Hydroprocessing of straight run diesel mixed with light cycle oil from fluid catalytic cracking,using sulfide NiMo catalyst on zeolite-containing supports

It is proposed that the sulfide NiMo system supported on alumina-SAPO-31 composite (NiMo/Al₂O₃-SAP catalyst) be used to obtain high-quality diesel fuel from a mixture of straight run diesel (SRGO) and light cycle oil (LCO) produced by fluid catalytic cracking (FCC). It is shown that the use of this catalyst ensures the synthesis of diesel fuel of higher quality upon hydroprocessing a feedstock with 30 wt % LCO, compared to the traditional sulfide NiMo/Al₂O₃ or CoMo/Al₂O₃ catalysts. It is found that the content of aliphatic hydrocarbons is raised in the products of hydrotreatment, compared to the initial feedstock. This confirms the ability of NiMo/Al₂O₃-SAP catalyst to facilitate the reaction of ring opening. Using the proposed catalyst should improve the quality of diesel fuels obtained via the hydroprocessing of LCO-containing feedstock.     

A comparative study on the effect of promoter content of hydrodesulfurization catalysts at different evaluation scales

CoMo and NiMo supported Al₂O₃ catalysts have been investigated for hydrotreating of model molecule as well as industrial feedstock. Activity studies were carried out for thiophene and SRGO hydrodesulfurization (HDS) in an atmospheric pressure and batch reactor respectively. These activities on sulfided catalysts were evaluated as a function of promoter content [M/(M + Mo) = 0.30, 0.34, 0.39; M = Co or Ni] using fixed (ca. 8 wt.%) molybdenum content. The promoted catalysts were characterized by textural properties, XRD, and temperature programmed reduction (TPR). TPR spectra of the Co and Ni promoter catalysts showed that Ni promotes the easy reduction of Mo species compared with Co. With the variation of promoter content NiMo catalyst was found to be superior to CoMo catalyst for gas oil HDS, while at low-promoter content the opposite trend was observed for HDS of thiophene. The behavior was attributed to the several reaction mechanisms involved for gas oil HDS. A nice relationship was obtained for hydrodesulfurized gas oil refractive index (RI) and aromatic content, which corresponds to the Ni hydrogenation property.     

Characterization of hydrodesulfurization catalyst prepared by impregnating cobalt nitrate solution onto the sulfided MoO3/Al2O3 catalyst

CoMo/Al₂O₃ catalysts were prepared by impregnating Cobalt nitrate solution into oxidic or sulfided Mo/Al₂O₃. The properties of CoMo/Al₂O₃ catalysts were characterized by XRD, TPS, oxygen chemisorption and ESR. Catalytic activity of CoMo/Al₂O₃ catalyst was evaluated by thiophene HDS as a probe reaction. When CoMo/Al₂O₃ catalyst was prepared by impregnating Cobalt nitrate solution into sulfided Mo/Al₂O₃, the interaction between Mo and alumina became weaker and the formation of synergic phase was facilitated. These structural changes may explain higher HDS activity of CoMo/Al₂O₃ catalyst prepared by impregnating Cobalt nitrate solution into sulfided Mo/Al₂O₃.     

Effect of catalyst composition on the hydrodesulphurization and hydrodemetallization of atmospheric residual oil

A series of CoMo/Al₂O₃ catalysts containing a third additive, a Si, Ti, or P compound, were prepared using a consecutive impregnation method. The activities for the hydrodesulphurization (HDS), hydrodemetallization (HDM) and Conradson carbon residue (CCR) reduction of atmospheric residual oil were tested in a semi-batch basket type reactor. Cycle-aging tests were carried out for comparison of catalyst stability. The intrinsic rate constants of HDS from a semi-empirical calculation were used to test the coke tolerance of the catalysts. The CoMo/Al₂O₃ catalyst with a titanium compound added exhibited the highest activity enhancement for HDS and HDM reactions. It was also found that the surface activity maintenance can be effectively improved by the addition of an appropriate amount of titanium compound. The activity and stability of CoMo and NiMo catalysts for the HDS and HDM reactions were also compared.     

