(56i) Towards a Sustainable Biorefinery: Biomass for Energy and Biochar for Water Treatment

Towards
a Sustainable Biorefinery: Biomass for Energy and Biochar for Water Treatment

Sai Teja Neeli

The Russell School of Chemical Engineering, The University of Tulsa, OK, 74104, United States

Research
Interests:

With the increase in
energy, there is a growing concern for replacing or at least complementing
depleting fossil fuels with alternative sources of energy. Biomass can be regarded as one of the abundant sources of renewable
energy for the production of transportation fuels and could be an important
part of a more sustainable future energy system. Biomass has a complex
structure wherein cellulose, hemicellulose and lignin are
intertwined. My research interest lies in how to explore biomass so that
even its by-products can be converted to value-added
products. In order to be able to transform any biomass derived products, the
fundamental science behind the processes have to be unraveled. I am interested
to learn the behavior of each of these biomass model compounds to have a better
understanding of biomass as a whole. Investigating the model compounds in
biomass will reveal which one (s) are responsible for maximum product
formation. In my research, I applied hydrothermal water as the medium for the
production of biocrude and biochar,
a carbon rich by product. Hydrothermal technology has many advantages such as
high heat and mass transfer rates, feedstock flexible and no drying step is
required. To achieve a sustainable biorefinery, it is
necessary to utilize all the products and minimize the waste. Therefore, after
liquefying biomass model compounds hydrothermally to obtain biocrude
(bio-oil), the biochar left as residue was converted to an adsorbent for the adsorption of heavy
metals.  Throughout my research, I
utilized the fundamentals of a chemical engineering to design and optimize a
process while drawing key principles from organic chemistry and materials
synthesis to understand the mechanism of product formation.   

Research
Experience:

During my doctoral
studies, I helped my advisor to set up her new research lab. In the process, I
ordered and built my experimental set up from scratch and organized the
laboratory. I not only used sub- and supercritical water to convert biomass to biocrude and biochar but I also
synthesized carbon encapsulated iron nanoparticles
(CEINP) derived from biochar. Some of my other duties
include maintaining and troubleshooting analytical instruments and writing
standard operating procedures for each equipment and experiment. Also, I was selected as a researcher in Oklahoma Catalyst
Program which helps graduate students to turn their research into a business.
Through this program, I got to learn crucial concepts
in entrepreneurship such as intellectual property issues, funding opportunities,
identifying customers and understanding a problem.   

Below are the details of the research projects I am
involved with:

1.      Biofuel production

During my Ph.D., I
studied the effect of a hydrogen donor (calcium formate)
on the liquefaction of biomass model compounds. Experiments were
carried between 350 and 400 °C in a stainless steel batch reactor. A
detailed analysis of the chemical composition of biocrude
through GC-MS provided information on the possible reactions in sub- and
supercritical water with formate salt. The formate salt improved the biocrude
yields and quality (rich in alkylated phenols) appreciably during lignin liquefaction
through hydrodeoxygenation reactions. Calcium from
the formate salt enhanced the gasification of
cellulose in hydrothermal media, and the excess hydrogen improved the quality
of biocrude (rich in aromatics) restricting the formation
of PAHs. GC-MS results of biocrude from xylan liquefaction with calcium formate
showed the presence of phenolic compounds and cyclic ketone. In this study, the
presence of calcium formate creates an alkaline
environment catalyzing the decomposition of xylan to phenolics and ketones via aldol condensation reactions in
sub- and supercritical water. In this work, I proposed reaction mechanisms for
the transformation of biomass to biocrude in the
presence of hydrogen donor. This reaction not only enabled me to learn
analytical techniques like Higher Heating Value (HHV), GC-MS but also made me
dig deep into the chemistry of the reactions so that I could postulate new hydrodeoxygenation reactions. 

