Petroleum Coke Research Articles

Sulphur retention and in-situ preparation of metal sulphide catalysts during activation of petroleum coke

Petroleum coke (petcoke) containing sulphur has limited direct applications, but stockpiling the material creates an environmental issue. Although chemical activation can be used to valorise the petcoke to activated carbon, sulphur is released creating alternative environmental problems. In this study, a new activation method for high sulphur content (∼6.5 wt%) petcoke was developed to retain sulphur and prepare transition metal sulphide catalysts simultaneously. Petcoke was mixed with tungsten and nickel precursors and then activated by KOH at 600 °C in the presence of steam. After washing, the activated petcoke had a sulphur content of 5.1 wt%, which was much higher than that in the absence of steam during activation (0.4 wt%). Sulphur was also retained (>4 wt% of sulphur) when other transition metals including molybdenum and cobalt were used. Characterization by XRD, XPS, and SEM-EDS suggested that sulphur was retained on the activated petcoke in the form of metal sulphides. Further thermodynamic analysis of the system revealed that in the presence of steam an H2S/H2 mixture was generated, and this mixture promoted the formation of the metal sulphide species when metal precursors were introduced. The prepared metal sulphide catalysts were active for several reactions including the photoreduction of CO2. Overall, this study provided an effective method to prepare metal sulphide catalysts from sulphur containing carbonaceous waste.

Laboratory Coking and a New Optical Texture Classification Parameter: Screening of Petroleum Refinery Streams for Premium Needle Coke Production

Laboratory Coking and a New Optical Texture Classification Parameter: Screening of Petroleum Refinery Streams for Premium Needle Coke Production

Effect of CaO/Fe2O3 on ash fusibility during petroleum coke gasification and combustion

Ash fusibility is closely related to ash melting, sintering and slagging, which is commonly used to guide the utilization of petroleum coke in boiler and gasifier. Calcium (Ca) and iron (Fe) show significant influence on the ash fusibility of petroleum coke. To quantify the influence of CaO/Fe2O3 mass ratio on petroleum coke ash fusibility, ash fusion temperatures (AFTs) analysis, X-ray diffraction (XRD), and FactSage were applied to investigate the characteristics of petroleum coke ash fusibility with various CaO/Fe2O3 mass ratios. The results showed that AFTs were closely associated with the CaO/Fe2O3 ratio and showed different performances in different atmospheres. In the reducing atmosphere, with the increasing of CaO/Fe2O3 ratio, the AFTs presented in turn a rapid decrease (from 0 to 2) and a smooth region (from 2 to ∞). The rapid decrease of AFTs was mainly attributed to the disappearance of high-melting point coulsonite (FeV2O4) and the formation of low temperature eutectics anorthite (CaAl2Si2O8) and gehlenite (Ca2Al2SiO2). The formation of high-melting point calcium orthosilicate (Ca2SiO4) inhibited the formation of CaAl2Si2O8/Ca2Al2SiO2 to keep the AFTs at a stable level. In the oxidizing atmosphere, with the increasing of CaO/Fe2O3 ratio, the AFTs presented in turn a rapid decrease (from 0 to 1), a smooth region (from 1 to 5), and a fast decrease once again (from 5 to ∞), respectively. The decline of AFTs was attributed to the substitution of NiFe2O4 by fusible minerals (Ca2V2O7/CaAl2Si2O8). The synergy effect of the refractory SiO2 and fusible minerals prevented the further decline of the AFTs.

Preparation of needle coke composite cathode and its treatment of RhB wastewater

A novel Fe-loaded needle coke composite electro-Fenton electrode was prepared, characterized, and investigated as the heterogeneous catalytic cathode for oxygen reduction and OH generation for the first time. The novel electro-Fenton system constructed with the cathode and DSA anode was employed to degrade rhodamine B (RhB) in an aqueous solution. Optimal conditions for electrode preparation for the treatment of RhB were obtained by single-factor experiments. The occurrence of the Fenton reaction was verified by hydroxyl radical quenching experiments, and the RhB degradation pathway was inferred by spectroscopic analysis. The decolorization rate of RhB of nearly 100% and the COD removal efficiency of 81.6% were achieved. RhB was degraded by N-de-ethylation, chromophore cleavage, opening-ring, and mineralization in the presence of reactive oxygen species, mainly OH. The cost of RhB simulated wastewater treatment was estimated at RMB 13 yuan per cubic meter of wastewater. As a cheap carbon cathode material, needle coke can catalyze the two-electron transfer of O2 to produce H2O2, reducing the material cost of the electrode, and also increasing the conductivity of the electrode, reducing the cost of water treatment. The needle coke composite electrode can serve as a cost-effective electro-Fenton cathode in the field of refractory organic wastewater treatment represented by dye wastewater.

