Study On The Removal Of Trace Olefins From Aromatics By Alkylation Of Solid Acid Catalyst

The rapid development of the polyester industry has led to the increasing demand for raw materials,paraxylene.The production process of paraxylene will bring out trace amount of olefins.This part of olefins has a greater impact on the subsequent treatment process and should be removed.The traditional clay treatment can result in solid waste pollution,and hydro refining has disadvantage of aromatics loss.Therefore,we takes the alkylation of olefins and aromatic to produce long-chain alkylbenzene as the target reaction,and has high catalytic activity and reusable sulfated zirconia and Y-type molecular sieve as the research objects to explore the impact of the modification process.Research on sulfonated zirconia.The effects of the feeding method on the precursor Zr(OH)4,the concentration of the methane sulfonic acid,the metal modification and the calcination temperature were investigated through experiments.X-ray diffraction,N2 adsorption-desorption experiment,thermogravimetric analysis,pyridine-Fourier transform infrared spectrometer were used to characterize the catalysts,and the performance of catalytic removal trace olefins from aromatics was investigated on a micro-fixed bed reactor.The results show that the feeding method for preparing the carrier Zr(OH)4 has a greater influence on the reaction rate.The Zr(OH)4 carrier prepared by the reverse addition method(ZrOCl2·8H2O solution is added dropwise to ammonia)has a higher catalytic activity;The optimal concentration of the impregnating solution is 2 mol/L.The lower concentration cannot provide enough acid centers,and the higher concentration is easy to form salts;the aluminum-modified sulfonated zirconia calcined at 650℃(AlMSZ-650)is superior to zinc-modified sulfonated zirconia,which has the characteristics of high catalytic activity,slow deactivation rate,and reusability.The analysis found that AlMSZ-650 has a large specific surface area and a suitable pore size structure,retaining the distribution of active components on the catalyst surface.The pyridine-FTIR found that the aluminum-modified sulfonated zirconia has a larger amount of Lewis acid,and the initial catalytic reaction rate has close relation with the weak Bronsted acid.Study on NH4F/HF modified Y-type molecular sieve.NH4F/HF-modified USY was characterized by SEM scanning electron microscope,N2 adsorption-desorption experiment,X-ray diffraction,27Al MAS NMR,FTIR,pyridine-FTIR and other analytical methods.The study found that NH4F/HF modification can effectively adjust the pore structure and acidity of USY molecular sieves.The large rings are etched during the modification process,the volume and pore size of mesopores and macropores increase.The proportion of Si-OH-Al groups in the molecular sieve framework decreases,and the amount of Br■nsted acid decreases.The framework aluminum is removed and deposited in the pore channel,the pore volume of the micropores remains unchanged,but the pore size decreases.Due to the increase of extra-framework aluminum,the amount of Lewis acid of the NH4F/HF modified USY molecular sieve is 3 times than before.The reaction rate of NH4F/HF modified USY molecular sieve is high,and the deactivation rate is very slow.In addition,we study the formation of NH4F/HF modified USY molecular sieve.Result shows that,compared with pseudo-boehmite molding and aluminum sol molding,using kaolin as an extrusion molding aid has little effect on the inherent acidity and structure of molecular sieve catalysts.