Characterization of Al2O3–ZrO2 Mixed Oxide Supported Mo Hydrotreating Catalyst

Abstract

A series of molybdenum catalysts supported on Al₂O₃–ZrO₂ mixed oxide containing 50% ZrO₂ and 50% Al₂O₃ were prepared by incipient wetness technique and characterized by BET surface area, X-ray diffraction, temperature programmed reduction and oxygen chemisorption. The catalytic activities for hydrodesulphurization (HDS), hydrogenation (HYD), and hydrocracking (HYC) were determined using thiophene, cyclohexene, and cumene as model compounds, respectively. Results indicate that up to 8 wt% Mo loading, the catalyst is well dispersed and crystallite growth occurred beyond this loading. Also both oxygen uptake and catalytic activities increase with Mo loading up to 8 wt% and then decreases at higher loading. A linear correlation was obtained between oxygen uptake and all catalytic activities and the correlation coefficients obtained suggest that the order of catalytic activities for HDS, HYD, and HYC is: HDS > HYD > HYC. Furthermore, the catalytic activities of the mixed oxide supported catalyst for HDS, HYD, and HYC were higher than those supported on pure alumina and pure zirconia. The incorporation of 3% Co on 8% Mo catalyst was determined to result in enhanced activity for HDS, HYD, and HYC.     

邻甲酚加氢脱氧还原型催化剂的实验研究

以邻甲酚为生物质热解油模型化合物,研究了几种还原型加氢催化剂的催化脱氧性能的差异。采用孔饱和浸渍法制备了Mo/Al₂O₃、CoMo/Al₂O₃和CoMoEDTA/Al₂O₃加氢脱氧催化剂,采用H₂ -TPR、XRD对它们进行了表征;在H2气氛下对催化剂进行了还原,并在连续流动固定床加氢微反装置中,考察了邻甲酚在不同还原态催化剂催化下加氢脱氧反应的转化率和产物的选择性。结果表明,在相同的加氢反应条件下,CoMoEDTA/Al₂O₃的催化活性和稳定性均比Mo/Al₂O₃和CoMo/Al₂O₃催化剂高;在反应过程中,Mo/Al₂O₃催化剂表现出较高的直接脱氧选择性,而CoMo/Al₂O₃和CoMoEDTA/Al2O3催化剂表现出较高的加氢脱氧选择性。     

The Support Effect on Hydrogenolysis of Thiophene and Gas–Oil

Abstract

Results are reported on the support effect on the catalytic activity in thiophene hydrodesulfurization (HDS) of sulfided Ni-Mo catalysts supported on pure niobia, mixed oxides of Nb₂O₅-TiO₂ prepared by sol-gel method, and Nb₂O₅/TiO₂ and Nb₂O₅/Al₂O₃ prepared by surface deposition. The prepared samples were characterized using N₂ adsorption at ?196°C, X-ray diffraction (XRD), and temperature-programmed reduction (TPR) techniques. This study showed activity variation as a function of support composition. The activity of niobia-rich catalysts was no longer promoted by the synergy between Ni and Mo. The absence of synergy between molybdenum and nickel on niobia can be explained by the strong interaction of each metal with niobia at the expense of interaction with each other. It was found that 5 wt% Nb₂O₅/TiO₂-supported catalyst was the better catalyst for thiophene HDS. It was shown that by means of an adequate support design it is possible to significantly increase the functionalities of HDS catalysts. Semiconducting supports like TiO₂ can improve the HDS activity by exerting electronic effects on the active phase, helping in this way the formation of sulfur vacancies. The 5 wt% Nb₂O₅/TiO₂ was also tested at high pressure with gas oil feedstock. It is observed with the hydrogeolysis of sulfur compounds against time-on-stream that the activity of this catalyst decreases fast with time.     

钒作为加氢催化剂活性组分的研究 Ⅱ 钒对NiMo/Al2O3催化剂渣油加氢活性的影响

 采用浸渍法制备了一系列含V的NiMo/Al₂O₃催化剂。对硫化态含V的NiMo/Al₂O₃催化剂进行了XPS和TEM表征;以科威特常压渣油为原料,考察了V对NiMo/Al₂O₃催化剂渣油加氢活性的影响。结果表明,由于渣油中金属和硫的存在形态不同,并且V-Mo-S相和V-S相对于加氢脱金属的催化作用大于加氢脱硫的催化作用,因此V能引起NiMo/Al₂O₃催化剂上渣油脱金属率的增加;但是V含量较高时,V会造成NiMo/Al₂O₃催化剂上渣油脱硫率的降低。     

