Coke Fractions Research Articles

The application of Ni and Zr modified ZSM-5 nanosheet in upgrading of lignite pyrolysis volatiles coupling with methanol to light aromatics

Ni and Zr modified nanosheet ZSM-5 zeolites as tandem catalysts were designed using co-impregnation method (Zr-Ni/S-Z5) or combining in-situ hydrothermal synthesis of Ni@S-Z5 and sequential impregnation of Zr (Zr/Ni@ S-Z5). Their applications in upgrading of lignite pyrolysis volatiles coupling with methanol to light aromatics were investigated. The results demonstrated that nanosheet zeolites with larger surface areas and shorter b-axis length benefited the production of light aromatics due to exposing more active sites and improved diffusion limitation compared with conventional ZSM-5 zeolites. Adding Ni and Zr into tandem catalysts further enhanced BTEXN yields, which was attributed to the induction of oxyphilic ZrO2 for activating CAr-O bonds combining the promotion of Ni for hydrogenation. Comparing to Zr-Ni/S-Z5 catalyst, lower BTEXN yield was observed due to the decrease in exposing active sites over Zr/Ni@ S-Z5 catalyst. Moreover, enhancing diffusion behaviors in shorter b-axis length and the presence of more fractions of external coke indicated less effective in blocking pore channels, thus nanosheet zeolite series showed lower deactivation rates.

Production of Carbon Sorbents from Medium-Temperature Coke Siftings of Coking Plants in Central Kazakhstan

The possibility of obtaining carbon sorbents from a fine fraction of medium-temperature coke for the removal of phenols from industrial water and wastewater was demonstrated. This excludes the carbonization of coal material as one of the economically costly stages. The resulting samples were tested for the ability to absorb phenol. The phenol content of water after purification with K12 and ShK sorbents decreased from 251.00 to 0.0572 and 0.737 mg/L, respectively.

Tailored chemical modification of ZSM-5 zeolite supports for Mo-based catalysts optimized for methane dehydroaromatization: Hydrothermal dealumination was key to improving the selectivity of desired aromatic compounds

In this study, we considered Mo-impregnated H-ZSM-5 zeolite catalysts (denoted by Mo/Z) for methane dehydroaromatization (MDA). In particular, we attempted to reduce the amount of Brønsted acid sites (BAS) of the H-ZSM-5 supports via hydrothermal dealumination to disfavor the final product of the MDA (i.e., coke) and, thus, improve the intermediate aromatic compounds (mainly, benzene and toluene: BT). In fact, the hydrothermal treatment of H-ZSM-5 supports at ca. 400 °C prior to Mo-impregnation (the resulting catalyst is denoted by Mo/Z_400) improved the BT formation rates over the 12-h reaction relative to Mo/Z. In particular, coke analyses on the spent catalysts recovered after different reaction times revealed that Mo/Z_400 suppressed the formation of hard coke fractions and, accordingly, increased the intermediate BT products, as compared to Mo/Z. For this, thermogravimetric analysis complemented with micropore analysis clearly indicated that the chemically modified property (here, BAS), not the physical counterpart (here, 10-membered-ring micropores), was key to achieving such activity and, furthermore, their gradual decrease could account for the deactivation behavior as a function of time. In addition, the coke formed outside was likely to contribute to the deactivation as well. However, higher hydrothermal treatment temperatures (500, 600, or 700 °C) rather deteriorated the catalytic activity, suggesting that extensive dealumination of the zeolite framework resulted in the excessive loss of desired BAS. Such improvement based on the optimal modification of BAS allowed for competitive MDA performance to be as good as those of other complex post-processed, high-performance Mo-based ZSM-5 zeolites reported in the literature.

Factors Affecting the Formation the Carbon Structure of Coke and the Method of Stabilizing Its Physical and Mechanical Properties

The raw materials (coals different stages of metamorphism) and technological factors (period and temperature) of the coke-making that determine the carbon structure of blast furnace coke, and its physical and mechanical properties are analyzed. The change granulometric composition of the coke as a function of the coal batch properties is described in detail. The installation determines the possibility of influencing the carbon structure of coke, its granulometric composition in its production in order to increase the yields of the most valuable fractions, and improving its quality characteristics to achieve high-performance blast furnaces. Analysis of the results indicates that, with no changes in the coking conditions, the granulometric composition depends significantly on the ash content and packing density of the coal batch. Research has shown that the petrographic composition of the coal batch also affects the structure and size of the coke. The closest relationship is established between the magnitude of the fusinized components ΣFC and the output of the coke fractions 80–60 mm, 40–25 mm, and <25 mm. The method of mechanical treatment and stabilizing of blast furnace coke is proposed, which includes the improvement of the initial indexes of its quality M25, M10, and class >80 mm in continuous or periodically working open or closed industrial cylindrical oblique stabilizer drum.

