The selective aqueous-phase glycerol hydrogenolysis is a promising reaction to produce commercially useful 1,3-propanediol(1,3-PDO).The Pt-WOx bifunctional catalyst can catalyse the glycerol hydrogenol-ysis but the ca...The selective aqueous-phase glycerol hydrogenolysis is a promising reaction to produce commercially useful 1,3-propanediol(1,3-PDO).The Pt-WOx bifunctional catalyst can catalyse the glycerol hydrogenol-ysis but the catalyst deactivation via sintering,metal leaching,and coking can predominantly occur in the aqueous phase reaction.In this work,the effect of reaction temperature,pressure and second promoter(Cu,Fe,Rh,Mn,Re,Ru,Ir,Sn,B,and P)on catalytic performance and deactivation behaviour of Pt/WOx/-Al2O3 was investigated.When doped with Rh,Mn,Re,Ru,Ir,B,and P,the second promoter boosts catalytic activity by promoting great dispersion of Pt on support and increasing Pt surface area.The increased Bronsted acid sites lead to selective synthesis of 1,3-PDO than 1,2-propanediol(1,2-PDO).The characterization studies of fresh and spent catalysts reveal that the main cause of catalyst deactivation is the Pt sintering,as interpreted based on XRD,CO chemisorption,and TEM analyses.The Pt sintering is affected depending on the second promoter that can either or reduce the interaction between Pt,WO_(χ)/γ and Al_(2)O_(3).As an electron acceptor of Pt in Pt/WO_(χ)/γ-Al_(2)O_(3),Re and Mn as second promoters resulted in increased Pt^(2+) on the catalytic surface,which strengthens the contact between Pt andγ-Al_(2)O_(3) and WO_(χ),resulting in a decrease in Pt sintering.The metal leaching and coking are not affected by the presence of second promoter.The catalyst modified with a second promoter possesses improved catalytic activity and 1,3-PDO production,however the stability continues to remain a challenge.The present work unrav-elled the determining parameters of catalytic activity and deactivation,thus providing a promising pro-tocol toward effective catalysts for glycerol hydrogenolysis.展开更多
Alpha-lactalbumin(α-LA)is a major whey protein found in breast milk and plays a crucial role in the growth and development of infants.In this study,Bacillus subtilis RIK1285 harboring AprE signal peptide(SP)was selec...Alpha-lactalbumin(α-LA)is a major whey protein found in breast milk and plays a crucial role in the growth and development of infants.In this study,Bacillus subtilis RIK1285 harboring AprE signal peptide(SP)was selected as the original strain for the production ofα-LA.It was found thatα-LA was identified in the pellet after ultrasonic disruption and centrifugation instead of in the fermentation supernatant.The original strain most likely only producedα-LA intracellular,but not extracellular.To improve the expression and secretion ofα-LA in RIK1285,a library of 173 homologous SPs from the B.subtilis 168 genome was fused with target LALBA gene in the pBE-S vector and expressed extracellularly in RIK1285.SP YjcN was determined to be the best signal peptide.Bands in supernatant were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and purified by nickel column to calculate the highest yield signal peptide.In addition,different promoters(P_(aprE),P_(43),and P_(glv))were compared and applied.The results indicated that the strain RIK1285-pBE-P_(glv)-YjcN-LALBA had the highestα-LA yield,reaching 122.04μg/mL.This study demonstrates successful expression and secretion of humanα-LA in B.subtilis and establishes a foundation for simulating breast milk for infant formulas and developing bioengineered milk.展开更多
CO_(2)reformation of methane(CRM)and CO_(2)methanation are two interconnected processes with significant implications for greenhouse gas reduction and sustainable energy production for industrial purposes.While Nibase...CO_(2)reformation of methane(CRM)and CO_(2)methanation are two interconnected processes with significant implications for greenhouse gas reduction and sustainable energy production for industrial purposes.While Nibased catalysis suffers from poor stability due to coke formation or sintering,we report a super stable remedy.The active sites of mesoporous MgO were loaded using wet impregnation.The incorporation of Ni and promoters altered the physical features of the catalysts.Sm–Ni/MgO showed the smallest crystallite size,specific surface area,and pore volume.The Sm–Ni/MgO catalyst was selected as the most suitable candidate for CRM,with 82%CH4 and H2/CO ratio of approximately 100%and also for CO_(2)methanation with the conversion of carbon dioxide(82%)and the selectivity toward methane reaches 100%at temperatures above 300ᵒC.Furthermore,the Sm–Ni/MgO catalyst was stable for 900 min of continuous reaction,without significant carbon deposition.This stability was largely due to the high oxygen mobility on the catalyst surface in the presence of Sm.Overall,we demonstrated the efficacy of using promoted Ni catalysts supported by mesoporous magnesia for the improved reformation of greenhouse gases.展开更多
Long-range interactions between regulatory elements and gene promoters play key roles in transcriptional regulation.The vast majority of interactions are uncharted,constituting a major missing link in understanding ge...Long-range interactions between regulatory elements and gene promoters play key roles in transcriptional regulation.The vast majority of interactions are uncharted,constituting a major missing link in understanding genome control.Here,we use promoter capture Hi-C to identify interacting regions of 31,253 promoters in 17 human primary hematopoietic cell types.We show that promoter interactions are highly cell type specific and enriched for links between active promoters and epigenetically marked enhancers.Promoter interactomes reflect lineage relationships of the hematopoietic tree,consistent with dynamic remodeling of nuclear architecture during differentiation.Interacting regions are enriched in genetic variants linked with altered expression of genes they contact,highlighting their functional role.We exploit this rich resource to connect non-coding disease variants to putative target promoters,prioritizing thousands of disease-candidate genes and implicating disease pathways.Our results demonstrate the power of primary cell promoter interactomes to reveal insights into genomic regulatory mechanisms underlying common diseases.展开更多
The effects of Mg,La and Ca promoters on primary and secondary CO2 and H2O formation pathways during Fischer-Tropsch synthesis on precipitated Fe/Cu/SiO2 catalysts are investigated.The chemisorbed oxygen atoms in the ...The effects of Mg,La and Ca promoters on primary and secondary CO2 and H2O formation pathways during Fischer-Tropsch synthesis on precipitated Fe/Cu/SiO2 catalysts are investigated.The chemisorbed oxygen atoms in the primary pathway formed in the CO dissociation steps reacted with co-adsorbed hydrogen or carbon monoxide to produce H2O and CO2,respectively.The secondary pathway was the water-gas shift reaction.The results indicated that the CO2 production led to an increase in both primary and secondary pathways,and H2O production decreased when surface basicity of the catalyst increased in the order Ca 〉 Mg 〉 La.展开更多
