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Side-reactions during dehydrochlorination of III. Reaction conditions: i) H 2 O; ii) dehydrochlorination; iii) dehydration.
Source publication
The influence of pre-reactor and reactor temperatures on the conversion of 1,3-dichloropropan-2-ol and the selectivity of its transformation to epichlorohydrin in continuous dehydrochlorination for two modes of the reaction product collection was studied. The dehydrochlorination process and mechanism of diglycidyl ether formation are described.
Context in source publication
Citations
... The composition of the reactive mixtures was studied [97], concluding that 1,2-DCH is much less reactive than 1,3-DCH, although primary alkyl alcohols are more acidic than secondary alkyl alcohols. The influence of the reactor on the reaction kinetics [98,99] and of the cation on the 1,3-DCH dehydrochlorination [59,61,97,100] was also studied. ...
Crude glycerol (C3H8O3) is a major by-product of biodiesel production from vegetable oils and animal fats. The increased biodiesel production in the last two decades has forced glycerol production up and prices down. However, crude glycerol from biodiesel production is not of adequate purity for industrial uses, including food, cosmetics and pharmaceuticals. The purification process of crude glycerol to reach the quality standards required by industry is expensive and dificult. Novel uses for crude glycerol can reduce the price of biodiesel and make it an economical alternative to diesel. Moreover, novel uses may improve environmental impact, since crude glycerol disposal is expensive and dificult. Glycerol is a versatile molecule with many potential applications in fermentation processes and synthetic chemistry. It serves as a glucose substitute in microbial growth media and as a precursor in the synthesis of a number of commercial intermediates or fine chemicals. Chlorinated derivatives of glycerol are an important class of such chemicals. The main focus of this review is the conversion of glycerol to chlorinated derivatives, such as epichlorohydrin and chlorohydrins, and their further use in the synthesis of additional downstream products. Downstream products include non-cyclic compounds with allyl, nitrile, azide and other functional groups, as well as oxazolidinones and triazoles, which are cyclic compounds derived from ephichlorohydrin and chlorohydrins. The polymers and ionic liquids, which use glycerol as an initial building block, are highlighted, as well.
The utilization of fossil fuels has been the leading choice in the industrial revolution despite its negative environmental impact. Biodiesel is a well-known alternative to replace fossil fuels because it is a renewable and environmentally friendly fuel. The use of biodiesel increases every year, causing new problems. The transesterification reaction to produce biodiesel also produces a by-product of glycerol. Glycerol is among the world’s 12 most essential chemical raw materials. The abundance of glycerol has not been followed by the level of consumption, so it is necessary to increase the value of the glycerol. The transformation of glycerol into high-value-added chemicals is a promising solution to utilizing abundant glycerol. Glycerol transformation can be done through several reaction pathways catalyzed by zeolite. Zeolite is a heterogeneous catalyst with acid-base sites and good framework selectivity, making it suitable for catalytic glycerol transformation. Zeolite can be used to catalyze glycerol through various reactions into high-value-added chemicals such as glycerol oxidation to produce dihydroxyacetone, glycerol hydrogenolysis to produce propylene glycol, glycerol dehydration to produce acrolein, glycerol transesterification with dialkyl carbonate to produce glycerol carbonate, glycerol pyrolysis to produce syngas, and glycerol etherification to produce glycerol ethers.
Glycerol, the by-product of the Biodiesel manufacturing from vegetal and animal fats, is an important bio-resource, which can be transformed into a significant number of valuable products, by catalytic, enzymatic, or biological technologies. This paper presents a review of published studies on the kinetics of the main catalytic transformations of glycerol into valuable products, along with information regarding the catalytic reactors experienced or proposed for these transformations. In the kinetic description of the glycerol catalytic transformations, the most used are the rate expressions based on the Langmuir-Hinshelwood-Hougen-Watson (LHHW) theory and the empirical ones, of the power law type. The published results are evidencing that, in addition to the general technical and economic advantages, the liquid phase continuous processes of glycerol transformation are more efficient, ensuring, in many cases, a higher selectivity of the transformation and a slower deactivation of the catalyst.
