The present work shows that the introduction of 0.25–1.25 wt% lanthanum to the composition of aluminum hydroxide at the stage of its hydrothermal synthesis allows increasing the content of the ...pseudoboehmite phase in the product up to 95 wt% and, as a consequence, reduces the content of the “amorphous” component. Lanthanum uniformly distributes over the surface of aluminum hydroxide as isolated cations with a surface density of 10–15 cations per 10 nm2. During plasticizing of lanthanum-modified pseudoboehmite followed by granulation and heat treatment, the formation of the oxide form of La is not observed, and the cations retain their isolated state. The specific surface area of La-modified alumina increases by 18–26 m2/g compared to the unmodified sample, while the pore volume remains the same and the average pore diameter slightly reduces. It was found that when the content of La in pseudoboehmite was 1 wt%, the temperature of reaching a residual sulfur content of 10 ppm in the hydrotreated diesel fuel was 5 °C lower comparing to the unmodified sample.
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•The effect of La addition at the stage of pseudoboehmite preparation was studied.•La promotes the formation of pseudoboehmite phase.•La is present as isolated cations on the surface of pseudoboehmite and alumina.•Catalyst with 1 wt% La shows the highest HDS and HDN activity.
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•Influence of HDT depth on material balance of FCC process was studied.•Hydrotreating does not influence valuable olefins yield.•Prehydrotreating decreases sulfur in liquid ...products.•Removal of N compounds increases activity of FCC catalyst.•Increase of HDT depth results in the increase of hydrogen transfer coefficient.
The present work studies the influence of nitrogen compounds in hydrotreated fluid catalytic cracking (FCC) feedstock on the material balance of FCC process focused on petrochemistry. Vacuum gas oil was hydrotreated at the temperatures of 340–370 °C in typical FCC pretreatment conditions. The obtained hydrotreated products contained 370−750 ppm of nitrogen and 150−820 ppm of sulfur. Hydrotreated feedstock was exposed to the FCC process over a zeolite catalyst at the laboratory unit with a fixed bed catalyst at 527 °C and catalyst/oil ratio - 2−6. The FCC feedstock before and after hydrotreatment and FCC products were characterized by different methods to study the effect of nitrogen compounds on the FCC process.
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•Different shapes of commercial catalyst were tested under particulates trapping.•The developed discrete model allows simulating clogging of hydrotreating reactor.•VGO hydrotreating ...reactor was simulated based on experimental filter coefficients.•Optimized scheme of guard-beds demonstrated the lowest pressure drop.
A new approach to optimize grading guard systems for gas oil hydrotreating reactor based on the phenomenon of clogging of catalyst beds with microparticulates and coke deposits was developed. Pellets with different shapes have been tested to obtain dynamic dependencies of filter coefficient and pressure drop buildup. The experiments were performed in the trickle-flow regime with different ensembles of microparticulates having sizes from 15 to 165 μm. The observed effect of a filter cake formation was characterized in terms of average porosity of the interface beds and it was introduced in simulations plugging of catalyst bed. Estimation of the growth of coke deposits was made using modified Voorhies’s equation and experimental samples obtained in the microreactor under hydrotreating process conditions using foulants of industrial gas oil hydrotreater. The analysis of coked samples was carried out using TGA. Based on the discrete model and experimental data, optimization procedure of grading guard systems was carried out using brute force search. All combinations of schemes of guard-beds were compared using integrated hydrodynamic resistance as a criterion. It was shown that an optimized scheme of guard-beds can reduce hydrodynamic resistance as compared to the schemes without guard-beds or with non-optimized guard-beds.
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•Influence of catalysts order and ratio in the bed loading was studied.•NiMo/Al2O3 had the highest HDS and HDN activities of the model and real feed.•SRVGO should be treated firstly ...by NiMo and then by CoMo catalysts.•The best ratio of NiMo/Al2O3 to CoMo/Al2O3 and catalysts was 40/60 vol%.
The influence of the order of catalysts and their ratio in the bed for FCC feedstock hydrotreatment was investigated. CoMo/Al2O3 and NiMo/Al2O3 catalysts were prepared in the laboratory and studied by nitrogen adsorption–desorption, XPS and HRTEM methods. The catalysts were tested in hydrotreatment of model feedstocks. It was found that NiMo/Al2O3 catalyst had the highest activity in conversion of the model feedstock containingsulfur and nitrogen compounds. The best results were obtained for the feedstockfirstly treated by NiMo/Al2O3 and then by CoMo/Al2O3. Catalysts were tested separately and together in hydrotreatment of SRVGO. The order of catalysts and their ratio were varied. The best combination included NiMo/Al2O3 catalyst at the top of the reactor and CoMo/Al2O3 at the bottom of the reactor in the ratio of 40/60 vol%.
