Biobased polymer molecules are a goal for the future. Here, the different intermediate pathways toward renewable structural constituents, which can substitute petrochemically derived unsustainable ...ones, are evaluated. Various biomass resources are covered, such as cellulose, hemicellulose, lignin, lipids, and proteins, as well as their building blocks, such as sugars, glycerol, or itaconic acid. Further emphasis is put on the impact of the impurities in the biobased monomers and the possible separations steps to remove them. The kinetics of the radical polymerization process of reacting acrylic monomers, methacrylic monomers, and styrene is reviewed. Classical elementary mechanisms are briefly discussed, while focus is put on secondary chemical reactions that influence rates greatly at elevated system temperatures, starved-feed conditions, and unideal-mixed reactor units. These functional measures have now become a common standard practice in resin production manufacturing. Described breaking/forming transformations are the styrene self-initiation step, macromonomer carrier propagation, backbiting, long chain branching, β-scission, and methacrylate continuous depropagation. The effect of the copolymerization on involved occurring changes is also overviewed. Likewise, functionality now plays a much greater role than it used to, is linked to final formulation characteristics, and is thus an integral related part of this theoretical methodology. Cross-linking mechanisms are briefly discussed. Last but not least, an insight into modeling is presented with an emphasis on lumping, the method of moments, Monte Carlo applications, and simulating conversions, as well as correlated molecular mass distributions.
Detailed reaction kinetics of oil transesterification were studied based on mechanism and reaction scheme of individual triglyceride, diglyceride, monoglyceride, glycerol and fatty acid methyl ester ...containing different combinations of gadoleic, iinoleic, linolenic, oleic, palmitic and stearic acids determined by high-performance liquid chromatography. Pre-exponential factors and activation energies were correlated with molecular structure in terms of chain lengths and double bonds by response surface models. The activation energies of forward reactions were 47-61 kJ mol super(-1) with backward ones being 31-49 kJ mol super(-1), depending on component structure. Mass transfer during initial emulsion phase was acknowledged by determining diffusivities, distribution coefficients, molar volumes, boiling points and viscosities of individual components. Model was validated for a wide range of temperatures, hydrodynamic conditions, dispersed and continuous phase ratios, and methanolysis catalyst concentrations. Rotational speed had the most profound influence on the duration of transport phenomena-limited region spanning the latter to 27 min upon use of 100 rpm. Economics of the process were finally evaluated in terms of alcoholysis cost and price breakdown. Proposed methodology may be usefully applied to transesterification syntheses employing heterogeneous catalysis and enzymes, as well as various renewable resources such as microalgae lipids, waste oils, bioethanol and biobutanol.
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•Solvent-free hydrotreatment of levulinic acid was studied over sulphided NiMo/Al2O3.•Micro-kinetics of catalytic and homogeneous HDO, decarboxylation and dimerization.•Higher ...decarboxylation Ea than catalytic hydrogenation lowers GVL yield at high T.•External mass transfer limitations play an important role at low agitation rate.•Dimerization of levulinic acid via aldol addition and HDO forms spirolactone.
Levulinic acid (LA) hydrotreatment at solvent-free conditions was studied in a slurry reactor over the sulphide form of NiMo/Al2O3 catalyst. The influence of process parameters on the H2 equilibrium solubility in the liquid (calculated by Soave–Redlich–Kwong, EOS), on the external and internal mass transfer limitations, adsorption and desorption rates and the rates of surface and homognenous reactions were determined experimentally and computationally by utilizing a newly-developed micro-kinetic model. Main catalytic hydrodeoxygenation (HDO) product γ-valerolactone (GVL) was formed on NiMoSx phase (surface sites concentration of 0.33μmolm−2 was determined) exclusively by LA hydrogenation to hydroxypentanoic acid, and its subsequent intramolecular esterification, while cyclisation of LA to angelica lactones and their saturation was negligible. Activation energies determined by the regression analysis for the rate-determining step of catalytic LA HDO (Ea 39kJmol−1) and competitive LA decarboxylation in bulk liquid (Ea 134kJmol−1) show, that the temperature increase from 225°C to 275°C accelerated the decarboxylation rates much faster than HDO, which reflected in the drop of selectivity towards GVL formation from 90 to 42%, while its yield was not significantly affected (2.5±3molL−1 within 60min at final temperature). LA oligomerization by aldol addition and subsequent dehydrative cyclisation is reported for the first time and its rate was independent of the catalyst loading or H2/N2 pressure. Internal mass transfer had no influence on the global reaction rate, while the external mass transfer was eliminated at high agitation rate.
