Hydrogenation of heavy liquids from a direct coal liquefaction residue for improved oil yield

For hydrogenation of heavy liquids in direct coal liquefaction residue (DCLR) within the direct coal liquefaction (DCL) process, heavy liquids in a DCLR derived from a bench-scale Shenhua DCL process using Shenhua coal are evaluated under two conditions. One simulates the coal liquefaction conditions of the Shenhua plant in the presence of a Fe-based Shenhua catalyst; the other one simulates the online hydrotreating conditions in the presence of a NiMo/Al₂O₃ catalyst. The results show that the heavy liquids of DCLR can be hydrogenated under these two conditions yielding less heavy products; hydrogenating the heavy liquids under the online hydrotreating conditions is more effective than that under the coal liquefaction conditions; the preasphaltene fraction is a main problem that yields non-soluble materials under these hydrogenation conditions. The results suggest that hydrogenation of toluene soluble and tetrahydrofuran soluble fractions of the DCLR under the coal liquefaction and online hydrotreating conditions is feasible, but their conversion to lighter products are inapparent under the coal liquefaction conditions, and elimination of the formation of tetrahydrofuran insoluble fraction in the online hydrotreator should be considered.     

Hydrotreating of gas oil on SBA-15 supported NiMo catalysts

The siliceous and the metal substituted (B or Al)-SBA-15 molecular sieves were used as a support for NiMo hydrotreating catalysts (12 wt.% Mo and 2.4 wt.% Ni). The supports were characterized by X-ray diffraction (XRD), scanning electron microscopy and N₂ adsorption–desorption isotherms. The SBA-15 supported NiMo catalysts in oxide state were characterized by BET surface area analysis and XRD. The sulfided NiMo/SBA-15 catalysts were examined by DRIFT of CO adsorption and TPD of NH₃. The HDN and HDS activities with bitumen derived light gas oil at industrial conditions showed that Al substituted SBA-15 (Al-SBA-15) is the best among the supports studied for NiMo catalyst. A series of NiMo catalysts containing 7–22 wt.% Mo with Ni/Mo weight ratio of 0.2 was prepared using Al-SBA-15 support and characterized by BET surface area analysis, XRD and temperature programmed reduction and DRIFT spectroscopy of adsorbed CO. The DRIFT spectra of adsorbed CO showed the presence of both unpromoted and Ni promoted MoS₂ sites in all the catalysts, and maximum “NiMoS” sites concentration with 17 wt.% of Mo loading. The HDN and HDS activities of NiMo/Al-SBA-15 catalysts were studied using light gas oil at temperature, pressure and WHSV of 370 °C, 1300 psig and 4.5 h⁻¹, respectively. The NiMo/Al-SBA-15 catalyst with 17 wt.% Mo and 3.4 wt.% of Ni is found to be the best catalyst. The HDN and HDS activities of this catalyst are comparable with the conventional Al₂O₃ supported NiMo catalyst in real feed at industrial conditions.     

Hydroconversion of resids with dispersed molybdenum catalysts derived from phosphomolybdates

Phosphomolybdic acid (PMA) and cobalt, nickel and potassium phosphomolybdates have been found very active catalyst precursors for the conversion of coal- and petroleum-derived resids when they are impregnated onto coal and Al₂O₃. They are mostly stable up to 400–450°C in the presence of He and H₂, but significant change in stability occurs in the presence of H₂S, transforming these materials into an active form of catalyst. Their solubility in water provides highly dispersed catalysts in the reaction media. PMA and these bimetallic materials were tested at the concentration of 15, 150 and 1500 mg Mo per kg feed for reaction times of 30 and 90 min, and compared to a commercial NiMo/Al₂O₃ catalyst (AKZO-60). In the 30 min reactions, increasing Mo concentration did not provide a significant improvement in resid conversions compared to the non-catalyzed case. However, in the 90 min reactions, improvements were observed in conversion of coal and Mayan resids to distillate boiling below 525°C. The results indicate that thermal reactions play an important role in the 30 min reactions, and catalytic reactions resulting in increased resid conversions become more important in the 90-min reactions. Higher conversions with nickel phosphomolybdate supported on Al₂O₃ were observed with Mayan resid compared with coal resid. Nickel phosphomolybdate has been found to have promising catalytic activity for hydroconversion processes.     

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.     

