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71.
在双筐并流氨合成塔中使用了A110-1-H/A110-1型氨合成催化剂,使用寿命达1740天,累计产氨438378t.该催化剂组合具有低温活性好、易还原、高催化活性、高抗毒能力、良好的热稳定性与破碎强度等优点. 相似文献
72.
Aspartate ammonia lyase (Asp) is one of three types of ammonia lyases specific for aspartate or its derivatives as substrates, which catalyzes the reversible reaction of l-aspartate to yield fumarate and ammonia. In this paper, the catalytic mechanism of Asp has been studied by using combined quantum-mechanical/molecular-mechanical (QM/MM) approach. The calculation results indicate that the overall reaction only contains two elementary steps. The first step is the abstraction of Cβ proton of l-aspartate by Ser318, which is calculated to be rate limiting. The second step is the cleavage of CαN bond of l-aspartate to form fumarate and ammonia. Ser318 functions as the catalytic base, whereas His188 is a dispensable residue, but its protonation state can influence the active site structure and the existing form of leaving amino group, thereby influences the activity of the enzyme, which can well explain the pH dependence of enzymatic activity. Mutation of His188 to Ala only changes the active site structure and slightly elongates the distance of Cβ proton of substrate with Ser318, causing the enzyme to remain significant but reduced activity. 相似文献
73.
This paper reports a study on the distribution of dinitrogen between the atmosphere, floodwater and porewater of the soil in a flooded rice field after addition of15N-labelled urea into the floodwater.Microplots (0.086 m2) were established in a rice field near Griffith, N.S.W., and labelled urea (80 kg N ha–1 containing 79.25 atoms %15N) was added to the floodwater when the rice was at the panicle initiation stage. Emission of nitrous oxide and dinitrogen was measured directly during the day and overnight, using a cover collection method and gas chromatographic and mass spectrometric analytical methods. Ammonia volatilization was calculated with a bulk aerodynamic method from measurements of wind speed and floodwater pH, temperature and ammoniacal nitrogen concentration. Seven days after urea application the15N2 content of the floodwater and soil porewater was determined and total fertilizer nitrogen loss was calculated from an isotopic balance.Throughout the experimental period gas fluxes were low; nitrous oxide, ammonia and dinitrogen flux densities were less than 5, 170 and 720 g N ha–1 d–1, respectively. The greatest dinitrogen flux density was observed two days after urea addition and this declined to ~ 100 g ha–1 d–1 after seven days.The data indicate that, of the urea nitrogen added, 0.02% was lost to the atmosphere as nitrous oxide, 0.9% was lost by ammonia volatilization, and 3.6% was lost as dinitrogen gas during the 7 days of measurement. At the end of this period 0.028% and 0.002% of the added nitrogen was retained as dinitrogen gas in the floodwater and soil porewater respectively. Recovery of the15N applied as nitrogen gases, plant uptake, and soil and floodwater constituents totaled about 94% of the nitrogen added. 相似文献
74.
A series of experiments was conducted under controlled soil moisture and temperature conditions in a growth chamber to examine the effect of a range of nutrient seed coatings on the emergence to wheat (Triticum aestivum L. cv. Kite) and oats (Avena sativa L. cv. Blackbutt) sown in a coarse sandy loam soil. Final emergence of oats was not reduced by a coating containing 10 kg P ha–1 (as monocalcium phosphate [MCP]) whereas the same coating reduced wheat emergence by 15%. The emergence of both wheat and oats was severely reduced by urea coatings (supplying 10 kg N ha–1) to 33 and 13% respectively; this injury was lessened markedly by the inclusion of phenyl phosphorodiamidate (PPD) in the urea coatings at 1% (w/w) (emergence increased to 66 and 56% respectively).Low soil moisture (67% of field capacity [FC]) resulted in almost no emergence of wheat coated with urea (± bentonites of different pH). In soil at FC, the addition of bentonite of pH 5 (B5) to urea coatings permitted greater emergence (54%) than when bentonite of pH 9 (B9) was added (32%) which, in turn, permitted greater emergence than urea coating alone (10%). When PPD and bentonite (B5 or B9) were combined either singly or together with urea in seed coatings, PPD was more effective than either of the bentonites in reducing injury and masked the slight positive effect of B5.Coatings containing various combinations of N and P sources (at 3.6 and at 8 kg ha–1 respectively) all reduced the emergence of wheat compared to raw seed (91% emergence). When applied alone, MCP was least damaging (74%); the combination of MCP with ammonium sulfate (AS) caused somewhat more injury (68%) whilst combination with calcium nitrate (CN) caused most injury (29%). In contrast, CN alone caused relatively little damage (73%) whilst AS alone was more damaging (50%). There was no significant regression found between percentage emergence and either the calculated partial salt index or the pH of the nutrient coatings. Further work is needed to examine the mechanisms of injury due to nutrient seed coatings so that safe but effective formulations can be developed. 相似文献
75.
T.V. Choudhary A.K. Santra C. Sivadinarayana B.K. Min C.-W. Yi K. Davis D.W. Goodman 《Catalysis Letters》2001,77(1-3):1-5
Ammonia decomposition on Ir(100) has been studied over the pressure range from ultrahigh vacuum to 1.5 Torr and at temperatures ranging from 200 to 800 K. The kinetics of the ammonia decomposition reaction was monitored by total pressure change. The apparent activation energy obtained in this study (84 kJ/mol) is in excellent agreement with our previous studies using supported Ir catalysts (Ir/Al2O3 82 kJ/mol). Partial pressure dependence studies of the reaction rate yielded a positive order (0.9±0.1) with respect to ammonia and negative order (–0.7 ±0.1) with respect to hydrogen. Temperature-programmed desorption data from clean and hydrogen co-adsorbed Ir(100) surfaces indicate that ammonia undergoes facile decomposition on both these surfaces. Recombinative desorption of N2 is the rate-determining step with a desorption activation energy of 63 kJ/mol. Co-adsorption data also indicate that the observed negative order with respect to hydrogen pressure is due to enhancement of the reverse reaction (NH
x
+ H NH
x+1, x=0–2) in the presence of excess H atoms on the surface. 相似文献
76.
本文试图论述现有合成氨厂改变产品结构,采取以生产化肥为主,联产化工产品。通过对钾芒硝法工艺及联碱工艺技术路线的选择,技术经济分析,以期提高化肥厂的经济效益。 相似文献
77.
78.
79.
合成气中氨含量测定方法的改进 总被引:1,自引:0,他引:1
用快速测定仪测定气体中的氨含量,采气量为50ml,可准确测出高含量氨体积百分比含量为80%-100%和低含量氨体积百分比含量为1%-20%的样气,该仪器结构简单,易于制造,测定过程简单,结果准确,一目了然。 相似文献
80.