美国高浓度液体肥料——无水液氨

高浓度肥料与液体肥料是国际肥料的发展方向,高浓度肥料的优点是养分浓度高,可以降低贮存和运输的成本,并有利于农民使用,减少施肥成本,液体肥料符合集约化农业发展,可以结合农业灌溉和精准施肥,液体肥料可采用管道满足现代农业需要,成为现代农业肥料的趋势。     

Phosphate-bonded composite electrodes for hydrogen evolution

A new process of cementing metallic powders to produce high surface area cathodes for alkaline water electrolysis is described. The binding compound is a tridimensional polymer of aluminium phosphate (AlPO₄). Phosphate-bonded composite electrodes give a low-polarization performance for hydrogen evolution in 1m KOH aqueous solution in the case of 95 wt% Pt and 98 wt% Ni. When electrode materials are prepared with nickel powder, the electrocatalytic activity for the hydrogen evolution reaction, the chemical stability and the electrical conductivity depend on the Ni content and morphology of the electrode. The best performance and chemical stability with Ni as the starting material are obtained for spiky filamentary particles produced by the decomposition of nickel carbonyl.     

Cathodic reduction of pyridine in liquid ammonia

In liquid ammonia at ?40°, pyridines give a single reduction peak corresponding to the formation of the radical anion. Alternative electrochemical kinetic techniques have been used to determine rate constants for the dimerisation of the radical anions. The chemical stability of the resulting dimeric dianion has been examined and the kinetics of its anodic oxidation investigated. The mechanism of the oxidation of the same species by molecular oxygen is discussed. The reaction of the dianions with alkyl halides differs in the cases of pyridine and 4-methylpyridine, the latter giving the N,N′-dialkyl derivative but pyridine yielding only polymer. Pyridine radical anions react with alkyl bromides only in a simple charge transfer reaction.     

Cathodic reductions of cyanopyridines in liquid ammonia

The electrochemical behaviours of the three isomeric cyanopyridines have been studied in liquid ammonia by cyclic voltammetry and controlled potential coulometry. Reaction mechanisms are proposed on the basis of the observed electrochemical behaviour of products and the mass spectra of products produced by the alkylation of the electrogenerated organic anions. The kinetics of charge transfer reactions have been examined by interfacial impedance measurements and the rate of dimerisation of the radical anions of 3-cyanopyridine evaluated.     

Electrolytic equipment for reductions in liquid ammonia

We have developed static and circulating electrolytic equipment for liquid ammonia (or low molecular weight amines) to perform reductions of compounds bearing at least one reducible group. The equipment contains undivided electrochemical cells including consumable magnesium anodes. Birch and Bouveault-Blanc reductions are performed with substrate weight percents up to 10%. A circulating electrolytic cell working at room temperature is described which may be adaptable to large scale production.     

Iron(III) protoporphyrin IX—single-wall carbon nanotubes modified electrodes for hydrogen peroxide and nitrite detection

Iron(III) protoporphyrin IX (Fe(III)P), adsorbed either on single-walled carbon nanotubes (SWCNT) or on hydroxyl-functionalized SWCNT (SWCNT-OH), was incorporated within a Nafion matrix immobilized on the surface of a graphite electrode. From cyclic voltammetric measurements, performed under different experimental conditions (pH and potential scan rate), it was established that the Fe(III)P/Fe(II)P redox couple involves 1e⁻/1H⁺. The heterogeneous electron transfer process occurred faster when Fe(III)P was adsorbed on SWCNT-OH (11 s⁻¹) than on SWCNT (4.9 s⁻¹). Both the SWCNT-Fe(III)P- and SWCNT-OH-Fe(III)P-modified graphite electrodes exhibit electrocatalytic activity for H₂O₂ and nitrite reduction. The modified electrodes sensitivities were found varying in the following sequences: S_{SWCNT-OH-Fe(III)P} = 2.45 mA/M ≈ S_{SWCNT-Fe(III)P} = 2.95 mA/M > S_Fe(III)P = 1.34 mA/M for H₂O₂, and S_{SWCNT-Fe(III)P} = 3.54 mA/M > S_Fe(III)P = 1.44 mA/M > S_{SWCNT-OH-Fe(III)P} = 0.81 mA/M for NO₂⁻.     

