分置式膜反应器中TS-1催化苯酚羟基化的稳定性

Stability of continuous phenol hydroxylation over ultrafine TS-1 in side-stream membrane reactor

研究了分置式膜反应器中TS-1催化苯酚羟基化反应的稳定性。膜反应器系统可连续运行20 h以上,苯酚转化率、苯二酚选择性分别保持在11%,95%左右,膜过滤阻力逐渐增加。采用系列技术对使用前后的TS-1催化剂及陶瓷膜进行了表征。场发射扫描电子显微镜显示使用后的TS-1催化剂团聚加重,紫外可见分光光谱、红外光谱、N2吸附-脱附、热质量损失分析结果表明使用后TS-1催化剂的表面及孔道内存在有机物;X射线衍射结果表明:使用后TS-1催化剂的骨架钛有流失,二者共同造成TS-1催化剂失活,使反应初期苯酚转化率下降。将使用后的TS-1催化剂在600℃下锻烧6 h进行再生,在苯酚羟基化反应中考察其催化性能,并与新鲜及使用后TS-1催化剂的催化性能进行比较。高温煅烧再生后TS-1催化剂的活性略有提高,但仍低于新鲜催化剂。场发射扫描电子显微镜分析结果显示,使用后陶瓷膜表面吸附一层由TS-1催化剂与有机物组成的滤饼层,是导致膜过滤阻力上升的主要原因。酸碱清洗可恢复陶瓷膜通量,反应过程中陶瓷膜保持良好的结构稳定性。

The stability of continuous phenol hydroxylation over ultrafine TS-1 in a side-stream membrane reactor was investigated. The membrane reactor system could be continuously operated over 20 h. The phenol conversion and dihydroxybenzene selectivity remained stable at about 11% and 95%, respectively. The filtration resistance increased through the operation process. The fresh and used TS-1 catalysts and ceramic membranes were characterized by different methods. The results of field emission scanning electron microscopy （FESEM） show more aggregation of used TS-1 catalysts than that of fresh ones. It demonstrates that some organic matters exist on the surface and in the channels of used TS-1 catalysts by the results of ultraviolet-visible spectroscopy （UV-vis）, Fourier transform infrared spectroscopy （FF-IR）, N2 adsorption-desorption and thermogravimetry （TG）. The results of X-ray diffraction （XRD） indicate that the content of titanium in the framework of used TS-1 catalysts is partly lost. Both of them together cause the deactivation