The synthesis of Co-doped SAPO-5 molecular sieve and its performance in the oxidation of cyclohexane with molecular oxygen

Silicoaluminophosphate（SAPO） molecular sieves doped with cobalt（Co-SAPO-5） were synthesized hydrothermally with different concentrations of Co.Each sample was characterized by X-ray diffraction,N2 adsorption-desorption,scanning electron microscopy,ultraviolet-visible spectroscopy,temperature-programmed desorption of NH3（NH3-TPD）,and infrared spectrascopy of adsorbed pyridine（Py-IR）.The results showed that Co was highly dispersed in the Co-SAPO-5 samples.In addition,a part of the Co content had been incorporated into the SAPO-5 framework,while the remainder existed on the surface as extra-framework Co.The surface areas of the Co-SAOP-5 samples were similar to the SAPO-5 sample.However,the pore volumes of the Co-SAOP-5 samples were lower than that of the SAOP-5 sample.As the concentration of Co increased,the pore volume gradually decreased because extra-framework cobalt oxide was present on the catalyst surface.NH3-TPD and Py-IR results revealed that the amount of Br（？）nsted acid and the total amount of acid for the Co-SAPO-5 samples were higher than that for the SAPO-5 sample.These values were also higher for samples with higher Co content.The catalytic activity of the Co-SAPO-5 samples was evaluated for the oxidation of cyclohexane with molecular oxygen.When Co was added to the SAPO-5 catalyst,the catalytic activity of the Co-SAPO-5 catalysts improved.In addition,the conversion of cyclohexane increased as the Co content in the Co-SAPO-5 catalysts increased.However,with a high conversion of cyclohexane（6.30%）,the total selectivity of cyclohexanone（K） and cyclohexanol（A） decreased sharply.The K/A ratio ranged from 1.15 to 2.47.The effects of reaction conditions（i.e.,reaction temperature,reaction time,initial oxygen pressure,and the catalyst amount） on the performance of the Co-SAPO-5 catalysts have also been measured.Furthermore,the stability of the Co-SAPO-5 catalyst was explored and found to be good for the selective oxidation of cyclohexane by molecular oxygen.

A SAPO-11 Silicoaluminophosphate Molecular Sieve with Stable Crystal Structure

A SAPO-11 silicoaluminophosphate molecular sieve with stable crystal structure was synthesized for the first time. After removing template by calcination, its crystal space group still retains Icm2 which the as-synthesized has. The catalyst deriving from the present SAPO-11 materials shows higher isomerization selectivity and higher paraffin hydroisomerization yield than those reported elsewhere.

Synthesis of ZSM-22/SAPO-11 composite molecular sieve-based catalysts with small crystallites and superior n-alkane hydroisomerization performance

To improve oil quality,ZSM-22/SAPO-11 composite molecular sieves were synthesized by adding ZSM-22 into a synthetic gel of SAPO-11 for n-decane hydroisomerization.The mass ratios of ZSM-22/(ZSM-22+SAPO-11)in the composite molecular sieves were optimized and the optimal ZSM-22/SAPO-11 composite(ZS-9)was obtained.The electrostatic repulsions between the ZSM-22 precursors and the SAPO-11 crystalline nuclei produced small ZSM-22 and SAPO-11 crystallites in ZS-9,which increased the specific surface area and mesopore volume and thereby exposed more acid sites.In comparison with conventional SAPO-11,ZSM-22 and their mechanical mixture,ZS-9 with smaller crystallites and the optimal medium and strong Brønsted acid centers(MSBAC)content displayed a higher yield of branched C_(10) isomers(81.6%),lower cracking selectivity(11.9%)and excellent stability.The correlation between the i-C_(10) selectivity and the MSBAC density of molecular sieves indicated that the selectivity for branched C_(10) isomers first increased and then decreased with increasing MSBAC density on the molecular sieves,and the maximum selectivity(87.7%)occurred with a density of 9.6×10^(−2)μmol m^(−2).

