Effect of preparation methods and content of phosphorus on hydrotreating activity

The effect of phosphorus content and preparation methods is studied in this present investigation. Three different methods are employed for preparation of catalysts. The catalysts are characterized by pore size distribution, X-ray diffractogram and temperature programmed reduction. Thiophene hydrodesulfurization (HDS), cumene hydrocracking (HC), gas oil HDS and Maya heavy crude HDS and hydrodemetallization (HDM) activities are performed. It is found that specific surface area gradually decreases with P loading. The addition of phosphorus increases the formation of polymolybdate species which are more active for hydrotreating reaction. It is also observed that reducibility of these species also increases with P loading. However, at higher P loading the crystalline MoO₃ is formed at the expense of these multilayer polymeric molybdates. The increment in the activity is more in the catalyst prepared by co-impregnation method. The activity increases with P loading up to 1 wt% P content. At higher loading the activity decreases. It is also noted that P inhibits coke formation on the catalyst during hydrotreating of heavy crude oil. Phosphorus can also modify the Brønsted acidity of the catalyst and hence cumene hydrocracking activity slightly increases.     

Alumina-silica binary mixed oxide used as support of catalysts for hydrotreating of Maya heavy crude

Alumina-silica binary mixed oxide support is used to prepare catalysts for hydrotreating of Maya heavy crude. Support is prepared by urea hydrolysis. Sequential incipient wetness and co-impregnation techniques are employed for preparation of catalysts. Ammonium heptamolybdenum is used as precursor of MoO₃. Catalysts are characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR) and the pore size distribution. Hydrodemetallation (HDM), hydrodesulfurization (HDS), hydrodenitrogenation (HDN), and asphaltene conversion (HDAsp) reactions are studied on these catalysts. One reference catalyst is also taken for comparison. Coke and metals depositions on spent catalysts are measured. The catalyst deactivation rate is also studied. The X-ray diffraction (XRD) results reveal that molybdenum atoms are well dispersed into CoMo catalyst, whereas MoO₃ crystalline phases are found in PCoMo and PNiMo catalysts. TPR reduction profiles are different for different catalysts. The laboratory made catalyst is reduced at one temperature, whereas the reference catalyst shows two reduction profiles. The reference catalyst shows the highest activities among four catalysts. The highest HDM and HDAsp activities of the reference catalyst may be due to its bigger pore diameter. The presence of TiO₂ in the reference catalyst enhances HDS and HDN activities. The CoMo catalyst shows higher activities than those of PCoMo and PNiMo catalysts. The presence of crystalline MoO₃ causes for lower activities of catalysts PCoMo and PNiMo.     

磷改性拟薄水铝石性能及在蜡油加氢催化剂中的应用

在碳化法拟薄水铝石生产过程中加入磷改性剂制备磷改性拟薄水铝石。考察了磷含量对拟薄水铝石和模式载体的物理性能和酸性能的影响。结果表明,随着磷含量的增加,拟薄水铝石和载体的孔容和比表面积增大,但到一定程度后,孔容和比表面积下降,磷存在最佳加入量。磷改性后的拟薄水铝石和模式载体随着磷含量的增加,弱酸量增加,中强酸量降低,总酸量减少。以磷改性拟薄水铝石和不合磷碳化法拟薄水铝石为原料,制备了不同磷含量的氧化铝载体及催化剂,采用中国石油胜利炼油厂生产的减压蜡油在100mL小型加氢装置上进行评价实验,优化制备出适宜的蜡油加氢处理催化剂。     

浆态床渣油加氢催化剂研究进展

渣油加氢技术主要有固定床、沸腾床、移动床和浆态床。浆态床技术不存在催化剂的失活问题,几乎能处理各种性质的原料,是近年来的研究热点。浆态床技术通过加入催化剂达到劣质渣油改质的目的,使用的催化剂可分为不具有加氢活性的添加剂和具有加氢活性的催化剂两大类,添加剂的作用在渣油高转化率下较明显,所起的作用是阻隔生焦中间相的聚集以减少生焦;催化剂主要通过提供活性氢抑制大分子自由基的缩合和生焦并改质劣质渣油。对浆态床渣油加氢催化剂和添加剂的使用情况与机理进行总结,对未来发展进行展望,认为低成本有加氢活性的催化剂是未来浆态床渣油加氢催化剂的研究重点。     