Structural and compositional design of core-shell structure is an effective strategy towards enhanced catalysis.Herein,amorphous MnO2 nanosheets and K+-intercalated layered MnO2 nanosheets are controllably assembled o...Structural and compositional design of core-shell structure is an effective strategy towards enhanced catalysis.Herein,amorphous MnO2 nanosheets and K+-intercalated layered MnO2 nanosheets are controllably assembled over Fe2O3 spindles,in which the MnO2 nanosheets are perpendicularly anchored to the surface of Fe2O3.Such a core shell structure contributes to a high specific surface area and abundant pore channels on the surface of catalysts.In addition,the existence of K+provides large numbers of basic sites and restrains the formation of unpleasant(Fe1-xMnx)3O4.Benefiting from the merits in structure and composition,CO adsorption is enhanced and remaining time of intermediates is prolonged on the surfaces of catalysts during the Fischer–Tropsch synthesis(FTS),facilitating to the formation of active iron carbides and C–C coupling reactions.Resultantly,the Fe2O3@K+-Mn O2 shows both a high CO conversion of 82.3%and a high C5+ selectivity of 73.1%.The present study provides structural and compositional rationales on design high-performance catalysts towards FTS.展开更多
Objective: To study the correlation of the methylation of the promoters of hMLH1 and hMSH2 with microsatellite instability (MSI) in the tissues of gastric carcinomas. Methods: A total of 68 sporadic cases of gastric c...Objective: To study the correlation of the methylation of the promoters of hMLH1 and hMSH2 with microsatellite instability (MSI) in the tissues of gastric carcinomas. Methods: A total of 68 sporadic cases of gastric carcinoma were studied. Ten specimens of normal gastric mucosa served as control. Methylation of hMLHl and hMSH2 was observed with methylation-specific PCR, and MSI analyzed with PCR-based techniques. Results: No methylation of hMLHl and hMSH2 was found in 10 specimens of normal gastric mucosa. Methylation of hMLHl was detected in 11 cases (16. 2%) of gastric cancers and MSI in at least one locus was found in 17 cases (25%) of the 68 with aid of 5 microsatellite markers, in which eight were MSI-H (≥2loci showed instability) nine MSI-L (only one locus showed instability), and fifty-one were MSS (no instability at any marker). The frequency of methylation was significantly high in MSI-H (87. 5%) than in MSI-L (11.1%) and MSS (5. 9%). CP<0. 01 - 0. 001) but there was no difference of methylation frequency between the cases with MSI-L and those with MSS. Conclusion: Methylation of hMLHl promoter is involved to the MSI pathway but not to the loss of heterozygosity (LOH) pathway in gastric carcinogenesis.展开更多
The 9-cis-epoxycarotenoid dioxygenase(NCED)gene is rate-limiting in abscisic acid(ABA) biosynthesis.In this study, an NCED gene, designated FvNCED3(KY008746), was cloned from velvet ash(Fraxinus velutina Torr.) with a...The 9-cis-epoxycarotenoid dioxygenase(NCED)gene is rate-limiting in abscisic acid(ABA) biosynthesis.In this study, an NCED gene, designated FvNCED3(KY008746), was cloned from velvet ash(Fraxinus velutina Torr.) with a RACE method. The full length c DNA of FvNCED3 encodes a 573-amino acid polypeptide.Sequencing analysis showed that the FvNCED3 protein was highly homologous to other NCED proteins. The expression patterns of FvNCED3 in different ash organs were analyzed by real-time PCR which revealed that FvNCED3 expression levels were highest in leaves and lowest in roots. The gene expression patterns of FvNCED3 under abiotic stress indicated that its expression increased under drought, salt and ABA stress and decreased due to high and low temperatures. There were no obvious changes under ultraviolet light. The 1094-bp upstream sequence 5' flank regulation region of the FvNCED3 gene was also cloned from ash using the Genome Walking method. To assess the activity of the FvNCED3 promoter, a p FvNCED3 p::GUS plant expression vector was constructed for tobacco transformation. GUS expression of the FvNCED3 GUS enzyme activity was detected in almost all transgenic tobacco tissues, especially in the young leaves,stigma, anther, ovule and ovary. After treating the transgenic tobacco with NaCl and placing it under drought stress, GUS staining of tobacco leaves increased compared with that under normal growth conditions. This result indicates that gene expression driven by the FvNCED3 promoter can be induced by salt and drought stress.展开更多
The effects of Manganese （Mn） incorporation on a precipitated iron-based Fischer-Tropsch synthesis （FTS） catalyst were investigated using N2 physical adsorption, air differential thermal analysis （DTA）, H2 tempe...The effects of Manganese （Mn） incorporation on a precipitated iron-based Fischer-Tropsch synthesis （FTS） catalyst were investigated using N2 physical adsorption, air differential thermal analysis （DTA）, H2 temperature-programmed reduction （TPR）, and Mǒssbauer spectroscopy. The FTS performances of the catalysts were tested in a slurry phase reactor. The characterization results indicated that Mn increased the surface area of the catalyst, and improved the dispersion of （α-Fe2O3 and reduced its crystallite size as a result of the high dispersion effect of Mn and the Fe-Mn interaction. The Fe-Mn interaction also suppressed the reduction of （α-Fe2O3 to Fe3O4, stabilized the FeO phase, and （or） decreased the carburization degree of the catalysts in the H2 and syngas reduction processes. In addition, incorporated Mn decreased the initial catalyst activity, but improved the catalyst stability because Mn restrained the reoxidation of iron carbides to Fe3O4, and improved further carburization of the catalysts. Manganese suppressed the formation of CH4 and increased the selectivity to light olefins （C2-4^=）, but it had little effect on the selectivities to heavy （C5＋） hydrocarbons. All these results indicated that the strong Fe-Mn interaction suppressed the chemisorptive effect of the Mn as an electronic promoter, to some extent, in the precipitated iron-manganese catalyst system.展开更多
A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and character...A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and characterized by ICP-OES,HRTEM,BET,N2O chemisorption,TPR,XPS and CO2-TPD techniques.The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst.Copper surface area(SCu)and dispersion(DCu)were slightly decreased by incorporation of ZnO promoter.Nevertheless,SCuand DCuwere remarkably decreased when ZnO content was exceeded beyond 3 wt%.The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃,respectively.The promotion of CuZrO2/CNFs catalyst with 3 wt%of ZnO enhanced methanol synthesis rate from 32 to 45 g kg^-1 h^-1.Notably,with the ZnO promotion the selectivity to methanol was enhanced to 92%compared to 78%of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion.In addition,the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.展开更多
