Electrochemical membrane reactor modelling for lignin

Subscriber access provided by University of Rhode Island | University Libraries

Article

Electrochemical membrane reactor modelling for lignin depolymerization Bander Bawareth, Davide Di Marino, T. Alexander Nijhuis, Tim Jestel, and Matthias Wessling ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b04670 • Publication Date (Web): 03 Dec 2018 Downloaded from http://pubs.acs.org on December 4, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 45 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

ACS Sustainable Chemistry & Engineering

Electrochemical membrane reactor modelling for lignin depolymerization Bander Bawareth,†,‡ Davide Di Marino,¶,‡ T. Alexander Nijhuis,† Tim Jestel,§ and Matthias Wessling∗,¶,‡ †SABIC-Glycols, Oxygenates and Functional Chemicals, 11551 Riyadh, Saudi Arabia. ‡AVT.CVT, Forckenbeckstr. 51, 52074 Aachen, Germany. ¶DWI - Leibniz Institute for Interactive Materials, Forckenbeckstr. 50, 52074 Aachen, Germany. §AVT.EPT, Forckenbeckstr. 51, 52074 Aachen, Germany. E-mail: [email protected] Phone: +49 241 80 95488. Fax: +49 241 80 92252

Abstract Valorization of lignin into value-added chemicals becomes an interesting research topic for sustainable and renewable product formation. A conceptual study of lignin valorization through an electrochemical membrane reactor process is presented. The membrane reactor model is able to predict a larger aromatic product formation yield because the product is permeating out before it degrades. Different process parameters were examined, in an electrochemical membrane reactor process, via sensitivity analysis. Through the analysis, the objective was to manipulate the process parameters in order to maximize the aromatics production yield. These parameters are considering the membrane characteristics, in terms of membrane pore diameter and area, and process parameters, in terms of trans-membrane pressure and reaction residence time. The

1

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 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

sensitivity study revealed that a membrane with a molecular weight cut-off (MWCO) of 750 Da and pore diameter of 1 nm is an optimum nano-filtration membrane for a continuous tubular membrane reactor. The aromatic product yield could be increased from 0.01%, in the batch reactor, to 11%, in the membrane reactor. Diluted lignin concentration was found to be a process drawback with regard to the product recovery from the permeate.

Keywords polymer degradation, kinetic modelling, over-oxidation; sensitivity analysis, organic acid, aromatic products, random scission, chain-end scission.

Introduction Lignocellulosic material is a very important alternative source to fulfill the increment in the global energy demand. Biorefinery is the process to convert biomass content into biofuels, such as bioethanol. The biorefinery can be economically feasible if high value chemicals are produced along with the low value but necessary fuels. 1 The US Department of Energy has proposed an ambitious target that 25% of the chemical products should be produced from lignocellulose by 2030 that is accompanied by 20% of biofuels production. 2 Similarly, the European lignocellulosic ethanol production is expected to be increased from 31 million L in 2017 to 2.75 billion L in 2030 in 56 plants, as shown in Figure 1a. 3 However, about 40% of the lignin, extracted from the biorefineries, is burned to meet these plants energy requirement. The potential aim to start up new biorefineries is restricted by the low economical value of these plants. Therefore, to achieve these goals, the economic value of these biorefineries has to be increased by utilizing lignin in downstream added value products. For aromatic feedstocks, lignin has the highest abundance of aromatic content in nature. It is a heterogeneous and amorphous polymer which decomposes to three different monomers 2


Page 2 of 45

Page 3 of 45 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


connected by C−C or β−ether bonds. These basic monomers are guaiacyl (C10 H12 O3 ), syringyl (C11 H14 O4 ) and p-hydroxyphenol (C9 H10 O2 ). 4,5 The concentration of each monomer varies depending on lignins source to another. Due to this heterogeneity, it is challenging to find a commercial and selective process to generate a high yield of a certain aromatic product. One of these valuable products is vanillin which is produced with an annual production of 20 ktons worldwide. Vanillin is conventionally produced by the condensation of the glyoxylic acid into guaiacol which is then oxidized to synthetic vanillin. 6 The vanillin is used mainly as an aroma ingredient in the food and cosmetics products. 3000 tons yr−1 of bio-based vanillin is produced from lignin and 50 tons yr−1 from vanilla orchid. However, it costs 10 times higher than the petrochemical-based vanillin. 7,8 Despite the high value of the vanillin, its demand is limited compared with the abundance of lignin and high demand on other aromatics products that can be produced from lignin, as presented in Figure 1b. 9–11 Aromatics, especially BTX (benzene, toluene and xylene) and phenol, are important building blocks in the petrochemical industry and are used as raw materials for producing a wide range of products, such as solvents, plastics, nylon and polystyrene. The global market of BTX and phenol are 103 and 10 million tons yr−1 , respectively. 12,13 Depolymerization processes of lignin, such as thermal, photochemical and oxidation, are energy extensive processes. 18 However, electro-oxidation is a low energy process that takes place at ambient conditions. Yet, it lacks the selective formation of aromatic products, which is usually degraded in the reaction environment. Due to the over-oxidation, lignin and the cleaved aromatic products are degraded to organic acids, CO2 and water. 19 The selectivity of the reaction can be enhanced by an optimized reactor design. In order to design an electrochemical reactor properly, electrodes material, solvent, reactants concentration and reactor geometry have to be investigated simultaneously. The proper design should be able to obtain commercial valuable products out of lignin. 20–22 One of the main process design aspects, needs to be focused on, is the in situ product separation from

3



70

12000

[a]

60

8000

20 0.5

0.0 0 2016

2019

2022

2025

2028

1500 1000 500

Kraft

BTX

-1

10

Guaiacol

Acetic Acid

lignin

Energy

1.0

Eugenol

Phenol

30

4000

Ligno-

40

1.5

Number of Plants

50

Market Price [$ ton ]