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•Commercially available zeolites with different Si/Al ratio and amorphous silica-alumina were used for preparation NiW catalysts for second stage hydrocracking.•The increase of Si/Al ...ratio in zeolite results in decrease of catalyst activity and rise of selectivity to middle distillates.•Absence of zeolite in catalyst results in drastic drop of catalyst activity.
The effect of Si/Al ratio of zeolite Y on the performance of NiW catalysts for second stage hydrocracking was studied. The zeolites were characterized by IR spectroscopy of adsorbed pyridine, low-temperature N2 adsorption, and temperature-programmed desorption of ammonia. The observed decrease of Brønsted and Lewis acid sites concentration relates to the increase of Si/Al ratio in zeolites. According to HRTEM and XPS, sulfide component of catalysts differs in morphology, NiWS phase content and tungsten sulfidation degree. The catalysts were tested in hydrocracking of model (squalane) and real feedstock (unconverted oil (UCO) from two-stage industrial hydrocracker) at different temperatures. The increase of Si/Al ratio in zeolites was found to result in the decrease of catalytic activity and the increase of selectivity to middle distillates. However, similar selectivity of 52 and 53% at the 50% of UCO conversion was observed for catalysts containing zeolites with Si/Al ratio 24 and 37 respectively. This can be attributed mainly to the differences in the textural properties of the zeolites. The catalyst based on amorphous silica-alumina (without zeolites) was found to have a higher selectivity to middle distillates and lower activity as compared to zeolite-based catalysts.
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•Influence of reactivation of HDS catalysts poisoned Si compounds were studied.•Active component particles dispersion increase in reactivated catalysts poisoned by Si.•Activity in HDS ...reactions of DBT and HDN reactions of quinoline increases after reactivation of catalysts poisoned by Si.•CoMo/Al2O3 catalyst with less than 3 wt.% of Si can be completely restored in HDS activity.
The feasibility of the reactivation of CoMo/Al2O3 hydrotreating catalysts poisoned by Si compounds has been studied. CoMo/Al2O3 catalysts poisoned with 3, 4 and 5 wt.% of silicon were obtained during hydrotreating of diesel fraction contaminated with decamethylcyclopentasiloxane. Catalysts poisoned by different amount of silicon were regenerated by oxidative treatment and subsequently reactivated using citric acid solution. The catalysts were studied by nitrogen adsorption-desorption method, CHNS analysis, UV–vis, thermal analysis, SEM, HRTEM, XPS. It was shown that the hydrodesulfurization activity of regenerated catalysts decreased with increasing silicon content. According to UV–vis results, the increase in Si content on the spent catalyst leads to the formation of CoOx oxides after oxidative regeneration. Probably, cobalt oxides do not promote MoS2 slabs during sulfidation, convert to inactive Co species and decrease hydrodesulfurization activity. After reactivation procedure, there was the increase in active component particles dispersion, while catalytic activity in hydrodesulfurization of dibenzothiophene and hydrodenitrogenation of quinoline increased. It was established that hydrodesulfurization and hydrodenitrogenation activities of CoMo/Al2O3 catalyst with less than 3 wt.% of Si could be completely restored by reactivation.
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•NiW/Y-ASA-Al2O3 catalysts were prepared, studied using physical-chemical techniques and tested in second stage hydrocracking.•The higher the zeolite content the higher the activity ...of the catalyst and the concentration of Brønsted acid sites are.•Increase of zeolite content leads to decrease of selectivity to diesel.•Increase of nitrogen content in feed results in a drop of catalyst activity and in almost no change of selectivity to diesel.
NiW catalysts for second stage hydrocracking were prepared by impregnation of granulated supports with ultrastable zeolite Y content of 5−30 wt%; amorphous silica-alumina content of 45−20 wt%; and γ-Al2O3 content of 50 wt%. The catalysts were studied by low-temperature N2 adsorption, HRTEM, XPS and IR spectroscopy of adsorbed pyridine. Sulfide NiWS particles have been revealed to be similar in all the catalysts according to HRTEM and XPS. It has been shown that concentration of Brønsted acid sites increases with increasing of zeolite content in the catalysts. Hydrocracking tests were carried out at a pressure of 16.0 MPa, a LHSV of 1.4 h−1 and H2 to oil ratio of 750 (v/v). Two samples of unconverted oil with nitrogen content of 11 and 65 ppm obtained from the products of VGO hydrocracking under different severities were used as the feedstocks. The higher zeolite content the higher activity of the catalyst was achieved. However, the increase of zeolite content leaded to the decrease of selectivity to diesel. It has been found that increasing of nitrogen content in the feedstock was followed by a sharp decline in catalyst activity while the change in selectivity to diesel was insignificant. Optimal zeolite content in the support for studied conditions and feedstock with nitrogen content of 65 ppm was 20 wt%.
