Synthesis Strategies and Applications for Pitch-Based Anode: From Industrial By-Products to Power Sources.

It is significant for saving energy to manufacture superb-property batteries. Carbon is one of the most competitive anode materials in batteries, but it is hard for commercial graphite anodes to meet the increasingly higher energy-storage requirements. Moreover, the price of other better-performing carbon materials (such as graphene) is much higher than graphite, which is not conducive to massive production. Pitch, the cheap by-product in the petroleum and coal industries, has high carbon content and yield, making it possible for commercialization. Developing pitch-based anodes can not only lower raw material costs but also realize the pitch's high value-added utilization. We comprehensively reviewed the latest synthesis strategies of pitch-derived materials and then introduced their application and research progress in lithium, sodium, and potassium ion batteries (LIBs, SIBs, and PIBs). Finally, we summarize and suggest the pitch's development trend for anodes and in other fields.

Physical and Chemical Properties of Coal Gasification Fine Slag and Its Carbon Products by Hydrophobic-Hydrophilic Separation.

Coal gasification fine slag is a kind of solid waste with low resource utilization rate. The complex embedding of residual carbon and inorganic minerals (ash materials) is the main reason restricting the efficient resource separation and utilization of residual carbon or ash materials. Hydrophobic-hydrophilic separation (HHS) is a separation technology in which mineral particles with different surface hydrophobicity values are enriched in the water phase and oil phase under the action of mechanical stirring. The water on the surface of hydrophobic particles is replaced by the oil phase to form flocs, which are enriched in the hydrophobic liquid phase, while hydrophilic particles are dispersed into the aqueous phase. In this study, the HHS process was used to separate the carbon/ash from the fine gasification slag produced by a Shenning gasifier, Texaco gasifier, and GSP gasifier of Ningxia Coal Industry Co., Ltd. The physicochemical properties of the original sample and the residual carbon products obtained by hydrophobic-hydrophilic separation were analyzed. The results show that HHS can separate the carbon/ash in the three kinds of fine slag to varying degrees. The carbon element is enriched into the hydrophobic phase to form the concentrates, while the silicon element, oxygen element, and metal element enter the tailings. The spherical ash with different particle sizes distributed on the surface of residual carbon and the gap of the matrix is basically removed, while the ash in the carbon-ash melt is difficult to remove. The ash contents of the concentrate and tailings of fine slag of the Shenning gasifier are 22.58 and 96.28%, respectively, which reach the best ash index compared with that of the other two gasifiers. From the change of mineral surface properties after HHS, the distribution of oxygen-containing groups, benzene rings, Si-O, and clay minerals or carbonate minerals in the three kinds of fine slag residual carbon products is basically similar. Compared with the other two gasifier products, the GSP gasifier concentrate has a larger specific surface area and less ash material, more amorphous carbon structures (less graphitic), and more active sites, resulting in a stronger combustion activity.

Carbon precursors in coal tar: Extraction and preparation of carbon materials.

Coke resources are abundantly available worldwide and are a large by-product of tar production. Moreover, their utilization presents a series of environmental pollution problems. Common technologies for coal tar production applications urgently need to be upgraded because coal tar is listed as a national hazardous waste. This review associates coal tar development with deep processing technology for extracting environmentally beneficial compounds from coal tar, which have never been reported. Recent studies on the innovative approaches for extracting phenols and nitrogen-containing compounds from coal tar have been addressed, as well as a preparation method of carbon materials with high catalytic activity and a well-ordered structure by confined polymerization. Tremendous demand for further research and exploration of selectively extracted compounds from coal tar implies a new opportunity for polymerizing the resin and a great challenge for the current technology implemented for valorizing coal tar into ordered carbon materials. Consequently, more concerted efforts should be implemented to achieve a wide range of polymer resin applications and improve the quality of carbon precursors extracted from the coal tar, thus increasing the economic benefit and scientific value of coal tar.

Catalytic Upgrading of Coal Pyrolysis Volatiles by Porous Carbon Materials Derived from the Blend of Biochar and Coal.

