Elimination of Product Inhibition by Ethanol Competitive Adsorption on Carbon Catalyst Support in a Maleic Acid Electrochemical Hydrogen Pump Hydrogenation Reactor

摘要

src="http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ascecg/2017/ascecg.2017.5.issue-10/acssuschemeng.7b01520/20170926/images/medium/sc-2017-01520r_0011.gif">In the present work, a special competitive adsorbent, ethanol, is proposed for in situ release product inhibition of a hydrophobic product system from a hydrophobic carbon catalyst support. Product inhibition is serious in electrochemical hydrogen pump hydrogenation reactors (EHPRs) due to slow molecular diffusion of the products through the microporous flow channels (1–10 μm). The hydrogenation rate of maleic acid decreases rapidly with reaction time, only 37.4% retention after 10 h reaction. By introducing ethanol in the aqueous solution, both reaction rate and conversion after 10 h reach 1.46 folds of those without ethanol. Evidenced by competitive adsorption, the adsorption capacity of the product amber acid is decreased by 98% on carbon particles compared with that without ethanol. Ethanol takes most of the place of amber acid due to much better affinity with carbon support, which releases more amber acid molecules into the bulk solution and relieves product inhibition. Kinetics parameters are fitted with modified Langmuir–Hinshelwood kinetics by considering the influence of ethanol competitive adsorption on maleic acid hydrogenation performance.