Hydrogenation Of Aromatic Compounds Research Articles

Rhodium/Graphite for the Hydrogenation of Aromatic Compounds

Rhodium on graphite (Rh/Gr, C24Rh) was prepared with a view to using it for the hydrogenation of carbocyclic and heterocyclic ­aromatic compounds. Thus, the hydrogenation of aromatic compounds (1-2 mmol) was carried out in the presence of Rh/Gr to give the corresponding reduced products (21 examples). The Rh/Gr catalyst was recovered by filtration, and was reused three times with loss of catalytic activity.

Aromatic reduction of residue oil of naphtha cracking over bimetallic Pt−Pd catalysts supported on mesoporous molecular sieve

An Al-containing mesoporous molecular sieve (Al-MMS) was prepared by hydrolysis of H2SiF6 and Al(NO3)3·9H2O. NH3-TPD results suggest that the acidity of Al-MMS was less than that of dealuminated zeolite. Y. The potential use of mesoporous molecular sieve as a new support material for dearomatization of residue oil of naphtha cracking was described. In case of C9+ and PGO feed, Pt−Pd/Al-MMS showed a higher activity than Pt−Pd/dealuminated zeolite Y catalyst. This is ascribed to its better accessibility of bulky molecules, and much less cracking activity due to mild acidity, indicating high yield of liquid. Thus, Pt−Pd/Al-MMS catalyst can be applied effectively to the hydrogenation of aromatic compounds in the residue oil of a commercial naphtha cracker.

Experimental and Kinetics Studies of Aromatic Hydrogenation in a Two-Stage Hydrotreating Process using NiMo/Al2O3 and NiW/Al2O3 Catalysts

In this work, hydrogenation of aromatic compounds in light gas oil derived from Athabasca bitumen was carried out using a single- and two-stage hydrotreating processes. Experiments were performed in a trickle-bed reactor using two catalysts namely NiMo/Al2O3 and NiW/Al2O3. NiMo/Al2O3 was used in the first stage for nitrogen and sulphur containing heteroatoms removal whereas NiW/Al2O3 was used in the second stage for saturation of the aromatic rings in the hydrocarbon species. Temperature and liquid hourly space velocity (LHSV) were varied from 350-390°C and 1.0-1.5 h−1, respectively, while pressure was maintained constant at 11.0 MPa for all experiments. Results from single-stage were compared with those from two-stage process on the basis of reaction time. Kinetic analysis of the single-stage hydrotreating process showed that HDA and HDS activities were retarded by the presence of hydrogen sulphide that is produced as a by-product of the HDS process. However, with inter-stage removal of hydrogen sulphide in the two-stage process, significant improvement of the HDA and HDS activities were observed. On a réalisé dans ce travail l'hydrogénation de composés aromatiques dans du gasoil léger dérivé de bitumes d'Athabasca à l'aide de procédés d'hydrotraitement mono et bi-étagé. Des expériences ont été menées dans un réacteur à lit ruisselant avec deux catalyseurs, à savoir NiMo/Al2O3 et NiW/Al2O3. NiMo/Al2O3 a été utilisé dans le premier étage pour l'azote et le retrait des hétéroatomes contenant du soufre, tandis que NiW/Al2O3 a été utilisé dans le second étage pour la saturation des anneaux aromatiques dans les espèces d'hydrocarbures. On a fait varier la température et le volume par volume par heure (LHSV) de 350-390°C et de 1,0-1,5 h−1, respectivement, tandis que la pression est maintenue constante à 11,0 MPa pour toutes les expériences. Les résultats du procédé mono-étagé sont comparés à ceux du procédé bi-étagé sur la base du temps de réaction. L'analyse cinétique du procédé d'hydrotraitement mono-étagé montre que les activités de l'HDA et l'HDS sont retardées par la présence de sulfure d'hydrogène qui est produit par le procédé HDS. Toutefois, avec le retrait de l'hydrogène sulfuré entre les deux étages dans le procédé bi-étagé, on observe une amélioration importante des activités de l'HDA et l'HDS.

