Decalin Dehydrogenation Research Articles

INVESTIGATION OF THE TRANSFORMATION OF MODEL PETROLEUM RAW MATERIALS UNDER CRACKING CONDITIONS OVER A REGENERATED SPENT HYDROTREATMENT CATALYST

The physicochemical properties and catalytic activity of regenerated spent aluminium-cobalt-molybdenum hydrotreatment catalyst have been investigated under cracking conditions in the model systems n-dodecane - toluene and decalin - toluene - n-hexane. A series of experiments to study the catalytic activity of the sample was carried out using a flow-type laboratory installation within the temperature range 430-470 °C, nitrogen pressure 1.6 MPa, liquid hourly space velocity 0.5-3.0 h-1. The directions of transformation were determined for paraffin and naphthenic hydrocarbons by means of gas chromatography - mass spectrometry. Paraffin hydrocarbons enter into cracking, isomerisation and compaction reactions. Naphthenic hydrocarbons are transformed into the products of isomerisation, dehydrogenation and compaction. Predominant dehydrogenation of decalin with the formation of naphthalene and hydrogen is observed in the system under investigation. A positive role of hydrogen in thermodestructive processing of heavy oil residues is observed due to the hydrogenation of nonlinear olefin hydrocarbons and aromatic hydrocarbon intermediates, which decreases the rate of coke formation. The corresponding reaction rate constants were calculated, and the results were analysed. Conclusions are drawn about the prospects of introducing a regenerated spent hydrotreatment catalyst into the procedure of thermodestructive processing of heavy oil residues.

Comparative Study of the Dehydrogenation of Decalin on Pd/SiO2, Pd/MCM-48, and Pd/SBA-15 Catalysts

Comparative Study of the Dehydrogenation of Decalin on Pd/SiO2, Pd/MCM-48, and Pd/SBA-15 Catalysts

Dehydrogenation of cycloalkanes over Pt/SBA-15 for endothermic cooling

Dehydrogenation of cyclohexane, methylcyclohexane, and decalin was studied on Pt/SBA-15 between 773 and 873 K for application to engine cooling in hypersonic aircraft. While the reactions were unstable at 1 bar, the reactions showed no evidence for deactivation at pressures of 20 and 60 bar for at least 4 h. Selectivities for dehydrogenation of cyclohexane to benzene and methylcyclohexane to toluene were greater than 90% in all cases. The reaction of decalin proceeded sequentially, forming primarily tetralin at low reactor space times and naphthalene at higher space times. The reaction of 50% mixtures of n-dodecane and decalin at 773 K showed negligible conversion of n-dodecane but the reaction of decalin was similar to what was observed for a pure decalin feed. Heat measurements gave endothermicities that were in good agreement with standard reaction enthalpies.

Effect of light alkanes and aromatics on decalin dehydrogenation over noble metal catalysts: A new strategy for the development of naphthalene-based LOHCs

The use of the naphthalene/decalin pair as a liquid organic hydrogen carrier has gained increasing interest due to its high hydrogen loading capacity and industrial availability. However, a major challenge in its application is the fact that naphthalene is a solid at ambient conditions, leading to the solidification of the unloaded organic carrier. To address this limitation, small amounts of light organics, such as monoaromatics or cycloalkanes, can be added. In this study, we investigated the dehydrogenation of decalin over various supported precious catalysts (Pt, Pd, Rh, Ru; supported on both activated carbon and alumina) in a stirred batch reactor at 200 °C. Initial experiments were conducted with pure decalin, and we found that Pt/C provided the best performance. Subsequently, we studied the dehydrogenation of decalin in mixtures with different solvents (cyclohexane, methylcyclohexane, benzene, and toluene in the concentration range of 10–40% of the light hydrocarbon). Our results show that the addition of cycloalkanes did not affect the main reaction, while aromatic compounds exhibited weak inhibition. A Langmuir-Hinshelwood kinetic model has been proposed for predicting this behavior, taking into account the significant inhibitory impacts of naphthalene and, when present, the aromatic additive.

