Acetaldehyde Production from Ethanol by Eco-Friendly non-Chromium

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Applied Chemistry

Acetaldehyde Production from Ethanol by Eco-Friendly nonChromium Catalysts Consisting of Copper and Calcium Silicate Atsushi Segawa, Akio Nakashima, Ryoichi Nojima, Naohiro Yoshida, and Masaki Okamoto Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b02498 • Publication Date (Web): 09 Aug 2018 Downloaded from http://pubs.acs.org on August 11, 2018

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Industrial & Engineering Chemistry Research

Acetaldehyde Production from Ethanol by Eco-Friendly non-Chromium Catalysts Consisting of Copper and Calcium Silicate

Atsushi Segawa†, ††, Akio Nakashima‡, Ryoichi Nojima‡‡, Naohiro Yoshida††, §, §§ and Masaki Okamoto*, #

†

Central Technical Research Laboratory, JXTG Nippon Oil & Energy Corporation, 8

Chidoricho, Naka-ku, Yokohama, Kanagawa 231-0815, Japan ††

Department of Environmental Chemistry and Engineering, Interdisciplinary Graduate

School of Science and Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8502, Japan ‡Sakai

Chemical Industry Co., Ltd., Development Section, Production Department,

Catalysts Operations Division, 5-1, Ebisujima-Cho, Sakai-ku, Sakai, Osaka 590-0985, Japan ‡‡Osaki

Industry Co., Ltd., Hofu Plant Chemicals Division, 75, Kohama, Hamakata, Hofu,

Yamaguchi 747-0833, Japan §

Department of Chemical Science and Engineering, School of Materials and Chemical

Technology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama, Kanagawa 226-8502, Japan § §

Earth-life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama,

Meguro-ku, Tokyo 152-8552, Japan #Department

of Chemical Science and Engineering, School of Materials and Chemical

1 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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Technology, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan

* Corresponding author E-mail: [email protected] (M. Okamoto)

Abstract The authors developed eco-friendly non-chromium catalysts for acetaldehyde production through

bioethanol

dehydrogenation,

consisting

of

copper

and

calcium

silicate.

Acetaldehyde selectivity was higher over copper calcium silicate catalysts with a CuO content of 40 wt% or more, since the number of acid sites on the calcium silicate was reduced, which helped prevent formation of by-products. It was found that high ethanol conversion (39%–57%) and high acetaldehyde selectivity (91%–95%) could be achieved simultaneously at high temperature and high WHSV conditions. Furthermore, it was shown that stable acetaldehyde production could be maintained over 20 h of time-on-stream. These catalysts were prepared from commercially available precursors, and could be used in place of conventional copper chromite catalysts.

1. Introduction Acetaldehyde is an important chemical, of which over 10 6 tons/year are produced worldwide.1 Most acetaldehyde is produced industrially by the direct oxidation of ethylene1,2 and is used as a raw material to make acetic acid, 1-butanol, ethyl acetate,


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crotonaldehyde, 1-butanal, and many other products. 3 Bio-based acetaldehyde produced by bioethanol dehydrogenation could be used to make a variety of eco-friendly, bio-based chemicals.4 In 1931, Adkins et al. reported that a copper chromite catalyst was active for the dehydrogenation of various organic chemicals. 5 Copper chromite catalysts have been characterized in numerous studies. The participation of not only Cu0 and Cu2+, but also Cu+ species has been proposed. Rao et al. reported that Cu0 increased and CuCrO2 formed from CuCr2O4 during reduction of copper chromite catalysts.6 There are numerous papers concerning ethanol dehydrogenation over copper chromite catalysts. The main products in ethanol dehydrogenation are acetaldehyde and ethyl acetate. It has been reported that ethyl acetate is formed via hemiacetal from the reaction between ethanol and the produced acetaldehyde over copper catalysts. 7,8 Ethyl acetate production favors high pressure conditions.8 Carotenuto et al. reported ethyl acetate production by ethanol dehydrogenation over a commercial copper chromite catalyst. At 240 °C and 20 atm, ethanol conversion and ethyl acetate selectivity were 64% and 99%, respectively.7 Santacesaria et al. reported 61% ethanol conversion and 98% ethyl acetate selectivity at 240 °C and 2 MPa over a commercial copper/copper chromite catalyst, BASF Cu-1234.8 Chang et al. reported that a catalyst consisting of copper on rice husk ash (>99% SiO2) showed 80% initial ethanol conversion and the catalyst deactivation after 3 h due to Cu sintering at 300 °C under ambient pressure. 9 In the paper of [9], they quoted previous papers10-12 that the acetaldehyde selectivity can be assumed to be 100% at a temperature below 300 °C and the dehydration reaction is considered negligible at lower



