Abstract
Catalytic behavior of alkali treated mordenite (H-MOR) in selective synthesis of ethylenediamine (EDA) via condensation amination of monoethanolamine (MEA) was investigated. Changes in the structural and acidic properties of alkali treated H-MOR were systematically investigated by N2 adsorption/desorption isotherms, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), temperature programmed ammonia desorption (NH3-TPD), pyridine adsorption was followed by infrared spectroscopy (Py-IR), and X-ray fluorescence (XRF) analyses. The results show that alkali treatment produces more opening mesopores on the H-MOR crystal surfaces and leads to an increase in the number of B acid sites and the strength of the acid sites. The mesopores effectively enhance the rate of diffusion in the bulk catalyst. Moreover, the B acid sites are active sites in selective synthesis of EDA. Due to improvements in the diffusion conditions and reactivities, alkali treated H-MOR shows an excellent catalytic performance under mild reaction conditions. The conversion of MEA was 52.8% and selectivity to EDA increased to 93.6%, which is the highest selectivity achieved so far. Furthermore, possible mechanism for the formation of EDA is discussed.
Highlights
Ethylenediamine (EDA) is an important organic intermediate that can be used for the preparation of chelating reagents, surfactants, fabric softeners, lubricating oil additives, fungicides, insecticides, and resinous polymers [1,2,3,4]
The N2 adsorption/desorption isotherm of H-MOR is characteristic of microporous materials and the isotherm for the samples after alkali treatment had shifted from type I to a combination of types I and IV with a pronounced hysteresis loop (Figure 1a), which indicated the formation of intra-crystalline mesopores [23]
The Barret Joyner Halenda (BJH) pore size distributions of the samples before and after alkali treatment (Figure 1b) show a well-defined distribution of the samples before and after alkali treatment (Figure 1b) show a well-defined distribution of mesopores mesopores approximately 4 nm in size and a comparable pattern, and only the volume of the approximately 4 nm in size and a comparable pattern, and only the volume of the mesopores increased mesopores increased with increasing NaOH concentration (Table 1)
Summary
Ethylenediamine (EDA) is an important organic intermediate that can be used for the preparation of chelating reagents, surfactants, fabric softeners, lubricating oil additives, fungicides, insecticides, and resinous polymers [1,2,3,4]. EDA is synthesized by ammonolysis of ethylene dichloride with ammonia [2]. This process suffers from the co-production of sodium chloride, corrosion associated with chlorides and poor product selectivity to EDA. EDA can be produced via reductive amination of monoethanolamine (MEA) with hydrogen and ammonia over nickel or cobalt catalysts [3]. A higher reaction pressure (10–20 MPa) of hydrogen is an essential prerequisite to achieve satisfactory catalytic performance in the above process [1,4], which makes this manufacturing process potentially dangerous for use in industry.
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