Study on the hydrodesulfurization and the hydrodenitrogenation over Al2Oa-ZrO2 supported Ni2P catalysts

采用浸渍-沉淀法制备Al2O3-ZrO2复合氧化物,通过程序升温还原法制备Ni2P/Al2O3-ZrO2催化剂。运用X射线衍射、N2吸附-脱附、X射线光电子能谱技术对载体和催化剂进行表征,并以噻吩加氢脱硫、吡啶加氢脱氮反应为探针考察复合氧化物对Ni2P催化剂加氢活性的影响。结果表明,在Al2O3表面引入少量ZrO2,既保持了γ-Al2O3大比表面积的结构优势,又减少了P或Ni与Al2O3表面的接触,促进Ni2P的形成。载体中ZrO2质量分数20%的Ni2P/Al2O3-ZrO2催化剂活性最高,载体焙烧温度过高会导致催化剂活性下降。     

MoS2基催化剂加氢脱硫反应活性相和作用机理研究进展

加氢脱硫工艺在清洁油品生产过程中发挥着重要作用，而MoS₂基催化剂是加氢脱硫的主要催化剂，因此对MoS₂基催化剂活性相和催化反应机理的深入研究有助于从原子层面上对催化剂进行优化设计。本文首先介绍了国内外有关MoS₂基催化剂活性相形貌结构的研究，着重探讨了硫化气氛、助剂和载体类型对活性相结构的影响，以及现有表征技术在MoS₂基催化剂活性相形貌结构研究中所面临的挑战，总结了不同条件下活性相的微观结构特征；同时，从MoS₂基催化剂的活性相组成和结构角度分析了噻吩的加氢脱硫机理，发现了加氢脱硫活性与催化剂微观结构之间的紧密联系；最后展望了理论计算在设计和开发高效加氢脱硫催化剂过程中的重要指导作用。     

氢等离子体法制备Ni_2P催化剂及加氢脱硫性能

采用氢等离子体还原法制备了体相Ni2P,新鲜制备的Ni2P在移入固定床反应器之前用体积分数10%H2S/Ar钝化,以保护其结构不被破坏。实验证明:氢等离子体(PR)还原法制备的Ni2P催化剂的加氢脱硫活性高于程序升温还原(TPR)法制备的催化剂。XRD表征结果表明,氢等离子体还原法制备的Ni2P的粒度较小,活性中心较多,其高活性可归于其活性中心数量的增加。氢等离子体还原法制备的Ni2P具有良好的反应稳定性。     

柴油加氢脱硫催化剂的研究进展

随着环保问题越来越受到世界各国的重视,各国相继推出了高质量的清洁燃料标准。低硫化是柴油清洁利用的发展趋势,研制开发高效稳定的加氢脱硫催化剂是加氢脱硫技术研究的主要方向之一。本文主要阐述了国内外在柴油加氢脱硫方面的研究成果,主要分析了柴油加氢脱硫反应机理、柴油加氢脱硫催化剂的主催化剂、助剂和载体的研究进展。分析表明,柴油加氢脱硫的主要路径是直接脱硫和加氢路径,而柴油中受空间位阻影响大的4.6-二甲基二苯并噻吩的脱除路径主要是加氢路径和烷基转移路径。文章从柴油加氢脱硫催化剂的组成和结构分析了催化剂的加氢脱硫机理,得到加氢脱硫活性与催化剂的表面微观结构紧密相关。分析了近年来催化剂载体的研究进展,发现柴油加氢脱硫催化剂的载体主要是氧化铝及改性的氧化铝。     

加氢脱硫催化剂载体的研究进展

综述了加氢脱硫催化剂载体的研究现状及其发展趋势,分别从单组分载体、复合氧化物载体、分子筛和改性载体4个方面论述了加氢脱硫催化剂载体各自的优缺点。单组分载体重点介绍了A12O3、TiO2、炭载体;复合氧化物载体主要对铝基、钛基二元复合氧化物以及三元复合氧化物载体进行了综述;并且对以MCM-41、SBA-15和KIT为代表的介孔分子筛做了介绍;还描述了近年来以改性MCM-41、SBA-15、活性炭为主要研究对象的改性的分子筛。最后指出改性载体尤其是改性分子筛将是未来研究的焦点。     

Al2O3-ZrO2负载Ni2P催化剂加氢脱硫脱氮活性

采用浸渍-沉淀法制备Al2O3-ZrO2复合氧化物,通过程序升温还原法制备Ni2P/Al2O3-ZrO2催化剂。运用X射线衍射、N2吸附-脱附、X射线光电子能谱技术对载体和催化剂进行表征,并以噻吩加氢脱硫、吡啶加氢脱氮反应为探针考察复合氧化物对Ni2P催化剂加氢活性的影响。结果表明,在Al2O3表面引入少量ZrO2,既保持了γ-Al2O3大比表面积的结构优势,又减少了P或Ni与Al2O3表面的接触,促进Ni2P的形成。载体中ZrO2质量分数20%的Ni2P/Al2O3-ZrO2催化剂活性最高,载体焙烧温度过高会导致催化剂活性下降。     