Catalytic pyrolysis of Athabasca bitumen in H2 atmosphere using microwave irradiation

Microwave-assisted catalytic pyrolysis was carried out for upgrading of Athabasca bitumen. The bitumen can be heated to the desired target temperature (430 °C) for pyrolysis with silicon carbide (SiC), a heating element, in approximately 10 min under microwave irradiation. However, the pyrolysis with SiC only resulted in heavy and viscous liquid product having an API gravity of 17.14°. Addition of Nickel and Molybdenum nanoparticles as catalysts enhanced the pyrolysis performance in terms of liquid yield and quality. In the pyrolysis with Mo nanoparticles, the yield and the API gravity of the liquid product were 72.0 wt% and 20.98°, respectively. However, the separate existence of nanoparticles and SiC in the reactor and the recovery problem of nanoparticles, might limit their application in microwave-assisted pyrolysis. In order to prepare a composite with microwave susceptibility and catalytic activity in one body, transition metals were loaded on alumina coated SiC. When it is compared to the direct application of metal nanoparticles to the pyrolysis of bitumen, the NiMo/Al₂O₃/SiC catalyst showed enhanced catalytic performance. The API gravity and sulfur contents of the liquid products from the pyrolysis with NiMo/Al₂O₃/SiC were 22.42° and 2.84 wt%, respectively.     

Mechanisms of hydrodenitrogenation of alkylamines and hydrodesulfurization of alkanethiols on NiMo/Al2O3, CoMo/Al2O3, and Mo/Al2O3

The simultaneous hydrodenitrogenation (HDN) of alkylamines and hydrodesulfurization (HDS) of alkanethiols, with the NH₂ and SH groups attached to primary, secondary, and tertiary carbon atoms, were studied at 270–320 °C and 3 MPa over sulfided NiMo/Al₂O₃, CoMo/Al₂O₃, and Mo/Al₂O₃ catalysts. Pentylamine and 2-hexylamine reacted by substitution with H₂S to form alkanethiols and with another amine molecule to form dialkylamines. Alkenes and alkanes were not formed directly from pentylamine and 2-hexylamine, but indirectly by elimination and hydrogenolysis of the alkanethiol intermediates, as confirmed by their secondary behavior and the similar alkene/alkane ratios in the simultaneous reactions of amines and thiols. Only 2-methyl-2-butylamine, with the NH₂ group attached to a tertiary carbon atom, produced alkenes as primary products by E1 elimination. NiMo/Al₂O₃ and CoMo/Al₂O₃ have a higher activity for the HDS of alkanethiols than does Mo/Al₂O₃; H₂S has a negative influence. This shows that the thiols react on vacancies on the catalyst surface (Lewis acid sites). Mo/Al₂O₃ is the best HDN catalyst; H₂S has a positive influence on the HDN of amines with the NH₂ group attached to a secondary and a tertiary carbon atom. This indicates that the HDN of alkylamines occurs on Brønsted acid sites.     

Hydrodeoxygenation of stearic acid using Mo modified Ni and Co/alumina catalysts: Effect of calcination temperature

Abstract

The calcination temperature (Cal-Temp) plays a vital role in the performance of supported metal catalysts. In this work, the alumina supported Ni, NiMo, Co, and CoMo catalysts were prepared at different Cal-Temp. The catalysts were characterized by various techniques to identify the catalytically active different surface species to correlate their role in the hydrodeoxygenation of stearic acid. With increasing Cal-Temp, the metal dispersion was increased for Ni, NiMo, and CoMo catalyst (up to 973 K) and decreased for Co catalyst. With increasing Cal-Temp, the catalytic activity was thus increased for Ni and NiMo catalyst and decreased for Co catalyst. The activity of CoMo catalyst was, however, enhanced with rising Cal-Temp up to 973 K and declined slightly after that. The optimum Cal-Temp for Ni, NiMo, Co, and CoMo catalyst was found to be 1023 K, 973 K, 773 K, and 973 K. The reaction followed the decarbonylation route over active metallic centers (Ni and Co) and the HDO route over oxophilic M²⁺?MoO₂ (M = Ni/Co) and reducible cobalt oxide species. The C₁₇ alkane was thus the principal product over Ni catalyst, whereas C₁₈ alkane was the primary product over CoMo and NiMo catalyst. In contrast, both C₁₇ and C₁₈ alkanes were significant over Co catalyst.     

