Tonghua Sun

Recent advances of sodium borohydride reduction in coal water slurry desulfurization: integration of chemical and electrochemical reduction

Clean fuel technologies have been widely developed in current society because fuel combustion can directly bring about the emission of hazardous gasses, i.e. SO2, sulfate particulate matter (SPM), resulting in environmental pollution and other related problems that endanger public heath and community property; as well as reducing the life of the engine due to corrosion. The research efforts for developing conventional hydrodesulfurization (HDS) and alternative desulfurization methods such as selective adsorption, biodesulfurization, oxidation/extraction (oxidative desulfurization), etc. for removing these refractory sulfur compounds from liquid fuel products are on the rise. The reductive desulfurization method under ambient conditions has rarely been researched. This paper reviews the current status of various desulphurization techniques being studied worldwide. It presents an overview of novel emerging technologies of chemical and electrochemical reduction (CECR) for deep desulfurization of coal water slurry (CWS) so as to provide a new way of thinking about ultra-clean fuel technology.

Low temperature H2S removal with 3-D structural mesoporous molecular sieves supported ZnO from gas stream

A series of 3-dimensional (3-D) structural mesoporous silica materials, SBA-16, MCM-48 and KIT-6, was synthesized and supported with different ZnO loadings (10, 20, 30, and 40 wt%) by the incipient wetness method to evaluate the performances on H2S removal at room temperature. These materials were characterized by N2 adsorption, XRD, and TEM to investigate their textural properties. All the ZnO-loaded adsorbents exhibited the H2S removal capacity of bellow 0.1 ppmv. With the best ZnO loading percentage of 30 wt% on MCM-48 and KIT-6, 20 wt% on SBA-16 according to the results of breakthrough test, further increasing ZnO loading caused the decrease of the adsorption capacity due to the agglomeration of ZnO. Besides, the H2S adsorption capacities of the supports materials varied in the order of KIT-6>MCM-48>SBA-16, which was influenced primarily by their pore volume and pore size. With the largest pores in these 3-D arrangement materials, KIT-6 showed the best performance of supported material for ZnO, due to its retained superior physical properties as well as large pore diameter to allow faster gas-solid interaction and huge pore volume to disperse ZnO on the surface of it.

Rapid desulfurization of CWS via ultrasonic enhanced metal boron hydrides reduction under ambient conditions

The present work investigated a rapid desulfurization method for industrial coal water slurry (CWS) using ultrasound-assisted metal boron hydrides (NaBH4, KBH4) reduction. Under ambient pressure and temperature conditions of ultrasonic time (10 min), ultrasonic frequency (20 KHz), deoxidizer concentration (10 mM), CWS concentration (60 g L−1) and coal particle size (≤ 120 mesh), the desulfurization efficiency of CWS can reach about 42% (NaBH4) and 45% (KBH4), respectively. On addition of Ni2+ catalyst (1 mM), the desulfurization efficiency, up to a maximum value of 57%, was significantly improved. Meanwhile, the nitrogen reduction (N) of CWS was reduced by 11.5%. The decrease of S and N greatly cut down SOx and NOx emissions from CWS combustion. After the processing, the ash content and volatile matter were decreased contributing to the slight improvement of combustion characteristics.

Indirect hydrodesulfurization of gasoline via sodium borohydride reduction with nickel catalysis under ambient conditions

The present work introduced a novel indirect hydrodesulfurization (HDS) method for gasoline fuel at room temperature using an excellent reductant of sodium borohydride (NaBH4), which produces active hydrogen with Ni–B catalysis. Then the active hydrogen can convert S-compounds into hydrogen sulfide (H2S) or S2−, released from the gasoline. Under the optimized conditions the maximal desulfurization efficiencies of original and experimental gasoline can reach about 36.6% and 88%, respectively. It is a relatively clean and moderately indirect HDS method; after the process the Ni–B catalyst produced in the filtrate can be reused for the further desulfurization work. Moreover, the realization of the filtrate recycling, the evaluation of the hydrogen releasing and the exploration of catalyst development will be further helpful in cost reduction in future work.

