Hydrodenitrogenation of Petroleum

A high level of hydrodenitrogenation (HDN) is required to achieve a desirable conversion of other hydroprocessing reactions. This results from a strong adsorption of nitrogen‐containing compounds on catalytic sites that slows down the hydrogen activation process and hinders the adsorption of other reactants. Studies on model compounds and real feeds indicate that less than 50 ppm of nitrogen in the feed can poison catalytic sites. Kinetic studies determined adsorption constants of various nitrogen‐containing compounds and concluded that at least four different catalytic sites are required to interpret experimental observations in contrast with a dual site site?concept, which only considered two sites. The advancements in experimental techniques allowed identification of products formed during very early stages of hydrodenitrogenation. These results confirmed that the removal of the amino group from saturated amines, as the last step in hydrodenitrogenation, is governed by the type of carbon to which the amino group is attached rather than the number of hydrogen atoms attached to carbon in α and β position to nitrogen

Performance of conventional Co(Ni)Mo(W)/Al₂O₃ catalysts during hydrodenitrogenation was enhanced by combination with various additives and by replacing the traditionally used γ‐Al₂O₃ support with novel supports. Catalytic functionalities could be modified by using different precursors of active metals and varying conditions during preparation. Progress has been made in the development of catalysts possessing a high selectivity for hydrodenitrogenation. In this case, the nonconventional catalysts based on the carbides and nitrides of transition metals exhibited high activity and selectivity. Noble metal sulfides alone or supported on different supports were active for HDN as well. Feedstocks used for catalyst evaluation included model compounds and mixtures of model compounds as well as real feeds. The challenges in the development of catalysts for hydrodenitrogenation of heavy feeds containing asphaltenes and metals have been identified.     

Hydrodenitrogenation of isoquinoline

To determine the formation and reactivity of addition compounds produced during hydrodenitrogenation (HDN), we investigated the HDN of isoquinoline for a sulfided Ni–Mo/Al₂O₃ catalyst operated under a hydrogen pressure of 12 MPa (cold charge) in the temperature range 300–375°C. The reaction products were classified into five groups of compounds:

1. hydrogenated derivatives of isoquinoline (tetrahydroisoquinolines, decahydroisoquinolines, and their isomers);

2. nitrogen-containing ring-opened products (1-amino-2-(2-methylphenyl)ethane and 1-amino-1-(2-ethylphenyl)methane);

3. denitrogenated products (1-ethyl-2-methylbenzene, 1-ethyl-2-methylcyclohexane, and their isomers);

4. addition products (hydrocarbons with molecular weights of 238, 244, and 250 and nitrogen-containing compounds with molecular weights of 249, 251, and 257); and

5. cracked products (toluene, ethylbenzene, dimethylbenzenes, and their hydrogenated derivatives).

Most of the nitrogen-containing addition compounds appear to be substituted on the nitrogen atom. The HDN of isoquinoline was more than 10 times faster than the HDN of quinoline, whereas the hydrogenation of isoquinoline was difficult compared to the hydrogenation of quinoline. The reaction network for the HDN of isoquinoline is also presented.     

加氢脱氮反应与加氢脱氮催化剂的研究进展

介绍石油馏分中主要含氮组分和其结构特性，以及典型含氮化合物的加氢脱氮反应网络、反应机理、反应动力学，阐述了加氢脱氮催化剂改性的不同途径：载体的改性、活性组分和助剂的选择、活化方法的改进等。     

Hydrodenitrogenation of pyridine over alumina-supported iridium catalysts

The catalytic properties of alumina-supported Ir catalysts (≈1 wt% Ir) were studied in the hydrodenitrogenation (HDN) of pyridine at 320°C and 20 bar of pressure in the absence as well as presence of parallel hydrodesulfurization (HDS) of thiophene. The effects of Ir precursor (Ir(AcAc)₃, Ir₄(CO)₁₂, H₂IrCl₆, (NH₄)₂IrCl₆), metal dispersion and sulfur addition were investigated. Ir₄(CO)₁₂ gave the most active catalyst which was ascribed to a lower amount of contaminants originated from the starting Ir compounds rather than to a better Ir dispersion. The decrease of Ir dispersion by sintering in air led to much higher decrease of the rate of C–N bond hydrogenolysis than that of pyridine hydrogenation. The Ir dispersion determined partly the HDN selectivity; a better dispersed Ir phase gave a lower amount of intermediate piperidine. Presulfidation of the reduced catalyst led to 20% decline of the rates of both consecutive HDN steps. An additional and much larger activity decline was caused by the simultaneous execution of HDS. The competitive adsorption of thiophene (or H₂S) was selectively affecting C–N bond hydrogenolysis more than pyridine hydrogenation. The alumina-supported Ir catalysts possessed much higher HDN activity and HDN/HDS selectivity than a conventional NiMo system.     

