Characterization and Activity of Cr, Cu and Ga Modified ZSM-5 for Direct Conversion of Methane to Liquid Hydrocarbons

Direct conversion of methane using a metal-loaded ZSM-5 zeolite prepared viaacidic ion exchange was investigated to elucidate the roles of metal and acidity in the formation ofliquid hydrocarbons. ZSM-5 (SiO_2/Al_2O_3=30) was loaded with different metals (Cr, Cu and Ga)according to the acidic ion-exchange method to produce metal-loaded ZSM-5 zeolite catalysts. XRD,NMR, FT-IR and N_2 adsorption analyses indicated that Cr and Ga species managed to occupy thealuminum positions in the ZSM-5 framework. In addition, Cr species were deposited in the pores ofthe structure. However, Cu oxides were deposited on the surface and in the mesopores of the ZSM-5zeolite. An acidity study using TPD-NH_3, FT-IR, and IR-pyridine analyses revealed that the totalnumber of acid sites and the strengths of the Broensted and Lewis acid sites were significantlydifferent after the acidic ion exchange treatment. Cu loaded HZSM-5 is a potential catalyst fordirect conversion of methane to liquid hydrocarbons. The successful production of gasoline via thedirect conversion of methane depends on the amount of aluminum in the zeolite framework and thestrength of the Broensted acid sites.

Methane to Liquid Hydrocarbons over Tungsten-ZSM-5 and Tungsten Loaded Cu/ZSM-5 Catalysts

Metal containing ZSM-5 can produce higher hydrocarbons in methane oxidation. Many researchers have studied the applicability of HZSM-5 and modify ZSM-5 for methane conversion to liquid hydrocarbons, but their research results still lead to low conversion, low selectivity and low heat resistance. The modified HZSM-5, by loading with tungsten （W）, could enhance its heat resistant performance, and the high reaction temperature （800 ℃） did not lead to a loss of the W component by sublimation. The loading of HZSM-5 with tungsten and copper （Cu） resulted in an increment in the methane conversion as well as CO2 and C5＋ selectivities. In contrast, CO, C2-3 and H2O selectivities were reduced. The process of converting methane to liquid hydrocarbons （C5＋） was dependent on the metal surface area and the acidity of the zeolite. High methane conversion and C5＋ selectivity, and low H20 selectivity are obtained over W/3.0Cu/HZSM.

Dual-Bed Catalytic System for Direct Conversion of Methane to Liquid Hydrocarbons

A dual-bed catalytic system is proposed for the direct conversion of methane to liquid hydrocarbons. In this system, methane is converted in the first stage to oxidative coupling of methane （OCM） products by selective catalytic oxidation with oxygen over La-supported MgO catalyst. The second bed, comprising of the HZSM-5 zeolite catalyst, is used for the oligomerization of OCM light hydrocarbon products to liquid hydrocarbons. The effects of temperature （650-800 ℃）, methane to oxygen ratio （4-10）, and SIO2/Al2O3 ratio of the HZSM-5 zeolite catalyst on the process are studied. At higher reaction temperatures, there is considerable dealumination of HZSM-5, and thus its catalytic performance is reduced. The acidity of HZSM-5 in the second bed is responsible for the oligomerization reaction that leads to the formation of liquid hydrocarbons. The activities of the oligomerization sites were unequivocally affected by the SiO2/Al2O3 ratio. The relation between the acidity and the activity of HZSM-5 is studied by means of TPD-NH3 techniques. The rise in oxygen concentration is not beneficial for the C5＋ selectivity, where the combustion reaction of intermediate hydrocarbon products that leads to the formation of carbon oxide （CO＋CO2） products is more dominant than the oligomerization reaction. The dual-bed catalytic system is highly potential for directly converting methane to liquid fuels.

