Pyrolysis of mixed plastics for the recovery of useful products

Thermal and catalytic pyrolysis of polystyrene (PS) with low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), poly-ethylene terephthalate (PET) plastics were carried out in a 25 cm³ stainless steel micro reactor at around 430–440 °C under 5.5–6.0 MPa of N₂ gas pressure for 1 h. Three reactions of each plastic with PS were conducted in the ratio of 1:1, 1:2 and 1:3. The amount of PS was varied to explore its role and reactivity. In all coprocessing reactions, ratio 1:1 afforded the best yields in the form pyrolytic oils. SIM distillation of hexane soluble portion showed that the low boiling fractions were not found and fractions were obtained only after 96 °C + boiling point. It could be due to the vaporization of high volatile components. In most of the binary pyrolysis, light cycle oil (LCO) fractions have low recovery than heavy cycle oil (HCO). GC identified some very important chemical compounds present in the liquid products obtained from the pyrolysis of mixed plastics. The results obtained from this study have shown usefulness and feasibility of the pyrolysis process of the mixed plastics as an alternative approach to feedstock recycling.     

Recycling polymeric wastes by means of pyrolysis

Different polymeric wastes, which include materials from the automobile industry, such as tyres, automobile shredder residues (ASR) and sheet moulding compound (SMC), and materials from municipal solid wastes (MSW), such as cardboard, tetrabrik and plastics (LDPE, PP, PS, PET and PVC), pure and mixed, have been pyrolysed in a 3.5 dm³ autoclave at 500 °C for 30 min in a nitrogen atmosphere. The amount and characteristics of the solid, liquids and gases obtained are presented. The suitability of the different materials for the pyrolysis recycling process is discussed. It is concluded that pyrolysis is a very promising technique for recycling tyres, SMC, one type of ASR (heavy ASR), and LDPE, PP and PS, either pure or mixed; with all of them valuable solid, liquid and gaseous products are obtained in pyrolysis. On the contrary, light ASR, tetrabrik and cardboard do not yield valuable products in the pyrolysis process and therefore their recycling by pyrolysis is not of interest, except as a way of volume reduction. PET and PVC turned out to be troublesome in the pyrolysis experiments; for a proper study of their recycling by pyrolysis other operating conditions and installations are required. © 2002 Society of Chemical Industry     

Copyrolysis of oils/waxes of individual and mixed polyalkenes cracking products with petroleum fraction

Copyrolysis of 10 mass% solutions (oils/waxes from individual or mixed polymers with heavy naphtha) is a route for treatment of plastic waste. Linear low-density polyethylene (LLDPE), mixture of high-density polyethylene/low-density polyethylene/linear low-density polyethylene/polypropylene (HDPE/LDPE/LLDPE/PP = 1:1:1:1mass) and linear low-density polyethylene/low-density polyethylene/polypropylene/high-density polyethylene/polyvinyl chloride/polyethylene terepthalate/polystyrene (LLDPE/LDPE/PP/HDPE/PVC/PET/PS = 1:1:2:2:0.05:0.05:0.156 mass) were converted to oils/waxes, gases and solid residues by thermal decomposition in batch reactor at 450 °C. Oils/waxes were dissolved in virgin heavy naphtha to create the feedstock. The influence of residence time from 0.08 to 0.51 s at temperatures 780 °C and 820 °C on product distribution during the copyrolysis was studied. The yields obtained from gaseous and liquid products of solutions are compared to the yields obtained from virgin heavy naphtha. It was studied how addition of the oil/wax influences formation of C₂ and C₃ hydrocarbons (mainly ethene and propene) and aromatics in comparison to the virgin heavy naphtha. The ethene and propene yields from copyrolysis of solutions are comparable or higher than from virgin heavy naphtha. Copyrolysis of solution LLDPE/LDPE/PP/HDPE/PVC/PET/PS gives the maximum yields of propene from all studied oils/waxes. The result suggests that oils/waxes from polymers are suitable feedstocks for copyrolysis with virgin heavy naphtha.     

