生物质与塑料催化共热解制芳烃研究进展

芳烃是多用途的化学品,主要来源于石油和煤焦油等。以生物质和塑料为原料制取芳烃,可以缓解能源短缺和环境污染,实现生物质和塑料的资源化利用。催化剂能够增强共热解的协同效应,生物质与塑料进行催化共热解可以提高产物品质,改善热解产物分布,提高轻质芳烃的产率和选择性,抑制焦炭的生成。本文综述了生物质与塑料催化共热解制取芳烃的协同热解机理及影响因素,总结了不同种类催化剂的共热解研究进展,以期为生物质与塑料催化共热解定向调控制备芳烃工艺的改进和优化提供参考。     

改性分子筛催化褐煤微波热解挥发分提质研究

为了实现褐煤的清洁高效利用,采用微波热解技术,探究微波反应器中ZSM-5分子筛催化剂对先锋褐煤热解挥发分的催化提质作用。通过浸渍法制备了Fe、Co、Ni改性的ZSM-5分子筛催化剂,采用SEM、XRD、BET和NH3-TPD对催化剂进行了表征,研究了微波功率和不同催化剂对产物产率和焦油中芳烃生成特性的影响。结果表明：微波热解的最佳功率为700 W,在此功率下,通过微波催化热解,有效提升了气体产物中有效组分H₂+CO的含量;金属的引入显著提高了焦油中芳香烃的产率以及对轻质芳烃的选择性;其中,Ni@ZSM-5获得了最高气体有效组分体积分数(93.20%)、最高芳香烃产率(质量分数72.92%),轻质芳烃产率较未催化提升了34.08个百分点。     

Fe-Zn共改性ZSM-5催化作用下生物质快速热解特性研究

选取木屑和花生壳作为原料进行生物质热解,研究有机产物分布,催化剂使用Fe、Zn两种金属元素进行改性。通过X射线衍射（XRD）、扫描电镜（SEM）、傅里叶红外（FT-IR）、比表面积测试（BET）对Fe-Zn改性的ZSM-5进行分析。使用闪速裂解-气质联用仪（PY-GC/MS）对原料进行热解,探究生物质催化热解的产物分布变化。催化剂的使用使得芳烃类产物产率获得较大提升,在木屑热解中,Fe负载的分子筛催化获得了酚类的最高产率,比ZSM-5催化热解产率提升18.30%。金属改性催化剂在花生壳热解中,大幅提升了芳烃类产物产率,其中Zn负载催化剂芳烃类产物产率最高,Zn负载催化热解比直接热解的酚类产率降低了18.92%。Zn负载催化获得了最低的酮类产率,与直接热解相比酮类产率降低19.74%,显示出较强的脱羟基效果。此外Zn负载催化和Fe-Zn双金属负载催化在花生壳热解中都大幅降低了酸类产物产率,与直接热解相比酸类产率分别降低了30.46%、36.71%。     

生物质与废塑料催化热解制芳烃(Ⅰ):协同作用的强化

采用两段式固定床对比研究了纤维素与高密度聚乙烯（HDPE）的单独物料催化热解、混合物催化热解和分段催化热解,对热解产物分布、目标产物产率及选择性以及催化剂积炭量等参数进行考察,拟从模型化合物水平探索生物质与塑料催化热解制芳烃过程强化协同作用的可能性。结果表明,纤维素与HDPE的共催化热解（混合和分段催化热解）对芳烃的形成具有协同作用,且分段催化热解较混合催化热解表现出更显著的协同作用,可获得更高的芳烃产率及选择性,提高纤维素热解转化率并降低催化剂的积炭,其协同作用符合"双烯合成"反应理论。并结合HDPE催化热解验证实验对分段催化热解制芳烃过程协同作用的强化机理进行阐述。     

