可逆与不可逆吸附氢在合成甲醇反应中的作用

在自行设计和建立的加压动态分析装置上研究了合成甲醇催化剂上氢的吸附和反应行为。结果表明:在反应条件下催化剂上吸附的氢可分为可逆吸附氢和不可逆吸附氢;不可逆吸附氢又可分为能被CO顶替出来的和不能被CO顶替出来的两部分;能被CO顶替出来的不可逆吸附氢对CO的吸附起促进作用,不能被CO顶替出来的不可逆吸附氢是合成甲醇催化剂必不可少的“组分”或称“促进剂”;同时甲醇的生成是可逆吸附氢与一氧化碳作用的结果。     

一类新的4-取代胂酸型变色酸偶氮多卤显色剂的合成及其与稀土元素显色反应的研究

本文研究了五个结构新颖的显色剂与稀土元素的显色反应。其中的二溴羧基偶氮氯肿(CAsA-DBK)与稀土元素反应具有对比度大、灵敏度高、选择性好等优点。在0.6mol/LHClO_4介质中,不加任何掩蔽剂条件下,只与铈组稀土显色,与钇组稀土几乎不显色,是一个较有特色的铈组稀土试剂。     

在涂层TiO2改性铜催化剂上甲醇脱氢制甲酸甲酯

在常压和２５０℃下，考察了涂层ＴｉＯ２改性铜催化剂上甲醇脱氢生成甲酸甲酯的活性和选择性以及催化剂的稳定性。结果表明，涂层ＴｉＯ２明显提高了铜催化剂的活性和稳定性。在所考察的铜催化剂中，以Ｃｕ／ＴｉＯ２／ＡｌＯ３的催化活性最高，甚至高于离子交换法制备的Ｃｕ（ｅｘ）／ＳｉＯ２催化剂。ＸＰＳ分析表明，Ｃｕ／ＴｉＯ２／ＡｌＯ３中存在着两种化学环境不同的ＣＵ（０），即负载在ｒ－ＡＬＯ３和ＴｉＯ２－Ａｌ２Ｏ３     

2,6—二氯—4—溴偶氮胂光度法测定微量铀（Ⅵ）

本报道用了２，６－二氯－４－溴偶氮胂作显色剂测定微量铀（Ⅵ）的光度法。在Ｈ２ＳＯ４介质中，铀（Ⅵ与）２，６－二氯－４－溴偶氮胂形成１：２络合物，其λｍａｘ＝６４０ｎｍ；表观摩尔吸光系数为１．１×１０＾５Ｌ．ｍｏｌ＾－＾１．ｃｍ＾－＾１；铀的浓度在０．０－２２．０μｇ／ｍｌ内符合比耳定律。方法具有灵敏度高，选择性好，操作方便等特点并已用于废水及矿样中微量铀（Ⅵ）的测定。     

5—Br—PAN—S光度法测定微量锌的研究

研究了锌与5-Br-PAN-S的显色反应.在pH8.5,Zn(Ⅱ)与5-Br-PAN-S反应生成1:2的红色络合物,其最大吸收峰为568nm,表观摩尔吸光系数为4.80×10~4,Zn(Ⅱ)浓度在0～30μg/25ml服从比耳定律.用本法测定了水样和头发中的微量锌,结果满意.     

示波极谱法直接测定水中超痕量钨

本文对钨—溴邻苯三酚红极谱催化波进行了研究,发现体系中加入四乙基碘化铵后,极谱渡高明显增加,体系的稳定性显著提高,检出限达1.8×10~(-11)mol/L。确定了最佳条件,拟定了不经分离富集直接测定水中痕量钨的方法。此外还对极谱波性质进行了探讨,证明该极谱波为配合物吸附催化氢波,讨论了阳离子表面活性物质对催化氢波的作用机理。     

由XPS研究CO2在低压甲醇合成中的作用

本文应用XPS,在模拟工业催化剂和实际操作条件下,对低压甲醇合成铜基催化剂的表面形态进行了研究.结果表明,在还原及反应状态下,催化剂表面没有稳定的Cu~(2+)、Cu~+离子存在,仅Cu~0能被检测到;ZnO被还原,形成缺氧结构ZnOx(X≤1),表面出现氧空位.认为高度分散的Cu~0与其紧密接触的部分还原的ZnOx联合组成了甲醇合成的表面活性中心,也即表面上的Cu-Zn-O(“口”为氧空位)构成了最佳合成活性单元.提出反应原料气中适量CO_2的加入有助于金属Cu微晶的分散,认为CO_2的作用主要是使反应气氛中含有一定的氧化势,它与原料气中的CO+H_2一起,对金属Cu微晶起氧化还原作用.CO_2可将Cu~0氧化成Cu~(?+)(甚至Cu~+).但Cu~(?+)会马上被CO+H_2还原成Cu~0.通过这样的氧化还原循环,阻止了Cu微晶的聚集长大,延长了催化剂的使用寿命.     