Comments on the Mechanisms of Heterogeneous Catalysis of the Hydrodenitrogenation Reaction

The purpose of this commentary is to draw from recent observations in these laboratories and from literature examples to propose logical mechanisms that describe the catalytic pathways by which heterogeneous catalysts catalyze hydrodenitrogenation.     

Comments on the Mechanisms of Heterogeneous Catalysis of the Hydrodenitrogenation Reaction

The purpose of this commentary is to draw from recent observations in these laboratories and from literature examples to propose logical mechanisms that describe the catalytic pathways by which heterogeneous catalysts catalyze hydrodenitrogenation.     

Hydrodenitrogenation of Simple Aromatic Amines on Molybdena Catalysts

The hydrotreatment of some aromatic amines was studied at temperatures ranging from 400 to 450°C and P_H2=1 atm under flow conditions. Hydrogenolysis of aromatic amines involves direct cleavage of the C(sp²)N bond without saturation of the aromatic ring. The presence of hydrogen sulphide in the reaction stream has a promotional effect on the hydrogenolysis of C(sp³)N bond and an inhibitive effect on the hydrogenolysis of C(sp²)N bond. The use of a saturated hydrocarbon as diluent facilitates CN bond hydrogenolysis in the presence of hydrogen, irrespective of the carbon being sp² or sp³ hybridized.     

渣油加氢脱氮催化剂的研究

本研究用简便的混捏法制备高活性的渣油加氢脱氮催化剂,制备技术的关键是采用合适的扩孔剂、助剂和焙烧温度,以克服混捏法所固有的缺点。     

Bromination of p-Bromophenol in the Presence of Pyridine

The role of pyridine (Py) in the bromination of p-bromophenol (ArH) in CCl₄ has been investigated. At constant concentrations of ArH and Br₂, the rate of disappearance of Br₂ increases to reach a limiting value as the concentration of Py is increased. The mechanism suggested to account for the rate expression, Rate = constant [ArH] [Br₂]_T[Py]_T, obtained from the initial rate studies, involves the interaction between ArH and the brominating species Py. Br₂, in the rate determining step. Py acts as a catalyst probably by virtue of its ability to polarise the Br-Br bond.     

吡啶羧酸类化合物吡啶环4位上连接氨甲基的方法探讨

文章探讨了两种在吡啶羧酸类化合物吡啶环4位上连接氨甲基的方法,发现路线2是可行的:将吡啶环4位先连接上羟甲基,用PBr3将羟甲基溴代为溴甲基,再用Na N3将溴甲基化合物转化为叠氮化合物,最后在Pd-C催化剂作用下H2将叠氮基还原为氨基,即得到产物4-氨甲基-2,6-吡啶二甲酸二甲酯(L)。最后一步的产率为74.5%。并讨论了路线1没有得到产物(L)的原因。     

Hydrodenitrogenation of Quinoline Over a Dispersed Molybdenium Catalyst Using in situ Hydrogen

Hydrodenitrogenation (HDN) of quinoline using a Mo-based dispersed catalyst was studied in a batch reactor using H₂ generated in situ via the water gas shift reaction. In situ H₂ was found to be more active for HDN than externally supplied H₂. Both water and H₂S have an effect on HDN.     

吡啶类农药的研究进展(续)

本文根据具有生物活性的吡啶衍生物的结构特征，简要分类叙述了近10年来含吡啶类农药的研究进展。     

Hydrodenitrogenation of pyridine over a Co-Mo-AI2O3 catalyst

The vapour phase hydrogenation of pyridine was investigated in an integral flow reactor at a pressure of 5.62 MPa over an alumina-supported cobalt-molybdate catalyst. The effect of various process variables, viz. temperature, reactant ratio and space time, on the conversion of pyridine was studied. The kinetics of the hydrogenation of pyridine to form piperidine have been investigated. The reaction showed pseudo-second order behaviour and the order of the reaction rate in the initial pyridine concentration was found to vary with temperature.     