Oxidative Desulfurization of Petroleum Coke

Oxidative Desulfurization of Petroleum Coke

Effects of Coal-Fired Flue Gas Components on Mercury Removal by the Mechanochemical S-Modified Petroleum Coke.

In this work, the effects of coal-fired flue gas components (O2, CO2, SO2, and NO) on the Hg0 removal by the promising mercury removal adsorbent mechanochemical S-modified petroleum coke were characterized and analyzed in terms of the Hg0 removal efficiency, mercury adsorption capacity, and mercury mass balance. The results show that the mechanochemical S-modified petroleum coke with a theoretical sulfur content of 21% (named TSC-21) is the best candidate for mercury removal based on the Hg0 removal efficiency, Hg0 removal capacity, and difference ratio of Hg0 removal capacity (anti-interference ability) in the basic and full-component simulated flue gas atmosphere (N2 + O2 + CO2, N2 + O2 + CO2 + SO2 + NO). The maximum value (MV) and stable value (SV) of the Hg0 removal efficiency of TSC-21 in the basic simulated flue gas atmosphere are 99.25% (MV) and 91.17% (SV), respectively. O2, CO2, and NO all promote the Hg0 removal by the adsorbent, but they benefit the Hg0 oxidation while inhibiting the Hg0 adsorption. The promoting effect of O2 on the Hg0 removal by TSC-21 is affected by the reaction time, which is especially obvious after 1 min. The presence of SO2 inhibits the oxidation and adsorption of Hg0, which in turn reduces the Hg0 removal performance of the adsorbent. The improving effects on the oxidative escape of Hg0 by CO2 is higher than that by NO and O2. TSC-21 acts more as an oxidant than an adsorbent for Hg0 removal.

Synthesis of needle coke by co-carbonization of coal liquefaction pitch and refined soft pitch

ABSTRACT Needle coke was a type of engineering material and function artificial carbon material that was extensively utilized as a raw material for the synthesis of ultra-high power electrodes and nuclear graphite. The characteristics of the pitch have a considerable influence on the generation of needle coke of high quality. To study the potential of coal liquefaction pitch (CLP) for the synthesis of high-quality needle coke, refined soft pitch was utilized as an additive to generate needle coke via the co-carbonization method. The optical microscope (OM), scanning electron microscopy (SEM), X-ray diffraction, Raman spectrum, and curve-fitted method were used to analyze the microstructure, true density, carbon crystalline distribution, and micro-strength of the generated needle coke, respectively. Factually, the blending of CLP and refined soft pitch was an essential method to adjust the thermal stability of the pitch mixtures. In addition, co-carbonization of CLP and refined soft pitch was an effective technique for preparing needle coke of high quality with a true density of 2.206 g/cm−3 and a fibrous structure and leaflet structure content of 94.44%.

Analyzing Relationships of Conductivity and Alkalinity Using Historical Datasets from Streams in Northern Alberta, Canada