A 5＇ flanking region of the well-conserved Toll/interleukin-1 receptor domain （TIR）-encoding sequence was isolated from the genomic DNA ofMelampsora magnusiana Wagner resistant clones of hybrid triploid poplars [（...A 5＇ flanking region of the well-conserved Toll/interleukin-1 receptor domain （TIR）-encoding sequence was isolated from the genomic DNA ofMelampsora magnusiana Wagner resistant clones of hybrid triploid poplars [（Populus tomentosa × P. bolleana） × P. tomentosa]. Sequencing results and alignment analysis show that the obtained TIR-specific promoter （named as PtTIRp01） was 1,732 bp in length; moreover 3＇ region of the PtTIRp01 contains a responds to the 5＇ composition of TIR-NBS type gene PtDRG02, of 747 bp long 5＇ region of TIR-NBS type gene PtDRG02 and its 398 bp complete TIR-encoding sequence, which significantly corindicating that the obtained TIR-specific promoter region consists upstream region of promoter （985 bp）. It was found that the 5＇ region of TIR-NBS type gene PtDRG02 was characterized in the downstream region of the transcriptional start, named as 5＇-untranslated region （5＇ UTR）, consisting of one 93 bp 5＇-untranslation exon, one 213 bp intron and one 441 bp TIR-encoding open reading frame （ORF）. In addition, several putative cis-acting motifs were present in the obtained TIR-specific promoter of PtDRG02, including one TATA box, one GC-rich, one AT-rich, one P-box, one 3-AF1 binding site, two CAAT boxes, two GT-1 motifs, three typical W-boxes, four I-boxes, and one multi-cis-acting fragment （MCF）. The latter contains five types of regulatory elements （E4, G-box, ABRE motif, box 1 and HVA 1 s）, most of which were homologous to the cis-acting regulatory elements involved in the activation of defense genes in plants. Thus, it can be suggested that TIR-specific promoter might be a pathogen-inducible promoter and be necessary for the inducible expression of defense-related genes. Key words Toll/interleukin- 1 receptor domain, promoter, Cis-acting element, poplar展开更多
Carbon dioxide(CO_(2) ) capture and conversion is the key route for the mitigation of the greenhouse effect and utilization of carbon sources to obtain value-added products or fuels.Much attention is paid to the devel...Carbon dioxide(CO_(2) ) capture and conversion is the key route for the mitigation of the greenhouse effect and utilization of carbon sources to obtain value-added products or fuels.Much attention is paid to the development of novel materials with high CO_(2) adsorption capacity and conversion rate.MXene is the graphene-like two-dimensional metal carbide/nitride/carbonitride owning favorable structure,morphology,high surface-bulk ratio,and physicochemical properties.Here,we review the CO_(2) capture,sensing,and conversion by MXene and MXene-based materials.Furthermore,the underlying mechanism involved the capture,sensing,and conversion of CO_(2) is summarized.This review would open a new horizon for CO_(2) valorization with high efficiency and promising widespread applications.展开更多
Hydrogenation of methyl acetate is a key step in ethanol synthesis from dimethyl ether carbonylation and Cu-based catalysts are widely studied.We report here that the hydrogenation activity of Cu/ZnO catalysts can be ...Hydrogenation of methyl acetate is a key step in ethanol synthesis from dimethyl ether carbonylation and Cu-based catalysts are widely studied.We report here that the hydrogenation activity of Cu/ZnO catalysts can be enhanced by the addition of MgO promoter.The evolution of crystal phases during coprecipitation and the physicochemical properties of calcined and reduced catalysts by X-ray diffraction(XRD),thermogravimetric(TG)-mass spectrometry(MS),Brunauer-Emmett-Teller(BET),transmission electron microscopy(TEM),N_(2)O titration,in situ CO-Fourier transform infrared spectroscopy(FTIR)and H_(2)-temperature programmed reduction(H_(2)-TPR)reveal that the promoter effect likely lies in the presence of Mg^(2+).A proper amount of Mg^(2+)mediates the precipitation process of Cu and Zn,leading to preferable formation of aurichalcite(Cu_(x)Zn_(1-x))5(CO_(3))_(2)(OH)_(6) crystal phase and a small amount of basic carbonates such as hydrozincite Zn_(5)(CO_(3))_(2)(OH)_(6) and malachite Cu_(2) CO_(3)(OH)_(2).The presence of aurichalcite strengthens the interaction between Cu and Zn species,and thus enhances the dispersity of CuO species and helps generation of Cu^(+)species on reduced catalysts.Furthermore,the performance of Cu/ZnO catalysts exhibits an optimal dependence on the Mg loading,i.e.,17.5%.However,too much Mg^(2+)in the precipitation liquid prohibits formation of aurichalcite but enhances formation of basic nitrates,leading to a dramatically reduced hydrogenation activity.These findings may find applications for optimization of other Cu-based catalysts in a wider range of hydrogenation reactions.展开更多
Rare-earth （La, Ce, Yb） promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catal...Rare-earth （La, Ce, Yb） promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal＇s dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.展开更多
A series of Ni/SBA-15 catalysts with 5wt% to 15wt% Ni content as well as a series of 12.5%Ni/Cu/SBA-15 catalysts with 1% to 10% copper content were prepared by the impregnation method. The catalytic performance for pa...A series of Ni/SBA-15 catalysts with 5wt% to 15wt% Ni content as well as a series of 12.5%Ni/Cu/SBA-15 catalysts with 1% to 10% copper content were prepared by the impregnation method. The catalytic performance for partial oxidation of methane was investigated in a continuous flow microreactor under atmospheric pressure. The textural and chemical properties of the catalysts were characterized by XRD, TEM, BET and Hz-TPR techniques. The results indicated that the catalysts modified with Cu promoter showed better performance than those without modification. For the 12.5%Ni/2.5%/Cu/SBA-15 catalyst, at 850 ℃ the conversion of CH4 reached 97.9% and the selectivity of CO and H2 reached 98.0% and 96.0%, respectively. In XRD patterns of the Ni/Cu/SBA-15 catalyst with 7.5 to 10% Cu contents there were CuO characteristic peaks beside NiO characteristic peaks. The mesoporous structure of SBA-15 was retained in all of the catalysts. TPR analysis of the catalysts revealed that a strong interaction between Ni, Cu promoter and SBA-15 support may be existed. This interaction enhanced significantly the redox properties of the catalysts resulting in the higher catalytic activity.展开更多
