Influence of Addition of ZnO on Property of Fe_2O_3-K_2O System Catalyst for Ethylbenzene Dehydrogenation to Styrene

The incorporation of ZnO into Fe2O3-K2O system increases its activity, enhances its moisture stability and mechanical strength. The origin of the enhancement in activity and moisture stability is discussed in the light of experimental results obtained by BET, XRD, XPS. It was found that the addition of ZnO to Fe2O3-K2O system strengthens the interaction between Fe2O3 and K2O, reduces the formation temperature of KFe11O17 at least by 50 oC, and promotes the transformation of Fe3+ to Fe2+ further.

Theoretical and Experimental Study on Reaction Coupling: Dehydrogenation of Ethylbenzene in the Presence of Carbon Dioxide

Dehydrogenation of ethylbenzene （EB） to styrene （ST） in the presence of CO2, in which EB dehydrogenation is coupled with the reverse water-gas shift （RWGS）, was investigated extensively through both theoretical analysis and experimental characterization. The reaction coupling proved to be superior to the single dehydrogenation in several respects. Thermodynamic analysis suggests that equilibrium conversion of EB can be improved greatly by reaction coupling due to the simultaneous elimination of the hydrogen produced from dehydrogenation. Catalytic tests proved that iron and vanadium supported on activated carbon or Al2O3 with certain promoters are potential catalysts for this coupling process. The catalysts of iron and vanadium are different in the reaction mechanism, although ST yield is always associated with CO2 conversion over various catalysts. The two-step pathway plays an important role in the coupling process over Fe/Al2O3, while the one-step pathway dominates the reaction over V/Al2O3. Coke deposition and deep reduction of active components are the major causes of catalyst deactivation. CO2 can alleviate the catalyst deactivation effectively through preserving the active species at high valence in the coupling process, though it can not suppress the coke deposition.

THE PREPARATION CHEMISTRY OF V/MgO CATALYST FOR OXIDATIVE DEHYDROGENATION OF ETHYLBENZENE

The structures and catalytic performances of V_2O_5, Mg_3V_2O_8 and V/MgO catalysts have been correlated by means of XRD, FTIR, TPR and flow micro-reactor tests. The postulation about active site has been made. Based on it, better catalysts have been first prepared via grafting and modification with Sb which are better than that via impregnation.

Sn-decorated CeO_(2) with different morphologies for direct dehydrogenation of ethylbenzene

Three Sn-decorated ceria catalysts with various morphologies(rods,particles,and cubes)were prepared and applied to the direct dehydrogenation of ethylbenzene.Multi-technology characterizations,including X-ray photoelectro n spectroscopy(XPS),H_(2)-tempe rature programmed reduction(H_(2)-TPR),and Raman spectroscopy,prove that the oxygen vacancies are the active sites for ethylbenzene dehydrogenation,which can be regulated by engineering CeO_(2) morphology and enhanced via introducing metal Sn.Given the results of activity test,the catalytic activities for ethylbenzene dehydrogenation over different samples are closely dependent on the amount of oxygen vacancies.The reduced Sn-decorated CeO_(2) catalyst with nanoparticles morphology exhibits better dehydrogenation performance than the other two studied catalysts at 600℃.This work provides an effective approach to regulate the active oxygen vacancies and further enhance the dehydrogenation activities through engineering the surface morphology of the catalyst and introducing suitable additives.

An efficient nanodiamond-based monolithic foam catalyst prepared by a facile thermal impregnation strategy for direct dehydrogenation of ethylbenzene to styrene

Nanodiamond(ND)has long been recognized as an effective carbocatalyst for synthesizing styrene via direct dehydrogenation(DDH).However,the induced drastic pressure drop of its powder form limits its industrial application in heterogeneous catalytic process.In this work,we report a facile hexamethylenetetramine nitrate(HN)-assisted thermal impregnation(HNTI)strategy for fabricating a novel nanodiamondbased monolithic foam(ND/CNT-SiC-ms-HN)catalyst through a two-step approach:One is to soak the carbon nanotube-modified Si C foam(CNT-SiC)with the slurry composed of HN,KCl,Li Cl,and dispersed ND,and the other is to heat the slurry-soaked CNT-SiC(ND-HN-KCl-Li Cl/CNT-SiC)in N_(2) atmosphere at750℃.The as-synthesized ND/CNT-SiC-ms-HN monolithic foam features the enriched surface kenotic C=O by promoted ND dispersion and O-doping,abundant stuctural defects,and improved nucleophilicity by N-doping,originating from the promoted ND dispersion by thermal impregnation(TI)in KCl-LiCl molten salt(MS)and the presence of HN in the annealing process.As a result,the ND/CNT-Si C-ms-HN monolithic foam catalyst by HNTI strategy exhibits 1.5 folds higher steady-state styrene rate(5.49 mmol g^(-1)h^(-1))associated with 98.4%of styrene selectivity compared to the ND-based monolithic foam catalyst(ND/CNT-SiC).Moreover,the ND/CNT-Si C-ms-HN monolithic foam shows excellent long-term stability for the direct dehydrogenation of ethylbenzene to styrene.This work also comes up with a novel way of preparing other highly-dispersed nanocarbons-based monolithic foam catalysts with promising catalytic performance for diverse transformations.

Fully-exposed Pt clusters stabilized on Sn-decorated nanodiamond/graphene hybrid support for efficient ethylbenzene direct dehydrogenation

The pursuit of energy conservation and environmental protection has always been a hot topic in the catalytic fields,which is inseparable from the rational designing of efficient catalysts and an in-depth understanding of the catalytic reaction mechanism.In this work,fully-exposed Pt clusters were fabricated on the atomically dispersed Sn decorated nanodiamond/graphene(Sn-ND@G)hybrid support and employed for direct dehydrogenation(DDH)of ethylbenzene(EB)to styrene(ST).The detailed structural characterizations revealed the fully-exposed Pt clusters were stabilized on Sn-ND@G,assisted by the spatial separation of atomically dispersed Sn species.The as-prepared Pt/Sn-ND@G catalyst showed enhanced ST yield(136.2 molEB·molpt-1·h-1 EB conversion rate and 99.7%ST selectivity)and robust long-term stability at 500℃for the EB DDH reaction,compared with the traditional ND@G supported Pt nanoparticle catalyst(Pt/ND@G).The ST prefers to desorb from the fully-exposed Pt clusters,resulting in the enhanced DDH catalytic performance of the Pt/Sn-ND@G catalyst.The present work paves a new way for designing highly dispersed and stable supported metal catalysts for DDH reactions.

Characterization and Dehydrogenation Activity of SBA-15 and HMS Supported Chromia Catalysts

SBA-15 and HMS supported chromia catalysts were prepared and characterized. Chromia is highly dispersed on the mesoporous supports when its loading is 7 wt%. The supported catalysts display high activity, selectivity and stability for dehydrogenation of ethylbenzene and propane. ESR measurement of the catalysts before and after reaction shows that the active species for dehydrogenation reaction might be Cr3+ species on the catalyst surface, and the activity of the catalyst is probably correlated with the dispersion of Cr3+ species.