Shengjun Hu

Characterization of Crude Glycerol from Biodiesel Plants

Characterization of crude glycerol is very important to its value-added conversion. In this study, the physical and chemical properties of five biodiesel-derived crude glycerol samples were determined. Three methods, including iodometric-periodic acid method, high performance liquid chromatography (HPLC), and gas chromatography (GC), were shown to be suitable for the determination of glycerol content in crude glycerol. The compositional analysis of crude glycerol was successfully achieved by crude glycerol fractionation and characterization of the obtained fractions (aqueous and organic) using titrimetric, HPLC, and GC analyses. The aqueous fraction consisted mainly of glycerol, methanol, and water, while the organic fraction contained fatty acid methyl esters (FAMEs), free fatty acids (FFAs), and glycerides. Despite the wide variations in the proportion of their components, all raw crude glycerol samples were shown to contain glycerol, soap, methanol, FAMEs, water, glycerides, FFAs, and ash.

Production and characterization of biopolyols and polyurethane foams from crude glycerol based liquefaction of soybean straw.

The feasibility of using crude glycerol to liquefy soybean straw for the production of biopolyols and polyurethane (PU) foams was investigated in this study. Liquefaction conditions of 240 °C, >180 min, 3% sulfuric acid loading, and 10-15% biomass loading were preferred for the production of biopolyols with promising material properties. Biopolyols produced under preferential conditions showed hydroxyl numbers from 440 to 540 mg KOH/g, acid numbers below 5 mg KOH/g, and viscosities from 16 to 45 Pa.s. PU foams produced under preferential conditions showed densities from 0.033 to 0.037 g/cm3 and compressive strength from 148 to 227 kPa. These results suggest that crude glycerol can be used as an alternative solvent for the liquefaction of lignocellulosic biomass such as soybean straw for the production of biopolyols and PU foams. The produced biopolyols and PU foams showed material properties comparable to their analogs from petroleum solvent based liquefaction processes.

Polyols and Polyurethanes from the Liquefaction of Lignocellulosic Biomass

Polyurethanes (PUs), produced from the condensation polymerizations between polyols and isocyanates, are one of the most versatile polymer families. Currently, both polyols and isocyanates are largely petroleum derived. Recently, there have been extensive research interests in developing bio-based polyols and PUs from renewable resources. As the worlds most abundant renewable biomass, lignocellulosic biomass is rich in hydroxyl groups and has potential as a feedstock to produce bio-based polyols and PUs. Lignocellulosic biomass can be converted to liquid polyols for PU applications through acid- or base-catalyzed atmospheric liquefaction processes using polyhydric alcohols as liquefaction solvents. Biomass liquefaction-derived polyols can be used to prepare various PU products, such as foams, films and adhesives. The properties of biomass liquefaction-derived polyols and PUs depend on various factors, such as feedstock characteristics, liquefaction conditions, and PU formulations.

Thermochemical conversion of crude glycerol to biopolyols for the production of polyurethane foams

This study aimed to produce biopolyols from crude glycerol via a novel thermochemical conversion process. The effect of operational parameters, including sulfuric acid loading and reaction temperature and time, on the properties of the produced biopolyols was investigated. Biopolyols produced under preferred reaction conditions of 200°C, 90 min, and 3% sulfuric acid loading showed a hydroxyl number of around 481 mg KOH/g, an acid number of around 5mg KOH/g, and a viscosity of around 25.0 Pas. The resulting polyurethane (PU) foams showed a compressive strength of around 184.5 kPa and a density of around 43.0 kg/m(3), comparable to those of some petroleum-based analogs. Characterization of the biopolyols via pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), gas chromatography (GC), and thermogravimetrical analysis (TGA) showed that the major reactions of this process were the formation of monoglycerides and diglycerides through the esterification and transesterification of different components in crude glycerol.