Effects of thermal pretreatment in helium on the pyrolysis behaviour of Loy Yang brown coal

A wire-mesh reactor capable of multi-step heating/holding and minimising secondary reactions of volatiles was used to investigate the effects of thermal pretreatment in inert gas on the subsequent rapid pyrolysis behaviour of Loy Yang brown coal. Our results indicate that the presence of small amounts (<10 wt%) of moisture in brown coal has little influence on the tar and char yields from the pyrolysis of brown coal at 1000 K s⁻¹. While the hydrogen bonds between the moisture and the O-containing functional groups in the brown coal have little effects on its pyrolysis behaviour, the hydrogen bonds among the O-containing functional groups tend to induce cross-linking reactions to reduce the tar yields. Preheating the brown coal at >250 °C leads to reduced tar and increased char yields. However, the characterisation of tars using UV-fluorescence spectroscopy indicates that significant decreases in the release of larger aromatic ring systems are only observed after preheating at >380 °C for 30 min. The presence of ion-exchangeable cations (e.g. Ca²⁺) in the brown coal tends to stabilise the carboxylate groups and only preheating at >350 °C would result in changes in pyrolysis yields during the subsequent pyrolysis at 1000 K s⁻¹. These results may be explained by considering the formation of cross-links involving peripheral groups at low preheating temperatures and the formation of cross-links involving aromatic ring systems at elevated temperatures.     

Pyrolysis kinetics of olive residue/plastic mixtures by non-isothermal thermogravimetry

The TGA studies of a pyrolytic decomposition of mixtures of olive residue/plastic were carried out. The investigation was made at the temperature ranging from 300 to 1273 K) in the nitrogen atmosphere at four heating rates β = 2, 10, 20 and 50 K min^− 1. High density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP) and polystyrene (PS) were selected as plastic samples. Based on the results obtained, three thermal stages were identified during the thermal degradation. The first two were dominated by the olive residue pyrolysis, while the third was linked to the plastics pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on pyrolysis olive residue/plastic mixtures. The maximum degradation temperatures of each component in the mixture were higher than those of the individual components. These experimental results indicate a significant synergistic effect during olive residue and plastic co-pyrolysis at the high temperature region. In addition, a kinetic analysis was performed to fit thermogravimetric data. A reasonable fit to the experimental data was obtained for all materials and their mixtures.     

Investigation on pyrolysis of Moroccan oil shale/plastic mixtures by thermogravimetric analysis

Thermal degradation processes for a series of mixtures of oil shale/plastic were investigated using thermogravimetric analysis (TGA) at four heating rates of 2, 10, 20 and 50 K min^− 1 from ambient temperature to 1273 K. High density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) were selected as plastic samples. Based on the results obtained, three thermal stages were identified during the thermal degradation. The first is attributed to the drying of absorbed water; the second was dominated by the overlapping of organic matter and plastic pyrolysis, while the third was linked to the mineral matter pyrolysis, which occurred at much higher temperatures. Discrepancies between the experimental and calculated TG/DTG profiles were considered as a measurement of the extent of interactions occurring on co-pyrolysis. The maximum degradation temperatures of each component in the mixture were higher than those of the individual components; thus an increase in thermal stability was expected. In addition, a kinetic analysis was performed to fit thermogravimetric data. A reasonable fit to the experimental data was obtained for all materials and their mixtures.     

Integrated coal pyrolysis with CO2 reforming of methane over Ni/MgO catalyst for improving tar yield

A new process to integrate coal pyrolysis with CO₂ reforming of methane over Ni/MgO catalyst was put forward for improving tar yield. And several Chinese coals were used to confirm the validity of the process. The experiments were performed in an atmospheric fixed-bed reactor containing upper catalyst layer and lower coal layer to investigate the effect of pyrolysis temperature, coal properties, Ni loading and reduction temperature of Ni/MgO catalysts on tar, water and char yields and CH₄ conversion at fixed conditions of 400 ml/min CH₄ flow rate, 1:1 CH₄/CO₂ ratio, 30 min holding time. The results indicated that higher tar yield can be obtained in the pyrolysis of all four coals investigated when coal pyrolysis was integrated with CO₂ reforming of methane. For PS coal, the tar, water and char yield is 33.5, 25.8 and 69.5 wt.%, respectively and the CH₄ conversion is 16.8%, at the pyrolysis temperature of 750 °C over 10 wt.% Ni/MgO catalyst reduced at 850 °C. The tar yield is 1.6 and 1.8 times as that in coal pyrolysis under H₂ and N₂, respectively.     

