Thiophenic Sulfur Research Articles

Excellent electrocatalytic performance of metal-free thiophene–sulfur covalent organic frameworks for hydrogen evolution in alkaline medium

Two metal-free 2D COF materials were synthesized by Schiff base reaction, which showed excellent HER activity in alkaline medium. The two structures were through DFT calculated, and the relationship between band gap and overpotential was analyzed.

Effect of desilication of NaY zeolite on sulfur content reduction of gasoline model in presence of toluene and cyclohexene

The presence of sulfur compounds in transportation fuels have always been one of the most important issues discussed in scientific and industrial associations. In recent years, due to the adoption of global policies to address environmental problems, the study of efficient systems for desulfurization of fuels has attracted much attention. In this study, the effects of alkaline treatment with NaOH and NaOH/TPAOH mixtures with different concentrations on adsorption desulfurization of NaY adsorbent were investigated. The adsorbents were characterized by XRD, FE-SEM, BET, EDX, ICP-OES and FT-IR techniques. It was found that alkaline treatment in the NaOH/TPAOH solution with TPAOH/(TPAOH + NaOH) = 0.5 had the highest total surface area followed by the highest adsorption capacity among the desilicated adsorbents. In order to increase the adsorption capacity, copper and cerium metals were impregnated individually and in pairs on this adsorbent at 80 °C. The results showed that impregnating of metal ions increases the adsorption capacity of adsorbents so that CuCe-0.5R adsorbent with values of 21.02 and 24 mg/g had the highest adsorption capacity of thiophene and dibenzothiophene sulfur compounds, respectively. In this regard, the competitive adsorption of toluene and cyclohexene was also investigated in different model fuels containing isooctane as a solvent. The adsorption capacity reduction of sulfur compounds for different adsorbents was in order of Cu-0.5R > CuCe-0.5R > Ce-0.5R, respectively, in the presence of toluene and cyclohexene. Thermodynamics studies showed that the adsorption process is endothermic. The kinetic models in adsorbing the sulfur compounds followed the pseudo-second-order equation.

Ag modification of SBA-15 and MCM-41 mesoporous materials as sorbents of thiophene

Zeolites and some mesoporous materials modified by Ag possess excellent desulfurization performances toward the adsorption of thiophenic compounds. However, Ag in Ag-based sorbents has different forms, and the interactions between different forms of silver and thiophene still require further studies. In this paper, pure silica SBA-15 and MCM-41 mesoporous materials with weak acidity were loaded with Ag from the silver ammonia solution to form Ag/SBA-15 and Ag/MCM-41 sorbents. By comparing the desulfurization efficiencies of the sorbents in the simulated solution of thiophene-cyclohexane, thiophene-benzene, tetrahydrothiophene-cyclohexane and tetrahydrothiophene-benzene, it is found that the adsorption of sorbent for thiophene was accompanied by S-Ag and π complexation, and the adsorption performances of thiophene by the sorbents were greatly affected by benzene. The XPS results show that most Ag in Ag/SBA-15 and Ag/MCM-41 sorbents was metallic Ag, and some Ag strongly interacting with the carrier led to the formation of Ag-O-Si bonds as the main active center of thiophenic compounds. In addition, the sulfur atomic mulliken charges (e-) of different thiopheic compounds (thiophene, tetrahydrothiophene, methylthiophene) will affect the interactions between active components Ag and thiophene sulfur compounds. The desulfurization efficiencies of the sorbents in thiophene-cyclohexane, 2-methylthiophene-cyclohexane, and 3-methylthiophene-cyclohexane showed that the decrease in mulliken charges (e-) of sulfur atoms facilitated the S-Ag bond interaction between the sulfur atom of thiophenic compounds and active component in the sorbent. In conclusion, to obtain the Ag-based sorbent with good adsorption performance for thiophenic compounds, the carrier should contain a certain content of silicon hydroxyl and the suitable pore structure. During the preparation of SBA-15 and MCM-41 mesoporous materials modified by Ag, the Ag-O-Si bonds are more easily formed when silver ammonia interacts with the silicon hydroxyl group on the surface of the carrier. The suitable pore size can inhibit agglomerate to form metallic Ag during the calcination process. These conclusions will provide theoretical guidance for the preparation of silver-based sorbents for thiophene.

