煤焦油加氢脱氮反应网络及催化剂研究进展

煤焦油加氢精制生产车用燃料是提高煤焦油附加值及煤焦油清洁利用的有效手段,煤焦油中含氮化合物复杂多样,如何高效脱出含氮化合物中的氮原子是开发煤焦油加氢脱氮催化剂的研究重点.本文简述了煤焦油中含氮化合物的分布情况及特点,综述了煤焦油中吡啶、喹啉、吲哚等典型含氮化合物的加氢脱氮反应网络的研究现状;加氢脱氮催化剂的研究现状从加氢脱氮反应机理、活性组分、载体、助剂4个方面进行了论述.最后针对煤焦油中含氮组分复杂多样的特性提出了研发高效煤焦油加氢脱氮催化剂的一些新方向.     

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。     

加氢脱氮催化剂及反应机理研究进展

介绍了各馏分油品中含氮化合物的分布规律和特点,概述了加氢脱氮反应过程中含氮化合物进行加氢和C-N键断裂的反应机理及典型含氮化合物的反应网络;总结了传统加氢脱氮催化剂及其载体的制备、改性和调变方法,论述了新型金属碳化物、氮化物、磷化物催化剂的结构特性及各类催化剂的加氢脱氮反应性能.关联了催化剂的物理化学性质对加氢脱氮反应的影响,提出了高活性加氢脱氮催化剂的研制思路和途径.     

中低温煤焦油加氢脱氮催化剂研究进展

详细介绍了煤焦油加氢技术,将现有煤焦油加氢转化技术划分为轻组分加氢,脱酚加氢,加氢裂化-加氢改质和全馏分加氢四种,分别介绍了每种技术的工艺流程特点和发展状况。阐述了国内外加氢催化剂研究进展,分析了催化剂中活性金属、载体和助剂的种类及对催化剂性能的影响;结合煤焦油加氢催化特点,展望了加氢脱氮催化剂的研究方向,旨在为煤焦油加氢催化剂研究提供一定的理论依据。     

煤焦油加氢脱硫脱氮催化剂研究进展

随着石油资源的日趋减少,煤焦油加工技术受到关注。汽车尾气中含有的硫和氮污染环境,各国对油品中的硫和氮含量进行了严格限制,脱硫和脱氮成为煤焦油化工行业的重要课题。介绍煤焦油加氢工艺,综述金属碳化物、氮化物、磷化物和硫化物作为催化剂的研究现状。贵金属催化剂具有较强的加氢能力,并且通过使用强酸性载体分子筛和双金属催化剂的方法提高贵金属催化剂的抗硫毒性。碳化物催化剂具有较高的熔点和硬度、较好的机械稳定性和热稳定性,室温下几乎可以耐各种腐蚀性物质。根据金属源和碳源的不同,介绍使用程序升温还原法、气相法、热分解法和液相反应法制备碳化物催化剂的制备工艺。过渡金属磷化物催化剂具有优异的加氢脱硫和加氢脱氮选择性,添加钒的磷化物催化剂能改变加氢脱氮路径的选择性,明显增加咔唑加氢脱氮反应活性,钙的添加明显提高磷化物催化剂的加氢脱硫活性。工业上通常以ⅥB族和ⅧB族金属为活性物质制备过渡金属硫化物催化剂,使用的贵金属主要包括Pt、Pd和Ru,非贵金属主要包括W、Mo、Co和Ni等,其中,贵金属通常使用Al₂O₃或SiO₂为载体。ZrO₂载体可与活性组分产生较强的相互作用,热力学稳定性较高,但比表面积小,价格昂贵。Al₂O₃载体机械强度大,比表面积高,ZrO₂-Al₂O₃复合载体将两者的优良性能结合,可以获得性能更加优异的载体。     

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。     

Y分子筛的改性及在加氢脱氮反应中的催化性能

采用水热法与草酸脱铝相结合法对Y分子筛进行改性,用孔体积饱和浸渍法制备了Ni-W/γ-Al2O3-USY加氢精制催化剂,考察了改性Y分子筛对催化剂的酸性及催化剂的HDN活性的影响,并对制备的催化剂进行了酸性表征。随着草酸加入量的增多,催化剂的总酸量减少;随着处理温度的增高,弱酸和强酸量分别有不同程度的增多。催化剂中适量的USY可以明显提高催化剂的总酸量,并提供对喹啉HDN的适中酸强度,明显提高催化剂的HDN活性。     

加氢脱氮催化剂研究进展

对加氢脱氮催化剂进行论述,从催化剂活性组分、助剂和载体方面介绍了国内外载体的发展趋势。加氢活性组分的过渡金属碳化物、过渡金属氮化物和过渡金属磷化物成为研究热点,特殊功能的助剂加入到催化剂中,提高了催化剂酸性或活性组分分散度。新型催化材料用于催化剂载体,改性Al_2O_3、TiO_2复合载体和纳米材料复合载体有望替代传统载体。     

反应条件对轻质页岩油加氢脱氮性能的影响

在固定床加氢微反装置上,采用硫化态NiMoW/Al2O3催化剂,以东宁轻质页岩油(＜350℃馏分)为原料,考察反应条件对加氢脱氮性能的影响.结果表明,适当降低反应空速、提高反应压力、提高反应温度均有利于提高催化剂加氢脱氮反应活性,提高产物的质量.在反应温度380℃、反应压力8.0MPa、体积空速0.8h-1、氢/油体积比750∶1的条件下,加氢生成油的硫、氮、芳烃含量均明显降低,石脑油馏分可作为化工轻油,柴油馏分可直接作为清洁柴油调和组分使用.     

