reductive amination of 2-propanol to monoisopropylamine over Co/γ-Al2O3 catalysts

Co/γ-Al2O3 catalysts with 4–27wt% cobalt loadings were prepared by incipient-wetness impregnation and used to catalyze the synthesis of monoisopropylamine by the reductive amination of 2-propanol in the presence of hydrogen and ammonia. The catalysts were characterized by X-ray diffraction, H2-temperature programmed reduction, N2-sorption, and H2-chemisorption. 23wt% Co loading resulted in the highest catalytic activity and a long-term stability of up to 100h on stream. 2-Propanol conversion was related to the exposed metal surface area and the number of exposed cobalt atoms. In the absence of hydrogen, the catalyst was progressively deactivated; its initial activity and selectivity were completely recovered upon re-exposure to hydrogen. The deactivation was due to the formation of metal nitride caused by the strong adsorption of ammonia on the surface of the metal phase. Excess hydrogen hindered the phase transition to metal nitride, preventing deactivation.