Effect of preparation methods on the hydrocracking performance of NiMo/Al2O3 catalysts

In this work, NiMo catalysts with various contents of MoO_3 were prepared through incipient wetness impregnation by a two-step method(NM-x A) and one-pot method(NM-xB). The catalysts were then characterized by XRD, XPS, NH_3-TPD, H_2-TPR, HR-TEM, and N2 adsorption–desorption technologies.The performance of the NiMo/Al_2O_3 catalysts was investigated by hydrocracking low-temperature coal tar. When the MoO_3 content was 15 wt%, the interaction between Ni species and Al_2O_3 on the NM-15 B catalyst was stronger than that on the NM-15 A catalyst, resulting in the poor performance of the former.When the MoO_3 content was 20 wt%, MoO_3 agglomerated on the surface of the NM-20 A catalyst, leading to decreased number of active sites and specific surface area and reduced catalytic performance. The increase in the number of MoS_2 stack layers strengthened the interaction between Ni and Mo species of the NM-20 B catalyst and consequently improved its catalytic performance. When the MoO_3 content reached 25 wt%, the active metals agglomerated on the surface of the NiMo catalysts, thereby directly decreasing the number of active sites. In conclusion, the two-step method is suitable for preparing catalysts with large pore diameter and low MoO_3 content loading, and the one-pot method is more appropriate for preparing catalysts with large specific surface area and high MoO_3 content. Moreover, the NMx A catalysts had larger average pore diameter than the NM-xB catalysts and exhibited improved desulfurization performance.     

Rey-zeolite and silica-alumina mixed support for hydrotreating heavy gas oil

Rare earth exchanged Y-type zeolite (REY-zeolite) was dispersed in a silica-alumina gel to prepare catalyst supports with better hydrogenolysis activity. Such support material showed improved hydrotreating properties compared to commercial catalysts, especially for heavy gas oils. Statistical experimental designs used to optimize the composition of such mixed supports suggested a composition of 10 wt.% silica, 25 wt.% zeolite and 65 wt.% alumina as optimum for hydrotreating a heavy gas oil (343°C to 525°C fraction) obtained from hydrocracking of Athabasca bitumen. The kinetic parameters were then evolved for the optimum catalyst.     

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.     

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.     

Hydrocracking Brazilian Marlim vacuum residue with natural limonite. Part 1: catalytic activity of natural limonite

An experimental study examined the catalytic effects of natural Australian (AL) and Brazilian (BL) limonites used in hydrocracking Brazilian Marlim vacuum residue (ML-VR). The catalytic behavior of the limonites was compared with a conventional NiO-MoO₃-Al₂O₃ (NiMo) catalyst. Diphenylmethane (DPM) and 1-methylnaphthalene (1-MN) were used as standards. The order in which coke and gas formation were suppressed during hydrocracking of ML-VR was NiMo>BL>AL, which is the same order as for the hydrogenation activity observed with the standard compounds. By contrast, the limonite catalysts exhibited relatively higher conversions and distillate yields in ML-VR hydrocracking than did the NiMo catalyst with the order of conversion and distillate yield (yield of the fraction with boiling point of 540 °C) being AL>BL>NiMo, which is the same order obtained for catalytic cracking of the two standards. Coke formation was effectively suppressed at high hydrogen pressures. The limonite catalysts showed lower activities for nitrogen and sulfur removal than did NiMo, but both proved to have a larger activity for nickel removal.     

Hydrogen Yield from Low Temperature Steam Reforming of Ethanol

Low temperature steam reforming of ethanol in the temperature range of 200–360°C was studied to maximize the production of H₂. The optimum reaction conditions in presence of a suitable catalyst can produce mainly the desired products H₂ and CO₂. Cu/Al₂O₃ catalysts with six different concentrations ranging from 0 to 10 wt.% Mn, were prepared, characterized and studied for the ethanol-steam reforming reaction. Maximum ethanol conversion of 60.7% and hydrogen yield of 3.74 (mol H₂ / mol ethanol converted) were observed at 360°C for catalyst with 2.5 wt.% Mn loading.     

Production of middle distillate through hydrocracking of paraffin wax over NiMo/TiO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> catalysts

Titania-silica (TS(X), X=19, 26, 55, 70, and 79) supports with different titania content (X, wt%) were prepared by a precipitation method. NiMo/TS(X) catalysts prepared by an incipient wetness method were then applied to the production of middle distillate through hydrocracking of paraffin wax. Successful formation of NiMo/TS(X) (X=19, 26, 55, 70, and 79) catalysts was confirmed by ICP-AES and XRD measurements. NH₃-TPD experiments were conducted to measure the acid property of NiMo/TS(X) (X=19, 26, 55, 70, and 79) catalysts. It was revealed that acidity of the catalyst played an important role in determining the catalytic performance in the hydrocracking of paraffin wax. Conversion of paraffin wax increased with increasing acidity of the catalyst, while yield for middle distillate showed a volcano-shaped curve with respect to acidity of the catalyst. Among the catalysts tested, NiMo/TS(26) retaining moderate acidity showed the highest yield for middle distillate.     