In this study, Cr and Co promoted, as well as unpromoted vanadium phosphate （VPO） catalysts were synthesized by the reaction of V2O5 and o-H3PO4 in organic medium followed by calcination in n-butane/air environment ...In this study, Cr and Co promoted, as well as unpromoted vanadium phosphate （VPO） catalysts were synthesized by the reaction of V2O5 and o-H3PO4 in organic medium followed by calcination in n-butane/air environment at 673 K. The physico-chemical properties and the catalytic behavior were affected by the addition of Cr and Co dopants. H2-TPR was used to investigate the nature of oxidants in the unpromoted and promoted catalysts. The results showed that both the Cr and Co promoters remarkably lowered the temperature of the reduction peak associated with V^5＋. The amount of oxygen species originated from the active phase, V^4＋, removed was significantly increased for Co and Cr-promoted catalysts. Both Cr and Co dopants improve strongly the n-butane conversion without sacrificing the MA selectivity. A good correlation was observed between the amount of oxygen species removed from V^4＋ phase and the activity for n-butane oxidation to maleic anhydride. This suggested that V^4＋-O was the center for the activation of n-butane.展开更多
At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons （C2-C4） and aromatics （C6-C10）, through its reaction over rare metals modi...At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons （C2-C4） and aromatics （C6-C10）, through its reaction over rare metals modified Zn/HZSM-5 zeolite catalysts without undesirable carbon oxides formation. Methane can get 37.3% conversion over the above catalysts under low temperature, and the catalysts show a longer lifetime than usual metal supported HZSM-5 zeolite catalysts without adding any rare earth metals. The effects of methane activation over various rare earth metal promoted Zn/HZSM-5 catalysts on the products and influences of several reaction conditions such as temperature, catalyst lifetime and molar ratio of CH4/C2H4 have been discussed.展开更多
A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and...A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.展开更多
2%Fe-10%Co/SiO2 catalysts with different potassium or zirconium loadings were prepared by aqueous incipient wetness impregnation and tested for Fischer-Tropsch synthesis in a flow reactor, using H2/CO = 1.6 （molar ra...2%Fe-10%Co/SiO2 catalysts with different potassium or zirconium loadings were prepared by aqueous incipient wetness impregnation and tested for Fischer-Tropsch synthesis in a flow reactor, using H2/CO = 1.6 （molar ratio） in the feed, under the condition of an overall pressure of 1 MPa, GHSV of 600 h^-1 and temperature of 503 K. The zirconium and potassium promoters remarkably influenced hydrocarbon distribution of the products. CO conversion increased on the catalysts with the increase of zirconium loadings, which indicated that zirconium enhanced the activity of iron-cobalt catalysts. Low potassium loadings also enhanced the activity of the catalysts. However, high potassium loading made CO conversion on the catalysts decrease and weakened the secondary hydrogenations. The catalyst was characterized by BET, XRD and TPR. The catalyst characterization revealed that the Co3O4 phase was presented on the fresh catalyst, whereas the spinel phase of Fe-Co alloy and CoO existed on the used catalyst.展开更多
Catalytic ethane dehydrogenation(EDH) to ethylene over Pt-based catalysts has received increasing interests in recent years as it is a potential alternative route to conventional steam cracking. However, the catalysts...Catalytic ethane dehydrogenation(EDH) to ethylene over Pt-based catalysts has received increasing interests in recent years as it is a potential alternative route to conventional steam cracking. However, the catalysts used in this reaction often suffer from rapid deactivation due to serious coke deposition and metal sintering. Herein, we reported the effects of Zn modification on the stability of Pt/Al2 O3 for EDH.The Zn-modified sample(PtZn2/Al2 O3) exhibits stable ethane conversion(20%) with over 95% ethylene selectivity. More importantly, it exhibits a significantly low deactivation rate of only 0.003 h-1 at 600 °C for70 h, which surpasses most of previously reported catalysts. Detailed characterizations including in situ FT-IR, ethylene adsorption microcalorimetry, and HAADF-STEM etc. reveal that Zn modifier reduces the number of Lewis acid sites on the catalyst surface. Moreover, it could modify Pt sites and preferentially cover the step sites, which decrease surface energy and retard the sintering of Pt particle, then prohibiting the further dehydrogenation of ethylene to ethylidyne. Consequently, the good stability is realized due to anti-sintering and the decrease of coke formation on the Pt Zn2/Al2 O3 catalyst.展开更多
基金funded by the National Research Council of Thailand (NRCT)the Second Century Foundation (C2F),Chulalongkorn University,ThailandResearcher Supporting Project RSP2024RR400,King Saud University,Saudi Arabia
文摘The selective aqueous-phase glycerol hydrogenolysis is a promising reaction to produce commercially useful 1,3-propanediol(1,3-PDO).The Pt-WOx bifunctional catalyst can catalyse the glycerol hydrogenol-ysis but the catalyst deactivation via sintering,metal leaching,and coking can predominantly occur in the aqueous phase reaction.In this work,the effect of reaction temperature,pressure and second promoter(Cu,Fe,Rh,Mn,Re,Ru,Ir,Sn,B,and P)on catalytic performance and deactivation behaviour of Pt/WOx/-Al2O3 was investigated.When doped with Rh,Mn,Re,Ru,Ir,B,and P,the second promoter boosts catalytic activity by promoting great dispersion of Pt on support and increasing Pt surface area.The increased Bronsted acid sites lead to selective synthesis of 1,3-PDO than 1,2-propanediol(1,2-PDO).The characterization studies of fresh and spent catalysts reveal that the main cause of catalyst deactivation is the Pt sintering,as interpreted based on XRD,CO chemisorption,and TEM analyses.The Pt sintering is affected depending on the second promoter that can either or reduce the interaction between Pt,WO_(χ)/γ and Al_(2)O_(3).As an electron acceptor of Pt in Pt/WO_(χ)/γ-Al_(2)O_(3),Re and Mn as second promoters resulted in increased Pt^(2+) on the catalytic surface,which strengthens the contact between Pt andγ-Al_(2)O_(3) and WO_(χ),resulting in a decrease in Pt sintering.The metal leaching and coking are not affected by the presence of second promoter.The catalyst modified with a second promoter possesses improved catalytic activity and 1,3-PDO production,however the stability continues to remain a challenge.The present work unrav-elled the determining parameters of catalytic activity and deactivation,thus providing a promising pro-tocol toward effective catalysts for glycerol hydrogenolysis.
