Plastics are engineering marvels that have found widespread use in all aspects of modern life. However, poor waste management practices and inefficient recycling technologies, along with their extremely high durability, have caused one of the major environmental problems facing humankind: waste plastic pollution. The upcycling of waste plastics to chemical feedstock to produce virgin plastics has emerged as a viable option to mitigate the adverse effects of plastic pollution and close the gap in the circular economy of plastics. Pyrolysis is considered a chemical recycling technology to upcycle waste plastics. Yet, whether pyrolysis as a stand-alone technology can achieve true circularity or not requires further investigation. In this study, we analyzed and critically evaluated whether oil obtained from the non-catalytic pyrolysis of virgin polypropylene (PP) can be used as a feedstock for naphtha crackers to produce olefins, and subsequently polyolefins, without undermining the circular economy and resource efficiency. Two different pyrolysis oils were obtained from a pyrolysis plant and compared with light and heavy naphtha by a combination of physical and chromatographic methods, in accordance with established standards. The results demonstrate that pyrolysis oil consists of mostly cyclic olefins with a bromine number of 85 to 304, whereas light naphtha consists of mostly paraffinic hydrocarbons with a very low olefinic content and a bromine number around 1. Owing to the compositional differences, pyrolysis oil studied herein is completely different than naphtha in terms of hydrocarbon composition and cannot be used as a feedstock for commercial naphtha crackers to produce olefins. The findings are of particular importance to evaluating different chemical recycling opportunities with respect to true circularity and may serve as a benchmark to determine whether liquids obtained from different polyolefin recycling technologies are compatible with existing industrial steam crackers’ feedstock.

Prior studies found that the carburization tendency is negligible for technically developed materials at temperatures below 900 °C, especially for Al-containing alloys compared to non-Al-containing alloys applied in steam cracking reactors. However, it is unclear whether this benefit remains at higher temperatures. This work compared coke deposition tendencies of recently developed alloys to each other and to a conventional material when cracking ethane at a higher temperature (950 °C) than previously reported. Under the studied experimental conditions, coking rates vary in the range of 1.22 × 10–6 to 20.5 × 10–6 kg/(m2·s) for Al-containing alloys, while for non-Al-containing alloys, coke deposition rates fall in a range of 4.95 × 10–6 to 33 × 10–6 kg/(m2·s). In general, aluminum-containing alloys showed less coke formation and improved stability against aging after five cracking cycles compared to the non-aluminum-containing materials. The results also showed that substantially less, if any, carburization could be detected in developed alloys even at high temperatures, in contrast to the results from a reference conventional alloy of 27/34 Cr–Ni. At higher temperatures, the protective oxide surface layer of the Al-containing alloys remained noticeably durable and integrated with negligible spallation compared to the ones of non-Al-containing alloys. In fact, the 27/34 Cr–Ni alloy showed the highest coking rate and carburization, implying the most vulnerable oxide surface layer relative to the other alloys. However, energy-dispersive X-ray (EDX) results showed no signs of carburization or deterioration of the surface of 27/34 Cr–Ni after experiments at 880 °C, indicating that both the temperature and matrix composition can play significant roles in determining the suitability of an alloy for application in steam crackers.

Crude tall oil is a by-product obtained from the manufacture of chemical wood pulp. The residue obtained after the distillation of this product is known as tall oil pitch (TOP). This complex fraction is a highly viscous liquid that consists mainly of free fatty acids, fatty acids derivatives, rosin acids and additives. Given its complex composition, it is commonly used as fuel for heat production. In this work, steam cracking is proposed as an alternative treatment for this residue. Steam cracking can convert TOP into a valuable product gas that can be used in different applications including the production of green chemicals, moving towards a carbon circular economy. The experimental tests were performed in the Chalmers pilot scale Dual Fluidized Bed, consisting of a steam cracker and a combustor. For these experiments, the thermochemical decomposition of 150–175 kg/h TOP was performed at the steam cracker at two different temperatures (775 and 825 °C) to evaluate the influence of this parameter on the obtained products. Wood pellets were also tested as reference material for the highest temperature. The distribution of the obtained products was analysed. Results show that TOP can be regarded as a by-product instead of a residue and used as feedstock for the recovery of chemical building blocks and syngas via thermochemical recycling. Between 40 and 50 % of the carbon present in the fuel is kept in the permanent gases, while about 20 % is in aromatic hydrocarbons. Compared to biomass, the aromatics yield obtained for TOP is much higher (190 g/kg for TOP and 13 g/kg for biomass). Among the species found, benzene, toluene and xylene, represent between 62 and 72 % of the total measured aromatics. Regarding the gas fraction, the production of valuable light hydrocarbons (such as ethylene and propylene) is more pronounced in the TOP residue than in the biomass. In addition, an energy balance over the system was estimated and showed that TOP thermochemical recycling can be self-sustained in a Dual Fluidized Bed if the non-valuable products are combusted. The results obtained in this work indicate that this TOP could be an appealing option to consider as a source of biorefinery revenue leading to the circular use of waste.

