Hydrogenation Of Naphthalene Research Articles

Asymmetric Hydrogenation of Naphthalenes with Molybdenum Catalysts: Ligand Design Improves Chemoselectivity

Asymmetric Hydrogenation of Naphthalenes with Molybdenum Catalysts: Ligand Design Improves Chemoselectivity

Sulfur Vacancies are the Active Sites in the Iron Sulfide Catalyst for the Hydrogenation of Naphthalene

AbstractIron sulfide catalysts could boost the hydrogenation of polycyclic aromatic hydrocarbons, and have been widely employed in direct coal liquefaction owing to their low price and good activity. In the past, the Fe deficient structure on Fe1−xS was normally considered as the active site. Herein, the promotion effect of S vacancies on the performance in the naphthalene hydrogenation reaction was revealed. Additional S vacancies on the prepared Fe1−xS catalyst were introduced by a heat‐treatment under H2. Multiple characterization techniques verified that the density of S vacancies on catalyst surface increased with the prolonged H2 treatment time, while the Fe deficient structure displayed an opposite trend. The performance in the hydrogenation of naphthalene to tetralin was used to evaluate the catalyst activity. It was found that the sequence of naphthalene conversion over catalysts was consistent with the corresponding content of S vacancies, indicating that S vacancies were more efficient active sites. DFT calculation results revealed that both molecular H2 and naphthalene exhibited a pronounced inclination towards adsorption on S vacancies as compared to intact surface of Fe1−xS. The increasing amount of S vacancies facilitated the adsorption of reactants and the weakening of naphthalene C−C bonds.

The formation of carbon deposits on catalyst during sulfurization of iron-oxides with aromatics as liquid medium

To obtain the proper catalyst activity for direct coal liquefaction, the iron-oxides, as a precursor of iron-based catalysts, were sulfurized in the liquid medium before use. The hydrogen-donating solvent, a promising liquid medium, benefited the process design. However, it was found to be not conducive to the catalyst activity. Herein, the influence on catalysts from aromatics was investigated. Synthetic iron-oxides were sulfurized under H2S flow in the mixtures of decalin and selected aromatics including xylene, naphthalene, phenanthrene and pyrene. The catalyst activity was evaluated based on its performance in the catalytic hydrogenation of naphthalene. It was found that pyrene had a significant negative effect on catalyst activity, which was mainly related to the condensation of pyrene on the catalyst. The fact was that the amount and condensation degree of carbon deposits on the tested catalysts were inversely proportional to their activities. The condensation of pyrene was related to both elemental sulfur and iron species. The effect from the two factors separately on pyrene condensation was limited, while the synergetic effect when they worked together made the condensation extent increased significantly. The elemental sulfur reacted with pyrene at elevated temperatures and induced the condensation of pyrene. Besides, density-functional-theory calculation results revealed that the chemical bonds of both elemental sulfur and pyrene were weakened by iron-sulfides.

Ultrafine Pt particles on hollow hierarchical porous β zeolites for selective hydrogenation of naphthalene

It is crucial to develop effective heterogeneous catalysts for the production of decalin as a high-density liquid hydrogen storage material from naphthalene hydrogenation. In this work, hollow hierarchical Pt/Hβ catalysts with ultrafine Pt particles were successfully synthesized successfully. The construction of hollow cavity optimized the metal-support interaction and reduced the resistance of mass diffusion. The ultrafine Pt species could expose more active sites for effective hydrogenation of naphthalene. The optimized Pt/Hβ-2 with hollow structure catalyst displayed the remarkable catalytic performance with the naphthalene conversion of 94.2 % and the decalin yield of 81.4 % at 220 °C, which was superior to the reaction performance of the catalysts reported in the literature under similar reaction condition. Besides, Pt/Hβ-2 presents higher turnover frequency (25.4 h−1) and reaction rate constant (9.9 × 10-3 min−1), which is because of the relatively low activation energy (30.86 kJ mol−1) for the naphthalene hydrogenation.