The related immense versatility of a ceria-promoted transition metal catalyst, utilized for the hydrogenation of 5-hydroxymethylfurfural (HMF), is demonstrated in this research study. We reveal a ...strategy to achieve considerable selective yields of three important high-value HMF-derived compounds by simply modifying the analysed reaction conditions and/or water-containing process medium.
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•Experimental and ab-initio study of eugenol HDO over Pt, Pd, Rh, Ru, Ni, Cu on C.•Micro-kinetics modelling of adsorption, desorption, bulk and surface reactions.•The lowest ...hydrogenation/deoxygenation ratio found for Ru/C, the highest for Pd/C.•Hydrogenation of demethoxylated aromatics is facilitated.•Ru closest to the top of the volcano dependency: TOF vs. eugenol adsorption energy.
In this integrated in silico and experimental study, the activity, selectivity and mechanisms of commercially-available noble and transition metal heterogeneous catalysts, on neutral (carbon) support were investigated for hydrodeoxygenation (HDO) of eugenol. The latter was selected as a model compound of lignin building blocks. An influence of the process operating conditions (temperature, pressure and initial solid loading) on the reaction pathway and product distribution was studied as well. The previously-proposed reaction network for phenols HDO over Ru/C was found valid also for other platinum-group- (Pd, Pt and Rh) and non-noble (Cu or Ni) metallic clusters supported on C. Ru/C system exhibited the best HDO turnover performance, followed by the Rh/C, which especially demonstrated an excellent hydrogenation activity. Pt and Pd showed low deoxygenation and moderate hydrogenation activity. Kinetic parameters for all reactions on the surface were determined for all tested metals with a micro-kinetic model, by regression analysis on the foundation of 5760 experimentally-determined concentration values. Computation took into account resistances caused by transport phenomena, adsorption/desorption kinetics, and especially surface and bulk reaction kinetics. Ratio between adsorption and desorption rate constants for dissolved saturated, aromatic and hydrogen species were predicted, indicating a notable coverage effect on the catalyst reactivity. The saturation of functionalised benzene ring was approximately 3-, 11-, 32-, 10-, and 6-times faster than the C–O hydrogenolysis over ruthenium, platinum, palladium, rhodium and nickel, respectively. Methoxy group removal is easier from aromatics, compared to aliphatic species and also compared to the hydroxyl group removal. The heteroatom bond breaking for 2-methoxy-4-propylcyclohexanol proceed mostly via catechol-type diol formation, and subsequently, de-hydroxylation, particularly observable on Pt.
•Solvolysis of cellulose, hemicellulose, lignin and wood in ionic liquids and glycerol.•Simultaneous solid biomass depolymerisation and hydrolysis, followed by deoxygenation.•Liquefaction model based ...on lignocellulosic biomass composition, particle size and structure.•Catalytic hydrodeoxygenation, hydrogenation and hydrocracking of solvolytic oil over NiMo/Al2O3.•Application of HDO kinetic model based on lumped group reactivity using FTIR analysis.
Solvolysis of wood, cellulose, hemicellulose and lignin in glycerol was investigated in the presence of homogeneous imidazolium-based ionic liquid (IL) catalysts, where the influence of the IL type, reaction time, temperature and mass transfer limitations on decomposition rate was investigated. The selection of anions (acetate, hydrogen sulphate or chloride/metal halide complex to form a Lewis acid) and cations (butyl-, methyl- or allyl-functionalised imidazolium) importantly influenced conversion, which was as high as 64.4 and 91.5wt% for the beech wood liquefaction at 150 and 200°C within 60min. By following the mass of solid particles and their specific surface area (BET method) as a function of time and temperature, a novel kinetic model for the solvolysis of biomass and its components was developed, where reactive surface area is a key parameter that dictates the rate of solid–liquid reaction; kinetic model also considered different depolymerisation reactivity of main three wood components. Liquefied biomass was consequently hydrodeoxygenated at 225–275°C in the presence of commercially available sulphide-form NiMo/γ-Al2O3 catalyst. Rates and selectivity of hydrogenolysis, decarbonylation, decarboxylation, hydrogenation and (hydro)cracking were followed and modelled by using previously developed lumped kinetic model, based on the Fourier transformed infrared spectroscopy (FTIR) analysis. The oxygen content of the oil phase of was less than 1.7wt%.