Pechini Sol-Gel Synthesis and Characterization of NiWO4/W5O14/WO3 Nanocomposite for Photocatalytic Desulfurization of Thiophene

One of the most important problems in the oil industry is the presence of sulfur and sulfur compounds in crude oil. Sulfur compounds in crude oil can have detrimental effects on the environment, equipment, catalysts, and end products. One of the most important goals of researchers in recent years is to sweeten petroleum products from these compounds. This study aims to use NiWO4/W5O14/WO3 composite nanostructure to solve this problem using the photocatalytic oxidative desulfurization method. This composite nanostructure has been synthesized by Pechini sol-gel method with high purity at low temperature and examined by XRD, EDS, FESEM, and FT-IR analysis. Due to the presence of WO3 in the composition, the bandgap was greatly reduced and the efficiency was increased. As a result, the nanostructure could degrade more than 73% of the sulfur in thiophene in 180 min under visible light. By optimizing the amount of photocatalyst and irradiation time, the efficiency can be improved.

Sulfur types distribution and the fast thermal-cracking behaviors of sulfur-containing compounds in Buton oil sand bitumen

The distribution of various types of sulfur in Buton oil sand bitumen (OSB) were investigated at the level of group-fractions corresponding to saturates, aromatics, resins and asphaltens (SARA). The separation of different types of sulfur-containing compounds (SCCs) in saturates and aromatics with weak polarity was performed using selective oxidization coupled with alumina column chromatography. However, various types of SCCs were isolated from resins via selective oxidization combined with solvent fractional extraction. It was found that sulfide sulfur, thiophenic sulfur and sulfoxide/sulfone sulfur accounted for 39.31%, 53.93% and 6.74% in total sulfur of OSB, respectively. Sulfidic sulfur and thiophenic sulfur in OSB had the highest enrichment in aromatics, followed by that in asphaltenes and resins. In order to further link the theoretical study with the actual process of thermal cracking process, the fast thermal cracking of OSB to produce oil sand oil under different temperature and over silica sand, calcium aluminate and FCC catalyst was conducted by a laboratory-scale fluidized bed reactor. The composition and classes of SCCs existed in oil sand oil were evaluated via GC–MS, which were indispensable to gain an in-depth insight into thermal cracking behavior of SCCs in OSB. Results indicated that SCCs in oil sand oil obtained under different temperature and over different heat carriers had the distinct composition, and yet were all classified into up to 11 classes. The detected SCCs in oil sand oil obtained over silica sand at different temperatures all contained AT&AM, thiophenes, BTs, HydroDBTs, DBTs, HydroNTs, and NTs. The composition and classes of SCCs in oil sand oil, nonetheless, were inclined to be enriched as the temperature enhanced. Furthermore, the detected SCCs in oil sand oil obtained over calcium aluminate featured the most abundant class distribution, followed by that over silica sand and FCC catalyst. The relative content of AT&AM, thiophenes and BTs, the relative content of NTs and four species of Hydrothiophenes, and the relative content of DBTs, PTs and BNTs accounting for SCCs in oil sand oil was largest when the heat carriers were silica sand, calcium aluminate and FCC catalyst, respectively.

