Naphthalene Conversion Research Articles

The conversion of naphthalene on SOFC anodes and its impact on the cell performance

The operation of a SOFC with biomass-derived syngas would provide convincing solutions for combined heat and power production from renewable sources. In principle, the tar components in the wood gas can be reformed on Ni-based SOFC anodes, hence, giving access to additional hydrogen as fuel. The investigation of the kinetic-limited conversion process on anodes and its effect on the electrochemical processes of the SOFC is yet still insufficient. This paper presents the experimental study of the conversion of naphthalene on a single planar electrolyte-supported cell with varying temperature and naphthalene concentration. Thereby the impact of the incomplete conversion of naphthalene on open circuit voltage, methane conversion and cell performance is investigated. A 1-D kinetic model reveals the correlation between the slow naphthalene reforming and the open circuit voltage. The adsorption of naphthalene on the Ni catalyst not only impedes the reforming of methane, but also slows down the kinetics of electrochemical reaction. However, the produced hydrogen from steam reforming reaction is still beneficial in terms of preventing Ni re-oxidation under higher fuel utilization in H2 gas mixture.

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.

Cu2O@TiO2 core-shell microspheres for naphthalene oxidation

New Cu2O@TiO2 core-shell microspheres were successfully prepared for the first time in this paper. The XRD, N2 adsorption-desorption, SEM, TEM, EDX and XPS characterizations were utilized to investigate the physical and chemical properties. The liquid phase oxidation of naphthalene was also carried out to test their catalytic performance. The characterization results indicating that the Cu2O microspheres were firstly formed by hydrothermal treatment and the rutile TiO2 coating on the surface would be formed by the hydrolysis of tetrabutyl titanate. The Cu2O@TiO2-5.0 catalyst with the molar ratio of copper to titanium species as high as 5.0 has the largest surface area and maximum pore volume resulting from the integrated microspheres with rougher surface thickness of about 6.3 nm, and it showed higher catalytic performance in the liquid phase oxidation of naphthalene. Naphthalene conversion of 43.2%, 1, 4-naphthoquinone selectivity of 26.7% and phthalic anhydride selectivity of 53.4% can be obtained, and it only slightly decreased even after repeated use for 5 times. The method would provide a valuable theoretic reference for the hindrance of Cu2O rapid deactivation and the industrial application of the naphthalene oxidation to produce high valuable chemicals.

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.

Highly Dispersed Nickel Nanoparticles on Hierarchically Ordered Macroporous Al2O3 and Its Catalytic Performance for Steam Reforming of 1-Methyl Naphthalene

In this study, we investigate the effect of a hierarchically ordered macroporous structure of alumina support on the steam reforming of 1-methyl naphthalene with mesoporous alumina-supported nickel and potassium (xK/Ni–MeAl), and macroporous alumina-supported nickel and potassium (xK/Ni–MaAl) catalysts. Hierarchically ordered macroporosity in Al2O3 supports plays an important role in maintaining the high Ni dispersion through multiple interactions in Ni–K over AlO4 tetrahedra in alumina. This, in turn, improves the catalytic performance of steam reforming, including high gas yields, turnover frequency for hydrogen production, and 1-methyl naphthalene conversion. At high K content, the Ni active sites over xK/Ni–MeAl catalysts significantly decrease, resulting in almost zero steam reforming rate in the reaction test. Conversely, the potassium–alumina interaction in xK/Ni–MaAl catalysts not only diminishes the formation of the inactive nickel aluminate phase but also maintains the highly dispersed Ni active sites, resulting in a high steam reforming rate.

“ZnAlCrOx&HZSM-5” bifunctional catalyst for one-step alkylation of naphthalene and syngas

