脱砷剂的研究进展及制备

在石油烃中,砷多与烃基形成有机化合物,砷化物按沸点高低分别进入不同馏分中.加工过程中,砷能使催化剂中毒失活,目前油品中砷主要通过物理吸附和加氢进行脱除,根据不同原理,脱砷剂分为吸附脱砷剂、氧化脱砷剂和加氢脱砷剂,其中加氢脱砷剂通过载体负载活性金属制备,应用最为广泛,脱砷效果较好.综述了脱砷剂的国内外研究进展及主要产品型号,同时介绍了加氢脱砷剂的制备过程,并对脱砷剂的发展趋势进行了展望.     

精制磷酸脱砷技术研究

研究了以硫化钠作为脱砷剂脱除工业磷酸中砷的脱砷方法。重点分析了硫化钠加入量、反应温度、反应时间和陈化时间对工业磷酸脱砷效果的影响。结果表明：以硫化钠作为脱砷剂能有效脱除磷酸中的砷,脱砷率可达95.7%以上。     

DZAs-1石脑油加氢脱砷剂的研制和工业应用

介绍了DZAs-1加氢脱砷剂的实验室研制和工业应用情况,并对脱砷剂的脱砷活性和容砷性能进行了实验室评价。研制的脱砷剂在炼油厂石脑油脱砷装置中首次工业应用结果表明,其脱砷效果良好,工业应用获得成功。     

煤制烯烃工业中砷的危害及解决方法探究

对煤制烯烃的工业技术进行了分析,从砷平衡的角度分析了砷在煤制烯烃工业中的危害。综述了目前在化学工业中可以采用的有效脱砷技术和方法,包括控制气化原料煤中的砷含量、采用湿法技术脱除合成气中的砷、采用脱砷催化剂脱砷。重点介绍了铜系、铅系、锰系和镍系等4类脱砷催化剂的研究进展。对煤制烯烃脱砷方案提出了建议。     

硝酸脱除褐煤粉煤灰中的砷

基于砷在褐煤粉煤灰中的赋存状态,建立了酸法脱除粉煤灰中部分砷的新方法,考察了反应温度、时间、pH值等对脱砷率的影响. 结果表明,褐煤灰中的砷大多富集在煤灰表面并以砷酸钙等砷酸盐形式存在,脱砷率与pH值和反应温度成反比. 综合考虑脱砷率、溶损率等因素,确定酸法最优脱砷条件为pH=1、反应温度20℃、反应时间1 h,此时脱砷率为66.34%.     

KTA-2型脱砷剂在炼厂丙烯精制中的工业应用

介绍了锦西石化公司15万t/a聚丙烯装置丙烯脱砷流程,结合KTA-2型脱砷剂的实际应用过程及生产运行数据,对KTA-2型丙烯脱砷剂在炼厂丙烯精制中的工业应用进行了总结。工业应用表明:KTA-2型脱砷剂具有较好的脱砷活性,精制丙烯中含砷化合物的质量分数小于20×10-9,脱砷率达99.1%以上,满足高效催化剂对丙烯中砷含量要求;KTA-2型脱砷剂具有较高的砷容,穿透砷容(w)可达10%。     

钢水中有害元素砷的脱除

通过加入以Ca-Fe合金为基础的脱砷剂对钢水进行了一系列脱砷实验研究. 结果表明,随钢中O含量降低脱砷率逐渐升高,当钢中O含量为1.0695′10-4(w)时,脱砷率达到37.5%;脱砷率随Ca-Fe合金加入量增加而增大,当Ca-Fe合金加入量为试样质量的18%时,脱砷率达50%;钢中原始砷含量越高,脱砷率越大,当原始砷含量为8.00′10-4(w)时,脱砷率高达77.5%;Ca-Fe合金与添加剂共同作用更有利于砷的去除,脱砷率最高达到81%.     

