Gasoline Range Hydrocarbons Research Articles

Upcycling of post-industrial multilayer plastic packaging waste through gasoline-equivalent hydrocarbon-targeted pyrolysis by an environmentally friendly catalyst

This study’s novelty lies in investigating the performance of calcined cement kiln dust (CCKD) as a new, low-cost catalyst in the flash pyrolysis of EVOH-containing multilayer plastic packaging waste (MLPW). An analytical pyrolyzer, connected with gas chromatographic separation and mass spectrometry detection (Py–GC/MS), was employed to investigate the catalytic pyrolysis of MLPW. Py-GC/MS experiments have shown that condensable volatiles from catalytic pyrolysis of MLPW exhibit higher yields of aromatics (24.7 %) and cyclic aliphatic compounds (26.3 %). The catalytic pyrolysis of MLPW yields C5–C12 hydrocarbons (76.2 %), while the non-catalytic conversion yields C8–C24 hydrocarbons (95.4 %). These results underscore the efficacy of catalytic pyrolysis in recovering gasoline-range hydrocarbons from MLPW, selectively enhancing the yield of cyclic aliphatics and aromatic compounds. Thus, within the circular economy’s horizon, flash pyrolysis can be scaled up to process large amounts of MLPW using CCKD as a low-cost catalyst, converting MLPW into a potential gasoline-range transportation fuel.

Production of Branched Alkanes by Upcycling of Waste Polyethylene over Controlled Acid Sites of SO4/ZrO2-Al2O3 Catalyst.

Branched alkanes, which enhance the octane number of gasoline, can be produced from waste polyethylene. However, achieving highly selective production of branched alkanes presents a significant challenge in the upcycling of waste polyethylene, and the maximum selectivity for branched alkanes reported up to date is about 70%. Here, we report a one-pot process to convert polyethylene into gasoline-range hydrocarbons (C4-C13) with yield of 73.3% over SO42-ZrO2-Al2O3 catalyst at 280 °C. The proportion of branched alkanes reaches 90.1% within the C4-C13 fraction. Incorporation of sulfate group endows the catalyst with strong Lewis acid sites and weak and moderate Brønsted acid sites. In situ X-ray absorption, in situ infrared spectroscopy, in situ small angle neutron scattering, and DFT calculations reveal that polyethylene activation occurs through the synergy between sulfate groups and strong Lewis acid sites (Zr sites). The weak and moderate Brønsted acid sites preferentially catalyze the isomerization and type A β-scission processes, which favors the formation of branched alkanes, while suppressing competing reactions that produce straight-chain alkanes.

New Insights for High-Throughput CO2 Hydrogenation to High-Quality Fuel.

In the case of CO2 thermal-catalytic hydrogenation, highly selective olefin generation and subsequent olefin secondary reactions to fuel hydrocarbons in an ultra-short residence time is a huge challenge, especially under industrially feasible conditions. Here, we report a pioneering synthetic process that achieves selective production of high-volume commercial gasoline with the assistance of fast response mechanism. In situ experiments and DFT calculations demonstrate that the designed NaFeGaZr presents exceptional carbiding prowess, and swiftly forms carbides even at extremely brief gas residence times, facilitating olefin production. The created successive hollow zeolite HZSM-5 further reinforces aromatization of olefin diffused from NaFeGaZr via optimized mass transfer in the hollow channel of zeolite. Benefiting from its rapid response mechanism within the multifunctional catalytic system, this catalyst effectively prevents the excessive hydrogenation of intermediates and controls the swift conversion of intermediates into aromatics, even in high-throughput settings. This enables a rapid one-step synthesis of high-quality gasoline-range hydrocarbons without any post-treatment, with high commercial product compatibility and space-time yield up to 0.9 kggasoline ⋅ kgcat -1 ⋅ h-1. These findings from the current work can provide a shed for the preparation of efficient catalysts and in-depth understanding of C1 catalysis in industrial level.

