Stable Vapor-phase Catalytic Conversion of Pinacolone into 2,3-Dimethyl-1,3-butadiene

Abstract

In the vapor-phase synthesis of 2,3-dimethyl-1,3-butadiene from pinacolone over modified alumina catalysts, it was found that alumina modified with transition metals such as Co stabilized the conversion of pinacolone and produced 2,3-dimethyl-1,3-butadiene selectively under hydrogen flow conditions, whereas the catalytic activity of pure alumina was seriously deteriorated irrespective of its high initial activity.

Cyclodehydration of diethylene glycol over Ag-modified Al2O3 catalyst

“…only in H 2 flow [20][21][22]. In this study, the reaction performed in H 2 flow gives the highest DEG conversion, the most stable selectivity to DOX and the smallest amount of accumulated carbon.…”

“…3 shows the difference in TG profiles between fresh and used catalysts. The used samples were prepared by being recovered after the reaction at 250 • C for 5 h. In contrast to the fresh catalyst with a gradual weight decrease, all the used catalysts had a steep decrease in weight at temperatures higher than 200 • C. The difference in the weight loss between fresh and used catalysts must attribute to the carbon deposition [20][21][22]. The carbon content, which was calculated by the difference in the TG curves between fresh and used catalysts, was 16.5, 14.6, 9.8 Thus, it is assumed that carbon is relatively difficult to be accumulated on Al 2 O 3 because of the weak acidic property of Al 2 O 3 .…”

“…We have reported several papers dealing with the catalyst deactivation [20][21][22]. It is found that the modification of acid catalysts by loading some metal contents is effective for inhibiting the catalyst deactivation: Cu-modified Al 2 O 3 exhibits stable catalytic activity with high selectivity to DHP in THFA dehydration [20]; Comodified Al 2 O 3 stabilizes the conversion of pinacolone to produce 2,3-dimethyl-1,3-butadiene [21]; Ag-modified SiO 2 Al 2 O 3 gives stable and increased selectivity to propanal in 1,2-propanediol dehydration [22].…”

“…Since H 2 carrier gas is indispensable for inhibiting the catalyst deactivation in our precious research [20][21][22], the effect of the carrier gas was studied at 250 • C ( Table 6). The reactions were performed in N 2 , H 2 + N 2 , H 2 + CO 2 , H 2 + NH 3 and H 2 flow over Al 2 O 3 -Ag-1 at a W/F of 26.1 g h mol −1 and a flow rate of 20 cm 3 min −1 individually.…”

“…In our group, an effective operation on the stabilization of catalytic activity of solid acids has been reported [20][21][22]. For example, the vapor-phase dehydration of 1,2-propanediol to propanal can be catalyzed by acidic SiO 2 Al 2 O 3 , whereas both the conversion of 1,2-propanediol and the selectivity to propanal over SiO catalyst exhibits stable catalytic activity with high selectivity to propanal under hydrogen flow conditions.…”