Study on Stability of Ion-exchange Resin Catalysts:Ⅱ. Desulfonation during Isobutylene Dimerization

The performance of ion-exchange resin catalysts during isobutene (IB) dimerization was investigated under different IB contents,temperatures and liquid-volume hourly space velocity (LHSV) using a plug flow reactor in the absence of any selectivity enhancing component.High IB content and temperature resulted in a high conversion and C12 selectivity bu low C8 selectivity.The influence of LHSV was related with the IB content:LHSV had great effect at high IB content,while the performance of ion-exchange resin changed little with LHSV if IB content was low.The effect of water on the stability of resins was also studied.Desulfonation was observed during the C4 dimerization reaction when water was added to the feed.Chlorinated resin was more stable than conventional polystyrene-based resins during the test.

Study on the Stability of Ion-exchange Resin Catalysts:Ⅰ. TGA as a Rapid Evaluating Method

The thermal stability of five commercial ion-exchange resin catalysts was studied by means of thermal gravimetric analysis （TGA） at elevated temperatures of up to 600℃ and isothermal temperatures in the range of 150℃ and 200 ℃. Resin samples with different initial water contents were also investigated. The study indicated that TGA, as a complementary evaluating method for the plug flow reactor system approach, could be used as a fast analyzing means for study on the thermal stability of ion-exchange resin catalysts. The stoichiometric calculation of the isothermally treated resin catalysts based on the FTIR analysis and acid capacity confirmed that the weight loss of the resins at 150℃ and 200℃ was caused by the desulfonation process and that desulfonation occurred mainly at the para-position of the benzene ring in the resins. H＋ ions and moisture played an important role in the desulfonation process.

沉默circRNA hsa_circ_0103809表达抑制胶质瘤细胞增殖和侵袭

目的:通过研究环状RNA(circRNA) hsacirc0103809对胶质瘤细胞增殖和侵袭的影响,来明确hsacirc0103809在胶质瘤进展中所起到的作用。方法:采用qRT-PCR检测hsacirc0103809在胶质瘤细胞系U251和正常脑胶质细胞系HEB中表达水平的差异。U251细胞经小干涉RNA(siRNA)介导下调hsacirc0103809的表达水平后,采用qRT-PCR检测沉默效率。将U251细胞分为两组,即siRNA-circ沉默实验组和siRNA-NC阴性对照组,实验组转染hsacirc0103809的siRNA,对照组转染siRNA对照序列,后续分别使用CCK-8实验、EdU实验和Transwell实验检测hsacirc0103809的表达下调对U251细胞增殖和侵袭的影响。结果:hsacirc0103809在胶质瘤U251细胞中的表达水平明显高于正常脑胶质HEB细胞(P<0.01)。在U251细胞中转染siRNA-hsacirc0103809后其表达水平明显降低(P<0.01)。CCK-8实验结果显示,沉默hsacirc0103809的表达后,U251细胞在24 h和48 h的光密度(OD)值和对照组无明显差异,但实验组在72 h的OD值明显低于对照组(P<0.01)。EdU实验结果显示,沉默hsacirc0103809的表达后,U251细胞的增殖能力较对照组明显降低(P<0.01)。Transwell实验结果显示,沉默hsacirc0103809的表达后,U251细胞的侵袭能力较对照组明显降低(P<0.001)。结论:hsacirc0103809在胶质瘤U251细胞中高表达,沉默hsacirc0103809表达可显著抑制胶质瘤细胞的增殖和侵袭。