新型磷酸硅铝分子筛SAPO-53的合成与表征

以氢氧化已烷双铵(R(OH)2)为模板剂,采用水热条件合成了高结晶度的SAPO-53分子筛。并采用XRD、SEMEDX、FT-IR、MAS NMR、电泳仪、N2吸附-脱附、TG-DTG等手段对合成的分子筛进行表征。考察了硅铝比、磷铝比、模板剂的用量以及晶化时间等条件对合成SAPO-53分子筛的作用。29Si MAS NMR表明,Si主要以四配位形式进入了AlPO4-53的骨架中,SAPO-53相对结晶度先增加后开始缓慢下降,Zeta电位值先增加后保持不变,与以甲胺为模板剂合成相比,氢氧化已烷双铵的用量比甲胺减少了一半,同时缩短了晶化时间,降低了合成的难度。通过计算得到SAPO-53的表观生长速率大于成核速率,说明成核过程是速率控制步骤。

SAPO-34 synthesized with n-butylamine as a template and its catalytic application in the methanol amination reaction

SAPO-34 was synthesized with n-butylamine（BA） as a template for the first time.Crystallization temperature and initial Si amount were important factors leading to successful syntheses.Lamellar AlPO-kanemite tends to form as the major phase or as an impurity of SAPO-34 at lower crystallization temperatures,though a higher initial Si amount may offer a positive effect on the crystallization of SAPO-34 that mitigates the low temperature.Higher temperature（240℃） can effectively suppress the generation of lamellar materials and allow the synthesis of pure SAPO-34 with a wider range of Si incorporation.The crystallization processes at 200 and 240℃ were investigated and compared.We used the aminothermal method to synthesize SAPO-34-BA at 240℃ and also found n-propylamine is a suitable template for the synthesis of SAPO-34.The SAPO-34-BA products were characterized by many techniques.SAPO-34-BA has good thermal stability,crystallinity and porosity.BA remained intact in the crystals with ~1.8 BA molecule per chabazite cage.The catalytic performance of SAPO-34 was tested in the methanol amination reaction,which showed high methanol conversion and selectivity for methylamine plus dimethylamine under the conditions investigated,suggesting that this material is a good candidate for the synthesis of methylamines.

n-Nonane hydroisomerization over hierarchical SAPO-11-based catalysts with sodium dodecylbenzene sulfonate as a dispersant

To enhance the gasoline octane number,low-octane linear n-alkanes should be converted into their high-octane di-branched isomers via n-alkane hydroisomerization.Therefore,hierarchical SAPO-11-based catalysts are prepared by adding different contents of sodium dodecylbenzene sulfonate(SDBS),and they are applied in n-nonane hydroisomerization.When n(SDBS)/n(SiO2)is less than or equal to 0.125,the synthesized hierarchical molecular sieves are all pure SAPO-11,and as the SDBS content increases,the submicron particle size decreases,and the external surface area(ESA)increases.Additionally,these hierarchical SAPO-11 have smaller submicron particles and higher ESA values than conventional SAPO-11.When n(SDBS)/n(SiO2)is greater than 0.125,with increasing SDBS content(n(SDBS)/n(SiO2)=0.25),the synthesized SAPO-11 contains amorphous materials,which leads to a decline in the ESA;with the further increase in SDBS content(n(SDBS)/n(SiO2)=0.5),the products are all amorphous materials.These results indicate that in the case of n(SDBS)/n(SiO2)=0.125,the synthesized SAPO-11 molecular sieve(S–S3)has the most external Brønsted acid centers and the highest ESA of these SAPO-11,and these advantages favor generation of the di-branched isomers in hydrocarbon hydroisomerization.Among these Pt/SAPO-11 catalysts,Pt/S–S3 displays the highest selectivity to entire isomers(83.4%),the highest selectivity to di-branched isomers(28.1%)and the minimum hydrocracking selectivity(15.7%)in n-nonane hydroisomerization.