Synergetic effect of Pt–Pd bimetallic nanoparticle on MgAl2O4 support in hydrogen production from decalin dehydrogenation

Synergetic effect of Pt–Pd bimetallic nanoparticle on MgAl2O4 support in hydrogen production from decalin dehydrogenation

Preparation of Pt/MgAl2O4 Decalin Dehydrogenation Catalyst for Chemical Hydrogen Storage Application

Preparation of Pt/MgAl2O4 Decalin Dehydrogenation Catalyst for Chemical Hydrogen Storage Application

Efficient and stable Pt/CaO-TiO2-Al2O3 for the catalytic dehydrogenation of cycloalkanes as an endothermic hydrocarbon fuel

The dehydrogenation of liquid hydrocarbon fuel is a potential endothermic reaction for the regenerative cooling of advanced aircraft. The high active and stable dehydrogenation catalyst plays a vital role in the catalytic heat exchange process. Herein, we show that a CaO-modified TiO2-Al2O3 supported Pt catalyst (Pt/CTA) is efficient and stable for the dehydrogenation of cycloalkanes (methylcyclohexane and decalin) under a supercritical condition. Adding an appropriate content of CaO (5 wt%) improves the catalyst durability. For the decalin dehydrogenation reaction (600 °C, 4 MPa, and WHSV = 208.8 h−1), the Pt/CTA maintains 27.9 wt% conversions at 600 min. For the methylcyclohexane dehydrogenation reaction (600 °C, 4 MPa, and WHSV = 188.4 h−1), the Pt/CTA maintains 42.6 wt% conversions at 600 min. The declines of cycloalkanes dehydrogenation conversion are < 7.0 % within 600 min, and no obvious sintering of Pt particles is observed. For a comparison, γ-Al2O3 supported Pt catalyst (Pt/A) exhibits poor catalytic activity and stability, and the conversion decreases to below 10 wt% at 180 min due to severe coke deposition and sintering of Pt particles over the catalysts. The characterization analyses demonstrate that the addition of CaO facilitates the formation of oxygen vacancy defects, thereby increasing the electron density of Pt particles (electronic effect) and promoting encapsulation of Pt particles (geometric effect). Furthermore, the addition of CaO reduces the acid amount and weakens the strength of acid sites over TiO2/Al2O3, inhibiting catalyst deactivation by mitigating coke formation. However, excessive CaO addition (10 wt%) rapidly decreases the surface area of the support, resulting in low dispersion and sintering of Pt particles, ultimately leading to poor catalytic activity and stability.

Efficient and Stable Pt/CaO-TiO &lt;sub&gt;2&lt;/sub&gt;-Al &lt;sub&gt;2&lt;/sub&gt;O &lt;sub&gt;3&lt;/sub&gt; for Catalytic Dehydrogenation of Decalin as an Endothermic Hydrocarbon Fuel

Efficient and Stable Pt/CaO-TiO &lt;sub&gt;2&lt;/sub&gt;-Al &lt;sub&gt;2&lt;/sub&gt;O &lt;sub&gt;3&lt;/sub&gt; for Catalytic Dehydrogenation of Decalin as an Endothermic Hydrocarbon Fuel

Effect of decalin as hydrogen-donor for in-situ upgrading of heavy crude oil in presence of nickel-based catalyst

The effect of decalin as hydrogen-donor on the catalytic and non-catalytic hydrothermal upgrading of heavy crude oil was studied. The donating (dehydrogenation) capacity and conversion of decalin in presence of nickel-based catalyst (nickel (II) stearate) were evaluated. In addition, the changes in composition of dehydrogenated products, release and consumption of hydrogen during decalin dehydrogenation in presence and absence of Ni-stearate and heavy crude oil were studied. All of the upgrading and dehydrogenation experiments were carried out at 300 °C, 72 bar (1044.27 psi) and 24 h of reaction time. The upgrading of heavy crude oil in presence of decalin and Ni-stearate exhibited a good performance for conversion of decalin as well as for promoting the in-situ upgrading of heavy crude oil. The maximum decalin conversion level was found to be 21.95% in the presence heavy crude oil, water and nickel stearate. Ni-stearate was mainly in-situ transformed into particles of NiO and Ni3S2, which took the role of active phases for catalyzing the dehydrogenation of decalin and promoting heavy crude oil upgrading. The use of decalin as a hydrogen-donor together with catalyst resulted in high viscosity reduction (69.2%), increase of saturates content (especially low molecule weight alkanes C10-C20), decrease of resins and asphaltenes content, and removal of sulfur and nitrogen.