Performance of Pd and Pt noble metal impregnated on Lapindo mud-based mesoporous silica on hydrotreatment of waste cooking oil into biogasoline

In the present work, an alternative pathway to produce liquid biogasoline with low aromatic value was done via catalytic hydrotreatment of waste cooking oil (WCO) over noble metal (Pd and Pt) loaded on cost-effective mesoporous silica (MS) synthesized from Lapindo mud. The implementation of 1.82 and 1.53 SiO2/CTAB (cetyltrimethylammonium bromide) weight ratio successfully produced Lp-MS with average diameters of 5.1 (Lp-MS1) and 4.7 nm (Lp-MS2), respectively. The XRD analysis showed a better dispersion for Pt with a considerably smaller particle size and TEM image revealed that while Pt was shown to occupy both external and internal surface of Lp-MS1, Pd was only present on the outer part of Lp-MS2. During the hydrotreatment of WCO using a semi-batch reactor, Pd/Lp-MS2 exhibited a superior deoxygenation and hydrogenation capacity than Pt/Lp-MS1 by generating over 60.9% liquid biofuel with 86.75% selectivity towards gasoline-range hydrocarbon. The liquid product obtained from the catalytic hydrotreatment contained very low aromatic compound (<4%) which was known to be responsible in the emission of harmful gas during fuel combustion. This result can be maintained for at least 4 consecutive runs. This study offers another efficient pathway to produce a cleaner source of energy in the form of biogasoline fuel.

Single-step and stepwise pyrolysis to recover high-value chemicals from mixed polyolefins and polylactide

Biodegradable plastics are increasingly utilized due to environmental concerns but are typically disposed of together with conventional plastics. Valuable chemicals could be recovered from waste plastics by chemical recycling, but the mixing of different types of waste plastic affects the efficiency of the process. In this study, high-value chemicals were produced from a mixture of polyolefins and biodegradable polylactide by single and stepwise pyrolysis processes. The pyrolysis of polyolefins yielded fuel-like hydrocarbons, and the pyrolysis of polylactide yielded lactide and lactic acid. In the stepwise process, oxygenated compounds were only produced in the low-temperature step, and fuel-like hydrocarbons produced in the high-temperature step were not contaminated by oxygenated compounds. The influence of different catalysts on yields was investigated in the single-step and stepwise processes. The yield and selectivity of each product were significantly influenced by the type of catalyst and the composition of the plastic feedstock. Using a mixed feedstock of polyolefins and polylactide, low-temperature pyrolysis with a zeolite LTA catalyst favored the formation of lactide and lactic acid, while diesel-range hydrocarbons were obtained in the second step at a higher temperature. Aromatic and gasoline-range hydrocarbons were preferably produced from the single-step pyrolysis of polyolefins with spent FCC catalyst.

Catalytic flash pyrolysis for recovery of gasoline-range hydrocarbons from electric cable residue using a low-cost natural catalyst: An analytical Py–GC/MS study

This investigation’s novelty and objective reside in exploring catalytic flash pyrolysis of cross-linked polyethylene (XLPE) plastic residue in the presence of kaolin, with the perspective of achieving sustainable production of gasoline-range hydrocarbons. Through proximate analysis, thermogravimetric analysis, and heating value determination, this study also assessed the energy-related characteristics of cross-linked polyethylene plastic residue, revealing its potential as an energy source (44.58 MJ kg−1) and suitable raw material for pyrolysis due to its low ash content and high volatile matter content. To understand the performance as a low-cost catalyst in the flash pyrolysis of cross-linked polyethylene plastic residue, natural kaolin was subjected to characterization through thermogravimetric analysis, X-ray diffractometry (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray fluorescence (XRF). Cross-linked polyethylene plastic residue was subjected to thermal and catalytic pyrolysis in an analytical microreactor coupled to gas chromatography-mass spectrometry (Py–GC/MS system), operating at 500 °C, to characterize the distribution and composition of volatile reaction products. The application of kaolin as a catalyst resulted in a decline of the relative concentration of hydrocarbons in the diesel range (C8-C24) from approximately 87 % to 28 %, and a reduction in lubricating oils (C14-C50) from about 70 % to 13 %, while concomitantly increasing the relative concentration of lighter hydrocarbons in the gasoline range (C8-C12) from around 28 % to 87 %. Therefore, catalytic flash pyrolysis offers the potential for converting this plastic waste into a new and abundant chemical source of gasoline-range hydrocarbons. This process can be deemed viable and sustainable for managing and valorizing cross-linked polyethylene plastic residue.

