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Pyrolysis gasoline (Py gas) is used as an octane enhancer of gasoline as it is rich in aromatics. However, removal of carcinogenic benzene from Py gas before blending with gasoline is important to meet the fuel specifications. The main focus of this present study is to determine the sorption kinetics and sorption isotherm of a fabricated insitu nano silver/polyvinyl alcohol (insitu nano Ag/PVA) membrane for pervaporative separation of benzene from model Py gas [mixture of benzene (aromatic) and 1-octene (aliphatic)]. The thickness, surface morphological structure (Atomic Force Microscopy) and degree of swelling of the fabricated membrane were determined. The highest pervaporation separation index achieved for the selected system was 14.259 kg/m2/h at 303 K, with 30 volume% benzene in model Py gas using a downstream pressure of 1 mm of Hg. The sorption kinetics of benzene in insitu nano Ag/PVA membrane obeyed the Elovich model while the Temkin isotherm model fitted the experimental data of the chosen system most accurately.

Pyrolysis gasoline (PyGas) is an unstable byproduct of the pyrolysis of naphtha and other hydrocarbons for the production of olefins. PyGas is stabilized by hydrogenation at mild conditions. The hydrogenation of styrene to ethylbenzene is considered a model test reaction for studying the selectivity of the catalysts because it has the slowest rate of conversion. The catalytic activity and selectivity of two bimetallic co-impregnated Pd–Ni catalysts supported on γ-alumina were assessed and compared to those of a commercial monometallic Pd catalyst (AXENS LD265). The laboratory-prepared catalysts had different metal content and Pd:Ni atomic ratios (1:1 and 1:7). Catalytic tests of selective hydrogenation of styrene to ethylbenzene were made in a batch stirred tank reactor and in a continuous fixed bed trickle bed reactor. The sulfur resistance of the bimetallic catalysts in semicontinuous condition, was assessed by means of the same operational conditions using thiophene as a model poison compound. The support, Pd–Ni co-impregnated catalysts and LD265 commercial catalysts were further characterized by N2 chemisorption, EPMA, OM, ICP elemental analysis, temperature programmed reduction, XPS and X-Ray diffraction. The results indicated the presence of different metal species: Pd0, Pdδ+, Ni0 and NiO. The lab-prepared bimetallic catalysts were found to be active for the selective hydrogenation of styrene (both in the batch and continuous system). During the continuous evaluations, the commercial LD265 catalyst had an intermediate activity level that lied between the values corresponding to the Pd–Ni bimetallic catalysts: PdNi(1:1) ≫ LD265 > PdNi(1:7). During the poison free semicontinuous evaluations, the pattern of conversion as a function of contact time of co-impregnated Pd–Ni catalysts are quite similar to that of commercial LD265 catalyst, though the catalytic activity is slightly better for PdNi(1:1). After 90 min of contact time the order of conversion was: PdNi(1:1) > LD265 > PdNi(1:7). On the other hand, during the poison semicontinuous tests (with 300 pp of thiophene), the initial reaction rates of the co-impregnated catalysts decreased, pointing a poisoning of the active sites by thiophene. PdNi(1:1) had higher initial reaction rate than PdNi(1:7) during poison free or poisoned in both conditions. PdNi(1:7) was more sulfur resistant than PdNi(1:1). The higher activity of the PdNi(1:1) catalyst was attributed to the presence of Pd0 and Pdn+/Nim+ species that favored respectively, the homolytic cleavage of the H–H bond and the adsorption of styrene. The higher sulfur resistance of the PdNi(1:7) catalyst would be associated with the higher Cl/Al surface atomic ratio in this catalyst (electronic effect) and the presence of electrodeficient species of Pd (Pdxδ+OyClz) that prevented the adsorption of thiophene by steric hindrance (geometrical effect of the large species) or by electronic effects. The authors are thankful to the Consejo Nacional de Investigaciones Científicas y Técnicas (National Council for Scientific and Technological Research, CONICET, Argentina), the Agencia Nacional de Promoción Científica y Tecnológica (National Agency of Scientific and Technological Promotion, ANPCyT, Argentina): PICT 2016-1453, PICT 2017-1250, and the Universidad Nacional del Litoral (National University of the Litoral): CAI+D 2016 N° 50420150100028LI for the financial support.

