Benzene Hydrogenation Activity Research Articles

Effect of Co and Ni on benzene hydrogenation and sulfur tolerance of Pt/H-MOR

The activity and sulfur resistance of Pt promoted by Co and Ni in MOR have been studied in benzene hydrogenation. The highest benzene hydrogenation activity is observed for Pt/H-MOR and is attributed to its high acid site concentration and the higher electron deficiency of Pt. XANES studies show that the presence of Co and Ni decreases the Pt white line intensity suggesting an increase of the Pt apparent electronic density. This has been correlated with decreasing catalytic activity and sulfur tolerance of the catalysts. Brønsted acid sites seem to be involved and beneficial for benzene hydrogenation.

High temperature reduction with hydrogen, phase composition, and activity of cobalt/silica catalysts

The evolution of the morphology, phase composition, and activity in benzene hydrogenation of Co/SiO 2 catalysts, prepared from cobalt nitrate and porous (390 m 2/g) or nonporous (35 m 2/g) silica, upon reduction with hydrogen at 350–900 °C have been studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), magnetic measurements, oxygen uptake, BET, and hydrogen chemisorption. A rapid decline of the activity of Co/SiO 2 catalysts to zero was observed with reduction temperature increasing from 400 to 600 °C. This effect could not be simply explained by a sintering of cobalt particles or by the reaction of Co with the support and alloys or compound formation. The TEM, H 2 chemisorption, O 2 uptake, and magnetic measurements revealed that at T red⩾500 °C coverage (encapsulation) of the metal with a thin, most probably SiO 2, overlayer was likely to be the reason. Both Co/SiO 2 catalysts reduced at T red>500 °C exhibited a higher and growing with reduction temperature resistance to oxidation when exposed to oxygen or air as it was evidenced by oxygen uptake, magnetic data, and decreasing H 2 chemisorption capacity. At higher temperature (⩾700 °C) the formation of a thicker, easily observable with TEM, SiO 2 or SiO x , overlayer covering the Co particles took place. As a consequence, the catalysts reduced at 900 °C were nearly insensitive to the exposure to air. Oxygen uptake and magnetic measurements ruled out the hypothesis on the Co–Si solid solution or cobalt silicide formation at least in quantities higher than the reliability limits of the experimental methods used. The sintering of Co particles and the significant growth of the mean size of Co crystallites was observed at reduction temperatures of 800 and 850 °C for nonporous and porous silica, respectively. An apparent growth of the cobalt content to 107 and 114% of the initial value was noted after reduction at 700 and 900 °C, respectively, for both catalysts studied, probably due to the strong support dehydroxylation and/or partial reduction.

Pt/H-ZSM-12 as a catalyst for the hydroisomerization of C 5–C 7n-alkanes and simultaneous saturation of benzene

Hydroisomerization of a mixture of C 5–C 7 n-paraffins and simultaneous saturation of benzene was studied over bifunctional Pt/H-ZSM-12 catalysts, with a sulfur free feed and with the feed containing 200 ppm of thiophene. The performance of a Pt/H-ZSM-12 catalyst was also compared with a Pt/H-beta and a Pt/H-mordenite catalyst having a similar Si/Al ratio. The three Pt/H-ZSM-12 catalysts, having different Si/Al ratios, showed very similar activity and selectivity characteristics. Presence of benzene in the feed had no effect on the isomerization over the Pt/H-ZSM-12 catalysts. Compared to the Pt/H-beta catalyst, Pt/H-ZSM-12 and Pt/H-mordenite required higher temperatures to achieve the same conversion level. The lower activity of Pt/H-ZSM-12 and Pt/H-mordenite is in agreement with the behavior expected from a one-dimensional structure. However, at comparable conversion levels, cracking reactions, especially that of heptane, occurred to a lesser extent over the Pt/H-ZSM-12 catalyst resulting in a significantly higher yield of the branched paraffins than over Pt/H-beta or Pt/H-mordenite. In the presence of 200 ppm of thiophene, both the isomerization and the benzene hydrogenation activity of the Pt/H-ZSM-12 and Pt/H-mordenite catalysts decreased but the Pt/H-beta catalyst was affected only to a small extent. Moreover, in the presence of sulfur, cracking occurred to a greater extent at the same conversion level over all the catalysts. The estimated research octane number (RON) of the C 5+ products varied in the same manner with respect to the conversion over all the catalysts, but a higher yield of these products is obtained over Pt/H-ZSM-12 in the absence of sulfur. Although Pt/H-beta is much more active and has better sulfur resistance, the capability of Pt/H-ZSM-12 to provide a significantly higher yield of isomers makes it an attractive catalyst.