Enhanced catalytic activity of Sm/CeO2 to produce gasoline-range hydrocarbons from pyrolysis of spent coffee grounds

This study investigated the application of Sm/CeO2 catalyst for hydrocarbon production in catalytic pyrolysis (CP) of spent coffee grounds (SCGs). A temperature range of 450–750 °C and catalyst/biomass (C/B) ratios of 0.5–4 were employed in the CP. The results showed that an increase in pyrolysis temperature consistently increased the quantity of hydrocarbons and considerably decreased the oxygenated compounds like acids and phenols. At temperatures of 450 and 550 °C, C/B ratios of 2 or 1 generated the maximum amount of hydrocarbons. At 650 and 750 °C temperatures, C/B ratios of 0.5 and 1 were capable to achieve a higher content of hydrocarbons in bio-oils, suggesting the synergistic effect of temperature and catalyst activity. The hydrocarbons in bio-oils were found in the gasoline range, mainly containing benzene, toluene, ethylbenzene, xylene (BTEX), olefins, and cycloalkenes. Primary reactions involved to convert oxygenated compounds into hydrocarbons were dehydration, decarboxylation, decarbonylation, dehydrogenation, isomerization, and aromatization reactions.

Geochemistry and Petrology of Reservoir and Cap Rocks in Zar-3 Pilot CO2 Storage Complex, SE Czechia

The planned pilot CO2 storage Zar-3 is an oil field with a gas cap in the final production stage in the SE Czech Republic. It is composed of a dolomite Jurassic reservoir sealed by three different formations that differ significantly in lithology. Previous studies left open questions on the nature of pore space and connectivity and the quality of the seal in the future CO2 storage complex. Microscopic petrography of the reservoir suggests dolomitisation in shallow water followed by karstification and brecciation with fracture-correct-dominated porosity. The seal horizons have porosity limited to the micro- and nanoscales. The oil consists of significantly biodegraded black oil of Jurassic origin mixed with less biodegraded gasoline-range hydrocarbons. Biomarkers in the caprock bitumens trapped in nanopores show a genetic relationship to the reservoir oil. Gas in the not yet fully depleted gas cap of the field is of thermogenic origin with no contribution of microbial methane. The formation water has total dissolved solids typical of isolated brines not diluted by infiltrated fresh water. The geochemical characteristics of the storage system together with the fact that the initial oil column is about 105 m tall with another 150 m of gas cap suggest that the seals are efficient and the Zar-3 future storage complex is tight and safe.

Porous Carbon-Supported Cobalt Catalyst for CO Hydrogenation to Gasoline Range Hydrocarbons

Porous Carbon-Supported Cobalt Catalyst for CO Hydrogenation to Gasoline Range Hydrocarbons

Partitioning of Per‐ and Polyfluoroalkyl Substances to Weathered Light Non‐Aqueous Phase Liquid

AbstractPer‐ and polyfluoroalkyl substances (PFAS) and weathered petroleum hydrocarbons can be co‐contaminants at sites where aqueous film‐forming foam (AFFF) was used to extinguish high‐temperature petroleum fires. Here, we report on the partitioning of six PFAS between water and a weathered diesel and gasoline range hydrocarbon light non‐aqueous phase liquid (LNAPL) collected from the subsurface of a decommissioned refinery. Results showed that both the structural features of PFAS and the characteristics of LNAPL exhibited significant impacts on the magnitude of PFAS partitioned to the LNAPL. The LNAPL–water partition coefficients (Kl) of PFOA and PFOS to the weathered LNAPL measured in this work were nearly or more than 10 times greater than Kl values calculated by others for partitioning to single‐component, unweathered NAPLs, indicating that laboratory studies evaluating LNAPL–water partitioning studies using single component NAPLs can largely underestimate the Kl expected to be encountered at contaminated AFFF sites. Interactions with LNAPL can be important controllers of PFAS fate and transport, and the Kl values estimated in this work suggest that LNAPL could be a significant transport sink for PFAS in the field. Results from this work suggest that PFAS partitioning to weathered LNAPL is an important process to be considered when designing remedial strategies, particularly those incorporating monitored natural attenuation or natural source zone depletion.

