正十二烷在Pt/ZSM-22和Pt/ZSM-23上的加氢异构反应性能

采用常规水热合成法合成了ZSM-22和ZSM-23分子筛,进而制备了分别含有上述分子筛的催化剂,并借助XRD、SEM、NH3-TPD和Py-IR表征了这两种分子筛和催化剂的结构和酸性,同时以正十二烷为模型化合物,采用固定床反应器研究了Pt/ZSM-22和Pt/ZSM-23催化剂上正十二烷加氢异构反应性能。结果表明,在这种模型反应基础上,催化剂的反应活性和选择性主要取决于催化剂的酸量和酸强度以及酸分布,相对而言,ZSM-22分子筛催化剂由于其弱酸和中等强度酸的含量较高,具有更佳的异构化选择性。     

硅源与硅含量对合成的SAPO分子筛催化正十二烷异构化性能的影响

利用非水法合成了SAPO-11分子筛,并采用X射线衍射(XRD)、能量色散型X荧光光谱仪(XRF)、扫描电子显微镜(SEM)和氨-程序升温脱附实验(NH3-TPD)等手段表征了催化剂的物化性能,考察了硅源与硅铝比对SAPO-11分子筛的正十二烷异构化性能的影响.结果表明,非水法合成的SAPO-11分子筛的颗粒与水热合成的分子筛接近,但其微晶尺寸明显小于后者.采用非水合成法时,单体硅源以及较低的硅铝比(物质的量之比小于或等于0.2)有利于合成晶粒小的SAPO-11分子筛.在所有合成催化剂中,以正硅酸乙醑为硅源,SiO2与Al2O3物质的量之比为0.05的条件下,通过非水法制备的SAPO-11分子筛为载体制备的Pt/SAPO-11催化剂,因具有较小的微晶尺寸与适宜的酸而具有较高的正十二烷异构化收率(89.8%).     

ZSM-11分子筛的碱处理及其正十二烷催化裂解性能

研究了碱处理对ZSM-11分子筛的微观结构、酸性质和催化裂解性能的影响。采用不同浓度的氢氧化钠对ZSM-11分子筛进行碱处理,得到了级孔ZSM-11分子筛。用XRD,SEM,TEM, NH₃-TPD,N₂低温吸附-脱附等手段对碱处理后的分子筛进行了表征。以正十二烷为模型燃料,在550 ℃、4 MPa的条件下评价了分子筛的催化裂解性能。结果表明,碱处理导致HZSM-11分子筛晶粒内形成介孔、比表面积和酸量增加。碱处理的ZSM-11分子筛表现出较高的催化裂解活性。其中,用浓度为0.1 mol/L的氢氧化钠溶液处理的HZSM-11分子筛,催化活性最高。与未处理的HZSM-11分子筛相比,正十二烷的平均转化率提高了约58%。     

Hydroisomerization of Long-Chain Alkane Over Pt/SAPO-11 Catalysts Synthesized from Nonaqueous Media

SAPO-11 molecular sieves were synthesized from nonaqueous media. The effects of Si and Al sources as well as solvents on the catalytic performance of SAPO-11 were investigated by the hydroisomerization reaction of n-dodecane. The samples were characterized by XRD, XRF, N₂-adsorption, SEM, NH₃-TPD, IR-NH₃ and ²⁹Si CP MAS NMR. The SAPO-11 samples synthesized with tetraethoxysilane as the Si source showed higher Si incorporation contents than the SAPO molecular sieves prepared with polymeric Si sources (fumed silica and Si colloidal gel). The reaction results showed that Pt/SAPO-11 catalysts synthesized from ethylene glycol and glycerol media with the monomeric Si and Al sources (tetraethoxysilane, aluminum isopropoxide) exhibited higher catalytic activities than those catalysts with the polymeric Si or Al (pseudo-boehmite) sources, due to the larger external surface area and higher acidity of the former ones. Especially, the catalyst synthesized in an ethylene glycol medium possessed the highest catalytic activity. Over this catalyst, 88% conversion of n-dodecane was achieved at a low temperature of 250 °C.     