Inhibition of the Hydrogenation and Hydrodesulfurization Reactions by Nitrogen Compounds over NiMo/Al2O3

The inhibiting effect of nitrogen compounds on the hydrogenation of aromatic compounds and on the hydrodesulphurization (HDS) of dibenzothiophene (DBT) and 4,6-dimethyl dibenzothiophene (4,6 DMDBT), has been systematically investigated over a commercial NiMo hydrotreating catalyst. Amongst the different nitrogen compounds considered, interestingly ammonia was found to have the strongest inhibition effect on hydrogenation as well as on hydrodesulfurization reactions. The inhibiting effects were found to increase in the order quinoline < tetrahydroquinoline < indole < indoline < ammonia for phenanthrene/tetralin hydrogenation and HDS reactions. The molecules with nitrogen atoms having higher negative Mulliken charges showed higher adsorption constants.

Hydrogenation of aromatic compounds during gas oil hydrodewaxing: I. Effect of ruthenium content and method of nickel catalyst preparation

Ni-based (8 wt.% NiO) dewaxing catalysts for the hydroconversion of the hydroraffinate of oil fraction ( d 20 °C = 0.845 g/cm 3; cloud point (CP) = −2 °C; aromatics = 25.8 wt.%; S = 25 ppm) were modified with Ru. The effect of Ru content (0.6, 0.75 and 0.9 wt.% of RuO 2) and the methods of Ni catalyst preparation were examined. The catalysts were characterised by N 2 sorption, TPR, ICP, XRD, SEM, XPS, H 2 chemisorption. Activity was tested in a continuous-flow system at 6 MPa (LHSV, 2.5 h −1; H 2:CH, 350 N m 3/m 3). NiO and RuO 2 were found to exert a synergic effect on catalytic activity. The rise in RuO 2 content from 0.6 to 0.9 wt.% increased the HDA of HON from 23 to 65% at 240 °C and was parallelled by a drop in CP (by about 15 °C). The effect of Ru was found to depend on the method of Ni catalyst preparation.

Performance Evaluation Studies of First- and Second-Stage Hydrocracking Catalysts Using Kuwait Vacuum Gas Oil Feedstocks

In a two-stage hydrocracking process, two types of catalyst are used to remove undesirable contaminants (such as S, N, hydrogenation of aromatic compounds, etc.) and convert the heavy feedstock to lighter products. In the present work, individual set of experiments were conducted to obtain information regarding activity and selectivity with emphasis on the evaluation of kinetic parameters of first- and second-stage commercial catalysts used in hydrocracking process. The performance tests were conducted in a down-flow fixed-bed hydrocracking pilot plant using a single reactor. The hydrotreating type A catalyst and hydrocracking type B catalyst were used individually with typical Kuwaiti refinery feedstocks, namely, hydrotreated vacuum gas oil (HVGO) and unconverted residual oil (UCRO), respectively. The order of reaction in this study shows first-order kinetics for HDS and HDN over CAT-A, and first-order hydrocracking conversion over CAT-B. For CAT-A the activation energies were found for HDS and HDN reactions at 22 and 27.3 kcal/gmole, while for CAT-B activation energies were 27.4 kcal/gmole.

Synthesis of Bipyridine‐Stabilized Rhodium Nanoparticles in Non‐Aqueous Ionic Liquids: A New Efficient Approach for Arene Hydrogenation with Nanocatalysts

AbstractA new approach to stabilize metal nanoparticles with polynitrogen ligands in ionic liquids (ILs) is described. Zerovalent metal nanospecies in the size range of 2.0 nm were easily prepared in various ionic liquids by chemical reduction of a rhodium salt with an excess amount of sodium borohydride (NaBH4) and efficiently stabilized by 2,2′‐bipyridine. The influence of the bipyridine ratio in various ILs according to the nature of the cation‐anion association was investigated. These nanocatalysts were evaluated in the hydrogenation of aromatic compounds in ILs under various catalytic conditions (P=1–40 bar, T=20–80 °C).

Rh/C-Catalyzed Hydrogenation of Aromatic Compounds in Water

A mild and facile method for hydrogenation of aromatic rings in water was successfully developed. Thus, arenes were treated with H2 in the presence of Rh/C in H2O to afford the corresponding cyclohexane derivatives in 73-95% yield (eq. 1). Hydrogenation of heteroaromatic compounds was also successfully performed. Thus, 2-amylfurane (eq. 2), 3-hydroxypyridine, and 3-pyridinecaxamide (eq. 3) were hydrogenated to afford the corresponding saturated compounds in 90%, 96%, and 97% yield, respectively.

