Microwave-assisted catalytic decomposition of polyetherimide with a focus on hydrogen and high-value hydrocarbons production

A comparative thermodynamic assessment of microwave-assisted and conventional pyrolysis of biomass in poly-generation systems using coupled numerical and process simulations

Microwave assisted and conventional pyrolysis of MDF – Characterization of the produced biochars

Absorption of microwaves by various materials is accompanied by heating of varying degree [1]. The purpose of this work is to study the dependence of the heating temperature of briquetted SiC powders on the microwave radiation time and power. Study of the influence of time from 1 min. up to 3 min. and power from 350 W to 700 W on the heating temperature of the investigated powder materials was carried out due to the absorption of microwave radiation with a frequency of 2.45 GHz . Six samples of silicon carbide synthesized under different conditions were used: 1 – synthesized from electrode graphite and Si; 2 – synthesized from petroleum coke and SiO₂; 3 – synthesized from thermally expanded graphite (TEG) and Si; 4 –ground ceramics infiltrated TEG by Si at 2000°С; 5 – synthesized from TEG and Si and purified in HF; 6 – ground reaction-bonded silicon and boron carbide (SiC-B₄C-Si). The weak dependence of the heating temperature on the time of microwave action at a power of 350 W for samples 1, 2 and 4 is due to the presence of crystalline silicon in the compositions of synthesized silicon carbide powders. The monotonous increase in the heating temperature of samples 3.5 and 6 from the time of microwave exposure is evidence of their high dielectric properties in a wide temperature range. An increase in temperature over 950°C during of 3 minutes is a main evidence of cubic modification silicon carbide in the form of a solid solution of carbon in silicon carbide. Dissolved carbon in the form of planar carbon clusters with sp3 hybridization of atoms leads to an increase in dielectric properties. The phase composition of sample 6 is characterized by the presence mainly of hexagonal 4H-SiC, as well as crystalline silicon. However, the presence of silicon does not affect microwave absorption. A monotonous increase in temperature up to 750°C is observed during 3 minutes.

Synthesis of alkoxyphenols-rich bio-oil by microwave-assisted catalytic pyrolysis of wood over MoS2 catalyst

This project employed microwave assisted pyrolysis (MWAP) to recover resources from stockpiled biosolids from Victoria, Australia. Biosolids are the stabilised sludge that results from sewage wastewater treatment. The presence of contaminants, unpleasant odours and poor public acceptance make biosolids disposal challenging. Over three million tonnes of biosolids are currently stockpiled in Victoria, having no identified end use. MWAP applies a microwave electromagnetic field to biosolids in a low-oxygen environment, which heats the material, thermally decomposing the organic matter into volatile bio-oils and incondensable gases, leaving behind a biochar. This work focused on assessing the feasibility of generating bio-oil from MWAP of the Victorian biosolids, with a particular focus on analysing the composition of the bio-oil and identifying ways to enhance the process value. A comparative study was also done using local biosolids. MWAP was carried out using a single-mode microwave pyrolysis unit with a nitrogen-gas purge, enabling condensers to trap the resultant bio-oil. Biosolids mixed with a microwave susceptor that absorbed the microwave energy and re-emitted it as heat (activated carbon) were pyrolyzed in sets of experiments where the oil composition and yield were evaluated. As bio-oil produced from MWAP can contain hundreds of organic compounds, a method was developed to analyse the yield of selected compounds with Gas Chromatography Mass Spectrometry and Gas Spectrometry Flame Ionization Detection. To improve the separation of the bio-oil in the chromatography column, samples were first derivatized using N,O-Bis(trimethylsilyl)trifluoroacetamide (BSTFA). The bio-oil derived from stockpiled biosolids contained a range of compounds, with the largest groups being phenols and carboxylic acids, and had a calorific value similar to that of bio-diesel. Bio-oil yield was low due to the degradation of the biosolids from the extended periods of stockpiling. The MWAP also consumed a large amount of energy per unit mass of biosolids pyrolysed. Under some conditions the MWAP was cost competitive against land application, which costs an average $300/dry tonne. MWAP of stockpiled biosolids cost as little as $218/dry tonne, though >90% of the savings were due to mass reduction and not bio-oil in this case. Larger scale tests are needed to determine whether the costs and technical complexity of the process could be managed. Unidentified components of the bio-oil that were not quantified may improve the economics.

