Hydrogenation Of Naphthalene Research Articles

Effect of phosphorus modification on the catalytic properties of NiW/γ-Al2O3 in the hydrogenation of aromatics from coal tar

Modified with different contents of phosphorus, the NiW/γ-Al2O3 catalysts prepared using the impregnation method were used to catalyze the hydrogenation reaction of naphthalene and the aromatics compounds separated from low temperature coal tar in a fixed-bed reactor. The properties of the catalysts were characterized by N2 adsorption, XRD, H2-TPR, XPS and NH3-TPD. The products were analyzed by GC-MS and GC×GC-TOFMS. Results showed that the addition of P can enhance the distribution of Ni and W compounds on the surface of supports and expand the pore diameter. Adding 1.0%–1.5% P could generate more Ni-W-O phase and increase the proportion of the weak acid. The results of naphthalene hydrogenation indicated that the highest conversion rate of nearly 80% and the decalin yield of over 50% were achieved when using the NiW+1.0%P catalyst. For the tests using the catalyst with 1.0%P to catalyze the hydrogenation of enriched aromatics compounds from coal tar, the results indicated that the effect of transforming aromatics into cycloalkanes and the removal of heteroatoms were remarkable in the presence of the catalyst.

Investigation of co-effect of 12-tungstophosphoric heteropolyacid, nickel citrate and carbon-coated alumina in preparation of NiW catalysts for HDS, HYD and HDN reactions

Effects of activated carbon in a carbon-coated alumina (CCA) support, active phase morphology and its composition of Ni6-PW12S/Cx/Al2O3 catalysts in hydrotreating of model compounds were studied. The catalysts were synthesized using 12-tungstophosphoric heteropolyacid, nickel citrate and CCA and characterized with multiple methods: N2 physisorption, X-ray powder diffraction, H2 temperature programmed reduction, temperature-programmed desorption of ammonia, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. The catalytic properties were determined using a fixed-bed microreactor in hydrotreating of dibenzothiophene, naphthalene and quinoline. It was found that with the increase of carbon content in the CCA up to 5wt.%, reducible reactivity, sulphidation degree, average length and stacking number of WS2 crystallites in the catalysts increased. Observed changes can be explained by weakening interaction between metal oxide species and carbon-coated support. Full promotion of the NiWS edges by nickel was achieved in the catalysts supported on the CCA with carbon content equal 0.3wt.% and more. Activities of the catalysts in dibenzothiophene hydrodesulphurization, naphthalene hydrogenation and quinoline hydrodenitrogenation were essentially depended on the carbon content in the CCA-support. Ni6-PW12S/C1/Al2O3 catalyst showed maximal conversions of the substrates in studied reactions. This result was achieved due to an optimal balance between turnover frequency value of the active sites and their content.

Design of mesoporous KA zeolite supported sulfur-tolerant noble metal catalyst for naphthalene hydrogenation

As the demand for the high-quality transportation fuels grow rapidly, deep hydrogenation of diesel for aromatics reduction plays an important role in petroleum refinery. In this paper, a sulfur-tolerant noble metal hydrogenation catalyst, Pt/mesoporous KA zeolite (Pt/MKAZ), was developed based on the shape selective and hydrogen spillover concepts. Different kinds of catalysts were prepared by carefully adjusting the contents of Pt in the cages of MKAZ and its additional mesopore channels, and their performances were tested in naphthalene hydrogenation with either 3 mol% of H2S in hydrogen or 3000 ppm of dibenzothiophene (DBT) in naphthalene feedstock. The results indicated that the distributions of Pt in both cages and mesopore channels of MKAZ could be controlled well and the resultant catalyst with an optimized nanostructure showed an excellent sulfur resistance in naphthalene hydrogenation due to a synergetic effect of Pt confined in the cages and mesopore channels. (C) 2015 Elsevier Ltd. All rights reserved.

