Characterization and catalytic activity of coal mineral matter: 2. Hydrodesulfurization of thiophene

Intrinsic catalytic activity was evaluated for nine low-temperature ash samples (LTAs) from U.S. coals, a sample of SRC solids, and reference constituents of coal for the hydrodesulfurization (HDS) of thiophene. A pulse micro-reactor, gas-chromatograph system was used to determine conversion by measuring the C₄s produced at 673 K. Activity ranking placed Kentucky Homestead as the best HDS catalyst by a factor of 14.3 times the activity of the lignite, which gave the lowest conversion. SRC solids from a Pittsburgh seam coal were evaluated and showed moderate HDS activity. This activity was similar to that of the mineral matter of two other Pittsburgh seam coals (Ireland and Bruceton). The catalytic activity of the LTAs was much smaller than measured conversions using a commercial cobalt molybdate catalyst. The SRC solids gave the highest hydrogenation activity (HA) of all the LTAs tested. The LTAs were found to be very poor hydrogenation catalysts. The worst HDS catalysts, lignite, gave the highest HA while Kentucky No. 11 had the lowest HA activity. More than 95% of the products were butenes or 1,3-butadiene. Surface area for the LTAs increased after catalyst testing, and the HDS activity correlated strongly with surface area while hydrogenation activity showed no such correlation. Favorable element correlations showed potassium to be the most favored for predicting HDS activity. The potassium in the LTAs was present as illite or feldspar. Results are also given for several reference clays and a synthetic mixture of mineral matter constituents.     

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.     

Effect of EDTA on hydrotreating activity of CoMo/γ-Al2O3 catalyst

γ-Al₂O₃ supported Co (0–4.5 wt%) Mo (9.0 wt%) sulfide catalysts were prepared in the presence and the absence of ethylenediaminetetraacetic acid (EDTA). The hydrodenitrogenation (HDN) activity of these catalysts was studied in the model reaction of 2,6-dimethylaniline (DMA) at 300 °C under 4 MPa. The CoMo/Al₂O₃ catalysts prepared with the EDTA showed higher HDN of DMA than those prepared without EDTA. The maximum of 36% increase in rate constant of HDN of DMA was observed over the catalyst with 3% Co prepared using EDTA. The FT-IR spectroscopy of adsorbed CO on CoMo catalysts showed that EDTA addition promoted the formation of catalytically active “CoMoS” phase as evidenced from increases in intensity of band at 2070 cm⁻¹, which is maximum for 3% Co loaded catalysts. The HDN and hydrodesulfurization (HDS) activity of 3% Co loaded catalyst prepared using EDTA was tested and compared with those catalyst prepared without EDTA in a trickle bed reactor using heavy gas oil derived from Athabasca bitumen in the temperature range 370–400 °C and 8.8 MPa. Improved HDN and HDS conversion of heavy gas oil was obtained for the catalyst prepared with EDTA.     

Synthesis, characterization and hydrotreating performance of supported tungsten phosphide catalysts

Supported tungsten phosphide catalysts were prepared by temperature-programmed reduction of their precursors (supported phospho-tungstate catalysts) in H₂ and characterized by X-ray diffraction (XRD), BET, temperature-programmed desorption of ammonia (NH₃-TPD) and X-ray photoelectron spectroscopy (XPS). The reduction-phosphiding processes of the precursors were investigated by thermogravimetry and differential thermal analysis (TG-DTA) and the suitable phosphiding temperatures were defined. The hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) activities of the catalysts were tested by using thiophene, pyridine, dibenzothiophene, carbazole and diesel oil as the feedstock. The TiO₂, γ-Al₂O₃ supports and the Ni, Co promoters could remarkably increase and stabilize active W species on the catalyst surface. A suitable amount of Ni (3%–5%), Co (5%–7%) and V (1%–3%) could increase dispersivity of the W species and the BET surface area of the WP/γ-Al₂O₃ catalyst. The WP/γ-Al₂O₃ catalyst possesses much higher thiophene HDS and carbazole HDN activities and the WP/TiO₂ catalyst has much higher dibenzothiophene (DBT) HDS and pyridine HDN activities. The Ni, Co and V can obviously promote the HDS activity and inhibit the HDN activity of the WP/γ-Al₂O₃ catalyst. The G-Ni5 catalyst possesses a much higher diesel oil HDS activity than the sulphided industrial NiW/γ-Al₂O₃ catalyst. In general, a support or promoter in the WP/γ-Al₂O₃ catalyst which can increase the amount and dispersivity of the active W species can promote its HDS and HDN activities.     