Determining the amount of ‘green’ coke generated when co‐processing lipids commercially by fluid catalytic cracking

AbstractCo‐processing biogenic feedstocks in oil refineries will reduce the greenhouse gas emissions normally associated with fossil‐derived transportation fuels. The fluid catalytic cracker (FCC) within a refinery is a robust processing unit and will probably be a preferred insertion point if biocrudes, produced by the liquefaction of biomass, are co‐processed within a refinery. Fluid catalytic cracking results in a wide range of intermediate products which can be upgraded to gasoline, diesel, heavy fuel oil and liquified petroleum gas blendstocks. Coke is also produced and provides heating for feedstocks, the endothermic catalytic cracking reactions and the regeneration of the FCC catalyst. However, coke combustion also generates carbon dioxide and is a significant source of refinery greenhouse gas emissions. As detailed here, the continuous nature of the process makes the physical evaluation of any biogenic coke fraction, via methods such as C14 isotope analysis, quite challenging. However, quantifying the stack gases provides one way of assessing the renewable content of the carbon dioxide derived from coke combustion. The hourly data from 1 year of commercial operation was assessed using linear and Bayesian ridge regression to quantify the burning coefficient of the coke when co‐processing lipids at the FCC. When a bootstrap method was used to reduce the uncertainties of the coefficients, this allowed us to quantify the renewable (green) fraction of the coke component, indicating the reduction in carbon dioxide emissions when commercially co‐processing biogenic feedstocks. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

Product composition and coke deposition in the hydrocracking of polystyrene blended with vacuum gasoil

The upgrading of polystyrene (PS) together with vacuum gasoil (VGO) by means of hydrocracking has been investigated. The aim of the work has consisted on explaining, based on the hydrocracking mechanism, the effects of the co-feeding and of the operating conditions on products distribution and catalyst deactivation. For this purpose hydrocracking tests have been carried out in a batch reactor for a PS/VGO blend (10/90 in mass) under the following conditions: 380–420 °C; 80 bar; contact time, 30–300 min; and C/O ratio, 0.1 gcatalyst goil−1. The liquid products have been extensively characterized by chromatographic means, exposing that the naphtha and LCO (light cycle oil) fractions produced at 400 and 420 °C are suitable to be used in the blending of automotive fuels. Finally, coke fraction has been characterized by different techniques exposing that at low temperature the PS has a strong influence on catalyst deactivation, whereas at high temperature its effects are not so notably. Thus, the results expose that by co-feeding PS to a hydrocracking unit, it can effectively be converted it into streams of interest for refinery without causing any operational issue.

Chlorination behaviors for green and efficient vanadium recovery from tailing of refining crude titanium tetrachloride

The refined tailing, generated from refining of titanium tetrachloride (TiCl4) for vanadium (V) removal, is a hazardous material to environment due to the high content of V. Aiming at effective and selective extraction of V from the refined tailing, a fluidized chlorination process was proposed in present work. The chlorination behaviors of the refined tailing which determine the efficiency and selectivity of V extraction were emphatically investigated. A resultant 96.36% of V and 4.23% of Ti can be synchronously extracted from the tailing at the optimum conditions of 800 °C for 60 min, with the pressure fraction of chlorine [P(Cl2)/P(Cl2 +N2)] = 0.5 and the mass fraction of petroleum coke in raw materials for chlorination at 10 wt%. High purity vanadium oxytrichloride (VOCl3, higher than 99.99 wt%) can be finally obtained via further simple purification of the collected chloride product. Moreover, the chlorination residue containing concentrated TiO2 has the potential to be further utilized for Ti extraction. Thus the process provides a new prospect for effective, clean and comprehensive utilization of the refined tailing, which can solve the hazardous waste recycle and environmental concerns simultaneously.