Nickel–Aluminum Intermetallic Compounds as Highly Selective and Stable Catalysts for the Hydrogenation of Naphthalene to Tetralin

AbstractSelective hydrogenation of naphthalene to tetralin was conducted by using Ni–Al intermetallic compounds (IMCs) prepared by a chemical synthetic route. Ni–Al IMC catalysts achieved a lasting high conversion with 100 % selectivity up to 125 h. During the synthesis process, the Ni–Al IMCs underwent the following phase transformation as a function of the content of the Al source (LiAlH4): Ni(cubic)→Ni3Al(tetragonal)→NiAl(cubic)→Ni2Al3(hexagonal). In the selective hydrogenation of naphthalene, the catalytic activity of NiAl was much higher than that of metallic Ni and other Ni–Al IMCs (Ni3Al and Ni2Al3). The results can be understood by a combination of site isolation and alteration of the electronic structure by chemical bonding. Ni atoms are scattered and spatially isolated by Al atoms, which in turn resists carbon deposition. The findings provide a useful approach to tailor the catalytic properties of transition metals by formation of IMCs, which could be applicable in heterogeneous catalysis.

Nickel-tungsten sulfide polyaromatic hydrocarbon hydrogenation nanocatalysts prepared in an ionic liquid

Nickel-tungsten sulfide nanocatalysts for the hydrogenation of aromatic hydrocarbons (HCs) have been prepared by the in situ decomposition of nickel thiotungstate precursors in an ionic liquid (IL) using the [BMPip]2Ni(WS4)2 nickel thiotungstate complex as a precursor and the thermally stable IL 1-butyl-1-methylpiperidinium trifluoromethanesulfonate BMPipCF3SO3 as a solvent for the precursor. The Ni-W-S particles in situ synthesized in the IL have been characterized by X-ray photoelectron spectroscopy and TEM. It has been shown that the particles are 0.5-nm-wide nanoplates associated in agglomerates with a diameter of 100–150 nm. Catalytic activity has been studied using the example of naphthalene hydrogenation in various solvents in a batch reactor at a temperature of 350°C and a pressure of 5.0 MPa. It has been shown that the IL can be used for the selective hydrogenation of aromatic HCs in a mixture with olefins.

Selective hydroconversion of naphthalenes into light alkyl-aromatic hydrocarbons

2-Ring aromatics such as naphthalene and alkyl-naphthalenes constitute a high fraction in the diesel boiling point range by-products from oil refining and petrochemical plants. A two-step catalytic process, consisting of a selective hydrogenation of naphthalenes to tetralins and a subsequent hydrocracking of tetralins into light alkyl-aromatic hydrocarbons rich in BTX (benzene, toluene, xylenes), was postulated and studied in a fixed bed down-flow reactor under a moderate pressure of 3–4MPa. For the selective hydrogenation of naphthalenes to tetralins, it was found that the catalytic performances of Mo2C-supported catalysts were superior in terms of tetralins yield as well as selectivity to the conventional metal-supported catalysts such as Pt, Co, Ni and NiW supported catalysts. The hydrocracking of tetralin was demonstrated to produce light alkyl-aromatic hydrocarbons rich in BTX over a monofunctional H-Beta and a bifunctional Ni/H-Beta catalyst. For the high per pass yield of BTX in the hydrocracking of tetralin in which chemical equilibrium limits its conversion and product selectivity, the bifunctional Ni/H-Beta catalyst was found to be highly promising compared with the monofunctional H-Beta catalyst. The bifunctional Ni/H-Beta showed the BTX selectivity in liquid product and the total BTX yield as high as 69.5% and 40.7wt%, respectively, at the tetralin conversion of 99.5% at 450°C under 4MPa. The catalytic behavior of Ni/H-Beta suggests that BTX yield can be much improved by properly controlling the hydrogenation power of metallic sites (i.e., suppressing the hydrogenation activity), the acidity of H-Beta and their balance on the bifunctional hydrocracking catalysts.