Waste tyre pyrolysis gasoline (WTPG) contain significant amount of aromatics such as benzene, toluene and xylenes (BTX) and thus provide a good source for these value-added chemicals. Separation of aromatics from aliphatic media as obtained in WTPG and naphtha is done commercially by solvent extraction using volatile organic solvents such as sulfolane (SUF), dimethylformamide (DMF) and diethylene glycol (DEG). The high cost of this state-of-the art separation method and environmental consideration have necessitated search for non-volatile and green solvent such as deep eutectic solvent (DES). This study intends to conduct a comparative evaluation of the performance of five solvents (SUF, DMF, DEG, and two DESs) for the extraction of BTX from WTPG. The two DESs are choline chloride/ethylene glycol (DES1) and choline chloride/glycerol (DES2) in molar ratios 1:2. An ASPEN plus simulation was carried out to generate liquid–liquid equilibria (LLE) data for the pseudo-ternary systems {WTPG + BTX + solvent (SUF/DMF/DEG/DES)}. Performance evaluation was based on selectivity (S) and solute (BTX) distribution coefficient (D). The propriety of the simulation protocol was validated using literature data. The results revealed the following maximum values of selectivity and distribution coefficients for the solvents: DES2 (S = 378.283, D = 0.656); DES1 (S = 77.364, D = 1.423); SUF (S = 55.371, D = 0.756); DMF (S = 25.336, D = 0.786) and DEG (S = 17.531, D = 0.793). The DESs therefore performed better than the organic solvents and can suitably replace same in the extraction of BTX from waste tyre pyrolysis gasoline.

Conversion of olefin-rich side streams of petroleum distillate cracking operations, pyrolysis gasoline (pygas), to hydrocarbon resins (HRs) represents a promising technology to upgrade the pygas by...

Summary The separation of benzene derivatives is energy intensive and laborious as a result of the overlapping physicochemical properties of these isomers. Here, we report on the separation of ortho-disubstituted benzene isomers using cucurbit[7]uril (CB7) aqueous solution with more than 92% selectivity. Thermodynamic and kinetic analysis proves that the ortho-isomer has stronger binding ability and slower decomplexation rate constant than the para- and meta-isomers when hosted by CB7. Optimized host-guest models indicate that the ortho-isomer with the smallest aspect ratio well matches the spherical interior cavity of CB7, resulting in highly stable complexes. Furthermore, laboratory scale-up experiments using commercial xylenes and C8 aromatic fraction of pyrolysis gasoline proved that CB7 is able to separate ortho-xylene (OX) with a remarkable selectivity of up to 83%. We believe that this work accentuates the role of molecular recognition studies using macrocyclic hosts to improve the quality and energy bill of critical industrial separations. Video Abstract Download : Download video (27MB)

A non-noble NiZn3/α-Al2O3 catalyst was prepared by a urea co-precipitation method, which showed good stability and high selectivity to styrene (ST) (92% selectivity at above 99% conversion of pheny...

Pyrolysis gasoline is applied to extract aromatics and to be gasoline blending stock, and its stabilization by catalytic hydrogenation under mild temperature is an important reaction in petrochemical field. Thereinto, styrene hydrogenation was considered as an example for the assessment of the catalysis performance for pyrolysis gasoline hydrogenation. In this work, the adsorption and diffusion of reactants (styrene and H) and the activation energy of styrene hydrogenation on Pd(111), Pd(100), and Pd(110) surfaces are discussed by density functional theory calculations. The adsorption energy of reactants (styrene and H) decreases in the order of Pd(110) > Pd(111) > Pd(100). The activation barriers with feasible intermediate products are investigated and the reaction activity based on the activation barriers follows the order of Pd(111) > Pd(100) > Pd(110). In addition, the diffusion barrier for styrene or H is smaller than the reaction barrier of styrene hydrogenation, indicating the true rate limiting step is the process of hydrogenation rather than the diffusion. Our results provide theoretical guide for the prepared catalyst with feasible surfaces by careful selection of preparation techniques in experiments.

Studies of the influence of acidity of alumina supports on properties of supported palladium particles were aimed at improving the activity of catalysts for hydrogenation of unsaturated hydrocarbons of pyrolysis gasoline fraction. High-disperse palladium particles demonstrate the high catalytic activity but their electron deficiency make them suffering from blocking with unsaturated hydrocarbons. NH3 TPR, TEM and XPS techniques were used for studying aluminopalladium catalysts; different acidities of the catalyst supports resulted from their chemical modification with various agents. The catalysts were tested for lab-scale hydrogenation of butadiene-1,3. Against the non-modified samples, the catalysts supported on modified alumina provided a lower conversion of butadiene-1,3 but a higher selectivity to butene-1. A higher conversion of butadiene-1,3 at the preserved selectivity to butene-1 and butane was observed in the presence of the catalyst supported on base-modified alumina.