PET pyrolysis and hydrolysis mechanism in the fixed pyrolyzer

In the conventional polyethylene terephthalate (PET) pyrolysis process, the formation of char by excessive pyrolysis is mainly due to the dehydration mechanism, so water is considered an auxiliary agent that can effectively inhibit excessive pyrolysis. The preparation of terephthalic acid (TPA) by steam-assisted pyrolysis of PET is an effective method to achieve closed-loop recycling of waste PET. To ensure that the reaction is mild enough to reduce excessive cracking products such as char and benzoic acid and thus increase the yield of TPA, it is critical to reduce the reaction rate while maintaining a sufficient excess steam coefficient. Under the optimal operating conditions, when the temperature rise rate was 0.5 °C min⁻¹ and the excess steam coefficient was 150, the yield of TPA was 72.5 wt.%, and the purity was 85.5%. Noticeably, the steam-assisted pyrolysis system is a heterogeneous reaction system whose reaction mechanism is different from the conventional hydrolysis and pyrolysis reactions and has a unique reaction path. The mechanistic study indicates that, in addition to the thermal cracking of PET molecules occurring in conventional pyrolysis, hydroxyl attack and transfer, and supplementation of benzene ring hydrogen also occur between water and intermediate molecules. Meanwhile, it has also been proven that the intermolecular hydrogen transfer between intermediate molecules and water molecules is the key to reduce the intensity of the reaction and inhibit the formation of char. This discovery illustrates the mechanism of the reaction between water and PET in the steam-assisted pyrolysis process in the fixed pyrolyzer and justifies the distinction between it and the pyrolysis and hydrolysis processes of PET. It provides a theoretical basis for optimizing the pyrolysis process of PET, which is essential for the industrialization of TPA preparation from PET steam-assisted pyrolysis.     

Effect of in situ fibrillation on polyethylene/poly(ethylene terephthalate)/multiwalled carbon nanotube electromagnetic shielding foams

In this study, polyethylene (PP)/polyethylene terephthalate (PET)/multiwalled carbon nanotube (MWCNT) nanocomposites with nanofibrillary structure were processed by hot drawing-assisted extrusion technology, and nonfoaming and microfoaming samples were processed by injection molding machine. Scanning electron microscope micrographs showed that when PET content was 2.5 wt%, PET fibers had a larger aspect ratio, which brought an outstanding promotion on microfoaming of PP matrix, and further details were provided by DSC and rheology analysis. When foaming sample loaded with 2.5 wt% PET and 3 wt% MWCNT, the best shielding effectiveness achieved 29.91 dB·cm³·g⁻¹ in the test frequency range about 8.2–12.4 GHz. The results proved that the introduction of PET fibers optimized the microfoaming effect, and the uniform cell structure promoted the MWCNT dispersion and internal reflection of electromagnetic wave. Therefore, the shielding property is absorption-dominated type and meets the requirements of lightweight and ultraefficient shielding demand of industry.     

Intercalated montmorillonite by cyclotriphosphazene imidazole derivative and its thermal properties used in polyester

Montmorillonite (MMT) and hexachlorocyclotriphosphazene (HCCP) are two focal materials to investigate in improving the thermal properties of polymer in recent years. They are used to improve the thermal performance of polymer from different aspects. MMT usually could play an important role in preventing or slowing down the penetration of heat and flame by layers of the mineral. However, making polymer dehydrate and carbonize and generating incombustible ammonia, which can dilute the concentration of combustible gas, are the major ways from HCCP. In this study, a novel intercalated MMT containing high content of phosphorus and nitrogen was synthesized by MMT and HCCP (HCCP‐in‐MMT). It was applied to improve the thermal performance of polyethylene terephthalate (PET) polymer. ¹H NMR and ³¹P NMR technology were used to track the structures of a series of intermediates. The composites were prepared by melt‐blending neat PET with HCCP‐in‐MMT and named as PET/HCCP‐in‐MMT material. Three levels of HCCP‐in‐MMT (1, 3, and 5 wt%) were considered for the blends. The preliminary application in improving the thermal performance of PET was studied by thermo‐gravimetric (TG) analysis and pyrolysis–gas chromatography–mass spectrometry; pyrolysis–gas chromatography–mass spectrometry study showed that the introduction of HCCP‐in‐MMT would inhibit the pyrolysis of PET during heating or burning. The flame retardancy performance of PET composites was characterized by limiting oxygen index tests and UL‐94 test. The result showed that the composites could pass UL‐94 V‐1 and limiting oxygen index value 28.3% just only containing 5 wt% of HCCP‐in‐MMT. TEM showed that the inserted layer structure was formed between PET matrix and synthetic flame retardant HCCP‐in‐MMT. Copyright © 2016 John Wiley & Sons, Ltd.     

