Simultaneous Hydrodenitrogenation Research Articles

Simultaneous hydrodenitrogenation and hydrodesulfurization on unsupported Ni-Mo-W sulfides

The catalytic properties of unsupported Ni-Mo-W sulfides (composites of Ni-Mo(W)S2 mixed sulfides and Ni3S2) obtained from precursors synthesized via co-precipitation, hydrothermal, and thiosalt decomposition were explored for hydrodenitrogenation (HDN) of o-propylaniline or quinoline in presence and absence of dibenzothiophene undergoing hydrodesulfurization (HDS). The conversion rates varied with the reacting substrate and were related to specific catalyst properties such as morphology, texture, surface and composition. For the HDN of o-propylaniline and the HDS of dibenzothiophene in presence of o-propylaniline, high concentrations of coordinatively unsaturated cationic sites (as characterized by NO adsorption) and the specific surface areas determined the rates of reaction. For the HDN of quinoline and the HDS of dibenzothiophene in the presence of quinoline, the high hydrogenation activity of tungsten sulfide and length of the slabs was found to be more important than in the cases with o-propylaniline. Overall, the activity of unsupported catalysts relates to the size of sulfide slabs provided that Ni is present at the perimeter of the slabs.

Performance of Ni-rich bimetallic phosphides on simultaneous quinoline hydrodenitrogenation and dibenzothiophene hydrodesulfurization

A series of Ni-rich bimetallic phosphides incorporating different metals were successfully prepared by initial wetness impregnation, followed by temperature-programmed reduction. Catalyst characterization indicates that the bulk structure and physical properties maintained after adding 2.5mol% another metal on Ni2P. Electron transfer from the second metal to Ni was found on Mo0.05Ni1.95P, Co0.05Ni1.95P, and Fe0.05Ni1.95P, except on W0.05Ni1.95P. Simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene (DBT) over phosphides and a commercial metal sulfide were studied at 320–380°C, 3MPa, weight hourly space velocity of 6h−1, and H2/feed ratio of 500:1. Metal phosphides show higher HDN of quinoline and the same HDS of dibenzothiophene activities than that of a commercial catalyst at 380°C. Mo0.05Ni1.95P shows the best performance and lowest N and S content adsorbed on the catalyst, due to the active M(2) sites. HDS conversion and product selectivities are seriously impacted by the adsorption of N-containing compounds on active sites of catalysts. Increasing temperature to 360°C or/and decreasing N content to less than 1000ppm quinoline in the feed are suggested to obtain simultaneous efficient removal of N and S.

Effects of the Support on the Performance and Promotion of (Ni)MoS2Catalysts for Simultaneous Hydrodenitrogenation and Hydrodesulfurization

MoS2 and Ni-promoted MoS2 catalysts supported on γ-Al2O3, siliceous SBA-15, and Zr- and Ti-modified SBA-15 were explored for the simultaneous hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrodenitrogenation (HDN) of o-propylaniline (OPA). In all cases, OPA reacted preferentially via initial hydrogenation, and DBT was converted through direct sulfur removal. HDN and HDS activities of MoS2 catalysts are determined by the dispersion of the sulfide phase. Ni promotion increased its dispersion and activity for DBT HDS and also increased the rate of HDN via enhancing the rate of hydrogenation. On nonpromoted MoS2 catalysts, HDS was strongly inhibited by NH3, and the addition of Ni dramatically reduced this inhibiting effect. The conclusion is that HDS is proportional to the concentration of Mo and Ni on the edges of sulfide particles. In contrast, the direct hydrodenitrogenation of OPA occurs only on accessible Mo cations and, hence, decreases with increasing Ni substitution. The nature of the support influences the dispersion of the nonpromoted catalysts as well as the decoration degree of Ni on the edges of the Ni–Mo–S phase. Furthermore, the acidity of the support influences the acidity of the supported sulfide phase, which may play an important role in HDN.

