Evaluation of Base for Catalytic Hydrodechlorination of 2,4-Dichlorophenol in Cocurrent Downflow Contactor Reactor

The catalytic hydrodechlorination of 2,4-dichlorophenol (2,4-DCP) as a model pollutant has been conducted for evaluation of optimum base in laboratory scale cocurrent downflow contactor reactor (CDCR). 2,4-DCP was completely dechlorinated with an initial concentration of 3.0 and 6.0 mmol, at 303 K temperature and 0.1 MPa pressure. Hydrogen flow rate was remained at 0.3 L/min, and catalyst loading of 0.2 g/L of 5 % Palladium/carbon (Pd/C) catalyst was used. Different bases like triethylamine (N(CH2CH3)3)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\hbox {N(CH}_{2}\hbox {CH}_{3})_{3})$$\end{document}, sodium acetate trihydrate (CH3COONa·3H2O)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\hbox {CH}_{3}\hbox {COONa}\cdot 3\hbox {H}_{2}\hbox {O})$$\end{document}, sodium hydroxide (NaOH), ammonium hydroxide (NH4OH)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$(\hbox {NH}_{4}\hbox {OH})$$\end{document} and potassium hydroxide (KOH) were used for evaluation of optimum base. The same reaction was studied without base, and it was observed that more reaction time was required for hydrodechlorination of 2,4-DCP as compared to the presence of a base as production of HCl decreased the rate of reaction. During the hydrodechlorination reaction, 4-chlorophenol (4-CP) was also formed as an intermediate product along with 2-chlorophenol (2-CP). Significant amount of 4-CP produced when no alkali or weak alkalis like N(CH2CH3)3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {N(CH}_{2}\hbox {CH}_{3})_{3}$$\end{document}, CH3COONa·3H2O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CH}_{3}\hbox {COONa}\cdot 3\hbox {H}_{2}\hbox {O}$$\end{document} were used. No inhibitory effects of N(CH2CH3)3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {N(CH}_{2}\hbox {CH}_{3})_{3}$$\end{document} were observed during hydrodechlorination reaction of 2,4-DCP in CDCR. The addition of strong inorganic base helped with dechlorination of 2,4-DCP in predominantly fast reaction, and rate of neutralization using different bases was observed and found that the KOH had highest rate of reaction and CH3COONa·3H2O\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {CH}_{3}\hbox {COONa}\cdot 3\hbox {H}_{2}\hbox {O}$$\end{document} had lowest, whereas NaOH, NH4OH\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {NH}_{4}\hbox {OH}$$\end{document} and N(CH2CH3)3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hbox {N(CH}_{2}\hbox {CH}_{3})_{3}$$\end{document} had intermediate reaction time. The presence of strong base kept pH in the basic region after neutralization of all HCl formed during the reaction.