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1.
Heavy Maya crude has been hydrotreated with NiMo/alumina-titania catalysts in which titania was incorporated by two different methods. Titania added to boehmite followed by calcination in order to promote formation of Ti–O–Al bonds, and Ti added to alumina in order to promote the formation of TiO 2 structures on the surface. The reaction results indicate that hydrodesulfurization (HDS), hydrodemetallization (HDM) and hydrodenitrogenation (HDN) activities are improved by the incorporation of Ti to the catalyst. In all cases, catalysts prepared by the method leading to the formation of surface TiO 2 structures show superior performance in the three functionalities (HDS, HDM and HDN). Raman analysis of the supports gives clear evidence of the differences in Ti oxide structures on the surface. The characterization of the catalysts indicates that Ti-modified catalysts have increased surface acidity (evaluated by pyridine adsorption) and greater number of coordinatively unsaturated sites (titrated by NO adsorption). Ti-containing catalysts seem to be also more stable with time-on-stream. 相似文献
2.
The effect of the TiO 2–Al 2O 3 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 TiO 2 into the support, and particularly over rich- and pure-TiO 2-based catalysts. It is suggested that the increase in activity be due to an improvement in reducing and sulfiding of molybdena over TiO 2. 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 TiO 2 content and large differences are observed between the catalysts supported on pure Al 2O 3 and pure TiO 2. In contrast, in the case of the thiophene test, the pure Al 2O 3-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 Al 2O 3-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 Al 2O 3- and pure TiO 2-based catalysts is relatively small and dependent on the H 2 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 H 2 partial pressure on the thiophene HDS, and on the effect of H 2S concentration on gasoil HDS demonstrate the importance of these parameters, in addition to the nature of the reactant, to perform an adequate catalyst ranking. 相似文献
3.
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 MoO 3. 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 MoO 3 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 TiO 2 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 MoO 3 causes for lower activities of catalysts PCoMo and PNiMo. 相似文献
4.
Three different supports were prepared with distinct magnesia–alumina ratio x = MgO/(MgO + Al 2O 3) = 0.01, 0.1 and 0.5. Synthesized supports were impregnated with Co and Mo salts by the incipient wetness method along with 1,2-cyclohexanediamine- N, N, N′, N′-tetraacetic acid (CyDTA) as chelating agent. Catalysts were characterized by BET surface area, Raman spectroscopy, SEM-EDX and HRTEM (STEM) spectroscopy techniques. The catalysts were evaluated for the thiophene hydrodesulfurization reaction and its activity results are discussed in terms of using chelating agent during the preparation of catalyst. A comparison of the activity between uncalcined and calcined catalysts was made and a higher activity was obtained with calcined MgO–Al 2O 3 supported catalysts. Two different MgO containing calcined catalysts were tested at micro-plant with industrial feedstocks of heavy Maya crude oil. The effect of support composition was observed for hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodeasphaltenization (HDAs) and hydrodenitrogenation (HDN) reactions, which were reported at temperature of 380 °C, pressure of 7 MPa and space-velocity of 1.0 h −1 during 204 h of time-on-stream (TOS). 相似文献
5.
Evaluation of Co---Mo catalysts prepared on various TiO 2-Al 2O 3 supports has been made for thiophene under atmospheric pressure, dibenzothiophene under high pressure and gasoil in a classical pilot plant. Comparison of activities indicates DBT as more representative of a real feedstock and the Co---Mo/TiO 2 (50%)-Al 2O 3 (50%) catalyst appears more active than the Co---Mo/Al 2O 3 sample toward HDS, HDN and hydrodearomatization. 相似文献
6.
Al 2O 3–SiO 2 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 SiO 2 in Al 2O 3 promotes a weak interaction between the active phases and particularly catalyst that predominated with SiO 2 content. The oxide and sulfided catalysts characterization indicated that the effect of support is responsible to form different catalytic sites. Crystallization of MoO 3 phases and a relatively longer crystal of MoS 2 in the sulfided catalyst were attributed to an increasing SiO 2 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 SiO 2 content in the support. 相似文献
7.
