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。     

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。     

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.     

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。     

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.     

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.     

Promoting effect of NiAl2O4 for supported Ni particles on sprayed Ni/Al2O3 catalysts

Ni/Al₂O₃ catalysts were prepared by the spray reaction method. The NiO particles supported on NiAl₂O₄ were stabilized against the aggregation and converted into smaller Ni particles by H₂ reduction. The Ni particles stabilized on NiAl₂O₄ marked anomalous high activity for CO hydrogenation, due to the stronger interaction between Ni and NiAl₂O₄. This revised version was published online in July 2006 with corrections to the Cover Date.     

氢等离子体法制备Ni_2P和Ni_2P/SiO_2加氢脱硫催化剂

采用免焙烧的方法,直接将Ni(NO3)2和(NH4)2HPO4盐的前驱体,或是担载Ni(NO3)2和(NH4)2HPO4盐的前驱体通过氢等离子体法(PR)制备了Ni2P-NC-PR,Ni2P(25)/Si O2-NC-PR加氢脱硫催化剂。以质量分数为0.8%的二苯并噻吩/十氢萘溶液为模型化合物,考察了催化剂的HDS反应性能,并用XRD对催化剂晶相进行了表征。新鲜制备的催化剂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,PR还原法制备的Ni2P-NC-PR催化剂的加氢脱硫活性高于Ni2P-C-PR催化剂,PR还原法制备的Ni2P(25)/Si O2-NCPR催化剂的加氢脱硫活性高于Ni2P(25)/Si O2-C-PR催化剂。XRD表征结果表明:Ni2P-NC-PR或Ni2P(25)/Si O2-NC-PR催化剂的颗粒尺寸都小于Ni2P-C-PR或Ni2P(25)/Si O2-C-PR催化剂的颗粒尺寸,催化剂的活性中心较多,其高活性可归于其活性中心数量的增加。     

Synergism between Brønsted acid sites and metal sulfide particles in the hydrodesulfurization of thiophene on ultrastable Y zeolite catalysts W/USY and Ni/USY

The influence of the acidity of ultrastable Y (USY) zeolite-supported tungsten or nickel sulfide catalysts, prepared at different pH values, on thiophene hydrodesulfurization activity has been studied. The acidity affects the catalysts' deactivation. The results of the initial activity clearly show a synergic effect between the metal sulfide centers and the Brønsted acid sites present in the zeolites. © 1998 SCI     

Preparation of alumina supported molybdena catalysts by new slurry impregnation method: MoO3/Al2O3 sulfide hydrodesulfurization catalyst

A new slurry impregnation method (SIM) of the preparation of a catalyst or catalyst precursor MoO₃/Al₂O₃ is described. Aqueous slurry of powdered MoO₃ is mixed with alumina extradátes and the mixture is refluxed. A low solubility of MoO₃ is sufficient for transport of MoO₃ from powder form via solution to the surface of the support. The catalysts were tested by hydrodesulfurization of thiophene at 1.6 MPa and 280–400°C. Their activity was similar to the activity of industrial and laboratory MoO₃/Al₂O₃ samples prepared by conventional impregnation with solution of ammonium heptamolybdate. The advantage of the SIM method is that calcination, producing nitrogeneous waste gases, is not required and that all deposited molybdenum species are adsorbed and not precipitated.     

ICP-AES法测定活性炭负载型催化剂中铂、镍的含量

用电感耦合等离子光谱法,测定了活性炭负载型催化剂中铂、镍元素的含量。Pt的相对标准偏差为2.31~3.82,回收率为97%~102%;N i的相对标准偏差为0.59~0.83,回收率为95%~104%。该方法简便,易操作,数据重复性好,加标回收率高。     

磷对Ni(Co)Mo(W)/Al2O3加氢处理催化剂的影响研究进展

Ni(Co)Mo(W)/Al2O3催化剂是工业中最常用的加氢处理催化剂.磷作为Ni(Co)Mo(W)/Al2O3加氢处理催化剂中较为常用的添加剂,用于改善催化剂的物理化学性质.本文从磷对Ni(Co)Mo(W)/Al2O3加氢催化剂孔结构、酸性、活性组分分散度等理化性能以及磷对加氢脱硫(HDS)和加氢脱氮(HDN)催化性能两个方面的影响对文献研究结果进行了综述,对磷添加剂的研究结果、存在的分歧以及研究机会进行了分析讨论.     

Sequential production of H2 and CO over supported Ni catalysts

Methane decomposition into H₂ and carbon nanofibers at 823 K and subsequent gasification of the carbon nanofibers with CO₂ into CO at 923 K were performed over supported Ni catalysts (Ni/SiO₂, Ni/TiO₂ and Ni/Al₂O₃). Supported Ni catalysts were deactivated for CH₄ decomposition with time on stream due to deposition of a large amount of carbon nanofibers. Subsequent contact of CO₂ with carbon nanofibers on the deactivated catalysts resulted in the formation of CO with a conversion of the carbons higher than 95%. In addition, gasification with CO₂ regenerated the activity of supported Ni catalysts for CH₄ decomposition, indicating that H₂ formation through CH₄ decomposition and CO formation through gasification with CO₂ could be carried out repeatedly. Conversions of carbon nanofibers into CO were kept higher than 95% in the repeated gasification over all the catalysts, while change in the catalytic activity for CH₄ decomposition with the repeated cycles depended on the kind of catalytic supports. Catalytic activity of Ni/SiO₂ for CH₄ decomposition was high at early cycles, however, the activity decreased gradually with the repeated cycles. On the other hand, Ni/TiO₂ and Ni/Al₂O₃ showed high activity for CH₄ decomposition and the activity was kept high during the repeated cycles. These changes of catalytic activities for CH₄ decomposition could be explained by changes in particle sizes of Ni metal, i.e. Ni metal particles in Ni/SiO₂ aggregated into ones larger than 150 nm with the repeated cycles, while the particle sizes of Ni metal in Ni/TiO₂ and Ni/Al₂O₃ remained at an effective range for CH₄ decomposition (60-100 nm).