Basudeb Saha

Rapid synthesis of graphene quantum dots using a continuous hydrothermal flow synthesis approach.

A rapid, continuous, environmentally benign and innovative approach is employed for the synthesis of green fluorescent graphene quantum dots (GQD) with low cytotoxicity by utilising a Continuous Hydrothermal Flow Synthesis (CHFS) process as an efficient cutting tool in combination with calix[4]arene tetrasulfonic acid (SCX4) as an effective particle size limiting agent.

Efficient and selective molybdenum based heterogeneous catalyst for alkene epoxidation using batch and continuous reactors

A polystyrene 2-(aminomethyl)pyridine supported molybdenum(VI) complex (Ps·AMP·Mo) has been prepared, characterised and used as a catalyst for epoxidation of 1-hexene and 4-vinyl-1-cyclohexene (4-VCH) using TBHP as an oxidant. The catalytic performance of the polymer supported Mo(VI) complex has been evaluated for epoxidation of 1-hexene and 4-VCH in a classical batch reactor. Experiments have been carried out to study the effect of reaction temperature, feed molar ratio of alkene to TBHP and catalyst loading on the yield of epoxide for optimisation of reaction conditions in a batch reactor. The long term stability of the polymer supported Mo(VI) catalyst has been evaluated by recycling the catalyst several times in batch experiments using conditions that form the basis for continuous epoxidation studies. The extent of Mo leaching from the polymer supported catalyst has been investigated by isolating any residue from reaction supernatant studies after removal of heterogeneous catalyst and using the residue as potential catalyst for epoxidation. The efficiency of Ps·AMP·Mo catalyst has been assessed for continuous epoxidation of 1-hexene and 4-vinyl-1-cyclohexne with TBHP as an oxidant using a FlowSyn reactor by studying the effect of reaction temperature, feed molar ratio of alkene to TBHP and feed flow rate on the conversion of TBHP and the yield of epoxide. The catalyst was found to be active and selective for batch and continuous epoxidation of the substrates using TBHP as an oxidant. The continuous epoxidation in a FlowSyn reactor has shown considerable time savings, high reproducibility and selectivity along with remarkable improvements in catalyst stability compared with the reactions carried out in a batch reactor.

An experimental-based energy integrated process for biodiesel production from waste cooking oil using supercritical methanol

Biodiesel has been recognised as one of the effective, green, renewable and sustainable fuels. It is derived from renewable living resources either animal fats or vegetable oils. Biodiesel production in the absence of catalyst using supercritical methanol has recently been receiving significant attention. Non-catalytic transesterification reaction eliminates the difficulties of catalyst preparation and separation processes. Although it has shown high conversion for the reactants with relatively short reaction time in comparison with the conventional catalytic transesterification processes, it has some disadvantages including higher reaction temperature and pressure, large excess of methanol to oil (M:O) molar ratio and higher energy consumption. In an attempt to mitigate these problems, an experimental study followed by process design/integration for biodiesel production from waste cooking oil (WCO) has been performed. A low-quality WCO collected from local restaurants has been selected as a feedstock for the reaction. The experimental phase of the transesterification reaction together with an optimisation procedure resulted in the optimised conditions of M:O molar ratio of 37:1, reaction temperature of 253.5 oC, reaction pressure of 198.5 bar in 14.8 min. The maximum yield was 91%. In addition, kinetics of the reaction has been studied concluding an irreversible pseudo first order reaction with a reaction rate constant of 0.0006 s-1. Moreover, thermodynamics of the reaction has been studied at a temperature range of 240 - 270 oC with resulting frequency factor and activation energy of 4.05 s-1 and 50.5 kJ/mol. A kinetic reactor has been simulated using the experimentally determined kinetic and thermodynamic data. The enthalpy content of the reactor product stream has been used to separate most of the unreacted methanol in an adiabatic flash drum. Finally, a scheme has been developed for an energy integrated process in order to maximise the heat recovery. Energy savings resulted from the developed heat exchanger network (HEN) have been concluded as 32.2 % and 23.8 % for both heating and cooling energies respectively, in comparison with an existing process energy requirements in the literature. The amount of heat exchanged for each unit has been determined in addition to composition, temperature and pressure of the streams. Vacuum distillation column has been designed to separate the unreacted triglycerides from biodiesel in order to fulfil the quality restrictions of the final biodiesel product.

A comparative study on biodiesel production from waste cooking oils obtained from different sources using supercritical methanol

