二苯并噻吩类硫化物在非负载型NiMoW催化剂上加氢脱硫反应机理

研究了二苯并噻吩(DBT)、4-甲基二苯并噻吩(4-MDBT)和4,6-二甲基二苯并噻吩(4,6-DMDBT)在非负载型NiMoW催化剂上的加氢脱硫反应产物分布及反应机理,给出了它们在非负载型催化剂上加氢脱硫反应网络。研究发现,由于甲基的空间位阻效应,二苯并噻吩类化合物加氢脱硫转化率顺序为4,6-DMDBT≈4-MDBT<DBT,而非负载型NiMoW催化剂具有很高的芳环加氢活性,有利于烷基取代的芳环加氢,减弱空间位阻效应,使烷基取代的二苯并噻吩类化合物得到有效脱除。DBT的脱硫产物会被进一步加氢,其产物分布与联苯加氢产物相似。4-MDBT有两种预加氢脱硫反应路径,甲基取代的苯环由于甲基的供电子效应会被优先加氢。非负载型催化剂存在的L酸中心会使部分4-MDBT和4,6-DMDBT通过脱甲基反应生成DBT再进行脱硫反应。

非负载型NiMoW加氢催化剂的制备、表征和性能评价

以NiMoW复合氧化物为前躯体制备高活性非负载型NiMoW加氢催化剂,考察了制备过程中黏结剂、胶溶剂、熟化处理等因素对催化剂性能的影响。采用BET、XRD、SEM、TEM、强度测定、堆密度测定等手段对催化剂进行表征,采用模拟柴油体系和真实柴油为原料对催化剂进行活性评价。结果表明,选择合适的黏结剂、胶溶剂以及适宜的熟化处理方法,不但可以保持催化剂原有活性相结构,而且能减小催化剂颗粒度,增大比表面积及孔容、孔径,提高催化剂的机械强度。在345℃、7.0 MPa、空速2.0h-1条件下,采用熟化处理制备的NiMoW-H催化剂,可将柴油中的硫质量分数由3690μg/g降低到9μg/g,而NiMoP/Al2O3参比催化剂仅降低到103μg/g。

Synthesis of Ni_2P promoted trimetallic NiMoW/γ-Al_2O_3 catalysts for diesel oil hydrotreatment

The Ni2P promoted and γ-Al2O3 supported NiMoW sulfide catalyst consisting of 4 wt% Mo, 22 wt% W, 2 wt% Ni and 2.5 wt% Ni2P was synthesized by a co-impregnation method. The catalysts were characterized by N2 adsorption-desorption, X-ray diffraction （XRD）, diffuse reflectance infrared Fourier transform （DRIFT） spectroscopy, NH3 temperature-programmed desorption （NH3-TPD） and transmission electron microscopy （TEM）. The results showed that Ni2P, Ni, Mo and W species were highly dispersed over γ-Al2O3. The hydrodesulfurization （HDS） of dibenzothiophene （DBT） showed that the presence of Ni2P brought a strong promotional effect on the HDS activity, which was further confirmed by the HDS and hydrodenitrogenation （HDN） of diesel oil under industrial conditions. The enhancement in HDN activity and stability by Ni2P addition could be attributed more to the effect of new active sites of Ni2P than that of acidity modification. The as-prepared Ni2P-NiMoW/γ-Al2O3 catalyst showed better hydrotreating performance than NiMoW/γ-Al2O3 and commercial catalysts.

Synthesis, characterization and hydrodesulfurization activity of silica-dispersed NiMoW trimetallic catalysts

Silica-dispersed NiMoW trimetallic hydrodesulfurization catalysts were prepared by deposition-precipitation method. For comparative pur- poses, bulk NiMoW trimetallic catalysts were obtained by co-precipitation. Silica was employed to disperse active metals for full utilization of active components and silica-dispersed NiMoW catalyst had high active metal content. BET analysis showed that silica-dispersed NiMoW trimetallic catalysts had a high surface area （165.1 m2/g） and pore volume （0.27 ml/g）. Transmission electron microscopy results proved that active components were well dispersed. Hydrodesulfurization activity of silica-dispersed NiMoW catalysts was much higher than that of comparative catalysts and up to twice greater than those of commercial NiMo alumina-supported systems per gram of catalyst.

Deep Hydrodesulfurization of Diesel Fuel over Diatomite-dispersed NiMoW Sulfide Catalyst

Diatomite-dispersed NiMoW catalyst was prepared and characterized,and the activity of catalyst samples was tested during the HDS reaction of FCC diesel.Sulfur compounds in the feedstock and the hydrogenated products obtained over different catalysts were determined by GC-PFPD.The test results showed that the diatomite-dispersed NiMoW catalyst had high hydrodesulfurization activity for FCC diesel,which could be contributed to the excellent hydrogenation performance of the said catalyst.Characterization of catalyst by TEM and XRD indicated that the diatomite-dispersed NiMoW catalyst possessed higher layer stacking,larger curvature of MoS2or WS2,and segregated Ni3S2crystals relative to the supported catalyst.This kind of structure leads to high hydrogenation activity of the diatomite-dispersed NiMoW catalyst.

柴油超深度加氢脱硫非负载型Ni-Mo-W催化剂的研究

采用化学合成法制备了多孔金属固溶体,以此固溶体为前驱体制备了非负载型Ni-Mo-W加氢催化剂,采用XRD、TEM方法对硫化态非负载型催化剂进行表征,并以大庆低硫FCC柴油、中东高硫柴油为原料对非负载型催化剂进行深度加氢脱硫性能试验。结果表明,非负载型硫化态Ni-Mo-W催化剂中活性相形态主要为Ni_3S_2和MoS_2/WS_2,其中MoS_2/WS_2堆叠层数为3～8,远高于普通负载型催化剂。该非负载型Ni-Mo-W催化剂对国内外低硫和高硫柴油加氢脱硫反应均表现出较高的活性和稳定性。

桦甸页岩油柴油馏分中氮化物的加氢反应性能

采用硫化态NiMoW/Al2O3催化剂、在微型固定床加氢反应装置上,考察了反应温度、反应压力、停留时间和氢油体积比对桦甸页岩油柴油馏分中氮化物脱除率的影响,计算了加氢脱氮反应的表观动力学常数。实验结果表明,升高反应温度和反应压力或延长停留时间都能使碱性氮、非碱性氮及总氮的脱除率增加,但三者的增幅不同;增大氢油体积比使碱性氮、非碱性氮及总氮的脱除率先显著增加后略有减小。碱性氮、非碱性氮及总氮的加氢反应均符合拟一级反应动力学方程,在较低温度(340℃)下,总氮的脱除速率由碱性氮的脱除速率决定;而在较高温度(380℃)下,总氮的脱除速率由非碱性氮的脱除速率决定。NiMoW/Al2O3催化剂可有效降低加氢脱氮反应的表观活化能,具有较高的加氢脱氮活性。

超(超)临界机组高温构件用材料的性能、发展与应用

基于火电技术向高参数化超(超)临界方向的发展,按照低合金钢、奥氏体钢和镍基合金向9%-12%Cr铁素体钢的发展路线,对机组高温零部件所用材料的性能特点、发展历程和应用状况进行综合分析、论述与展望,重点介绍超超临界汽轮机高温构件所用材料1Cr10NiMoW2VNbN钢的研究与应用。