Rice Husk Ash:A New Silicon Source for Preparing SAPO-34 Catalysts Used in the Methanol-to-Olefins Reaction

SAPO-34 molecular sieves were synthesized directly by hydrothermal method with rice husk ash(RHA)used as the silicon source.The crystal structure,composition,surface morphology and acidity of the synthesized products weresieves had a high crystallinity,without any impure phase.Compared with the SAPO-34 prepared by the silica sol,RHA-SAPO-34 had similar acid properties in strength.The methanol to olefins(MTO)experiments showed that the SAPO-34molecular sieve synthesized from RHA exhibited both a good catalytic activity and ethylene selectivity.

Conversion of methanol to propylene over SAPO-14:Reaction mechanism and deactivation

Methanol to olefins(MTO)reaction as an important non-oil route to produce light olefins has been industrialized,and received over 80% ethylene plus propylene selectivity.However,to achieve high single ethylene or propylene selectivity towards the fluctuated market demand is still full of challenge.Small-pore SAPO-14 molecular sieve is a rare MTO catalyst exhibiting extra-high propylene selectivity.It provides us a valuable clue for further understanding of the relationship between molecular sieve structure and MTO catalytic performance.In this work,a seconds-level sampling fixed-bed reactor was used to capture real-time product distributions,which help to achieve more selectivity data in response to very short catalytic life of SAPO-14.Changes in product distribution,especially during the low activity stage,reflect valuable information on the reaction pathway.Combined with in situ diffuse reflectance infrared Fourier-transform spectroscopy,in situ ultraviolet Raman measurements and ^(12)C/^(13)C isotopic switch experiments,a reaction pathway evolution from dual cycle to olefins-based cycle dominant was revealed.In addition,the deactivation behaviors of SAPO-14 were also investigated,which revealed that polymethylbenzenes have been the deactivated species in such a situation.This work provides helpful hints on the development of characteristic methanol to propylene(MTP)catalysts.

Cu-SAPO-17:A novel catalyst for selective catalytic reduction of NOx

The high-temperature(HT) and low-temperature(LT) hydrothermal stabilities of molecular-sieve-based catalysts are important for the selective catalytic reduction of NOx with ammonia(NH3-SCR). In this paper, we report a catalyst, Cu2+ loading SAPO-17, synthesized using cyclohexylamine(CHA), which is commercially available and inexpensive and is utilized in NH3-SCR reduction for the first time. After systematic investigations on the optimization of Si and Cu2+ contents, it was concluded that Cu-SAPO-17-8.0%-0.22 displays favorable catalytic performance, even after being heated at 353 K for 24 h and at 973 K for 16 h. Moreover, the locations of CHAs, host–guest interaction and the Bronsted acid sites were explored by Rietveld refinement against powder X-ray diffraction data of as-made SAPO-17-8.0%. The refinement results showed that two CHAs exist within one eri cage and that the protonated CHA forms a hydrogen bond with O4, which indicates that the proton bonding with O4 will form the Bronsted acid site after the calcination.

Preparation and Property of Ni/TiO₂-SAPO-11 Catalyst for N-Heptane Isomerization

For enhancing the activity of Ni/TiO2-SAPO-11 catalyst, SAPO-11, the precursor was prepared by hydrothermal crystallization, and TiO2-SAPO-11 complex carrier was prepared by sol-gel method, then Ni/TiO2-SAPO-11 was produced by the final product. The catalytic performance of Ni/TiO2-SAPO-11 was studied in n-heptane isomerization, and the impact of catalyst preparation conditions on n-heptane isomerization was discussed in detail. The results showed that, with 20% of TiO2 composition, 2% of Ni capacity percentage and calcined temperature at 500°C, conversion of n-heptane and isomerization selectivity was up to 40.94% and 88.97% respectively.

