Coke Yield Research Articles

Catalytic fast pyrolysis of cellulose in a microreactor system using hierarchical zsm-5 zeolites treated with various alkalis

Hierarchical ZSM-5 catalysts were prepared by desilication using NaOH, Na2CO3 and TPAOH with different concentrations under the same treatment conditions. Their structures and acidities were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), N2 adsorption and desorption (N2-BET) and ammonia temperature-programmed desorption (NH3-TPD). The catalytic fast pyrolysis (CFP) of cellulose to produce aromatics over the hierarchical ZSM-5 catalysts prepared using different alkali treatments was investigated. The alkali treatment by Na2CO3 (0.4∼0.8M) was much milder than treatment by NaOH, which allowed the desilication process to be highly controllable, resulting in an increase of both the amount and strength of the strong acid sites, and the formation of hierarchical structures combining micro- and mesoporosity. The organic hydroxide TPAOH did not change the pore structure of ZSM-5, but it greatly increased the relative crystallinity. The CFP of cellulose with HZSM-5 produced 35.5% liquid aromatic hydrocarbons and 32.7% coke. The yield of aromatics increased after Na2CO3 treatment but decreased after NaOH treatment. In addition, the yield of coke showed the opposite trend. The highest aromatic yield (38.2%) and lowest coke yield were obtained in the CFP of cellulose with the desilicated zeolite treated with 0.6M Na2CO3. The increased acidity in hierarchical ZSM-5 treated with Na2CO3 increased the selectivity of highly valuable aromatics, such as benzene, toluene, and xylene, and decreased the selectivity of large aromatics. TPAOH-treated HZSM-5 showed a slightly increased yield of aromatics due to the repair effect of TPAOH, but this treatment did not form a mesoporous structure.

Ex-situ catalytic upgrading of vapors from microwave-assisted pyrolysis of low-density polyethylene with MgO

Ex-situ catalytic upgrading of vapors from microwave-assisted pyrolysis of LDPE using MgO as the base catalyst was investigated and the effects of catalyst to reactant ratio, pyrolysis temperature, and catalytic reaction temperature on the yields and chemical profiles of products were examined. 24.2–38.5wt.% of ex-situ upgraded liquid yield were obtained under varied reaction conditions. Productive gas yield (higher than 56.6wt.%) and low solid residue yield (less than 7.1wt.%) were obtained as long as the pyrolysis temperature was over 500°C during the ex-situ upgrading process. The coke yield was negligible, ranging from 0.14wt.% to 1.94wt.% based on LDPE mass. The conversion of alkenes to aromatics was improved at higher catalyst to feedstock ratios, higher pyrolysis temperatures, and higher catalytic reaction temperatures. The total percentage of gasoline fraction in the upgraded pyrolysis oil ranged from 79.5% (37.3% mono-aromatics and 42.2% C5-C12 aliphatics) to 96.0% (39.7% mono-aromatics and 56.3% C5-C12 aliphatics) under various conditions, compared with 10.5% mono-aromatics and 30.2% C5-C12 aliphatics from non-catalytic pyrolysis. The main composition of gas product was hydrogen, C1-C3 olefins and paraffins, varying with reaction condition. Both free radical and carbanion mechanisms for the conversion of LDPE with MgO were proposed.

Kinetic model for liquid-phase liquefaction of asphaltene by hydrogenation with industrial distillate narrow fraction as hydrogen donor

Hydrogenation in liquid phase is a competitive process for converting asphaltene to distillate with minimum coke formation compared with thermal cracking. Some Industrial distillates, which contain rich naphthenic aromatics, are a suitable substitution serving as inexpensive industrial distillates hydrogen donor. In this paper furfural extract oil with boiling point of 430–450°C was selected as industrial distillate hydrogen donor. The liquid-phase liquefaction behaviors of asphaltene with industrial distillates hydrogen donor were investigated in an autoclave. The effects of reaction conditions, including reaction temperature and time, on product distributions and selectivity were studied. The results showed that the asphaltene conversion and coke yield increased with the reaction severity increasing. However, the selectivity of maltene decreased with the reaction severity increasing. Two kinetic models were developed for describing the behavior of liquid-phase liquefaction of asphaltene. In model one, which was only considering the reaction of asphaltene conversion, asphaltene liquefaction was in good agreement with the first-order reaction kinetic with apparent activation energy of 106.09kJmol−1 under the condition of coke yield less than 3wt%. In model two, a four-lump kinetic model including asphaltene, maltene, gas, and coke lumps, the activation energies varied from 100.14 to 117.58kJmol−1. The product yield predicted by the developed four-lump kinetic model exhibited good consistency with the experimental data. Additionally, the kinetic model two can well predict the reaction behavior with relative error lower than 4%.

