Hydrogenation Of Naphthalene Research Articles

Analysis of the HDS of 4,6-DMDBT in the presence of naphthalene and carbazole over NiMo/Al 2O 3–SiO 2( x) catalysts

NiMo catalysts were prepared on γ-Al 2O 3 modified with SiO 2 (0 and 10 wt% SiO 2). Catalysts were characterized by HRTEM in sulfided state and evaluated in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT), hydrogenation (HYD) of naphthalene, hydrodenitrogenation (HDN) of carbazole and in the simultaneous reaction of 4,6-DMDBT–naphthalene–carbazole. The kinetic parameters of Langmuir–Hinshelwood type equations for all the reaction systems were estimated. Although naphthalene and carbazole present a competitive inhibition effect for the HDS of 4,6-DMDBT, the inhibiting effect of naphthalene was mainly due to its high concentration, whereas the inhibition caused by carbazole was due to its strong adsorption over the catalytic active sites. The addition of SiO 2 to the catalysts enhanced the hydrogenation activity and therefore the HDS of 4,6-DMDBT, HYD of naphthalene and HDN of carbazole leading to more active catalysts when a mixture of the three compounds was hydrotreated.

Behavior of catalysts with rhodium in simultaneous hydrodesulfurization and hydrogenation reactions

The behavior of catalysts containing rhodium was evaluated in hydrotreating (HDT) reactions at 583 K and 5 MPa. The influence of the temperature and the nature of the activating agent were analyzed for the monometallic Rh/γ-Al 2O 3 catalyst in simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation (HYD) of naphthalene (NT). H 2, H 2S, N 2 and H 2S (15 vol.%)/H 2, H 2S (85 vol.%)/H 2 mixtures were used as activating agents. Bimetallic RhMo/γ-Al 2O 3 catalysts with different Rh/Mo ratios were also tested in the same reactions. Some of the catalysts were characterized by XPS. The results show that for the Rh monometallic catalyst, the H 2S present in the activating mixture leads to an increase in the selectivity to HDS. Synergy in both HDS and HYD reactions was detected for the bimetallic catalysts, and it presents a slight increase with the Rh/(Rh + Mo) atomic ratio. These results lead to speculate about the possible role of Rh in bimetallic catalysts.

Characterization of Pd catalysts supported on USY zeolites with different SiO2/Al2O3 ratios for the hydrogenation of naphthalene in the presence of benzothiophene

A series of ultra-stable Y-type (USY) zeolites with different SiO2/Al2O3 ratios in the range of 10–80 were used as supports for preparing Pd/USY at 2 wt% Pd loading. The FT-IR of hydroxyl groups of USY zeolites, the n-butylamine chemisorption and the temperature-programmed desorption were used in combination to characterize the zeolite acidity. TPR, H2-TPD and chemisorption using H2 were used to characterize the Pd reduction and dispersion. The hydrogenation of naphthalene was conducted at 200 °C in the presence of benzothiophene at different sulfur/metal ratios. The hydrogenation activity, selectivity, and the sulfur tolerance strongly depended on the SiO2/Al2O3 ratio (thus the acidity) of the zeolites. The activity decreased with increasing SiO2/Al2O3 in this range. The IR and n-butylamine TPD showed that both the amount and strength of Brönsted acidity decreased with the increase of the SiO2/Al2O3 ratio. The good relationship between the acidity modification and catalytic performance suggests that the sulfur tolerance of Pd/USY zeolite might be due to the desired metal-support interaction, which resulted in larger amount of electron-deficient Pd. However, as shown in TGA and TPO-IR studies, the higher hydrogenation performance on more acidic zeolite also caused higher amount of carbonaceous species on the catalyst.

Hydrogenation of naphthalene on NiMo- Ni- and Ru/Al 2O 3 catalysts: Langmuir–Hinshelwood kinetic modelling

The importance of the hydrodearomatisation (HDA) is increasing together with tightening legislation of fuel quality and exhaust emissions. The present study focuses on hydrogenation (HYD) kinetics of the model aromatic compound naphthalene, found in typical diesel fraction, in n-hexadecane over a NiMo (nickel molybdenum), Ni (nickel) and Ru (ruthenium) supported on trilobe alumina (Al 2O 3) catalysts. Kinetic reaction expressions based on the mechanistic Langmuir–Hinshelwood (L–H) model were derived and tested by regressing the experimental data that translated the effect of both naphthalene and hydrogen concentration at a constant temperature (523.15 and 573.15 K over the NiMo catalyst and at 373.15 K over the Ni and Ru/Al 2O 3 catalysts) on the initial reaction rate. The L–H equation, giving an adequate fit to the experimental data with physically meaningful parameters, suggested a competitive adsorption between hydrogen and naphthalene over the presulphided NiMo catalyst and a non-competitive adsorption between these two reactants over the prereduced Ni and Ru/Al 2O 3 catalysts. In addition, the adsorption constant values indicated that the prereduced Ru catalyst was a much more active catalyst towards naphthalene HYD than the prereduced Ni/Al 2O 3 or the presulphided NiMo/Al 2O 3 catalyst.