Selective Oxidation of Methane to Methanol Using Molecular Oxygen on MoOx／（LaCoO3＋Co3O4） Catalysts

Comparatively high CH3OH selectivity (60.0%) and yield (6.7%) were obtained on MoOx/(LaCoO3 Co3O4) catalysts in selective oxidation of methane to methanol using molecular oxygen as oxidant. The interaction between MoOx and La-Co-oxide modified the molecular structure of molybdenum oxide and the ratio of O^-/O^2- on the catalyst surface, which controlled the catalytic performance of MoOx/(LaCoO3 Co3O4) catalysts.     

烯土—铌（钽）复合溴氧化物的结构与光谱特性

用高温固相法合成了系列化合物ＲＥ０．０６Ｌａ０．９４Ｍ２Ｏ６Ｂｒ（Ｍ＝Ｎｂ，Ｔａ；ＲＥ＝Ｅｕ，Ｔｂ，Ｐｒ，Ｓｍ），并测定了其激发和发射光谱。室温下Ｅｕ＾３＋，Ｔｂ＾３＋，Ｐｒ＾３＋，Ｓｍ＾３＋在稀土－铌（钽）复合溴氧化物中呈现特征激发谱线，但Ｎｂ和Ｔａ的光谱特性稍有不同。     

探究Cu/ZnO相互作用对CO2加氢制甲醇反应性能的影响

Using renewable green hydrogen and carbon dioxide (CO₂) to produce methanol is one of the fundamental ways to reduce CO₂ emissions in the future, and research and development related to catalysts for efficient and stable methanol synthesis is one of the key factors in determining the entire synthesis process. Metal nanoparticles stabilized on a support are frequently employed to catalyze the methanol synthesis reaction. Metal-support interactions (MSIs) in these supported catalysts can play a significant role in catalysis. Tuning the MSI is an effective strategy to modulate the activity, selectivity, and stability of heterogeneous catalysts. Numerous studies have been conducted on this topic; however, a systematic understanding of the role of various strengths of MSI is lacking. Herein, three Cu/ZnO-SiO₂ catalysts with different strengths of MSI, namely, normal precipitation Cu/ZnO-SiO₂ (Nor-CZS), co-precipitation Cu/ZnO-SiO₂ (Co-CZS), and reverse precipitation Cu/ZnO-SiO₂ (Re-CZS), were successfully prepared to determine the role of such interactions in the hydrogenation of CO₂ to methanol. The results of temperature-programmed reduction (H₂-TPR) and X-ray photoelectron spectroscopy (XPS) characterization illustrated that the MSI of the catalysts was considerably affected by the precipitation sequence. Fourier transform infrared reflection spectroscopy (FT-IR) results indicated that the Cu species existed as CuO in all cases and that copper phyllosilicate was absent (except for strong Cu-SiO₂ interaction). Transmission electron microscopy (TEM), X-ray diffraction (XRD), and N₂O chemical titration results revealed that strong interactions between the Cu and Zn species would promote the dispersion of Cu species, thereby leading to a higher CO₂ conversion rate and improved catalytic stability. As expected, the Re-CZS catalyst exhibited the highest activity with 12.4% CO₂ conversion, followed by the Co-CZS catalyst (12.1%), and the Nor-CZS catalyst (9.8%). After the same reaction time, the normalized CO₂ conversion of the three catalysts decreased in the following order: Re-CZS (75%) > Co-CZS (70%) > Nor-CZS (65%). Notably, the methanol selectivity of the Re-CZS catalyst was found to level off after a prolonged period, in contrast to that of Co-CZS and Nor-CZS. Investigation of the structural evolution of the catalyst with time on stream revealed that the high methanol selectivity of the catalyst was caused by the reconstruction of the catalyst, which was induced by the strong MSI between the Cu and Zn species, and the migration of ZnO onto Cu species, which caused an enlargement of the Cu/ZnO interface. This work offers an alternative strategy for the rational and optimized design of efficient catalysts.