Catalytic steam cracking of heavy crude oil with molybdenum and nickel nanodispersed catalysts

The catalytic steam cracking (CSC) of heavy crude oil with high amount of sulfur (4.3 wt %) and high-boiling fractions (>500°C) is studied using Mo and Ni nanodispersed catalysts under static conditions (in an autoclave) at 425°C. Experiments on thermal cracking, steam cracking, and catalytic cracking without water are performed to compare and identify the features of CSC. The relationship between the composition and properties of liquid and gaseous products and process conditions, the type of catalyst, and water is studied. Using Ni catalyst in CSC raises the H: C ratio (1.69) in liquid products, compared to other types of cracking, but also increases the yield of coke and gaseous products, so the yield of liquid products falls. When Mo catalyst is used in CSC, low-viscosity semi-synthetic oil with a higher H: C ratio (1.70) and the lowest amount of sulfur in liquid products (2.8 wt %) is produced. XRF and HRTEM studies of the catalyst-containing solid residue (coke) show that under CSC conditions, nickel is present in the form of well-crystallized nanoparticles of Ni9S8 15–40 nm in size, while molybdenum exists in two phases: MoO2 and MoS2, the ratio between which depends on the conditions of the transformation of heavy crude oil. The findings indicate that CSC is a promising process for improving heavy crude oil.

Synthesis of Cumene from Lignin by Catalytic Transformation

Cumene is an important intermediate and chemical in chemical industry. In this work, directional preparation of cumene using lignin was achieved by a three-step cascade process. The mixture aromatics were first produced by the catalytic pyrolysis of lignin at 450 °C over 1%Zn/HZSM-5 catalyst, monocyclic aromatics with the selectivity of 85.7 wt% were obtained. Then, the catalytic dealkylation of heavier aromatics resulted in benzene-rich aromatics with 93.6 wt% benzene at 600 °C over Hβ catalyst. Finally, the cumene synthesis was performed by the aromatic alkylation, giving cumene selectivity of 91.6 C-mol% using the [bmim]Cl-2AlCl3 ionic liquid at room temperature for 15 min. Besides, adding a small amount of methanol to the feed can efficiently suppress the coke yield and enhance the aromatics yield. The proposed transformation potentially provides a useful route for production of cumene using renewable lignin.

Catalytic copyrolysis of cork oak and bio-oil distillation residue

The atmospheric distillation residue (ADR) of cork oak (CO) pyrolysis oil was used as the co-feeding material for the catalytic pyrolysis of CO over HZSM-5 catalysts to improve the formation of aromatic hydrocarbons. Although the non-catalytic copyrolysis of CO and ADR did not improve the formation of aromatic hydrocarbons, the catalytic copyrolysis of CO and ADR promoted the synergistic formation of aromatic hydrocarbons. HZSM-5(30), having a lower SiO2/Al2O3(30), showed better performance for the formation of aromatic hydrocarbons than HZSM-5(80) because of its higher acidity. The catalytic copyrolysis of CO and ADR also decreased the formation of coke. The largest quantity of aromatic hydrocarbons was obtained from the catalytic copyrolysis of CO and ADR over HZSM-5 (30) at 600°C, whereas the lowest coke yield was achieved at 700°C. When the catalyst to sample ratio was increased from 2:1 to 5:1, the synergistic formation of aromatic hydrocarbons was limited, resulting in a lower experimental yield of aromatic hydrocarbons than the theoretical yield. A lower coke yield was also achieved at a high catalyst to sample ratio (5:1).

