Catalytic Upcycling of Polyethylene into Naphtha Using Commercial Heterogeneous Catalysts

Hydrodechlorination of tetrachloroethylene over sulfided catalysts: kinetic study

Many commercial heterogeneous catalysts are complex structures that contain metal active sites promoted by multiple additives. Developing fundamental understanding about the impact of these perturbations on the local surface reactivity is crucial for catalyst development and optimization. In this contribution, we develop a general framework for identifying underlying mechanisms that control the changes in the surface reactivity of a metal site (more specifically the adsorbate-surface interactions) upon a perturbation in the local environment. This framework allows us to interpret fairly complex interactions on metal surfaces in terms of specific, physically transparent contributions that can be evaluated independently of each other. We use Cs-promoted dissociation of O2 as an example to illustrate our approach. We concluded that the Cs adsorbate affects the outcome of the chemical reaction through a strong alkali-induced electric field interacting with the static dipole moment of the O2/Ag(111) system.

Hydrothermal liquefaction of corn stalk under CO atmosphere with three commercial heterogeneous catalysts was performed in a high pressure autoclave. The structure and reducibility of the catalysts were studied by X-ray diffraction and differential thermal gravity under H2 atmosphere. The results indicated that the catalysts greatly increased the conversion of cornstalk yield and heating value of liquid product. The activity order of the catalysts is as follows: JT203 > JT201 > JB-1, which is consistent with the high surface area and low reduction temperature of JT203. The catalysts might favor a hydrothermal liquefaction process through the active H produced by water-gas shift reaction.

The catalytic activity and stability of sulfonic-based UiO-66(Zr) materials were tested in the Friedel-Crafts acylation of anisole with acetic anhydride. The materials were prepared using microwave-assisted synthesis, producing microporous materials with remarkable crystallinity and physicochemical features as acid catalysts. Different ratios between both organic ligands, terephthalic acid (H2BDC) and monosodium 2-sulfoterephthalic acid (H2BDC-SO3Na), were used for the synthesis to modulate the sulfonic content. The sulfonic-based UiO-66(Zr) material synthesized with a H2BDC/H2BDC-SO3Na molar ratio of 40/60 exhibited the best catalytic performance in the acidic-catalyzed Friedel-Crafts acylation reaction. This ratio balanced the number of sulfonic acid sites and their accessibility within the UiO-66 microporous structure. The catalytic performance of this material increased remarkably at 200 °C, outperforming reference acids and commercial heterogeneous catalysts such as Nafion-SAC-13 and Amberlyst-70. Additionally, the best sulfonic-based UiO-66(Zr) material proved to be stable in four successive reaction cycles, maintaining both its catalytic activity and its structural integrity.

Recent legislation directed at reducing nitrogen levels in fossil fuels has led to numerous studies of the hydrodenitrogenation (HDN) process, whereby nitrogen is removed from organic compounds in petroleum feedstocks. In this review a comprehensive study of the coordination, activation, hydrogenation, hydrogenolysis and denitrogenation of N-heterocycles assisted by transition metal complexes in either fluid solution or single-site systems, is reported. Furthermore, similarities to the reactions occurring in the HDN process over commercial heterogeneous catalysts are also discussed.

Short-chain fatty acids (SCFAs) have been used as raw materials in wide range of chemical and medical applications. One technique to produce SCFAs is oxidative cleavage of long-chain fatty acids (LCFAs). However, unless the LCFAs are unsaturated, the yield of SCFAs is often very low because the carboxylic group of the fatty acid is more active than other part of the molecule. This work explores the idea of introducing a double bond into saturated LCFA, i.e., stearic acid, via selective dehydrogenation using commercial heterogeneous catalysts. However, cracking of the LCFA is also catalysed. Different type of metals was therefore investigated to study the effect of metals on the cracking and dehydrogenation. The experiments were conducted in an autoclave reactor under inert atmosphere. The temperature was in the range of 250–350°C. The products were analysed by gas chromatography equipped with mass spectroscopy (GC/MS). The results reveal that the introduction of double bond in the aliphatic chain of the stearic acid is possible although the yields of the unsaturated LCFAs are low. Effects of various parameters, such as temperature, pressure, and reaction time, were also investigated and reported.

Molecular hydrogenation catalysts have been co-entrapped with the ionic liquid [Bmim]NTf(2) inside a silica matrix by a sol-gel method. These catalytic ionogels have been compared to simple catalyst-doped glasses, the parent homogeneous catalysts, commercial heterogeneous catalysts, and Rh-doped mesoporous silica. The most active ionogel has been characterised by transmission electron microscopy, X-ray photoelectron spectroscopy, and solid state NMR before and after catalysis. The ionogel catalysts were found to be remarkably active, recyclable and resistant to chemical change.

