Phosphoric acid activation is currently the main method for industrial production of biomass-based activated car-bon,but the higher ash content limits its application in high-end fields such as medicine and food.Based on this,the effect of activation conditions(temperature,time,etc.)and washing conditions(medium,acid concentration,temperature,etc.)on the ash content and properties of activated carbon was investigated by using wet phosphoric acid as the activator and waste wood chips as the carbon source,and the surface properties and microstructure of activated carbon were analyzed by using TG,FT-IR,XRD,SEM and TEM characterization.The results showed that insoluble phosphate was the main factor in the generation of activated carbon ash,and that the activated carbon ash,iodine and methylene blue values could be regulated by controlling the activated carbon preparation process and washing process.The optimal process conditions were activation temperature of 500℃,phosphoric acid concentration of 70%,acid to chip ratio of 2∶1,activation time of 60 min,N2 protec-tion,washing solution dosage of 100 mL,washing solution concentration of 20%,washing medium of H3PO4,washing tem-perature of 80℃and washing time of 60 min.The activated carbon prepared under these conditions had an ash content of 1.07%,iodine value of 1 241.4 mg/g,methylene blue value of 285 mg/g,specific surface area of 2 290 m2/g,indicating that the activated carbon prepared by this technology had the potential to be applied in high-end industries such as food and medicine.
Fluorite tailings-based lightweight high-strength ceramsite was prepared by sintering with fluorite tailings and clay as raw materials and silicon carbide（SiC） as foaming agent. The effects of the amount of fluorite tailings,sintering temperature,sintering duration and SiC external dosage on the properties of ceramsite were systematically investi-gated. The crystal phase and microstructure of the obtained ceramsite samples were also analyzed by thermodynamic calculation,X-ray diffraction spectrum,scanning electron microscope and other detection methods. The results showed that when the proportion of fluorite tailings was 70%（mass fraction）,the proportion of clay was 30%（mass fraction）,the external proportion of SiC was 0.5%（mass fraction）,the preheating temperature was 450 ℃,the preheating time was 15 min,the sintering temperature as 1 210 ℃,the sintering time was 30 min,and the heating rate was 5 ℃/min,the fracturing force of the obtained fluorite tailings ceramisite was 527.9 N,the apparent density was 0.89 g/cm3,the water absorption rate was 0.21% in 1 h,and the cylinder compressive strength was 4.63 MPa,the bulk density was 594.6 kg/m3,which met the requirements of Grade 600 high-strength ceramsite for lightweight aggregates in GB/T 17431.1—2010“Lightweight Aggregates and Experimental Methods”.The research results could provide a new method for the resource utilization of fluorite tailings.
Propylene is an important industrial raw material mainly used in the production of polypropylene,acrylonitrile,isopropyl alcohol,acetone and propylene oxide.With the increasing demand for propylene,the technology of propane dehy-drogenation has been widely used in the industrial production of propylene.Although platinum-based and chromium-based catalysts have high activity in propane dehydrogenation,they are also prone to poisoning and deactivation.Metal oxides have attracted widespread attention as alternative non-precious metal catalysts.Firstly,the reaction pathway and deactivation mechanism of propane dehydrogenation catalyzed by metal oxides were introduced.It was pointed out that enhancing the C—H activation ability,alleviating the reconstruction and reduction of active components were the key to improving the pro-pane dehydrogenation performance of metal oxide catalysts.Then,several representative metal oxide catalysts were reviewed in detail,the mechanism of action and active species of various catalysts were summarized,and the existing problems of cor-responding catalysts were analyzed and discussed.Finally,key research directions for future propane dehydrogenation cata-lysts were proposed,which was expected to provide new ideas for the direct production of chemicals through the activation of low-carbon alkanes.
The effects of initial digestion water temperature,stirring speed,water-ash mass ratio and pressurized digestion on the morphological structure,particle size and specific surface area of the reaction product calcium hydroxide were inves-tigated by using industrial grade quicklime as raw materials,and the product calcium hydroxide was characterized by Mal-vern laser particle size distribution instrument,scanning electron microscope(SEM)and specific surface area analyzer.The results showed that the digestion rate was accelerated with the increase of the initial temperature of water,and when the stir-ring speed was 500 r/min,the initial temperature of water was 45～80℃,and the mass ratio of water to ash was 4∶1,the pro-duced calcium hydroxide had the narrowest particle size distribution and the maximum specific surface area was 18.23 m2/g.When the initial temperature of digested water was 25～45℃,the morphology of the product calcium hydroxide showed a"dendritic"shape,and when the initial temperature of the digestion water was 65～80℃,the shape of product calcium hy-droxide grew into"granular".The pressurized digestion method could obtain a large specific surface area of calcium hydrox-ide and its shape was"petal-like",and the maximum specific surface area was 29.32 m2/g.
The effect of pre-reduction treatment by adding aluminum powder to titanium oxysulfate solution containing mag-nesium,aluminum,and iron impurities and changing the valence of some elements on the process of iron removal from tita-nium liquid by hydrothermal hydrolysis was investigated.Under the guidance of electrode potential theory,all Fe(Ⅲ)in tita-nium liquid was reduced to Fe(Ⅱ),and a small amount of Ti(Ⅳ)was reduced to Ti(Ⅲ).Subsequently,hydrothermal reac-tion was conducted at 120℃for 4 h.Titanium hydrolysis efficiency of samples with and without pre-reduction were 98.59%and 97.47%,and iron content in the hydrolysate was 115 mg/kg and 11 710 mg/kg(based on TiO2),respectively.Combining the thermodynamic equilibrium constant of each reaction at 110～150℃with the relevant equilibrium equation,the concen-tration of each component in the equilibrium system at different temperatures was obtained by Newton-Raphson iterative method,and the change law of Mg,Al and Fe impurities in the solution with and without pre-reduction during the hydrother-mal hydrolysis process was illustrated.The strengthening mechanism of pre-reduction on the deferrization in the hydrother-mal hydrolysis process of titanium sulfate solution containing impurities was revealed through mutual verification of experi-ments and thermodynamics.