Synthesis, characterization and evaluation of NiMo/SiO 2–Al 2O 3 catalysts prepared by the pH-swing method

NiMo/( X)SiO 2–Al 2O 3 catalysts were synthesized with various SiO 2 contents ( X = 0, 10, 25 and 50 wt%) using the pH-swing method. In order to find the optimum SiO 2 content, the catalysts were evaluated in the hydrodesulfurization of 4,6-DMDBT, hydrogenation of naphthalene and hydrodenitrogenation of carbazole. Kinetic parameters of Langmuir–Hinshelwood type equations for all the reaction systems were estimated. FTIR analysis of CO adsorption for the sulfided catalysts shows that the amount of coordinatively unsaturated Mo sites promoted by nickel (CUS-NiMoS) follows the order NiMo/10ASA > NiMo/25ASA > NiMo/0ASA. This tendency agrees with the results obtained in catalytic activity.

Acidity and deactivation of Mo2C/HY catalysts used for the hydrogenation and ring opening of naphthalene

The selective ring opening (SRO) of naphthalene over a series of Mo2C/HY catalysts with 7–27 wt% Mo2C, is reported. Pulsed adsorption and temperature programmed desorption of n-propyl amine showed that increased Mo2C content of the Mo2C/HY catalysts significantly decreased the amount and strength of the catalyst acid sites, especially the Brönsted acid sites necessary for SRO. Carbon deposition was the main cause of catalyst deactivation and thermogravimetric analysis of the used catalysts indicated that accumulation of carbonaceous species over the surface of the acidic HY support with time-on-stream led to deactivation of the Mo2C/HY catalysts, whereas no significant carbon deposition occurred on the Mo2C. Catalyst activity tests showed a synergistic effect between the Mo2C and the acidic support (HY) that was not readily obtained with a mechanical mixture of the two catalyst components.

Preparation and characterization of Beta/MCM-41composite zeolite with a stepwise-distributed pore structure

A Beta/MCM-41 composite zeolite with a stepwise-distributed pore structure was prepared with a silica-alumina source originated from alkaline treatment of zeolite Beta. The material was characterized by various techniques. The results indicated that this composite possesses a mesopore system of MCM-41 and the microporous structure of Beta zeolite. Hydrothermal stability and acidity was improved over MCM-41 due to the introduction of Beta building units into the mesopore walls. The composite was used as the support of a Pd-Pt catalyst for the hydrogenation of naphthalene in the presence and absence of 4, 6-dimethyldibenzothiophene. It was demonstrated that the catalyst has an enhanced activity and sulfur tolerance during naphthalene hydrogenation.

High hydrogenation performance of the mesoporous NiMo/Al(Ti, Zr)–HMS catalysts

Hexagonal mesoporous silica (HMS) material with and without Al, Ti and Zr ions (Si/X, X = Al, Ti or Zr atomic ratio of 40) were used as support for the preparation of the hydrotreating NiMo catalysts. The samples were characterized by 29Si NMR, S BET, XRD, HRTEM, Raman spectroscopy, FT-IR spectroscopy of adsorbed NO on freshly sulfided samples, XPS of the used samples and H 2 chemisorption. The catalytic activity of the samples was evaluated in the reaction of hydrogenation of naphthalene. All samples showed high hydrogenation activity in the first step of the reaction when tetraline is formed. However, in the second step of the reaction leading to the formation of cis-decaline and trans-decaline, the presence of Al, Ti and Zr ions increased the hydrogenation ability of the samples. The NiMo/HMS and a reference (NiMo/ γ-Al 2O 3) catalysts were good for mild hydrogenation (tetraline formation), while in the NiMo/(Al, Ti, Zr)–HMS catalysts were superior when deep hydrogenation is necessary ( cis-decaline and trans-decaline formation). We found three interesting correlations, (i) oxidized Ni species in the sulfided samples with the deep (complete) hydrogenation (tetraline to decalines), (ii) the dispersion of the sulfided Ni and Mo species with the rate constant of the naphthalene consumption and, (iii) the population of Mo O T species (T terminal bonding) with the second hydrogenation step (tetraline transformation to decaline).