Effect of TiO2 on hydrodenitrogenation performances of MCM-41 supported molybdenum phosphides

The effect of TiO₂ on the hydrodenitrogenation (HDN) performance of MoP/MCM-41 was investigated using quinoline and decahydroquinoline as the model molecules. The catalysts were characterized by XRD, CO chemisorption, TEM, TPR and pyridine FT-IR. Addition of TiO₂ enhanced the C–N bond cleavage activity of MoP/MCM-41 but inhibited its dehydrogenation activity. A maximum HDN activity was observed when the TiO₂ loading was 5 wt%. The characterization results indicated that introduction of TiO₂ did not affect the formation of MoP phase. The TiO₂-containing catalysts possessed higher CO uptake than MoP/MCM-41, but no significant differences in the acid properties and particle size distributions were observed for all the catalysts. XPS results revealed a surface enrichment of TiO₂ in Ti-containing catalysts and small amount of these surface TiO₂ can be partially reduced to Tiⁿ⁺ (n < 4). It is suggested that these Tiⁿ⁺ (n < 4) species may be responsible for the promoting effect of TiO₂ on the HDN performance of MoP/MCM-41.     

Catalytic Activity of Exfoliated MoS2 in Hydrodesulfurization, Hydrodenitrogenation and Hydrogenation Reactions

The activity of exfoliated MoS₂ in the hydrodesulfurization (HDS) of dibenzothiophene, the hydrodenitrogenation (HDN) of carbazole and the hydrogenation of naphthalene has been determined. The catalytic activity was compared to MoS₂ prepared by the decomposition of molybdenum naphthenate (MoNaph). Exfoliated MoS₂ was found to give better overall HDS activity compared to MoNaph derived MoS₂ catalyst, whereas MoNaph derived MoS₂ was found to give higher hydrogenation and HDN activity. These results are discussed in terms of the morphology of the two catalysts. The relative activity of the two catalysts in the hydrotreating reactions is shown to be different to that obtained during Cold Lake bitumen hydrocracking.     

The activity of transition metal nitrides for hydrotreating quinoline and thiophene

An investigation has been conducted of the activity of AlN, BN, TiN, VN, Mo₂N, and W₂N as catalysts for quinoline hydrodenitrogenation (HDN). The activity of Mo₂N and VN for thiophene hydrodesulfurization (HDS) and the concurrent hydrotreatment of quinoline and thiophene have also been examined. Bulk AlN, BN, and TiN were obtained with low surface areas and found to be inactive for the HDN of quinoline. Bulk Mo₂N, W₂N, and VN could be obtained with high surface area. Each of these nitrides exhibited high activity for quinoline HDN, the turnover frequency for this reaction decreasing in the order Mo₂N>W₂N>VN. Highly dispersed VN supported on SiO₂ was found to have a specific activity for quinoline HDN identical to that of bulk VN. Both bulk Mo₂N and 27% VN/SiO₂ exhibit high activity for the HDS of thiophene. The behavior of these two catalysts for the concurrent hydrotreatment of quinoline and thiophene is also discussed.     