Classification of volatile products evolved during temperature-programmed co-pyrolysis of low-density polyethylene (LDPE) with polypropylene (PP)

Temperature programmed co-pyrolysis of low-density polyethylene (LDPE) with polypropylene (PP) was investigated. The aim of this research was to determine the volatile product distribution and product evolution rate of co-processing of LDPE with PP. A series co-pyrolysis operation was performed with LDPE and PP using a 1:3, 1:1, 3:1 total carbon ratio of LDPE to PP. A fixed bed reactor was used to pyrolyse small sample of LDPE and PP mixture under an inert gas flow (argon). A special sampling technique was used for collecting organic products eluted from the reactor at different temperature and time intervals. The co-pyrolysis products were analyzed by capillary gas chromatography and the total product evolution rate was investigated as a function of temperature and time. n-paraffins and 1-olefins in aliphatic fraction of co-pyrolysis products were classified as a carbon number. In addition, the recovery of total organic carbon as an organic volatile product was determined. The assessments were based on incorporating the results on temperature-programmed pyrolysis of LDPE and PP. The effect of co-processing of LDPE with PP was determined by calculating the difference between the experimental and the hypothetical mean value of conversion of total organic carbon into volatile products. Conversion into volatile hydrocarbons was found to be higher, with the increasing PP ratio in the co-pyrolysis operation.     

Structural characterization of fractions of petroleum pitch and ethylene pyrolysis tar by 1H and 13C n.m.r. spectroscopy

A petroleum pitch and > 288 °C fraction of an ethylene pyrolysis tar are separated by sequential solvent extraction into fractions differing in average molecular weight. Average molecular parameters for each fraction are obtained using their H and ¹³C n.m.r. spectra. Average molecular structures which correlate with the observed data are drawn. The data presented here suggest that the average molecule of the fractions of both petroleum pitch and pyrolysis tar can be represented by an oligomeric structure in which small aromatic clusters are joined by aliphatic bridges and/or biaryl linkages. This contradicts the accepted assumption that the aromatic ring system in petroleum-derived products is fully condensed. Although the average molecular structure of the fractions of pitch and ethylene pyrolysis tar are basically similar, they differ in the number and types of ring-saturated carbons.     

Thermogravimetric characteristics and kinetic study of biomass co-pyrolysis with plastics

The pyrolysis of pure biomass, high density polyethylene (HDPE), polypropylene (PP) and polyethylene terephthalate (PET), plastic mixtures [HDPE+PP+PET (1: 1: 1)], and biomass/plastic mixture (9: 1, 3: 1, 1: 1, 1: 3 and 1: 9) were investigated by using a thermogravimetric analyzer under a heating rate at 10 °C/min from room temperature to 800 °C. Paper was selected as the biomass sample. Results obtained from this comprehensive investigation indicated that biomass was decomposed mainly in the temperature range of 290–420 °C, whereas thermal degradation temperature of plastic mixture is 390–550 °C. The percentage weight loss difference (W) between experimental and theoretical ones was calculated, which reached a significantly high value of (−)15 to (−)50% at around 450 °C in various blend materials. These thermogravimetric results indicate the presence of significant interaction and synergistic effect between biomass and plastic mixtures during their co-pyrolysis at the high temperature region. With increase in the amount of plastic mixture in blend material, the char production has diminished at final pyrolysis temperature range. Additionally, a kinetic analysis was performed to fit with TGA data, the entire pyrolysis processes being considered as one or two consecutive first order reactions.     