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temperature. On the other hand, it was reported that the acetaldehyde selectivity was not 100% over Cu/SiO2 even at low temperatures.13-14 Thus, it seems to be difficult to obtain 100% acetaldehyde selectively over Cu/SiO 2 at low temperatures. Furthermore, Chang et al. reported that the addition of Cr 2O3 increased the Cu0 surface area, improved the catalytic activity, and prevented the sintering of the Cu, resulting in a catalyst that showed little decline in activity after 6 h.15 Their results showed it is important to increase the amount of surface Cu0 for high catalytic activity. Some studies have been done on non-chromium copper catalysts. Freitas et al. studied the behavior of Cu/ZrO2 in ethanol conversion.2 They investigated the effect of copper content on ethyl acetate and acetaldehyde selectivity under ambient pressure. In their study on ethyl acetate production from ethanol, Inui et al. reported 51% ethanol conversion and 93% ethyl acetate selectivity over a Cu-Zn-Zr-Al-O catalyst in reaction conditions of 150 °C and 0.8 MPa. They also showed the possible reaction routes of various compounds.16 In the dehydrogenation of bioethanol into acetaldehyde, copper/graphite and copper/graphene catalysts showed 98%–100% selectivity and 3 h stability at 250 °C using a feed either of pure ethanol or one that contained water.17 Copper chromite catalysts contain Cr 3+ in Cr2O3, not the toxic hexavalent Cr6+. But there is always a risk that Cr6+ could form during the industrial production, industrial use, and disposal of chromite catalysts. Thus, anticipation is high for non-chromium copper catalysts. Calcium silicate is a porous material having a surface area of 100–130 m2/g. It has been used as a liquid absorber 18, or a floating carrier. 19 Calcium silicate ceramics have been


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synthesized for biomedical applications 20, and spray-dried microparticles have been prepared for drug delivery.21 Calcium silicate has also shown promise as a catalyst support. Calcium is added to silica to reduce the acidity of the catalyst and to improve the formability and strength of the catalyst. 22,23 Moreover, the use of calcium silicate should translate to improved Cu dispersion, since it is difficult to disperse Cu on silica.24,25 Acetaldehyde selectivity in ethanol dehydrogenation over Cu/SiO 2 is not always reported to be 100%. 13,14 The addition of calcium is expected to lead to an increase in the selectivity. In this paper, we report the development of eco-friendly non-chromium catalysts consisting of copper and calcium silicate. We focused our efforts on the following: (1) determining suitable compositions for copper calcium silicate catalysts, (2) determining optimal reaction conditions, (3) confirming catalyst durability, and (4) proposing a process flow for industrial production.

2. Experimental 2.1. Catalyst preparation Aqueous solutions of copper nitrate trihydrate (Wako Pure Chemicals Co., Ltd., Japan) and sodium hydroxide (Wako Pure Chemicals Co., Ltd., Japan) were prepared. The copper nitrate solution was dripped into the sodium hydroxide solution at 80 oC while stirring. The precipitate was filtered and washed with ion exchanged water. The washed precipitate was repulped using water, and calcium silicate (2CaO-xSiO2-yH2O, x: 4-5, y: 2-3, Trade name: FLORITE R, Tomita Pharmaceutical Co., Ltd., Japan) was added. 26, 27 The filtered solid was dried overnight at 120 oC and extruded, then cut into cylinders. Before the catalysts were



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prepared, the cylinders were calcined at 450 °C for 5 h. A conventional copper chromite catalyst (BASF Cu0203T) was used for comparison.