Silica-supported palladium nanoparticles show remarkable hydrogenation catalytic activity

Palladium nanoparticles (1.9 nm) stabilized on silica were obtained from the reduction of an organometallic precursor (palladium(II) bis-dibencylidene acetone) with dihydrogen. This material was investigated in the hydrogenation catalysis of different substrates (1-hexene, cyclohexene, benzene, 2-hexanone, cyclohexanone and benzonitrile). The solid was used as a heterogeneous catalyst. The highest hydrogenation rate was found with 1-hexene with a TOF of 38,250 mole of product/(mole of metal/h) at 25 °C and 30 psi pressure. The [Pd/SiO2] nanocatalyst has shown remarkably high activity for the catalytic hydrogenation of cyclohexene (TOF 33,000) and benzene (TOF 10,000). This is the first reported palladium nanocatalyst with high catalytic activity towards the hydrogenation of 2-hexanone TOF 16,000, cyclohexanone TOF 15,000 and benzonitrile TOF 5000 reported to the date.

Highly dispersed activated carbon supported platinum catalysts prepared by OMCVD: a comparison with wet impregnated catalysts

This study shows that the air oxidation treatment of an activated carbon originates drastic changes in its chemical surface composition leading to the formation of a less acidic surface with thermally stable oxygenated groups, mainly hydroxyl and carbonyl groups. The oxidation treatment also induces changes in the textural properties, although less pronounced than the extent of the chemical changes. The degree of oxidation was characterized by temperature programmed desorption (TPD). Pt/AC catalysts were prepared on the activated carbon supports by organometallic chemical vapor deposition (OMCVD). Another set of catalysts was prepared on the same supports by the classical incipient wetness impregnation method. The platinum loading of each sample was kept fixed at 1wt.%. These Pt/AC catalysts were characterized by H2 adsorption, temperature programmed reduction (TPR), electron microscopy (TEM), infrared spectroscopy (DRIFTS) and tested for their activity in benzene hydrogenation. The changes in the physical and chemical structures of the activated carbons have pronounced effects on the characteristics of both impregnated and OMCVD samples. The results revealed that the preparation by OMCVD on the air oxidized support leads to a drastic increase in both Pt dispersion and catalytic activity. No pronounced differences were observed between the dispersion and activity of impregnated and OMCVD samples that were prepared on the non-oxidized activated carbon.

MCM-41 mesoporous molecular sieves supported nickel—physico-chemical properties and catalytic activity in hydrogenation of benzene

Siliceous, aluminosilicate and niobosilicate mesoporous molecular sieves of MCM-41 type have been used as matrices for nickel incorporated via the wet impregnation. The N 2 adsorption, XRD, H 2-TPR and Ni dispersion study were applied for the characterization of the prepared catalysts. The metal–support interaction (MSI) was the highest in Ni/NbMCM-41 material as indicated from H 2-TPR results, in which the highest dispersion of nickel occurs. Hydrogen chemisorption strength and the reducibility of Ni-species are inversely proportional to MSI strength. Both parameters determine the catalytic activity of the mesoporous materials in the hydrogenation of benzene at higher temperatures (423–473 K), whereas their activity at lower temperatures increases with increasing Ni dispersion. The kinetic study allows the determination of the activation energy in the benzene hydrogenation on Ni/MCM-41 which is very low, 36.5 kJ mol −1.

