纤维结构化纳米Au（Pd）催化剂的原电池反应制备及其催化气相草酸二甲酯加氢性能

煤经由合成气的草酸二甲酯（DMO）气相加氢合成乙二醇（EG），是煤化工领域的热点之一。针对该气相加氢反应的强放热特点及现有催化剂低导热和稳定性差的问题，提出新型微结构化催化剂研制新策略，以实现优异的催化加氢活性和良好导热性的统一，消除高温热点以抑制产物深度加氢和减缓催化剂烧结失活，同时又能及时移走反应热。基于三维开放网络的烧结金属纤维（2-20微米Cu、Ni等）结构载体，利用HAuCl4及其盐或(NH4)2PdCl6与金属纤维表面的自发原电池反应，对Au（Pd）催化剂进行宏（反应器尺度制备）-微（织构均一调控）-纳（纳米分散和锚定）设计合成。研究金属纤维表面性质、原电池反应条件和Au（Pd）前体等，对Au（Pd）颗粒尺寸/形貌、表面与化学环境和锚定强度及催化加氢性能的影响，阐明纤维结构化催化剂的构筑和织构/晶构的调控规律，揭示表面特性-催化性能规律和织构-流动与传递-反应过程强化构效关系。

The synthesis of ethylene glycol (EG) from syngas, though catalytic coupling of CO with methyl nitrite to dimethyl oxalate (DMO) and subsequent gas-phase hydrogenation of DMO, is a hot subject in the chemical processing of coal. However, effective and efficient solutions are urgently required to overcome the difficult problems associated with strong exothermicity of the hydrogenation process as well as the poor durability of traditional catalysts and their weak thermal conductivity. One promising way is to use and develop novel microstructured catalytic bed reactors, which can provide unique combination of high thermal conductivity, excellent hydrogenation activity/selectivity and long-term stability. Regarding the strong exothermicity, it is strongly desirable to enhance the intrebed heat transfer, which is quite helpful to quickly dissipate a great quantity of reaction heat liberated rapidly thereby making the bed temperature close to isothermal. This will not only suppress deep hydrogenation but also retard the catalyst sintering deactivation. Our strategy in this effort is to devolop a new-type microfibrous structured nano-Au (or Pd) catalysts with excellent heat transfer ability for the gas-phase hydrogenation of DMO. To accomplish this goal, a new carrier class of thin-sheet sinter-locked metal fibers (such as 2 to 20 um Ni, Cu, and Fe fibers) will be devopped firstly, being characterized with a special three-dimensional network, open structure and especially high thermal conductivity. The Au and/or Pd will be then firmly embedded into the thin-sheet metal-fiberous matrixes with the aid of a simple galvanic exchange reaction deposition method (e.g., 3Ni + 2HAuCl4 = 2Au + 3NiCl2 + 2HCl, driving by the large electrode potential difference between Ni2+/Ni0 (-0.22 V) and Au3+/Au0 (1.5 V) pairs). This new approach allows for one-step fabrication of such microfibrous Au (or Pd) nanocatalysts in reactor scale together with uniform geography design of catalyst bed in meso-scale and chemically and morphologically tuning of the active sites in nano-scale. The effects of metal-fiber surface properties, galvanic reaction conditions, and Au (or Pd) precursors, will be investigated systematically, on the Au (or Pd) particles in terms of size/morphology, surface chemical properties, embedment strength and catalytic hydrognation performance. The galvanic exchange reaction deposition method will be established for a new-class transient-metal-supported precious metal catalyst system with textural and nano-structural controllability. The relationship between the catalytic performace and the special nano-structure of Au (or Pd) particles galvanically deposited onto the metal fibers will be deeply revealed. Computational fluid dynamics (CFD) code FLUENT will be employed to simulate the temperature and reaction distributions inside such microfibrous-structured catalytic bed, demonstrating the process intensification benefitted form enhanced heat/mass transfer.