Effect of Glycerol Pretreatment on Levoglucosan Production from Corncobs by Fast Pyrolysis

Dual Utilization of Lignocellulose Biomass and Glycerol Waste to Produce Fermentable Levoglucosan via Fast Pyrolysis

Glycerol waste was combined with microwave to pretreat lignocellulose before fast pyrolysis. After pretreatment, most alkali and alkaline earth metals (87.9%) and lignin (52.6%) were removed, and a higher crystallinity was obtained. Comparatively, glycerol waste combined with microwave was proven to be more efficient than glycerol with conventional heating. During fast pyrolysis, higher content of levoglucosan in glycerol waste–pretreated products (27.5%) was obtained, compared with those pretreated by pure glycerol (18.8%) and untreated samples (5.8%). Production of fermentative toxic aldehyde and phenol by-products was also inhibited after glycerol waste treatment. Following mechanistic study had validated that microwave in glycerol waste solvent could effectively ameliorate structure and components of lignocellulose while selectively removing lignin. Notably, under the optimal condition, the levoglucosan content in pyrolytic products was enhanced significantly from 5.8% to 32.9%. In short, this study provided an archetype to dually utilize waste resources for ameliorating lignocellulose structure and precisely manipulating complex fast pyrolysis.

Crude Glycerol as a Potential Feedstock for Future Energy via Thermochemical Conversion Processes: A Review

Biodiesel is an emerging substitute for petroleum-based products. It is considered an ecologically safe and sustainable fuel. The high cost of biodiesel production is linearly related to its feedstock. Crude glycerol, which is a by-product of the biodiesel industry, is also a major challenge that must be addressed. A large volume of crude glycerol needs to be disposed of, and this involves processing, dumping, and land requirements. This increases the cost of biodiesel production. One way to decrease the cost of biodiesel production is to utilize its by-product to make valuable products. Crude glycerol can be processed to produce a variety of chemicals and products. The present utilization of crude glycerol is not enough to bring down its surplus availability. Thermochemical conversion processes can utilize crude glycerol as a starting feedstock and convert it into solid, liquid, and gaseous fuels. The utilization of crude glycerol through integrated thermochemical conversion processes could lead to an integrated biorefinery. This review paper highlights the research scope for areas where crude glycerol could be utilized as a feedstock or co-feedstock in thermochemical conversion technology. Various thermochemical conversion processes, namely, gasification, pyrolysis, combustion, catalytic steam reforming, liquefaction, and supercritical water reforming, are discussed and shown to be highly suitable for the use of crude glycerol as an economical feedstock. It is found that the integration of crude glycerol with other thermochemical conversion processes for energy production is a promising option to overcome the challenges related to biodiesel production costs. Hence, this paper provides all the necessary information on the present utilization status of crude glycerol in thermochemical conversion processes, as well as identifying possible research gaps that could be filled by future research studies.

High-Precision Monitoring of Average Molecular Weight of Polyethylene Wax from Waste High-Density Polyethylene

High-density polyethylene (HDPE) is a major component of polyethylene waste, yet only under 29.9% of waste HDPE is recycled. As an important additive, polyethylene wax (PEW) is increasingly used in many industries such as plastics, dyes, and paints. The preparation of PEW has received considerable interest because recycling and precisely controllable production can bring huge economic benefits. In this study, to recycle waste HDPE, a single screw extruder was innovatively combined with a connecting pipe to prepare PEW from the pyrolysis of waste HDPE. Using a test platform, PEWs were prepared under different pyrolysis temperatures and screw speeds, and corresponding number-average molecular weights (NAMWs) of PEWs were measured. To precisely monitor NAMW of PEW, a program was developed in MATLAB. First, the relationship between NAMW and pyrolysis ratio was obtained, and a measure-point-independence verification was conducted. Then, modified Arrhenius equations and time-dependent pyrolysis temperature were for the first time introduced into the HDPE pyrolysis model. Furthermore, the screw-speed-dependent inverse method was proposed and validated for high-precision monitoring of NAMW of PEW from the pyrolysis of waste HDPE by extrusion. PEW of desired molecular weight was able to be precisely obtained from waste HDPE.

Novel crude glycerol pretreatment for selective saccharification of sugarcane bagasse via fast pyrolysis

Pretreatment is a vital process for efficient saccharification and utilization of lignocellulose. In this study, crude glycerol derived from biodiesel production was used for pretreatment to facilitate selective saccharification via fast pyrolysis. Due to the efficient removal of alkali and alkaline earth metals (>95.0%) and lignin (79.4%) by crude glycerol pretreatment, the yield of levoglucosan was evaluated to 25.2% as compared to those from pure glycerol pretreated (14.4%) and untreated sugarcane bagasse (8.4%). Meanwhile, the production of inhibitors (e.g. acetic acid, phenol) to biocatalysts was also obviously inhibited from crude glycerol pretreated biomass. Consequently, this work provided a cost-effective and eco-friendly pretreatment mode, which could not only make full utilization of crude glycerol, but also improve the fermentability of lignocellulosic pyrolysate.

Thinking Green: Sustainable Polymers from Renewable Resources

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