Hierarchical porous Pt/Hβ catalyst with controllable acidity for efficient hydrogenation of naphthalene

A series of hierarchical porous Pt/Hβ catalysts with different mesopores-acidity were synthesized without using secondary template. The pore structures of the catalysts were altered by constructing mesopores through alkali etching to reduce the mass transfer resistance. Moreover, the metal-support interaction (MSI) was optimized to improve the dispersion of the Pt metal particles. The smaller metal species could expose more active sites during the hydrogenation process, along with a more pronounced electron-deficiency effect. Furthermore, the effect of acid sites distribution on the hydrogenation reaction path and product distribution were also investigated. The strong acid-mesopores-metal factor (X) was defined to describe the relationship with the yield of decalin. The yield of decalin was well correlated with a high R2 value of 0.97. The Pt/Hβ-75 catalyst showed the best synergistic effect between acidity, mesopore and Pt species, leading to the optimal naphthalene conversion (96.7%) and higher yield of decalin (76.7%) at a relatively low temperature, which exhibited a better activity than other catalysts reported in literature for hydrogenation of naphthalene at a similar reaction condition. Besides, the hydrogenation reaction mechanism of naphthalene over Pt supported catalysts was further investigated by density functional theory, and the effect of Pt NPs size on the catalytic reaction process and activity was preliminarily revealed.

АКТИВНОСТЬ НИКЕЛЬ-МОЛИБДЕНОВОГО КАТАЛИЗАТОРА, РЕГЕНЕРИРОВАННОГО МЕТОДОМ СВЕРХКРИТИЧЕСКОЙ ФЛЮИДНОЙ ЭКСТРАКЦИИ

The activity of selective hydrogenation catalyst samples after supercritical fluid extraction regeneration at a temperature of 473 K and a pressure of 20 MPa with pure supercritical carbon dioxide and modified with hexane and ethanol was evaluated. The selectivity and chemical activity of the nickel-molybdenum catalyst LD-145 was determined on a model substance by the rate of the chemical reaction of hydrodesulfurization of the substance with the formation of dibenzotifene and the hydrogenation reaction of the substance with the formation of naphthalene in a flow-through experimental setup. The qualitative composition of the hydronisate was determined by gas-liquid chromatography on a Kristall-2000 chromatograph. The activity in the target reaction of naphthalene hydrogenation of the deactivated catalyst was 41.3%; catalyst regenerated with pure supercritical carbon dioxide - 43.4%; sample regenerated with a mixture of supercritical carbon dioxide + ethanol - 45.5%; and the sample regenerated with a mixture of supercritical carbon dioxide + hexane - 57%. Thus, the highest hydrogenation capacity was achieved on the sample regenerated with modified supercritical carbon dioxide hexane. Thus, the test results indicate an increase in the catalytic activity of catalyst samples that were regenerated by the supercritical fluid extraction method. It has been established that both the hydrogenating and hydrodesulfurizing functions of the catalyst can be restored. The level of recovery of the target hydrogenating activity of the catalyst achieved in this work is 57%. The level of recovery of catalytic activity of the spent catalyst samples can be improved by optimizing the conditions of supercritical fluid extraction process, more successful selection of the physical and chemical nature of the extractant and possibly earlier abandonment of the method of oxidative regeneration of the investigated catalyst during its operation.

Seed-assisted synthesis of a nanosheet-assembled hierarchical SSZ-13 zeolite by coupling a small amount of TMAdaOH with TPOAC

A nanosheet-assembled SSZ-13-TP0.03 was synthesized with TMAdaOH and TPOAC. Pt/SSZ-13-TP0.03 showed enhanced naphthalene hydrogenation compared to other catalysts.

CoPMoV Sulfide Catalysts Supported on Natural Halloysite Nanotubes in Hydrotreating of Dibenzothiophene and Naphthalene

Mixed sulfided CoMo catalysts supported on γ-Al2O3 and halloysite nanotubes (HNTs) were synthesized by incipient wetness impregnation with salt solutions of Keggin-type phosphorus- and vanadium-containing heteropolyacids. The synthesized materials were characterized by low-temperature nitrogen adsorption, energy dispersive X-ray fluorescence analysis, temperature-programmed reduction (both for the oxide and sulfide catalysts), and Raman spectroscopy, and were tested in hydrogenation of naphthalene and hydrodesulfurization of dibenzothiophene. The HNT-supported catalyst exhibited a greater activity in these reactions.

Effect of Quinoline Additions on the Activity of In Situ Formed NiWS Catalysts

The effect of quinoline additions and amount of the sulfiding agent added on the activity of the in situ prepared NiWS catalyst in naphthalene hydrogenation was studied. In the presence of 1 wt % quinoline, the obtained catalyst shows high activity (95% naphthalene conversion). The physicochemical properties of the catalyst were studied by XPS, X-ray diffraction analysis, and TEM. At the W : substrate molar ratio of 1 : 40 and 360°С, an increase in the amount of the sulfiding agent from 1 to 5 wt % leads to a decrease in the selectivity with respect to decalins from 68 to 39%, respectively. The degree of decoration with nickel on adding 1 wt % sulfiding agent is 0.1. As the amount of the sulfiding agent added is increased to 5 wt %, the degree of decoration with nickel increases to 0.3.