# of plants

2.0

Vanillin

sulfonates

2.5

[b]

lignin

Production capacity

High grade

3.0

-1 Production Capacity [BL yr ]

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 4 of 45

101 102 103 104 105 106 107 108

2031

-1

Year [yr]

Global Demand [ton yr ]

Figure 1: a) Potential production of lignocellulosic ethanol in Europe (left) and number of biorefinery plants to 2030 (right). b) Market price vs. global demand for lignin based products. 14–17 electrochemical reaction environment by using a membrane reactor. 23–25 A membrane reactor can selectively remove the products of lignin depolymerization. Therefore, an over-oxidation of the desired product is minimized and a higher product yield could be achieved. 26,27 Zabkova et al. has investigated the integration of an ultrafiltration membrane in a second stage after a bubble column reactor. The lignin is oxidized in alkaline solution at 160 ◦ C and 10 bar with maximum vanillin yield of 3%. The vanillin product is separated by ultrafiltration membrane followed by cation exchange resin to remove the product from the alkaline solution. However, there was no discussion on the advantage of using the membrane within the reactor to avoid over-oxidation of the product. 28,29 The electrochemical membrane reactor (EMR) is an attractive concept that can guide many sustainable processes to commercial applications. The most popular example is the membrane cell for chlor-alkali electrolysis process to produce sodium hydroxide, chlorine and hydrogen from brine. 30,31 Another emerging application is the treatment of metalcontaminated wastewater through an EMR. 32,33 The wastewater from pulp and paper indus-

4


Page 5 of 45 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


try, which contains lignin, suspended and dissolved solids can be treated electrochemically via complete oxidation of the organics to CO2 and water. Utilizing T i/RuO2 as an anode, the organic matter was reduced from 120,000 mg L−1 to 90 mg L−1 which matches the wastewater effluent requirements. 34 Furthermore, the EMR can be used to generate high value chemicals such as formate from carbon dioxide reduction, quaternary ammonium hydroxide from its halide and aromatic products out of lignin. 35–37 Similarly, glucose can be produced from electrochemical depolymerization of cotton cellulose which has to be hydrothermally pretreated under acidic condition. 38,39 In our previous work, we successfully modelled the depolymerization of lignin in an electrochemical batch reactor. 40 In the batch reactor, over-oxidation of the desired aromatic products is found to be disadvantageous, as presented in this work. Therefore, the objective of this paper is to estimate the optimum process parameters and membrane characteristics for an in situ EMR providing that the maximum aromatic product yield is achieved. We can get knowledge from the model to enhance future experimental set up in order to avoid over-oxidation and increase the aromatic yield.

Materials and Methods Product degradation Model compound degradation experiments were conducted by dissolving 250 mg L−1 of vanillin or vanillic acid in 0.2 L of 1 M NaOH water solution. The solution was pumped through a swiss-roll electrochemical reactor equipped with nickel foam electrodes. The electrodes were hosted in an acrylic glass tube which has length of 15 cm and inner diameter of 1.2 cm. A more detailed description of the reactor system can be found in Bawareth et al. 40 Voltage applied was 2.5 and 3.5V over 120 min with a flow rate of 50 ml min−1 . Samples were taken after 10, 20, 30, 40, 60, 80, 100 and 120 min. The concentration of vanillin and vanillic acid as well as the identification and quantification of the degradation products were 5



conducted by means of LC-ToF-MS. 41

Degradation kinetics The kinetics of the reactor was detailed in the work done by our group where the model developed for a batch electrochemical reaction. 40 The depolymerization mechanisms were lumped into two basic reactions, as follows: • Random degradation/recombination: K

R (i) A(x0 ) ←−→ A(x) + A(x0 − x)

Kr

• Specific degradation (chain-end Scission): K

(ii) A(x0 ) −−CE −→ A(xi ) + A(x0 − xi ) where xi is the molecular weight (MW) of an aromatic product A(xi ) that is detached from a polymer A(x0 ) with a MW of x0 . The rate coefficient for degradation of A(x0 ) are KR (x0 ) in the random scission and KCE (x0 ) in the chain-end scission. Kr is the random recombination rate coefficient. A(x) is an unspecific polymer that is cleaved from A(x0 ) and has x MW. For high MW polymer, degree of polymerization (DP) is used instead of MW which is the ratio of MW for each molecule to its monomer. 42,43 The degradation of lignin can produce a wide product spectrum; starting from aromatics such as vanillin and phenol to a different variation of organic acids, CO2 and water. 26 These products are difficult to quantify due to analytical limitations and the continued product degradation in the batch reactor. Therefore, aromatic products, represented by vanillin and vanillic acid, degradation rate are monitored in the same reaction condition of the lignin electrochemical depolymerization set up. Vanillin has phenolic and aldehydic function groups, hence it is subjected to many types of reaction. Additional to its capability in converting to other aromatics, vanillin could be subjected to aromatic ring opening to form organic acids. 19,44,45 The aromatic product A(xi ) degradation is considered to be as follows:

6


Page 6 of 45

Page 7 of 45 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


• Product A(xi ) degradation to organic acids (OA): K

(iii) A(xi ) −−D→ OA + CO2 + H2 O where KD is the product degradation rate constant. The degradation reaction does not consider the electrochemical water splitting for the electrolyte which provides the oxidizing agent, as indirect oxidation. In the indirect oxidation, the oxidation takes place via oxygen transfer and/or via activated oxygen, such as hydroxyl radical and hydrogen peroxide. In addition, the organic components can be oxidized via electron transfer directly on the electrode surface. 20,46 Considering all of these mechanisms will increase the models complexity, especially due to the lack of data about these mechanisms. In the results from Di Marino et al, mainly three organic acids are found, in the lignin electrochemical depolymerization, with a total yield of 25%, after 420 min of reaction time. These acids are listed in Table 1. The other acids, malonic, succinic and malic acids, are present in a very low yield. For simplicity, the organic acids are lumped in one organic acid (OA) component with weight average MW of 69 g mol−1 . The rate constant is calculated based on the slope of the first order vanillin and vanillic acid degradation rate. Table 1: Yields for the identified products coming from the lignin electrochemical depolymerization at 3.5 V and after 420 min of reaction time. Organic acid MW [ g mol−1 ] Yield [%] Oxalic acid