Ethylene is mainly produced by steam cracking of naphtha or light alkanes in the current petrochemical industry. However, the high-temperature operation results in high energy demands, high cost of gas separation, and huge CO2 emissions. With the growth of the verified shale gas reserves, oxidative dehydrogenation of ethane (ODHE) becomes a promising process to convert ethane from underutilized shale gas reserves to ethylene at a moderate reaction temperature. Among the catalysts for ODHE, MoVNbTeOx mixed oxide has exhibited superior catalytic performance in terms of ethane conversion, ethylene selectivity, and/or yield. Accordingly, the process design is compact, and the economic evaluation is more favorable in comparison to the mature steam cracking processes. This paper aims to provide a state-of-the-art review on the application of MoVNbTeOx catalysts in the ODHE process, involving the origin of MoVNbTeOx, (post-) treatment of the catalyst, material characterization, reaction mechanism, and evaluation as well as the reactor design, providing a comprehensive overview of M1 MoVNbTeOx catalysts for the oxidative dehydrogenation of ethane, thus contributing to the understanding and development of the ODHE process based on MoVNbTeOx catalysts.

Ethylene is one of the most consumed products in the world, as it has many uses such as the production of nylon from its polymeric compound, the production of vinyl chloride, which is polymerized to polyvinyl chloride for the production of plastics, the production of ethylene oxide, used as a ripening agent for fruits, etc. The conventional method adopted in the production of ethylene is by steam cracking of naphtha at high temperatures. Naphtha is a hydrocarbon, so when cracked, it releases harmful carbon dioxide (CO2) into the atmosphere, and this brought about looking for alternative methods of producing ethylene. As discovered, ethylene can be produced by catalytic dehydration of ethanol, but the main limitation of this process is that the purity of ethylene produced by this approach may not be up to the desired polymer grade of 99.97%. As such, this work has been carried out to model, with the aid of Aspen Plus, and develop control techniques that would enable the process to meet up with the desired output maximum purity from the distillation column (100% ethylene at the top product of the distillation column). In line with that, P-only, PI, and PID controllers tuned with the Tyreus-Luyben technique, Zeiger-Nichols method, and a modified Tyreus-Luyben approach have been used for the control of this process. It was discovered that the PID controller tuned with the modified Tyreus-Luyben parameter had the lowest Integral Absolute Error (IAE) of 1.474 and Integral Time Absolute Error (ITAE) of 4.767 and, hence, it was found out that it could be adopted for proper control of this process, although limited to small upsets caused by disturbances in the system. It is, therefore, recommended that the PID control system developed should be applied on a physical set-up plant to study its real effect.

Optimized scalable CuB catalyst with promising carbon footprint for the electrochemical [formula omitted] reduction to ethylene

Natural gas hydrates of Bulgaria and Romania in the Black Sea have been subject to studies by several European research projects. The current understanding of the hydrate distribution, and the total amounts of hydrate in the region, makes it interesting to evaluate in terms of commercial potential. In this study, we have evaluated some well-known hydrate production methods. Thermal stimulation and adding chemicals are considered as not economically feasible. Pressure reduction may not be efficient due to the endothermic dissociation of hydrates and long-term cooling of the sediments. Chemical work due to pressure reduction is an additional mechanism but is too slow to be commercially feasible. Adding CO2/N2, however, has a dual value. In the future, CO2 can be stored at a price proportional to a CO2 tax. This is deducted from the value of the released natural gas. The maximum addition of N2 is around 30 mol% of the CO2/N2 mixture. A minor addition (in the order of 1 mol%) of CH4 increases the stability of the hydrate created from the injection gas. The maximum N2 amount is dictated by the demand for the creation of a new hydrate from injection gas but also the need for sufficient heat release from this hydrate formation to dissociate the in situ CH4 hydrates. An additional additive is needed to accelerate the formation of hydrate from injection gas while at the same time reducing the creation of blocking hydrate films. Based on reasonable assumptions and approximations as used in a verified kinetic model it is found that CH4/CO2 swapping is a feasible method for Black Sea hydrates. It is also argued that the technology is essentially conventional petroleum technology combined with learning from projects on aquifer storage of CO2, and a thermodynamic approach for design of appropriate injection gas. It is also argued that the CH4/CO2 swap can be combined with well-known technology for steam cracking of produced hydrocarbons to H2 and CO2 (for re-injection).