Many measurements, tools, and approaches are used to identify and track the influence of human activities on the physicochemical status of streams. Commonly, chemical concentrations are utilized, but in some areas, such as downstream of coal mines, capacity indices such as specific conductivity have also been used to estimate exposure and risk. However, straightforward tools such as conductivity may not identify human influences in areas with saline groundwater inputs, diffuse exposure pathways, and few discharges of industrial wastewater. Researchers have further suggested in conductivity relative to alkalinity may also reveal human influences, but little has been done to evaluate the utility and necessity of this approach. Using data from 16 example sites in the Peace, Athabasca, and Slave Rivers in northern Alberta (but focusing on tributaries in Canada’s oil sands region) available from multiple regional, provincial, and national monitoring programs, we calculated residual conductivity and determined if it could identify the potential influence of human activity on streams in northern Alberta. To account for unequal sampling intervals within the compiled datasets, but also to include multiple covariates, we calculated residual conductivity using the Generalized Estimating Equation (GEE). The Pearson residuals of the GEEs were then plotted over time along with three smoothers (two locally weighted regressions and one General Additive Model) and a linear model to estimate temporal patterns remaining relative to known changes in human activity in the region or adjacent to the study locations. Although there are some inconsistencies in the results and large gaps in the data at some sites, many increases in residual conductivity correspond with known events in northern Alberta, including the potential influence of site preparation at oil sands mines, reductions in particulate emissions, mining, spills, petroleum coke combustion at one oil sands plant, and hydroelectric development in the Peace basin. Some differences in raw conductivity measurements over time were also indicated. Overall, these analyses suggest residual conductivity may identify broad influences of human activity and be a suitable tool for augmenting broad surveillance monitoring of water bodies alongside current approaches. However, some anomalous increases without apparent explanations were also observed suggesting changes in residual conductivity may also be well-suited for prompting additional and more detailed studies or analyses of existing data.

Microstructural features transformation at various temperature stages and multi-scale atomistic representations of calcined petroleum coke based on HRTEM

Calcined petroleum coke is a high-quality precursor for graphitic electrodes, and the heating temperature is an essential parameter for the key calcination process. Microstructural features (including lattice fringes length, stacking, orientation, and curvature) transformation at various temperature stages and multi-scale atomistic representations of the calcined coke were investigated by combining HRTEM lattice fringes analysis, XRD, XPS, XRF, mathematical function fittings, computational scripts, molecular dynamics relaxation, and DFT calculation. In the temperature range of 289 to 1873 K, the average lattice fringe length, total stacking frequency, 45° contribution, and curved fringe length frequency changed from 7.36 to 12.03 Å, 10.26 % to 50.63 %, 44.91 % to 98.71 %, and 58.74 % to 36.13 %, respectively. The variation patterns of most microstructure features fitted well with the quadratic function pattern in the temperature range of 298 to 873 K and the Logistic regression model in the temperature range of 873 to 1873 K. The trends of the fitted curves indicated that the microstructure of the calcined coke evolved to slight disorder below 873 K and significant order above 873 K. The mathematical equations of the fitted curves could reliably predict the value of the features at a given temperature stage. The typical molecular-scale (∼70 atoms) models, lattice-scale (3990 atoms) 3D model, and nano-scale (31909 atoms) 3D model of the calcined coke were constructed via the image-guided construction strategy with controllable order degree (utilizing Fringe3D and Packmol). The model data of the H/C ratio, functional groups proportion, trace metals content, true density, and structural features were similar to experimental data. The calculated FT-IR and XRD spectra validated the aromaticity and order degree of the representations.

Hydrocracking of vacuum residue in a slurry phase reactor: effect of reaction temperature and properties of feedstock

Abstract The slurry phase hydrocracking was carried out in a 150 kg/d pilot plant with a change of reaction temperature and different feedstocks including vacuum residue (VR), thermal cracking residue (TCR), 58% VR + 42% DOA (VRD) and 32% VR + 27% DOA + 41% TCR (VRDT). The results demonstrated that the conversions of residue and asphaltene, and hydrogen consumption had a linear relationship with the increment of reaction temperature. The TCR, VRD and VRDT with high content of asphaltene had the characteristic of higher asphaltene conversion and coke yield, but the coke yield was still low, and less than 1.3%. In addition, the removal rate of sulfur was much higher than that of nitrogen, while that of nickel and vanadium reach above 77 and 88%, respectively. The light liquid fraction product could further transform into high value-added chemical materials or clean transport fuel, and the heavy liquid fraction product could utilized as a very good raw material for high quality products as needle coke and carbon-based materials.

