CAJ | 학술논문

考察了稀释蒸汽中Na+及积炭对甲醇制丙烯(MTP)催化剂物理化学性质和催化性能影响,及离子交换后催化性能.采用 X 射线衍射(XRD)、扫描电镜(SEM)、X 射线荧光(XRF)光谱、N2吸附-脱附、程序升温氨脱附(NH3-TPD)和热重(TG)分析等方法对失活和再生催化剂进行了表征,并在101325 Pa、470°C 和甲醇空速(WHSV)为1.0-3.0 h-1的反应条件下,采用连续流动固定床微型反应器考察其催化甲醇制丙烯性能.结果表明: MTP反应970 h后的催化剂晶体结构和形貌没有受到明显破坏,但稀释蒸汽中Na+极易扩散至催化剂表面,部分取代H质子的位置,从而使催化剂酸性逐渐下降而中毒失活;另外, MTP催化剂表面的积炭导致分子筛微孔堵塞是造成其失活的主要原因,可通过烧炭再生过程消除,而水蒸汽脱铝对催化剂性能的影响缓慢但更严重.用再生和离子交换处理后, Na+中毒催化剂MTP反应性能基本完全恢复.在470 h反应过程中,甲醇转化率保持在99%以上,丙烯选择性大于46%,且随着反应时间的延长,丙烯选择性逐渐升高、乙烯选择性逐渐下降.
고찰료희석증기중Na+급적탄대갑순제병희(MTP)최화제물이화학성질화최화성능영향,급리자교환후최화성능.채용 X 사선연사(XRD)、소묘전경(SEM)、X 사선형광(XRF)광보、N2흡부-탈부、정서승온안탈부(NH3-TPD)화열중(TG)분석등방법대실활화재생최화제진행료표정,병재101325 Pa、470°C 화갑순공속(WHSV)위1.0-3.0 h-1적반응조건하,채용련속류동고정상미형반응기고찰기최화갑순제병희성능.결과표명: MTP반응970 h후적최화제정체결구화형모몰유수도명현파배,단희석증기중Na+겁역확산지최화제표면,부분취대H질자적위치,종이사최화제산성축점하강이중독실활;령외, MTP최화제표면적적탄도치분자사미공도새시조성기실활적주요원인,가통과소탄재생과정소제,이수증기탈려대최화제성능적영향완만단경엄중.용재생화리자교환처리후, Na+중독최화제MTP반응성능기본완전회복.재470 h반응과정중,갑순전화솔보지재99%이상,병희선택성대우46%,차수착반응시간적연장,병희선택성축점승고、을희선택성축점하강.
The effects of Na+ in dilution steam and coke deposition on the physicochemical properties and catalytic performance of ZSM-5 catalysts for the methanol-to-propylene (MTP) reaction were investigated. The deactivated and regenerated catalysts were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF) spectrum, nitrogen adsorption/desorption, temperature-programmed desorption of ammonia (NH3-TPD), and thermogravimetry (TG). Their catalytic performance for MTP reaction was tested in a continuous flow fixed-bed micro-reactor at 470 °C, 101325 Pa, and with methanol weight hourly space velocity (WHSV) in the range of 1.0-3.0 h-1. The results indicated that the catalyst crystal structure and morphology was not significantly altered after 970 h on stream. In the MTP reaction, Na + in the dilution steam can easily enter the pore channels of the catalyst, and partial y replace H protons, thereby gradual y decreasing the amount of acidity and acid strength of the catalyst, which eventual y causes deactivation. In addition, coke deposits on the catalyst surface blocking its micropores are the main reason for deactivation of the MTP catalyst. Coke deposits are mostly eliminated through the burning charcoal regeneration process. The effect of framework dealumination from the catalyst by steam in the MTP process is slow but more serious. Through regeneration and ion exchange process, the catalytic activity of the deactivated catalyst can be ful y restored. The conversion of methanol is consistently above 99%, and propylene selectivity is greater than 46% even after 470 h on stream. With increasing reaction time, the propylene selectivity gradual y increases, while ethylene selectivity gradual y decreases.