In this study, the performance of chromium oxide catalysts supported on Al 2 O 3 was evaluated. The effects of the percent loading of Cr on Al 2 O 3 and the pretreatment conditions on the activity and the selectivity of the catalysts in the oxidative dehydrogenation of i-C 4 H 10 to i-C 4 H 8 were also tested. Different types of Al 2 O 3 were tested as supports for chromium oxide, and the activity and selectivity of these samples were correlated with the alumina properties. The obtained results show that the optimum loading of Cr on Al 2 O 3 lies between 5 and 15%. Also, it has been observed that the calcination temperature affects the conversion at lower reaction temperatures, whereas its influence on product selectivity is limited by O 2 availability in the reaction mixture. The catalyst samples were characterized by FTIR and XPS measurements. The XPS analysis confirmed the presence of Cr 6+ and Cr 3+ on the surface of the catalyst. Cr 3+ was dominant in the spent catalyst.

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A new simple and reliable spectrophotometric method is described to determine glyoxylic acid in its synthesis reaction mixture containing oxalic acid, glycolic acid, acetic acid, glyoxal, and ethylene glycol by means of a modified Hopkins–Cole reaction between glyoxylic acid and tryptophan in presence of ferric chloride and concentrated sulphuric acid. The linear range of glyoxylic acid concentration is 0–0.028 M. The limits of detection (LOD) and quantitation (LOQ) are 0.0019 M and 0.00577 M, respectively. The LOD, LOQ, standard deviation, relative standard deviation, and recovery ratio of the proposed method are comparable with a selected HPLC reference method. Both methods displayed same precision and credibility. Reaction stoichiometry between tryptophan and glyoxylic acid is assumed to be 2 : 3. Reaction mechanism has been postulated based on identified molar ratios of reactants. Glyoxal gave a negative test with tryptophan although it is a dialdehyde.