助剂对沸腾床渣油加氢催化剂性能的影响

制备含有不同助剂的沸腾床渣油加氢催化剂,对催化剂进行系统地表征,同时在高压釜上进行活性评价,以考察助剂对沸腾床渣油加氢催化剂性能的影响。结果表明：助剂的加入改变了催化剂酸强度分布、还原性质及金属分散性质,加入助剂P制备的催化剂其加氢性能较好。     

磷对MoNi/γ-Al2O3加氢处理催化剂性能的影响

采用分步浸渍法制备了不同磷含量的MoNiP/γ-Al₂O₃加氢预处理催化剂。采用TPR、HRTEM和XPS技术对催化剂进行表征,以噻吩和喹啉为模型化合物,考察催化剂的加氢脱硫和加氢脱氮活性。结果表明,磷与活性组分相互作用形成新Mo-Ni-O-P相,增加了低温还原峰面积,使还原峰峰顶温度升高。磷的引入提高了活性金属组分的硫化度,使催化剂的MoS₂片晶层数更多,片层长度更长,有助于噻吩和喹啉克服空间位阻吸附在活性中心位上;但过量磷会使MoS₂发生团聚,降低活性中心位数目,不利于提高催化剂活性。添加适量磷对催化剂表面和活性相进行有限度的改变,使催化剂具有最佳的脱硫和脱氮活性。     

Support effects in the hydrotreatment of model molecules

The support effect on the activity of hydrotreating catalysts using model molecules was analyzed for catalysts supported on TiO₂, SiO₂ and MgO. The results reported in the literature indicate that adequate design of the characteristics of the catalytic support is of great importance in the development of better hydrotreating catalysts. It was shown that by means of an adequate support design it is possible to increase significantly the HDS, HYD and HDN functionalities of hydrotreating catalysts. Semiconducting supports like TiO₂ can improve the HDS and HYD activities by exerting electronic effects on the active phase, helping in this way the formation of sulfur vacancies. Alumina supports modified by SiO₂ can facilitate the sulfidation of the active species, leading to better-promoted type II active sites with increased HDS and HYD catalyst functionalities. The nature of the support affects the sulfidation and dispersion of the catalysts even when chelating agents are used during catalyst preparation.     

Surface characterization of Al2O3–SiO2 supported NiMo catalysts: An effect of support composition

Al₂O₃–SiO₂ mixed oxide has been investigated as a support for hydrotreating catalyst with variation of its composition [Si/(Si + Al) = 0.06, 0.12, 0.31, 0.56, 0.78] and its interaction with the surface active metals (NiMo). The composition of support and surface species (NiMo) of catalysts were characterized by specific surface area, atomic absorption, SEM-EDX, XRD, temperature programmed reduction (TPR), Raman analysis, scanning electron microscopy (STEM) and transmission electron microscopy (TEM). Incorporation of SiO₂ in Al₂O₃ promotes a weak interaction between the active phases and particularly catalyst that predominated with SiO₂ content. The oxide and sulfided catalysts characterization indicated that the effect of support is responsible to form different catalytic sites. Crystallization of MoO₃ phases and a relatively longer crystal of MoS₂ in the sulfided catalyst were attributed to an increasing SiO₂ content in the support. The catalytic behavior of the NiMo supported catalysts is explained in terms of structural changes on the surface due to the support and active metal interactions. The activity of the different catalysts evaluated in the thiophene hydrodesulfurization reaction was higher for the catalyst having lower SiO₂ content in the support.     

