# N-Propanol Dehydration with Distillation and Pervaporation: Experiments and Modelling

## Abstract

**:**

## 1. Introduction

## 2. Materials and Methods

#### 2.1. Hydrophilic Pervaporation Experiments

^{2}effective membrane area (A). The capacity of the feed tank was 0.5 L (500 mL). Cross-flow type circulation was realized at the permanent value of ∼182 L/h [7].

#### 2.2. Modelling of Pervaporation

_{0}) was infinitely big compared to the $\overline{{D}_{i}}$ which made this layer’s resistance negligible. Therefore the first part of Equation (7) and Equation (8) can be ignored [31]. The models, as mentioned earlier, were simplified in the following way during practical calculations:

^{®}software. Verification of the accuracy of the model can be achieved with objective function (OF), which minimizes the deviation of the measured and the modelled values (Equation (13)).

#### 2.3. Simulation of Hybrid Distillation and Pervaporation Method

## 3. Results and Discussion

^{®}program environment.

^{2}. These settings achieved the desired product purities (99.9 m/m% of water and n-propanol), as seen in Figure 3.

^{2}. These settings achieved the desired product purities (99.9 m/m% of n-propanol and min. 99.9 m/m% of water), as seen in Figure 3. Table 5 shows the composition of the water and n-propanol product in the function of different membrane areas.

^{2}).

## 4. Conclusions

^{2}h over the feed water content range of 32–43 m/m% at 70–90 °C feed temperature. The highest separation factor of 1420 and the second highest permeate flux (1.22 kg/m

^{2}h) were measured with a flat-sheet PVA membrane. It was found that PERVAP™ 1201 had a relatively high pervaporation separation index value compared to other published PSI data in the case of the n-propanol–water system. The figures represented that total flux and selectivity were in inverse relation, which was in line with the literature.

## Funding

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Nomenclature

$A$ | Membrane transfer area | $\left[{\mathrm{m}}^{2}\right]$ |

$B$ | Constant in Model II | $\left[-\right]$ |

$D$ | Distillate product | |

${\overline{D}}_{i}$ | Transport coefficient of component $i$ | $\left[\mathrm{k}\mathrm{m}\mathrm{o}\mathrm{l}/\left({\mathrm{m}}^{2}\mathrm{h}\right)\right]$ |

${\overline{D}}_{i}^{*}$ | Relative transport coefficient of component $i$ | $\left[\mathrm{k}\mathrm{m}\mathrm{o}\mathrm{l}/\left({\mathrm{m}}^{2}\mathrm{h}\right)\right]$ |

${E}_{i}$ | Activation energy of component $i$ in Equation (12) for temperature dependence of the transport coefficient | $\left[\mathrm{k}\mathrm{J}/\mathrm{m}\mathrm{o}\mathrm{l}\right]$ |

$F$ | Feed | |

$i$ | Component number | |

$j$ | Component number | |

${J}_{total}$ | Total flux | $\left[\mathrm{k}\mathrm{g}/\left({\mathrm{m}}^{2}\mathrm{h}\right)\right]$ |

${J}_{i}$ | Partial flux | $\left[\mathrm{k}\mathrm{g}/\left({\mathrm{m}}^{2}\mathrm{h}\right)\right]$ |

N | Number of theoretical stages | [-] |

$P$ | Permeate | |

${p}_{i0}$ | Pure i component vapour pressure | $\left[\mathrm{b}\mathrm{a}\mathrm{r}\right]$ |

${p}_{i1}$ | Partial pressure of component $i$ on the liquid phase membrane side | $\left[\mathrm{b}\mathrm{a}\mathrm{r}\right]$ |

${p}_{i3}$ | Partial pressure of component $i$ on the vapour phase membrane side | $\left[\mathrm{b}\mathrm{a}\mathrm{r}\right]$ |

${p}_{3}$ | Pressure on the permeate side | $\left[\mathrm{b}\mathrm{a}\mathrm{r}\right]$ |