Activity of Co(Ni)MoS/Al2O3 catalysts, derived from cobalt(nickel) salts of H6[Co2Mo10O38H4], in hydrogenolysis of thiophene and hydrogen treatment of diesel fraction

Co(Ni)MoS/Al₂O₃ catalysts have been prepared from ammonium 10-dodecamolybdodicobaltate (NH₄)₆[Co₂Mo₁₀O₃₈H₄] (further, Co₂Mo₁₀HPC) and cobalt(nickel) salts of 10-dodecamolybdodicobaltic acid H₆[Co₂Mo₁₀O₃₈H₄] (hereinafter, Co₂Mo₁₀HPA). It has been found that a high activity of the Co(Ni)₃-Co₂Mo₁₀HPA/Al₂O₃ catalysts in the hydrodesulfurization and hydrogenation reactions is due to the formation of a nanostructured type II CoMoS phase via the contact of the metals (Mo and Co(Ni)) at the molecular level. The use of Ni as a copromoter in the Ni₃-Co₂Mo₁₀HPA/Al₂O₃ catalyst leads to a simultaneous increase, compared with Co₃-Co₂Mo₁₀HPA/Al₂O₃, in the linear size of nanoparticles and the number of MoS₂ layers in the packing of active phase. The nature of the promoter X has a substantial effect on the properties of X₃Co₂Mo₁₀HPC/Al₂O₃ catalysts. It has been found that the catalysts with X = Co exhibit the highest activity in the hydrodesulfurization reactions and those with X = Ni, in hydrogenation reactions.     

Sulfuration Pretreatment of Ni/Al2O3 Catalyst to Remove Butadiene in FCC C4 Fraction

Abstract

The Ni-based catalysts have more advantages than the most widely used Pd-based catalysts in selective hydrogenating of the butadiene in fluid catalytic cracking (FCC) C₄ fraction. But the selectivity and stability of the Ni-based catalysts aren't good. The sulfuration pretreatment is an effective process to improve the performance of the Ni/Al₂O₃ catalysts. The sulfuration conditions of the Ni/Al₂O₃ catalyst have been studied in this article. The results showed the fittest conditions are that the catalyst was in-situ presulfurized for 60 min by the solution of S concentration 0.07 mol/L. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis indicated that the presulfurization declined the Ni crystal dimension.     

PREPARATION OF NEW TYPE CATALYST WITH GOOD PROPERTIES FOR HYDRODESULFURIZATION

ABSTRACT

The CoMo/TiA catalyst for hydrodesulfurization (HDS) and its composite support TiA with industrial scale had been produced through the certain process and the studied range of ratio of TiO₂/(TiO₂ + Al₂O₃) was enlarged. The good properties of the support TiA were attributed to its special pore structure. When the ratio of TiA/(TiA + Al₂O₃) was 0.80, the specific surface area of the support and its pore volume reached their maximum respectively. The range of atom ratio of Co/(Co + Mo) of the catalyst CoMo/TiA from 0.25–0.31 proved best, during which activity of the catalyst reached the maximum. The disperse state of TiO₂ on the surface of TiA and effect of the promoter Co content on the surface structure of the catalyst had been studied by XRD, LRS and XPS. The analytic results showed that 0.47 g TiO₂/g γ-Al₂O₃ was the schwellenwert for the coverage of TiO₂ on the surface of TiA. Beyond this, TiO₂ lies on the surface of TiA with a single layer; otherwise, it existed in the form of TiO₂ crystal phase (anatase phase). When adding a few promoters Co into the catalyst, the dispersity of MoO₃ on the surface of the support TiA increased remarkably and activity of this catalyst was also improved.     

Hydrogen production by catalytic methane decomposition over Ni,Co, and Ni-Co/Al2O3 catalyst

Hydrogen is a chief source of energy. Catalytic decomposition produces hydrogen and carbon. In this work, x%M/Al₂O₃ (where M is Ni, Co and combined Ni-Co, and x is 10%, 15%, and 30%) has been successfully employed as a catalyst. The effect of activation temperature and active metal type and loading on catalyst perfomance was investigated. The catalysts were characterized with BET, XRD, TPO, TPR, TEM, XPS, and Raman. The results displayed that the 30%Co/Al₂O₃ catalyst activated at 500°C provided the greatest catalytic performance toward methane conversion. 30%Co/Al₂O₃ catalyst activated at 500°C formed amorphous carbon.     

