Ammonia

About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.

Solid solution for catalytic ammonia synthesis from nitrogen and hydrogen gases at 50 °C.

Abstract: The lack of efficient catalysts for ammonia synthesis from N2 and H2 gases at the lower temperature of ca. 50 °C has been a problem not only for the Haber–Bosch process, but also for ammonia production toward zero CO2 emissions. Here, we report a new approach for low temperature ammonia synthesis that uses a stable electron-donating heterogeneous catalyst, cubic CaFH, a solid solution of CaF2 and CaH2 formed at low temperatures. The catalyst produced ammonia from N2 and H2 gases at 50 °C with an extremely small activation energy of 20 kJ mol−1, which is less than half that for conventional catalysts reported. The catalytic performance can be attributed to the weak ionic bonds between Ca2+ and H− ions in the solid solution and the facile release of hydrogen atoms from H− sites. Ammonia synthesis via the Haber–Bosch process typically takes place at an elevated temperature in order to achieve a reasonable rate. Here the authors report on a CaFH solid solution with low activation energy for catalytic ammonia synthesis at lower temperatures.

Ammonium nitrate particles formed in upper troposphere from ground ammonia sources during Asian monsoons

Abstract: The rise of ammonia emissions in Asia is predicted to increase radiative cooling and air pollution by forming ammonium nitrate particles in the lower troposphere. There is, however, a severe lack of knowledge about ammonia and ammoniated aerosol particles in the upper troposphere and their possible effects on the formation of clouds. Here we employ satellite observations and high-altitude aircraft measurements, combined with atmospheric trajectory simulations and cloud-chamber experiments, to demonstrate the presence of ammonium nitrate particles and also track the source of the ammonia that forms into the particles. We found that during the Asian monsoon period, solid ammonium nitrate particles are surprisingly ubiquitous in the upper troposphere from the Eastern Mediterranean to the Western Pacific—even as early as in 1997. We show that this ammonium nitrate aerosol layer is fed by convection that transports large amounts of ammonia from surface sources into the upper troposphere. Impurities of ammonium sulfate allow the crystallization of ammonium nitrate even in the conditions, such as a high relative humidity, that prevail in the upper troposphere. Solid ammonium nitrate particles in the upper troposphere play a hitherto neglected role in ice cloud formation and aerosol indirect radiative forcing. Solid ammonium nitrate particles are formed in the upper troposphere during the Asian monsoons, which bring large amounts of ground ammonia to this altitude, according to integrated analyses of measurements on ammoniated aerosol, together with model simulations.

Urea Transformations and Fertilizer Efficiency in Soil

Abstract: Publisher Summary This chapter discusses urea transformations and fertilizer efficiency in soil. Urea has less tendency to coalesce and compact than ammonium nitrate, is less corrosive than other nitrogen fertilizers, and is suitable as a carrier for a number of herbicides. Much of the urea in the United States is applied as urea ammonium nitrate solution prepared by combination of urea with ammonium nitrate. Although urea is frequently equivalent to other nitrogenous fertilizers poor crop responses to urea have frequently been observed. The rapid hydrolysis of urea in the soil can result in high soil pH values and high ammonium ion concentrations, which are conducive to the accumulation of ammonia. The major problems observed in urea fertilization are the loss of volatile ammonia gas and ammonia toxicity to germinating seedling. This chapter discusses environmental, chemical, and physical soil conditions, which must be considered in regard to controlling urea transformations in the field. It also elaborates studies that have directly measured urea transformations in the field or under simulated field conditions. New classes of urease inhibitors that may improve the efficiency of urea under field conditions are also described.