吡啶类农药的研究进展

本文根据具有生物活性的吡啶生物的结构特征，简要分析叙述了近10年来含比啶类农药的研究进展。     

Catalytic Activity of Exfoliated MoS2 in Hydrodesulfurization, Hydrodenitrogenation and Hydrogenation Reactions

The activity of exfoliated MoS₂ in the hydrodesulfurization (HDS) of dibenzothiophene, the hydrodenitrogenation (HDN) of carbazole and the hydrogenation of naphthalene has been determined. The catalytic activity was compared to MoS₂ prepared by the decomposition of molybdenum naphthenate (MoNaph). Exfoliated MoS₂ was found to give better overall HDS activity compared to MoNaph derived MoS₂ catalyst, whereas MoNaph derived MoS₂ was found to give higher hydrogenation and HDN activity. These results are discussed in terms of the morphology of the two catalysts. The relative activity of the two catalysts in the hydrotreating reactions is shown to be different to that obtained during Cold Lake bitumen hydrocracking.     

Hyperfine Interactions in the Lowest Triplet State of Pyridine

Results are reported of nitrogen and deuterium hyperfine studies of the triplet state of pyridine-d₅ as a guest in a single crystal of benzene at 1.2 K. Through the use of electron spin echo (ESE) techniques complete hyperfine tensors have been obtained: for nitrogen from the ESE detected EPR spectra and for the para-deuterium atom from the modulations of the ESE envelope. These tensors unambiguously show that the molecule is no longer planar in the lowest triplet state T₀. Pyridine's structure considerably changes upon excitation, but the mirror plane perpendicular to the molecule is preserved. Experimental and theoretical evidence is presented for the fact that this deformation is an intrinsic property of T₀ and is not induced by the crystal field. About fourty percent of the triplet electron spin density is found to be localised in the π-orbital of nitrogen, about ten percent in the lone pair orbital of nitrogen and somewhat more than thirty percent in the π-orbital of the para-carbon atom.     

The Effect of CeO2 on the Hydrodenitrogenation Performance of Bulk Ni2P

Bulk Ni₂P and CeO₂-containing bulk Ni₂P (Ce?CNi₂P(x), where x represents the Ce/Ni atomic ratio) were prepared by a co-precipitation method followed by an in situ H₂ temperature-programmed reduction procedure. The catalysts were characterized by XRD, CO chemisorption, TEM, N₂ adsorption?Cdesorption, XPS and X-ray absorption spectroscopy (XAS). Their hydrodenitrogenation performances were studied using quinoline (Q) and decahydroquinoline as the model compounds. Both the hydrogenation and C?CN bond cleavage activities of Ni₂P were improved by the introduction of CeO₂. CeO₂ mainly accelerated the denitrogenation of Q to propylcyclohexane rather than to propylbenzene. XRD and XPS measurements revealed that the Ce species in Ce?CNi₂P(x) were mainly in the oxide form and both Ce⁴⁺ and Ce³⁺ species coexisted on the surface of the catalysts. Addition of CeO₂ significantly decreased the particle size of Ni₂P, resulting in increased specific surface areas and CO uptakes, possibly due to the strong interaction between the Ce species and Ni₂P. At a Ce/Ni atomic ratio higher than 0.25, segregation of CeO₂ took place. XAS results of the passivated catalysts showed that CeO₂ not only affected the oxidability of Ni₂P but also led to the formation of metallic Ni. The promoting effect of CeO₂ was discussed by considering the electronic interactions between Ce species and Ni₂P as well as the presence of the amorphous Ni and low valence Ce³⁺ species.     

重质油加氢脱硫和加氢脱氮催化剂的开发及工业应用

本文简要地介绍了重质油加氢脱硫、加氢脱氮催化剂的开发过程, 催化剂工业产品与国外同类催化剂的加氢活性对比情况, 以及催化剂在工业装置中的运行情况。工业使用表明, 所开发的催化剂具有良好的加氢处理活性和稳定性。     

具有除草活性的吡啶类化合物研究进展

按照结构类型对吡啶类化合物进行了分类,综述了吡啶类化合物在除草方面的应用,展望了该类化合物的发展趋势。