The conversion of naphthalene into high value-added intermediate, 2,6-dimethylnaphthalene (2,6-DMN), using methanol as an alkylating agent has been widely studied. However, the low conversion of naphthalene and the easy deactivation of catalysts due to carbon deposition still pose challenges for industrialization. This is attributed mainly to the huge difference in the conversion kinetics of naphthalene and methanol. Herein, we report the first one-step process for the synthesis of 2,6-DMN from naphthalene by direct alkylation with syngas over “ZnAlCrOx&HZSM-5″ bifunctional catalyst. Compared to the traditional alkylation process of naphthalene with methanol, the direct alkylation of naphthalene with syngas not only shortened the process route and improved the reaction balance of syngas to methanol, but also improved the effective utilization rate of CO (29.87 %), naphthalene conversion, and catalyst stability. Results indicated that the alkylation of naphthalene could be improved by appropriately narrowing the spacing between the ZnAlCrOx oxide and HZSM-5. The acid strength and acidity on the external surface of HZSM-5 were modified by P or Si to improve the initial conversion of naphthalene and the selectivity for 2,6-DMN. The difficulty in determining the deactivation point of catalysts with multiple active sites under complex catalytic systems was solved by adopting a strategy of ”improve shortcomings“. The decline of metal activity in this reaction was found to be the main reason for catalyst deactivation. Doping of Ce into ZnAlCrOx helped to improve the stability of the catalyst from 80 h to 120 h.

Mechanism for the catalytic thermal polycondensation of naphthalene at low temperature

Naphthalene is an important component of high temperature coal tar and its content can reach more than 10%. Catalytic polycondensation of naphthalene is an effective way to prepare mesophase pitch and functional carbon materials. In this work, anhydrous AlCl3 was used as a catalyst for the polymerization of naphthalene under atmospheric pressure below 170 °C and the reaction mechanism was then systematically investigated. The results indicate that at 110 °C, the polymer product is mainly composed of tricyclic compounds and the content of heavy products is only 29.5%. At 150 °C, four to five peri-condensed aromatic compounds turn to be the main components and the content of medium components remains about 50%. At 170 °C, there appear a large number of six-ring aromatic cores and the conversion of naphthalene reaches 90.7%. The polymer products exhibit good fluidity and solubility in THF, which can facilitate the high-temperature thermal polycondensation and subsequent graphitization process. With an AlCl3/naphthalene molar ratio of 1/100, the second to seventh order naphthalene oligomers are obtained by the simulation of the short chain oligomerization of naphthalene. In contrast, when the AlCl3/naphthalene molar ratio exceeds 10/100, acetylene and methylnaphthalene are produced by the catalytic pyrolysis of naphthalene. The mechanism of “Oligomerization-Pyrolysis-Aromatization” was then proposed to explain the molecular transformation from naphthalene to pitch, which should be useful for the production of mesophase pitch precursor.

Kovar Tube as a Potential Catalyst for Conversion of Tar Produced from Biomass Gasification

A pre-oxidized Kovar tube was employed as a reforming catalyst for the conversion of naphthalene. Under dry reforming condition, 24.7% naphthalene conversion could be achieved, whereas 36.6 and 42.3 % naphthalene conversion could be achieved when steam was added to the producer gas at the volume ratio of 0.06 and 0.11, respectively. Increasing the reforming temperature to 1173 K enhanced the catalytic removal of naphthalene to 91.5%. The activation energy and frequency factor values were found to be 136 kJ/mol and 3.07107 cm3cm-2min-1, respectively.

Azulene-Naphthalene, Naphthalene-Naphthalene, and Azulene-Azulene Rearrangements.

The mechanism(s) of thermal rearrangement of azulenes have been enigmatic for several decades. Herein, we have employed density functional theory (DFT) calculations at the M06-2X/6-311+G(d,p) level together with single-point calculations at the CCSD(T) level to assess possible mechanisms of the experimentally observed azulene and naphthalene automerizations. Of the two mechanisms proposed for naphthalene automerization, it is found that the benzofulvene (BF) route is favored over the naphthvalene mechanism by ∼6 kcal/mol and is energetically lower than the norcaradiene-vinylidene mechanism (NVM) for the azulene-naphthalene rearrangement (Ea ∼ 76.5 (74.6) kcal/mol). Moreover, contrary to older reports, we observe that a pathway involving indenylcarbene intermediates is a viable, alternate mechanism. Therefore, the naphthalene automerization is expected to take place during azulene pyrolysis, especially under conditions of low-pressure FVP, where it will be aided by chemical activation. Furthermore, thermal azulene-azulene isomerization is feasible through vinylidene-acetylene-vinylidene (VAV), dehydrotriquinacene (DTQ), and azulvalene (AV) pathways with activation energies lying below that required for the azulene-naphthalene conversion, i.e., the NVM. These results, together with the previously published NVM, provide reasonable explanations for most of the products of the thermal azulene-naphthalene rearrangement.