Kinetic model development and simulation of simultaneous hydrodenitrogenation and hydrodemetallization of crude oil in trickle bed reactor

One of the more difficult tasks in the petroleum refining industries that have not been considered largely in the literature is hydrotreating (HDT) of crude oil. The accurate calculations of kinetic models of the relevant reaction scheme are required for obtaining helpful models for HDT reactions, which can be confidently used for reactor design, operating and control. In this work, an optimization technique is employed to evaluate the best kinetic models of a trickle bed reactor (TBR) process utilized for hydrodenitrogenation (HDN) and hydrodemetallization (HDM) that includes hydrodevanadization (HDV) and hydrodenickelation (HDNi) of crude oil based on pilot plant experiments. The minimization of the sum of the squared errors (SSE) between the experimental and estimated concentrations of nitrogen (N), vanadium (V) and nickel (Ni) compounds in the products is used as an objective function in the optimization problem to determine the kinetic parameters.A series of experimental work was conducted in a continuous flow isothermal trickle bed reactor, using crude oil as a feedstock and the commercial cobalt–molybdenum on alumina (Co–Mo/γ-Al2O3) as a catalyst.A three-phase heterogeneous model based on two–film theory is developed to describe the behaviour of crude oil hydroprocessing in a pilot–plant trickle bed reactor (TBR) system. The hydroprocessing reactions have been modelled by power law kinetics with respect to nitrogen, vanadium and nickel compounds, and with respect to hydrogen. In this work, the gPROMS (general PROcess Modelling System) package has been used for modelling, simulation and parameter estimation via optimization. The model simulations results were found to agree well with the experiments carried out in a wide range of the studied operating conditions. The model is employed to predict the concentration profiles of hydrogen, nitrogen, vanadium and nickel along the catalyst bed length in three phases.

Catalytic performance of platinum doped tungsten carbide in simultaneous hydrodenitrogenation and hydrodesulphurization

The simultaneous hydrodesulphurization (HDS) and hydrodenitrogenation (HDN) reactions of refractory model compounds were performed for the first time over tungsten carbide doped with platinum before and after preparation (0.3wt%). It was then compared to that of a pure non-modified W2C. The model compounds were 4,6-dimethyldibenzothiophene (4,6-DMDBT) and carbazole. The catalysts were characterized by X-ray diffraction (XRD). The surface properties were determined by N2 BET specific surface area and chemisorption of CO. Addition of platinum before synthesis of carbide decreased the uptake of CO chemisorption, but did not change significantly the specific surface area and the crystallographic structure of tungsten carbide—β-W2C. Addition of platinum after preparation of carbide did not decreased significantly the specific surface area of W2C but extremely increased the uptake of chemisorption of CO. No influence of platinum on the HDS activity was observed for contact times between 0.08 and 0.31s. At longer contact time (tc>0.31s) the highest activity was observed over W2C–Pt catalyst (platinum doped after preparation) for the HDS of 4,6-DMDBT. The main products were 3,3-DMBPh (along DDS route) and MCHT (along HYD route).A strong influence of platinum, added after preparation (W2C–Pt), was observed for the HDN of carbazole. Indeed, this catalyst was found to be more active in the whole range of applied contact times than W2C and Pt–W2C. It was also more active in the consecutive reaction of isomerization of the main product of the HDN reaction, i.e. bicyclohexyl (BCH) transformed into methylcyclopenthylcyclohexane (MCPCH). Furthermore the activity in HDN over the W2C–Pt catalyst was shown to be highly dependent on the amount of metallic sites introduced by platinum.

Catalytic performances of platinum doped molybdenum carbide for simultaneous hydrodenitrogenation and hydrodesulfurization

The hydrotreating activity of molybdenum carbide doped with platinum (0.3 wt.%) was studied and compared to that of a pure, non-modified Mo 2C. 4,6-Dimethyldibenzothiophene (4,6-DMDBT, 300 ppm of S) and carbazole (100 ppm of N) were designated as model compounds and subjected to hydrodesufurization (HDS) and hydrodenitrogenation (HDN) processes either separately or simultaneously. In both cases the molybdenum carbide doped with platinum (Mo 2C-Pt) turns out to be more active than Mo 2C. The increase of the hydrotreating activity, owing to the presence of platinum in molybdenum carbide can be related to the raise of hydrogenation activity of the modified catalyst. The platinum modified molybdenum carbide was stable ( displays a long lifetime) under HDN and HDS reaction conditions. The predominant reaction products are bicyclohexyl (BCH) for the HDN process or 3,3′-dimethylbiphenyl (3,3′-DMBPh) and methylcyclohexyltoluene (MCHT) for the HDS process, respectively.