基金This work was funded by National Natural Science Foundation of China(32272279)the Key R&D project of Qingdao Science and Technology Plan(22-3-3-hygg-29-hy).
文摘Alpha-lactalbumin(α-LA)is a major whey protein found in breast milk and plays a crucial role in the growth and development of infants.In this study,Bacillus subtilis RIK1285 harboring AprE signal peptide(SP)was selected as the original strain for the production ofα-LA.It was found thatα-LA was identified in the pellet after ultrasonic disruption and centrifugation instead of in the fermentation supernatant.The original strain most likely only producedα-LA intracellular,but not extracellular.To improve the expression and secretion ofα-LA in RIK1285,a library of 173 homologous SPs from the B.subtilis 168 genome was fused with target LALBA gene in the pBE-S vector and expressed extracellularly in RIK1285.SP YjcN was determined to be the best signal peptide.Bands in supernatant were observed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and purified by nickel column to calculate the highest yield signal peptide.In addition,different promoters(P_(aprE),P_(43),and P_(glv))were compared and applied.The results indicated that the strain RIK1285-pBE-P_(glv)-YjcN-LALBA had the highestα-LA yield,reaching 122.04μg/mL.This study demonstrates successful expression and secretion of humanα-LA in B.subtilis and establishes a foundation for simulating breast milk for infant formulas and developing bioengineered milk.
基金supports rendered by Zhejiang Normal University(Grant No.YS304221928)Iran National Science Foundation.No.:4002219Yonsei University Mirae Campus.
文摘CO_(2)reformation of methane(CRM)and CO_(2)methanation are two interconnected processes with significant implications for greenhouse gas reduction and sustainable energy production for industrial purposes.While Nibased catalysis suffers from poor stability due to coke formation or sintering,we report a super stable remedy.The active sites of mesoporous MgO were loaded using wet impregnation.The incorporation of Ni and promoters altered the physical features of the catalysts.Sm–Ni/MgO showed the smallest crystallite size,specific surface area,and pore volume.The Sm–Ni/MgO catalyst was selected as the most suitable candidate for CRM,with 82%CH4 and H2/CO ratio of approximately 100%and also for CO_(2)methanation with the conversion of carbon dioxide(82%)and the selectivity toward methane reaches 100%at temperatures above 300ᵒC.Furthermore,the Sm–Ni/MgO catalyst was stable for 900 min of continuous reaction,without significant carbon deposition.This stability was largely due to the high oxygen mobility on the catalyst surface in the presence of Sm.Overall,we demonstrated the efficacy of using promoted Ni catalysts supported by mesoporous magnesia for the improved reformation of greenhouse gases.
文摘Long-range interactions between regulatory elements and gene promoters play key roles in transcriptional regulation.The vast majority of interactions are uncharted,constituting a major missing link in understanding genome control.Here,we use promoter capture Hi-C to identify interacting regions of 31,253 promoters in 17 human primary hematopoietic cell types.We show that promoter interactions are highly cell type specific and enriched for links between active promoters and epigenetically marked enhancers.Promoter interactomes reflect lineage relationships of the hematopoietic tree,consistent with dynamic remodeling of nuclear architecture during differentiation.Interacting regions are enriched in genetic variants linked with altered expression of genes they contact,highlighting their functional role.We exploit this rich resource to connect non-coding disease variants to putative target promoters,prioritizing thousands of disease-candidate genes and implicating disease pathways.Our results demonstrate the power of primary cell promoter interactomes to reveal insights into genomic regulatory mechanisms underlying common diseases.
文摘The effects of Mg,La and Ca promoters on primary and secondary CO2 and H2O formation pathways during Fischer-Tropsch synthesis on precipitated Fe/Cu/SiO2 catalysts are investigated.The chemisorbed oxygen atoms in the primary pathway formed in the CO dissociation steps reacted with co-adsorbed hydrogen or carbon monoxide to produce H2O and CO2,respectively.The secondary pathway was the water-gas shift reaction.The results indicated that the CO2 production led to an increase in both primary and secondary pathways,and H2O production decreased when surface basicity of the catalyst increased in the order Ca 〉 Mg 〉 La.
基金funding support from the National Natural Science Foundation of China (51722404, 51674177, 91845113 and 51804221)the “1000-Youth Talents Plan”+3 种基金the Fundamental Research Funds for the Central Universities (2042017kf0200)National Key R&D Program of China (2018YFE0201703)the China Postdoctoral Science Foundation (2018M642906 and 2019T120684)Hubei Provincial Natural Science Foundation of China (2019CFA065)。
文摘Structural and compositional design of core-shell structure is an effective strategy towards enhanced catalysis.Herein,amorphous MnO2 nanosheets and K+-intercalated layered MnO2 nanosheets are controllably assembled over Fe2O3 spindles,in which the MnO2 nanosheets are perpendicularly anchored to the surface of Fe2O3.Such a core shell structure contributes to a high specific surface area and abundant pore channels on the surface of catalysts.In addition,the existence of K+provides large numbers of basic sites and restrains the formation of unpleasant(Fe1-xMnx)3O4.Benefiting from the merits in structure and composition,CO adsorption is enhanced and remaining time of intermediates is prolonged on the surfaces of catalysts during the Fischer–Tropsch synthesis(FTS),facilitating to the formation of active iron carbides and C–C coupling reactions.Resultantly,the Fe2O3@K+-Mn O2 shows both a high CO conversion of 82.3%and a high C5+ selectivity of 73.1%.The present study provides structural and compositional rationales on design high-performance catalysts towards FTS.
