Esterification of levulinic acid with butanol over ion exchange resins

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 80 °C 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

Catalytic hydroxyalkylation/alkylation of 2‑methylfuran with butanal to form a biodiesel precursor using acidic ion-exchange resins

The catalytic hydroxyalkylation/alkylation of 2-methylfuran (2MF) with butanal has been investigated over several acidic ion-exchange resins within the temperature range 50−90 °C and at a stoichiometric reactant molar ratio of 2MF/butanal (2:1). Butanal conversion increases with temperature and also the formation of undesired 2-methylfuran oligomers, leading to a decrease in yield to the target product. The highest butanal conversion (90%) is achieved at 50 °C over Dowex 50Wx2 with a negligible formation of 2-methylfuran oligomers. The observed catalytic activity and final yield to the target product have been rationalized on the basis of morphological properties of resins and their dynamic behavior within the present reaction medium. The findings reveal that gel-type resins are more active and render higher product yields than their macroreticular congeners due to the enhanced accessibility to acid centers because of their improved ability to swell throughout the reaction. Macroreticular resins with a low cross-linking degree, e.g., Amberlyst 39, also produce interesting catalytic results. The stability of the most promising catalyst has been evaluated after three reaction cycles, and the full reusability outcome speaks for its appropriateness as a potential catalyst for the studied process

Kinetics of 1-pentanol etherification without water removal

The effect of water on the kinetics of the liquid-phase dehydration of 1-pentanol to di-n-pentyl ether (DNPE) and water over Amberlyst 70 is revisited. To explain the strong inhibitor effect of water, two approaches were compared. First, a model stemming from a Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was used, wherein the inhibitor effect of water was explained by the competitive adsorption of water and pentanol. Second, a modified Eley-Rideal (ER) model was used that includes an inhibition factor, in which a Freundlich-like function is used to explain the inhibitor effect of water by blocking the access of pentanol to the active centers. Both models fitted data quite well, although the best results were obtained with the modified ER model. The activation energy was 118.7 ± 0.2 kJ/mol for the LHHW model and 114.0 ± 0.1 kJ/mol for the modified ER one

Influence of acid ion-exchange resins morphology in swollen state on the synthesis of ethyl octyl ether from ethanol and 1-octanol

Ethyl-octyl ether (EOE) liquid phase synthesis from ethanol and 1-octanol over ion-exchange resins is feasible at 423K, though di-ethyl ether and di-n-octyl ether were also formed. The influence of the catalyst morphology on the reaction was checked by testing twenty-two acidic resins. Gel-type resins of low crosslinking degree yielded the higher amounts of EOE, whereas macroreticular ones of high crosslinking degree gave mainly di-ethyl ether. Ethanol conversion highly depends on the resin acid capacity, [H+], whereas 1-octanol conversion and selectivity to EOE depends on the specific volume of swollen polymer, Vsp, and porosity. The variation of ethanol and 1-octanol conversion, selectivity to EOE with respect to both alcohols as well as ethers TOF as a function of [H+]/Vsp suggests that a part of the active sites does not take part in the EOE synthesis reaction on highly cross-linked resins. Amberlyst 70 could be interesting in industry due to its selectivity to EOE and higher thermal stabilit

Kinetics of 1-hexanol etherification on Amberlyst 70

The kinetics of the liquid-phase etherification of 1-hexanol to di-n-ethyl ether and water on the ion-exchange resin Amberlyst 70 in the temperature range 423-463 K is studied. The strong inhibition effect of water is considered following two approaches. First, a model stemming from a Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanism was used, wherein the inhibitor effect of water was explained by the competitive adsorption of water and hexanol. Secondly, a modified Eley-Rideal (ER) model that includes an inhibition factor, in which a Freundlich-like function is used to explain the inhibitor effect of water by blocking the access of hexanol to the active centers. Both models fitted data quite well, although the best fitting results were obtained with the modified ER model. The activation energy was 125 ± 3 kJ/mol for the LHHW model and 121 ± 3 kJ/mol for the modified ER on

Liquid-phase synthesis of butyl levulinate with simultaneous water removal catalyzed by ion exchange resins

The liquid-phase synthesis of butyl levulinate by esterification of levulinic with an excess of 1-butanol (initial molar ratio 1:3) and simultaneous water removal has been studied at atmospheric pressure and at the boiling point of the reacting medium. The catalytic performance of ten commercial sulfonic resins has been compared: four gel-type and six macroreticular. For both type of resins the levulinic acid conversion was complete after 4-6h and no byproducts derived from the acid were detected. Selectivity of 1-butanol towards the ester was about 95%, di-butyl ether and butenes being the detected 1-butanol-derived byproducts. Among the tested catalysts, gel-type resins with low crosslinking degree showed the highest activity, what could be attributed to a higher accessibility to active centers in polar medium. In additional experiments where initial reactants content was at stoichiometric relation, the levulinic acid conversion was lower (82-85%), while selectivity of 1-butanol towards the ester was slightly higher, because of the lower 1-butanol concentration