Determination of trace metals by ICP-OES in petroleum cokes using a novel microwave assisted digestion method

Trace metals must be strictly controlled in petroleum coke when it is used as anode, as the function of electrodes depends on their concentration, being detrimental in process operations affecting the purity of the final product.In this research, the determination of Si, Fe, V, Ni, Ca, Na, P, Al, Ti, Mg, K, Zn, Mo, Ba, and Co at trace level in green and calcined petroleum cokes using a new digestion method was performed. The method involved microwave-assisted digestion of the sample using a single-reaction chamber (SRC) followed by ICP-OES measurement. This method aimed for a low sample preparation time and a quantitative extraction of the analytes.After optimization of the digestion process it was found that the best condition to digest green and calcined cokes was mixing 9 g HNO3 and 3 g HCl, heating at a temperature of 260 °C for 55 min, and taking 0.5 g of sample, leading to a recovery higher than 98% for all the elements analyzed. In addition, the developed method allowed the determination of the elements in 1.5 h versus the standard method, which takes about 8 h. The validation of the developed methodology was carried out analyzing certified reference materials and using independent methods, such as, wavelength dispersive X-ray fluorescence spectrometry (WD-XRF).The developed methodology is faster, more accurate and more environmentally friendly than other available methodologies as it does not require the decomposition process involving high temperatures and waste generation is minimized. In addition, low limits of quantification and low uncertainties have been reached enabling this method to be used as a control method.

Coking of Pt/γ-Al2O3 catalyst in landfill gas deoxygen and its effects on catalytic performance

Catalytic oxidation of CH4 has been proved to be an attractive option for landfill gas (LFG) upgrading. However, coking of catalysts in catalytic LFG deoxygen has been clearly observed in industrial applications. In this regard, it is necessary to investigate whether coke deposition originates from CH4 or volatile organic compounds present in LFG, and the influence of coke deposition on catalytic performance. Herein, we evaluate the LFG deoxygen on Pt/γ-Al2O3 catalyst in simulated LFG (CH4, CO2, O2, N2) and its co-feed with representative volatile organic compounds, ethylbenzene, toluene, benzene and cyclohexane. The results show that the coking of the catalyst is originated from volatile organic compounds rather than CH4. The Pt/γ-Al2O3 catalyst does not deactivate during LFG deoxygen process, even significant amount of coke deposited, up to 18.15% (mass). Characterization analyses reveal that although coke deposition overall covers the catalyst surface, resulting in mesopores blockage and a reduced number of accessible Pt sites, however, the coke formed, H-rich carbonaceous components, behaves as counterpart for O2 elimination. Besides, the coke deposited is mainly filamentous. Thus, coke formation has little negative effect on the overall catalytic performance of Pt/γ-Al2O3 catalyst ultimately. The results obtained in this work are helpful for the rational design of robust Pt based catalysts for LFG deoxygen without undue attention to their coking properties, and also favor the innovation of more attractive purification scheme configurations.

Quality assessment of needle coke used in the production of graphite electrodes for metallurgical furnaces

Needle coke is a special kind of carbon material that has a developed anisotropic fibrous structure, high current conductivity in the fiber direction and low coefficient of linear thermal expansion. This material has found a wide application in steel industry where it is used for the production of graphite electrodes of the SHP (50–75 kA) and UHP (up to 100 kA) grades designed for high-power electric arc furnaces. This paper describes the results of assessing the quality of the needle coke that is commercially used at El 6 for the production of carbon and graphite products. The quality of the material was analyzed based on two groups of techniques: spectral analysis (SEM and optical microscopy, XRD, Raman spectroscopy) and analysis of physical and chemical properties (CTE, real density, sulfur, ash, moisture, electrical resistivity). A study and a comparative analysis were carried out using seven samples of calcined petroleum and pitch needle cokes. Six of them are used commercially (imported) and one was produced in laboratory conditions from Russian raw materials. The study confirmed that a better needle coke structure tends to form from petroleum coke versus pitch coke. Using the results of spectral analysis, the studied samples of needle cokes were classified into three groups based on their morphology and structure, which correlates with the results of the analysis that looked at their physical and chemical properties. The combination of research and data processing techniques presented in the paper ensures a comprehensive analysis of the studied needle coke and suggests that the material in view can be used in the production of graphite electrodes.The authors would like to thank Evgeny S. Gorlanov, deputy director of the Research Center for the Problems of Processing Mineral and Man-Made Resources at Saint Petersburg Mining University, and Andrey L. Kvanin, who oversees research and engineering projects at El 6, for their valuable advice and assistance in preparing this paper.This research was carried out as part of the State Assignment 0792-2020-0010 by the Ministry of Education and Science of the Russian Federation: Elaborating the innovative technologies of processing heavy hydrocarbons into environmentally friendly motor fuels and new carbon materials with controllable macro- and microstructures of the mesophase”.

