High energy demand from the market due to the rapid increment of the human population worldwide has urged society to explore alternatives to replace non-renewable energy. Renewable diesel produced from biomass could be the next potential energy source for its high stability, long-term storage, and comparable performance with diesel fuels. In producing renewable diesel, the application of catalyst is essential, and the catalyst support is synthesized with the catalyst to enhance the reaction rate and catalytic properties. The application of the supported catalyst in increasing the selectivity and yield of renewable diesel is significant, in which the catalytic properties depend on the interaction between catalyst and catalyst support. The supported catalyst as a favorable substance to assist in enhancing renewable diesel yield could lead to a sustainable and greener future for the biofuel industry in Malaysia.
Type of support | ||||||
Type of Support | ||||||
---|---|---|---|---|---|---|
Type of catalyst | ||||||
Elemental Composition | ||||||
Composition of the active phase | ||||||
Surface Area | ||||||
Surface area | ||||||
Pore Volume | ||||||
Pore volume | ||||||
Remarks | ||||||
Remarks | ||||||
Reference | ||||||
Reference | ||||||
AC | NiP | Ni: 5.14 wt% P: 2.23 wt% |
Micropore: 739 m2/g External: 15 m2/g |
Micro: 0.22 cm3/g Total: 0.25 cm3/g |
Charcoals from Iwasaki kiln | [25] |
AC | NiP | Ni: 4.66 wt% P: 2.24 wt% |
Micropore: 851 m2/g External: 16 m2/g |
Micro: 0.26 cm3/g Total: 0.31 cm3/g |
Charcoals from tube furnace | [25] |
AC | Ni2P | - | BET: 612 m2/g | - | Total acidity: 1.3 mmol/g | [31] |
AC | Ni | O (on the surface): 9.4% | BET: 807.26 cm2/g | Total: 0.185 cm3/g | - | |
AC | Mo2C | Mo(II): 52% Mo(IV): 8% Mo(VI): 40% |
Total: 417.02 m2/g | Total: 0.22 cm3/g | - | [32] |
AC | Mo2C | Mo2C (II): 52.17% MoO2 (IV): 8.2% MoO3 (VI): 39.63% |
BET: 322.20 m2/g | Total: 0.202 cm3/g | - | [28] |
AC | Co-Ag | C: 63.41 wt% O: 13.26 wt% P: 1.45 wt% Co: 9.57 wt% Ag: 12.31 wt% |
BET: 793 m2/g | Total: 1.67 cm3/g | Acidity: 8502.3 µmol/g Total basicity: 6220.2 µmol/g |
[29] |
AC | CoP | - | BET: 822.9 m2/g | Micro: 68.79% Meso: 31.21% Total 0.43 cm3/g |
Acidity: 52.5 µmol/g | [30] |
AC | C: 90.03 % H: 0.557% N: 0.367% S: 0.069% O: 8.98% C/H: 161.6 |
Micropore: 775 m2/g External: 15 m2/g |
Micro: 0.23 cm3/g Total: 0.26 cm3/g |
Charcoals from Iwasaki kiln | [37] | |
AC | C: 80.71 % H: 1.146% N: 1.094% S: 0.078% O: 16.97% C/H: 70.4 |
Micropore: 1202 m2/g External: 20 m2/g |
Micro: 0.39 cm3/g Total: 0.42 cm3/g |
Charcoals from tube furnace | [37] | |
AC | - | BET: 1484.33 cm2/g | Total: 1.038 cm3/g | Acid sites: 3.96 mmol NH3/g catalysts | [45] | |
AC | - | BET: 266.1 m2/g | Total: 0.17 cm3/g | Pre-treated with a nitric acid solution | [46] | |
AC | C: 88.57 wt% O: 8.01 wt% P: 3.42 wt% |
BET: 350 m2/g | Total: 1.88 cm3/g | Total acidity (144 °C): 1055.3 µmol/g Total acidity (852 °C): 2064.7 µmol/g Total basicity (902 °C): 1086.6 µmol/g |
[47] | |
AC | C: 79.1 w/w% H: 0.9 w/w% N: 0.9 w/w% O: 19.2 w/w% |
BET: 964 m2/g | Micro: 77.92% Meso: 22.08% Total: 0.57 cm3/g |
- | [48] | |
Type of support | Type of catalyst | Composition of the active phase | Surface area | Pore volume | Remarks | Reference |
AC | NiP | Ni: 5.14 wt% P: 2.23 wt% |
Micropore: 739 m2/g External: 15 m2/g |
Micro: 0.22 cm3/g Total: 0.25 cm3/g |
Charcoals from Iwasaki kiln | [37] |
AC | NiP | Ni: 4.66 wt% P: 2.24 wt% |
Micropore: 851 m2/g External: 16 m2/g |
Micro: 0.26 cm3/g Total: 0.31 cm3/g |
Charcoals from tube furnace | [37] |
AC | Ni2P | - | BET: 612 m2/g | - | Total acidity: 1.3 mmol/g | [49] |
AC | Ni | O (on the surface): 9.4% | BET: 807.26 cm2/g | Total: 0.185 cm3/g | - | [45] |
AC | Co-Fe | Co: 8.67 wt% Fe: 3.52 wt% |
Micropore: 459.91 m2/g | Micro: 0.22 cm3/g Total: 0.44 cm3/g |
- | [43] |
AC | Mo2C | Mo(II): 52% Mo(IV): 8% Mo(VI): 40% |
Total: 417.02 m2/g | Total: 0.22 cm3/g | - | [50] |
AC | Mo2C | Mo2C (II): 52.17% MoO2 (IV): 8.2% MoO3 (VI): 39.63% |
BET: 322.20 m2/g | Total: 0.202 cm3/g | - | [46] |
AC | Co-Ag | C: 63.41 wt% O: 13.26 wt% P: 1.45 wt% Co: 9.57 wt% Ag: 12.31 wt% |
BET: 793 m2/g | Total: 1.67 cm3/g | Acidity: 8502.3 µmol/g Total basicity: 6220.2 µmol/g |
[47] |
AC | CoP | - | BET: 822.9 m2/g | Micro: 68.79% Meso: 31.21% Total 0.43 cm3/g |
Acidity: 52.5 µmol/g | [48] |
Metal oxides are well known as catalyst supports for industrial catalysts, for example, alumina, zirconia and silica
