Beneficiation of by-products from biofuel plant processes for the production of an ecofriendly polyurethane foam LC Muller, Sanette Marx, Idan Chiyanzu 11 th Annual World Congress on Industrial Biotechnology, 14 May, Philadelphia
Problem statement Increase profitability of biodiesel and bioethanol production processes Utilize by-products to generate additional revenue Minimize waste production. 2
Cellulosic ethanol - Lignin Removal of lignin from biomass improves cellulosic ethanol production yield. 1 Agricultural waste Lignin content (% of dry weight ) 1 Wheat straw 15 Corn stover 19 US estimated 250 million gall. of cellulosic ethanol installed capacity in 2015. 3 This would require approx. 2.2 million tons of corn stover. 4 Many pre-treatment processes focus on the removal of lignin and lignin may likely in future be produced in large volumes as byproduct. 2 3
Biodiesel Crude glycerol Produce 0.1 kg/1 kg of biodiesel through transesterification. 5 US produced 135.1 million gall. biodiesel in December 2013. 6 Crude glycerol for same period should be approx. 44000 ton. EIA estimates refiners receive $0.03/gallon of crude glycerol. 7 4
Polyurethane (PUR) Numerous options for beneficiating aforementioned by-products being investigated to generate additional diversified revenue for refiners. Polyurethane amongst these. PUR made-up 7.3% of total plastic produced in Europe in 2012. 8 U.S. PUR industry's 2010 output totalled $59.9 billion. 9 1.9 million tons. 9 44% used in building & construction, appliances and packaging. A major part in the form of rigid polyurethane foam. 5
Polyurethane (PUR) Polyurethane foam made with polyols to create a structure that is three-dimensionally highly cross-linked. The result is a rigid, lightweight foam. 10 Polyols are largely petroleum derived. 11 It is however possible to prepare polyols out of lignocellulose in a range of solvents. Active research into use of agricultural waste as source of lignocellulose. 6
Renewable polyols Lignocellulose + Solvent Polyol Liquefaction / Oxy-propylation Lignocellulose Wheat straw Soy straw Corn stover Corn stalk Dried distillers grains Waste paper Lignin Lignin Sugarcane bagasse Wood Solvents Polyethylene glycol (PEG) + Glycerol Crude glycerol Crude glycerol PEG + Glycerol Ethylene carbonate PEG + Glycerol PEG + Glycerol Propylene oxide Ethylene glycol PEG + Glycerol 7
Lignin Proposed model structure for Pine kraft lignin. 12 Hydroxyl groups and free positions in the aromatic ring are the most characteristic functions in lignin; they determine its reactivity and constitute the reactive sites to be exploited in macromolecular chemistry. 13 8
Crude glycerol components Glycerol: Glycerides: Monoglyceride Diglyceride Triglyceride Biodiesel: Minor components: Alcohol, water, catalysts, soap, free fatty acids. 9
Liquefaction Fragments lignocellulose. 14 Fragments rebind and bind to solvent chains. 15 Phenolic hydroxyl content are decreased while aliphatic primary and secondary hydroxyl groups are introduced. 15 Branched liquid polymers are formed 13, with accessible hydroxyl groups 17, which are suitable for rigid polyurethane formation. 10
Experimental Liquefaction: 160 C, 90min, 9:1 (weight solvent : weight lignin), H 2 SO 4 catalyst. Technical lignins: Kraft (Softwood) Lignosulfonates (Hardwood) Organosolv lignin (Sugarcane bagasse) Crude glycerol: Transesterification of sunflower oil with ethanol. Catalyst: KOH. Lignin + Crude glycerol Polyol Liquefaction 11
Results: Polyols Polyol viscosity Kraft Lignosulfonate Organosolv Crude glycerol Viscosity* (mpa.s) 610 210 80 85 *Determined according to ASTM D4878-08 Polyol hydroxyl number (OH#) Kraft Lignosulfonate Organosolv Crude glycerol OH#* (mgkoh/g) 410 590 220 770 *Determined according to ASTM D4274-11 Method D Liquefaction yield Kraft Lignosulfonate Organosolv Biopolyol / Lignin (g/g) 5.6 5.5 6.5 Solid residue / Lignin (g/g) 1.2 1.3 0.8 12
Results: Polyurethane foam Kraft Lignosulfonate Organosolv Foam properties Kraft Lignosulfonate Compressive strength* (kpa) 350 220 Density (kg/m 3 ) 80 160 *Determined according to ASTM D1621-10 13
Biodegradability Depending on PUR application, biodegradability may or may not be desirable. Polyether PUR highly resistant to microbial degradation. Polyester PUR is susceptible. 18 Polyols made from crude glycerol and lignin are plant derived and may therefore show enhanced biodegradability. Lignin contains many ether bonds and degrades slowly in the environment. 19 Crude glycerol on the other hand contains esters. Crude glycerol based PUR shown to have enhanced biodegradability. 20 14
Overview: Polyurethane preparation Byproducts Biodiesel : Crude glycerol Cellulosic ethanol: Liquefaction Renewable polyol Polyurethane foam Lignin Benefits: Crude glycerol and lignin are renewable. Crude glycerol is unrefined, minimize waste. Different technical lignin types suffice and yield distinctive polyols. Different types of pre-treatments methods may therefore be suitable. Polyurethane foam show high compressive strength. Potential of increased biodegradability. 15
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Contact: Prof S Marx, Pr Eng NRF Research Chair in Biofuels School of Chemical and Minerals Engineering North-West University (Potchefstroom Campus) Tel: (018) 299 1995 Fax: (018) 293 5257 Email: Sanette.Marx@nwu.ac.za www.nwu.ac.za Acknowledgements: This work is based on the research supported by the South African Research Chairs Initiative of the Department of Science and Technology and National Research Foundation of South Africa. Any opinion, finding and conclusion or recommendation expressed in this material is that of the author(s) and the NRF does not accept any liability in this regard 17
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