No abstract

Electrochemical CO2 reduction reaction (CO2RR) provides a promising approach to curbing harmful emissions contributing to global warming. However, several challenges hinder the commercialization of this technology, including high overpotentials, electrode instability, and low Faradic efficiencies of desirable products. Several materials have been developed to overcome these challenges. This mini-review discusses the recent performance of various cobalt (Co) electrocatalysts, including Co-single atom, Co-multi metals, Co-complexes, Co-based metal–organic frameworks (MOFs), Co-based covalent organic frameworks (COFs), Co-nitrides, and Co-oxides. These materials are reviewed with respect to their stability of facilitating CO2 conversion to valuable products, and a summary of the current literature is highlighted, along with future perspectives for the development of efficient CO2RR.

Among several known zeolites, silicoaluminophosphate (SAPO)‐34 zeolite exhibits a distinct chemical structure, unique pore size distribution, and chemical, thermal, and ion exchange capabilities, which have recently attracted considerable research attention. Global carbon dioxide (CO2) emissions are a serious environmental issue. Current atmospheric CO2 level exceeds 414 parts per million (ppm), which greatly influences humans, fauna, flora, and the ecosystem as a whole. Zeolites play a vital role in CO2 removal, recycling, and utilization. This review summarizes the properties of the SAPO‐34 zeolite and its role in CO2 capture and separation from air and natural gas. In addition, due to their high thermal stability and catalytic nature, CO2 conversions into valuable products over single metal, bi‐metallic, and tri‐metallic catalysts and their oxides supported on SAPO‐34 were also summarized. Considering these accomplishments, substantial problems related to SAPO‐34 are discussed, and future recommendations are offered in detail to predict how SAPO‐34 could be employed for greenhouse gas mitigation.

The transhydrogenation of pentane (P) and 1-hexyne (1HY) was investigated over 4% CrO x /Al 2 O 3 and potassium-doped 4% CrO x /Al 2 O 3 catalysts over a range of temperatures (523-773 K) with a 5:1 P:1HY ratio. Over the CrO x /Al 2 O 3 catalyst, transhydrogenation clearly occurred at temperatures below 625 K where the yield of alkenes was higher for the co-fed system than for a combination of the individual yields. Due to the acidic nature of the alumina, many of the products were alkylated olefins and alkylated hydrocarbons formed by coincident alkylation and isomerisation. When pentane was added to a feed containing 1-hexyne, the extent of carbon deposition was reduced. By comparing transhydrogenation to limited hydrogen 1-hexyne hydrogenation at 623 K, it was shown that the processes of hydrogenation and transhydrogenation were different, with hydrogenation favouring alkanes, while transhydrogenation favoured alkenes. This may be because pentane dehydrogenation only releases two hydrogen atoms, which only allows 1-hexyne to hydrogenate to 1-hexene. Therefore, if the rate of alkene isomerisation and desorption is faster than that of pentane dehydrogenation, only alkenes will be observed. The latter proposal would suggest that the dehydrogenation/hydrogenation process is closely coupled and would be consistent with pentane influencing 1-hexyne surface chemistry. The effect of the potassium doping was to increase the yield of alkenes. The reason for this may be related to changes in the nature of the surface chromia species. The potassium also neutralised the acid sites on the alumina, reducing the extent of alkylation and hydrogenolysis, which suppressed the formation of other alkynes in the product mix.

No abstract

The persistent growth in the global population has accounted for the continuous increase in the use

The production of high premium fuel is an issue of priority to every refinery. The trans-hydrogenation process is devised to convert two low valued refinery cracked products to premium products; the conversion processes involve the combination of dehydrogenation and hydrogenation reaction as a single step process. The paper reviews the recent literature on the use of catalysts to convert low value refinery products (i.e. alkanes and alkynes or alkadienes) to alkenes (olefins) by trans-hydrogenation. Catalysts based on VO x , CrO x and Pt all supported on alumina have been used for the process. However, further studies are still required to ascertain the actual reaction mechanism, mitigating carbon deposition and catalyst deactivation, and the role of different catalysts to optimize the reaction desired products.

Setting a conventional cement plug is nearly unsuccessful when there is any wellbore flow especially for the zechstein formations. As such, the used of sodium silicate remain the common option. The silicate polymerization and gelation has been used in well formation to plug holes and reduce the catastrophic flow which cause a lot of production loses. This is usually encountered during drilling rocks zone producing large amount of water or brine. This could result in large volume of the drilling fluid lost into the formation and consequently reduce the effectiveness of the drilling operations. The total successfulness of sodium silicate/cement squeeze depends strongly on whether the cement placed in the desired place without any contamination. Contamination from Oil Base Mud (OBM), Brine influx in the formation can affect the properties of the cement and lead to the failure of it is placement. Other factors include too low concentration of the silicate and or fresh water dilution may also contribute to some extent as tentatively drawn from a bottle test. The thesis focuses on the laboratory evaluation of the likelihood of this contaminant resulted in the sodium silicate/cement squeeze failure in Swift well. The chemistry of their interaction with the cement slurry is discussed. The zechstein brine is prepared using a programmed spread-sheet provided by Shell UK Company based on typical Molln formation as produced from a well in Germany Compressive strength, thickening time and consistency of the source contaminant were measured varying the volume of the contaminant to see their influences comparing to the neat cement and to see how the extent of these contaminations affected the cement properties. Conclusions were made base on the change of these properties observed on what potentially contribute to it is failure