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This paper provides an overview of the enormous challenge in processing heavier fluid catalytic cracking (FCC) feedstock and producing higher qualified liquid fuels. Besides optimizing the operation conditions of the FCC unit, it is crucial to design new catalysts especially for heavier and inferior feedstock. In this paper, a new concept, stepwise...
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In the past several decades, SINOPEC has devoted continuously great efforts to the development of DCC technology, the only commercial process using heavy feeds aiming at propylene production. Recently, a series of research breakthroughs have been achieved in molecular refining. Based on the detailed analysis on the complex DCC reaction network, an...
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... Alkyl benzene Fig. 3 Reaction pathways for the RFCC processes for (a) residue conversion catalysts. Reproduced from [94] Likewise, initiation and cracking can arise via paraffin's reaction and a Bronsted acid 530 site creating a carbonium ion, which can subsequently react via b-scission to a carbenium ion 531 and smaller paraffin or undertake H2 elimination to a large carbenium ion. Fig. 3 ...
The catalysts used for residue fluid catalytic cracking must have good catalyst activity, selectivity, hydrothermal stability, coke selectivity and metals tolerance to high concentrations of heteroatoms such as N, S, Fe, Na, Ni, and V. Recent increase in energy demand leads to the processing of heavy feedstocks such as atmospheric residue that hitherto have been disfavoured. Processing these feedstocks comes with several challenges due to the presence of
these heteroatom poisons that are detrimental to catalysts as they either permanently or temporarily deactivate or poison the catalysts, thereby promoting undesirable reactions such as dehydrogenation and coke production. To give perspective on these challenges, RFCC technologies, catalysts, and catalyst deactivation are discussed.
The differences and limitations of conventional fluid catalytic cracking and contemporary residue fluid catalytic cracking are also highlighted. This study emphasises the passivation of Ni using antimony, rare earth metals,
bismuth and boron compounds and passivation of V using tin, rare earth metals, and basic alkaline earth
compounds such as Mg. The work also presents new illustrations of nickel and vanadium poisoning mechanisms. While antimony successfully mitigates nickel’s deleterious effects; it leads to NOx emissions and increased bottom fouling. Boron does not exhibit such a problem and has been shown to be a good substitute for antimony
in mitigating the harmful effect of nickel.
... Thus, the demand of fuel will suffer a sharp drop in coming years in favor of gasoline, diesel and other petroleum products, which are lighter. To remain competitive and give added value to heavy oil residues, the refineries are stepping up their research to improve the fluid catalytic cracking (FCC) process [9,19]. The FCC process consist to convert heavy oil feeds into light products. ...
... The zeolites used in FCC catalysts are mainly synthetic faujasite Y type zeolites and high silica Y zeolites, which are the main contributor to the catalytic activity and selectivity of the FCC catalyst [13]. The matrix is made of different constituents such as aluminosilicates and additives which are solid compounds added to improve its properties [4,9]. Nevertheless, the high cost of these commercial catalysts could be a barrier to their use in development countries. ...
Two semi-synthetic clay-based catalysts were prepared. These catalysts were obtained by incorporating lanthanum oxide (Cat1) and chromium oxide (Cat2). They were then tested for catalytic cracking of a heavy petroleum residue (fuel). The two formulations were carried out in the presence of silica to improve their acidity then underwent an acid activation. The catalysts obtained were characterized by various methods (XRD, FTIR, ICP-OES, SEM). The results showed that the incorporation of oxides and the addition of silica improves the structural characteristics of the final products. The support used was a kaolinite rich clay, having a specific surface area of 15.26 m ² /g and acidity of 14 meq/g. These values increase, respectively, to 456.14 m ² /g and 50 meq/g for Cat1 and to 475.12 m ² /g and 57 meq/g for Cat2. The influence of the type of oxide incorporated, the specific surface area, the porosity and the acidity of the catalysts on their catalytic activity was studied. The nature of the oxide used proved to be decisive on the quality of the catalyst. Thus Cat1, prepared with lanthanum oxide, showed the best performance in cracking the petroleum residue achieving a conversion rate of 74.13% compared to 66.53% for cat2.