Simulation of Lignite Pyrolysis and Gasification in Equilibrium

The development of lignite pyrolysis and gasification technology is helpful to improve the utilization value of lignite which is abundant in China. From the point of view of mass and energy balance, simulation of lignite pyrolysis and gasification process in equilibrium were conducted. The effects of moisture and ash in lignite and fixed carbon retention rate on reaction results were systematically discussed. The results were shown that yield and quality of gas and coke yield decreased with the increase of moisture in lignite. With the increase of ash content, the coke yields increased, the carbon content of coke decreased and the coke quality became poor. As the retention rate of fixed carbon increased from 50% to 100%, both coke yield and quality increased, the carbon content of coke rose from 47.04% to 94.09% and coke yield rose from 88.84% to 94.09%.

Study on the pyrolysis products of two different hardwood lignins in the presence of NiO contained-zeolites

Several NiO contained-zeolites (NiO/H-ZSM-5, NiO/H-BETA and NiO/H-Y) prepared by a mechanochemical dry milling (MCDM) were tested in the pyrolysis of two hardwood lignins: Eucalyptus (EUC) and a mixture of birch and aspen woods (BA). All prepared catalysts increased the yield of aromatics and decreased the yield of oxygenates as compared to non-catalytic experiment. The catalytic activity depends on the lignin type and zeolite structural features. The highest liquid and gas yields and lowest coke yield was obtained with NiO/H-Y which also increased the amounts of desirable and decreased undesirable pyrolysis products, giving a high concentration of hydrogen in the gaseous phase. The highest yield of aromatics and the lowest yield of oxygenates was obtained with NiO/H-ZSM-5. The obtained results showed that BA is a more suitable feedstock, producing higher yields of liquids and aromatics and lower yields of coke and oxygenates.

Effect of titanium additives on carbon anode reactivity

In order to ascertain the impact of titanium additives on carbon anode reactivity, different titanium content of carbon anodes were prepared with the single factor experimental method, and test its reactivity in CO2 and air atmosphere respectively. The micro structure of carbon anodes and pitch cokes were tested by XRD. The pyrolysis process of pitch was tested with the TG-DTG method. The results show that the residual rate and chalking rate of carbon anode can also be significantly improved by increasing titanium content. Titanium additives can refine the crystallite size of carbon anode, promote the asphalt carbonization. The titanium additives can increase the apparent activation energy and pitch coke yield of the pyrolysis process, when the titanium content is 1.5%, E a is 56.405 KJ/ mol, reaction order is 6.4, and the rate of pitch coke yield is 50.5%.

Influence of Riser Length of a Fluid Catalytic Cracking Pilot Plant on Catalyst Residence Time and Product Selectivity

The design and operation of a circulating fluid catalytic cracking (FCC) riser pilot plant is presented in the paper. Emphasis is given on the effect of riser length on feedstock conversion and coke yield. Riser lengths considered in the study were 1.46 and 9.95 m. The effect of catalyst residence time on feedstock conversion and coke yield at constant feed rate and reactor temperature (526 °C) is presented. The catalyst residence time varies with reactor volume and catalyst circulation rate. It is shown that for the same feed conversion, high catalyst circulation rates are required with the lower riser volume. Lower gasoline and lower coke yields are experimentally observed with the short riser length. A second-order kinetic model is used to correlate the variation in conversion and coke yield. Commercial results validate the pilot plant design as a useful tool for guiding commercial operations.

Exploring structural features of USY zeolite in the catalytic cracking of Jatropha Curcas L. seed oil towards higher gasoline/diesel yield and lower CO2 emission

Fluid catalytic cracking (FCC) is one of the main processes for gasoline/diesel production in the oil refining industry, it is a challenge to design catalyst towards high gasoline/diesel yield and low coke formation (i.e. lower CO2 emission). Take this into account, a set of ultra-stable Y (USY) zeolites with varied mesopore structures were designed and prepared for the catalytic cracking of a renewable oil source Jatropha Curcas L. seed oil (JCO). Reaction temperature and catalyst-to-oil (C/O) ratio were also investigated. It was found that, the catalyst with larger mesopore volume showed enhanced gasoline/diesel selectivities, higher olefins and lower aromatics yield in gasoline which gave rise to lower octane number. The catalyst with smaller mesopore volume enhanced hydride transfer activity, and gave the lowest coke yield and the highest octane number. To obtain high gasoline/diesel yield, large USY mesopore volume, low reaction temperature and low C/O ratio is required. With the aim of low coking and high octane gasoline, small USY mesopore volume, moderate reaction temperature (such as 480°C) and moderate C/O ratio (such as 6, wt/wt) is good choice for gasoline/diesel production via JCO catalytic cracking. As such, the catalyst prepared from mesoporous USY may find application for obtaining liquid hydrocarbon fuels from JCO.