Preventing self-poisoning in [Pt/Al 2O 3 + SO 42−-ZrO 2] mixed catalysts for isomerization-cracking of heavy alkanes by prereduction of the acid function

The activity and stability of composite catalysts obtained by mixing Pt/Al 2O 3 with SO 4 2−-ZrO 2, were studied in the reaction of hydroisomerization-cracking of n-octane (300 °C, 1.5 MPa, WHSV=4 h −1, H 2/ n-C 8=6) obtaining light isoalkanes (isobutane, isopentane, isohexane), very important components of the pool of reformulated gasoline. Both components of the composites were pretreated in H 2 before mixing. Prereduction eliminated the fraction of SO 4 2− reducible at low temperature, thought to produce SO 2 during reaction, a poison for the metal function. A reduction in the poisoning of the metal, produced by adsorption of S compounds, was tried in order to get a higher metal activity for the production of atomic H, needed for the hydrogenation of coke precursors and the prevention of deactivation. The pretreatment temperature was adjusted between 300 and 500 °C in order to keep a suitable amount of sulfate, needed for a sustainable isomerizing-cracking activity and for the stabilization of the tetragonal crystal phase of ZrO 2, the most catalytically active crystal phase. When compared to non-reduced catalysts, composites reduced at 300–350 °C displayed improved activity and stability for benzene hydrogenation, a metal-catalyzed reaction, and the results were addressed to a decrease in S poisoning. In the pretreated composites the SO 4 2−-ZrO 2 active tetragonal phase was maintained in spite of the loss of S. For isomerization-cracking of n-octane, the pretreated catalysts showed a higher selectivity to isobutane and a fairly longer stability than non-pretreated catalysts, like Pt/SO 4 2−-ZrO 2 and SO 4 2−-ZrO 2 mixed with Pt/Al. TPO tests showed that the catalysts were essentially free of coke. This fact was addressed to a lower coking rate on prereduced sites and to a higher metal activity for hydrogenation of coke precursors.

Study of Residual Oxygen Species over Molybdenum Carbide Prepared During In Situ DRIFTS Experiments

In situ diffuse reflectance infrared Fourier transform spectroscopy was applied to monitor the temperature-programmed carburization of molybdenum trioxide. This technique indicated the existence of surface residual oxygen species on Mo2C synthesized even up to 973 K, indicating incomplete carburization. The presence of residual oxygen species on the carbide was deduced from the IR band at 790 cm-1. It was observed that the Mo2C sample, prepared with a final temperature of 1023 K, presented a higher density of sites titrated by carbon monoxide and a higher activity in benzene hydrogenation than the samples prepared at 923 or 973 K. This higher density of sites and activity were interpreted in terms of improved degrees of carburization at the surface of the carbide. The temperature-programmed desorption of benzene over those three Mo2C samples showed that the higher the activity in benzene hydrogenation, the lower the maximum desorption temperature: the tendency also observed going from Mo to Ru. This desorption temperature evolution could be explained in terms of an increased degree of carburization, which conferred to Mo2C a reactivity toward benzene closer to that of Ru.

Sol-derived Pd/SiO 2 catalyst: characterization and activity in benzene hydrogenation

Pd/SiO 2 catalysts were prepared by adsorption of Pd sols on support Aerosil 200 and characterized by transmission electron microscopy (TEM), CO chemisorption and temperature programmed oxidation (TPO). The Pd hydrosols were generated from PdCl 2 solution and ethanol as reducing agent in the presence of poly(diallyldimethylammonium chloride), PDDA. The pH of the solution was increased to ensure adsorption of the Pd sol with high concentration of PDDA. The catalytic activity was tested in benzene hydrogenation. The presence of organic impurities and the role of morphology affecting the activity have been discussed in terms of the preparation procedure applied.

Sulfur-Tolerant Pt-Supported Catalysts for Benzene Hydrogenation: II. Influence of Cation Exchange Level for Pt/MOR-Based Catalysts

Two reaction pathways are described for the hydrogenation of benzene over Pt/MOR, i.e., (i) on the metal particles and (ii) on Brønsted acid sites of MOR at the boundary to the metal, with atomic hydrogen being dissociated on the metal. The ratio between the two pathways depends on the zeolite acid site concentration and on the available metal surface sites. The deactivation of fully H+ ion exchanged zeolites and the markedly slower intrinsic rate on Na+ ion exchanged samples led to a pronounced maximum in the steady-state activity for benzene hydrogenation with partly H+ exchanged samples. At high pressure and in the presence of thiophene, the benzene hydrogenation activity of Pt/MOR was higher via the pathway involving Brønsted acid sites than via the pathway involving only Pt. Therefore, in the presence of thiophene the type of alkali cation exchanged did not significantly influence activity, whereas Brønsted acid site concentration did. The relative sulfur tolerance of Pt/MOR during benzene hydrogenation was shown to depend on (i) the acid site concentration, which increases both the benzene conversion and the rate of C–C bond breaking leading to coke formation, and (ii) the partial pressure of hydrogen, which increases the concentration of hydrogen atoms available for hydrogenating benzene molecules activated via both pathways.