2.2. Catalytic activity test Commercially available ethanol (Junsei Chemical Co Ltd., Japan, Purity: 99.5%) was mixed with ion exchanged water and used as a feed. The mixing ratio of ethanol/water was 96/4 w/w. The catalysts were pretreated with hydrogen before the reactions as follows. About 2 g of the catalyst was loaded into a tubular flow reactor. With the catalyst bed heated to 120 °C, 1000 mL/min of nitrogen and 10 mL/min of hydrogen were introduced into the reactor. After that, the catalyst bed temperature was kept at 150 °C for 90 min. To complete the pretreatment, 400 mL/min of nitrogen and 100 mL/min of hydrogen were introduced and fed for 20 minutes as the catalyst bed was held at 200 °C. The ethanol/water feed was preheated at 200 °C and introduced into the tubular flow reactor in the gas phase without a carrier gas. The reaction was carried out at 225–330 °C under ambient pressure. The weight hourly space velocity (WHSV) of ethanol in the feed was 7–37 h-1. The reaction conditions were varied by changing the WHSV and reaction temperature. The catalyst durability test was conducted in the same way. All products (liquid and gas) were collected in a gas bag in a tank filled with dry ice and methanol. The liquid was analyzed by GC-FID and the gas volume was measured. The material balance calculated from the difference in weight before the reaction and after was between 98% and 100%. The liquid product analysis was carried out on an Agilent


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Technologies GC6850 gas chromatograph equipped with an Agilent 19091Z-436E HP-1 methyl siloxane capillary column (60.0 m long, 0.25 mm i.d. and 0.25 µm film) and a flame ionization detector (FID). A calibration plot for each product was constructed from commercially available standards. Moreover, the reaction products were confirmed by GC-MS. Ethanol conversion (mol%) and acetaldehyde selectivity (mol%) were determined using the following formulas. Ethanol conversion = {1 - (remaining ethanol / ethanol in feed)} x 100 Acetaldehyde selectivity = (acetaldehyde yield / ethanol conversion) x 100 (Acetaldehyde yield = (acetaldehyde produced / ethanol in feed) x 100)

Considering the reproducibility, the conversion was indicated by two digits and the selectivity was expressed as one decimal.

2.3. Characterization The chemical compositions of the catalysts were measured by X-ray fluorescence (XRF) (ZSX Primus II, Rigaku Corporation). The surface areas and pore volumes of the catalysts were determined by nitrogen adsorption (BELSORP mini, BEL Japan Inc.). The acidic properties of the catalysts before reduction were studied using temperature-programmed desorption of ammonia (NH 3-TPD, BEL-CAT, MicrotracBEL Corporation). The number of surface copper atoms was determined by the amount of N 2 generated by the reaction between N2O and Cu (2Cu + N2O --> Cu2O + N2). To do this, around 0.15 g of



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catalyst was packed into an Inconel 600 tube (i.d. 8 mm) and reduced, after which N 2O was supplied at 90 °C by the pulse technique and the N 2 generated was measured using GC. During the reduction, the temperature was maintained at 150 °C for 90 min., then raised to 200 °C by 10 °C/min and held there for 20 min. under hydrogen flow.

3. Results and Discussion 3.1. Catalytic activity of copper calcium silicate catalysts in dehydrogenation of ethanol The chemical compositions, surface areas, pore volumes, amounts of adsorbed ammonia, and amounts of surface Cu 0 of four different catalysts (CAT-1, 2, 3, and 4) are shown in Table 1. The amounts of copper oxide ranged from 17 wt% (CAT-1) to 55 wt% (CAT-4). There was little difference in the surface areas and pore volumes among the four catalysts. The amounts of ammonia adsorbed were the same for CAT-2, 3, and 4, at 0.13 mmol/g-cat, while that for CAT-1 was 0.24 mmol/g-cat, suggesting that CAT-1 had a greater number of acid sites. The amount of surface Cu 0 increased with increasing CuO content, suggesting the amount of surface Cu0 was determined by the amount of CuO used in the preparation of the catalysts (Figure S1 of Supporting information). Table 2 shows the performance of CAT-1 & CAT-2 and the composition of the reaction products (WHSV =20 h-1). With CAT-1, ethanol conversion increased from 22% to 66% as the reaction temperature increased, while acetaldehyde selectivity decreased from 91.8% to 86.6%. With CAT-2, ethanol conversion increased from 26% to 76% as the reaction temperature increased, while acetaldehyde selectivity decreased from 94.0% to 91.6%.


