Preparation Of Sterically Hindered Amines And Their Application In Gas Desulfurization

Natural gas is a clean, efficient energy sources and chemical raw materials, But the natural gas exploited from gas Wells contains acid gases (H2S, CO2, etc.), in different degrees. The harm of H2S is especially serious, so natural gas desulfurization is an important part of China's industrial development. Since the energy crisis is more severe and the environmental requirements are increasingly stringent, the industry demand for natural gas desulfurization selectivity is higher and higher, traditional alcohol amine solvent can not adapt to the demand, so we must seek the solvents with higher activity and selectivity. In recent years, the research of selectively removal of H2S in natural gas by using sterically hindered amines has attracted widespread attention, it has become one of important development direction in the field of natural gas purification.Two sterically hindered amine TBGA and BTBE have been synthesized, The structure of the synthesized product was characterized by infrared spectroscopy and NMR spectroscopy, the results show that the molecular structure of target product synthesized was basically consistent with TBGA and BTBE; The synthesis conditions of TBGA and BTBE were optimized through single factor and orthogonal experiment. The optimal conditions of TBGA are as follows:reaction solvent is ethanol, reaction time is 5h, the reaction temperature is 100?, reactant ratio bettwen tertiary amine and 2-chloroethoxy ethanol is 4:1, solvent dosage is 80ml; BTBE optimal synthesis conditions are as follows:reaction solvent is tetrahydrofuran, reaction time is 4h, reaction temperature is 130?, reactant ratio of Tert-butylamine and dichloro ethyl ether is 5:1, the amount of solvent is 110ml.The pKa value was obtained by using the conductivity method, The pKa value of sterically hindered amines TBGA and BTBE is 10.12 and 10.27 at a temperature of 20? respectively, which is higher than MEA and MDEA, the H2S reactivity of organic amine was compared,the order was BTBE>TBGA>MEA>DIPA>MDEA; The foaminess and foam stability of TBGA and BTBE solution were higher than MDEA solution; The acid gas desorbed from TBGA and BTBE rich fluid is higher than MDEA rich solution at the same time with the same desorption desorption temperature, the regeneration performance of TBGA and BTBE solution is better to MDEA solution.The H2S absorption properties of sterically hindered amines TBGA and BTBE solution were evaluated by static absorption device, and the desulfurization performance was compared with commonly used amine solution, the results show that the removal rate and load of H2S absorption of the TBGA and BTBE solution are higher, besides the TBGA and BTBE solution has better selectivity of H2S absorption in a high CO2/H2S ratio, the selectivity of TBGA and BTBE solution is about 3 to 5 times of MDEA solution, the results prove the superiority in desulfurization performance of sterically hindered amines. And desulfurization performance of sterically hindered amines BTBE is better than that of TBGA.The influence of the absorption temperature, air speed, load and other factors on the acid gas absorption properties were further investigated, the results showe that the low temperature is conducive to the H2S removal of solution; The increase of acid gas absorption load will lead to decrease of H2S selectively of the solution, but TBGA and BTBE solution can maintain a high H2S selectively over a wide load range of acid gas absorption load; As the gas velocity of feed gas increased, the H2S selectively of amine solution got higher, but H2S removal rate of the amine solution reduced; The selectiveity of BTBE solution was superior than TBGA solution, it indicated that the enhance of amine molecules space steric effect could improve the desulfurization selectivity;Add BTBE into MDEA solution to prepare the MDEA-BTBE complex solution, and the desulfurization performance of the MDEA-BTBE complex solution was measured. The results show that the BTBE in MDEA solution can significantly improve the desulfurization performance of the solution, reduce the decreasing tendency over time of H2S removal rate of solution; When the acid gas load is increased by approximately 69%, MDEA solution decreased 71%, while the selectivity of MDEA-BTBE complex solution decreased only 45% under the same conditions. The absorption properties of MDEA-BTBE composite solution improved as the BTBE quantity increased, but when the added amount of BTBE reached a certain value, the increasing trend droped. When the amount of acid gas feed gas and CO2/ H2S ratio changed, the MDEA-BTBE complex solution could still show a higher H2S load and selectivity compared with MDEA solution, the MDEA-BTBE complex solution can better adapt to desulfurization of different composition of feed-gas than the MDEA solution.