Plastic recycling stripped naked - from circular product to circular industry with recycling cascade

This perspective combines various expertise to develop and analyse the concept of technology cascade for recycling waste plastics with the goal of displacing as much fossil crude oil as possible. It thereby presents archetype recycling technologies with their strengths and weaknesses. It then combines them in various cascades to process a representative plastic mix, and determines how much (fossil) naphtha could be displaced and at which energy consumption. The cascades rely on a limited number of parameters that are fully reported in supplementary information and that were used in a simple and transparent spreadsheet model. The calculated results bust several common myths in plastic recycling, e. g. by prioritizing here recycled volume over recycling efficiency, and prioritizing circular industry over circular products . It unravels the energy cost of solvent-based recycling processes, shows the key role of gasification and the possibility to displace up to 70 % of the fossil feedstock with recycled carbon, a recycling rate that compares well with that aluminium, steel or paper. It suggests that deeper naphtha displacement would require exorbitant amount of energy. It therefore argues for the need to complement recycling with the use of renewable carbon, e. g. based on biomass, to fully defossilise the plastic industry.

Furfural to Cyclopentanone - a Search for Putative Oligomeric By-products

We report here on the reductive rearrangement of biomass-derived furfural to cyclopentanone, a promising non-fossil feedstock for fuels and chemicals. An underreported aspect of this reaction is the inevitable formation of heavy byproducts. To mitigate its formation, process condition such as, solvent, catalyst, temperature, acidity, and feed concentration were varied to unravel the chemistry and improve the reaction performance. Water medium was confirmed to play a crucial role, as organic solvents were unable to deliver cyclopentanone or heavy by products. Copper-based catalyst showed the highest selectivity for ring-rearrangement, reaching 50 mol % under the conditions investigated. The main factor influencing the yields of cyclopentanone (CPO), and promote oligomer formation, are the feed concentration and the pH, as high feed concentrations and high acidity facilitate the self-polymerization of furfuryl alcohol (FALC). This was confirmed by dedicated experiments using FALC and the hydroxypentenone intermediate as feed. The concentration challenge could be mitigated by slowly dosing the feed, which increased the desired product yields by 4-12 mol %. Nevertheless, most oligomers appeared to fall in the range of common liquid fuels and could be converted to diesel by hydrodeoxygenation.

Polyurethane Recycling: Thermal Decomposition of 1,3-Diphenyl Urea to Isocyanates

Substituted urea linkages are formed during the production of polyurethane foam. To chemically recycle polyurethane toward its key monomers via depolymerization (i.e., isocyanate), it is essential to break the urea linkages to form the corresponding monomers, namely, an isocyanate and an amine. This work reports the thermal cracking of a model urea compound (1,3-diphenyl urea, DPU) into phenyl isocyanate and aniline in a flow reactor at different temperatures. Experiments were performed at 350-450 °C, with a continuous feed of a solution of 1 wt.% DPU in GVL. In the temperature range studied, high conversion levels of DPU are achieved (70-90 mol%), with high selectivity towards the desired products (close to 100 mol%) and high average mole balance (∼95 mol%) in all cases.

Polyurethane Recycling: Conversion of Carbamates-Catalysis, Side-Reactions and Mole Balance

Diisocyanates, a key monomer in polyurethane, are generally lost during recycling. Polyurethane alcoholysis to carbamate and subsequent cracking to isocyanate represents a promising, phosgene-free recycling route. This work reports the thermal and catalytic cracking of a model carbamate (Methyl N-phenyl carbamate, MPC) to isocyanate (Phenyl isocyanate). Multiple catalysts (ZnO, Bi₂O₃, Al₂O₃, and Montmorillonite K-10) were evaluated in a closed system (batch autoclaves) to decompose MPC at temperatures of 160-200 °C, with a thorough analysis of the products and high (≥90%) mole balance. The thermal reaction was very limited at these temperatures, whereas the catalytic reaction led mainly to aniline and urea and seemed to be dominated by water adsorbed on the catalyst surface.