基金Supported by National Natural Science Foundation of China (No. 30070043) , and "the Tenth five-year Plan"Scientific Research Foundation of Chinese PLA (No. 01Z075)
文摘Objective: To study the correlation of the methylation of the promoters of hMLH1 and hMSH2 with microsatellite instability (MSI) in the tissues of gastric carcinomas. Methods: A total of 68 sporadic cases of gastric carcinoma were studied. Ten specimens of normal gastric mucosa served as control. Methylation of hMLHl and hMSH2 was observed with methylation-specific PCR, and MSI analyzed with PCR-based techniques. Results: No methylation of hMLHl and hMSH2 was found in 10 specimens of normal gastric mucosa. Methylation of hMLHl was detected in 11 cases (16. 2%) of gastric cancers and MSI in at least one locus was found in 17 cases (25%) of the 68 with aid of 5 microsatellite markers, in which eight were MSI-H (≥2loci showed instability) nine MSI-L (only one locus showed instability), and fifty-one were MSS (no instability at any marker). The frequency of methylation was significantly high in MSI-H (87. 5%) than in MSI-L (11.1%) and MSS (5. 9%). CP<0. 01 - 0. 001) but there was no difference of methylation frequency between the cases with MSI-L and those with MSS. Conclusion: Methylation of hMLHl promoter is involved to the MSI pathway but not to the loss of heterozygosity (LOH) pathway in gastric carcinogenesis.
基金supported by National Key R&D Program of China(2017YFC0505904)the National Natural Science Foundation of China(31400525)+2 种基金the Natural Science Foundation of Shandong Province,China(ZR2014CQ028)Project funded by China Postdoctoral Science Foundation(2016M592235)the Postdoctoral Foundation of Shandong Agricultural University
文摘The 9-cis-epoxycarotenoid dioxygenase(NCED)gene is rate-limiting in abscisic acid(ABA) biosynthesis.In this study, an NCED gene, designated FvNCED3(KY008746), was cloned from velvet ash(Fraxinus velutina Torr.) with a RACE method. The full length c DNA of FvNCED3 encodes a 573-amino acid polypeptide.Sequencing analysis showed that the FvNCED3 protein was highly homologous to other NCED proteins. The expression patterns of FvNCED3 in different ash organs were analyzed by real-time PCR which revealed that FvNCED3 expression levels were highest in leaves and lowest in roots. The gene expression patterns of FvNCED3 under abiotic stress indicated that its expression increased under drought, salt and ABA stress and decreased due to high and low temperatures. There were no obvious changes under ultraviolet light. The 1094-bp upstream sequence 5' flank regulation region of the FvNCED3 gene was also cloned from ash using the Genome Walking method. To assess the activity of the FvNCED3 promoter, a p FvNCED3 p::GUS plant expression vector was constructed for tobacco transformation. GUS expression of the FvNCED3 GUS enzyme activity was detected in almost all transgenic tobacco tissues, especially in the young leaves,stigma, anther, ovule and ovary. After treating the transgenic tobacco with NaCl and placing it under drought stress, GUS staining of tobacco leaves increased compared with that under normal growth conditions. This result indicates that gene expression driven by the FvNCED3 promoter can be induced by salt and drought stress.
基金Foundation item:the National Outstanding Young Scientists Foundation of China(20625620)the National Key Basic Research Program of China(973 Program,2007CB216401)+1 种基金the National Natural Science Foundation of China(20590360)the Natural Science Foundation of Shanxi Province(2006021014).
文摘The effects of Manganese （Mn） incorporation on a precipitated iron-based Fischer-Tropsch synthesis （FTS） catalyst were investigated using N2 physical adsorption, air differential thermal analysis （DTA）, H2 temperature-programmed reduction （TPR）, and Mǒssbauer spectroscopy. The FTS performances of the catalysts were tested in a slurry phase reactor. The characterization results indicated that Mn increased the surface area of the catalyst, and improved the dispersion of （α-Fe2O3 and reduced its crystallite size as a result of the high dispersion effect of Mn and the Fe-Mn interaction. The Fe-Mn interaction also suppressed the reduction of （α-Fe2O3 to Fe3O4, stabilized the FeO phase, and （or） decreased the carburization degree of the catalysts in the H2 and syngas reduction processes. In addition, incorporated Mn decreased the initial catalyst activity, but improved the catalyst stability because Mn restrained the reoxidation of iron carbides to Fe3O4, and improved further carburization of the catalysts. Manganese suppressed the formation of CH4 and increased the selectivity to light olefins （C2-4^=）, but it had little effect on the selectivities to heavy （C5＋） hydrocarbons. All these results indicated that the strong Fe-Mn interaction suppressed the chemisorptive effect of the Mn as an electronic promoter, to some extent, in the precipitated iron-manganese catalyst system.
基金the Ministry of Higher Education Malaysia for providing financial support to this work via FRGS No:FRGS/1/2011/SG/UTP/02/13Universiti Teknologi PETRONAS
文摘A series of novel carbon nanofibers(CNFs)based Cu-ZrO2 catalysts were synthesized by deposition precipitation method.To investigate the influence of promoter,catalysts were loaded with 1,2,3 and 4 wt%ZnO and characterized by ICP-OES,HRTEM,BET,N2O chemisorption,TPR,XPS and CO2-TPD techniques.The results revealed that physicochemical properties of the catalysts were strongly influenced by incorporation of ZnO to the parent catalyst.Copper surface area(SCu)and dispersion(DCu)were slightly decreased by incorporation of ZnO promoter.Nevertheless,SCuand DCuwere remarkably decreased when ZnO content was exceeded beyond 3 wt%.The catalytic performance was evaluated by using autoclave slurry reactor at a pressure and temperature of 30 bar and 180℃,respectively.The promotion of CuZrO2/CNFs catalyst with 3 wt%of ZnO enhanced methanol synthesis rate from 32 to 45 g kg^-1 h^-1.Notably,with the ZnO promotion the selectivity to methanol was enhanced to 92%compared to 78%of the un-promoted Cu-ZrO2/CNFs catalyst at the expense of a lowered CO2 conversion.In addition,the catalytic activity of this novel catalyst system for CO2 hydrogenation to methanol was compared with the recent literature data.