Mathematical modelling of catalytic cracking riser reactor

The quality and the yield of gasoline and light olefins from the catalytic cracking unit depend on a broad range of operation indicators including the feedstock composition, the process conditions, the type and activity of the catalyst. The aim of research is to develop the mathematical model of catalytic cracking reactor on the basis of the formalized mechanism of hydrocarbon conversion taking into account the catalyst deactivation by coke. The experimental research of the feedstock and the product of catalytic cracking using a liquid-adsorption chromatography, gas chromatography–mass spectrometry, gas-liquid chromatography and the structural-group composition methods allowed determining the list of the catalytic cracking reactions. According to the discovered reactions, the thermodynamic analysis was performed using the methods of quantum chemistry. Thermo-gravimetric analysis of the coked catalyst allowed estimating the coke structure formed on the catalyst surface. The developed mathematical model allows to predict the product yields including the content of propane-propylene (PPF) and butane-butylene (BBF) fractions, the group composition and octane number of the gasoline depending on the feedstock composition, the process conditions of reactor-regenerator unit and the catalyst activity. As a result, the high theoretical yield of the gasoline (60.4 wt.%, RON 93.5) according to requirements for the content of olefins and benzene can be achieved at the process temperature of 533°C. This temperature is possible at the keeping the catalyst circulation ratio of 6.9 toncat/tonfeed at the catalyst flow temperature after regeneration (685.8°C) with the catalyst activity of 0.79 unit and the feedstock temperature (328.0°C). The yields of rich gas and coke are 24.0wt% and 4.5 wt%, the concentrations of PPF and BBF are 31.5 and 34.8 wt%.

Effect of mixing and vapor residence time on thermal cracking of bitumen in a Mechanically Fluidized Reactor

Fluid Coking™ is a non-catalytic carbon rejection process that is utilized to convert petroleum residues into more valuable light and middle distillates. In this process, heavy oil is sprayed into a fluidized bed of hot coke particles; the liquid heats up and undergoes endothermic thermal cracking to vapors, non-condensable gas and solid coke. This study shows that liquid distribution on hot coke particles affects the products yields and the liquid product quality. The vapor residence time also affects the products yields and the liquid product quality.The Mechanically Fluidized Reactor has been successfully developed and implemented for Fluid Coking applications. Multiple vapor phase residence times can be investigated simultaneously while reducing intrinsic errors present in a complex system such as coking. The impact of applied bed mixing and vapor phase cracking on Fluid Coking yields, as well as on product oil quality can, thus, be accurately evaluated.Applying mechanical mixing to the bed of coke particles results in better liquid distribution on coke particles and reduces coke yields. It also increases the yield of low viscosity, low molecular weight liquid at short vapor residence times. At long vapor phase residence times, however, vapors crack to gas, resulting in a concentration of higher viscosity, higher-molecular weight compounds in the liquid phase. The additional vapors that are produced in the bed thanks to enhanced mixing are more reactive and easily crack to gas at long vapor residence times. Realizing the full benefit of enhanced liquid distribution therefore requires minimization of the vapor residence time.

