构建LDHs层间微型催化反应器催化酯化原油脱酸

Processing highly acidic crude oil is a serious problem for the refinery in China. Among various deacidification methods, catalytic esterification is attractive due to its mild reaction conditions and low cost. Layered double hydroxides (LDHs) can be used as catalysts for deacidification of crude oil via esterification between naphthenic acids and ethylene glycol (EG). However, the catalytic efficiency needs to be further improved. This research aims to construct LDHs interlayer catalytic esterification microreactor by virtue of the abundant nanosized interlayer space, exchangeable interlayer anions and metal catalytic sites in brucite-like sheets. Firstly, EG intercalated LDHs (EG-LDHs) are synthesized. Secondly, naphthenic acids enter the interlayer space of EG-LDHs and react with the pre-immobilized EG under the catalysis of metal ions in sheets. By the interlayer catalytic microreactor, it is hoped to increase the reaction space, eliminate the diffusion limitation of highly viscous EG entering the interlayer, increase the collision frequency between reactants, and thus improve the catalytic efficiency. This project focuses on systemically studying the synthesis and property tuning of EG-LDHs, the interlayer catalytic reaction mechanism and the correlation between structural property and catalytic performance of the confined interlayer. Based on this research, the scientific essence of the catalytic esterification in the confined interlayer space of LDHs will be well understood and the structure-performance relationship in LDHs interlayer catalytic microreactor and its controlling method will be attained.

高酸值原油的加工是炼厂面临的严峻问题，在各种原油脱酸方法中，催化酯化法有较好的应用前景。水滑石类化合物（LDHs）在原油酯化脱酸中有良好的催化活性，但仍需提高其催化效率。本项目拟利用LDHs丰富的纳米层内空间、层间阴离子可调控性和层板金属对酯化反应的催化作用，首先制备乙二醇（EG）插层LDHs，然后环烷酸扩散进入LDHs层间，在层板金属离子的催化作用下，与层间EG发生催化酯化反应，构建LDHs层间微型催化酯化反应器，从而增加反应场所，克服EG进入层间的扩散限制，增加反应物之间的碰撞几率，提高催化效率。通过研究EG插层LDHs的制备和结构性质调控方法、层间催化酯化反应行为和层内限域空间结构性质与催化性能的关联规律，深入认识LDHs层内限域空间催化酯化反应的科学本质，掌握层间催化反应器的构效关系和操控方法。

本研究利用层状双金属氢氧化物（LDHs）灵活的结构性质可调变性，将乙二醇（EG）插入LDHs层间，将具有催化活性的金属构筑在LDHs层板上，从而构建层间微型催化反应器，促进原油催化酯化脱酸。研究了EG插层LDHs、EG插层层状氢氧化物盐（LHSs）和12-磷钨酸（HPW）插层LDHs的合成和性质调控方法、层间催化酯化特征等，获得如下结果。.（1）采用微波辅助的离子交换法在<30 min内可快速合成高结晶度的EG插层NiAl和ZnAl LDHs；通过合成条件（微波温度、干燥温度等）可调变LDHs的层间距及EG在层间的排列方式。.（2）EG插层LDHs层间距扩大，环烷酸分子扩散到层间，与亲核性增强的EG阴离子在层板金属离子的酸催化作用下发生酯化反应，生成的酯进入溶液；反应后，空气中的CO2（原油体系）或部分环烷酸阴离子（模型油体系）进入层间作为补偿阴离子。EG扩散阻力消除，层内限域空间增加了反应物之间的碰撞频率，EG插层LDHs的脱酸率和EG转化率均比体相催化反应高5倍以上。.（3）层板M2+/Al的提高增加了催化中心数量，但造成层板过剩正电荷减少，层间EG数量下降，Ni2+的活性高于Zn2+；高的层间距对催化活性有利；环烷酸分子的空间位阻和分子尺寸影响催化活性。.（4）采用微波辅助的离子交换法在<30 min快速合成高结晶度的EG插层NiZn LHSs，水的引入可调变LHSs层间距；与LDHs相比，其催化中心含量更高，层间EG数量更大，催化活性更高。.（5）将HPW催化中心引入LDHs层间，反应物分子进入层间发生酯化反应。层间距1.05 nm的物相是HPW与层板嫁接形成的稳定结构，并非杂多酸盐杂质。催化活性主要由总酸量决定，通过离子交换条件可调变LDHs层间距，高的层间距有利于催化反应。.本项目构建了催化中心位于层板，反应物位于层间的新型LDHs和LHSs层间微型催化反应器用于原油催化酯化脱酸；揭示了层间催化酯化反应的特征、历程和机理，并通过LDHs结构性质的调变获得了层间反应的影响因素；发现了HPW插层LDHs新的存在形式。