酱香型白酒除杂后长期大剂量饮用对小鼠生长的影响研究

为探讨长期大剂量饮用经酒用除杂炭分子筛处理后的53%vol酱香酒与普通53%vol酱香酒对KM小白鼠体重、生育、脏体系数及死亡率的影响,将60只KM小白鼠(雌雄各半)随机分为Ⅰ组(53%vol酱香酒)、Ⅱ组(除杂后53%vol酱香酒)、对照组三组,每组20只(雌雄各半),每日灌胃给酒1次,连续5 d后停灌2 d而后继续灌胃5 d,连续60 d,剂量20 mL/kg·d。结果表明,Ⅰ组、Ⅱ组与对照组相比体重增长显著降低(P<0.01),Ⅱ组体重增长显著高于Ⅰ组(P<0.01);Ⅰ组、Ⅱ组与对照组生育率分别为64.9%、70.5%、81.3%;Ⅰ组的心脏系数和肾脏系数显著高于对照组(P<0.01,P<0.05),脾脏系数和胸腺系数显著低于对照组(P<0.05,P<0.01),Ⅱ组的各脏器系数与对照组无显著差异(P>0.05);Ⅰ组、Ⅱ组死亡率分别为70%、55%。53%vol酱香经酒用除杂炭分子筛除杂后显著降低了对小鼠的影响。

The synergic effects of highly selective bimetallic Pt-Pd/SAPO-41 catalysts for the n-hexadecane hydroisomerization

The hydroisomerization of n-hexadecane over Pt-Pd bimetallic catalysts is an effective way to produce clean fuel oil.This work reports a useful preparation method of bimetallic bifunctional catalysts by a co-impregnation or sequential impregnation process.Furthermore,monometallic catalysts with loading either Pt or Pd are also prepared for comparison.The effects of the metal species and impregnation order on the characteristics and catalytic performance of the catalysts are investigated.The catalytic test results indicate that the maximum iso-hexadecane yield over different catalysts increases as follows:Pt/silicoaluminophosphate SAPO-41<Pd/SAPO-41<Pt^(*)-Pd/SAPO-41(prepared by sequential impregnation)<Pt-Pd/SAPO-41(prepared by co-impregnation).Owing to the synergic effects between Pt and Pd,the Pt-Pd/SAPO-41 catalyst prepared by the co-impregnation method demonstrates the effective promotion of(de)hydrogenation activity.Therefore,this catalyst exhibits the highest iso-hexadecane yield of 89.4%when the n-hexadecane conversion is 96.3%.Additionally,the Pt-Pd/SAPO-41 catalyst also presents the highest catalytic activity and best stability even after 150 h long-term tests.

Effects of the SAPO-11 synthetic process on dehydration of ethanol to ethylene

The effects of the synthetic condition of SAPO-11 molecular sieves on ethanol dehydration to ethylene were studied.Product-compositions,ethanol conversion,and selectivity to ethylene of synthesized and commercial SAPO-11 molecular sieves were compared.Results are as follows:the optimal synthetic conditions for SAPO-11 molecular sieves are adding pseudoboehmite before orthophoshporic,using di-npropylamine as the template,having a mass fraction of 40%colloidal silica as the silica source and the starting gel obtained,and running at 200℃ for 48 h.From the patterns of NH3-TPD,the amount of acid synthesized by SAPO-11 molecular sieves is less than that by commercial SAPO-11 molecular sieves,and has a stronger weak acid.Also,ethanol conversion and selectivity to ethylene reached 99%at 280℃ on synthesized SAPO-11,lower by 20℃ compared to commercial SAPO-11.For two SAPO-11 molecular sieves,the by-products in the gas phase are mainly ethane,propane,propene,isobutane,n-butane,propadiene,butylene and some higher hydrocarbons.The by-products in the liquid phase are ethyl ether and acetaldehyde.