Simulation and Performance Comparison for CO2 Capture by Aqueous Solvents of N-(2-Hydroxyethyl) Piperazine and Another Five Single Amines

N-(2-Hydroxyethyl) piperazine (HEPZ) has a chemical structure similar to PZ and has less volatility. It is not easy to volatilize in a continuous operation device. It is studied to replace PZ as a promotor to increase the CO2 capture rate. This paper researches the lowest energy consumption and absorbent loss of HEPZ/H2O in the absorption-regeneration process, and compares it with another five amines, including PZ, MEA, 1-MPZ, AMP and DMEA. Based on the thermodynamic model, this work establishes a process simulation based on the equilibrium stage, assuming that all stages of the absorption and desorption towers reach thermodynamic equilibrium and CO2 recovery in the absorption tower is 90%. By optimizing the process parameters, the lowest thermodynamic energy consumption and absorbent loss of process operation are obtained. Our results show that HEPZ as a promotor to replace PZ and MEA has significant economic value. The lowest reboiler energy consumption of HEPZ with the optimal process parameters is 3.018 GJ/tCO2, which is about 35.2% lower than that of PZ and about 11.6% lower than that of MEA, and HEPZ has the lowest solvent loss. The cyclic capacity is 64.7% higher than PZ and 21.6% lower than primary amine MEA.

Measurement and Thermodynamic Modeling for CO2 Solubility in the N-(2-Hydroxyethyl) Piperazine + Water System

Amine scrubbing is the most important technique for capturing CO2. The cyclic diamine N-(2-Hydroxyethyl)-piperazine (HEPZ), a derivative of piperazine, with good mutual solubility in aqueous solution, a low melting point, and a high boiling point, has the potential to replace PZ as an activator added in the mixed amine system to capture CO2. In this study, the solubility of CO2 in aqueous HEPZ solutions was determined for three HEPZ concentrations and four temperatures. The VLE data for HEPZ-H2O were obtained using a gas–liquid double circulation kettle at pressure 30–100 kPa, and the thermodynamic model for the HEPZ-H2O-CO2 system was built in Aspen Plus based on the electrolytic non-random two-liquid (ENRTL) activity model. The physical parameters for HEPZ and the interaction parameters for ENRTL, along with reaction constants of carbamate reactions, were regressed. Using the thermodynamic model, the CO2 cyclic capacity, speciation with loading, and heat of reaction for the CO2 capture system by the aqueous HEPZ solution are predicted and analyzed.

The use of HEPES-buffer in the production of gallium-68 radiopharmaceuticals – time to reconsider strict pharmacopoeial limits?

HEPES (4-(2-hydroxyethyl) piperazine-1-ethanesulfonic acid) is a buffer that is used in the radiolabelling of gallium-68 compounds. The beneficial effects of HEPES on molar activity in bioconjugates have been well described. Current strict regulations on the HEPES content in radiopharmaceuticals limit its use when intended for parenteral administration.This short communication summarizes data from the literature on the toxicity of HEPES in dogs after intravenous infusion and the subsequent use in humans. We also highlight the use of HEPES in an FDA labelled intravenous drug formulation. Regulatory institutions may consider this data to review current strict limits.

ON REACTIVITY OF PIPERAZINE AMINOGRUPS IN INTERACTION WITH ETHYLENE OXIDE

Currently, the main method for producing N-(2-hydroxyethyl) piperazine in industry is the cyclization of ethylene glycols and ethanolamines in the presence of ammonia and hydrogen. The main disadvantage of this method is the production of a wide range of products and, as a consequence, low selectivity for N-(2-hydroxyethyl) piperazine. In this work, the object of study is the piperazine hydroxyethylation reaction in the presence of an “inert” solvent under the reaction conditions, as the most selective way to obtain N-(2-hydroxyethyl) piperazine. The solvent molecule acts as a homogeneous catalyst of the acid type and is characterized by the presence of a mobile proton for opening the oxirane ring of ethylene oxide by the acid-base mechanism. There was studied the dependence of the yield of reaction products on the parameters of the process in the temperature range of 60 - 130 ° C; solvent concentration (water, methylcellosolve) 1 - 75% wt. and molar ratio of reagents (ethylene oxide / piperazine) 0.2 - 1. Analysis of the reaction mass by gas-liquid chromatography showed that the main by-product is N, N'-bis (2-hydroxyethyl) piperazine - the product of the hydroxyethylation of N-(2-hydroxyethyl ) piperazine in the second amino group. The hydroxyl group of hydroxyethylation products are formed in a negligible amount. It was found that the composition and concentration of the solvent, as well as the temperature regime of hydroxyethylation, do not significantly affect the selectivity of the process. It was shown that piperazine hydroxyethylation is described by the kinetics of series-parallel reactions. The results obtained in the study may be of interest for the development of piperazine hydroxyethylation process technology, in terms of simplifying the mathematical model of the reactor unit by excluding from the description factors that do not significantly affect the selectivity of the formation of N-(2-hydroxyethyl) piperazine.

9,10-Bis[(4-(2-hydroxyethyl)piperazine-1-yl)prop-2-yne-1-yl]anthracene: Synthesis and G-quadruplex Selectivity

G-quadruplex DNA is the target of several natural and synthetic small molecules with antiproliferative and antiviral activity. We here report the synthesis through Sonogashira reaction and A3 coupling of a disubstituted anthracene derivative, 9,10-bis[(4-(2-hydroxyethyl)piperazine-1-yl)prop-2-yne-1-yl]anthracene. The binding of this compound to G-quadruplex and double stranded DNA sequences was evaluated using electrospray ionization mass spectrometry (ESI-MS), demonstrating selectivity for the first structure. The interaction pattern of the ligand with G-quadruplex was investigated by molecular docking and stacking was found to be the preferred binding mode.