Introduction
High-pressure hydrocracking is a catalytic refining process allowing an upgrade of rather heavy petroleum fractions such as vacuum distillates into gasoline or middle distillates, kerosene, and gas oil[1], [2], [3], [4]. It is also used to upgrade some products obtained from other processes, such as deasphalted oils and cycle oils from fluid catalytic cracking[1], [5]. A major interest of hydrocracking is its great versatility since it is possible to equilibrate supply (gasoline or middle distillates) and demand. The growing demand for middle distillates, which cannot be obtained using fluid catalytic cracking, makes hydrocracking a strategic process in a modern refinery[2], [6], [7].
Moreover, in addition to the cracking of the molecules, the hydrocracking process ensures the elimination of sulfur- and nitrogen-containing compounds as well as a deep saturation of aromatics. This allows the production of high-quality fuels which will match the future and more stringent specifications[1], [8].
Hydrocracking catalysts are bifunctional, associating a hydro-dehydrogenating function with an acidic one. Since the feeds to be treated contain significant amounts of heteroatoms (sulfur and nitrogen), the catalysts must resist poisoning by hydrogen sulfide and ammonia. That is why the hydro-dehydrogenating function of industrial hydrocracking catalysts is generally provided by mixed sulfides of group VI and VIII metals, such as molybdenum or tungstene promoted by nickel or cobalt.
If gasoline is the required product, the acidic component of the catalyst will be preferably a zeolite, the strong acidity of which will favor successive cracking reactions of the feed molecules with formation of the desired light products[9]. On the contrary, the catalysts which would allow an optimal gas oil yield which would possess a moderate acidity, halfway between that of zeolites (low selectivity) and that of aluminas (too low activity). Amorphous supports like silica-aluminas could have such an acid strength[2], [10], [11], [12].
Our objective was to study hydrocracking catalysts allowing a selective transformation of vacuum distillates into gas oil. For the reasons explained above, a sulfided NiW/silica-alumina catalyst was chosen, and was compared to a strongly acidic NiW/USHY zeolite catalyst. The model reaction used was the hydrocracking of n-decane, under conditions similar to the industrial ones: fixed-bed dynamic reactor, high hydrogen pressure, presence in the feed of sulfur- and nitrogen-containing compounds. In this work the nature and the repartition of the reaction products were examined andthe reaction scheme established. The different selectivities were measured, in particular the isomerization/cracking selectivity which can be considered as representative of the selectivity of the catalyst for the production of middle distillates. To obtain a better understanding of the behavior of the NiW/silica-alumina catalyst, we also studied the transformation of n-decane on a nonacidic NiW/alumina catalyst, on an unpromoted W/silica-alumina catalyst, and finally on NiW/silica-alumina in the absence of nitrogen-containing compound in the feed.
Section snippets
Experimental
n-Decane hydrocracking was carried out in a flow reactor at 380°C under a 6 MPa total pressure, with a hydrogen/n-decane molar ratio equal to 20. Dimethyl disulfide and aniline were added to n-decane in order to generate H2S (pH2S= 6.1 kPa) and NH3 (pNH3= 5kPa), respectively. The catalysts were first sulfided in the reactor by a n-heptane/dimethyl disulfide/aniline mixture, under the same pressures as those used for the n-decane hydrocracking reaction, and at a 0.27-min contact time (1/WHSV).
