HDS and HDN activity of molybdenum and nickel–molybdenum catalysts supported on alumina–titania carriers

Alumina–titania supports containing 5–50 wt.% of TiO₂ were prepared by coprecipitation method using inorganic precursors (sodium aluminate and titanium chloride). DTA-TGA, XRD, SEM, TPD_NH3, and IR spectroscopy were used to characterise these materials. The study shows that the promoting effect of nickel on the HDS activity of molybdenum catalysts supported on Al₂O₃TiO₂ is significantly lower than that for molybdenum catalyst supported on Al₂O₃, and depends on the TiO₂ content. The SEM results show that in the case of rich Al support (20 wt.% of TiO₂) molybdenum was aggregated on the external surface of the catalyst, whereas it was uniformly dispersed on the external surface of alumina. Results also show that molybdenum is preferably supported on aluminum oxide. Application of Al₂O₃TiO₂ oxides enhances the HDN activity of nickel–molybdenum catalysts. The highest HDN efficiency was obtained for the NiMo/Al₂O₃TiO₂ catalyst containing 50 wt.% of TiO₂. HDN activity was found to depend on protonic acidity and anatase content.     

环戊酮硫醇化反应钼基催化剂中镍的促进作用

在系列NiMo/Al2 O3 催化剂上考察了环戊酮转化为环戊硫醇的反应。根据反应结果推断 ,该硫醇化反应分两步进行 ,第一步为环戊酮和H2 S生成环戊硫酮 ,第二步为环戊硫酮加氢生成环戊硫醇。在部分所用催化剂上发现了环戊硫酮中间产物。Ni和Mo对反应具有协同作用 ,Ni的加入明显加速了第二步反应的进行 ,使反应活性和选择性大大提高     

Hydrodesulfurization of hindered dibenzothiophenes: an overview

Hydrodesulfurization is a well-documented process which has been commonly used in the refining of crude oil for over 60 years. It is a process for which interest is frequently renewed due to the requirement to use new feedstocks and the application of more severe environmental legislation, for example, the need to reduce sulfur levels in fuels. Of particular importance in achieving low sulfur levels in fuels is the problem posed by a particular class of compounds, namely hindered dibenzothiophenes, e.g. dibenzothiophene, 4-methyldibenzothiophene and 4,6-dimethyldibenzothiophene. Dibenzothiophenes demonstrate resilience to hydrodesulfurization using current catalyst formulations. This overview addresses the key area of hydrodesulfurization chemistry concerning the desulfurization of highly hindered sulfur containing molecules.     

工业NiW/Al2O3催化剂上喹啉的加氢脱氮宏观动力学

以喹啉为含氮模型化合物,在高压滴流床反应装置中考察了工业NiW/Al2O3催化剂RN-10上的加氢脱氮动力学规律,研究了反应温度330～420℃、氢分压1.2～5.2MPa、氢油比200～800(v/v)、重量空速(WHSV)20～70 h-1等反应条件对喹啉的加氢脱氮反应结果的影响.结果表明,反应温度对喹啉的脱氮率影响较大,提高反应温度可有效提高喹啉的脱氮率;同时,氢分压也是喹啉加氢脱氮的一个重要的影响因素,但是,当氢分压和氢油比较大时,氢分压和氢油比的变化对喹啉的脱氮率基本无影响.采用修正的n(n＜1)级反应动力学模型对实验数据进行拟合,求得了喹啉加氢脱氮反应的表观活化能为180.4 kJ·mol-1.经检验,模型计算结果与实验结果能较好地吻合.     

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.     

Catalytic activities of Co(Ni)Mo/TiO2–Al2O3 catalysts in gasoil and thiophene HDS and pyridine HDN: effect of the TiO2–Al2O3 composition