Catalytic Hydroprocessing of p-Cresol: Metal, Solvent and Mass-Transfer Effects

A systematic study of the comparative performances of supported Pt, Pd, Ru and conventional CoMo/Al₂O₃, NiMo/Al₂O₃, NiW/Al₂O₃ catalysts as well as the effects of solvent, H₂ pressure and temperature on the hydroprocessing activity of a representative model bio-oil compound (e.g., p-cresol) is presented. With water as solvent, Pt/C catalyst shows the highest activity and selectivity towards hydrocarbons (toluene and methylcyclohexane), followed by Pt/Al₂O₃, Pd and Ru catalysts. Calculations indicate that the reactions in aqueous phase are hindered by mass-transfer limitations at the investigated conditions. In contrast, with supercritical n-heptane as solvent at identical pressure and temperature, the reactant and H₂ are completely miscible and calculations indicate that mass-transfer limitations are eliminated. All the noble metal catalysts (Pt, Pd and Ru) show nearly total conversion but low selectivity to toluene in supercritical n-heptane. Further, conventional CoMo/Al₂O₃, NiMo/Al₂O₃ and NiW/Al₂O₃ catalysts do not show any hydrodeoxygenation activity in water, but in supercritical n-heptane, CoMo/Al₂O₃ shows the highest activity among the tested conventional catalysts with 97?% selectivity to toluene. Systematic parametric investigations with Pt/C and Pt/Al₂O₃ catalysts indicate that with water as the solvent, the reaction occurs in a liquid phase with low H₂ availability (i.e., low H₂ surface coverage) and toluene formation is favored. In supercritical n-heptane with high H₂ availability (i.e., high H₂ surface coverage), the ring hydrogenation pathway is favored leading to the high selectivity to 4-methylcyclohexanol. In addition to differences in H₂ surface coverage, the starkly different selectivities between the two solvents may also be due to the influence of solvent polarity on p-cresol adsorption characteristics.     

Synthesis and catalytic performance of novel hierachically porous material beta-MCM-48 for diesel hydrodesulfurization

Novel hierachically porous material Beta-MCM-48 was successfully synthesized from Beta zeolite seeds by two-step hydrothermal crystallization method using Cetyltrimethylammonium Bromide as the mesostructure directing agent. Beta-MCM-48 composite synthesized at the optimization conditions possessed Beta microporous structure and cubic Ia $ \overline{ 3} $ 3 ¯ d mesoporous structure simultaneously. Meanwhile, the acidity of Beta-MCM-48 was similar to Beta zeolite and higher than MCM-48 mesoporous material. A series of Al₂O₃-Beta-MCM-48 supported NiMo catalysts with different Beta-MCM-48 contents were prepared by the incipient-wetness impregnation method. The catalytic performances were evaluated using DaQing Fluid Catalytic Cracking diesel as feedstock in a high pressure microreactor. Hydrodesulfurization results indicated that NiMo/Al₂O₃-Beta-MCM-48 catalyst exhibited better activities than that of NiMo/Al₂O₃ traditional catalyst. NiMo/Al₂O₃-Beta-MCM-48 catalyst obtained the highest activity as the Beta-MCM-48 content in the support was 20 wt %, and the corresponding sulfur content of the hydrotreated product reached to 23.02 μg g^?1.     