A suite of carbon materials is prepared from biochar and coal at three different blending ratios with 10, 20, and 30% biochar by mass. These carbon materials are activated by steam to obtain porous structures. The effect of the inactivated and activated carbon materials on the cracking of coal pyrolysis volatiles is evaluated. The results indicate that the inactivated carbon materials are beneficial to improve the yield of light oil with a boiling point below 170 °C. The steam-activated carbon materials are more conducive to cracking tar pitch than the inactivated carbon materials due to the increased defects in carbon structure. However, it is also easy to form more coke deposits. More components rich in hydrogen are cracked to generate radicals that could combine with the phenols' precursor over carbon materials, and the content of phenols in tar is increased. The carbon materials prepared from biochar and coal using this method show distinct advantages as filter media in the granular bed duster. It can improve the quality of tar along with reducing the dust content in tar.

Effect of hydrogen-rich gas from char gasification on rapid pyrolysis products of low rank coal in a downer pyrolyzer.

For guiding a novel integrated process of low-rank coal pyrolysis and gasification with char gasification gas as a heat carrier, this study investigated the effect of simulated coal gas from char gasification (SCGG) on rapid pyrolysis products of low rank coal from 550 to 700 °C in a downer pyrolyzer. Results indicated that the component of SCGG directly affected the distribution and composition of pyrolysis products. Compared with N2, SCGG facilitated the formation of tar below 600 °C. H2 in SCGG and that from water gas shift reaction (WGS: CO + H2O → CO2 + H2) increased the tar yield by reacting with solid-phase free radicals in coal and inhibiting the secondary reaction of gas-phase volatile radicals. Also, CO2 in SCGG raised the tar yield due to its promotion to coal cracking. When the pyrolysis temperature exceeded 600 °C, the reforming reactions of nascent tar with steam occurred, resulting in a reduced tar yield. SCGG could distinctly reduce the coke yield (coke-S) and pitch content in tar due to the inhibiting effect of H2 from SCGG and WGS on the polycondensation reactions of volatile radicals and reforming reactions of nascent tar. The chemical composition analysis of tar by GC × GC-MS demonstrated that compared with under N2, the contents of phenols, oxygenated compounds, and heterocyclic compounds in tar under SCGG were decreased while the content of aromatics was the opposite mainly due to hydrogenation and reforming reactions of nascent tar. Also, the H/C and O/C ratios of char under the action of SCGG were higher than those under N2 at the same temperature.

Effect of impregnation sequence of Pd/Ce/γ-Al2O3 sorbents on Hg0 removal from coal derived fuel gas.

This study attempted to investigate the effect of impregnation sequence of the Pd/Ce/γ-Al2O3 sorbents on Hg0 removal. To this end, five kinds of sorbents were prepared and tested in simulated coal derived fuel gas (N2-H2-CO-H2S-Hg), including Pd/γ-Al2O3, Ce/γ-Al2O3 and three kinds of Pd-based sorbents with Ce impregnation on γ-Al2O3 substrate. The tests were conducted at 250 and 300 °C respectively. According to the results, bimetallic Ce-Pd/γ-Al2O3 sorbent prepared by simultaneously impregnating Pd and Ce showed much higher and more stable removal efficiency of Hg0 than the other three kinds of sorbents. The Hg0 removal efficiency of Ce-Pd/γ-Al2O3 sorbent reached above 98% within 480 min at 250 °C and 91% within 200 min at 300 °C. Characterization results indicated that the sorbent Ce-Pd/γ-Al2O3 prepared by the co-impregnation method had bigger specific surface area (216.6 m2/g) than the other three kinds of Pd-based sorbents. The content Pd and Ce on the sorbent Ce-Pd/γ-Al2O3 surface is 0.21% and 0.61%, which proved higher than that of the other three kinds of Pd-based sorbents, and observation from STEM-XEDS maps showed it demonstrated the highest dispersion. It is found that Ce is likely to promote the dispersion of Pd on the support surface during the preparation of the sorbent under the co-impregnation method. Meanwhile, Ce enhanced the H2S resistance of the sorbent. Thereby, Ce-Pd/γ-Al2O3 sorbent is found to have the optimal performance of mercury removal. In this study, the Hg0 removal mechanism of the Pd/Ce/γ-Al2O3 sorbents in the simulated coal derived fuel gas was also elaborated.