Co-hydrotreating of straight-run diesel fraction and vegetable oil on Co(Ni)-PMo/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts

The process of co-hydrotreatment of straight-run diesel fraction (DF) and vegetable oil (VO) on Co(Ni)-PMo/Al₂O₃ catalysts prepared from H₃PMo₁₂O₄₀ and cobalt (nickel) citrate has been studied. It has been shown that under conditions close to those in the industry, the complete conversion of fatty acid triglycerides (FATG) is achieved on the catalysts of both types to give an ultraclean hydrotreating product in a 97% yield and a cetane number of 5 points above that of the hydrotreating product of the DF alone. The degree of hydrodesulfurization (HDS) is reduced more significantly on the Co-PMo/Al₂O₃ catalyst than in the case of Ni-PMo/Al₂O₃. The catalysts are more susceptible to deactivation in the hydrotreating of the blended feedstock containing VO. The Co-PMo/Al₂O₃ sample is less stable than Ni-PMo/Al₂O₃. Examination of the spent catalysts by transmission electron microscopy has shown that the average particle length of the active phase of Co-PMo/Al₂O₃ increases, whereas this increment for Ni-PMo/Al₂O₃ is insignificant, indicating higher stability of particles of the NiMoS phase. Thus, the co-hydrotreating of petroleum fractions and vegetable oil is more reasonable to carry out on NiMo/Al₂O₃ catalysts.     

A Comparative Study of Surface Characteristics of Nickel Supported on Silica Gel, γ-Alumina,Aluminosilicate

Abstract

Surface characteristics of the prepared nickel catalysts containing 7, 10, and 13 wt% Ni w/w over different supports—silica gel, γ-alumina, and aluminosilicate—were investigated. Surface areas, total pore volumes, and average pore radii were determined for all catalysts. Pore analysis was discussed based on V_l-t plots and pore size distribution. The measured surface areas and pore volumes of pure supports increased in the following order: γ-alumina < aluminosilicate < silica gel. Pore analysis showed that SiO₂ and Al₂O₃-SiO₂ and their supported Ni samples were characterized by presence of narrower mesopores of ink-bottle type. Al₂O₃ was distinguished by presence of two distinct pore types, both showing continual increase in fraction with a shift to larger dimensions upon loading with nickel. Penetration and/or incorporation process of Ni particles took place at the expense of their interaction with Al⁺³. SiO₂ revealed a gradual increase in surface parameters upon loading with nickel. For Al₂O₃-SiO₂—supported samples, the result proposed the interaction of Ni with both alumina and silica contents of the support regardless of the penetration process.     

Catalytic Performance of Modified HZSM-5/Al2O3 Catalysts for Nonhydrodewaxing

The HZSM-5/Al₂O₃ molecular sieve catalyst was modified by phosphoric acid, tetraeth-oxysilane, tetrabutyl titanate, and boric acid, respectively. Properties of modified catalysts are characterized. The results show that the specific surface area declines and the acid density increases after modification of the catalysts, and the strong acid strength of Si/HZSM-5/Al₂O₃ catalyst enhanced. Modified catalysts performances are evaluated on fixed bed reactor using hydrocracking tail oil from a refinery as raw material. Results show that the Si/HZSM-5/Al₂O₃ catalyst has better catalytic dewaxing effect and stability than the other modified catalysts.     

Various characteristics of Ni and Pt–Al2O3 nanocatalysts prepared by microwave method to be applied in some petrochemical processes

Alumina-supported metal nanocatalysts were prepared via the microwave method, by loading nano Ni particles (at 1, 3 and 5 wt%) or nano Pt particles (at 0.3, 0.6 and 0.9 wt%). Structural and adsorption features of the nano catalysts were revealed through XRD, DSC-DTA, TEM, H₂-chemisorption and N₂-physisorption. N₂-adsorption–desorption isotherms of type IV were related typically to mesoporous materials with H₂ class of hysteresis loops characterizing ink bottle type of pores. The well dispersed nano-sized metal particles were evidenced in the studied catalytic systems, exhibiting marked thermal stability up to 800 °C. The catalytic performances of different catalyst samples were assessed during cyclohexane, normal hexane and ethanol conversions, using the micro-catalytic pulse technique at different operating conditions. The 5% Ni–γ–Al₂O₃ sample was found to be the most active in dehydration of ethanol to produce ethylene, as well as in n-hexane cracking. However, the 1% Ni–Al₂O₃ sample showed the highest dehydrogenation activity for selective production of benzene from cyclohexane. On the other hand, the 0.9% Pt–γ–Al₂O₃ sample exhibited the highest activity in the dehydration of ethanol and in the dehydrogenation of cyclohexane. The 0.3% Pt–γ–Al₂O₃ sample was the most active in the dehydrocyclization of normal hexane, as compared to the other catalyst samples under study.     