In situ QEXAFS investigation at Co K-edge of the sulfidation of a CoMo/Al2O3 hydrotreating catalyst

In situ sulfidation of a commercial alumina-supported CoMo hydrotreating catalyst (3 wt% Co, 12.3 wt% Mo) has been studied by QEXAFS at Co K-edge. Sulfidation was performed by heating progressively the oxide precursor from room temperature (RT) up to 673 K in a H₂/10% H₂S flow (ramp 4 K/min). XAFS spectra were recorded each 10 K with an acquisition time of only 30 s. The obtained XANES and EXAFS data were compared with those of a Co/Al₂O₃ (2.36 wt% Co) used as reference sample. It is evidenced that sulfidation of Co atoms in a CoMo/Al₂O₃ catalyst starts at room temperature while the sulfidation of a Co/Al₂O₃ catalyst begins at 473 K.     

Hydrodeoxygenation of guaiacol on noble metal catalysts

Hydrodeoxygenation (HDO) performed at high temperatures and pressures is one alternative for upgrading of pyrolysis oils from biomass. Studies on zirconia-supported mono- and bimetallic noble metal (Rh, Pd, Pt) catalysts showed these catalysts to be active and selective in the hydrogenation of guaiacol (GUA) at 100 °C and in the HDO of GUA at 300 °C. GUA was used as model compound for wood-based pyrolysis oil. At the temperatures tested, the performance of the noble metal catalysts, especially the Rh-containing catalysts was similar or better than that of the conventional sulfided CoMo/Al₂O₃ catalyst. The carbon deposition on the noble metal catalysts was lower than that on the sulfided CoMo/Al₂O₃ catalyst. The performance of the Rh-containing catalysts in the reactions of GUA at the tested conditions demonstrates their potential in the upgrading of wood-based pyrolysis oils.     

Comparison of product selectivity during hydroprocessing of bitumen derived gas oil in the presence of NiMo/Al2O3 catalyst containing boron and phosphorus

A detailed experimental study was performed in a trickle-bed reactor using bitumen derived gas oil. The objective of this work was to compare the activity of NiMo/Al₂O₃ catalyst containing boron or phosphorus for the hydrotreating and mild hydrocracking of bitumen derived gas oil. Experiments were performed at the temperature and LHSV of 340-420 °C and 0.5-2 h⁻¹, respectively, using NiMo/Al₂O₃ catalysts containing 1.7 wt% boron or 2.7 wt% phosphorus. In the temperature range of 340-390 °C, higher nitrogen conversion was observed from boron containing catalyst than that from phosphorus containing catalyst whereas in the same temperature range, phosphorus containing catalyst gave higher relative removal of sulfur than boron containing catalyst. Phosphorus containing catalyst showed excellent hydrocracking and mild hydrocracking activities at all operating conditions. Higher naphtha yield and selectivity were obtained using phosphorus containing catalyst at all operating conditions. Maximum gasoline selectivity of ∼45 wt% was obtained at the temperature, pressure, and LHSV of 400 °C, 9.4 MPa and 0.5 h⁻¹, respectively, using catalyst containing 2.7 wt% phosphorus.     

Hydrotreating of heavy gas oil using CoMo/γ-Al2O3 catalyst prepared by equilibrium deposition filtration

CoMo/γ-Al₂O₃ catalyst containing 16.0 wt% MoO₃ and 3.2 wt% CoO was prepared by equilibrium deposition filtration method (EDF). The CoMo oxidic catalyst was characterized by elemental analysis, N₂ adsorption, XRD, and TPR. The sulfided catalyst was characterized by FTIR of adsorbed CO at 30 °C. Hydrodesulfurization (HDS) and hydrodearomatization activities were evaluated for heavy gas oil (HGO) in a trickle bed reaction system using the following conditions: reaction temperatures of 340, 360, 380 and 400 °C, a reaction pressure of 20, 35, 50 and 65 bar, a liquid hourly space velocity (LHSV) of 1.0, 1.5, 2.0, 2.5 and 3 h⁻¹ and a H₂/feed ratio of 400 L L⁻¹. The experimental results were used to determine apparent reaction orders and activation energies. The dispersion, nature of active sites and hydrotreating activity of this catalyst were compared with the conventionally prepared CoMo/γ-Al₂O₃ catalyst containing similar wt% of MoO₃ and CoO. The CoMo catalyst prepared by equilibrium deposition filtration method has higher HDS and HDA rate constants than the conventional catalyst due to an improved dispersion of MoS₂.     