MoCx species embedded in ordered mesoporous silica framework with hierarchical structure for hydrogenation of naphthalene

An integrated route to accomplish the incorporation of MoCx species into ordered mesoporous silica framework (OMSF) was presented. The MoVI–melamine hybrids were used as the single-source precursors for molybdenum carbides and participated in the assembling process of the silica building blocks that gave rise to the OMSF preform. The pore diameter and the volume of the resulting MoCx@OMSF samples were characterized by gradually increasing with the amount of the added hybrids, which, among other things, maximized the space inside the silica tubes at the highest Mo loading. The thermal decomposition of the P123 micelles with the catalysis of the in situ formed Mo species generated the tube-like carbon framework within the silica tubes. The finely incorporation of the MoCx species to the carbon framework was supposed to account for the good stability of the carbide phase in the hydrogenation of naphthalene. Ultra-high selectivity of ∼98% to tetralin was achieved on the MoCx@OMSF samples thanks to the moderate hydrogenating ability of the carbide phase, indicating potential use of molybdenum carbide based composites as low-cost selective catalysts for industrially relevant partial hydrogenations.

The Hydrogenation of Aromatic Compounds under Mild Conditions by Using a Solid Lewis Acid and Supported Palladium Catalyst

AbstractAl2O3 or SiO2 particles with abundant surface hydroxyl groups can prevent side reactions of aromatic compounds with AlCl3 completely; this Lewis acid can potentially destroy the stable structure of aromatic compounds to a large extent. This discovery was successfully utilized in the highly efficient hydrogenation of benzene, toluene, and naphthalene under mild conditions co‐catalyzed by AlCl3 and Pd/Al2O3 or Pd/SiO2. Pd, AlCl3, and the surface hydroxyl groups on the support show excellent cooperative effects for the hydrogenation reactions. Theoretical studies indicate that formation of a complex, by an interaction between benzene, AlCl3, and the solid oxides, plays a key role in the highly efficient hydrogenation reactions.

Simultaneous naphthalene and thiophene hydrogenation over Ni(X)–Pt/HMOR catalysts

A series of Ni(X)–Pt/HMOR catalysts (X=0, 0.5, 1.0, 1.5 and 2.0wt% of Ni and a fixed quantity of Pt=1wt%) were prepared and tested in the hydrogenation (HYD) of naphthalene with and without thiophene and also in the hydroconversion of thiophene. The catalysts were characterized using N2 physisorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and TEM-EDS elemental analysis. The TPR and TEM results indicate that Pt is mainly located inside the pore system of the mordenite, whereas Ni is located on both the external surface and inside the pore system of the mordenite zeolite. Naphthalene hydrogenation exhibited a high conversion for all the catalysts. In the presence of a sulfur compound and for naphthalene hydrogenation, all the tested catalysts present a fast deactivation. Ni/HMOR catalyst was less active and presents complete deactivation. However, the Ni(0.5)–Pt/HMOR and Pt/HMOR catalysts are able to convert thiophene and produce mainly tetrahydrothiophene. This hydrogenation activity was stable, at least for 12h, showing that the catalytic system can preserve some of the hydrogenating capability. The values of thiophene hydroconversion and the selectivity to tetrahydrothiophene are much higher than the reported for similar systems. The hydrogenation activity is most likely due to the hydrogen spillover.

Promotion of Ni/MCM-41 Catalyst for Hydrogenation of Naphthalene by co-Impregnation with Polyols

The activities of nickel supported on MCM-41 catalysts, prepared by co-impregnation with polyols (ethylene glycol, glycerol, xylitol, sorbitol and glucose), were investigated by hydro- genation of naphthalene. Compared with the conventional wetness impregnation, addition of moderate polyols into the metal nitrate aqueous solution could enhance interaction with support surface, resulting in formation of very small NiO particle size (<5 nm), high dispersion of the active phase and significant catalytic activity. Particle size of Ni0 decreased from 36.1 nm to below 5 nm; meanwhile the complete hydrogenation of naphthalene was dependent on the Ni0 particle size. The hydrogenation activities of the catalysts prepared by co-impregnation with polyols were very high with 100% conversion even at low temperature of 55 °C.