Mechanisms of hydrodenitrogenation of alkylamines and hydrodesulfurization of alkanethiols on NiMo/Al 2O 3, CoMo/Al 2O 3, and Mo/Al 2O 3

The simultaneous hydrodenitrogenation (HDN) of alkylamines and hydrodesulfurization (HDS) of alkanethiols, with the NH 2 and SH groups attached to primary, secondary, and tertiary carbon atoms, were studied at 270–320 °C and 3 MPa over sulfided NiMo/Al 2O 3, CoMo/Al 2O 3, and Mo/Al 2O 3 catalysts. Pentylamine and 2-hexylamine reacted by substitution with H 2S to form alkanethiols and with another amine molecule to form dialkylamines. Alkenes and alkanes were not formed directly from pentylamine and 2-hexylamine, but indirectly by elimination and hydrogenolysis of the alkanethiol intermediates, as confirmed by their secondary behavior and the similar alkene/alkane ratios in the simultaneous reactions of amines and thiols. Only 2-methyl-2-butylamine, with the NH 2 group attached to a tertiary carbon atom, produced alkenes as primary products by E1 elimination. NiMo/Al 2O 3 and CoMo/Al 2O 3 have a higher activity for the HDS of alkanethiols than does Mo/Al 2O 3; H 2S has a negative influence. This shows that the thiols react on vacancies on the catalyst surface (Lewis acid sites). Mo/Al 2O 3 is the best HDN catalyst; H 2S has a positive influence on the HDN of amines with the NH 2 group attached to a secondary and a tertiary carbon atom. This indicates that the HDN of alkylamines occurs on Brønsted acid sites.

XAFS Characterization of Highly Active Alumina-Supported Molybdenum Phosphide Catalysts (MoP/Al2O3) for Hydrotreating

Alumina-supported molybdenum phosphide (MoP/Al2O3) catalysts were prepared by temperature-programmed reduction of supported phosphate precursors in H2 at 0.083 K s-1 to 1123 K. The catalysts had excellent activity in the simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene at realistic conditions [P = 3.1 MPa (450 psig) and T = 643 K (370 °C)]. The catalysts surpassed the performance of a sulfided commercial Ni−Mo−S/Al2O3 catalyst in both HDN and HDS. X-ray absorption fine structure (XAFS) analysis of the supported samples indicated the presence of dispersed species retaining metallic bonding with a characteristic Mo−P distance of 0.243 nm but showing considerable attenuation in Mo−Mo linkages.

Supported Bimetallic Nb−Mo Carbide: Synthesis, Characterization, and Reactivity

The temperature programmed synthesis technique was employed for the preparation of a new bimetallic oxycarbide-supported system, Nb−Mo−O−C/Al2O3 (Mo/Nb = 1.2;1.6;2.0). The catalysts were characterized by CO chemisorption, BET surface area measurement, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS). The supported bimetallic materials were tested for simultaneous hydrodenitrogenation (HDN) of quinoline and hydrodesulfurization (HDS) of dibenzothiophene. The supported bimetallic oxycarbide was found to be highly active for both HDN and HDS, demonstrating higher activities than a commercial sulfided Ni−Mo/Al2O3 when compared on the basis of active sites. NEXAFS analysis indicated that the electronic properties of the oxycarbide were modified by the interaction with the Al2O3 support.

Hydrotreatment of Naphtha with Molybdenum Nitride Catalysts

Nanoscale, high surface area bulk molybdenum nitrides have been synthesized using two methods : a laser pyrolysis technique (LPT) and a temperature-programmed reaction (TPR). The activities of these materials for the simultaneous hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) of Illinois No. 6 naphtha were determined. Both catalysts were active for the HDN and HDS reactions and, on an unit mass basis, exhibited the same activity and selectivity.