5 - Microwave-assisted fast pyrolysis of hazardous waste engine oil into green fuels

Methanation of biosyngas in a fluidized bed reactor

The alloying synergistic flame retardant effect was studied by using polyetherimide (PEI) and aluminum diethylphosphinate (ADP) for polyamide 6 (PA6), which can endow PA6 composites with excellent mechanical properties and flame retardancy simultaneously. On the one hand, because the molecular structures of PEI and PA6 are similar, adding PEI with PA6 can form PEI‐PA6 alloy by the hydrogen bond effect and nice homogeneous phase, which can endow PA6 composites with excellent mechanical properties. On the other hand, the test results of flame retardancy show that 9ADP/10PEI‐PA6 composite can obtain higher LOI value (LOI = 31%), and excellent flame retardant rating (UL94 V‐0) with 9%ADP and 10%PEI. From the results of cone calorimetry test, the pk‐HRR and THR of 9ADP/10PEI‐PA6 are reduced by 24.4% and 24.7%, respectively, compared to PA6, and higher char residue rate was obtained, which shows that ADP combined with PEI‐PA6 alloying exerts an excellent flame retardant synergistic effect. Through the study of flame retardant mechanism found that ADP works together with PEI can effectively increase the quenching effect in the gas phase, promote thermal stability, and delay the decomposition process of PA6 matrix during the combustion process. Meanwhile, it also increases the char yield to exert a synergistic effect in the condensed phase by ADP/PEI‐PA6. The residual char rate reached 36.6%, higher than neat PA6 about 4.6 wt.%. Thus, the alloying flame retardant method using ADP/PEI‐PA6 can endow PA6 with better flame retardancy and more excellent mechanical properties. Importantly, it provides a new direction for developing high‐performance halogen‐free flame retardant materials.

Covalently bound self-passivating silica layer enhances polyetherimide stability in harsh space conditions

Microwave-assisted pyrolysis with chemical activation, an innovative method to convert orange peel into activated carbon with improved properties as dye adsorbent

As recycling plastics through microwave-assisted pyrolysis becomes gradually popular, the selection of microwave absorbents is therefore of great importance because plastics generally have low microwave absorption capacities, and microwave absorbents are then required to improve the heating and pyrolysis processes. In this study, conversion of polystyrene plastic into aviation fuel through microwave-assisted pyrolysis as affected by iron-based microwave absorbents (Fe, Fe3O4, and FeS2) was studied and reported for the first time. The heating performance, product yields, oil higher heating values, and aviation oil compositions with different microwave absorbents, microwave powers, and microwave absorbent loads were detailed. The results showed that Fe3O4 exhibited the highest average heating rate of 119.23 °C/min, and Fe had good selectivity for cycloalkenes, while FeS2 had good selectivity for olefins. The highest oil yield (97.67 wt %) was obtained at a pyrolysis temperature of 460 °C, microwave power of 650 W, and Fe load of 90 g, and the oil compositions were mainly monocyclic aromatic hydrocarbons, polycyclic aromatic hydrocarbons, olefins, and cycloalkenes with abundant C8–C16 hydrocarbons of 52.041–77.880 area%. The results indicated that polystyrene can be well converted into aviation fuel through microwave-assisted pyrolysis by screening the iron-based microwave absorbents.

Microwave-assisted pyrolysis and activation of pulp mill sludge

A commercial activated carbon (AC) was modified through iron oxide incorporation to obtain microwave absorbers (MWAs) for microwave-assisted pyrolysis. The influence of iron oxide content (5 and 20 wt% Fe3O4) and the modification methods were tested as follows: (1) in situ co-precipitation + washing step with Milli-Q; (2) in situ co-precipitation + washing step with Milli-Q/ethanol; and (3) physical iron oxide blending. The resulting MWAs were evaluated on the microwave-assisted pyrolysis of hardwood in a Milestone Flexiwave microwave reactor. The biochar yield varied from 24 wt% to 89 wt% and was influenced by the modification method rather than the iron oxide addition. The MWAs with physically blended iron oxide resulted in biochar yields comparable to conventional biochar (450 °C). Furthermore, the addition of iron oxide-activated carbon composites during the microwave-assisted pyrolysis caused a significant decrease in the biochar’s 16 EPA polycyclic aromatic hydrocarbons, mainly by reducing the amount of pyrene in the biochar.

Microwave-assisted co-pyrolysis of Chlorella vulgaris and wood sawdust using different additives

Catalytic pyrolysis of Athabasca bitumen in H2 atmosphere using microwave irradiation