Acidity of the supports
Silica-alumina possessed only one type of terminal OH groups, already observed by Knözinger and colleagues[14]. On the contrary, several OH groups were observed on the USHY zeolite[13]: terminal OH groups, similar to those observed on silica-alumina, bridging OH in large cavities or in small cavities, and OH interacting with extraframework aluminum species. Five OH bands were observed on alumina[15]: OH coordinated to octahedral or to tetrahedral Al, and OH bridging tetrahedral and
Discussion
Pyridine adsorption experiments clearly confirm that silica-alumina is much less acidic than the USHY zeolite, which is widely known. Compared to zeolite, silica-alumina has only few Brønsted acid sites. Moreover the strength of this sites is rather moderate, while a wide distribution in the acid strength is observed on zeolite. However, one can reasonably suppose that the strongest Brønsted acid sites of the zeolite do not participate in n-decane hydrocracking because they are irreversibly
Conclusion
The results obtained in the present work indicate that the behavior of the NiW/silica-alumina catalyst for n-decane hydrocracking in the presence of nitrogen-containing compounds is very different from that of classical hydrocracking catalysts such as NiW/USHY zeolite. The main reaction observed is the transformation of n-decane into monobranched isomers, the bifunctional transformation of which into multibranched isomers and into cracking products being hardly observed. On NiW/zeolite the
Effect of SiO<inf>2</inf>/Al<inf>2</inf>O<inf>3</inf> ratio in Ni/Zeolite-Y and Ni-W/Zeolite-Y catalysts on hydrocracking of heptane
2022, Molecular Catalysis
This study investigated the effect of the SiO2/Al2O3 ratio in the range of 5-80 in zeolite Y (ZY) as a support for the bi-functional reaction of heptane hydrocracking. Bi-metallicity impact, through the addition of W on Ni in the supported metal catalysts was also examined. The catalytic activity was assessed at 350°C and 400°C in order to deduce an optimized composition of the catalyst in terms of metal composition and Si/Al ratio. The results were correlated to the catalysts’ surface and bulk properties, the latter after employing a number of material characterization techniques. It was shown that Ni-W bimetallic catalysts demonstrated better catalytic activity (conversion, 78% to 91%) than Ni-based monometallic counterpart catalysts (conversion, 74.2% to 82.7%), with NiO-WO3-ZY30 (SiO2/Al2O3 ratio equal to 30) exhibiting the highest conversion. This was attributed to the bimetallic's enhanced metal dispersion and smaller particle size, evaluated using temperature-programmed desorption (TPD) of H2 and high-resolution transmission electron microscopy (HR-TEM) imaging. The stronger acidity, as quantified by total acidity calculations, of zeolite Y having higher Si/Al ratio, and their balanced ratio of micro- and meso-porosity played a vital role in their catalytic performance. This study provides useful design guidelines on how to adjust both the Si/Al ratio in the zeolite Y support and the catalyst's bimetallicity for enhanced hydrocracking performance.
Heteropolyacids supported on clay minerals as bifunctional catalysts for the hydroconversion of decane
2021, Applied Catalysis B: Environmental
The role of heteropolyacid (HPA) was studied as a precursor for the generation of NiMo and CoMo catalysts supported on a vermiculite and a bentonite previously delaminated and bolstered with the incorporation of AlZr and AlCe species. The solids were characterized using X-ray diffraction (XRD), N2 adsorption, Scanning Electron Microscopy (SEM) and High-Resolution Transmission (HR-TEM), Raman spectroscopy, Temperature-Programmed Reduction (H2-TPR), IR spectroscopy with probe molecule (NH3-DRIFTS) and acidity analysis “in-situ”, electronic X-ray spectroscopy (XPS,) and the catalytic performance was evaluated in the hydroconversion of decane. The controlled modulation of the properties of natural clay minerals combined with the anchoring of the active phase from the HPA type precursor, generates supported catalysts with different ranges of catalytic performance. The stability of the HPA type structure was evidenced even after the calcination and pre-reduction process. The catalysts in the present work register better physicochemical properties (textural, acidic, reducible species and metallic dispersion) and a superior catalytic performance in the hydroconversion of decane, compared with catalysts obtained from a conventional salt reported in the literature.
Homogeneous catalyst for in-situ hydrotreating of heavy oils
2019, Applied Catalysis A: General
Citation Excerpt :
It is known that the disappearance rates of thiophene type compounds with increasing numbers of aromatic rings decrease while nonthiophenic aromatic sulfur compounds react more quickly than dibenzothiophenes, and due to the inherent difficulty of the alkyl substituted dibenzothiophenes for reacting, it is clear that they persist in the hydrotreated products. As for hydrodesulfuration, it can proceed via two pathways; the first one is hydrogenolysis in which both carbon-sulfur bonds are replaced by carbon-hydrogen bonds, which lead to ring opening; in the second one, hydrogenation can occur initially and then, the intermediate product undergoes a hydrogenolysis step [45–47]. The predominant HDN pathway proceeds via the breaking of the C (sp3) bond.