Effect of different treatments on Aerosil silica-supported Pd nanoparticles produced by ‘controlled colloidal synthesis’

Pd nanoparticles were prepared by ‘controlled colloidal synthesis’ (CCS) using aerosil silica support. On SiO2, 1–2 nm thick ethanol-rich adsorption layer in ethanol–toluene and ethanol–water mixtures was formed into which Pd(II) ions diffused and were reduced there by ethanol. Using Pd(II)-acetate precursor in an ethanol–toluene mixture (sample G1) and PdCl2 precursor in an ethanol–water mixture (sample G2), palladium particles of 7.0 and 8.8 nm size, respectively, were produced. Effects of treatments in air and hydrogen were studied on the Pd/SiO2 samples. The Pd particles showed a twofold/threefold increase in the catalytic activity in benzene hydrogenation after treatment in air at 573 K. The activity increase cannot be explained by a change in the particle size as indicated by transmission electron microscopy (TEM) and CO chemisorption data. Augmentation of turnover number is interpreted by the removal of carbonaceous residues and by the restructuring of the surface caused by carbon removal followed by PdO/Pd transition in the subsequent hydrogen treatment.

Amorphous Ni-B/γ-Al 2O 3 catalyst prepared in a modified drying approach and its excellent activity in benzene hydrogenation

A two-step dying approach was proposed for the preparation of supported amorphous Ni-B/γ-Al 2O 3 catalyst. After wetness impregnation of NiCl 2 aqueous solution, the catalyst precursor was dried at 343 K first, followed by drying at 383 K before KBH 4 reduction (denoted as Ni-B/γ-Al 2O 3 (LT)). For comparison, the precursor was directly dried at 383 K and reduced by KBH 4 (denoted as Ni-B/γ-Al 2O 3 (HT)). Liquid phase hydrogenation of benzene to cyclohexane was employed as the probe reaction. While X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy (XPS) and turnover frequency (TOF) revealed no considerable electronic or structural difference between the active components of these two catalysts, scanning electron micrography (SEM), H 2 chemisorption and XPS intensity analysis demonstrated the higher dispersion of active component in the Ni-B/γ-Al 2O 3 catalyst prepared by the two-step drying approach, which can account for the superior catalytic performance of Ni-B/γ-Al 2O 3 (LT) to Ni-B/γ-Al 2O 3 (HT) in benzene hydrogenation.

The effects of different activated carbon supports and support modifications on the properties of Pt/AC catalysts

Two commercial activated carbons were used as catalyst supports in Pt/AC catalysts. Activated carbons were used in their unoxidized form or after either liquid phase oxidation with HNO 3 or gas phase oxidation with 5% O 2. All six activated carbons were characterized by nitrogen adsorption, TPD, and SEM. Selected samples were tested by XPS. The types and abundance of the oxygen bearing surface groups on each of the activated carbon supports were determined from the deconvolution of the TPD profiles of the activated carbons. An evaluation of the results obtained from TPD and XPS together indicates that both oxidation treatments led to a nearly homogeneous increase of oxygen bearing groups on the outer surface as well as interior surfaces. XPS analysis revealed that the HNO 3 oxidized samples have the highest concentration of oxygen bearing groups on the outermost surface. Pt/AC catalysts (1 wt.%) were prepared on these supports. The catalysts were characterized by TPR, H 2 adsorption, SEM–EDS and tested in structure insensitive benzene hydrogenation as well. The results obtained indicate that the oxidation treatments affect drastically the properties of the activated carbons as well as the catalysts prepared on them. A comparison between benzene hydrogenation activities validates the dispersion values obtained from H 2 adsorption at room temperature.