Dimethyl ether conversion to light olefins in slurry and fixed‐bed reactors: coke nature and location on Mg/ZSM‐5 catalyst

AbstractBACKGROUNDThe goal of this study was to investigate the deactivation of ZSM‐5 in the DTO process (dimethyl ether to light olefins) in a slurry reactor (SLR) in polydimethylsiloxane dispersion medium compared with its deactivation in a fixed‐bed reactor (FBR), and to unveil reasons behind the rapid deactivation of the catalyst in the SLR.RESULTSUnder suspension conditions coke formation proceeds more slowly compared with fixed‐bed conditions: The amount of coke formed under suspension conditions is less than under fixed‐bed conditions, 1.4 mg versus 1.7 mg, respectively. Also, in terms of the chemical composition the coke is lighter (xylenes and trimethylbenzenes versus С4,5,6‐substituted benzenes). Using thermogravimetric analysis and gas chromatography/mass spectrometry pyrolytic system, it was shown that the decomposition products of the dispersion medium contribute to the blocking of micropores and the rapid deactivation of the catalyst in SLR. The localization of coke in both SLR and FBR occurs primarily in the microporous channels of the zeolite (>60%). In SLR, the weight fraction of coke on the external catalyst surface was 11% higher than that on the FBR. This finding can be attributed to the blocking of micropores by decomposition products of the dispersion medium.CONCLUSIONUnder suspension conditions, сoke formation in the DTO process proceeds more slowly compared with fixed‐bed conditions. The rapid loss of catalyst activity in the SLR was related not to coke formation, but instead to the blocking of catalyst pores by products of thermal decomposition of the dispersion medium. For the same reason, in SLR the weight fraction of coke on the external surface of the catalyst was higher than that in the FBR. © 2021 Society of Chemical Industry (SCI).

Feasibility of online pre-reforming step with dolomite for improving Ni spinel catalyst stability in the steam reforming of raw bio-oil

This work studies the effect that a pre-reforming step (PSR) with low-cost catalyst (dolomite) has on the stability of a Ni-spinel catalyst in the steam reforming (SR) of raw bio-oil. PSR temperature varied in the 400–700 °C range, while SR conditions were kept at 700 °C, space-time = 0.14 gcatalysth/goxygenates, and Steam/Carbon = 3. Deactivated catalysts (characterized by XRD, Raman, TPO, and TEM) showed two types of amorphous coke, whose relative amount depends on the feed composition to SR step, which in turn depends on the prior PSR conditions. Phenols and aromatics (main products of the PSR at 700 °C) favor the formation of coke deposited mainly on Ni sites, whereas non-aromatic oxygenates (major products of the PSR at low temperature) are precursors of coke deposited all over the catalyst surface. PSR at 400 °C leads to low amounts of both coke fractions, enhancing the stability of the Ni spinel catalyst.

Yield and Quality of Coke Fractions from Batch with a High Content of Gas Coal

Yield and Quality of Coke Fractions from Batch with a High Content of Gas Coal

Bulk and molecular composition variations of gold-tube pyrolysates from severely biodegraded Athabasca bitumen

Gold-tube pyrolysis experiments were performed on two Athabasca oil sand bitumens at 300 °C to 525 °C with 2 °C/h rate and 25 °C step under 50 MPa. Pyrolysis temperature of 425 °C is critical for weight loss of bulk bitumen and hydrocarbon generation and destruction. Polar compounds are the main source of saturated and aromatic hydrocarbon, gas and coke fractions. Molecular compositions in pyrolyzates vary systematically with increasing pyrolysis temperatures. High molecular weight n-alkanes (C26+) are gradually destructed during pyrolysis due to thermal cracking. Moderate molecular weight n-alkanes (C21–C25) show the highest thermal stability in designed pyrolysis temperatures. The loss of low molecular weight n-alkanes (C20−) might be caused by volatilization during pyrolysis, which may alter commonly used molecular parameters such as ∑n-C20−/∑n-C21+, Pr/n-C17 and Ph/n-C18. Aromatic hydrocarbons were generated from 300 to 425 °C, then condensation and dealkylation have been initiated at 425 °C as evidenced by decreased summed alkylnaphthalenes to alkylphenanthrenes ratios and increased unsubstituted aromatics to substituted homologs ratios in higher temperatures. The occurrence of anthracene and benz[a]anthracene in pyrolysates indicates pyrogenic origin, while fluoranthene shows unexpected behaviors during pyrolysis. Ratios derived from them are not always reliable for pyrogenic source input diagnosis in environmental samples.

Influence of Carbon-Containing Additives in the Composition of Copper-Based Friction Material on Boundary Friction in Mineral and Synthetic Oils

This study provides the results of analyzing the influence of carbon-containing powder additives in the form of powders of fine GK-1 pencil graphite, GE-1 coarse graphite, and foundry coke fractions smaller than 63 and 100–200 μm on the setting and transfer of materials using mineral and synthetic oils. It is established that foundry coke powder allows for improving the resistance of material during seizure. Thus, an increase in the seizure load from 1.4 to 1.7 MPa for mineral oil and from 1.0 to 1.4 MPa for synthetic oil is registered at a sliding speed of 2 m/s. The use of finely dispersed pencil graphite as part of the friction material during friction in synthetic oil increases the speed during seizure; thus, an increase in speed up to 4 m/s is registered at a load of 1 MPa, while an increase in speed for pure 12% bronze is not higher than 2 m/s.