Effect of ash – ZnO heat carrier on sulfur migration behavior during pyrolysis of coal

In this paper, the effects of ash heat carrier (AHC) and ash-ZnO heat carrier (A-ZHC) on the release and transformation of sulfur during the pyrolysis of Yuandatan (YDT) high-sulfur bituminous coal were studied. The samples were pyrolyzed in a fixed-bed reactor, the composition of sulfur in char, crystal structure of inorganic sulfur, and species of sulfur in pyrolysis gas were analyzed by XPS, XRD and GC. Compared with AHC, the A-ZHC can better inhibit sulfur migration to tar and gas during coal pyrolysis so as to obtain more pure volatile products. Both the AHC and A-ZHC promote the formation of CaS and FeS. The presence of ZnO in the A-ZHC promotes the formation of ZnS, and the interaction between ZnS and FeS can produce solid solutions (Zn,Fe)S, which further reduces the release of H2S and COS and advances the increase of sulfide sulfur content. In addition, the catalytic effect of ZnO in A-ZHC promotes the conversion of thiophene sulfur to sulfide sulfur in char at high temperature. The catalytic effect of ZnO also promotes the conversion of tar sulfur to sulfide and sulfone sulfur in char by reacting with metal-oxides and oxygen-containing groups during the secondary reaction stage.

Sulfur-modified chitosan derived N,S-co-doped carbon as a bifunctional material for adsorption and catalytic degradation sulfamethoxazole by persulfate

N,S-co-doped carbons were synthesized through the calcination of sulfur-modified chitosan for the first time, and utilized as persulfate activators for sulfamethoxazole (SMX) remediation in water. The chitosan and sulfonyl chloride underwent one-step sulfonylation reaction to generate S-modified chitosan. The catalyst NSC-3 showed both excellent adsorption and catalytic oxidation efficiency, corresponding 98.62% removal and 81.34% mineralization rate within 90 min. The rate constant (kobs) was up to 0.0578 min−1, with 75.60-folders higher than that of sulfur-free catalyst NC (7.6580 ×10−4 min−1). The synergy of N and S contributed to the improvement of removal efficiency. The adsorption and oxidation performance were highly depended on the S/N atomic ratio. At the S/N ratio of 0.18, the maximum adsorption and oxidation capability were obtained. The NSC-3/PS system exhibited outstanding adaptability at the wide pH range from 3.07 to 9.28, while the inhibitory effect occurred at strong basic conditions (pH = 11.01). The thiophene sulfur and structural defects were identified as the catalytic sites in activating PS. Both radical and non-radical pathways were responsible for degradation process, where 1O2 played a major role, SO4·-exerted a minor contribution, and O2·- acts as the precursor for the production of 1O2. Another source of 1O2 was assigned to the activation of PS by structure defects. This work indicates that N,S-co-doped carbon at an optimal S/N atomic ratio effectively catalyzes persulfate, and provides an innovative method to construct bifunctional carbon materials of adsorption and oxidization.

Chemical Thermodynamics and Kinetics of Thiophenic Sulfur Removed from Coal by Microwave: A Density Functional Theory Study

The increasing use of high-sulfur coal contradicts with the stringent environmental pressure in metallurgical industry. Microwave has been confirmed to have efficient effect for coal desulfurization. However, the removal behavior of thiophenic sulfur, as the most difficult sulfur to remove from coal, is still unclear in microwave field. In this work, the feasibility of removing thiophenic sulfur from coal by microwave was evaluated by dielectric properties test, the chemical thermodynamics and kinetics of thiophenic sulfur migration with microwave irradiation were further analyzed by density functional theory (DFT) calculation. Dielectric properties test indicates that thiophenic sulfur is strong for converting electric field energy to heat energy than coal, which means the thiophenic sulfur will be selectively heated in the process of coal desulfurization by microwave. The magnetic loss powers of coal and thiophenic sulfur are very small and can be ignored. DFT calculation shows that under microwave irradiation, the energy barrier and activation energy of rate-limiting step for thiophenic sulfur removal decrease by 7.6 kJ/mol and 2.24 kcal/mol, and the logarithm of rate constant increases by 11.2 s−1. It suggests that the thiophenic sulfur removal is promoted by catalyzing the breaking of C–H and C–C bonds. In addition, the optimal removal path of thiophenic sulfur is also changed, accompanying the variation of sulfur-containing products from carbon monosulfide (CS) to thioketene (C2H2S). These findings reveal the catalytic mechanism of microwave on the thiophenic sulfur removal from coal, which are conducive to the sustainable utilization of high-sulfur coal in metallurgy process.Graphical Abstract