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Under all reaction conditions, increase of the effluent gas was almost equal to the volume of the formed hydrogen calculated from the product selectivity. The possible formation routes of the detected by-products are shown in Figure 1. The by-products can be broadly divided into three categories: ethers formed by intermolecular condensation of alcohols, acetaldol derivatives formed through the aldol reaction of acetaldehyde, and hemiacetal derivatives formed through the reaction between ethanol and acetaldehyde.16,28 The formation of the three kinds of by-products is promoted by acid sites in the catalysts. The ethers in Table 2 are the totals of diethyl ether and ethyl vinyl ether. Ether selectivity decreased as the reaction temperature increased, suggesting that higher reaction temperatures are preferable for avoiding ether formation. This may be because, at higher temperatures, ethanol conversion increases and ethanol partial pressure decreases, which helps prevent condensation of the ethanol. With both CAT-1 and CAT-2, ethyl acetate selectivity increased with reaction temperature, suggesting that lower reaction temperatures are preferable for avoiding ethyl acetate formation. It is thought that the acetaldehyde partial pressure increased as the temperature rose, promoting the reaction between acetaldehyde and ethanol. 1-Butanal, 2-butanone, 2-butanol, crotonaldehyde, and crotyl alcohol are acetaldol derivatives formed from acetaldehyde through the aldol reaction. It has been reported that 2-butanone and 2-butanol are formed through the dehydrogenation and hydrogenation of acetaldol, as shown in Figure 1.16 The total acetaldol derivatives (Table 2) also increased,



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from 2.0% to 6.6% with CAT-1 and from 1.1% to 3.7% with CAT-2, as the reaction temperature increased. It is thought that an increase in the acetaldehyde partial pressure accelerated the reaction between acetaldehyde molecules, which led to increased production of acetaldol derivatives. In Table 2, "Other" means the totals of heavy by-products and unidentified compounds. Comparing the ethanol conversion results for CAT-1 and CAT-2 (Table 2), we found that CAT-2 had higher activity than CAT-1. The amount of CuO in CAT-2 is 40 wt%, compared to 17 wt% in CAT-1, and CAT-2 has a greater number of Cu 0 atoms at the surface (Table 1). Together, these factors likely explain the higher activity of CAT-2. CAT-2 also showed better acetaldehyde selectivity than CAT-1. Comparing the by-product selectivity of CAT-1 and CAT-2, CAT-2 showed lower selectivity for ethers, ethyl acetate, and acetaldol derivatives than CAT-1 at all reaction temperatures between 250 and 330 oC (Table 2). The formation of ethers, ethyl acetate, and acetaldol derivatives is promoted by the acid sites of the catalysts. The amounts of adsorbed NH 3 for CAT-1, CAT-2, and the catalyst support (calcium silicate) were 0.24, 0.13, and 0.28 mmol/g (Table 1), respectively. This suggested that the acid sites on the catalysts are found primarily in the catalyst support. Since CAT-1 has more acid sites than CAT-2 (Table 1), it showed higher selectivity for by-products. This could explain why CAT-2 showed higher acetaldehyde selectivity than CAT-1. It was thus found that, for acetaldehyde production, CAT-2 is preferable to CAT-1. Next, we looked at catalysts having larger amounts of CuO. Figure 2 shows the catalytic performance at WHSV = 25 h -1 for ethanol dehydrogenation of CAT-2 (CuO: 40 wt%), CAT-3 (CuO: 47 wt%), and CAT-4 (CuO: 55 wt%) along with their product compositions


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(Table S1 of Supporting Information). With CAT-2, CAT-3, and CAT-4, ethanol conversion increased with the reaction temperature, while acetaldehyde selectivity decreased. In the reactions at 260 °C, ethanol conversion was 34% with CAT-2, 41% with CAT-3, and 44% with CAT-4, which can be explained by the increasing amounts of CuO and surface Cu 0 (Table 1). Equilibrium conversion of this reaction at 260 °C is calculated to be about 60%. It is suggested that the equilibrium conversion causes the small difference between CAT-3 and CAT-4 in ethanol conversion. NH3 adsorption was the same for the three catalysts, at 0.13 mmol/g (Table 1), while acetaldehyde selectivity was high at 93%–95%. Little difference was found among the three catalysts (Table S1 of Supporting Information).