Effect of catalyst contact mode and gas atmosphere during catalytic pyrolysis of waste plastics

In the present study, polyethylene (PE), polypropylene (PP), polystyrene (PS) and polyethylene terephthalate (PET) were pyrolyzed using HZSM-5 zeolite in a tandem micro-pyrolyzer to investigate the effects of plastic type, catalyst and feedstock contact mode, as well as the type of carrier gas on product distribution. Among the four plastics, PS produced highest aromatic yields up to 85% whereas PE and PP mainly produced aliphatic hydrocarbons. In comparison to ex-situ pyrolysis, in-situ pyrolysis of the plastics produced more solid residue but also promoted the formation of aromatic hydrocarbons, except PS. For PS, ex-situ pyrolysis produced a higher yield of aromatics than in-situ pyrolysis, mostly contributed by high styrene yield. During in-situ pyrolysis, the catalyst reduced the decomposition temperatures of the plastics in the order of PE, PP, PS and PET from high to low. Hydrogen carrier gas reduced solid residue and also increased the selectivity of single ring aromatics in comparison to inert pyrolysis. Hydrogen was more beneficial to PS and PET than PE and PP in terms of reducing coke yield and increasing hydrocarbon yield. The present study also showed that catalytically co-pyrolyzing PS and PE, or PET and PE increases the yield of aromatics and reduces the yield of solid residue due to hydrogen transfer from PE to PS or PET and alkylation reactions among the plastic-derivatives.

CaO and isopropanol transesterify and crack triglycerides to isopropyl esters and green diesel

Fatty acid methyl esters (biodiesel) synthesized by transesterifying vegetable oil and fats with methanol are unsuitable for northern climates and alpine regions. Isopropyl esters derived from oil and isopropanol have superior cold flow properties and lower cloud point but reaction rates are slow in batch liquid phase processes. To accelerate the reaction rates by several orders of magnitude, we atomize mixtures of canola oil and isopropanol into a fluidized bed of CaO/Al2O3 operating at 450°C. Coke, CO, CO2, isopropyl esters and hydrocarbons in the C5-C19 range form at contact times less than 1s. A solenoid valve cycles the feed composition between oil/isopropanol and air, which maximizes the reaction rates and maintains a constant level of coke. The dwell time of the catalyst in oil/isopropanol and air is 2min. The coke yield ranges from 3.5% to 34% and the isopropyl esters yield varies from 2% to 31% for isopropanol:triglycerides molar ratios equal to 28, 35 and 51. The coke yield decreases with isopropanol:triglycerides molar ratios and O2 flow during the regeneration step while the isopropyl esters yield increases. The highest hydrocarbons yield was 42%.

Bio-oil production from sequential two-step catalytic fast microwave-assisted biomass pyrolysis

A sequential two-step fast microwave-assisted pyrolysis (fMAP) for high quality bio-oil production was investigated. In the process, fMAP was followed by catalytic cracking and upgrading using a packed bed catalyst reactor with HZSM-5 as the catalyst. Effects of pyrolysis temperature, catalyst loading, and catalyst bed temperature on the product distribution were investigated. Results showed that maximum bio-oil and aromatic hydrocarbons yields were obtained when pyrolysis temperature reached 550°C With the increase in the catalyst loading, the bio-oil yield decreased linearly while the aromatic hydrocarbons yield increased. The catalyst bed temperature also has a significant effect on the product chemical profiles. The aromatic hydrocarbons proportion of the bio-oil was found to increase with increasing catalyst bed temperature and reached its maximum of 26.20% at 425°C. In addition, coke yield increased with increasing catalyst to biomass ratio and decreasing catalyst bed temperature.

Behaviors of coking and radicals during reaction of volatiles generated from fixed-bed pyrolysis of a lignite and a subbituminous coal

The reaction of volatiles generated from coal during pyrolysis determines the yield and quality of products. To understand this reaction in detail particularly on the condensation reaction that forms coke, this paper studies the reaction of volatiles generated from a lignite and a subbituminous coal using a two-stage fix-bed reactor, with the first stage for coal pyrolysis and the second stage for reaction of volatiles. The yields of tar, gas and coke formed on the wall and presented in tar at a second-stage temperature range of 440–700°C and a residence time range of 1.5–6.9s are quantified. The concentration, g value and linewidth of radicals in tars, mainly in coke presented in tars, are measured by electron spin resonance (ESR) and discussed to explore the transformation of coke in structure. It is found that the reactions of volatiles generated from the lignite and the subbituminous coal are different in the temperature range studied but the structure of coke formed in these two volatiles differs mainly at temperatures lower than 600°C. The proportion of coke formed on the reactor wall is small at 440°C, but large at 650 and 700°C, close to 50% in 4.2s. The increase in concentration and decreases in g value and linewidth of radicals with increasing temperature over time suggest that the coke undergoes condensation, leading to loss in oxygen and increase in aromaticity.