An Investigation of the Deactivation Behavior of Industrial Mo/Al2O3 and Ni-Mo/Al2O3 Catalysts in Hydrotreating Kuwait Atmospheric Residue

Abstract

The catalyst system for fixed-bed residue hydrotreating processes usually consists of different types of catalysts designed to promote hydrodemetallation (HDM), hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactions to desired levels. Overall catalyst life is determined by the performance of the individual catalysts in the different reactors. Therefore, information about the activity, stability, selectivity, and deactivation behavior of the individual catalyst is highly desirable to design improved catalysts that can prolong catalyst life, increase stream efficiency, and improve process economics. In the present work, residue hydrotreating experiments were conducted on two types of industrial hydrotreating catalysts, namely Mo/Al₂O₃ and Ni-Mo/Al₂O₃, that have been used as HDM and HDS catalysts, respectively, in an industrial ARDS process. The primary objective of the study was to compare the deactivation behavior of both types of catalyst. The characterization of the used catalysts by elemental analysis, surface area, pore volume, and pore size measurements along with TPO-MS, ¹³C NMR, and electron microprobe analysis showed significant differences in the nature of the coke and metal deposits on the two types of catalysts. The role of initial coking, the relative importance of the coke, and metal depositions on the deactivation of the two types of catalyst are discussed.     

Synthesis,Characterization, and Evaluation of Mesoporous MCM-41-supported Molybdenum Hydrotreating Catalysts

Abstract

Mesoporous MCM-41 material with high surface area and narrow pore size distribution was synthesized and used as a support for Mo, CoMo, and NiMo catalysts. The molybdenum loading was varied from 2–14 wt% on MCM-41. On 10 wt% Mo/MCM-41, the promoter Co or Ni concentration was varied from 1–5 wt%. All the catalyst samples were characterized by surface area, low temperature oxygen chemisorption, x-ray diffraction (XRD), and temperature programmed reduction methods. Characterization results show that Mo is well dispersed on MCM-41 up to 10 wt%. The catalytic activities were evaluated for thiophene hydrodesulphurization (HDS), cyclohexene hydrogenation (HYD), and furan hydrodeoxygenation (HDO). All three catalytic functionalities vary in a similar manner to that of oxygen chemisorption as a function of Mo loading, indicating that there is a correlation between oxygen uptake and catalytic sites. The activities of these catalysts were compared with γ-Al₂O₃- and amorphous SiO₂-supported catalysts. It was found that MCM-41-supported Mo catalysts displayed superior activities.     

Synthesis of carbon nanotubes by CCVD of natural gas using hydrotreating catalysts

Carbon nanotubes have been successfully synthesized using the catalytic chemical vapor deposition (CCVD) technique over typical refining hydrotreating catalysts (hydrodesulfurization and hydrodenitrogenation) containing Ni–Mo and Co–Mo supported on Al₂O₃ catalysts at 700°C in a fixed bed horizontal reactor using natural gas as a carbon source. The catalysts and the as-grown CNTs were characterized by transmission electron microscopy, HRTEM, X-ray diffraction patterns, EDX and TGA–DTG. The obtained data clarified that the Ni–Mo catalyst gives higher yield, higher purity and selectivity for CNTs compared to Co–Mo catalyst. XRD, TEM and TGA reveal also that the Ni–Mo catalyst produces mostly CNTs with different diameters whereas the Co–Mo catalyst produces largely amorphous carbon.     

COMPARISON BETWEEN THE PERFORMANCE OF CONVENTIONAL AND HIGH-METAL Co-Mo AND Ni-Mo CATALYSTS IN DEEP DESULFURIZATION OF KUWAIT ATMOSPHERIC GAS OIL

ABSTRACT

Due to environmental constraints, sulfur content of diesel fuel has been restricted to very low levels (500 ppm maximum) in many countries. As a result, a greater emphasis has been placed in recent years on the development of catalysts and processes for deep desulfurization of diesel blending streams to produce low sulfur diesel fuel. In the present work we have compared the performance of a conventional Co-Mo catalyst with that of high metal loading Co-Mo and Ni-Mo catalysts in deep desulfurization of Kuwait atmospheric gas oil. The tests were carried out in a fixed bed reactor unit using 75 ml of catalyst under the conditions: P=32 bar; LHSV = 4h^?1; H₂/oil ratio = 100 ml/ml; temperature range = 330 ? 390°C. HDS activity of the high molybdenum Co-Mo catalyst was superior to that of the conventional Co-Mo hydrotreating catalyst. High metal loading Co-Mo/Al₂O₃ catalyst also showed a substantially higher HDS activity than the Ni-Mo/Al₂O₃ catalyst containing a similar high metal loading. The unreacted sulfur compounds remaining in the product after high severity hydrotreating were identified as dibenzothiophenes with alkyl substituents next to the sulfur atom. The desulfiirization of such low reactive alkyl dibenzothiophenes was found to occur at a substantially lower temperature over the high metal loading Co-Mo catalyst compared with the conventional Co-Mo catalyst. The results have been explained on the basis of the stacking and dispersion of MoS₂ slabs as well as in terms of the nature of the sulfur vacancies in the MoS₂ layers in these catalyst systems.     