The effect of the TiO₂–Al₂O₃ mixed oxide support composition on the hydrodesulfurization (HDS) of gasoil and the simultaneous HDS and hydrodenitrogenation (HDN) of gasoil+pyridine was studied over two series of CoMo and NiMo catalysts. The intrinsic activities for gasoil HDS and pyridine HDN were significantly increased by increasing the amount of TiO₂ into the support, and particularly over rich- and pure-TiO₂-based catalysts. It is suggested that the increase in activity be due to an improvement in reducing and sulfiding of molybdena over TiO₂. The inhibiting effect of pyridine on gasoil HDS was found to be similar for all the catalysts, i.e., was independent of the support composition. The ranking of the catalysts for the gasoil HDS test differed from that obtained for the thiophene test at different hydrogen pressures. In the case of gasoil HDS, the activity increases with TiO₂ content and large differences are observed between the catalysts supported on pure Al₂O₃ and pure TiO₂. In contrast, in the case of the thiophene test, the pure Al₂O₃-based catalyst appeared relatively more active than the catalysts supported on mixed oxides. Also, in the thiophene test the difference in intrinsic activity between the pure Al₂O₃-based catalyst appeared relatively more active than the catalysts supported on mixed oxides. Also in the thiophene test, the difference in intrinsic activity between the pure Al₂O₃- and pure TiO₂-based catalysts is relatively small and dependent on the H₂ pressure used. Such differences in activity trend among the gasoil and the thiophene tests are due to a different sensitivity of the catalysts (by different support or promoter) to the experimental conditions used. The results of the effect of the H₂ partial pressure on the thiophene HDS, and on the effect of H₂S concentration on gasoil HDS demonstrate the importance of these parameters, in addition to the nature of the reactant, to perform an adequate catalyst ranking.     

脂肪酸甲酯加氢脱氧和加氢脱氮制备生物烷烃

以源于废弃油脂的脂肪酸甲酯(FAMEs)为原料,以Ni Mo/Al2O3为催化剂,采用加氢脱氧和加氢脱氮两步法制备生物烷烃并对反应工艺进行了优化。结果表明,加氢脱氧的最佳反应条件为:反应温度380℃、氢气压力2 MPa、氢气和FAMEs体积比为1000,空速1h–1;加氢脱氮的最佳反应条件为:反应温度310℃、氢气压力2 MPa、氢气和烷烃体积比为2000,空速0.25 h–1。在该优化反应条件下,硫化后的Ni Mo/Al2O3催化FAMEs加氢脱氧能够获得正构烷烃质量分数高于97%的生物烷烃,所得产品采用Ni Mo/Al2O3催化剂进行二次加氢脱氮能够进一步移除超过90%的含氮化合物。硫化后的Ni Mo/Al2O3催化剂在FAMEs加氢脱氧反应中具有良好的结构稳定性和抗积碳性能,使用1000 h后其晶相结构无明显改变且表面积碳量仅为3.18%。     

Effect of the order of potassium introduction on the texture and activity of Mo/Al2O3 catalysts in water gas shift reaction

The effect of deposition and order of potassium introduction on the texture and activity of Mo/γ-Al₂O₃ catalysts in water gas shift (WGS) reaction was investigated. The samples were synthesised by incipient wetness impregnation of the carrier with aqueous solutions of the corresponding salts followed by drying and calcination after each deposition step. The prepared catalyst precursors were sulphided at 400°C for 2 h with 6% H₂S in H₂ before testing in WGS reaction in a glass flow apparatus at 400°C under atmospheric pressure.

The results show that potassium deposition alone on the bare γ-Al₂O₃ (sample K/Al₂O₃) decreases the specific surface after calcination by blocking the constrictions between the pores in the primary porous texture. In the WGS reaction conditions part of the pores are deblocked and a redistribution in the pore volumes occurs.

The deposition of the Mo (sample Mo/Al₂O₃) also results in a decrease in both specific surface and total pore volume with respect to the bare support. However after catalytic activity test no substantial changes in its texture were observed.

The addition of K to the Mo (sample KMo/Al₂O₃) leads to nonuniformity in distribution of molybdenum–oxygen entities due to partial migration of the MoO_x species to the external surface. The specific surface is not changed during the reaction test.

The deposition of Mo on K/Al₂O₃ contributes to the uniform distribution of oxomolybdenum species in the porous texture of the support. This uniformity is preserved to a high extent in the catalytic reaction as well. The activity in the synthesised samples in the WGS reaction decreases in the order MoK/Al₂O₃ > Mo/Al₂O₃ > KMo/Al₂O₃.     