SBA-15-supported nickel phosphide hydrotreating catalysts

A series of Ni₂P and Ni₁₂P₅ hydrotreating catalysts supported on SBA-15 ordered mesoporous silica were prepared by impregnation of nickel phosphate precursors followed by reduction in hydrogen at 873 K. The major product was Ni₂P with additional phosphate species when a high excess of phosphorus was used (P/Ni = 2). When a stoichiometric amount of P was used (P/Ni = 0.5), the sole product was Ni₁₂P₅ without Ni₂P and phosphate byproducts. The active site density as determined by CO chemisorption for such Ni₁₂P₅ phases was about three times higher than typically found for Ni₂P/SiO₂ catalysts and in good accord with active site densities following from particle size. The excess phosphorus results in mesopore blocking by unreduced phosphate species, impeding the accessibility of the Ni₂P active sites as probed by CO chemisorption. The catalysts exhibited lower hydrodesulfurization (HDS) but similar or somewhat higher hydrodenitrogenation (HDN) activities than reference alumina-supported NiMo or CoMo catalysts in simultaneous thiophene HDS and pyridine HDN, as well as parallel dibenzothiophene HDS and ortho-methyl aniline HDN hydrotreating reactions. In general, the intrinsic activities of the Ni₂P catalysts were higher than those of Ni₁₂P₅ catalysts. The activities of these phosphide catalysts were found to be stable or increasing with reaction time. X-ray photoelectron studies of reduced catalysts exposed to a sulfiding mixture suggest that this increase is due to in situ sulfidation of the nickel phosphide to nickel phosphosulfide. Thus, it seems reasonable that surface phosphosulfides form the active catalytic surface in these catalysts.     

Dibenzothiophene hydrodesulfurization using in situ generated hydrogen over Pd promoted alumina-based catalysts

Catalytic hydrodesulfurization (HDS) of dibenzothiophene (DBT) was carried out in a temperature range of 320-?400 °C using in situ generated hydrogen via steam reforming of ethanol and the effect of some organic additives was studied for the first time. Four kinds of alumina-based catalysts, i.e. Co?-Mo/Al₂O₃, Ni-Mo/Al₂O₃ and their corresponding Pd promoted catalysts Pd-?Co-?Mo/Al₂O₃ and Pd-?Ni-?Mo/Al₂O₃, prepared through incipient impregnation method, were used for the desulfurization process. Catalytic activity was investigated in a batch autoclave reactor in the complete absence of external hydrogen gas. Experiments showed that organic additives like diethylene glycol (DEG), phenol, naphthalene, anthracene, o-xylene, tetralin, decalin and pyridine can affect the HDS activity of the catalysts in different ways, and only naphthalene is inhibitive for the catalytic activity towards HDS. The results showed that Ni-based catalysts are more active than Co-based ones while Pd shows a high promotion effect. DBT conversion of up to 97% was achieved with Pd-?Ni-?Mo/Al₂O₃ catalyst at 380 °C temperature and 13 h reaction time. Catalyst systems followed the HDS activity order of: Pd-?Ni-?Mo/Al₂O₃ > Ni-?Mo/Al₂O₃ > Pd-?Co-?Mo/Al₂O₃ > Co?-Mo/Al₂O₃ at all conditions. Qualitative analysis of the products stream was carried out using GC?-MS technique. The present HDS process using in situ generated hydrogen might be applied as an alternative approach for the catalytic HDS of DBT on industrial level due to its cost effectiveness, mild operating conditions and high activity of the catalysts.     

Desulfurization of model coal sulfur compounds by coal mineral matter and a cobalt molybdate catalyst—I.: Thiophene

A continuous-flow differential reactor was used to obtain rate equations for the reaction of thiophene and hydrogen over coal mineral matter and a commercial cobalt-molybdate catalyst (Nalcomo 471). Coal mineral matter in its least altered state was obtained by low temperature ashing of Western Kentucky ?9 and ?11 coals in an oxygen plasma. Conversion was determined from the C₄ gases separated by gas chromatography. Pretreatment of both coal mineral matter and catalyst with hydrogen sulfide increased thiophine reaction rates considerably, but introduction of the gas with reactants markedly decreased the rate.     