Gas Cleaning and Hydrogen Sulfide Removal for COREX Coal Gas by Sorption Enhanced Catalytic Oxidation over Recyclable Activated Carbon Desulfurizer

This paper proposes a novel self-developed JTS-01 desulfurizer and JZC-80 alkaline adsorbent for H2S removal and gas cleaning of the COREX coal gas in small-scale and commercial desulfurizing devices. JTS-01 desulfurizer was loaded with metal oxide (i.e., ferric oxides) catalysts on the surface of activated carbons (AC), and the catalyst capacity was improved dramatically by means of ultrasonically assisted impregnation. Consequently, the sulfur saturation capacity and sulfur capacity breakthrough increased by 30.3% and 27.9%, respectively. The whole desulfurizing process combined selective adsorption with catalytic oxidation. Moreover, JZC-80 adsorbent can effectively remove impurities such as HCl, HF, HCN, and ash in the COREX coal gas, stabilizing the system pressure drop. The JTS-01 desulfurizer and JZC-80 adsorbent have been successfully applied for the COREX coal gas cleaning in the commercial plant at Baosteel, Shanghai. The sulfur capacity of JTS-01 desulfurizer can reach more than 50% in industrial applications. Compared with the conventional dry desulfurization process, the modified AC desulfurizers have more merit, especially in terms of the JTS-01 desulfurizer with higher sulfur capacity and low pressure drop. Thus, this sorption enhanced catalytic desulfurization has promising prospects for H2S removal and other gas cleaning.

The removal of styrene using a dielectric barrier discharge (DBD) reactor and the analysis of the by-products and intermediates

As a kind of volatile organic compound, styrene is a typical industrial pollutant with high toxicity and odorous smell. In this study, the removal of malodorous styrene simulation waste gas was carried out in a self-made wire-tube dielectric barrier discharge reactor. The decomposition efficiency of the reaction was investigated under different applied voltages and flow rates. The results showed that nearly 99.6xa0% of styrene could be removed with a concentration of 3,600xa0mg/m3 and the applied voltage of 10.8xa0kV. However, the selectivity of CO2 and CO showed that the mineralization efficiency of styrene was less than 25xa0%. The by-products of the reaction, including O3, NOx and other intermediates, were also detected and analyzed under different applied voltages. The relationships between the applied voltage and the quantity of final product (CO2) and by-products (intermediate organics, NOx, O3) were investigated. The reaction mechanism was also described according to the bond energy and the intermediates that formed.

A coal desulfurization process via sodium metaborate electroreduction with pulse voltage using a boron-doped diamond thin film electrode

A preliminary study was conducted on the coal desulfurization process via NaBO2 electroreduction with pulse voltage using a boron-doped diamond (BDD) thin film electrode. It has been proved that NaBO2 was converted into NaBH4 by 11B NMR. The factors that influence the conversion rate of NaBO2 into NaBH4 and coal desulfurization efficiency were investigated. Under the conditions of −1.5 V forward pulse voltage, +0.5 V reverse pulse voltage, 0.2 mol L−1 NaBO2 concentration, 0.5 mol L−1 NaOH concentration, 2 s forward pulse duration, 1 s reverse pulse duration, 50 g L−1 coal concentration, 0.8 mmol L−1 NiCl2 concentration and 2.5 h electrolytic time, a higher desulfurization efficiency (64%) was obtained compared with the common electrochemical desulfurization (ECDS) process using a Pt electrode. By analyzing and comparing the coal samples and electrolytes before and after desulfurization it was indicated that the removed S from the coal sample in the form of gaseous H2S was mainly converted into Na2S and Na2Sx and boron (B) recycling was realized during coal desulfurization. Particularly, the combustion characteristics of coal were improved after desulfurization. Finally, the desulfurization mechanism was proposed. All these results indicated that the desulfurization process via NaBO2 electroreduction with pulse voltage using a BDD thin film electrode is effective and highly promising for coal desulfurization.