Hydrocracking Marlim vacuum residue with natural limonite. Part 2: experimental cracking in a slurry-type continuous reactor

Disposable Australian iron-slurry (AL) and NiO-MoO₃-Al₂O₃ (NiMo) catalysts were used in hydrocracking experiments to convert Marlim vacuum residue (ML-VR) in a slurry-bed continuous flow reactor at temperatures of 440-460 °C, under a hydrogen pressure of 14.7 MPa and an LHSV of 0.5. The degree of conversion ranged from 54 to 83%, depending on the reaction temperature and catalyst used, with AL giving more complete conversion than NiMo. AL also proved more active in the removal of nickel. Hydrogen consumption was linearly correlated with conversion regardless of the catalyst used.     

Trends for mono‐aromatic compounds hydrogenation over sulfided Ni, Mo and NiMo hydrotreating catalysts

The relative hydrogenation activity in typical hydrotreating conditions of toluene, mxylene, 1,3,5trimethylbenzene and 1,2,4,5tetramethylbenzene was unexpectedly found to decrease over a sulfided NiMo/Al₂O₃ catalyst and to increase over sulfided Ni/Al₂O₃ and Mo/Al₂O₃ catalysts. This change of activity trend is tentatively interpreted by the formation of a mixed NiMoS phase with a different electronic state compared to Ni or Mo sulfide phases. The nature of the aromatic compound influences strongly the magnitude of the promotion effect of Ni on the activity of the Mo in the sulfided NiMo/Al₂O₃ catalyst.     

Exact solution of catalyst inhibition problems: Application to hydrodesulfurization for clean fuel production

In catalyst development, a targeted reaction often is inhibited by a strongly adsorbed species. To help develop mitigation means, it is important to quantitatively relate the inhibition dynamics to catalyst properties. The present study develops a combined modeling and experimental approach to address this problem. A general mathematical model consisting of three nonlinear partial differential equations is reduced to quadratures or two first-order ordinary differential equations. The result is a simple parameter estimation method, which is used for kinetic characterization of an unsupported CoMo sulfide catalyst for desulfurizing 4,6-diethyldibenzothiophene with 3-ethylcarbazole as the inhibitor. The active site densities and adsorption-reaction rate constants are determined from modeling of transient response experiments. The unsupported CoMo catalyst has a higher hydrodesulfurization turnover frequency than a commercial sulfided Co_zMo/Al₂O₃–SiO₂ catalyst in the absence of 3-ethylcarbazole. However, the unsupported CoMo sulfide is about three times less resilient to 3-ethylcarbazole inhibition than the Co_zMo/Al₂O₃–SiO₂ catalyst.     

The role of nickel in pyridine hydrodenitrogenation over NiMo/Al2O3

Al₂O₃ supported Mo, Ni, and NiMo/Al₂O₃ catalysts with various Ni contents were prepared to investigate the role of Ni as a promoter in a NiMo bimetallic catalyst system. The hydrodenitrogenation (HDN) reaction of pyridine as a catalytic probe was conducted over these catalysts under the same reaction conditions and the catalysts were characterized using BET surface area measurement, infrared spectroscopy, temperature programmed reduction, DRS and ESR. According to the results of reaction experiments, the NiMo/Al₂O₃ catalyst showed higher activity than Mo/Al₂O₃ catalyst in the HDN reaction and particularly the one with atomic ratio [Ni/(Ni+Mo)]=0.3 showed the best activity for the HDN of pyridine. The findings of this study lead us to suggest that the enhancement in the HDN activity with nickel addition could be attributed to the improvement in the reducibility of molybdenum and the formation of Ni-Mo-O phase.     