Solketal has been identified as one of the most promising chemical entities among oleochemicals. Process intensification protocols such as continuous flow technology add a new dimension and a promising toolbox for ketalisation of bio-based abundant polyol, glycerol. This review discusses recent advances in the catalytic ketalisation of glycerol encompassing homogeneous catalysts, commercial heterogeneous catalysts and specifically designed heterogeneous catalysts in the laboratories.

A study on hydrogen uptake and release of a eutectic mixture of biphenyl and diphenyl ether

Solid surfaces act as catalysts for many important chemical processes, including commodity chemicals production, energy conversion and pollution mitigation. The outcome of catalytic processes is mainly governed by interactions of adsorbates with active sites on the catalyst surface. These interactions can be dramatically affected by the changes in the local characteristics of the active site, which can be accomplished by an introduction of various promoters and poisons, or by alloying with other metal atoms. In fact, many commercial heterogeneous catalysts contain metal nanoparticles promoted by various additives. Our goal is to develop fundamental understanding about the impact of perturbations in the local geometry of a catalytic site on the local surface reactivity. These insights are crucial for a more systematic and rational catalyst design. The project aims to advance the field of catalysis by formulating reliable structure/performance relationships and utilizing these relationships to identify novel catalytic materials. Benefits for DOE and our society are in the development of fundamental theories that guide the process of discovery of energy-efficient and environmentally friendly heterogeneous catalysis.

The growing need for alternative sources of transportation fuels encourages the development of new hydrotreatment catalysts. These catalysts must be active and more hydrogen efficient than the current commercial hydrotreatment catalysts. Molybdenum nitrides and carbides are attractive candidate materials possessing properties that are comparable or superior to those of commercial sulfide catalysts. This research investigated the catalytic properties of γ-Al2O3-supported molybdenum nitrides and carbides. These catalysts were synthesized via temperature-programmed reaction of supported molybdenum oxides with ammonia or methane/hydrogen mixtures. Phase constituents and compositions were determined by X-ray diffraction, elemental analysis, and neutron activation analysis. Oxygen chemisorption was used to probe the surface properties of the catalysts. Specific activities of the molybdenum nitrides and carbides were competitive with those of a commercial sulfide catalyst for hydrodenitrogenation (HDN), hydrodesulfurization (HDS), and hydrodeoxygenation (HDO). For HDN and HDS, the catalytic activity on a molybdenum basis was a strong inverse function of the molybdenum loading. Product distributions for the HDN, HDO, and HDS of a variety of heteroatom compounds indicated that several of the nitrides and carbides were more hydrogen efficient than the sulfide catalyst.

It is predictable that liquid fuels will be needed for long distance transport sector for quite some years. Thus, it is imperative to find alternative fuels to reduce the dependency on petroleum derived fuels and to decrease the negative environmental impact. Co-liquefaction of coal and wastes, like plastics, to produce liquid fuels and raw materials for several industries may play an important role in the near future, because it will decrease the problems associated with the dependency of only one raw material and also it will allow taking profit of the suitable properties of each one, while diluting the disadvantageous characteristics of coal. The use of plastics, namely polyethylene (PE) favoured coal liquefaction, as PE macromolecules are easier to break down and to form smaller liquid molecules than coal. To improve the production of liquid compounds by coal liquefaction solvents with different hydrogen donor capabilities were tested, such as: methylnaphthalene and tetralin. Tetralin led to the highest liquid yields and conversion, due to its hydrogen donor capacity. Some commercial available catalysts, like FCC (Fluid Catalytic Cracking) and Co-Mo based were also tried. Coal impregnated with some metals like iron (Fe) and molybdenum (Mo) was also tested. Impregnated coal, especially with Mo showed to have a better performance than the commercial catalysts. Liquid yield obtained during co-liquefaction of coal and PE when coal was impregnated with Mo was around 66 wt%. The use of tetralin allowed increasing this value around 44 %.

Sulfide cluster‐derived ensembles are promising models of the active sites in commercial hydrotreatment catalysts. A series of sulfide clusters were adsorbed intact onto high‐surface‐area γ‐alumina, magnesium oxide and activated carbon supports, then pretreated to produce highly dispersed catalytic ensembles with sizes similar to those of their precursor clusters. The activities of the bimetallic cluster‐derived catalysts were significantly higher than those of the monometallic catalysts. We took this as evidence that direct interactions between molybdenum and the promoter element cause the promotional effect observed in commercial hydrotreatment catalysts. The hydrodesulfurization and hydrodenitrogenation activities correlated with the extent of molybdenum reduction. Our results suggested that the active sites in promoted hydrotreatment catalysts are centered on molecular‐scale ensembles containing molybdenum, sulfur and the promoter element.

