煤焦油裂解催化剂制备及催化裂解特性

Preparation and catalytic cracking characteristics of coal tar cracking catalyst

煤快速热解/循环流化床燃烧/催化反应器耦合分级转化工艺易于操作维护,经济效益显著,是实现煤炭资源清洁、高效利用的有效途径之一。但由于煤快速热解工艺产生的焦油油质偏重、污染元素含量较高,造成催化剂频繁失活及再生,因此制备了一种廉价高效的非再生性催化剂。在固定床催化反应装置上,以低温煤焦油为原料,以天然白云石为研究对象,考察催化剂煅烧温度及改性方式对煤焦油催化裂解特性的影响。在催化剂最佳制备条件下制备了1%Ni/2%Fe-白云石催化剂,考察了反应温度对煤焦油催化裂解的影响。结果表明,随煅烧温度升高,促进白云石主要组分CaCO_(3)和MgCO_(3)转化为CaO和MgO活性物质,天然白云石催化剂活性逐渐升高后趋于稳定,最佳煅烧温度为750℃;单独引入Fe后并未促进焦油裂解,同时引入Ni和Fe,明显改善了天然白云石催化剂的催化活性,最佳改性方式为1%Ni/2%Fe-白云石;助剂Fe的引入保护了活性组分Ni的硫中毒失活,同时引入Ni和Fe缓解了催化剂的烧结现象,且Fe作为助剂可减缓催化过程中积碳的产生,Ni改性后白云石催化剂促进了脂肪族化合物及含硫化合物的裂解,茚和萘类化合物并未出现裂解反应但出现加氢茚及加氢萘等产物。

The coal fast pyrolysis/circulating fluidized bed combustion/catalytic reactor coupled fractionation conversion process is easy to operate and maintain,with significant economic benefits,which is one of the effective ways to achieve clean and efficient utilization of coal resources.However,due to the poor tar quality and high pollution element content produced by the rapid coal pyrolysis process,the cata⁃lyst is frequently deactivated and regenerated.Therefore,a cheap and efficient non regenerative catalyst has been prepared in this paper.The effects of calcination temperature and modification method of catalyst on the catalytic cracking characteristics of coal tar were investi⁃gated in a fixed bed catalytic reactor with low-temperature coal tar as raw material and natural dolomite as research object.The 1%Ni/2%Fe dolomite catalyst was prepared under the optimum preparation conditions,and the effect of reaction temperature on the catalytic crack⁃ing of coal tar was investigated.The results show that with the increase of calcination temperature,the main components of dolomite,such as CaCO_(3) and MgCO_(3) is promoted to convert into CaO and MgO active substances,and the activity of natural dolomite catalyst gradually increases and tends to be stable,with the optimal calcination temperature of 750℃.The cracking of tar is not promoted by introducing Fe alone,but the catalytic activity of natural dolomite catalyst is significantly improved by introducing Ni and Fe at the same time.The best modification method is 1%Ni/2%Fe dolomite.The introduction of Fe as a promoter protects the sulfur poisoning deactivation of the active component Ni,while the introduction of Ni and Fe alleviates the sintering phenomenon of the catalyst.Fe can be used as an auxilia⁃ry agent to slow down the generation of carbon deposits in the catalytic process.The dolomite catalyst modified by Ni promotes the cracking of aliphatic compounds and sulfur-containing compounds.Indene and naphthalene compounds do not undergo cracking reactions,but products such as hydroindene and hydronaphthalene appear.