Comparative investigations of the catalytic properties of an anodic Al2O3-coated catalyst and of α- and γ-Al2O3 bulk catalysts

The catalytic properties of an Al₂O₃-coated catalyst formed by anodic oxidation of aluminium were compared with those of α- and of γ-Al₂O₃- bulk catalysts in the dehydration of 2-propanol and in the isomerization of n-butenes. In the dehydration reaction both the Al₂O₃-coated catalyst and the γ-Al₂O₃ bulk catalyst show approx. the same activities and activation energies. However, the reaction rate based on the unit of the surface area for the Al₂O₃-coated catalyst is approx. 30 times larger than that for the γ-A1₂O₃ bulk catalyst. In the isomerization of the individual isomeric n-butenes the Al₂O₃-coated catalyst was more active than the γ-Al₂O₃, bulk catalyst and under otherwise equal conditions equilibrium was reached at approx. 80 K lower temperature.     

Two-stage coal liquefaction using sequential mineral and hydrotreating catalysts

Two-stage coal liquefaction offers significant improvements over single-stage processing in terms of product yields. The proposed two-stage operation utilizes an inexpensive and readily available mineral or disposable catalyst in the first stage followed by a commercial hydrotreating catalyst in the second stage. Single stage processing at 450°C and 425°C both show metal sulfides, i.e. pyrite, to be effective in increasing oil yields. In two-stage processing at 450°/410°C the sequence of pyrite followed by NiMo/Al₂O₃ is the most effective combination for producing oil (pentane soluble materials). Two stage processing at 425°/425°C utilizing sulfided liquefaction residue ash or pyrite as first-stage catalysts yields the highest percentage of oil. The improvements shown by solubility product distributions are verified by distillation curves of the reaction product. Evidence of pore diffusion limitation is apparent in the pelletized NiMo/Al₂O₃. Changes in catalyst morphology may be necessary to achieve maximum yields.     

Mesoporous silica–alumina as support for Pt and Pt–Mo sulfide catalysts: Effect of Pt loading on activity and selectivity in HDS and HDN of model compounds

The potential of mesoporous silica–alumina (MSA) material as support for the preparation of sulfided Pt and Pt–Mo catalysts of varying Pt loadings was studied. The catalysts were characterized by their texture, hydrogen adsorption, transmission electron microscopy, temperature programmed reduction (TPR) and by activity in simultaneous hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine. Sulfided Pt/MSA catalysts with 1.3 and 2 wt.% Pt showed almost the same HDS and higher HDN activities per weight amounts as conventional CoMo and NiMo/Al₂O₃, respectively. The addition of Pt to sulfided Mo/MSA led to promotion in HDS and HDN with an optimal promoter content close to 0.5 wt.%. The results of TPR showed strong positive effect of Pt on reducibility of the MoS₂ phase which obviously reflects in higher activity of the promoted catalysts. The activity of the MSA-supported Pt–Mo catalyst containing 0.5 wt.% Pt was significantly higher than the activity of alumina-supported Pt–Mo catalyst. Generally, Pt–Mo/MSA catalysts promoted by 0.3–2.3 wt.% Pt showed lower HDS and much higher HDN activities as compared to weight amounts of CoMo and NiMo/Al₂O₃. It is proposed that thiophene HDS and pyridine hydrogenation proceed over Pt/MSA and the majority of Pt–Mo/MSA catalysts on the same type of catalytic sites, which are associated with sulfided Pt and MoS₂ phases. On the contrary, piperidine hydrogenolysis takes place on different sites, most likely on metallic Pt fraction or sites created by abstraction of sulfur from MoS₂ in the presence of Pt.