A simple and reproducible method for the synthesis of silica-supported rhodium nanoparticles and their investigation in the hydrogenation of aromatic compounds

Colloidal suspensions of rhodium nanoparticles have been easily prepared in aqueous solution by chemical reduction of the precursor RhCl3·3H2O in the presence of the surfactant N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride (HEA16Cl) and further used to immobilize rhodium nanoparticles on silica by simple impregnation. The obtained silica-supported rhodium nanoparticles have been investigated by adapted characterization methods such as transmission electron microscopy and X-ray photoelectron spectroscopy. A particle size increase from 2.4 to 5 nm after the silica immobilization step and total elimination of the surfactant has been observed. This “heterogeneous” catalyst displayed good activities for the hydrogenation of mono-, di- alkylsubstituted and/or functionalized aromatic derivatives in water under atmospheric hydrogen pressure and at room temperature. In all cases, the catalyst could be recovered several times after a simple decantation or filtration and reused without any significant loss in catalytic activity. This supported catalyst has also been tested under higher hydrogen pressure giving rise to TOFs reaching 6430 h−1 at 30 bar and in terms of catalytic lifetime 30 000 TTO in 8.5 h for pure anisole hydrogenation at 40 bar.

Gas-Phase Kinetic Studies of Tetralin Hydrogenation on Pt/Alumina

The hydrogenation of aromatic compounds is a reaction of relevance in the improvement of diesel fuel quality. In this work, the kinetics of tetralin (1,2,3,4-tetrahydronaphthalene) hydrogenation over Pt/Al2O3 catalysts have been studied in an integral fixed bed reactor at 500 psig in the temperature range 553−573 K. A semiempirical Langmuir−Hinshelwood equation has been used to model the kinetics. The values of the kinetic parameters were determined by a nonlinear fitting, while the heats of adsorption for the hydrocarbons involved (tetralin and cis- and trans-decalin) were experimentally obtained by temperature-programmed desorption. The adsorption competition between tetralin and the hydrogenated products (cis- and trans-decalin) for surface active sites can be quantitatively traced to the higher heat of adsorption of tetralin compared to those of cis- and trans-decalins. As a result, while the activation energy for the cis−trans isomerization is significantly lower than the one for tetralin hydrogenati...

Control of pore size and shape selective catalysis of Pt-promoted acidic alkaline salts of dodecatungstophosphoric acid

Three kinds of shape selective reactions were realized over 0.5 wt% Pt M 2.1H 0.9PW 12O 40 (abbreviated as 0.5 wt% Pt–M2.1, M = Cs, Rb, and K) and 1.0 wt% Pt–Rb2.1 catalysts. The adsorption studies of argon, nitrogen, and organic molecules with different molecular sizes revealed that the pore distributions of all the catalysts were unimodal in micropore range and the pore sizes increased with increasing the sizes of alkaline ions. On 0.5 wt% Pt–Cs2.1 (pore width: 0.50 nm), n-butane (molecular size: 0.43 nm) was oxidized more easily than isobutane (0.50 nm). In contrast, both butanes were oxidized at similar rates on 0.5 wt% Pt–Rb2.1 (pore width: 0.60 nm) and 0.5 wt% Pt–K2.1 (larger than 0.60 nm) catalysts. In the hydrogenation of aromatic compounds over the 0.5 wt% Pt–Rb2.1, the high activity ratio of benzene (molecular size: 0.59 nm) to m-xylene (0.64 nm) suggests that reactant shape selectivity occurs due to its pore width. One weight % Pt–Rb2.1 promoted the highly selective skeletal isomerization of n-butane and n-pentane while 0.5 wt% Pt–Cs2.1 did not. The high selectivity of 1 wt% Pt–Rb2.1 is attributed to the pore size, together with the high acid strength estimated by NH 3-TPD.

Hydrodechlorination and hydrogenation of aromatic compounds over palladium on alumina in hydrogen-saturated water

The catalytic transformations of 1,2-dichlorobenzene, chlorobenzene, 4-chlorobiphenyl, γ-hexachlorocyclohexane (Lindane), naphthalene and phenanthrene were studied over palladium on alumina in hydrogen-saturated water (Pd/Al 2O 3/H 2) at room temperature and ambient pressure. The chlorinated benzenes were rapidly hydrodechlorinated and Lindane was dehydrochlorinated to benzene. Partial or complete hydrogenation was observed for biphenyl and the polycyclic aromatic hydrocarbons. The phenanthrene ring was cleaved at the 9,10-position. In general dechlorination reactions were faster than hydrogenation reactions.