Low temperature hydrogenation of aromatics over Pt–Pd/SiO2–Al2O3 catalyst

Bimetallic Pt–Pd catalysts supported on amorphous silica–alumina (ASA), having different amounts of SiO2 (1.5, 5, 20, 40, and 70%), are prepared by conventional impregnation method. The prepared catalysts are characterized using nitrogen adsorption–desorption isotherms at 77K and X-ray diffraction (XRD) technique, respectively. Temperature Programmed Desorption (TPD) of ammonia and CO chemisorption experiments are used to study the role of support composition on catalyst acidity and surface active noble metal content, respectively. The effect of noble metal loading and support properties on hydrogenation reaction is investigated via toluene hydrogenation reaction under varying operating conditions (temperature=383–523K, pressure=20bar, weight hourly space velocity (WHSV)=1–12h−1). Based on the obtained results, Pt (0.18wt.%)–Pd (0.18wt.%) loaded ASA catalyst with 40wt.% silica showed excellent toluene hydrogenation activity. Such trend is further reinforced from naphthalene hydrogenation studies wherein complete conversion with about 90% selectivity for decalin is noticed at 453K. Accordingly, possible advantage w.r.t. minimal noble metal loading to employ Pt (0.18wt.%)–Pd (0.18wt.%)/ASA (40% silica) catalyst for hydrogenation aromatics in transportation fuels, and producing specialty solvents such as DAK (De-aromatized Kerosene) has been envisaged.

Chemical loop systems for biochar liquefaction: hydrogenation of Naphthalene

Liquefaction of biochar from liquid-phase pyrolysis was carried out in the solvent Tetralin. Tetralin is able to act as hydrogen donor during liquefaction of biochar and is itself rearranged into Naphthalene. Naphthalene must be re-hydrogenated to Tetralin to allow for further use in the liquefaction reaction (chemical loop system). Therefore Naphthalene hydrogenation was investigated, applying a full factorial design of experiments approach. The yield of Tetralin was chosen as response variable, while two-level-factors for temperature (150 °C and 200 °C), pressure (20 bar and 50 bar) and Raney-Nickel catalyst load (5 wt% and 10 wt%) were selected. The Design of Experiments approach showed a rising influence of all three factors in the order: temperature < pressure < catalyst load. The reaction kinetics of the hydrogenation of Naphthalene to Tetralin and Decalin was then investigated at 150 °C and 200 °C. The reaction proceeds stepwise and not in consecutive steps. In a first step Naphthalene reacts selectively with 96% yield to Tetralin, while the reaction of Tetralin to Decalin does not start until all Naphthalene is consumed. The rate-constant of the reaction of Naphthalene to Tetralin is one magnitude higher than that for the reaction of Naphthalene to Decalin. This is in agreement with the findings from the design of experiments approach. The results of these investigations indicate that the chemical-loop system Naphthalene–Tetralin is suitable for usage in the liquefaction of biochar.

Highly dispersed Ni/SBA-15 catalysts prepared with different nickel salts as nickel precursors: Effects of activation atmospheres

With nickel nitrate and nickel acetate as nickel precursors, a series of Ni/SBA-15 catalysts were prepared by using the impregnation method and activating in air or hydrogen atmosphere. The Ni/SBA-15 catalysts were characterized with XRD, H2-TPD, N2 physisorption and online mass spectroscopy. Their catalytic properties were evaluated with hydrogenation of naphthalene as a model reaction. It was shown that activation in hydrogen greatly increased the Ni dispersion and catalytic activity of Ni/SBA-15 prepared with nickel nitrate, while activation in air significantly improved the sample prepared with nickel acetate. In terms of the thermal decomposition products of the catalyst precursors activated in different atmospheres, the affecting mechanism of the activation atmosphere on the Ni/SBA-15 catalysts prepared with different nickel precursors was proposed.