生物质与供氢甲醇共催化热解耦合集成优化制备芳烃的研究

为了提高目标产物的产率以及选择性,以HZSM-5介孔分子筛为催化剂,采用高有效氢碳比化合物——甲醇与生物质进行催化共热解,探讨热解温度、催化温度、有效氢碳比以及醇的种类对芳烃的产率、选择性以及催化剂的抗积碳性能的影响。结果表明,芳烃的产率以及选择性随着生物质与供氢试剂共催化热解时有效氢碳比的增加而显著增加,尤其是二甲苯的选择性,二者之间存在协同效应,当热解温度为400℃,催化温度550℃,甲醇的进样量为2 mL/min,氮气流速为200 mL/min时,其苯及其同系物等芳烃含量达到81.34%,单环芳烃(S_(BTXE))含量达到71.75%,而二甲苯的选择性达到40.81%,同时,供氢甲醇的添加提高了催化剂的抗结焦能力,使其石墨化焦炭含量增加。     

生物质与供氢甲醇共催化热解耦合集成优化制备芳烃的研究

为了提高目标产物的产率以及选择性,以HZSM-5介孔分子筛为催化剂,采用高有效氢碳比化合物——甲醇与生物质进行催化共热解,探讨热解温度、催化温度、有效氢碳比以及醇的种类对芳烃的产率、选择性以及催化剂的抗积碳性能的影响。结果表明,芳烃的产率以及选择性随着生物质与供氢试剂共催化热解时有效氢碳比的增加而显著增加,尤其是二甲苯的选择性,二者之间存在协同效应,当热解温度为400℃,催化温度550℃,甲醇的进样量为2 mL/min,氮气流速为200 mL/min时,其苯及其同系物等芳烃含量达到81.34%,单环芳烃(S_(BTXE))含量达到71.75%,而二甲苯的选择性达到40.81%,同时,供氢甲醇的添加提高了催化剂的抗结焦能力,使其石墨化焦炭含量增加。     

生物质与废塑料催化热解制芳烃(Ⅰ):协同作用的强化

采用两段式固定床对比研究了纤维素与高密度聚乙烯(HDPE)的单独物料催化热解、混合物催化热解和分段催化热解,对热解产物分布、目标产物产率及选择性以及催化剂积炭量等参数进行考察,拟从模型化合物水平探索生物质与塑料催化热解制芳烃过程强化协同作用的可能性。结果表明,纤维素与HDPE的共催化热解(混合和分段催化热解)对芳烃的形成具有协同作用,且分段催化热解较混合催化热解表现出更显著的协同作用,可获得更高的芳烃产率及选择性,提高纤维素热解转化率并降低催化剂的积炭,其协同作用符合"双烯合成"反应理论。并结合HDPE催化热解验证实验对分段催化热解制芳烃过程协同作用的强化机理进行阐述。     

聚乙烯塑料与重油催化共热解工艺研究

以低密度聚乙烯作为塑料的模型化合物,以固体石蜡作为重油的模型化合物,以HZSM-5分子筛作为催化共热的催化剂,采用热重实验分析了两者在热解过程中的相互作用,采用固定床热解实验分析了不同物料配比下共热解产物组分分布情况。研究发现,在催化条件之下低密度聚乙烯与固体石蜡的共热解相互作用较非催化条件下要显著增强;低密度聚乙烯与固体石蜡催化共热解能够促进热解重油的轻质化,能够降低热解重油中C21+重油馏分选择性与提升C21-轻油馏分及芳烃的选择性,促使更多的气相产物、更少的油相产物及固相残渣生成,且固体石蜡在原料中的比例越大,催化共热解产物中的轻质组分与芳烃占比越多。     

