【作者】 张哲；

【导师】 李殿卿；

【作者基本信息】 北京化工大学 ， 化学工程与技术， 2025， 博士

【摘要】 过氧化氢是一种重要的绿色无机化学品,在化工合成、造纸、纺织和污水处理等领域应用广泛。目前工业上采用蒽醌法大规模制备过氧化氢,该方法主要包括烷基蒽醌的催化加氢、加氢产物的氧化、过氧化氢的萃取和工作液的后处理等步骤,其中的催化加氢过程是整个制备工艺的核心步骤,决定了装置产能、产品品质和制造成本等。加氢过程可采用固定床或流化床两种工艺。近年来,因装置规模大以及技术经济和安全性指标占优等特点,国内采用流化床工艺的装置不断增加,但由于该工艺对所用微球形催化剂的活性、杂质含量、耐磨性和稳定性等指标要求较高,因此催化剂目前仍依赖进口。本文采用双铝法制备拟薄水铝石前驱体,经喷雾成型制备载体,再负载活性组分制成微球形催化剂,主要研究内容如下:（1）双铝法制备拟薄水铝石目前多采用釜式反应器,原料浓度在反应器内的分布并不均匀,尤其是投料口附近的浓度显著高于体相。此外,在不同时间成核的拟薄水铝石颗粒在釜内停留时间不同,这些因素导致制备的产品粒度大、粒径分布宽,性能难以控制。因此,本文以北京化工大学化工资源有效利用全国重点实验室开发的制备纳米材料的旋转液膜反应器为主要设备,采用成核-晶化隔离法制备拟薄水铝石。研究了原料浓度、原料流量和反应器转速等因素对拟薄水铝石的粒径和孔结构的影响,并与釜式反应器制备的样品进行了对比。研究结果表明,成核-晶化隔离法可使原料快速、均匀分散,实现了成核过程中过饱和度在空间上的均匀分布,因此制备的拟薄水铝石平均粒径更小,粒径分布更窄,孔径分布也更集中。另外,双铝法合成拟薄水铝石时不可避免地引入SO₄^2-和Na⁺等杂质,去除这些杂质是非常重要的。首先制备了SO₄^2-含量不同的拟薄水铝石样品,并使用这些样品制成催化剂,通过结构表征和催化性能评价,研究了制备过程中SO₄^2-的变化规律及其对催化性能的影响,发现拟薄水铝石前驱体中SO₄^2-含量较高时会堵塞孔道、增加载体表面酸量,从而影响负载过程Pd的分散,对催化剂性能造成不利影响。为了得到纯度较高的拟薄水铝石,研究了滤饼洗涤条件对不同杂质的脱除效果,形成了拟薄水铝石纯化的新工艺,制备的拟薄水铝石的杂质含量与市售催化剂相当。（2）喷雾成型法是大规模制备微米级颗粒材料较为经济的方法,论文设计了新型的弧面格栅形雾化器结构,使浆液在雾化器内分布均匀,抑制卫星液滴生成。研究了胶溶过程中拟薄水铝石固含量和酸用量等条件和成型过程中雾化器转速等对制备的微球形氧化铝的影响规律。研究结果表明,适当提高胶溶时拟薄水铝石的固含量可明显改善微球颗粒的耐磨性;降低雾化器转速可增加微球形氧化铝的尺寸,平均粒径最大可达100μm,实现了粒径的可控调节。为了更好地评价微球形氧化铝的耐磨性,建立水分散-预筛分新方法,解决了现有测试方法中存在的颗粒夹带和细颗粒干扰测试结果的问题。随后通过正交试验确定了测试条件,并对该方法进行了重复性评价。（3）以Na₂PdCl₄为活性金属前驱体,采用等体积浸渍法制备微球形催化剂,评价催化性能发现,催化活性随使用次数增加而明显下降,催化剂结构表征也表明,使用后的催化剂中Pd纳米颗粒尺寸明显增大,是失活的主要原因。为了抑制Pd的团聚,延长催化剂寿命,建立络合浸渍新方法,基于络合剂与Pd的相互作用和物理阻隔效应增大了Pd颗粒间距,并结合液相还原方法调节了Pd颗粒尺寸,改善了催化剂在使用过程中的稳定性。借助高分辨扫描电镜等测试手段,研究还原速率和焙烧温度等关键条件对催化剂结构和性能的影响规律发现,发现适当降低还原速率或提高焙烧温度有助于改善催化剂的稳定性,但同时降低了催化活性;选择适中的还原速率和焙烧温度有助于制备活性较高、稳定性较好的微球形催化剂。在流化床模型试验装置中对催化剂进行长周期运行考核并与市售催化剂进行了对比,结果表明本文制备的微球形催化剂在400 h长周期连续运行中性能稳定,使用后粒度变化不明显,耐磨性优异,综合性能优于市售进口催化剂,具有工业应用价值和前景。更多还原

