Recent advances in the science and technology of ultra low sulfur diesel (ULSD) production

The preparation, characterization, and catalytic activity of supported metal phosphides are reviewed. Reduction of metal compounds together with phosphate is a convenient method to prepare metal phosphides, but requires high temperature. Reduction with phosphite, hypophosphite, or phosphine and the plasma reduction of phosphate can be carried out at lower temperatures, which leads to smaller metal phosphide particles and more active catalysts. Organometallic routes allow the separate synthesis of metal phosphide nanoparticles, which have to be added to the support in a second step. LEED, STM, XPS, and DFT studies have shown that the surfaces of Ni2P reconstruct to P-rich surfaces. The investigation of metal phosphides as catalysts for hydrotreating reactions continues to be a topic of considerable research with recent advances realized in using bimetallic and noble metal phosphides to achieve high activities and tailored selectivities. Finally, hydrodeoxygenation catalysis over metal phosphides is a growing area of research given the need to develop catalysts for upgrading biomass to transportation fuels.

Metal Phosphides: Preparation, Characterization and Catalytic Reactivity

Biomass pyrolysis oil has been reported as a potential renewable biofuel precursor. Although several review articles focusing on lignocellulose pyrolysis can be found, the one that particularly focus on lignin pyrolysis is still not available in literature. Lignin is the second most abundant biomass component and the primary renewable aromatic resource in nature. The pyrolysis chemistry and mechanism of lignin are significantly different from pyrolysis of cellulose or entire biomass. Therefore, different from other review articles in the field, this review particularly focuses on the recent developments in lignin pyrolysis chemistry, mechanism, catalysts, and the upgrading of the bio-oil from lignin pyrolysis. Although bio-oil production from pyrolysis of biomass has been proven on commercial scale and is a very promising option for production of renewable chemicals and fuels, there are still several drawbacks that have not been solved. The components of biomass pyrolysis oils are very complicated and related to the properties of bio-oil. In this review article, the details about pyrolysis oil components particularly those from lignin pyrolysis processes will be discussed first. Due to the poor physical and chemical property, the lignin pyrolysis oil has to be upgraded before usage. The most common method of upgrading bio-oil is hydrotreating. Catalysts have been widely used in petroleum industry for pyrolysis bio-oil upgrading. In this review paper, the mechanism of the hydrodeoxygenation reaction between the model compounds and catalysts will be discussed and the effects of the reaction condition will be summarized.

Lignin Pyrolysis Components and Upgrading—Technology Review

Exploration of sustainable alternatives to chemicals derived from petro-based industries is the current challenge for maintaining the balance between the needs of a changing world while preserving nature. The major source for sustainable chemicals is either the natural existing plant sources or waste generated from agro-based industries. The utility of such resources will supplement new processed materials with different sets of properties and environmental friendliness due to their biodegradability and low toxicity during preparation, usage and disposal. Amongst other polymers used on a day-to-day basis, phenolic resins account for vast usage. Replacement of petro-based monomers such as phenol and its derivatives either partly or completely utilized for the synthesis of such resins is ongoing. Extraction of natural phenolic components from cashew nut shell liquid, lignin, tannin, palm oil, coconut shell tar or from agricultural and industrial waste, and their utilization as synthons for the preparation of bio-based polymers and properties obtained are reviewed in this paper. This review article is designed to acknowledge efforts of researchers towards the “3C” motto – not only trying to create but also adapting the principles to conserve and care for a sustainable environment. This review paper describes how extraction, separation and recovery of desired phenolic compounds have occurred recently; how substituted phenol compounds, unmodified and modified, act as monomers for polymerization; and how the presence of sustainable phenolic material affects the properties of polymers. There are about 600 references cited and still there is a lot to uncover in this research area.

