| Vitex is widely distributed,easy to grow,large biomass,and resistant to flat stubble.It is the main tree species for forestry biomass energy in my country.The rational development and utilization of forest biomass resources,including vitex,is very important to alleviate the shortage of oil and gas resources in my country.Biomass pyrolysis tar is a promising substitute for fossil fuels because it also has the advantages of easy storage,transportation and cleanliness.However,bio-oil contains more acids which make it corrosive,which limits the promotion and utilization of bio-oil.The introduction of catalysts is the most effective means to obtain high-quality bio-oil.This article studies the effect of CaO on the pyrolysis process of Vitex,hoping to improve the quality of bio-oil through this cheap alkaline oxide.In this paper,the influence of CaO on the pyrolysis weight loss process and pyrolysis gas release characteristics of Vitex quinquefolia was studied by infrared thermogravimetric test.The pyrolysis process of Vitex is divided into four stages:drying stage（<137℃）,pre-pyrolysis stage（137℃-161℃）,main pyrolysis stage（161℃-405℃）,carbonization stage（>405℃）.Because CaO,as an alkaline oxide,will fix the"CO2-like active intermediate"generated during the pyrolysis process of cellulose during the reaction,CO2 is not released in this temperature range,but in a higher temperature range.The calcium carboxylate or organic calcium formed by the reaction of CaO with the acids in the volatiles decomposes at 395℃-465℃,and Ca CO3decomposes at 590℃-720℃.CaO promotes the pyrolysis of lignin at high temperatures.The influence of CaO on the yield of the three-phase product of Vitex pyrolysis was studied by means of a tube furnace and a fixed-bed test bench.With the increase of CaO content,the yield of Vitex semi-coke gradually increases,and it increases significantly when the content of CaO is 10%to 20%.The yield of pyrolysis gas phase products,namely non-condensable gas,and semi-coke show The opposite trend occurred.When the CaO content increases from 0%to10%and from 20%to 30%,the non-condensable gas yield does not change significantly,but when the CaO content increases from 10%to 20%,the non-condensable gas yield also decreases.Very quickly.The yield of the liquid phase product of pyrolysis,that is,the oil-water mixture,gradually decreases,and the downward trend is relatively stable.The effect of CaO on the gas-liquid product composition of Vitex officinalis pyrolysis was studied by MS and GC-MS.The fixation effect of CaO on CO2 causes the CO2 content in the non-condensable gas to decrease with the increase of CaO content,that is to say,CaO absorbs part of CO2 to generate Ca CO3.CaO promotes the pyrolysis of lignin and generates more CH4,but high temperature also promotes a substantial increase in H2 content,leading to an increase in CH4 production but a decrease in relative content.CaO and high temperature can promote calcium ion and hydroxyl to form a metal ion effect that can increase the free hydrogen content,thereby increasing the production of H2,so the production of H2 increases with the increase of CaO content and pyrolysis temperature.CaO will react with carboxylic acids to form calcium carboxylate,and it will also react with moisture to form hydrogen.CaO then reacts with phenols to form organic calcium.This is caused by the adsorption of CaO on the hydroxyl groups in acids and phenols,because it is The exothermic reaction is therefore suppressed at high temperatures.At low temperature,CaO can promote the pyrolysis of cellulose and hemicellulose to form ketones and esters,while at high temperature CaO can promote the decarbonylation reaction of ketones and esters. |