Upgrading of thiophenic compounds from fuels over a silver-modified MoO3 catalyst under ambient conditions

The demand for heterocyclic sulfur compounds is increasingly in fine chemical industry, where the thiophenic sulfur impurities in fuels can be a potential recyclable feedstock. In this work, the catalytic upgrading of thiophenic sulfur compounds over a silver-modified MoO3 catalyst under ambient conditions was reported. Br2 and H2O2/HBr were used to convert thiophenic compounds in alkane and alcohol solutions. The conversion of various thiophenic compounds (thiophene, benzothiophene and dibenzothiophene) to the corresponding bromides reached up to 81.6 ~ 99.8%. The bromination path undergoes electrophilic substitution mechanism, and the transformation of mono- to dibromides is identified as the rate-determining step. The introduction of MoAg2O4 phase on MoO3 is rationalized to boost the conversion of mono-bromothiophene, which results in the selectivity of 2,5-dibromothiophene increased from 10% to over 50%. The optimized silver loading was 10% due to its high thiophene conversion and selectivity of dibromides. Silver modification of MoO3 rods not only stabilized the textural property of catalysts but also improved its bromination activity compared to the bulk MoO3 indicated by SEM and FTIR characterization. Density functional theory (DFT) calculation suggested that the formation of 2-bromothiphene and 2,5-dibromothiophene were preferred on the MoO3(111) and MoAg2O4(111) sites, respectively. The catalytic upgrading approach paves the way for the efficient utilization of thiophenic sulfur impurities in fuels to their value-added under mild conditions.

Theoretical Study on the Unimolecular Pyrolysis of Thiophene and Modeling.

Thiophenic sulfur is the most stable and abundant organic sulfur species in petroleum. Removal of thiophenes has profound significance in environmental protection. In this work, we investigate the unimolecular pyrolysis of thiophene from a kinetic perspective. High-level ab initio methods have been employed to deduce the potential energy surface. Rate coefficients of the elementary reactions are computed using variational transition-state theory at the CCSD(T)/CBS level to develop a kinetic model. By comparison with preceding experimental results, the kinetic model shows good performance in calculating the thiophene pyrolysis rate. The Arrhenius expression for thiophene unimolecular pyrolysis has been redetermined as k = 1.21 × 1013 × exp[(78.96 kcal/mol)/(RT)]. The unimolecular pyrolysis of thiophene is mainly initiated by the ring-H migrations, whereas the C–S bond rupture has limited contribution to the overall pyrolysis rate. Thioketene (SC2H2) and ethyne (C2H2) are the major pyrolysis products at all temperatures. Significant amounts of the thioformyl (HCS) radical and CS could also be yielded. By contrast, atomic sulfur and H2S are difficult to be directly produced. Possible secondary reactions in the products have also been discussed.

Rational Construction and Performance Regulation of an In(III)-Tetraisophthalate Framework for One-Step Adsorption-Phase Purification of C2H4 from C2 Hydrocarbons.

