Alkyl levulinates are biobased chemicals with a great number of applications and great biofuel potential for blending to conventional diesel or gasoline. The present work focuses on the liquid-phase synthesis of butyl levulinate (BL) by esterification of levulinic acid (LA) with 1-butanol (BuOH) using a set of acidic ion-exchange resins. Experiments were performed at 80ºC and 2.5 MPa in a batch reactor by using an initial molar ratio AL/BuOH of 1/3 and a catalyst loading of 0.8%. It has been found that BL could be successfully obtained over ion-exchange resins with a selectivity higher than 99.5%. LA conversions ranged from 64% (Amberlyst 46, macroreticular, surface sulfonated) to 94% (Dowex 50Wx2, gel-type resin, conventionally sulfonated) at 8 h reaction time. By comparing their catalytic behavior, it was seen that resins morphology plays a very important role in the synthesis of BL making easier the access of reactants to acid sites. Accessibility of LA and BuOH to acid centers was high over highly swollen and low polymer density resins. Thus, gel-type resins with low divinylbenzene (DVB) content have been found as the most suitable to produce BL, e.g. Dowex 50Wx2, Dowex 50Wx4 and Purolite® CT224. Among them, Dowex 50Wx2 (2% DVB) is the most efficient catalyst tested.
8Ethyl-octyl ether (EOE) liquid phase synthesis from ethanol and 1-octanol over ion-exchange 9resins is feasible at 423K, though di-ethyl ether and di-n-octyl ether were also formed. The 10 influence of the catalyst morphology on the reaction was checked by testing twenty-two acidic 11 resins. Gel-type resins of low crosslinking degree yielded the higher amounts of EOE, whereas 12 macroreticular ones of high crosslinking degree gave mainly di-ethyl ether. Ethanol conversion 13 highly depends on the resin acid capacity, [H + ], whereas 1-octanol conversion and selectivity to 14 EOE depends on the specific volume of swollen polymer, V sp , and porosity. The variation of 15 ethanol and 1-octanol conversion, selectivity to EOE with respect to both alcohols as well as 16 ethers TOF as a function of [H + ]/V sp suggests that a part of the active sites does not take part in 17 the EOE synthesis reaction on highly cross-linked resins. Amberlyst 70 could be interesting in 18 industry due to its selectivity to EOE and higher thermal stability. 19
7The effect of water on the kinetics of the liquid-phase dehydration of 1-pentanol to di-n-8 pentyl ether (DNPE) and water over Amberlyst 70 is revisited. To explain the strong 9 inhibitor effect of water, two approaches were compared. Firstly, a model stemming from a 10Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was used, wherein the 11 inhibitor effect of water was explained by the competitive adsorption of water and pentanol. 12 Secondly, a modified Eley-Rideal (ER) model that includes an inhibition factor, in which a 13Freundlich-like function is used to explain the inhibitor effect of water by blocking the 14 access of pentanol to the active centers. Both models fitted data quite well, although the 15 best results were obtained with the modified ER model. The activation energy was 118.7 ± 16 0.2 kJ/mol for the LHHW model and 114.0 ± 0.1 kJ/mol for the modified ER one. 17 18
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