Ozonation assisted synthesis of well-dispersed Pt on HY zeolite as highly efficient catalyst for deep hydrogenation of naphthalene

Supported Pt catalysts are widely applied for the hydrogenation of polycyclic aromatic hydrocarbons, but it remains a challenge to achieve deep hydrogenation with high atomic utilization. Herein, a novel approach that combines physical vapor deposition with ozonation treatment was developed to construct the highly dispersed Pt on HY zeolite. The high concentration of O3 was utilized to remove the ligand of acetylacetone platinum under mild condition due to its strong oxidizing properties, which markedly inhibited the aggregation of the Pt species. The hydrogenation of naphthalene and anthracene was investigated on such catalysts and compared with the catalyst prepared by traditional calcination approach, it was found that the co-existence of Pt single-atom and cluster on HY of 1Pt/HY-O3 exhibited significantly high catalytic performance in the hydrogenation of naphthalene and anthracene, which was beneficiated from the synergistic effect of Pt single-atoms and clusters on HY support.

CoPMoV Sulfide Catalysts Supported on Natural Halloysite Nanotubes in Hydrotreating of Dibenzothiophene and Naphthalene

Mixed sulfided CoMo catalysts supported on γ-Al2O3 and halloysite nanotubes (HNTs) were synthesized by incipient wetness impregnation with salt solutions of Keggin-type phosphorus- and vanadium-containing heteropolyacids. The synthesized materials were characterized by low-temperature nitrogen adsorption, energy dispersive X-ray fluorescence analysis, temperature-programmed reduction (both for the oxide and sulfide catalysts), and Raman spectroscopy, and were tested in hydrogenation of naphthalene and hydrodesulfurization of dibenzothiophene. The HNT-supported catalyst exhibited a greater activity in these reactions.

Selective Hydrogenation of Naphthalene to Produce Tetralin over a Ni/S950 Catalyst under Mild Conditions

Tetralin is an essential chemical that can be generated by the partial hydrogenation of naphthalene. However, it is a challenge to design a catalyst with high efficiency, low-temperature activity, high tetralin selectivity, and a low cost to produce tetralin. A Ni/S950 catalyst with well-dispersed metal particles and high catalytic activity was prepared with an ion-exchange method. A complete conversion of naphthalene and a high tetralin yield of 95.6% were achieved over the Ni/S950 catalyst under 200 °C, 2 h, and 2 MPa H2. Compared with Co/S950 and Cu/S950, both the hydrogenation activity and the selectivity of tetralin over Ni/S950 are much higher due to its well-dispersed Ni particles with a smaller particle size of 6.8 nm and numerous active Ni0 sites.

Highly Dispersed Pt Catalysts on Hierarchically Mesoporous Organosilica@Silica Nanoparticles with a Core–Shell Structure for Polycyclic Aromatic Hydrogenation

Hydrogenation of naphthalene can effectively reduce the content of aromatics in oil and generate high-value products. A series of Pt-based aluminum-modified core-shell-structured hierarchically periodic mesoporous organosilica@mesoporous silica nanoparticles (Pt/Al-x-PMOs@MSNs) were successfully synthesized and tested for the hydrogenation properties, with preferable mass transfer of macromolecular reactants in the pores and increasing the total acidity of the catalysts. Moreover, the physicochemical properties of the core-shell-structured Pt-based catalysts were systematically analyzed using various characterization techniques. At 300 °C, the naphthalene conversion on the Pt/Al-10-PMOs@MSNs catalyst reached up to 100%, the selectivity of trans-decalin reached 83.9%, and the rate constants (k1, k2) and TOF were 13.2 × 10-6 mol·g-1·s-1, 1.7 × 10-7 mol·g-1·s-1, and 218.8 h-1, respectively. In the presence of sulfur, the naphthalene hydrogenation over the Pt/Al-10-PMOs@MSN catalyst first decreased to around 40% and then recovered to the original level, which originated from the synergistic effect of the texture and chemical properties over the Pt/Al-10-PMOs@MSNs with an excellent performance.

