Preparation Of NaY Zeolite Adsorbent And Its Adsorption Effect On Volatile Organic Compounds

Volatile organic compounds?VOCs?are the main substances causing air pollution in China,which have a great impact on the environment and human health.The industrial source is the most important source of current VOCs,and the exhaust gas emitted by it has the characteristics of large air volume and low concentration.The adsorption method is widely used as a VOCs purification process at home and abroad.The method has the characteristics of wide treatment range,economical energy saving,etc.,and the core of the treatment efficiency of the adsorption method is the adsorbent.NaY molecular sieve raw powder is rich in micropores,large in specific surface area,stable in property,and easy to desorb.It is a hot trend in recent years to prepare adsorbents for the purification of VOCs.However,the research is still in its infancy,and there are still many problems in the synthesis of NaY molecular sieve raw powder,such as complicated steps,long service time and high raw material cost,and there is no plan for making it into industrial adsorbent.Therefore,this thesis designs experiments for the above problems,including the synthesis of NaY molecular sieve raw powder,the formation of the adsorbent and the evaluation of the adsorption performance of the adsorbent.It provides a new idea for the preparation of NaY molecular sieve adsorbent and provides theoretical support for its application in the field of adsorbing VOCs.The experiment firstly used industrial grade water glass,NaAlO₂ and NaOH as raw materials to prepare NaY molecular sieve raw powder by using a directing agent?seed?hydrothermal synthesis method.The synthesis was studied from the aspects of crystallization temperature,crystallization time,crystallization conditions,and seed crystal optimization scheme.The products were tested and characterized by XRD,XRF,static adsorption and thermogravimetric desorption experiments.The analysis results show that the synthesis conditions of the original powder of NaY molecular sieve are as follows:the mass ratio of water glass,NaAlO₂,NaOH and H₂O in the seed gel is 14.05:1:3.35:9.6,the aging temperature is 60°C,the aging time is 2 h;The mass ratio of the four substances was 13.83:1:0.11:10.28,the crystallization temperature was 100°C,and the crystallization time was 9 h.The synthesized NaY molecular sieve raw powder has a crystallinity of 99.39%,a specific surface area of547.72 m²/g,a static saturated adsorption amount of p-xylene of about 220 mg/g,and an optimum desorption temperature of 137.70°C.In order to prepare the prepared NaY raw powder into an adsorbent having a certain mechanical strength,the method of dip coating is firstly used to use the most commonly used cordierite honeycomb ceramic as a carrier,and the NaY original powder and the surfactant,the binder,the water was mixed in a certain ratio to form a coating slurry,which was loaded and examined for coating rate and coating amount to determine an optimum coating slurry formulation.The adsorbent preparation scheme is further optimized by the coating effect of the specific slurry on different supports and the influence of the addition of the pore former on the adsorption performance of the adsorbent.The experimental results show that the surfactant is sodium polyacrylate,the binder is attapulgite,and the mass ratio of sodium polyacrylate,attapulgite,NaY powder and water is 0.01:1:19:66.67 is the most ideal coating.Overlay.The slurry had the best single coating effect on the alumina ceramic balls,the optimum number of coatings was 3 times,and the coating rate was 48.99%.Adding a pore former to the slurry of 1%by mass of the total solid material can increase the adsorption capacity of the adsorbent p-xylene with alumina ceramic balls as a carrier.The inlet flow rate is 10 L/min and the inlet concentration is about 500mg/m³.Under the conditions,the equilibrium adsorption amount reached 140.26 mg/g.The adsorption effect of the adsorbent on VOCs under different conditions was further evaluated by dynamic adsorption experiments.Firstly,the adsorption effect of adsorbent on methanol,acetone,ethyl acetate and xylene was investigated.The effect of the inlet flow rate and inlet concentration on the adsorption effect was investigated with xylene as the target material.A penetration model fit was performed on the experimental data to correct experimental errors and obtain instructive data.Finally,the adsorbent was subjected to thermal desorption experiments and cyclic adsorption experiments to investigate its regeneration performance.The experimental results show that the NaY molecular sieve adsorbent has certain adsorption effect on methanol,acetone,ethyl acetate and xylene.The closer the adsorption molecular diameter is to the adsorption capacity of NaY molecular sieve.The adsorption capacity decreases with the increase of the inlet flow rate,and gradually increases with the increase of the inlet concentration.However,the adsorption capacity does not change substantially when the concentration exceeds 500 mg/m³,the equilibrium adsorption capacity of p-xylene is about 140¹45mg/g..The results of penetration model fitting show that the correlation coefficient between Yoon-Nelson model and Thomas model is more than 0.95,which can describe the dynamic adsorption process of VOCs exhaust gas by NaY molecular sieve adsorbent.The optimal desorption temperature of the adsorbent was 138.59°C.After 15 cycles of recycling,the adsorption capacity of the adsorbent did not change significantly,and the regeneration performance of the adsorbent was good.