Synthesis, characterization, and hydrotreating activity of carbon-supported transition metal phosphides

A series of nickel, molybdenum, and tungsten metal phosphides deposited on a carbon black support (Ni₂P/C, MoP/C, and WP/C) were synthesized by means of temperature-programmed reduction. The samples were characterized by BET surface area, CO uptake, X-ray diffraction (XRD), elemental analysis, and extended X-ray absorption fine structure (EXAFS) measurements. The activity of these catalysts was measured at 613 K and 3.1 MPa in a three-phase, packed-bed reactor for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) with a model liquid feed containing 500 ppm sulfur as 4,6-dimethyldibenzothiophene (4,6-DMDBT), 3000 ppm sulfur as dimethyl disulfide, and 200 ppm nitrogen as quinoline. The Ni₂P/C catalyst was found to exhibit the best hydroprocessing performance based on equal CO chemisorption sites (70 μmol) loaded in the reactor. An optimum Ni loading for HDS and HDN activity was found as 1.656 mmol g⁻¹ (11.0 wt.% Ni₂P) which gave an HDS conversion of 99% and an HDN conversion of 100% at a molar space velocity of 0.88 h⁻¹. These were much higher than those of a commercial Ni-Mo-S/γ-Al₂O₃ catalyst which gave an HDS conversion of 68% and an HDN conversion of 94%, and a previously reported best Ni₂P/SiO₂ catalyst which gave an HDS conversion of 76% and an HDN conversion of 92%. The use of carbon instead of silica as a support gave rise to other differences, which included smaller particle size, higher CO uptake, lessened retention of P on the support, and reduced sulfur deposition. The stability of the 11.0 wt.% Ni₂P/C catalyst was also excellent with no deactivation observed over 110 h of time on stream. The activity and stability of the Ni₂P/C catalyst were affected by the phosphorous content, both reaching a maximum with an initial Ni/P ratio of 1/2. EXAFS and elemental analysis of the spent samples indicated the formation of a surface phosphosulfide phase on the Ni₂P, which was beneficial for hydrotreating activity, while the bulk structure of the phosphides was maintained during the course of reaction as revealed from the XRD patterns.     

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.     

WP/γ-Al2O3催化剂的制备、表征及加氢脱硫和加氢脱氮活性

Two series of WP/Al2O3 catalyst precursors with WP mass loading in the range 18.5%-37.1% were prepared using the impregnation method and mixing method, respectively, and the catalysts were then obtained by temperature-programmed reduction of supported tungsten phosphate (precursor of WP/Al2O3 catatlysts) in H2 at 650℃ for 4h. The catalysts were characterized by XRD, BET, TG/DTA, XPS and 31p MAS-NMR. The activities of these catalysts were tested in the hydrodenitrogenation (HDN) of pyridine and hydrodesulfurization (HDS) of thiophene at 340℃ and 3.0MPa. The results showed that owing to the stronger interaction of the support with the active species, the precursor of WP/Al2O3 catalyst was more difficultly phosphided and a greater amount of W species was in a high valence state W6 on the surface of the catalyst prepared by the impregnation method than that by the mixing method. 31p MAS-NMR results indicated that 31p shift from 85% H3PO4 of 2.55 × 10-4 for WP and 2.57 × 10-4 for WP/γ-Al2O3 catalysts prepared by mixing method. Such WP/Al2O3 catalysts showed higher HDN activities and lower HDS activities than those prepared by the impregnation method under the same loading of WP.WP/γ-Al2O3 catalysts with weak interaction between support and active species were favorable for HDN reaction while the WP/γ-Al2O3 catalysts with strong interaction were favorable for HDS reaction.     

Inhibition and deactivation in staged hydrodenitrogenation and hydrodesulfurization of medium cycle oil over NiMoS/Al2O3 catalyst

Hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of a commercial medium cycle oil (MCO) were performed over a commercial NiMoS/Al₂O₃ catalyst through both single- and two-stage hydrotreatments at 340°C. The reaction atmosphere was replaced with fresh hydrogen, with or without additional dose of catalyst, for the second-stage treatment to determine the mechanism of reduced activity. Sulfur and nitrogen molecular species in MCO were identified by gas chromatography with an atomic emission detector (GC-AED) to quantify their respective reactivities and susceptibilities to inhibition. Under single-stage (30 min) conditions, the reactivity orders in HDS and HDN were BT>DBT>4-MDBT>4,6-DMDBT and In>alkylIn>Cz>1-Cz>1,8-Cz, respectively. Additional reaction time beyond the initial 30 min, without atmosphere or catalyst replacement, gave little additional conversion. Replacement of the first-stage gas with fresh hydrogen strongly improved second-stage conversions, particularly those of the more refractory species. An additional dose of catalyst for the second stage with hydrogen renewal facilitated additional HDS of dibenzothiophene (DBT), 4-monomethylated DBT (4-MDBT), and 4,6-dimethylated DBT (4,6-DMDBT) which was independent of their initial reactivity, while HDN of carbazole (Cz), 1-Cz, and 1,8-Cz was improved, the least reactive species being most denitrogenated. Such results suggest the strong inhibition of the gaseous products H₂S and NH₃. The catalyst deactivation was most marked with HDN of 1,8-Cz, suggesting that acidity is essential to the reaction. H₂S is suspected to inhibit both S elimination and hydrogenation of S and N species at the level of concentration obtained during desulfurization. The inhibition by remaining substrates may still influence the HDS and HDN of refractory species in the second stage, even if their contents were reduced by the first stage. It appears very important to clarify the inhibition factor of all species on the refractory sulfur species, and to determine the inhibition susceptibility of these species at their lowered concentration to enable the effective achievement of 50 ppm sulfur level in distillate products. The conversions of inhibitors must be accounted for during reactions. Catalyst and reaction configuration to reduce the inhibition by the gaseous products are the keys for deep refining.     

Determination of organic oxygen content of coals

Fast neutron activation analysis has been used to determine organic oxygen (O_org) content of coals by subtracting the oxygen content of the mineral matter from the total oxygen content of the coals. Mineral matter was isolated by low temperature ashing in an oxygen plasma. Optimum ashing conditions produce minimal changes in chemical composition of mineral matter; these changes were taken into account when calculating the O_org content. The O_org contents of whole coals are substantially different — in some cases by as much as 47% — from the ASTM oxygen contents and those calculated on a dry, mineral matter free basis from the ultimate analysis data. Excellent agreement between the FNAA O_org contents of the whole and demineralized coals lends support to the reliability of this experimental approach.     

Preparation of Highly Active Alumina-Pillared Clay Montmorillonite-Supported Platinum Catalyst for Hydrodesulfurization

Effect of Pt precursor and pretreatment on hydrodesulfurization (HDS) activity of Pt/Al-PILM catalyst was examined to prepare highly active Pt-supported HDS catalyst. The order of HDS activities of Pt/alumina-pillared clay montmorillonite (Al-PILM) catalysts prepared by various Pt precursors was Pt(C₅H₇O₂)₂ > H₂PtCl₆ · 6H₂O > [Pt(NH₃)₄](NO₃)₂ > [Pt(NH₃)₄]Cl₂ · H₂O > H₂Pt(OH)₆. This order was in accordance with that of Pt dispersion. Thus, high Pt dispersion is essential factor to prepare highly active Pt/Al-PILM catalyst for HDS reaction. On the other hand, the effect of pretreatment on the HDS activities of Pt/Al-PILM catalysts prepared by various Pt precursors was also evaluated. The UC-TPS Pt/Al-PILM catalyst showed the highest HDS activity among various pretreated Pt/Al-PILM catalysts, in which uncalcined catalyst was sulfided by temperature programmed sulfidation (TPS). We assumed that high HDS activity of UC-TPS Pt/Al-PILM catalyst is caused by partly sulfided Pt particle with high dispersion. It is concluded that the highly active Pt/Al-PILM catalyst for the HDS reaction could be prepared by using Pt(C₅H₇O₂)₂ as a precursor and UC-TPS treatment.     

