Preparation Of Alkylchlorides Using Ionic Liquid Catalyst And Gas Phase Process

Carbon tetrachloride (CTC) is an ozone depleting substance (ODS). It is mainly used as feedstock of chlorofluorocarbons (CFCs), such as CFC-11, CFC-12. As feedstock of CFCs, it is to be phased out according to theMontreal Protocol by Jan 2010 in China. However, its output as an inevitable byproduct in chloromethanes industry is about 5-10%. In contrast, the feedstock use of CTC in producing non-ODS products is not restricted; hence the development of CTC conversion technology is an urgent subject.In recent years, ionic liquids (ILs), which have many unique physicochemical properties, such as none measurable vapour pressure, wide liquid range, acidity and super acidity, catalysts as well as solvents in reaction receive widely attention. They are called "green solvents", also the related research is very vigorous.In this thesis, we study the preparation of alkylchlorides, which are non-ozone depleting substance, via CTC alcoholysis reaction using ILs as catalyst under gas phase condition. The main research includes four parts as follows:1. Preparation of eight ionic liquids or their precursors. The ILs can be divided into three categories:â‘ ILs with differing alkyl length for the cations ([hMIM]Cl, [BMIM]Cl, [OMIM]C1);â‘¡ILs with different cation type ([hMIM]Cl, [Et₃NH]Cl, [(CH₂)₆N₄H]Cl, [PyH]Cl);â‘¢ILs with different anion type ([hMIM]Cl, [hMIM]HSO₄, [hMIM]H₂PO₄).2. Preparation of n-butyl chloride using hydrochloric acid as chlorating agent. The catalytic performance of four ionic liquids ([Et₃NH]Cl, [hMIM]Cl, [PyH]Cl, [BMIM]Cl) coated on granular active carbon were studied for the gaseous phase hydrochlorination reaction of n-butanol, and a good catalyst, [Et₃NH]Cl, was selected. The optimal conditions were obtained as follows: the catalyst loading of 5%, temperature between 140-180℃, n(hydrochloride acid): n (n-butanol) =1:1. Under the given conditions, the conversion rate of n-butanol reached 91% while the selectivity of n-chlorobutane reached 97%.3. Preparation of n-butyl chloeide via CTC alcoholysis reaction. Eight types of ionic liquids([Et₃NH]Cl, [(CH₂)₆N₄H]Cl, [hMIM]Cl, [PyH]Cl, [BMIM]Cl, [OMIM]Cl, [hMIM]HSO₄, [hMIM]H₂PO₄) were used as catalysts in the gaseous phase CTC alcoholysis reaction. The result indicated that the conversion of CTC increases with temperature rising, and the selctivity of n -butyl chloride increases gradually before 160℃, and then decreases with temperature. Regarding ILsâ‘ , the catalytic activity drops with alkyl length of cations growing, namely [hMIM]Cl> [BMIM]Cl> [OMIM]Cl; regarding ILsâ‘¡,the catalytic activity follows [Et₃NH]Cl> [hMIM]Cl> [(CH₂)₆N₄H]Cl> [HPy]Cl; regarding ILsâ‘¢, the selectivity of n-butyl chloride follows the acidity order of ILs, namely [hMIM]HSO₄> [hMIM]H₂PO₄> [hMIM]Cl.4. Preparation of other alkylchlorides using CTC as feedstock. As the carbon number of alcohols increases, the conversion of CTC drops slightly, for example, when n=3 or 4 the conversion is nearly 100%, and when n=8, the conversion is only about 90%; as for the selectivity of alkyl chloride, it drops moderately with carbon number of the corresponding alcohols, when n≤6, the conversion maintains above 95%, but when n=8, it drops noticeably to 75%.