Jorge Beltramini

Chemoselective catalytic conversion of glycerol as a biorenewable source to valuable commodity chemicals

New opportunities for the conversion of glycerol into value-added chemicals have emerged in recent years as a result of glycerols unique structure, properties, bioavailability, and renewability. Glycerol is currently produced in large amounts during the transesterification of fatty acids into biodiesel and as such represents a useful by-product. This paper provides a comprehensive review and critical analysis on the different reaction pathways for catalytic conversion of glycerol into commodity chemicals, including selective oxidation, selective hydrogenolysis, selective dehydration, pyrolysis and gasification, steam reforming, thermal reduction into syngas, selective transesterification, selective etherification, oligomerization and polymerization, and conversion of glycerol into glycerol carbonate.

Catalytic conversion of lignocellulosic biomass to fine chemicals and fuels

Lignocellulosic biomass is the most abundant and bio-renewable resource with great potential for sustainable production of chemicals and fuels. This critical review provides insights into the state-of the-art accomplishments in the chemocatalytic technologies to generate fuels and value-added chemicals from lignocellulosic biomass, with an emphasis on its major component, cellulose. Catalytic hydrolysis, solvolysis, liquefaction, pyrolysis, gasification, hydrogenolysis and hydrogenation are the major processes presently studied. Regarding catalytic hydrolysis, the acid catalysts cover inorganic or organic acids and various solid acids such as sulfonated carbon, zeolites, heteropolyacids and oxides. Liquefaction and fast pyrolysis of cellulose are primarily conducted over catalysts with proper acidity/basicity. Gasification is typically conducted over supported noble metal catalysts. Reaction conditions, solvents and catalysts are the prime factors that affect the yield and composition of the target products. Most of processes yield a complex mixture, leading to problematic upgrading and separation. An emerging technique is to integrate hydrolysis, liquefaction or pyrolysis with hydrogenation over multifunctional solid catalysts to convert lignocellulosic biomass to value-added fine chemicals and bio-hydrocarbon fuels. And the promising catalysts might be supported transition metal catalysts and zeolite-related materials. There still exist technological barriers that need to be overcome (229 references).

Transforming Triglycerides and Fatty Acids into Biofuels

Fuels derived from biobased materials are attracting attention for their potential in securing the energy supply and protecting the environment. In this Minireview, we evaluate the use of biobased sources, particularly fatty acids and triglycerides from seed oils and animal fats, as fuels. The physical and chemical properties of these fatty acids and triglycerides are discussed, including the link to their sources and current availability to meet fuel demands. The current technologies, also known as the first-generation ones, for converting triglycerides into fuels are covered, including conventional methods such as transesterification, pyrolysis, cracking, and emulsions. Recent, second-generation technological developments that lead to more commercially viable biofuels based on diesel-like hydrocarbons are also discussed.

Conversion of cellulose to polyols over promoted nickel catalysts

Sorbitol is one of the key platform chemicals that can be applied to several industrial applications, including bio-fuels and hydrogen production. Presently there is no commercial heterogeneous catalytic process to produce sorbitol from cellulose due to the low yield and high cost of noble metals required for the conversion. In this paper we describe an aqueous phase hydrolysis–hydrogenation process to convert cellulose to sorbitol using a cheap Ni based catalyst. Monometallic Ni catalysts showed little activity for the reaction, but with the addition of a small amount of Pt to the Ni catalyst (Ni : Pt = 22 : 1 atom ratio), the activity was greatly enhanced. Results showed that the bimetallic Ni–Pt catalysts supported on mesoporous alumina gave a hexitol (sorbitol + mannitol) yield of 32.4% compared to only 5% with a Ni catalyst. Moreover, Ni–Pt supported on a mesoporous beta zeolite support provided even higher yield of 36.6%. These results were obtained after only 6 hours of run at 200 °C and 50 bar H2 pressure (at room temperature). The presence of a small amount of Pt promotes the protonation of water and hydrogen molecules, which spill over to Ni sites creating in situ acid sites to catalyse hydrolysis of cellulose.

Catalytic Conversion of Glucose to 5‐Hydroxymethyl‐furfural with a Phosphated TiO2 Catalyst

Nanosized phosphated TiO2 catalysts with different phosphate contents were synthesized and tested for the conversion of glucose to 5‐hydroxymethylfurfural. The resulting materials were characterized by using N2‐adsorption, XRD, inductively coupled plasma atomic emission spectroscopy, X‐ray spectroscopy, TEM, temperature‐programmed desorption of ammonia, and FTIR spectroscopy of pyridine adsorption techniques to determine their structural, bulk, surface, and acid properties. We found that TiO2 nanoparticles catalyzed this reaction under mild conditions in a water–butanol biphasic system. The incorporation of phosphorus into the TiO2 framework remarkably enhances the target product selectivity, which is ascribed to increased surface area, enhanced acidity, as well as thermal stability resulting from the TiOP bond formation. Under optimal reaction conditions, phosphated TiO2 was found to exhibit excellent catalytic performance, which resulted in 97 % glucose conversion and 81 % HMF yield after 3 h of reaction at 175 °C. More importantly, the catalyst showed good stability and could be reused for several reaction cycles.