The development of porous materials for ethylene (C2H4) separation and purification, a very important separation process in the chemical industry, is urgently needed but quite challenging. In particular, the realization of selectivity-reversed adsorption (namely, C2H4 is not preferentially adsorbed) and the simultaneous capture of multinary coexisting impurities such as ethane (C2H6) and acetylene (C2H2) will significantly simplify process design and reduce energy and cost consumption, but such porous materials are quite difficult to design and have not yet been fully explored. In this work, by employing an aromatic-rich bithiophene-based tetraisophthalate ligand, we solvothermally fabricated an anionic In(III)-based framework termed ZJNU-115 featuring In(COO)4 as an inorganic secondary building unit as well as one-dimensional channels. Due to the absence of unsaturated metallic sites, together with aromatic-rich channel surface decorated with abundant hydrogen-bonding acceptors of carboxylate oxygen and thiophene sulfur atoms, desolvated ZJNU-115 exhibited an unusual adsorption relationship with respect to C2 hydrocarbons, namely, simultaneous and preferable capture of C2H6 and C2H2 over C2H4 at the temperatures investigated, thus representing a rare metal-organic framework (MOF) with the promising potential for one-step adsorption-phase purification of C2H4 from a trinary C2 hydrocarbon mixture. Compared to a few of the MOFs reported for such an application, ZJNU-115 displayed simultaneously good adsorption selectivities of both C2H2 and C2H6 over C2H4. Furthermore, its separation potential can be postsynthetically tailored by substituting dimethylammonium (Me2NH2+) counterions with tetraalkyl ammonium ions (NR4+; R = Me, Et, or n-Pr). More importantly, ZJNU-115 was stable in various organic solvents as well as aqueous solutions with pH values ranging from 5 to 9, thus laying a solid foundation for its practical applications. The design principle and the performance regulation strategy adopted in this work will offer valuable guidance for the contrapuntal construction of porous MOFs employed for direct multicomponent purification of C2H4 with improved performance.

Unimolecular Pyrolysis Mechanism of Thiophene and Furan: An Ab Initio Comparative Study

Thiophene sulfur is the most stable and abundant organic sulfur species in petroleum. In this work, the unimolecular pyrolysis mechanism of thiophene was investigated using high-level ab initio methods. As a contrast, similar reactions of furan were computed using the same methods. It was found that the most likely initiation reactions for thiophene unimolecular pyrolysis are 2,3-H and 3,2-H transfers. The 3,2-H shift forms buta-2,3-dienethial, which subsequently decomposes to CS + CH₃C₂H and HC₂CH₂ radical (*) + HCS*, whereas the 2,3-H migration corresponds to α-carbene and ultimately leads to C₂H₂ + SCCH₂, CS + CH₃C₂H, HC₂CH₂* + HCS*, and S + C₂CHC₂H. H₂S is supposed to be yielded through secondary reactions. Combined with thermodynamics, the favored products are concluded to be C₂H₂ + SCCH₂. Thiophene is kinetically and thermodynamically more stable due to the higher energy barrier of the reaction pathway and the lower thermal stability of the products.

Fundamental research on the influence of mercaptan and thioether structure on the solvent extraction of fluid catalytic cracking naphtha

The thioether and mercaptan components (over 50–100 mg/kg) of fluid catalytic cracking (FCC) naphtha must be removed to satisfy the rigorous sulfur content standard of the vehicle gasoline. Owing to the difference between the structures of thioether and mercaptan and that of thiophenic sulfur, the desulfurization process is usually divided. A serious loss of octane number (ON) occurs during typical desulfurization when the sulfur content is reduced to 10 mg/kg. With the oriented separation of FCC naphtha critical components process, the standard of sulfur content with losing 1 unit of ON can be satisfied. However, thioether and mercaptan require individual technologies for removal. Thioether, mercaptan, and thiophenic sulfur must be synchronously removed to improve the efficiency, simplify the technology, and reduce the energy consumption. In this study, quantum chemical calculation and ternary liquid–liquid equilibrium experiment were combined to investigate the effect of thioether and mercaptan structures on the sulfoxide solvent extraction performance. The results showed that the Van der Waals’ force was the main interaction between the thioether/mercaptan and the solvent because the peaks of solvent and sulfide by RDG analysis were located at −0.01 to 0.01 a.u. In addition, the dipole moment, steric hindrance, and displacement affected the solvent extraction performance. The selectivity coefficient θ¯ of C3 thioether and mercaptan was 5.80 and 6.48 by DMSO solvent, respectively, which were greater than those of C4 sulfides (4.48 and 5.56). The interaction energy Eint of DMSO-ethyl methyl sulfide and DMSO- propanethiol were −32.75 and −33.68 kJ/mol while DMSO-diethyl sulfide and DMSO- butanethiol were −24.72 and −29.20 kJ/mol. It also proves that the C3 thioether and mercaptan could better extract into the solvent. In this way, the extractive desulfurization rate of the real FCC naphtha by DMSO was 80%. Therefore, the use of sulfoxide composite solvent can simultaneously extract the thioether, mercaptan, and thiophenic sulfur. This analytical method could be used to predict the synchronous extraction performance for FCC naphtha sulfides by other typical solvents.