柴油非加氢脱氮技术研究进展

介绍了柴油非加氢脱氮技术的研究现状和发展前景,分析了酸精制、溶剂精制、配合法脱氮、吸附精制法、组合脱氮法、生物脱氮法和微波脱氮法等柴油脱氮技术的原理、优缺点。     

Reaction network of indole hydrodenitrogenation over NiMoS/γ-Al2O3 catalysts

The reaction network of indole hydrodenitrogenation (HDN) was investigated over γ-Al₂O₃ supported NiMo sulfide catalysts in an effort to acquire a fundamental understanding of the different reaction pathways in the mechanism. Experiments were performed primarily at 1000 psig, using a wide range of temperatures and feed concentrations. The effect of H₂S on different reaction steps of the network was also investigated. Two major pathways were proposed to account for the formation of ethylcyclohexane (ECH) and ethylbenzene (EB) which are the two main HDN products from indole. One route occurs from the hydrogenolysis of indoline to o-ethylaniline (OEA) and the other from the hydrogenation of indoline to octahydro-indole. Also included in the proposed mechanism is a secondary route from o-ethylcyclohexylamine (OECHA) to ethylcyclohexene (ECHE), that occurs through a nucleophilic substitution reaction. The product distribution was a strong function of temperature and H₂S concentration. H₂S enhanced the hydrogenolysis reactions but inhibited the hydrogenation reactions.     

碳化钼催化剂的喹啉加氢脱氮反应性能

用程序升温还原法在CH4/H2气氛中将MoO₃碳化制备了Mo₂C催化剂, 并对Mo₂C催化剂进行了XRD和BET表征。以喹啉/环己烷溶液为模型化合物, 通过高压微反评价实验考察了Mo2C催化剂的喹啉加氢脱氮活性。结果表明, MoO₃在CH₄/H₂气氛中程序升温至终点温度675 ℃,并在此终点温度下还原碳化150 min,可制得高纯度的β-Mo2C。当还原碳化温度高于675 ℃,随着还原碳化温度的升高,Mo₂C催化剂的比表面积降低, 表面积炭增多, 导致喹啉加氢脱氮活性下降。而当还原碳化时间少于150 min时,MoO₃未能充分转化为Mo2C,导致喹啉加氢脱氮活性较低。因此,较适宜的Mo2C催化剂的合成条件为：还原碳化温度675 ℃,还原碳化时间150 min。在反应压力3.0 MPa、 空速8 h-1、H₂与原料液体积比500∶1以及 氮含量为1 000 ng·μL^-1的喹啉/环己烷溶液中, Mo2C催化剂的喹啉加氢脱氮活性明显高于MoS₂和MoO₃催化剂。Mo₂C催化剂在反应温度360 ℃的喹啉加氢脱氮转化率达到58.69%,表现出较高的喹啉加氢脱氮活性。     

A study of hydrodenitrogenation of pyridine over molybdenum nitride catalysts and their characterization

A series of molybdenum nitride (Mo₂N) catalysts were prepared by a topotactic synthesis method using a TPR (Temperature Programmed Reaction) at various conditions (temperature ramping rate, NH₃ gas flow rate, final preparation temperature). The surface property and acidity of Mo₂N catalysts prepared at various prepared conditions were studied by SEM, XRD, BET, FTTR and TGA. The hydrodenitrogenation (HDN) of pyridine in n-heptane over Mo₂N catalyst (Al) was studied in a fixed bed continuous flow reactor (CATATEST) at the temperatures between 250–450°C , the pressure at 20–40 X 10₅ Pa and the contact time between 0.01-0.05 g cat.hr./ml feed. The microstructure of M0₂N catalyst was not changed at various preparation conditions by topotactic reaction. The XRD and BET studies showed that the extent of the crystallinity and the surface area of the prepared Mo₂N catalysts increased when the final preparation temperature increased and the temperature ramping rate was lowered. In addition, from the TGA curve, the acid strength increased with the increase of the NH₃ gas flow rate. The results of pyridine hydrodenitrogenation (HDN) over Mo₂N catalyst showed that the catalytic activity (conversion % ) increased as reaction temperature, reaction pressure, and contact time increases. The selectivity for piperidine possessed a maximum at 350°C regardless of the reaction pressure. Also, the selectivity for cracked products increased as reaction temperature and pressure increased. The activation energy was determined 7.16 kcal/mol by Arrehenius plot.     