湿法磷酸脱砷实验研究

研究了以化学沉淀法对湿法磷酸进行脱砷处理,考察了脱砷剂用量、反应温度、反应时间、陈化时间对磷酸脱砷的影响。实验结果表明,化学沉淀法能有效降低湿法磷酸中砷的含量,砷的脱除率能达92%。     

煤制合成气脱砷技术及净化剂的研究开发

本文介绍了煤制合成气脱砷技术及脱砷剂的开发及工业应用结果。试验表明, TAS-02 型脱砷剂适用于高水汽比、高CO水煤气气氛的脱砷净化, 稳定性良好, 有较高的砷容和脱砷净化效果。     

TAS-15型脱砷剂用于催化汽油脱砷

对TAS-15型脱砷剂用于催化汽油脱砷的性能进行了研究。结果表明,TAS-15型脱砷剂能有效脱除催化汽油中的砷化物,具有较高的脱砷活性。在反应压力0.6 MPa、反应温度(20～50) ℃和空速(1～3) h^-1条件下,脱砷剂在1 600 h较长周期运行期间,出口汽油中砷含量≤5×10^-9,可用于催化汽油中砷化物的脱除。     

催化裂化汽油砷化物分布规律

采用自动快速蒸馏装置对脱砷前后的催化裂化汽油进行窄馏分切割,利用原子荧光光谱法对各窄馏分砷化物含量进行分析,研究催化汽油脱砷前后砷化物分布规律,为催化裂化汽油脱砷剂开发及脱砷工艺流程选择提供指导。实验结果表明：随着各窄馏分沸点增加,砷化物所占比例逐渐增大,90%以上砷化物均分布在80℃以上的重汽油组分中,尤其170℃以上馏分砷化物所占比例陡增,占总砷化物65.82%~96.31%。吸附脱砷剂对汽油150℃之前馏分中砷化物实现了全部脱除,而对150℃之后的重馏分脱砷率略有下降;临氢脱砷剂对汽油中80℃之前轻馏分和170℃之后重馏分中砷化物具有较高的脱除率,达到90%以上,而对中间馏分中砷化物脱除率较低。     

二乙氨基二硫代甲酸银分光光度法测定洗发护发液中总砷含量

4种洗发、护发液用HNO3、H2SO4和HC lO4湿法消化后,用二乙氨基二硫代甲酸银分光光度法测定总砷(As)含量。方法简单,结果可靠。     

Thermal oxidation of gallium arsenide with transition metal nanolayers on the surface

The physicochemical features of the interaction between nanofilms of iron triad metals and the gallium arsenide surface during thermal oxidation are analyzed. The role of oxides formed upon oxidation of iron, cobalt, and nickel metal films in the course of thermal oxidation of gallium arsenide is demonstrated, and the influence of the metal deposition method on the kinetics of oxidation, the composition, and the properties of the prepared samples is determined. Schemes are proposed for the development of the oxidation processes under investigation with due regard for the chemical specific features of the iron triad metals and their compounds.     

Pressure Sintering of Gallium Arsenide

Pressure sintering of gallium arsenide was studied in vacuum at 900° to 1000 °C and 9000 to 43,200 psi. The optical transmission of nearly theoretically dense gallium arsenide was about one-fourth less than that of equally thick single crystals. Density-time curves indicated that at least two densification mechanisms occur and apparently overlap. Microscopic observations indicated that plastic flow was one of the mechanisms. Plastic flow was further evidenced by the crystallographic texture of the grains, as determined by X-ray diffractometry. The rapid initial plastic flow densification stage is not adequately described by the McClelland densification rate equation. Diffusional secondary densification mechanisms may be operative at higher densities.     

