Zn/Co-HMS催化氧化异戊醇生成异戊酸
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摘要
以正硅酸四乙酯为硅源,十二胺为模板剂,通过溶胶凝胶法制备了HMS,Co掺杂的六方介孔硅分子筛(Co-HMS(100));以Co-HMS(100)为载体,硝酸锌、乙酸锌、硫酸锌、氯化锌为Zn源,通过浸渍法制备了负载型催化剂Zn/Co-HMS(100)-N,Zn/Co-HMS(100)-Ac,Zn/Co-HMS(100)-S和Zn/Co-HMS(100)-Cl。通过XRD,FT-IR,TG,NH3-TPD,SEM和N2吸附脱附对不同催化剂进行了表征,并研究了不同催化剂对异戊醇催化氧化生成异戊酸的影响。结果表明:掺杂Co与负载Zn未改变HMS分子筛的六方介孔结构;在550℃焙烧温度下只有硝酸锌和乙酸锌以Zn O的形式存在于载体中;Zn O有助于降低催化剂弱酸含量,有利于反应进行;掺杂Co可以增加催化剂的孔径,有利于反应物与产物扩散。此外,以硝酸锌为Zn源的催化剂Zn/Co-HMS(100)-N较其他3种Zn源催化剂表现出更好的催化效果。在Zn/Co-HMS(100)-N用量为0.5g、反应温度为120℃、反应时间为8h条件下,异戊醇的转化率、异戊酸的收率与选择性分别达到52.2%,26.9%和51.5%;而催化剂Zn/Co-HMS(100)-S和Zn/Co-HMS(100)-Cl几乎没有催化效果。最后,对该催化反应机理进行了初步探讨,发现该反应符合自由基反应过程。
Zn/Co-HMS(100) was prepared via wetness impregnation with Co-doped hexagonal mesoporous silica zeolite(HMS) as the support,which was synthesized by sol-gel method and [Zn(NO_3)_2· 6H_2O],[Zn(CH_3COO)_2·2H_2O],[ZnSO_4·7H_2O],ZnCl_2 as Zn precursor. The prepared catalysts were characterized by XRD,FT-IR,TG,NH3-TPD,SEM and N2 adsorption-desorption technique,and their performances of catalyzing isoamyl alcohol to isovaleric acid were also investigated. The results suggested that doping and loading did not alter the hexagonal mesopore structure of HMS; only [Zn(NO_3)_2· 6H_2O] and [Zn(CH_3COO)_2·2H_2O] can exist in catalysts as Zn O form under 550℃,which can decrease the amount ofweak acids. Besides,doping Co can increase the diameter of catalysts,facilitating the transit of the substrates and outputs. Using [Zn(NO_3)_2· 6H_2O] as the precursor to prepare Zn/Co-HMS(100)-N can reduce the particle diameter of the catalyst and thus increase its uniform distribution. Furthermore,Zn/Co-HMS(100)-N exhibited the highest catalytic performance than the other catalysts. Under the condition of 0. 5 g of Zn/CoHMS(100)-N added,reaction temperature 120℃,reaction time 8 h,the conversion rate of isoamyl alcohol and the yield and selectivity of isovaleric acid were 52. 2%,26. 9% and 51. 5%,respectively. Finally,the catalytic mechanism of Zn/Co-HMS(100)-N was discussed and the reaction mechanism of the catalyst was found to fit free radical reaction.
Zn/Co-HMS(100) was prepared via wetness impregnation with Co-doped hexagonal mesoporous silica zeolite(HMS) as the support,which was synthesized by sol-gel method and [Zn(NO_3)_2· 6H_2O],[Zn(CH_3COO)_2·2H_2O],[ZnSO_4·7H_2O],ZnCl_2 as Zn precursor. The prepared catalysts were characterized by XRD,FT-IR,TG,NH3-TPD,SEM and N2 adsorption-desorption technique,and their performances of catalyzing isoamyl alcohol to isovaleric acid were also investigated. The results suggested that doping and loading did not alter the hexagonal mesopore structure of HMS; only [Zn(NO_3)_2· 6H_2O] and [Zn(CH_3COO)_2·2H_2O] can exist in catalysts as Zn O form under 550℃,which can decrease the amount ofweak acids. Besides,doping Co can increase the diameter of catalysts,facilitating the transit of the substrates and outputs. Using [Zn(NO_3)_2· 6H_2O] as the precursor to prepare Zn/Co-HMS(100)-N can reduce the particle diameter of the catalyst and thus increase its uniform distribution. Furthermore,Zn/Co-HMS(100)-N exhibited the highest catalytic performance than the other catalysts. Under the condition of 0. 5 g of Zn/CoHMS(100)-N added,reaction temperature 120℃,reaction time 8 h,the conversion rate of isoamyl alcohol and the yield and selectivity of isovaleric acid were 52. 2%,26. 9% and 51. 5%,respectively. Finally,the catalytic mechanism of Zn/Co-HMS(100)-N was discussed and the reaction mechanism of the catalyst was found to fit free radical reaction.
