Abstract
In this work; a response surface methodology (RSM) was implemented to investigate the process variables in a hydrogen production system. The effects of five independent variables; namely the temperature (X1); the flow rate (X2); the catalyst weight (X3); the catalyst loading (X4) and the glycerol-water molar ratio (X5) on the H2 yield (Y1) and the conversion of glycerol to gaseous products (Y2) were explored. Using multiple regression analysis; the experimental results of the H2 yield and the glycerol conversion to gases were fit to quadratic polynomial models. The proposed mathematical models have correlated the dependent factors well within the limits that were being examined. The best values of the process variables were a temperature of approximately 600 °C; a feed flow rate of 0.05 mL/min; a catalyst weight of 0.2 g; a catalyst loading of 20% and a glycerol-water molar ratio of approximately 12; where the H2 yield was predicted to be 57.6% and the conversion of glycerol was predicted to be 75%. To validate the proposed models; statistical analysis using a two-sample t-test was performed; and the results showed that the models could predict the responses satisfactorily within the limits of the variables that were studied.
Highlights
There has been a greatly increased consumption of energy over the past few decades, because of the growing world population and industrialization [1]
The investigation of process variables, namely the temperature, the feed flow rate, the catalyst weight, the catalyst loading and the glycerol-water molar ratio, in the steam reforming of glycerol for producing hydrogen has been performed via response surface methodology (RSM) using a central composite design (CCD)
A thermodynamic study revealed that the high temperature > 600 °C was more favorable for hydrogen production [33,34]
Summary
There has been a greatly increased consumption of energy over the past few decades, because of the growing world population and industrialization [1]. The combustion of fossil fuels causes the production of a large amount of greenhouse gases, such as CO2 and CH4, and toxic gases, such as NOx and SO2 These gases adversely impact the global warming issue and cause acid rain [2]. It has been reported that biomass-derived glycerol can be potentially used as a renewable substrate for hydrogen production via the steam reforming process [8,11,12,13,14,15,16]. The investigation of process variables, namely the temperature, the feed flow rate, the catalyst weight, the catalyst loading and the glycerol-water molar ratio, in the steam reforming of glycerol for producing hydrogen has been performed via RSM using a central composite design. To the best of our knowledge, there is no published work on exploring the process conditions for glycerol steam reforming to produce hydrogen over a xerogel Ni/Al2O3 catalyst, which was prepared by a sol-gel process using polyethylene glycol as a surfactant material
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