Exploring the potential of clay catalysts in catalytic pyrolysis of mixed plastic waste for fuel and energy recovery

Developing low-cost and high-activity catalysts is one of the keys to promoting the catalytic pyrolysis of waste plastics to fuels for plastic recycling. This work studied the effect of clay as the catalyst on mixed plastic pyrolysis for fuel and energy recovery. Four kinds of clay, including nanoclay, montmorillonite, kaolin, and hydrotalcite, were used as catalysts for the pyrolysis of mixed plastic consisted of polyethylene terephthalate, polystyrene, polypropylene, low-density polyethylene, and high-density polyethylene. The product yield and distribution varied with different clay in pyrolysis. The highest yield of oil was 71.0 % when using montmorillonite as the catalyst. While the highest contents of gasoline range hydrocarbons and diesel range hydrocarbons in the oil were achieved when using kaolin and nanoclay, respectively as catalysts. For the gas products, the CO, C2H4, C2H6, C3H6, and C4H10 increased with decreased CO2 in the gaseous products when using clay as catalysts. In general, the mild acidity of clay catalyst was essential to improve the oil yields and the proportion of the gasoline or diesel range fuels in the catalytic pyrolysis of mixed plastic waste.

One-Step Conversion of n-Butanol to Aromatics-free Gasoline over the HZSM-5 Catalyst: Effect of Pressure, Catalyst Deactivation, and Fuel Properties as a Gasoline.

Sustainable production of gasoline-range hydrocarbon fuels from biomass is critical in evading the upgradation of combustion engine infrastructures. The present work focuses on the selective transformation of n-butanol to gasoline-range hydrocarbons free from aromatics in a single step. Conversion of n-butanol was carried out in a down-flow fixed-bed reactor with the capability to operate at high pressures using the HZSM-5 catalyst. The selective transformation of n-butanol was carried out for a wide range of temperatures (523-563 K), pressures (1-40 bar), and weight hourly space velocities (0.75-14.96 h-1) to obtain the optimum operating conditions for the maximum yields of gasoline range (C5-C12) hydrocarbons. A C5-C12 hydrocarbons selectivity of ∼80% was achieved, with ∼11% and 9% selectivity to C3-C4 paraffin and C3-C4 olefins, respectively, under optimum operating conditions of 543 K, 0.75 h-1, and 20 bar. The hydrocarbon (C5-C12) product mixture was free from aromatics and primarily olefinic in nature. The distribution of these C5-C12 hydrocarbons depends strongly on the reaction pressure, temperature, and WHSV. These olefins were further hydrogenated to paraffins using a Ni/SiO2 catalyst. The fuel properties and distillation characteristics of virgin and hydrogenated hydrocarbons were evaluated and compared with those of gasoline to understand their suitability as a transportation fuel in an unmodified combustion engine. The present work further delineates the catalyst stability study for a long time-on-stream (TOS) and extensive characterization of spent catalysts to understand the nature of catalyst deactivation.

Investigating the role of promoters (Ga, Nb, La, and Mg) on In2O3-based catalysts: Advancing on CO2 hydrogenation to C5+ hydrocarbons