A gasolina de pirólise pesada, também conhecida por PYGAS pesada (do acrônimo em inglês “pyrolysis gasoline”), é uma mistura de hidrocarbonetos majoritariamente maiores que 8 carbonos, obtida a partir do fracionamento dos produtos obtidos a partir do craqueamento da nafta. PYGAS pesada tem seu controle no processo produtivo realizado por análises de destilação, segundo o ASTM D86, e composição por cromatografia em fase gasosa com uso de detector de ionização por chama. Uma vez que o volume de amostra para a análise de destilação é muito superior ao de cromatografia (100:1) e existe o risco de princípio de incêndio em destilações se houver vidraria trincada ou montagem inadequada do sistema, foi desenvolvido o trabalho de predizer os valores de destilação de PYGAS pesada a partir dos resultados de cromatografia em fase gasosa, com aplicação de calibração multivariada. Neste trabalho foram aplicadas Regressão Linear Múltipla (MLR) e Regressão pelo Método dos Quadrados Mínimos Parciais (PLS), comparando os resultados obtidos entre os dois métodos de regressão e com os valores de referência de repetibilidade e reprodutibilidade do ASTM D86 de 2018. Para os pontos de destilação 20%, 30%, 40%, 50%, 60%, 70%, 80% e 90%, tanto no MLR quanto no PLS, os valores de erro médio quadrático da predição (RMSEP) ficaram inferiores 1 ℃ e r maior que 0,94 e os valores de erro obtidos ficaram dentro do intervalo de reprodutibilidade para cada ponto. Para o Ponto Inicial de Ebulição, o RMSEP foi de 7,5 ℃ para o MLR e 9,9 ℃ para o PLS, enquanto os valores de r foram de 0,4 e -0,1, respectivamente. O Ponto Inicial de Ebulição predito obteve resultados insatisfatórios quando comparado aos valores de repetibilidade e reprodutibilidade da referência. Para destilação 5%, os RMSEPs foram de 2,4 ℃ e 3,1 ℃ e os valores de r foram de 0,78 e 0,73, respectivamente para MLR e PLS. O ponto de destilação 10% teve valores semelhantes aos pontos 20% e 30% no MLR, porém no PLS os resultados ficaram um pouco diferentes, com RMSEP de 1,5 ℃ e r de 0,8. No comparativo com o ASTM D86, com resultados foram satisfatórios. Para os pontos de destilação 95% e Ponto Final de Ebulição, os valores de RMSEP foram entre 1,5 ℃ e 2,5 ℃ e os valores de r foram superiores a 0,94 nos dois métodos, bem como os erros de cada ponto ficaram dentro do intervalo de reprodutibilidade do ASTM D86. O resíduo de destilação não tem valores de repetibilidade ou reprodutibilidade na referência, porém ficou evidente a impossibilidade do MLR e do PLS de predizerem valores menores 0,5% v/v, o que pode ser explicado pela etapa manual inerente a esta leitura. Comparativamente, os valores de MLR se apresentaram semelhantes ou melhores que PLS, porém nenhum dos dois métodos de calibração multivariada foi capaz de predizer os valores de Ponto Inicial de Ebulição da destilação de PYGAS pesada. The heavy pyrolysis gasoline, also known as heavy PYGAS, is a mixture of hydrocarbons mostly composed by more than 8 carbons, obtained through the fractionation of the products obtained in the fractionation of naphtha. The control of heavy PYGAS production process is developed through distillation analysis, according to ASTM D86, and chromatography composition through flame ionization detector usage. Since the sample volume is considerably higher compared to the chromatography volume (100:1), and there is a risk of fire onset in distillation if the glassware is cracked or if the system is improperly assembled, a work to predict the values of heavy PYGAS distillation was developed from the gas chromatography results, with multivariate calibration application. In this work, Multiple Linear Regression (MLR) and Partial Least Square (PLS) were applied to compare the results obtained between both methods and the reference values of ASTM D86 from 2018 repeatability and reproducibility. For the distillation values of 20%, 30%, 40%, 50%, 60%, 70%, 80% and 90%, both for MLR and PLS, the root mean square error of prediction (RMSEP) values were 1 ºC inferior, presented a r higher than 0.94 and the error values obtained were in the reproducibility interval for each point. For Initial Boiling Point, the RMSEP value was 7.5 ºC to the MLR and 9.9 ºC to PLS, whilst the r values were 0.4 and -0.1, respectively. For a 5% distillation, the RMSEPs were 2.4 ºC and 3.1 ºC and the r value were 0.78 and 0.73, respectively for MLR and PLS. The 10% distillation point reached similar values to the 20% and 30% points in MLR, however, the PLS results were slightly different, with RMSEP of 1.5 ºC and r value of 0.8. According to the results comparison with the ASTM D86, the results were satisfactory. For the 95% distillation points and Final Boiling Point, the RMSEP were 1.5 ºC and 2.5 ºC, the r values were higher than 0.94 for both methods, as well as the errors for each point, which were in the ASTM D86 repeatability range. The distillation residue did not present reproducibility or repeatability values in the reference, yet the impossibility of MLR and PLS predictability for values inferior than 0.5% v/v became evident, which can be explained by the inherent manual step of this reading. In comparison, the MLR values were presented in similarity, or better, with the PLS, but none of the multivariate calibration methods were capable to predict the Initial Boiling Point distillation values for the heavy PYGAS.