[3351]. They often consist of a metal cation and oxide anion, which form bases through reaction with water and form salts through reaction with acids. The nature of metal oxides varied with the oxidation states, where the metal oxides are more stable and more acidic with higher oxidation states as compared to lower oxidation states. The properties of metal oxides such as stability, strength and chemical nature are influenced by the type of metal/element as shown in the periodic table, with increasing basic nature and solubility of metal oxides observed down the column
[3452]. The metallic elements also dominate their wide range of attractive physicochemical properties, from the aspects of morphological, electronic, textural, structural, and redox
The catalyst support, alumina (Al2O3) also known as the aluminium oxides, is often found compatible with a mixture of catalysts (containing two or more than two types of catalysts). It was reported that the catalyst, 4Pt-8MOx (where M includes Sn, W, Mo and Re) has exhibited improved catalytic activity on hydrodeoxygenation compared to “neat” Pt supported on alumina
[361]. These metal oxides impregnated with Pt have affected the electronic and textural properties of Pt, resulting in hydrodeoxygenation reaction rather than decarboxylation or decarbonylation reaction during deoxygenation. The metal oxides such as MoOx and ReOx have higher weak (100-200 oC) and moderate (200-350 oC) acid sites than “neat” Pt; while the SnOx and WOx have less weak acid sites and higher strong (>350 oC) acid sites than the “neat” Pt. The good compatibility of NiMo with Al
2
3 was proved in another study as high product yield (80 wt%), with relatively stable activity if NiMo is sulphided even after 5 cycles of re-use [37]. Parameters such as reaction pressure and time possess a positive effect on the yield of the product while the negative effect was observed in temperature.
Silicon oxide known as silica (SiOThe up-gradation of biodiesel to renewable diesel can be performed using zeolites supported catalysts. The study of Fani et al. concluded that Ni catalysts supported on activated natural MOR led to the production of 25 wt% renewable diesel using the highest loading of Ni as catalyst
[4557]. The highest loading of Ni leads to the balanced amount of weak and strong acid sites along with the highest Ni surface area, to produce the highest efficiency for renewable diesel production. Another study reported on the application of Fe/natural zeolite (NZ) showed enhancement in catalytic properties and selectivity towards hydrocarbons with straight-chain alkanes (C15-C18), and the presence of Fe did not change the morphology and crystal structure of zeolites supports [46]. The Fe particles were found to be well-dispersed on the natural zeolite support although the Fe/NZ tends to be agglomerated. It was observed that the impregnation of Fe on NZ led to reduced BET surface area and pore volumes due to the micropore blocking, which was in agreement with the study of Rostamizadeh et al. (2016) [46][47]. The mentioned study has achieved 89% conversion of palm oil into renewable diesel using Fe/natural zeolites as compared to pure natural zeolites as catalysts (58%), showing the maleficent results of natural zeolites as catalyst support.
Synthetic zeolites with optimized structure and surface characteristics can be produced via a thermal process by controlling the composition of materials and process temperature during synthesis. The synthesis of synthetic zeolites can be completed using natural raw materials via microwave-assisted synthesis, dialysis, fusion method, ultrasonic method, molten salt method, alkali activation and hydrothermal synthesis
[501]. However, the synthesis of synthetic zeolites from the chemical source of alumina and silica is expensive. Therefore, the raw material namely kaolin can be studied as a precursor of zeolite due to their silica and alumina ratio.
Short synthesizing time, the versatility of catalytic properties in synthetic zeolites and the possibility to generate desired zeolite structures are the advantages of synthetic zeolites over natural zeolites as catalyst support. Ni was found a versatile catalyst working well with synthetic zeolites as catalyst support. The compatibility of Ni with zeolites is found in agreement with the study of Li et al., where 79% to 90% of diesel range alkanes were produced using both H-ZSM-5 and H-MOR as catalyst support