Abstract
The chromium oxide catalysts supported on silicalite-1 zeolite (Cr/S-1) with a Cr content between 0.5% and 7% were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N2 adsorption, TEM-EDX, UV-vis, DRIFTS, 29Si MAS NMR, XPS, H2-TPR, and NH3-TPD. The optimum 3%Cr/S-1 catalyst with 3%Cr is more active and stable than SBA-15-supported one with the same Cr content, which is a consequence of a higher content of Cr6+ in the fresh 3%Cr/S-1 catalyst and a higher content of Cr6+ retained on the former catalyst during the reaction. The 3%Cr/S-1 catalyst affords an isobutane conversion of 36.5% with 71.2% isobutene selectivity. The catalytic activity is well correlated with the content of Cr6+ in the fresh catalysts. Carbon dioxide displays a promoting effect on the dehydrogenation reaction.
Highlights
Isobutene is an important industrial chemical employed to produce butyl rubber, gasoline oxygenates, and antioxidants [1,2]
A comparison of 3%catalysts supported on silicalite-1 zeolite (Cr/S-1) and 3%catalyst supported on SBA-15 (Cr/SBA) catalysts indicates that the initial isobutane conversion is higher on 3%Cr/S-1 than 3%Cr/SBA (Figure 9, 36.5% vs. 33.5%), which is caused by the fact that the former catalyst possesses a higher content of Cr6+ than the latter one (1.19% vs. 1.05%)
We have explored the silicalite-1-supported chromium oxide catalysts for isobutane dehydrogenation assisted by CO2
Summary
Isobutene is an important industrial chemical employed to produce butyl rubber, gasoline oxygenates (e.g., ethyl tert-butyl ether), and antioxidants (e.g., butylated hydroxyanisole) [1,2]. Due to the shortage of petroleum and environmental consideration, the dehydrogenation of small alkanes to alkenes assisted by CO2 has attracted more attention recently [3,4,5,6,7,8,9,10,11,12,13]. Compared to the oxidative dehydrogenation of light alkanes with O2 , the beneficial employment of CO2 as a soft oxidant comprises improving the product selectivity as well as decreasing CO2 emissions [14,15]. This route opens up a new way to utilize greenhouse CO2. The catalysts which were attempted for isobutane dehydrogenation assisted by CO2 includes
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