Durene is obtained from complex mixtures of aromatics from oil-refining processes (“reformate gasoline”) or from cracking processes in olefin manufacture (“pyrolysis gasoline”). More recently the methanol to gasoline process, which went on-stream in New Zealand in 1986, has been found to produce large quantities of durene as a by-product. It is estimated that as much as 60 million pounds of durene may be isolated from this source. Normally, one of the disadvantages of homogeneous catalysis is the separation of the products from the catalyst. With durene (as well as with a number of other methylaromatic compounds) this is not a problem. Upon cooling to room temperature, 93% to 95% of the pyromellitic acid precipitates in the reactor and is removed by filtration. Zirconium is a remarkable substance in autoxidations since, with the proper experimental conditions, it results in much higher activity and yields to desired products.

Styrene made from raw pyrolysis gasoline contains sulfur impurities such as 2-vinyl thiophene. We prepared three sorbents, namely, AgY, AgNO3/γ-Al2O3, and AgNO3/SiO2, to remove 2-vinyl thiophene from styrene. All three sorbents showed good desulfurization performance while AgY had the highest sulfur capacity. This was due to π-complexation, where the silver cations in AgY can bond 2-vinyl thiophene more strongly than styrene. The desulfurization capacity of AgNO3/γ-Al2O3 was better than that of AgNO3/SiO2 when taking its lower silver loading and surface area into consideration. Moreover, prewetting the sorbents was critical for desulfurization but can cause polymerization. Comparison between desulfurization of gasoline and styrene, using AgY, shows its superior sulfur adsorption capacity for desulfurization of styrene. A possible mechanism on the preferential adsorption for 2-vinyl thiophene over styrene by Ag+ is given via the comparison between thiophene and benzene.

Selective hydrogenation of linear alkenes in the presence of aromatics is desired to prevent gum formation in pyrolysis gasoline (PYGAS) upgrading. To examine the competitive hydrogenation between linear alkenes and aromatics, we investigate ethylene and benzene competitive hydrogenation on different catalysts. Through density functional theory (DFT) calculations, we show the adsorption energies of benzene and ethylene correlate on monometallic close-packed surfaces, with benzene binding stronger for the same C to surface metal atom ratio. DFT calculations demonstrate Bronsted–Evans–Polanyi and scaling relationships hold, and these are fed into microkinetic modeling to predict the rate of ethylene and benzene hydrogenation with only ethylene and hydrogen binding energies as the surface descriptors. Due to stronger binding, benzene adsorption will dominate the surface. Higher barriers for benzene hydrogenation versus ethylene hydrogenation lead to benzene poisoning at temperatures at which ethylene hydroge...

A graphical method is proposed to optimize the two-stage pyrolysis gasoline (pygas) hydrogenation reactor based on the hydrogen network integration. The relation between the hydrogen utility adjustment (HUA) and the parameters of pyrolysis gasoline (pygas) hydrogenation reactor in different situations is deduced based on the hydrogenation reaction kinetics and integration of hydrogen network, and the variation of HUA with temperature is analyzed with the proposed quantitative diagrams. Based on this method, the temperature of first-stage and second-stage reactors can be optimized separately or simultaneously, and the product quality can be taken into consideration to make the results more accurate. The case study shows that this method can identify the optimal reaction temperature in each stage reactor accurately under different conditions and can give significant guidance for pygas hydrogenation unit design and improvement.