Effect of lignite as support precursor on deep desulfurization performance of semicoke supported zinc oxide sorbent in hot coal gas.

In this study, four different semicoke supported zinc oxide sorbents were prepared by combining high-pressure impregnation and heat treatment using four different lignites (Zhaotong, Xiaolongtan, Huolinhe, and Shengli districts) as precursors of supports and zinc nitrate as precursor of the active component. Their desulfurization performances were studied in a fixed-bed reactor at 400 °C in simulated coal gas. The physico-chemical properties of raw lignites were investigated using chemical titration, nitrogen adsorption and thermogravimetry (TG). The physico-chemical structures of sorbents were characterized by atomic absorption spectrometry (AAS), X-ray diffraction analysis (XRD), nitrogen adsorption, and scanning electron microscopy (SEM). The results indicate that the lignite as support precursor plays a critical role in the desulfurization performance of the sorbent. It affects the desulfurization activity of the prepared sorbent by influencing the loading content and utilization rate of the active component of the sorbent. The sorbent HPZn/C(Z) prepared using Zhaotong lignite presents the best desulfurization performance owing to its higher content and utilization rate of the active component, with a 13.74 h breakthrough time with the breakthrough sulfur capacity of 3.69 g sulfur/100 g sorbent. It is found that the loading content of the active component depends on the pore structure of the raw lignite, how its pore structure changes in high-pressure impregnation process and the content of oxygen-containing functional groups on its surface. The utilization rate of the active component is associated with the pore structure properties of the sorbent formed during heat treatment.

Regeneration of the Waste Selective Catalytic Reduction Denitrification Catalyst by Nitric Acid Washing.

In this study, the waste V2O5-WO3/TiO2 denitrification catalysts from the coal-fired power plant were washed with water or nitric acid, followed by impregnating different contents of V2O5. The effects of the HNO3 concentration and the additional amount of vanadium on the low-temperature selective catalytic reduction denitrification activity were investigated under the condition of high concentration of SO2 and H2O. The catalysts were characterized by inductively coupled plasma optical emission spectrometry, X-ray powder diffraction , N2 adsorption/desorption, H2-temperature-programmed reduction, NH3-temperature-programmed desorption , Fourier transform infrared spectroscopy , and Raman spectroscopy. The evaluation results revealed that optimum activity was achieved by using 0.8 mol/L HNO3 solution and loading 1.60 wt % V2O5 to make the total V2O5 reach 2.3 wt %. The characterization results showed that nitric washing can remove most of the ammonium salts deposited on the surface of the waste catalyst and produce crystalline WO3, which can effectively inhibit the agglomeration of vanadium species in the process of impregnation. Furthermore, it can also increase the amount of oligomeric VO x , which can improve the denitration activity.

Evolution of Pore Structure during Pressurized Dewatering and Effects on Moisture Readsorption of Lignite.

