Hydrodenitrogenation Of Indole Research Articles

Rational design of titanium-doped Y zeolite for hydrodenitrogenation of aromatic N-heterocyclic compounds

Ti modified Y zeolites with different Ti content were synthesized by in-situ hydrothermal crystallization method and used as the support of hydrodenitrogenation (HDN) catalyst. The forms of Ti species in the zeolites and the effect of Ti incorporation on the active metal states of the corresponding catalysts were investigated by XRD, UV–Vis DRS, XPS, HAADF-STEM, ICP-OES, Py-FTIR, H2-TPR, HRTEM, and DFT calculation. The results show that the incorporation of in-situ Ti species into Y zeolite led to a decrease in the Brønsted acid sites (BAS) /Lewis acid sites (LAS) value of the corresponding catalyst, but effectively enhanced the stacking layer number of the WS2 active phase by weakening the interaction between the active metals and the supports, which is manifested in the improvement of the hydrogenolysis activity and the decrease of the hydrogenation activity of the catalyst. When the hydrogenolysis activity and hydrogenation activity in the catalyst match to a certain extent, that is, the BAS/LAS value and the stacking layer number of the active phase reach an appropriate value, the HDN catalyst exhibited the highest catalytic activity. The NiW/Y-0.1Ti catalyst with suitable amount of BAS and stacking layer number of active phase showed the maximum kHDN values (11.7 × 10-4 mol·g−1·h−1 and 3.9 × 10-4 mol·g−1·h−1) and TOFs (1.91 h−1 and 1.04 h−1) of quinoline and indole HDN.

On Catalytic Behavior of Bulk Mo2C in the Hydrodenitrogenation of Indole over a Wide Range of Conversion Thereof

The catalytic activity of bulk molybdenum carbide (Mo2C) in the hydrodenitrogenation (HDN) of indole was studied. The catalyst was synthesized using a temperature-programmed reaction of the respective oxide precursor (MoO3) with the carburizing gas mixture of 10 vol.\% CH4/H2. The resultant material was characterized using X-ray diffraction, CO chemisorption, and nitrogen adsorption. The catalytic activity was studied in the HDN of indole over a wide range of conversion thereof and in the presence of a low amount of sulfur (50 ppm), which was used to simulate the processing of real petroleum intermediates. The molybdenum carbide has shown high activity under the tested operating conditions. Apparently, the bulk molybdenum carbide turned out to be selective towards the formation of aromatic products such as ethylbenzene, toluene, and benzene. The main products of HDN were ethylbenzene and ethylcyclohexane. After 99% conversion of indole HDN was reached (i.e., lack of N-containing compounds in the products was observed), the hydrogenation of ethylbenzene to ethylcyclohexane took place. Thus, the catalytic behavior of bulk molybdenum carbide for the HDN of indole is completely different compared to previously studied sulfide-based systems.

Ring-opening and hydrodenitrogenation of indole under hydrothermal conditions over Ni, Pt, Ru, and Ni-Ru bimetallic catalysts

The activity and selectivity of activated-carbon-supported Ni, Pt, Ru, and Ni-Ru bimetallic catalysts was examined for hydrothermal denitrogenation of indole. The molar yield of pyrrole ring-opening compounds, without an added hydrogen source, are in the order: Ni < Pt < Ni90Ru10 < Ni75Ru25 < Ni50Ru50 ~ Ni25Ru75 ~ Ru. Ru-containing catalysts facilitated production of hydrocarbons (hydrodenitrogenation (HDN) products) when used with added formic acid (hydrogen source). We elucidated catalytic hydrothermal HDN pathways for indole based on the product distributions and the variation of their yields with time. Hydrogenation of indole to indoline is the primary pathway and ring-opening of indoline to form alkyl anilines is faster than forming HDN products (alkyl benzenes). DFT calculations confirmed experimental activity trends, showing Ru is more active than Ni for indole ring opening and for o-toluidine deamination. If no hydrogen source is present, directly breaking the N-C bond in the pyrrole ring is more favorable than breaking the C-N bond with an aromatic carbon. If a H source is provided, the pyrrole ring hydrogenates first, forming indoline, followed by cleavage of the C-N bond.

Magnetic Fe3O4@SiO2-Pt and Fe3O4@SiO2-Pt@SiO2 Structures for HDN of Indole.

