Studied On Supported Cu-based Catalyst Prepared By Solid-state Ion-exchange And Its Catalytic Performance On Oxidative Carbonylation Of Methanol

The oxidative carbonylation of methanol has been drawing attention from researchers due to its simple process, low cost and environmental friendly. Supported single metal Cu and bimetal Cu-Pd chloride catalysts have been studied. It is well known that the deactiviation of these kinds of catalysts is mainly due to the loss of chloride. The Cu-zeolite catalyst prepared by solid-state ion-exchange in which Cl- was replaced by zeolite anion has more stable catalytic activity because of avoiding the loss of chloride.In this thesis, a series of Cu-base catalysts were prepared by solid-state ion-exchange method using H-zeolite as support .The catalytic activity were evaluated in continuous flow system witha fixed bed reactor at ambient pressure. The catalysts' supports, preparation condition and reaction condition were studied. Comparing with the results of evaluation and characterization of catalysts by XRD, XPS, SEM (EDS), TEM, TG-DTA and FTIR etc., following conclusions are obtained mainly.(1) Zeolite supports have remarkable influence on catalytic activity and selectivity. All catalysts supported on the four used kinds of zeolite prepared by solid-state ion-exchange have catalytic activity for synthesis of DMC by gas-phase oxidative carbonylation of methanol. The catalytic activity and selectivity increase with the decrease of SiO2/Al2O3 ratio. The active sequence is DASY(8.l) > DASY2.0 (8.1) > H(3(20-30) > HZSM-5 (55.6).(2) When used the same kind of zeolite (H(3) as support, the reaction activity of catalysts increase with the ratio of SiO2/Al2O3 decreasing. This further testifies that acidity decrease and the number of H+ of Br nsted acid increase and the number of CuI exchanged increase, so the catalytic activity is improved.(3) As for Cu'/HY catalyst, the best preparation temperature is 650 C, preparation time is 4 h, reaction temperature is 140 C.(4) With the improvement of ratio of CO/O2, methanol conversion and DMC space-time yield (STY) increase initially and then decrease, while DMC selectivity always increases, when flux of oxygen is fixed at 1 ml min-1. So, the best ratio of CO/O2 is 10/ 1; the best space speed is 720 h-1, when ratio of CO/O2is5/l.(5) The characterization of XRD demonstrates some conclusions: (1) CuCl is dispersed or adsorbed on the surface of the zeolite, meanwhile CuCl sublimates or vaporizes. (2) H+ in zeolite is exchanged with CuI in CuCl and bonded with Cl- and released in HCl form. So, we can see that the peak of CuCl of the catalyst became weak in XRD patters. (3) When preparation temperature is higher than 550 C, the catalysts have well catalytic activity because CuI was exchanged completely and dispersed well on surface of zeolite.(6) When copper chloride hydroxides (Cu2(OH)3Cl) wassynthesized in preparation, the catalytic activity and selectivity improved remarkably , and have good performance in life time.(7) The characterization of XRD, XPS, SEM (EDS), TEM, TG-DTA and FTIR shows that: CD The improved performance of catalysts was closely related with the existence of Cu2(OH)3Cl. (2) An excellent correlation was observed between the XRD peak intensity and catalytic activity. (3) Because of the crystal particle increased and particle clustered, the activity of catalysts decreased after reaction.