Hydrocracking of Low-Temperature Coal Tar over CoMo Catalysts Supported on ZrO2-Al2O3 Composite Oxides

A series of CoMo/ZrO2-Al2O3 catalysts with different contents of ZrO2 were prepared and characterized through XRD,XPS,NH3-TPD,H2-TPR,HR-TEM,and N2 adsorption-desorption technologies.The performance of the catalysts for low-temperature coal tar(LTCT)hydrocracking reaction was investigated.The interaction between active metals and Al2O3 was weakened with the introduction of ZrO2,which increased the MoS2 content and the stack layer number of MoS2 slabs to further promote the catalytic performance.At the same time,the amount of acid sites increased with an increasing ZrO2 content.When the ZrO2 content reached 32%,the pore volume of the catalyst decreased significantly.This phenomenon reduced the content of MoS2 and the stack layer number of MoS2 slabs,which were not conducive to improving the catalytic performance.The catalyst containing 24%of ZrO2 exhibited the best catalytic performance for hydrocracking reaction,with the residue conversion and the total yield of gasoline and diesel fractions reaching 60.64%and 66.54%,respectively,which could fulfill the requirements for hydrocracking LTCT.

The dynamic change of pore structure for low-rank coal under refined upgrading pretreatment temperatures

Pore structure characteristics are significant factor in the evaluation of the physical characteristics of low-rank coal.In this study,three low-rank coal samples were collected from the Xishanyao Formation,Santanghu Basin,and low-temperature liquid-nitrogen adsorption(LP-N2A)measurements were taken under various pretreatment temperatures.Owing to the continuous loss of water and volatile matter in low-rank coal,the total pore volume assumes a three-step profile with knee temperatures of 150°C and 240°C.However,the ash in the coal can protect the coal skeleton.Pore collapse mainly occurs for mesopores with aperture smaller than 20 nm.Mesopores with apertures smaller than 5 nm exhibit a continuous decrease in pore volume,whereas the pore volume of mesopores with apertures ranging from 5 to 10 nm increases at lower pretreatment temperatures(<150°C)followed by a faint decrease.As for mesopores with apertures larger than 10 nm,the pore volume increases significantly when the pretreatment temperature reaches 300°C.The pore structure of low-rank coal features a significant heating effect,the pretreatment temperature should not exceed 150°C when the LP-N2A is used to evaluate the pore structure of low-rank coal to effectively evaluate the reservoir characteristics of low-rank coal.

Modification mechanism of caking and coking properties of Shenmu subbituminous coal by low-temperature rapid pyrolysis treatment

Shenmu(SM)subbituminous coal without caking property was treated by low-temperature rapid pyrolysis(LTRP)to modify its caking and coking properties.The treated samples were characterized by Fourier transform infrared spectrometry,vitrinite reflectance,and X-ray diffraction to determine the modification mechanism.Moreover,caking index(G)and coking indices(mechanical strength,coke reactivity,and coke strength after reaction)were employed to evaluate caking and coking properties,respectively.The results showed that SM coal was gradually upgraded with increasing processing temperature.Furthermore,the G values for the treated samples were significantly higher than that for SM coal,and G reached the maximum value at 450℃,implying the modification of caking property and the existence of an optimum temperature(450℃).Additionally,laboratory coking determinations showed that LTRP increased the mechanical strength of coke and coke strength after reaction and decreased coke reactivity when the treated coals were used in the coal blends instead of raw SM coal.Overall,LTRP treatment is effective to improve the caking and coking properties of SM coal.A mechanism was proposed for the modification.Suitable upgrading degree with suitable molecular masses and some releasable hydrogen-rich donor species present within the coal,which dominate the development of caking property,is important.

Directional preparation of naphthalene oil-rich tar from Beisu low-rank coal by low-temperature catalytic pyrolysis

Low-rank coal(LRC)can be converted to high value-added naphthalene and its alkylated derivatives through low-temperature catalytic pyrolysis.In this paper,the catalytic pyrolysis of Beisu LRC in a fixed-bed at low temperature was investigated.And the catalytic effects of HZSM-5,low-temperature carbocoal(LtC),and LtC-HZSM-5 on the content and yield of naphthalene oil were examined.The results showed that the generation of naphthalene oil in low-temperature LRC pyrolysis(LT-LP)process could be improved when LtC(prepared at 550℃)or HZSM-5 was individually used as a catalyst.Compared with sole pyrolysis of raw LRC,the addition of the LtC-HZSM-5 catalyst increased the content of naphthalene oil from 11.19 wt.%to 31.49 wt%.And the yield of naphthalene oil was increased from 1.07 wt%to 5.31 wt%.The reactions of micromolecular hydrogen-containing radicals(⋅MHCR)were optimized by LtC.⋅MHCR could be captured in relatively low-temperature region(200-400℃)and released at high temperature by LtC.The generation of phenolics was inhibited by HZSM-5.As a result,the naphthalene oil-rich tar was obtained through low-temperature LtC-HZSM-5 catalytic pyrolysis of Beisu LRC.