See AlsoNNPC Fuel Price: Petrol begin sell from N488 upwards as Nigerian National Petroleum Corporation confam increase - BBC News Pidgin2021 [Other] COMMOSA 10X46 For Sale - 29,500 USD | Cat UsedUS Patent for Catalysts and process for liquid hydrocarbon fuel production Patent (Patent # 11,660,587 issued May 30, 2023)Operation Approval for Commercial Airborne Wind Energy Systems.The upgrading of the physical and chemical properties of heavy oil by hydrotreating using a liquid Ni-Mo catalyst was studied through bench-scale tests aiming at developing "inside-reservoir" technology. The liquid Ni-Mo catalyst was synthesized by a very simple method consisting in preparing and mixing solutions at room temperature under acidic conditions. Mixtures of liquid Ni-Mo catalyst and heavy oil were evaluated in a 500-mL batch reactor at 350, 390 and 400 °C for 30, 60 and 90 min. The results showed that the liquid Ni-Mo catalyst improved the crude oil properties by increasing the API gravity from 12.5 to 22 and decreasing the kinematic viscosity from 13,490 to 72 cST at 15.6 °C; the sulfur content from 5.5 to 3.1% and the nitrogen content from 750 to 392 ppm were also reduced. Furthermore, the volume of gasoline and diesel by Simulated Distillation were increased to 8 and 14 vol. %, due to the change in chemical composition. Aromatic and saturated hydrocarbon compounds increased at the expense of asphaltenes and resins.
n-Decane hydro-conversion over bi- and tri-metallic Al-HMS catalyst in a mini-reactor
2018, Chinese Journal of Chemical Engineering
Bi-metallic (Pt–Sn and Sn–Ni) and tri-metallic (Pt–Sn–Ni) catalysts, supported on Al-containing hexagonal mesoporous silica (Al-HMS) (Si/Al = 20) materials, were synthesized. N2 adsorption–desorption, X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) test, and temperature programed desorption (NH3-TPD) were used to characterize physicochemical characteristics and textural properties of the Al-HMS catalysts. Catalytic performances on hydro-cracking of n-decane at different reaction conditions were studied in a micro-reactor. Comparison between Pt–Sn, Sn–Ni and Pt–Sn–Ni catalyst under different hydro-cracking conditions was made. The experimental results indicate that the proper balance between the acid and metal functions is the key in synthesizing a catalyst with a better performance in hydro-cracking. Tri-metallic catalyst exhibits the best catalytic performance in n-decane hydro-cracking than two bi-metallic catalysts.
Incorporation of Ni and Mo on delaminated clay by auto-combustion and impregnation for obtaining decane hydroconversion catalysts
2017, Catalysis Today
Citation Excerpt :
As noted above, the autocombustion method increases the redox properties of the catalyst and probably maintains the appropriate distance between the metallic and acidic sites so as to accomplish the balance required in the bifunctional reaction. It is important to emphasize that the excellent yield of cracking products of Mo15Ni5-EQ suggests a good performance for hydrocracking of heavy molecules [38,39]. Supported catalysts of Ni–Mo were synthesized on mineral clay delaminated (Bentonite).
A series of solids was synthesized by the incorporation of Ni and Mo active species on delaminated clay with novel acidic properties, by impregnation and auto-combustion. The resulting solids were characterized by X-ray fluorescence, X-ray diffraction (XRD), textural analysis by N2 physisorption, temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and, in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS). Decane hydroconversion was used to evaluate the potential of the materials as hydrocracking catalysts for vacuum bottoms. XRD was used to confirm modification of the material and good active phase dispersion. TPR revealed an important decrease in the reduction temperatures with auto-combustion method. Low-temperature reducible species play a key role in the catalytic performance for decane hydroconversion.
Multiscale Aspects in Hydrocracking: From Reaction Mechanism Over Catalysts to Kinetics and Industrial Application
2016, Advances in Catalysis
Citation Excerpt :
The nitrogenous poisons generally comprise five- and six-membered heteroatom rings and anilines, of which the latter two have the most strongly inhibiting character. Pyridine and aniline are therefore often used as model components to investigate the corresponding poisoning effect (7,76,398). Galperin (234) on the other hand used tributylamine which rapidly decomposed to ammonia that covers the acid sites of the catalyst.
Hydroisomerization and hydrocracking are widely recognized as versatile reactions. They allow not only converting feeds of various origin and quality into high-value blendstocks but also identifying the opportunities brought about by different solid acids with characteristic framework structures to tailor activity and product selectivity. The bifunctional reaction mechanism is an essential feature in this respect. It comprises acid-catalyzed rearrangement and cracking in addition to metal-catalyzed (de)hydrogenation and is effective at relatively mild operating conditions. Innumerable combinations of metal and acid functions, ranging, respectively, from sulfided transition metals to noble ones and from crystalline, microporous to wider pore, amorphous materials are available for ensuring the required catalytic performance to convert the feed into the desired product slate. An adequate understanding of the detailed reaction mechanism represents a crucial element in this endeavor. Over the years an interesting evolution from simple, lumped model toward advanced ones accounting for all potentially occurring elementary steps could be discerned. Hydrocracking has been among the first reactions involved in hydrocarbon fuel production and regained popularity in the last years because of the processing of ever more heavy crudes. Its horizon, however, extends beyond the fossil era with applications in bio-fuel production and plastic waste valorization. It ensures a bright future for a historical and reliable conversion process.