Synthesis and characterization of LiFePO4/(Ag + C) composite cathodes with nano-carbon webs

LiFePO₄/(Ag + C) composite cathodes with a new type of nano-sized carbon webs were synthesized by two methods of an aqueous co-precipitation and a sol-gel process, respectively. Simultaneous thermogravimetric-differential thermal analysis indicates that the crystallization temperature of LiFePO₄ is about 455-466 °C, which is close to the pyrolysis temperature of polypropylene, 460 °C. The silver and carbon co-modifying does not affect the olivine structure of LiFePO₄ but improves its kinetics in terms of discharge capacity and rate capability. Discharge capacities were improved from 153.4 mA h g^− 1 of LiFePO₄/C to 160.5 mA h g^− 1and 162.1 mA h g^− 1 for LiFePO₄/(Ag + C) cathodes synthesized by the co-precipitation and sol-gel methods, respectively. The possible reasons for the small difference in discharge capacity of two LiFePO₄/(Ag + C) cathodes were discussed. AC impedance measurements show that the Ag + C co-modification decreases the charge transfer resistance of LiFePO₄/(Ag + C) cathodes.     

Protonation of polyaniline by surface-functionalized polymer substrates

The protonation of solution-coated emeraldine (EM) base by sulfonic and carboxylic acid groups on surface-functionalized low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polytetrafluoroethylene (PTFE) films were characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and conductivity measurements. Surface functionalizations were achieved by sulfonation (for LDPE, HDPE, PP, and PET), by hydrolysis (for PET), and by near-UV-light-induced surface graft copolymerization with the Na salt of styrene sulfonic acid and acrylic acid (for all substrates). The efficiency of surface functionalization by graft copolymerization is substantially enhanced for substrates pretreated with O₃ or Ar plasma. Protonation levels of 50% can be readily achieved for EM coated on sulfonic acid, but not carboxylic acid, functionalized surfaces. The extent of protonation, however, is also dependent on the microstructures of the modified substrate surfaces. In all cases, charge transfer interactions between the EM layer and the functionalized substrates readily result in good adhesion of the electroactive polymer on the polymer substrates to give rise to conductive surface structures. © 1995 John Wiley & Sons, Inc.     

Two stages catalytic pyrolysis of olive oil waste

A study of the pyrolysis of a waste from the extraction of olive oil has been carried out. The work objective was to characterize the char, tar and gaseous phases generated in the process for their possible utilization in energy generation. On the other hand, the influence of a set of variables has been studied, including the efficacy of the dolomite as catalyst. Finally, as previous step to the design of industrial installations, a kinetic study of the process (catalyzed and uncatalyzed), based in the generation of the principal gases, has been carried out. In the uncatalyzed process only the influence of temperature (400–900 °C) was studied. In the catalytic process, the influence of temperature (500–800 °C) and mass of catalyst (0–100 g) was studied. Also, the dolomite effectiveness as catalyst was evaluated. For this motive, consecutive experiments, without reactivating dolomite, were carried out (0–6 runs), and the yields of solids, liquids and gases were determined. An increase in reaction temperature leads to a decrease in char and tar yield and to an increase in the gas phase yield. When the catalyst is present and when the mass of the same is increased, an important decrease in the tar yield and a high increase in the gas phase yield are produced. This increment in the yield of gases is very significant in the case of hydrogen. In addition, the catalyst is very stable. Your activity remains constant during six consecutive pyrolysis experiments, without need to carry out the reactivation of the same. In the kinetic study carried out, it has been considered that the gases are formed through parallel independent first-order reactions, with different activation energy. For uncatalyzed experiments, the experimental data, once adjusted to the model, provided activation energies of 77.8, 38.6, 70.5 and 16.9 kJ mol^− 1 and the Arrhenius pre-exponential factors of 210.1, 9.9, 775.3 and 0.43 min^− 1 for H₂, CO, CH₄, and CO₂, respectively. For catalyzed experiments (following the same sequence) the activation energies were 15.6, 16.5, 12.7 and 23.3 kJ mol^− 1 and the Arrhenius pre-exponential factors 3.8, 1.4, 4.3 and 3.5 min^− 1.     

