Journal of Catalysis p. 199 - 211 (1994)
Update date:2022-08-11
Topics:
Broennimann, C.
Bodnar, Z.
Hug, P.
Mallat, T.
Baiker, A.
The selective oxidation of the C1 hydroxyl group of L-sorbose to a carboxylic group without protection of the four other hydroxyl functions was investigated.The reactions were performed in slightly alkaline aqueous solutions with molecular oxygen over various alumina- and carbon-supported Pt and Pd catalysts.Optimum reaction conditions were 50 deg C, pH 7.3, and a catalyst:reactant ratio of 1:4 (wt/wt).The lower the pH and the temperature, the higher the selectivity toward 2-keto-L-gulonic acid.Catalyst deactivation was also found to increase with lower pH and temperature.A 5 wtpercent Pt/alumina catalyst showed the best catalytic performance (67percent selectivity at 58percent conversion).Promotion with Bi or Pb had a detrimental effect on selectivity for 2-keto-L-gulonic acid.Electrochemical measurements indicated that the reaction occurs in a rather narrow potential range, which corresponds to a moderate oxygen coverage of Pt or Pd.Four types of catalyst deactivation processes were identified, based on XPS and ICP-AES analysis and on the in situ determination of the oxidation state by monitoring the catalyst potential during reaction.A significant chemical poisoning of the active noble metal sites occurred during the initial, destructive adsorption of L-sorbose and during the oxidation reaction.The successive contamination of active sites resulted in overoxidation (too high oxygen coverage of Pt or Pd).The partially oxidized promoters and noble metals were corroded and dissolved in the presence of 2-keto-L-gulonic acid, resulting in an irreversible deactivation.
View MoreContact:+86-512-56795332
Address:No227 Shuanglong Rd, Fenghuang, Zhangjiagang
Guilin Zhenda Bio-Tech Co., Ltd.
Contact:86-773-3568977
Address:-Yangtang shangshui industry park, Lingui county,
Wuhan Fortuna Chemical Co.,Ltd
website:http://www.fortunachem.com
Contact:86-27-59207850
Address:Add: Room 2015, No.2 Building, Kaixin Mansion No.107 Jinqiao Avenue, Wuhan, China
Hangzhou Share Chemical Co., Ltd
Contact:+86-57187093700
Address:Hang Xing Road
hangzhou verychem science and technology co.ltd
website:http://www.verypharm.com
Contact:+86-571-88162785; 88162786
Address:F1502, 753 Shenhua road, Hangzhou, China
Doi:10.1021/jo00828a070
(1970)Doi:10.1021/ja01193a004
(1947)Doi:10.1016/S0022-1139(99)00012-3
(1999)Doi:10.1021/jp026190c
(2002)Doi:10.1135/cccc2010096
(2010)Doi:10.1021/acs.jmedchem.5b01865
(2016)