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•Si capacity increases with increase of OH groups.•Increase of OH groups quantity can be predicted.•Catalysts with higher surface area have lower interaction of Ni and support.•Length ...of NiMoS slabs proportional to the length of Al2O3.
The influence of alumina precursors on NiMo/γ-Al2O3 catalysts for silicon removal from gas oil have been studied. Alumina precursors were prepared by hydrothermal treatment of gibbsite, precipitation of aluminum nitrate by ammonia and precipitation of aluminum nitrate in autoclave. Alumina precursors, supports and catalysts were studied by XRD, nitrogen adsorption-desorption, IR spectroscopy, UV–vis, XPS, SEM, HRTEM. Series of NiMo/γ-Al2O3 catalysts differed in preparation method of alumina precursors was tested in hydrotreating of diesel fraction contaminated with decamethylcyclopentasiloxane as a model silicon compound. It was shown that prepared alumina precursors were boehmites and dawsonite, which had different particle size. The supports prepared from these alumina precursors were γ-Al2O3 with different particles size. It was shown that there was a dependence of the surface area of the support on the size of primary particles measured by XRD. The higher surface area results in the higher content of OH groups and silicon sorption capacity. Morphology of the sulfide active component also depends on the size of primary particles. The higher length of the particles, the higher slab length of NiMoS phase. The catalyst with the lowest particle size of alumina and highest length of active component had the highest HDS activity.
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•Textural properties of alumina depend on the time of hydrothermal stabilization.•Alumina samples prepared by hydrothermal treatment have bimodal pore distribution.•The initial ...alumina has an impact on the share of CoMoS phase in the catalysts.•The hydrothermal method is more preferable to obtain CoMoP-catalysts.
The influence of alumina precursors on catalytic activity CoMoP/Al2O3 hydrotreating catalysts has been studied. Alumina precursors were prepared by eco-friendly technology including hydrothermal treatment at different stabilization time of a flash calcined gibbsite. One sample was synthesized with the addition of boric acid. A reference sample of pseudoboehmite was obtained by precipitation from aluminum nitrate with aqueous ammonia. Alumina precursors, supports and catalysts were studied by XRD, nitrogen adsorption/desorption, XPS, HRTEM. CoMoP/Al2O3 catalysts were tested in hydrotreating of model feed and fuel mixture.
It is shown that the samples obtained from the product of flash calcination of gibbsite, besides pseudoboehmite, also include the amorphous phase, while the reference sample, synthesized by precipitation, is a pure pseudoboehmite. The introduction of boron prevents the crystallization of pseudoboehmite. Textural properties of the catalysts depend of initial support: alumina samples prepared by hydrothermal treatment have a bimodal pore distribution with peaks at 60–70 Å and 150–200 Å, the support synthesized through reprecipitation has a unimodal distribution with a maximum at 80 Å.
The initial alumina used as a catalyst support has a significant impact on the share of CoMoS phase of type II. The highest activities in the hydrotreating of model feed (dibenzothiophene, quinoline and naphthalene in undecane) and fuel mixture shown catalyst prepared using hydrothermal treatment of flash calcined gibbsite without addition boric acid and with short stabilization time.
The effect that calcination of an alumina–chromia catalyst containing 13 wt % Cr with additions of Na
+
and Zr
4+
in an air–water vapor atmosphere (from 0 to 80 vol % water vapor) at 750°С and a ...pressure of 1 bar exerts on the physicochemical properties of the catalyst and its activity in
n-
butane dehydrogenation was studied. The steam treatment leads to a slight decrease in the specific surface area (by up to 10%), partial decomposition of Cr(VI) compounds (up to 60%), and Cr
2
O
3
crystallization. The catalytic activity decreases with an increase in the water vapor : air ratio. Low water vapor concentration (10 vol %) favors a significant decrease in the amount of the coke formed (by 60%) without significantly affecting the yield of alkenes. Thus, introduction of water vapor into the calcination atmosphere allows control of the Cr(VI) amount and catalyst selectivity.