文摘A 5＇ flanking region of the well-conserved Toll/interleukin-1 receptor domain （TIR）-encoding sequence was isolated from the genomic DNA ofMelampsora magnusiana Wagner resistant clones of hybrid triploid poplars [（Populus tomentosa × P. bolleana） × P. tomentosa]. Sequencing results and alignment analysis show that the obtained TIR-specific promoter （named as PtTIRp01） was 1,732 bp in length; moreover 3＇ region of the PtTIRp01 contains a responds to the 5＇ composition of TIR-NBS type gene PtDRG02, of 747 bp long 5＇ region of TIR-NBS type gene PtDRG02 and its 398 bp complete TIR-encoding sequence, which significantly corindicating that the obtained TIR-specific promoter region consists upstream region of promoter （985 bp）. It was found that the 5＇ region of TIR-NBS type gene PtDRG02 was characterized in the downstream region of the transcriptional start, named as 5＇-untranslated region （5＇ UTR）, consisting of one 93 bp 5＇-untranslation exon, one 213 bp intron and one 441 bp TIR-encoding open reading frame （ORF）. In addition, several putative cis-acting motifs were present in the obtained TIR-specific promoter of PtDRG02, including one TATA box, one GC-rich, one AT-rich, one P-box, one 3-AF1 binding site, two CAAT boxes, two GT-1 motifs, three typical W-boxes, four I-boxes, and one multi-cis-acting fragment （MCF）. The latter contains five types of regulatory elements （E4, G-box, ABRE motif, box 1 and HVA 1 s）, most of which were homologous to the cis-acting regulatory elements involved in the activation of defense genes in plants. Thus, it can be suggested that TIR-specific promoter might be a pathogen-inducible promoter and be necessary for the inducible expression of defense-related genes. Key words Toll/interleukin- 1 receptor domain, promoter, Cis-acting element, poplar
基金Natural Science Foundation of Hebei Province (B2019408018, E2020048004)the Fundamental Research Funds for the Universities in Hebei Province (JYQ201902, JYT201901)+4 种基金Program for the Top Young Talents of Higher Learning Institutions of Hebei Province (BJ2020047)College Students’ Innovation and Entrepreneurship Training Program Project Fund of Langfang Normal University (202010100001, S202010100011)National Natural Science Foundation of China (21773307)Hebei Higher Education Teaching Reform Research and Practice Project (2019GJJG357)Research Project of Langfang Teachers University (LSLB201701) for financial support。
文摘Carbon dioxide(CO_(2) ) capture and conversion is the key route for the mitigation of the greenhouse effect and utilization of carbon sources to obtain value-added products or fuels.Much attention is paid to the development of novel materials with high CO_(2) adsorption capacity and conversion rate.MXene is the graphene-like two-dimensional metal carbide/nitride/carbonitride owning favorable structure,morphology,high surface-bulk ratio,and physicochemical properties.Here,we review the CO_(2) capture,sensing,and conversion by MXene and MXene-based materials.Furthermore,the underlying mechanism involved the capture,sensing,and conversion of CO_(2) is summarized.This review would open a new horizon for CO_(2) valorization with high efficiency and promising widespread applications.
基金supported from the National Natural Science Foundation of China(Grant Nos.21972141,21991094,21991090)the“Transformational Technologies for Clean Energy and Demonstration”,Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21030100)。
文摘Hydrogenation of methyl acetate is a key step in ethanol synthesis from dimethyl ether carbonylation and Cu-based catalysts are widely studied.We report here that the hydrogenation activity of Cu/ZnO catalysts can be enhanced by the addition of MgO promoter.The evolution of crystal phases during coprecipitation and the physicochemical properties of calcined and reduced catalysts by X-ray diffraction(XRD),thermogravimetric(TG)-mass spectrometry(MS),Brunauer-Emmett-Teller(BET),transmission electron microscopy(TEM),N_(2)O titration,in situ CO-Fourier transform infrared spectroscopy(FTIR)and H_(2)-temperature programmed reduction(H_(2)-TPR)reveal that the promoter effect likely lies in the presence of Mg^(2+).A proper amount of Mg^(2+)mediates the precipitation process of Cu and Zn,leading to preferable formation of aurichalcite(Cu_(x)Zn_(1-x))5(CO_(3))_(2)(OH)_(6) crystal phase and a small amount of basic carbonates such as hydrozincite Zn_(5)(CO_(3))_(2)(OH)_(6) and malachite Cu_(2) CO_(3)(OH)_(2).The presence of aurichalcite strengthens the interaction between Cu and Zn species,and thus enhances the dispersity of CuO species and helps generation of Cu^(+)species on reduced catalysts.Furthermore,the performance of Cu/ZnO catalysts exhibits an optimal dependence on the Mg loading,i.e.,17.5%.However,too much Mg^(2+)in the precipitation liquid prohibits formation of aurichalcite but enhances formation of basic nitrates,leading to a dramatically reduced hydrogenation activity.These findings may find applications for optimization of other Cu-based catalysts in a wider range of hydrogenation reactions.
基金supported by the National Natural Science Foundation of China (No. 20776016 and 21006005)
文摘Rare-earth （La, Ce, Yb） promoted Ni/γ-Al2O3 catalysts were prepared by impregnation method. Activity and carbon formation resistance of the prepared catalysts were evaluated under various reaction conditions. Catalyst characterizations with TG, TPR and H2 chemisorption were carried out to investigate the promoting mechanism. Experimental results show that rare-earth promoters, especially Yb promoter, obviously improve the activity and carbon formation resistance of Ni/γ-Al2O3 catalyst, and Yb-Ni catalyst shows even higher performance than several commercial catalysts. According to the characterization results, Yb promoter enhances the interaction between the active metal and support, thus increasing the active metal＇s dispersion and improving its performance. Furthermore, the obvious difference in diesel conversion between Yb-Ni catalyst and others was shown in the temperature range of 450-550 °C, which would be the reason for its excellent carbon resistance.
基金supported by the National Basic Research Program of China (Project No. 2005CB221405)the National "863" Project of China (No.2006AA10Z425)
文摘A series of Ni/SBA-15 catalysts with 5wt% to 15wt% Ni content as well as a series of 12.5%Ni/Cu/SBA-15 catalysts with 1% to 10% copper content were prepared by the impregnation method. The catalytic performance for partial oxidation of methane was investigated in a continuous flow microreactor under atmospheric pressure. The textural and chemical properties of the catalysts were characterized by XRD, TEM, BET and Hz-TPR techniques. The results indicated that the catalysts modified with Cu promoter showed better performance than those without modification. For the 12.5%Ni/2.5%/Cu/SBA-15 catalyst, at 850 ℃ the conversion of CH4 reached 97.9% and the selectivity of CO and H2 reached 98.0% and 96.0%, respectively. In XRD patterns of the Ni/Cu/SBA-15 catalyst with 7.5 to 10% Cu contents there were CuO characteristic peaks beside NiO characteristic peaks. The mesoporous structure of SBA-15 was retained in all of the catalysts. TPR analysis of the catalysts revealed that a strong interaction between Ni, Cu promoter and SBA-15 support may be existed. This interaction enhanced significantly the redox properties of the catalysts resulting in the higher catalytic activity.
