Preparation Of Mesoporous Silica/Carbon Composite Filler From Coal Gasification Fine Slag And Its Application In Polypropylene

As the solid waste in the production process of coal chemical enterprises,coal gasification slag has a huge amount of emissions.The current treatment method of coal gasification slag is mainly landfill treatment,which wastes a lot of land resources and brings serious pollution to the environment,which has become the bottleneck and technical challenge of the development of coal chemical enterprises.Therefore,the research on resource utilization of coal gasification slag is imminent.Filler is one of the commonly used components in polymer resin products.By adding specific fillers,the polymer resin can be strengthened and toughened,and the resin can be saved and the cost can be reduced.At present,the commonly used resin fillers,such as calcium carbonate,kaolinite,and talc,are mostly mineral fillers,and their production not only consumes a lot of precious ore resources,but at the same time,due to the complicated production process,the production cost is relatively high.This paper takes the gasification slag solid waste produced by the coal chemical industry as the object,and by studying its unique physical and chemical properties and particle morphology characteristics,attempts to prepare a composite filler by certain physical and chemical means,making it a low-cost high value-added filler product to replace traditional rubber and plastic fillers.The coal gasification process mainly produces two kinds of tailings,which are divided into fine coal gasification slag and coarse coal gasification slag according to their discharge location and particle size.The coal gasification fine slag is mainly composed of amorphous spherical glass microbeads and flocculent residual carbon.The glass microbeads include silica and metal oxides(Al₂O₃,Ca O,Fe₂O₃,etc.),which have high reactivity and are easy to react with dilute acid.The residual carbon has rough surface and porous structure,which has a positive effect on the compatibility of filler and matrix.In this paper,according to the chemical characteristics of fine coal gasification slag,mesoporous silica/carbon composite filler was successfully prepared and used as polypropylene filler,which can replace the traditional plastic filler,and the preparation process is simple and easy to operate,low cost,and can effectively realize the resource utilization of coal gasification slag.In this paper,coal gasification fine slag filler products with different carbon contents were obtained by calcination at different temperatures,and applied to the reinforcement of polypropylene,and the influence of different carbon contents of coal gasification fine slag on polypropylene composites properties was explored.The results show that the addition of coal gasification fine slag with different carbon content can enhance the bending resistance and thermal stability of polypropylene composite,but reduce its elongation at break and impact strength.The polypropylene composites filled with coal gasification fine slag with high carbon content have higher tensile strength,while the elongation at break,impact strength and flexural strength of PP composites increase first and then decrease with the decrease of carbon content.This is because the decrease of hydrophilicity caused by the decrease of carbon content is beneficial to the compatibility of filler and matrix,while the decrease of activity and specific surface area is not conducive to the compatibility of filler and matrix.When the calcination temperature is 450°C,the carbon content is 5.07%,the above effects reach the optimal balance,the polypropylene composite material has the best comprehensive properties.Through the chemical reaction between hydrochloric acid and glass microbeads in coal gasification fine slag,acid leaching dissolves metal oxides and forms mesoporous channels,and then calcining to remove residual carbon,a mesoporous spherical silica material can be successfully prepared.It was applied to polypropylene to explore the effect of the pore structure of mesoporous silica on the properties of composites.The results show that the addition of mesoporous silica enhanced the flexural strength and thermal stability of the composites,but decreased the elongation at break and impact strength.The mechanical strength(tensile,impact,and flexural strength)of polypropylene composites showed a trend of first increasing and then decreasing with the increase of hydrochloric acid dosage.When the acid solubility is too low,the spherical particle pore structure cannot be fully formed,and when the acid solubility is too high,the active silicon will react with HCl and the pores will be destroyed.When the HCl molecules in the hydrochloric acid solution just react completely with the metal oxides in the glass beads,that is,when the acid-ash ratio is 1.0,the pore volume of mesoporous silica is the largest,and the polyprepylene composite has the best properties.According to the above-selected optimum acid-ash ratio,the coal gasification fine slag is treated with hydrochloric acid acid solution for pore formation,and then calcined to control the carbon content to obtain mesoporous silica/carbon composite filling materials with different carbon contents.It was used as a filler of polypropylene,and the effect of the structure of the composite filler on the properties of polypropylene composites was explored.The results show that the addition of composite fillers can significantly enhance the mechanical strength of polypropylene composites.With the decrease of carbon content,the gradual decrease of specific surface area and the weakening of the chemical bond between carbon and silicon are unfavorable for the reinforcement effect of fillers,but the decrease of filler particle size and the increase of non-polarity have positive effects on the compatibility of filler and matrix.When the calcination temperature is 450°C,the carbon content is 14.47%,the above effects reach the balance.At this time,the polypropylene composite filler has the best mechanical strength.When the filler content is 20 phr,the polypropylene composite reaches the best tensile strength(34.96 MPa),the matrix has the highest crystallinity(34.06%).The interfacial interaction analysis results show that show that the composite filler with a carbon content of 14.47%has the largest interfacial interaction parameter with polypropylene,and the adhesion between the filler and the matrix is the strongest.In addition,the addition of composite filler can reduce the thermal conductivity of composite materials,indicating that mesoporous silica/carbon composite fillers also have broad application prospects in the field of thermal insulation.By comparing the effects of composite filler and heavy calcium powder on the properties of polypropylene composites,it is known that composite filler can replace1250 mesh heavy calcium powder as polypropylene filler.At present,the composite filler prepared by this process has achieved mass production,and a series of technologies have been successfully industrialized.