From CO2 methanation to ambitious long-chain hydrocarbons: alternative fuels paving the path to sustainability

The clean and sustainable CO2 reutilization toward products of higher value is of great interest in a background of established environmental concerns and reducing the use of fossil fuels. As promising alternative fuels, hydrocarbons are more valuable than CO, alcohols or formate and can be directly used in existing infrastructures with high energy densities. The prominent development of catalysts capable of selectively converting CO2 into hydrocarbons, from methane to short olefins and long carbon-chains, has been reflected in an expanding volume of exploratory works, which suitably demand interpretive and continuous revision. In the past decades, conventional studies on the thermochemical conversion of CO2 have consistently unlocked meaningful pathways toward the synthesis of hydrocarbons covering a fairly wide range of molecular weights. Conversely, both electrochemically and photochemically driven reactions have only now started to unveil encouraging results, with an extensive number of critical citations outlining the continuous emergence of very recently published reports. In a field in need of urgent development, the authors provide, in a clear form, a detailed retrospective on benchmark catalysts, pioneering approaches and competitive developments in this subject, mechanistic difficulties, emerging stability issues, and reactor design, while highlighting the latest noteworthy reports. Most importantly, this review highlights the advances toward an increase in the hydrocarbon chain-length in the synthesis of highly competitive alternative fuels. Comparisons of valuable thermochemical, electrochemical and photochemically driven strategies in the conversion of CO2 to hydrocarbons are expected to serve as guidelines to disclose promising pathways in a field where mechanistic uncertainties remain a bottleneck for determining the product selectivity. The authors summarize leading and inquisitive perspectives with a focus on the viability and practicability of each approach at a larger scale, while tentatively paving the way to stimulate progress in this field.</p

From CO2 methanation to ambitious long-chain hydrocarbons: alternative fuels paving the path to sustainability

The clean and sustainable CO2 reutilization toward products of higher value is of great interest in a background of established environmental concerns and reducing the use of fossil fuels. As promising alternative fuels, hydrocarbons are more valuable than CO, alcohols or formate and can be directly used in existing infrastructures with high energy densities. The prominent development of catalysts capable of selectively converting CO2 into hydrocarbons, from methane to short olefins and long carbon-chains, has been reflected in an expanding volume of exploratory works, which suitably demand interpretive and continuous revision. In the past decades, conventional studies on the thermochemical conversion of CO2 have consistently unlocked meaningful pathways toward the synthesis of hydrocarbons covering a fairly wide range of molecular weights. Conversely, both electrochemically and photochemically driven reactions have only now started to unveil encouraging results, with an extensive number of critical citations outlining the continuous emergence of very recently published reports. In a field in need of urgent development, the authors provide, in a clear form, a detailed retrospective on benchmark catalysts, pioneering approaches and competitive developments in this subject, mechanistic difficulties, emerging stability issues, and reactor design, while highlighting the latest noteworthy reports. Most importantly, this review highlights the advances toward an increase in the hydrocarbon chain-length in the synthesis of highly competitive alternative fuels. Comparisons of valuable thermochemical, electrochemical and photochemically driven strategies in the conversion of CO2 to hydrocarbons are expected to serve as guidelines to disclose promising pathways in a field where mechanistic uncertainties remain a bottleneck for determining the product selectivity. The authors summarize leading and inquisitive perspectives with a focus on the viability and practicability of each approach at a larger scale, while tentatively paving the way to stimulate progress in this field.</p

Mesostructured Zeolites

Mesoporous materials constructed with microporous zeolitic frameworks (i.e., mesoporous zeolites) are of great interest owing to the very short diffusion path lengths across thin zeolite layers and the presence of large external surfaces containing strong Brønsted acid sites. These characteristics of mesoporous zeolites are highly advantageous for a wide range of applications, particularly in heterogeneous catalysis. The mesoporous materials show unprecedentedly high catalytic performances (e.g., high catalytic conversion and catalytic longevity) as zeolites in various petrochemical reactions and fine-chemical organic reactions and especially in reactions involving bulky molecules. In this chapter, we describe the various methods currently available for the synthesis of mesoporous zeolites.</p

Method for converting paraffin feedstock from biomass into middle distillate bases using at least one catalyst based on the IZM-2 zeolite