Assessing the CO2 emission reduction potential of steam cracking furnace innovations via computational fluid dynamics: From high-emissivity coatings, over coil modifications to firing control

Cracking of F-T refined wax for producing linear α-olefin

Selective production of light olefins over zeolite catalysts: Impacts of topology, acidity, and particle size

Emergency shutdowns of propylene production plants: Root cause analysis and availability modeling

Global warming is becoming an increasing issue, and greenhouse gas (GHG) emissions represent the engine of such a phenomenon. This review aims to identify the origin of GHG emissions and focus in detail on the ones related to (petro) chemical industries. The industrial sector is the primary GHG emitter among all the other anthropogenic sources. The chemical industry is the first in charge of that (having accounted for about 6.5% of the global GHG emissions in 2018). Thought-provoking data such as yearly productivities and emission factors related to the predominant chemicals prompt the reader to acquire a sense of the critical activities responsible for carbon-intensive emissions, which should be the first to be decarbonized. Specifically, ammonia synthesis and steam cracking resulted in the most polluting processes of the chemical industry, being responsible for the release of about 440 and 228 Mt-CO2,eq/y, respectively, in 2020. The same approach also applies to oil refining. Due to the massive amounts of oil barrels produced daily, oil refining is a key player in industrial GHG emissions (about 3% of the global emissions in 2018). Indeed, in 2020, refineries emitted nearly 1313 Mt-CO2,eq/y.

Electrified steam cracking for a carbon neutral ethylene production process: Techno-economic analysis, life cycle assessment, and analytic hierarchy process

Ethane and ethanol are produced through steam cracking and fermentation into ethylene respectively, which is then hydrolysed into monoethylene glycol (MEG). The disadvantages of both processes included used of easily oxidized substance and large quantities of water in order to minimize by-products such as diethylene glycol and triethylene glycol. Apart from that, MEG can also be produced by catalytic hydrogenation of biomass at extreme temperature and pressure with presence of catalyst. At the same time, this process uses lignocellulosic waste that have a high cellulose content such as residues from the agricultural and food industries. However, lignocellulosic biomass has to be treated to remove lignin content that may lower the rate of hydrogenation activity. In addition, most studies have found that the temperature in range of 240 °C to 280 °C and pressure of 5 MPa to 6 MPa are able to produce 18 wt% to 64 wt% of MEG. Meanwhile, the catalyst that have attract the researchers’ attention are nickel and tungsten species which are able to increase the MEG yield by overcoming the activation energy of the hydrogenation process. Factors such as lignocellulose’s pre-treatment, operating temperature and pressure, and the presence of catalyst will be discussed further.

Highly efficient mesoporous ZSM-5 for trace olefin removal from aromatic stream

Background/Aim: Steam crackers (SCs) convert gas feedstocks into ethylene and propylene (the building blocks of plastics) at high temperatures and release toxic/carcinogenic chemicals and greenhouse gases (GHGs). The recent shale boom in the United States (US) has incentivized the expansion of SCs, but analyses of their potential environmental health and justice impacts are limited. We described SC operations, constructed a US SC emissions inventory, and evaluated socioeconomic characteristics of populations residing in proximity to SCs. Methods: We searched peer-reviewed and gray literature to describe SC operations. We constructed an inventory using publicly available datasets from industry, government, and non-governmental sources. We used descriptive statistics and data visualization to sumarize emissions from the US Environmental Protection Agency’s (EPA’s) Toxic Release Inventory (TRI) and EPA’s GHG Reporting Program. We compared population characteristics from US Census block groups (BGs) less than versus greater than 5km of an SC, within counties with a SC. Results: SC operations include: (1) pyrolysis, (2) quenching, (3) compression, cooling, and drying, and (4) fractionation. Major toxic emission sources include furnaces, fugitive emissions, and flaring. We identified 32 SC facilities across five states, with most in the Gulf Coast of Texas and Louisiana. TRI chemicals with the highest self-reported cumulative air-emission volumes from 1987-2019 were: ethylene, propylene, hydrochloric acid, benzene, n-hexane, 1,3-butadiene, ammonia, toluene, vinyl acetate, and methanol. SC facilities emitted >650 million metric tons (carbon dioxide equivalents) of GHGs in total from 2010-2019. We found that 752,465 people live in census BGs within 5km of an SC. BGs closer to SCs had higher proportions of residents who were Black, had non-professional occupations, lower educational attainment, and lower median household income. Conclusion: SC operations have the potential for adverse human health impacts and environmental inequities, underscoring the need for additional research on hazards of petrochemical infrastructure. Keywords: plastics, petroleum