Electrochemical modeling of hydrogen storage in hydride-forming electrodes

An electrochemical kinetic model (EKM) is developed, describing the electrochemical hydrogen storage in hydride-forming materials under equilibrium conditions. This model is based on first principles of electrochemical reaction kinetics and statistical thermodynamics and describes the complex, multi-stage, electrochemical (de)hydrogenation process. A complete set of equations have been derived, describing the equilibrium hydrogen partial pressure and equilibrium electrode potential as a function of hydrogen content in both solid-solution and two-phase coexistence regions. The EKM has been applied to simulate the isotherms of thin film Pd electrodes of various thicknesses. Good agreement between experiment and theory is found in all cases. Relevant energy and kinetic parameters are obtained from the simulations.     

Cathodic reduction and alkylation of quinoline in liquid ammonia

Alternative electrode kinetic methods have been used to study the rates of the coupling reaction between the quinoline radical anion and alkyl halides at ?40°. The rate of the dimerisation reaction of the radical anions has been determined using 0.5 M potassium bromide as the electrolyte. The behaviour of the radical anions in a tetraethylammonium salt electrolyte has been investigated and protonation by the cation is shown to occur.     

Iron intercalated in graphite as catalysts for ammonia synthesis

Catalysts for ammonia synthesis based on iron intercalated in graphite precursors were prepared. This study reveals that the catalysts' activity is associated with a broad electron paramagnetic resonance (EPR) line, and that the iron co-ordinated by both carbon and potassium influences both the intensity of the EPR signal and activity.     

Permeability of silicone polymers to ammonia and hydrogen sulfide

Permeability coefficients, P?, for NH₃ AND H₂S in 11 different types of silicone membranes were measured in the temperature range from 10.0 to 55.0°C and at pressures up to 115 psig (～ 7.8 atm). The values of P? for NH₃ and H₂S in different silicone polymers decrease considerably as the bulkiness of the functional groups in the side and backbone chains of these polymers increases. the substitution of Si? O bonds with stifer Si? C bonds in the backbone chains also results in a considerable decrease in gas permeability. the values of P? for NH₃ and H₂S increse exponentially with incresing δp, the pressure difference across the membrancs. The temperature dependence of NH₃ and H₂S varies greatly: P? can increase, decrease, or pass through a minimum with increasing temperature, depending on the nature of the silicone polymer. The temperature dependence of P? is also affected in some cases by Δp. The permeability behavior of silicone polymers to NH₃ and H₂S is compared with that to other penetrant gases, and the factors which might affect this behavior are discussed.     

液氨储罐腐蚀分析与防止措施

对可能引起液氨储罐腐蚀的几个方面进行了分析,并提出了相应的防护措施     

Poisoning of platinized platinum electrodes by hydrogen in dimethylsulphoxide

A study of hydrogen sorption on platinized platinum in dimethylsulphoxide solutions has shown that there is a heterogeneous reaction between hydrogen and dimethylsulphoxide to form a tightly bound film of reduction products, probably dimethylsulphide.     

Electroreduction of nitric oxide to ammonia at chemically modified electrodes

The electroreduction of NO has been studied using various modified electrodes with the mediators including cobalt phthalocyanine(CoPc) and a redox polymer. Selective conversion of NO into ammonia was obtained at a CoPc-coated glassy carbon electrode with a maximum selectivity of 92.3%. A similar result was obtained with a Pc-coated electrode, but the yield of ammonia was not so high as with the CoPc-coated electrode. A bright platinum as well as Fe(II)-poly(4-vinylpyridine) film-coated nesa glass was less active for the NO conversion into ammonia.     

液氨流量计的选用分析

针对工业生产过程中液氨流量计测量不准确的问题,为了能够正确的选择与使用液氨流量计,通过对几种流量计工作原理进行分析,找出影响测量误差的原因,对影测量误差的因素进行判断和调效,从而实现工业生产中对液氨流量的准确监控。     

合成氨弛放气、排放气的氢气回收技术

介绍了从合成氨排放气、弛放气中回收氢气的膜分离技术、变压吸附技术和深冷分离技术 ,并对该三种方法进行了比较     

液氨管线带压开孔技术

介绍了在液氨管线上进行不停输带压开孔的具体实施步骤,并对安全施工要点作了总结。