${P}_{i}/\delta $ | Permeance of component $i$ | $\left[\mathrm{m}\mathrm{o}\mathrm{l}/\left({\mathrm{m}}^{2}\mathrm{h}\mathrm{b}\mathrm{a}\mathrm{r}\right)\right]$ |

Q_{0} | Permeability of the porous supporting layer of the membrane | [$\mathrm{k}\mathrm{m}\mathrm{o}\mathrm{l}/\left({\mathrm{m}}^{2}\mathrm{h}\mathrm{b}\mathrm{a}\mathrm{r}\right)$] |

$R$ | Retentate | |

Ʀ | Gas constant | $\left[\mathrm{k}\mathrm{J}/\left(\mathrm{k}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{K}\right)\right]$ |

$T$ | Temperature | $\left[\xb0C\right]$ |

${T}^{*}$ | Reference temperature: 293 $K$ | |

${x}_{F}$ | Feed n-propanol weight fraction in $y-x$ vapour-liquid equilibrium (VLE) diagram (Figure 5) | $\left[-\right]$ |

${x}_{i1}$ | Concentration of component $i$ in the feed | $\left[\mathrm{m}/\mathrm{m}\%\right]$ |

$y$ | Permeate n-propanol and water weight fraction in $y-x$ vapour-liquid equilibrium (VLE) diagram (Figure 5) | $\left[-\right]$ |

${y}_{i}^{PV}$ | Permeate concentration in Membrane Flash Index (MFLI) | $\left[\mathrm{m}/\mathrm{m}\%\right]$ |

${y}_{i}^{D}\left[VLE\right]$ | Equilibrium distillation value in Membrane Flash Index (MFLI) | $\left[\mathrm{m}/\mathrm{m}\%\right]$ |

## Abbreviations

HPV | Hydrophilic pervaporation | |

hydr | hydrophilic | |

MFLI | Membrane Flash Index | $\left[-\right]$ |

NPA | n-propanol | |

OF | Objective function | |

PSI | Pervaporation Separation Index | $\left[\mathrm{k}\mathrm{g}/\left({\mathrm{m}}^{2}\mathrm{h}\right)\right]$ |

PVA | Polyvinyl alcohol | |

PV | Pervaporation | |

VLE | Vapour-Liquid Equilibrium | |

Greek letters | ||

$\alpha $ | Separation factor | |

$\beta $ | Selectivity | |

${\overline{\gamma}}_{i}$ | $\mathrm{Average}$ | |

${\gamma}_{i1}$ | $\mathrm{Activity}$ in the feed | |

δ | Membrane thickness | $\left[{\displaystyle \mathrm{\mu}}\mathrm{m}\right]$ |

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**Figure 1.**Flowchart of modelling and simulation of hydrophilic pervaporation in the case of n-propanol dehydration (based on the flowchart of Haaz and Toth [6]).

**Figure 3.**Simulated hybrid distillation and hydrophilic pervaporation method for separating n-propanol–water binary mixture.

**Figure 4.**Separation achievement as a function of feed content at different operating temperatures for PERVAP™ 1201 membrane (70 °C: ; 80 °C: ; 90 °C: ), (

**A**) Total flux, (

**B**) Separation factor, (

**C**) PSI, (

**D**) Selectivity.

**Figure 5.**Experimental permeate n-propanol weight fractions (also enlarged version) of hydrophilic pervaporation on the n-propanol–water VLE diagram.

**Figure 6.**Experimental water and n-propanol fluxes ( ) compared to calculated partial fluxes with Model I ( ) and Model II ( ) in a function of feed water concentration with PERVAP™ 1201 membrane.

**Table 1.**Summary of measured data for hydrophilic pervaporation of n-propanol–water mixture (based on, expanded [14]).