Partial positively charged Pt in Pt/MgAl2O4 for enhanced dehydrogenation activity

Platinum group metals hold pronounced potential for the dehydrogenation process of liquid organic hydrogen carriers (LOHCs) such as decalin, but the strong adsorption of dehydrogenation product has suppressed the moving forward of these catalysts. Herein, we described that the strong interactions between Pt and MgAl2O4 trigger partial positively charged Pt, which mitigates the adsorption of naphthalene on highly active Pt sites, thus achieving an outstanding decalin dehydrogenation activity that is nearly twice that of state-of-the-art Pt/CNF catalysts. As revealed by various characterization outcomes and DFT calculations, the strong electronic interactions between Pt and spinel oxygen surface resulted in partial positively charged Pt on MgAl2O4, which inhibits the electron transfer from Pt to unsaturated carbon of naphthalene, thus weakening the bond strength between Pt and naphthalene. As a result, the combination of small-sized Pt nanoparticles and facile desorption of products endows tremendous dehydrogenation activity of Pt/MgAl2O4. This study may shed new light on the rational construction of highly efficient metal catalysts for the application of LOHCs.

Carbon nanotubes-supported Pt catalysts for decalin dehydrogenation to release hydrogen: A comparison between nitrogen- and oxygen-surface modification

The effect of carbon nanotubes (CNT) surface chemistry on supported Pt catalytic performance in decalin dehydrogenation to release hydrogen was investigated through modifying CNT surface with nitrogen and oxygen functional groups. The results indicate that the mechanism of improving Pt dispersion is different for nitrogen and oxygen groups. Although oxygen groups can improve Pt dispersion, their electron donating feature inhibits the electron transfer from Pt to carbon support. DFT calculations have clarified the negative effect of oxygen group on decalin dehydrogenation in aspect of adsorption energy. Moreover, the abundant oxygen species on catalyst surface lead to a bad wettability of catalyst in non-polar reaction liquid, which significantly weaken the approaching of reactant onto catalyst. Therefore, the introduction of oxygen groups is unfavorable to the catalyst activity. In contrast, the highly dispersed Pt nanoparticles anchored by nitrogen groups may be one reason for the high activity of Pt supported on CNT modified with nitrogen groups. Furthermore, nitrogen groups promote the electron transfer from Pt to CNT, leading to lower Pt d-band and weaker naphthalene adsorption. Meanwhile little change happened on the non-polar characteristics of CNT during nitrogen doping treatment. Therefore, the introduction of nitrogen functional groups is conducive to the catalytic dehydrogenation.

Hydrogen Release from Decalin by Catalytic Dehydrogenation over Supported Platinum Catalysts

Pt catalysts supported on the commonly used supports Al2O3, SiO2 and on mesostructured silicates SBA-15 and MCM-48 were examined in the dehydrogenation of decalin, that is the promising liquid organic hydrogen carrier (LOHC). Synthesized catalysts were studied by low-temperature nitrogen adsorption, temperature programmed reduction, high-resolution transmission electron microscopy. The catalysts are characterized by various dispersion of platinum. The activity of catalysts in decalin dehydrogenation decreases in the following order Pt/MCM-48 > Pt/SBA-15 > Pt/SiO2 > Pt/Al2O3. Pt/MCM-48 catalyst allows to release hydrogen in the decalin amount of 5.7 wt% and can be considered the promising LOHC hydrogen storage technology.