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 Mo₂C. 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 (Mo₂C-Pt) turns out to be more active than Mo₂C. 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.     

Effect of Re loading on the structure, activity and selectivity of Re/C catalysts in hydrodenitrogenation and hydrodesulphurisation of gas oil

A series of Re-containing catalysts supported on activated carbon, with Re loading between 0.74 and 11.44 wt.% Re₂O₇, was prepared by wet impregnation and tested in the simultaneous hydrodesulphurisation (HDS) and hydrodenitrogenation (HDN) of a commercial gas oil. Textural analysis, XRD, X-ray photoelectron spectroscopy (XPS) and surface acidity techniques were used for physicochemical characterisation of the catalysts. Increase in the Re concentration resulted in a rise in the HDS and HDN activity due to the formation of a monolayer structure of Re and the higher surface acidity. At Re concentrations >2.47 wt.% Re₂O₇ (0.076 Re atoms nm⁻²) the reduction in the catalytic activity was related to the loss in specific surface area (BET) due to reduction in the microporosity of the carbon support. The magnitude of the catalytic effect was different for HDS and HDN, and depended strongly on the Re content and reaction temperature. The apparent activation energies were about 116–156 kJ mol⁻¹ for HDS and 24–30 kJ mol⁻¹ for HDN. This led to a marked increase in the HDN/HDS selectivity with decreasing temperature (values >3 at 325 °C), due to the large differences in the apparent activation energies of HDS and HDN found for all catalysts. A gradual increase in the HDN/HDS selectivity with increased Re loading was also found and related to the observed increase of catalyst acidity. The results are compared with those obtained for a series of Re/γ-Al₂O₃ catalysts.     

Hydrodenitrogenation of indole over Mo2C catalyst: Insights into mechanistic events through DFT modeling

The molecular reaction mechanism of hydrodenitrogenation of indole was studied using density-functional theory calculations of the adsorbed o-ethylaniline surrounded by mobile hydrogen atoms. It was found that the hydrogenation of o-ethylaniline occurs through two steps: consisting in redistribution of the π electron density to form multiple partial MoC(ring) bonds with the surface upon adsorption, and a subsequent hydrogen attack directed on the aromatic ring or the amine group. The direction of the hydrogen attack and the associated energy barriers determine the rate constants of the early (DDN, direct denitrogenation) and late (HYD, hydrogenation) nitrogen removal steps, and thus rules the selectivity of indole hydrodenitrogenation to ethylcyclohexane or ethylbenzene.     

Ni//Mo synergism via hydrogen spillover,in pyridine hydrodenitrogenation

The pyridine hydrodenitrogenation (HDN) over physically separated stacked Ni//Mo beds was investigated using a continuous-flow high pressure (3 MPa) stainless steel microreactor. Results prove the existence of synergism between physically separated beds of Ni-/γ-Al₂O₃ and Mo/γ-Al₂O₃ catalysts for the pyridine hydrodenitrogenation reaction. This synergism is explained by the formation of hydrogen spillover. Product analysis of the pyridine hydrodenitrogenation over Ni//Mo stacked beds suggested that the hydrogen spillover modified the active sites of the MoS₂ by increasing the hydrogenation sites.     

四氯化硅氢化技术进展

四氯化硅作为西门法高纯多晶硅生产中产量最大的副产物,是一种具有强腐蚀性的毒害物质。目前,国内多晶硅的大规模生产即将兴起,解决其副产物四氯化硅的最有效的方法是转化为三氯氢硅。着重介绍了热氢化、冷氢化、氯氢化、等离子体氢化等国内外四氯化硅氢化技术的工艺特点和研究进展。     

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.     

Iminium cations as intermediates in the hydrodenitrogenation of alkylamines over sulfided NiMo/γ-Al2O3

The mechanism of the hydrodenitrogenation of the mixed dialkyl- and trialkylamines C₁NHC₆ and C₁N(C₆)₂ was studied over sulfided NiMo/γ-Al₂O₃ at 280 °C and 3 MPa. C₁NHC₆ reacted by disproportionation to C₁N(C₆)₂ as well as C₆N(C₁)₂ and by substitution by H₂S to methylamine and hexanethiol as well as hexylamine and methanethiol. C₁N(C₆)₂ reacted by substitution with H₂S to C₁NHC₆ and C₆NHC₆ and methane- and hexanethiol. The probability of breaking the C₁N bond was only slightly smaller than of breaking the C₆N bond in C₁N(C₆)₂. In the reaction of an equimolar mixture of C₅NHC₅ and C₁N(C₆)₂ both C₁N(C₅)₂ and C₆N(C₅)₂ were formed. The transfer of the methyl group in these reactions cannot be explained by imine and enamine intermediates, only iminium cation intermediates can explain all the products in the hydrodenitrogenation of monoalkyl-, dialkyl- and trialkylamines.