引文
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[31]LIU P,DEGIRMENCI V,HENSEN E J M.Unraveling the synergy between gold nanoparticles and chromium-hydrotalcites in aerobic oxidation of alcohols[J].Journal of Catalysis,2014,313(313):80-91.
[32]BESSON M,GALLEZOT P.Selective oxidation of alcohols and aldehydes on metal catalysts[J].Catalysis Today,2000,57(1):127-141.
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[34]陈治明.有机合成原理及路线设计[M].北京:化学工业出版社,2010:50-58.
[2]WANG X,KAWANAMI H.Selective oxidation of alcohols to aldehydes and ketones over Ti O2-supported gold nanoparticles in supercritical carbon dioxide with molecular oxygen[J].Applied Catalysis A General,2008,349(1):86-90.
[3]HADDADI H,KORANI E M,HAFSHEJANI S M,et al.Highly selective oxidation of sulfides to sulfones by H2O2catalyzed by porous capsules[J].Journal of Cluster Science,2015,26(6):1-10.
[4]MA C Y,CHENG J,WANG H L,et al.Characteristics of Au/HMS catalysts for selective oxidation of benzyl alcohol to benzaldehyde[J].Catalysis Today,2010,158(3-4):246-251.
[5]ZHOU L,CHEN M,Wang Y,et al.Au/mesoporousTi O2,as catalyst for the oxidation of alcohols to carboxylic acids with molecular oxygen in water[J].Applied Catalysis A General,2014,475(1):347-354.
[6]CHEN Y,LIM H,TANG Q,et al.Solvent-free aerobic oxidation of benzyl alcohol over Pd monometallic and Au-Pd bimetallic catalysts supported on SBA-16mesoporous molecular sieves[J].Applied Catalysis A General,2010,380(1-2):55-65.
[7]MA C Y,DOU B J,LI J J,et al.Catalytic oxidation of benzyl alcohol on Au or Au-Pd nanoparticles confined in mesoporous silica[J].Applied Catalysis B Environmental,2009,92(1):202-208.
[8]JIA L,ZHANG S,GU F,et al.Highly selective gasphase oxidation of benzyl alcohol to benzaldehyde over silver-containing hexagonal mesoporous silica[J].Microporous&Mesoporous Materials,2012,149(1):158-165.
[9]马帅,陈郑,王家喜.氧化石墨烯掺杂锌铝类水滑石负载钯金催化剂的制备及催化性能[J].化工进展,2017,36(11):4087-4092.
[10]BHOWARE S S,SHYLESH S,KAMBLE K R,et al.Cobalt-containing hexagonal mesoporous molecular sieves(Co-HMS):Synthesis,characterization and catalytic activity in the oxidation reaction of ethylbenzene[J].Journal of Molecular Catalysis A Chemical,2006,255(1):123-130.
[11]白永燕,陈平.介孔材料HMS的改性及在催化反应中的应用[J].现代化工,2016(10):54-58.
[12]WANG G J,ZENG N.Preparation and catalytic properties of Zn-HMS molecular sieves[J].Advanced Materials Research,2012,560-561:300-304.
[13]SALADINO M L,MARTINO D F C,KRALEVA E,et al.Effect of the cerium loading on the HMS structure.Preparation,characterization and catalytic properties[J].Catalysis Communications,2013,36(36):10-15.
[14]纪红兵,钱宇,王婷婷,等.负载钌的HMS催化剂催化氧化醇[J].化工学报,2006,57(3):577-581.