The effect of a second porous SiO2 shell in the activity and selectivity of the Fe3O4@SiO2–Pt catalyst in the hydrodenitrogenation of indole is reported. The double Fe3O4@SiO2–Pt@SiO2 structure was prepared by coating Fe3O4 nanoparticles with tetraethyl orthosilicate (TEOS) with a further impregnation of 1.0 wt.% of Pt on the (3-aminopropyl)triethoxysilane functionalized Fe3O4@SiO2 structures. The second porous SiO2 shell, obtained by using a hexadecyltrimethylammonium bromide (CTAB) template, covered the Fe3O4@SiO2–Pt catalyst with a well-defined and narrow pore-sized distribution. The full characterization by TEM, inductively coupled plasma-optical emission spectroscopy (ICP-OES), XRD, and N2 adsorption isotherm at 77 K and vibrating sample magnetometry (VSM) of the catalysts indicates homogeneous core@shell structures with a controlled nano-size of metallic Pt. A significant effect of the double SiO2 shell in the catalytic performance was demonstrated by both a higher activity to eliminate the nitrogen atom of the indole molecule present in model liquid fuel and the improvement of the catalytic stability reaching four consecutive reaction cycles with only a slight conversion level decrease.

High Yield of Hydrocarbons from Catalytic Hydrodenitrogenation of Indole under Hydrothermal Conditions

We report herein on a new method to achieve a high yield of hydrocarbons from hydrothermal catalytic hydrodenitrogenation (HDN) of indole, which is higher than that from conventional pyrolysis methods. The main hydrocarbon products were aromatic hydrocarbons and alkanes, which are similar to fossil oils to be used as liquid fuels in the future. Catalyst screening experiments show that noble metal catalysts (e.g., 5 wt % Pt, Pd, or Ru) supported on porous solids (e.g., carbon, Al2O3) enhanced the conversion of indole to hydrocarbons under hydrothermal condition. Of those different catalysts, Pd/γ-Al2O3 shows the greatest influence on the yield of hydrocarbons, which we focus on the catalyst Pd/γ-Al2O3 in more details. On the basis of the Pd/γ-Al2O3 catalyst, the effects of time, temperature, and H2 pressure on the hydrocarbons were discussed. HDN of the indole reaction at 450 °C, 0.015 g/cm3 water density, 5 MPa H2, and 50 wt % Pd/γ-Al2O3 loading led to a maximum yield (51 mol %) of hydrocarbons at 120 min...

Indole Hydrodenitrogenation over Alumina and Silica–Alumina-Supported Sulfide Catalysts—Comparison with Quinoline

A detailed kinetic model was proposed to analyze experimental data obtained from indole hydrodenitrogenation (HDN) over γ-Al2O3 and amorphous silica–alumina (ASA)-supported NiMo catalysts. The goal was to investigate the support acidity effects on indole HDN and compare with a recent study on quinoline HDN. Similarly to quinoline HDN, indole HDN occurred via hydrogenation of the aromatic ring, followed by N-ring opening and exocyclic C–N bond breaking. The high support acidity of NiMo(P)/ASA exhibited a promoting effect for N-removal steps and adsorption of nitrogen compounds. However, in contrast to quinoline HDN, it did not clearly induce a positive effect for the hydrogenation step. The acidic function of ASA also favored the formation of byproducts such as toluene, cyclohexane, dimer, and trimer of indole. Catalytic conversion of a quinoline and indole mixture revealed a strong inhibiting effect of quinoline on indole HDN, whereas the inhibiting effect of indole on quinoline HDN was weak. The inhibiti...

Novel Preparation of Titania-Modified CMK-3 Nanostructured Material as Support for Ir Catalyst Applied in Hydrodenitrogenation of Indole

Iridium catalyst was prepared using a novel titanium oxide-CMK-3 support synthesized as a replica of Ti-SBA-15. The catalyst was applied in the hydrodenitrogenation of indole. The activity was compared with an iridium catalyst supported over a grafted titanium-CMK-3. Structural and textural characterization of the catalysts was performed by means of N2 adsorption, XRD, UV–Vis–DRS, Raman spectroscopy, XPS, TEM and H2 Chemisorption. Ir-Ti-CMK-3 was the most active catalyst for the hydrodenitrogenation reaction at mild conditions. Titanium oxide contained in carbon ordered mesoporous CMK-3 promotes a very good anchorage of iridium metallic clusters in the carbon framework reaching high active site distribution and more stable nanoclusters.