Energy optimization of second distillation tower of a pyrolysis gasoline hydrogenation unit has been studied by the thermal cycle of vapor recompression method. The mentioned cycle is connected to the second distillation tower of the stabilizer of pyrolysis gasoline, and the results are found promising. The composite pinch curve for both the current and the optimized methods are shown. Moreover, an increase in the heat transfer rate in heat exchanger E-1014 causes energy recovery in reboiler. According to simulation results, by vapor recompression to 1970 kPa and using this heat source for thermal integration, condenser and reboiler’s energies are decreased by 56.93 and 30.4 percentage, respectively.

Fuel quality control is mandatory and has different specifications in each country. For this, the percentage value of evaporation distillation represents a key parameter to show that the fuel meets current regulations. Distillation, however, is a very unsafe method that exposes the analyst to vapor and risk of fire. In order to find some alternative to distillation method without an increase in cost, this work proposes the use of a hydrocarbon composition of heavy PYGAS that includes aromatic and non-aromatic compounds estimated by gas chromatography to predict the percentages evaporated during distillation (initial boiling point – IBP, 5%, 10%, 20%, 30%, 40, 50%, 60%, 70%, 80%, 90%, 95%, final boiling point - FBP, and residue) curve by means of partial least squares regression. The proposed method was useful to achieve accuracy compatible with current specifications. The relative prediction error (REP) for fit and validation was between 0.43 and 2.32; 0.58 and 2.42 respectively, except for IBP and FBP, which presented higher values. When the models were applied to an external set, the same level of accuracy was achieved which confirms the predictive capacity of the models. Therefore, this work shows that it is possible to exploit data from the standard chromatographic procedure at large petrochemical plants in order to feed other quality parameters such as distillation. Last, but not least, the proposed approach is environmentally friendly, in line with green chemistry and has potential to increase profits if properly used.

The ionic liquids (ILs) have been widely studied as potential replacements of conventional solvents in the extraction of aromatic hydrocarbons from alkanes. However, most of the literature is focused in obtaining liquid-liquid equilibria experimental data without studying the complete extraction and IL regeneration process. In this paper, a computer-aided methodology combining COSMO-based molecular simulations and Aspen Plus process simulations has been used to study the extraction process of aromatic hydrocarbons from pyrolysis gasoline employing a binary mixture of 1-ethyl-4-methylpyridinium bis(trifluoromethylsulfonyl)imide ([4empy][NTf2]) and the 1-ethyl-3-methylimidazolium dicyanamide ([emim][DCA]) ILs as solvent. An extensive comparison (more than 600 points) between experimental data and the predictions obtained by the COSMO-based thermodynamic model of liquid–liquid and vapor–liquid equilibria and ILs physical properties was made for validation purposes. Process simulations were performed in three system configurations: with one, two, or three flash distillations in the IL recovery section. The potential advantage of using binary IL-IL mixture as extracting solvent was studied in the whole range of composition. The configuration with three flash distillations and the binary IL-IL mixture with a 75% of [4empy][NTf2] were selected as the optimal conditions to increase aromatic recovery and purity, improving the separation performance respect to the neat ILs, The authors are grateful to Ministerio de Economía y Competitividad (MINECO) of Spain for financial support of Projects CTQ2014-52288-R and CTQ2014–53655-R and to Comunidad Autónoma de Madrid for the Project S2013/MAE-2800. Noemí Delgado-Mellado also thanks MINECO for awarding them an FPI grant (Reference BES–2015–072855) and Marcos Larriba also thanks MINECO for awarding him a Juan de la Cierva-Formación Contract (Reference FJCI-2015-25343). Pablo Navarro thanks Fundação para a Ciência e a Tecnologia for awarding him a postdoctoral grant (Reference SFRH/BPD/117084/2016).

To obtain aromatic compounds from a crude mixture such as reformate or pyrolysis gasoline, three different processes are simulated with the realistic composition of reformate and product specification. Simulations were performed by Aspen Plus supported with COSMO-RS method to predict the physical and thermodynamic properties of ionic liquid. Furthermore, utility analysis and economic evaluation are presented. Conventionally, aromatic compounds are extracted from a crude mixture either by extraction or by extractive distillation using a solvent such as sulfolane and separated by a series of distillation columns. In this study, the sulfolane-based commercial process is first introduced, and two novel processes that use 4-methyl-N-butylpyridinium tetrafluoroborate ionic liquid as solvent are proposed. The second process shows that energy consumption has successfully decreased, but the high price of ionic liquid offset the cost advantage. The third process is therefore proposed to reduce the amount of ionic l...