Promotion of Ni/clay catalytic activity for hydrogenation of naphthalene by organic modification of clay

A Ni/montmorillonite (MMT) catalyst was prepared by an impregnation method using cetyltrimethylammonium bromide (CTAB)-pillared MMT as the supporting matrix and was characterized using infrared spectroscopy, X-ray diffraction, H 2 temperature-programmed desorption, N 2 adsorption-desorption, and ultraviolet diffuse reflectance spectroscopy. The catalytic activity of the Ni/MMT for the hydrogenation of naphthalene was also evaluated. The results show that the organic modification of MMT greatly improved the Ni dispersion and textural properties of the Ni/MMT catalyst. The as-prepared Ni/MMT catalyst showed high naphthalene conversion (88.2%) in the hydrogenation reaction; this is much higher than those achieved using Ni supported on pristine MMT (13.1%), Al 2 O 3 -pillared MMT (24.2%), and SBA-15 (68.2%). As a result of thermal decomposition of CTAB pillars during reduction of the Ni/MMT catalyst, the CTAB pillars mainly play a role in the Ni/MMT catalyst during impregnation. A mechanism for the promotion of the Ni/MMT catalytic activity by organic modification during impregnation is proposed. The catalytic activity of Ni/MMT is greatly promoted by using CTAB-pillared MMT as a support. The CTAB pillars enlarge the basal spacing of MMT, and occlude and complex with the introduced Ni 2+ ions during impregnation.

Study on reaction characteristics of phenolic hydroxyl in coal by using the model compound during direct coal liquefaction

The reaction characteristics of phenolic hydroxyl group were studied under the conditions of direct coal liquefaction. 2-naphthol was used as a coal model compound in this study. Under the conditions of with and without catalysts, a series of experiments were conducted at different temperatures, pressures and reaction time. Gas chromatography-mass spectrometry and gas chromatography were used to identify and quantify the reactants and products respectively. The conversion of 2-naphthol rises with the increase of reaction temperature, initial pressure and catalyst amount. The results indicated that temperature had a significant effect on 2-naphthol conversion, which promoted the dehydroxylation reaction. However, initial pressure had an important influence on the hydrogenation of 2-naphthol and naphthalene. The iron catalyst plays a significant role of cracking instead of hydrogenation. It is concluded that the harsh reaction conditions of high temperature, high pressure, and more catalyst are conducive to promoting dehydroxylation of 2-naphthol. The reaction mechanism was put forward based the experimental results, in which 2-tetralone was an intermediate.

Oil-soluble Ni-Mo sulfide nanoparticles and their hydrogenation catalytic properties

Oil-soluble bimetallic Ni-Mo sulfide nanoparticles (NiMoS) with narrow size distribution were successfully synthesized through a composite-surfactants-assisted-solvothermal process. The surface functionality and lipophilicity of the Ni-Mo sulfides were shown by transmission electronic microscopy, Fourier transform infrared and ultraviolet spectroscopy. The as-prepared Ni-Mo sulfides supported on activated carbon (NiMoS/AC) exhibited enhanced catalytic activity towards naphthalene hydrogenation instead of cracking. For comparison, CoMoS/AC and MoS2/AC catalysts were also prepared through similar procedures, and it was found that their catalytic performance decreased in the order of NiMoS/AC>CoMoS/AC>MoS2/AC. Furthermore, the activity of the bimetallic NiMoS nanocatalyst can be effectively tuned via variation of the atomic ratio of Ni/(Ni+Mo).

Effect of activation atmosphere on the reduction behaviors, dispersion and activities of nickel catalysts for the hydrogenation of naphthalene