聚烯烃塑料与液体石蜡共热解工艺研究

利用热重分析仪(TGA)研究了低密度聚乙烯(LDPE)、液体石蜡(LP)及LDPE/LP共混物的热解特性,探讨了LDPE与LP在热解过程中的相互作用,进一步根据Coats-Redfern方法进行了反应动力学研究。结果表明,LDPE、LP及LDPE/LP共混物热解过程均符合一级反应动力学,LDPE/LP共热解反应活化能显著低于LDPE单独热解。为了验证LDPE和LP之间的协同效应,利用高压反应釜分别对LDPE、LP及LDPE/LP的共混物进行了热解研究。结果表明,LDPE与LDPE/LP共混物热解所得气体产物与液体产物组分相似,气体产物多为C_1～C_4的烷烃和烯烃,液体产物多为C_5～C_(23)的正构烷烃;LDPE/LP共热解所得液体产物中轻质烷烃组分(C_5～C_9)含量显著高于LDPE和LP单独热解,证实了LDPE和LP之间的协同作用。LP的加入改善了热解过程中的传质传热,抑制了LDPE单独热解时因局部过热而引起的结焦现象,促进了液体产物的轻质化。     

聚烯烃塑料与液体石蜡共热解工艺研究

利用热重分析仪(TGA)研究了低密度聚乙烯(LDPE)、液体石蜡(LP)及LDPE/LP共混物的热解特性,探讨了LDPE与LP在热解过程中的相互作用,进一步根据Coats-Redfern方法进行了反应动力学研究。结果表明,LDPE、LP及LDPE/LP共混物热解过程均符合一级反应动力学,LDPE/LP共热解反应活化能显著低于LDPE单独热解。为了验证LDPE和LP之间的协同效应,利用高压反应釜分别对LDPE、LP及LDPE/LP的共混物进行了热解研究。结果表明,LDPE与LDPE/LP共混物热解所得气体产物与液体产物组分相似,气体产物多为C_1～C_4的烷烃和烯烃,液体产物多为C_5～C_(23)的正构烷烃;LDPE/LP共热解所得液体产物中轻质烷烃组分(C_5～C_9)含量显著高于LDPE和LP单独热解,证实了LDPE和LP之间的协同作用。LP的加入改善了热解过程中的传质传热,抑制了LDPE单独热解时因局部过热而引起的结焦现象,促进了液体产物的轻质化。     

纤维素快速热解反应气体的在线催化裂解

通过浸渍法制备MHZSM-5(M Fe,Zr,Co)催化剂,采用激光粒度分析仪、比表面积及孔径分析仪和X射线衍射仪(XRD)对催化剂的性质进行表征,并在立式两段加热炉上进行纤维素快速热解蒸汽的在线催化实验。对不同催化剂条件下的产物分布特性及生物油组成特性进行分析,结果表明,随着催化剂的引入,液相产率从52.06%最大下降至23.63%,气相产率从42.39%最大提高至70.84%,CoHZSM-5对于热解蒸汽的催化气化效果最为明显;纤维素快速热解生物油中以1,6-脱水-β-D-吡喃葡萄糖(左旋葡聚糖)为主,引入催化剂对纤维素热解蒸汽进行在线催化重整后,产物中芳烃类物质显著增加,以FeHZSM-5和ZrHZSM-5效果最佳;HZSM-5催化下生物油中左旋葡聚糖的含量提高至63.78%;催化后热解油中乙酸及丙酸含量均减少,但降低幅度有限。综合催化剂对产率及组分的影响效果来看,FeHZSM-5和ZrHZSM-5对纤维素快速热解蒸汽的催化调控作用较为显著。     

热解温度对纤维素和木质素成炭结构的影响

从纤维素、木质素和半纤维素热解转化特征及分子重构建行为着手,利用TG、TEM、Raman、XRD、FT-IR等分析手段探究这3种物质的热解炭化机理.实验结果表明:半纤维素在炭化过程中几乎完全分解;链状结构的纤维素热分解脱除氢氧后,形成的碳自由基发生芳构化重排,大部分构成生物质热解炭中的结晶区;木质素分子结构复杂,呈交联...     