A Highly Stable Bimetallic Transition Metal Phosphide Catalyst for Selective Dehydrogenation of n‐Heptane

AbstractIn this work, we demonstrate RuP2‐MoP catalysts being highly stable and selective for the dehydrogenation of long‐chain alkanes like n‐heptane. Compared to a monometallic MoP catalyst, the bimetallic system substantially increases n‐heptene selectivity from 40 % towards 80 %. This effect can be traced back to a reduced surface acidity, suppressing the competitive hydrogenolysis reaction. The active transition metal phosphide is, furthermore, compared to its phosphorous‐free RuMo‐counterpart. As revealed by STEM‐EDX investigations, incorporation of phosphorous results in the formation of separated metal phosphide clusters instead of an intermetallic alloy. In the dehydrogenation of n‐heptane the phosphorous modification clearly avoids catalyst deactivation and maintains the high n‐heptene selectivity. X‐ray diffraction, elemental analysis and STEM‐EDX further reveal that catalyst coking and the formation of less active molybdenum carbide phases is effectively suppressed by phosphorous incorporation, making RuP2‐MoP an attractive system for selective dehydrogenation of long‐chain alkanes.

Treatment of membrane concentrated landfill leachate by a heterogeneous electro-Fenton process with an iron-loaded needle coke cathode

Mature membrane concentrated landfill leachate is one of the most recalcitrant wastewaters due to its high pollutant concentration, poor biodegradability, and stable organic structure. In this study, a heterogeneous electro-Fenton system was constructed using a Fe-loaded needle coke composite electrode as a cathode to treat the membrane concentrated landfill leachate from a local closed landfill. The reaction conditions were evaluated and optimized by the response surface method based on Box-Behnken design. A second-order polynomial model with COD removal rate as the response and initial pH, plate spacing, and applied voltage as independent variables were established. After treatment by the heterogeneous electro-Fenton process with the needle coke composite cathode under the optimal conditions of applied voltage 10 V, initial pH 3.6, and the plate spacing 1.4 cm, the COD and color removal rates of the membrane concentrate were up to 71.9% and 99.8%, respectively, and the biodegradability was significantly improved with the BOD5/COD increasing from 0.003 to 0.379. Various spectral analyses of the wastewater before and after electro-Fenton treatment with the needle coke composite cathode demonstrated that most of the macromolecular organic pollutants in the landfill leachate concentrate including aromatic compounds, simple aromatic protein compounds, soluble microbial by-products, and humic acid were significantly degraded. As a result, the electro-Fenton technique with the needle coke composite cathodes is one of the cost-effective options for treating membrane concentrated landfill leachate.

Boosting of reversible capacity delivered at a low voltage below 0.5 V in mildly expanded graphitized needle coke anode for a high-energy lithium ion battery

The rate performance and cycle stability of graphitized needle coke (GNC) as anode are still limited by the sluggish kinetics and volume expansion during the Li ions intercalation and de-intercalation process. Especially, the output of energy density for lithium ion batteries (LIBs) is directly affected by the delithiation capacity below 0.5 V. Here, the mildly expanded graphitized needle coke (MEGNC) with the enlarged interlayer spacing from 0.346 to 0.352 nm is obtained by the two-step mild oxidation intercalation modification. The voltage plateau of MEGNC anode below 0.5 V is obviously broadened as compared to the initial GNC anode, contributing to the enhancement of Li storage below the low voltage plateau. Moreover, the coin full cell and pouch full cell configured with MEGNC anode exhibit much enhanced Li storage ability, energy density and better cycling stability than those full cells configured with GNC and commercial graphite anodes, demonstrating the practical application value of MEGNC. The superior anode behaviors of MEGNC including the increased effective capacity at low voltage and superior cyclic stability are mainly benefited from the enlarged interlayer spacing, which not only accelerates the Li ions diffusion rate, but also effectively alleviates the volume expansion and fragmentation during the Li ions intercalation process. In addition, the above result is further confirmed by the density functional theory simulation. This work provides an effective modification strategy for the NC-based graphite to enhance the delithiation capacity at a low voltage plateau, dedicated to improving the energy density and durability of LIBs.

