The_Catalyst_Review_June_2023 - 9

SPECIAL FEATURE
For example, Zeolite catalysts, especially ZSM-5 and HZSM-5, favor the production
of naphtha and aromatics, while carbon nanotubes (CNT) are suitable catalysts for
the FCC production of propylene.
Integrated gasification and Fischer-Tropsch Synthesis (FTS) technology consists
of biosyngas production (H2
and converting the biosyngas to a broad spectrum of hydrocarbons (C1
/COx/H2O mixture), gas cleaning and conditioning,
to C100
)
utilizing a heterogeneous catalyst coupled with refining. Among all transition metals
(group VIII), nickel-based catalysts are considered a suitable choice due to their
effectiveness in converting tar into H2
However, only iron (Fe) and cobalt (Co) catalysts have proven economically feasible
on an industrial scale.
, CH4, CO, and CO2 in the gasification process.
Members of CAP have access to the
reports excerpted herein, plus a library
of similar technical assessments built
over the program's 20-plus years.
Further details about CAP can be
attained by contacting Chris Dziedziak
at cdziedziak@catalystgrp.com or
+1.215.628.4447.
Biochemical upgrading relies primarily on the fermentation of sugars to produce
alcohols, paraxylene, furfural, lactic acid, and succinic acid, although hybrid
thermochemical-biochemical conversion technologies can also be employed. After pretreatment, simple sugars from biomass can be
transformed into smaller molecules by enzymes secreted by microorganisms like cellulase, hemicellulase, and ligninases.
Concerning cellulose hydrolysis, recent studies have focused on solid rather than liquid acids, such as HZSM-5, HY, y-Al2
O3, FeCl3
/silica,
and Carbonaceous Solid Acid (CSA), to facilitate these reactions since solid acids give better product separation, reusability, and recovery
of catalyst. Of the types of solid acid catalysts that have been investigated, CSAs seem to be the most effective. In biomass conversion
into bioethanol, the most employed microorganisms are yeasts. Bio-butanol production can be achieved via Acetone-Butanol-Ethanol
(ABE) fermentation of sugars extracted from biomass. The most widely used bacteria for butanol production via ABE are clostridium
acetobutilicum and clostridium cellulolyticum.
While the advantages of biomass energy are plentiful, certain shortcomings must be overcome to utilize biofuel and biochemical
products fully. Technological challenges in biomass conversion include seasonal biomass productivity, the infeasibility of large-scale
production, high capital costs, and elevated risk associated with innovative technologies. From an environmental perspective, it is critical
to ensure the sustainability of bioenergy production processes concerning GHG emissions, degradation of soil, loss of biodiversity, and
water resources quality.
Rubber Waste Conversion
Waste tires are available in enormous
quantities. Traditional recycling fails to
keep up with the volumes available and
often yields low-value products such
as those used in paving and synthetic
surfaces. However, the incorporation
of graphene as a rubber additive does
result in the formation of higher-value
materials. Because rubber products are
primarily petroleum-derived, they are
an obvious energy source and have
recently been used to generate fuels via
pyrolysis. However, fossil fuels contribute
to greenhouse gas emissions regardless of
their source. Additionally, the presence of
sulfur in the fuels contributes to acid rain
formation unless it is effectively removed.
Finding simultaneous devulcanizationdesulphurization
methods that don't
produce large quantities of problematic wastes is challenging.
Figure 2. Suggested reaction pathway in Pd/NT-Ti catalyzed pyrolysis of waste tire rubber.
Source: Osorio-Vargas et al., 2021
Nonetheless, pyrolysis remains an effective method to valorize waste rubber, and using metallic catalysts can shift the product balance,
including the production of single-ring aromatic compounds. Maximum oil yields are obtained at temperatures around 500o
C, with
higher temperature leading to higher proportions of less valuable solids. Using catalysts and alternative heating strategies, notably
exposure to microwaves, can change these conditions and make valorization processes more successful (Figure 2).
The Catalyst Review
June 2023
9

The_Catalyst_Review_June_2023

Table of Contents for the Digital Edition of The_Catalyst_Review_June_2023