HDN of indole over Ir-modified Ti-SBA-15

The hydrodenitrogenation of indole has been studied over a series of Ti-modified SBA-15 supports and their respective Ir-catalysts. Ti-SBA-15 was synthesized using sol-gel method and Ti was added during the synthesis using Tetraethyl Orthotitanate. Iridium was added by wetness impregnation. The acidity of Ti-SBA-15 was modified adding F or Al in order to improve the catalytic activity. The catalysts prepared were extensively characterized by X-ray diffraction (XRD), N2 adsorption isotherms, UV–vis-DRS, Raman spectroscopy, 27Al-MAS-NMR spectroscopy, XPS, TEM-EDS, Py-FTIR, H2-Chemisorption and TPR. UV–vis-DRS and Raman spectroscopy confirmed that Ti was incorporated in tetrahedral coordination in the framework of the SBA-15. The analysis showed that the mesoporous structure was maintained after F or Al incorporation. 27Al-MAS-NMR spectroscopy indicated that aluminum was incorporated mainly in Td positions. The results showed that Ti incorporation helps to reduce significantly the size of iridium crystallites and improves its dispersion considerably. Ir/Ti-SBA-15 modified with Al, with Bronsted acidity, was the most active catalyst for indole HDN, in mild conditions in a Batch reactor. The experimental data for indole hydrodenitrogenation was quantitatively represented by a Langmuir–Hinshelwood type rate equation.

Mutual influences of hydrodesulfurization of dibenzothiophene and hydrodenitrogenation of indole over NiMoS/y-Al 2O 3 catalyst

The influence of indole on the hydrodesulfurization (HDS) of dibenzothiophene (DBT) and the influence of DBT on the hydrodenitrogenation (HDN) of indole were investigated over a presulfided NiMoS/γ-Al 2O 3 catalyst in a fixed-bed high-pressure microreactor. A significant negative effect of indole on the HDS of DBT was observed. The inhibitory effect of indole on the hydrogenation route (HYD) was stronger than on the direct desulfurization route (DDS). Indole and its HDN intermediate products suppressed HDS of DBT through the competitive adsorption on active sites of the catalyst. DBT and H 2S produced in situ promoted the conversion of coordinatively unsaturated sites (CUS) to Brønsted acid sites on the catalyst surface, which in turn facilitated the cleavage of C( sp 3)—N bond in indoline; the conversion of indole and the relative concentration of o-ethylanline (OEA) then increased. Although the presence of sulfur atoms is essential for the formation of active sites on the catalyst for HDN, a small amount of sulfur species is sufficient to maintain the HDN active sites; higher content of sulfides may bring on a negative influence on the HDN of indole.

Hydrodenitrogenation of indole over Mo 2C catalyst: Insights into mechanistic events through DFT modeling

The molecular reaction mechanism of hydrodenitrogenation of indole was studied using density-functional theory calculations of the adsorbed o-ethylaniline surrounded by mobile hydrogen atoms. It was found that the hydrogenation of o-ethylaniline occurs through two steps: consisting in redistribution of the π electron density to form multiple partial Mo C(ring) bonds with the surface upon adsorption, and a subsequent hydrogen attack directed on the aromatic ring or the amine group. The direction of the hydrogen attack and the associated energy barriers determine the rate constants of the early (DDN, direct denitrogenation) and late (HYD, hydrogenation) nitrogen removal steps, and thus rules the selectivity of indole hydrodenitrogenation to ethylcyclohexane or ethylbenzene.

Comparative kinetic study of the hydrodenitrogenation of indole over activated carbon black composites (CBC) supported molybdenum carbides

A carbon black composite (CBC) support was synthesized and activated with HNO 3 for three time periods 0.5, 2, 3 h. These samples were impregnated by ammonium heptamolybdate and carburized to prepare the molybdenum carbide active phase. Characterization of the samples by X-ray diffraction, temperature programmed reaction, CO chemisorption and surface area measurements showed that the HNO 3 treatment of the carbon increased the dispersion of the active phase. This was clearly evidenced by transmission electron microscopy which showed a corresponding decrease in Mo 2C particle size. The kinetic study of the hydrodenitrogenation of indole demonstrated that the catalyst activity was dependent on the active phase dispersion and the global kinetic order were found to vary between zero and one, depending on the dispersion of the active phase on carbon support.