The objective of this research is optimizing a process of recycling residues called olive cake (stones) for renewable energy use and Pomace for animal feed industry use. This study includes a drying and separation of solid residues from pulp and store final product for an expedition to recommended user. Drying will proceed continuously in parallel with the existing production process of olive oil. Introduction The olive tree has been present in the Mediterranean since the last glaciations. The first traces of the oleastre date from 6000 years ago. The domestication of the olive tree dates from 5500 BC to the south of Haifa (Near East). Morocco has been producing for over 2000 years. In 1970 about 230,000 Hectares of olive grove. Since 1986 a massive program of planting by the Kingdom to increase production. Today more than 400 000 hectares with more than 400 000 tons of olives. This plantation has a serious environmental implication for the future at the national level. The olive oil industry generates a significant amount of residues that impact not only the country but the entire planet by mainly polluting the soil. Their recycling is still partial for technical and economic reasons. However, in the majority of cases, the cost factor limits the use of these resources. Public pressure and environmental constraints are pushing governments to strike a balance between financial constraints and social pressure. In order to optimize costs it is important to implement a logistics system for an efficient collection; Which can be managed by a local contractor or a power conversion operator. On the other hand, residues with a high humidity of 45 to 55% can not be stored indefinitely or converted into energy without drying. This dehumidification requires a high energy consumption to reach levels between 10 and 15% to be a source of renewable energy. The existence of technical constraints relating to high humidity and economic limitations related to logistics and energy consumption in order to make the residues usable leads us to consider a study of an integrated economic process to respond to this issue. The objective of this research is the eco-design of an economic system to recover the residues of the olive oil olive cake in view of their reuse in the energy supply for the case of the pomace and in industry for pulp. The design includes the separation of pomace and pulp before storage for shipment to the recommended uses. This separation will be carried out in continuous mode in parallel with the existing production process.Biodiesel has been considered as a reasonable replacement fuel for petroleum diesel. It has many advantages over petroleum diesel including its biodegradability and non-toxicity. In addition, it provides free aromatics and sulphur combustion and it is a greener fuel with lower carbon monoxide and hydrocarbons emissions. However, biodiesel has lower heating value and it is relatively more expensive than petroleum diesel. In an attempt to reduce the cost of biodiesel, waste cooking oil (WCO) has been considered as a competitive feedstock. It also provides more sustainability for the produced biodiesel as it is a result of transformation of waste to greener source of energy. The main concern for using WCO as a feedstock for biodiesel production is the presence of high concentration of free fatty acids (FFA), which result in saponification reaction while using the conventional alkaline catalysed process. Saponification lowers the biodiesel yield by preventing the separation of biodiesel from the product. In this study, a non-catalytic method for biodiesel production from WCO using supercritical methanol has been investigated. Two different feedstocks with different FFA concentration have been examined. Response surface methodology (RSM) using Box Behnken Design (BBD) and Central Composite Design (CCD) has been employed to analyse the effect of different reaction variables including methanol to oil (M:O) molar ratio, temperature, pressure and time on biodiesel yield. Numerical optimisation has been applied to determine the optimum conditions for maximum production of biodiesel for each feedstock. It has been concluded that the feedstock with higher FFA concentration produce higher biodiesel yield within the same reaction conditions. This result indicates the significance of using supercritical methanol technique for feedstocks with high FFA concentration as it enhances both esterification of FFA and transesterification of triglycerides (TG) to fatty acids methyl esters (FAME).A possible solution is studied to solve the global solid waste, air pollution, and energy crisis issues. Rice straw is an abundant biomass that is often disposed of by open-field burning. The carbohydrates and sugars in rice straw can be acid hydrolysed to produce furans which are the building blocks of a fuel known as ethoxymethyl furfural, which has an energy density similar to gasoline. A model was created to represent the concentration of the different components present in the reactor with respect to residence time.

Optimising biodiesel production from high acid value waste cooking oil using supercritical methanol

In this study, biodiesel production from a typical Egyptian waste cooking oil (WCO) with high acid value content (18 mg KOH/g oil) has been analysed by studying the main factors affecting biodiesel and glycerol yields. Response Surface Methodology (RSM) via Central Composite Design (CCD) has been used to analyse the effect of four independent variables, i.e. methanol to oil (M:O) molar ratio, temperature, pressure and time on the reaction responses. A quadratic model for each response has been concluded representing the interrelationships between reaction variables and reaction responses. In addition, the predicted models’ adequacy has been evaluated through Analysis of Variance (ANOVA) method. Numerical optimisation technique has been applied to conclude the optimum reaction conditions for maximum production of biodiesel resulting in 98% and 2.05% for biodiesel and glycerol yields at M:O molar ratio, temperature, pressure and time of 25:1, 265oC, 110 bar and 20 minutes, respectively. Experimental validation has been analysed for the predicted optimum conditions resulting in 98.82% biodiesel yield with 0.83% relative error.

Greener route to 4-vinyl-1-cyclohexane 1,2-epoxide synthesis using batch and continuous reactors

Abstract Polystyrene 2-(aminomethyl)pyridine (Ps.AMP) supported molybdenum (Mo)(VI) complex (Ps.AMP.Mo) was prepared, characterized and assessed as a catalyst for batch and continuous epoxidation of 4-vinyl-1-cyclohexene (4-VCH) using tert-butyl hydroperoxide (TBHP) as an oxidant. The effect of various parameters such as reaction temperature, feed molar ratio (FMR) of 4-VCH to TBHP and catalyst loading on the conversion of TBHP to 4-vinyl-1-cyclohexane 1,2-epoxide (4-VCH 1,2-epoxide) was studied to optimize reaction conditions in a batch reactor. The long-term stability of Ps.AMP.Mo was evaluated by recycling a sample of the catalyst several times in batch experiments. A detailed evaluation of Mo leaching from the polymer supported catalyst was investigated by isolating any residue from reaction supernatant solutions and then using these residues as potential catalysts in epoxidation reactions. The efficiency of Ps.AMP.Mo catalyst for continuous epoxidation studies was assessed using a FlowSyn continuous flow reactor by studying the effect of reaction temperature, feed flow rate and FMR of 4-VCH to TBHP on the conversion of TBHP and the yield of 4-VCH 1,2-epoxide. The experimental results confirmed very high selectivity and efficiency of Ps.AMP.Mo catalyst for batch and continuous epoxidation.