Virtual Control for High Conversion of Methane Over Supported Pt

A transient model for oxidation of methane over Pt/Al₂O₃ monolith catalysts has been developed by rigorous consideration of mass- and heat transport and mean-field treatment of the reaction kinetics. By coupling a virtual regulator using the reactant slip, methane or oxygen partial pressures, or oxygen surface coverage as feedback variable(s) as such or in combinations for control of feed composition, the influence of gas composition changes on the methane conversion has been investigated.     

Sorbitol Hydrogenolysis Over Ni, Pt and Ru Supported on NaY

The hydrogenolysis of sorbitol into 1,2-propanediol (PD), ethylene glycol (EG) and glycerol (G) was investigated over Ni, Pt and Ru supported on NaY at 220 °C and 60 bar in a batch reactor. Ni(6 %)–NaY was investigated in detail at different process conditions, including its recyclability. Attempts have been made to rationalize the experimentally observed conversion and product selectivity obtained over the different catalysts with results of Density Functional Theory calculations of adsorption energy and bond length changes in sorbitol adsorbed over various planes of Ni, Pt and Ru.     

Performance of Pt/MgAPO-11 Catalysts in the Hydroisomerization of n-dodecane

MgAPO-11 molecular sieves with varying Mg contents synthesized by the hydrothermal method were used as supports for bifunctional Pt/MgAPO-11 catalysts. MgAPO-11 molecular sieves and the corresponding catalysts were characterized by X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), temperature-programmed desorption of NH₃ (NH₃-TPD), differential thermogravimetric (DTG) analysis, temperature-programmed reduction of H₂ (H₂-TPR), H₂ chemisorption and catalytic reaction evaluation. The results indicated that the acidity generated via the substitution of Mg²⁺ for Al³⁺ in the framework increased with the Mg content. Acting as acidic components, the MgAPO-11 molecular sieves loaded with Pt were tested in the hydroisomerization of n-dodecane. Optimum isomer yield was obtained over the Pt/MgAPO-11 catalyst that had neither the highest acidity nor the highest Pt loading among the tested catalysts. In fact, the activity and the isomer yield both could attain a maximum on 0.5 wt.% Pt/MgAPO-11 catalysts with differing Mg contents. A lower Mg content resulted in an insufficient acidity, whilst a higher Mg content weakened the dehydrogenation/hydrogenation function of the Pt. These inappropriate balances between the acidic and the metallic functions of the catalysts would lead to low activities and isomer yields. On the other hand, the 0.5 wt.% Pt/MgAPO-11(3) catalyst was found to have a good balance between the acidic and the metallic functions, and thus exhibited both high activity and isomer yield in comparison with the conventional 0.5 wt.% Pt/SAPO-11 catalyst.     

酸处理对Pt/ZSM-22物化及其催化性能的影响

采用HCl溶液对ZSM-22分子筛载体进行酸处理,在改性后的载体上负载金属Pt制备Pt/ZSM-22催化剂。采用XRD、N2吸附-脱附和NH3-TPD等研究酸处理对载体孔结构及酸性质造成的影响,考察改性催化剂在F-T轻组分蜡制备润滑油基础油反应中的加氢异构性能。结果表明,酸处理没有破坏ZSM-22分子筛结构,可提高孔容,产生大孔径介孔,改变载体酸量。酸处理后的催化剂表现出优异的加氢异构性能,所得润滑油基础油收率、异构化率、低温性能和黏度指数明显提高。     

Hydroisomerization of Renewable and Fossil n-Alkanes over Bifunctional Dealuminated ZSM-5 Catalysts

The hydroisomerization of two long-chain n-alkane mixtures was investigated over bifunctional Pt/H-ZSM-5 catalysts before and after dealumination of preshaped zeolite/binder pellets. The hydroisomerization over the dealuminated catalysts leads to more isomers and less cracking products. Consequently, higher ratios of multi- to mono-branched isomerization products are formed as expected for large- rather than medium-pore zeolites. This indicates a higher availability of space in the vicinity of the active sites and provides an attractive route to make medium-pore zeolites suitable for upgrading higher boiling hydrocarbon feeds.     