Naturally occurring phenolic sources: monomers and polymers

The reduction of the sulfur content in gasoline and diesel fuel has been a subject of intense investigation in recent years because the sulfur level must in many countries be reduced to 10 ppm by the year 2010 for environmental reasons, while for fuel-cell applications the sulfur content should be below 0.1 ppm. To reach this low level, even highly refractory molecules such as 4,6-dimethyldibenzothiophene (4,6-DMDBT) must be desulfurized. However, because of steric hindrance by the methyl groups adjacent to the sulfur atom, desulfurization of 4,6-DM-DBT mainly takes place after the molecule has first been hydrogenated. Therefore, the hydrogenating ability of the catalyst is of critical importance for deep hydrodesulfurization (HDS). Recent studies have shown that noble-metal-supported catalysts have much better hydrogenation performance than conventional metal sulfides in HDS, and may be used in the second reactor of a deep HDS process. Not only the active catalyst, but also the support plays an important role in the catalytic performance of catalysts. Acidic supports can increase the conversion of dibenzothiophene (DBT) and of 4,6-DM-DBT. One explanation for this is that they enable dealkylation and isomerization reactions of the alkyl substituents, which may transform refractory components into more reactive species and thus accelerate HDS. Moreover, acidic supports may also improve the catalytic activity of the catalyst particles. Since partial electron transfer can occur from the metal particles to acidic sites of the support, the resulting electron-deficient metal particles are deemed to have a better resistance to sulfur poisoning by decreasing the interaction with H2S. [5b,6] Another explanation for this improvement is the creation of a second hydrogenation pathway by spillover of hydrogen atoms from the metal particles to the aromatic sulfurcontaining molecules that are adsorbed on acidic sites in the vicinity of the metal particles. While the metal particles become poisoned by sulfur, they can still dissociate hydrogen molecules, and thus the hydrogenation pathway involving spillover would still be possible. It is well known that zeolites possess strong acidity, high stability, and a regular pore array, and are for these reasons applied in many industrial catalytic reactions. However, their small pore size means that relatively large molecules such as 4,6-DM-DBT cannot enter the pores; they can only react on the outer surface of the zeolites and cannot reach many active centers. A support with strong acidity and relatively large pores would, therefore, be preferred. The recent discovery of mesoporous zeolites with their hierarchical porosity and strong acidity opens the possibility of using them as supports in HDS. However, until now their use as a support in HDS has not been reported. Herein we report on Pt, Pd, and Pt-Pd catalysts supported on mesoporous Na-ZSM-5. The catalytic activity and selectivity of these catalysts were studied in the HDS of 4,6-DMDBT, and the hydrocarbon products as well as the hydrogenated intermediates were analyzed. Compared with conventional Na-ZSM-5or g-Al2O3-supported catalysts, the mesoporous Na-ZSM-5-supported catalysts exhibited much better catalytic performance for hydrodesulfurization. The powder XRD patterns of mesoporous Na-ZSM-5 (MNZ-5) and Na-ZSM-5 (NZ-5, see Figure S1 in the Supporting Information) show well-resolved peaks which are characteristic of the ZSM-5 zeolite structure. MNZ-5 exhibited a type IV N2 adsorption/desorption isotherm (see Figure S2 a in the Supporting Information) typical for mesoporous materials. In contrast, NZ-5 showed a type I isotherm, which is typical of microporous materials. Moreover, a uniform pore distribution centered at around 4.9 nm was observed for MNZ-5 (see Figure S2b in the Supporting Information). The detailed sorption data of both samples are listed in Table 1. The BET special surface area and mesoporous volume for MNZ-5 are 579 m g 1 and 0.44 cm g , respectively, much higher than those of NZ-5. The isomerization of 2-methyl-2-pentene (2M2P) is a good model reaction to evaluate the acidity of solid acids. The molar ratio of trans-3-methyl-2-pentene (trans-3M2P, obtained by shift of a methyl group) to transand cis-4methyl-2-pentene (transand cis-4M2P, respectively, obtained by shift of an H atom) in the product reflects the acidity of solid acids. The higher the molar ratio is, the stronger the acidity is. Table 1 shows that MNZ-5 resulted in a higher conversion in the isomerization of 2M2P than did NZ-5; this observation may be attributed to the high BET surface area of MNZ-5. The analysis of the Na content in the two zeolites showed that only 90 % of the Al atoms were charge-compensated by Na cations, so that about 10 % protons existed in NZ5 and MNZ-5, thus suggesting that they are indeed acidic supports. g-Al2O3, on the other hand, gave a lower conversion [*] Dr. Y. Sun, Prof. Dr. R. Prins Institute for Chemical and Bioengineering, ETH Z rich 8093 Z rich (Switzerland) Fax: (+ 41)44-632-1162 E-mail: prins@chem.ethz.ch

Hydrodesulfurization of 4,6-dimethyldibenzothiophene over noble metals supported on mesoporous zeolites.

Hydrodesulfurization of 4,6-dimethyldibenzothiophene and dibenzothiophene over alumina-supported Pt, Pd, and Pt-Pd catalysts

Hydrodesulfurization of 4,6-dimethyldibenzothiophene over Pt, Pd, and Pt–Pd catalysts supported on amorphous silica–alumina

Pyridine and piperidine inhibited the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DM-DBT) over Pt, Pd, and Pt−Pd catalysts supported on amorphous silica−alumina. Pyridine was a ...

Influence of Nitrogen-Containing Compounds on the Hydrodesulfurization of 4,6-Dimethyldibenzothiophene over Pt, Pd, and Pt−Pd on Amorphous Silica−Alumina Catalysts

Pyridine and piperidine inhibited the hydrodesulfurization of 4,6-dimethyldibenzothiophene (4,6-DM-DBT) over alumina-supported Pt, Pd, and Pt–Pd catalysts. The Pd catalyst was least sensitive and the Pt–Pd catalysts were most sensitive to the nitrogen-containing compounds. Pyridine was a stronger inhibitor than piperidine at low initial pressure, but the reverse was true at high initial pressure. Hydrogenation of the tetrahydro to the hexahydro and on to the perhydro sulfur-containing intermediate as well as the removal of sulfur from these intermediates was slowed down by piperidine and pyridine. The hydrogenation pathway in the hydrodesulfurization of 4,6-DM-DBT was inhibited much more than the direct desulfurization pathway. The hydrogenation of the desulfurized products 3,3′-dimethylcyclohexylbenzene and 3,3′-dimethylbiphenyl over the Pt–Pd catalysts was suppressed by piperidine and pyridine. Piperidine and pyridine substantially decrease the ability of noble metal particles to convert refractory molecules like 4,6-DM-DBT and diminish the advantage of bimetallic Pt–Pd over monometallic Pt or Pd catalysts.

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Adeline Niquille-Röthlisberger

Papers

Hydrodesulfurization of 4,6-dimethyldibenzothiophene and dibenzothiophene over alumina-supported Pt, Pd, and Pt-Pd catalysts

Hydrodesulfurization of 4,6-dimethyldibenzothiophene over Pt, Pd, and Pt–Pd catalysts supported on amorphous silica–alumina

Influence of Nitrogen-Containing Compounds on the Hydrodesulfurization of 4,6-Dimethyldibenzothiophene over Pt, Pd, and Pt−Pd on Amorphous Silica−Alumina Catalysts

Influence of nitrogen-containing components on the hydrodesulfurization of 4,6-dimethyldibenzothiophene over Pt, Pd, and Pt–Pd on alumina catalysts