Determination of parameters of the carbon­containing materials gasification process in the rotary kiln cooler drum

An assessment of the feasibility of using the existing equipment of a rotary kiln cooler drum for heat treatment of a carbon-containing filler to produce synthesis gas using production waste in the form of a dust fraction of heat-treated petroleum coke or anthracite is carried out. A mathematical model of the process of gasification of carbon particles is formulated in the continuous-discrete formulation, including thirteen global reactions, of which four are heterogeneous and nine are homogeneous. A numerical model of gasification of a dust fraction of a carbon-containing filler in the rotary kiln cooler drum in the axisymmetric formulation is developed. The convergence of the numerical solution of the gasification problem by the grid step is investigated. It is found that the computational grid, which includes 73,620 cells and 75,202 nodes, leads to an error in determining the main parameters of the model of no more than 1–2 %. Verification of the developed numerical model is performed. It is found that the difference between the molar fractions of CO and H 2 , the values of which were obtained by various software products (Fluent, NASA CEA), is in the range of (2.8...5.8) %. Using the developed numerical model of the process of gasification of a carbon-containing filler in the rotary kiln cooler drum, the quantitative composition of the combustible components of the syngas for different initial parameters is determined. It is found that with the ratio О 2 /С=(42.7...51.6) %, the predicted quantitative composition of the combustible gases of synthesis gas in molar fractions is СО=(32.8...36.9 )%, Н 2 =(17.1...18.4) % and CH 4 =(0.03...0.16) %. The possibility of using the NASA CEA program, intended for operational calculations of equilibrium chemistry, for engineering calculations of the material composition of synthesis gas of industrial furnace equipment, is shown

Lessening coke formation and boosting gasoline yield by incorporating scrap tire pyrolysis oil in the cracking conditions of an FCC unit

We have studied the effect of adding scrap tire pyrolysis oil (STPO) as feed or co-feed in the cracking of vacuum gasoil (VGO) using a commercial equilibrated catalyst. The cracking experiments were performed in a laboratory scale fluid catalytic cracking (FCC) simulator using VGO, STPO, or a blend of the two (20 wt% of STPO), contact time = 6 s, catalyst/feed ratio = 5, and 530 °C. The composition of the different feeds has been correlated with the yield of products and the amount-location-nature of the deactivating species (coke). Our results indicate that adding STPO increases proportionally the gasoline yield, synergistically increase the yield of light cycle oil while uncooperatively decrease the yields of heavy cycle oil and coke. We further investigated the effect on coke formation, characterizing deeply the coked catalyst and coke. In fact, the coke deposited under the cracking of STPO is more aliphatic, lighter, and located in the micropores of the catalyst. The complete analysis of the coke fractions (soluble and insoluble) have lighted the peculiar chemistry of these species as a function of the type of feed used. The results point to a viable and economically attractive valorization route for discarded tires.

Assessment of coke deposits on lamellar metal-modified MFI zeolites in ethylene transformation to aromatic liquids

The effects of meso-/microporous structure and metal-additive (Ga or Zn) of lamellar MFI catalysts on the characteristics of coke deposits during ethylene-to-aromatic liquids conversion were investigated. The nature, composition, and location of coke deposits in spent lamellar catalysts were analyzed and compared to those on the microporous MFI counterparts, using FTIR, UV–Vis, GC–MS, and argon adsorption-desorption. The total amount of coke and the changes in coke nature during catalyst regeneration were studied by MS/FTIR combined with temperature programmed oxidation. The lamellar meso-/microporous structure of MFI reduces the coke quantity and the heavy coke fractions. The coke preferentially deposites on external surface of lamellar zeolite due to the lower diffusion limitation for bulky coke precursors. Metal-additive changes the catalyst acidity and decreases the coke formation rate, especially when zinc is used. Therefore, the coke formation on zeolite can be tuned by modulating the textural and acidity properties of the metal-modified catalyst.