文摘In this study, Cr and Co promoted, as well as unpromoted vanadium phosphate （VPO） catalysts were synthesized by the reaction of V2O5 and o-H3PO4 in organic medium followed by calcination in n-butane/air environment at 673 K. The physico-chemical properties and the catalytic behavior were affected by the addition of Cr and Co dopants. H2-TPR was used to investigate the nature of oxidants in the unpromoted and promoted catalysts. The results showed that both the Cr and Co promoters remarkably lowered the temperature of the reduction peak associated with V^5＋. The amount of oxygen species originated from the active phase, V^4＋, removed was significantly increased for Co and Cr-promoted catalysts. Both Cr and Co dopants improve strongly the n-butane conversion without sacrificing the MA selectivity. A good correlation was observed between the amount of oxygen species removed from V^4＋ phase and the activity for n-butane oxidation to maleic anhydride. This suggested that V^4＋-O was the center for the activation of n-butane.
基金supported by the National Natural Science Foundation of China (Grants No. 20273021)the Key Project of Shanghai Science and Technology Committee (No. 05JC14070, 06DZ05025, 0552nm042, 08JC1408600)Scientific Research Foundation of the Education Department of Heilongjiang Province (No.11544005)
文摘At low temperature of 723 K, methane can be easily activated in the presence of ethylene in the feed, and converted to higher hydrocarbons （C2-C4） and aromatics （C6-C10）, through its reaction over rare metals modified Zn/HZSM-5 zeolite catalysts without undesirable carbon oxides formation. Methane can get 37.3% conversion over the above catalysts under low temperature, and the catalysts show a longer lifetime than usual metal supported HZSM-5 zeolite catalysts without adding any rare earth metals. The effects of methane activation over various rare earth metal promoted Zn/HZSM-5 catalysts on the products and influences of several reaction conditions such as temperature, catalyst lifetime and molar ratio of CH4/C2H4 have been discussed.
基金the National Basic Research Program ofChina (Project No. 2005CB221405)the National "863" Project ofChina (No. 2006AA10Z425)the Beijing Natural Science Foun-dation (Project No: 8062023)
文摘A series of Ni/SBA-15 catalysts with Ni contents ranging from 5 wt% to 15 wt%, as well as another series of 10%Ni/MgO/SBA-15 catalysts, in which the range of the MgO content was from 1 wt% to 7 wt%, were prepared, and their catalytic performances for the reaction of combined steam and carbon dioxide reforming of methane were investigated in a continuous flow microreactor. The structures of the catalysts were characterized using the XRD, H2-TPR and CO2-TPD techniques. The results indicated that the CO selectivity for this reaction was very close to 100%, and the H2/CO ratio of the product gas could be controlled by changing the H2O/CO2 molar ratio of the feed gas. The simultaneous and plentiful existing of steam and CO2 had a significant influence on the catalytic performance of the 10%Ni/SBA-15 catalyst without modification. After reacting at 850 °C for 120 h over this catalyst, the CH4 conversion dropped from 98% to 85%, and the CO2 conversion decreased from 86% to 53%. However, the 10%Ni/3%MgO/SBA-15 catalyst exhibited a much better catalytic performance, and after reacting for 620 h, the CO2 conversion over this catalyst dropped from 92% to around 77%, while the CH4 conversion was not decreased. Oxidation of the Ni0 species as well as carbon deposition during the reaction were the main reasons for the deactivation of the catalyst without modification. On the other hand, modification by the MgO promoter improved the dispersion of the Ni0 species, and enhanced the CO2 adsorption affinity which in turn depressed the occurring of carbon deposition, and thus retarded the deactivation process.
基金supported by the Doctoral Foundation (NO. 20050251006)Scholastic Foundation of Henan University of Science and Technology
文摘2%Fe-10%Co/SiO2 catalysts with different potassium or zirconium loadings were prepared by aqueous incipient wetness impregnation and tested for Fischer-Tropsch synthesis in a flow reactor, using H2/CO = 1.6 （molar ratio） in the feed, under the condition of an overall pressure of 1 MPa, GHSV of 600 h^-1 and temperature of 503 K. The zirconium and potassium promoters remarkably influenced hydrocarbon distribution of the products. CO conversion increased on the catalysts with the increase of zirconium loadings, which indicated that zirconium enhanced the activity of iron-cobalt catalysts. Low potassium loadings also enhanced the activity of the catalysts. However, high potassium loading made CO conversion on the catalysts decrease and weakened the secondary hydrogenations. The catalyst was characterized by BET, XRD and TPR. The catalyst characterization revealed that the Co3O4 phase was presented on the fresh catalyst, whereas the spinel phase of Fe-Co alloy and CoO existed on the used catalyst.
基金supported by the National Natural Science Foundation of China (NNSFC 21573232, 21576251, 21676269, 21878283)the Strategic Priority Research Program of Chinese Academy of Sciences Grant No. XDB17000000+2 种基金National Key Projects for Fundamental Research and Development of China (2016YFA0202801)The Youth Innovation Promotion Association CAS (2017223)Department of Science and Technology of Liaoning province under contract of 2015020086-101。
文摘Catalytic ethane dehydrogenation(EDH) to ethylene over Pt-based catalysts has received increasing interests in recent years as it is a potential alternative route to conventional steam cracking. However, the catalysts used in this reaction often suffer from rapid deactivation due to serious coke deposition and metal sintering. Herein, we reported the effects of Zn modification on the stability of Pt/Al2 O3 for EDH.The Zn-modified sample(PtZn2/Al2 O3) exhibits stable ethane conversion(20%) with over 95% ethylene selectivity. More importantly, it exhibits a significantly low deactivation rate of only 0.003 h-1 at 600 °C for70 h, which surpasses most of previously reported catalysts. Detailed characterizations including in situ FT-IR, ethylene adsorption microcalorimetry, and HAADF-STEM etc. reveal that Zn modifier reduces the number of Lewis acid sites on the catalyst surface. Moreover, it could modify Pt sites and preferentially cover the step sites, which decrease surface energy and retard the sintering of Pt particle, then prohibiting the further dehydrogenation of ethylene to ethylidyne. Consequently, the good stability is realized due to anti-sintering and the decrease of coke formation on the Pt Zn2/Al2 O3 catalyst.
