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    CO2加氢制甲醇工业催化剂结构及操作条件影响模拟研究

    Effects of industrial catalyst structure and operating conditions on CO2 hydrogenation to methanol: A simulation study

    • 摘要: 二氧化碳加氢合成甲醇是一种有效的减碳技术,其关键在于开发高性能甲醇合成工业催化剂。基于颗粒分辨计算流体力学,建立了CO2加氢合成甲醇体系从工业催化剂颗粒到固定床反应器的双尺度模型,并利用该模型研究工业催化剂颗粒结构与操作条件对甲醇合成反应的影响。首先,通过对比试验测得催化剂床层压降,验证了颗粒分辨计算流体力学模型的准确性,其中通过模拟计算得到的压降与试验值相差小于10%。接着,研究了催化剂颗粒的孔径、孔隙率以及粒径对甲醇合成反应的影响,发现当催化剂颗粒孔径为50 nm、孔隙率为0.4时,二氧化碳具有较高转化率的同时,还拥有较高的甲醇选择性,当粒径为8 mm时,在保持高二氧化碳转化率与甲醇选择性时,还能降低床层压降。最后,考察了流速、压力、温度与二氧化碳浓度对反应的影响,发现流速的提高不仅会快速降低二氧化碳转化率,还会增加床层压降;压力的增加使得反应器内的反应物浓度提高,这有利于二氧化碳转化率与甲醇选择性的提高;对于入口温度在515 K附近时,拥有较高的二氧化碳转化率与甲醇选择性,若低于515 K,则反应受到动力学限制不利于二氧化碳转化率提高,若高于515 K则甲醇合成反应受到热力学限制的影响,二氧化碳转化率略微下降;二氧化碳入口浓度的提高则会降低二氧化碳转化率与甲醇选择性。研究结果可以为甲醇合成反应中催化剂结构与操作条件的优化提供一定的理论指导。

       

      Abstract: CO2 hydrogenation to methanol is an effective carbon reduction technology, the key of which is developing high-performance industrial catalysts. Based on particle-resolved computational fluid dynamics, a dual-scale model for CO2 hydrogenation to methanol is established, spanning from industrial catalyst particle to fixed-bed reactor. Utilizing this model, the impact of industrial catalyst particle structure and operating conditions on the performance of methanol synthesis is investigated. First, the accuracy of the particle-resolved computational fluid dynamics model was verified by comparing the experimentally measured pressure drop across the catalyst bed. The simulated pressure drop differed from the experimental value by less than 10%. Next, the effects of catalyst particle pore size, porosity, and particle diameter on methanol synthesis were investigated. It was found that when the catalyst particle pore size was 50 nm and the porosity was 0.4, a high CO2 conversion rate was achieved along with high methanol selectivity. Additionally, when the particle diameter was 8 mm, the bed pressure drop was reduced while maintaining high CO2 conversion and methanol selectivity. Finally, the influences of flow velocity, pressure, temperature, and CO2 concentration on the reaction were examined. The results showed that increasing the flow velocity not only rapidly decreased CO2 conversion but also raised the bed pressure drop. Higher pressure increased the reactant concentration in the reactor, which improved both CO2 conversion and methanol selectivity. When the inlet temperature was around 515 K, both CO2 conversion and methanol selectivity were relatively high. Below 515 K, the reaction was kinetically limited, hindering CO2 conversion, while above 515 K, the methanol synthesis reaction was thermodynamically constrained, leading to a slight decline in CO2 conversion. Increasing the inlet CO2 concentration reduced both CO2 conversion and methanol selectivity. This work can provide a reference for the development of industrial catalysts and fixed-bed reactors used in CO2 hydrogenation to methanol.

       

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