2.  Nanoparticle synthesis

The second part of
research uses biochar, the by
product from my first research to produce carbon encapsulated iron
nanoparticles (CEINP). I used biochar from all three
biomass model compounds for comparison since they are structurally and
chemically different. The synthesized catalysts were
characterized for physiochemical properties using various analytical
techniques like X-ray diffraction (XRD), Fourier Transform Infrared (FT-IR)
spectroscopy, Transmission Electron Microscope (TEM), Scanning Electron Microscope
(SEM), Brunauer-Emmett-Teller (BET) surface area, Thermogravimetric analysis (TGA). In short, the carbon
supported iron nanoparticles preparation includes iron impregnation onto the biochar followed by annealing the mixture at 1000 °C
resulting in CEINP. These nanoparticles typically consist of a core-shell
structure with iron/iron-carbide core surrounded by graphitic carbon shell. Highly-ordered graphitic layers were observed in the CEINP
from cellulose and hemicellulose biochar while
disordered graphitic carbon was observed in CEINP from lignin biochar encapsulating the iron nanoparticles. Based on the
observed characterization results, I proposed a detailed mechanism explaining
the formation of CEINP.

3.  Waste water treatment

The carbon
encapsulated iron nanoparticles were used for the removal of heavy
metals from aqueous solutions is tested. Heavy metals are toxic to both human
and other living forms posing a serious environmental concern nowadays. United
States Environmental Protection Agency (US EPA) has enforced regulations to
limit the level of inorganic chemicals in drinking water. Present technologies
such as precipitation, membrane filtration and ion-exchange
are being employed to remove metal pollutants from water. Unlike these methods,
adsorption has proven to be economical and efficient for removing heavy metals.
Batch experiments were conducted to test the ability
of carbon encapsulated iron nanoparticles for removal of heavy metals (Cr (VI),
As (III), Cu (II) and Pb (II)) from aqueous
solutions. Higher removal efficiencies (close to 90%) were obtained at pH: 3 for chromium and arsenic while at pH: 7 copper was removed
completely. Due to the magnetic property of iron, CEINP can
be easily removed from the solutions by applying external magnetic
field. Also, these nanoparticles can be potentially
reused after heavy metal treatment. Cellulose biochar
alone without Fe annealed at 1000 ºC was less efficient (<20% efficiency) in
removing chromium and arsenic.

Teaching
and Mentoring Experience:

Apart from my research
career, I have been a Teaching Assistant since the beginning of my graduate
program. Occasionally, I was teaching undergraduate level Heat and Mass
Transfer courses. Furthermore, I assisted students in performing laboratory
experiments related to enzyme kinetics, composition analysis, bomb calorimeter and pump performance. During my graduate
study, I had the privilege of mentoring 8
undergraduate students who worked directly with me. I closely mentored the
students working on different parts of my research in which they had to apply
concepts related to heat and mass transfer, fluid mechanics and reaction
engineering to understand the chemical reactions involved. These students went
on to present their research at several international conferences and some of
them pursued graduate studies. Since I my mentor’s first graduate student, I
also mentored two graduate students who joined our lab. I trained them on
safety, lab practices, equipment handling and conduct reactions.   

Service:

As a STEM student, I
strongly believe in giving back to the community. I volunteered at the
2015-2018 International Petroleum Environmental Conference (IPEC) organized by
The University of Tulsa. At this conference over the years, I moved from being
a student volunteer, being responsible for registration to being a session
chair. I also volunteered to be a judge for undergraduate student poster
competitions at 2016-2017 American Institute of Chemical Engineers (AIChE) conference.

Scholarly
Achievements:

·        
Peer Reviewed Journal articles: 2 published (first authored)

·        
Conference Presentations: 9

·        
Graduate Student Research Grant, The
University of Tulsa

·        
Recipient of Chapman Graduate Scholarship,
The University of Tulsa

·        
Recipient of Phillips 66 R&D
Fellowship

·        
Tube Fitting Installation &
Certification, Swagelok, Oklahoma

Selected Peer
Reviewed Publications:

1.     
Neeli, S.T.; Shakya, R.; Adhikari, S.; Ramsurn, H., Effect
of calcium formate on hydrodeoxygenation
of biomass model compounds, Energy
& Fuels, 2019; DOI: 10.1021/acs.energyfuels.8b04205

2.     
Neeli, S.T.; Ramsurn, H., Synthesis and
formation mechanism of iron nanoparticles in graphitized carbon matrix using biochar from biomass model compounds as a support. Carbon 2018, 134, 480-490; DOI: 10.1016/j.carbon.2018.03.079