ZSM-5催化生物质三组分和松木热解生物油组分分析

Component analysis of pyrolysis bio-oil from three major components of biomass and Pinus yunnanensis by ZSM-5 catalytic

为了更清晰地研究三大组分(纤维素、木聚糖、木质素)在介孔ZSM-5参与下的催化热解过程,该研究首先对生物质的三大基本组分和云南松木粉进行热解,然后在介孔ZSM-5催化剂存在的条件下对微晶纤维素、木聚糖、碱性木质素三大组分和云南松进行催化热解。采用气质联用仪对生物油的化学组分进行分析。通过对比ZSM-5参与前后的生物油的主要化学组分的变化,对催化剂的催化机理进行探究。研究结果表明,催化热解过程中,介孔ZSM-5将纤维素直接热解得到的β-D阿洛糖、糠醛、3-丙基戊二酸和2,4-戊二烯酸转化为1-甲基萘、2,6-二甲基萘,纤维素催化热解得到的生物油中的芳烃含量为63.89%。半纤维素催化热解过程中,催化剂将生物油中的糠醛从67.78%降低为2.66%,有效提高芳烃化合物,包括萘、2-甲基萘的含量,催化热解后得到的生物油中总芳烃含量达到36.81%。木质素催化热解过程中,介孔ZSM-5有效降低生物油中2,6-二叔丁基对甲酚的量(从82.33%降至77.97%),并大幅地提高1,8-二甲基萘和1,7-二甲基萘的量,生物油中总芳烃相对含量达到14.14%。云南松催化热解过程中,催化剂有效降低云南松直接热解得到生物油中2-甲氧基-4-甲基苯酚和(Z)-异丁子香酚的含量,并将芳烃化合物总量提高到53.99%(主要是1-甲基萘、1-亚甲基-1氢-茚和2,6-二甲基萘)。随着催化剂使用次数的增加,生物油中含氧化合物相对含量增加,烃类化合物的相对含量明显降低,从53.99%降至43.32%,元素分析结果表明生物油中的碳含量逐渐减少,氧含量逐渐增加。但是,催化剂经过焙烧再生后,催化活性基本完全恢复。

In order to study the catalytic pyrolysis process of the three components(Cellulose, hemicellulose and lignin) with participation of mesoporous ZSM-5, Firstly the pyrolysis of three major components in biomass and wood powder ofPinus yunnanensis were conducted. Then catalytic pyrolysis of the three major components (microcrystalline cellulose, xylan and alkali lignin) and wood powder ofPinus yunnanensiswere carried out with the mesoporous ZSM-5 as catalyst. Compositions of the derived bio-oil were identified by gas chromatograph-mass spectrometer (GC-MS). By comparing the product distribution in bio-oil between pyrolysis and catalytic pyrolysis of three major components and wood powder, the catalytic pyrolysis mechanism of biomass was studied. What is more, ZSM-5 was analyzed by N2 adsorption-desorption and XRD diffraction, and ultimate analysis of bio-oil obtained were also identified. The results indicated that during catalytic pyrolysis of three major components andPinus yunnanensis, mesoporous ZSM-5 showed different performance. The results of XRD diffraction pattern and N2absorption/desorption demonstrated ZSM-5 used had abundant mesopores with mean pore size of 6.23nm. Through pyrolysis cellulose was mainly converted intoβ-D-allose (20.39%), furfural, 2,6-di-tert-butyl-4-methylphenol, 3-propyl glutaric acid, and 2,4-Pentadienoic acid. In the process of catalytic pyrolysis, ZSM-5 transformedβ-D-allose (20.39%), furfural, 3-Propyl glutaric acid, and 2,4-Pentadienoic acid into 1-methylnaphthalene and 2,6-dimethylnaphthalene. ZSM-5 performed the supreme catalytic activity for cellulose among 4 feedstocks, and the relative content of total aromatics in bio-oil obtained from catalytic pyrolysis of cellulose was 63.89%. The raw bio-oil from hemicellulose pyrolysis mainly contained furfural (67.78%) and 2,6-di-tert-butyl-4-methylphenol. But in the course of catalytic pyrolysis, the relative content of furfural reduced drastically to 2.66% while the relative content of aromatics increased to 36.81%, especially, naphthalene and 2-methylnaphthalene. The primary composition in bio-oil from lignin pyrolysis was 2,6-di-tert-butyl-4-methylphenol (82.33%), which was converted into 1,7-Dimethylnaphthalene and 1,8-dimethylnaphthalene by ZSM-5 through catalytic pyrolysis. The content of 2,6-di-tert-butyl-4-methylphenol decreased to 77.97% while the relative content of total aromatics increased to 14.14%. The bio-oil obtained from Pinus yunnanensis pyrolysis contained 2,6-di-tert-butyl-4-methylphenol (9.73%), 2-methoxy-4 methyl phenol, (Z)-isoeugenol, and 4-hydroxy-3-tert- butylanisole. Through catalytic pyrolysis 2-methoxy-4 methyl phenol and (Z)-isoeugenol were obviously converted into 1-methylnaphthalene, 1-methylene-1 hydrogen-indene, and 2,6-dimethylnaphthalene, and the total aromatics in bio-oil reached at 53.99%. When thePinus yunnanensis was used as feedstock, the reusability and regeneration of mesoporous ZSM-5 were studied by comparing the chemical components and ultimate analysis of bio-oil. With the use time of ZSM-5 increasing from 1 to 3, in bio-oil the amount of oxygen compounds augmented while aromatics content reduced from 53.99% to 43.32%, and the ultimate analysis showed O content increased with the decreased C content. However, the full catalytic performance of regenerated mesoporous ZSM-5 restored almost. After regeneration ZSM-5 yielded bio-oil with aromatics content of 52.14% and O content of 26.89%.