【Abstract】 Hydrogen peroxide,an important green inorganic chemical,is widely used in fields such as chemical synthesis,papermaking,textile processing and wastewater treatment.Currently,the anthraquinone method is adopted industrially for large-scale production of hydrogen peroxide.This method mainly involves catalytic hydrogenation of alkyl anthraquinone,oxidation of the hydrogenation products to generate hydrogen peroxide,extraction and post-treatment.The catalytic hydrogenation process is the core step of the entire production process,determining the production capacity,product quality and manufacturing cost of the device.The hydrogenation process can be carried out using either fixed-bed or fluidized-bed process.In recent years,due to the large scale of the devices,advantages of technical economy and safety indicators,the number of domestic devices using fluidized-bed processes has been increasing.However,because this process has high requirements for the activity and selectivity,impurity content,attrition resistance and stability of the spherical catalysts,the catalysts are still dependent on imports.In the present thesis,the double-aluminum method was used to prepare pseudo-boehmite（PB）,the precursor of alumina;spray drying and impregnation were utilized to prepare microspherical alumina and microspherical catalyst,respectively.The main research contents are as follows:（1）The preparation of PB by double-aluminum method mostly employs batch reactors.The concentration of raw materials is unevenly distributed within the reactor,especially near the feed inlet where the concentration is significantly higher than the bulk phase.Moreover,the particles of PB formed at different times in the reactor have different residence time.These factors result in large particle size,wide distribution and difficulty in performance control.To solve the problem,the rotating liquid film reactor,which is developed by the State Key Laboratory of Chemical Resource Engineering of Beijing University of Chemical Technology,is used as the main equipment,and the nucleation-crystallization separation method was adopted to prepare PB in this study.The effects of raw material concentration,raw material flow rate and rotating speed on the particle size and pore structure of PB were investigated,and comparisons were made with samples prepared by the batch reactor.The results show that the nucleation-crystallization separation method enables fast and well distribution of raw material solutions,and therefore uniform distribution of supersaturation within the reactor,making the average particle size of PB prepared by the method smaller,particle size distribution narrower,and the pore size distribution more concentrated.Additionally,during the synthesis of PB using the double-aluminum method,impurities such as SO₄^2-and Na⁺are inevitably introduced.Removing these impurities is very important.First,PB samples with different SO₄^2-contents were prepared,and these samples were used to prepare catalysts.Through structural characterization and catalytic performance evaluation,the variation patterns of SO₄^2-during the preparation process and its impact on catalytic performance were studied.It was found that when the content of SO₄^2-in PB was high,pores would be partially blocked,and the amount of acid would also increase,which negatively affected the dispersion of Pd during the impregnation process,and thereby reduced the performance of the catalyst.To obtain PB with higher purity,the effect of filter cake washing conditions on removal efficiency of different impurities was studied,and a new purification process was formed.The impurity content in PB was comparable to that in the commercial catalysts.（2）The spray drying is a relatively economical way to prepare micro-sized particle materials industrially.In the thesis,a new arc-shaped grid-type atomizer structure was designed,which could make slurry uniformly distributed within the atomizer and inhibit the production of satellite droplets.The influences of the content of PB,the amount of acid during the gelation process,and the atomizer rotation speed during the drying process on the prepared micro-spherical alumina were studied.The results showed that appropriately increasing the solid content of PB could significantly improve the attrition resistance of the micro-spherical particles;the use of the arc-shaped grid-type atomizer made it possible to prepare larger-sized micro-spherical alumina,and reducing the atomizer rotation speed could increase the size of the micro-spherical alumina,with the average particle size reaching up to 100μm,making it possible to adjust the particle size in a controllable way.To better evaluate the attrition resistance of micro-spherical alumina,a new test method,consisting of water dispersion and pre-sieving,was established,and the problems of particle carry-over and interference with fine particles were solved.The orthogonal experiment was designed to determine testing conditions of the new method,and repeatability of the method was then evaluated.（3）Microspherical catalysts were prepared by the incipient wetness impregnation,in which Na₂PdCl₄was used as the precursor of active component.The catalytic performance was evaluated and it was found that the catalytic activity decreased with the increase in the number of uses.The structural characterization of the catalyst also indicated that the size of Pd nanoparticles in the spent catalysts increased,which was the main cause of deactivation.To inhibit the agglomeration of Pd NPs and extend the catalyst’s lifespan,a new complex impregnation method was established.Space among Pd NPs was increased due to the interaction between Pd and complex agent and its spatial separation effect;The size of Pd NPs could be adjusted by liquid reduction.As a result,catalyst stability was significantly improved.Through testing methods such as high-resolution scanning electron microscopy,the influences of key conditions such as reduction rate and calcination temperature on the structure and performance of the catalyst were studied.It was found that fast reduction or high calcination temperature could help improve the stability of the catalyst,but at the same time reduce the catalytic activity.Choosing an appropriate reduction rate and calcination temperature is conducive to preparing microsphere catalysts with higher activity and better stability.In the fluidized-bed model experiment equipment,the catalyst was subjected to long-term operation assessment and compared with commercial catalysts.The results showed that the microspherical catalyst prepared in this study had stable catalytic activity and excellent attrition resistance（with no obvious change in particle size after use）during the long-term continuous operation,demonstrating superior comprehensive performance compared to commercial imported catalysts,and good industrial application value and prospects.更多还原