Characterization of highly dispersed Ni/Al2O3 catalysts by EXAFS analysis of higher shells

The size and morphology of Ni/Al₂O₃ catalysts in the oxidic, reduced, and passivated state were determined by EXAFS analysis of the higher shells around the Ni atoms. In the oxidic state, the Ni cations were present in small NiO_x particles with predominant (111) plane. Below 4.5 wt% Ni loading, the NiO_x particles consisted of one Ni layer, and of two or three Ni layers above 4.5 wt% Ni. A Ni–Al contribution was observed in samples with low Ni loading. The layer which is in contact with the Al₂O₃ surface is affected by the support surface and its structure is highly distorted, while the other layers were not distorted and have a structure similar to that in bulk NiO. In the reduced state, the number of Ni metal atoms in the reduced Ni particles was smaller than 100 with a narrow distribution below a loading of 15.6 wt% Ni. Above this loading, the particle size suddenly increased and the distribution became wider. The distances and Debye–Waller factors were similar to those of bulk nickel which suggested a weak interaction between the particles and the support. In the passivated state, Ni kernels with 20–40 metal atoms were covered by a one layer thick NiO skin. This revised version was published online in June 2006 with corrections to the Cover Date.     

Mechanistic considerations on the involvement of dihydrointermediates in the hydrodesulfurization of dibenzothiophene-type compounds over molybdenum sulfide catalysts

The mechanism of the hydrodesulfurization of dibenzothiophene-type compounds involving their dihydroderivatives as intermediates was examined in the light of previous experimental results dealing with the effect of cobalt and nickel promoters on the selectivity of the reaction. It is suggested that the orientation of the hydrodesulfurization reaction regarding the so-called direct desulfurization or hydrogenation pathways depends on various factors: the distribution of the dihydrointermediates (two of them only among nine possible isomers can lead directly from dibenzothiophene to biphenyl); the availability of dissociated hydrogen on the catalytic centers on which they adsorb and the basicity of the sulfur anions associated to the catalytic centers.     

Extended X-ray absorption fine structure study of sulphur poisoned Ni/SiO2 catalysts

Extended X-ray absorption fine structure analysis was performed of the oscillations at the Ni K edge of Ni/SiO₂ catalysts completely deactivated by thiophene and partially regenerated by oxidationreduction cycles. The obtained data demonstrates that during the regeneration process sintering of the metalparticles takes place. Besides this, the best fit of the completely sulphided catalysts requires the presence of a sulphur shell in the nickel coordination sphere. The average coordination number of sulphur as well as the Ni-S distance suggest the formation of an in depthsulphide layer during the poisoning process. This implies a reconstruction of the metal particles when interacting at 0.034 kPa and 473 K with thiophene.     

Surface structure of Ni/MgO catalysts: Effects of carbon and hydrogen on the reactivity towards CO. HRTEM and FTIR studies

CO adsorption on high loading Ni/MgO samples treated at 800 and 900°C has been studied by using IR spectroscopy. Linear and bridged monocarbonyls are produced under low CO pressure and the Boudouard reaction occurs producing C, adsorbed on the metal particles, and CO₂, stabilized on the MgO matrix. Effects of hydrogen and carbon on surface reactivity have been studied. The morphology of the catalysts and of carbonaceous deposits produced by heating in CO at high temperature are examined by HRTEM.     

Synthesis of alumina-nitrogen-doped carbon support for CoMo catalysts in hydrodesulfurization process

More stringent environmental legislation imposes severe requirements to reduce the sulfur content in diesel to ultra-low levels with high efficient catalysts.In this paper,a series of CoMo/NDC@alumina cat-alysts were synthesized by combination of the chemical vapor deposition of nitrogen-doped carbon(NDC) using 1,10-phenanthroline and co-impregnation of Mo and Co active components.The optimal cat-alyst with additive of 25％ 1,10-phenanthroline was screened by a series of property characterization and the hydrodesulfrization (HDS) active test.The amount of "CoMoS" active phase of the optimal CoMo/C3 catalyst increased 5.3％ as compared with the CoMo/γ-Al2O3.The introduction of NDC improved the sul-fidation degree of Mo by 21.8％ as compared to the CoMo/γ-Al2O3 catalyst,which was beneficial to form more active sites.The HDS conversion of the NDC supported catalysts are higher than CoMo/γ-Al2O3 whether for the dibenzothiophene (DBT) or 4,6-dimethyl dibenzothiophene (4,6-DMDBT).Further hydroprocessing evaluation with Dagang diesel revealed that the CoMo/C3 catalyst possessed higher HDS property and the removal rate of DBTs in the diesel increased by 4％-11％ as compared to the CoMo/γ-Al2O3 catalyst.     