Research article
Immigrant Pantoea agglomerans embedded within indigenous microbial aggregates: A novel spatial distribution of epiphytic bacteria
Journal of Environmental Sciences, Volume 26, Issue 2, 2014, pp. 398-403
Immigrant bacteria located on leaf surfaces are important to the health of plants as well as to people who consume fresh fruits and vegetables. However, the spatial distribution and organization of these immigrant bacteria on leaf surfaces are still poorly understood. To examine the spatial organization of these strains, two bacterial strains on tobacco leaves: (1) an indigenous strain, Pseudomonas stutzeri Nov. Y2011 labeled with green fluorescent protein, and (2) an immigrant strain Pantoea agglomerans labeled with cyan fluorescent protein isolated from pear, were studied. Under moist conditions, P. agglomerans cells quickly disappeared from direct observation by laser-scanning confocal microscopy, although elution results indicated that large amounts of live cells were still present on the leaves. Following exposure to desiccation stress, particles of cyan fluorescent protein-labeled P. agglomerans were visible within cracked aggregates of P. stutzeri Nov. Y2011. Detailed observation of sectioned aggregates showed that colonies of immigrant P. agglomerans were embedded within aggregates of P. stutzeri Nov. Y2011. Furthermore, carbon-resource partitioning studies suggested that these two species could coexist without significant nutritional competition. This is the first observation of an immigrant bacterium embedding within aggregates of indigenous bacteria on leaves to evade harsh conditions in the phyllosphere.
Research article
Structural characterization and electron density distribution studies of (La0.8Ca0.2)(Cr0.9−xCo0.1Mnx)O3
Physica B: Condensed Matter, Volume 493, 2016, pp. 25-34
The doped lanthanum chromite (La0.8Ca0.2)(Cr0.9−xCo0.1Mnx)O3 (x=0.03, 0.06, 0.09 and 0.12) were synthesized by solid state reaction technique. The samples have been characterized by X-ray diffraction for structural and charge density analysis. XRD data show that the grown samples are orthorhombic in structure with single phase. The spatial charge density distribution in the unit cell for the synthesized samples has been studied using maximum entropy method. Further, the samples were analyzed by UV–visible spectrometry for optical properties and scanning electron microscopy for surface morphology. From the optical data, it was found that the direct band gap of the samples range from 2.27 to 2.46eV. The samples were also investigated by vibrating sample magnetometry for magnetic properties. From VSM data, it is inferred that all the samples in this series are found to be predominantly antiferromagnetic in nature. Since the doped lanthanum chromites have good mechanical properties and electrical conductivity at high temperature, these materials are used in solid oxide fuel cells (SOFC).
Research article
The relation of the energy of electronic state with the interior periodic potential in quantum dot given by matrix method
Physica B: Condensed Matter, Volume 481, 2016, pp. 137-143
In this paper, we mainly investigate the effect of the interior periodic potential and the surface potential on the energy of electronic state in quantum dot. Based on Chebyshev polynomials of the second kind and matrix theory, we deduced one expression, which can clearly describe the relation of energy of electronic state with the surface and interior periodic potential. The theoretical analysis shows that the energy of electronic state in quantum dot strongly depend on surface potential and the interior periodic potential. For the same quantum dot with different surface potential, the energy of electronic state with the determined quantum number is different. For the quantum dot of same size with different interior periodic potential, the energy of electronic state with the determined quantum number is also different. The further study indicates that there are two different energy of electronic state in quantum dot for the decided quantum number.