Study of accelerated deactivation of hydrotreating catalysts by vanadium impregnation method

The main causes of catalysts deactivation for hydrotreating are coking and metals deposition. In this present work, accelerated deactivation of hydrotreating catalysts was studied. In this respect, vanadium which is deposited with nickel during hydrotreating reaction was impregnated into the fresh hydrotreating catalyst. Different percentage of vanadium was impregnated and their hydrodemetalization (HDM) and hydrodesulfurization (HDS) activities were studied in bench-scale reactor of heavy crude oil. Accelerated deactivations for both HDM and HDS were observed on vanadium impregnated catalysts. The rate of HDS deactivation was faster than that of HDM reaction. The rapid deactivation of HDS may be due to the coverage of active sites by impregnated vanadium atom. The deactivation is slower when the V loading is low; but above 10 wt% loading a rapid deactivation is observed. A comparison of deactivation is made in between normal deactivation and the deactivation by vanadium impregnation. It was found that deactivation by vanadium impregnation is lower than that of normal deactivation. It suggests that at initial stage the formation of coke causes deactivation of the catalyst whereas at later stage when metals sulfides deposition is quite high, these sulfides take part in deactivation.     

Simultaneous oxidative conversion and CO2 reforming of methane to syngas over Ni/vermiculite catalysts

Modified-vermiculite supported Ni catalysts were prepared and characterized by XRD, BET, TGA, TPR and TEM. The catalytic activity of these catalysts for simultaneous oxidative conversion and CO₂ reforming of methane to syngas was evaluated. The results indicated that vermiculite has a great potential as a support of Ni component due to its excellent thermal stability. Among these catalysts, the expanded-vermiculite supported Ni catalyst exhibited the highest catalytic activity and stability. It was found that Ni oxides supported on vermiculite was reduced more easily and also Ni-based vermiculite catalysts suppressed coke depositing in the reaction, in comparison with alumina-supported Ni catalyst.     

Coke study on MgO-promoted Ni/Al2O3 catalyst in combined H2O and CO2 reforming of methane for gas to liquid (GTL) process

MgO-promoted Ni/Al₂O₃ catalysts have been investigated with respect to catalytic activity and coke formation in combined steam and carbon dioxide reforming of methane (CSCRM) to develop a highly active and stable catalyst for gas to liquid (GTL) processes. Ni/Al₂O₃ catalysts were promoted through varying the MgO content by the incipient wetness method. X-ray diffraction (XRD), BET surface area, H₂-temperature programmed reduction (TPR), H₂-chemisorption and CO₂-temperature programmed desorption (TPD) were used to observe the characteristics of the prepared catalysts. The coke formation and amount in used catalysts were examined by SEM and TGA, respectively. H₂/CO ratio of 2 was achieved in CSCRM by controlling the feed H₂O/CO₂ ratio. The catalysts prepared with 20 wt.% MgO exhibit the highest catalytic performance and have high coke resistance in CSCRM. MgO promotion forms MgAl₂O₄ spinel phase, which is stable at high temperatures and effectively prevents coke formation by increasing the CO₂ adsorption due to the increase in base strength on the surface of catalyst.     

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。     

逆水煤气变换耦合乙烷脱氢反应中载体对氧化铬催化剂性能的影响

研究了在逆水煤气变换耦合乙烷脱氢反应中担载型氧化铬催化剂的活性,考察了多种载体对于催化剂反应性能的影响。结果表明,不同的载体所担载的氧化铬催化剂具有不同的催化性能。其中二氧化硅担载的氧化铬催化剂具有较高的乙烷转化率和乙烯选择性,在700℃时分别达到30.7%和96.5%。CO₂的作用是通过与H₂反应促进乙烷脱氢、并减少催化剂表面积炭。运用XRD、TPR、 XPS、UV-DRS和微量吸附量热技术对催化剂体相与表面结构、表面酸性和铬物种价态等进行了表征,结果显示催化剂表面酸中心适当的强度、数量和分布有利于乙烷的活化和催化转化,Cr³⁺和Cr⁶⁺物种是反应的活性中心。     

