Deactivation of heterogeneous catalysts is a ubiquitous problem that causes loss of catalytic rate with time. This review on deactivation and regeneration of heterogeneous catalysts classifies deactivation by type (chemical, thermal, and mechanical) and by mechanism (poisoning, fouling, thermal degradation, vapor formation, vapor-solid and solid-solid reactions, and attrition/crushing). The key features and considerations for each of these deactivation types is reviewed in detail with reference to the latest literature reports in these areas. Two case studies on the deactivation mechanisms of catalysts used for cobalt Fischer-Tropsch and selective catalytic reduction are considered to provide additional depth in the topics of sintering, coking, poisoning, and fouling. Regeneration considerations and options are also briefly discussed for each deactivation mechanism.

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Heterogeneous Catalyst Deactivation and Regeneration: A Review

Homogeneous, heterogeneous and enzymatic catalysis for transesterification of high free fatty acid oil (waste cooking oil) to biodiesel: a review.

Recent advancements in natural dye applications: a review

Accurate and reliable temperature measurement of many special inaccessible objects is a challenging task. Optical temperature sensing is a promising method to achieve it. The current status of optical thermometry of rare-earth ion doped phosphors is reviewed in detail. Based on the mechanisms of optical temperature sensing of different phosphors, temperature dependent luminescence spectra, the fluorescence intensity ratio technique in the data fitting process, and errors of the energy difference between thermally coupled levels, we describe the recent developments in the use of optical thermometry materials. The most important results obtained in each case are summarized, and the main challenges that we need to overcome are discussed. Research in the field of phosphor sensors has shown that they have significant advantages compared to conventional sensors in terms of their properties like greater sensitivity, freedom from electromagnetic interference, long path monitoring, and independence of compatibility with electronic devices.

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Optical temperature sensing of rare-earth ion doped phosphors

Heterogeneous catalysis is widely applied in industry due to important advantages it offers to chemical processes such as improved selectivity and easy catalyst separation from reaction mixture, reducing process stages and wastes. This is the reason why nowadays heterogeneous catalysts are being developed to produce biodiesel. Several catalytic materials have been showed in bibliography: acid solids capable to carry out free fatty acids esterification reaction, base solids which are able to carry out triglycerides transesterification reaction and bifunctional solids (acid–base character) which show ability to simultaneously catalyze esterification and transesterification reaction. This review discusses the latest advances in research and development related with heterogeneous catalysts used to produce biodiesel.

Recent developments on heterogeneous catalysts for biodiesel production by oil esterification and transesterification reactions: A review

Photocatalysis with solar energy: Sunlight-responsive photocatalyst based on TiO2 loaded on a natural material for wastewater treatment

Complete recycling of waste edible oil has recently attracted considerable attention as a worldwide social problem. Production of a biodiesel fuel from used vegetable oil is considered an important step in reducing and recycling waste oil. This technology employs used vegetable oil as a potential renewable alternative resource to fossil diesel fuel, and the transesterification reaction is the usual process to obtain biodiesel. The objective of this work is to study the transesterification of waste oil with methanol in the presence of several Y-type zeolites with different Al2O3 content. In this study, the reaction is carried out in a continuous tubular steel reactor using zeolite Y as catalyst, being tested at atmospheric pressure within a reactor temperature range of 200–476 °C and methanol/oil molar ratio of 6. The results show an important decrease of viscosity of the product obtained until values close to biodiesel specifications.

Zeolite Y as a Heterogeneous Catalyst in Biodiesel Fuel Production from Used Vegetable Oil

Natural dyes extraction from cochineal (Dactylopius coccus). New extraction methods

The use of a heterogeneous catalyst in the transesterification reaction of sunflower oil and waste oil for the production of methyl esters (biodiesel) has been studied. The basic hydrotalcite catalyst used showed a high activity for transesterification reactions in the operation conditions studied. The experiments were performed in a temperature range between 80 and 160 °C, in a batch reactor. The methanol/oil molar ratio in the reaction mixture and catalyst concentration ranges used were from 12:1 to 48:1 (mol/mol) and 3−12 (wt % of the initial vegetable oil mass) respectively. Calcined forms of the catalyst were tested. The catalyst was characterized with SEM, XRD, IR, and DTA-TG methods.

Biodiesel Production from Waste Oil Using Mg−Al Layered Double Hydroxide Catalysts

A natural porous silica, pumice, was studied as heterogeneous catalyst in the transesterification reaction of sunflower oil and frying oil with methanol for biodiesel production. This low cost natural porous material was subjected to ion exchange with a KOH aqueous solution in order to increase its activity. The dependence of the reaction variables such as temperature, reaction time, catalyst loading and methanol/oil molar ratio were studied using sunflower oil and waste oil as feedstock. Moreover, in order to save production costs, the reusability of the catalyst in the transesterification reaction was studied.

M.E. Borges

Papers

Photocatalysis with solar energy: Sunlight-responsive photocatalyst based on TiO2 loaded on a natural material for wastewater treatment

Zeolite Y as a Heterogeneous Catalyst in Biodiesel Fuel Production from Used Vegetable Oil

Natural dyes extraction from cochineal (Dactylopius coccus). New extraction methods

Biodiesel Production from Waste Oil Using Mg−Al Layered Double Hydroxide Catalysts

High performance heterogeneous catalyst for biodiesel production from vegetal and waste oil at low temperature