A Novel Approach to Ultra-Deep Desulfurization of Transportation Fuels by Sulfur-Selective Adsorption for Pollution Prevention at the SourceEPA Grant Number: R831471
Title: A Novel Approach to Ultra-Deep Desulfurization of Transportation Fuels by Sulfur-Selective Adsorption for Pollution Prevention at the Source
Investigators: Song, Chunshan , Subramani, Velu , Ma, Xiaoliang
Current Investigators: Song, Chunshan , Kim, Jae Hyung , Clemons, Jennifer L , Zhou, Anning , Yoosuk, Boonyawan , Sundararaman, Ramanathan , Subramani, Velu , Ma, Xiaoliang , Wang, Xiaoxing
Institution: Pennsylvania State University
EPA Project Officer: Klieforth, Barbara I
Project Period: October 15, 2003 through October 14, 2006 (Extended to August 31, 2007)
Project Amount: $325,000
RFA: Technology for a Sustainable Environment (2003) RFA Text | Recipients Lists
Research Category: Sustainability , Pollution Prevention/Sustainable Development
This project addresses an important issue of reducing the sulfur pollutant at the source. The sulfur content in the transportation fuels, particularly in gasoline and diesel, is a very serious environmental concern because upon combustion, sulfur is converted to SOx, which not only contributes to acid rain, but also poisons the catalytic converter for exhaust emission treatment. Because SOx is harmful to people and the environment, the U.S. Environmental Protection Agency (EPA) classifies it as a criteria pollutant. In order to reduce the sulfur pollutant at the source, the new EPA regulation requires reduction of sulfur content in the gasoline from the current average of 300 ppmw to 30 ppmw by 2006 and in diesel from 500 ppmw to 15 ppmw by 2006. Further reduction of sulfur from 30 ppmw in gasoline and 15 ppmw in diesel to well below 1 ppmw will be required for developing advanced gasoline/diesel-based fuel cell cars as well as ultra-clean liquid fuel-based stationary and portable fuel cell systems. It is very difficult or too expensive to use the conventional hydrodesulfurization (HDS) technology to reduce the sulfur content to below 10 ppmw. New approaches that are more economical and convenient will be required for producing ultra-clean gasoline and diesel fuels meeting the current and future EPA regulations as well as for producing fuel cell-grade transportation fuels for fuel cell applications. The primary objective of the proposed research is to explore a new desulfurization process by integrating the Selective Adsorption for Removing Sulfur (SARS) concept under ambient conditions and HDS of concentrated sulfur fraction recovered by solvent washing the adsorbed sulfur compounds. The objectives of the research comprise (1) designing new adsorbents with high selectivity for removing sulfur compounds from transportation fuels under ambient temperature and pressure, (2) developing new and advanced catalysts for the HDS of concentrated sulfur fractions, and (3) understanding the fundamentals of adsorption-desorption and catalytic HDS processes by using a combined experimental and computational analysis.
The transportation fuels, particularly gasoline, diesel and jet fuel, contain organo sulfur compounds, mainly thiophene and its derivatives together with 5-50 wt % of aromatics and olefins. The major challenge for separating the sulfur compounds from the transportation fuels is to find a suitable adsorbent that selectively adsorbs the sulfur compounds under ambient conditions leaving the coexisting aromatics and olefins intact. The thiophenic sulfur compounds can be adsorbed either by p complexation using the delocalized p electrons of the thiophenic ring or by the formation of h1S or S-m3-bonding using unshared electrons present on the sulfur atom. In the present research, new adsorbents that will selectively adsorb thiophenic sulfur compounds by the formation of h1S or S-m3-bonding will be designed and tested. The adsorbed sulfur compounds will be recovered by washing the spent adsorbent with a suitable solvent followed by evaporation of the solvent. The concentrated sulfur compounds will be hydrodesulfurized in a small HDS reactor using a new and advanced HDS catalyst developed in this project. New adsorbents based on hydrotalcite-like anionic clays, metal compounds supported porous materials and nano-sized metal sulfides will be synthesized and their adsorption performance will be evaluated using a fixed-bed adsorption device. New HDS catalysts containing Ni, Co and Mo with higher metal loading on mesoporous supports such as MCM-41 and SBA-15 will be designed and their performance will be evaluated in the HDS of concentrated sulfur compounds. Quantum chemical calculations using semi-empirical quantum chemistry method in computer aided chemistry (CAChe) molecular orbital package (MOPAC) and/or density functional theory (DFT) will be employed to understand the fundamentals of surface adsorption-desorption mechanism for the development of a novel sulfur-selective adsorbent and also to reveal the key factors involved in the HDS of concentrated refractory sulfur fraction over the new, laboratory-made catalysts and the commercial HDS catalysts. Based on this work, a new desulfurization technology integrating the adsorption of sulfur compounds under ambient conditions by SARS process in the first step and a small scale HDS of concentrated refractory sulfur compounds obtained from regeneration of the spent adsorbent by solvent washing in the second step will be developed to produce ultra-clean transportation fuels.
The proposed research can change the way of thinking in the field and lead to the development of a more efficient, economical and novel technology for the production of sulfur-free ultra-clean transportation fuels, meeting the current and future EPA regulations for the automotive fuels as well as for future fuel cell cars. The new technology developed will significantly contribute to achieving sustainable long-term economic growth while maintaining a cleaner environment. This research will significantly contribute to the improvement of the global air quality and minimize the public health hazards due to the sulfur poisons. The proposed work in molecular simulation will result in the application of advanced computational molecular simulation technology to the investigation of adsorptive desulfurization and HDS. The method developed will enable us to estimate heat of adsorption and to explore adsorptive mechanisms of various compounds over solid surface. It will greatly improve our knowledge in adsorption on solid surface and result in using the advanced computational molecular simulation methodology to predict the potential adsorbents and to guide the experiments. Consequently, it can lead to a huge saving in time, money, and other resources.