Pt Nanoparticles Supported on Nitrogen doped Carbon as an Efficient Catalyst for Decalin Dehydrogenation

A novel Pt/CN catalyst was synthesized by sodium borohydride treatment. The physical and chemical properties of Pt/CN catalyst were characterized by X-ray diffraction (XRD), brunner-emmet-teller (BET), transmission electron microscope (TEM) and High-resolution transmission electron microscopy (HRTEM). The characterized results showed that the catalyst has a high specific surface area, mesoporous structure and the mean size of Pt nanoparticles is 2.59 nm. Subsequently, the catalytic performance of Pt/CN catalyst for decline dehydrogenation was studied. Pt/CN catalyst exhibited excellent performance in decalin dehydrogenation with the conversion of decalin was 30.70%, and the selectivity of naphthalene was 90.86% at 200 ℃ for 150 minutes. When the reaction temperature increased to 210 ℃, the conversion of catalyst increased to 52.02%, and the selectivity of naphthalene reduced to 90.21%. The possible reason may be attributed to the difficulty in converting decalin to tetralin. This paper would provide a novel method for the synthesis of efficient dehydrogenation catalyst of decalin..

Density functional theory study of decalin dehydrogenation for hydrogen release on Pt(111) and Pt(211)

The catalytic dehydrogenation of organic hydrides on transition metal surfaces is of fundamental importance to hydrogen storage technologies based on organic hydrides. Density functional theory (DFT) calculations were performed to study the dehydrogenation of both trans- and cis-decalin on flat Pt(111) and stepped Pt(211) surfaces. Considering that long-range van der Waals (vdW) forces play an important role in the adsorption and reaction of large organic molecules on metal surfaces, a recently developed vdW-inclusive method (optB88-vdW) was adopted in the computational procedure for accurate adsorption results. It revealed that the adsorption energies of decalin on Pt(111) and Pt(211) have little difference due to the dominant role of vdW forces during adsorption instead of chemical interaction. The possible dehydrogenation pathways of decalin on Pt(211) and Pt(111) are found to be clearly dependent on the isomeric molecular structures of decalin and the metal crystal facets. The dehydrogenation is more favourable for cis-decalin than for trans-decalin when on Pt(211) compared to on Pt(111). Taking the Gibbs free energy calculated for the experimental conditions (500 K, 1 atm) as the descriptor, it was observed that the energy barrier for the desorption of reaction product (naphthalene) is much higher than that of every elementary dehydrogenation step. Therefore, desorption of naphthalene is critical in determining the dehydrogenation reaction rate, especially on stepped Pt surfaces.

Searching for efficient defect types in carbon nanofibers to promote supported Pt catalytic activity for dehydrogenation reaction

• Three CNFs with different defective degrees are synthesized and identified. • N-doping of CNFs is implemented using in-situ synthesis and post treatment methods. • Thermal treatment of N-doped CNFs is adopted for generating edge-like defects. • Pt catalysts supported over various CNFs display different catalytic activity in dehydrogenation. • Edges and edge-like defects in CNFs are proven to be the most efficient active sites in catalysis. Three kinds of carbon nanofibers (CNFs) with different microstructures: platelet CNFs (CNFs-P), fishbone CNFs (CNFs-F) and tubular CNFs (CNFs-T) were synthesized as Pt catalyst supports for decalin dehydrogenation to release hydrogen. Different types of defects including doped nitrogen and edge-like sites were purposefully introduced into three pristine CNFs by employing N-doping and thermal treatment methods. The defective properties of the CNFs were identified by combining the intensity ratio and full width at half maximum of D and G bands derived from Raman spectra of the CNFs. It was revealed together with XPS analysis of Pt 4f 7/2 binding energy that the electronic property of Pt nanoparticles is very sensitive to the surface defect density of CNF supports. Further catalytic performance evaluation showed that Pt supported on the CNFs-P which are featured of the largest quantity of exposed edge sites can provide the most proper electronic property of the catalyst due to suitable metal-support interaction, thereby affording the highest catalytic activity. Moreover, N-doping by both in-situ synthesis and post-treatment manner can favor the Pt catalysts on the tubular and fishbone CNFs to increase their activity, but do harm to the activity of the Pt/CNFs-P. Thermal treatment of N-doped CNFs can generate new edge-like defects by removing N-species, thus beneficial to the activity of Pt catalysts on either tubular or fishbone CNFs. Therefore, the edge sites and edge-like defects on the surface of CNFs are proven to be the best ones, which can promote the catalytic activity of the supported Pt nanoparticles for the dehydrogenation reaction efficiently.