90

10.26

Formic acid

46

9.10

Acetic acid

60

4.10

Other acids

avg. 118.8

0.85

152

0.01

Vanillin

The aromatic product degradation rate and products formation rate become as follows: dA(xi , t) = dt

∞

Z

KCE (x0 )n(x0 , t)Q(xi , x0 )dx0 − KD [A]

x

7


(1)


dOA = υOA KD [A] dt

(2)

dCO2 = υCO2 KD [A] dt

(3)

dH2 O = υH2 O KD [A] dt

(4)

where υOA , υCO2 and υH2 O are the stoichiometric coefficients for the formation of the organic acid, CO2 and water, respectively. Knowing the MW of CO2 and water and assuming that the average organic acid (OA) has a MW of 69 [g mol−1 ], we can consider that the stoichiometric coefficients, for CO2 and water, are equal to 1 while it is equal to 1.5 for OA, to conserve the mass balance and validate the experimental results, in terms of total organic acids content and TOC results. 250

[a]

[b]

5

-1

-1

200

Mass Concentration [g L ]

Aromatics

Mass Concentration [g L ]

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 8 of 45

OA

150 Oxalic Acid Model

100 Exp.

CO

50

2

Lignin

Exp.

4

Model

1.0 Organic Acids

0.5 CO

2

Water

Water

0 0

Aromatics

0.0

20

40

60

80

100 120

0

Reaction Time [min]

100

200

300

400

Reaction Time [min]

Figure 2: The concentration profile for aromatics, represented by vanillin and vanillinic acid, degradation and b) lignin degradation to OA, CO2 and water.

Figure 2a indicates that the aromatics, represented by the vanillin and vanillic acid, are degraded completely to organic acids (OA), CO2 and water in a first order reaction behavior. A break down of organic acids, such as oxalic, formic and acetic acids, can be determined by incorporating the MW and stoichiometry for every acid. For example, the formation of

8


Page 9 of 45 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


oxalic acid is determined by fitting the result of its formation rate through non-linear leastsquares fitting (lsqcurvefit) in MATLAB. As a result, a stoichiometric coefficient equals to 0.7 gives the best fitting, as indicated in Figure 2a. However, considering all acids adds unnecessary complexity to the model hence it is more convenient to assume that we have only one organic acid (OA) in the product degradation kinetics. Based on this assumption, the product degradation kinetics is incorporated in the lignin depolymerization kinetics and the resulted concentration profile is presented in Figure 2b. The yield of organic acids formation is about 25%, after 420 min of reaction time, which is similar to the experimental result. In addition, there is about 10% yield of undesired product (CO2 and water) which is also confirmed by the TOC result. A membrane reactor can selectively increase the yield of the aromatic product by minimizing the product degradation rate.

Pump

Buffer volume

Purge

Lignin feed Electro-oxidation Membrane

Permeate

Figure 3: Proposed process diagram for lignin depolymerization via electrochemcial membrane reactor.

9



Modeling Methodology Process scheme In order to selectively produce more aromatics product than organic acids and reduce the CO2 and water formation, a membrane reactor model is developed in a process scheme. The proposed process scheme is to continuously feed a 5 g L−1 of Kraft lignin dissolved in 1 M aqueous NaOH solution. The flow through the reactor is adjusted to 125 ml min−1 and average permeance of 20 L (m2 hr bar)−1 , for membrane with pore diameter (Dp ) of 1.0 nm, based on our previous published communication by Stiefel et al. 24 In these experimental trails, the permeance found to be increased gradually due to continuous lignin depolymerization until it reaches steady state. The trans-membrane pressure is set at 1.4 bars in order to have short residence time for the permeated product in the reactor. A purge provision is considered, in case a low production rate is noticed. A fresh lignin make-up solution is added to maintain the level in the buffer volume vessel constant, as illustrated in Figure 3.

Membrane rector model The model is developed based on the following assumptions: • The reactor configuration is a tubular membrane reactor with cocurrent permeate flow. • An inert (uncharged) membrane is considered in the model, such as ceramic membrane. 28,47 Therefore, the membrane-components interaction is neglected along and through the membrane. • The electrochemical membrane reactor is operated at fixed temperature, pressure, density and voltage. Changes in the current and the power were not considered in the model. The isothermal reactor is assumed, considering that the reactor has enough heat exchange capacity to keep the temperature constant.

10


Page 10 of 45

Page 11 of 45 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


• Components rejection is predicted based on the Mark-Houwink equation. Therefore, constant selectivity and permeability along and through the membrane are considered, as indicated in Table S1. 47 • Interaction between the components is not considered in the model. • The liquid density along the membrane is constant and the osmotic pressure is neglected. • Concentration polarization is neglected considering that the high molecular weight components are continuously depolymerized at the membrane surface.