Thermal Cracking Characteristics and Kinetics of Oil Sand Bitumen and Its SARA Fractions by TG–FTIR

The thermal cracking process of oil sand bitumen was investigated via studying the thermal cracking behaviors and online-gas-releasing characteristics of its SARA fractions (saturates, aromatics, resins, asphaltenes) by using TG–FTIR. The results showed that the asphaltenes contributed the most to coke formation of oil sad bitumen according to its largest weighted coke yield compared with that of others. The online FTIR analysis for the gases evolved from the thermal cracking process of oil sand bitumen and its SARA fractions indicated that the gaseous products in the main reaction stage showed more complex composition than those in the volatilization stage, and predominantly consisted of CO2, CO, methane, ethylene, other light alkanes and olefins, light aromatics, and hydrogen sulfide. Moreover, the release behaviors of typical gaseous products (CO2, CO, methane, ethylene, and light aromatics) for oil sand bitumen and its SARA fractions were different due to the different composition and structure. The t...

Kinetic modeling for catalytic cracking of pyrolysis oils with VGO in a FCC unit

A 5-lump kinetic model is proposed and validated to mean the catalytic cracking of pyrolysis oils with equilibrium fluid catalytic cracking catalyst (E-CAT) in an advanced cracking evaluation (ACE-R) FCC unit. In the present work a blend of fast pyrolysis oil (FPO) with vacuum gas oil (VGO); hydrodeoxygenated oil (HDO) with VGO; and VGO are used as raw materials. The kinetic modeling of lumped systems is carried out using a sequential approach. This approach decreased the number of simultaneous equations and hence estimated parameters. A 5-lump model, derived from 3- and 4-lumps, is used to represent the experimental data and used to estimate the kinetic constants and hence the yields of gasoline, LPG, dry gases, coke and feedstocks. In the sequential approach, the kinetic parameters have been estimated for a 3-lump model, and then the information is used to estimate the 4-lump parameters using a 4-lump model. Finally, the kinetic constants obtained from 4-lump are used to estimate the kinetic parameters for 5-lump model. A set of new experiments have been performed for catalytic cracking of pure VGO and coprocessing of FPO with VGO and HDO with VGO, by varying WHSV from 6 to 24h−1, at a constant reaction temperature and C/O ratio of 530°C and 5, respectively. The optimized process conditions were maintained to produce higher gasoline yield from VGO by catalytic cracking over equilibrium FCC catalyst. The process parameters obtained from lumped modeling, for catalytic cracking of pure VGO, have been compared with the kinetic parameters obtained from 4-lumped model available in the literature, and approximately 2% deviation were found in the products yields with respect to experimental data.

Catalytic Steam Cracking of Heavy Oil in the Presence of Molybdenum- and Nickel-Containing Nanodisperse Catalysts

The process of catalytic steam cracking (CSC) of heavy oil with high contents of sulfur (4.3 wt %) and high-boiling fractions (>500 °C) was studied in the presence of Mo- and Ni-containing nanodisperse catalysts under static conditions (autoclave) at 425 °C. Experimental studies of thermal and steam cracking, as well as of water-free catalytic cracking were carried out for comparison and identification of specific features of CSC. Dependencies of the composition and properties of the liquid and gaseous products on the process conditions, catalyst nature and the presence of water were determined. It was established that the application of Ni-catalysts for CSC causes an increase in the H : C ratio (1.69) in the liquid products against that of the other cracking processes, while the yields of coke and gaseous products increase that results in a decrease in the liquid product yield. With the Mo-catalyst, the produced low-viscous semisynthetic oil is characterized by a higher H : C ratio (1.70 wt %) and the lowest sulfur content (2.8 wt %) in the liquid products. XPS and HRTEM studies of the catalyst-containing solid residue (coke) revealed that in CSC nickel is as well-crystallized nanoparticles Ni 9 S 8 of 15–40 nm in size, and molybdenum as two phases MoO 2 and MoS 2 at the ratio depending on the conditions of heavy oil transformation. The data obtained demonstrate that CSC is a promising process of upgrading heavy oil.