Hydrogenation of Aromatic Compounds with a Rhodium Catalyst in Biphasic Systems

The reaction conditions for the catalytic reduction of single-ring aromatic compounds such as tetralin with chloro(1,5-hexadiene)rhodium(I) dimer in a biphasic mixture of hexane and an aqueous buffer containing a surface active agent have been investigated. The reaction proceeds most effectively in a dilute alkaline buffer with a low concentration of a surfactant. Under these conditions, the hydrogenation of tetralin provided cis- and trans-decalin in high yield with no apparent decrease in the catalytic activity after eight catalyst cycles. The reaction rate increases as the pressure and the temperature are increased. The reaction system is effective for the reduction of tetralin in the presence of coal liquids.

Role of catalyst in hydrocracking of residues from Alberta bitumens

Vacuum residues (424°C+) from Cold Lake and Lloydminster bitumens were hydrocracked at 430°C, 13.9 MPa, over five materials: fresh and spent commercial Ni/Mo on γ-alumina, Mo supported on γ-alumina, a commercial demetallization catalyst, and γ-alumina. Athabasca residue was tested using fresh and spent Ni/Mo on γ-alumina catalyst and was coked at atmospheric pressure in a batch apparatus. The product distributions from thermal (i.e., γ-Al 3 O 3 or coker) experiments were similar to those from catalytic experiments; therefore, the catalysts served mainly to promote hydrogen transfer to the oil and hydrogenation of aromatic compounds. The activity of the catalysts for residue conversion, heteroatom removal, and hydrogenation of Cold Lake and Lloydminster residue was Ni/Mo on γ-alumina>Mo on γ-alumina>demetallization>>γ-alumina

Syntheses of new diphenylphosphinoacetatorhodium(I) complexes and their catalytic reactivities in hydrogenation of aromatic compounds

The diphenylphosphinoacetic acid Ph 2PCH 2COOH was readily converted to its silver salt [Ag(Ph 2PCH 2COO)] ( 1), and subsequent reactions of 1 with [Rh(cod)Cl] 2 (cod=1,5-cyclooctadiene) and [Rh(CO) 2Cl] 2 gave [Rh(cod)(Ph 2PCH 2COO)] ( 2) and [Rh(CO) 2(Ph 2PCH 2COO)] ( 3), respectively. Spectroscopic data and some physical properties of these new compounds are described. The complexes 2 and 3 at 50 °C showed catalytic hydrogenation activities towards benzene and a variety of substituted benzenes. The turn-over number ( TN) for the arene hydrogenations with 2 under 5 kg/cm 2 of H 2, decreased with the following sequence: benzene>; toluene>;anisole>;ethylbenzene>; p- and m-xylenes>;methyl benzoate. Benzonitrile and nitrobenzene did not yield any products with hydrogenated benzene-ring moieties, and the latter substrate gave only aniline. The activity sequence observed for the arene hydrogenation resulted from steric and electron-withdrawing effects of the substituents of the benzene rings. In benzene hydrogenation with 2 under 50 kg/cm 2 of H 2 at 50 °C for 36 h, the TN value was found to be about 5800. Complex 2 also showed similar hydrogenation activities towards 1,2,3,4-tetrahydronaphthalene and furan.

Development of Cobalt-Molybdenum Hydrodesulfurization Catalysts

The Co-Mo catalysts have been prepared on laboratory scale by controlled impregnation of extruded γ-alumina with aqueous solutions of suitable active components, and their activity has been tested in the hydrodesulfurization and hydrogenation of aromatic compounds in gas oil. The kinetics of impregnation of the carrier, the effect of its nature, the order of impregnation of precursors of the individual active components, and the effect of their nature on the activity of the catalyst prepared have been studied. The samples prepared have been compared with selected commercial catalysts.

Highly active heterogeneous rhodium catalysts for the liquid‐phase hydrogenation of aromatic and other unsaturated compounds under mild conditions

