Article pubs.acs.org/IECR
Novel Process for 1,3-Dihydroxyacetone Production from Glycerol. 1. Technological Feasibility Study and Process Design Zhi Zheng, Min Luo, Jianer Yu, Jianli Wang,* and Jianbing Ji College of Chemical Engineering and Materials Science, Zhejiang University of Technology, No. 18, Chaowang Road, 310014, Hangzhou, China ABSTRACT: A novel and efficient conversion process of glycerol to 1,3-dihydroxyacetone (DHA) via indirect oxidation was developed. The idea is to oxidize the middle hydroxyl group of glycerol to a carbonyl group with the help of a group protection technique, and then the protection reagent is removed by hydrolysis. With this new process, the conversion is conducted in three steps, namely, acetalization, oxidation, and hydrolysis. The oxidation step is the focus of this conversion process. In our work, three oxidant systems (CrO3 anion resin oxidant system, TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl)/NaBr/NaClO system, and TEMPO/NaBr/Air system) were experimentally examined to verify the feasibility of this new process. The process of this conversion is also preliminarily designed on the basis of the laboratory procedure described in the experimental section, which offers a potential foundation for the large-scale production of DHA from glycerol.
1. INTRODUCTION The recent escalating production and utilization of biodiesel worldwide has spawned a large amount of glycerol.1,2 Glycerol, a versatile biomass-derived compound, can be used as an important raw material for the manufacture of valuable chemicals.1−4 The selective oxidation of glycerol is a desirable conversion due to the industrial importance of the obtainable oxygenated derivatives. 1,3-Dihydroxyacetone (DHA), the main active ingredient in sunless tanning skin-care preparations and an important precursor for the synthesis of various fine chemicals, is produced on an industrial scale by microbial fermentation of glycerol over Gluconobacter oxydans.5 Although microbial fermentation processes can provide high selectivity to DHA, they have some drawbacks such as low productivity and high production cost. Besides, both glycerol and DHA have an inhibitory effect on bacteria growth.6 As a result, production has not reached the required yield to satisfy the commercial demand. Recent advances in the direct catalytic oxidation of glycerol to DHA have produced a range of possible oxidation products (as shown in Scheme 1),7−12 such as glyceraldehyde, dihydroxyacetone, glyceric acid, tartronic acid, hydroxypyruvic acid, glycolic acid, glyoxylic acid, oxalic acid, and mesoxalic acid, but few catalysts are selective for DHA. Electrocatalytic oxidation of glycerol to DHA catalyzed by TEMPO (2,2,6,6tetramethylpiperidine-1-oxyl) obtained 30% yield.11 Aerobic glycerol oxidation with Pt−Bi catalysts yielded DHA with a selectivity of 60% at 80% conversion.12 Good selectivity to DHA at high glycerol conversion is difficult to achieve because of the trihydroxyl structure of glycerol and rapid overoxidation of DHA.11 The problem caused by low conversion and selectivity in the direct catalytic oxidation method makes the purification of DHA difficult. For these cases, only low-efficiency and high-cost column separation can be applied to purify the product.13 Therefore, © 2012 American Chemical Society
Scheme 1. Possible Reaction Pathways to Oxygenated Derivatives of Glycerol
an efficient chemical process capable of generating DHA from glycerol at low cost is desirable. In this paper, enlightened by the indirect reduction of glycerol reported by Hawley,14 we developed an efficient process capable of producing DHA from glycerol in high yield comparable to that of the microbial fermentation process. The feasibility verification and process design of each step were also presented to explore a potential alternative to the current DHA production methods. Received: Revised: Accepted: Published: 3715
August 9, 2011 January 10, 2012 February 7, 2012 February 7, 2012 dx.doi.org/10.1021/ie201710h | Ind. Eng. Chem. Res. 2012, 51, 3715−3721
Industrial & Engineering Chemistry Research
Article
2. PROCESS DESCRIPTIONS As illustrated in Scheme 2, the essential feature of this process is the formation of the six-membered ring cyclic acetal, which is
batch. Once that balance level is reached, no additional HMPD will be produced. The second step of this process is the oxidation of HPD, which is the focus of this conversion process. With the protection of the end hydroxyl groups, the acetalized glycerol HPD can be oxidized thoroughly to the corresponding acetalized dihydroxyacetone (PDO, 2-phenyl-1,3-dioxan-5one) at a mild condition without overoxidation. A high yield of PDO (96%) was achieved in our experiment. Pure PDO can be obtained by recrystallization which ensures the subsequent production of DHA with a high purity. The final step of this process is a hydrolysis reaction. Pure PDO was hydrolyzed to produce the target product DHA as colorless viscous oil. The DHA crystals were obtained by the subsequent crystallization. The last step also regenerates benzaldehyde, which can be recycled back to another acetalization batch in the first-step conversion.