High-Coverage Screening of Sulfonamide Metabolites in Goat Milk by Magnetic Doped S Graphene Combined with Ultrahigh-Performance Liquid Chromatography-High-Resolution Mass Spectrometry.

Currently, there are more than 1000 varieties of synthetic sulfonamides universally used as antibiotics causing severe results of potential carcinogenicity and drug resistance for human health due to excessive residue of animal-derived food. A facile and novel approach for untargeted screening of sulfonamides (SAs) and metabolites was proposed based on magnetic solid-phase extraction-ultrahigh-performance liquid chromatography-tandem high-resolution mass spectrometry (MSPE-UHPLC-HRMS). Compared with QuEChERS without the clean-up procedure and SPE in terms of matrix effect and absolute recovery, magnetic doped S graphene (S-doping level: 2.82%) synthesized via a solid-state microwave approach and the aggregation wrap mechanism was used as a novel adsorbent for nonspecific extraction of desired analytes by the noncovalent interaction between electron-deficient thiophene sulfur and electron donors such as amino or amide as well as π-π stacking interactions. Combined with variable data-independent acquisition, characteristic fragment-ion filtering (m/z 156.01138 or m/z 108.04439) and assignment of extracted-ion chromatograms of marked fragment ions were successfully utilized to screen the desired analytes and subsequently confirmed with the availability of reference standards. The optimized and validated approach for spiked 26 SAs and 9 metabolites in control goat milk demonstrated satisfactory accuracy (80.1-112.6%) and precision (RSDs < 6.4%) for matrix-matched standard addition. After applying suspect goat milk samples, untargeted SA analytes including sulfanilamide or an N4-acetylsulfamethazine metabolite with concentration ranging from 66.3 to 398.5 ng L-1 were determined in 5 of 45 goat milk samples.

Enhanced organics degradation by three-dimensional (3D) electrochemical activation of persulfate using sulfur-doped carbon particle electrode: The role of thiophene sulfur functional group and specific capacitance

For further enhancing the electrochemical oxidation performance, sulfur-doped carbon particle electrode was employed in the three-dimensional (3D) electro-assisted activation of persulfate process (ACS/PS/EC). Herein, an in situ S-doped activated carbon (ACS) was prepared and applied as the particle electrode as well as catalyst in ACS/PS/EC system. Several carbon particle electrodes with different annealing temperature were prepared and characterized via EA, BET, XPS and Raman spectra. Cyclic voltammetry (CV) was perform to obtain the specific capacitance and investigate the interfacial electron transfer of ACS particle. The results of comparative experiments showed significant synergy between electric and catalytic activations of PS. Especially, the as-prepared sample treated at 850 °C (ACS-850) exhibited an outstanding catalytic performance, and the phenol degradation rate was greatly improved by nearly 100% with the application of electric field. By comparing of several carbon particle electrodes with different functional groups and specific capacitances, it is revealed that thiophene sulfur functional group is the mainly active site for both electric and catalytic activation of PS, and the specific capacitance acts as assistant factor. Quenching experiments proved that the 3D electro-assisted activation of PS proceeded through both radical and non-radical pathway. Possible mechanism for ACS/PS/EC electrochemical process was proposed.

