Wood-derived olefins by steam cracking of hydrodeoxygenated tall oils

The merit of pressure dependent kinetic modelling in steam cracking

Renewable cracking feedstocks from plastic waste and the need for novel reactor designs related to electrification of steam crackers drives the development of accurate and fundamental kinetic models for this process, despite its large scale implementation for more than half a century. Pressure dependent kinetics have mostly been omitted in fundamental steam cracking models, while they are crucial in combustion models. Therefore, we have assessed the importance of pressure dependent kinetics for steam cracking via in-depth modelling and experimental studies. In particular we have studied the influence of considering fall-off on the product yields for ethane and propane steam cracking. A high-pressure limit fundamental kinetic model is generated, based on quantum chemical data and group additive values, and supplemented with literature values for pressure dependent kinetic parameters for β-scission reactions and homolytic bond scissions of C₂ and C₃ species. Model simulations with high-pressure limit rate coefficients and pressure dependent kinetics are compared to new experimental measurements. Steam cracking experiments for pure ethane and propane feeds are performed on a tubular bench-scale reactor at 0.17 MPa and temperatures ranging from 1058 to 1178 K. All important product species are identified using a comprehensive GC × GC-FID/q-MS. For homolytic bond scissions, the inclusion of pressure dependent kinetics has a significant effect on the conversion profile for ethane steam cracking. On the other hand, pressure dependence of C₂ β-scissions significantly influences conversion and product species profiles for both ethane and propane steam cracking. The C₃ β-scissions pressure dependence has a negligible effect in ethane steam cracking, while for propane steam cracking the effect is non-negligible on the product species profiles.

Next generation of polyolefin plastics: improving sustainability with existing and novel feedstock base

Abstract

In this account, we present an overview of existing and emerging olefin production technologies, comparing them from the standpoint of carbon intensity, efficiency, feedstock type and availability. Olefins are indispensable feedstock for manufacture of polyolefin plastics and other base chemicals. Current methods of olefin production are associated with significant CO2 emissions and almost entirely rely of fossil feedstock. In order to assess potential alternatives, technical and economic maturity of six principal olefin production routes are compared in this paper. Coal (brown), oil and gas (grey), biomass (green), recycled plastic (pink) as well as carbon capture and storage (purple) and carbon capture and utilization (blue) technologies are considered. We conclude that broader adoption of biomass based “green” feedstock and introduction of recycled plastic based olefins may lead to reduced carbon footprint, however adoption of best available technologies and introduction of electrocracking to existing fossil-based “grey” olefin manufacture process can be the way to achieve highest impact most rapidly. Adoption of Power-to-X approaches to olefins starting from biogenic or atmospheric CO2 and renewable H2 can lead to ultimately carbon–neutral “blue” olefins in the long term, however substantial development and additional regulatory incentives are necessary to make the solution economically viable.

Article highlights

Assessing the feasibility of chemical recycling via steam cracking of untreated plastic waste pyrolysis oils: Feedstock impurities, product yields and coke formation

Chemical recycling of plastic waste to base chemicals via pyrolysis and subsequent steam cracking of pyrolysis oils shows great potential to overcome the limitations in present means of plastic waste recycling. In this scenario, the largest concern is the feasibility. Are plastic waste pyrolysis products acceptable steam cracking feedstocks in terms of composition, product yields and coke formation? In this work, steam cracking of two post-consumer plastic waste pyrolysis oils blended with fossil naphtha was performed in a continuous bench-scale unit without prior treatment. Product yields and radiant coil coke formation were benchmarked to fossil naphtha as an industrial feedstock. Additionally, the plastic waste pyrolysis oils were thoroughly characterized. Analyses included two dimensional gas chromatography coupled to a flame ionization detector for the detailed hydrocarbon composition as well as specific analyses for heteroatoms, halogens and metals. It was found that both pyrolysis oils are rich in olefins (∼48 wt%) and that the main impurities are nitrogen, oxygen, chlorine, bromine, aluminum, calcium and sodium. Steam cracking of the plastic waste derived feedstocks led to ethylene yields of ∼23 wt% at a coil outlet temperature of 820 °C and ∼28 wt% at 850 °C, exceeding the ethylene yield of pure naphtha at both conditions (∼22 wt% and ∼27 wt%, respectively). High amounts of heavy products were formed when steam cracking both pyrolysis oils, respectively. Furthermore, a substantial coking tendency was observed for the more contaminated pyrolysis oil, indicating that next to unsaturated hydrocarbons, contaminants are a strong driver for coke formation.

Utilization of agricultural and forest industry waste and residues in natural fiber-polymer composites: A review

Natural fiber-polymer composites (NFPCs) are becoming increasingly utilized in a wide variety of applications because they represent an ecological and inexpensive alternative to conventional petroleum-derived materials. On the other hand, considerable amounts of organic waste and residues from the industrial and agricultural processes are still underutilized as low-value energy sources. Organic materials are commonly disposed of or subjected to the traditional waste management methods, such as landfilling, composting or anaerobic digestion. The use of organic waste and residue materials in NFPCs represents an ecologically friendly and a substantially higher value alternative. This is a comprehensive review examining how organic waste and residues could be utilized in the future as reinforcements or additives for NFPCs from the perspective of the recently reported work in this field.

Potential of genetically engineered hybrid poplar for pyrolytic production of bio-based phenolic compounds

Wild-type and two genetically engineered hybrid poplar lines were pyrolyzed in a micro-pyrolysis (Py-GC/MS) and a bench scale setup for fast and intermediate pyrolysis studies. Principal component analysis showed that the pyrolysis vapors obtained by micro-pyrolysis from wood of caffeic acid O-methyltransferase (COMT) and caffeoyl-CoA O-methyltransferase (CCoAOMT) down-regulated poplar trees differed significantly from the pyrolysis vapors obtained from non-transgenic control trees. Both fast micro-pyrolysis and intermediate pyrolysis of transgenic hybrid poplars showed that down-regulation of COMT can enhance the relative yield of guaiacyl lignin-derived products, while the relative yield of syringyl lignin-derived products was up to a factor 3 lower. This study indicates that lignin engineering via genetic modifications of genes involved in the phenylpropanoid and monolignol biosynthetic pathways can help to steer the pyrolytic production of guaiacyl and syringyl lignin-derived phenolic compounds such as guaiacol, 4-methylguaiacol, 4-ethylguaiacol, 4-vinylguaiacol, syringol, 4-vinylsyringol, and syringaldehyde present in the bio-oil.

Opportunities for Bio-Based Solvents Created as Petrochemical and Fuel Products Transition towards Renewable Resources

The global bio-based chemical market is growing in size and importance. Bio-based solvents such as glycerol and 2-methyltetrahydrofuran are often discussed as important introductions to the conventional repertoire of solvents. However adoption of new innovations by industry is typically slow. Therefore it might be anticipated that neoteric solvent systems (e.g., ionic liquids) will remain niche, while renewable routes to historically established solvents will continue to grow in importance. This review discusses bio-based solvents from the perspective of their production, identifying suitable feedstocks, platform molecules, and relevant product streams for the sustainable manufacturing of conventional solvents.