File Name: ammonia catalysis and manufacture .zip
This paper has presented data on such textures as the specific surface area, the pore volume, the average diameter of particles and pores, the fraction of the surface occupied by free iron and so forth, and on such structures as the lattice constant in the oxidic state and the crystallite width after the synthesis run of individual catalysts of the magnesia-promoted type, together with data on both a pure magnetite and a catalyst of the alumina-promoted type. It has also included the results of the examination of the catalysts by means of optical and electron microscopy. Although the magnesia used as a promoter may be surface-inactive at the earlier stage of reduction, it tends at the later stage to cover the major portion of the particle surface and acts to retard the particle growth as well as the crystallite growth. The retarding effect on the growth is cancelled out when potash is added as the second promoter, but it is considerably pronounced in the presence of silica.
Ammonia is a promising carbon-free energy carrier, but is currently synthesized industrially under harsh conditions. Synthesizing ammonia using lower temperatures and pressures could therefore improve its prospects as a chemical means to store and transport energy.
Here we report that alkali and alkaline earth metal imides function as nitrogen carriers that mediate ammonia production via a two-step chemical looping process operating under mild conditions. Nitrogen is first fixed through the reduction of N 2 by alkali or alkaline earth metal hydrides to form imides and, subsequently, the imides are hydrogenated to produce NH 3 and regenerate the metal hydrides.
Late 3d metals accelerate the reaction rates of both steps. All prices include VAT for Germany. Tax calculation will be finalised during checkout. The data that support the plots within this paper and other finding of this study are available from the corresponding author upon reasonable request.
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Ammonia Catalysis and Manufacture With contributions by K. Aika, L. Christiansen, I. Dybkjaer, 1. Hansen, P. Views 5 Downloads 1 File size 8MB.
Ammonia is one of the most highly produced inorganic chemicals. There are numerous large-scale ammonia production plants worldwide, producing a total of million tonnes of nitrogen equivalent to million tonnes of ammonia in Ammonia is also used for the production of plastics, fibers, explosives, nitric acid via the Ostwald process and intermediates for dyes and pharmaceuticals. Before the start of World War I , most ammonia was obtained by the dry distillation of nitrogenous vegetable and animal products; by the reduction of nitrous acid and nitrites with hydrogen ; and also by the decomposition of ammonium salts by alkaline hydroxides or by quicklime , the salt most generally used being the chloride sal-ammoniac. Today, most ammonia is produced on a large scale by the Haber process with capacities of up to 3, tonnes per day. In this process, N 2 and H 2 gases are allowed to react at pressures of bar. A typical modern ammonia-producing plant first converts natural gas , liquified petroleum gas , or petroleum naphtha into gaseous hydrogen.
The presence of alkaline earth or alkali metals is found to be essential for accelerating the reaction rate for the ammonia synthesis process. TEM images reveal the local structure of the catalysts obtained upon pyrolysis of the metal phthalocyanine precursor, with metal nanoparticles 5—50 nm confined in a nitrogen-doped carbon mesoporous matrix, where the alkali metal promoters are located on the top of the iron nanoparticles but also on the carbon support. Furthermore, this kinetic analysis suggests that the rate-determining step shifts from nitrogen activation to NH x formation, which only few catalysts have achieved. Material from this article can be used in other publications provided that the correct acknowledgement is given with the reproduced material and it is not used for commercial purposes. Information about reproducing material from RSC articles with different licences is available on our Permission Requests page. Fetching data from CrossRef. This may take some time to load.
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Ammonia is produced by the reaction of hydrogen and nitrogen, dubbed the "Haber-Bosch process". Depending on the feedstock that is being used, the two main hydrogen production processes used in ammonia production are:. The type of feedstock used to produce ammonia plays a significant role in the amount of energy used and CO 2 produced.
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