Naphthalene hydrogenation over a NiMo/γ-Al 2O 3 catalyst: Experimental study and kinetic modelling

A kinetic study of the liquid phase naphthalene hydrogenation over a commercial and sulphided NiMo/γ-Al 2O 3 was performed using experimental data obtained in a Robinson–Mahoney reactor at 523–583 K and 2.0–4.0 MPa. The effect of H 2S on the hydrogenation rate was investigated varying its partial pressure from 0.09 to 0.89 MPa. Under these conditions, an exponential decrease in the hydrogenation rate was observed as the H 2S partial pressure increased. The naphthalene conversion ranged from 6 to 89% with tetralin as the main hydrogenation product with selectivities of at least 89%. Reaction networks were formulated based on stepwise hydrogenation mechanisms assuming that both hydrogen and hydrogen sulphide could be dissociated either homolytically or heterolytically on both coordinatively unsaturated metal ion sites (CUS) and sulphur anions (SA) of the sulphided catalyst. Langmuir–Hinshelwood rate equations were derived and discriminated through model regression to experimental data. Two models best describe the experimental data according to a statistical analysis and the physical meaning of the parameter estimates. These models correspond to the third hydrogen addition chemisorbed on CUS and supplied from either homolytic or heterolytic hydrogen dissociation, as rate-determining step. The calculated catalyst surface species concentrations indicate that hydrogen and sulphydril groups are the most abundant species under the investigated operating conditions while the hydrocarbons surface concentration is almost negligible.

Hydrogenation of naphthalene on NiMo- and Ni/Al 2O 3 catalysts: Pre-treatment and deactivation

Nickel (Ni) and nickel molybdate (NiMo) supported on alumina (Al 2O 3) catalysts, both in a presulphided and prereduced forms, were investigated for the hydrogenation (HYD) of naphthalene. The deactivation of the catalysts with time on stream and sulphur (S) content in feed was studied and a detailed characterization of the catalysts was performed. The catalytic activity of the presulphided NiMo/Al 2O 3 catalyst was found to be 2.5 times higher than the prereduced form, at the same HYD conditions. Testing the commercial prereduced Ni catalyst, it was observed that, although the catalyst aged quite quickly, it gave a higher turnover frequency at a temperature that was significantly lower than the one needed for the presulphided NiMo/Al 2O 3 catalyst. The presulphided Ni/Al 2O 3 catalyst showed a low activity towards naphthalene HYD, for the same experimental conditions applied to the prereduced form. The presulphided form of this catalyst was not the active site for this HYD. The Ni catalyst should be used in a sulphur free environment in order to fully make use its hydrodearomatisation (HDA) properties, whereas the NiMo/Al 2O 3 catalyst exhibited a higher HYD activity in the presulphided form.

Bottom-mounted ATR probes: Pitfalls that arise from gravitational effects

For practical reasons, ATR-IR probes are usually mounted in the bottom of an autoclave, inside a small cavity. Using a transparent mock-up, we observed that it is very likely that catalyst particles settle inside this cavity, right above the crystal. The impeller speed needed to remove these deposited particles depends on the impeller dimensions and the density of the catalyst particles. Trends in this catalyst settling behaviour agreed with the Zwietering’ correlation indicating poor mixing characteristics due to the presence of the cavity. The presence of a layer of catalyst particles on the crystal leads to overestimation of the observed reaction rates measured by ATR-IR. Several indicative experiments of the hydrogenation of naphthalene to decalin over Pd-based catalysts, involving step changes, showed dynamic responses and trends in observed reaction rates that can be used to reveal these effects in closed autoclaves. A simple model that assumes an ideally mixed bulk phase and a stagnant layer of catalyst particles in the cavity describes the observed phenomena well.

Hydrogenation and ring opening of naphthalene on bulk and supported Mo2C catalysts