Effect of Different Al2O3 Supports on the Synthesis of Tetralin by Selective Catalytic Hydrogenation of Naphthalene

Different Al2O3 carriers were synthesized by co-precipitation and sol-gel method. From them, 4%NiO-20%MoO3/Al2O3 catalysts were prepared by incipient wetness impregnation. The catalysts were characterized by X-ray diffraction analysis (XRD), N2 adsorption-desorption, NH3-temperature programmed desorption (TPD) and H2-temperature programmed reduction (TPR) and subsequently used for selective hydrogenation of naphthalene to high-value tetralin. The results showed that Ni-Mo/so-ge Al2O3 (900) exhibited better catalytic performance than Ni-Mo/commercial Al2O3, achieving 99.56% naphthalene conversion and 99.43% tetralin selectivity.

The impact of nitrogen-containing compounds on the S-vacancies over the iron-based catalysts for direct coal liquefaction during the pre-sulfurization process

To advance the direct coal liquefaction (DCL) technology by a “Catalytic cycle of hydrogen donor solvents” pathway, it wasimportantfor the iron-based DCL catalyst to be pre-sulfurized under a suitable condition. In this report, the effect of liquid medium in the slurry bed pre-sulfurization process on iron-based catalyst was studied. Catalysts were pre-sulfurized under a variety of liquid mediums including alkanes, aromatics and heteroatom-containing compounds and the activity were evaluated according to their performance on hydrogenation of naphthalene. It was observed that, the nitrogen-containing medium give rise to the significant negative influence on the catalytic activity (with only 2.5 %-15.3 % of naphthalene conversions). Multiple spectroscopic and microscopic analyses of catalysts exhibited that the decrease of S vacancies was mainly responsible for the low activity. It was due to the promotion effect on Fe1-xS crystallization and troilite generation. S vacancies of the iron-based catalysts was considered as Lewis acid sites to catalyze the hydrogenation reaction. The new findings from this work is beneficial for the development and optimization of pre-sulfurization technology.

Synthesis of wrinkle silica nanospheres by solvent evaporation-induced self-assembly method for hydrogenation reaction

Wrinkle silica nanoparticles (WSNs) possess the typical characteristics in their short diffusion path and central-radial pore structure, which are favorable to use in a wide range of practical application. In this research, a solvent evaporation-induced self-assembly strategy was adopted for the preparation of WSN materials to give an insight into the formation mechanism of the WSNs. Through one-step temperature-controlled method, it was found that the WSNs could be successfully synthesized under the temperature of 60 °C, while the pore sizes and particle sizes were both gradually decreased as the synthesis temperature continued to increase. Comparably, a two-step temperature-controlled method was employed through modulating the stirring time length in order to synthesize silica nanospheres with large pore size and small particle size. The results showed that Ni2P/WSNs-8+16 catalyst performed the highest naphthalene hydrogenation activity (almost 100% conversion at 300 °C) when the stirring time in the first stage and the second stage was 8 h and 16 h, respectively.

The formation of high energy density fuel via the hydrogenation of naphthalene over Ni catalyst: The combined DFT and microkinetic analysis

Decalin is the major ingredients of High-energy-density jet fuel JP-900, in which cis-decalin possesses more excellent combustion performance than trans-decalin. The various coordination environments on metal catalysts are crucial to evaluate activity of catalyst and selectivity of cis-decalin, the density functional theory and microkinetic modeling are applied to investigate the effect of various active sites on the process of naphthalene hydrogenation. Active sites with generalized coordination numbers of 7.50, 6.67, 5.57, and 5.50 from four Ni surfaces including Ni(1 1 1), Ni(1 0 0), Ni(1 1 0) and Ni(2 1 1) are built, respectively. To screen surfaces with preferable selectivity to cis-configuration, the four reaction paths are firstly considered including desorption of NA8H, direct hydrogenation of NA8H to cis- or trans-NA9H, and NA8H to trans-NA9H by hydrogen transfer on four surfaces. And the Ni(1 0 0) and Ni(1 1 1) surfaces exhibit optimal selectivity to cis-decalin by comparing energy barrier of the four paths and calculating the energy barrier gap between direct hydrogenation to cis- and H transfer to trans- configuration, which is the result of 9th C atom receiving more electrons in the process of generating trans-decalin. In addition, reaction mechanism of the whole reaction process from naphthalene hydrogenation to decalin was explored and finding that the rate-determining step of reaction lies in the process of the second-ring hydrogenation. Furthermore, the activity of the Ni(1 0 0) surface is not worse than that of Ni(1 1 1) by comparing the energy barrier of the rate-determining step, which is consistent with the analysis of the d-band-center for different surfaces and the adsorption energy for naphthalene. Microkinetic analysis shows that the temperature between 473 K and 553 K favors the selectivity to cis-decalin for metal Ni catalyst. Therefore, this study provides guide for screening surfaces with different coordination numbers with high activity of naphthalene hydrogenation and high selectivity to cis-decalin.

