(201a) Improvement of Transportation Fuels Sustainability Via Co-Hydroprocessing of Lipid-Feedstocks and Petroleum Fractions

Improvement of transportation fuels sustainability
via co-hydroprocessing of lipid-feedstocks and petroleum fractions

Stella Bezergianni*, Centre for
Research & Technology Hellas, Thermi-Thessaloniki, Greece

Athanasios Dimitriadis, Centre for
Research & Technology Hellas, Thermi-Thessaloniki, Greece

Loukia Chrysikou, Centre for Research
& Technology Hellas, Thermi-Thessaloniki, Greece

Vasilios Dimitropoulos, Hellenic
Petroleum, Thessaloniki, Greece

Maria Maggiliotou, Hellenic Petroleum,
Thessaloniki, Greece

Spyridon Kiartzis, Hellenic Petroleum,
Thessaloniki, Greece

Biography

Dr. Bezergianni is a principal researcher at
the Centre for Research & Technology Hellas, active in R&D of new
environmentally friendly fuels and biofuels. She is involved in new biofuel
production technologies regarding the valorization of bio-based feedstocks for
the production of drop-in alternative fuels and as well as of hybrid fuels via
the integration of bio-based feedstocks in refineries. Dr. Bezergianni has an
extended academic (numerous scientific publications and monographs) and
research record (scientific advisor of various European and national research
projects and direct collaboration with national and international partners), as
well as prior industrial experience in and out of Europe (ExxonMobil, FMC
Corporation, Air Liquide). She is an active member National Technical Chamber
of Greece and a committee member of the American-Hellenic Chamber of Commerce.

Abstract

Even though biofuels are promoted as one of
the most significant substitutes of fossil fuels with a considerable share
growth in recent years, they are still associated with high investment costs,
uncertain environmental benefits and questionable compatibility with
conventional combustion systems [1]. One alternative approach for promoting a
drastic increase of biomass utilization for the production of greener fuels for
the transportation sector is co-processing of bio-based feedstocks in
conventional refining conversion units [2]. An R&D project, driven by the
Centre for Research and Technology Hellas and Hellenic Petroleum on integrating
waste cooking oil in a conventional heavy gasoil hydrotreatment unit,
highlighted the technical feasibility as well as environmental and economic
potential. The positive prospects are currently evaluated via a pilot scale
test for a Hellenic Petroleum refinery. This presentation will focus on key
R&D perspectives, challenges and potential for integrating residual lipids
in conventional catalytic hydroprocessing units. The presentation will provide
practical and useful information for the refiners, in order to enable a fast
integration of biomass within existing conventional refineries for the production
of high bio-content fuels.

Introduction

The proof-of-concept was initially addressed
via the SustainDiesel research project funded by the Greek Secretariat for
Research & Technology where both the technical and environmental potential
benefits from integrating waste cooking oil were estimated (see Figure 1).

Figure
1. Overview of SustainDiesel project results [3-5]

The positive research results have driven
Hellenic Petroleum to explore further this technology, via a self-funded
project on exploring the potential co-hydroprocessing of waste lipids in
underlying hydrotreating units.

Methodology

The project involved a) an evaluation of
valiable lipid feedstocks for co-feeding with heavy gas oil, b) an assessment
of the optimal lipid management strategy within refinery, and c) an extended
pilot testing of co-hydrotreating heavy gas oil with lipids for hybrid fuels
production validation.

Evaluation of available lipid feedstocks for co-feeding
with heavy gas oil

Three tests were performed for the
evaluation of the effect of different lipid type (sunflower oil, raw/crude
waste cooking oil and refined waste cooking oil). For each test, three phases
were considered, a nominal phase 1 where the heavy oil defined the basic
hydrogenation activity, a main phase 2 where the lipid feedstock was introduced
aiming to obtain a product with <10 wppm sulphur content and a third phase
where only heavy oil was used that was intended to identify any permanent loss
of activity for the employed catalytic system.