Additive and pyrolysis atmosphere effects on polysiloxane-derived porous SiOC ceramics

Porous silicon oxycarbide (SiOC) is emerging as a much superior ultrahigh surface area material that can be stable up to high temperatures with great tailorability through composition and additive modifications. In this study, bulk SiOCs were fabricated from a base polysiloxane (PSO) system by using different organic additives and pyrolysis atmospheres followed by hydrofluoric acid (HF) etching. The additives modify the microstructural evolution by influencing the SiO₂ nanodomain formation. The SiOC ceramics contain significantly less SiC and more SiO₂ with Ar + H₂O atmosphere pyrolysis compared to Ar atmosphere pyrolysis. Water vapor injection during pyrolysis also causes a drastic increase in specific surface areas. The addition of 10 wt% tetraethyl orthosilicate (TEOS) with Ar + H₂O pyrolysis produces a specific surface area of 1953.94 m²/g, compared to 880.09 m²/g for the base PSO pyrolyzed in Ar. The fundamental processes for the composition and phase evolutions are discussed as a novel pathway to creating ultrahigh surface area materials. The ability to drastically increase the specific surface area through the use of pyrolysis atmosphere and organic additives presents a promising processing route for highly porous SiOC ceramics.     

Comparative analysis of pyrolysis oils and its subfractions under different atmospheric conditions

In this paper comparative analysis of bio-oils and their subfraction from static, sweeping gas and steam pyrolysis of apricot pulp, a food industry waste, was investigated. Experimental studies were conducted in a well-swept fixed-bed reactor with a heating rate of 5 °C min^{− 1}, to a final pyrolysis temperature of 550 °C. The oil yield which was 22.4% at the static atmosphere reached to the value of 23.2% in the sweeping gas atmosphere by using 100 cm³ min^{− 1} N₂ flow rate. The yield of liquid product in steam pyrolysis was higher (27.2%) than the static and inert gas atmosphere.The elemental analyses of the pyrolysis oils were determined, and the chemical compositions of the oils were investigated using chromatographic and spectroscopic techniques. The liquid products were fractionated into pentane solubles and insolubles (asphaltenes). Pentane solubles were then solvent fractionated into pentane, toluene, and methanol subfractions by fractionated column chromatograpy. The aliphatic subfractions of the oils were then analysed by capillary column gas–liquid chromatography and GC/MS. For further structural analysis, the pyrolysis oils' aliphatic, aromatic and polar subfractions were conducted using FTIR and ¹H NMR spectra.     

Mathematical modelling of lignin pyrolysis

Seven lignins from different sources were pyrolysed (i) isothermally in vacuum over the temperature range 300–1300 °C and (ii) at a constant heating rate of 30 °C min^?1 and a pressure of 0.1 MPa over the temperature range 150–900 °C. The mass fraction of each product—char, tar and gas species—and the elemental composition of the char and the tar were determined for the flash pyrolysis experiments. The evolution rates of the gas species and the tar versus the dynamic temperature of pyrolysis were determined for the constant heating rate pyrolysis experiments. Although the amount of each product species varied from lignin to lignin, the evolution rates were insensitive to the lignin source and the extraction process. To model the data, modifications were made to a recently developed model of coal pyrolysis. The model proved to be successful in simulating both the data from vacuum flash pyrolysis and constant heating rate pyrolysis of Iotech lignin.     

3D printing of high solid loading zirconia feedstock via screw-based material extrusion

Zirconia ceramic (3Y-TZP) feedstocks with solid loadings from 50 vol% to 68 vol%, in a 60:40 paraffin wax to LDPE ratio binder system, were prepared and printed using a screw-based material extrusion printer. A two-step debinding process involving solvent debinding (cyclohexane + ethanol) and thermal debinding (140 °C–600 °C at 0.2 °C/min) followed by sintering at 1500 °C for 2 h was employed. Tests performed include TGA, density test, Vickers hardness and fracture toughness, XRD, and SEM. The TGA result showed two significant drops in weight starting at 180 °C and 380 °C, which corresponds to the decomposition of paraffin wax and LDPE, respectively. A minimum of 40 wt% of soluble binder was removed from the green sample after solvent immersion for 3 h at 40 °C for solid loadings ≥55 vol%. High solid loading feedstocks produced samples with comparable density, Vickers hardness and fracture toughness, which are 97.5%, ∼12.3 GPa, and ∼5.5 MPa m^1/2, respectively; while XRD and SEM shows no adverse tetragonal to monoclinic phase transformation and grain growth, respectively. This study demonstrates that 3D printing of granular 3Y-TZP ceramic feedstock via screw-based material extrusion technique is feasible even with high solid loadings, which is usually difficult to fabricate into flexible filaments and print due to high viscosity.