Studies on nickel-based catalysts for carbon dioxide reforming of methane

The catalytic activity and coke resistance of La₂O₃ promoted nickel-based catalysts are investigated in a fixed-bed flow reactor. The contents of carbon deposited on catalysts were measured by a carbon combustion method. Catalysts were characterized by CO–TPD, CO₂–TPD, TPR, XPS and XRD techniques, and the results were correlated with the coke resistance of the catalysts. It is found that the catalytic activity, resistance to carbon deposition and the stability of the catalysts can be greatly improved with the addition of a rare earth oxide. It is found that BaTiO₃ is an ideal support. Thus 5.0 wt.% Ni–0.75 wt.% La–BaTiO₃ catalyst shows great resistance to coke formation and higher thermal stability as well as higher catalytic activity, than the catalysts 5.0 wt.% Ni/La–BaTiO₃ (Ba/La = 1/0.002) and 5.0 wt.% Ni–1.5 wt.% La/BaTiO₃.     

Carbon formation and its influence on ethanol steam reforming over Ni/Al2O3 catalysts

Ethanol steam reforming was studied over Ni/Al₂O₃ catalysts. The effect of support (- and γ-Al₂O₃), metal loading and a comparison between conventional H₂ reduction with an activation method employing a CH₄/O₂ mixture was investigated. The properties of catalysts were studied by N₂ physisorption, X-ray diffraction (XRD) and temperature programmed reduction (TPR). After activity tests, the catalysts were analyzed by scanning electron microscopy (SEM) and thermogravimetric analysis (TG/DTA). Ni supported on γ-Al₂O₃ was more active for H₂ production than the catalyst supported on -Al₂O₃. Metal loading did not affect the catalytic performance. The alternative activation method with CH₄/O₂ mixture affected differently the activity and stability of the Ni/γ-Al₂O₃ and the Ni/-Al₂O₃ catalyst. This activation method increased significantly the stability of Ni/-Al₂O₃ compared to H₂ reduction. SEM and TG/DTA analysis indicate the formation of filamentous carbon during the CH₄/O₂ activation step, which is associated with the increasing catalyst activity and stability. The effect of temperature on the type of carbon formed was investigated; indicating that filamentous coke increased activity while encapsulating coke promoted deactivation. A discussion about carbon formation and the influence on the activity is presented.     

磷镍复合改性HZSM-5催化乙醇脱水制乙烯积炭行为研究

开发了镍改性HZSM-5,对分子筛进行了孔道和酸性的初步调变,在260 ℃下获得了较高的活性和选择性,但存在的问题是寿命较短,易积炭失活。因此,在Ni-HZSM-5的基础上,继续采用等体积浸渍法制备了不同磷酸负载量的复合改性HZSM-5,虽然提高了催化性能,但是仍然存在着失活的问题。通过对催化剂失活原因分析表明,反应过程中并没有发生磷的流失,且积炭对比表面积和孔道结构的影响较小,研究认为催化剂失活主要是由积炭对酸性位的覆盖导致。对积炭过程和积炭物种进行研究发现,随反应时间延长,催化剂表面积炭速率越来越低,且高温型积炭在积炭中所占比重逐渐增加,说明积炭不饱和度增加。积炭物种主要是含碳碳双键的烯烃聚合物、芳香族化合物和含酯基的物质。     

Synthesis and characterization of P-modified mesoporous CoMo/HMS–Ti catalysts

A hexagonal mesoporous siliceous material with a wormhole framework structure incorporating Ti (HMS-Ti; Si/Ti atomic ratio of 40) was modified with variable amounts of phosphorous and used as support for CoMo phases. The catalysts were prepared by successive impregnation, with Mo being introduced first. The supports and catalysts were characterized by N₂ adsorption–desorption, High-resolution transmission electron microscopy, X-ray diffraction, FT-IR study of the framework vibrations, DRIFT spectra in the OH region, ¹H NMR, FT-IR spectra of adsorbed NO, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The catalysts were tested in the reaction of hydrodesulfurization (HDS) of dibenzothiophene (DBT) and their activity compared with that of a commercial P-containing CoMo/γ-Al₂O₃ catalyst. The physical and chemical characterization of the P-modified HMS–Ti substrates shows that the presence of P₂O₅ on the support surface does not change its mesoporous character, but modifies its surface properties. In addition, characterization data of the oxide catalysts show that phosphate favors the dispersion of the active phases and increases the population of octahedral Co²⁺ ions associated to Mo species. As a result, HDS activity was strongly enhanced upon P-loading, which reached a maximum of 0.64 wt%. This catalyst is 3.7 times more active than the commercial one and 2.4 times more active than its P-free counterpart. The highest activity of this catalyst was explained in terms of the specific electronic properties of its active phases and the largest Mo surface exposure on the support.     