3.2

Achieving both high conversion and high selectivity

A reaction temperature of 230–240 oC and WHSV of ethanol = 25 h -1 resulted in high acetaldehyde selectivity of 93%–95% (Table 2). On the other hand, ethanol conversion was around 20%, which is not high enough for industrial production. In industrial production, when ethanol conversion is low, the amount of ethanol recycled increases, which leads to higher costs. Therefore, from a cost perspective, ethanol conversion should be at least 40%. With this in mind, we studied reactions at high temperature and high WHSV, with the aim of improving ethanol conversion and maintaining high acetaldehyde selectivity simultaneously. Figure 3 shows the catalytic performance CAT-2, CAT-3, and CAT-4 for ethanol dehydrogenation at WHSV = 37 h -1, along with their product compositions in Table S2 of



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Supporting information. It was found that the ethanol conversion with the three catalysts was improved by increasing the reaction temperature to 270–290 °C, while high acetaldehyde selectivity was maintained. This suggested that the high WHSV helped inhibit formation of hemiacetal and acetaldol derivatives, compared with the result of Figure 2, while the high temperature helped inhibit formation of diethyl ether (Table S2 of Supporting information). For CAT-2, XRD measurement was carried out on samples after reduction at 200 °C and after dehydrogenation at 270 °C for 5 h. As a result, there was almost no change in the XRD patterns and Cu crystallite diameter was maintained at about 7 nm (Figure S2 of Supporting information). A catalyst durability test was performed with CAT-2, which showed the highest acetaldehyde selectivity (95%) in these reaction conditions. The result is shown in Figure 4. Ethanol conversion of 40% and acetaldehyde selectivity of 95% were maintained during 20 h of time-on-stream, and no catalyst deterioration was observed. Our results showed that by using a copper calcium silicate catalyst with a CuO content of 40% or higher (CAT-2, CAT-3, and CAT-4), and by optimizing the reaction conditions (high temperature and WHSV), high ethanol conversion and high acetaldehyde selectivity could be achieved simultaneously.

3.3 Comparison with a commercial copper chromite catalyst Over a commercial copper chromite catalyst (BASF Cu0203T) containing Cu (60 wt%) and Cr (10 wt%) (its property is shown in Table 1), the catalytic performance for ethanol


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dehydrogenation in various reaction conditions was studied. The results are shown in Figure 5. Ethanol conversion ranged from 27% to 73% while acetaldehyde selectivity ranged from 86% to 92% at reaction temperatures between 225° and 350

o

C. The

commercial copper chromite catalyst performed similarly to CAT-2, CAT-3, and CAT-4, in that a high reaction temperature and high WHSV were preferable for high ethanol conversion and high acetaldehyde selectivity. Ethanol conversion of 42% and acetaldehyde selectivity of 92.2% were achieved at 330 oC and WHSV = 14 h-1 (Table S3 of Supporting information). These results were similar to those for CAT-2 (Figure 3). An advantage of the copper calcium silicate catalyst is that it can be used at temperatures lower and WHSVs higher than the commercial copper chromite catalyst. The reason is thought to be that the commercial copper chromite (produced by tableting) has a low surface area of 7 m2/g and low pore volume of 0.14 mL/g, while our copper calcium silicates (extruded) have higher surface areas (82–98 m2/g) and pore volumes (0.48–0.65 mL/g) as shown in Table 1. In total, the results indicate that copper calcium silicate catalysts could be used as an eco-friendly substitute for copper chromite catalysts.

3.4 Process flow design On the basis of the results of this study, we present a process flow for industrial acetaldehyde production in Figure 6. Ethanol containing 4 wt% of water was used as the feed in this study. For industrial production, using water-containing ethanol is preferable to anhydrous ethanol from a cost standpoint.