In Situ XANES Study of Pt/Mordenite during Benzene Hydrogenation in the Presence of Thiophene

The influence of the Na+/H+ ratio on the benzene hydrogenation activity and the sulfur tolerance of Pt supported on mordenite (MOR) was studied by in situ XANES. An increase of the Pt white line was observed with increasing concentrations of thiophene up to 400 ppm, which indicates that an equilibrium exists between the thiophene concentration in the gas phase and the sulfur compounds present on the metal surface. Above a certain concentration of thiophene the Pt white line was constant, indicating a saturation of the metal surface with thiophene. The effect of sulfur poisoning on the metal surface was more effective for Pt supported on H-MOR compared to the more basic Pt/Na-MOR catalysts, which is attributed to the more pronounced decomposition of thiophene and the formation of H2S on Brønsted acid sites. During benzene hydrogenation, a decrease of the Pt white line resulting from the adsorption of benzene and other reaction intermediates on the Pt surface was observed. In the presence of sulfur, the increase of the Pt white line intensity during benzene hydrogenation suggests a higher sulfur coverage of the metal for Pt/H-MOR compared to Pt/NaH-MOR. An optimum concentration of acid sites was found with respect to the benzene hydrogenation rate and sulfur tolerance of the catalysts, which is attributed to the presence of two reaction pathways for benzene hydrogenation, i.e., one which is catalyzed by Pt and another in which acid sites close to Pt particles are the catalitycally active sites.

Partial Hydrogenation of Benzene on Ru-Zn Nanoparticle Catalysts (Short Communication)

A series of ruthenium-zinc catalysts with various Ru/Zn ratios were synthesized. These catalysts were characterized with elemental analysis, nitrogen sorption and transmission electron microscopy (TEM). The results of nitrogen sorption and TEM show that these samples were nano-size. Partial hydrogenation reaction of benzene over these catalysts was carried out in a batch reactor at 625 psig and 425 K. Large amount of water and zinc sulfate were used to have high yield of cyclohexene. The activity of benzene hydrogenation decreased with an increase of the Zn content. However, the selectivity and the yield to cyclohexene significantly increased with an increase of the Zn content. Ruthenium and zinc should be in a close proximity so that the catalytic behavior of ruthenium is altered in a delicate way.

Bimetallic Pt–Sn catalysts supported on activated carbon: I. The effects of support modification and impregnation strategy

A commercial activated carbon (AC) was used as a support either after washing with HCl or after further oxidation with air or HNO 3. The supports were characterized by N 2 adsorption, TPD and SEM. The results indicated the drastic change in physical and surface chemical properties of activated carbons due to the oxidation treatments. Three sets of catalysts were prepared on these supports. In each set, monometallic Pt/AC and bimetallic Pt–Sn/AC catalysts were prepared. Bimetallic catalysts were prepared either by coimpregnation or by sequential impregnation in which the Sn precursor was introduced first. In all catalysts, the Pt loading was kept fixed as 1 wt.%. Two levels of Sn loading, 0.25 and 0.50 wt.%, were applied in bimetallic samples. The catalysts were characterized by H 2 adsorption, TPR, SEM-EDX, XRD, XPS and tested in a structure insensitive reaction (benzene hydrogenation). The results indicated the pronounced changes in catalytic properties depending on the abundance of surface oxide groups of the supports and Pt–Sn interaction. Coimpregnation favored Pt–Sn interaction and alloy formation. The type of alloy formed was affected by the surface chemistry of the activated carbon; oxidized samples favored the formation of Pt 3Sn. XPS results indicated the migration of Pt from surface to interior sites which is driven by decomposition of oxygen bearing anchoring sites during the reduction. The migration was stabilized up to a point by the introduction of Sn as the second metallic phase and, as a consequence, by the Pt–Sn interaction. The interaction between metallic phases and alloy formation led to striking decreases in benzene hydrogenation activity, which indicates the lower amount of active Pt sites available. Very high H 2 adsorption capacities of bimetallic samples compared to their benzene hydrogenation activities point out to the H 2 adsorption capacities of the Pt–Sn alloys formed.

Preparation, Characterization, and Catalytic Activity of Molybdenum Carbide or Nitride Supported on Platinum Clusters Dispersed in EMT Zeolite

Bimetallic Pt–Mo catalysts were prepared by vapor deposition of Mo(CO)6 onto nanometer size platinum particles previously dispersed on EMT zeolite. Subsequent decomposition of the Mo precursor formed a supported molybdenum carbide phase whereas reaction of the precursor with ammonia formed a supported nitride phase. Results from high-resolution transmission electron microscopy and X-ray absorption spectroscopy at the Mo K and Pt LIII edges showed conclusively that highly dispersed particles containing both transition metals were synthesized by the vapor deposition method. Coverage of Pt by Mo suppressed both the total capacity for dihydrogen chemisorption and the catalytic activity for benzene hydrogenation. However, compared to monometallic Mo carbide or nitride clusters supported on EMT zeolite, the bimetallic catalysts were much more active in the catalytic reactions of n-heptane at 623 K. The low thickness of the carbide or nitride phase (about 0.3 nm) allowed for a synergistic influence of the Mo phase on the small areas of exposed Pt and/or a direct activation of the nitride or carbide for catalysis.

