纤维素热解气催化提质制备呋喃类化合物研究

Catalytic Upgrading of Cellulose Pyrolysis Vapor for Furan Compounds

采用共沉淀法合成了MnCo2O4催化剂,并采用水热法合成了氧化锰八面体分子筛(OMS-2)催化剂,与NaY分子筛催化纤维素热解效果对比后对NaY进一步改性,采用浸渍法制备了Co/NaY、Sn/NaY以及Co-Sn/NaY,并研究了所制备催化剂对纤维素热解气催化重整制备呋喃类化合物的影响。采用氮气吸附-脱附、X射线衍射(XRD)仪、扫描电镜显微镜(SEM)和氨气吸附-脱附法(NH3-TPD)对催化剂进行表征。实验结果表明:金属Co、Sn分散在NaY表面,且没有改变NaY的晶体结构和形貌;负载后催化剂的比表面积和孔容减小,平均孔径增大,且比表面积远大于MnCo2O4、OMS-2;负载Sn几乎不改变NaY分子筛的酸性位点,而Co会减少酸性位点。几种催化剂的加入均促进了醇类、酸类、醛类的生成,抑制了糖类的生成。在纤维素与催化剂的质量比为1∶14的条件下,NaY和Co/NaY均能够显著提高呋喃类化合物质量分数,从未添加催化剂的15.34%分别提高到了48.16%和61.88%,金属负载NaY催化剂均促进了呋喃酮的生成,抑制了呋喃的产生。

Two catalysts—MnCo2O4 and manganese oxide octahedral molecular sieves(OMS-2)were synthesized using co-precipitation and hydrothermal methods,respectively.On comparing these with the NaY molecular sieve for the catalytic pyrolysis of cellulose,the NaY molecular sieve was further modified to improve its catalytic activity.Co/NaY,Sn/NaY,and Co-Sn/NaY were prepared using the impregnation method.Catalytic upgrading of cellulose pyrolysis vapors for the preparation of furan compounds with different catalysts were investigated.The prepared catalysts were characterized through nitrogen adsorption-desorption,X-ray diffraction(XRD),scanning electron microscopy(SEM),and ammonia adsorption-desorption(NH 3-TPD)methods.Experimental results showed that Co or Sn metal was dispersed on the NaY surface keeping the crystal structure and morphology of NaY intact.However,the specific surface area and pore volume of the catalyst decreased after metal loading,while average pore size increased.The acidic sites of the NaY zeolite remained virtually unchanged after Sn loading,but decreased after Co loading.The specific surface area of NaY and modified NaY were much larger than those of MnCo2O4 and OMS-2 but the average pore size was smaller.Addition of catalysts promoted the production of alcohols,acids,and aldehydes but inhibited sugar production.The furan content increased significantly from 15.34%(non-catalytic pyrolysis)to 48.16%and 61.88%on using NaY alone and Co/NaY,respectively,albeit the mass ratio of cellulose to catalyst was 1∶14.Both the Co and Sn metals-supported NaY catalysts promoted furanone production but inhibited furan production.