The typical physico-chemical properties and their hydrodesulfurization activities of NiMo/TiO 2-Al 2O 3 series catalysts with different TiO 2 loadings were studied. The catalysts were evaluated with a blend of two kinds of commercially available diesels in a micro-reactor unit. Many techniques including N 2-adsorption, UV–vis DRS, XRD, FT-Raman, TPR, pyridine FT-IR and DRIFT were used to characterize the surface and structural properties of TiO 2-Al 2O 3 binary oxide supports and the NiMo/TiO 2-Al 2O 3 catalysts. The samples prepared by sol–gel method possessed large specific surface areas, pore volumes and large average pore sizes that were suitable for the high dispersion of nickel and molybdenum active components. UV–vis DRS, XRD and FT-Raman results indicated that the presence of anatase TiO 2 species facilitated the formation of coordinatively unsaturated sites (CUS) or sulfur vacancies, and also promoted high dispersion of Mo active phase on the catalyst surfaces. DRIFT spectra of NO adsorbed on the pure MoS 2 and the catalysts with TiO 2 loadings of 15 and 30% showed that NiMo/TiO 2-Al 2O 3 catalysts possessed more CUS than that of pure MoS 2. HDS efficiencies and the above characterization results confirmed that the incorporation of TiO 2 into Al 2O 3 could adjust the interaction between support and active metals, enhanced the reducibility of molybdenum and thus resulted in the high activity of HDS reaction. 相似文献
8.
In the present work, with the aim of searching for new, highly effective catalysts for deep HDS, a series of NiMo catalysts with different MoO 3 loadings (6–30 wt.%) was prepared using SBA-15 material covered with ZrO 2-monolayer as a support. Prepared catalysts were characterized by N 2 physisorption, small- and wide-angle XRD, UV–vis diffuse reflectance spectroscopy, temperature-programmed reduction, SEM-EDX and HRTEM, and their catalytic activity was evaluated in the 4,6-dimethyldibenzothiophene hydrodesulfurization (HDS). It was observed that ZrO 2 incorporation on the SBA-15 surface improves the dispersion of the Ni-promoted oxidic and sulfided Mo species, which were found to be highly dispersed, up to 18 wt.% of MoO 3 loading. Further increase in metal charge resulted in the formation of MoO 3 crystalline phase and an increase in the stacking degree of the MoS 2 particles. All NiMo catalysts supported on ZrO 2-modified SBA-15 material showed high activity in HDS of 4,6-DMDBT. The best catalyst having 18 wt.% MoO 3 and 4.5 wt.% NiO was almost twice more active than the reference NiMo/γ-Al 2O 3 catalyst. High activity of NiMo/Zr-SBA-15 catalysts and its evolution with metal loading was related to the morphological characteristics of the MoS 2 active phase determined by HRTEM. 相似文献
9.
ZrO 2–TiO 2 mixed oxide (30–70 mol/mol) was prepared by low-temperature sol–gel followed by solvo-thermal treatment (1 day) at various temperatures (40, 80, 120, 160 and 200 °C). Selected samples of the corresponding single oxides were also prepared. Materials characterization was carried out by N 2 physisorption, XRD, thermal analysis (TG-DTA) and UV–vis DRS, infra-red and Laser-Raman spectroscopies. Binary solids of enhanced pore volume and pore size diameter were obtained by increasing the post-treatment severity. Anatase TiO 2 micro-segregation was evidenced by Raman spectroscopy for the mixed oxide solvo-treated at the highest temperature. This solid also showed the highest crystallization temperature to ZrTiO 4 (702 °C). Mo impregnated (2.8 atom nm −2) on various mixed oxides was sulfided under H 2S/H 2 (400 °C, 1 h), the catalysts being tested in the dibenzothiophene hydrodesulfurization (HDS, T = 320 °C, P = 5.59 MPa). By increasing the severity of the solvo-treatment improved supports for MoS 2 phase were obtained. The HDS activity of the catalyst with carrier post-treated at 200 °C was 40% higher (in per total mass basis) than that of sulfided Mo supported on the binary oxide solvo-treated at 80 °C. The ZrO 2–TiO 2-supported catalysts showed higher selectivity to products from the hydrogenation route than their counterparts supported on either single oxide. 相似文献
10.
The catalytic performance of MoS 2-based hydrotreating catalysts strongly depends on their morphology and orientation on the support. The effects of the morphology and orientation of MoS 2 clusters on supports, typically Al 2O 3 and TiO 2, on the catalytic performance are reviewed here, focusing on recently reported epitaxial relationships at the interface between MoS 2 clusters and the support. 相似文献
11.