Effect of temperature on activity and selectivity of carbon supported Mo sulfide in simultaneous hydrodenitrogenation of pyridine and hydrodesulfurization of thiophene

Activity and selectivity of carbon supported Mo catalyst was tested in parallel hydrodenitrogenation (HDN) of pyridine and hydrodesulfurization (HDS) of thiophene in the temperature range 260–350 °C at 2 MPa of hydrogen pressure and compared with that of commercial NiMo-alumina catalyst Shell 324. The main advantages of carbon supported Mo sulfide over commercial NiMo catalyst can be summarized as follows: the markedly higher HDN and better HDS activities normalized to moles of active metals, the lower content of piperidine in the reaction products and the distinctly better selectivity towards HDN reaction.

Simultaneous hydrodenitrogenation of pyridine and hydrodesulfurization of thiophene over carbon-supported platinum metal sulfides

The activity and selectivity in parallel hydrodenitrogenation and hydrodesulfurization of carbon-supported sulfides of Ru, Rh, Pd, Ir, and Pt were evaluated using the simultaneous reaction of pyridine and thiophene at 280 °C and under 2 MPa. The properties of these sulfldes were also compared with the behavior of commercial NiMo/alumina and CoMo/alumina Shell catalysts. The carbon-supported sulfides of platinum metals were better hydrodesulfurization catalysts and much better hydrodenitrogenation catalysts than the commercial bimetallic systems. The HDN HDS selectivity of the Rh, Ru, and Pd catalysts was similar to the selectivity of CoMo and NiMo systems but the Ir and Pt catalysts were extremely selective for hydrodenitrogenation. The results suggest that the use of active carbon as the support contributed to the exceptional hydrodenitrogenation properties of the sulfides of platinum metals.

Simultaneous hydrodenitrogenation and hydrodeoxygenation of model compounds in a trickle bed reactor

In selected binary mixtures of a heterocyclic nitrogen compound and a phenolic or heterocyclic oxygen compound and in the presence of H 2S, the rate of hydrodeoxygenation (HDO) was considerably decreased in comparison to that observed with the same compound individually at the same reaction conditions. In mixtures, the rate of hydrodenitrogenation (HDN) of quinoline was increased and the effect on the HDN rate of o-ethylaniline depended on the specific oxygen compound. Small concentrations of water vapor increase hydrodenitrogenation, especially if H 2S is also present. In the hydrodeoxygenation of an ethyl phenol, substantial quantities of an ethyl cyclohexene are formed as an intermediate. The final products are ethylcyclohexane and ethylbenzene, the former predominating.

Catalytic hydrodeoxygenation: III. Interactions between catalytic hydrodeoxygenation of m-cresol and hydrodenitrogenation of indole

Simultaneous hydrodenitrogenation (HDN) and hydrodeoxygenation (HDO) is studied with indole/ m-cresol conversions over a sulfided CoMo HDS catalyst. The mutual inhibition of indole (and indoline) on HDO and of m-cresol on HDN is established. As with HDS/HDO reported in paper II, the HDN/HDO reactions appear to proceed on the same site. The relative reactivity of the indole and cresol, as well as an HDN intermediate, o-ethyl aniline, is m-cresol ⪢ o-ethyl aniline > indole (indoline). Under the conditions of our study ( P H 2 = 69 atm, T = 250–350 °C), the indole-indoline hydrogenation equilibrium is essentially achieved. The pure component conversion kinetics are adequately described by a two-site Longmuir-Hinshelwood form, the rate and binding constant values indicating correctly the relative reactivity and mutual inhibition magnitudes, thus confirming that simultaneous HDO and HDN proceed on the same surface sites. At the lower HDN temperatures, the intermediate o-ethyl aniline is converted to ethylbenzene, then ethylcyclohexane, while at or above 300 °C some ring hydrogenation to o-amino ethylcyclohexane precedes HDN. Hydrogenation, HDO, and HDN activities are completely recovered by 400 °C regeneration, in contrast to activity loss noted in paper II for simultaneous HDS/HDO.