0

j-1

j

j+1

N

Feed

Retentate 𝑁𝑅 , j

𝑁𝑅, j+1

𝑁𝑀, j-1

𝑁𝑀 , j

𝑁𝑀, j+1

𝑁𝑃, j-1

𝑁𝑃 , j

𝑁𝑃, j+1

𝑁𝑅, j-1 Membrane

Solvent

Feed

Reactor

Membrane

Permeate

Retentate

Permeate

1

Figure 4: Illustration of the tubular membrane reactor model used in gPROMS. The model is divided into a number of segments N and every segment consists of a reactor and a membrane to separate the products, as shown in Figure 4. In order to use the batch kinetics model for a continuous membrane reactor, the model has to be developed in a discontinuous configuration, as described in Figure S2. In this configuration, every membrane reactor segment is considered as a standalone process unit in which the subsequent segment 11



Page 12 of 45

is operated after the process in the previous segment is elapsed. This means the initial conditions for the kinetics equations are reinitialized in every reactor segment based on the retentate from the previous membrane segment. The permeation of component (i) through every membrane segment (j), Nmi , is calculated based on size-exclusion for a pressure driven process as follows:

Nmi = Rmi Φ(1 −

CPi )A ∆P CRi

(5)

where Φ is the average membrane permeance [L(m2 min bar)−1 ], CPi and CRi are the molar concentration [mol L−1 ] for component i in the permeate and retentate, respectively, ∆P [bar] is the trans-membrane pressure, A is the membrane area [m2 ] and Rmi is the component membrane retention which is calculated based on Mark-Houwink equation which is detailed in the supporting information. 48,49 The mass balance equations in every segment, based on Figure 4, are: • Retentate: NRi,j−1 − NRi,j − Nmi,j−1 = 0

(6)

NPi,j−1 − NPi,j + Nmi,j−1 = 0

(7)

• Permeate:

The required boundary conditions are:

NRi,0 = Fi

(8)

NPi,0 = 0

(9)

where Fi is the feed flow rate of component i [g min−1 ]. Considering the lignin’s aromatic monomer has MW of 152 g mol−1 (vanillin), the kinetics and membrane models parameters are listed in Table 2. 12


Page 13 of 45 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


Table 2: Input and model parameters for lignin depolymerization via membrane reactor with 1.0 nm pore diameter. The permeance and MWCO depends on the DP . Input Parameters Maximum DP

Unit

Value

L

6270

g L−1

Initial mass concentration of the polymer Monomer MW (vanillin)

g mol

Kinetics model Parameters

−1

5 152

Unit

Value

Chain-end degradation rate constant

min−1

0.02

Monomer degradation rate constant

min−1

0.05

−1

Random degradation rate constant

min

0.005

Random recombination rate constant

min−1

0.0043

Unit

Value

Da

750

Membrane model Parameters MWCO

2

Membrane Area

m

0.015

Trans-membrane pressure

bar

1.4

L (m2 min bar)−1

20.0

Average permeance

Results and Discussion Defining the desired added-value products of lignin depolymerization is the key factor to investigate the modeling parameters to get the highest yield. Therefore, four product cuts are selected in order to find the influence of the membrane characteristics in the production of these products. The first product is obviously the aromatic monomer product. Although the organic acids have less value than aromatics, they are still regarded as a valuable product. 14,50,51 The third product, which could be interesting, is the total production of the aromatic monomer with the organic acids. In addition, the intermediate aromatics product, from 152 to 1000 g mol−1 , is considered a valuable product especially if a downstream processing system is involved to selectively generate a desired aromatic product. Fixing the feed for every membrane reactor segment implies that the retentate in every membrane is maintained constant by adding a fresh lignin solution equals to the quantity of the permeated flow. Four membranes with pore diameters (DP ) of 0.5, 1.0, 1.5 and 2.0 nm 13



are used to analyze the membrane reactor influence in the production yield. In term of aromatic monomer formation, the permeates of DP 0.5 and 1.0 nm contain similar aromatic yield, between 11 and 12 %, whereas about 0.01% is present in the batch electrochemical reactor. However, DP 0.5 nm gives a higher organic acid formation because the MWCO of this membrane is 180 Da only. This is resulting a higher residence time for the intermediate aromatic product (152 to 1000 g mol−1 ) and hence higher yields of organic acid and aromatic monomer are achieved, as shown in Figure 5a, b and c. Based on these results, a membrane that has a pore size distribution between 0.5 nm and 1.0 nm is adequate for this process. Similarly, the MWCO for the DP 1.5 and 2.0 nm membranes are 1800 and 3100 Da, respectively, whereas DP 1.0 nm has a MWCO of 750 Da. Therefore, the membrane with DP 1.0 nm maintains a high quantity of the intermediate micromolecules of lignin in the retentate. Hence, a higher intermediate aromatic product is achieved, compared with DP 1.5 and 2.0 nm membranes, as illustrated in Figure 5d. However, in the membranes with DP 1.5 and 2.0 nm, the residence time of the intermediate components is not optimum to maximize the product yield. This infers that higher pore diameters have two main disadvantages. First, it dilutes the permeate stream due to the higher solvent permeation rate. For instance, the permeated solvent in 1 nm membrane is 14% of the solvent content in the initial feed while the membrane with pore diameter of 2 nm permeating 40% of the solvent in the initial feed, after 300 min of processing time. Second, the membrane with DP 2 nm removes the intermediate MW components before degrading to the desired aromatics product. Using high pore diameter could be helpful if the depolymerization of lignin is considered only as a pretreatment process which can produce a defined MW cut of lignin. After that, this intermediate product is fed to a selective process to produce high value aromatics. In addition, a sensitivity analysis has been implemented in the membrane reactor in terms of pore diameter, membrane area, trans-membrane pressure and number of membrane reactor segments. The sensitivity analysis is showing the influence of these process parameters on

14


Page 14 of 45

Page 15 of 45

12

[a]

[b]

D =0.5 nm

D =0.5 nm

p

p

6 p

8

OA Yield [ % ]

Monomer Yield [ % ]

D =1nm

D =1.5nm p

4

D =2 nm p

D =1nm

4

p

D =1.5nm p

2 D =2 nm p

0 0

100

200

0 0

300

Reaction Time [min]

20

200

300

Reaction Time [min]

30

[c]

100

D =0.5 nm

[d]

p

D =1nm p

24

15 Total Yield [ % ]

OA + Monomer Yield [ % ]

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


D =1nm p

10

D =1.5nm p

5 0 0

D =2 nm p

100

200

D =0.5 nm

18

p

D =1.5nm p

12

D =2 nm p

6 0 0

300

Reaction Time [min]

100

200

300

Reaction Time [min]

Figure 5: Influence of membrane pore diameter on the production yield, in the permeate, of (a) aromatic monomer , (b) organic acid , (c) aromatic monomer with organic acid product and (d) intermediate aromatic product (152 to 1000 g mol−1 ).