Dehydration of 1-octanol to di-n-octyl ether in liquid phase with simultaneous water removal over ion exchange resins: Effect of working state morphologies

The influence of the concentration of polar reactants and products on the working-state morphology of ion exchange catalysts has been investigated over different acidic ion-exchange resins for di-n-octyl ether (DNOE) synthesis from 1-octanol dehydration at 423-448 K and atmospheric pressure in a batch reactor equipped with a Dean & Stark device. By removing water formed 1-octanol conversion was practically complete; the olefin formation being the main secondary reaction. When 1-octanol is completely consumed the working-state morphology of ion exchange resins changes, which influences the selectivities towards products. At this point, for microporous resins all reactions stop while with macroreticular ones DNOE decomposes and significant amounts of olefin dimers appears. The best selectivity to DNOE was found in gel-type and macroreticular resins with low crosslinking degree. Macroreticular resins with medium or high crosslinking give good results in olefin formation

Catalytic activity dependence on morphological properties of acidic ion-exchange resins for the simultaneous ETBE and TAEE liquid-phase synthesis

The simultaneous liquid-phase synthesis of 2-ethoxy-2-methylpropane (ETBE) and 2-ethoxy-2-methylbutane (TAEE) has been studied over fifteen commercial acidic ion-exchange resins. Kinetic experiments were carried out in a batch reactor at T = 335 K and initial molar ratios of alcohol to olefins (R°A/O) and between olefins (R°C4/C5) of 1.1 and 1, respectively. The catalytic activity, measured as intrinsic initial etherification rates, has been found to decrease in the order: Amberlyst¿ 35 > Amberlyst¿ 48 > Purolite® CT-275 > Amberlyst¿ 15 > Purolite® CT-175 > Amberlyst¿ 40 > Amberlyst¿ 36 > Amberlyst¿ 16 > Purolite® CT-482 > Amberlyst¿ 39 > Amberlyst¿ DT > Amberlyst¿ 45 > Purolite® CT-124 > Purolite® MN-500 > Amberlyst¿ 46. This catalytic activity rank is related to the morphological properties of the resins in both dry and swollen states. The ratio of acid capacity to specific volume of the swollen polymer has been found to be the main catalyst properties that determine their activity: the higher the ratio, the higher the activity

Kinetics of the liquid phase dehydration of 1-octanol to di-n-octyl ether on Amberlyst 70

The kinetics of the liquid phase dehydration of 1-octanol to di-n-octyl ether (DNOE) over Amberlyst 70 was studied at 413-453K. Mechanistic rate models assuming water and 1-octanol adsorbed on the resin, and the free sites fraction negligible, were selected from 1-octanol dehydration experiments. Next, the influence of DNOE, water and 1,4-dioxane (solvent) concentration was evaluated. DNOE and 1,4-dioxane do not affect significantly the reaction rate, while water inhibits it strongly. Water effect was quantified by splitting the rate constant into a 'true one' and a correction factor related to the fraction of active sites blocked by water. The best kinetic model stemmed from an Eley-Rideal mechanism with water adsorbed onto the resin and DNOE released directly to the liquid phase, with a correction factor for water inhibitory effect based on a Freundlich isotherm-like function; activation energy being 110±5 kJ·mol-1 based in line with literature data on homologous reactions

Ion exchange resins as catalysts for the liquid-phase dehydration of 1-butanol to di-n-butyl ether

This work reports the production of di-n-butyl ether (DNBE) by means of 1-butanol dehydration in the liquid phase on acidic ion-exchange resins. Dehydration experiments were performed at 150 ºC and 40 bar on 13 styrene-codivinylbenzene ion exchangers of different morphology. By comparing 1-butanol conversions to DNBE and initial reaction rates it is concluded that oversulfonated resins are the most active catalysts for 1-butanol dehydration reaction whereas gel-type resins that swell significantly in the reaction medium as well as the macroreticular thermostable resin Amberlyst-70 are the most selective to DNBE. The highest DNBE yield was achieved on Amberlyst 36. The influence of typical 1-butanol impurities on the dehydration reaction were also investigated showing that the presence of 2-methyl-1-propanol (isobutanol) enhances the formation of branched ethers such as 1-(1-methylpropoxy) butane and 1-(2-methylpropoxy) butane, whereas the presence of ethanol and acetone yields ethyl butyl ether and, to a much lesser extent, diethyl ether