A Metal-Organic Framework with Immobilized Ag(I) for Highly Efficient Desulfurization of Liquid Fuels

A Metal-Organic Framework with Immobilized Ag(I) for Highly Efficient Desulfurization of Liquid Fuels

Minhui Huang†, Ganggang Chang†, Ye Su†, Huabin Xing†, Zhiguo Zhang†, Yiwen Yang†, Qilong Ren†, Zongbi Bao*†

Key Laboratory of Biomass Chemical Engineering of Ministry of Education,°°College of Chemical and Biological Engineering, Zhejiang University,°°Hangzhou 310027, P. R. China

Abstract

There is a stringent demand to reduce the sulfur content of diesel fuels to ultralow levels (~10 ppm) with the aim of lowering the diesel engine's harmful exhaust emissions and improving air quality. Compared with the hydrodesulfurization technology, the adsorptive desulfurization is one of the most promising technologies because of the advantage to remove thiophene derivatives to produce ultra-clean fuels under mild conditions through convenient process without the consumption of hydrogen. Metal-organic frameworks (MOFs), featuring high surface areas, adjustable pore dimensions and chemical tunability, have received some interests as novel adsorbents for sulfur removal at moderate conditions. Current research has been mainly focused on tuning the pores and porosities to enhance their uptakes, but it is very difficult to remove these compounds to very low contents because of no specific sites for their strong binding of these thiophene derivatives.

Herein, we, for the first time, developed a new strategy to incorporate Ag(I) into a well-known porous metal-organic framework (Cr)-MIL-101-SO₃H for its highly efficient desulfurization. An optimized (Cr)-MIL-101-SO₃Ag systematically takes up much more thiophene derivatives than (Cr)-MIL-101-SO₃H, and about ten times dibenzothiophene°°(DBT) (31.0 g S/kg MOFs) compared to (Cr)-MIL-101-SO₃H (2.14 g S/kg MOFs). Furthermore, it has the highest DBT capacity of 5.30 g S/kg MOF at 10 ppm S of thiophene derivatives among the best examined MOFs including HKUST-1 and UMCM-150, underlying the very promise of such immobilizing Ag(I) ions into metal-organic frameworks for ultra-deep desulfuriaztion applications, particularly for diesel and gasoline that have low sulfur levels. Breakthrough and regeneration studies indicate that the (Cr)-MIL-101-SO₃Ag is practically feasible for the practical applications.

Scheme 1 Metal-organic frameworks with ¨CSO₃Ag for adsorptive desulfurization.

The following pictures are some relative results:

Figure 1. Adsorption isotherms of (Cr)-MIL-101-SO₃Ag (olive) and (Cr)-MIL-101-SO₃H (pink) for DBT from n-octane solutions at 30 °C. The curves represent a fit to the Langmuir equation.

Figure 2. Breakthrough curves for 0.4 mg/mL DBT in n-octane for (Cr)-MIL-101-SO₃Ag (olive) and (Cr)-MIL-101-SO₃H (pink) in n-octane at room temperature.

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