The pyrolysis gasoline is one of the main sources of aromatic hydrocarbons as a result of their high content in these compounds. Organic solvents such as sulfolane are currently employed in the extraction of aromatic but the ionic liquids (ILs) have been recently proposed as potential replacement. In this work, we have studied the use of the bis(1-ethyl-3-methylimidazolium) tetrathiocyanatocobaltate ([emim]2[Co(SCN)4]) and bis(1-butyl-3-methylimidazolium) tetrathiocyanatocobaltate ([bmim]2[Co(SCN)4]) ILs in the extraction of aromatic hydrocarbons from pyrolysis gasoline. The extractive properties of both tetrathiocyanatocobaltate-based ILs were compared to those of other promising ILs and sulfolane, showing the highest values. To perform the simulation of the whole process, we have experimentally studied the liquid-liquid extraction of aromatics from pyrolysis gasoline and the recovery of the extracted hydrocarbons from the ILs. In addition, a thermophysical characterization of the ionic solvents was performed measuring their densities, viscosities, thermal stabilities, maximum operation temperatures, and specific heats. Employing the experimental data, the extractor was simulated using the Kremser equation whereas the recovery section formed by flash distillation units was simulated using a new algorithm specifically design to the case of a high concentration of non-volatile compounds.

Reformer and pyrolysis gasolines are the main benzene, toluene, ethylbenzene, and xylenes (BTEX) sources. In our previous works, the aromatic extraction from reformer and pyrolysis gasoline models formed by three n-alkanes, benzene, toluene, and xylenes were studied using a binary mixture of ionic liquids (ILs). The results showed that the {[4empy][Tf2N] + [emim][DCA]} IL mixture with [4empy][Tf2N] mole fraction of 0.3 required a comparable countercurrent extraction column to that of the Sulfolane process, and extracted BTEX had quite a higher purity using the IL mixture in the three gasoline models analyzed. Here, we have studied the hydrocarbon recovery from the extract stream obtained in these works. For that purpose, the vapor–liquid equilibria (VLE) data involving the extracted hydrocarbons and the IL mixed solvent have been determined by the headspace–gas chromatography (HS–GC) technique for several temperatures. Afterward, the simulation of two new process configurations based on adiabatic flash di...

In most ethylene plants, the caustic sections suffer from red-oils formation which results from the polyaldol condensation of some oxygenate species in basic media. These red-oils lead to solid material deposition which is generically referred to as fouling and which can cause severe energy losses or operational issues. This specific red-oil fouling can be successfully mitigated by regularly washing the caustic scrubber with a hydrocarbon washing stream which acts as a solvent. However, such washing streams can be further rerouted to the quench water system, increasing the risk of emulsion formation due to its amphiphilic components, i.e., red-oils, compromising the safe operation of the whole plant. The complexity of red-oil structures renders its analysis and characterization challenging. Consequently, there has been no study showing the effect of the type of hydrocarbon wash on the red-oils structure and its potential emulsifying properties. This study describes an in-house developed analytical technique based on UPLC-High resolution QTOF which allows characterizing hydrocarbon streams with complex mixtures of oxygenated species. This method has been successfully applied to monitor red-oil structures during a plant trial where Pyrolysis Gasoline and Toluene-Xylene hydrocarbon washes were successively applied. The data revealed that reactive compounds from the Pyrolysis Gasoline react with the polyaldol species, likely through a Diels–Alder mechanism, thus increasing the diene adduct concentration in the red-oil. It was further found that toluene-xylene washes hindered the emulsifying properties of the red-oils more effectively than Pyrolysis Gasoline washes, in that they could best inhibit the formation of polyaldols adducts.

The valorization of light cycle oil (LCO) and pyrolysis gasoline (i.e. Pygas) via ring opening reaction (ROR) presents an industrial opportunity for improving the cetane and octane properties of diesel and gasoline fuels, respectively. One major challenge is the design of suitable catalysts that are optimally active, selective and very stable. The paper therefore covered a review of critical studies conducted with the view of achieving these properties. Catalysts based on metals-promoted oxides, carbides, sulfides and modified-zeolites have so far been investigated. The paper therefore discusses the progress made and identified issues for further investigations. Issues such as the role of catalyst compositions, acidity, topology and textural properties on the activity–stability properties were examined.