... To select the right catalyst for the FCC process in such a dynamical environment is a major challenge, because one catalyst can be the best option for a given feed, but not the optimum selection for a feed with a variable quality. FCC catalyst performance is feedstock-dependent [6][7][8][9][10][11][12][13][14]. Six catalysts were explored in this study, four of which were employed in the LNB FCCU during processing a feedstock with a variable quality. ...
This paper studies the effect of the quality of ebullated bed vacuum residue H‐Oil hydrocracking gas oils cracked in a commercial fluid catalytic cracking unit (FCCU) on its performance. Six different catalysts were employed in this study. Four were used in the commercial FCCU, and two were tested in laboratory FCCU. It was found that the increase of the H‐Oil hydrocracker reaction temperature was associated by a decrease of Kw‐factor of the H‐Oil gas oils. The diminished Kw‐factor of H‐Oil gas oils resulted in a lower FCCU conversion and higher regenerator temperatures. The FCC conversion at the point of the maximum gasoline yield is best predicted by the feed Kw‐factor. The higher activity, higher ∆ coke selectivity catalyst is unfavorable for the FCCU performance because of the excessive regenerator temperature excursions requiring a reduction of the through‐put.
... Zeolites are crystals consisting of high specific surface area and extensively micropore structure developed by framework silicon and aluminum oxygen tetrahedrons, having potential applications in the fields of petrochemical reactions [4,5], water purification, the purification of gas [6], and catalytic reactions of green chemistry, etc. [7][8][9][10][11]. Amongst, ZSM-5 zeolite is a three-dimensional crystalline aluminosilicate with silicon and aluminum tetrahedral that form frameworks with a relatively high SiO 2 /Al 2 O 3 ratio [12,13]. ...
Using ZSM-5 zeolites as catalysts for the methanol to propylene (MTP) reaction is being widely investigated and has been industrially applied. In this study, pure ZSM-5 zeolite was successfully synthesized by a direct hydrothermal method using the fly ash of coal gasification as an additional raw material. Various analysis methods such as X-ray diffraction, N2 sorption, scanning electron microscopy, and infrared spectroscopy, were employed to characterize the physicochemical properties of parent and modified zeolites. Then, the prepared ZSM-5 catalysts were tested in the MTP reaction. The results showed that pure ZSM-5 could be directly synthesized in the optimized conditions using fly ash as additional silicon and aluminum sources, and those ZSM-5 catalysts turned out to be candidate catalysts for the MTP reaction. Whereas their catalytic lifetimes were not good enough due to the strong acid sites and needed improving.
... It is well known that the catalytic cracking of naphtha occur on both Brönsted and Lewis acid sites of zeolite catalysts through the carbocations transition states [7,8]. Generally, Brönsted acid sites, mainly generated by the framework tetrahedral Al sites, are considered as the prime active sites for naphtha conversion; in contrast, Lewis acid sites, originated from the nonframework Al species, are inclined to induce thermal cracking and/or dehydrogenation instead of catalytic cracking reaction [9][10][11][12]. ...
... Notably, the selectivity to ethylene and propylene for Z5-ACE was relatively high with the increase of time on stream. According to the proposed mechanisms of catalytic cracking [45,46], paraffin cracking was first catalyzed to form carbocations (carbonium ions and carbenium ions) on acid sites via protonation reaction and/or dehydrogenation, then consecutive reactions such as the break-up of C-C bonds and hydrogen transfer reactions occurred through the carbocations transition states [7,8]. It has been widely recognized that the cracking of carbocations transition states proceeds via both classical β-scission cracking routes (i.e., bimolecular cracking mechanism and carbenium ion cracking mechanism) and the monomolecular protolytic cracking pathway (i.e., Haag-Dessau cracking mechanism and carbonium ion cracking mechanism) [46]. ...