In this study, pressurized method was used to dry lignite at moderate temperature to change its pore structure but preserve its oxygen-containing functional groups. The effects of drying conditions (time, pressure, and temperature) on equilibrium moisture content (EMC) and pore structure of dewatered coals were investigated, and the correlations between pore structure and EMC were also evaluated. The pore structure parameters of raw coal and dewatered coals were measured by nitrogen adsorption experiments. The EMC of dewatered coals was obtained by gravimetric method. The results indicated that the porous structure of dewatered coal was jointly affected by three factors (drying time, pressure, and temperature) in the initial pressurized drying stage. The drying pressure exhibited obvious effect in the initial stage of drying lignite. Destruction of pores under pressure was prevented due to the water present in these pores. To further improve the pore structures of dehydrated coals obtained by high-pressure treatment, the temperature was increased to above 140 °C under 3 MPa; thus, a large number of macropores were evolved into mesopores. Furthermore, the experiments on water reabsorption by dewatered coals indicated that the EMC (0.15-0.18) of dehydrated coal was the lowest when the pressure was 3 MPa, temperature was 140-160 °C, and the time required was 30 min. The moisture readsorption contents of dehydrated coals were found to be positively correlated with its pore volume at high relative humidity. When the relative humidity was below 20%, they were related to specific surface areas or oxygen-containing functional groups. Therefore, pressure in the process of drying lignite was the main factor influencing the pore structure and the water reabsorption of dewatered coals, and the drying temperature was dominant under the pressurizing conditions.

Influence of modifications on the deep desulfurization behavior of NaY and Na13X zeolites in gasoline.

NaY and Na13X zeolites were modified by different modification manners including H+ modification, metal ion modification (Cu2+, Ni2+, or Ce3+), and H+ modification followed by metal ion modification to investigate their deep desulfurization behavior in gasoline. The sorbents were characterized by X-ray diffraction, FTIR of chemisorbed pyridine, N2 adsorption, and scanning electron microscope (SEM). The desulfurization performance of these sorbents was evaluated in model gasoline containing thiophene and cyclohexane with thiophene concentration of 500 mg/L, and the results were analyzed to investigate the effect of preparation methods on adsorption desulfurization behavior. The result indicates that H+ modification or metal ion modification could all improve the desulfurization performance of both NaY and Na13X zeolites, except for Na13X modified by Cu2+ and Ni2+. For Cu2+ or Ni2+ ion exchanging, the crystal structure of Na13X would be destroyed, resulting in a much lower desulfurization efficiency than that of the parent Na13X. The desulfurization efficiency of sorbents prepared via H+ modification followed by metal ion modification is higher than that of sorbents prepared by single H+ modification or single metal ion modification, because the former is more conducive to improve the content of metal elements on the sorbents than the latter. In addition, the increase of the specific surface area and pore volume of the sorbents would directly lead to the improvement of desulfurization performance of the sorbents. Compared with Na13X, the H+ modification on NaY zeolite can significantly enhance the desulfurization performance of the sorbents. Among those prepared sorbents, the CuHY has the highest desulfurization efficiency. The influence of thiophene concentration (100-1000 mg/L) on desulfurization efficiency of CuHY sorbent was evaluated. The results indicate that the desulfurization efficiency of CuHY sorbent is nearly 100% at room temperature, when the thiophene concentration is lower than 300 mg/L. Moreover, its desulfurization behavior could be described by Langmuir isothermal equation. Graphic abstract .

A Magnetically Recoverable Fe3O4-NH2-Pd Sorbent for Capture of Mercury from Coal Derived Fuel Gas.

A sort of magnetical material named Fe3O4-NH2-Pd was prepared by loading varying amounts of immobilizing Pd on the surface of the magnetic Fe3O4-NH2 microspheres. This magnetical material was used firstly for capturing Hg° from coal derived fuel gas based on its recoverability. The experimental results showed that the loading Pd on the amine-functionalized magnetite nanoparticles can greatly improve the efficiency of removing Hg° at a high temperature range between 200 and 300 °C. The magnetic Fe3O4-NH2-Pd sorbent with 5% Pd loaded exhibited significantly high activity and stability in capturing Hg°, affording over 93% capture efficiency at 200 °C for more than 8 hrs. Compared to the Fe3O4-NH2 sorbent that converted the Hg° as HgS, this Fe3O4-NH2-Pd sorbent can remove the Hg° by forming Pd-Hg amalgam and HgS. In addition, the experimental tests indicated that the as-synthesized Fe3O4-NH2-Pd sorbent still showed stable magnetic properties after two regeneration cycles in removing Hg°, which provided the opportunity for preparing a recyclable sorbent which can be easily separated and recovered for Hg° removal.

