Cold Rich Bypass to Strippers for CO2 Capture by Concentrated Piperazine

Cold rich bypass to the stripper in CO₂ capture by alkanolamines will usually reduce the total heat duty. Bypass reduces the stripping steam in the overhead vapor and balances the temperature approach in the main cross exchanger. This process improvement reduces the energy requirement of any configuration, but it is most beneficial when the overhead vapor is not already countercurrently contacted with incoming rich solution. Therefore, the 2‐stage flash configuration was evaluated in this work, and it had an improvement of 11 % over the no bypass case. Its improvement was better than what was observed with a simple stripper and interheated column. An optimized cool rich bypass for a pilot scale 2‐stage reduces the equivalent work.     

CO2 Capture by Liquid Solvents and their Regeneration by Thermal Decomposition of the Solid Carbonated Derivatives

The chemical capture of CO₂ by either aqueous Na₂CO₃ and K₂CO₃ or nonaqueous solutions of the amines 2‐amino‐2‐methyl‐1‐propanol (AMP) or piperazine (PZ) is described. The captured CO₂ is stored as solid NaHCO₃, KHCO₃, and AMP or PZ carbamates. Solid NaHCO₃ and KHCO₃ are decomposed at 200 °C and 250 °C, respectively, to regenerate the carbonates for their reuse. In the experiments with AMP or PZ, the solid carbamates are decomposed at 80 °C–110 °C to regenerate the free amines. The absence of water in the desorption‐regeneration step is intriguing and could have the potential of reducing one of the major disadvantages of aqueous absorbents, namely the energy cost of the regeneration step and amine degradation, yet preserving the efficiency of the absorption in the liquid phase.     

A new cationic surfactant N,N′-dimethyl-N-acryloyloxyundecyl piperazinium bromide and its pH-sensitive gels by microemulsion polymerisation

A piperazine-based cationic surfactant, N,N′-dimethyl-N-acryloyloxyundecyl piperazinium bromide (DAOUPB) was synthesised by a two-step procedure. The monomer was polymerised in two new microemulsion systems: (i) DAOUPB/water/methyl methacrylate (MMA):hydroxyethylmethacrylate (HEMA) and (ii) DAOUPB/water/acrylonitrile with ethyleneglycol dimethacrylate (EGDMA) as the crosslinking agent. Transparent solid polymeric materials were obtained by photo-initiated polymerisation of some of these microemulsion compositions. Most of the bicontinuous microemulsions investigated gelled within 10 min resulting in transparent solid polymers. The electron micrographs of the polymers obtained from microemulsion compositions containing MMA:HEMA did not show any micropores, while those obtained using acrylonitrile revealed the existence of open-cell type micropores and also of the bicontinuous nature of the system. The width of the bicontinuous structure (micropores) was about 33 nm in the dry state, with long and winding channels of random distribution. The swelling of the gels was highly sensitive to pH.     

Synthesis of 1,9-bis[glycidyloxypropyl]penta(1′H,1′H,2′H,2′H-perfluoroalkylmethylsiloxane)s and copolymerization with piperazine

A series of 1,9-bis[glycidyloxypropyl]pentasiloxanes (IV-VI) were prepared by the platinum catalyzed hydrosilylation of 1,9-dihydridodecamethylpentasiloxane (I), 1,9-dihydrido-3,5,7-tris(3′,3′,3′-trifluoropropyl)heptamethylpentasiloxane (II), and 1,9-dihydrido-3,5,7-tris(1′H,1′H,2′H,2′H-perfluorooctyl)heptamethylpentasiloxane (III) with allyl glycidyl ether. Subsequently, IV-VI were copolymerized with piperazine to form high molecular weight copoly(carbosiloxane)s (VII-IX). The structures of the 1,9-bis[glycidyloxypropyl]penta-siloxanes (IV-VI) and copoly(carbosiloxane)s (VII-IX) were determined by ¹H, ¹³C, ²⁹Si, and ¹⁹F NMR as well as IR spectroscopy. The molecular weight distributions (M_w/M_n) of VII-IX have been characterized by gel permeation chromatography and their thermal properties measured by differential scanning calorimetry and thermal gravimetric analysis.     