Utilizing carbon dioxide (CO2) as a sustainable feedstock for producing chemicals and renewable fuels is of paramount importance, particularly in the face of intricate climate changes. However, despite significant CO2 hydrogenation advancements to different C1 chemicals, synthesizing value-added products with more carbons remains challenging due to the extreme inertness of CO2 and the high C–C coupling barrier. Thus, herein, we introduce a series of In2O3-promoted catalysts with different basicities (Ga/In2O3, Nb/In2O3, La/In2O3, and Mg/In2O3) to evaluate their role in the production of methanol that was used as an intermediate for the production of gasoline-range hydrocarbons after going through an HZSM-5 zeolite bed. While oxygen vacancies on the catalysts' surfaces are undoubtedly crucial, we have observed that the basicity of the promoters plays a significant role in their effectiveness. Interestingly, there seems to be a threshold regarding this matter, meaning that the promoter must possess an intermediate level of basicity. However, CO2 adsorption becomes excessively strong when the promoter is too basic, favoring the undesired reverse-water gas shift (RWGS) reaction and CH4 formation with acid counterparts. Our findings showed that the Ga-promoted In2O3 catalyst with intermediate basicity balances activity and selectivity, resulting in a higher yield of hydrocarbons. The observed outcome highlights the significant role of catalyst component interactions in suppressing undesirable reactions and improving overall performance. The Ga-promoted catalyst exhibited higher selectivity for hydrocarbons, averaging 61%, compared to In2O3, which achieved a selectivity of 54%.

Enhanced methanol to gasoline performance using nanosheet-like SAPO-11 catalyst

Herein, spherical and nanosheet-like SAPO-11s were successfully synthesized hydrothermally and utilized to catalyze the methanol-to-gasoline (MTG) process. The nanosheet-like SAPO-11 (SAPO-11-A) had a thickness of about 10 nm, while the spherical SAPO-11 (SAPO-11-B) had a particle size of around 11 μm. Compared to SAPO-11-B, the property of SAPO-11-A was enhanced by 42.9% in specific surface area (SSA), 38.1% in mesopore volume (Vme) and 20.2% in acid amounts, respectively. In terms of catalytic performance during the MTG reaction, SAPO-11-A demonstrated superior results not only in the methanol conversion (95.82%), gasoline-range hydrocarbons selectivity (58.76%) and iso/nparaffin ratio (8.17) but also in suppressed coke deposition (2.56%) compared with those (90.63%, 50.95%, 4.75 and 5.73%, respectively) of SAPO-11-B. Additionally, the optimal MTG process conditions were identified utilizing SAPO-11-A, demonstrating a methanol conversion rate of 98.34%, a gasoline hydrocarbon selectivity of 67.61%, an isoparaffin selectivity of 36.01% and an iso/nparaffin ratio of 10.94 at 380 °C, weight hourly space velocity (WHSV) of 2 h−1 and 1 MPa. These results highlight the potential of nanosheet SAPO-11 to produce gasoline-range hydrocarbons rich in isoparaffins.

Characteristic studies on sustainable upgraded bio-oil produced using green TiO2/AlSBA-15 nano composite

The march towards electric vehicles have commenced, but still, this would be deadly to already existing vehicles. The research in bioliquid fuels is yet to be uncompromised and a proper fuel would be a head turner. This work focuses on the in-situ synthesis of composite material TiO2/AlSBA-15 (10%-60%) where nano TiO2 is made using organic reducing agent; lemon peel extract. The catalyst was characterized using XRD, BET, N2 sorption studies, SEM, EDX, and TEM analysis. SEM pictures displayed the uniform coating of TiO2 over SBA-15 and hence the catalyst is termed as core–shell model. Pyrolyzed used cooking oil (UCO) was further reformed by upgrading by prepared catalysts. TiO2/SBA-15––30% exhibited best activity than the precursor materials by converting 97.7% of UCO into 89.9% of condensable liquids, and the GC MS analysis of the fuel revealed the presence of 91.3% of gasoline range hydrocarbons. The NMR spectra showed the presence of alkyl groups, aromatic alkanes, iso & n-paraffins. The characteristics of the prepared bioliquid light fuel was studied to understand its features such as calorific value, flash & fire point, pour & cloud point. The biofuel produced showed remarkably high calorific value (48.7 MJ/Kg) and least viscosity (1.9 Cst).

