Pilot-Scale Twin Screw Extrusion and Chemical Pretreatment as an Energy-Efficient Method for the Production of Nanofibrillated Cellulose at High Solid Content

Abstract

Production of nanofibrillated cellulose (CNF) has gained increasing attention during the last decades with its recent industrialization, but such a process consumes still too high of an amount of energy. Here, cellulose nanofibrils at high solid content (20−25 wt %) and consuming 60% less energy compared to conventional processes were produced from enzymatic and TEMPO-oxidized cellulose fibers thanks to a twin screw extruder equipped with kneading disks and fully flighted conveying screws. The morphology and properties of the produced CNF were characterized using optical microscopy, atomic force microscopy (AFM), mechanical properties, and light transmittance. CNF with a width in the range of 20−30 nm and mechanical properties close to those obtained with commercial CNF (Young's modulus around 15 GPa) were produced. However, results from the degree of polymerization and crystallinity showed that twin screw extrusion (TSE) degrades the fibers as far as the supermasscolloider grinder is concerned. TSE appears as a new mechanical treatment that allows producing CNF at high solid contents and with low energy demand, which is a real asset for nanocellulose industrialization.

Transparent lignin-containing wood nanofiber films with UV-blocking, oxygen barrier, and anti-microbial properties

“…In addition, low viscosity might enable the production of CWNFs with a high solid content, for example, using a twin-screw extruder. 52 TEM analysis showed that cationic wood disintegrated into individual nanobers with a width of approximately 5 nm (Table 1 and Fig. 2).…”

Nanocellulose Production: Exploring the Enzymatic Route and Residues of Pulp and Paper Industry

“…In the particular case of CNFs production, the enzymatic hydrolysis is commonly followed by a mechanical step of fibrillation, such as homogenization [ 38 , 44 ], microfluidization [ 49 , 50 ], extrusion [ 25 , 51 ], and sonication [ 27 , 52 ], among others. Few studies have also reported no mechanical treatment step after hydrolysis [ 12 , 53 , 54 , 55 ], hence totally relying on the enzymes to produce the nanofibers.…”

“…While these benefits from enzymes are consensual, there is a clear lack of accurate estimations of the putative energetic savings introduced by enzymes. As pointed out by Rol et al [ 51 ], this comparison should be carefully conducted since distinct extraction processes may produce NC particles with different modification rates and dimensions. A recent study by Espinosa et al [ 25 ], employing an extrusion process after hydrolysis, reported a reduction of 37% of the energy consumption.…”

“…A recent study by Espinosa et al [ 25 ], employing an extrusion process after hydrolysis, reported a reduction of 37% of the energy consumption. In addition, Rol et al [ 51 ] observed that the energy consumed to produce CNFs by extrusion (seven passes) decreased from over 15,000 kWh/t to approximately 5000 kWh/t when enzymes were employed; similar estimations of this type are, however, scarce.…”

Preparation and mechanism analysis of morphology‐controlled cellulose nanocrystals via compound enzymatic hydrolysis of eucalyptus pulp

“…Recently, various methods have been adopted for the preparation of CNCs, in which mechanical and hydrolyzed methods are the two main kinds. The mechanical methods include high‐pressure homogenization, grinding, sonication, and so forth, whose main drawback is high energy consumption . Although the chemical hydrolyzed method has advantages of high reaction efficiency and CNC yield, it has the disadvantages of high chemical additions and environmental pollution at the same time .…”