Conversion of a paraffinic feedstock having 9-25 carbon atoms, is claimed, where: the paraffinic feedstock is produced from renewable resources; is obtained by a process involving performing Fischer-Tropsch method using a catalyst that comprises at least one hydrogenating-dehydrogenating metal that consists of metals of group VIB and group VIII of the periodic table and a substrate comprising at least one IZM-2 zeolite and at least one binder; and a total quantity of hydrogen is mixed with the feedstock such that the hydrogen/feedstock ratio is 70-2000 Nm 3>/m 3> of feedstock. Conversion of a paraffinic feedstock having 9-25 carbon atoms, is claimed, where: the paraffinic feedstock is produced from renewable resources; is obtained by a process involving performing Fischer-Tropsch method using a catalyst that comprises at least one hydrogenating-dehydrogenating metal that consists of metals of group VIB and group VIII of the periodic table and a substrate comprising at least one IZM-2 zeolite and at least one binder; the Fischer-Tropsch method is performed at a temperature of 150-500[deg] C, a pressure of 0.1-15 MPa and an hourly volumetric flow rate of 0.1-10 h -> 1>; and a total quantity of hydrogen is mixed with the feedstock such that the hydrogen/feedstock ratio is 70-2000 Nm 3>/m 3> of feedstock.</p

Mesostructured Zeolites

Mesoporous materials constructed with microporous zeolitic frameworks (i.e., mesoporous zeolites) are of great interest owing to the very short diffusion path lengths across thin zeolite layers and the presence of large external surfaces containing strong Brønsted acid sites. These characteristics of mesoporous zeolites are highly advantageous for a wide range of applications, particularly in heterogeneous catalysis. The mesoporous materials show unprecedentedly high catalytic performances (e.g., high catalytic conversion and catalytic longevity) as zeolites in various petrochemical reactions and fine-chemical organic reactions and especially in reactions involving bulky molecules. In this chapter, we describe the various methods currently available for the synthesis of mesoporous zeolites.</p

Method for converting paraffin feedstock from biomass into middle distillate bases using at least one catalyst based on the IZM-2 zeolite

Conversion of a paraffinic feedstock having 9-25 carbon atoms, is claimed, where: the paraffinic feedstock is produced from renewable resources; is obtained by a process involving performing Fischer-Tropsch method using a catalyst that comprises at least one hydrogenating-dehydrogenating metal that consists of metals of group VIB and group VIII of the periodic table and a substrate comprising at least one IZM-2 zeolite and at least one binder; and a total quantity of hydrogen is mixed with the feedstock such that the hydrogen/feedstock ratio is 70-2000 Nm 3>/m 3> of feedstock. Conversion of a paraffinic feedstock having 9-25 carbon atoms, is claimed, where: the paraffinic feedstock is produced from renewable resources; is obtained by a process involving performing Fischer-Tropsch method using a catalyst that comprises at least one hydrogenating-dehydrogenating metal that consists of metals of group VIB and group VIII of the periodic table and a substrate comprising at least one IZM-2 zeolite and at least one binder; the Fischer-Tropsch method is performed at a temperature of 150-500[deg] C, a pressure of 0.1-15 MPa and an hourly volumetric flow rate of 0.1-10 h -> 1>; and a total quantity of hydrogen is mixed with the feedstock such that the hydrogen/feedstock ratio is 70-2000 Nm 3>/m 3> of feedstock.</p

Mesoporous EU-1 zeolite as a highly active catalyst for ethylbenzene hydroisomerization

The hydroisomerization of ethylbenzene is an important industrial reaction to maximize the production of xylenes, and in particular, para-xylene. Zeolite EU-1 (with EUO topology) is commercially utilized in a physical mixture with a metallic phase (Pt/Al2O3). Herein, we have developed a micro-mesoporous EUO zeolite with a significant volume of intercrystalline mesoporosity to improve its catalytic performance in the industrial hydroisomerization of ethylbenzene. The use of a multivalent cationic surfactant as a capping agent was ideal to prevent uniform crystal growth and their aggregation, and to ensure the potential industrial applicability of the strategy. The corresponding mesoporosity and textural properties of nanosponge-like EUO were tuned according to the amount of the capping agent. The catalytic performance reflected the remarkable impact of a large exposed surface area (up to 55%) and a high amount of easily accessible Brønsted acid sites (up to 29%) in the EU-1 nanosponge on the catalytic yield. Our best catalyst revealed a three-fold increase in the conversion of ethylbenzene with no detrimental effects on the attained hydroisomerization yield. This approach presents a potential industrial capability in a wide range of catalytic applications as evidenced here in the hydroisomerization of ethylbenzene.</p