The effect of the basic (NaOH) and/or acid (citric acid and EDTA-2Na) treatment of ZSM-5 zeolite has been studied comparing the structural and acidic features and their catalytic performance in n-heptane cracking. The properties of the catalysts have been elucidated using XRD, N2 low-temperature sorption, ²⁷Al and ²⁹Si NMR, pyridine adsorbed FTIR, NH3–TPD, SEM and TEM analysis. The results showed that the degree of desilication and dealumination of ZSM-5 zeolites was greatly dependent on the agents. NaOH obviously created new mesopores on parent ZSM-5 zeolites by desilication. Citric acid contributed to the removal of nonframework Al species, causing the increase of micropore surface area. EDTA-2Na promoted desilication and simultaneously converted part of removed framework Al species into nonframework Al species. The treatment of ZSM-5 combined with those three agents was very effective to obtain a hierarchical structure with partial breakdown of the crystallites and high acid amounts of both Brönsted and Lewis acid sites. Catalytic tests showed that the post-treated ZSM-5 catalysts had higher activity and stability than parent ZSM-5 catalyst at the same reaction temperature. The synergetic effect of Brönsted acid and Lewis acid of ZSM-5 catalyst (Z5-ACE) probably facilitated n-heptane conversion, while more clean micropore and newly created mesopores facilitated the slight increase of olefin selectivity and suppressing the formation of coke deposition in its inherent micropores to some extent.
... However, the shale oils contain a considerable amount of nitrogen compounds, condensed aromatics and unsaturated hydrocarbons, which may cause many problems during the transportation, storage and processing [5]. As crude oil supply all over the world is becoming heavier and inferior in quality and the demand for middle distillate is larger, fluid catalytic cracking (FCC) process is still the key process in oil refinery and is now in rapid development [6] . The retardation effects of nitrogen compounds and condensed aromatics in FCC process have to be figured out if shale oil is used to produce clean fuel. ...
Untreated shale oil, shale oil treated with HCl aqueous solution and shale oil treated with HCl and furfural were used to do comparative experiments in fixed bed reactors. Nitrogen compounds and condensed aromatics extracted by HCl and furfural were characterized by electrospray ionization Fourier transform cyclotron resonance mass spectrometry and gas chromatography and mass spectrometry, respectively. Compared with untreated shale oil, the conversion and yield of liquid products increased considerably after removing basic nitrogen compounds by HCl extraction. Furthermore, after removing nitrogen compounds and condensed aromatics by both HCl and furfural, the conversion and yield of liquid products further increased. In addition, N1 class species are predominant in both basic and non-basic nitrogen compounds, and they are probably indole, carbazole, cycloalkyl-carbazole, pyridine and cycloalkyl-pyridine. As for the condensed aromatics, most of them possess aromatic rings with two to three rings and zero to four carbon atom.
This chapter emphasized a comparison between biodiesel, green diesel and petrol diesel. In general, diesel is referred to any liquid fuel specifically designed for the automotive engine as a fuel. Generally, biodiesel is an alternative fuel that has similar properties to conventional diesel fuel. Biodiesel can be produced from vegetable oils, animal fats or waste cooking oil via catalysed transesterification process. Biodiesel is renewable energy, nontoxic and biodegradable and may reduce net carbon monoxide emission by 78% compared to petrol diesel. Green diesel is one of the alternative fuels which has a similar molecule structure as petrol diesel and yet it provides better diesel properties in terms of higher heating value, energy density, very high cetane numbers and outstanding cold flow properties compared to conventional biodiesel. Green diesel is produced by hydrotreating triglycerides in vegetable oils with hydrogen. The most common type of diesel fuel is petrol diesel. It is produced from the fractional distillation of crude petroleum between the temperature of 200 and 350 °C at atmospheric pressure resulting in a mixture of carbon chains that typically contain between 8 and 21 carbon atoms per molecule.KeywordsBiodieselGreen dieselPetrodieselComparative analysis
Increasing the cracking ability of catalyst by adjusting its surface acid property is of great significance for oil refining industry. The effects of boric acid on the structure and surface acidity of ultra stabilized Y (USY) and FCC equilibrium catalyst during the modification were investigated. The structural and surface properties of the prepared samples were characterized by low-temperature N2 sorption, XRD, ²⁷Al and ²⁹Si MAS NMR, and FTIR using pyridine probe molecule. Modified USY and equilibrium catalyst possessed reduced Lewis acid sites. The Brönsted/Lewis acid ratios of USY increased from 0.64 to 1.56 after modification, at the same time, the microporous surface areas increased, due to the nonframework and framework dealumination during the modification. The catalytic cracking tests were performed on a bench-scale micro reactor at 500 °C and atmospheric pressure, using n-dodecane as a modeling reactant and vacuum gas oil as conventional feedstock. The results showed that modified samples with high Brönsted acid sites had better cracking abilities and increased hydrogen transfer activity than raw samples.