Catalytic hydrotreating of 1-methylnaphthalene as a screening test

Catalytic hydrotreating of 1-methylnaphthalene, a component of most recycle vehicles in coal liquefaction processes, can provide a useful screening test for three catalytic functions: ring hydrogenation, hydrodemethylation (HDM), and ring hydrocracking to give substituted benzenes. Detailed information is obtained from the pressure change on reaction and from gas chromatographic analyses of both the product gas and the product liquid. A commercial Co/Mo/Al₂O₃ catalyst tested at 450°C shows very little incremental HDM compared with a no-catalyst control, no ring hydrocracking, but subtantial ring hydrogenation. At 500°C, all reactions are more extensive. A low-temperature ash from Kentucky coal is relatively inactive at 450°C except for HDM.     

Metal-ion pillared clays as hydrocracking catalysts (II): effect of contact time on products from coal extracts and petroleum distillation residues

Novel catalysts have been prepared, based on montmorillonite (a natural clay) and laponite (a synthetic clay) pillared with tin, chromium and aluminium pillars as well as layered double hydroxides based on polyoxo-vanadate and -molybdate as previously described. These novel catalysts were compared initially with a standard Ni/Mo catalyst supported on alumina and a dispersed catalyst, Mo(CO)₆ in hydrocracking a coal extract for a short contact time of 10 min at 440 °C in a microbomb reactor with tetralin solvent and hydrogen at a pressure of 190 bar. In the present work, the best of the novel catalysts, chromium montmorillonite calcined at 500 °C and tin laponite, have been compared with the supported catalyst and a dispersed catalyst (Mo(CO)₆) in the repeated hydrocracking of fresh coal extract over three sequential periods of 1 h. Also, the chromium montmorillonite calcined at 500 °C has been used in the hydrocracking of primary coal extracts, prepared in the flowing solvent liquefaction rig from Pittsburgh #8 and Illinois #6 coals, for reaction times of 10 min and 2 h. Further, the chromium montmorillonite calcined at 500 °C and tin laponite, have been compared with the supported catalyst and in the absence of a catalyst, in the hydrocracking of a petroleum distillation residue with 10 min and 2 h reaction times. Results were compared by size exclusion chromatography in NMP solvent and by UV-fluorescence and evaluated by the extent of the shift of the SEC profile to small molecules and by the shift of the synchronous UV-fluorescence profiles to shorter wavelengths. The performances of both catalysts at short, long or repeated reaction times are seen to be better than that of the conventional NiMo catalyst for the hydrocracking of coal-derived materials and a petroleum residue. Trials on a longer time scale are necessary in the next level of evaluation.     

Hydro-thermal cracking of heavy oils and its model compound

Liquid-phase cracking of vacuum gas oil (VGO) was performed over NiMo supported nonacidic catalysts under 713 K and 8.0 MPa of hydrogen in a batch reactor, which is termed hydro-thermal cracking. Compared with VGO thermal cracking under the same reaction conditions the new process showed the suppressed naphtha yield (from 22.4 to 13.5 wt.%) and VGO conversion (from 65.7 to 64.0 wt.%) and increased the middle distillate yield (from 44.3 to 49.3 wt.%). At the same conversion level, the yield ratio of middle distillates to naphtha for this new process was two times higher than that for VGO hydrocracking. The VGO hydrocracking over USY-supported NiMo proceeded at much lower temperatures but gave higher naphtha yields. Both the thermal cracking and the hydro-thermal cracking of n-dodecyl benzene (C₆H₅(CH₂)₁₁CH₃) yielded toluene as the major aromatic product, whereas its hydrocracking over NiMo/USY yielded benzene as the major aromatic product. The reaction mechanism of this new process was assumed to consist of thermal cracking of hydrocarbon molecules via the free radical chain mechanism and the catalytic hydroquenching of free radicals.     

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.     