Synthesis and structure of AlPO4-9: An unacquainted member in the family of microporous aluminophosphates

In the family of microporous aluminophosphate, AlPO₄-9 is one of the members reported first in 1982. However, its structure and characteristics have not been known up to now, and this makes it a special member. In the present work, AlPO₄-9 has been synthesized using piperazine as the structure-directing agent and the mixture of H₂O and EG as the solvent. Structure refinement from single crystal X-ray diffraction data shows that AlPO₄-9 is a material with the composition of C₂H₇Al_5.50NO₂₅P₆. It crystallizes in the monoclinic space group C2/c (No: 15), with a = 24.230(5) Å, b = 14.026(5) Å and c = 16.197(3) Å, β = 119.87(4)°, V = 4773(2) Å³, Z = 8. The open-framework of AlPO₄-9 is built of alternating corner-sharing PO₄ tetrahedra and AlO₄ tetrahedra (AlO₆ octahedra) to construct a curved one-dimensional 8-ring channel system running along [1 0 1]. Meanwhile, the strict alternative of PO₄ tetrahedra and AlO₄ tetrahedra (AlO₆ octahedra) results in a negative framework in AlPO₄-9. Thermal stability has been determined on a thermal analyzer and by calcination. It reveals that AlPO₄-9 framework is thermally stable and has a potential to be a catalytic material.     

哌嗪的技术与市场

综述了哌嗪的应用开发及合成技术进展,分析了哌嗪的市场前景。     

β-羟乙基乙二胺环化合成哌嗪

本文研究了β 羟乙基乙二胺的催化加氢环合反应及几种铜系催化剂环合反应的催化性能。以甲苯为溶剂可显著提高β 羟乙基乙二胺环合生成哌嗪的选择性。反应的工艺参数优化结果表明 ,以Cu/γ Al2 O3 为催化剂、甲苯为溶剂、氢气初压3 0MPa和反应温度 1 80℃～ 1 90℃时 ,哌嗪收率可稳定在 85 %以上     

环丙沙星哌嗪化缩合方法的研究

采用无水哌嗪、活化喹啉环和活化哌嗪三种缩合方法制备了环丙沙星，并比较了它们各自的反应摩尔比、温度、时间及反应收率，优选得到了其最佳哌嗪化缩合方法为活化哌嗪法，该法收率高、产品质量好，易于工业化生产     

气固相催化合成哌嗪的反应动力学

气固相催化合成哌嗪的反应动力学胡望明，李昌圣，王丽华，吴兆立（浙江大学化工系，杭州３１００２７）关键词哌嗪，一乙醇胺，气固相催化反应１前言哌嗪是一种重要的乙烯环胺类化合物，可用于制造多种重要药物，也可用于制造高性能聚合物、表面活性剂、染料、聚氨酯发泡...     

Synthesis and characterization of zeolite mazzite analogue in Na<Subscript>2</Subscript>O–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>–Piperazine–H<Subscript>2</Subscript>O

Zeolite Mazzite (MAZ) analogue was synthesized directly using piperazine as a structure directing agent. The reactive gel composition used was (5.0–7.0) piperazine:(6.0–7.0) Na₂O:Al₂O₃:20.0SiO₂:400H₂O. Using this composition, the reaction time was shortened greatly to 4 days and the crystallization time was reduced as well. The DTA data showed that piperazine, in as-synthesized zeolite omega decomposed easily. The decomposition of the piperazine occurred at 400–480°C. NH₃-TPD analysis proved that zeolite H-omega from piperazine had strong surface acidity with ammonia desorption temperature up to 590°C.