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In Figure 6, a feed of water-containing ethanol (ethanol/water =96/4 w/w) is preheated and supplied to a catalyst-packed reactor. After dehydrogenation, all products including the feed are cooled and sent to distillation column A, where acetaldehyde and hydrogen are separated from the others. Next, the acetaldehyde (Bp. 20 oC) and hydrogen are separated in cooling column B. The residues in column A are transferred to distillation column C, where the unreacted ethanol and light by-products are removed. These light by-products include diethyl ether (Bp. 35 oC), ethyl vinyl ether (Bp. 36 oC), ethyl acetate (Bp. 77 oC), and other unidentified light fractions. Unreacted ethanol is separated from the light by-products in distillation column D and recycled to the reactor. The residues in column C are water and heavy by-products. The heavy by-products include 1-butanal (Bp. 85 oC), 2-butanone (Bp. 80 oC), 2-butanol (Bp. 99 oC), crotonaldehyde (Bp. 104 oC), crotyl alcohol (Bp. 121 oC), and other unidentified heavy fractions. Since the boiling points of ethyl acetate and 2-butanone are close to that of ethanol, it is difficult to separate them by distillation in column C and D. The number of theoretical plates in the distillation columns will have to be optimized, taking into account the required product purity and the extent to which by-products accumulate in the recycled ethanol. An advantage of this process is that the coproduced hydrogen could be utilized for catalyst pretreatment or other processes.

4. Conclusions A non-chromium catalyst consisting of copper and calcium silicate was prepared from commercially available precursors. It was found that this catalyst could be used as an


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eco-friendly substitute for conventional copper chromium catalysts. Catalytic activity tests and catalyst characterization indicate that the catalyst should have a CuO content of 40 wt% or higher, and it was found that high reaction temperatures and a high WHSV are preferable for achieving both high conversion and selectivity. With this catalyst, catalyst durability of 20 h, ethanol conversion of 40%, and acetaldehyde selectivity of 95% were achieved simultaneously.

AUTHOR INFORMATION Corresponding author *E-mail: [email protected] (M. Okamoto)

ORCID Masaki Okamoto: 0000-0001-8532-8096

Notes The authors declare no competing financial interest.

Supporting information Supporting data associated with this article can be found, in the online version, at http://



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(28) Gines, M. J. L.; Iglesia, E. Bifunctional Condensation Reactions of Alcohols on Basic Oxides Modiﬁed by Copper and Potassium. J. Catal. 1998, 176, 155.



Page 20 of 36

Table 1. Properties of catalysts Surface area Pore volume NH3 adsorption Surface Cu0 m2/g mL/g μmol/g mmol/g

Entry

Chemical composition wt% CuO CaO SiO2

CAT-1

17

24

59

98

0.65

0.24

80

CAT-2

40

17

43

82

0.50

0.13

149

CAT-3

47

15

38

86

0.48

0.13

n.d.

CAT-4

55

12

33

88

0.48

0.13

232

7

0.14

n.d.

n.d.

Commecial

CuCr-Cat

60 wt% Cu - 10 wt% Cr 1)

1) BASF Cu0203T, the information from web

Table 2. Catalytic performance for ethanol dehydrogenation (WHSV = 20 h -1) Entry

