Catalyst In Fixed-bed Reactor Research Articles

Regulating light olefins or aromatics production in ex-situ catalytic pyrolysis of biomass by engineering the structure of tin modified ZSM-5 catalyst

Valorization of biomass to olefin or aromatics harbours tremendous practical value due to growing concerns about sustainable production of chemicals. Herein, the olefin or aromatics yields of ex-situ catalytic pyrolysis of pine can be regulated by impregnating Sn on hollow-structured ZSM-5 (M-ZSM-5) and microporous ZSM-5 catalysts in fixed-bed reactor, respectively. Results showed that Sn/ZSM-5 catalyst simultaneously increased medium acidic sites and maintained strong acidic sites, which obtained the maximum carbon yield of aromatics (33.77%) due to enhanced cracking and deoxygenation reactions. In addition, Sn boosted alkylation between olefin and aromatics, generating more alkylbenzene. In contrast, Sn/M-ZSM-5 catalyst produced the highest olefins carbon yield (12.39%) because the reduction of strong acidic sites and microporous volume inhibited the olefin aromatization. Moreover, olefins were easier to desorb from Sn/M-ZSM-5 due to the enhanced mass transfer ability, which weakened the alkylation reactions. The synergistic effect harbours great significance to manipulate the distribution of products.

Modelling and optimization of Fischer–Tropsch products through iron catalyst in fixed-bed reactor

The most important issue for alternative renewable energy source instead of fossil fuels is environmental concern. Human energy supply from carbon waste has an important role in environmental health. Fischer–Tropsch synthesis is a reaction whereby carbon waste such as woods, foodstuffs, sewage, and any material that contains carbon in their structure, produces all oil derivatives including gasoline, diesel, etc. In this paper, the products model and the effective parameters of the model and also, the interaction between the parameters were investigated. PH2 and T∗PH2 are effective parameters and interaction in the model, respectively. Finally, the optimization of products was discussed. The best operating conditions for minimizing CO2 and CH4 and maximizing C2H4 and C2H6 were investigated. This method can be suitable for environmental purposes.

Acidity-regulation for enhancing the stability of Ni/HZSM-5 catalyst for valeric biofuel production

Valerate esters as a new class of cellulosic transportation fuels showed great industrial prospect. Here we developed a non-noble Ni/HZSM-5 bifunctional catalyst with excellent stability for the cascade transformation of levulinic acid to valerate esters. The acidity-regulation of Ni/HZSM-5 catalyst by potassium addition decreased the strong acidity, meanwhile tuned the proportion of Brönsted acidity/Lewis acidity. Coke analysis indicated that acidity-regulation by potassium addition changed the heavier coke component (alkylated poly-aromatics) to the lighter one (alkylated mono-aromatics), thus effectively prolonged the lifetime of Ni/HZSM-5 catalyst in fixed-bed reactor. The relationship of the nature of coke deposits and the acidity-regulation of catalysts could contribute to intensively understand the catalyst deactivation and the choice of stable catalyst for upgrading of biomass and its platform molecules.

Selective hydrogenolysis of raw glycerol to 1,2-propanediol over Cu-ZnO catalysts in fixed-bed reactor.

The catalytic properties of Cu-ZnO catalysts for glycerol hydrogenolysis to 1,2-propanediol (1,2-PDO) were tested in a fixed-bed reactor at 250 °C and 2.0 MPa H2. The relation between composition, surface properties, and catalytic performance of glycerol hydrogenation of Cu-ZnO catalysts was studied using nitrogen adsorption (BET methods), XRD, H2 temperature-programmed reduction, and N2O chemisorptions. It was found that there was a close link between the surface CuO amount of Cu-ZnO catalyst and the reactivity for glycerol hydrogenation. The Cu-ZnO catalyst (Cu/Zn = 1.86) which had the highest surface Cu amount showed the best catalytic activity for glycerol hydrogenolysis. Furthermore, Cu-ZnO catalyst presented good stability and remarkable catalytic activity for glycerol hydrogenolysis to 1,2-PDO using raw glycerol derived from the fat saponification as feedstock.

Separating the initial growth rate from the rate of deactivation in the growth kinetics of multi-walled carbon nanotubes from ethene over a cobalt-based bulk catalyst in a fixed-bed reactor

The initial growth kinetics of multi-walled carbon nanotubes (CNTs) was investigated using a highly active Co-based mixed-oxide catalyst in a tubular fixed-bed reactor under plug-flow conditions with ethene as carbon source. The growth temperature and the ethene concentration were systematically varied in the range from 758 to 923K and from 5 to 45vol.%, respectively. The carbon mass accumulation was derived from the ethene conversion and analyzed by a kinetic model, from which the initial CNT growth rate and the mean lifetime of the active sites were derived permitting the prediction of the maximum theoretical CNT yield. With increasing growth temperatures up to 923K both the initial growth rate and the mean lifetime of active sites increased strongly with a significantly prolonged lifetime above 848K. The initial growth rate was slow at lower ethene concentrations, but the mean life time was very high. Increasing the ethene concentration up to 45vol.% led to a much higher initial growth rate, but shortened the mean lifetime strongly. Due to the fast deactivation at high ethene concentrations, the predicted maximum yield decreased considerably approaching the yield obtained after 5min of time on stream.

Production of Syngas by Combination of CO2 Reforming and Partial Oxidation of CH4 over Ni/Al2O3 Catalysts in Fixed-bed Reactor

Ni/Al2O3 catalysts were synthesized by sol-gel method with various nickel loadings. Chemical and physical properties of the catalysts were characterized by XRD and TPR techniques. X-ray diffraction patterns showed no peaks due to NiO species. Temperature-programmed reduction (TPR) indicated that the nickel species mainly presented in NiAl2O4 phase. The effect of nickel loading on the catalytic activity of Ni/Al2O3 catalysts, selectivity of products, yield of hydrogen production and H2/CO ratio was investigated in the combination of dry reforming and partial oxidation of methane (DRPOM) reaction. The results indicated that these parameters are greatly dependent on the amount of nickel loading. The results also revealed that the catalyst with 20 percent nickel loading had the highest activity for syngas production after 270 min reaction on stream. The SEM images of spent catalysts showed the formation of filamentous carbon on the 20Ni/Al and 30Ni/Al catalysts.