Effects of parameters in Ni–Mo catalysed hydrocracking of vacuum residue on composition and quality of obtained products

The laboratory findings were presented for a single-stage hydrocracking process of vacuum residue (VR) of Ural crude. The Ni–Mo/Al₂O₃ catalyst in suspension was used in tests. The amounts and quality of the obtained products were related to process parameters. Hydrocracking of VR was carried out in a continuous flow reactor, at the temperature of 410–450 °C and pressure of 12–20 MPa, at the liquid space velocity (LHSV) of 0.25–0.75 h^− 1, and at the gas space velocity of 2500 h^− 1.The studied catalyst Ni–Mo/Al₂O₃ was found moderately active in the VR cracking process, while it turned out an efficient catalyst for the hydrofining processes. The catalyst concentration and hydrogen pressure had no effect on hydrocracking of VR, and hydrofining of cracking products was affected slightly only over the studied scope of parameters. The reaction temperature and LHSV exerted dramatic effects on hydrocracking of VR and on the asphaltenes and CCR contents, while their effect on hydrofining of cracking products was much lower. The temperature of 430 °C resulted in VR conversion to distillates (b.p. < 538 °C) of 61.6–88.7 wt.% and in sulphur conversion of 70–85 wt.%.     

Coupled hydrogenation and ring opening of tetralin on potassium modified Pt/USY catalysts

Coupled hydrogenation and ring opening of tetralin (THN) on Pt/USY catalyst were performed on a high-pressure fixed-bed reactor. The effect of reaction temperature in range of 100–300 °C and the nature of the catalyst (metal and acid sites) on the catalytic performance were studied. The results indicated that the extent of hydrocracking, a sequential reaction of ring opening, should be reduced in order to maintain high yields of the ring opening products (ROP). Introduction of the Pt component accelerated the hydrogenation and ring opening of the THN significantly. It was also found to be an effective way to optimize the acid properties of the catalysts by introducing an appropriate amount of potassium to the catalyst, such that the strong acid sites of the catalysts were diminished, and a higher ROP yield could be obtained as a result of the inhibiting of the hydrocracking activity of the catalyst. When the yield of the C10 fractions could be maintained at 90 wt.%, then a maximal ROP yield of 35.6 wt.% could be obtained on a 0.5 wt.% Pt/USY catalyst loaded with 2.0 wt.% of K.     

Effect of supercritical deposition synthesis on dibenzothiophene hydrodesulfurization over NiMo/Al2O3 nanocatalyst

The synthesis of two NiMo/Al₂O₃ catalysts by the supercritical carbon dioxide/methanol deposition (NiMo‐SCF) and the conventional method of wet coimpregnation (NiMo‐IMP) were conducted. The results of the physical and chemical characterization techniques (adsorption–desorption of nitrogen, oxygen chemisorption, XRD, TPR, TEM, and EDAX) for the NiMo‐SCF and NiMo‐IMP demonstrated high and uniform dispersed deposition of Ni and Mo on the Al₂O₃ support for the newly developed catalyst. The hydrodesulfurization (HDS) of fuel model compound, dibenzothiophene, was used in the evaluation of the NiMo‐SCF catalyst vs. the commercial catalyst (NiMo‐COM). Higher conversion for the NiMo‐SCF catalyst was obtained. The kinetic analysis of the reaction data was carried out to calculate the reaction rate constant of the synthesized and commercial catalysts in the temperature rang of 543–603 K. Analysis of the experimental data using Arrhenius' law resulted in the calculation of frequency factor and activation energy of the HDS for the two catalysts. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

Catalysts based on zeolite ZSM-23 for isodewaxing of a lubricant stock

Granular Pt/(ZSM-23-γ-Al₂O₃) catalysts with different platinum and zeolite contents have been synthesized with the aim of developing efficient isodewaxing catalysts for lowering the pour point of lubricants and diesel fuels. Their physicochemical properties have been studied by X-ray diffraction, temperature-programmed desorption of ammonia, and low-temperature nitrogen adsorption/desorption. The effects of catalyst composition and process conditions (1.0–3.0 MPa, 220–400°C) on the outcomes of the isodewaxing of the 280°C-EBP lubricant fraction isolated from the hydrocracking product of vacuum gas oil have been investigated. The highest yields of products with the same pour points have been obtained with a 0.30 wt % platinum catalyst supported on the 20 wt % zeolite ZSM-23 + 80 wt % γ-Al₂O₃ material. An analysis of the basic performance characteristics of the isodewaxing catalysts based on zeolite ZSM-23 and dewaxing catalysts based on zeolite ZSM-5 has demonstrated that the catalysts based on ZSM-23 ensure higher yields of dew-axed products than the laboratory and commercial catalysts based on ZSM-5.     

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.