In Figure 2 the results of the tree tests
are outlined indicating that the least impact was for sunflower oil and refined
waste cooking oil. The slightly largest impact of waste cooking oil can be
expected as this lipid source contains unsaturated oxygenated hydrocarbons as
well as free fatty acids. The permanent loss of the catalyst effectiveness is
also more clearly indicated for raw waste cooking oil, which can be primarily attributed
to the free fatty acids, as well as on the negative effect of the CO₂
and CO (by-products of co-hydroprocessing resulting from hydro-deoxygenation
reactions) on the catalyst active sites [6-7].

Figure 2. Normalized reaction temperature
indicating hydrotreating effectiveness for suflower oil, raw waste cooking oil
and c) refined waste cooking oil co-hydroprocessing with heavy gas-oil

Assessment of the optimal lipid management strategy
within refinery

The evaluation of the potential logistics
for handling lipid feedstocks within a refinery complex was performed via
extended storage studies that evaluated the sunflower oil and refined waste
cooking oil 6-12 month storage. As the lipid feedstocks have a tendency to
oxidize that leads to further water formation, the water content and acidity
were monitored throughout the extended storage studies. The studies have shown
that for a 6-month storage period the water content was not significantly changed
however the acidity of sunflower oil increased as indicated in Figure 3. As the
water content and acidity of the lipid source has been identified as potential
causes of the catalyst hydrogenation activity limitation affecting the catalyst
active sites, the consideration of the 6-mont storage as a maximum time-span
for storing the lipid sources is of particular essence to the industrial
application of this technology.

Extended pilot testing of co-hydrotreating heavy gas oil
with lipids for hybrid fuels production

 Upon the evaluation of the different
lipid-sources with respect to the impact on heavy gas oil hydrotreatment as
well as on the extended storage, a prolonged pilot testing was performed,
validating the effectiveness of hybrid fuels production via lipid
co-hydroprocessing with heavy gas oil. The testing was performed in the large
scale pilot plant of CERTH for 6 months, proving the effectiveness of
sustainability of the proposed technology.

The testing was conducted with refined waste
cooking oil (5% v/v) with standard heavy gas oil, over a commercial CoMo/Al₂O₃
catalytic system and respecting the operating window of heavy gas oil
hydrotreatment of the refinery. The testing provided evidence that the
technology can be scaled up to industrial plants, expecting high quality fuels
and minimal additional energy expectations.

Figure 3. Water content and Total Acid
Number (TAN) of sunflower oil (orange) and refined waste cooking oil (red) for
an extended 6-month storage period

Conclusions

The integration of lipid sources (primarily
refined waste cooking oil and raw vegetable oils) within an underlying
hydroprocessing plant of a refinery is feasible and renders high quality
products. The additional H₂ required for co-hydroprocessing lipid feedstocks
up to 5% are not significant and the resulting hybrid fuels are of high quality
and abide by the fuel standards.

References

[1]     
A.
Dimitriadis, I. Natsios, A. Dimaratos, D. Katsaounis, Z. Samarasm S.
Bezergianni, K. Lehto. Frontiers in Mechanical Engineering (2018) https://doi.org/10.3389/fmech.2018.00007

[2]     
Bezergianni,
S., Dimitriadis, A., Kikhtyanin, O., Kubička, D. Refinery co-processing of
renewable feeds, Progress in Energy and Combustion Science 68, pp. 29-64, 2018

[3]      L.P. Chrysikou, V.
Dagonikou, A. Dimitriadis, S. Bezergianni. Journal of Cleaner Production 10
(2019) 566-575

[4]      Bezergianni, S.,
Dimitriadis, A., Karonis, D. Diesel decarbonization via effective catalytic
Co-hydroprocessing of residual lipids with gas-oil, Fuel, 136, pp. 366-373,
2014

[5]      Bezergianni, S.,
Dimitriadis A, Meletidis, G., Effectiveness of CoMo and NiMo Catalysts on
Co-Hydroprocessing of Heavy Atmospheric Gas Oil - Waste Cooking Oil Mixtures,
Fuel, 125, pp. 129-136, 2014

[6]     
S.
Bezergianni, V. Dagonikou. Journal of Chemical  Engineering 93 (2015) 1017-23

[7]     
S.
Bezergianni, V. Dagonikou, S. Sklari. Fuel Processing Technology 144 (2016)
20-6.