Effect of precursor and preparation method on manganese based activated carbon sorbents for removing H2S from hot coal gas.

Activated carbon (AC) supported manganese oxide sorbents were prepared by the supercritical water impregnation (SCWI) using two different precursor of Mn(NO(3))(2) (SCW(N)) and Mn(Ac)(2)·4H(2)O (SCW(A)). Their capacities of removing H(2)S from coal gas were evaluated and compared to the sorbents prepared by the pore volume impregnation (PVI) method. The structure and composition of different sorbents were characterized by XRD, SEM, TEM, XPS and XANES techniques. It is found that the precursor of active component plays the crucial role and SCW(N) sorbents show much better sulfidation performance than the SCW(A) sorbents. This is because the Mn(3)O(4) active phase of the SCW(N) sorbents are well dispersed on the AC support, while the Mn(2)SiO(4)-like species in the SCW(A) sorbent can be formed and seriously aggregated. The SCW(N) sorbents with 2.80% and 5.60% manganese are favorable for the sulfidation reaction, since the Mn species are better dispersed on the SCW(N) sorbents than those on the PV(N) sorbents and results in the better sulfidation performance of the SCW(N) sorbents. As the Mn content increases to 11.20%, the metal oxide particles on AC supports aggregate seriously, which leads to poorer sulfidation performance of the SCW(N)11.20% sorbents than that of the PV(N)11.20% sorbents.

Process effects on activated carbon with large specific surface area from corn cob.

The main factors that affect the large specific surface area (SSA) of the activated carbon from agricultural waste corn cobs were studied by chemically activated method with solution of KOH and soap which acted as surfactant. The experiment showed that not only the activation temperature, activation time and the mass ratio of KOH to the carbonized material, but also the activated methods using activator obviously influenced the SSA of activated carbon. The experimental operating conditions were as follows: the carbonized temperature being 450 degrees C and keeping time being 4 h using N2 as protective gas; the activation temperature being 850 degrees C and holding time being 1.2 h; the mass ratio of KOH to carbonized material being 4.0; the time of soaking carbonized material in the solution of KOH and soap being 30 min. Under the optimal conditions, the SSA of activated carbon from corn cobs reached 2700 m2/g. And the addition of the soap as surfactant may shorten the soaking time. The structure of the activated carbon prepared had narrow distribution of pore size and the micro-pores accounted for 78%. The advantages of the method described were easy and feasible.

Pyrolytic behavior of waste corn cob.

The powder of the agricultural waste corn cob was pyrolyzed in a tube-typed stainless steel reactor of 200 ml volume under N2 atmosphere. The compositions of the gases and liquid obtained at different pyrolytic temperatures below 600 degrees C at the heating rate of 30 K/min were analyzed. With the increment of the pyrolytic temperature, the yields of the solid and the liquid products were decreased, but the yield of gas products was increased. The liquid products were approximately 34-40.96% (wt%), the gas products were 27-40.96% (wt%) and the solid products 23.6-31.6% (wt%). There were less changes for the yields of these products above 600 degrees C. The gas products were analyzed by gas chromatography (GC) as CO2, CO, H2, CH4, C2H4, C3H6, C3H8, etc. When the temperature was 350-400 degrees C, the gases had CO2 and CO 80-95% (v/v). When the temperature increased continuously, yields of H2, CH4, C2H4, C3H6 and C3H8 gradually increased. The liquid products were identified by GC-MS as phenols, 2-furanmethanol, 2-cyclopentanedione, etc. The Fourier transform infra-red spectrophotometer (FT-IR) analysis of the liquid product showed a strong -OH group absorption peak. Differential thermogravimetric analysis (DTG) showed that thermal decomposition process involves two steps. The heating rate affects not only the activation energy of the decomposition reaction, but also the path of the reaction. With the increment of the heating rate, the maximum rate temperature of the decomposition reaction was shifted to a higher temperature, and the order and activation energy of the total decomposition reaction were decreasing.