Hydroisomerization of n-Heptane Over Cr Promoted Pt-bearing H3PW12O40 Catalysts Supported on Dealuminated USY Zeolite

The Pt-bearing H₃PW₁₂O₄₀ (PW) catalysts, promoted by Cr or La, supported on dealuminated USY zeolite were prepared and their catalytic activities were evaluated in the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The catalysts were characterized by XRD, BET, IR and H₂-chemisorption. The results showed that the dealuminated USY support retained the Y zeolite structure and the PW well kept its Keggin structure in the supported PW catalysts and the doping of Cr or La into the catalysts enhanced the dispersion of Pt on the catalyst surface. The Pt-bearing PW catalysts doped with Cr or La, especially Cr, exhibited much higher catalytic activity and selectivity than the catalysts without dopants. Both the conversion and selectivity were discussed in relation with physicochemical properties of catalysts.     

Direct Hydrogenolysis of Highly Concentrated Glycerol Solutions Over Supported Ru,Pd and Pt Catalyst Systems

Abstract  

The evaluation of supported precious metal catalysts, in combination with and without solid acids, for the hydrogenolysis of highly concentrated glycerol solutions, with the aim to produce lower alcohols, in particular 1-propanol was studied. GCMS analysis of the product mixtures obtained has shed some light on the possible mechanism leading to unwanted condensation products, as well as the composition of these compounds.     

NiMoS/ZSM-5-MCM-41催化剂的制备及其加氢脱硫性能

以十六烷基三甲基溴化铵作为模板剂,将ZSM-5用不同浓度NaOH处理脱硅,并利用重结晶法成功合成了具有较强酸性的ZSM-5-MCM-41复合分子筛[记为ZMC-M(x),M=1.5、2.0、2.5,x=n(SiO_2)/n(Al_2O_3)]。然后,采用浸渍法制备了Mo S2/ZMC和Ni-MoS_2/ZMC催化剂。考察了不同浓度NaOH脱硅对复合分子筛ZMC结构和性质的影响。同时以噻吩为模型化合物,考察了ZMC的硅铝比、NiMo双金属硫化物对噻吩加氢脱硫的影响。结果表明,随着NaOH浓度的增加,复合分子筛ZMC会生成更多的介孔相,但是过高浓度NaOH处理后会破坏ZSM-5的结构,确定了最佳NaOH处理浓度为2.0 mol/L。随着ZMC硅铝比的增加,催化剂加氢脱硫活性提高,并且复合分子筛负载Ni Mo双金属硫化物的加氢脱硫性能优于复合分子筛负载MoS_2。在H2压力3 MPa、温度280℃、40 mL(1 mg/L)噻吩/十四烷溶液中,0.1 g的20%MoS2/ZMC-2.0(70)和20%Ni-MoS2/ZMC-2.0(70)[m(Mo)∶m(ZMC)=1∶5,n(Ni)∶n(Mo)=1∶1]催化剂对噻吩的转化率分别达到84.1%和95.2%。     

哌啶对负载型Pt催化剂加氢脱硫性能的影响

将ZSM-5溶于偏硅酸钠水溶液,用水热合成法以十六烷基三甲基溴化铵作模板剂自组装合成了ZSM-5/MCM-41介孔硅铝分子筛(ZM)。以二苯并噻吩(DBT)和哌啶作为模型含硫和含氮化合物,考察了含氮化合物对ZM担载的Pt催化剂加氢脱硫(HDS)反应性能的影响。结果表明,DBT在Pt/ZM催化剂上主要通过直接脱硫(DDS)反应路径脱硫,引入哌啶显著抑制了DBT的HDS反应。与DDS相比,哌啶对加氢路径(HYD)抑制作用更强,并且几乎完全抑制了HYD路径含硫中间体的脱硫。动力学分析表明,DBT的HDS反应和DDS路径级数为一级而其HYD路径则为零级,说明DDS和HYD反应可能是在Pt/ZM不同活性中心上进行的。