Microwave assisted pyrolysis of kraft lignin at reduce pressure in a multimode oven

Lignin is the third-most abundant natural polymer after cellulose and hemicellulose[1] and the only renewable source of aromatics in nature. Moreover lignin is the most relevant waste from industry of paper and bioethanol[2]. Nowadays the common way to dispose it is combustion but the possibility to recovery aromatic moiety from thermochemical conversion of lignin has been received a grown attention. In this field the most promising approach is pyrolysis[3] and particularly interesting is use of microwave (MW) like heating source[4]. Microwave assisted pyrolysis (MAP) was successfully applied in the treatment of plastic materials[5, 6] and biomasses[7]. In this work MAP kraft lignin at reduced pressure was studied to magnify functionalized aromatic moieties recovery. For this reason, MAP processes were performed at different pressure (1 bar, 0.13 bar, 0.013 bar) with and without a fractionating system in a multimode MW batch reactor using carbon like MW absorber. Particularly this study was devoted to correlate quantity and composition of Bio-oils recovered with residence time into reactor. Bio-oils obtained were dark brown liquids and showed a low viscosity and density (close to 1cP and 1 g/mL respectively). The most relevant achievements were gained at residual pressure of 0.013 kPa whit a 37 wt% of Bio-oil collected without fractionating and at residual pressure of 0.013 kPa with fractionating when process was carried out in 9 min. Compositions of Bio-oils were evaluated through 1H-NMR, FT-IR ATR and A quatitative GC-MS method that allowed to evaluation concentration of Bio-oils compounds[8, 9]. Analysis showed high concentration of multisubstituted aromatic ring and few light hydrocarbons/organic acids (C1-C4) from advanced thermal degradation of lignin structure.Data collected showed that MAP at reduced pressure of kraft lignin was a reliable way to process it to recovery high quantity of complex mixture of aromatic compounds. Please click Additional Files below to see the full abstract

Bio-oils from microwave assisted pyrolysis of cellulose using a multi mode batch reactor

The end of fossil fuels era is becoming day by day [1] however the request of raw materials and fuels from industry is growing every year [2]. As a consequence research for renewable resource to supply oil is became very attractive [3]. Biomasses are very promising sources to satisfy the growing request of energy and raw materials [4-6] and in the same time to reduce the environmental impact due to their production [7]. Cellulose is particular interesting among different available biomasses because it is not interfere with the availability of resource for alimentation [8]. It is the main component of woody biomasses (until 50%) [9], and it is the most abundant polysaccharide and it may be the source of chemicals through a pyrolysis process [10]. Pyrolysis of cellulose through a classic heating was reported in several papers [11, 12] together with kinetic of the process and the main decomposition mechanism [13, 14] where a high formation of levoglucosan is proposed [15]. Levoglucosan is an anhydrosugar employed for the production of unhydrolysable glucose polymers [16] or in the production of bioethanol [17]. Furthermore through pyrolysis of cellulose a great variety of very attractive furanosidic compounds like furfural and hydroxyfurfural [18] may be obtained. In recent year the classical thermal heating is flanked with a new systems based on the use of microwave (MW) heating [19] because microwave assisted pyrolysis (MAP) is an interesting way to perform pyrolysis in a very short time and with the possibility of an easy control of the energy employed in the process [20, 21]. MAP was used to process different waste polymeric materials [22-25] in different conditions [26] to produce chemicals and fuels. Microwave are not absorbed and converted into heat by every materials, so MAP was frequently performed in the presence of a MW absorber. MAP of biomass has proven to be a reliable tool to employ waste biomass as the raw material for the process [27, 28] in the presence or the absence of a MW absorber and its conversion into chemicals [29] with good yields of bio-oils was reported. However the use of a MW absorber affects the quality and quantity of bio-oils as reported by Undri et al. [30]. Please click Additional Files below to see the full abstract

Microwave assisted pyrolysis of waste from short rotation coppice of poplar

Poplar short rotation coppice (SRC) plays an important role in biomass production because they are largely employed both in industry or used as solid fuel [1]. Recently there is a great interest in the below-ground biomass recovery (stump-root system) of poplar SRC because: a) it accounts for about 20% of the total plant dry weight [2] and the average poplar chips can yield 18 ton/ha of root biomass; b) it is easily accessible and harvested (sand-loamy soils); c) the root wood often has higher heating values than tops and branches, and may prove to be a better fuel [3]. Furthermore, the removal of the stump-roots systems does not require the payment of a concession, and using efficient recovery systems, the delivered cost might range from 28 to 66 €/ton[4]. The most common method to dispose waste from forestry biomass is combustion, which is an environmentally unfriendly process. Recently a remarkable interest has been focused on microwave assisted pyrolysis (MAP) of biomass due to the fast and efficient heating and the appealing characteristics of the products obtained [5]. Biomass are able to absorb microwave (MW) and even if a MW absorber is not strictly necessary, it may have some positive effects on the quality of products and pyrolysis time [6]. In this work MAP of residues from SRC of different poplar clones have been studied in a multimode batch oven.. MAP of stump-roots and leaves residues from different poplar clones were thoroughly investigated to produce high quantity and quality of bio-oils. They were obtained with high yield (up to 32.0%) and small water percentage (up to 17.5 %)and showed low density and viscosity and they were fluid at room temperature. Among bio-oils a sample with high acetic acid concentration (543.3 mg/mL) was obtained. Bio-oils were characterized with several analytical techniques: 1H-NMR, IR-ATR, density and viscosity measurements, and an original and innovative quatitative GC-MS method[7, 8]. These techniques let to make possible a detailed study on the bio-oils to define a correlation between their chemical and rheological properties with the parameters of the process. Please click Additional Files below to see the full abstract

Mixed or Contaminated Waste Plastic Recycling through Microwave - Assisted Pyrolysis

A single type of thermoplastic polymer is easily recycled through a mechanical process, but this way can’t be followed in the presence of mixed or contaminated plastic. In this case, one of the main followed solutions is a thermochemical process and among them, microwave-assisted pyrolysis is one of the emerging technologies. This chapter offers an update of the microwave-assisted pyrolysis of mixed or contaminated waste plastic as a very promising example of chemical recycling. Furthermore, some unpublished results in this field will be reported such as the pyrolysis of waste lead containing polyethylene coming from end cycle batteries or the pyrolysis of waste polypropylene from facemasks used for covid protection. Finally, some examples of pilot plants will be described and commented as well as several industrial cooperations