Catalytic decomposition of methane to COx-free hydrogen and carbon nanotubes over Co–W/MgO catalysts

Bimetallic catalysts containing a series of Co/W at 40/10, 30/20, 20/30 and 10/40 wt% supported on MgO with a total metal content of 50 wt% were prepared and used for the catalytic decomposition of methane to CO_x-free hydrogen and multi-walled carbon nanotubes (MWCNTs). The solid fresh and exhausted catalysts were characterized structurally and chemically through XRD, TPR, BET, TGA, TEM and Raman spectroscopy. The 40%Co–10%W/MgO catalyst exhibited the highest activity for the production of both hydrogen and MWCNTs. The formation of a large amount of non-interacted Co₃O₄ species is considered as the main reason for the catalyst superiority in its activity. On the contrary, catalysts formulations of 20%Co–30%W and 10%Co–40%W demonstrated the formation of a large amount of hardly reducible CoWO₄ and MgWO₄ particles causing lower activity of these catalysts toward methane decomposition as evidenced through the XRD and TPR results.     

Catalytic Coprocessing of Delayed Coker Light Naphtha with Light Straight-run Naphtha/FCC Gasoline

Abstract

Upgrading of delayed coker light naphtha (DCLN) is difficult due to its high diolefin and silicon content. Mixtures of light straight-run naphtha (LSRN) and DCLN fractions were hydrotreated in two stages over NiMo/Al₂O₃ and CoMo/Al₂O₃ catalysts (diolefin saturation followed by hydrodesulphurization (HDS). Naphtha fractions free of diolefins, olefins, sulfur, and silicon were produced, which are excellent feeds for naphtha isomerization. One-stage selective HDS tests were also conducted with blends of DCLN (up to 5 vol%) and fluid catalytic cracked (FCC) gasoline over CoMo/Al₂O₃. Diolefin-free products of <10 mg/kg sulfur could be produced with a research octene number (RON) loss of max. 3.     

EFFECTS OF SUPPORTS ON THE ACTIVITY OF NICKEL CATALYST FOR CH4 REFORMING WITH CO2

ABSTRACT

Nickel catalyst is an effective catalyst for reforming CH₄ with CO₂. The reaction between CO₂ and CH₄ at 1073 K. in the pressure of 0·1 MPa has been studied over different materials supported nickel metal in a fixed-bed reactor. Different catalysts before and after reaction were characterized by SEM, XRD, XPS. Results shows that CO and H₂ are basically produced at the same ratio. When the feed ratio CO₂/CH₄ is less than 0·5, less C₂?C₄ hydrocarbons are detected. When the feed ratio CO₂/CH₄ is 1, Ni/a- Al₂O₃ catalyst has the highest activity. However, when the feed ratio CO₂/CH₄ is greater than 1, Ni/y- A1/O₃, Ni/a- A1₂O₃, Ni/SiO₂ and Ni/HZSM-5 had higher activity; Ni/clinoptilolite basically no activity. Different kinds of carbon deposit are established.     

The Effect of Pd Precursors on the Catalytic Activity of a Pd/Al2O3 Catalyst for Cumene Hydroperoxide Hydrogenation

Abstract

Abstract Pd/Al₂O₃ catalysts were prepared by wet impregnation using K₂PdCl₄, (NH₄)₂PdCl₄, and Pd(NO₃)₂ as precursors. All catalysts were characterized by means of inductively coupled plasma-atomic emission spectroscopy (ICP-AES), temperature-programmed reduction (TPR), X-ray diffraction (XRD), and CO chemisorption. The results obtained in the hydrogenation of cumene hydroperoxide (CHP) to α-cumyl alcohol (CA) showed that Pd/Al₂O₃ catalyst prepared from Pd(NO₃)₂ exhibited the highest turnover frequency (TOF) value and the greatest deactivation extent, whereas Pd/Al₂O₃ catalyst prepared from (NH₄)₂PdCl₄ displayed the lowest TOF value but the best stability.