Effect of support activation on the kinetics of indole hydrodenitrogenation over mesoporous carbon black composites-supported molybdenum carbide

The catalytic activity of supported molybdenum carbide was examined versus activation of the carbon support. A mesoporous carbon black composite (CBC) support was used and activated with either HNO 3 or H 2O 2 for 0.5 h. After impregnation and carburisation, the β-Mo 2C hexagonal compact crystallographic phase was obtained as the unique active phase. Several techniques (porosity measurements, X-ray diffraction (XRD), elemental analysis) were used in order to characterise the catalyst's physical properties. The temperature-programmed reduction (TPR) analysis and CO titration performed on these samples underlined an effect of oxidative treatment with H 2O 2 and HNO 3 on the active phase dispersion. The kinetic study of the hydrodenitrogenation (HDN) of indole on these carbon materials-supported molybdenum carbide was improved when the support was activated.

Investigation of the Reaction Network of Benzofuran Hydrodeoxygenation over Sulfided and Reduced Ni–Mo/Al2O3 Catalysts

The hydrodeoxygenation (HDO) network of benzofuran was investigated over alumina-supported Ni–Mo sulfided and reduced catalysts. The effect of reaction temperature, pressure, hydrogen sulfide feed concentration, and pretreatment procedure on the product distribution, hydrogenolysis, and hydrogenation activity of each catalyst was studied. The differences and similarities between the observed benzofuran HDO network and the networks proposed in the literature were examined. Parallels between HDO and hydrodenitrogenation (HDN) were investigated by comparing the benzofuran HDO findings with previous results obtained for indole HDN. Reaction studies were carried out in a fixed-bed vapor-phase reactor using a wide range of feed concentrations at 120–360°C and 300–800 psig. Over the sulfided catalyst, one major route is observed for the benzofuran HDO network; it starts with the hydrogenation of benzofuran to 2,3-dihydrobenzofuran followed by its hydrgenolysis to 2-ethylphenol. Over the reduced catalyst, however, an additional route is observed that begins with the hydrogenation of 2,3-dihydrobenzofuran. This route contains several other oxygen-containing intermediate species that are not observed over the sulfided catalyst, and hydrocarbon products are formed by this route at significantly lower temperatures. The product distribution for both catalysts is found to be a strong function of temperature and H2S feed concentration where the hydrogenolysis reactions were promoted and the hydrogenation reactions were inhibited by H2S in the feedstream.

Kinetics of the Hydrodenitrogenation of Indole

The hydrodenitrogenation (HDN) reactivity of indole (IND) was determined over a NiMo/Al2O3 catalyst and a CoMo/Al2O3 catalyst using a fixed-bed reactor at 631 K and 3.5 MPa pressure. Conversions and product distribution data were obtained at various feed compositions of indole and space times. The kinetics of the individual steps in the HDN pathways were determined by application of Langmuir−Hinshelwood kinetics to a reaction model proposed by Zhang and Ozkan. All reaction paths were inhibited by indole and three different active sites were required to correlate the data. Under comparable conditions, the CoMo catalyst was more active for the initial conversion of indole, but the NiMo catalyst gave higher HDN conversion. The former catalyst gave higher yields of N-containing intermediates than the latter. An increase in hydrogen sulfide concentration had little effect on the total conversion and decreased the HDN conversion for the NiMo catalyst, whereas total conversion increased while HDN conversion was ...

Reaction network of indole hydrodenitrogenation over NiMoS/γ-Al 2O 3 catalysts

The reaction network of indole hydrodenitrogenation (HDN) was investigated over γ-Al 2O 3 supported NiMo sulfide catalysts in an effort to acquire a fundamental understanding of the different reaction pathways in the mechanism. Experiments were performed primarily at 1000 psig, using a wide range of temperatures and feed concentrations. The effect of H 2S on different reaction steps of the network was also investigated. Two major pathways were proposed to account for the formation of ethylcyclohexane (ECH) and ethylbenzene (EB) which are the two main HDN products from indole. One route occurs from the hydrogenolysis of indoline to o-ethylaniline (OEA) and the other from the hydrogenation of indoline to octahydro-indole. Also included in the proposed mechanism is a secondary route from o-ethylcyclohexylamine (OECHA) to ethylcyclohexene (ECHE), that occurs through a nucleophilic substitution reaction. The product distribution was a strong function of temperature and H 2S concentration. H 2S enhanced the hydrogenolysis reactions but inhibited the hydrogenation reactions.

Catalytic hydrodenitrogenation of indole over molybdenum nitride and carbides with different structures

The hydrodenitrogenation (HDN) of indole has been studied over Mo 2N and Mo 2C with different structures. The difference in activity was modest and the structure of the catalysts exerted a more significant effect than the chemical composition. More evident difference was observed in selectivity, and here the composition was the most important factor. Sonochemically prepared Mo 2C was an active catalyst for HDN reaction. It formed plate-like aggregates of loosely packed Mo 2C (fcc) particles. The crystallinity of sonochemically prepared Mo 2C was improved during the reaction, and its behavior in HDN became similar to Mo 2C (fcc) prepared by the TPR method.

