不同结构硫化钼催化剂上酚类模型化合物的加氢脱氧

Several MoS2 catalysts of different structure, prepared by in situ decomposition of ammonium heptamolybdate （AHM） and molybdenum naphthenate （MoNaph）, and by MoS2 exfoliation （TDM）, were characterized by BET, X-ray diffraction （XRD）, Energy Dispersive X-ray （EDX） and transmission electron microscopy （TEM）. The analysis showed that MoS2 structure was dependant upon the preparation procedure. The activity of the catalysts was determined by measuring the hydrodeoxygenation （HDO） of phenol, 4-methylphenol and 4-methoxyphenol using a batch autoclave reactor operated at 2.8 MPa of hydrogen and temperatures ranging from 320-370℃. By comparing the conversion, the reactivity order of the catalysts was： AHM〉TDM-D〉MoNaph〉thermal〉MoS2 powder〉 TDM-W. Also, the effect of reaction temperature on the HDO conversion was explained in terms of equilibrium of reversible reaction kinetics. The main products of the HDO for phenolic compounds were identified by gas chromatography/mass spectrometry （GC/MS）. The results showed that the product distribution and the HDO selectivity were correlated with the reaction temperature. Two parallel reaction routes, direct hydrogenolysis and combined hydrogenation-hydrogenolysis, were confirmed by the analysis of the product distribution. High temperature favored hydrogenolysis over hydrogenation for HDO of phenol and 4-methoxyphenol, whereas for 4-methylphenol the reverse was true.     

以钴钼废催化剂为原料制备仲钼酸铵试验研究

进行了以钴钼废催化剂为原料制备仲钼酸铵试验研究，采用加碱焙烧、湿式球磨、沉钼酸和氨溶工艺路线。研究结果表明，焙烧温度、时间和纯碱加入量对钼的提取率均有一定的影响，沉钼酸过程除P效果较好，产品仲钼酸铵质量稳定。     

不同工艺条件下耐硫甲烷化催化剂的反应活性研究

考察了钼基耐硫甲烷化催化剂在不同反应温度下的催化活性,结果表明反应温度在560℃附近时甲烷化活性最高。在此温度下研究了空速、原料气中H2S、H2O、CO2、CH4、H2/CO等浓度对反应活性的影响,结果表明,原料气中H2S含量的增加有利于提高催化剂的甲烷化反应活性;H2O的加入促进了水煤气变换反应的进行但抑制了甲烷化反应,因此CO转化率虽没有下降但甲烷化效率却有所降低;添加CH4对甲烷化反应没有明显影响,而添加CO2则明显抑制了甲烷的生成。结合催化剂表征结果进一步对各因素的影响机理进行了分析,这为耐硫甲烷化工艺条件优化及催化剂设计提供了重要依据。     

钼酸铵生产技术发展现状

钼酸铵可用作生产钼粉、钼金属制品的前驱体,可广泛用作化学试剂、催化剂、阻燃剂及药物等。简要介绍了钼酸铵的品种,国内外生产概况及生产工艺。重点介绍了近几年钼酸铵生产工艺的技术创新,如表面活性剂的应用,蒸发设备的改进,连续结晶器的引入,循环萃取-反萃法的采用以及浸出剂的添加等,并对中国钼酸铵行业的发展提出建议。     

水热法合成一维纳米级MoO_3微粉

以仲钼酸铵为钼源,选用强弱不同的酸使仲钼酸铵酸化水解生成中间体,经洗涤、干燥、焙烧,制备了淡灰蓝色纳米级MoO3微粉;研究了溶液酸度、钼酸铵浓度、焙烧温度等因素对MoO3微粉相对结晶度、晶体尺寸和形貌的影响。     

均匀沉淀法制备超细钼粉

以浓硝酸酸沉一定浓度的仲钼酸铵溶液,控制反应条件,使其快速均匀沉淀得到胶状的钼酸沉淀,干燥并煅烧后进行氢气还原得到超细钼粉.通过扫描电镜、X射线衍射和BET比表面仪分析实验结果.结果表明,用该方法制备的钼粉的BET平均粒径为66.8 nm.     

七钼酸铵质量攻关试验研究

对七钼酸铵松装体积波动大、挥发物含量较高的问题针对性地进行分析和研究,经试验取得了较佳工艺条件,达到了预期目的,为该产品工业化生产奠定了基础。     

钼酸铵研究进展

简述了钼酸铵的现状,主要介绍了制取七钼酸铵、二钼酸铵和β型四钼酸铵的生产工艺和钼酸铵废水治理的方法,并对钼酸铵存在的问题提出了几点建议和展望。     

In situ analysis of metal-oxide systems used for selective oxidation catalysis: how essential is chemical complexity?

The mode of operation of selective oxidation reactions is described by a series of chemical rules defining the catalyst and some reaction intermediates. In contrast to catalytic processes over metallic elements, little is known, however, about the atomistic details of selective oxidation. In particular, the participation of the subsurface region of the catalyst in the kinetically relevant elementary steps (Mars–van Krevelen mechanism) is not positively verified. Using in situ X-ray absorption techniques to study binary and ternary molybdenum oxides the present contribution shows that it is possible to tackle some of the problems in selective oxidation by direct experimental observation. The modification of the Mo–O local bonding interaction upon thermal reduction of MoO₃to MoO_3-x is illustrated. This was also found for mixed Mo–V oxides in which the chemical state of the vanadium seemed unaffected by the reaction but the surface Mo:V ratio varied substantially with the gas phase composition. It is further shown that the solid-state phase transformation between reduced and oxidised forms of molybdenum oxides occur so rapidly, that possibly relevant suboxide cannot be identified by ex situ phase analysis. Observation of the time-law of redox transformations showed that lattice oxygen is only available for selective oxidation if the associated solid-state transformation occurs in the kinetic regime of reaction control and not in that of diffusion control.     

食品营养强化剂钼酸铵产品标准的制定

目的确定食品营养强化剂钼酸铵产品标准拟设置的技术指标,并建立各指标的检测方法。方法根据现有的钼酸铵国内外标准和资料,美国药典USP34、美国药典USP42、韩国食品公典、ACS Reagent Chemicals Book、GB/T 3460-2017《钼酸铵》以及GB/T 657-2011《化学试剂四水合钼酸铵(钼酸铵)》确定技术指标和试验方法,并对10批次钼酸铵产品进行实样验证。结果钼酸铵产品标准拟设置的技术指标有色泽、状态、气味、钼酸铵含量、不溶性杂质、氯化物、硫酸盐、盐酸不溶物、镁及碱金属、硝酸盐、砷盐、磷酸盐与硅酸盐、磷酸盐、铅(Pb)、重金属(以Pb计)。10批次产品均符合要求。结论拟设置的技术指标和建立的试验方法具有可行性。