Transfer Hydrogenation of Cellulose-based Oligomers over Carbon-supported Ruthenium Catalyst in a Fixed-bed Reactor

Ru supported on activated carbon was found to be active for the transfer hydrogenation of cellulose oligomers, which were produced by the milling of acidulated microcrystalline cellulose. A C6 sugar alcohol yield of 85 % was obtained in less than 1 h reaction time in a batch reactor. Optimum reaction conditions for transfer hydrogenation were determined as 180 °C and a pH above 2.2 using glucose as a substrate. Use of deuterium as a marker established that direct transfer of hydride species from 2‐propanol to glucose occurs through the dihydride mechanism. Formation of molecular hydrogen from 2‐propanol dehydrogenation was found to be a side reaction, with little influence on the glucose hydrogenation step. Conversion of cellulose oligomers to hexitols was also achieved in a continuous flow fixed‐bed reactor with 36.4 % yield at a liquid hourly space velocity of 4.7 h−1. The catalytic activity did not decrease even after 12 h of the onstream reaction.

Direct Production of 5‐Hydroxymethylfurfural via Catalytic Conversion of Simple and Complex Sugars over Phosphated TiO2

A water-THF biphasic system containing N-methyl-2-pyrrolidone (NMP) was found to enable the efficient synthesis of 5-hydroxymethylfurfural (HMF) from a variety of sugars (simple to complex) using phosphated TiO2 as a catalyst. Fructose and glucose were selectively converted to HMF resulting in 98 % and 90 % yield, respectively, at 175 °C. Cellobiose and sucrose also gave rise to high HMF yields of 94 % and 98 %, respectively, at 180 °C. Other sugar variants such as starch (potato and rice) and cellulose were also investigated. The yields of HMF from starch (80-85 %) were high, whereas cellulose resulted in a modest yield of 33 %. Direct transformation of cellulose to HMF in significant yield (86 %) was assisted by mechanocatalytic depolymerization-ball milling of acid-impregnated cellulose. This effectively reduced cellulose crystallinity and particle size, forming soluble cello-oligomers; this is responsible for the enhanced substrate-catalytic sites contact and subsequent rate of HMF formation. During catalyst recyclability, P-TiO2 was observed to be reusable for four cycles without any loss in activity. We also investigated the conversion of the cello-oligomers to HMF in a continuous flow reactor. Good HMF yield (53 %) was achieved using a water-methyl isobutyl ketone+NMP biphasic system.

Guaiacol hydrodeoxygenation reaction catalyzed by highly dispersed, single layered MoS2/C

Highly disordered MoS2, dispersed on a carbon support was prepared by a microemulsion technique and its application as a catalyst for hydrodeoxygenation of guaiacol, a typical model compound of lignin, was investigated. The deoxygenation reaction was the predominant route, producing phenol as a major product. It is also demonstrated that the single layered MoS2/C catalyst showed superior activity and better deoxygenation and hydrogenation properties than the stacked MoS2/C catalyst. The reusability test showed good catalyst stability after 4 catalytic cycles were performed. Catalyst surface morphological changes, sulphur loss and its effect on conversion of guaiacol and selectivity to products were studied using multiple analytical methods such as TEM, XPS, CHNS, N2 adsorption and Raman analyses. The performance of the MoS2-based catalyst during guaiacol HDO reactions indicated its potential for upgrading of lignin.

High yield conversion of cellulosic biomass into 5-hydroxymethylfurfural and a study of the reaction kinetics of cellulose to HMF conversion in a biphasic system

Catalytic technology for cellulosic biomass conversion has been proven to be a promising approach for valuable chemical feedstock production. However, its recalcitrant nature is a major limitation to unlocking the carbohydrate biopolymer content and their subsequent conversion into 5-hydroxymethylfural (HMF). This paper investigates the production of HMF using glucose, cellulose, sugarcane bagasse and rice husk as the feedstocks. Acid dehydration of the carbohydrate sources was conducted in a biphasic system of water–MeTHF modified with N-methyl-2-pyrrolidone (NMP) over a phosphated TiO2 catalyst. The catalyst displayed a very good catalytic performance for the conversion of glucose into HMF (91% yield). More so, it is suitable for the selective conversion of mechanocatalytic depolymerized cellulose to 74.7% yield of HMF. Cellulosic biomass could also be directly converted into HMF and furfural in reasonable yields. The efficiency of biomass-to-HMF production was further advanced after biomass fractionation treatment. Remarkable yields of 72% and 65% HMF were produced from sugarcane bagasse and rice husk, respectively. Finally, the reaction kinetics of solubilized cellulose to HMF conversion was investigated and a simplified kinetic model comprising two reaction steps was developed: (1) hydrolysis of cello-oligomers to glucose and (2) glucose dehydration to HMF.

Recent advances in hybrid periodic mesostructured organosilica materials: opportunities from fundamental to biomedical applications

Surfactant-mediated periodic mesoporous organosilicas (PMOs) with different organic and inorganic functions in the framework structure were discovered in 1999. The silica inorganic function gives a strong mechanical stability to the framework structure and the organic functionality creates more structural flexibility. As a result, their use is optimal for a large number of applications including catalysis, microelectronics, chromatographic supports, selective adsorbents, sensors, protein folding, biomedical devices and light-harvesting devices. These new materials showed also superior stability when compared to pure mesoporous silica (PMS) framework structures. Based on the recent discoveries, since 2012, this review mostly provides a comprehensive overview of their multidisciplinary options for various applications.