High activity Ni/MoS2 catalysts obtained from alkylthiometalate mixtures for the hydrodesulfurization of dibenzothiophene

An efficient method for improving the catalytic properties of unsupported Ni/MoS₂ catalysts is mixing thiometalate precursors applying the appropriate precursors and thermal conditions. High active catalysts for the hydrodesulfurization (HDS) of dibenzothiophene (DBT) are prepared by the controlled decomposition of physical mixtures of Ni(diethylentriamine)₂MoS₄ (NDTA-TM) and [(Propyl)₄N)]₂MoS₄ (TPA-TM). The catalysts with a higher content of NDTA-TM are very active with a high selectivity for the direct desulfurization pathway (DDS) due to the synergistic effect of nickel. In addition the presence of a large amount of carbon may produce single-slabs of nickel promoted carbon containing molybdenum sulfides. The activity enhancement is attributed to an increased number of NiMoS active sites originated by the chemical interaction between the precursors NDTA-TM and TPA-TM during the mixing procedure. Furthermore, the carbon content in the final products is related to the enhancement of the activity and the preference of the DDS pathway. The controlled decomposition of mixtures of NDTA-TM + TPA-TM yields catalysts which are about twofold more active than an industrial NiMo/Al₂O₃ catalyst. This improvement may be attributed to an intense interaction of the precursors during the synthesis causing a re-dispersion of nickel atoms from NDTA-TM over the surface of carbon containing molybdenum sulfide provided by the precursor TPA-TM, increasing the amount of active sites. The catalysts from mixtures of (NH₄)₂MoS₄ (A-TM) and NDTA-TM behave similarly to the pure precursors.     

Strong metal-support interaction in Ni/TiO2 catalysts: in situ EXAFS and related studies

In situ EXAFS and X-ray diffraction investigations of Ni/TiO₂ catalysts show that NiTiO₃ is formed as an intermediate during calcination of catalyst precursors prepared by the wet-impregnation method; the intermediate is not formed when ion-exchange method is used for the preparation. On hydrogen reduction, NiTiO₃ gives rise to Ni particles dispersed in the TiO₂(rutile) matrix. The occurrence of the anatase-rutile transformation of the TiO₂ support, the formation and subsequent decomposition/reduction of NiTiO₃ as well as the unique interface properties of the Ni particles are all factors of importance in giving rise to metal-support interaction. Active TiO₂(anatase) prepared from gel route gives an additional species involving Ni³⁺.     

制备条件对Co-Mo/TiO_2-Al_2O_3汽油HDS催化剂性能的影响

以蔗糖为辅助剂,采用溶胶-凝胶法制备了介孔氧化铝及相应的Co-Mo/TiO2-Al2O3汽油脱硫催化剂,并对其进行了TEM、XRD和N2吸附表征。以FCC汽油重馏分为原料,重点考察了不同条件下制得的Al2O3对催化剂选择性加氢脱硫性能的影响。结果表明,蔗糖(sucrose)添加量和pH值对Al2O3织构产生影响,进而影响到对应催化剂的加氢脱硫性能;在Al/sucrose摩尔比1∶1、pH值5.4时Al2O3的比表面积最大、孔径分布最窄,对应催化剂的选择性加氢脱硫活性最好;Al2O3的最可几孔径随pH值的增加而增大;溶胶老化温度对Al2O3的比表面积和孔容影响较大,但对最可几孔径和孔径分布影响较小。与Co-Mo/TiO2-sAl2O3(以sAl2O3表示市售Al2O3)催化剂相比,Co-Mo/TiO2-Al2O3催化剂具有较好的选择性加氢脱硫活性,在考察的条件范围内,脱硫率相同时其对应的烯烃饱和度低5%～15%左右。     

制备条件对Ni2P/TiO2-Al2O3催化剂加氢脱硫性能的影响

采用溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体, 以柠檬酸为络合剂, 浸渍法制备了负载型Ni₂P/TiO₂-Al₂O₃催化剂前体, 程序升温H₂还原法制备了Ni₂P/TiO₂-Al₂O₃催化剂, 并用 X 射线衍射(XRD)、N₂吸附比表面积(BET)测定技术对催化剂的结构和性质进行了表征, 考察了浸渍方法、Ni/P摩尔比、Ni₂P负载量对其进行的二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响。结果表明, 当Ni/P比低于1:1时, 能得到单一的Ni₂P物相;当Ni/P比为2:1时, 开始出现Ni₃P物相。采用Ni/P比为1:1、Ni₂P负载量为30%、采用共浸渍方法制备的Ni₂P/TiO₂-Al₂O₃催化剂具有最好的活性, 在360℃、3.0MPa、氢油比500 (体积比)、液时体积空速2.0h^-1的条件下反应4h时, 二苯并噻吩转化率为99.5%。     