AbstractHighly active heterogeneous rhodium hydrogenation catalysts ‐ rhodium on support ‐ have been prepared by pyrolysis of commercially available Rh4(CO)12, highly dispersed on a suitable support, e.g. SrTiO3, TiO2‐anatase, TiO2‐rutile, BaTiO3 or SrZrO3. The inactive materials initially obtained were activated by exposure to air at room temperature. The activities of these catalysts were determined in the liquid‐phase hydrogenation of aromatic compounds at atmospheric pressure and at low temperatures (max. 70 °C). They appear to be at least twice as active as catalysts prepared from impregnated RhCl3 or [RhCl(CO)2]2 on SrTiO3 or a commercially available catalyst (5% Rh on Al2O3).The gas‐phase hydrogenation of benzene at room temperature takes place exothermally. Very high activities were also found in the liquid‐phase hydrogenation of alkenes and alkynes, whereas low activities were shown in the hydrogenation of nitriles. Almost no activity was observed in the liquid‐phase hydrogenation of nitro compounds and ketones.Catalysts, prepared from Rh6(CO)16, showed lower activities as compared with those prepared from Rh4(CO)12. Hardly any activity was found using Ir4(CO)12 as starting carbonyl cluster and no activity was observed when Ru3(CO)12, Co4(CO)12, Os3(CO),2 or Fe3(CO)12 was used.

小型高圧示差熱分析装置による硫黄化合物の水素化脱硫反応の研究

A specified small differential thermal analysis unit was applied to the studies on hydrogenation of aromatic compounds and hydrodesulfurization of sulfur compounds in order to reveal the relationship between the hydrogenation reactions and exothermic peaks on the DTA curves and also to understand the characteristics of hydrodesulfurization of some organic sulfur compounds.The unit consists of two identical cylindrical cavities drilled symmetrically in a stainless steel block, which are available for above reactions.Hydrogenation of benzene and naphthalene was carried out with stabilized nickel as catalyst under 100 kg/cm2 G of initial hydrogen pressure and with a heating rate of 12. 4°C/min. One exothermic peak was observed for benzene and two ones for naphthalene. Chemical analysis showed that the peaks were based on the hydrogenation of benzene to cyclohexane, and of naphthalene to tetralin or tetralin to decalin.The DTA curves according to hydrodesulfurization of six sulfur compounds were also measured with molybdenum disulfide as catalyst under 100 kg/cm2 G of initial hydrogen pressure and with the same heating rate as the above. Exothermic peaks were observed for all sulfur compounds. These peaks were due to the hydrodesulfurization of them. The exothermic peak temperature shifted to higher temperatures in the order of thiol<diphenyldisulfide<phenylsulfide<thiophen <benzothiophen. This indicates that severer reaction conditions are required for the hydrodesulfurization of the above sulfur compounds in this order described.It is concluded that the above analysis unit is available to check high pressure hydrogenation with ease using a very small charge (ca. 30 mg).

石炭水添液化反応における循環溶剤の組成変化 Ｉ ＨＰＬＣ‐ＧＣ／ＭＳ法による化合物タイプの分布

A hydrogenation reaction of Akabira coal with recycle solvent was car-ried out, using hydrogenated anthracene oil as a starting solvent. Also, one through exper-iment using anthracene oil as a solvent under the same reaction conditions was carried out as a comparisonThe compound type analyses on the product oil of one through experiment and recycle solvent were performed by means of HPLC-GC/MS method, which has been proposed pre-viously. The amounts of hydroaromatic compounds in recycle solvents decrease and those of aromatic compounds increase with the recycle number. But, with more than five recycling runs the amounts of hydroaromatic compounds seem to gradually increase.This is due to hydrogen donation of hydroaromatic compounds to fragments created by thermal rupture of the coal structure during the initial stage of the run. During further runs, hydroaromatic compounds were produced by hydrogenation of aromatic compounds in solvent and by hydrogenolysis of coal under Red mud-S as a catalyst. Therefore, an im-provement in hydrogen donor ability for solvents is expected again with further experimen-tal runs. In this experiment, in the last sixth recycle solvent, the donor ability did not rise to a satisfactory level and the composition of this solvent was still not in equilibrium.

Hydrogenation of aromatic compounds in synthetic crude distillates catalyzed by sulfided [formula omitted

A presulfided NiW γ-Al 2O 3 catalyst was used to hydrogenate aromatic compounds contained in middle-distillate fractions of Alberta synthetic crudes, in a continuous-flow high-pressure reactor system. The study incorporates detailed compositional analyses of feedstocks and products performed using low-resolution mass spectrometry and 13C NMR. Experimental conditions were such that the effects of thermodynamic equilibria were covered. Differences in reactivity with respect to hydrogenation and cracking were observed for various aromatic species. These allowed comparison of the reaction kinetics and discussion of some mechanistic aspects of catalytic hydrogenation for complex mixtures of hydrocarbons which are not revealed by model compound studies.