15



the production yield. It is not used to measure the input parameters uncertainty to the predicted outputs and therefore it has no influence on the model assumptions. Based on the analysis, operating and design window can be considered in future experimental studies. Membrane with pore diameter of 1 nm and lower produce similar aromatic monomer yield, as illustrated in Figure 6a, while the membrane area, ∆P and number of segments are fixed at 0.015 m2 , 1.4 bars and 660 segments, respectively. Figure 6b and c indicate that there are optimum membrane area and ∆P which are 0.01 m2 and 1.4 bars, respectively. Increasing these optimum parameters has no major influence on the production yield while it increases the capital cost of the membrane unit and the operation cost of the pump. Similarly, the other process parameters are fixed during the sensitivity analysis for the membrane area and ∆P . Figure 6d is describing the influence of the number of segments on the production yield. As discussed earlier, the definition of a membrane reactor segment, in the model, is a batch reactor that is fed from the retentate of the previous membrane segment, except for segment 0. Increasing the number of segments while keeping the process time at 300 min, implies that the residence time of every reactor segment is reduced subsequently, i.e. 300 segments with 1 min as a residence time for every segment compile a processing time of 300 min. Therefore, less amount of organic acid, CO2 and water is generated. However, the computational time is increased accordingly. For instance, an experimental trial was done by Stiefel et al, where the reactor residence time is about 1.34 min and the membrane permeance was 3.4 L (m2 hr bar)−1 . 37 The vanillin yield was only 0.5% while the presented membrane reactor model gives about 4% yield of aromatic product at the same residence time. This is because the permeance in the experiment was 5 times lower than the modeled membrane reactor. Therefore, the aromatic product, from the experiments, is effectively subjected to a higher residence time due to continuous circulation. Nevertheless, the results of the membrane reactor model must be validated with experimental results in order to include other parameters and enhance the model prediction.

16


Page 16 of 45

Page 17 of 45

[b]

[a]

12

Monomer Yield [ % ]

Monomer Yield [ % ]

12

8

4

0.5

1.0

1.5

2.0

8

4

0.00

0.01

Pore Diameter [nm]

12 Monomer Yield [ % ]

12

8

4

0

1

2

3

4

0.02

0.03

Membrane Area [nm]

[c]

Monomer Yield [ % ]

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


0

Segment Residence Time [min]

4

6

8

10

200

400

600

800

1000

8

4

0

5

2

[d]

Segments

P [bar]

Figure 6: Sensitivity analysis for the influence of (a) membrane pore diameter, (b) membrane area, (c) ∆P across the membrane (d) number of membrane reactor segments (bottom xaxis) and the reaction residence time for every segment (top x-axis) on the aromatic monomer yield, in the permeate.

17



Future work could focus on the weight of the most important input parameters affecting the production yield and the economic impact of the associated process. In the previous analysis, a constant feed in every segment is considered, in order to have similar retentate process parameters, such as concentration and lignin content, for every membrane reactor segment. However, in reality, a process designer would prefer to accept a lower retentate flow for the subsequent segment and design the process accordingly. For that, a variable retentate feed in every segment is considered in the membrane with pore diameter of 1 nm and allow the process to run till the production yield of aromatic product, in the permeate, approach to a plateau. Figure 7a shows that the aromatic and organic acid yield, in the permeate, reached to 41% and 6%, respectively, after complete degradation of lignin is attained. When the production plateau is reached, addition of a fresh lignin solution should be considered in order to make the process continuous. 2 .0

[a ]

[b ]

4 0 A r o m a tic s

1 .5

C O 2

] Y ie ld [ %

]

3 0

Y ie ld [ %

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 18 of 45

2 0

W a te r

0 .5

1 0

0

1 .0

0

O r g a n ic A c id s

5 0 0

1 0 0 0

1 5 0 0

0 .0

2 0 0 0

0

R e a c tio n T im e [m in ]

5 0 0

1 0 0 0

1 5 0 0

2 0 0 0


Figure 7: Detailed result from the membrane reactor with pore diameter of 1.0 nm,a) yield of aromatic product and organic acids, b) is for CO2 and water. On the other hand, Figure 8 presents the concentration profile for the electrochemical batch reactor till the reaction time reach to 2200 min and compare it with the membrane reactor. The batch reactor converts all the lignin to 70% organic acid while the aromatic 18


Page 19 of 45

70 OA Batch

60 50

Yield [ % ]

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


Monomer Membrane

40 30 20 Monomer Batch

10 0 0

500

1000

OA Membrane

1500

2000

Reaction Time [min] Figure 8: Comparison between the aromatic product and organic acid formation in batch reactor and membrane reactor. product degrades continuously. It is also important to reduce the content of the undesired products which are, in our case, the CO2 and water. Figure 7b highlights that the yield of the undesired product, in the membrane reactor, is below 2 % while the batch reactor gives about 30 % of CO2 and water, after 2200 min of reaction time, as in indicated in Figure S1.