Research article
Catalytic hydrogenation, hydrocracking and isomerization reactions of biomass tar model compound mixture over Ni-modified zeolite catalysts in packed bed reactor
Renewable Energy, Volume 167, 2021, pp. 409-424
Gas-phase conversion of a model mixture of biomass tar (5wt% naphthalene and 95wt% of 1-methylnaphthalene) into 2-methylnaphthalene liquid product and ethylene and propane gas mixture was carried out over different zeolites and metal promoted zeolites in a packed-bed reactor for the first time. In the present work, a series of MFI (H-ZSM-5), BEA (H-β), FAU (H-Y, H-USY), and MOR (H-Mordenite) zeolites were investigated. The effect of Ni metal addition on the promotion of parent zeolite catalysts was studied. The most successful catalysts were characterized by BET, ICP-AES, XRD, HRSEM, STEM-HAADF, and STEM-BF with EDXS, NH3-TPD, H2-TPR, TGA, and pyridine-DRIFT techniques. The superior performance in comparison to the other studied catalysts was established over the 5wt%Ni/H-ZSM-5 (SiO2/Al2O3=30) with 96.2mol% of selectivity to 2-methylnaphthalene in the liquid phase, 90mol% total conversion with the highest part (82.9wt%) of ethylene and propane in the gas phase after 24h time-on-stream. This high catalytic performance of the 5wt%Ni/H-ZSM-5 catalyst can be attributed to the presence of the high mesopore volume, pore diameter, and high mesopore surface area, the existence of the redox active sites, and the presence of strong Lewis acid sites due to synergetic interaction between Ni metal species and zeolite acid support. Based on the product distributions observed, the reaction scheme of the conversion of biomass tar model mixture of naphthalene and 1-methylnaphthalene over studied catalysts was proposed. Our catalytic results obtained over pristine and Ni-modified zeolite catalysts shed light on the potential use of these catalysts in the biomass tar valorization process under atmospheric pressure.
Research article
The application of the photo-electro-Fenton process in the treatment of wastewater reduces the abundance of genes associated with pathogenicity factors, antibiotic resistance, and metabolism: A metagenomic analysis.
Journal of Environmental Chemical Engineering, Volume 11, Issue 3, 2023, Article 109937
The objective of this work was to determine the effect of advanced oxidation systems on the taxonomic and functional diversity of pathogenic microorganisms in the effluent of the wastewater treatment plant in Bogotá - Colombia (“El Salitre” WWTP) by metagenomics analysis. The taxonomic and functional diversity of the microorganisms, before and after oxidation treatment, was determined by Illumina mass sequencing, detecting human pathogenic genera as Pseudomonas (28.0%), Arcobacter (10.0%), Aeromonas (4.0%), Sulfurospirillum (4.0%), Salmonella (3.0%), and Clostridiales (3.0%). Likewise, pathogenicity factors such as antimicrobial resistance genes (ARGs) also were detected in high abundances (∼5% of metagenome reads). In the effluent treated with the photoelectro-Fenton system (for 5, 30, and 60min), a significant reduction of pathogenicity factors was observed in all cases. ARGs, chemotaxis, quorum sensing, secretion systems, and toxins of pathogenic bacteria (such as Arcobacter, Pseudomonas, Serratia, and Salmonella) were reduced at near-zero log2 values, demonstrating that the photoelectro-Fenton process is a promising alternative to reduce the biological risk associated with this pathogenicity factors.
Research article
WOx domain size, acid properties and mechanistic aspects of glycerol hydrogenolysis over Pt/WOx/ZrO2
Applied Catalysis B: Environmental, Volume 242, 2019, pp. 410-421
Supported WOx catalysts are widely investigated in glycerol hydrogenolysis for their high selectivity to 1,3-propanediol (1,3-PDO). The high performance is often related to surface Brönsted acid site. However, the intrinsic structure of Brönsted acid is unclear and its controllable preparation has not been investigated in detail. In addition, many reaction mechanisms have been proposed up to now, but with few direct evidences in spectroscopy studies. In this work, Pt/WOx/ZrO2 catalysts containing various amounts of WOx were studied in glycerol hydrogenolysis. The reaction is found to be structurally sensitive to WOx domain size, with medium polymerized WOx shown to benefit the formation of 1,3-PDO. By doping a suitable amount of Mn into monolayer covered WOx/ZrO2, large amounts of WOx with medium polymerization degree were created. Thus, the turnover frequency of 1,3-PDO (TOF1,3-PDO/W) increased 2.6 times in comparison to the best result of none Mn-doping Pt/WOx/ZrO2 catalysts. Characterizations of WOx structure and acid properties indicate that super strong Brönsted acid site is created by the interaction between medium polymerized WOx and Pt particle. This type of acid is linearly correlated with the formation rate of 1,3-PDO. The adsorption state of glycerol was studied using infrared spectroscopy, and the secondary −OH is found to be strongly adsorbed to Brönsted acid site on WOx containing catalyst, while its interaction with Pt/ZrO2 is much weaker. The natural structure of the active site is proposed to be Pt-(WOx)n-H, integrating super strong Brönsted acid site and metallic Pt site together. Combined with FTIR investigations of different surface hydrogen species and in situ 2-propanol conversion, the reaction mechanism was also determined.
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