A comprehensive set of Global Positioning System (GPS) vehicle location data from Lexington, Kentucky, households was analyzed to determine if such data can be helpful in improving path choice assumptions in traffic assignment models. The portion of the data used consisted primarily of a reconstruction of the street network and the lists of street segments in each path. Analysis was based on matches of trips (e.g., pairs of trips with similar origins and destinations). Matches were obtained for trips within households and for trips across households. Statistics used to compare trips in matches were a path deviation index and the percentage of identical links. It was found that the path chosen on a trip was quite sensitive to the location of the origin and destination and that the chosen path most often differed considerably from the shortest time path across the network. Paths for trips made by the same driver were very consistent over time; paths by different drivers showed more deviations even when the trip ends were the same or very similar. As a result of this research, recommendations are made as to how GPS data on path choice can be better collected in the future for improvement of traffic assignment models.
Hydropyrolysis of Lignin using Pd/HZSM-5 Oliver D. Jan Chair of the Supervisory Committee:Dr. Fernando Resende
School of Environmental and Forest SciencesThe aim of this work was to study the formation of cycloalkanes from hydropyrolysis of lignin with HZSM-5 and Pd/HZSM-5 catalysts. We observed that palladium supported on HZSM-5 catalyzed hydrogenation and deoxygenation reactions that converted phenolic compounds into aromatic hydrocarbons and cycloalkanes. This study analyzed the effect of the catalyst-to-lignin ratio, H 2 partial pressure, and temperature on the yields of hydrocarbons with HZSM-5 and Pd/HZSM-5. Pd/HZSM-5 produced 44% more aromatic hydrocarbons than HZSM-5 at a catalyst-to-lignin ratio of 20:1, 650ºC, and a constant H 2 partial pressure of 1.7 MPa. The presence of palladium led to significant difference in yields only at 1.7 MPa H 2 partial pressure.In both the in-situ and ex-situ experiments conducted, hydropyrolysis temperature played a substantial role in the equilibrium conversion of hydrogenation reactions that led to cycloalkanes directly from lignin.iv Dedication This thesis is dedicated to my family for all their love and support v Acknowledgements
We
report results for the oligomerization of ethylene in a continuous
packed bed reactor loaded with Ni–Hβ. We performed a
parametrized study of the effects of temperature (50–190 °C),
ethylene partial pressure (8.5–25.6 bar), and weight hourly
space velocity (WHSV, 2.0–5.5 h–1) on the
ethylene conversion and product selectivity. The steady-state ethylene
conversion increased from 38 to 57% as the pressure increased from
8.5 to 25.6 bar, due to increased concentration of the reactant ethylene
and lower linear velocities at higher pressures. Higher temperatures
led to the formation of larger oligomers and coke, but the effect
of temperature on the ethylene conversion was small. The WHSV played
an important role on ethylene conversion and product selectivity.
An increase in the WHSV from 2.0 to 5.5 h–1 resulted
in a 13% decrease in conversion. At a low space velocity (2.00 h–1), we observed 57% conversion, whereas a high space
velocity (5.50 h–1) resulted in 44% conversion and
higher selectivities to butene (74.9 wt %). The parametric analysis
provided the basis for a 78 h on-stream study to examine the deactivation
of Ni–Hβ. We conducted this study at 19.0 bar partial
pressure of ethylene, 120 °C, and 3.1 h–1 WHSV.
Catalyst deactivation took place only during the initial startup period
largely due to coke formation. However, negligible coke formation
occurred after the initial 8 h, and the conversion remained steady
at 47% for the duration of the experiment. Our results indicate that
Ni–Hβ is a viable catalyst for ethylene oligomerization.
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