Saturation of aromatics and aromatization of C 3 and C 4 hydrocarbons over metal loaded pillared clay catalysts

Saturation of aromatics (benzene, xylene or mesitylene) over Pt (or Pd)/PLC catalysts and commercial Pt (or Pd)/γ-Al 2O 3 was studied. The results show that the benzene hydrogenation activity of Pt (or Pd)/PLC is similar to that of Pt (or Pd)/γ-Al 2O 3. Pt (or Pd)/PLC shows the shape-selectivity in the hydrogenation of xylene and mesitylene because of its regular larger pore structure. The bimetallic Pt–Pd/Al–PLC catalyst has a higher activity for hydrogen saturation and a stronger stability to sulfur poisoning. The study of C 3 and C 4 hydrocarbon aromatization over Zn/Al–PLC and Zn/HZSM-5 shows that the Zn/HZSM-5 has a much higher activity than the Zn/Al–PLC catalyst due to their characteristic difference in acidity. In addition, it is found that C 3 is mainly converted to benzene and C 4 to xylene over Zn/PLC, while both C 3 and C 4 are mostly converted to toluene over Zn/HZSM-5. Among the pillared clays, the Ga–PLC is most effective for aromatization. In order to improve the C 3 and C 4 aromatization property over Zn/Al–CLM, bimetallic catalysts were studied. Combining Ga 3+ and Pt 4+ improves the selectivity of aromatics as well as the total conversion.

Physicochemical and catalytic properties of iron-promoted Raney-nickel catalysts obtained by mechanical alloying

Raney‐type catalysts were prepared by means of a two‐step procedure: (i) mechanical alloying of the metals and (ii) alkaline aluminum leaching. Mechanical alloying is a novel alternative related to the synthesis of skeletal Ni catalysts. Catalysts characterization was performed by atomic absorption, X‐ray diffraction, electron microscopy, and Mossbauer spectroscopies. Textural studies were also carried out. Binary Al–Ni and ternary Al–Ni–Fe alloys were produced by mechanical alloying from pure metallic powders; in particular, the intermetallic α‐(AlNi) phase was formed with a fine microstructure as a non‐equilibrium phase; then, aluminum was selectively removed. After aluminum leaching the α‐(AlNi) phase was transformed into the more stable nickel fcc structure. The effect of iron addition to the Ni–Al catalysts depends on iron concentration and reduction temperature; both parameters determine catalysts composition and activity. This work reports physicochemical properties and benzene hydrogenation activity of these materials, compared with conventional catalysts obtained by melting and leaching.

Catalytic properties of lanthanide amide, imide and nitride formed by thermal degradation of liquid ammonia solutions of Eu and Yb metal

The catalytic properties of lanthanide amide, imide and nitride prepared by the use of liquid ammonia solutions of lanthanide metals (Ln=Eu and Yb) were studied for catalytic hydrogenation. The reaction of Eu or Yb metal solutions in liquid ammonia with silica yielded SiO2-grafted lanthanide amide in the divalent state. The divalent amide showed catalytic activity for the selective hydrogenation of dienes and benzene. It was found that partial hydrogenation of benzene occurred with a very high selectivity for cyclohexene. Amides of calcium, strontium and barium were examined similarly in connection with catalytic studies on divalent amides. Imide and nitride, into which the lanthanide (Ln/AC) deposited by impregnation of active carbon (AC) with liquid ammonia solutions of lanthanide metals were converted thermally, were studied catalytically. It was concluded that imide or imide-like species generated during the thermal degradation of lanthanide amide to nitride were very active in the hydrogenation of ethene. Lanthanide nitride was virtually inactive, but the nitride highly dispersed on active carbon was activated when subjected to evacuation treatment above about 1000K.