MASS SPECTROMETRY STUDIES OF FAST PYROLYSIS OF BIOMASS AND OF DETERMINATION OF THE AGE OF USED SYNTHETIC POLYMERS
Creators: name: Xu, Lan
Publisher: name: Purdue University Graduate School
Year: 2024
Subjects: classificationCode: 340199
subject: Analytical chemistry not elsewhere classified

description: Lignocellulosic biomass is a significant sustainable carbon source that may facilitate the reduction of the dependency on fossil fuel and meeting of the ever-rising need for energy and chemicals. The main components in biomass include cellulose, hemicellulose, and lignin.<sup> </sup>Fast pyrolysis, rapid heating in the absence of oxygen, has been demonstrated to be a promising technique for converting biomass into valuable small chemicals, such as drop-in fuel.Lignin is the most abundant aromatic biopolymer in nature. The proportional content of the phenylpropanoid monomeric units (4-hydroxyphenyl (H), guaiacyl (G), and syringyl (S)) in lignin is usually determined using a tedious and slow method (taking two days per sample) involving derivatization followed by reductive cleavage (DFRC) combined with GC/MS or NMR analysis. Therefore, a fast mass spectrometric method for the determination of the monomer content was developed. This method is based on fast pyrolysis of a lignin sample inside the ion source area of a linear quadrupole ion trap mass spectrometer. The evaporated pyrolysis products are promptly deprotonated via negative-ion mode atmospheric pressure chemical ionization ((-)APCI) and analyzed by the mass spectrometer to determine the monomer content. The results obtained for the wild-type and six genetic variants of poplar were consistent with those obtained by the DFRC method. However, the mass spectrometry method requires only a small amount of sample (50 μg) and the use of only small amounts of three benign chemicals, methanol, water, and ammonium hydroxide - as opposed to DFRC, which requires substantially larger amounts of sample (10 mg or more) and large amounts of several hazardous chemicals. Furthermore, the mass spectrometry method is substantially faster (three minutes per sample), more precise, and data interpretation is more straightforward, as only nine ions measured by the mass spectrometer are considered.Understanding the various factors affecting the fast pyrolysis product distribution of biomass is critical for achieving a fast pyrolysis process with high energy- and carbon-efficiencies. The presence of inorganic salts (sodium, potassium, calcium, etc.) within the lignocellulosic feed is known to impact the product distribution. Cellulose, the most abundant biopolymer, has a simple linear structure consisting of glucose anhydride (dehydrated glucose) monomers connected through glycosidic bonds. By studying the primary and secondary products, as well as char yields, obtained upon fast pyrolysis of undoped cellobiose samples (a model compound of cellulose) and those doped with inorganic salts, mechanistic insights were obtained on the influence of inorganic compounds on the product distributions by using fast pyrolysis/atmospheric pressure chemical ionization mass spectrometry (py/APCI MS) and fast pyrolysis/gas chromatography with flame ionization and low-resolution mass spectrometry detection (py-GC/FID/MS).Polyurethane, a synthetic polymer, has many applications in various fields due to its versatile properties. One such application is the use as insulating material in submarines. However, the varying conditions of temperature, humidity, and salinity pose a significant challenge in predicting the lifetime of polyurethane due to aging and degradation. The degradation products of polyurethane foams were investigated by using electrospray ionization/mass spectrometry (ESI/MS). Adipic acid was found to be a degradation indicator that is associated with changes in the chemical composition and mechanical condition of polyurethane foams. An ESI/MS method was developed for monitoring adipic acid content, providing a potential tool for predicting the lifetime and performance of polyurethane foams. Both naturally aged and artificially aged foam samples were studied. The results show that humidity facilitates the degradation process of polyurethane foams. This quantitative method will greatly facilitate predicting the lifetime and performance of polyurethane foams, especially from the point of view of on-board maintenance examinations in submarines.