Study On The Interaction Of Hydroxypropyl Methyl Cellulose And Montmorillonite In A Carbonization Process

Nowadays,CO2_ emission problems have become increasingly prominent with the global industrialization and rapid development.In order to solve the problems of environment and resources,the development and utilization of biomass carbon materials are vital.There are a lot of coexistence systems of high content biomass and minerals in nature.Therefore,the association of natural mineral and carbon materials has become a new research focus in the world.The effect of carbonization on the mineral surface in the environment and the changes of carbonization product structure and characteristics properties at each stage are explored.The possible mechanism is proposed to provide a scientific basis for the controllable preparation of new carbon materials from coexistence system of minerals and biomass.In this paper,the montmorillonite and cellulose composites were synthesized by hydrothermal treatment and pyrolysis treatment.The structure morphology and performance of the product were characterized through a variety of testing methods.We focus on montmorillonite surface effect and the interaction of montmorillonite and cellulose in carbonization process.The effects of carbonization on the structure and surface properties of montmorillonite and the influence of montmorillonite on biomass carbon were discussed.Firstly,we get optimization condition of hydrothermal carbonization from experimental variables with hydrothermal temperature and doping ratio.The optimum reaction temperature is 230 oC and the mass doping ratio is 1:1 according to the XRD and FT-IR analysis.The preparation of composite is treated at 230 oC for different time from 0.5 h to 16 h.It is found that hydrochar diversely influences the structure and properties of montmorillonite in different degree.In terms of structure,HPMC can be adsorbed on the surface of montmorillonite.The stability of composite improves over hydrothermal time.The state of cellulose has a significant effect on the order of montmorillonite.In terms of performance,the zeta potential of composite is mainly affected by montmorillonite when HPMC is not completely carbonized butfollowed by hydrochar after the end of carbonization.Compared to raw montmorillonite,specific surface area of the composite decreases more sharply.The results also indicate that montmorillonite plays a protective role on the hydrochar,so the thermal stability of hydrochar is improved.Secondly,we study the properties and structure of hydrothermal composite materials with different mass doping ratio at high temperature.In terms of structure,Montmorillonite is decomposed into amorphous silicon aluminum oxide and hydrochar greatly hinders the binding of Al2O3 and SiO2 at high temperature.The carbon content is higher,the hindering effect is more obvious.Composite added into HPMC will transform to different phases(cordierite or cristobalite)at high temperature.The hydrochar has not been ordered at 1200 oC which is still in amorphous form.In terms of performance,specific surface area of the montmorillonite is only about 1 m2/g after 900 oC due to the destruction of interlayer structure.The phase transition of composite causes the dramatic change of the Zeta potential at high temperature.Finally,we study the performance and the structure of calcium and sodium composites synthesized with different recombination methods and calcination atmosphere in pyrolysis treatment.The calcination atmosphere is divided into air and air-free atmosphere.Compared to air atmosphere,air-free atmosphere exacerbates the destruction of montmorillonite structure.Therefore,the structure collapse temperature decreases 50 oC.The hydrochar carbonization accelerates the dehydroxylation process.Interlayer recombination is easier to destroy eight surface layers than surface recombination.Therefore,the dehydroxylation temperature decreases 100 oC.Interlayer recombination causes a certain degree of stripping layer.Meanwhile,outer surface damage of montmorillonite is caused by surface recombination before decomposition of montmorillonite.So it makes the specific surface area reduced and surface charge changeable.At the same temperature,Na-montmorillonite is much more seriously damaged than Ca-montmorillonite,because the large interlayer spacing and much specific surface area provide more room for prochar which does not turn into carbon spheres.The prochar formed by the hydrothermal carbonization ofthe cellulose in the presence of montmorillonite does not exist in the form of a sphere.