Steam cracking of naphtha is an important process for the production of olefins. Applying artificial intelligence helps achieve high-frequency real-time optimization strategy and process control. This work employs an artificial neural network (ANN) model with two sub-networks to simulate the naphtha steam cracking process. In the first feedstock composition ANN, the detailed feedstock compositions are determined from the limited naphtha bulk properties. In the second reactor ANN, the cracking product yields are predicted from the feedstock compositions and operating conditions. The combination of these two sub-networks has the ability to accurately and rapidly predict the product yields directly from naphtha bulk properties. Two different feedstock composition ANN strategies are proposed and compared. The results show that with the special design of dividing the output layer into five groups of PIONA, the prediction accuracy of product yields is significantly improved. The mean absolute error of 11 cracking products is 0.53wt% for 472 test sets. The comparison results show that this indirect feedstock composition ANN has lower product prediction errors, not just the reduction of the total error of the feedstock composition. The critical factor is ensuring that PIONA contents are equal to the actual values. The use of an indirect feedstock composition strategy is a means that can effectively improve the prediction accuracy of the whole ANN model.

The olefins are produced by steam cracking furnaces in the petrochemical industry. The olefins production is strongly affected by the furnace run length. The coke deposition inside the cracking coil determines the furnace run length. Dimethyl disulfide (DMDS) is mainly utilized in steam crackers as coke and CO inhibitors. A cracking setup is utilized for studying the influence of various concentrations of DMDS on cracking performance. The simulation model utilized to evaluate furnace run length showed excellent performance in the prediction of the furnace run length (average absolute error = 0.83%). The ethane conversion, ethylene selectivity, carbon monoxide (CO) formation, coking rate, coke morphology, and metal migration to coke are vital parameters in olefin performance and furnace run length. Accordingly, different concentrations of DMDS including the industrial dosage are selected, evaluated, and optimized by the experimental method. The results show that the minimum coke formation is achieved when the DMDS concentration is 20 ppmw, in which the coking rate for steam cracking is 52% less than that of industrial dosage (111 ppmw). Moreover, a 50% decrease in CO formation is observed when DMDS concentration changed from 111 to 20 ppmw. Based on the simulation model, the optimum DMDS dosage results in an increase in the run length from 60.21 to 95.12 days.

Abstract Helically ribbed coils are commonly applied in steam cracking furnaces. To fully understand the impact of these ribbed wall modifications on the local heat transfer and associated pressure drop throughout the reactor, detailed experimental, and numerical studies have been performed. Experimental data based on stereo‐particle image velocimetry (S‐PIV) and liquid crystal thermography have been used to validate the numerical results from wall‐resolved large eddy simulations using OpenFOAM. The validation shows an excellent agreement in terms of mean and fluctuating velocities, pressure drop, and heat transfer behavior in a discontinuously ribbed tube. Compared with the pressure drop in a continuously ribbed tube, an approximately 40% lower pressure drop is obtained with a discontinuously ribbed tube, at the cost of a slightly decreased heat transfer enhancement. This makes the discontinuously ribbed tube design particularly interesting for steam cracking applications. The results also show that the nonuniform heat transfer at the wall is inherently linked to the flow reattachment and recirculation zones caused by the rib. Finally, the validated numerical model was used to study comparable designs and propose novel helical rib designs. Based on the results of the study, enlarging the trailing edge of the conventional ribbed geometry will improve the thermal enhancement performance, and is therefore found most promising for steam cracking reactor design.

Ethylene is an important feedstock for the production of many key-valued compounds, especially polymers. About 60% of the total ethylene produced is utilized for the production of polyethylene, while ethylene is normally produced by steam cracking of naphtha along with traces of ethane, which is undesirable. Considering the energy-intensive nature of the current technology to obtain ultrapure ethylene, the development of novel materials for separating ethylene from ethane by adsorption is of great significance, yet it remains challenging owing to the close molecular sizes and physical properties of the two compounds. Both ethylene- and ethane-selective adsorbents are reviewed in this work. Yet, as the industrial feed is rich in ethylene with traces of ethane, in order to obtain polymer grade ethylene, multiple adsorption–desorption cycles are required, which is yet again energy-demanding. Thus, ethane-selective adsorbents are energetically favorable; hence, in this Review, we pay particular focus on ethane-selective adsorbents. The rationale behind reverse-selective adsorbents is critically reviewed and discussed. Most of the ethane-selective adsorbents have been reported to exhibit low selectivity compared to ethylene-selective ones, as reverse-selectivity is mostly based on weak van der Waals interactions. In addition, we focused on various reported mechanisms behind the adsorptive separation of ethane/ethylene mixtures, as well as modifications and surface functionalization techniques reported for different types of adsorbents investigated for this separation.