Selective hydrotreating and hydrocracking of FCC light cycle oil into high-value light aromatic hydrocarbons

This is the first ever study assessing the possibility of dimethyl ether (DME) production through gasification of Victorian brown coal. This project involves gasification of Victorian brown coal and catalyst development for syngas to DME conversion process. Victoria has large reserves of brown coal, 430 billion tonnes at current estimate. Use of Victorian brown coal is currently limited mostly to mine-mouth power generation because of high moisture content of the as-mined coal and high reactivity of the dried coal; both these properties make Victorian brown coal, raw or dried, unexportable. Gasification based alternative processing paths can provide export market for brown coal derived products, and more energy efficient application of brown coal. Syngas from Victorian brown coal can be catalytically converted into DME with higher energy efficiency and at potentially lower CO₂ emission. DME is a non-toxic, non-carcinogenic and non-corrosive compound. In addition, it has wide application as a fuel in cars, gas turbines, fuel cells and household applications. A process simulation for as-mined Victorian brown coal to DME was performed using ASPEN Plus. The simulation study shaped the experimental matrix as it provided a realistic range of operating conditions (e.g. gasification temperature and syngas H₂ to CO ratio). CO₂ Gasification kinetics for raw parent coal as well as demineralised and catalyst-loaded (Ca, Fe) coals were studied using a thermogravimetric analyser. Pyrolysis and gasification of the coal was performed in an entrained flow reactor (EFR) and the solid, liquid and gaseous products were characterised. DME synthesis experiments were performed in a high pressure fixed-bed reactor, using commercial and developed catalysts, and synthetic syngas consisting H₂ and CO. A 3² factorial experimental design was used to optimise catalyst composition and syngas ratio (H₂ to CO). The developed catalysts were prepared based on the information generated from preliminary experiments with commercial catalysts. Physical mixing and coprecipitation-impregnation methods were used for the preparation of bi-functional DME synthesis catalysts. Performance (CO conversion, DME yield and DME selectivity) of the developed catalysts was compared with that of commercial catalysts. Effects of sulphur poisoning on CO-conversion, DME yield and DME selectivity were also studied. Process simulation using ASPEN plus showed that the low temperature gasification at 900 °C can produce syngas with appropriate H₂ to CO ratio. The ratio was found to be 0.81 at the gasifier outlet (before the recycle stream) and 1.41 at the DME reactor inlet (after the recycle stream). The overall process efficiency was found to be ∼ 32% after considering the energy penalty for CO₂ separation, higher than the power generation efficiency of 28% (without CO₂ separation). Two kinetic models (Grain model and random pore model) were used to find the intrinsic CO₂ gasification kinetics. Random pore model predicted the experimental results better than the grain model. The activation energy for char-CO₂ gasification was ∼189 kJ/mol. Ca-loaded coal char showed better gasification reactivity. However, addition of iron did not show any improvement. The results indicate that the effect of minerals become insignificant at 1000 °C or above and catalytic gasification showed be carried out below this temperature. EFR studies showed that the tar yield rapidly decreased as the gasification temperature was increased. The residence time and gasification temperature in the EFR were not enough for complete carbon conversion. In situ synchrotron radiation X-ray diffraction on methanol and DME synthesis catalysts showed rapid catalyst deactivation at temperatures above 300 °C, resulted from phase mobility and thermal sintering. The extent of deactivation was higher for the bi-functional DME catalyst compared to the methanol synthesis catalyst. Regression analysis on the yield data, obtained using commercial catalysts, showed that a H₂ to CO ratio of 1.45 and a catalyst consisting 58% methanol synthesis component results maximum DME yield. Among the four developed catalysts (DSC-1, DSC-2, DSC-M, DSC-1-PRE), three catalysts (except DSC-1-PRE) showed performance similar or better than the commercial catalyst mixture M1A1. CO conversion was between 67-70% for the DSC-1 catalyst, best among the developed catalysts, compared to 58-60% conversion for the M1A1 catalyst. DME yield was 36-40% and 35-38% for the DSC-1 and M1A1, respectively. A 10 hour exposure of the catalyst to 103 ppm H₂S showed at least 12% reduction in conversion and yield, indicating rapid deactivation in the catalyst activity. All the results were at least duplicated, and triplicated in most of the cases. The obtained results positively indicate that the conversion of syngas from Victorian brown coal to DME is a feasible option.