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posted by CoolHand on Wednesday August 31 2016, @07:09AM   Printer-friendly
from the serious-chemistry dept.

Arthur T Knackerbracket has found the following story:

Nearly half of the world's population is fed by industrial N2 fixation, i. e., the [Haber-Bosch] process. Although exergonic in nature, NH3 synthesis from N2 and H2 catalyzed by the fused Fe has to be conducted at elevated temperatures and high pressures. It consumes over 1 percent of the world's annual energy supply. Developing efficient catalysts that enable NH3 synthesis under mild conditions is a grand scientific challenge and is of great practical need.

The ideal catalyst for NH3 synthesis should have strong activation to N2 (small activation energy Ea) but relatively weak binding to the activated N species (small EN), which is, unfortunately, unattainable by transition metals (TM) themselves because of the linear scaling relations between Ea and EN, i.e., a transition metal catalyst having strong activation to N2 will have strong binding to the activated N, and vice versa. Such relations determine the rate of NH3 synthesis over the TM catalyst, and therefore, although tremendous research efforts have been applied, the industrial catalyst used today is essentially the same as the original one developed by Mittasch in 1909.

The Dalian Institute of Chemical Physics (DICP) research group led by Prof. CHEN Ping demonstrates, for the first time, that the scaling relations on catalytic NH3 synthesis can be broken. Thus, NH3 synthesis under mild reaction conditions can be achieved at an unprecedentedly high rate over a new set of catalysts.

The key element leading to this change is the employment of ionic hydride LiH. Distinctly different from proton or atomic H applied in biochemical, organometallic, and heterogeneous NH3 formation, H in LiH bears a negative charge that ensures that LiH is a strong reducing agent breaking the TM-N bond, and an immediate H source abstracting N to Li to form LiNH2. LiNH2 can further split H2, heterolytically giving off NH3 and regenerating LiH. Through this mechanism (See Figure a), the activation of N2 and the subsequent hydrogenation of N are carried out separately over the two reactive centers, i.e., TM and LiH, respectively, so that the direct influence of TM on the NH3 formation rate is broken.


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  • (Score: -1, Offtopic) by Anonymous Coward on Wednesday August 31 2016, @07:36AM

    by Anonymous Coward on Wednesday August 31 2016, @07:36AM (#395615)

    COULD IT BE USED FOR TERRORISM

    DEATH TO WEST

    PRAISE ALLAH

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