Co–Mo model sulfide catalysts, in which CoMoS phases are selectively formed, were prepared by means of a CVD technique using Co(CO) 3NO as a precursor of Co. It is shown by means of XPS, FTIR and NO adsorption that CoMoS phases form selectively when the Mo content exceeds monolayer loading. A single exposure of MoS 2/Al 2O 3 to a vapor of Co(CO) 3NO at room temperature fills the edge sites of the MoS 2 particles. It is suggested that the maximum potential HDS activity of MoS 2/Al 2O 3 and Co–Mo/Al 2O 3 catalysts can be predicted by means of Co(CO) 3NO as a “probe” molecule. An attempt was made to determine the fate of Co(CO) 3NO adsorbed on MoS 2/Al 2O 3. The effects of the support on Co–Mo sulfide catalysts in HDS and HYD were investigated by use of CVD-Co/MoS 2/support catalysts. XPS and NO adsorption showed that model catalysts can also be prepared for SiO 2-, TiO 2- and ZrO 2-supported catalysts by means of the CVD technique. The thiophene HDS activity of CVD-Co/MoS 2/Al 2O 3, CVD-Co/MoS 2/TiO 2 and CVD-Co/MoS 2/Al 2O 3 is proportional to the amount of Co species interacting with the edge sites of MoS 2 particles or CoMoS phases. It is concluded that the support does not influence the HDS reactivity of CoMoS phases supported on TiO 2, ZrO 2 and Al 2O 3. In contrast, CoMoS phases on SiO 2 show catalytic features characteristic of CoMoS Type II. With the hydrogenation of butadiene, on the other hand, the Co species on MoS 2/TiO 2, ZrO 2 and SiO 2 have the same activity, while the Co species on MoS 2/Al 2O 3 have a higher activity. 相似文献
12.
The effects of fluorine, phosphate and chelating agents on hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) are reviewed. All three additives enhance the activity of NiMo/Al 2O 3 catalysts in HDN but have only a slightly positive or even a negative effect on the HDS activity of CoMo/Al 2O 3 and NiMo/Al 2O 3 catalysts. The positive effect on HDN is due to the enhancement of the hydrogenation of aromatic rings. On the other hand, these three additives diminish the rates of C–N bond breaking and alkene hydrogenation reactions. All three additives are hard basic ligands that may interact strongly with hard acids such as coordinatively unsaturated Al3+ cations on the alumina surface. A strong interaction with the alumina support has several effects. First, molybdate and tungstate anions are no longer strongly bonded to the support and are predominantly present as polyanions, which can be easily sulfided to MoS2 and WS2 crystallites. The weaker interaction with the smaller support surface also leads to larger MoS2 and WS2 crystallites with a lower dispersion. Second, the Ni2+ and Co2+ cations will also interact more weakly with the alumina, and this makes the formation of Ni and Co promoter atoms in the catalytically active Ni–Mo–S and Co–Mo–S phases more efficient. Third, the weaker interaction of Mo and W with the support leads to a higher stacking of the MoS2 and WS2 crystallites and, thus, to the more active type II Ni–Mo–S and Co–Mo–S phases. The increased stacking is beneficial for geometrically demanding reactions such as the hydrogenation of aromatics. For less demanding reactions, such as alkene hydrogenation, aliphatic C–N bond breaking and thiophene HDS, the loss in dispersion is important. 相似文献
13.
The influence of H 2S (0-559.6 kPa) on Maya crude hydrotreating is investigated in an integral fixed bed up-flow micro reactor. The added H 2S inhibits hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) while asphaltene conversion (HDAs) remained almost unaffected. On the other hand, a promotional effect is found for hydrodemetallization (HDM). The observed variation in HDS and HDM conversions suggests a dual nature of catalytic sites particularly at high partial pressure of hydrogen sulfide. The promotional effect for HDM may be interpreted in terms of adsorption of metal-porphyrins on Brönsted acid sites (sulfhydryl group), which enhance hydrogenation of metal-porphyrins and convert them into the corresponding metal-chlorin structure in a first step of reaction. The final step in the HDM is essentially hydrogenolysis (metal-nitrogen) and requires the presence of an anionic vacancy (CUS). The conversion of asphaltene is also depending on the acidic nature of sulfided catalyst that is remaining either uninhibited or slightly enhanced with H 2S. 相似文献
14.
Mo/TiO 2 catalysts were modified with Nb by two different methods, sol–gel and surface deposition, in order to study the effect of Nb incorporation on the thiophene HDS activity. The results show that the formation of Nb–Ti mixed oxides leads to catalysts with poor HDS activity while the deposition of Nb oxide species on the surface of TiO 2 leads to catalysts with activities larger than those of Mo/Al 2O 3 and Mo/TiO 2. This increase in activity was attributed to the formation of a larger population of Mo sulfur anionic vacancies when Nb was surface deposited on the TiO 2. 相似文献
15.
A carbon-based sulfonated catalyst was prepared by direct sulfonation and carbonization (in moderate conditions:200 °C, 12 h) of red liquor solids, a by-product of paper-making process. The prepared sulfonated cata-lyst (SC) had aromatic structure, composed of carbon enriched inner core, and oxygen-containing (SO3H, COOH, OH) groups enriched surface. The SO3H, COOH, OH groups amounted to 0.74 mmol·g^-1, 0.78 mmol·g^-1, 2.18 mmol·g^-1, respectively. The fresh SC showed much higher catalytic activity than that of the traditional solid acid catalysts (strong-acid 732 cation exchange resin, hydrogen type zeolite socony mobile-five (HZSM-5), sulfated zir-conia) in esterification of oleic acid. SC was deactivated during the reactions, through the mechanisms of leaching of sulfonated species and formation of sulfonate esters. Two regeneration methods were developed, and the catalytic activity can be mostly regenerated by regeneration Method 1 and be fully regenerated by regeneration Method 2, respectively. 相似文献
16.