Abatement of Naphthalene by Persulfate Activated by Goethite and Visible LED Light at Neutral pH: Effect of Common Ions and Organic Matter

Naphthalene (NAP) has received particular attention due to its impact on the environment and human health, mandating its removal from water systems. In this work, the abatement of NAP in the aqueous phase was achieved using persulfate (PS) activated by Fe (III) and monochromatic LED light at a natural pH. The reaction was carried out in a slurry batch reactor using goethite as the Fe (III) source. The influence of the PS concentration, goethite concentration, irradiance, temperature and presence of organic matter, chloride, and bicarbonate on the abatement of NAP was studied. These variables were shown to have a different effect on NAP removal. The irradiance showed a maximum at 0.18 W·cm−2 where the photonic efficiency was the highest. As for the concentration of goethite and PS, the influence of the first one was negligible, whereas for PS, the best results were reached at 1.2 mM due to a self-inhibitory effect at higher concentrations. The temperature effect was also negative in the PS consumption. Regarding the effect of ions, chloride had no influence on NAP conversion but carbonates and humic acids were affected. Lastly, this treatment to remove NAP has proved to be an effective technique since minimum conversions of 0.92 at 180 min of reaction time were reached. Additionally, the toxicity of the final samples was decreased.

Plasma-Catalytic Reforming of Naphthalene and Toluene as Biomass Tar over Honeycomb Catalysts in a Gliding Arc Reactor.

Biomass gasification is a promising and sustainable process to produce renewable and CO2-neutral syngas (H2 and CO). However, the contamination of syngas with tar is one of the major challenges to limit the deployment of biomass gasification on a commercial scale. Here, we propose a hybrid plasma-catalytic system for steam reforming of tar compounds over honeycomb-based catalysts in a gliding arc discharge (GAD) reactor. The reaction performances were evaluated using the blank substrate and coated catalytic materials (γ-Al2O3 and Ni/γ-Al2O3). Compared with the plasma alone process, introducing the honeycomb materials in GAD prolonged the residence time of reactant molecules for collision with plasma reactive species to promote their conversions. The presence of Ni/γ-Al2O3 gave the best performance with the high conversion of toluene (86.3%) and naphthalene (75.5%) and yield of H2 (35.0%) and CO (49.1%), while greatly inhibiting the formation of byproducts. The corresponding highest overall energy efficiency of 50.9 g/kWh was achieved, which was 35.4% higher than that in the plasma alone process. Characterization of the used catalyst and long-term running indicated that the honeycomb material coated with Ni/γ-Al2O3 had strong carbon resistance and excellent stability. The superior catalytic performance of Ni/γ-Al2O3 can be mainly ascribed to the large specific surface area and the in situ reduction of nickel oxide species in the reaction process, which promoted the interaction between plasma reactive species and catalysts and generated the plasma-catalysis synergy.

Effective catalytic steam reforming of naphthalene over Ni-modified ZSM-5 via one-pot hydrothermal synthesis

Ni-modified ZSM-5 catalysts are prepared by a one-pot hydrothermal synthesis method and applied to the steam reforming of naphthalene as a tar model compound. The effects of the reaction temperature, silica-alumina ratio (Si/Al) and metal content on the catalytic performance for reforming naphthalene are investigated. Characterization results indicate that the Ni-modified ZSM-5 catalysts maintain the original MFI structure of ZSM-5 and a portion of Ni is successfully introduced into the zeolite structure. When the reaction temperature is 800 °C, the conversion efficiency of naphthalene achieves 91.5% with a high yield (6.75%) of hydrogen. Zeolite catalysts with higher Si/Al ratios improve the conversion of naphthalene to syngas, demonstrating their better catalytic activity. An appropriate active metal content (2.4 wt%) contributes to the catalytic performance of the catalyst owing to the strong metal-support interaction, resulting in resistance to sintering and carbon deposition. The reaction mechanism involved in the catalytic reforming of naphthalene is proposed. The application of a novel one-pot hydrothermal synthesis method greatly promoted the catalytic activity of Ni@ZSM-5, which provided an appropriate and universal approach for the improvement and optimization of tar reforming catalysts.

