镁法脱硫中双功能型催化/吸附剂的反应调控机理

Magnesia desulfurization is a promising candidate for reclaiming the sulfur resource from the flue gas. The concentration of desulfurization byproduct, magnesium sulfate, can be effectively and economically boosted by heterogeneous catalysis of magnesium sulfite oxidation. However, the heavy metals dissolved in the desulfurization slurry might incur secondary pollution. It can also be adhered and concentrated on the surface of catalyst, resulting in severe toxic effect on the catalysis of sulfite oxidation. In this project, a novel magnesia desulfurization was put forward by decoupling the absorption of SO2 and sulfite oxidation process. The bi-functional material for simultaneous catalysis for magnesium sulfite oxidation and adsorption for heavy metals is to be developed. This bi-functional catalyst/adsorbent featured a high catalysis activity and adsorption rate and capacity. The competition and interaction between the adsorption and catalysis sites will be investigated, so that the mechanism on toxic effect of the catalyst derived by the concentrated heavy metals is revealed. Based on the mass balance model, the environmental fate of the heavy metals in the magnesia desulfurization will be illuminated. The lifespan of bi-functional material is to be estimated. The kinetics of heavy metals desorpted from different catalysts, including carbon-based catalysts, molecular sieve catalysts, and metal-organic framework catalysts, is to be investigated in order to reveal the mechanism of desorption of heavy metals. Consequently, the regeneration method for the bi-functional material is developed. The results can serve as a basis to ensure the maintenance of magnesia desulfurization and improve the quality of reclaimed byproduct and reduce the heavy metals pollution.

镁法脱硫是一种潜力巨大的硫资源回收型烟气治理技术。通过多相催化氧化亚硫酸镁，可经济有效地提浓回收硫酸镁。然而，镁法脱硫液中的重金属易引发二次污染，且富集于催化剂表面产生毒性效应。本项目基于一种脱硫和氧化解耦的镁法脱硫新工艺，开发双功能型亚硫酸镁氧化催化剂/重金属吸附剂，使其兼具高催化氧化亚硫酸镁活性和高吸附重金属速率及吸附容量；研究重金属吸附位与催化剂活性位的竞争与交互影响，探明催化剂因多种重金属富集引起的中毒效应及反应过程机制；建立重金属的物料平衡模型，揭示亚硫酸镁催化氧化反应条件下各种重金属的环境归宿；评估双功能型催化/吸附剂的生命周期；研究重金属在不同种催化剂（碳基催化剂、分子筛类催化剂、MOF类催化剂）表面的脱附动力学，探明重金属的脱附过程机制，开发双功能型催化/吸附剂的再生技术。研究结果为确保镁法脱硫工艺稳定运行、提升副产物回收品质、解决重金属污染奠定了基础。

镁法脱硫是一种潜力巨大的硫资源回收型烟气治理技术。通过多相催化氧化亚硫酸镁，可经济有效地提浓回收硫酸镁。然而，镁法脱硫液中的重金属易引发二次污染，且富集于催化剂表面产生毒性效应。本项目基于一种脱硫和氧化解耦的镁法脱硫新工艺，开发了一系列双功能型亚硫酸镁氧化催化剂/重金属吸附剂，包括Co-TUD-1/S、Co−N−C NSs、Co-SBA-15-SH、NZV-Co2Fe1等，兼具高催化氧化亚硫酸镁活性和高吸附重金属速率及吸附容量，开发的功能型亚硫酸镁氧化催化剂/重金属吸附剂将亚硫酸镁催化氧化性能有效提升了5-10倍，汞、砷、硒等脱除效率均高达90%以上。本项目以脱硫浆液中高浓度亚硫酸盐和痕量汞、砷、硒等重金属为主要控制目标，利用多种现代表征方法对双功能催化/吸附剂进行了物化性质分析，阐明了双功能催化/吸附剂表面的催化活性位与吸附活性位物种组成及其空间位置差异，考察了重金属吸附位与催化剂活性位的竞争与交互影响，明晰了双功能催化/吸附剂与亚硫酸盐氧化反应及重金属脱除性能间的构效关系，探明了催化剂因多种重金属富集引起的中毒效应及反应过程机制；建立了各类重金属的物料平衡模型，揭示了亚硫酸镁催化氧化反应条件下各种重金属的环境归宿；利用DFT理论计算手段，从分子层面探明了双功能型催化/吸附剂表面的亚硫酸盐多相催化氧化反应路径和微观反应机制，以及各类重金属微观限域吸附同步控制机理。研究结果为镁法脱硫工艺的稳定运行、脱硫副产物的高品质资源回收、共存重金属污染控制等奠定了详实的理论基础，具有重要的理论意义和应用价值。