采用改进溶胶-凝胶法制备的TiO_2-Al_2O_3作复合载体,制备不同柠檬酸引入方式改性的CoMo/TiO_2-Al_2O_3加氢脱硫催化剂。利用低温N_2吸附-脱附、XRD、SEM和H_2-TPR等对催化剂进行表征,并采用固定床反应器对催化剂加氢脱硫性能进行评价。结果表明,后处理法制备的催化剂比表面积相对较大,孔道结构较好,活性金属组分以无定形形态均匀分散在载体表面,一定程度上减弱了其与载体间的相互作用;该催化剂可以延缓Co硫化,并且络合生成较多易于硫化还原的Mo物种,利于MoS_2在催化剂表面的堆叠,生成更多的Co-Mo-S(Ⅱ)活性相,因而相应的CoMo催化剂对噻吩加氢脱硫转化率显著提高。 相似文献
17.
以氧化铝为载体,Ni和Mo为金属活性组分,添加不同含量乙二胺四乙酸,采用等体积浸渍法制备系列Ni Mo(x)/Al_2O_3(x为乙二胺四乙酸与Ni物质的量比)重质油加氢处理催化剂,考察乙二胺四乙酸加入量对催化剂加氢脱氮性能的影响,并采用N_2物理吸附-脱附、XRD和HRTEM等对催化剂进行表征。结果表明,乙二胺四乙酸的加入增强了金属组分与氧化铝载体间的相互作用,降低了MoS_2活性相的堆垛层数和片层长度,促进了活性相的分散。乙二胺四乙酸与Ni物质的量比为0.5时,MoS_2活性相堆垛层数和片层长度达到良好的结合,对应的催化剂Ni Mo(0.5)/Al_2O_3具有最优的加氢脱氮性能。 相似文献
18.
Catalytic hydrodesulfurization (HDS) technique is widely used for clean gasoline production. However, traditional HDS catalyst (CoMo/ γ-Al 2O 3) exhibits high hydrogenation performance of olefins (HYDO), resulting in the loss of gasoline octane number. To achieve high HDS/HYDO ratio, the key issue is to reduce the interaction between active metals and the support, therefore, in this research, the modified CoMo/ γ-Al 2O 3 catalysts with various boron amounts were investigated under traditional or microwave heating. The effects of preparing methods as well as boron amounts on the active phase, acidic properties and HDS catalytic activities were examined. Results show that the modification, especially under microwave treatment, can significantly weaken the interaction between the active component and the support by enlarging the surface area and pore diameter, and reducing the acidity of the support. As a result, the stacking numbers of MoS 2 slabs were obviously improved by the modification and microwave treatment, contributing to higher edge/rim ratio, and resulting in higher HDS performance and selectivity to olefin. 相似文献
19.
The support effect on the activity of hydrotreating catalysts using model molecules was analyzed for catalysts supported on TiO 2, SiO 2 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 TiO 2 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 SiO 2 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. 相似文献
20.
The present paper gives a detailed review of the different studies under investigation in our laboratory concerning the use of TiO 2 and TiO 2–Al 2O 3 composites prepared by chemical vapor deposition (CVD) as support for sulfide catalysts in the HDS of dibenzothiophene (DBT) derivatives. The supports investigated here are: TiO 2 (from Degussa, 50 m 2/g), Al 2O 3 (Nikki, 186 m 2/g) and TiO 2–Al 2O 3 supports prepared by CVD of TiCl 4 on alumina. Using several characterization techniques, we have demonstrated that the support composite presents a high dispersion of TiO 2 over γ-Al 2O 3 without forming precipitates up to ca. 11 wt.% loading. Moreover, the textural properties of the support composite are comparable to those of alumina. XPS investigations of Mo and NiMo catalysts supported on the different carriers show that Mo-oxide species exhibit a higher degree of sulfidation on the surface of TiO 2 and TiO 2–Al 2O 3 than on alumina. The HDS tests of 4,6-DMDBT under mild operating conditions (573 K, 3 MPa) show that sulfide catalysts supported on the composite support (ca. 11 wt.%) are more active than those supported on to TiO 2 or Al 2O 3. This higher HDS catalytic activity is attributed to the promotion of the hydrodesulfurization pathway, whereby the pre-hydrogenation of one of the aromatic rings adjacent to the thiophenic one may reduce the steric hindrance caused by the two methyl groups adjacent to the sulfur atom during the C–S bond cleavage. 相似文献
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