Two-step sequential liquefaction of lignocellulosic biomass by crude glycerol for the production of polyols and polyurethane foams

A two-step sequential biomass liquefaction process was developed to produce bio-based polyols and polyurethane (PU) foams using crude glycerol as a liquefaction solvent. The first step, acid-catalyzed liquefaction, was highly effective in liquefying biomass, while the second step, base-catalyzed liquefaction, featured extensive condensation reactions. By using the developed two-step liquefaction process, the polyols produced from lignocellulosic biomass and crude glycerol containing 26-40% organic impurities showed hydroxyl numbers ranging from 536 to 936mgKOH/g, viscosities from 20.6 to 28.0Pas, and molecular weights (Mw) from 444 to 769g/mol. The PU foams produced had densities ranging from 0.04 to 0.05g/cm(3), compressive strengths from 223 to 420kPa, and thermal conductivities from 32.2 to 38.9mW/mK. Polyols and PU foams produced from the two-step liquefaction process had improved properties over their analogs derived from a one-step biomass liquefaction by crude glycerol process catalyzed by acid or base.

Polyols and Polyurethanes from Vegetable Oils and Their Derivatives

Vegetable oils and their derivatives have been widely used for the production of various polymers including polyols and polyurethanes. Vegetable oil derivatives, such as fatty acids, fatty acid esters, and crude glycerol, can be obtained via hydrolysis or transesterification of vegetable oils. Polyols and polyurethanes with properties comparable to those of petroleum-based analogs have been prepared from vegetable oils and their derivatives for various applications such as foams, coatings, adhesives, etc. This chapter reviews the structures and compositions of vegetable oils and their derivatives, synthetic methods of producing polyols from vegetable oils and their derivatives, properties of these polyols, and performance and applications of the resulting polyurethanes.

Lignocellulosic Biomass-Based Polyols for Polyurethane Applications

Recently, there has been increased interest in developing bio-based polyols and polyurethanes (PUs) from lignocellulosic biomass. As the world’s most abundant renewable feedstock, lignocellulosic biomass is rich in hydroxyl groups and has potential as a feedstock to produce bio-based polyols for PU applications. Lignocellulosic biomass can be converted to liquid polyols through oxypropylation or liquefaction processes. The produced liquid polyols from lignocellulosic biomass can be used to prepare various PU products, such as foams, films, and adhesives. The properties of lignocellulosic biomass-derived polyols and PUs depend upon various factors, such as feedstock characteristics, reaction parameters, and PU formulations. The major challenge for lignocellulosic biomass-based polyols is the consumption of solvents, which comprise a large fraction of the reactants, during liquefaction processes.

Introduction to Bio-based Polyols and Polyurethanes

Polyurethanes (PUs) are one of the most versatile polymers and are widely used in our daily lives for rigid and flexible foams, coatings, films, and other products. PUs are generally synthesized through reactions between isocyanates and polyols. A brief overview of the chemical structures, origin, synthetic methods, and properties of polyols and isocyanates is given in this chapter. Currently, most polyols are petroleum-based, but increasing concerns over the depletion of petroleum resources, environment, and sustainability have led to considerable efforts to develop bio-based polyols and PUs from renewable resources. Bio-based polyols and isocyanates for the production of bio-based PUs are discussed in this chapter.

Polyols and Polyurethanes from Protein-Based Feedstocks

Feedstocks that have high protein contents, such as soy protein, are promising materials for extensive polyol and polyurethane (PU) applications, such as foams, films, and coatings, due to the characteristic structures and properties of proteins. Currently, most research has been focused on the direct use of these protein-based feedstocks in combination with polymers for PU production. Although proteins have multiple reactive functional groups, such as amino and carboxyl groups, reports on the modification of protein-based feedstocks for the production of liquid polyols are limited. This chapter reviews sources, compositions, structures, and processing of protein-based feedstocks; synthetic methods and properties of protein-based polyols; and performance and applications of the derived PUs.