Influence of the operating conditions on the behavior and deactivation of a CuO-ZnO-ZrO2@SAPO-11 core-shell-like catalyst in the direct synthesis of DME

The behavior of the CuO-ZnO-ZrO2@SAPO-11 core-shell catalyst in the direct synthesis of DME from H2 + CO + CO2 mixtures has been assessed. The effect of the reaction conditions (temperature, pressure, space-time) and feed composition (CO2 and H2 concentration) on the DME yield and selectivity, CO2 and COx (CO2+CO) conversions and stability of the catalyst have been studied. The experiments have been carried out in a fixed-bed reactor in the following condition ranges: 250–325 °C; 10–50 bar; space-time, 1.25–15 g h molC−1; CO2/COx molar ratio in the feed, 0–1; and H2/COx molar ratio in the feed, 2.5–4; time on stream, up to 48 h. Under mild conditions (275–300 °C range, 20–30 bar, space-time over 5 g h molC−1, CO2/COx molar ratio in the 0.5–0.75 range, and H2/COx molar ratio around 3) a good compromise is reached between the yield of DME and the conversion of CO2, with high catalyst stability. Coke deposition is the main cause of catalyst deactivation, formed by condensation of the hydrocarbon byproducts, blocking the metallic sites in the core. The formation rate of this fraction of coke is greater than that of the coke deposited in the SAPO-11 of the shell. Increasing reaction temperature favors the formation of coke, while co-feeding CO2 attenuates this formation, due to the increase of H2O concentration.

Economic operation of a fluid catalytic cracking process using self-optimizing control and reconfiguration

For economic operation of the fluid catalytic cracking (FCC) process, a control reconfiguration method is proposed based on the self-optimizing control (SOC) methodology. Firstly, the primary controlled variables are considered as measurement combinations, which are tracked at constant setpoints to maintain near-optimal operations. In the obtained controlled variables, the weight fraction of coke on the regenerated catalyst is identified as an important variable, which is however difficult to measure online and cannot be used directly. Two alternatives are considered, with either the composition variable estimated by a soft-sensor or adopting a suboptimal solution without using the composition variable. Then, the classic Hicks control structure for the FCC process is reconfigured using the obtained schemes, where the setpoint of reactor temperature is automatically optimized by the added SOC configurations. Finally, simulations are carried out to verify the economic improvements.

Production of Carbon Adsorbent from Petroleum Coke by Carbonization with Potassium Hydroxide

Samples of carbon adsorbent are prepared by carbonization of petroleum coke with potassium hydroxide at 600–1000°C; the KOH/coke ratio is (0.5–9.0)/1.0. After repeated washing by hydrochloric acid solution and distilled water, the product is a powder with low packing density (0.15–0.80 g/cm3); its specific surface is 3000 m2/g or more. With increase in the alkali content and the carbonization temperature, the yield declines, while the specific surface of the powder increases. The characteristics of the product are practically independent of the particle size of the initial coke. That permits the use of a broad coke fraction (0.2–2.0 mm).

Insight into the Deactivation and Regeneration of HZSM-5 Zeolite Catalysts in the Conversion of Dimethyl Ether to Olefins

The impact of different process variables affecting the coking and rejuvenation of HZSM-5 zeolite catalyst has been studied during the conversion of dimethyl ether (DME) to olefins in a fixed bed reactor. Those variables involve the effect of (i) the matrix material with mesopores; (ii) temperature; (iii) space time; (iv) acidity of the catalyst; (v) steam, inert or air in the reaction-regeneration medium. Used catalysts have been characterized through N2 adsorption-desorption and temperature-programmed oxidation, and the presence of three coke fractions has been identified, deposited within the zeolite micropores, the external surface of the crystals and the mesopores of the matrix. Low Si/Al ratios (140) and temperatures (350 °C), and cofeeding water with DME, reduce the formation of coke within the zeolite micropores, favoring the stability of the catalyst. Reaction-regeneration cycles confirm that catalysts totally recover the activity through combustion of coke during a heating ramp up to 550 °C.

Structure and Evolution of Confined Carbon Species during Methane Dehydroaromatization over Mo/ZSM-5

Surface carbon (coke, carbonaceous deposits) is an integral aspect of methane dehydroaromatization catalyzed by Mo/zeolites. We investigated the evolution of surface carbon species from the beginning of the induction period until the complete catalyst deactivation by the pulse reaction technique, TGA, 13C NMR, TEM, and XPS. Isotope labeling was performed to confirm the catalytic role of confined carbon species during MDA. It was found that “hard” and “soft” coke distinction is mainly related to the location of coke species inside the pores and on the external surface, respectively. In addition, MoO3 species act as an active oxidation catalyst, reducing the combustion temperature of a certain fraction of coke. Furthermore, after dissolving the zeolite framework by HF, we found that coke formed during the MDA reaction inside the zeolite pores is essentially a zeolite-templated carbon material. The possibility of preparing zeolite-templated carbons from the most available hydrocarbon feedstock is important for the development of these interesting materials.