一种提高Mo—Ni／Al2O3催化剂金属分散度的方法研究

提出了一种提高Ｍｏ－Ｎｉ／Ａｌ２Ｏ３催化剂金属分散度的方法，并采用ＸＰＳ及连续流动高压微反等手段进行考查和评价。研究结果表明，向浸渍液中加入适当的有机酸，要明显提高Ｍｏ，Ｎｉ的分散度，进而改善了催化剂的活性及选择性。     

Hydroisomerization and hydrocracking of long chain n-alkanes on Pt/amorphous SiO2–Al2O3 catalyst

The hydroisomerization and hydrocracking of n-hexadecane, n-octacosane and n-hexatriacontane on a 0.3% platinum/amorphous silica–alumina (MSA/E) catalyst was investigated in a stirred microautoclave at 345, 360 and 380°C and between 2 and 13.1 MPa hydrogen pressure. For each n-paraffin, the reaction pathway and the kinetic parameters were determined. The results were used to elucidate the effect of chain length and operating conditions on isomerization and cracking selectivity. The conversion of the n-paraffins lead to the formation of a mixture of the respective isomers, as the main product, together with cracking products. At every temperature, the iso-alkane/n-alkane ratio of cracking products increased considerably with increasing conversion degree. At the same conversion level, higher reaction temperatures lead to cracking products characterized by a lower iso-alkane/n-alkane ratio. The conversion rate constants showed a considerable increase between n-C₁₆ and n-C₂₈, whereas a slight decrease between n-C₂₈ and n-C₃₆ was observed. The hydroisomerization selectivities showed a decrease as a function of chain length and with increasing conversion levels. The increase in reaction temperature leads to a small decrease in the isomerization selectivities only at low-medium conversion degrees and at the highest temperature investigated, while the effect of this parameter on the maximum yields achievable in iso-C16, iso-C28 and iso-C36 was negligible. The results indicate that the conversion of the n-paraffins follows a first-order kinetic in hydrocarbon while the order in hydrogen pressure was −1.1 ± 0.21 for n-C₁₆ and −0.66 ± 0.15 for n-C₂₈. Furthermore, an increase in hydroisomerization selectivity at higher hydrogen pressure for n-C₂₈ conversion was observed.     

On the dynamic behavior of “NOx-storage/reduction” Pt–Ba/Al2O3 catalyst

The NO_x storage and reduction functions of a Pt–Ba/Al₂O₃ “NO_x storage–reduction” catalyst has been investigated in the present work by applying the transient response and the temperature programmed reaction methods, by using propylene as the reducing agent. It is found that: (i) the storage of NO_x occurs first at BaO and then at BaCO₃, which are the most abundant sites following regeneration of catalyst with propylene; (ii) the overall storage process at BaCO₃ is slower than at BaO; (iii) CO₂ inhibits the NO_x storage at low temperatures; (iv) the amount of NO_x stored up to catalyst saturation at 350 °C corresponds to 17.6% of Ba; (v) the reduction of stored NO_x groups is fast and is limited by the concentration of propylene in the investigated T range (250–400 °C); (vi) selectivity to N₂ is almost complete at 400 °C but is significantly lower at 300 °C due to the formation of NO which can be tentatively ascribed to the presence of unselective Pt–O species.     

Al2O3-SiC熔沟浇注料研制

介绍了进口熔铜保温炉熔沟材料的剖析和研制熔沟浇注料的过程。着重介绍了防爆技术的应用和基质中Al2O3/SiO2及防氧化剂的调整对研制料烘烤抵抗开裂能力和热态强度的影响,从而使全部采用国产原料研制的熔沟浇注料理化性能超过了进口料的实测水平,实物质量更胜一筹。     

Preparation, characterization and deactivation studies of Co–Mo/γ–Al2O3 deoxidizing catalyst

A deoxidizing catalyst was prepared in this paper. Several characterization techniques (XRD, SEM–EDS, TEM, TPD and TPR) were used to study its structure and properties. A normal pressure micro-reactor was built to study its deoxidizing performance. Results show that when inlet O₂ concentration was 0.1%, space velocity was 3000–12 000 h⁻¹ and operation temperature was above 80 °C, the outlet residual O₂ can be as low as 1.0 × 10⁻⁶ (v/v). 300 h continuous operation shows that its deoxidizing activity was stable. Through comparison of the deoxidizing activities for fresh and deactivated catalyst and by simulating the water vapor contents in system, the mechanism of deactivation and reactivation was studied.     