Bifunctional Behavior of Bulk MoOxNyand Nitrided Supported NiMo Catalyst in Hydrodenitrogenation of Indole

Oxynitrides of early transition metals are bifunctional catalysts (metallic and acidic sites) active in hydrodenitrogenation (HDN). The HDN of indole was used as a molecular probe reaction to study the metallic and acidic properties of the dual sites on oxynitrides. The behavior of those sites was found to be different from that of supported and sulfided NiMo. The reaction was conducted at low partial pressure of H2S over both a bulk MoOxNyand a supported NiMo catalyst, nitrided before the reaction. Under high hydrogen pressure, HDN of indole was shown to occur with or without prior hydrogenation of the aromatic ring of orthoethylaniline, leading to either ethylbenzene or ethylcyclohexane. Secondary reactions, such as the joining of heterocyclic rings (leading to 1-4 tetrahydroquinoline) and dimerization, were found to occur as a result of the presence of acidic sites. Hydrogenolysis of the lateral chain of orthoethylaniline was also observed.

Polymer formation during the HDN of indole

During kinetic studies of the hydrodenitrogenation (HDN) of indole (IND) over a NiMo/P–Al2O3 catalyst, it was found that material balances (representing loss of indole) were often low and varied depending on reaction conditions. Tests of IND with an alumina support, in which no reaction to HDN products occurred, also gave low material balances, which appeared to reach a line out value with space time. UV spectra of a liquid sample from this run showed evidence of species different than IND, which is attributed to a polymer. The low material balances were due to the failure of the GC analysis to detect the polymer in the product sample and possible loss of polymer by condensation in the lines leading to the sample collector. Material balances with the catalyst were related to conversion of IND to HDN reaction products. Low material balances were only obtained with IND, not with reaction products alone. It was concluded that the loss of IND is due to formation of a polymer. At low space time (low IND conversion), the polymer is rapidly formed in competition with conversion of IND to HDN products, while at high space time (high IND conversion), the polymer decreases due to back reaction to IND, followed by conversion to HDN products. The consequence of polymer formation, when it occurs, is that it represents a parallel reaction path to conversion of indole and needs to be accounted for in any kinetic analysis of the HDN of indole.

HDS, HDN and HYD activities and temperature‐programmed reduction of unsupported transition metal sulfides

Several transition metal sulfides have been shown to exhibit high catalytic activities in various hydrotreating reactions. The simultaneous catalytic activities for hydrodesulfurization of dibenzothiophene, hydrodenitrogenation of indole and hydrogenation of naphthalene have been studied using high surface area bulk sulfides: NbS2, MoS2, ReS2, RuS2 and Co9S8. The metal–sulfur bond strengths have been assessed by temperature‐programmed reduction of H2S‐pretreated sulfides, and it is demonstrated that this pretreatment is necessary to obtain reliable TPR data for the sulfides. The catalytic HDS activity is shown to follow the trend in the metal–sulfur bond strengths estimated by this improved method. Furthermore, the metal–sulfur bond strengths determined this way follow the trend estimated previously from theory. The TPR data suggest that a large number of sulfur vacancies exist in active catalysts under industrial reaction conditions. Such vacancies have recently been observed on model catalysts by use of STM.

Molybdenum Nitride and Carbide Prepared from Heteropolyacid: II. Hydrodenitrogenation of Indole

Hydrodenitrogenation (HDN) of indole has been studied over Mo2N prepared from MoO3, 12-molybdophosphoric acid (HPA) and MoO3+P2O5(a physical mixture of P2O5and MoO3with stoichiometry of P to Mo equal to that of HPA). It has been observed that Mo2N is an active catalyst for HDN of indole. It gave comparable activity (per unit mass) to that of Mo–Ni/γ-Al2O3but less hydrogen consumption. The initial activity of indole HDN was significantly increased by adding phosphorus in the catalysts despite its unfavorable pore and site blocking effects. However, P-containing Mo2N lost activity more readily than Mo2N itself. The deactivation did not result from carbon but probably was caused by nitrogen deposits from indole and loss of surface area. The bulk structure and morphology of the Mo2N catalysts were not changed after HND of indole. The reaction pathway did not appear to be altered by adding phosphorus.