Article pubs.acs.org/EF
Cite This: Energy Fuels XXXX, XXX, XXX−XXX
Compatibility Assessment of Fuel System Infrastructure Plastics with Bio-oil and Diesel Fuel Michael D. Kass,*,† Christopher J. Janke,† Raynella M. Connatser,† Samuel A. Lewis, Sr.,† James R. Keiser,† and Katherine Gaston‡ †
Fuels, Engines and Emissions Research Center, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, United States National Bioenergy Center, National Renewable Energy Laboratory, Golden, Colorado 80401, United States
‡
ABSTRACT: Bio-oil derived via fast pyrolysis is being developed as a renewable fuel option for petroleum distillates. The compatibility of neat bio-oil with 18 plastic types was evaluated using neat diesel fuel as the baseline. The plastic materials included polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyoxymethylene (POM), POM copolymer, high density polyethylene (HDPE), polybutylene terephthalate (PBT), polypropylene (PP), polyethylene terephthalate glycol (PETG), polythiourea (PTU), four nylon grades, and four thermosetting resins. Specimens of each material were immersed in the test fuels for a period of 16 weeks to achieve full saturation. Except for PP and HDPE, the plastic materials underwent higher volume expansion in bio-oil than in the baseline diesel (which was negligible in most cases). This volume increase corresponds to the higher polarity of the bio-oil. PPS, PET, and PTFE were unaffected by bio-oil exposure, but modest swelling (between 2 and 5%) occurred for the two acetals (POM and POM copolymer), Nylon-12, PBT, PETG, and the four resin grades. More moderate swelling (8−15%) was noted for Nylon-6, Nylon-6/6, and Nylon-11, and excessive swell (>40%) occurred for PTU. The nonpolar nature of PP and HDPE matches that of diesel, leading to higher solubility (swell) in this fuel type. The relatively low volume expansion following exposure indicates that many of the existing infrastructure plastics (excluding PTU) should be suitable for use with bio-oil.
■
INTRODUCTION The United States relies heavily upon petroleum imports to meet its domestic energy needs. A large percentage of imported petroleum crude is refined into distillates, such as diesel and fuel oil, which are subsequently used in transportation, home heating, and power generation. To reduce this dependency on foreign petroleum and fossil fuels, the United States, and other countries, is researching domestic, renewable fuels derived from biomass as alternatives to petroleum-derived distillates.1 One such fuel is bio-oil derived via fast-pyrolysis from woody biomass feedstocks. In fact, there has been limited introduction of bio-oil to fuel boilers for building heating applications and power generation. The feedstocks are primarily hardwood tree pulp, but softwoods and other biomass sources are also being evaluated. Feedstock type has been shown to significantly affect the resulting chemical profile of the fuel.2 As a result, the composition of these oils varies widely, but they usually contain significant quantities of oxygenates, ketones, and phenols.2,3 Fast pyrolysis consists of rapidly heating biomass feedstock (typically pelletized wood) at rates up to 1000 °C/s (or higher) in the absence of oxygen. Liquid yields can be as high as 75% depending on the reactor configuration, feedstock type, and processing. The oil produced via fast pyrolysis methods typically has high viscosity and water content (relative to diesel fuel), as shown in Table 1.4 At this stage, the bio-oil is immiscible with petroleum-based fuels and is denoted as a bio-oil intermediate or biointermediate. Additional upgrading steps, including hydrotreating and deoxygenation, are necessary for bio-oil to be used with conventional transport fuels such as diesel, kerosene, and gasoline.4 Much of the oxygen exists as ketones, aldehydes, © XXXX American Chemical Society
Table 1. List of Selected Properties for Pyrolysis Oil and Diesel4 Property Density at 20 °C, g/cm Viscosity at 20 °C, cStoke Lower heating value, MJ·kg Ash, wt % Water content, wt % Oxygen content, wt % 3
Pyrolysis Oil
Diesel
1.2 13 17.5 0.13 20.5 42.5
0.85 2.5 42.9
