Study On Absorptive Desulfurization Of Fuel Oil Over Activated Alumina Material

Due to the increasingly stringent environmental regulations on sulfur concentration in transportation fuels, ultra-deep desulfurization of fuel has become a more and more important research subject . This is because the sulfur compounds in the fuel are converted to SOx during combustion, which not only results in acid rain, but also poisons catalysts in catalytic converters for reducing CO and NOx . Consequently, the sulfur level in fuel must be reduced to 10μg/g by 2010 in the EU. Hydrodesulfurization (HDS) at high temperature (320℃–380℃) and high pressure (3–7 MPa) over CoMo or NiMo catalysts is currently a major process in petroleum refineries to reduce the sulfur in fuel. However, it is difficult or very costly to use the existing HDS technology to reduce the sulfur in fuel oil to less than 10μg/g.A number of alternative technologies including selectively adsorption, oxidation, extraction and bioprocessing are being explored to realize the ultra-deep desulfurization. Using adsorbents to selectively remove the sulfur compounds in liquid hydrocarbon fuels is one of the promising approaches for producing ultra clean fuels that not only meets the most stringent fuel specifications for transportation fuels, but also can be used for fuel cell applications. For the refinery applications, one potential new option is to use a sulfur-selective adsorption unit for ultra-deep removal of organic sulfur following a conventional HDS unit, and such a combination could remove all of the sulfur from the liquid fuel products.Liquid-phase adsorption of fuel over activated alumina was conducted in a fixed-bed adsorption system. Different breakthrough curves and selectivities for different compounds provided a new insight into the fundamental understanding of the adsorption mechanism over adsorbents.The Activated alumina adsorbent supported with non-noble metal is good for selective removal of the sulfur compounds, especially nickel-based Activated alumina, and 13% higher than the Activated alumina unloaded. When precursor activated alumina loaded with NiO 4.0wt.%, calcining at 450℃for 2.0h, fixed bed temperature 80℃, space velocity (4h-1), the adsorbent has the best desulphurization performance, desulfurization efficiency reached 88.2%.The Activated alumina adsorbent supported with CuO/ZnO is much better, 6.8% higher than the Activated alumina adsorbent loaded with NiO, When precursor activated alumina loaded with CuO/ZnO 1.5wt.%, 2:3, calcining at 350℃for 2.0h, fixed bed temperature 80℃, space velocity (4h-1), the adsorbent has the best desulphurization performance, desulfurization efficiency reached 90.5%.The desulphurization performance of activated alumina loaded with NiO/ZnO is explored at high temperature, When precursor activated alumina loaded with NiO/ZnO 3.0wt.%, 1:1,calcining at 400℃for 2.0h, fixed bed temperature 360℃, space velocity (2h-1),the adsorbent has the best desulphurization performance, desulfurization efficiency reached 64.0%.The desulphurization performance of activated alumina loaded with CuO/ZnO is studied in diesel oil, When precursor activated alumina loaded with CuO/ZnO 3.0wt.%, 2:1, calcining at 400℃for 2.0h, fixed bed temperature 80℃, space velocity (3h-1),the adsorbent has the best desulphurization performance, desulfurization efficiency reached 55.0%.Surface acidic and basic group content of activated alumina-based adsorbents were analysed. The results showed that basic group content was higher than acidic group content in the surface of activated alumina. Surface acidic and basic group content of activated alumina increased after loaded with non-noble metal. The spent desulfurizer is regenerated circularly with thermal, both the desulfurization efficiency and the breakthrough sulfur capacity decline slowly with time and regeneration cycles. What's more, clean gasoline and overall oil yield are over 86%.GC-FPD was used to detect the sulfur compounds in the gasoline before and after desulfurization. The results clearly showed that sulfur compounds in gasoline were adsorbed by adsorbent. It was also showed that activated alumina treated by metal oxide, especially preferred to remove benzothiophene and its derivatives.