Kinetic model for the dehydration of xylose to furfural from a boronate diester precursor

A comprehensive kinetic model describes the dehydration of xylose starting from the boronate diester-protected xylose (PBA2X). The model incorporates (de)esterification of PBA2X, partitioning, and xylose dehydration, and aims to evaluate the effects of the solvent system on these steps. The model explores the effect of the water contents in monophasic solvent systems, and that of ionic strength and mixing in biphasic aqueous-organic systems. At low water content, hydrolysis of PBA2X is the rate-limiting step, while xylose dehydration is fast. Conversely, in a monophasic three-solvent system, where the water content is higher, complete hydrolysis of the diester is achieved quickly. Under biphasic conditions, xylose dehydration is fast at high ionic strengths, but the slower partitioning/hydrolysis of PBA2X results in an overall slower furfural production. Furthermore, the observed different but high, constant xylose-to-furfural selectivities observed experimentally are tentatively ascribed to a higher order of parallel side-product formation.

Furfural to 1,4-Butanediol/Tetrahydrofuran - A Detailed Catalyst and Process Design

The feasibility to convert furan, a direct derivative of furfural, to a mixture of 1,4-butanediol (BDO) and tetrahydrofuran (THF) is demonstrated with industrially acceptable performances using mm-sized pellets of a carbon-supported RePd catalyst for 2000 h of operation. The reaction schemes were unraveled by spiking potential reaction intermediates and a full kinetic model was developed. Finally, we developed a comprehensive process flow scheme that integrates the conversion of furfural to furan, the recovery and purification of furan, its reductive hydration to BDO/THF as well as the recovery and purification of BDO and THF. This process concept appears economically viable at current furfural, BDO and THF market prices.

Fully Recyclable Bio-Based Thermoplastic Materials from Liquefied Wood

A novel, low-cost, and fully recyclable thermoplastic material is produced from liquefied lignocellulosic biomass and natural fibers. The matrix, which is the heavy fraction of the liquefaction product, is characterized in terms of molecular weight distribution, density, viscosity, softening point and tensile strength. It is possible to increase the mechanical strength of the matrix by a factor of up to 100 by reinforcing it with flax fibers. Specifically, the tensile strength increased from 0.4 MPa for the non-reinforced matrix, to 55 MPa for the matrix/flax composite with a fiber content of 20 wt %. These values are comparable to conventional thermoplastics, such as poly(methyl methacrylate), polyvinyl chloride, or polystyrene.

Don't Forget Product Recovery in Catalysis Research-Check the Distillation Resistance

When investigating a new catalytic reaction, scientists may wonder if the crude reaction product can be easily separated and purified. We present here a new concept-distillation resistance-to assess the potential of distillation as a purification technique and to guide catalyst formulation or operation at the very early stage of the research. Distillation resistance, which has been developed from the analysis of 15 industrial distillation trains, can be quickly calculated with knowledge of only the product composition and atmospheric boiling points of the components. It can be directly converted into a preliminary distillation cost that considers investment and energy cost. Its application and its potential guidance in catalysis research are illustrated through a few cases studies derived from biorefinery processes.

Catalysis for biorefineries – performance criteria for industrial operation

Make sure your biorefinery catalyst meets the performance criteria required for industrial application!

Liquefaction of Lignocellulose in Fluid Catalytic Cracker Feed: A Process Concept Study

We report a process concept for lignocellulose liquefaction in a refinery stream that will be coprocessed with the resulting biocrude and that, therefore, does not require the recovery and recycling of the liquefaction solvent. Light cycle oil and vacuum gas oil were found to be the two most promising solvents. Both refinery streams could provide a liquid yield of 58 C % (64 % energy yield). A techno-economic assessment indicates that the biocrude could be produced at an energy-equivalent crude oil price of 51-64 $ per barrel at a wood cost of 85 $ per dry ton.

Renewable Feedstocks: The Problem of Catalyst Deactivation and its Mitigation

Much research has been carried out in the last decade to convert bio-based feedstock into fuels and chemicals. Most of the research focuses on developing active and selective catalysts, with much less attention devoted to their long-term stability. This Review considers the main challenges in long-term catalyst stability, discusses some fundamentals, and presents options for their mitigation. Three main challenges are discussed: catalyst fouling, catalyst poisoning, and catalyst destruction. Fouling is generally related to the deposition of insoluble components present in the feed or formed by degradation of the feed or intermediates. Poisoning is related to the deposition of electropositive contaminants (e.g. alkali and alkaline earth metals) on acid sites or of electronegative contaminants (e.g. N and S) at hydrogenation sites. Catalyst destruction results from the thermodynamic instability of most oxidic supports, solid acids/bases, and hydrogenation functions under hydrothermal conditions.

