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.

Successive reactions of gaseous trimethylaluminium and ammonia on porous alumina

Abstract: Successive reactions of gaseous trimethylaluminium (TMA) and ammonia on porous alumina were studied with the goal of finding suitable process conditions for preparing aluminium nitride (AlN) by atomic layer deposition (ALD), a technique based on separate saturating gas–solid reactions. The reaction of TMA was studied at 353–623 K on alumina dehydroxylated at 473–1073 K, and the following reaction of ammonia at 423–823 K. Reference samples were prepared by reacting ammonia at 623 and 823 K with alumina dehydroxylated at 833 K. The samples were characterised by elemental analysis of carbon and nitrogen and by IR and 1H NMR. TMA reacted with alumina in a saturating manner at 353–573 K. Reaction took place through ligand exchange with surface OH groups, with release of methane, and through dissociation of TMA on pairs of coordinatively unsaturated Al and O ions. Aluminium-bonded methyl groups remained on the surface. Decomposition of TMA occurred at 600 K and above. Ammonia had reacted with most of the methyl groups by 573 K, but 723 K was required to remove them all. Primary, secondary and tertiary amino groups were formed in the reaction, and ammonia molecules were adsorbed on the surface. The average H/N ratio in the amino groups decreased with increasing reaction temperature. Good temperatures for AlN deposition by ALD seem to be any temperature up to 573 K for the TMA reaction and 723 K or above for the ammonia reaction.

Incorporation of 15N into various nitrogenous compounds in intact soybean nodules after exposure to 15N2 gas

Abstract: The intact nodules attached to the upper part of soybean roots were exposed to 15N2 and the incorporation of 15N into various soluble nitrogen constituents was investigated. Results indicated that ammonia, a primary product of N2 fixation, was located in more than two compartments. Ammonia reduced from N2 gas seemed to be incorporated firstly into glutamine especially amido-group nitrogen. Newly fixed nitrogen was secondly incorporated into glutamic acid and alanine in this sequence. These results suggested that fixed ammonia was assimilated by glutamine synthetase/glutamate synthase pathway. Turn-over rate of allantoin plus allantoic acid and serine was relatively high, although apparently these compounds were not primary products of newly fixed ammonia. 15N content of allantoin was always higher than that of allantoic acid. 15N incorporation to aspartic acid and asparagine was relatively slow, especially in early period. In bacteroid fraction there is much amount of ammonia comparing with other...

Influence of ammonium and nitrate nutrition on enzymatic activity in soybean and sunflower.

Abstract: Under conditions of controlled pH, nitrate and ammonium are equally effective in supporting the growth of young soybean (Glycine max var Bansei) and sunflower (Helianthus annuus L var, Mammoth Russian) plans Soybean contains an active nitrate reductase in roots and leaves, but the low specific activity of this enzyme in sunflower leaves indicates a dependency upon the roots for nitrate reduction Suppression of nitrate reductase activity in sunflower leaves may be due to high concentrations of ammonia received from the roots Nitrate reductase activity in leaves of nitrate-supplied soybean and sunflower follows closely the distribution of nitrate reductase For the roots of both species, glutamic acid dehydrogenase activity was greater with ammonium than with nitrate The glutamic acid dehydrogenase of ammonium roots is wholly NADH-dependent, whereas that of nitrate roots is active with NADH and NADPH In leaves, an NADPH-dependent glutamic acid dehydrogenase appears to be responsible for the assimilation of translocated ammonia and ammonia formed by nitrate reductionIn soybean roots ammonia is actively incorporated into amides, much of which remains in the roots Sunflower roots are less active in amide formation but transfer much of it, together with ammonia, into the shoots Glutamine synthetase activity in leaves is 20- to 40-fold lower than in rootsGlucose-6-phosphate dehydrogenase activity appears to be correlated with the activity of the nitrate reducing system in roots, but not in leaves

Electrochemical treatment of ammonia in wastewater by RuO2–IrO2–TiO2/Ti electrodes

Abstract: This study investigated the removal of ammonia in wastewater by an electrochemical method using titanium electrodes coated with ruthenium and iridium (RuO2–IrO2–TiO2/Ti) with low chlorine evolution over-voltage. The effects of operating parameters, including chloride ion concentration, current density and initial pH, were also investigated. The results were evaluated primarily by considering the efficiency of the elimination of NH 4 + -N. The removal of ammonia by electrochemical oxidation mainly resulted from the indirect oxidation effect of chlorine/hypochlorite produced during electrolysis. The direct anodic oxidation efficiency of ammonia was less than 5%, and the current efficiency was less than 10%. The ammonia removal followed pseudo-first-order kinetics. The electrochemical process can be applied successfully as a final polishing step, or as an alternative method to biological nitrification. The process seems to be most beneficial for small coastal cities