TAs-15型FCC汽油脱砷剂的研究

极少量的砷化物可使加氢催化剂发生永久性中毒,为了保护加氢催化剂长期稳定运行,必须对催化裂化汽油中的砷化物进行脱除。对研制的TAs-15型FCC汽油脱砷剂进行原料适应性、1 600 h以上稳定性试验以及工艺条件对脱砷剂性能影响评价。结果表明,TAs-15脱砷剂具有较好的原料适应性及较高的脱砷性能,在反应温度（10～50） ℃、反应压力（0.5～2.0） MPa和空速（0.5～3.0） h^-1条件下,出口汽油中砷含量≤10×10^-9,完全可用于催化裂化汽油中砷化物的脱除。     

An automatic carrier concentration profile plotter using an electrochemical technique

A fully automatic system which directly plots semiconductor carrier concentration profiles to any required depth is described. An electrolytic Schottky barrier permits simultaneous controlled dissolution and capacitance-voltage measurements. Examples of profiles obtained in multiple epitaxial layer structures ofn-type gallium arsenide are given.     

Optical reflectivity studies of GaN and AlN chemical beam epitaxy on GaAs(100)

The deposition of gallium nitride and aluminium nitride thin films on GaAs(100) substrates by chemical beam epitaxy is reported. In-situ dynamic optical reflectivity has been used to compare growth rates of the nitride layers as a function of substrate temperature with their arsenide analogues. The relative growth efficiency of gallium nitride/gallium arsenide from triethyl gallium was found to be in the range 75–85%. The growth temperature for gallium nitride extends to higher temperatures, compared with gallium arsenide, probably due to lower evaporation rates of Ga bound to the nitride surface. At the same beam equivalent pressure, the growth rate of aluminium nitride from ethyldimethyl aluminium alane is approximately one-third of that for gallium nitride from triethyl gallium. Atomic force microscopy reveals that the gallium nitride surface formed at 500 °C is facetted, whereas an aluminium nitride surface deposited at 400 °C exhibits a rounded columnar type growth habit. Reflection anisotropy spectra indicate that atomic nitrogen readily reacts with the GaAs(100)-c(4×4) As stabilized surface at temperatures as low as 400 °C but without the gross facetting that has been observed at higher temperatures.     

Thermal oxidation of A<Superscript>III</Superscript>B<Superscript>V</Superscript> semiconductors with V<Subscript>2</Subscript>O<Subscript>5</Subscript> nanolayers on the surface

The specific features of the interaction of vanadium(V) oxide nanofilms with the surface of gallium arsenide and indium phosphide semiconductors under thermal oxidation conditions have been considered. The kinetics and mechanism of thermal oxidation of GaAs and InP with deposited V₂O₅ layers 15 and 25 nm in thickness have been studied. It has been revealed that vanadium(V) oxide exerts a specific effect on the oxidation of gallium arsenide and indium phosphide as compared to other d-metal oxides. It has been established that the oxidation occurs with the formation of a phase predominantly consisting of indium phosphates or gallium arsenates and intermediate products based on vanadium compounds in different oxidation states. Schemes have been proposed for the development of the oxidation processes with due regard for the chemical nature of vanadium(V) oxide.     

The electrochemical characterization of n-type gallium arsenide

A method for determining the carrier concentration of n-type gallium arsenide by an electrochemical technique is described. The minority carrier diffusion length is also obtained, and using subsidiary measurements the minority carrier lifetime can be estimated. The extension of this treatment to the characterization of epitaxial layers is discussed.     

Electrochemical capacitance characterization of n-type gallium arsenide

The depletion layer capacitance of n-type gallium arsenide was measured as a function of its anodic potential in an electrochemical cell. It was shown that these measurements can lead to accurate values of carrier concentration, and are compatible with stripping by electrochemical dissolution, provided that surface area is preserved. The experimental conditions required to maintain the electrolyte-semiconductor contact area constant, are described. Also, it is shown that excursions into regions outside those specified lead to significant enhancement of capacity (via real area increase). Under these conditions the carrier concentration can no longer be obtained but much can be learnt about the internal structure of the material.