Conclusions and Outlook The developed electrochemical membrane reactor model for lignin depolymerization reduces the effect of the over-oxidation towards the desired products. Therefore, the membrane reactor can increase the products yield compared to the batch electro-oxidation. In addition, the permeate contains only the products without lignin where products downstream processing is avoided. Sensitivity analysis revealed that the production yield of aromatics can increase up to 11% in the membrane reactor, with a pore diameter of 1.0 nm, compared with 0.01% yield in the batch reactor. Furthermore, the results of the membrane reactor model need to be validated with experimental results to account for other process parameters that can 19



influence the production rate and yield.

Supporting information The Supporting information is available free of charge on the ACS Publications website at DOI: Components rejection based on the Mark-Houwink equation is shown in the Supporting information; The details kinetics model results for the lignin degradation in the electrochemical batch reactor is shown in Figure S1; The membrane reactor model configuration in gPROMS is detailed in Figure S2; Estimated rejection for components cleaved from lignin, based on Mark-Houwink equation, compared with the published polymeric membrane rejection is tabulated in Table S1.

Author’s information Corresponding Author: Prof. Matthias Wessling E-mail: [email protected]

Note The authors declare no conflict of interests.

Acknowledgement The authors appreciate the financial support of Saudi Arabia Basic Industries Corporation (SABIC) and of the Marie Curie Action in the framework of SuBiCat (FP7) EU Marie Curie project (PITN-GA-2013-607044). We thank Malte Blindert and Pietro Postacchini for their support in the experiments.

20


Page 20 of 45

Page 21 of 45 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


References (1) Bozell, J. J.; Petersen, G. R. Technology development for the production of biobased products from biorefinery carbohydratesthe US Department of Energys Top 10 revisited. Green Chem. 2010, 12, 539–554, DOI: 10.1039/B922014C. (2) Chen, H. Biotechnology of Lignocellulose: Theory and Practice; Springer, 2014; DOI: 10.1007/978-94-007-6898-7. (3) Claire ethanol

Chudziak, in

G.

Europe

A.; to

Bauen, 2030.

2017;

A.

Ramp

up

of

lignocellulosic

http://www.e4tech.com/reports/

ramp-lignocellulosic-ethanol-europe-2030,(accessed_November11,2018). (4) Laine, C. Structures of hemicelluloses and pectins in wood and pulp. 2005; https: //aaltodoc.aalto.fi/handle/123456789/2571,(accessed_November11,2018). (5) Argyropoulos, D. S.; Menachem, S. B. Biotechnology in the Pulp and Paper Industry; Springer, 1997; pp 127–158, DOI: doi.org/10.1007/BFb0102073. (6) Huang, W.-B.;

Du, C.-Y.;

Jiang, J.-A.;

Ji, Y.-F. Concurrent synthesis of

vanillin and isovanillin. Res. Chem. Intermed. 2013,

39,

2849–2856,

DOI:

10.1007/s11164-012-0804-6. (7) Ragauskas, A. J. et al. Lignin valorization: improving lignin processing in the biorefinery. Science 2014, 344, 709–+, DOI: 10.1126/science.1246843. (8) Zakzeski, J.; Bruijnincx, P. C.; Jongerius, A. L.; Weckhuysen, B. M. The catalytic valorization of lignin for the production of renewable chemicals. Chem. Rev. 2010, 110, 3552–3599, DOI: 10.1021/cr900354u. (9) Strassberger, Z.; Tanase, S.; Rothenberg, G. The pros and cons of lignin valorisation in an integrated biorefinery. RSC Adv. 2014, 4, 25310–25318, DOI: 10.1039/C4RA04747H.

21



Page 22 of 45

(10) Cline, S. P.; Smith, P. M. Opportunities for lignin valorization: an exploratory process. Energy Sustain Soc. 2017, 7, 26, DOI: 10.1186/s13705-017-0129-9. (11) Biddy,

M.

J.

Lignin

Valorization;

2018;

pp

499–518,

and

tomorrow.

DOI:

10.1039/9781788010351-00499. (12) Bender,

M.

Global

aromatics

supply–today

2013;

https:

//oil-gas.de/petrochemistry/abstracts_content21/Bender.pdf,(accessed_ November11,2018). (13) Matar, S.; Hatch, L. F. Chemistry of petrochemical processes; Elsevier, 2001; DOI: 10.1016/B978-0-88415-315-3.X5000-7. (14) Pal, P.;

Nayak, J. Acetic acid production and purification:

critical review

towards process intensification. Sep. Purif. Technol 2017, 46, 44–61, DOI: 10.1080/15422119.2016.1185017. (15) Rusli, M. S. Efforts and Challenges for Sustainable Essential Oil Production

in

Indonesia.

2012;

http://www.academia.edu/download/41328984/

Rusli-Sustainable-Indonesia-EO.pdf,(accessed_November11,2018). (16) Ramachandra Rao, S.; Ravishankar, G. A. Vanilla flavour: production by conventional and biotechnological routes. J. Sci. Food Agric 2000, 80, 289–304, DOI: 10.1002/1097-0010(200002)80:33.0.CO;2-2. (17) Miller, J.; Faleiros, M. Lignin:

Technology, applications, and markets. RISI

Latin American Pulp & Paper Outlook Conference.[online]. 2016. MarketIntell LLC. https://events.risiinfo.com/latin-american-conference/sites/ default/files/presentations/2016/Miller,(accessed_November11,2018). (18) Gasson, J. R.; Forchheim, D.; Sutter, T.; Hornung, U.; Kruse, A.; Barth, T. Modeling the lignin degradation kinetics in an ethanol/formic acid solvolysis approach. Part 22