Scheme 2. Three-Step Conversion Process of Glycerol to DHA
3. EXPERIMENTAL SECTION Materials. The glycerol (≥99%) was supplied by Ningbo Jieseng Biodiesel Co., Ltd. The benzaldehyde (>98.5%) and ptoluenesulfonic acid (≥99%) were provided by Shanghai chemical reagents supply procurement of five chemical plants. The chromium trioxide (≥99%) was bought from Yixing No. 2 Chemical Reagent Factory. The TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl, >95%) and 1,3-dihydroxyacetone dimer (>96%) were purchased from Alfa Aesar Chemical Co., Ltd. The sodium bromide (≥99%) and sodium hypochlorite solution (available chlorine ≥ 5%) were bought from Shanghai No. 4 Reagent and H. V. Chemical Co., Ltd. The acid-type ionic resin CD550 (ionic exchange capacity 4.8 mmol/g, average particle size 0.20 mm) and anion exchange resin 717# (ionic exchange capacity 3.6 mmol/g, average particle size 0.75 mm) were obtained from Zhejiang Zhengguang Industrial Co., Ltd. Instrumentation. 1H NMR was recorded on a BRUKER AVANCE III spectrometer using tetramethylsilane as an internal standard and deuterated solvents (CDCl3, D2O). The yield and purity of the products were confirmed on an HPLC (Varian Prostar 210) using a Kromasil 100-5-C 18 column (Φ 4.6 mm × 250 mm), UV−vis detector, and MeOH/water fluid phase. Acetalization. In a typical experiment, glycerol (100.0 g, 1.09 mol), benzaldehyde (120.0 g, 1.13 mol), p-toluenesulfonic acid catalyst (1 g), and 1:1 petroleum ether−benzene mixture (100 mL) were refluxed in a flask equipped with a water separator at 80 °C. After 4 h, the reaction was completed, as evidenced by no more water being formed in the water separator. The reaction mixture was cooled, treated with 0.5 M NaOH solution (2 × 100 mL), dried over anhydrous K2CO3 (1 g), and finally filtrated. The desired HPD was crystallized from the reaction mixture at −10 °C and accomplished by filtration. The crude HPD was recrystallized in toluene−petroleum ether mixture (1:1) to give pure HPD as large, white, prismatic needles; 48.8 g, yield 25%. 1H NMR (500 MHz, CDCl3): δ (ppm) 3.07 (d, J = 10.0 Hz, 1H, OH), 3.61 (brd, J = 10.0 Hz, 1H), 4.09 (dd, J = 12.0 and 1.5 Hz, 2H), 4.17 (dd, J = 12.0 and 1.5 Hz, 2H), 5.54 (s, 1H), 7.36 (m, 3H), 7.49 (m, 2H). Recycle of Crystal Mother Liquor. The reactions of the supplemented glycerol (11 g, 0.119 mol) and benzaldehyde (13 g, 0.122 mol) were conducted in the recycled filtered liquid (crystal mother liquor), which contains the undesired HMPD and unrecovered trans-HPD. The reaction and isolation