Liquefaction of lignocellulosic biomass: solvent, process parameter, and recycle oil screening

The liquefaction of lignocellulosic biomass is studied for the production of liquid (transportation) fuels. The process concept uses a product recycle as a liquefaction medium and produces a bio-oil that can be co-processed in a conventional oil refinery. This all is done at medium temperature (≈ 300 °C) and pressure (≈ 60 bar). Solvent-screening experiments showed that oxygenated solvents are preferred as they allow high oil (up to 93% on carbon basis) and low solid yields (≈ 1-2% on carbon basis) and thereby outperform the liquefaction of biomass in compressed water and biomass pyrolysis. The following solvent ranking was obtained: guaiacol>hexanoic acid ≫ n-undecane. The use of wet biomass results in higher oil yields than dry biomass. However, it also results in a higher operating pressure, which would make the process more expensive. Refill experiments were also performed to evaluate the possibility to recycle the oil as the liquefaction medium. The recycled oil appeared to be very effective to liquefy the biomass and even surpassed the start-up solvent guaiacol, but became increasingly heavy and more viscous after each refill and eventually showed a molecular weight distribution that resembles that of refinery vacuum residue.

Furfural production by 'acidic steam stripping' of lignocellulose

Furfural and acetic acid are produced with approximately 60 and 90 mol % yield, respectively, upon stripping bagasse with a gaseous stream of HCl/steam and condensing the effluent to water/furfural/acetic acid. The reaction kinetics is 1(st)  order in furfural and 0.5(th)  order in HCl. A process concept with full recycling of the reaction effluents is proposed to reduce the energy demand to <10 tonsteam  tonfurfural (-1) and facilitate the product recovery through a simple liquid/liquid separation of the condensate into a water-rich and a furfural-rich phase.

Furfural--a promising platform for lignocellulosic biofuels

Furfural offers a promising, rich platform for lignocellulosic biofuels. These include methylfuran and methyltetrahydrofuran, valerate esters, ethylfurfuryl and ethyltetrahydrofurfuryl ethers as well as various C(10)-C(15) coupling products. The various production routes are critically reviewed, and the needs for improvements are identified. Their relative industrial potential is analysed by defining an investment index and CO(2) emissions as well as determining the fuel properties for the resulting products. Finally, the most promising candidate, 2-methylfuran, was subjected to a road trial of 90,000 km in a gasoline blend. Importantly, the potential of the furfural platform relies heavily on the cost-competitive production of furfural from lignocellulosic feedstock. Conventional standalone and emerging coproduct processes-for example, as a coproduct of cellulosic ethanol, levulinic acid or hydroxymethyl furfural-are expensive and energetically demanding. Challenges and areas that need improvement are highlighted. In addition to providing a critical review of the literature, this paper also presents new results and analysis in this area.

Sustainable chemical manufacturing: a matter of resources, wastes, hazards, and costs

Sustainable development is gaining importance in the chemical industry. It encompasses social, environmental, and economical aspects. Herein, sustainable development is translated into four basic dimensions, called "sustainability stresses": resources, wastes, hazards, and costs. These sustainability stresses are discussed in some detail and their usefulness is illustrated by applying them to three manufacturing processes applied commercially by Shell, namely Shell's OMEGA, SMPO, and "low monol" technologies for producing ethene diol, styrene/propene oxide, and polyether polyols, respectively. These examples show that large reductions in sustainable stresses have been achieved in a few decades. They also show that the economical, environmental, and social issues are not in conflict when tackled at their roots: they can be all addressed simultaneously.

Conversion of furfuryl alcohol into ethyl levulinate using solid acid catalysts

Furfural, a potential coproduct of levulinic acid, can be converted into levulinic acid via hydrogenation to furfuryl alcohol and subsequent ethanolysis to ethyl levulinate. The ethanolysis reaction is known to proceed in the presence of H(2)SO(4). We show here that several strongly acidic resins are comparably effective catalysts for this reaction. Optimal performance is achieved by balancing the number of acid sites with their accessibility in the resin. Acidic zeolites such as H-ZSM-5 also catalyze this reaction, although with a lower activity and a higher co-production of diethyl ether.

Towards ‘bio-based’ Nylon: conversion of γ-valerolactone to methyl pentenoate under catalytic distillation conditions

Methyl pentenoate, a promising Nylon intermediate, is produced in >95% yield via the transesterification of gamma-valerolactone, a bio-based intermediate, under catalytic distillation conditions.

Monolithic catalysts for the fixed-bed hydrogenation of polymers

Monolithic catalysts were successfully applied in a true fixed-bed hydrogenation of polymers such as SBS rubbers and polystyrene.