Multi-heteroatom-doped hollow carbon tubes as robust electrocatalysts for the oxygen reduction reaction, oxygen and hydrogen evolution reaction

Multi-heteroatoms-doping tunes the electronic structure of the catalyst, thereby optimizing the intrinsic catalytic activity of tri-functional metal-free electrocatalyst. • This work provides a self-sacrifice template engineering strategy to synthesize NSCHCT as tri-functional metal-free electrocatalyst. • NSCHCT shows an excellent bifunctional performance towards ORR/OER and has a small ORR/OER voltage difference of 0.85 V. • The hollow hierarchical porous structure and multi-heteroatom-doped provide rich reactive sites. • ZAB based on NSCHCT1000 displays long-term stability of 55 h, which can drive a LED. Developing non-noble metal-based electrocatalysts for oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) is highly desirable, while still facing challenges. Herein, a self-sacrifice template engineering strategy that feasible carbonization of the copolymer of melamine-trithiocyanurim wrapped by polydopamine was developed to fabricate N, S hollow co-doped carbon tube (NSCHCT) based trifunctional electrocatalyst. Owing to the hierarchical structure, including hollow and porous structure, the obtained catalyst exhibits rich active sites and favourable mass transfer advantage, boosting the kinetic of the catalytic process. Moreover, multiple heteroatoms-doping provides various active sites. Notably, the thiophene sulfur combining with pyridinic N(p-N/S) and thiophene sulfur combined with graphitic N (g-N/S) shows the lowest activation energy barrier for OER/ORR and HER, respectively. As a result, the NSCHCT assembled Zinc-air battery shows excellent performance with a power density of 109 mW cm −2 and a high open-circuit voltage of 1.44 V, comparable with the Pt/C + RuO 2 system.

A refined design concept for sulfur-tolerant Pd catalyst supported on zeolite by shape-selective exclusion and hydrogen spillover for hydrogenation of aromatics

Sulfur poisoning of noble metal catalysts has been a major challenge for decades. This work demonstrates the superior sulfur tolerance of a hybrid zeolite-supported Pd catalyst for hydrogenation of tetralin containing benzothiophene. The hybrid catalyst consists of Pd supported on a large-pore acidic zeolite Y (Pd/HY) and a small-pore zeolite A without (Pd/HA) or with surface metal passivation by chemical vapor deposition of SiO2 (SiO2-Pd/HA) and with potassium ion exchange (SiO2-Pd/KA). Pd/HY is very active for tetralin hydrogenation but quickly deactivates after exposure to benzothiophene at high concentration of 100 ppm sulfur. The SiO2-coated Pd/HA shows no activity for tetralin hydrogenation, but continues to activate H2 and serve as a source of hydrogen spillover from Pd/HA since these metal sites are protected from thiophenic sulfur due to size-selective exclusion. Adding K ion-exchanged and SiO2-coated catalyst SiO2-Pd/KA to Pd/HY is even more effective for enhancing sulfur tolerance, both for tetralin hydrogenation and for isomerization of cis-decalin to trans-decalin in the presence of benzothiophene. The turnover frequencies (TOF) of all the catalysts are similar at the exposed sulfur/Pd atomic ratio of around 0.5. With further increase in sulfur/Pd ratio, rapid decline in TOF was observed on Pd/HY, but SiO2-Pd/KA + Pd/HY hybrid catalyst shows a significantly higher TOF than that over Pd/HY, even though SiO2-Pd/KA or SiO2-Pd/HA alone shows no TOF for tetralin hydrogenation. Even after high-dose poisoning at 400 ppm sulfur, the SiO2-Pd/KA + Pd/HY hybrid recovered activity more quickly than SiO2-Pd/HA + Pd/HY, while the latter in turn is much better than Pd/HY alone. These results point to the higher activity for hydrogen spillover from SiO2-Pd/KA where Pd metal sites are protected from not only thiophenic sulfur but also inorganic sulfur H2S by shape-selective exclusion. The present work further establishes the validity of shape-selective exclusion and hydrogen spillover in the design concept proposed for a sulfur-tolerant bimodal acidic zeolite-supported metal catalyst for hydrogenation of naphthalene [C.S. Song, Chemtech, 29 (1999) 26–30], and refines the design concept further for limiting the size of small pore in hybrid catalysts to ∼ 3 Å for restricting access of H2S but allowing entrance of H2. This refined design concept is applicable to other supported monometallic and bimetallic catalysts.

