Schneider Denise, Kircheis Ralf, Wassersleben Susan, Einicke Wolf-Dietrich, Gläser Roger, Enke Dirk
Institute of Chemical Technology, Universität Leipzig, Leipzig, Germany.
Front Chem. 2019 Aug 13;7:575. doi: 10.3389/fchem.2019.00575. eCollection 2019.
This work introduces a cost and time efficient procedure to specifically increase mesopore volume and specific surface area of biogenic silica (specific surface area: 147 m g and mesopore volume: 0.23 cm g) to make it suitable for applications in adsorption or as catalyst support. The target values were a specific surface area of ~500 m g and a mesopore volume of ~0.40-0.50 cm g as these values are industrially relevant and are reached by potential concurring products such as precipitated silica, silica gel, and fumed silica. The applied process of partial pseudomorphic transformation was carried out as a single reaction step in a microwave reactor instead of commonly used convective heating. In addition, the conventionally used surfactant cetyltrimethylammonium bromide (CTABr) was substituted by the low-cost surfactant (Arquad® 16-29, cetyltrimethylammonium chloride (CTACl) aqueous solution). The influence of microwave heating, type of surfactant as well as the concentration of NaOH and CTACl on the textural and structural properties of the modified biogenic silica was investigated using nitrogen adsorption as well as scanning and transmission electron microscopy. The results show that the textural parameters of the modified biogenic silica can be exactly controlled by the amount of NaOH in the reaction solution. By variation of the NaOH concentration, specific surface areas in the range of 215-1,001 m g and mesopore volumes of 0.25-0.56 cm g were achieved after reaction at 393 K for 10 min. The presented microwave route using the low-cost surfactant solution decreases the reaction time by 99% and as shown in an example for German prices, lowers the costs for the surfactant by 76-99%.
这项工作介绍了一种具有成本效益和时间效率的方法，可专门增加生物源二氧化硅的中孔体积和比表面积（比表面积：147 m²/g，中孔体积：0.23 cm³/g），使其适用于吸附应用或作为催化剂载体。目标值是比表面积约为500 m²/g，中孔体积约为0.40 - 0.50 cm³/g，因为这些值与工业相关，并且沉淀二氧化硅、硅胶和气相二氧化硅等潜在竞争产品能够达到这些值。所应用的部分拟晶转变过程在微波反应器中作为单一反应步骤进行，而不是常用的对流加热。此外，传统使用的表面活性剂十六烷基三甲基溴化铵（CTABr）被低成本表面活性剂（Arquad® 16 - 29，十六烷基三甲基氯化铵（CTACl）水溶液）替代。使用氮气吸附以及扫描和透射电子显微镜研究了微波加热、表面活性剂类型以及NaOH和CTACl浓度对改性生物源二氧化硅的织构和结构性质的影响。结果表明，改性生物源二氧化硅的织构参数可以通过反应溶液中NaOH的量精确控制。通过改变NaOH浓度，在393 K下反应10分钟后，比表面积达到215 - 1001 m²/g，中孔体积达到0.25 - 0.56 cm³/g。所提出的使用低成本表面活性剂溶液的微波路线将反应时间减少了99%，并且如以德国价格为例所示，表面活性剂成本降低了76 - 99%。
