Study On The Preparation And Performance Of Coal Pitch-based Water-absorbing Resin

As a country with large coal resources,every year the development and utilization of coal tar produces a large amount of by-product coal tar pitch,among which many applications of coal tar pitch may cause a lot of natural pollution.Specific common applications are the preparation of carbon materials,impregnants,needle coke and road asphalt,etc.But its excessively high output far exceeds the consumption of these applications.Therefore,the efficient development and utilization of coal pitch resources is a general direction that needs to be solved urgently.Researchers focus on finding new conversion methods,broadening the scope of common applications,and increasing development efficiency.Among them,benzene polyacid derivatives can be obtained by using the higher aromatic degree in coal tar pitch,but the wide distribution range of this type of product and the cumbersome extraction operation will bring difficulties to the later separation of the product,and the application route is also relatively scarce.Therefore,how to effectively use a large number of carboxylic acid groups and benzene ring structures contained in the product,and develop and prepare a variety of new types of practical materials is the current research focus.Because a large number of carboxylic acid functional groups can increase the water absorption rate of super absorbent resin,at the same time,its high water absorption performance can help in agricultural and forestry crops,medical and health,construction and waste water treatment applications.Among them,the lower alkali resistance of humic acid resins will limit its application,and the collection cost of humic acid is relatively high,and the extraction process will pollute the environment.Because the benzene carboxylic acid prepared from coal tar pitch has a lot of similarities with humic acid,it can be selected as a raw material to prepare a new type of super absorbent resin with certain excellent properties.Therefore,this study provides more possibilities for the new application of coal tar pitch and the choice of raw materials for water-absorbing resins.In this thesis,a large number of aromatic carboxylic acid substances in the liquid phase product obtained after oxidation of coal tar pitch are used as an entry point,and they are used as functional additives to prepare super absorbent resin materials,and the preparation and performance of synthetic resins are studied.Mainly carried out the following three aspects of work:1.Used coal tar pitch as the raw material,O₂ as the oxidant,and alkaline aqueous solution as the medium,the effects of different liquid-to-solid ratios(water:coal tar pitch),solid-to-alkali ratio(coal pitch:potassium hydroxide),reaction time and reaction temperature on the oxidation of coal tar pitch were investigated the effect of weightlessness.The results showed that:coal tar pitch(30 g),potassium hydroxide(60 g),deionized water(200 ml),reaction time of 2 h,reaction temperature of 240?,the weight loss rate of coal tar pitch was31.3%.Infrared spectrometer and scanning electron microscope were used to characterize coal tar pitch and oxidized coal tar pitch.Compared with coal tar pitch,the aromatic degree and oxygen-containing functional groups of oxidized pitch increased,and the pore structure and roughness increased;and the coal pitch was treated with alkali oxygen The characterization of the product and coal acid showed that the liquid product contains more aliphatic carboxylic acids,hydroxyl groups,aromatic ethers or ester groups than coal acid,and the roughness is increased.2.The liquid phase product of coal pitch oxidation used 60%of acrylic acid quality,3.8%of acrylic acid quality ammonium persulfate as initiator,and 0.2%of acrylic acid quality of N,N,-methylenebisacrylamide as crosslinking agent,at 75°C,a super absorbent resin was prepared by solution polymerization.A large number of hydrophilic functional groups contained in the liquid product strengthened the resin's molecular action in the aqueous solution.The saturated water absorption rate was reached within 2 hours in deionized water and normal saline,which were 613.2 g/g and 42.2 g/g,respectively.The specific experimental part included,the preparation experiment of the water-absorbent resin was a single factor experiment and an orthogonal analysis experiment to determined the influence of each factor on the water absorption performance of the resin and the best reaction conditions;infrared spectroscopy,scanning electron microscopy and thermogravimetric analysis are used for synthesis characterization of the resin;speculate the specific reaction mechanism analysis of the synthetic resin;conduct a number of performance studies of the synthetic resin.The resin has more rigid aromatic rings,ester functional groups and hydrophilic carboxyl functional groups;the roughness and pore structure have been increased;it has better temperature resistance,alkali resistance and repeated applicability.3.Coal pitch oxidation liquid product,acrylic acid,acrylamide,polyethylene glycol(200),ammonium persulfate,N,N,-methylene bisacrylamide were selected as reactants(the specific raw material ratio was 1.2:2:0.2:0.06:0.004),the polymerization temperature was 80^oC,the water-absorbent resin was prepared,and the saturated water absorption rate(451.8 g/g and115.7 g/g)was reached in 1 hour in deionized water and physiological saline.The specific experiments were single factor,orthogonal analysis,structural characterization and performance research,to study the influence of various reaction factors on water absorption performance,established the best reaction conditions,infer these possible reaction mechanism,and explore various resin properties.The obtained resin had more aromatic ring-C=C-,-CONH2,-COOH,-O-C=O and other functional groups,contained more pore structure,increaseed the surface roughness and specific surface area,these features help improve the resin Salt resistance,reduce the time to reach the saturation water absorption rate,strengthen the strength of the three-dimensional gel resin,and at the same time have better temperature resistance.