Influence of Reduction Temperature on the Structure and Naphthalene Hydrogenation Saturation Performance of Ni2P/Al2O3 Catalysts

Jet fuel rich in hydroaromatics and cycloalkanes could be derived from direct coal liquefaction oil via the hydrogenation saturation process. Developing an efficient catalyst to transform naphthalene hydrocarbons to hydroaromatics and cycloalkanes with high selectivity plays a significant role in realizing the above hydrogenation saturation process. In this work, Ni2P/Al2O3 catalysts were prepared at different reduction temperatures via the thermal decomposition of hypophosphite. We investigated the influence of reduction temperature and the results showed that reduction temperature had an important impact on the properties of Ni2P/Al2O3 catalysts. When the reduction temperature was 400 °C, the Ni2P particle size of the Ni2P/Al2O3 catalyst was 3.8 nm and its specific surface area was 170 m2/g. Furthermore, the Ni2P/Al2O3 catalyst reduced at 400 °C obtained 98% naphthalene conversion and 98% decalin selectivity. The superior catalytic activity was attributed to the smaller Ni2P particle size, higher specific surface area and suitable acidity, which enhanced the adsorption of naphthalene on Ni2P/Al2O3 catalyst.

Catalytic Tar Conversion in Two Different Hot Syngas Cleaning Systems

Tar in the product gas of biomass gasifiers reduces the efficiency of gasification processes and causes fouling of system components and pipework. Therefore, an efficient tar conversion in the product gas is a key step of effective and reliable syngas production. One of the most promising approaches is the catalytic decomposition of the tar species combined with hot syngas cleaning. The catalyst must be able to convert tar components in the synthesis gas at temperatures of around 700 °C downstream of the gasifier without preheating. A Ni-based doped catalyst with high activity in tar conversion was developed and characterized in detail. An appropriate composition of transition metals was applied to minimize catalyst coking. Precious metals (Pt, Pd, Rh, or a combination of two of them) were added to the catalyst in small quantities. Depending on the hot gas cleaning system used, both transition metals and precious metals were co-impregnated on pellets or on a ceramic filter material. In the case of a pelletized-type catalyst, the hot gas cleaning system revealed a conversion above 80% for 70 and 110 h. The catalyst composed of Ni, Fe, and Cr oxides, promoted with Pt and impregnated on a ceramic fiber filter composed of Al2O3(44%)/SiO2(56%), was the most active catalyst for a compact cleaning system. This catalyst was catalytically active with a naphthalene conversion of around 93% over 95 h without catalyst deactivation.

The effect of steam concentration on hot syngas cleaning by activated carbons

Activated carbons are recognised as inexpensive, easily available, and efficient catalysts for tar cracking reactions at high temperatures. Their use in hot syngas cleaning is limited by the rapid deactivation resulting from the coke deposition, and the consequent masking phenomenon over the activated carbon surface. This study contributes to a better understanding of the problem and sheds light on possible solutions, by investigating how the temperature (750 °C–850 °C) and the steam concentration (0%–10%) can affect the extent of the water-gas and reforming reactions occurring between steam and the coke covering the catalyst surface. The activated carbons have been fully characterised before and after the tests utilizing naphthalene as a tar model compound, to study the evolution of their structure after long duration tests. Steam positively affects the naphthalene conversion efficiency, preserving the characteristics of the material. For example, at a temperature of 800 °C and a steam concentration of 7.5%, a naphthalene conversion of over 90% is achieved even after 7 h of testing. XRD and Raman spectroscopy analyses suggest that naphthalene cracking produces a coke layer that is more amorphous and, above all, more reactive towards the water gas reaction than the original activated carbon structure.

Catalytic conversion characteristics of tar at different temperatures during circulating fluidized bed gasification

Char catalytic conversion of tar at different temperatures was carried out on a laboratory-scale circulating fluidized bed to providing theoretical support for the removal of tar. Various modern detection techniques were used to analyze the gas, tar and char, such as the gas chromatograph, the specific surface area analyzer and the gas chromatograph mass spectroscopy (GC-MS). The efficiency of tar conversion (ETC) could be effectively improved by the increasing temperature, while transformation characteristics of the organic compounds of the used tar also changed. When the temperature increased from 850 °C to 900 °C, the catalytic capability of char was improved, resulting a reducing of the heavy polycyclic aromatic hydrocarbon compounds (heavy PAH compounds) of the produced tar. When the temperature increased from 900 °C to 950 °C, the catalytic capability of char weakened, so the heavy PAH compounds increased, caused by the intensifying of tar thermal cracking. At the tested temperature (850–950 °C), the conversion of naphthalene, the most abundant organic compound in the used tar, has not been seem a significant change, showing a selectivity of the char catalyst.