Mesoporous EU-1 zeolite as a highly active catalyst for ethylbenzene hydroisomerization

The hydroisomerization of ethylbenzene is an important industrial reaction to maximize the production of xylenes, and in particular, para-xylene. Zeolite EU-1 (with EUO topology) is commercially utilized in a physical mixture with a metallic phase (Pt/Al2O3). Herein, we have developed a micro-mesoporous EUO zeolite with a significant volume of intercrystalline mesoporosity to improve its catalytic performance in the industrial hydroisomerization of ethylbenzene. The use of a multivalent cationic surfactant as a capping agent was ideal to prevent uniform crystal growth and their aggregation, and to ensure the potential industrial applicability of the strategy. The corresponding mesoporosity and textural properties of nanosponge-like EUO were tuned according to the amount of the capping agent. The catalytic performance reflected the remarkable impact of a large exposed surface area (up to 55%) and a high amount of easily accessible Brønsted acid sites (up to 29%) in the EU-1 nanosponge on the catalytic yield. Our best catalyst revealed a three-fold increase in the conversion of ethylbenzene with no detrimental effects on the attained hydroisomerization yield. This approach presents a potential industrial capability in a wide range of catalytic applications as evidenced here in the hydroisomerization of ethylbenzene.</p

Impact of pore topology and crystal thickness of nanosponge zeolites on the hydroconversion of ethylbenzene

The gas-phase hydroconversion of ethylbenzene was investigated in the presence of intimate mixtures of *MRE, MFI and MTW-type zeolite nanosponges and a hydrogenating component (Pt/Al2O3). The nano-morphic zeolites were prepared using multiammonium surfactants acting as dual-porogenic agents directing the formation of micro- and mesopores simultaneously. The effects of the zeolite topology (pore size and dimensionality) and crystal thickness on the product selectivity of ultra-thin zeolite frameworks (<10 nm) were investigated. The enhanced catalytic activity confirmed the importance of improved molecular diffusion. These nanosponges were unique in producing more xylenes, suggesting lower confinement effects. The selectivity for p-xylene and the selectivity towards ethylbenzene hydroisomerization, dealkylation, disproportionation, transalkylation and hydrocracking were evaluated. Despite the similar <10 nm crystal thickness of all the nanosponge zeolites, the presence of spacious channel interconnections in MFI was concluded to remarkably impact the product selectivity compared to straight channels as in *MRE and MTW. Our findings clarify the relatively unexplored transformation of alkyl-aromatics over ultra-thin zeolite crystals, through five typical catalytic reactions of major industrial interest.</p

Impact of pore topology and crystal thickness of nanosponge zeolites on the hydroconversion of ethylbenzene

The gas-phase hydroconversion of ethylbenzene was investigated in the presence of intimate mixtures of *MRE, MFI and MTW-type zeolite nanosponges and a hydrogenating component (Pt/Al2O3). The nano-morphic zeolites were prepared using multiammonium surfactants acting as dual-porogenic agents directing the formation of micro- and mesopores simultaneously. The effects of the zeolite topology (pore size and dimensionality) and crystal thickness on the product selectivity of ultra-thin zeolite frameworks (<10 nm) were investigated. The enhanced catalytic activity confirmed the importance of improved molecular diffusion. These nanosponges were unique in producing more xylenes, suggesting lower confinement effects. The selectivity for p-xylene and the selectivity towards ethylbenzene hydroisomerization, dealkylation, disproportionation, transalkylation and hydrocracking were evaluated. Despite the similar <10 nm crystal thickness of all the nanosponge zeolites, the presence of spacious channel interconnections in MFI was concluded to remarkably impact the product selectivity compared to straight channels as in *MRE and MTW. Our findings clarify the relatively unexplored transformation of alkyl-aromatics over ultra-thin zeolite crystals, through five typical catalytic reactions of major industrial interest.</p