Hydrodenitrogenation and Hydrodesulphurization of Heavy Gas Oil Using NiMo/Al2O3 Catalyst Containing Phosphorus: Experimental and Kinetic Studies

In this work, a systematic study has been conducted to optimize the process conditions and to evaluate kinetic parameters for hydrodenitrogenation (HDN) and hydrodesulphurization (HDS) of heavy gas oil derived from Athabasca bitumen using NiMo/Al₂O₃ catalysts containing phosphorus (P). In the catalyst, the concentration of phosphorus was maintained at 2.7 wt%. Experiments were performed in a tickle‐bed reactor at the temperature, pressure and liquid hourly space velocity (LHSV) of 340‐420°C, 6.1‐10.2 MPa and 0.5‐2 h^?1, respectively. H₂ flow rate and catalyst weight were maintained constant at 50 mL/min and 4 g, respectively in all cases. Statistical analysis of all experimental data was carried out using ANOVA to optimize the process conditions for HDN and HDS reactions. Kinetic studies for HDN and HDS reactions were studied within the temperature range of 340‐400°C using the power law model as well as the Langmuir‐Hinshelhood model. The power law model showed that HDN and HDS of heavy gas oil follow first order kinetics. The activation energies for HDN and HDS reactions from the power law and Langmuir‐Hinshelwood models were 94 and 96 kJ/mol and 113 and 137 kJ/mol, respectively.     

Influence of mineral matter in coal on decomposition of NO over coal chars and emission of NO during char combustion

NO-char reaction and char combustion in the presence and absence of mineral matter were studied in a quartz fixed bed reactor. Eight chars were prepared in a fluidized bed at 950 °C from four Chinese coals that were directly carbonized without pretreatment or were first deashed before carbonization. The decomposition of NO over these coal-derived chars was studied in Ar, CO/Ar and O₂/Ar atmospheres, respectively. The results show that NO is more easily reduced on chars from the raw coals than on their corresponding deashed coal chars. Mineral matter affects the enhancement both of CO and O₂ on the reduction of NO over coal chars. Alkali metal Na in mineral matter remarkably catalyzes NO-char reaction, while Fe promotes NO reduction with CO significantly. The effect of mineral matter on the emission of NO during char combustion was also investigated. The results show that the mineral constituents with catalytic activities for NO-char reaction result in the decrease of NO emission, whereas mineral constituents without catalytic activities lead to the increase of NO emission. Correlation between the effects of mineral matter on NO-char reaction and NO emission during char combustion was also discussed.     

Effects of the operating variables on hydrotreating of heavy gas oil: Experimental, modeling, and kinetic studies

The effects of H₂ purity, pressure, gas/oil ratio, temperature, and LHSV on hydrotreating activities were investigated in a micro-trickle bed reactor using a commercial NiMo/γ-Al₂O₃ catalyst. Heavy gas oil (HGO) from Athabasca bitumen was used as feed. Due to their significant effects on H₂ partial pressure, H₂ purity, pressure, and gas/oil ratio were chosen and used in a central composite design (CCD) method. Experimental conditions used were H₂ purity, pressure, and gas/oil ratio were: 75-100 vol.% (with the rest methane), 7-11 MPa, and 400-1200 mL/mL, respectively. The effect of LHSV (0.65-2 h⁻¹) and temperature (360-400 °C) were studied in a separate set of experiments. Vapor/liquid equilibrium (VLE) calculations were performed to determine the inlet and outlet H₂ partial pressures. It was observed that the enhancing effects of H₂ purity on hydrodenitrogenation (HDN) and hydrodearomatization (HDA) activities were greater than that of gas/oil ratio; however, it was comparable to pressure. Hydrodesulphurization (HDS) activity was not considerably affected by H₂ purity, pressure, or gas/oil ratio. Increasing LHSV led to a decrease in HDS, HDN, and HDA activities while increasing temperature resulted in an increase in HDS and HDN; HDA had maximum activity at about 385 °C. Kinetic fitting of the data to a pseudo-first-order power law model suggested that conclusions on hydrotreating activities’ responses to a changing H₂ pressure could be equally drawn from either inlet or outlet H₂ partial pressure. However, from the catalyst deactivation standpoint, it is recommended that such conclusions are drawn from the outlet H₂ partial pressure.