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Figure 1 shows a 533K calcined AMT / SiO2(silicon dioxide) catalyst after different reaction times and TG-DTA spectrum Firing after regeneration can be seen, all samples were strong exothermic peak appears in the range of 550 ~ 900K, and with the reaction time, the peak area and the catalyst weight loss was significantly increased. according to the preliminary work of catechol and ethanol single etherification findings coke behavior in multicomponent phosphate catalyst surface can be considered low exothermic peak (about 610K) mainly corresponds to adsorbed on the surface of the catalyst reactants and products, and the exothermic peak temperature (650K or more) is mainly caused by the coke is generally believed that the product of catechol and o-hydroxyphenyl DME can occur further oxygen and carbon alkylation alkylation reaction of carbon-containing polymer and ultimately the formation of coke, with prolonged reaction time and temperature, the carbon chain length of the polymer will gradually increase, which requires higher firing temperatures to remove carbon. Therefore, we believe that prolonging the reaction time will significantly increase the amount of coke on the catalyst surface, which is the main reason for the catalyst deactivation.

The catalyst 615h after 673K after firing, there is still a small spectrum of the DTA exothermic peak temperature thereof, but also a small amount of weight loss on the TG spectrum, indicating 673K firing can only remove the majority of coke on the catalyst surface. It was found that calcination of AMT / SiO2(silicon dioxide) catalyst for catalytic activity and stability is relatively low, so no need to use higher temperatures to regenerate the catalyst and roasting after 673K regenerated catalyst DTA exothermic peak spectral response after 50h on through area was larger, and the peak exothermic peak position moves to higher temperature, to achieve the above 873K, indicating the nature of the active sites on the catalyst surface after regeneration treatment 673K (e.g., pH) has been changed, under the reaction conditions more susceptible to coke and eventually deactivation. this could also be the stability of AMT / SiO2 catalyst is poor mainly because of the high temperature calcination prepared.

Conclusion:

Calcined at different temperatures AMT / SiO2(silicon dioxide) catalyst due to the different degrees of decomposition AMT, resulting in a different catalyst surface acid-base properties of the center, resulting in catalyst performance vary. 

Catalyst activity and stability at low firing temperature calcination prepared much better than prepared catalyst weak acid weak base centers on the catalyst surface is catechol and methanol monoetherification reaction o-hydroxy anisole main activity centers. surface of the catalyst during the reaction of coke is the main reason for its reduced activity of catalyst deactivation after after calcination temperature higher regeneration treatment can restore the reactive moieties, but still significantly lower than the fresh catalyst, catalyst stability is poor and after the regeneration treatment. this may be due to the nature of the active centers of the catalyst surface of high temperature regeneration (including acid-base properties) has changed, so that the catalyst is regenerated more easily inactivated.


 

 

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