Atomic Layer Deposition Coated Filters in Catalytic Filtration of Gasification Gas

Steel filter discs were catalytically activated by ALD, using a coating of supporting Al2O3 layer and an active NiO layer for gas cleaning. Prepared discs were tested for model biomass gasification and gas catalytic filtration to reduce or eliminate the need for a separate reforming unit for gasification gas tars and lighter hydrocarbons. Two different coating methods were tested. The method utilizing the stop-flow setting was shown to be the most suitable for the preparation of active and durable catalytic filters, which significantly decreases the amount of tar compounds in gasification gas. A pressure of 5 bar and temperatures of over 850 °C are required for efficient tar reforming. In optimal conditions, applying catalytic coating to the filter resulted in a seven-fold naphthalene conversion increase from 7% to 49%.

Front Cover Picture: Semi‐Rational Engineering of Toluene Dioxygenase from Pseudomonas putida F1 towards Oxyfunctionalization of Bicyclic Aromatics (Adv. Synth. Catal. 21/2021)

The front cover picture, designed and donated by WesWizzArt and painted by the Mexican artist Way (Wayra Castillo-Guerrero), illustrates the toluene dioxygenase-catalyzed conversion of aromatics. The enzyme exhibits a high affinity for monocyclic, but only a low one for bicyclic substrates. A semi-rational designed mutant library opened the way for the conversion of the bicyclic substrates naphthalene, 1,2,3,4-tetrahydroquinoline and 2-phenylpyridine at unprecedented rates, enabling the biosynthesis of their products in substantial quantities. Variants at active site positions M220, A223 and F366 exhibited a major influence in product formation and selectivity. Details can be found in the Research Article by Bernhard Hauer and co-workers (J. L. Wissner, J. T. Schelle, W. Escobedo-Hinojosa, A. Vogel, B. Hauer, Adv. Synth. Catal. 2021, 363, 4905–4914; DOI: 10.1002/adsc.202100296).

Development of catalytic ceramic filter candles for tar conversion

A catalyst with a high activity in tar conversion, impregnated on the ceramic hot gas filter material was developed. The aim of the experiments was to estimate the light-off temperature of the catalytic filter elements for naphthalene (tar model compounds) conversion and the long-term catalytic stability at a temperature of 700 °C. Configuration of the catalyst was optimized through improvements in coking resistance and long-term stability. The composition and morphology parameters of the filter material were considered. Both the impregnation methods and the composition of the impregnation solution were investigated and validated. The catalyst composed of Ni, Fe, Cr oxides, promoted with Pt (AlSi-Cat43-Pt), and impregnated on the ceramic-fiber filter composed of Al2O3(44%)/SiO2(56%) was found to be the most active catalyst. The designated catalyst was catalytically active at temperatures of about 700 °C, with a naphthalene conversion of around 93% over 95 h without catalyst deactivation. We found that the steam and gas compositions had an influence on the catalytic activity of the filter elements. The same catalytic filter was catalytically active for 115 h at a low concentration of H2O (10 vol%) and H2 (3 vol%) with a naphthalene conversion of 98% at 790 °C without significant deactivation.

Alkylation of naphthalene with n-butene catalyzed by liquid coordination complexes and its lubricating properties

With the development of coal chemical industry, large amounts of naphthalene and n-butene are produced, and converting them into high value-added products through alkylation has gained particular importance and interest. In this work, liquid coordination complexes (LCCs) were used as acid catalysts for the first time in the naphthalene alkylation reaction under mild conditions to obtain multi-butylnaphthalenes with high yield. Various reaction conditions were thoroughly investigated. The LCC consisting of urea and AlCl3 showed excellent catalytic performance under optimal reaction conditions, giving 100% conversion of naphthalene and 99.66% selectivity towards multi-butylnaphthalenes. Combining the catalyst properties and catalytic results, a plausible reaction mechanism was proposed. The lubricating properties of the synthesized products were investigated for their potential application as lubricating base oils. The synthesized multi-butylnaphthalenes showed comparable physicochemical properties and tribological performances as the commercial cycloalkyl base oil.