Syngas to FCC-like gasoline range hydrocarbons with upgraded light olefin selectivity catalyzed by readily synthesized Fe-MOF

The global trend toward sustainability is due to the growing demand for synthetic chemicals and fuels relying on fossil crude oil with the associated concerns of climate change. The Fischer-Tropsch synthesis (FTS) process is a key sustainable pathway for supplying light olefins, gasoline, and other petrochemicals using green hydrogen and energy. Here we report a simple, green, cost-effective synthesis strategy to prepare an iron-based metal–organic framework (Fe-BTC MOF) at room temperature with a remarkable porous structure analogous to the commercially available Basolite F300. The catalyst shows a 97% syngas conversion to gasoline-range hydrocarbons (C5-C12) at high temperatures, with a selectivity of 48.3%, yield of 28%, low methane selectivity (15.5%) and low C13+ selectivity (1%). In addition, the catalyst is 29% selective to light olefin (C2-C4=), yielding 17%, besides an olefin/paraffin ratio (O/P) of 4.3 with 81% olefin selectivity of the C2-C4 fraction. The resulting gasoline is equivalent to gasoline produced by Fluid Catalytic Cracking (FCC) of crude oil. The highest C5-C12 selectivity reached 63.6%, yielding 12% at 29% CO conversion. The Fe-BTC/C catalyst showed excellent stability for time on stream >100 h and a high gas hourly space velocity (GHSV) value of 20000 mL g-1cat h−1 with an Fe-time yield of 165 µmolCO g-1Fe s−1. The prepared Fe-BTC catalyst, with a 2-fold larger pore volume than the previously prepared Fe-MIL-88B catalyst, has a higher olefin production capability by 2-fold, 7-fold higher O/P for the light fraction and 2.3-fold higher C5+ selectivity. The sustainable synthesis of catalysts with improved porous structure may significantly foster FTS technology for being economically practical to be scaled up and commercialized for national fuel and olefin production projects.

A versatile hybrid catalyst platform of Na/ZnFe2O4 and zeolite for selective hydrocarbon production from CO2 hydrogenation

Catalytic CO2 hydrogenation faces great challenges in both reaction rates and selectivity to desired high-value products. Herein, we present a one-pot reaction platform that converts CO2 into various long-chain hydrocarbons selectively by combining a Na/ZnFe2O4-based catalyst for CO2 activation and carbon–carbon coupling, and a zeolite for fine-tuning the selectivity of desired products by exploiting its shape selectivity. Thus, the Na/ZnFe2O4 catalyst without zeolite produces highly olefinic diesel range hydrocarbons, and a hybrid catalyst with ZSM-5 produces highly aromatic gasoline range hydrocarbons, that with ZSM-11 produces branched kerosene range hydrocarbons, and that with SSZ-13 produces hydrocarbons rich in C2-C4 olefins. In all cases, high CO2 conversions of over 35% and low CO selectivity of near 10% are maintained. Therefore, the hybrid catalyst platform proposed here demonstrates that an elaborate catalyst design enables fine-tuning of the reaction pathway of CO2 hydrogenation to produce selectively versatile value-added hydrocarbons.

Optimization of Polypropylene Waste Recycling Products as Alternative Fuels through Non-Catalytic Thermal and Catalytic Hydrocracking Using Fresh and Spent Pt/Al2O3 and NiMo/Al2O3 Catalysts

In this work, the conversion of waste polypropylene to alternative fuels (liquid and gas) was performed through non-catalytic thermal and catalytic hydrocracking over NiMo/Al2O3 and Pt/Al2O3 catalysts. The process was carried out in an autoclave batch reactor at a temperature of 450 °C and a pressure of 20 bar, which were selected based on experimental optimization. The spent catalyst was also successfully regenerated at 700 °C under a hot airflow. Experiments were conducted to determine the optimum conditions to completely separate the deactivated catalyst from the solid residue easily. The regenerated catalyst was reused to facilitate the economic cost reduction of the process. The reactivated catalysts have almost the same catalytic properties as the fresh catalysts; this was confirmed by several characterization techniques, such as TGA, XRD, SEM, EDX, BET and FTIR. The produced liquids/gases were quantified and classified into their fractions by the number of carbon atoms and gasoline to diesel ratio using GC/MS. The viscosity, density, API gravity, pour point and flash point of oil cuts were also investigated to evaluate the quality of the resulting liquid from the reactions. The NiMo/Al2O3 catalyst gave the highest liquid hydrocarbons yield of 86 wt%, while the highest weight products of gasoline range hydrocarbon fractions of 49.85 wt% were found over the Pt/Al2O3 catalyst. Almost the same catalytic behavior was found with the regenerated catalysts compared to the fresh catalysts. However, the highest gaseous products at 20.8 wt% were found in the non-catalytic thermal products with an increase in the diesel fuel range of 80.83 wt%. The kinetic model was implemented using six lumps and fifteen reactions, and the apparent activation energies for the gasoline and diesel fractions were calculated. In general, all primary and secondary reactions show greater activation energy values on the Pt/Al2O3 catalyst than on the NiMo/Al2O3 catalyst.