Modification of Activated Carbon and Its Application in Selective Hydrogenation of Naphthalene.

The MoS2/ACx catalyst for hydrogenation of naphthalene to tetralin was prepared with untreated and modified activated carbon (ACx) as support and characterized by X-ray powder diffraction, Brunauer-Emmett-Teller, scanning electron microscopy, temperature-programmed desorption of ammonia, X-ray photoelectron spectroscopy, and scaning transmission electron microscopy. The results show that the modification of activated carbon by HNO3 changes the physical and chemical properties of activated carbon (AC), which mainly increases the micropore surface area of AC from 1091 to 1209 m2/g, increases the micropore volume of AC from 0.444 to 0.487 cm3/g, increases the oxygen-containing functional groups of AC from 5.46 to 7.52, and increases the acidity of catalysts from 365.7 to 559.2 mmol/g. The modified catalyst showed good catalytic performance, and the appropriate HNO3 concentration is very important for the modified of activated carbon. Among all the catalysts used in this study, the MoS2/AC3 catalyst could achieve the highest yield of tetralin. It can be attributed to the moderate acidity of the catalyst, reducing the cracking of hydrogenation products. Also, the proper hydrogenation activity of MoS2 and the appropriate increase of oxygen-containing functional groups on the surface of modified activated carbon are beneficial to the dispersion of active components on the support, increasing the yield of tetralin. The catalytic performance of MoS2/AC3 is better than that of MoS2/Al2O3 catalyst, and the two catalysts show different hydrogenation paths of naphthalene.

Highly dispersed Pt on core–shell micro-mesoporous composites assembled by mordenite nanocrystals for selective hydrogenation of polycyclic aromatics

A core–shell Pt/MOR-PMOs-x@MSNs (Periodic mesoporous organosilica@mesoporous silica nanoparticles, PMOs@MSNs) catalysts with hierarchical pore structures and suitable acidities were prepared and showed excellent sulfur resistance in hydrogenation of polycyclic aromatic hydrocarbons. The hierarchical pore structure not only facilitates the accessibility of macromolecular aromatic compounds and active sites, but also reduces the mass transfer resistance of reactant and product molecules. The higher metal support interaction (MSI) can reduce the aggregation of active sites, and generate electron-deficient metals, improving the sulfur resistance of the catalyst. Among them, the Pt/MOR-PMOs-100@MSNs catalyst shows the higher activity of naphthalene hydrogenation that the conversion reaches nearly 100 % at 280 °C, the rate constant and turnover frequency (TOF) at 50 % conversion are 6.2 × 10−6 mol·g−1·s−1 and 81.5 h−1, respectively. Moreover, in the 9 h sulfur resistance test at 300 °C, the conversion of naphthalene hydrogenation is still 84.9 %, and the dibenzothiophene (DBT) desulfurization rate is 91.5 %. This is due to the fact that it has a certain specific surface area, synergistic MSI, and active metal Pt nanoparticles with an average size of about 3.5 nm. Moreover, the additions of mordenite (MOR) zeolites bring more acid sites, which in turn form “electron-deficient” adducts with small-sized Pt NPs, thereby raising the sulfur tolerance of the catalysts.

V-Containing Heteropoly Acids with Keggin Structure as Precursors of Sulfide Catalysts: Regularities of the Convertion of Dibenzothiophene and Naphthalene on Nonpromoted Mo–V Catalysts

Mixed PMoV heteropoly acids with Keggin structures H3+xPMo12–xVxO40 (x = 1–6) and modified sulfide catalysts on their basis were synthesized, their physicochemical characteristics were determined, and their performance in the reactions of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation of naphthalene was evaluated. Modification of the Mo-containing catalysts with vanadium by impregnation with a solution of mixed heteropoly acids was found to enhance their catalytic activity in the studied reactions, as well as to increase the selectivity for the direct hydrodesulfurization route of the DBT HDS reaction.