[15]贾丽华,张森,宋贺,等.铁改性HMS催化氧化苯甲醇合成苯甲醛[J].化工学报,2009,60(9):2210-2214.
[16]刘维桥,雷卫宁,尚通明,等.Zn对HZSM-5分子筛催化剂物化及甲醇芳构化反应性能的影响[J].化工进展,2011,30(9):1967-1971.
[17]Zh ANG P,ZHOU Y,FAN M,et al.Catalytic performance of Pd Cl2/Cu-HMS:Influence of hydrophobicity and structure of molecular sieves[J].Applied Surface Science,2014,295(6):50-53.
[18]PARSAFARD N,PEYROVI M H,RASHIDZADEH M.n-Heptane isomerization on a new kind of micro/mesoporous catalyst:Pt supported on HZSM-5/HMS[J].Microporous&Mesoporous Materials,2014,200:190-198.
[19]MATE V R,SHIRAI M,RODE C V.Heterogeneous Co3O4,catalyst for selective oxidation of aqueous veratryl alcohol using molecular oxygen[J].Catalysis Communications,2013,33(9):66-69.
[20]SELVARAJ M,LEE T G.t-Butylation of toluene with t-butyl alcohol over mesoporous Zn-Al-MCM-41 molecular sieves[J].Microporous&Mesoporous Materials,2005,85(1):59-74.
[21]ZHANG N,LI G,CHENG Z,et al.Rhodamine B immobilized on hollow Au-HMS material for naked-eye detection of Hg2+in aqueous media.[J].Journal of Hazardous Materials,2012,229-230(43):404-410.
[22]BI Y,WANG Y,CHEN X,et al.Methanol aromatization over HZSM-5 catalysts modified with different zinc salts[J].Chinese Journal of Catalysis,2014,35(10):1740-1751.
[23]赵新宇,李春忠,郑柏存,等.二水合醋酸锌热分解机理与动力学[J].华东理工大学学报,1997,23(2):191-195.
[24]李国强.无机含氧酸及其盐热稳定性研究[J].西安建筑科技大学学报(自然科学版),1997,29(1):69-73.
[25]戴长文.离子极化和硝酸盐热稳定性势标度[J].郑州大学学报(理学版),1985,32(2):67-72.
[26]Jia A,Lou L L,Zhang C,et al.Selective oxidation of benzyl alcohol to benzaldehyde with hydrogen peroxide over alkali-treated ZSM-5 zeolite catalysts[J].Journal of Molecular Catalysis A Chemical,2009,306(1-2):123-129.
[27]CANG R,LU B,LI X,et al.Iron-chloride ionic liquid immobilized on SBA-15 for solvent-free oxidation of benzyl alcohol to benzaldehyde with H2O2[J].Chemical Engineering Science,2015,137:268-275.
[28]RASOULI M,ATASHI H,MOHEBBI-KALHORI D,et al.Bifunctional Pt/Fe-ZSM-5 catalyst for xylene isomerization[J].Journal of the Taiwan Institute of Chemical Engineers,2017,78:438-446.
[29]ZHAO Y X,BAMWENDA G R,GROTEN W A,et al.The chain mechanism in catalytic cracking:The kinetics of 2-methylpentane cracking[J].Journal of Catalysis,1993,140(1):243—261.
[30]BARZETTI T,SELLI E,MOSCOTTI D,et al.Pyridine and ammonia as probes for FTIR analysis of solid acid catalysts[J].Journal of the Chemical Society Faraday Transactions,1996,92(8):1401-1407.
[31]LIU P,DEGIRMENCI V,HENSEN E J M.Unraveling the synergy between gold nanoparticles and chromium-hydrotalcites in aerobic oxidation of alcohols[J].Journal of Catalysis,2014,313(313):80-91.
[32]BESSON M,GALLEZOT P.Selective oxidation of alcohols and aldehydes on metal catalysts[J].Catalysis Today,2000,57(1):127-141.
[33]巨勇,席婵娟,赵国辉.有机合成化学与路线设计[M].北京:清华大学出版社,2007:116-121.
[34]陈治明.有机合成原理及路线设计[M].北京:化学工业出版社,2010:50-58.
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