The Preparation And Catalytic Research Of Chromium-base Catalysts Supported On Molecular Sieve For Ethylene Oligomerization

Ethylene molecule as one of the world’s biggest chemical products production,occupies a pivotal position in national economy.Linear alpha olefins in copolymerization monomer, surfactant, papermaking, oil additives, plasticizer with alcohol, and other fields shows excellent performance, based on this, the use of ethylene in the preparation of linear alpha olefins for the use of ethylene provides a very important way.The SBA - 15, MCM - 41, NaY and HY molecular sieve as the carrier was prepared by four kinds of chromium-base catalysts used in ethylene in molecular sieve .We used nuclear magnetic resonance , fourier transform infrared spectroscopy , thermogravimetric, scanning electron microscopy, energy spectrum analysis, specific surface area and pore structure analysis, X-ray powder diffraction,inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy and so on as characterization methods to analyze the characterization of the catalysts, the structure of catalyst was determined.We studied different reaction conditions,which included Al/Cr molar ratio, reaction temperature,pressure, solvent system,concentration of catalyst, promotor types to select the suitable reaction conditions,we also discussed the mechanism of ethylene oligomerization.The experimental results show that: (1) The Cr/TMCS/PNP/HY showed better in the activity and selectivity, in the n (Al)/n (Cr) = 3 00, reaction temperature =35℃, reaction pressure = 4 MPa, c[Cr] = 24 umol/L, cocatalyst = TIB A, solvent = cyclohexane under the condition of 100 mL.The activity of catalysts is 14.76 x 105 g/(molCr,h),1-C4=,1-C6=, 1-C8=selectivity were 8.18%, 73.24%, 15.09%. (2) Catalysts were supported on molecular, the activity of catalyst decreased, and its producs transfer to low carbon products.This may be because in ethylene trimerization to four poly ethylene process, seven yuan metal ring intermediates made after inserting ethylene molecule intermediates of larger diameter,because of the molecular sieve "nano confined effect", make the product of high carbon number is less.(3) Catalyst may be single or double metal or more metal ligand structure,this may be associated with catalyst carrier of aperture and channel structure.