Raw residual wood biomass, containing cellulose, hemicellulose and lignin, was liquefied at low temperature by ultrasound-assisted solvolysis and acidolysis by glycerol, diethylene glycol and ...p-toluenesulfonic acid. Liquefied biomass was consequently upgraded by hydrotreatment utilizing heterogeneous catalysis over NiMo/Al2O3 bifunctional catalyst. Effects of temperature (200−350 °C), heating rate (2.5–10.0 K min−1), hydrogen/nitrogen pressure (2−8 MPa), mixing (250−1000 min−1), hydrogen donor solvent (tetralin) and catalyst contents on deoxygenation were established. Reactions of liquefaction products, such as levulinic acid, were quantified based on their functional groups by Fourier transform infrared spectroscopy, whereas catalyst was examined by scanning electron microscopy, energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction analysis (XRD). Chemical kinetics of hydrodeoxygenation (HDO), decarbonylation and decarboxylation were determined by originally developed lumped model, based on reaction mechanisms and pathways, while the external mass transfer resistance proved to be negligible under the applied hydrodynamic conditions. The presence of hydrocracking reactions was confirmed by a decrease in product viscosity, and the upgrade for energetic or fuel applications by measurements of calorific value.
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•Liquefaction of waste lignocellulosic biomass with glycerol at low temperature.•Hydrotreatment, hydrocracking and hydrodeoxygenation of liquefied waste biomass.•Deoxygenation using heterogeneous catalysis over NiMo/Al2O3 bifunctional catalyst.•Proposal of reaction mechanism; chemical kinetics and mass transfer considerations.•Effect of temperature, heating rate, pressure, mixing, solvent and catalyst content.
Atmospheric-pressure dielectric barrier discharge plasma was used as a methodology for a crustacean shell waste pre-treatment process, resulting in intensified protein removal. This renewable ...electricity-based separation operation can serve as a scalable green alternative to the conventional chemical purification in the production of the chitin biopolymer, which applies unrecyclable mineral bases.
We have investigated the concept of an integrated system for small, manportable power units. The focus of this study is the direct thermal coupling of a methanol steam reformer (MSR) and a ...high-temperature proton exchange membrane fuel cell (HT PEMFC) stack. A recently developed low-temperature (LT) MSR catalyst (CuZnGaOx) was synthesized and tested in a designed reforming reactor. The experimental data show that at 200 °C the complete conversion of methanol is achievable with a hydrogen yield of 45 cm3 min−1 gCAT−1. An experimental setup for measuring the characteristics of the integrated system was designed and used to measure the characteristics of the two-cell HT PEMFC stack. The obtained kinetic parameters and the HT PEMFC stack characteristics were used in the modeling of the integrated system. The simulations confirmed that the integrated LT MSR/HT PEMFC stack system, which also includes a vaporizer, can achieve a thermally self-sustained working point. The base-case scenario, established on experimental data, predicts a power output of 8.5 W, a methanol conversion of 98.5%, and a gross electrical efficiency (based on the HHV) of the system equal to 21.7%. However, by implementing certain measures, the power output and the electrical efficiency can readily be raised to 11.1 W and 35.5%, respectively.
•LT MSR catalyst capable of operating below 200 °C was successfully synthesized.•Threefold increase in hydrogen yield compared to the most recent studies.•High activity of the LT MSR catalyst allows high current densities in the HT PEMFC stack.•Direct thermal coupling of the LT MSR and the HT PEMFC stack is possible at 200 °C.•Methods for further system optimization identified using the sensitivity analysis.
A model acknowledging reaction kinetics and thermal conduction during waste end-of-life (ELT) tyre pyrolysis was developed based on the individual consideration of elastomers, namely natural (NR), ...butadiene (BR) and styrene–butadiene (SBR) rubber; fabric, that is rayon, nylon and aramid; and wire. External diffusional and thermal film resistances proved to be negligible during the thermal cracking. An algorithm was developed to extract pre-exponential factors, activation energies, the orders of reactions, the enthalpies of reactions, and transport parameters. The pyrolysis of various formulations at different volumetric flow rates and heating rates was monitored by thermogravimetry (TG) and differential scanning calorimetry (DSC), whereas the pertinent thermodynamic properties (density, specific heat capacity, and thermal conductivity and diffusivity) were determined separately. The un-decomposable weight fraction containing carbon black, char and ash was 39% for the investigated rubber and 13% for the fabric formulation. The sensitivity analysis of the pyrolysis on compound and process (operating) conditions was performed. The obtained results (taking into account their drawbacks) with the additional measurements and modelling may be used for the thermo-chemical treatment reactor scale-up and optimization, and consequently, a suitable design of energy and products recovery instead of disposal or landfilling, thus minimizing hazardous waste and contamination to soil and water resources.
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► Pyrolysis of scrap rubber, other tyre components (fabric, etc.) and composites. ► Thermogravimetry (TG) and differential scanning calorimetry (DSC) measurements. ► Influence of volumetric flow rate and heating rate on rubber pyrolysis process. ► Modelling chemical reaction kinetics, external and internal mass and heat transfer. ► Evaluation of pyrolysis with sensitivity analysis (differing waste compositions).
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