A series of Mo 2 C catalysts have been investigated for the hydrogenation and ring opening (ROP) of naphthalene. At 573 K and 3 MPa H 2 , bulk Mo 2 C showed no selectivity for ROP whereas ROP yield on Mo 2 C/HY catalysts was dependent upon the HY zeolite SiO 2 :Al 2 O 3 ratio and the Mo 2 C loading, as shown in figure. A series of Mo 2 C catalysts have been investigated for the hydrogenation and ring opening of naphthalene. At 573 K and 3 MPa H 2 , bulk Mo 2 C showed no selectivity for ring-opening products (ROP) and, although treating the bulk catalysts in oxygen increased stability and naphthalene conversion, ROP selectivity remained low. Supporting the Mo 2 C on HY zeolites significantly increased the hydrogenation of naphthalene and the subsequent formation of ROP, as compared to the HY zeolites alone or the bulk materials. ROP yields were dependent upon the HY zeolite SiO 2 :Al 2 O 3 ratio and the Mo 2 C loading, the optimum loading being dependent upon the zeolite acidity. The maximum ROP yield of 33 wt.% was obtained with 7.4 wt.% Mo 2 C supported on HY zeolite of moderate acidity (SiO 2 :Al 2 O 3 ratio of 12) and the yield is comparable to yields reported for noble metal catalysts on acidic supports. The Mo 2 C/HY zeolite bifunctional catalysts are most effective for ring opening of naphthalene when the acidity is adjusted to an intermediate level that limits deactivation and the Mo 2 C loading provides sufficient hydrogenation capability to achieve high conversion to the primary product tetralin.

MCM-41 Overgrown on Y Composite Zeolite as Support of Pd−Pt Catalyst for Hydrogenation of Polyaromatic Compounds

A composite zoelite Y overgrown with a thin layer of mesoporous MCM-41 was prepared as the support of a sulfur-tolerant catalyst for aromatics reduction in diesel cut. This material is different from the mechanical mixture of the two zeolites in many aspects, that is, the FTIR spectra, appearance of particles, distribution of Si and Al, 29Si MAS NMR spectra, acid strength, and amount of acid sites on the surface. The composite was used as the support of a Pd−Pt catalyst for the hydrogenation of polyaromatic compounds, pyrene and naphthalene. Sulfur tolerance of the catalyst was investigated with naphthalene hydrogenation in the presence of thiophene and 4,6-dimethyldibenzothiophene. It was demonstrated that the introduction of mesopores enhances the activity of pyrene hydrogenation and the sulfur tolerance during naphthalene hydrogenation.

Hydrogenation of benzothiophene-free naphthalene over charcoal-supported metal catalysts in supercritical carbon dioxide solvent

Abstract Hydrogenation of benzothiophene-free naphthalene was examined over various transition metal (rhodium, ruthenium, palladium, and platinum) catalysts supported on charcoal in supercritical carbon dioxide (scCO 2 ) solvent at low temperature (313 K). Among these, a charcoal-supported rhodium catalyst was found to be the most active, while a charcoal-supported ruthenium catalyst was found to give the highest cis -decahydronaphthalene ( cis -decalin) selectivity. A systematic investigation of hydrogenations of naphthalene and tetrahydronaphthanele (tetralin) in scCO 2 revealed that naphthalene hydrogenation is a consecutive and cis - and trans -decalin were formed via tetralin.

Hydrogenation of Naphthalene and Tetralin in the Presence of CO over Various Supported Metal Catalysts

Hydrogenation of Naphthalene and Tetralin in the Presence of CO over Various Supported Metal Catalysts

ケミカルハイドライド法水素貯蔵における低品位水素の利用（7） CO存在下ナフタレン水素化反応における担持Pd触媒の担体効果

ケミカルハイドライド法水素貯蔵における低品位水素の利用（7） CO存在下ナフタレン水素化反応における担持Pd触媒の担体効果

Effects of the H2S partial pressure on the performance of bimetallic noble-metal molybdenum catalysts in simultaneous hydrogenation and hydrodesulfurization reactions

Abstract The influence of the H 2 S concentration on the activity and selectivity to hydrodesulfurization (HDS) of bimetallic noble-metal molybdenum (NM–Mo, NM = Pt, Ru, Pd) supported on γ-Al 2 O 3 catalysts was studied. The effect of H 2 S on the modification of the HDS pathway and the influence of the Mo loading on the sulfur resistance of catalysts were also analyzed. NM–Mo/γ-Al 2 O 3 and conventional CoMo/γ-Al 2 O 3 catalysts were prepared and evaluated in simultaneous dibenzothiophene (DBT) HDS and naphthalene hydrogenation (HYD) reaction cycles, in the presence of dimethyl disulfide (DMDS) in order to obtain H 2 S partial pressures of 10, 30 and 50 kPa. Catalysts were characterized by atomic absorption spectroscopy and temperature-programmed reduction of sulfides (TPRS). TPRS experiments after exposing catalysts to simulated reaction conditions (TPRS-SRC) were also performed. Results show that the H 2 S does not poison the studied catalysts, but an inhibition of both HYD and HDS reactions is observed. The inhibition of catalyst activities is attributed to the interconversion of HDS, HYD and inactive sites; this interconversion is influenced by the H 2 S/H 2 ratio, the nature of the NM and the composition of catalysts. Activity, TPRS and TPRS-SRC results confirmed this scheme. A modification of the reaction pathway was observed when the H 2 S partial pressure was increased; the direct desulfurization was principally affected. The interconversion of sites could explain this modification. Moreover, our results show that the Mo loading and specifically the Pt/Mo ratio, which determine the Pt dispersion, influence the sulfur resistance of the catalyst.