Membrane Type | T | F_{water} | J_{total} | α | PSI | Reference |
---|---|---|---|---|---|---|

[°C] | [m/m%] | [kg/m^{2}h] | [–] | [kg/m^{2}h] | ||

PVA cross-linked with citric acid | 30 | 10 | 0.08 | 141 | 11 | Burshe et al., 1997 [15] |

PVA/PAN | 60 | 5 | 0.15 | 90 | 13 | Gesing, 2004 [16] |

αAl_{2}O_{3}/PVA | 70 | 10 | 2.20 | 50 | 108 | Peters et al., 2006 [17] |

PERVAP™ 2201D (PVA/PAN) | 70 | 10 | 0.52 | 500 | 259 | Teleman et al., 2022 [14] |

PERVAP™ 2201D (PVA/PAN) | 60 | 10 | 0.26 | 2500 | 650 | Teleman et al., 2022 [14] |

Poly(urethane-imide)-PUI-2000 | 50 | 20 | 8.80 | 179 | 1566 | Sokolova et al., 2018 [18] |

Poly(urethane-imide)-PUI-530 | 50 | 20 | 5.10 | 437 | 2224 | Sokolova et al., 2018 [18] |

polyvinylamine/polyvinylsulphate | 59 | 10 | 1.20 | 6000 | 7199 | Toutianoush et al., 2002 [19] |

**Table 2.**${\overline{D}}_{i}$, ${E}_{i}$, and B values of n-propanol–water binary mixture estimated by STATISTICA

^{®}program environment.

PERVAP™ 1201 | Model I | Model II | ||
---|---|---|---|---|

Water | NPA | Water | NPA | |

${\overline{D}}_{i}$ [kmol/m^{2}h] | 7.15 × 10^{−3} | 4.20 × 10^{−5} | 2.40 × 10^{−5} | 2.32 × 10^{−3} |

${E}_{i}$ [kJ/kmol] | 2.4644 | 2.6053 | 2.7707 | 2.9966 |

B [−] | 8.38 | −12.08 |

PERVAP™ 1201 | Objective Function-Water | Objective Function-NPA |
---|---|---|

Model I | 1.369 | 2.468 |

Model II | 0.123 | 0.125 |

**Table 4.**Comparison of experimental and model fluxes for laboratory-size separation: model validation.

F_{water} | J_{total}—Measured (Experiment) | J_{total}—Calculated (Model) | Deviation |
---|---|---|---|

[m/m%] | [kg/m^{2}h] | [kg/m^{2}h] | [%] |

32 | 0.48 | 0.48 | 1.4 |

35 | 0.57 | 0.58 | 1.3 |

38 | 0.86 | 0.85 | −0.7 |

41 | 1.10 | 1.11 | 1.1 |

43 | 1.20 | 1.21 | −0.9 |

Membrane | Water Product (Bottom Product) | N-Propanol Product (Retentate) | ||
---|---|---|---|---|

Area | Water | N-Propanol | Water | N-Propanol |

[m^{2}] | [m/m%] | [m/m%] | [m/m%] | [m/m%] |

60 | 99.68 | 0.32 | 6.1 | 93.9 |

120 | 99.85 | 0.15 | 2.9 | 97.1 |

180 | 99.93 | 0.07 | 1.3 | 98.7 |

240 | 99.98 | 0.02 | 0.4 | 99.6 |

300 | 99.99 | 0.01 | 0.1 | 99.9 |

Calculated Heat Duties | Q_{Heating} [MJ/h] | Q_{Cooling} [MJ/h] | |
---|---|---|---|

Distillation | Reboiler | 501 | |

Condenser | −166 | ||

Post cooler | −317 | ||

Pervaporation | Feed preheating | 1 | |

Retentate heating | 44 | ||

Permeate cooler | −53 | ||

Post cooler | . | −9 |

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**MDPI and ACS Style**

Toth, A.J.
N-Propanol Dehydration with Distillation and Pervaporation: Experiments and Modelling. *Membranes* **2022**, *12*, 750.
https://doi.org/10.3390/membranes12080750

**AMA Style**

Toth AJ.
N-Propanol Dehydration with Distillation and Pervaporation: Experiments and Modelling. *Membranes*. 2022; 12(8):750.
https://doi.org/10.3390/membranes12080750

**Chicago/Turabian Style**

Toth, Andras Jozsef.
2022. "N-Propanol Dehydration with Distillation and Pervaporation: Experiments and Modelling" *Membranes* 12, no. 8: 750.
https://doi.org/10.3390/membranes12080750