Prediction of pyrolyzate yields by response surface methodology: A case study of cellulose and polyethylene co-pyrolysis

Selective recovery of pyrolyzates of biodegradable (PLA, PHBH) and common plastics (HDPE, PP, PS) during co-pyrolysis under slow heating

Pyrolytic synergistic interactions, in which the production of pyrolyzates is enhanced or inhibited, commonly occur during the co-pyrolysis of different polymeric materials, such as plastics and biomass. Although these interactions can increase the yield of desired pyrolysis products under controlled degradation conditions, the desired compounds must be separated from complex pyrolyzates and further purified. To balance these dual effects, this study was aimed at examining pyrolytic synergistic interactions during slow heating co-pyrolysis of biodegradable plastics including polylactic acid (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexaoate) (PHBH) and petroleum-based plastics including high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS). Comprehensive investigations based on thermogravimetric analysis, pyrolysis-gas chromatography/mass spectrometry, and evolved gas analysis-mass spectrometry revealed that PLA and PHBH decompose at lower temperatures (273-378 °C) than HDPE, PP, and PS (386-499 °C), with each polymer undergoing independent decomposition without any pyrolytic interactions. Thus, the independent pyrolysis of biodegradable plastics, such as PLA and PHBH, with common plastics, such as HDPE, PP, and PS, can theoretically be realized through temperature control, enabling the selective recovery of their pyrolyzates in different temperature ranges. Thus, pyrolytic approaches can facilitate the treatment of mixed biodegradable and common plastics.

Effect of Reaction Conditions on Energy Yield of Pyrolysis Gas from Apple Tree Branches

Although the annual branches of apple trees are substantial, most of them are discarded or incinerated, resulting in a significant waste of resources and environmental pollution concerns. Therefore, it has become necessary and urgent to recycle these branches. Compared with crop straw, apple tree pruning branches exhibit a relatively elevated lignin content, which makes them an optimal feedstock for generating high-quality pyrolysis gases. Energy yield can comprehensively measure the gas production and heat value of the pyrolysis gas. Herein, the effect of reaction conditions on the energy yield of the pyrolysis gas is systematically investigated. The single-factor experimental results show that the optimal conditions are 750 °C reaction temperature, 2 °C/min heating rate, and 120 min holding time. The central composite design test of the response surface establishes that temperature has the most impact, followed by heating rate and holding time. In addition, a regression model is constructed to predict the energy yield of the pyrolysis gas. The analysis of interactions between factors indicates that factors within the lower temperature zones, higher heating rate, and shorter holding time have a more significant influence on the energy yield. These findings provide crucial guidance for the efficient production of pyrolysis gas from apple tree branches.

Effect of Feed Mass, Reactor Temperature, and Time on the Yield of Waste Polypropylene Pyrolysis Oil Produced via a Fixed-Bed Reactor

This paper presents the results of investigations into the pyrolysis of waste polypropylene in a laboratory fixed-bed batch reactor. The experiments were designed and verified in such a way as to allow the application of the response surface methodology (RSM) in the development of an empirical mathematical model that quantifies the impacts mentioned above. The influence of the mass of the raw material (50, 100, and 150 g) together with the reactor temperature (450, 475, and 500 °C) and the reaction time (45, 50 and 75 min) was examined. It has been shown that the mass of the raw material, i.e., the filling volume of the reactor, has a significant influence on the pyrolysis oil yield. This influence exceeds the influence of reactor temperature and reaction time. This was explained by observing the temperature change inside the reactor at three different spots at the bottom, middle, and top of the reactor. The recorded temperature diagrams show that, with greater masses of feedstock, local overheating occurs in the middle part of the reactor, which leads to the overcracking of volatile products and, from there, to an increased formation of non-condensable gases, i.e., a reduced yield of pyrolytic oil.

Enhancing the solubility and antimicrobial activity of cellulose through esterification modification using amino acid hydrochlorides

Most amino acid molecules have good water solubility and are rich in functional groups, which makes them a promising derivatizing agent for cellulose. However, self-condensation of amino acids and low reaction efficiency always happen during esterification. Here, amino acid hydrochloride ([AA]Cl) is selected as raw material to synthesize cellulose amino acid ester (CAE). Based on TG-MS coupling technology, a significantly faster reaction rate of [AA]Cl compared to raw amino acid can be observed visually. CAE with the degree of substitution 0.412-0.516 is facilely synthesized under 130-170 °C for 10-50 min. Moreover, the effects of amounts of [AA]Cl agent, temperature, and time on the esterification are studied. The CAE can be well dissolved in 7 wt% NaOH aq., resulting in a 7.5 wt% dope. The rheological test of the dope demonstrated a shear-thinning behavior for Newtonian-like fluid, and a high gel temperature (41.7 °C). Further, the synthesized products show distinct antibacterial activity and the bacteriostatic reduction rate against E. coli can reach 99.5 %.

Valorization of floral foam waste via pyrolysis optimization for enhanced phenols recovery

Utilization of phenol formaldehyde foams is becoming increasingly widespread, especially in floral bouquets, generating toxic microplastics in the environment. The present study evaluated phenols recovery from floral foam waste (FFW) of floral bouquets through optimization of pyrolysis conditions. Compared to the biomass portion in the floral bouquet, FFW showed 55.1% higher carbon content, 56.9% lower nitrogen content, and 44.6% lower oxygen content, with the highest recorded calorific value of 27.43 MJ kg^-1. Thermogravimetric analysis showed the relative thermal stability of FFW with gradual weight loss and numerous small peaks at 70 °C (representing short chain volatiles such as formaldehyde and phenol), 450 and 570 °C (due to phenolic and aromatic products release), indicating the richness of FFW with phenolic compounds. Optimization of pyrolysis conditions showed the highest significant biocrude yield of 36.0% at 700 °C for 20 min using FFW load of 2.5 g. However, optimization of phenolic production suggested 520 °C, 30 min, and 3.49 g FFW load as optimum conditions for high biocrude yield with enhanced phenolic proportion. Experimental results using the aforementioned conditions showed phenolics potential of 0.22 g phenolics/g FFW, with 78.8% phenolic compounds composed mainly of phenol and its methyl derivatives.

Marine Biomass-Supported Nano Zero-Valent Iron for Cr(VI) Removal: A Response Surface Methodology Study

Heavy metal ions such as Cr(VI) pose great hazards to the environment, which requests materials and methods for decontamination. Nano zero-valent iron (nZVI) has emerged as a promising candidate for Cr(VI) removal. Herein, harnessing the merits of marine biomass, a heterogeneous water treatment system for the decontamination of Cr(VI) is developed based on the in situ immobilization of nZVI on the seashell powder (SP)-derived porous support. A response surface methodology (RSM) study involving three independent factors is designed and conducted to direct material synthesis and reaction design for products with optimal performances. Under optimal synthetic conditions, the nZVI-loaded seashell powder (SP@nZVI), which is characterized in detail by scanning electron microscope (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR), results in a 79% increase in the removal efficiency of Cr(VI) compared to free nZVI. Mechanism studies show that the removal of Cr(VI) by SP@nZVI conforms to the Langmuir adsorption model with a quasi-second order kinetic equation, in which redox reactions between nZVI and Cr(VI) occurred at the SP surface. The results of this work are expected to benefit the reuse of bioresource waste in developing environmental remediation materials.