Shape selective and hydrogen spillover approach in the design of sulfur-tolerant hydrogenation catalysts

This paper presents a novel approach to preparing sulfur-tolerant noble metal catalysts and the proof-of-concept experimental results. Our approach combines the concepts of shape selectivity and hydrogen spillover to the design of sulfur-tolerant catalysts. Platinum particles were encapsulated in the NaA-zeolite cages during zeolite synthesis. The pore opening was subsequently reduced by potassium ion exchange and chemical vapor deposition of tetraethyl orthosilicate (TEOS), allowing hydrogen molecules to enter but preventing hydrogen sulfide molecules from contacting the platinum particles. The success of platinum encapsulation in KA-zeolite was confirmed by XRD, H 2 and CO chemisorption, and TOF-SIMS techniques. A sulfur-tolerant catalyst was prepared by mixing TEOS-treated Pt/KA-zeolite with HY-zeolite and γ-alumina, and tested in the hydrogenation of naphthalene. Hydrogen species produced via dissociative adsorption of hydrogen molecules on platinum particles, situated inside KA-zeolite cages, migrated through surface diffusion to HY-zeolite and γ-alumina. Our experimental data demonstrated that the encapsulated platinum particles continuously generated hydrogen surface species that were used to hydrogenate naphthalene adsorbed on HY-zeolite and γ-alumina. These platinum particles showed resistance to sulfur poisoning when pure hydrogen was replaced by 3% H 2S in hydrogen in the naphthalene hydrogenation reaction.

Tailoring the pore size of zeolite Y as the support of diesel aromatic saturation catalyst

The molecular dimensions of typical aromatics and sulfur-containing compounds in diesel cuts were simulated. A pore configuration design was proposed for sulfur-tolerant metal catalyst. Modified zeolite Y with and without the presence of mesopores were used as a catalyst support. Pyrene and naphthalene were used as the model compounds for hydrogenation. Sulfur tolerance of the catalyst was investigated with naphthalene hydrogenation in the presence of thiophene. It was demonstrated that the generation of mesopores in zeolite Y can enhance the activity of pyrene hydrogenation, but lower the tolerance to thiophene.

Hydrogenation of Naphthalene over NiO/SiO 2–Al 2O 3 catalysts: Structure–activity correlation

A series of NiO–SiO 2–Al 2O 3 catalysts were synthesized by the sol–gel method. The samples were characterized by a wide array of techniques, including X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), H 2 temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD) of NH 3. The nature of Ni species on the support and their interaction with the support was studied. XPS and TPR studies showed that Ni was present as Ni 2+ on the support, and that there was no Ni 3+ or Ni 0 in the unreduced samples. Two kinds of NiO were observed on the support, one in which the Ni 2+ interacts with the support and the other known as “free” NiO—that is, with no metal–support interactions. The reducibility of NiO decreased with increasing interaction with the support. The extent of interaction between the Ni 2+ and the support depended on the total Ni content of the sample and its Si/Al ratio. Increasing the Ni content in the material led to an increase in the relative concentration of free NiO, as well as an increase in the particle size of NiO as seen on TEM. An increase in Si content led to a decrease in the relative free NiO concentration and an increase in the total acidity of the sample, measured by NH 3-TPD. The impact of these effects on the catalytic activity of the samples was evaluated in the vapor-phase hydrogenation of naphthalene at 1 atm. A correlation was made between the catalytic activities and the relative concentration of free NiO. Hydrogenation of naphthalene proceeds sequentially by formation first of the partially hydrogenated tetralin and then of the fully hydrogenated decalin. The yield of decalin increased with increasing conversion of naphthalene; however, tetralin was the major product of this reaction. Kinetic studies were carried out to investigate the variation in selectivity with conversion of naphthalene. The reaction was best described using a two-site Langmuir–Hinshelwood model. The adsorption constants and of naphthalene, K N , and tetralin, K T , were 4.10 × 10 −3 and 1.88 × 10 −3 m 3 / mol , respectively, at 200 °C. The low yield of decalin has been attributed to the weak adsorption of tetralin on the active site.