The influence of the activation atmosphere (air and hydrogen) on the properties of Ni/SBA-15 and Ni/γ-Al2O3 catalysts was investigated. The results show that calcination in H2 atmosphere has a great promotion on the dispersion of Ni/SBA-15 but little influence on the reduction behaviors of nickel species. On the contrary, calcination in H2 atmosphere has little influence on the dispersion of Ni/γ-Al2O3 catalyst but a great promotion on the reduction behaviors of nickel species. Therefore, the activities of Ni/SBA-15 and Ni/γ-Al2O3 catalysts for hydrogenation of naphthalene are promoted by calcination in H2 atmosphere, but the promotion effects on Ni/SBA-15 and Ni/γ-Al2O3 catalysts are difference. The promotion on Ni/γ-Al2O3 catalyst is due to the enhancement of its reduction degree, which is enhanced from 39.9 % by calcination in air to 96.5 % by calcination in H2. The promotion on Ni/SBA-15 catalyst is attributed to the improvement of its dispersion, which is improved from 11.9 % by calcination in air to 27.4 % by calcination in H2. As a result, the activity is improved about 260 % for Ni/γ-Al2O3 catalyst but only 100 % for Ni/SBA-15.

A simple method to prepare highly active and dispersed Ni/MCM-41 catalysts by co-impregnation

A simple method for preparing highly active and dispersed supported metal catalysts was developed by co-impregnation. Compared with conventional wetness impregnation, addition of moderate ethylene glycol into the metal nitrate aqueous solution could enhance interaction with MCM-41 surface, resulting in formation of very small NiO particle size (3.5nm) and high dispersion of the active phase. The Ni/MCM-41 catalysts using co-impregnation exhibited excellent catalytic performance for low temperature hydrogenation of naphthalene with 100% conversion at 55°C, which could rival the activity of commercial Raney Ni catalyst. The obtained catalysts were characterized by XRD, TEM, TG-DSC, FT-IR, BET and TPR.

The catalytic properties of transition metal sulfides synthesized from Anderson-type heteropoly compounds in hydrogenation, hydrodesulfurization, and hydrodenitrogenation reactions

XMo6HPC/Al2O3 catalysts based on Anderson-type heteropoly compounds (HPCs) with heteroatoms X = Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, and Al were synthesized. The catalytic properties of the prepared samples were studied in naphthalene hydrogenation, dibenzothiophene hydrodesulfurization, and quinoline hydrodenitrogenation. The highest activity was exhibited by the catalysts with X = Co and Ni; the lowest, with X = Cu. It was found that dibenzothiophene hydrodesulfurization and naphthalene hydrogenation occur on different active sites, whereas the sites of the hydrogenation of naphthalene and dibenzothiophene have a similar nature. Quinoline (at a nitrogen content of 100 ppm) had a different effect on the catalytic properties: it inhibited the hydrogenation of dibenzothiophene and naphthalene, but promoted the desulfurization of dibenzothiophene.

Using only the very accurately known experimental enthalpy of hydrogenation of ethylene as a reference standard in the atomization method

Theoretical Gn model chemistries yield slightly different values for the enthalpy of formation of the hydrogen molecule from the constituent protons and electrons. For example, the G3 model yields −1.92 kJ mol−1 at 298 K, which differs from zero by an acceptably small amount. However, using this G3 value for a stepwise series of hydrogenations of polyunsaturated molecules multiplies the error, e.g., by five times for the hydrogenation of naphthalene. For polyunsaturates, this can produce errors considerably greater than experimental uncertainties. We calculate enthalpies of hydrogenation by referring the calculated values to the accurately known experimental enthalpy of hydrogenation of ethylene. This approach is simpler than the atomization method that depends on several experimental enthalpies of formation of the constituent atoms of the target molecules. This method yields enthalpies of hydrogenation and of formation in excellent agreement with experiment for many polyunsaturated compounds and lends confidence to results obtained for others, for which no accurate experimental values exist or are disparate, for example azulene. Some new and surprising results are that the formally conjugated triple bonds of cyanoacetylene do not lead to stabilization, but to destabilization by 10.2 kJ mol−1. The conjugated triple bonds of cyanogen cause thermodynamic destabilization by 47.5 kJ mol−1. Stabilization by conjugation in acrylonitrile is near zero. The remarkable endothermic monohydrogenation of benzene (25 kJ mol−1), first noted by Kistiakowsky, is also found in toluene and naphthalene, leading to stability of the reactant relative to the product of ~30 and 22 kJ mol−1, respectively.