Hydrotreating of light gas oil using a NiMo catalyst supported on activated carbon produced from fluid petroleum coke

Nitric acid functionalized steam activated carbon (NAFSAC) was prepared from waste fluid petroleum coke (FPC) and used as a support material for the synthesis of a NiMo catalyst (2.5 wt-% Ni and 13 wt-% Mo). The catalyst was then used for the hydrotreatment of light gas oil. The support and catalysts were characterized by Brunauer-Emmett-Teller (BET) gas adsorption method, X-ray diffraction, H₂-temperature programmed reduction, NH3-temperature programmed desorption, CO-chemisorption, mass spetrography, scanning electron microscopy (SEM), Boehm titration, and Fourier transform infrared spectroscopy (FTIR). The SEM results showed that the carbon material retained a needle like structure after functionalization with HNO₃. The Boehm titration, FTIR, and BET results confirmed that the HNO₃ functionalized material had moderate acidity, surface functional groups, and mesoporosity respectively. The produced NAFSAC had an inert nature, exhibited the sink effect and few metal support interactions, and contained functional groups. All of which make it a suitable support material for the preparation of a NiMo hydrotreating catalyst. Hydrotreating activity studies of the NiMo/NAFSAC catalyst were carried out under industrial operating conditions in a laboratory trickle bed reactor using coker light gas oil as the feedstock. A parallel study was performed on the hydrotreating activity of NiMo/γ-Al₂O₃ as a reference catalyst. The hydrodesulfurization and hydrodenitrogenation activities of the NiMo/NAFSAC catalyst were 62% and 30%, respectively.     

Effect of alkaline earth promoters (MgO,CaO, and BaO) on the activity and coke formation of Ni catalysts supported on nanocrystalline Al2O3 in dry reforming of methane

Ni/Al₂O₃ promoted catalysts with alkaline earth metal oxides (MgO, CaO, and BaO) were prepared and employed in dry reforming of methane (DRM). The catalysts were prepared by impregnation method and characterized by XRD, BET, TPR, TPO, and SEM techniques. The obtained results showed that the addition of MgO, CaO, and BaO as promoter decreased the surface area of catalysts (S_BET). The catalysis results exhibited that adding alkaline earth promoters (MgO, CaO, and BaO) enhanced the catalytic activity and the highest activity was observed for the MgO promoted catalyst. TPR analysis showed that addition of MgO increased the reducibility of nickel catalyst and decreased the reduction temperature of NiO species. The TPO analysis revealed that addition of promoters decreased the amount of deposited coke; and among the studied promoters, MgO has the most promotional effect for suppressing the carbon formation. SEM analysis confirmed the formation of whisker type carbon over the spent catalysts.     

柠檬酸对Ni-W焦化蜡油加氢处理催化剂性能的影响

以含改性HY分子筛的TiO₂-SiO₂复合氧化物为载体,以Ni、W为活性金属组分,采用等体积溶液浸渍法制得了焦化蜡油加氢处理催化剂,考察了浸渍液中加入柠檬酸对催化剂性质及加氢精制性能的影响。BET、FT-IR、XRD、UV-Vis DRS和TG-DSC等表征结果表明,柠檬酸与金属组分间的络合作用提高了金属活性组分的分散度,改变了金属组分的存在状态,促进了单一形式的聚钨酸盐和高活性的六配位八面体Ni物种的形成。柠檬酸改性的Ni-W系催化剂对焦化蜡油的加氢精制性能明显改善,尤其是加氢脱氮性能得以大幅度提高。