A new sulfonic-phosphotungstic dual-acid hybrid catalyst based on silica coated magnetite nanoparticles (SCMNPs) containing two types of Bronsted acidic sites i.e. sulfonic acid (–SO₃H) and phosphotungstic acid (HPW) groups, was prepared with chemical and electrostatic interactions of these acidic functional moieties with piperazine-grafted propylsilyl spacer groups. Physicochemical techniques including FT-IR spectroscopy, elemental analysis and inductively coupled plasma-optical emission spectroscopy (ICP-OES), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the prepared solid acid catalyst. Acetalization reaction between benzaldehyde and ethylene glycol was done to investigate the catalytic activity of prepared catalyst and 97% conversion toward acetal production was reached in short reaction time. The lower conversion was also achieved for the same catalyst without any HPW species, demonstrated the positive role of the second acidic sites on progression of this reaction. In addition, this easily separable solid acid catalyst reused for four runs with no observable loss in benzaldehyde conversion.

一种新的磺酸-磷钨双酸杂化催化剂，其基于二氧化硅涂层的磁铁矿纳米颗粒（SCMNPs），包含两种类型的布朗斯台德酸性位点，即磺酸（–SO ₃H）和磷钨酸（HPW）基团是通过这些酸性官能团与哌嗪接枝的丙基甲硅烷基间隔基的化学和静电相互作用制备的。物理化学技术包括FT-IR光谱，元素分析和电感耦合等离子体发射光谱（ICP-OES），振动样品磁强（VSM），X射线衍射（XRD），能量色散X射线（EDX）分析，扫描电子显微镜（SEM）和透射电子显微镜（TEM）用于表征所制备的固体酸催化剂。进行了苯甲醛与乙二醇的缩聚反应，研究了所制得的催化剂的催化活性，并在较短的反应时间内达到了97％的缩醛转化率。对于没有任何HPW物质的相同催化剂，也实现了较低的转化率，证明了第二个酸性位点对该反应进程的积极作用。此外，这种易于分离的固体酸催化剂可重复使用四次，苯甲醛转化率没有明显损失。