Characteristics of hemicellulose,cellulose and lignin pyrolysis

The pyrolysis characteristics of three main components (hemicellulose, cellulose and lignin) of biomass were investigated using, respectively, a thermogravimetric analyzer (TGA) with differential scanning calorimetry (DSC) detector and a pack bed. The releasing of main gas products from biomass pyrolysis in TGA was on-line measured using Fourier transform infrared (FTIR) spectroscopy. In thermal analysis, the pyrolysis of hemicellulose and cellulose occurred quickly, with the weight loss of hemicellulose mainly happened at 220–315 °C and that of cellulose at 315–400 °C. However, lignin was more difficult to decompose, as its weight loss happened in a wide temperature range (from 160 to 900 °C) and the generated solid residue was very high (∼40 wt.%). From the viewpoint of energy consumption in the course of pyrolysis, cellulose behaved differently from hemicellulose and lignin; the pyrolysis of the former was endothermic while that of the latter was exothermic. The main gas products from pyrolyzing the three components were similar, including CO₂, CO, CH₄ and some organics. The releasing behaviors of H₂ and the total gas yield were measured using Micro-GC when pyrolyzing the three components in a packed bed. It was observed that hemicellulose had higher CO₂ yield, cellulose generated higher CO yield, and lignin owned higher H₂ and CH₄ yield. A better understanding to the gas products releasing from biomass pyrolysis could be achieved based on this in-depth investigation on three main biomass components.     

Structural evolution of chars from biomass components pyrolysis in a xenon lamp radiation reactor

The structural evolution of the chars from pyrolysis of biomass components(cellulose, hemicellulose and lignin)in a xenon lamp radiation reactor was investigated. The elemental composition analysis showed that the C content increased at the expense of H and O contents during the chars formation. The values of ΔH/C/ΔO/Cfor the formation of cellulose and hemicellulose chars were close to 2, indicating that dehydration was the dominant reaction. Meanwhile, the value was more than 3 for lignin char formation, suggesting that the occurrence of demethoxylation was prevalent. FTIR and XRD analyses further disclosed that the cellulose pyrolysis needed to break down the stable crystal structure prior to the severe depolymerization. As for hemicellulose and lignin pyrolysis, the weak branches and linkages decomposed firstly, followed by the major decomposition. After the devolatilization at the main pyrolysis stage, the three components encountered a slow carbonization process to form condensed aromatic chars. The SEM results showed that the three components underwent different devolatilization behaviors, which induced various surface morphologies of the chars.     

多级孔HZSM-5分子筛催化快速热解生物质制芳烃

采用酸和/或碱处理法制备了一系列多级孔HZSM-5分子筛,采用XRD、N2吸附、XRF、TEM、27Al MAS NMR和NH3-TPD等表征手段对其孔道结构和酸性进行表征。表征结果表明,采用碱处理方法,可获得孔径集中于3～6 nm的介孔结构,通过改变酸、碱处理次序,可调变酸中心数量和强酸/总酸中心比例。在Py-GC/MS装置上,以纤维素和水稻秸秆为原料,研究多级孔分子筛结构对催化快速热解(CFP)制芳烃反应的影响。反应评价结果表明,同商品级HZSM-5相比,采用先碱后酸处理获得的多级孔HZSM-5分子筛(HZ-OH/H),可将纤维素CFP芳烃碳产率由32.3%提高至43.6%,可将水稻秸秆CFP芳烃碳产率由23.0%提高至30.8%。多级孔HZ-OH/H分子筛的孔道结构和酸中心分布特征,对开发应用于生物质制芳烃的高效工业催化剂具有借鉴意义。     

生物质及生物质组分的慢速热解热效应研究

利用绝热加速量热仪(ARC)进行多种生物质及生物质组分的慢速热解,检测热解过程的吸放热情况,结果显示在缓慢升温过程中,纤维素的放热峰在256.2~279.2℃之间,放热量约为673.9J/g,质量分数为51.8%固体炭产物;而木聚糖在219.8~253.7℃之间有一尖锐的放热峰,放出热量约为873.3J/g,得到质量分数为68.7%的残余固体;木质素的热流曲线却在133.3~292.2℃有吸热趋势,吸收热量为340.1J/g,得到质量分数为80.4%的固体炭。各生物质的热流曲线中均有两个相连的放热峰出现,分别来源于半纤维素和纤维素。各生物质热流曲线特征值各异,但起始放热温度在190℃前后,第1个峰值温度在220℃左右,第2个放热峰峰值集中在255℃前后。     