Preparation of mesoporous activated carbon by preliminary oxidation of petroleum coke with hydrogen peroxide and its application in capacitive deionization

Capacitive desalination is a very promising method for the supply of high-tech industrial water in the future. In this study, activated carbon with both specific surface area and mesopores developed at the same time was prepared by preliminarily oxidized petroleum coke with hydrogen peroxide and then activating it with KOH. Hydrogen peroxide used for preliminary oxidation penetrates deep to the inside as well as the surface of petroleum coke to increase reactivity upon activation, forming pores to the depth of petroleum coke to create high specific surface area activated carbon with developed mesopores. Activated carbon prepared by preliminarily oxidized petroleum coke had high specific surface area and mesopores. In particular, OMC-35 had a specific surface area of 3032 m2/g and the highest mesopores of 0.82 cm3/g. As a result, OMC-35 had an excellent capacitance of 196.9 F/g at a scan rate of 5 mV/s. In addition, OMC-35 showed a salt adsorption capacity (SAC) of 19.5 mg/g and excellent desalination performance with a salt removal efficiency of 98.5 % in 250 ppm of NaCl solution. Thus, this work supports OMC-35 as a promising candidate for desalination of industrial water and large-scale application.

As2O3 removal from coal-fired flue gas by the carbon-based adsorbent: Effects of adsorption temperature and flue gas components

Gaseous As2O3 emitted from the coal-fired power plant is one of the most carcinogenic and harmful pollutants. In this work, the commercial activated carbon (AC), wood chip-based biomass coke (BC), and KOH activated high-sulfur petroleum coke (PC) were selected, and the effects of adsorption temperature and flue gas components on gaseous As2O3 removal of the carbon-based adsorbents were investigated. The results show that under the basic adsorption conditions, the As2O3 removal ability satisfies BC > PC > AC with the best arsenic removal ability of BC at 150 ℃. Increasing the adsorption temperature benefits the oxidation of As3+ to As5+ on the surface of the three carbon-based adsorbents. Oxygen-containing functional groups (C–O and O–C=O), Al2O3, K2S, and K2SO4 are the main active sites for As2O3 chemisorption. Overall, increasing adsorption temperature leads to the first increase and then decrease in arsenic removal ability of carbon-based adsorbents. Physical adsorption is the main reason for the change in their arsenic removal ability. The weakening degree of physical adsorption is higher than the promotion of chemisorption with increasing adsorption temperature. NO has inhibitory effects on the As2O3 removal by BC. Low concentration (<4000 ppm) SO2 can promote the As2O3 removal by BC due to the formation of SO42- and the increased content of oxygen-containing functional groups.

Investigation on aquathermolysis desulfurization by cutting off C-S bond in thiophene over Fe-Zr-Al catalyst facilitated by surfactants

ABSTRACT This study aimed to apply aquathermolysis technology to remove thiophene sulfur in vacuum residue to obtain qualified petroleum coke products based on a well-designed Fe-Zr-Al catalyst. A coprecipitation method was first developed to synthesize Fe-Zr-Al composite metal oxide catalyst. The thiophene model oil was selected as the reaction system to investigate the process conditions. By adding surfactants into the reaction system to strengthen the mass transfer process of oil–water two-phase, the desulfurization rate of aquathermolysis was improved. It was shown in this study that under the conditions of oil–water ratio of 3:7, temperature of 280°C, pressure of 4 MPa and reaction duration of 60 h, the desulfurization rate could reach 44.39%. The further introduction of 2.4% Sorbitan oleate into the above reaction system could significantly enhance the desulfurization rate to 60.20%. Under the action of Fe2O3 lattice oxygen, thiophene was oxidized and C-S bond was broken, so as to achieve the purpose of desulfurization. The decomposition of water generated active oxygen to continuously replenish lattice oxygen of Fe2O3. The current founding can provide a new way for the effective desulfurization of vacuum residue to produce qualified petroleum coke products.

Development of a Method for Predicting the Quality of Petroleum Coke

Development of a Method for Predicting the Quality of Petroleum Coke