Graphene modified porous organic polymer supported phosphotungstic acid catalyst for alkylation desulfurization

A new strategy of using graphene to modify porous organic solid acid catalyst for alkylation desulfurization is proposed by taking advantage of the π-π interaction between graphene and thiophenic sulfur. A graphene-modified sulfonated porous organic polymer (POP) supported phosphotungstic acid (HPW) catalyst (HPW/POP-G-SO3H) is successfully prepared by the solution polymerization-sulfonation-impregnation method. Steam adsorption experiment results show that graphene modification could increase the adsorption capacity of 3- methylthiophene (3-MT), but has little effect on the adsorption of isopentane; therefore, the selective adsorption of 3-MT could be enhanced. DFT calculations plus dispersion corrections also show that the adsorption energy of 3-MT on graphene is higher than that of isopentene on graphene and higher than those of 3-MT and isopentene on sulfonated POP. Subsequently, the catalytic activity test of alkylation desulfurization confirms that graphene-modified supported HPW catalyst shows higher alkylation desulfurization activity. This could support our assumptions. After recycles of 6 times, the 3-MT conversion on HPW/POP-G-SO3H catalyst decreases slightly, which possesses good recycling performance. Therefore, HPW/POP-G-SO3H catalyst will have broad application prospects in the field of alkylation desulfurization.

Metal-free aerobic oxidative desulfurization over a diethyltriamine-functionalized aromatic porous polymer

A new cross-linked aromatic porous polymer (CAPP) from bifonazole and 4,4′-bis(bromomethyl)biphenyl was prepared and functionalized with diethyltriamine (DETA). The product CAPP-DETA was applied as a catalyst for the removal of thiophenic sulfur compounds via oxidative desulfurization: 100% conversion of dibenzothiophene (DBT) was achieved with 50 mg of CAPP-DETA for 400 ppm DBT in decane at 120 °C after 4 h using O2 as the oxidant. The reaction was carried out under different reaction conditions of temperature (80 to 140 °C), catalyst amount (10 to 50 mg), and concentration (200 to 1000 ppm). Radical scavenger experiments indicated the reaction involving the triamine functionality in the catalyst generating the superoxide (O2•-) radicals. The conversion efficiency among the thiophenic compounds followed a sequence of dibenzothiophene > benzothiophene > thiophene. The catalyst was reusable for four repetitive cycles without deterioration in catalytic activity.

Characterization and genomic analysis of Gordonia alkanivorans 135, a promising dibenzothiophene-degrading strain

Sulfur is the third most abundant element in crude oil. Up to 70 % of sulfur in petroleum is found in the form of dibenzothiophene (DBT) and substituted DBTs. The aim of this work was to study the physiological, biochemical and genetical characteristics of Gordonia alkanivorans 135 capable of using DBT as the sole source of sulfur. The genome of G. alkanivorans 135 consists of a 5,039,827 bp chromosome and a 164,963 bp circular plasmid. We found the absence of dsz operon present in most DBT degrading bacteria, but discovered other genes that are presumably involved in DBT utilization by G. alkanivorans 135. The strain utilized 45.26 % of DBT within 150 h of growth at 26 °C. This is the first strain of Gordonia capable of absorbing thiophene sulfur without the aid of the dsz genes.