CAT-1

CAT-2

Temp. Ethanol oC conv. %

By-product selectivity Cmol%

Acetaldehyde selectivity Cmol%

Ethers

Ethyl 1-Butanal acetate

2-Butanone

2-Butanol Crotonaldehyde

Crotyl alcohol

Other

250

22

91.8

1.7

3.0

0.4

1.0

0.1

0.0

0.5

1.4

280

41

90.7

0.9

3.9

1.0

1.7

0.2

0.3

0.9

0.4

330

66

86.6

0.6

5.5

2.4

2.1

0.2

0.8

1.1

0.8

250

26

94.0

1.2

2.1

0.3

0.6

0.0

0.0

0.2

1.6

285

56

94.1

0.5

2.1

0.9

0.7

0.0

0.4

0.4

1.0

325

76

91.6

0.4

2.8

2.4

0.7

0.0

0.5

0.1

1.5


Page 21 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Ethanol

O

OH

-H2O

Ethyl vinyl ether -H2

O

OH Ethanol

Ethanol

Acetaldehyde

Ethanol -H2O

OH

O

-H2

O

O

Hemiacetal

Ethyl acetate

Acetaldehyde -H2

O

HO O Acetaldol

Diethyl ether

+H2

O

OH -H2O +H2

-H2O

OH

Crotyl alcohol

O

+H2

Crotonaldehyde +H2

O 2-Butanone +H2

O OH

2-Butanol

1-Butanal Figure 1. Possible by-product formation routes over copper & calcium silicate catalysts



100 90 80 70 60 50 40 30 20 10 0

Conv. & Sel., %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 36

Ethanol conv.

Acetaldehyde sel.

CAT-2

CAT-3

CAT-4

Figure 2. Catalytic performance for ethanol dehydrogenation (260 oC, WHSV = 25 h-1)


Page 23 of 36

100 90 80 70 60 50 40 30 20 10 0

Conv. & Sel., %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Ethanol conv.

Acetaldehyde sel.

CAT-2

CAT-3

CAT-4

Figure 3. Catalytic performance for ethanol dehydrogenation (WHSV = 37 h -1) (Reaction temp. CAT-2: 270, CAT-3: 280, CAT-4: 290 oC)


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Conv. & Sel., %


100 90 80 70 60 50 40 30 20 10 0

Page 24 of 36

● Ethanol conv. ■ Acetaldehyde sel.

0

5

10

15

Time on stream, h Figure 4. Durability test over CAT-2 (Reaction temp.: 270 oC, WHSV= 37 h-1)


20

25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Conv. & Sel., %

Page 25 of 36

100 90 80 70 60 50 40 30 20 10 0

Ethanol conv.

Acetaldehyde sel.

225℃, 11 260℃, 11 330℃, 14 (Reaction temp., WHSV h-1)

350℃, 7

Figure 5. Catalytic performance over a commercial CuCr catalyst for ethanol dehydrogenation



Page 26 of 36

Recycled ethanol Ethanol/Water = 96/4 w/w

Reactor Acetaldehyde Diethyl ether Ethyl vinyl ether Ethyl acetate Ethanol 2-Butanone 1-Butanal 2-Butanol Crotonaldehyde Crotyl alcohol

Bp. oC 20 35 36 77 78 80 85 99 104 121

Hydrogen Acetaldehyde + H2

B

A Acetaldehyde Ethanol + Water + By-products

Light by-products D

C Water Heavy by-products

Figure 6. Process flow scheme for acetaldehyde production


Page 27 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure captions and tables

Figure 1.

Possible by-product formation routes over copper & calcium silicate catalysts

Figure 2.

Catalytic performance for ethanol dehydrogenation (260 oC, WHSV = 25 h-1)

Figure 3.

Catalytic performance for ethanol dehydrogenation (WHSV = 37 h -1) (Reaction temp.

Figure 4.

CAT-2: 270, CAT-3: 280, CAT-4: 290 oC)

Durability test over CAT-2 (Reaction temp.: 270 oC, WHSV= 37 h-1)

Figure 5.

Catalytic performance over a commercial CuCr catalyst for ethanol

dehydrogenation

Figure 6.

Process flow scheme for acetaldehyde production

Table 1.

Properties of catalysts

Table 2.

Catalytic performance for ethanol dehydrogenation (WHSV = 20 h -1)



The TOC graphic


Page 28 of 36

Page 29 of 36 1 2 3 4 5 6 7 8 Entry 9 10 11CAT-1 12 13 CAT-2 14 15 16CAT-3 17 18 19CAT-4 20 21Commecial 22 CuCr-Cat 23 24 25 1) 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41


Table 1. Properties of catalysts Chemical composition wt% CuO CaO SiO2

Surface area Pore volume NH3 adsorption Surface Cu0 m2/g mL/g μmol/g mmol/g

17

24

59

98

0.65

0.24

80

40

17

43

82

0.50

0.13

149

47

15

38

86

0.48

0.13

n.d.