Optimization of methane conversion to liquid fuels over W-Cu/ZSM-5 catalysts by response surface methodology

The conversion of methane to liquid fuels is still in the development process. The modified HZSM-5 by loading with Tungsten （W） enhanced its heat resistant performance, and the high reaction temperature （800℃） did not lead to the loss of W component by sublimation. The loading of ZSM-5 with Tungsten and Copper （Cu） resulted in an increment in the methane conversion, CO2, and C5＋ selectivities. The high methane conversion and C5＋ selectivity, and low H2O selectivity are obtained by using W/3.0Cu/ZSM-5. The optimization of methane conversion over 3.0 W/3.0Cu/ZSM-5 under different temperature and oxygen concentration using response surface methodology （RSM） are studied. The optimum point for methane conversion is 19% when temperature is 753 ℃, and oxygen concentration is 12%. The highest C5＋ selectivity is 27% when temperature is 751 ℃. and oxwen concentration is 11%.

Review on the Relationship Between Liquid Aerospace Fuel Composition and Their Physicochemical Properties

The development of advanced air transportation has raised new demands for high-performance liquid hydrocarbon fuels.However,the measurement of fuel properties is time-consuming,cost-intensive,and limited to the operating conditions.The physicochemical properties of aerospace fuels are directly infl uenced by chemical composition.Thus,a thorough investigation should be conducted on the inherent relationship between fuel properties and composition for the design and synthesis of high-grade fuels and the prediction of fuel properties in the future.This work summarized the eff ects of fuel composition and hydrocarbon molecular structure on the fuel physicochemical properties,including density,net heat of combustion(NHOC),low-temperature fl uidity(viscosity and freezing point),fl ash point,and thermal-oxidative stability.Several correlations and predictions of fuel properties from chemical composition were reviewed.Additionally,we correlated the fuel properties with hydrogen/carbon molar ratios(n H/C)and molecular weight(M).The results from the least-square method implicate that the coupling of H/C molar ratio and M is suitable for the estimation of density,NHOC,viscosity and eff ectiveness for the design,manufacture,and evaluation of aviation hydrocarbon fuels.

Efficient selective activation of sorbitol C–O bonds over C–C bonds on CoGa(221)generated by lattice-induction strategy

Sorbitol is a primary platform compound in the conversion of cellulose.The conversion of sorbitol to C_(6) hydrocarbons requires a complete cleavage of C–O bonds and meanwhile the inhibition of C–C cleavage.Here,we demonstrated an efficient selective cleavage of C–O over C–C bond on the(221)facet of supported CoGa.A selectivity of 94%to C_(6) hydrocarbon with conversion of 97%has been achieved.The selective C–O cleavage was demonstrated by tuning the exposed facet as(221)or(110).The supported CoGa was prepared simply by reduction of Co and Ga-containing layered double hydroxides(CoZnGaAl-LDHs),the exposed facets of CoGa crystallites were controlled by tailoring the temperature-programmed rate in the reduction.By reducing CoZnGaAl-LDHs,CoGa(221)was exposed with a temperature-programmed rate of 5℃/min under the induction of ZnO lattice,while CoGa(110)was exposed with a rate of 10℃/min.

Selective production of guaiacol from black liquor:Effect of solvents

Lignin is generated as a waste biomass from pulp and paper industry.The majority of kraft lignin is currently combusted as a low-grade energy source.Lignin valorization has been considered a feasible option to sustainable production of chemicals and liquid fuels in the long run.This study reports a novel thermolysis process that selectively converts black liquor lignin into guaiacol and its derivatives in highboiling-point hydrocarbon solvents:n-hexadecane(n-H)and 1-methyl naphthalene(1-MN).The operating pressure for lignin thermolysis in n-H and 1-MN is much lower than those in lignin liquefaction with low-boiling-point solvents,such as water,methanol,and ethanol.1-MN performed better than n-H in terms of lignin conversion and liquid yield.The liquid products were 56 wt%and 24 wt%for 1-MN and n-H as solvent respectively.Reaction temperature and reaction time rotating were investigated.Low temperature and short reaction time are favorable for generating Guaiacol.Compared to 1-MN as solvent,n-H promotes the production of guaiacol.The reaction mechanisms of lignin depolymerization to chemicals in different solvents were proposed.Solvent chemical properties and H abstraction processes from solvents play a key role in the selectivity of guaiacol.