Nickel promoted Si-rich ZSM-5 nanocatalyst remarkably converts LDPE plastic waste to gasoline range hydrocarbons in a dual-bed semi-batch reactor at atmospheric pressure

Catalytic pyrolysis is an environmentally friendly recycling method, which has attracted remarkable attention due to worldwide issues of the production and accumulation of plastic wastes. In this work, the catalytic pyrolysis of Low-density polyethylene (LDPE) was carried out in a dual-bed semi-batch reactor over the Si-rich Ni/ZSM-5 nanocatalyst at atmospheric pressure. The parent nanocatalyst was prepared by hydrothermal technique and modified with nickel promoter (0–25 wt%). The properties of the nanocatalysts were characterized by XRD, FTIR, FE-SEM, EDX, TEM, BET, NH3-TPD, and TG-DTA techniques. The results showed the high crystallinity, spherical particles, and high specific surface area (376 m2g−1). The impact of operational conditions was evaluated to maximize the production of the high value-added compounds. The high percentage of the Ni promoter (25 wt%) led to the highest amount of gasoline range hydrocarbons (61%). The appropriate operational conditions were temperature of 525 °C, catalyst to plastic ratio of 1:20, and 2.5 ml min−1 nitrogen flow rate, resulting in the best product distribution: aromatics (39.4%), olefins (28.3%), and paraffins (15%). The reusability of the nanocatalyst showed high performance and more aromatic production. The characterization results of the used nanocatalyst confirmed the high stability through the pyrolysis reaction and lack of significant structural defect. The developed nanocatalyst represented the high activity through the pyrolysis of the real LDPE plastic waste, including the major product distribution in the gasoline range hydrocarbons.

Effects of ZSM-5 Morphology and Fe Promoter for Dimethyl Ether Conversion to Gasoline-Range Hydrocarbons

The synthesis of gasoline-range hydrocarbons by gas-phase dimethyl ether (DME) conversion was investigated on various ZSM-5 zeolites with different morphologies and Fe contents. The different morphologies of ZSM-5 significantly altered the distributions of the acidic sites, which showed different selectivities to gasoline-range hydrocarbons. Nanostructured ZSM-5 (N-ZSM-5) revealed the highest C5+ selectivity of 41.7% with an aromatics selectivity of 23.6% at ~100% DME conversion. The superior catalytic activity of N-ZSM-5 was attributed to the largest strong Brønsted acidic sites and smaller crystallite sizes, which were beneficial for the faster removal rate of heavy hydrocarbons due to its shorter diffusion pathlength compared to conventional ZSM-5 (C-ZSM-5). In addition, 10 wt% Fe-impregnated N-ZSM-5 revealed an enhanced C5+ selectivity of 60.6% with a smaller C1–C4 selectivity of 21.9%, which were attributed to the adjusted acidic sites by suppressing the cracking reactions of the surface intermediates, which are responsible for the selective formation of smaller light hydrocarbons. However, the excess amount of Fe on N-ZSM-5 showed a lower DME conversion of 83.5% with a lower C5+ selectivity of 38.5% due to the blockages of the active acidic sites. Nanostructured N-ZSM-5 possessing a larger amount of strong Brønsted acid sites with 10 wt% Fe modification clearly showed a higher formation rate of gasoline-range hydrocarbons due to an enhanced secondary oligomerization of surface intermediates to form heavier aromatic hydrocarbons.