UC Davis

Many industrial manufacturing processes are moving towards continuous production methods. These methods typically involve flowing liquids or moving materials from one step of the process to another continuously, as opposed to traditional, batch production where steps of the process occur in large immobile containers. The use of continuous manufacturing methods in chemical products, for example, is highly desirable, as increases in product yields and higher energy efficiencies are achieved. When designed and correctly implemented, these methods typically require less interaction with people and improve product quality control. With continuous manufacturing comes the need for inline process monitoring and control. This is typically performed with simple sensors (pressure, temperature, flow meters) or with advanced analytical devices. Together, the sensors and devices fall under the classification of a process analytical technology (PAT). The use of PATs is essential in success of continuous manufacturing processes, and advancements in spectroscopic PATs specifically allows for the implementation of new continuous manufacturing processes in historically batch-mode industries. Substantial development and use of spectroscopic PATs in continuous production has already happened with Raman and infrared spectroscopies. Nuclear magnetic resonance (NMR) PATs, however, have lagged behind these other spectroscopies. This is largely because much of the innovation in NMR has pushed the technology into using large, expensive, high-field, cryogenic magnets. These instruments, while powerful for molecular studies, are ill-equipped for in-line industrial environments. The samples studied with these instruments must conform to the geometric limitations of the instruments, and the instruments themselves cannot be near any

ferromagnetic materials. Lower field benchtop systems have another set of issues, as they are limited to small sample volumes and low fluid velocities. Finally, most of these systems are concerned with analyzing the sample on a molecular level, which is completely useless for studying complex aqueous mixtures during process. This work details the efforts involved in advancing the use of portable NMR relaxometry for process monitoring in flowing aqueous industrial systems. NMR relaxometry is advantageous for monitoring flowing systems as it is nondestructive, can be used to study complex mixtures inside pipes of various metal and plastic materials, and does not require a large superconducting magnet. Unfortunately, the technique does suffer from low signal to noise ratios and has limited past development for in-line industrial systems. Nevertheless, NMR relaxometry has the potential to be an inexpensive, powerful PAT once the development work is done. Chapter one discusses the fundamentals of NMR and describes two common pulse sequences for measuring the relaxation properties of protons. Chapter two shows evidence supporting the use of NMR relaxometry measurements for process monitoring of biomass pretreatment by ultrasound cavitation. The results show that relaxometry measurements are indicative of process outcomes, and that the measurements can be performed during flow. Successful performance of the measurements during flow is needed because the scale up process of cavitation pretreatment switches from ultrasound batch-mode to hydrodynamic flow-mode cavitation. Chapter three addresses the issues associated with performing NMR measurements on systems undergoing turbulent flow. A turbulent aqueous environment is the ideal industrial

system to study since water is the preferred solvent in most cases, yet most established NMR protocols fail to give useful information in these environments. This chapter explores alternative and forgotten techniques that work well in turbulent aqueous environments. The chapter concludes with examples of using these techniques to monitor aqueous sawdust extraction with hydrodynamic cavitation. Chapter four proposes a 3D printed solution to address the low signal to noise issue associated with using NMR relaxometry to study fast flowing aqueous systems. Details for a portable, industrial ready system are shown, along with attempts to use Earth’s magnetic field in place of a permanent magnet for analysis.