Experiments and model for the viscosity of carbonated 2-amino-2-methyl-1-propanol and piperazine aqueous solution

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Highlights

  • The viscosities of the carbonated AMP-PZ aqueous solutions were measured.

  • The experiments were modeled satisfactorily by using the Weiland equation.

  • The influence of the mass fractions of amines on the viscosity was illustrated.

  • The temperature and CO2 loading dependences of the viscosity were demonstrated.

Abstract

The viscosities (η) of carbonated 2-amino-2-methyl-1-propanol (AMP)-piperazine (PZ) aqueous solutions were measured by using a NDJ-1 rotational viscometer, with temperatures ranging from 298.15 K to 323.15 K. The total mass fraction of amines ranged from 0.3 to 0.4. The mass fraction of PZ ranged from 0.05 to 0.10. The Weiland equation was used to correlate the viscosities of both CO2-unloaded and CO2-loaded aqueous solutions and the calculated results agreed well with the experiments. The effects of temperature, mass fractions of amines and CO2 loading (α) on the viscosities of carbonated aqueous solutions were demonstrated on the basis of experiments and calculations.

Introduction

Aqueous solutions of amines have been widely used for the removal of CO2 from a variety of gas streams [1], [2], [3], [4], [5], [6], [7]. Among the amine series, the sterically hindered amines, e.g., 2-amino-2-methyl -1-propanol (AMP), is considered to be an attractive solvents for the removal of CO2 due to its absorption capacity, absorption rate, selectivity and degradation resistance advantages [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18]. Compared with N-methyldiethanolamine (MDEA), AMP has the same absorption capacity for CO2 (1 mol of CO2 per mol of amine) but much higher reaction rate [12]. When the aqueous solutions of AMP are used to absorb CO2, as AMP only forms bicarbonate and carbonate ions, the regeneration energy costs are relatively low. Adding small amounts of primary and secondary amines to an aqueous solution of AMP is helpful to promote the absorption of CO2, e.g., Mandal et al. [13], [14] showed that the addition of small amounts of monoethanolamine (MEA) and diethanolamine (DEA) to an aqueous solution of AMP significantly enhances the rate of absorption of CO2. For similar relative composition, the rates of absorption of CO2 in AMP-MEA and AMP-DEA aqueous solutions are higher than those in MDEA-MEA and MDEA-DEA aqueous solutions. Besides MEA or DEA, piperazine (PZ) is also considered to be an effective promoter. It has a greater capacity and higher reaction rates than MEA, e.g., 4.6 mol · L−1 PZ aqueous solution has about 75% greater CO2 capacity than 4.91 mol · L−1 MEA aqueous solution, and CO2 reaction rates for PZ are shown to be 2–3 times faster than MEA [19].

Solution viscosity is important in the mass transfer rate modeling of absorbers and regenerators because these properties significantly affect the liquid film coefficient for mass transfer. Viscosities of both CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions are required when designing or simulating an absorption column for CO2 absorption using AMP -PZ aqueous solutions. So far, there are some experiments concerning the viscosities of aqueous solutions containing AMP and PZ [20], [21], [22]. In particular, Murshid et al. [20], Samanta and Bandyopadhyay [21] measured the viscosities of aqueous solutions of PZ and aqueous blends of AMP-PZ at temperatures from 298.15 K to 333.15 K. Paul and Mandal [22] measured the viscosities of aqueous blends of AMP-PZ at the temperatures from 288 K to 333 K. Besides experiments, they [20], [21], [22] also proposed theoretical models and satisfactorily correlated their experiments as a function of temperature and concentration of amine. However, the experiments and theoretical work for the viscosities of CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions are rare.

The main purpose of this work is to investigate the viscosities of carbonated AMP-PZ aqueous solutions experimentally and theoretically, so as to demonstrate the effects of temperature, mass fractions of amines and CO2 loading on the viscosities. To this end, the viscosities of CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions were measured by using a NDJ-1 rotational viscometer, with the temperatures, mass fraction of PZ and CO2 loading, respectively, ranging from 298.15 K to 323.15 K, 0.05 to 0.10 and 0 to 0.6. The Weiland equation [23] was used to correlate the viscosities of both CO2-unloaded and CO2-loaded solutions.

Section snippets

Materials

AMP and PZ were purchased from the Huaxin Chemical Co. The provenance and sample purity are shown in table 1. They were used without further purification. Aqueous solutions of AMP-PZ were prepared by adding doubly distilled water. The uncertainty of the electronic balance is ±0.1 mg.

Apparatus and procedure

The carbonated AMP-PZ aqueous solutions were prepared according to the methods mentioned in the work of Weiland et al. [23], Amundsen et al. [24], and our previous work [25], [26], [27]: CO2-unloaded AMP -PZ aqueous

Results and discussion

The viscosities of CO2-unloaded and CO2-loaded AMP-PZ aqueous solutions are shown in table 2.

Besides experiments, theoretical work is also presented in this work. The Weiland equation [23] was applied to correlate the viscosities of both CO2-loaded and CO2-unloaded solutions. Compared with the widely used Eyring equation [28] and the Grunberg-Nissan equation [29], the Weiland equation [21] can simultaneously describe the temperature, mass fraction of amine and CO2 loading dependences.

When

Conclusions

In this work, the viscosities of carbonated AMP-PZ aqueous solutions were measured over wide ranges of CO2 loading, temperature and mass fraction of amines. The Weiland equation was used to correlate the viscosities. Our results showed that:

  • (1)

    For CO2-unloaded AMP-PZ aqueous solutions, the viscosity increases with the increase of the w1 at a given temperature and given w2, and exponentially decreases with the increase of temperature at a given w2 and w1;

  • (2)

    For CO2-loaded AMP-PZ aqueous solutions, the

Acknowledgments

The authors appreciate the financial support from the National Natural Science Foundation of China (Nos. 21276072 and 21076070), the Natural Science Funds for Distinguished Young Scholar of Hebei Province (No. B2012502076), the Fundamental Research Funds for the Central Universities (No. 13ZD16) and the 111 project (B12034).

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