a novel potential precursor for the production of DHA that can be obtained by the subsequent oxidation and acetal cleavage. With this new approach, the conversion of glycerol to DHA is completed in three steps, namely, acetalization, oxidation, and hydrolysis. The detailed descriptions of each step involved in this process are provided as follows. The first step of this process is the acetalization with benzaldehyde to protect the first and third hydroxyl groups of glycerol from being oxidized. The acetalization of glycerol with benzaldehyde as well as the facile isolation method of the desired 1,3-product (HPD, 5-hydroxyl-2-phenyl-1,3-dioxane) from the undesired 1,2-product (HMPD, 4-hydroxymethyl-2phenyl-1,3-dioxane) by crystallization were successfully developed in the literature.14−17 Moreover, the reaction has two important features: (a) it is nonselective (see Scheme 2); that is, only partial glycerol can be directly converted to HPD. (b) It is an equilibrium reaction, which involves an acid-catalyzed equilibrium between the HPD and HMPD (see Scheme 3). Scheme 3. Acid-Catalyzed Equilibrium between HMPD and HPD (Ring Transformation)
Because of the latter feature, the HMPD in the acetalization reaction can only accumulate to a certain level, which can be maintained by the recycling of the HMPD produced in the last 3716
dx.doi.org/10.1021/ie201710h | Ind. Eng. Chem. Res. 2012, 51, 3715−3721
Industrial & Engineering Chemistry Research
Article
conditions were the same as the descriptions in the above acetalization batch. The results are reported in Table 1. Table 1. Experimental Results of Each Acetalization Batcha batch
glycerol (mol)
benzaldehyde (mol)
HPD yieldb (%)
1 2c 3c 4c
1.090 0.119 0.119 0.119
1.130 0.122 0.122 0.122
25 97 98 98
a
The acetalization reactions were carried out in 1:1 toluene− petroleum, benzaldehyde, glycerol, p-toluenesulfonic acid catalyst, 80 °C, and 4 h. bIsolated yields. cThe crystal mother liquor in batch 1 was recycled for batches 2−4.
Oxidation. CrO3 Anion Resin Oxidant System. To a suspension of 717# resin (4 g) in benzene (25 mL), CrO3 (1.2 g, 12 mmol) was added. The mixture was stirred for 30 min to form the resin supported CrO3 (3 mmol CrO3/g resin), and then HPD (1.08 g, 6 mmol) was added to start the reaction. The reaction mixture was stirred at 65 °C for 24 h and filtrated. The solvent was removed by vacuum distillation. The crude PDO was recrystallized in diethyl ether to afford pure PDO as large, colorless, prismatic needles; 1.01 g, yield 94%. 1H NMR (500 MHz, CDCl3): δ (ppm) 4.49 and 4.51 (AB-pattern, JAB = 17.6 Hz, 2H), 5.90 (s, 1H), 7.39 (m, 3H), 7.53 (m, 2H). The other results are reported in Table 2.
Figure 1. Initial experimental results of HPD oxidation by TEMPO/ NaBr/NaClO system. The oxidation reactions were carried out in CH2Cl2−water at pH 9.1, 3 mmol of HPD, 0.5−2 mol % TEMPO, 10 mol % NaBr, 200 mol % NaClO, and 16 °C.
Table 3. Initial Experimental Results of the HPD Oxidation by TEMPO/NaBr/Air Systema
Table 2. Initial Experimental Results of the HPD Oxidation by CrO3−Anion Resin in Benzenea entry
T (°C)
time (h)
HPD:CrO3 (mol)
PDO yieldb (%)
1 2 3 4 5
65 65 65 65 25
6 6 6 24 6
1:1 1:2 1:3 1:2 1:2
20 48 66 94 14
entry
T (°C)
time (days)
HPD yieldb (%)
1 2 3 4 5
16 16 16 45 45
3 7 14 7 14
24 50 70