Effects of organic and inorganic metal salts on thermogravimetric pyrolysis of biomass components

Thermogravimetric analyzer (TGA) was employed to elucidate the catalytic effects of organic and inorganic metal salts (K₂CO₃, KAc, Na₂CO₃ and NaAc) on the pyrolysis of three biomass components (cellulose, hemicellulose and lignin). In case of cellulose, TG analysis results showed that all the four metal salts increased the yield of char products and decreased the weight loss rates of cellulose pyrolysis, which followed the order of Na₂CO₃>K₂CO₃>NaAc>KAc. In contrast to cellulose, the four organic and inorganic salts employed had no significant effects on the remaining two biomass components:, hemicellulose and lignin. However, the four metal salts led to the devolatilization reaction of hemicellulose to occur at lower temperature region, and the dehydration reaction of lignin was promoted more or less. An increase in the heating rate might augment the maximum degradation rate. Different mixing ratios had little influence on the progress of catalytic pyrolysis. Based on the observations, the potential mechanism of the catalytic pyrolysis of biomass components with metal salts was discussed.     

TG study on pyrolysis of biomass and its three components under syngas

Pyrolysis of sawdust and its three components (cellulose, hemicellulose and lignin) were performed in a thermogravimetric analyzer (TGA92) under syngas and hydrogen. The effect of different heating rates (5, 10, 15 and 20 °C/min) on the pyrolysis of these samples were examined. The pyrolysis tests of the synthesized samples (a mixture of the three components with different ratios) were also done under syngas. The distributed activation energy model (DAEM) was used to study the pyrolysis kinetics. It is found that syngas could replace hydrogen in hydropyrolysis process of biomass. Among the three components, hemicellulose would be the easiest one to be pyrolyzed and then would be cellulose, while lignin would be the most difficult one. Heating rate could not only affect the temperature at which the highest weight loss rate reached, but also affect the maximum value of weight loss rate. Both lignin and hemicellulose used in the experiments could affect the pyrolysis characteristic of cellulose while they could not affect each other obviously in the pyrolysis process. Values of k₀ (frequency factor) change very greatly with different E (activation energy) values. The E values of sawdust range from 161.9 to 202.3 kJ/mol, which is within the range of activation energy values for cellulose, hemicellulose and lignin.     

不同类型分子筛催化热解陈腐垃圾性能研究

选用3种不同类型的分子筛催化剂HZSM-5、HY和HBeta,以垃圾填埋场陈腐垃圾为原料,进行绝氧热解和催化热解对比研究。结果表明,分子筛催化剂的加入不仅对陈腐垃圾热解产物产率有明显影响,而且对热解气和热解油的品质有明显的提高。对比3种催化剂发现,HZSM-5更有利于热解气的产生,而且所得热解气的热值最高,为67.45 MJ·m^-3,所得热解油中汽油组分最多,为质量分数65.4%,而重馏分油组分仅为6.9%。HY和HBeta则得到相对更高的热解油产量,尤其是轻质柴油,质量分数分别为38.1%和41.4%。3种催化剂截然不同的催化热解产物产率和产品性质与其孔道结构、织构性质和酸性质均密切相关。     

Upgrading of aspen poplar wood oil over HZSM-5 zeolite catalyst

Thermally fractionated components of an oil prepared by the liquefaction of aspen poplar wood have been upgraded using a HZSM-5 zeolite catalyst to yield products rich in benzene, toluene, xylenes and higher molecular weight aromatics. The effect of reactor temperatures on the relative abundance of these products has been studied.