Page 23 of 45 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


1. Kinetic model development. Ind. Eng. Chem. Res. 2012, 51, 10595–10606, DOI: 10.1021/ie301487v. (19) Zazo, J.; Casas, J.; Mohedano, A.; Gilarranz, M.; Rodriguez, J. Chemical pathway and kinetics of phenol oxidation by Fenton’s reagent. Environ. Sci. Technol. 2005, 39, 9295–9302, DOI: 10.1021/es050452h. (20) Di Marino, D.; Stöckmann, D.; Kriescher, S.; Stiefel, S.; Wessling, M. Electrochemical depolymerisation of lignin in a deep eutectic solvent. Green Chem. 2016, 18, 6021–6028, DOI: 10.1039/C6GC01353H. (21) Parpot, P.; Bettencourt, A.; Carvalho, A.; Belgsir, E. Biomass conversion: attempted electrooxidation of lignin for vanillin production. J. Appl. Electrochem. 2000, 30, 727– 731, DOI: 10.1023/A:1004003613883. (22) Tolba, R.; Tian, M.; Wen, J.; Jiang, Z.-H.; Chen, A. Electrochemical oxidation of lignin at IrO2-based oxide electrodes. J. Electroanal. Chem 2010, 649, 9–15, DOI: 10.1016/j.jelechem.2009.12.013. (23) Di Marino, D.;

Aniko, V.;

Stocco, A.;

Kriescher, S.;

Wessling, M. Emul-

sion electro-oxidation of kraft lignin. Green Chem. 2017, 19, 4778–4784, DOI: 10.1039/C7GC02115A. (24) Stiefel, S.; Lölsberg, J.; Kipshagen, L.; Möller-Gulland, R.; Wessling, M. Controlled depolymerization of lignin in an electrochemical membrane reactor. Electrochem. Commun. 2015, 61, 49–52, DOI: 10.1016/j.elecom.2015.09.028. ˇ (25) Zabkov´ a, M.; da Silva, E. B.; Rodrigues, A. Recovery of vanillin from lignin/vanillin mixture by using tubular ceramic ultrafiltration membranes. J. Membr. Sci. 2007, 301, 221–237, DOI: 10.1016/j.memsci.2007.06.025.

23



Page 24 of 45

(26) Stiefel, S.; Marks, C.; Schmidt, T.; Hanisch, S.; Spalding, G.; Wessling, M. Overcoming lignin heterogeneity: reliably characterizing the cleavage of technical lignin. Green Chem. 2016, 18, 531–540, DOI: 10.1039/C5GC01506E. (27) Schmitt, D.; Regenbrecht, C.; Hartmer, M.; Stecker, F.; Waldvogel, S. R. Highly selective generation of vanillin by anodic degradation of lignin: a combined approach of electrochemistry and product isolation by adsorption. Beilstein J. Org. Chem. 2015, 11, 473, DOI: 10.3762/bjoc.11.53. (28) Zabkova, M.; da Silva, E. B.; Rodrigues, A. Recovery of vanillin from Kraft lignin oxidation by ion-exchange with neutralization. Sep. Purif. Technol. 2007, 55, 56–68, DOI: 10.1016/j.seppur.2006.10.027. (29) da Silva, E. B.;

Zabkova, M.;

Ara´ ujo, J.;

Cateto, C.;

Barreiro, M.;

Bel-

gacem, M.; Rodrigues, A. An integrated process to produce vanillin and lignin-based polyurethanes from Kraft lignin. Chem. Eng. Res. Des. 2009, 87, 1276–1292, DOI: 10.1016/j.cherd.2009.05.008. (30) Bergner, D. Membrane cells for chlor-alkali electrolysis. J. Appl. Electrochem. 1982, 12, 631–644, DOI: 10.1007/BF00617483. (31) Rihko-Struckmann, L.; Munder, B.; Chalakov, L.; Sundmacher, K. Solid electrolyte membrane reactors. Membrane Reactors: Distributing Reactants to Improve Selectivity and Yield 2010, 193–233, DOI: 10.1002/9783527629725.ch7. (32) Chen, G. Electrochemical technologies in wastewater treatment. Sep. Purif. Technol. 2004, 38, 11–41, DOI: 10.1016/j.seppur.2003.10.006. (33) Kurniawan, T. A.; Chan, G. Y.; Lo, W.-H.; Babel, S. Physico–chemical treatment techniques for wastewater laden with heavy metals. Chem. Eng. J. 2006, 118, 83–98, DOI: 10.1016/j.cej.2006.01.015.

24


Page 25 of 45 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


(34) Chanworrawoot, K.; Hunsom, M. Treatment of wastewater from pulp and paper mill industry by electrochemical methods in membrane reactor. J. Environ. Manage. 2012, 113, 399–406, DOI: 10.1016/j.jenvman.2012.09.021. (35) Alvarez-Guerra, M.; Quintanilla, S.; Irabien, A. Conversion of carbon dioxide into formate using a continuous electrochemical reduction process in a lead cathode. Chem. Eng. J. 2012, 207, 278–284, DOI: 10.1016/j.cej.2012.06.099. (36) Kumar, M.; Tripathi, B. P.; Saxena, A.; Shahi, V. K. Electrochemical membrane reactor:

Synthesis of quaternary ammonium hydroxide from its halide

by in situ ion substitution. Electrochim. Acta 2009, 54, 1630–1637, DOI: 10.1016/j.electacta.2008.09.049. (37) Stiefel, S.; Schmitz, A.; Peters, J.; Di Marino, D.; Wessling, M. An integrated electrochemical process to convert lignin to value-added products under mild conditions. Green Chem. 2016, 18, 4999–5007, DOI: 10.1039/C6GC00878J. (38) Wang, Z.-X.; Li, G.; Yang, F.; Chen, Y.-L.; Gao, P. Electro-Fenton degradation of cellulose using graphite/PTFE electrodes modified by 2-ethylanthraquinone. Carbohydr. Polym. 2011, 86, 1807–1813, DOI: 10.1016/j.carbpol.2011.07.021. (39) Yang, F.; Zhang, Q.; Fan, H.-X.; Li, Y.; Li, G. Electrochemical control of the conversion of cellulose oligosaccharides into glucose. J IND ENG CHEM 2014, 20, 3487–3492, DOI: 10.1016/j.jiec.2013.12.039. (40) Bawareth, B.; Di Marino, D.; Nijhuis, T. A.; Wessling, M. Unravelling electrochemical lignin depolymerization. ACS SUSTAIN CHEM ENG. 2018, 6, 7565–7573, DOI: 10.1021/acssuschemeng.8b00335. (41) Ferrer, I.; Thurman, E. M. Liquid chromatography/time-of-flight/mass spectrometry (LC/TOF/MS) for the analysis of emerging contaminants. TRAC-TREND ANAL CHEM 2003, 22, 750–756, DOI: 10.1016/S0165-9936(03)01013-6. 25



Page 26 of 45

(42) Wang, M.; Smith, J.; McCoy, B. J. Continuous kinetics for thermal degradation of polymer in solution. AlChE J. 1995, 41, 1521–1533, DOI: 10.1002/aic.690410616. (43) Stickel, J. J.; Griggs, A. J. Mathematical modeling of chain-end scission using continuous distribution kinetics. Chem. Eng. Sci. 2012, 68, 656–659, DOI: 10.1016/j.ces.2011.09.028. (44) Ma, R.; Xu, Y.; Zhang, X. Catalytic oxidation of biorefinery lignin to value-added chemicals to support sustainable biofuel production. ChemSusChem 2015, 8, 24–51, DOI: 10.1002/cssc.201402503. (45) Gierer, J. Chemistry of delignification. Wood Sci. Technol. 1985, 19, 289–312, DOI: 10.1007/BF00350807. (46) Dier, T. K.; Rauber, D.; Durneata, D.; Hempelmann, R.; Volmer, D. A. Sustainable electrochemical depolymerization of lignin in reusable ionic liquids. Sci. Rep. 2017, 7, 5041, DOI: 10.1038/s41598-017-05316-x. (47) Werhan, H.; Farshori, A.; von Rohr, P. R. Separation of lignin oxidation products by organic solvent nanofiltration. J. Membr. Sci. 2012, 423, 404–412, DOI: 10.1016/j.memsci.2012.08.037. (48) Kasaai, M. R. Dilute solution properties and degree of chain branching for dextran. Carbohydr. Polym. 2012, 88, 373–381, DOI: 10.1016/j.carbpol.2011.12.012. (49) Pellegrin, B.; Mezzari, F.; Hanafi, Y.; Szymczyk, A.; Remigy, J.-C.; Causserand, C. Filtration

performance

and

pore

size

distribution

of

hypochlorite

aged

PES/PVP ultrafiltration membranes. J. Membr. Sci. 2015, 474, 175–186, DOI: 10.1016/j.memsci.2014.09.028. (50) Cronin, D. J.; Zhang, X.; Bartley, J.; Doherty, W. O. Lignin Depolymerization to

26


Page 27 of 45 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


Dicarboxylic Acids with Sodium Percarbonate. ACS SUSTAIN CHEM ENG. 2017, 5, 6253–6260, DOI: 10.1021/acssuschemeng.7b01208. (51) Mäkelä, M.; Galkin, S.; Hatakka, A.; Lundell, T. Production of organic acids and oxalate decarboxylase in lignin-degrading white rot fungi. Enzyme Microb. Technol 2002, 30, 542–549, DOI: 10.1016/S0141-0229(02)00012-1.

27



Graphical TOC Entry Recycle

Pump Lignin feed

Purge

Electro-oxidation membrane reactor

Aromatic products

Membrane

Reactor

N

Integration of electrochemical membrane reactor in a sustainable process to bring the biorefinery concept closer to commercial realization.

28


Page 28 of 45

Page 29 of 45 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



ACS Sustainable Chemistry & Engineering 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


Page 30 of 45

Page 31 of 45 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



ACS Sustainable Chemistry & Engineering 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


Page 32 of 45

Page 33 of 45 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


Pump

Buffer volume

Purge

Lignin feed Electro-oxidation Membrane


Permeate

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

0

j-1


j

j+1

N

Feed

Page 34 of 45

Retentate 𝑁𝑅 , j

𝑁𝑅, j+1

𝑁𝑀, j-1

𝑁𝑀 , j

𝑁𝑀, j+1

𝑁𝑃, j-1

𝑁𝑃 , j

𝑁𝑃, j+1

𝑁𝑅, j-1 Membrane

Solvent

Feed

Reactor

Membrane

Permeate

Retentate


Permeate

1

Page 35 of 45 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





Page 36 of 45

Page 37 of 45 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





Page 38 of 45

Page 39 of 45 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





Page 40 of 45

Page 41 of 45 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





Page 42 of 45

Page 43 of 45

[a ]

4 0 A r o m a tic s

]

3 0

Y ie ld [ %

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


2 0

1 0

0 0

O r g a n ic A c id s

5 0 0

1 0 0 0


1 5 0 0


2 0 0 0

2 .0


[b ]

1 .5

C O 2

] Y ie ld [ %

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

Page 44 of 45

1 .0 W a te r

0 .5

0 .0 0

5 0 0

1 0 0 0


1 5 0 0


2 0 0 0

Page 45 of 45

70

OA Batch

60 50

Yield [ % ]

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


Aromatic Membarne

40 30 20 Aromatic Batch

10 0 0

500

1000


OA Membrane

1500

Reaction Time [min]

2000

Electrochemical membrane reactor modelling for lignin

Recommend Documents