55

12

33

88

0.48

0.13

232

7

0.14

n.d.

n.d.

60 wt% Cu - 10 wt% Cr 1) BASF Cu0203T, the information from web

ACS Paragon Plus Environment


Page 30 of 36

Table 2. Catalytic performance for ethanol dehydrogenation (WHSV = 20 h-1) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

Entry

CAT-1

CAT-2

Temp. Ethanol oC conv. %

By-product selectivity Cmol%

Acetaldehyde selectivity Cmol%

Ethers

Ethyl 1-Butanal acetate

2-Butanone

2-Butanol

Crotonaldehyde

Crotyl alcohol

Other

250

22

91.8

1.7

3.0

0.4

1.0

0.1

0.0

0.5

1.4

280

41

90.7

0.9

3.9

1.0

1.7

0.2

0.3

0.9

0.4

330

66

86.6

0.6

5.5

2.4

2.1

0.2

0.8

1.1

0.8

250

26

94.0

1.2

2.1

0.3

0.6

0.0

0.0

0.2

1.6

285

56

94.1

0.5

2.1

0.9

0.7

0.0

0.4

0.4

1.0

325

76

91.6

0.4

2.8

2.4

0.7

0.0

0.5

0.1

1.5


Page 31 of 36 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41


Ethanol

O

OH

-H2O

Ethyl vinyl ether -H2

O

OH Ethanol

Ethanol

Acetaldehyde

Ethanol -H2O

OH

O

-H2

O

O

Hemiacetal

Ethyl acetate

Acetaldehyde -H2

O

HO O Acetaldol

Diethyl ether

+H2

O

OH -H2O +H2

-H2O

OH

Crotyl alcohol

O

+H2

Crotonaldehyde +H2

O 2-Butanone +H2

O OH

2-Butanol 1-Butanal ACS Paragon Plus Environment Figure 1. Possible by-product formation routes over copper & calcium silicate catalysts


100 90 80 70 60 50 40 30 20 10 0

Conv. & Sel., %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

Page 32 of 36

Ethanol conv.

Acetaldehyde sel.

CAT-2

CAT-3

CAT-4

Figure 2. Catalytic performance for ethanol dehydrogenation (260 oC, WHSV = 25 h-1) ACS Paragon Plus Environment

Page 33 of 36

100 90 80 70 60 50 40 30 20 10 0

Conv. & Sel., %

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41


Ethanol conv.

Acetaldehyde sel.

CAT-2

CAT-3

CAT-4

Figure 3. Catalytic performance for ethanol dehydrogenation (WHSV = 37 h-1) (Reaction temp. CAT-2: 270, CAT-3: 280, CAT-4: 290 oC) ACS Paragon Plus Environment

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

Conv. & Sel., %


100 90 80 70 60 50 40 30 20 10 0

Page 34 of 36

● Ethanol conv. ■ Acetaldehyde sel.

0

5

10

15

Time on stream, h Figure 4. Durability test over CAT-2 (Reaction temp.: 270 oC, WHSV= 37 h-1) ACS Paragon Plus Environment

20

25

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41


Conv. & Sel., %

Page 35 of 36

100 90 80 70 60 50 40 30 20 10 0

Ethanol conv.

Acetaldehyde sel.

225℃, 11 260℃, 11 330℃, 14 (Reaction temp., WHSV h-1)

350℃, 7

Figure 5. Catalytic performance over a commercial CuCr catalyst for ethanol dehydrogenation


Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41

Page 36 of 36

Recycled ethanol Ethanol/Water = 96/4 w/w

Reactor Acetaldehyde Diethyl ether Ethyl vinyl ether Ethyl acetate Ethanol 2-Butanone 1-Butanal 2-Butanol Crotonaldehyde Crotyl alcohol

Bp. oC 20 35 36 77 78 80 85 99 104 121

Hydrogen Acetaldehyde + H2

B

A

Acetaldehyde Ethanol + Water + By-products

Light by-products D

C Water Heavy by-products

Figure 6. Process flow scheme for acetaldehyde production ACS Paragon Plus Environment

Acetaldehyde Production from Ethanol by Eco-Friendly non-Chromium

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