焙烧及还原条件对Ni2P/TiO2-Al2O3催化剂加氢脱硫性能的影响

采用溶胶-凝胶法制备了TiO₂-Al₂O₃复合载体, 以柠檬酸(CA)为络合剂采用浸渍法制备了Ni₂P负载的TiO₂-Al₂O₃复合载体催化剂, 并用 X 射线衍射(XRD)、N₂吸附比表面积(BET)测定技术对催化剂的结构和性质进行了表征, 考察了载体焙烧温度、催化剂焙烧温度、还原温度、还原压力对其进行的二苯并噻吩(DBT)加氢脱硫(HDS)性能的影响。结果表明, 升高载体焙烧温度有利于催化剂表面上活性物种的分散, 但焙烧温度过高会导致催化剂烧结, 适宜的载体焙烧温度为550℃。当还原温度为500～550℃时, 磷化镍主要以Ni₁₂P₅相形式存在, 且随着还原温度的升高, Ni₁₂P₅的衍射峰强度逐渐增强, 还原温度为700℃时, 可得到单一的Ni₂P物相。载体焙烧温度为550℃, 催化剂焙烧温度为500℃, 还原温度为700℃, 常压还原制备的Ni₂P/TiO₂-Al₂O₃催化剂具有最好的活性。在360℃、3.0MPa、氢油体积比500、液时体积空速2.0h^-1的条件下, 反应4h时, DBT转化率为99.5 %。     

载体对FCC汽油加氢脱硫催化剂性能的影响

主要介绍了载体的种类及性能对FCC汽油加氢脱硫效果的影响。指出在制备FCC汽油加氢脱硫催化剂时,应选择具有适当酸碱度的物质作为载体,保证催化剂具有较高的加氢脱硫／加氢选择性,从而使脱硫后的FCC汽油满足低硫含量高辛烷值的要求。     

Alkali-induced sieving effect in Ni on silica catalysts

It is suggested that the addition of potassium nitrate to a Ni/SiO₂ precursor results, after reduction, in a blocking of nickel particles by a K-containing compound. The potassium film is supposed to act as a molecular sieve: it is permeable to a small molecule (H₂) and inhibits the access of large molecules to the nickel.     

磷添加方式对NiMo/Al2O3催化剂加氢脱硫性能的影响

采用分步浸渍法制备了不同磷添加方式改性的NiMo/Al₂O₃催化剂,在固定床微反装置上考察了该系列催化剂对焦炉煤气中噻吩加氢脱硫（HDS）性能的影响,采用BET、X射线衍射（XRD）、H₂程序升温还原（H₂-TPR）、NH₃程序升温脱附（NH₃-TPD）、C₄H₄S(H₂)程序升温脱附[C₄H₄S(H₂)-TPD]、X射线光电子能谱（XPS）、高清透射电镜（HRTEM）和拉曼（Raman）等分析手段对催化剂进行表征。结果表明,不同磷添加方式制备NiMo/Al₂O₃催化剂的HDS性能存在较大差异。其中,催化剂PNi-Mo/Al和PMo-Ni/Al表面弱吸附解离活性位增强,对焦炉煤气中噻吩有较好的低温加氢脱硫活性,以含292.5mg/m³噻吩的模拟焦炉煤气为原料时,PNi-Mo/Al在250℃下对噻吩的脱硫率达61%。对于PNi-Mo/Al和PMo-Ni/Al催化剂,先浸渍P、Ni或者P、Mo时,P优先和载体Al₂O₃作用,减弱了活性金属组分Ni、Mo与载体间的相互作用,而又防止Ni或者Mo与载体间相互作用过低而聚集,提高了Ni、Mo在载体表面的均匀分散,生成能够促进硫化形成Ⅱ型活性相Ni-Mo-S的NiMoO₄物种。NiMoO₄和MoO₃之间的协同作用提高了催化剂的硫化度,使HDS活性得以提高。     

Hydrotreating properties of mixed NbxMo1−xS2 alumina supported catalysts

Niobium-molybdenum disulfide solid solution (Nb_xMo_1−xS₂) has been prepared in a dispersed state on gamma alumina. The existence of this solid solution supported on alumina carrier has been proven with the help of EXAFS technique. The catalytic properties of these materials have been studied in hydrogenation and hydrodesulfurization reactions. Interestingly, as already observed for niobium sulfide, the activity of the Nb_xMo_1−xS₂ solid solution (HDS of DBT, P_tot=33 bar) is not decreased in the presence of H₂S up to p(H₂S)=200 Torr, at least up to x=0.4.