Insight into the support effect on the particle size effect of Pt/C catalysts in dehydrogenation

The support effect and metal particle size effect, which are often intertwined, are two critical factors influencing the activity of a supported metal catalyst. To clarify each effect on the activity of carbon-supported Pt catalysts, a series of Pt/C catalysts were elaborately prepared by adopting two carbon materials with distinct microstructures—that is, carbon nanofibers (CNFs) vs carbon nanotubes (CNTs)—and by altering the Pt particle size from 1 to 9 nm on each support. The catalytic activity was assessed during the dehydrogenation of decalin to release hydrogen. Molecular dynamics simulations based on reactive force field and density functional theoretical calculations were employed in combination with catalyst characterization techniques. Significant differences in both the geometric structure and electronic properties of Pt clusters between two kinds of Pt/C catalysts have been found, especially in the Pt particle size range smaller than 2 nm. The edge planes of CNFs can interact much more strongly with Pt atoms than the basal planes of CNTs do, hence forming a more dispersive and simultaneously more active Pt-C boundary for reaction proceeding. The carbon support effect dominates the activity divergence in the smaller size range (<2 nm), while the Pt particle size effect prevails on the catalysts with medium Pt particles (2–4 nm). Both effects can fade out with continually increasing Pt particle size.

Synthesis of Pt/C Nanocatalysts by Galvanic Replacement for Dehydrogenation of Decalin

Synthesis of Pt/C Nanocatalysts by Galvanic Replacement for Dehydrogenation of Decalin

Different catalytic behaviors of Pd and Pt metals in decalin dehydrogenation to naphthalene

Decalin is more easily dehydrogenated on Pt catalyst than Pd while the dehydrogenation of tetralin is more facile on Pd than Pt.

Kinetic behavior of Pt catalyst supported on structured carbon nanofiber bed during hydrogen releasing from decalin

It is of great significance to develop practical catalysts with macroscopic sizes for hydrogen releasing. In the present study, two kinds of structured carbon nanofiber (CNF) monoliths synthesized by growing CNFs on the graphite fiber felt in NiC2H6 and FeCO systems respectively have been used as the supports of Pt catalysts. The catalytic performances have been evaluated in the dehydrogenation of decalin for hydrogen releasing in a tubular flowing reactor. The structure characterization and the reaction kinetic analysis have been conducted upon different supports and catalysts to clarify the main factors influencing the apparent reaction rate. A comparison study has been made with the Pt catalysts supported on activated carbon (AC) pellets. The results show that two structured Pt catalyst beds perform much better at the aspects of both intrinsic catalysis and mass transfer than the catalysts based on AC pellets. The superior catalytic activity of the structured Pt catalysts can be assigned to the smaller Pt particle size and more proper interaction between the metal and the support. The excellent mass diffusion efficiency on both the external and internal sides of fibrous CNF interface can be correlated to the high large-pore porosity and the thin CNF layer in the structured supports, which have been manifested by the calculation of the mass diffusion limitation criteria.

Pt@Cu/C Core-Shell Catalysts for Hydrogen Production Through Catalytic Dehydrogenation of Decalin

Pt@Cu/C core-shell catalysts were successfully prepared by impregnation of a carbon support with copper precursor, followed by transmetallation between platinum and copper. The Pt@Cu/C core-shell catalysts retained a core of copper with a platinum surface. The prepared catalysts were used for hydrogen production through catalytic dehydrogenation of decalin for eventual application to an onboard hydrogen supply system. Pt@Cu/C core-shell catalysts were more efficient at producing hydrogen via decalin dehydrogenation than Pt/C catalysts containing the same amount of platinum. Supported core-shell catalysts utilized platinum highly efficiently, and accordingly, are lower-cost than existing platinum catalysts. The combination of impregnation and transmetallation is a promising approach for preparation of Pt@Cu/C core-shell catalysts.