A homogeneously catalyzed gas-liquid process, glycerol hydrochlorination was studied in a semibatch reactor with gaseous hydrogen chloride (HCl) as a continuous phase and acetic acid as homogeneous catalyst. Several experiments were conducted varying the temperature in the jacket of the reactor in the range 70-115 °C and the catalyst mole fraction between 0-15 mol-%. The effects of HCl on the kinetics was investigated by changing the partial pressure of HCl in the range 0.25-1 atm by diluting HCl with inert gas, while the absolute pressure of the reactor was remained constant at atmospheric pressure. The experiments revealed new information about this particular reaction system. Considerable changes in the reactor temperature occurs, temperature changes close to 20 °C, which are an effect of the absorption process of gaseous HCl. The HCl uptake in the liquid phase exhibits a strange behavior at the beginning of the reaction, associated to the appearance of water and the temperature change during the experiments. The experiments also revealed that a part of the catalyst is transformed into esters in the presence of glycerol and 3-chloro-1,2-propanediol (α-MCP), particularly at high catalyst concentrations. These esters were detected and an improved gas-chromatographic method was developed to analyze these quantitatively. In long run, the the esters are converted back to the original catalyst, acetic acid, as the reaction stops because of lack of glycerol. The information provided by the experiments in this work gives better understanding of the reaction mechanism and thus they are the basis for a rational design of glycerol hydrochlorination reactors.
Alkaline earth metal‐based catalysts applied in the process of dichlorohydrin cyclization into epichlorohydrin were studied. A series of solid catalysts were prepared by the equivalent‐volume impregnation method using γ‐Al2O3 as a carrier, whereas nitrates and chlorides of the three alkaline earth metals (Mg, Ca, and Ba) were employed as precursors. Their catalytic performance was investigated and compared, taking into account the main factors influencing the catalytic efficiency, such as X‐ray diffraction (XRD), N2 adsorption–desorption, energy dispersive spectrometry (EDS) coupled with TEM, and CO2 temperature‐programmed desorption (CO2‐TPD). The results have shown that the specific surface area and the number of active base sites are the main factors that are affecting the catalytic efficiency. Among the series of as‐prepared catalysts, 10BaO/γ‐Al2O3 had improved catalytic performance. Based on the obtained results for the characterization of catalysts, the increased catalytic activity could be mainly attributed to the increase in base strength resulting from BaO loading onto the surface of γ‐Al2O3. Under optimized conditions, 98.4% conversion of 1,3‐DCH and approximately 90% of ECH selectivity were achieved using 10BaO/γ‐Al2O3 with a reaction temperature of 270°C. During the reaction process, the catalytic activity of 10BaO/γ‐Al2O3 remained consistently high, and its catalytic stability was excellent.
Epichlorohydrin is an important chemical intermediate, which can be obtained by valorisation of glycerol, an inexpensive raw material obtained as a stoichiometric co-product from biodiesel production. A continuous milliscale tubular reactor was developed to conduct the synthesis of epichlorohydrin and to measure the very rapid reaction kinetics. 1,3-dichloro-2-propanol (αγ-DCP) was dehydrochlorinated with sodium hydroxide at 30–70 °C. The residence times in the millireactor system were less than 25 s. The kinetic data were interpreted with a plug flow model and a rate equation based on a plausible reaction mechanism. The model – the rate equation and the plug flow concept – gave a perfect description of the experimental data.
The results of dehydrochlorination of 88 wt% aqueous solution of 1,3-dichloropropan-2-ol to epichlorohydrin are reported. The process was carried out in the reaction-stripping column system with a continuous removal of epichlorohydrin in the steam stream. Aqueous solutions of sodium and calcium hydroxides at concentrations in the range of 3-14 wt% were used for the dehydrochlorination. The influence of the type and concentration of dehydrochlorination agent on 1,3-dichloropropan-2-ol conversion, the selectivity of transformation to epichlorohydrin and by-products, and the composition of distillate and wastewater were studied.
The results of dehydrochlorination of 1,3-dichloropropan-2-ol to epichlorohydrin are reported. The process ran in the reaction-stripping column system with a continuous removal of epichlorohydrin in a steam stream. The influence of 10 wt% alkali solution (NaOH, Ca(OH)(2)) and the method of distillate collection on the 1,3-dichloropropan-2-ol conversion, selectivity of transformation to epichlorohydrin and by-products, and the composition of wastewater have been analysed.