Hydrogenation of naphthalene on NiMo- Ni- and Ru/Al2O3 catalysts: Langmuir–Hinshelwood kinetic modelling

The importance of the hydrodearomatisation (HDA) is increasing together with tightening legislation of fuel quality and exhaust emissions. The present study focuses on hydrogenation (HYD) kinetics of the model aromatic compound naphthalene, found in typical diesel fraction, in n-hexadecane over a NiMo (nickel molybdenum), Ni (nickel) and Ru (ruthenium) supported on trilobe alumina (Al₂O₃) catalysts. Kinetic reaction expressions based on the mechanistic Langmuir–Hinshelwood (L–H) model were derived and tested by regressing the experimental data that translated the effect of both naphthalene and hydrogen concentration at a constant temperature (523.15 and 573.15 K over the NiMo catalyst and at 373.15 K over the Ni and Ru/Al₂O₃ catalysts) on the initial reaction rate. The L–H equation, giving an adequate fit to the experimental data with physically meaningful parameters, suggested a competitive adsorption between hydrogen and naphthalene over the presulphided NiMo catalyst and a non-competitive adsorption between these two reactants over the prereduced Ni and Ru/Al₂O₃ catalysts. In addition, the adsorption constant values indicated that the prereduced Ru catalyst was a much more active catalyst towards naphthalene HYD than the prereduced Ni/Al₂O₃ or the presulphided NiMo/Al₂O₃ catalyst.     

光催化在印染废水深度处理中的应用研究

以钛酸四丁酯为钛源,A l2O3为载体,采用溶胶-浸渍法制备出负载型纳米TiO2/A l2O3催化剂。对实际印染废水进行光催化降解研究,考察了废水pH值、催化剂用量、光强、光照时间等对废水CODcr去除率的影响。结果表明,光催化处理染料废水的最佳工艺条件为:pH=4,催化剂用量为6 g/L,30 W紫外灯光照1 h,出水CODcr为46 mg/L左右,色度接近0,水质达到印染厂回用标准。     

碳酸二甲酯与碳酸二乙酯酯交换合成碳酸甲乙酯的研究

以Al2O3/SiO2为催化剂考察了碳酸二甲酯和碳酸二乙酯在液相条件下酯交换合成碳酸甲乙酯的过程.研究了活性组分负载量、催化剂用量、反应温度、反应时间等条件对酯交换反应的影响,并通过NH3-TPD和N2吸附脱附等手段对催化剂进行了表征.结果表明:以SiO2为载体,Al2O3负载量为12%的催化剂对碳酸二甲酯与碳酸二乙酯...     

Li掺杂对LaNi/Al2O3在焦油重整中催化性能的影响

采用浸渍法制备了LiLaNi/Al2O3催化剂,并用XRD, SEM, TPR等对其进行了表征. Li的加入对催化剂的结构、NiAl2O4的结晶度及Ni2+离子还原能力都有较大影响. 以甲苯为焦油的模型化合物,在固定床反应器中对高温焦炉煤气中焦油催化转化反应进行了评价. 结果显示,Li能显著改善LaNi/Al2O3催化剂的催化反应活性,提高产物中H2的含量. 在750℃、水/碳比为2.0的条件下,含0.5%(w) Li的LiLaNi/Al2O3催化剂能将甲苯完全转化为小分子气体,产物中H2含量显著增加.     

钛酸铝／氧化铝复合材料的制备及其抗铝液浸渗性能

以Al2O3,TiO2,MgO和Fe2O3粉末为起始原料制备出不同氧化铝含量的钛酸铝／氧化铝复合材料;通过考察浸于熔融铝液中试样断面显微结构和特征元素分布研究了复合材料抗铝液浸渗性能。研究表明,反应烧结得到的是含5％MgTi2O5（质量分数）和1％Fe2TiO5（质量分数）的钛酸铝复合固溶体与氧化铝组成的复合材料,复合材料的烧结致密度随试样中氧化铝含量的增加而增加。高钛酸铝含量的钛酸铝／氧化铝复合材料具有良好的抗铝浸渗性能。     

KF/Al2O3催化合成甲基乙烯基酮的研究

用KF／Al2O3催化丙酮和甲醛缩合制备乙酰乙醇,并采用固定床反应方式,简化工艺过程,提高了生产效率,催化缩合收率高,选择性好,已工业化生产。     

KF/Al_2O_3催化下亚胡椒基丙醛的合成

KF Al2O3作催化剂,催化洋茉莉醛和丙醛进行Claisen-Schmidt缩合反应合成了亚胡椒基丙醛。通过正交实验确定了适宜的工艺条件,洋茉莉醛∶丙醛为0 3∶0 42(摩尔比),14g催化剂,丙醛滴加时间2h,反应温度60℃～70℃,反应时间2h。平均摩尔收率80 2%。